WO2012009119A2

WO2012009119A2 - Stereoscopic imaging systems

Info

Publication number: WO2012009119A2
Application number: PCT/US2011/041560
Authority: WO
Inventors: Stuart Mcmuldroch
Original assignee: Illusion Camera Co., Llc
Priority date: 2010-06-28
Filing date: 2011-06-23
Publication date: 2012-01-19
Also published as: WO2012009119A3

Abstract

An imaging system for producing stereoscopic images of an object acquiring left and right eye views simultaneously using one lens unit (2). Specifically, a camera (1) has a lens unit (2) forming the image, a polarizing optical modulator (3), a means for separating polarization (4), light acquisition devices (5) for receiving images of the object, and a computing device (6) capable of providing coordinated operation so as to provide simultaneous stereo images through the optical elements.

Description

STEREOSCOPIC IMAGING SYSTEMS

BACKGROUND OF THE INVENTION

Technical Field

[0001] The present invention relates to a system for stereoscopic imaging.

Specifically, a polarizing device produces simultaneous stereoscopic images from a single lens unit and a camera with coordinated functions.

Related Art

[0002] There are many types of imaging systems for producing left and right eye equivalent stereo images. Most typically, these systems use one camera for forming a left eye image and another for forming the right eye image. The two cameras are spaced apart so as to create a parallax effect permitting the generation of stereo images. The amount of spacing between the optical axes of the cameras, normally known as the interaxial distance, governs the amount of parallax produced and the consequently the strength of the stereo effect.

Additionally, there are systems that use only one lens. In these cases, the parallax is formed within the lens itself. While the amount of parallax is restricted by the overall size of the lens, single lens solutions offer simplicity and do not possess some of the optical artifacts inherent with two lens solutions. Although there is considerable prior art in the area of single lens stereo imaging, there remain certain deficiencies.

[0003] US Pat. No. 5,222,477 to Lia describes a stereo imaging system for an endoscope that has an aperture plate within the optical train. The plate defines left and right eye pupils located either side of the optical axis. The left image passes through the left pupil and similarly the right image passes through the right pupil. The images pass down a common lens assembly to an imager that captures the left and right eye stereo images. The left and right eye images are distinguished either by the use of color filters located at the pupils or by switching between the left and right eye pupils using an alternating shutter.

Similarly, US Pat. No. 5,964,696 describes an aperture plate that attaches to an endoscope or borescope in the vicinity of its pupil. The plate defines left and right eye views and an optical switch alternately blocks light received from one of the two apertures. US Pat. No. 6,275,335, to Costales, defines the left and right eye portions using polarization techniques. The light forming the left and right views has different polarization states, established by having a polarizing filter or retarder at one of the lens apertures. The polarized light follows a common light path prior to being divided by a beamsplitter immediately prior to the image viewing or capture device.

[0004] US Pat No. 6,151,164 to Greening discloses a stereoscopic imaging system that uses an opaque leaf positioned between the lens system and a camera. The leaf moves laterally from left to right creating a left image and right image perspective. The leaf geometry and position can vary so as to produce alternating apertures of different sizes and of different separations and hence parallax. The leaf remains stationary in each position for a sufficient length of time for the camera to view the corresponding perspective. Again, the pupil of a single lens system is being divided into two sections and left / right eye images acquired sequentially. Greening's approach has the advantage of controlling the size and location of the apertures including configurations where the apertures are overlapping albeit separated in time.

[0005] US Pat No. 7,019,780, discloses a system that provides stereoscopic capability within a zoom lens. An electronic optical shutter located on a stage within the lens defines a left and a right portion. The electronic shutter can form an opening of any predetermined form. This permits control of the amount of parallax as a function of zoom in addition to being able to adjust the amount of light transmitted through the left and right apertures. The shutter alternates between left and right states being transmissive, creating alternating left and right views. In one embodiment, a double speed camera is used for taking pictures with a left and right view pair forming a stereo image.

[0006] The approaches listed above provide single lens stereo capability by defining a left and right eye perspective within the lens, most often by dividing an aperture, pupil, or conjugate into two or more portions. The light then passes further down the lens assembly along a common light path prior to being viewed. For certain approaches, the left and right portions are distinct existing together at the same time with the light from each portion being distinguished by its color or polarization upon being viewed. These approaches are limited, however, in that they cannot produce overlapping apertures thereby limiting the degree of control of parallax and aperture size. For the remaining approaches, the portions can overlap but not at the same time and the left and right images have to be viewed sequentially. The time delay between the left and right image views can be extremely problematic, however, as moving objects will shift relative to more distant objects between views. This creates additional parallax not related to the stereo effect. What is needed therefore is a stereo system that combines the advantages of both approaches by providing viewing at the same time with the increased flexibility of creating overlapping apertures within the lens. SUMMARY OF THE INVENTION

[0007] To solve the problem described above, the present invention includes a polarizing unit that generates multiple polarizing states within the lens and camera system. The polarizing states delineate varying portions of the lens view so that by viewing one or more of the states, one can generate left and right eye perspectives of multiple configurations including ones where the views overlap concurrently.

[0008] To achieve the above function, according to an aspect of the present invention, there is provided a stereo imaging camera comprising: a lens unit, a portion of the lens unit that may provide zoom function, one or more image viewing means, a polarizing unit placed within the lens or at least between the lens unit and the image viewing means, a unit that provides light adjusting means, and a computing device for controlling the polarizing unit and image viewing means.

[0009] Further, because an electronic polarizing modulator is used as the polarizing unit, fine opening patterns can be defined so that two or more polarizing light states can be generated simultaneously. Combining patterns of multiple different states permits a plurality of different configurations. Additionally, as such an electronic means is used, the patterns can be changed continuously to accommodate the optical configuration of the lens at that time to generate the desired stereo effect. Still further, as such electronic modulators are capable of operating at high speeds, the patterns can be defined and changed multiple times within the period over which the left and right images are simultaneously obtained.

[0010] Still further, the image viewing means can distinguish between the light of one or more different polarizing states thereby allowing the formation of images from multiple different patterns within one viewing period.

[0011 ] Still further, as a controllable polarizer is used, with the image viewing means being electronic, a computing device can coordinate operation between the lens unit configuration including zoom, f/#, or aperture and the polarizer unit and image viewing means. In such a way, the system can generate stereo effect by adjusting or accommodating all aspects of the system.

[0012] These and other objects are provide in an imaging system for producing stereoscopic images of an object acquiring left and right eye views simultaneously using one lens unit. Specifically, the imaging system has a camera comprising a lens unit forming the image, a polarizing optical modulator, a means for separating polarization, one or more light acquisition devices for receiving images of the object, and a computing device capable of providing coordinated operation so as to provide simultaneous stereo images through the said optical elements.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In drawings that illustrate embodiments of the present invention,

FIG. 1 is a schematic diagram of a stereoscopic camera system according to an embodiment of the present invention.

FIG. 2 is a diagram showing the structure of the light modulator of FIG. 1.

FIG. 3 is a diagram showing the light modulator forming a left side and a right side unit.

FIG. 4 A is a diagram showing a case where the unit separation and corresponding parallax is small.

FIG. 4B is a diagram showing a case where the unit separation and corresponding parallax is large.

FIG. 5 A is a diagram showing a case where the unit separation and corresponding parallax is small and the aperture is maximized resulting in overlapping units.

FIG. 5B is a diagram showing a case where the unit separation and corresponding parallax is large and the aperture is maximized resulting in overlapping units.

FIG. 6 A is a diagram showing a case where there are three patterns forming distinct units.

FIG. 6 A is a diagram showing a case where there are three patterns forming distinct units as distinguished by their polarization state.

FIG. 7 A is a diagram showing a case where the third unit is comprised of smaller areas each having the polarization properties of units one and units two.

FIG. 7B is a diagram showing a case where the third unit is comprised of smaller areas each having the polarization properties of units one and units two and where unit three is comprised of a plurality of patterns.

FIG. 8A is a diagram showing a standard aperture with minimal use of an iris.

FIG. 8B is a diagram showing a standard aperture with large use of an iris with the lens stopped down.

FIG. 8C is a diagram showing the case where the three units from FIG. 6 are limited in extent by use of an iris.

FIG. 8D is a diagram showing the case where the three units from FIG. 6 are further limited in extent by use of an iris. FIG. 9 is a diagram showing the case of how both the light controlling function and polarizing function can be incorporated within the light modulator.

FIG. 10A is a diagram showing both light control and polarizing function for the units with the parallax shown in FIG. 5A.

FIG. 1 OB is a diagram showing both light control and polarizing function for the units with the parallax shown in FIG. 5B.

FIG. IOC is a diagram showing both light control and polarizing function for the units with the parallax shown in FIG. 5A. In this case the equivalent left and right apertures are stopped down.

FIG. 10D is a diagram showing both light control and polarizing function for the units with the parallax shown in FIG. 5B. In this case the equivalent left and right apertures are stopped down.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The present invention concerns a camera for stereo imaging comprising at least a lens unit 2, a polarizing means to divide light between left and right views 3, a means to vary the light for each left and right view, a means to separate light into different polarizing states 4, light acquisition devices 5, and a computing device 6. The computing device controls the components mentioned and provides coordinated operation between them to produce imagery with the desired stereographic requirements.

[0015] There are many embodiments of the present system that produce useful stereoscopic imagery. Each permits interaxial adjustment and light control permitting production of stereo imagery with the desired depth and illumination affects. For each embodiment, subapertures are formed by the use of polarization with subapertures being permitted to overlap simultaneously or within a fraction of the time over which right and left eye images are obtained. For ease of description, we use simultaneously throughout this document as meaning at the same time or within a fraction of the period over which the left and right eye images are formed.. The light from each of these apertures is separated based on polarization and directed to one or more light collecting devices so as to produce corresponding left and right images. These embodiments have a plurality of configurations but have common attributes:

1. A system produces stereographic images of an object using a monocular objective or lens unit that generates different perspectives, including those of interaxial distances less than the diameter of the lens, such a system comprising: o A single lens system with simultaneous image capture of left and right perspectives.

o Light modulating means for simultaneously creating multiple sub-apertures of varying size and properties.

o Single lens system with light modulating means where sub-aperture regions, as identified by their optical properties, overlap creating left and right eye perspectives simultaneously. The distance between the centers of each of these sub-apertures, in the case of two sub-apertures, being the interaxial distance of the stereographic image pair accounting for optical magnification. o Single lens or groups optimized for the creation of sub-apertures of maximum separation, specifically lens geometries and ratios that maximize horizontal aspect of pupils.

o Electronics that permit simultaneous coordinated operation of the light

modulating and light capturing means thereby controlling stereo effect while minimizing unwanted stereo or motion artifacts.

Further to the foregoing, light modulating and controlling means are advantageously located in the optical train at one or multiple points, most probably at or near apertures, pupils or conjugates, comprising or consisting of:

o A first stage that polarizes light into one of several different polarizing states most probably linear. This stage may not necessarily be placed near an aperture or pupil.

o A second stage that simultaneously manipulates light into at least two but most probably three polarization states including a first state, a second state with orthogonal properties to the first state, and another third state that is a combined version of both.

As another aspect, an ability is provided to simultaneously separate states, for example employing:

o A third stage that separates light into non-coupled states where the light is directed to two different light sensors or detectors (or to one sensor or detector with independent sensitivity to multiple polarizations by area).

o A fourth stage that may be placed near the sensor or sensors to further

delineate light into different polarization states and to adjust the light intensity, polarization, or color as needed. 4. The states modulated by the stages described in number 2 above may be divided into different units of differing shapes within the area of the aperture or pupil. Specifically it is advantageous where:

o The second stage forms three units of differing or partially differing polarization states so that unit one has light of state one, unit two has light of state two, and unit three has light of state three.

o Where units one and three correspond to a left view and units two and three correspond to a right view.

5. Such units may be separated, specifically where:

o The third stage directs light from unit one and unit three to one sensor and directs light from unit two and unit three to another sensor or separate portion of the first sensor.

o The fourth stage balances the optical properties of units 1, unit 2, and unit 3 to reduce any color distortion, non-wanted polarization variation, or intensity variation introduced by any other stages to the three states.

6. A fifth stage may be placed before, after, or be incorporated within any of the other

stages, that totally or partially hinders light of any or a specific particular polarization state from propagating further down the optical path. This fifth stage partially or totally blocks light such that the spatial extent of units one, two, and three can be defined and limited as needed. In this way, the fifth stage acts as a partial iris for one or several of the individual units.

7. By providing the ability to adjust the size and relative position of the units according to the above, the stereo effect is adjusted and any change in optical magnification at the aperture or pupil can be accommodated.

8. An advantageous aspect is means for altering the properties of the polarization states defining the units, for example to accommodate manufacturing tolerances from the relative alignment of the stages and to minimize polarization cross-talk and maximize stereo effect.

9. Using two liquid crystal devices, stages 1, 2, and 5 may be accommodated into one

device.

[0016] According to these attributes and as described herein, a stereoscopic camera comprises:

o At least a first and second lens group that may or may not have zoom operation o A light modulator placed at or near a pupil between the first and second lens group with capability such as described above,

o A third lens, prism, or beam splitter located subsequent to the second lens group that creates two optical paths simultaneously directing light of differing polarizations to sensors or different portions of one sensor based on their polarization sensitivity

o A filter or filters to adjust optical properties within each optical path o A sensor or detector on each optical path that measures or records light

simultaneously with the other light capturing device thereby creating two simultaneous images corresponding to a left and right view,

o Electronics that control the detectors and the light modulator, should it be electronic, thereby providing coordinated operation,

o Electronics that adjust the control of the detectors or portions of the detectors, based on knowledge of the operating mode of the light modulator and the image thereby formed,

o Electronics that adjust the light modulator to provide continuous real-time adjustment of unit position and size to accommodate changing lens and optics parameters as well as desired stereo effect,

o Electronics that adjust the optical properties of the simultaneous images

captured by the detectors, such as light or color variations across or between each image, based on knowledge of the operating mode of the light modulator.

[0017] In one specific embodiment, in the camera of the present invention 1 , at least a substantial portion of the polarizing means 3 is located near the diaphragm within the lens that is used to adjust the light for each view. For this embodiment, the polarizing means is comprised of a combination of polarizing filters, waveplates, and liquid crystal devices. In the camera of the present invention, the polarizing means can describe a plurality of patterns, including ones distinct and interleaved, which have different polarizing states. These polarizing states or mixtures thereof are used to define the light from the left and right views. Further, the polarizing means can also act as the method of varying the light for each view. Still further a liquid or mechanical shutter may be used to vary the light for each view. In the camera of the present invention, a polarizing separating means 4 situated between the lens, polarizing means, and the light acquisition devices, separates the polarized light from the left and right views into different optical paths to form separate images. In the present invention, optical filters 7 are located between the polarizing separating means and the light acquisition device to adjust optical properties, including but not limited to polarization and color, to provide a higher quality image to the light acquisition devices. In the present invention, the light acquisition devices are portions of one or more electronic detectors or sensors. In the present invention, the computing device varies the pattern produced by the polarizing means to produce the desired stereo and parallax effect. The computing device adjusts the polarizing means to account for lens parameters such as f stop and zoom magnification to produce the desired stereo effect. Further, the computing device controls operation of the electronic detectors to ensure simultaneous image acquisition so as minimize motion artifacts. The computing device, having secured simultaneous light capture with a left and right view perspective, adjusts the image parameters as needed to produce stereo image pairs with attendant information. These images, with attendant information, are then produced with one of several formats known to those with knowledge of the field.

[0018] FIG. 1 shows the schematic details of a camera for acquiring stereo images according to one embodiment of the present invention. The camera consists of a lens unit 2, within which lies a polarizing light modulator 3, together with a beam splitter 4, optical filters 7, solid state image detectors 5, and computing electronics 6.

[0019] The lens unit 2 consists of multiple optical elements. For simplicity, the lens elements are described in terms of two lens groups with the modulator situated between them. There can in fact, especially in the case of zoom lenses, be many lens groups. To this effect, describing the lens elements as two groups shall not be determined to be limiting to two groups but should be representative of grouping of lens elements.

[0020] In this embodiment, the light modulator 3 is located at an aperture, pupil, or near the normal location of a diaphragm, between the lens elements. As in FIG. 2, the light modulator first stage 8 filters light for one polarization state. Although it is most preferable for this first stage to be situated near the aperture, it may be situated at a position earlier in the optical path. Next, the light modulator second stage, in this embodiment a liquid crystal device 9, alters the polarization state of the light into one or more additional states of different patterns. Alteration of polarization state in this way is common in a multitude of devices such as ones that change the configuration of nematic crystals as well as those that use other techniques. In this embodiment, as shown in FIG. 3, the polarizing liquid crystal device forms one unit 10A on the left most of the aperture and a second unit 10B on the right side of the aperture. Light passing through the left unit is given polarization of one state while light passing through the right unit is given polarization of another state. At the optical image plane, light can therefore be distinguished as coming from the respective units by selecting for the light's polarization state. Imaging light from the left unit forms a left eye view and imaging light from the right unit forms a right eye view of an object. By using a polarizing beam splitter or other similar device, light can be directed to areas of one or more sensors based on polarization state thereby permitting simultaneous acquisition of left and right eye imagery.

[0021] The amount of separation of two views of an object determines the parallax and magnitude of the stereo effect. It is therefore preferable to be able to vary this separation based on the desired need. In this embodiment, the separation is achieved by varying the distance between the centers of the first unit on the left from the second unit on the right. Adjustment of the separation distance controls stereo parameters, especially generation of depth perception, so as to produce a pleasurable viewing experience. By using a liquid crystal device that is comprised of a matrix structure, any pattern may be achieved and therefore the units may be separated to the limit of the lens aperture. FIG. 4A shows a configuration where the parallax is small producing less stereo effect where in FIG. 4B the stereo effect is larger and closer to the limit of the lens entrance pupil or limiting aperture 11. It is also preferable, however, to maximize the size of each unit while still maintaining the separation between their center points 12. Maximizing the possible size of each unit provides the maximum light through the lens corresponding to each view. For the same separation of the unit centers, maximizing the size requires that the two units overlap in some regions during the period in which left and right eye images are obtained. Correspondingly, FIGS. 5 A and 5B show configurations with similar parallaxes to that of FIGS. 4 A and FIG. 4B but with increased size for each unit. For practical purposes, this overlap can be considered as the formation of a third unit. In FIG. 6A, the aperture is divided into three units. The first unit 13A corresponds to the left most of the aperture, the second unit 13B to the right most, and the third unit 13C to the region common to both left and right parts. As the modulator is situated at or near an aperture, pupil, or conjugate thereof, rays passing through the third unit may form either left or right eye perspectives when viewed in the image plane. Consequently, in the image plane, light passing through units one 13A and unit three 13C form a left eye image and light passing through units two 13B and unit three 13C form a right eye image. In FIG. 6B, the liquid crystal modulator delineates the three units with three different polarizations states. For example, unit one 13A has a polarization that is linear, unit two 13B also a linear polarization but one oriented orthogonally at 90 degrees to that of unit one, and unit three 13C has a linear polarization state at 45 degrees to unit one. In this way, unit three has a polarization that is between that of unit one and two. It is well known that such a polarization can be considered as a vector sum of the orthogonal polarization states corresponding to those used to delineate units one and units two. In this embodiment, light from the polarization state of unit one is directed to one sensor by using a polarizing beam splitter. Light of the orthogonal polarization state from unit two is directed to another sensor by the same beam splitter. As light from unit three behaves as being comprised of light from each orthogonal state, light from unit 3 is split equally with some light going to each sensor. In this way, one sensor acquires the light from units one and three forming the left eye image while the other sensor acquires the light from units two and three forming the right eye image.

[0022] As the liquid crystal device operates as a matrix being able to form any pattern, unit three may be divided further into much smaller units of varying polarization states. According to a second embodiment, unit three may be divided into much smaller units 14A each corresponding to the polarization states of unit one or unit two. When considered together based on polarization state, these smaller units behave comparably to that of a contiguous larger unit. In this way, unit three has the polarization properties of both units one and unit two albeit varying between the two states on small distance scales within the extent of unit three itself. In this way, units may be formed as with the first embodiment, and polarized light separated prior to being acquired at the light sensing devices as with the first embodiment. FIG. 7A shows units one, two and three defined in this way using only two polarization states. It is understood that unit three may be divided into smaller areas of a multitude of different shapes and sizes.

[0023] According to a third embodiment, the polarization of unit 3 may be changed within the time period needed to form a left and right image. For practical purposes, the light acquisition device or devices may be limited in how fast they may be operated. By comparison, a light modulating means such as a liquid crystal device may be capable of operating at much higher speed. Accordingly, the light may be modulated many times within one operation period of the light acquisition device or sensor. Therefore, for one instance unit 3 may be formed and defined using the polarizing state of unit 1 while in the next instance unit 3 is defined using the polarizing state of unit 2. During these different instances, unit 1 and unit 2 may retain their same state and delineation while unit 3 effectively alternates between the two states. Providing the duration of such instances is many times less than the total period needed to form a complete image for the left and right eyes, then the state of unit 3 may be changed many times within the total period. The overlap defined by unit 3 therefore exists, for all practical purposes, simultaneously within the integration period. [0024] According to a further fourth embodiment, the delineation of the units may be changed within the time period needed to form a left and right image. For practical purposes, the light acquisition device or devices may be limited in how fast they may be operated. By comparison, a light modulating means such as a liquid crystal device may be capable of operating at much higher speed. Accordingly, the light may be modulated many times within one operation period of the light acquisition device or sensor. Therefore, for one instance unit 1 and unit 3 may be formed and defined using one polarizing state. In the next instance, unit 2 and unit 3 may be formed using another polarizing state. Providing the duration of such instances is many times less than the total period needed to form a complete image for the left and right eyes by the light acquisition device, then the units may be switched many times within the total period thereby effectively forming images at the same time. For example, in the case where the sensor or sensors are electronic, each instance of forming unit 1 and unit 3 and then forming unit 2 and 3 is a small fraction of the integration time required to form the left and right images prior to the next image capture. Multiple instances can therefore occur within one integration period. By interleaving views at high frequency within one integration period, one can minimize motion artifacts compared to capturing alternating left and right eye views in different integration periods. This approach minimizes the need to operate the detectors at high frequencies where often there is a degradation of performance.

[0025] According to a further fifth embodiment, unit three may be expanded to fill the majority if not the entirety of the aperture or pupil. In this embodiment, as the liquid crystal device operates as a matrix being able to form any pattern, unit three may be divided into much smaller units 14B, each with an orthogonal polarization state of differing patterns. This division may take a plurality of patterns one of which is shown in FIG. 7B. In this way, each part of the aperture or pupil is coded to have differing polarization states. As described later, light from each of these polarization states is captured separately by a light acquisition device or devices. Using the a priori knowledge of the form of the polarization pattern permits the use of coded aperture techniques familiar to those in the field. In this way, differing view perspectives may be generated in the image plane so as to simulate separation of the subapertures similar to those described in the previous embodiments. By changing this pattern the stereo effect, such as perception of depth, can be altered so as to provide a pleasurable viewing experience.

[0026] For controlling the effective size of the lens aperture, it is common to use a mechanical means to form an iris or diaphragm located at the aperture stop. Altering the size of this iris changes the effective aperture size thereby controlling the amount of light transmitted through the lens and the depth of field for which objects are in or out of focus. In the present invention, it is important that this function be maintained and be controllable for light that forms the left eye and right eye images. Correspondingly the units through which light passes to form the left and right eye paths must each have iris control. FIGS. 8 A and 8B show the use of a diaphragm 15 in a standard lens where FIG. 8B most strongly diminishes the light through the system by changing the effective aperture size and corresponding f/#. FIGS. 8C and 8D show the equivalent control for the present invention. Although a mechanical device may be used to achieve this function, this may also be accomplished using the liquid crystal device. FIG. 9 shows an embodiment in which the light modulator achieves both light adjustment control in addition to parallax control. In FIG. 9, the first stage 16 performs the function much like a standard liquid crystal shutter that blocks light throughput in certain areas and permits transmission of light in other areas where the light is output as polarized light. Consequently, in this embodiment, this first stage 16 behaves like the first stage 8 of the embodiments already described with the added functionality of light adjustment control. In one case, the light control is of sufficient magnitude that the modulator also performs as the shutter for the system thereby reducing the overall complexity of the system. Subsequent stages 17 of the light modulator adjust the polarization to define units one, two, and three as described already using a liquid crystal device.

[0027] FIG. 5 showed the configurations providing different parallaxes and different stereo effect. Similarly, FIGS. 10A-D show the units providing the same parallax but with different aperture sizes. Therefore the same stereo affect can be achieved while

simultaneously changing the amount of light and depth of field. Alternatively, the depth of field may be held constant and the parallax adjusted. This ability is advantageous in providing maximum control of the stereo and photographic aspects of any images that are acquired. Further, the separation between the left eye and right eye regions, and the corresponding delineation of the units, may be altered to accommodate a zoom function where the magnification changes at the pupil. In certain embodiments, the computing device alters the separation of the left and right eye regions to achieve the desired stereo effect and alters their separation and extent so as to maintain the same effect across varying optical magnifications.

[0028] In FIG. 1, item 4 is a device to separate polarization states. In this

embodiment, the light paths are separated by 90 degrees. This should not be considered to be limiting as the light paths may be separated by varying angles. In this embodiment, item 4 is a polarizing beam splitter where polarization of a first state is transmitted and one of another is reflected. The beam splitter may also be used in the configuration where the first state is reflected and the second state is transmitted. In other embodiments, a prism, a birefringent optic, or another polarizing separating device may be used to provide the same or similar function. In this embodiment, the beam splitter is positioned so as to direct polarized light to one or another of two light sensors capable of acquiring images. In the case of using linearly polarized light, the beam splitter is aligned to the orientations of the polarization states as defined by the liquid crystal device. Any relative misalignment, such as that caused by mechanical positioning error, can be corrected by changing the orientation of the polarizing states formed by the liquid crystal device. In another embodiment, item 4 separates polarization states as before but redirects the light paths so as to be incident on different sections of the same sensor. This is advantageous as this configuration eliminates the need for multiple detectors and associated electronics thereby simplifying the design and fabrication of the system.

[0029] Optical systems using polarization can sometimes suffer from color aberrations or polarization cross talk. In this embodiment, color aberrations may arise from the liquid crystal device or the polarizing separator. Additionally, the polarizing separator may not separate the polarization states perfectly leading to cross talk between the optical paths. If necessary, additional optical elements 7 A and 7B, situated between the polarizing separator and the light collecting means 5A and 5B, can ameliorate these conditions. In this embodiment, items 7A and 7B are filters positioned near the light acquisition devices that permit transmission of light polarized to a particular state. Filter 7A permits transmission of one polarization state while filter 7B permits transmission of polarized light of an opposite state. The insertion of these filters increases the effective polarization separation ensuring that the light acquisition device can detect only the polarization state that defines units one and three or units two and three respectively. These filters may also include a color adjustment capability. In certain embodiments, items 7A and 7B may be situated near or be an integral part of the polarizing separating device or alternatively the light acquisition devices or device.

[0030] In this embodiment, the light acquisition devices 5A and 5B are electronic sensors comprised of a multitude of sections each sensitive to light. Such devices are commonly used and may be of varying configurations. In another embodiment, 5A and 5B are differing areas of the same device. As light is transmitted along both light paths at the same time, left and right eye perspectives can be viewed simultaneously. Correspondingly, the sensor of the left eye can form an image at the same time as does the sensor for the right eye perspective. The computing device controls the operation of the sensors such that the left and right eye images are captured within the same detection period. Conventional stereo systems using two cameras can suffer from a time lag where the sensor detecting the left eye image is not operating contemporaneously with the sensor detecting the right eye image. This arises from using two sets of electronic controls, one for each sensor, with inadequate synchronization of operation between them. With the present invention, using one computing device to control both sensors, as well as situating the device close to the sensors minimizes time delays thereby facilitating simultaneous image acquisition. Further, in another embodiment, the light paths for the two polarization states may be separated to a small degree only thereby facilitating image acquisition by using two areas of just one sensor.

[0031] The computing device is comprised in this embodiment of a set of electronics.

The electronics ensure the coordinated operation of the light modulator and the sensors to produce the desired stereo effect. The electronics control the pattern of the units formed by the liquid crystal so as to provide differing parallaxes and iris sizes as FIG. 10.

[0032] In accordance with human anatomy, left eye and right eye stereo effect is produced from perspectives aligned horizontally to each other. Correspondingly, the electronics can control the orientation of the light modulator units so as to maintain the generation of parallax and differing perspectives in the horizontal plane even if the camera system experiences substantial roll or is being used in the so called portrait mode. This is easily done by determining the angle of the horizontal plane using an accelerometer or other such device and controlling the location of the units and irises so their relative positions remain parallel to that horizontal plane.

[0033] The electronics can also adjust the delineation of the units accommodating the magnification of the lens, the projected aperture size, the desired iris or stop, and the desired degree of parallax. These parameters are adjusted as needed across the entire operational range of the camera system. By integrating this functionality of both operating and knowing the liquid crystal device and lens unit state into the computing electronics, both the system complexity and the operators role are simplified permitting superior stereo production.

Specifically, the operator role is simplified as changes in optical performance or camera orientation that would produce unwanted changes in the stereo effect can be automatically compensated for by the computing device without operator intervention. Additionally, the combined knowledge of the liquid crystal device configuration and lens unit state permits the operator to manipulate the sensor images according to either the predicted or measured optical performance of the system so as to produce a superior stereo effect.

Claims

What is claimed is:

1. A system for producing stereographic images of an object, comprising: a monocular objective unit capturing different perspective images of a scene, including perspectives of inter-axial distances less than a diameter of the lens, wherein the objective unit comprises a unitary lens system developing images with left and right perspectives;

a light modulator configured to create multiple sub-apertures within the objective unit in which the left and right perspectives are substantially distinct; an image collection arrangement for presenting the left and right perspectives at an inter-axial distance such that left and right perspectives form a stereographic image pair.

2. The system of claim 1, wherein the inter-axial distance at which the left and right perspectives are presented corresponds to the inter-axial distance at which the perspectives are captured, accounting for optical magnification.

3. The system of claim 1, wherein the objective unit and light modulator are optimized for sub-apertures of maximum separation along a horizontal aspect corresponding to a viewer's pupils.

4. The system of claim 1, wherein the light modulator is configured for at least partly simultaneous coordinated capture of the left and right perspectives, thereby providing a stereovision effect while minimizing stereo and motion artifacts.

5. The system of claim 1 wherein the unitary lens system employs a single lens simultaneously capturing the left and right perspectives.

6. The system of claim 1 wherein the sub-apertures produced by the light modulator are distinguishable according to at least one optical property, into left and right eye viewing perspectives.

7. The system of claim 4 wherein the sub-apertures produced by the light modulator overlap so to enable certain left and right eye viewing perspectives.

8. The system of claim 1, further comprising a control coupled to the light modulator, the control and the light modulator effecting a first stage that selects light and a second stage that manipulates the light into at least two distinct polarization states.

9. The system of claim 1, further comprising a control coupled to the light modulator, the control and the light modulator effecting a first stage that selects light and a second stage that manipulates the light into at least three distinct polarization states of which the left and right perspectives have two distinguishable polarization states and the overlap has a third polarization state that is selectable together with either of said two distinguishable polarization states.

10. The system of claim 8, wherein the two distinct polarization states are orthogonal to one another.

11. The system of claim 9, wherein the light is directed simultaneously along light paths to at least one light detector operable to sense images from the left and right perspectives.

12. The system of claim 11, wherein the at least one detector comprises one of a sensor with distinct areas of polarization sensitivity by area and a diverting light path sensitive to polarization leading to plural respective sensors.

13. The system of claim 9, further comprising a fourth stage operable to adjust the left and right perspectives for at least one of light intensity, polarization state and color.

14. The system of claim 11, wherein the at least one detector comprises one of a sensor with distinct areas of polarization sensitivity by area and a diverting light path sensitive to polarization leading to plural respective sensors, further comprising a fourth stage operable to adjust the left and right perspectives for at least one of light intensity, polarization state and color, and wherein the fourth stage is adjacent to the sensors.

15. The system of claim 13, further comprising a fifth stage that is one of adjacent to and incorporated within one of said first through fourth stages, wherein the fifth stage at least partially hinders light of a predetermined particular polarization state from propagating further along an optical path.

16. The system of claim 2, wherein the system is configured for elements that are at least one of interchangeable and mechanically variable, to achieve a change in optical magnification.

17. The system of claim 2, comprising at least one liquid crystal along at least one light path, the liquid crystal being controllable to alter the polarization

18. A stereoscopic camera comprising:

at least a first lens group and a second lens group;

a light modulator located adjacent to a pupil defined between the first and second lens group, the light modulator being operable in conjunction with the first and second lens group simultaneously and continuously to provide distinct optical properties to left and right perspective images;

an optical element comprising at least one of a lens, a prism, a beam splitter and a liquid crystal device, subsequent to the second lens group, operable to direct the left and right perspective images along different optical paths;

at least one imaging detector along the optical paths arranged

simultaneously to receive the left and right perspective images.

19. The stereoscopic camera of claim 18, further comprising an electronic control operable for at least one of continuous real-time adjustment of unit position and size to accommodate at least one of changes in lens and optics parameters, orientation of the horizontal plane, relative mechanical positions of stages relative to each other, and adjustment of optical properties of images captured

simultaneously by the detectors.

20. The stereoscopic camera of claim 18, wherein the light modulator imparts distinct polarization characteristics to the left and right perspective images, wherein the left and right perspectives partly overlap, and wherein a controllable optical element comprising at least one liquid crystal and at least one polarization filter separate the left and right perspective images for simultaneous recording.