WO2015116999A1 - Stereo imaging with rotational-shear interferometry - Google Patents

Stereo imaging with rotational-shear interferometry Download PDF

Info

Publication number
WO2015116999A1
WO2015116999A1 PCT/US2015/013909 US2015013909W WO2015116999A1 WO 2015116999 A1 WO2015116999 A1 WO 2015116999A1 US 2015013909 W US2015013909 W US 2015013909W WO 2015116999 A1 WO2015116999 A1 WO 2015116999A1
Authority
WO
WIPO (PCT)
Prior art keywords
rotational
shear interferometer
interest
electromagnetic radiation
stereo imaging
Prior art date
Application number
PCT/US2015/013909
Other languages
French (fr)
Inventor
Leonard Rodenhausen WAYNE
Original Assignee
Wayne Leonard Rodenhausen
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Wayne Leonard Rodenhausen filed Critical Wayne Leonard Rodenhausen
Publication of WO2015116999A1 publication Critical patent/WO2015116999A1/en

Links

Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B30/00—Optical systems or apparatus for producing three-dimensional [3D] effects, e.g. stereoscopic images
    • G02B30/20—Optical systems or apparatus for producing three-dimensional [3D] effects, e.g. stereoscopic images by providing first and second parallax images to an observer's left and right eyes
    • G02B30/34—Stereoscopes providing a stereoscopic pair of separated images corresponding to parallactically displaced views of the same object, e.g. 3D slide viewers
    • G02B30/36—Stereoscopes providing a stereoscopic pair of separated images corresponding to parallactically displaced views of the same object, e.g. 3D slide viewers using refractive optical elements, e.g. prisms, in the optical path between the images and the observer

Definitions

  • the present invention relates generally to stereo imaging, and more particularly, to stereo imaging using rotational-shear interferometry.
  • Stereo imaging is a technique where an image of a scene is taken from each of two or more locations. These data provide information about the 3-D structure of a scene, where the third dimension is depth.
  • a difficulty with many current stereo imaging systems is the limited depth-of-field of the imaging systems.
  • Some regions of the image will appear in focus and some regions out of focus.
  • 3-D stereo information can be difficult to obtain in regions that are out of focus.
  • a designer of such a system may make tradeoffs against other system parameters. For example, in the case of a conventional microscope the designer may- decrease the numerical aperture of the microscope in order to increase the depth-of- field of the microscope and thus obtain 3-D stereo information through a larger scene depth, A decrease in the numerical aperture of a microscope degrades the lateral spatial resolution of the microscope, which is undesirable,
  • Another difficulty with many current stereo imaging systems is the limitation on the spatial resolution that can be achieved with a given numerical aperture (the metric often used with microscope systems and sometimes with camera systems) or a given aperture size (the metric often used with telescope systems and sometimes with camera systems).
  • many current stereo imaging systems use one or more conventional imaging systems such as conventional microscopes, conventional cameras, or conventional telescopes.
  • the spatial resolution of a conventional imaging system is limited in a way often referred to as the Rayleigh limit. This is a limit to image quality.
  • a stereo imaging system includes a first rotational-shear interferometer and a second rotational-shear interferometer.
  • the first rotational-shear interferometer includes a first rotational-shear interferometer and a second rotational-shear interferometer.
  • This stereo imaging system includes an imager other than a rotational-shear interferometer.
  • the imager comprises an image sensor.
  • the stereo imaging system further includes a rotational-shear interferometer comprising at least one image sensor.
  • the imager is configured for collecting first electromagnetic radiation from an object of interest.
  • the rotational-shear interferometer is configured for collecting second electromagnetic radiation from an object of interest.
  • a rotational-shear interferometer for providing stereo imaging.
  • the rotational-shear interferometer includes one or more fore-optics and at least two output ports. Each of the two output ports has an entrance pupil associated therewith. The entrance pupils are offset from each other to provide stereo imaging of an object of interest.
  • a method of performing stereo imaging includes steps of collecting, by a first rotational-shear interferometer, first electromagnetic radiation from an object of interest, collecting, by a second rotational-shear interferometer, second electromagnetic radiation from the object of interest, and processing the collected first and second electromagnetic radiation to provide stereo imaging of the object of interest.
  • FIG. 1 schematically illustrates a stereo imaging system that uses rotational-shear interferometry in accordance with an exemplary embodiment of the present invention
  • FIG. 2 schematically illustrates ail alternate embodiment in which two rotational-shear interferometers share a set of common fore-optics in accordance with an exemplary embodiment of the present invention
  • FIG. 3 schematically illustrates an alternate embodiment in which two rotational-shear interferometers have entrance pupils that overlap each other in accordance with an exemplary embodiment of the present invention
  • FIG. 4 schematically illustrates an alternate embodiment with a rotational-shear interferometer and a conventional imaging system in accordance with an exemplary embodiment of the present invention
  • FIGS. 5A and 5B schematically illustrate an alternate embodiment with two rotational-shear interferometers that face each other in accordance with an exemplary embodiment of the present invention.
  • FIGS . 6A and 6B schematically illustrate an alternate embodiment with a rotational-shear interferometer with two entrance pupils offset from each other in accordance with an exemplary embodiment of the present invention.
  • counter-tilt refers to an arrangement of two beams of light in which a change in the tilt angle of one beam is accompanied by a simultaneous change in the tilt angle of the other beam such that the two beams tilt towards each other or away from each other.
  • This arrangement could also be referred to as "counter change-in-tilt", though for conciseness of language the term “counter-tilt” is used.
  • the two beams do not have to tilt exactly towards each other or exactly away from each other, but may tilt at different angles, such as happens in a rotational-shear interferometer set to a shear angle other than 180 degrees.
  • the term "common fore-optics" refers to optics shared by two optical systems at the front end.
  • the system in total is composed of two rotational-shear interferometers.
  • Lens 210 and field stop 214 together constitute a set of "common fore-optics” that are shared by, and part of, each of the two rotational-shear interferometers.
  • a rotational-shear interferometer (RSI) is one of the many kinds of instruments that can be used to image a scene. Light that enters the instrument is split into two beams. The two beams are recombined so as to produce interference fringes which are analyzed to infer an image of the scene.
  • RSIs RSIs
  • a remarkable property of RSIs is their very long depth-of-field, a property rarely made use of. The reason the depth-of-field is so long is the wavefront curvature associated with defocus is common-mode between the two beams and mostly cancels out when the interference fringes are formed on the detector.
  • a conventional imager such as a conventional camera or a conventional microscope, generally has a much shorter depth-of-field than does an RSI.
  • exemplary embodiments of the present invention provide improved depth discrimination within an image by use of components (RSIs) that largely remove depth discrimination.
  • RSIs Another remarkable property of RSIs is their sharp lateral spatial resolution, at least in cases where spatially-incoherent light is used. Jn a single-beam imager, such as a conventional microscope, conventional camera, or conventional telescope, the Lagrange Invariant limits lateral spatial resolution in the following sense. It can be shown that if a device existed that could violate the Lagrange Invariant by a factor of "x", that device could be incorporated into a conventional imager to improve the lateral spatial resolution by the same factor "x". A single- beam device generally cannot violate the Lagrange Invariant. In an RSI there are two beams. The light in each of the two beams conforms to the Lagrange invariant.
  • RSI modulation transfer function
  • FIG. 1 schematically illustrates an exemplary configuration of a stereo imaging system 100 in accordance with an exemplary embodiment of the present invention, comprising a first and second rotational-shear interferometer 150, 151.
  • RS1s 150, 151 may collect light (as used herein, "light” includes all wavelengths of electromagnetic radiation, and is not limited to the visible spectrum) from an object under study.
  • FIG. 1 shows light arriving at stereo imaging system 100 from a distant point source (not shown).
  • FIG. 1 and the relevant figures described below are not intended to indicate that the devices and methods illustrated and described herein are limited to use with point sources. Rather, throughout the present disclosure, the object under study need not be a point source and can extend laterally and depthwise, and the stereo imaging systems described herein may be configured to collect light from other locations from the object to be imaged, as desired. Also, FIG.
  • FIG. 1 and the relevant figures described below are not intended to indicate that the devices and methods illustrated and described herein are limited to use with object points that are far away. Rather, throughout the present disclosure, the object under study may be close to, or far from, the stereo imaging system. Also, FIG. 1 and the relevant figures described below are not intended to indicate that curved mirrors may not be used instead of lenses. Rather, as those skilled in the art will appreciate, there are many instances where a lens may be replaced with a curved mirror.
  • input optics in the form of an objective lens 1 10 may be provided to collect light from a beam 108. While the objective lens 1 10 is illustrated as a singlet, those skilled in the art will appreciate that the objective lens 1 10, as well as all lenses disclosed herein, may contain multiple elements, cemented or otherwise, and need not comprise only a single element. Additional elements may be provided as desired to correct aberrations and improve image quality, for example. Arrows indicate the direction which light beam 108 from the object under study impinges on objective lens 1 10.
  • An aperture stop 1 12 may be provided to control the extent of the beam that travels through the rotational-shear interferometer 150. While the aperture stop 1 12 is illustrated at a particular location along the beam path from the object point to the detectors, those skilled in the art will appreciate that the aperture stop 1 12, as well as all aperture stops disclosed herein, may be located at many other places along the beam path. The location of an aperture stop is a design choice selected to satisfy various design goals and constraints.
  • Light that passes through the aperture stop 1 12 may be transmitted to a field stop 1 14 that blocks light from outside the desired field-of-view.
  • Light that passes through the field stop 1 14 may reflect off a fold mirror 1 16.
  • the fold mirror 1 16 is included to steer the beam in a direction convenient for drawing FIG. 1 , but is not required, as those skilled in the art will recognize.
  • Imaging optics 1 18 may be provided to image the aperture stop 1 12 onto detectors 134, 136. Again, while the imaging optics 1 18 are shown as a pair of lenses, any suitable configuration of optics may be used to achieve the desired imaging properties.
  • each arm of the rotational-shear interferometer 150 may include a plurality of mirrors 122, 124, 126, 128, 130, the configuration of which mirrors is designed to introduce counter-tilt between the two interfering beams that strike each detector 134, 136.
  • one arm of the rotational-shear interferometer 150 may include an even number of mirrors, such as a pair of mirrors 122, 124.
  • the other arm of the rotational-shear interferometer 150 may include an odd number of mirrors, such as the three mirrors 126, 128, 130.
  • having at least two mirrors 122, 124 m one arm and at least three mirrors 126, 128, 130 in the other arm allows for the optical path length in each arm to be made the same as the optical path length in the other arm by adjusting the relative spacings among the mirrors 122, 124, 126, 128, 130 and the beam splitters 120, 132.
  • the beams in each arm of the interferometer 150 may be combined at the second beam splitter 132, and the interference pattern of the combined beams may be received at detectors 134, 136.
  • the two beams that emerge from beam splitter 132 may be said to correspond to two "output ports" on the RSI 150.
  • Rotational- shear interferometer 151 includes the same components as rotational-shear interferometer 150, configured in a similar manner to the like-named components of rotational-shear interferometer 150. This includes an objective lens 1 1 1 , an aperture stop 1 13, a field stop 1 15, a fold mirror 1 17, imaging optics 1 19, beam splitters 121 , 133, fold mirrors 123, 125, 127, 129, 131 , and detectors 135, 137. Beam 109 from the object under study is incident on objective lens 1 1 1.
  • a fringe pattern may be recorded by one or both detectors 134, 135,
  • each RSI 150, 151 136, 137 in each RSI 150, 151 and outpuued.
  • Fringe data is required from only one of the two detectors in each RSI to determine an image of the scene in front of that RSI. However the data from both detectors within each RSI may be used, so as to provide an improved signal-to-noise ratio, for example.
  • Each recorded fringe pattern may be converted to an image. For example, sometimes a Fourier transfomi is used for the conversion.
  • An image from RSI 150 and an image from RSI 151 may be processed in the normal way stereo data is processed to obtain 3-D information about the object or scene under study.
  • the image recorded by an RSI is a conical projection (with the center of the RSI entrance pupil being the vertex of the cone), and the algorithm that combines the two images to obtain 3-D information may account for this.
  • FIG. 1 is not meant to indicate that a video monitor is the only way to display 3-D information about a scene under study. Rather, consistent with the present disclosure, there are many ways to impart 3-D information to a user. For example, head mounted displays may be used.
  • the stereo imaging system 100 may further comprise a computer- readable tangible medium on which software instructions are stored.
  • the computer processor 190 may be configured to access the computer-readable tangible medium to load and execute the software instructions to cause the computer to perform steps of receiving data from detectors 134, 135, 136, 137, performing calculations to convert data from each detector into an image of the scene under study, performing calculations to determine the 3-D structure of the scene under study or to arrange 2-D images in a manner for 3-D presentation, and outputting an image of the scene under study or the 3-D structure of the scene.
  • the computer-readable tangible medium may be any device known in the art capable of storing software instructions, such as a hard drive, solid-state memory, flash drive, etc.
  • All the exemplary embodiments described in the present disclosure may employ a processor, computer-readable tangible medium, monitor, and their associated features and functionalities described herein with respect to FIG 1 , for example.
  • the configuration illustrated in FIG. 1 may provide advantages over existing 3-D imaging systems. For example, a scene with greater depthwise extent may be studied in 3-D with only a single measurement. By comparison conventional 3-D imaging systems have a shorter depth-of-field, and for scenes with extended depth one must record multiple snapshots with the region of best focus aligned at different locations within the scene. The data may then be stitched together to obtain an extended-depth 3-D image of the entire scene. These realignments may be accomplished by movement of the scene relative to the imager, or movement of the imager relative to the scene, or movement of optical components within the imager.
  • the configuration illustrated in FIG. 1 has the advantage that it reduces the number of such alignments needed for a measurement. This improves system performance in a number of applications.
  • a reduction in the number of alignments may result in less time needed to perform the surgery, fewer robotic movements during the surgery, and less total robotic distance traveled during the surgery. These advantages may improve the efficiency of the surgeon's performance and thus enhance patient safety.
  • FIG. 1 Another advantage which may be provided by the configuration illustrated in FIG. 1 is improved stereo co-registration of features within the scene under study.
  • Stereo imaging provides depth information via the parallax of each feature within the scene. To determine the parallax of a feature, it is helpful when the feature appears as sharp as possible in each stereo image. The sharper the image, the better the stereo system is able to measure the depth coordinate of the feature of interest.
  • the configuration illustrated in FIG. 1 has the advantage that the depth-of- field is much longer than in a conventional system, so more of the features of interest may be in focus.
  • i also has the advantage of sharper lateral spatial resolution as compared to that of a conventional imager, by up to a factor of two, even when the conventional imager is at its best focus, as was discussed earlier.
  • the configuration illustrated in FIG. 1 may achieve better stereo co-registration, which may mean better determination of the depth coordinate of the feature of interest.
  • Improved depth measurement is an advantage for a number of applications. For example, returning to the example of robotic surgery, better depth measurement may improve the efficiency and accuracy of the surgeon's performance, and hence improve patient safety, which is an advantage. With better depth measurement, an image may be easier to interpret, with better identification of features within the image.
  • a stereo imaging system 200 in accordance with an exemplary embodiment of the present invention may be provided which includes two rotational-shear interferometers that share a set of common fore-optics with each other.
  • an objective lens 210 and a field stop 214 are each used by both RSIs and constitute a set of common fore-optics.
  • Light is emitted from an object point 202.
  • Solid lines represent a beam used by one RSI
  • dashed lines represent a beam used by the other RSI.
  • the remaining optics encountered by each beam are exclusive to each RSI.
  • the optics enclosed in outline 270 are exclusive to the RSI that uses the solid beam
  • the optics enclosed in outline 271 are exclusive to the RSI that uses the dashed beam.
  • FIG. 2 The elements in FIG. 2 are configured in a similar manner to the like- named and like-numbered components of the stereo imaging system 100 of FIG. I .
  • Fold mirrors 216, 217 redirect the beam path.
  • Optics 218, 219 image aperture stops 212, 213 to detectors 234, 236, 235, 237.
  • Each rotational-shear interferometer may include beam splitters 220, 232, 221 , 233, mirrors 222, 224, 226, 228, 230, 223 225, 227, 229, 231 , and detectors 234, 236, 235, 237.
  • Different choices may be made for which optics are shared by the two RSIs, depending on design considerations specific to an application.
  • each of the two RSIs may be desirable for each of the two RSIs to use its own exclusive field stop since this provides a system designer increased flexibility in how to arrange the fields-of-view of the two RSIs to overlap each other at a given object of interest.
  • FIG. 2 as compared to the configuration illustrated in FIG. 1 is the ability to position the optical system closer to the object under study.
  • there is only a single objective lens instead of two objective lenses side-by-side there is generally enough physical space to place the objective lens closer to the object under study.
  • a further advantage that may be provided by the configuration illustrated in FIG. 2 as compared to the configuration illustrated in FIG. 1 is easier alignment of the system field stop(s).
  • stereo imaging system 100 there are two field stops (1 14 and 1 15), and the two field stops are generally aligned relative to each other to provide the same or similar fields of view for the two RSIs.
  • stereo imaging system 200 there is only a single field stop (field stop 214), and the single field stop serves both RSIs, so an alignment step may be eliminated.
  • a stereo imaging system 300 in accordance with an exemplary embodiment of the present invention may be similar in certain respects to the stereo imaging system 200 of FIG. 2, but may include a beam splitter 31 1.
  • Such a configuration allows the entrance pupils of the two RSls to be located closer to each other, or even to overlap each other, if desired. This added flexibility may be an advantage in certain applications. For example, for a given stereo separation distance (the distance between the centers of the two entrance pupils) the widths of the entrance pupils may be larger, allowing more light from the object to reach the system detectors. More light may allow dimmer scenes to be viewed, and may also allow a shorter detector integration time for each image, which facilitates imaging objects in motion.
  • FIG. 3 The elements in FIG. 3 are configured in a similar manner to the like- named and like-numbered components of the stereo imaging system 200 of FIG. 2.
  • an objective lens 310, a field stop 314, and the beamsplitter 3 1 1 are common fore-optics each used by both RSIs.
  • Light is emitted from an object point 302.
  • Solid lines represent a beam used by one RSI
  • dashed lines represent a beam used by the other RSI.
  • the remaining optics encountered by each beam are exclusive to each RSI.
  • the optics enclosed in outline 370 are exclusive to the RSI that uses the solid beam
  • the optics enclosed in outline 371 are exclusive to the RSI that uses the dashed beam.
  • Optics 318, 319 image aperture stops 312, 313 to detectors 334. 336,
  • Each rotational-shear interferometer may include beam splitters 320, 332, 321 , 333, mirrors 322, 324, 326, 328, 330, 323 325, 327, 329, 331 , and detectors 334,
  • each RSI may be placed at many locations other than what is illustrated in FIG. 3.
  • a beamsplitter may be arranged to intercept light from the object of interest before the light encounters any other optics.
  • each RSI will use its own objective lens and its own field stop rather than sharing these components.
  • a stereo imaging system 400 in accordance with an exemplary embodiment of the present invention may be similar in certain respects to the stereo imaging system 100 of FIG. 1 , but may include a rotational-shear interferometer 450 and a conventional imager 481 other than a rotational-shear interferometer.
  • objective lenses 410, 41 1 collect light from an object (not shown), which passes through aperture stops 412, 413. Within the conventional imager 481 the light then focuses to a detector 463 where an image is recorded.
  • elements are configured in a similar manner to the like-named and like-numbered components of the stereo imaging system 100 of FIG. 1.
  • the rotational-shear interferometer 450 may include beam splitters 420, 432, mirrors 422, 424, 426, 428, 430, and detectors 434, 436.
  • FIG. 4 as compared to the configuration illustrated in FIG. 1 is fewer optical components may be required, which may reduce cost, for example, while advantages that come with the use of at least one RSI may still be present, such as an improved depth of field and improved spatial resolution.
  • the conventional imager 481 may be configured to have a wider field-of-view than the RSI 450, thus facilitating the initial search for a particular region of interest within a scene under study. For example, a user may first search for and locate an object of interest within a wide field of view provided by the conventional imager 481 , then adjust the orientation of the stereo imaging system 400 so that the region of interest is also within the field of view of the RSI 450.
  • the imaging systems 450, 481 may share some components with each other, similar to the stereo imaging system 200 in FIG. 2 or the stereo imaging system 300 in FIG. 3.
  • a beam splitter may be used in a similar manner to beam splitter 311 , FIG. 3, allowing the entrance pupils of the imaging systems 450, 481 to be located closer to each other or even partially overlap each other.
  • hybrid stereo configuralions that employ an RSI may provide other advantages while still preserving some of the advantages that come from use of at least one RSI in the stereo pair, such as a longer depth of field and sharper spatial resolution.
  • a stereo imaging system 500 in accordance with an exemplary embodiment of the present invention may be similar in certain respects to the stereo imaging system 100 of FIG. 1 , but the two RSIs face each other.
  • the scene being imaged might be a biological sample, for example.
  • An advantage of this configuration is more light from the sample may be collected, since light leaving the sample is collected in both directions. More light generally corresponds to reduced noise in the 3-D image, which is an advantage.
  • stereo imaging system 500 is composed of rotational-shear interferometers 550, 551.
  • Objective lenses 510, 51 1 may collect light from an object 557 under study after reflection by fold mirrors 554, 555. The light may pass through aperture stops 512, 513, and may focus to field stops 514, 515.
  • Fold mirrors 516, 517 may redirect the beam path.
  • Optics 518, 519 may image the aperture stops 512, 513 to detectors 534, 535, 536, 537.
  • Each rotational-shear interferometer may include beam splitters 520, 532, 521 , 533, and mirrors 522, 524, 526, 528, 530, 523 525, 527, 529, 53 1 .
  • a set of coordinate axes is labeled 502.
  • FIG. 5B illustrates how the 3-D stereo location of an object point is determined in this exemplary configuration.
  • Coordinate axes 502 are drawn to indicate the correspondence between FIGS.s 5A and 5B.
  • An object point 562 is located between aperture stops 512, 513.
  • the entrance pupils and the aperture stops are the same as each other.
  • the fold mirrors 554 and 555 are omitted from FIG. 5B for clarity.
  • the aperture stops 512, 513 are drawn differently in FIG. 5 A versus FIG. 5B.
  • the aperture stops are drawn with solid lines that indicate the opaque region of each aperture stop
  • FIG. 5B the aperture stops 512, 513 are drawn with solid lines that indicate the clear aperture.
  • FIG. 5 A the aperture stops are drawn with solid lines that indicate the opaque region of each aperture stop
  • FIG. 5B the aperture stops 512, 513 are drawn with solid lines that indicate the clear aperture.
  • FIG. 5 A the aperture stops are drawn with solid lines that indicate the opaque region of each aperture stop
  • FIG. 5B the
  • RSI 551 measures the angle alpha of object point 562
  • RSI 550 measures the angle beta of object point 562. From the values of alpha and beta one may calculate the 3-D spatial coordinates of object point 562 using straightforward trigonometry.
  • a stereo imaging system 650 in accordance with an exemplary embodiment of the present invention may be similar in certain respects to the stereo imaging system 100 of FIG. 1 , but only a single RSI is used and there are two aperture stops instead of one.
  • An advantage of this configuration is fewer optical components may be required, which may reduce cost and complexity.
  • the two aperture stops are co- located with the detectors 638, 644.
  • each detector face may be painted black over all but a clear area that is then the aperture.
  • the two aperture stops may be imaged differently from each other such that there are two entrance pupils 610, 612.
  • the entrance pupil is the image of the aperture, as seen from the object under study.
  • entrance pupil 610 may be the image of the aperture stop at detector 638, as determined by lenses 608, 618, 632, 636.
  • entrance pupil 612 may be the image of the aperture stop at detector 644, as determined by lenses 608, 618, 640, 642.
  • the entrance pupils 610, 612 are different sizes than each other, though a difference in size is not a requirement.
  • FIG. 6A Other components in FIG. 6A are configured in a similar manner to the like-named and like-numbered components of the stereo imaging system 100 of FIG. 1.
  • Objective lens 608 focuses light from an object point 604 into the plane of field stop 614.
  • the RSI 650 may include fold mirrors 616, 622, 624, 626, 628, 630 and beamsplitters 620, 632.
  • a set of coordinate axes are is labeled 602.
  • FIG. 6B illustrates how the 3-D stereo location of an object point is determined in this exemplary configuration.
  • Coordinate axes 602 are drawn to indicate the correspondence between FIG.S 6A and 6B,
  • An object point 604 is located a distance from entrance pupils 610, 612.
  • the entrance pupils 610, 612 are drawn differently in FIG. 6A versus FIG. 6B.
  • the entrance pupils are drawn with solid lines that indicate the opaque region of each aperture stop
  • FIG. 6B the entrance pupils 610, 612 are drawn with solid lines that indicate the clear aperture.
  • the center points of the entrance pupils are labeled 660, 662.
  • the signal at detector 644 (corresponding to entrance pupil 612) measures the angle alpha of object point 604, and the signal at detector 638 (corresponding to entrance pupil 610) measures the angle beta of object point 604. From the values of alpha and beta, and other known parameters such as the distance between entrance pupils 610, 612, one may calculate the 3-D spatial coordinates of object point 604 using straightforward trigonometry.
  • the image produced by an RSI is a conical projection.
  • the vertex of the cone is the center of the RSI entrance pupil.
  • use of the recorded RSI data to determine the 3-D structure of a scene should account for the conical projection of the RSI.
  • Hybrid systems that use imagers with both conical and conventional projections should account for this duality.
  • alternative methods of inducing counter- tilt between the two beams of the interferometer may be employed.
  • both arms could use an odd (or even) number of reflections, with the light in one arm made to pass through an intermediate focus while the light in the other arm is not.
  • counter-tilt may be introduced between the two arms of a rotational-shear interferometer by a pair of lenses provided in one arm the interferometer.
  • a single mirror may be provided in each arm between the beam splitters since the counter-tilt is introduced by the lenses.
  • the angle of rotational-shear on the RSls can be set to different values, depending on the application.
  • adaptive optics may be incorporated into each RSI. One use of adaptive optics may be to compensate for the otherwise- detrimental light-scattering properties of the sample.
  • the RSls may be constructed and used in a number of configurations, such as a Michelson or Mach- Zehnder configuration. Within each RSI the angle at which the two beams are incident on the detector can also be adjusted.
  • the two resulting beams can be incident on the detector at normal incidence or at some different angle (e.g., +/- 3 degrees). If the two beams are incident at normal incidence, there will be ambiguity (the twin image problem). If the angle-of- incidence of each beam corresponding to the center of the field-of-view is large enough, the twin image problem is avoided.
  • the RSls may be used in a modified form known as a quadrature -phase interferometer. Each RSI may also use fringe-scanning to obtain a time series of exposures with different phase differences between the two arms of the interferometer.
  • Each RSI may be configured to compensate or correct for differences in the polarization response of the two arms of the interferometer, for example by the addition of phase plates.
  • Each RSI may further be configured to achromatize the fringe pattern to increase the spectral bandwidth of the RSI.
  • Each RSI may use mirrors that may or may not contain a roofline through the middle of the mirror, and may optionally include a prism to steer light.
  • Different types of beam splitters may also be used within each RSI, such as cube or pellicle being splitters, or a glass plate that reflects off one of its external surfaces.
  • robotic control applications such as robotic surgery, product profiling in manufacturing settings (e.g., automated acceptance/rejection), patient examination in telemedicine settings (e.g., to discern the morphology of an injury), surveying, recreational photography, etc.

Abstract

A stereo imaging system and method for generating a three-dimensional image using at least two rotational-shear interferometers. An exemplary system includes a first rotational-shear interferometer and a second rotational-shear interferometer. The first rotational-shear interferometer is configured for collecting first electromagnetic radiation from an object of interest. The second rotational-shear interferometer is configured for collecting second electromagnetic radiation from the object of interest. The first rotational-shear interferometer and the second rotational-shear interferometer are positioned relative to one another to provide stereo imaging of the object of interest. An exemplary method includes steps of collecting, by a first rotational-shear interferometer, first electromagnetic radiation from an object of interest; collecting, by a second rotational-shear interferometer, second electromagnetic radiation from the object of interest, and processing the collected first and second electromagnetic radiation to provide stereo imaging of the object of interest.

Description

STEREO IMAGING WITH ROTATIONAL-SHEAR INTERFEROMETRY
Cross-Reference to Related Applications
[0001] The present application claims priority to U.S. Provisional Patent
Application No. 61/933,477, entitled "Stereo Imaging with Rotational-Shear Interferometry" and filed on Jan. 30, 2014, which is hereby incorporated by reference in its entirety. The present application also claims priority to U.S. Provisional Patent Application No. 62/053 ,222, entitled "Stereo Imaging with Rotational-Shear Interferometry" and filed on Sep. 21 , 2014, which is hereby incorporated by reference in its entirety. The present application also claims priority to U.S. Provisional Patent Application No. 62/056,328, entitled "Stereo Imaging with Rotational-Shear Interferometry" and filed on Sep. 26, 2014, which is hereby incorporated by reference in its entirety.
Field of the Invention
[0002] The present invention relates generally to stereo imaging, and more particularly, to stereo imaging using rotational-shear interferometry.
Background of the Invention
[0003J Stereo imaging is a technique where an image of a scene is taken from each of two or more locations. These data provide information about the 3-D structure of a scene, where the third dimension is depth.
[0004] A difficulty with many current stereo imaging systems is the limited depth-of-field of the imaging systems. As one example, consider a scene with a depth larger than the depth-of-field of the imaging system. Some regions of the image will appear in focus and some regions out of focus. 3-D stereo information can be difficult to obtain in regions that are out of focus. This is a limitation. To compensate, a designer of such a system may make tradeoffs against other system parameters. For example, in the case of a conventional microscope the designer may- decrease the numerical aperture of the microscope in order to increase the depth-of- field of the microscope and thus obtain 3-D stereo information through a larger scene depth, A decrease in the numerical aperture of a microscope degrades the lateral spatial resolution of the microscope, which is undesirable,
[0005] Another difficulty with many current stereo imaging systems is the limitation on the spatial resolution that can be achieved with a given numerical aperture (the metric often used with microscope systems and sometimes with camera systems) or a given aperture size (the metric often used with telescope systems and sometimes with camera systems). Indeed, many current stereo imaging systems use one or more conventional imaging systems such as conventional microscopes, conventional cameras, or conventional telescopes. The spatial resolution of a conventional imaging system is limited in a way often referred to as the Rayleigh limit. This is a limit to image quality.
[0006] There are many examples of the practical effects of these limitations.
To illustrate just one example consider a surgeon using a robotic assistance system equipped with a 3-D imaging system. In many cases, limits to depth-of-field and spatial resolution can interfere with the efficiency and accuracy of the surgeon's performance. This is seen in metrics such as the time required to perfonn the surgery (less is better), the number of robotic movements required (fewer is better), the total robotic distance traveled (less is better), and the number of errors made. These limits can negatively impact patient safety.
[0007] Thus, there is a need in the art for improved stereo imaging systems that may address, for example, one or more of the above-noted difficulties or additional difficulties.
Summary of the Invention
[0008] In accordance with an aspect of the present invention there is provided a stereo imaging system. The system includes a first rotational-shear interferometer and a second rotational-shear interferometer. The first rotational-shear
interferometer is configured for collecting first electromagnetic radiation from an object of interest. The second rotational-shear interferometer is configured for collecting second electromagnetic radiation from the object of interest. The first rotational-shear interferometer and the second rotational-shear interferometer are positioned relative to one another to provide stereo imaging of the object of interest. [0009] In accordance with another aspect of the present invention there is provided another stereo imaging system. This stereo imaging system includes an imager other than a rotational-shear interferometer. The imager comprises an image sensor. The stereo imaging system further includes a rotational-shear interferometer comprising at least one image sensor. The imager is configured for collecting first electromagnetic radiation from an object of interest. The rotational-shear interferometer is configured for collecting second electromagnetic radiation from an object of interest.
[0010] In accordance with yet another aspect of the present invention there is provided a rotational-shear interferometer for providing stereo imaging. The rotational-shear interferometer includes one or more fore-optics and at least two output ports. Each of the two output ports has an entrance pupil associated therewith. The entrance pupils are offset from each other to provide stereo imaging of an object of interest.
[0011] In accordance with still another aspect of the present invention there is provided a method of performing stereo imaging. The method includes steps of collecting, by a first rotational-shear interferometer, first electromagnetic radiation from an object of interest, collecting, by a second rotational-shear interferometer, second electromagnetic radiation from the object of interest, and processing the collected first and second electromagnetic radiation to provide stereo imaging of the object of interest.
Brief Description of the Drawings
[0012] The foregoing summary and the following detailed description of exemplary embodiments of the present invention may be further understood when read in conjunction with the appended drawings, in which:
[0013] FIG. 1 schematically illustrates a stereo imaging system that uses rotational-shear interferometry in accordance with an exemplary embodiment of the present invention; [0014] FIG. 2 schematically illustrates ail alternate embodiment in which two rotational-shear interferometers share a set of common fore-optics in accordance with an exemplary embodiment of the present invention;
[0015] FIG. 3 schematically illustrates an alternate embodiment in which two rotational-shear interferometers have entrance pupils that overlap each other in accordance with an exemplary embodiment of the present invention;
[0016] FIG. 4 schematically illustrates an alternate embodiment with a rotational-shear interferometer and a conventional imaging system in accordance with an exemplary embodiment of the present invention;
[0017] FIGS. 5A and 5B schematically illustrate an alternate embodiment with two rotational-shear interferometers that face each other in accordance with an exemplary embodiment of the present invention; and
[0018] FIGS . 6A and 6B schematically illustrate an alternate embodiment with a rotational-shear interferometer with two entrance pupils offset from each other in accordance with an exemplary embodiment of the present invention.
Detailed Description of the invention
[0019] As used herein the following terms have the following meanings.
[0020] The term "counter-tilt" refers to an arrangement of two beams of light in which a change in the tilt angle of one beam is accompanied by a simultaneous change in the tilt angle of the other beam such that the two beams tilt towards each other or away from each other. This arrangement could also be referred to as "counter change-in-tilt", though for conciseness of language the term "counter-tilt" is used. The two beams do not have to tilt exactly towards each other or exactly away from each other, but may tilt at different angles, such as happens in a rotational-shear interferometer set to a shear angle other than 180 degrees.
[0021] The term "common fore-optics" refers to optics shared by two optical systems at the front end. For example, in reference to the configuration illustrated in FIG. 2, the system in total is composed of two rotational-shear interferometers. Lens 210 and field stop 214 together constitute a set of "common fore-optics" that are shared by, and part of, each of the two rotational-shear interferometers. [0022] A rotational-shear interferometer (RSI) is one of the many kinds of instruments that can be used to image a scene. Light that enters the instrument is split into two beams. The two beams are recombined so as to produce interference fringes which are analyzed to infer an image of the scene.
[0023] A remarkable property of RSIs is their very long depth-of-field, a property rarely made use of. The reason the depth-of-field is so long is the wavefront curvature associated with defocus is common-mode between the two beams and mostly cancels out when the interference fringes are formed on the detector. A conventional imager, such as a conventional camera or a conventional microscope, generally has a much shorter depth-of-field than does an RSI. Although somewhat counterintuitive, exemplary embodiments of the present invention provide improved depth discrimination within an image by use of components (RSIs) that largely remove depth discrimination.
[0024] Another remarkable property of RSIs is their sharp lateral spatial resolution, at least in cases where spatially-incoherent light is used. Jn a single-beam imager, such as a conventional microscope, conventional camera, or conventional telescope, the Lagrange Invariant limits lateral spatial resolution in the following sense. It can be shown that if a device existed that could violate the Lagrange Invariant by a factor of "x", that device could be incorporated into a conventional imager to improve the lateral spatial resolution by the same factor "x". A single- beam device generally cannot violate the Lagrange Invariant. In an RSI there are two beams. The light in each of the two beams conforms to the Lagrange invariant. But working together, the two beams are able to beat the Lagrange Invariant by a factor of two. Counter-tilt is the key. Any system that breaks a beam of light in two and counter-tilts the two beams has an extremely-fundamental, factor-of-two advantage for achieving lateral spatial resolution. An RSI is one such instrument. When spatially incoherent light is used, a 180-degree RSI imager is characterized by a modulation transfer function (MTF) superior to that of a conventional imager by up to a factor of two, as measured by the area under the MTF curve. The MTF is a measure of the lateral spatial resolution of die imaging system.
[0025] Referring now to the figures, wherein like elements are numbered alike throughout, FIG. 1 schematically illustrates an exemplary configuration of a stereo imaging system 100 in accordance with an exemplary embodiment of the present invention, comprising a first and second rotational-shear interferometer 150, 151.
[0026] RS1s 150, 151 may collect light (as used herein, "light" includes all wavelengths of electromagnetic radiation, and is not limited to the visible spectrum) from an object under study. For illustration purposes FIG. 1 shows light arriving at stereo imaging system 100 from a distant point source (not shown). FIG. 1 and the relevant figures described below are not intended to indicate that the devices and methods illustrated and described herein are limited to use with point sources. Rather, throughout the present disclosure, the object under study need not be a point source and can extend laterally and depthwise, and the stereo imaging systems described herein may be configured to collect light from other locations from the object to be imaged, as desired. Also, FIG. 1 and the relevant figures described below are not intended to indicate that the devices and methods illustrated and described herein are limited to use with object points that are far away. Rather, throughout the present disclosure, the object under study may be close to, or far from, the stereo imaging system. Also, FIG. 1 and the relevant figures described below are not intended to indicate that curved mirrors may not be used instead of lenses. Rather, as those skilled in the art will appreciate, there are many instances where a lens may be replaced with a curved mirror.
[0027] Within the rotational-shear interferometer 150, input optics in the form of an objective lens 1 10 may be provided to collect light from a beam 108. While the objective lens 1 10 is illustrated as a singlet, those skilled in the art will appreciate that the objective lens 1 10, as well as all lenses disclosed herein, may contain multiple elements, cemented or otherwise, and need not comprise only a single element. Additional elements may be provided as desired to correct aberrations and improve image quality, for example. Arrows indicate the direction which light beam 108 from the object under study impinges on objective lens 1 10.
[0028] An aperture stop 1 12 may be provided to control the extent of the beam that travels through the rotational-shear interferometer 150. While the aperture stop 1 12 is illustrated at a particular location along the beam path from the object point to the detectors, those skilled in the art will appreciate that the aperture stop 1 12, as well as all aperture stops disclosed herein, may be located at many other places along the beam path. The location of an aperture stop is a design choice selected to satisfy various design goals and constraints.
[0029] Light that passes through the aperture stop 1 12 may be transmitted to a field stop 1 14 that blocks light from outside the desired field-of-view. Light that passes through the field stop 1 14 may reflect off a fold mirror 1 16. The fold mirror 1 16 is included to steer the beam in a direction convenient for drawing FIG. 1 , but is not required, as those skilled in the art will recognize. Imaging optics 1 18 may be provided to image the aperture stop 1 12 onto detectors 134, 136. Again, while the imaging optics 1 18 are shown as a pair of lenses, any suitable configuration of optics may be used to achieve the desired imaging properties.
[0030J To create the interference patterns, the rotational sheer interferometer
150 may include a pair of beam splitters 120, 132 which define the two arms of the interferometer 150, with the first beam splitter 120 serving to divide the light into two optical paths, and the second beam splitter 132 serving to recombine the two split optical paths. The beam splitters 120, 132 may be pellicle beam splitters, for example, though other forms of beam splitters may be used. After the first beam splitter 120 each arm of the rotational-shear interferometer 150 may include a plurality of mirrors 122, 124, 126, 128, 130, the configuration of which mirrors is designed to introduce counter-tilt between the two interfering beams that strike each detector 134, 136. In particular, one arm of the rotational-shear interferometer 150 may include an even number of mirrors, such as a pair of mirrors 122, 124. The other arm of the rotational-shear interferometer 150 may include an odd number of mirrors, such as the three mirrors 126, 128, 130. By having an even number of reflections in one arm of the interferometer 150 and an odd number in the other arm of the interferometer 150, eounter-tilt is introduced. In addition, having at least two mirrors 122, 124 m one arm and at least three mirrors 126, 128, 130 in the other arm, allows for the optical path length in each arm to be made the same as the optical path length in the other arm by adjusting the relative spacings among the mirrors 122, 124, 126, 128, 130 and the beam splitters 120, 132.
[0031] After passing through each respective group of mirrors 122, 124, 126,
128, 130 the beams in each arm of the interferometer 150 may be combined at the second beam splitter 132, and the interference pattern of the combined beams may be received at detectors 134, 136.
[0032] The two beams that emerge from beam splitter 132 may be said to correspond to two "output ports" on the RSI 150.
[0033] Rotational- shear interferometer 151 includes the same components as rotational-shear interferometer 150, configured in a similar manner to the like-named components of rotational-shear interferometer 150. This includes an objective lens 1 1 1 , an aperture stop 1 13, a field stop 1 15, a fold mirror 1 17, imaging optics 1 19, beam splitters 121 , 133, fold mirrors 123, 125, 127, 129, 131 , and detectors 135, 137. Beam 109 from the object under study is incident on objective lens 1 1 1.
[0034] The stereo separation distance between RSI 150 and RSI 151 is labeled 102.
[0035] A fringe pattern may be recorded by one or both detectors 134, 135,
136, 137 in each RSI 150, 151 and outpuued. Fringe data is required from only one of the two detectors in each RSI to determine an image of the scene in front of that RSI. However the data from both detectors within each RSI may be used, so as to provide an improved signal-to-noise ratio, for example. Each recorded fringe pattern may be converted to an image. For example, sometimes a Fourier transfomi is used for the conversion. An image from RSI 150 and an image from RSI 151 may be processed in the normal way stereo data is processed to obtain 3-D information about the object or scene under study. However, unlike the images recorded by some conventional imagers, the image recorded by an RSI is a conical projection (with the center of the RSI entrance pupil being the vertex of the cone), and the algorithm that combines the two images to obtain 3-D information may account for this.
[0036] Further illustrated in FIG. 1, within stereo imaging system 100, is a computer processor 190, a video monitor 194, and a cable 192 that connects computer processor 190 to video monitor 194. The fringe data from detectors 134, 135, 136, 137 may be transmitted to computer processor 190 via cables (not shown). Computer processor 190 may perform calculations to convert the data from one or both detectors 134, 135, 136, 137 in each RSI 150, 151 into an image of the scene under study. Computer processor 190 may also perform calculations to determine the 3-D structure of the scene under study. Computer processor 190 may transmit data through cable 192 to video monitor 194 for display in a fashion appropriate for 3-D interpretation. FIG. 1 is not meant to indicate that a video monitor is the only way to display 3-D information about a scene under study. Rather, consistent with the present disclosure, there are many ways to impart 3-D information to a user. For example, head mounted displays may be used.
[0037] The stereo imaging system 100 may further comprise a computer- readable tangible medium on which software instructions are stored. The computer processor 190 may be configured to access the computer-readable tangible medium to load and execute the software instructions to cause the computer to perform steps of receiving data from detectors 134, 135, 136, 137, performing calculations to convert data from each detector into an image of the scene under study, performing calculations to determine the 3-D structure of the scene under study or to arrange 2-D images in a manner for 3-D presentation, and outputting an image of the scene under study or the 3-D structure of the scene. The computer-readable tangible medium may be any device known in the art capable of storing software instructions, such as a hard drive, solid-state memory, flash drive, etc.
[0038] All the exemplary embodiments described in the present disclosure may employ a processor, computer-readable tangible medium, monitor, and their associated features and functionalities described herein with respect to FIG 1 , for example.
[0039] The configuration illustrated in FIG. 1 may provide advantages over existing 3-D imaging systems. For example, a scene with greater depthwise extent may be studied in 3-D with only a single measurement. By comparison conventional 3-D imaging systems have a shorter depth-of-field, and for scenes with extended depth one must record multiple snapshots with the region of best focus aligned at different locations within the scene. The data may then be stitched together to obtain an extended-depth 3-D image of the entire scene. These realignments may be accomplished by movement of the scene relative to the imager, or movement of the imager relative to the scene, or movement of optical components within the imager. The configuration illustrated in FIG. 1 has the advantage that it reduces the number of such alignments needed for a measurement. This improves system performance in a number of applications. For example, in the example given earlier of robotic surgery, a reduction in the number of alignments may result in less time needed to perform the surgery, fewer robotic movements during the surgery, and less total robotic distance traveled during the surgery. These advantages may improve the efficiency of the surgeon's performance and thus enhance patient safety.
[0040] Another advantage which may be provided by the configuration illustrated in FIG. 1 is improved stereo co-registration of features within the scene under study. Stereo imaging provides depth information via the parallax of each feature within the scene. To determine the parallax of a feature, it is helpful when the feature appears as sharp as possible in each stereo image. The sharper the image, the better the stereo system is able to measure the depth coordinate of the feature of interest. The configuration illustrated in FIG. 1 has the advantage that the depth-of- field is much longer than in a conventional system, so more of the features of interest may be in focus. The configuration illustrated in FIG. i also has the advantage of sharper lateral spatial resolution as compared to that of a conventional imager, by up to a factor of two, even when the conventional imager is at its best focus, as was discussed earlier. For both of these reasons (longer depth-of-fieid and sharper lateral spatial resolution) the configuration illustrated in FIG. 1 may achieve better stereo co-registration, which may mean better determination of the depth coordinate of the feature of interest. Improved depth measurement is an advantage for a number of applications. For example, returning to the example of robotic surgery, better depth measurement may improve the efficiency and accuracy of the surgeon's performance, and hence improve patient safety, which is an advantage. With better depth measurement, an image may be easier to interpret, with better identification of features within the image.
[0041] In a further exemplary configuration, illustrated in FIG. 2, a stereo imaging system 200 in accordance with an exemplary embodiment of the present invention may be provided which includes two rotational-shear interferometers that share a set of common fore-optics with each other. In this exemplary configuration, an objective lens 210 and a field stop 214 are each used by both RSIs and constitute a set of common fore-optics. Light is emitted from an object point 202. Solid lines represent a beam used by one RSI, and dashed lines represent a beam used by the other RSI. The remaining optics encountered by each beam are exclusive to each RSI. The optics enclosed in outline 270 are exclusive to the RSI that uses the solid beam, and the optics enclosed in outline 271 are exclusive to the RSI that uses the dashed beam.
[0042] The elements in FIG. 2 are configured in a similar manner to the like- named and like-numbered components of the stereo imaging system 100 of FIG. I . Fold mirrors 216, 217 redirect the beam path. Optics 218, 219 image aperture stops 212, 213 to detectors 234, 236, 235, 237. Each rotational-shear interferometer may include beam splitters 220, 232, 221 , 233, mirrors 222, 224, 226, 228, 230, 223 225, 227, 229, 231 , and detectors 234, 236, 235, 237. Different choices may be made for which optics are shared by the two RSIs, depending on design considerations specific to an application. For example, in some applications rather than have the two RSIs share a common field slop such as the field stop 214, it may be desirable for each of the two RSIs to use its own exclusive field stop since this provides a system designer increased flexibility in how to arrange the fields-of-view of the two RSIs to overlap each other at a given object of interest.
(0043] An advantage that may be provided by the configuration illustrated in
FIG. 2 as compared to the configuration illustrated in FIG. 1 is the ability to position the optical system closer to the object under study. For example, in the case of microscopy applications, it is often desirable to place an objective lens as close to the object as possible. When there is only a single objective lens instead of two objective lenses side-by-side, there is generally enough physical space to place the objective lens closer to the object under study.
[0044] A further advantage that may be provided by the configuration illustrated in FIG. 2 as compared to the configuration illustrated in FIG. 1 is easier alignment of the system field stop(s). In stereo imaging system 100 there are two field stops (1 14 and 1 15), and the two field stops are generally aligned relative to each other to provide the same or similar fields of view for the two RSIs. In stereo imaging system 200 there is only a single field stop (field stop 214), and the single field stop serves both RSIs, so an alignment step may be eliminated.
[0045] In a yet further exemplary configuration, illustrated in FIG. 3, a stereo imaging system 300 in accordance with an exemplary embodiment of the present invention may be similar in certain respects to the stereo imaging system 200 of FIG. 2, but may include a beam splitter 31 1. Such a configuration allows the entrance pupils of the two RSls to be located closer to each other, or even to overlap each other, if desired. This added flexibility may be an advantage in certain applications. For example, for a given stereo separation distance (the distance between the centers of the two entrance pupils) the widths of the entrance pupils may be larger, allowing more light from the object to reach the system detectors. More light may allow dimmer scenes to be viewed, and may also allow a shorter detector integration time for each image, which facilitates imaging objects in motion. These are advantages.
[0046] The elements in FIG. 3 are configured in a similar manner to the like- named and like-numbered components of the stereo imaging system 200 of FIG. 2. In this exemplary configuration, an objective lens 310, a field stop 314, and the beamsplitter 3 1 1 are common fore-optics each used by both RSIs. Light is emitted from an object point 302. Solid lines represent a beam used by one RSI, and dashed lines represent a beam used by the other RSI. The remaining optics encountered by each beam are exclusive to each RSI. The optics enclosed in outline 370 are exclusive to the RSI that uses the solid beam, and the optics enclosed in outline 371 are exclusive to the RSI that uses the dashed beam.
[0047] Optics 318, 319 image aperture stops 312, 313 to detectors 334. 336,
335, 337. Each rotational-shear interferometer may include beam splitters 320, 332, 321 , 333, mirrors 322, 324, 326, 328, 330, 323 325, 327, 329, 331 , and detectors 334,
336, 335, 337.
[0048] Those skilled in the art will recognize that a beamsplitter that separates light into the optics exclusive to each RSI may be placed at many locations other than what is illustrated in FIG. 3. For example, such a beamsplitter may be arranged to intercept light from the object of interest before the light encounters any other optics. In this case generally each RSI will use its own objective lens and its own field stop rather than sharing these components.
[0049] In a yet further exemplary configuration, illustrated in FIG. 4, a stereo imaging system 400 in accordance with an exemplary embodiment of the present invention may be similar in certain respects to the stereo imaging system 100 of FIG. 1 , but may include a rotational-shear interferometer 450 and a conventional imager 481 other than a rotational-shear interferometer. [0050] In this exemplary configuration, objective lenses 410, 41 1 collect light from an object (not shown), which passes through aperture stops 412, 413. Within the conventional imager 481 the light then focuses to a detector 463 where an image is recorded. Within the RSI 450, elements are configured in a similar manner to the like-named and like-numbered components of the stereo imaging system 100 of FIG. 1. Within the RSI 450 the light passes through a field stop 414. A fold mirror 416 redirects the beam path. Optics 418 image the aperture stop 412 to detectors 434, 436. The rotational-shear interferometer 450 may include beam splitters 420, 432, mirrors 422, 424, 426, 428, 430, and detectors 434, 436.
[0051] An advantage that may be provided by the configuration illustrated in
FIG. 4 as compared to the configuration illustrated in FIG. 1 is fewer optical components may be required, which may reduce cost, for example, while advantages that come with the use of at least one RSI may still be present, such as an improved depth of field and improved spatial resolution.
[0052] A further advantage that may be provided by the configuration illustrated in FIG. 4 as compared lo the configuration illustrated in FIG. 1 is the conventional imager 481 may be configured to have a wider field-of-view than the RSI 450, thus facilitating the initial search for a particular region of interest within a scene under study. For example, a user may first search for and locate an object of interest within a wide field of view provided by the conventional imager 481 , then adjust the orientation of the stereo imaging system 400 so that the region of interest is also within the field of view of the RSI 450.
[0053] Many variations of the configuration illustrated in FIG. 4 are possible.
For example, the imaging systems 450, 481 may share some components with each other, similar to the stereo imaging system 200 in FIG. 2 or the stereo imaging system 300 in FIG. 3. In addition a beam splitter may be used in a similar manner to beam splitter 311 , FIG. 3, allowing the entrance pupils of the imaging systems 450, 481 to be located closer to each other or even partially overlap each other.
[0054] Those skilled in the art will appreciate that apart from a hybrid system that includes a conventional imager, other hybrid stereo configuralions that employ an RSI may provide other advantages while still preserving some of the advantages that come from use of at least one RSI in the stereo pair, such as a longer depth of field and sharper spatial resolution.
[0055] In a yet further exemplary configuration, illustrated in FIG. 5A, a stereo imaging system 500 in accordance with an exemplary embodiment of the present invention may be similar in certain respects to the stereo imaging system 100 of FIG. 1 , but the two RSIs face each other. The scene being imaged might be a biological sample, for example. An advantage of this configuration is more light from the sample may be collected, since light leaving the sample is collected in both directions. More light generally corresponds to reduced noise in the 3-D image, which is an advantage.
[0056] The components in FIG. 5A are configured in a similar manner to the like-named and like-numbered components of the stereo imaging system 100 of FIG. 1. In this exemplary configuration, stereo imaging system 500 is composed of rotational-shear interferometers 550, 551. Objective lenses 510, 51 1 may collect light from an object 557 under study after reflection by fold mirrors 554, 555. The light may pass through aperture stops 512, 513, and may focus to field stops 514, 515. Fold mirrors 516, 517 may redirect the beam path. Optics 518, 519 may image the aperture stops 512, 513 to detectors 534, 535, 536, 537. Each rotational-shear interferometer may include beam splitters 520, 532, 521 , 533, and mirrors 522, 524, 526, 528, 530, 523 525, 527, 529, 53 1 . A set of coordinate axes is labeled 502.
[0057] FIG. 5B illustrates how the 3-D stereo location of an object point is determined in this exemplary configuration. Coordinate axes 502 are drawn to indicate the correspondence between FIGS.s 5A and 5B. An object point 562 is located between aperture stops 512, 513. In this example the entrance pupils and the aperture stops are the same as each other. The fold mirrors 554 and 555 are omitted from FIG. 5B for clarity. For convenience of illustration, the aperture stops 512, 513 are drawn differently in FIG. 5 A versus FIG. 5B. In FIG. 5 A the aperture stops are drawn with solid lines that indicate the opaque region of each aperture stop, whereas in FIG. 5B the aperture stops 512, 513 are drawn with solid lines that indicate the clear aperture. In FIG. 5B the center points of the aperture stops are labeled 560, 561. Since an RSI images with a conical projection, RSI 551 measures the angle alpha of object point 562 and RSI 550 measures the angle beta of object point 562. From the values of alpha and beta one may calculate the 3-D spatial coordinates of object point 562 using straightforward trigonometry.
[0058] In a yet further exemplary configuration, illustrated in FIG. 6A, a stereo imaging system 650 in accordance with an exemplary embodiment of the present invention may be similar in certain respects to the stereo imaging system 100 of FIG. 1 , but only a single RSI is used and there are two aperture stops instead of one. An advantage of this configuration is fewer optical components may be required, which may reduce cost and complexity.
[0059] In the example illustrated in FIG. 6A the two aperture stops are co- located with the detectors 638, 644. For example, each detector face may be painted black over all but a clear area that is then the aperture. The two aperture stops may be imaged differently from each other such that there are two entrance pupils 610, 612. The entrance pupil is the image of the aperture, as seen from the object under study. For example, entrance pupil 610 may be the image of the aperture stop at detector 638, as determined by lenses 608, 618, 632, 636. And entrance pupil 612 may be the image of the aperture stop at detector 644, as determined by lenses 608, 618, 640, 642. In this example the entrance pupils 610, 612 are different sizes than each other, though a difference in size is not a requirement. Other components in FIG. 6A are configured in a similar manner to the like-named and like-numbered components of the stereo imaging system 100 of FIG. 1. Objective lens 608 focuses light from an object point 604 into the plane of field stop 614. The RSI 650 may include fold mirrors 616, 622, 624, 626, 628, 630 and beamsplitters 620, 632. A set of coordinate axes are is labeled 602.
[0060] FIG. 6B illustrates how the 3-D stereo location of an object point is determined in this exemplary configuration. Coordinate axes 602 are drawn to indicate the correspondence between FIG.S 6A and 6B, An object point 604 is located a distance from entrance pupils 610, 612. For convenience of illustration, the entrance pupils 610, 612 are drawn differently in FIG. 6A versus FIG. 6B. In FIG. 6A the entrance pupils are drawn with solid lines that indicate the opaque region of each aperture stop, whereas in FIG. 6B the entrance pupils 610, 612 are drawn with solid lines that indicate the clear aperture. In FIG. 6B the center points of the entrance pupils are labeled 660, 662. Since an RSI images with a conical projection, the signal at detector 644 (corresponding to entrance pupil 612) measures the angle alpha of object point 604, and the signal at detector 638 (corresponding to entrance pupil 610) measures the angle beta of object point 604. From the values of alpha and beta, and other known parameters such as the distance between entrance pupils 610, 612, one may calculate the 3-D spatial coordinates of object point 604 using straightforward trigonometry.
[0061] Unlike the image produced by a conventional imager, the image produced by an RSI is a conical projection. The vertex of the cone is the center of the RSI entrance pupil. With all of the exemplary configurations, use of the recorded RSI data to determine the 3-D structure of a scene should account for the conical projection of the RSI. Hybrid systems that use imagers with both conical and conventional projections should account for this duality. In addition, in any of the interferometers of Figs. 1 , 2, 3, 4, 5A, 6A, alternative methods of inducing counter- tilt between the two beams of the interferometer may be employed. For example, instead of using an odd number of reflections in one arm and an even number of reflections in the other arm, both arms could use an odd (or even) number of reflections, with the light in one arm made to pass through an intermediate focus while the light in the other arm is not. For instance, counter-tilt may be introduced between the two arms of a rotational-shear interferometer by a pair of lenses provided in one arm the interferometer. In such a ease, a single mirror may be provided in each arm between the beam splitters since the counter-tilt is introduced by the lenses. Additionally, it should be understood that though the RSls illustrated herein are drawn as 2-dirnensional for simplicity of illustration, devices of the exemplary embodiments of the present invention may have a 3 -dimensional configuration.
[0062] Still further, for devices of exemplary embodiments of the present invention, the angle of rotational-shear on the RSls can be set to different values, depending on the application. In addition, adaptive optics may be incorporated into each RSI. One use of adaptive optics may be to compensate for the otherwise- detrimental light-scattering properties of the sample. Additionally, the RSls may be constructed and used in a number of configurations, such as a Michelson or Mach- Zehnder configuration. Within each RSI the angle at which the two beams are incident on the detector can also be adjusted. For a point at the center of the field-of- view, the two resulting beams can be incident on the detector at normal incidence or at some different angle (e.g., +/- 3 degrees). If the two beams are incident at normal incidence, there will be ambiguity (the twin image problem). If the angle-of- incidence of each beam corresponding to the center of the field-of-view is large enough, the twin image problem is avoided. In addition, the RSls may be used in a modified form known as a quadrature -phase interferometer. Each RSI may also use fringe-scanning to obtain a time series of exposures with different phase differences between the two arms of the interferometer. Each RSI may be configured to compensate or correct for differences in the polarization response of the two arms of the interferometer, for example by the addition of phase plates. Each RSI may further be configured to achromatize the fringe pattern to increase the spectral bandwidth of the RSI. Each RSI may use mirrors that may or may not contain a roofline through the middle of the mirror, and may optionally include a prism to steer light. Different types of beam splitters may also be used within each RSI, such as cube or pellicle being splitters, or a glass plate that reflects off one of its external surfaces.
[0063] There are also different ways to convert the fringe pattern recorded on each RSI detector into an image. One method is to Fourier-transform the fringe pattern, and a second method is to fit the fringe pattern with a set of orthogonal functions. In the case of a sparse image, a procedure exists to convert the fringe pattern recorded on the RSI detector into an image with spectral information for each point in the image.
[0064] The exemplary systems and methods described herein have numerous uses, including robotic control applications such as robotic surgery, product profiling in manufacturing settings (e.g., automated acceptance/rejection), patient examination in telemedicine settings (e.g., to discern the morphology of an injury), surveying, recreational photography, etc.
[0065] These and other advantages of the present invention will be apparent to those skilled in the art from the foregoing specification. Accordingly, it will be recognized by those skilled in the art that changes or modifications may be made to the above-described embodiments without departing from the broad inventive concepts of the invention. It should therefore be understood that this invention is not limited to the particular embodiments described herein, but is intended to include all changes and modifications that are within the scope and spirit of the invention as set forth in the claims.

Claims

Claims What is claimed is:
1. A stereo imaging system, comprising:
a first rotational-shear interferometer; and
a second rotational-shear interferometer,
wherein the first rotational-shear interferometer is configured for collecting first electromagnetic radiation from an object of interest,
wherein the second rotational-shear interferometer is configured for collecting second electromagnetic radiation from the object of interest, and
wherein the first rotational-shear interferometer and the second rotational-shear interferometer are positioned relative to one another to provide stereo imaging of the object of interest.
2. The stereo imaging system according to claim 1 , further comprising one or more common fore-optics shared by the first rotational-shear interferometer and the second rotational-shear interferometer,
3. The stereo imaging system according to claim 2, wherein the one or more
common fore-optics comprise a field stop configured to limit a field-of-view of each of the first rotational-shear interferometer and the second rotational -shear interferometer.
4. The stereo imaging system according to claim 2, wherein the one or more
common fore-opties comprise an objective lens.
5. The stereo imaging system according to any of claim 2 through claim 4, wherein: the first rotational-shear interferometer comprises one or more non-common optics,
the second rotational-shear interferometer comprises one or more non-common optics, and
the one or more common fore-optics further comprise a beamsplitter configured to intercept the first electromagnetic radiation from the object of interest and send the first electromagnetic radiation from the object of interest to the one or more non-common optics of the first rotational-shear interferometer and to intercept the second electromagnetic radiation from the object of interest and send the second electromagnetic radiation from the object of interest to the one or more non-common optics of the second rotational-shear
interferometer.
6. The stereo imaging system according to claim 5, wherein each of the first
rotational-shear interferometer and the second rotational-shear interferometer further comprises an entrance pupil associated therewith, and wherein the entrance pupils of the first rotational-shear interferometer and the second rotational-shear interferometer partially overlap each other.
7. The stereo imaging system according to claim 1, wherein the first rotational- shear interferometer and the second rotational-shear interferometer face each other.
8. The stereo imaging system according to any of claim 1 through claim 7, wherein: the first rotational-shcar interferometer further comprises a detector configured for sensing a first portion of the first electromagnetic radiation from the object of interest and outputting first fringe data; and
the second rotational-shear interferometer further comprises a detector
configured for sensing a first portion of the second electromagnetic radiation from the object of interest and outputting second fringe data.
9. The stereo imaging system according to claim 8, further comprising a processor configured for receiving the first fringe data from the detector of the first rotational-shear interferometer and the second fringe data from the detector of the second rotational-shear interferometer.
10. The stereo imaging system according to claim 9, wherein the processor is further configured for processing the first fringe data and the second fringe data to generate a three-dimensional image of the object of interest.
1 1. The stereo imaging system according to claim 9, wherein the processor is further configured for:
processing the first fringe data and the second fringe data to generate, respectively, first transformed fringe data and second transformed fringe data, and
combining the first transformed fringe data and the second transformed fringe data to generate a three-dimensional image of the object of interest.
12. A stereo imaging system, comprising:
an imager other than a rotational-shear interferometer, the imager comprising at least one detector; and
a rotational-shear interferometer comprising at least one detector, and wherein the imager is configured for collecting first electromagnetic radiation from an object of interest, and
wherein the rotational-shear interferometer is configured for collecting second electromagnetic radiation from an object of interest.
13. The stereo imaging system according to claim 12, further comprising one or more common fore-optics shared by the imager and the rotational-shear interferometer.
14. The stereo imaging system according to claim 13, wherein the one or more
common fore-optics comprise a field stop configured to limit a field-of-view of each of the imager and the rotational-shear interferometer.
15. The stereo imaging system according to claim 13, wherein the one or more
common fore-optics comprise an objective lens.
16. The stereo imaging system according to any of claims 13 through 15, wherein: the imager comprises one or more non-common optics,
the rotational-shear interferometer comprises one or more non-common optics, and
the one or more common fore-optics further comprise a beamsplitter configured to intercept the first electromagnetic radiation from the object of interest and send the first electromagnetic radiation from the object of interest to the imager and to intercept the second electromagnetic radiation from the object of interest and send the second electromagnetic radiation from the object of interest to the one or more non-common optics of the rotational-shear interferometer.
_2 J _
17. The stereo imaging system according to claim 16, wherein each of the imager and the rotational-shear interferometer further comprises an entrance pupil associated therewith, and wherein the entrance pupils of the imager and the rotational-shear interferometer partially overlap each other.
18. The stereo imaging system according to claim 16 or claim 17, wherein the imager and the rotational-shear interferometer face each other.
19. The stereo imaging system according to any of claim 12 through claim 18,
wherein the at least one detector of the imager is configured for sensing at least a portion of the first electromagnetic radiation from the object of interest and outputting detector data, and
wherein the at least one detector of the rotational-shear interferometer is
configured for sensing at least a portion of the second electromagnetic radiation from the object of interest and outputting fringe data.
20. The stereo imaging system according to claim 19, further comprising a processor configured for receiving the detector data from the at least one detector of the imager and for receiving the fringe data from the at least one detector of the rotational-shear interferometer.
21. The stereo imaging system according to claim 20, wherein the processor is
further configured for processing the detector data and the fringe data to generate a three-dimensional image of the object of interest.
22. The stereo imaging system according to claim 21, wherein processing performed by the processor comprises:
processing the fringe data to generate transformed fringe data, and
combining the detector data and the transformed fringe data to generate a three- dimensional image of the object of interest.
23. A rotational-shear interferometer for providing stereo imaging, the rotational- shear interferometer comprising:
one or more fore-optics; and
at least two output ports, each of the two output ports having an entrance pupil associated therewith, wherein the entrance pupils are offset from each other to provide stereo imaging of an object of interest.
24. A method of performing stereo imaging, the method comprising:
collecting, by a first rotational-shear interferometer, first electromagnetic
radiation from an object of interest;
collecting, by a second rotational-shear interferometer, second electromagnetic radiation from the object of interest; and
processing the collected first and second electromagnetic radiation to provide stereo imaging of the object of interest.
25. The method according to claim 24, further comprising:
passing the first electromagnetic radiation and the second electromagnetic
radiation through one or more common fore-optics shared by the first rotational-shear interferometer and the second rotational-shear interferometer.
26. The method according to claim 25, wherein the one or more common fore-optics comprise a field stop configured to limit a field-of-view of each of the first rotational-shear interferometer and the second rotational-shear interferometer.
27. The method according to claim 25, wherein the one or more common fore-optics comprise an objective lens.
28. The method according to any of claim 25 through claim 27, wherein the first rotational-shear interferometer comprises one or more non-common optics, and the second rotational-shear interferometer comprises one or more non-common optics, the method further comprising:
intercepting, by a beamsplitter, the first electromagnetic radiation from the object of interest;
sending, by the beamsplitter, the first electromagnetic radiation from the object of interest to the one or more non-common optics of the first rotational-shear interferometer;
intercepting, by the beamsplitter, the second electromagnetic radiation from the object of interest: and
sending, by the beamsplitter, the second electromagnetic radiation from the object of interest to the one or more non-common optics of the second rotational-shear interferometer.
29. The method according to claim 28, wherein each of the first rotational-shear interferometer and the second rotational-shear interferometer further comprises an entrance pupil associated therewith, and wherein the entrance pupils of the first rotational-shear interferometer and the second rotational-shear
interferometer partially overlap each other.
30. The method according to claim 28 or claim 29, wherein the first rotational-shear interferometer and the second rotational-shear interferometer face each other.
31. The method according to any of claims 24 through claim 30, further comprising: sensing, via a detector of the first rotational-shear interferometer, a first portion of the first electromagnetic radiation from the object of interest; and outputting first fringe data based on the sensing of the first portion of the first electromagnetic radiation from the object of interest,
32. The method according to claim 31 , further comprising:
sensing, via a detector of the second rotational -shear interferometer, a first portion of the second electromagnetic radiation from the object of interest; and
outputting second fringe data based on the sensing of the first portion of the second electromagnetic radiation from the object of interest.
33. The method according to claim 32, further comprising:
receiving, by a processor, the first fringe data from the detector of the first
rotational-shear interferometer; and
receiving, by the processor, the second fringe data from the detector of the
second rotational-shear interferometer.
34. The method according to claim 33, further comprising:
processing, by the processor, the first fringe data and the second fringe data to generate a three-dimensional image of the object of interest.
35. The method according to claim 33, further comprising: processing, by the processor, the first fringe data and the second fringe data to generate, respectively, first transformed fringe data and second transformed fringe data, and
combining, by the processor, the first transformed fringe data and the second transformed fringe data to generate a three-dimensional image of the object of interest.
PCT/US2015/013909 2014-01-30 2015-01-30 Stereo imaging with rotational-shear interferometry WO2015116999A1 (en)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
US201461933477P 2014-01-30 2014-01-30
US61/933,477 2014-01-30
US201462053222P 2014-09-21 2014-09-21
US62/053,222 2014-09-21
US201462056328P 2014-09-26 2014-09-26
US62/056,328 2014-09-26

Publications (1)

Publication Number Publication Date
WO2015116999A1 true WO2015116999A1 (en) 2015-08-06

Family

ID=53757778

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US2015/013909 WO2015116999A1 (en) 2014-01-30 2015-01-30 Stereo imaging with rotational-shear interferometry

Country Status (1)

Country Link
WO (1) WO2015116999A1 (en)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030030819A1 (en) * 2001-05-03 2003-02-13 Michael Kuechel Apparatus and method(s) for reducing the effects of coherent artifacts in an interferometer
US20080170232A1 (en) * 2007-01-12 2008-07-17 Buijs Henry L Two-beam interferometer for fourier transform spectroscopy with double pivot scanning mechanism
JP2008202958A (en) * 2007-02-16 2008-09-04 Sony Corp Vibration detecting device
US7787131B1 (en) * 2007-02-06 2010-08-31 Alpha Technology, LLC Sensitivity modulated imaging systems with shearing interferometry and related methods
US20120038928A1 (en) * 2009-04-02 2012-02-16 Teknologian Tutkimeskeskus Vtt System and method for optical measurement of a target

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030030819A1 (en) * 2001-05-03 2003-02-13 Michael Kuechel Apparatus and method(s) for reducing the effects of coherent artifacts in an interferometer
US20080170232A1 (en) * 2007-01-12 2008-07-17 Buijs Henry L Two-beam interferometer for fourier transform spectroscopy with double pivot scanning mechanism
US7787131B1 (en) * 2007-02-06 2010-08-31 Alpha Technology, LLC Sensitivity modulated imaging systems with shearing interferometry and related methods
JP2008202958A (en) * 2007-02-16 2008-09-04 Sony Corp Vibration detecting device
US20120038928A1 (en) * 2009-04-02 2012-02-16 Teknologian Tutkimeskeskus Vtt System and method for optical measurement of a target

Similar Documents

Publication Publication Date Title
US10291894B2 (en) Single-sensor system for extracting depth information from image blur
US9243888B2 (en) Image mapped optical coherence tomography
CA2805443C (en) Method and apparatus for imaging
US11163169B2 (en) Endoscope and imaging arrangement providing improved depth of field and resolution
EP3254606B1 (en) Endoscope and imaging arrangement providing depth of field
JP2014521461A5 (en)
JP2007512541A (en) Method and apparatus for three-dimensional spectrally encoded imaging
CN103251382A (en) All-eye frequency-domain optical coherence tomography system and method
US20160120397A1 (en) Endoscope image-acquisition device
US8610900B2 (en) Apparatus for low coherence optical imaging
JP2017208606A (en) Image processing apparatus, imaging device, image processing method and image processing program
RU2017118114A (en) STEREOSCOPIC VISUALIZING DEVICE
US20160004058A1 (en) Lightsheet microscopy with rotational-shear interferometry
US20210118177A1 (en) Method and system for calibrating a plenoptic camera system
JP5857887B2 (en) Wavefront measuring device
JP2012242488A (en) Imaging device, stereoscopic imaging optical system and program
US10178372B2 (en) Long focal length monocular 3D imager
WO2015116999A1 (en) Stereo imaging with rotational-shear interferometry
US20220113131A1 (en) Measurement apparatus, image capturing apparatus, measurement system, control method, and storage medium
CN106052874B (en) Inteference imaging spectrometer and interferometer
JP6598621B2 (en) Imaging device
CN110623626A (en) Two-dimensional-three-dimensional imaging converter for two-dimensional laparoscope
JPWO2016002693A1 (en) Tomography system
US11044460B1 (en) Polychromatic object imager
Zhao et al. Prism-based single-camera system for stereo display

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 15743745

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 15743745

Country of ref document: EP

Kind code of ref document: A1