WO2011127550A1

WO2011127550A1 - Adapter apparatus and method for generating three-dimensional image information

Info

Publication number: WO2011127550A1
Application number: PCT/CA2010/000554
Authority: WO
Inventors: Thomas N. Mitchell
Original assignee: Isee3D Inc.
Priority date: 2010-04-14
Filing date: 2010-04-14
Publication date: 2011-10-20
Also published as: TW201135286A; TWI486633B

Abstract

An adapter apparatus and method for generating three-dimensional image information is disclosed. The adapter apparatus generates three-dimensional image at an image plane of an image recorder in response to receiving light captured by an imaging lens having a single imaging path with an associated field of view. The apparatus includes a housing having a first interface for mounting to the image recorder and a second interface for mounting the imaging lens. The apparatus also includes a first relay lens for imaging an exit pupil of the imaging lens to an aperture plane location within the housing, an image modulator located at or proximate to the aperture plane location within the housing and operably configured to selectively permit light from respective first and second portions of the single imaging path to be directed toward the imaging plane, and a second relay lens for forming corresponding first and second images at the image plane. The first and second images together being operable to represent three dimensional spatial attributes of objects within the field of view of the imaging lens.

Description

ADAPTER APPARATUS AND METHOD FOR GENERATING THREE- DIMENSIONAL IMAGE INFORMATION

BACKGROUND OF THE INVENTION

1. Field of Invention

This invention relates generally to generating three-dimensional image information and more particularly to an adaptor for generating three- dimensional image information in response to receiving light captured by an imaging lens having a single imaging path.

2. Description of Related Art

In conventional two-dimensional (2D) imaging, rays of light representing objects in a three-dimensional (3D) scene are captured and mapped onto a 2D image plane, and thus depth information is not recorded. Stereoscopic optical systems are capable of producing images that represent depth information by producing separate images from differing perspective viewpoints. The depth information may be used to produce 3D measurements between points in the scene, for example. Alternatively, the separate images may be separately presented to respective left and right eyes of a user so as to mimic operation of the human eyes in viewing a real scene and allowing the user to perceive depth in the presented views. The separated or stereo images are generally produced by an optical system having either a pair of spatially separated imaging paths or by using different portions of a single imaging path to produce images having differing perspective viewpoints. The images may then be presented using eyewear that is able to selectively permit the separate images to reach the user's respective left and right eyes. Alternatively, a special display may be configured to project spatially separated images toward the user's respective left and right eyes. The use of stereoscopic imaging finds application in the filed of surgery where a 3D endoscope may be used to provide a 3D view to the surgeon. Stereoscopic imaging may also be useful in remote operations, such as undersea exploration for example, where control of a robotic actuator is facilitated by providing 3D image information to an operator who is located remotely from the actuator. Other applications of stereoscopic imaging may be found in physical measurement systems and in the entertainment industry.

SUMMARY OF THE INVENTION

In accordance with one aspect of the invention there is provided an adapter apparatus for generating three-dimensional image information at an image plane of an image recorder in response to receiving light captured by an imaging lens having a single imaging path with an associated field of view. The apparatus includes a housing having a first interface for mounting to the image recorder and a second interface for mounting the imaging lens. The apparatus also includes a first relay lens for imaging an exit pupil of the imaging lens to an aperture plane location within the housing, an image modulator located at or proximate to the aperture plane location within the housing and operably configured to selectively permit light from respective first and second portions of the single imaging path to be directed toward the imaging plane, and a second relay lens for forming corresponding first and second images at the image plane. The first and second images together are operable to represent three dimensional spatial attributes of objects within the field of view of the imaging lens.

The first relay lens may include a plurality of lenses.

The first relay lens may further include a lens group operably configured to cause light captured by the imaging lens to be formatted for the adaptor.

The lens group may include at least one moveable lens element. The image modulator may be operably configured to selectively transmit light from respective first and second portions of the single imaging path.

The image modulator may be operably configured to selectively transmit light by alternately blocking the first portion of the single imaging path while permitting light to be received through the second portion of the single imaging path, and blocking the second portion of the single imaging path while permitting light to be received through the first portion of the single imaging path.

The image modulator may include a blocker disposed in the single imaging path and operably configured to move between first and second positions.

The image modulator may include an optical element having first and second regions, the first and second regions operably configured to be selectively actuated to block the first and second portions of the single imaging path.

The image modulator may include an optical element having a plurality of individually actuated elements and the first and second regions may include first and second selectively actuated groups of the plurality of elements.

The image modulator may be operably configured to selectively vary an actuation pattern of the plurality of elements to cause the image modulator to reduce light transmission through each of the first and second regions.

The image modulator may be operably configured to selectively change a state of polarization of light from at least one of the first and second portions of the single imaging path. The image modulator may be operably configured to selectively transmit light from respective first and second portions of the single imaging path in response to a synchronization signal.

The second relay lens may include a plurality of lenses.

The second relay lens may further include a lens group operably configured to produce an image at the image plane having a format corresponding to a format of an image recorder disposed to record the image at the image plane.

The lens group may include at least one moveable lens element.

The image sensor may be operably configured to generate electrical signals representing the first and second images formed at the image plane.

In accordance with another aspect of the invention there is provided a method for generating three-dimensional image information at an image plane of an image recorder in response to receiving light captured by an imaging lens having a single imaging path with an associated field of view. The method involves imaging an exit pupil of the imaging lens to an aperture plane location within a housing, the housing having a first interface for mounting to the image recorder and a second interface for mounting the imaging lens. The method also involves causing an image modulator located at or proximate to the aperture plane location within the housing to selectively permit light from respective first and second portions of the single imaging path to be directed toward the imaging plane. The method further involves forming corresponding first and second images at the image plane, the first and second images together being operable to represent three dimensional spatial attributes of objects within the field of view of the imaging lens. Imaging the exit pupil may involve disposing a first relay lens within the housing to image the exit pupil to the aperture plane location.

Disposing the first relay lens may involve disposing a lens group to cause light captured by the imaging lens to be formatted for receipt by the first relay lens.

Disposing the lens group may involve disposing at least one moveable lens element within the housing. Causing the image modulator to selectively permit light from respective first and second portions of the single imaging path to be directed toward the imaging plane may involve causing the image modulator to selectively transmit light from respective first and second portions of the single imaging path.

Causing the image modulator to selectively transmit light may involve alternately blocking the first portion of the single imaging path while permitting light to be received through the second portion of the single imaging path, and blocking the second portion of the single imaging path while permitting light to be received through the first portion of the single imaging path.

Alternately blocking the first and second portions of the single imaging path may involve causing a blocker disposed in the single imaging path to move between first and second positions.

Alternately blocking the first and second portions of the single imaging path may involve selectively actuating first and second regions of an optical element to selectively block the first and second portions of the single imaging path. The image modulator may include a plurality of elements and alternately blocking the first and second portions of the single imaging path may involve selectively actuating elements in first and second regions to selectively block the first and second portions of the single imaging path.

The method may involve selectively varying an actuation pattern of the plurality of elements to cause the image modulator to reduce light transmission through each of the first and second regions.

Causing the image modulator to selectively permit light from respective first and second portions of the single imaging path to be directed toward the imaging plane may involve causing the image modulator to selectively change a state of polarization of light from at least one of the first and second portions of the single imaging path.

Causing the image modulator to selectively permit light from respective first and second portions of the single imaging path to be directed toward the imaging plane may involve causing the image modulator to selectively transmit light from respective first and second portions of the single imaging path in response to a synchronization signal.

Forming corresponding first and second images at the image plane may involve disposing a second relay lens within the housing to form corresponding first and second images at the image plane.

Disposing the second relay lens may involve disposing a plurality of lenses to form corresponding first and second images at the image plane.

Disposing the second relay lens may involve disposing at least one moveable lens element within the housing, and positioning the at least one moveable lens element to cause to form corresponding first and second images at the image plane.

Forming the corresponding first and second images at the image plane may further involve disposing at least one moveable focus lens within the housing and positioning the focus element to focus the corresponding first and second images at the image plane.

Forming corresponding first and second images at the image plane may involve forming first and second images at an image sensor operable to generate electrical signals representing the first and second images.

In accordance with another aspect of the invention there is provided an adapter apparatus for generating three-dimensional image information at an image plane of an image recorder in response to receiving light captured by an imaging lens having a single imaging path with an associated field of view. The apparatus includes a housing having a first interface for mounting to the image recorder and a second interface for mounting the imaging lens. The apparatus also includes provisions for imaging an exit pupil of the imaging lens to an aperture plane location within the housing, ands provisions for selectively permitting light from respective first and second portions of the single imaging path to be directed toward the imaging plane, the provisions for permitting being located at or proximate to the aperture plane location within the housing. The apparatus further includes provisions for forming corresponding first and second images at the image plane, the first and second images together being operable to represent three dimensional spatial attributes of objects within the field of view of the imaging lens.

The provisions for imaging the exit pupil may include at least one moveable lens element within the housing, and provisions for positioning the at least one moveable lens element to cause the exit pupil to be imaged to the aperture plane location.

The provisions for selectively permitting light to be directed toward the imaging plane may include provisions for selectively transmitting light from respective first and second portions of the single imaging path.

The provisions for selectively transmitting light may include provisions for alternately blocking the first portion of the single imaging path while permitting light to be received through the second portion of the single imaging path, and blocking the second portion of the single imaging path while permitting light to be received through the first portion of the single imaging path.

The provisions for alternately blocking the first and second portions of the single imaging path may include provisions for causing a blocker disposed in the single imaging path to move between first and second positions.

The provisions for alternately blocking the first and second portions of the single imaging path may include an optical element operably configured to selectively block the first and second portions of the single imaging path.

The provisions for causing the image modulator to selectively permit light from respective first and second portions of the single imaging path to be directed toward the imaging plane may include provisions for causing the image modulator to selectively change a state of polarization of light from at least one of the first and second portions of the single imaging path.

The provisions for forming corresponding first and second images at the image plane may include at least one moveable lens element within the housing, and provisions for positioning the at least one moveable lens element to cause to form corresponding first and second images at the image plane.

The provisions for forming the corresponding first and second images at the image plane may further include provisions for focusing the corresponding first and second images at the image plane.

The apparatus may include provisions for generating electrical signals representing the first and second images formed at the image plane.

Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

In drawings which illustrate embodiments of the invention,

Figure 1 is a partially cut away perspective view of an imaging system including an adaptor apparatus for generating three-dimensional image information in accordance with a first embodiment of the invention;

Figure 2 is a top schematic view of a prior art two-dimensional imaging system;

Figure 3 is a top schematic view of imaging system and the adaptor apparatus shown in Figure 1;

Figure 4 is a further top schematic view of imaging system and the adaptor apparatus shown in Figure 1; Figure 5 is a representation of first and second images produced by the imaging system shown in Figure 1 ;

Figure 6 is a perspective view of a liquid crystal image modulator used in the adaptor apparatus shown in Figure 1 ;

Figure 7 is a block diagram of a controller for controlling operation of the adaptor apparatus shown in Figure 1 ;

Figure 8 is a schematic view of a spatial modulator in accordance with ah alternative embodiment of the invention

Figure 9 is a graphical depiction of control signals for controlling the spatial modulator shown in Figure 8;

Figure 10 is a perspective view of an alternative embodiment of an actuator for use in the spatial modulator shown in Figure 8; and

Figure 11 is a top schematic view of an adaptor apparatus according to an alternative embodiment of the invention.

DETAILED DESCRIPTION

Referring to Figure 1 , an imaging system is shown generally at 100. The imaging system 100 includes an image recorder 102 and an imaging lens 104. The imaging lens 104 has a single imaging path with an associated field of view. The imaging system 100 also includes an adaptor apparatus 108 for generating three-dimensional image information at an image plane 106 of the image recorder 102 in response to receiving light captured by the imaging lens 104. The adaptor 108 includes a housing 110 having a first interface 112 for mounting to the image recorder 102 and a second interface 114 for mounting the imaging lens 104. The adaptor 108 also includes a first relay lens 116 for imaging an exit pupil of the imaging lens 104 to an aperture plane location 118. The adaptor 108 further includes an image modulator 120 located at or proximate to the aperture plane location 118 within the housing 110. The image modulator 120 is operably configured to selectively permit light from respective first and second portions of the single imaging path to be directed toward the imaging plane 106.

The adaptor 108 also includes a second relay lens 122 for forming corresponding first and second images at the image plane 106. The first and second images together include image data that may be processed or displayed so as to represent three dimensional spatial attributes of an object 132 within a field of view of the imaging lens 104.

In the embodiment shown the first relay lens 116 comprises a relay lens group of two individual lenses 124 and 126 and the second relay lens 122 comprises a relay lens group of two individual lenses 128 and 130. In other embodiments (not shown) the relay lenses 116 and 122 may comprise only a single lens or a group of more than two lenses.

Referring to Figure 2, in conventional two-dimensional (2D) imaging the imaging lens 104 would generally be directly coupled to the first interface 112 of the image recorder 102. In this embodiment the imaging lens 104 comprises a double-Gauss lens having a generally symmetrical plurality of lens elements (150, 152) located along a central axis 154 on either side of a central aperture stop 156. However, in other embodiments the lens 104 may be a zoom, telephoto, fisheye, or any of a number of different lens configurations used in forming images. The location of the exit pupil of the imaging lens 104 is shown at 158. The exit pupil of a lens is defined as the image of the aperture stop of the lens in image space i.e. the aperture stop as imaged by the lens elements 152 to the right of the aperture stop 156 in Figure 2. In this case the image of the aperture stop 156 is a virtual image. The location and size of the exit pupil

158 may be found by tracing the path of a chief ray 160 and a marginal ray 162 through the elements 152. The exit pupil 158 is located at a point where a projection 164 of the chief ray 160 crosses the central axis 154. A projection 166 of the marginal ray 162 defines the diameter of the exit pupil. The imaging lens 104 has a single imaging path, in that all light rays captured by the lens are transmitted through the same plurality of lens elements 150 and 152 and images formed at the image plane 106 do not provide any 3D image information. The exit pupil 158 is spaced apart from the image plane 106 by a distance D, which is generally maintained to within a certain tolerance to ensure proper image formation at the image plane. Failure to maintain D to within a range specific to the configuration of the imaging lens 104 may result in image formation problems such as overfill, underfill, or other vignetting of the image. In general an image recorder 102 will be able to operate with a set of imaging lenses having respective exit pupil locations within a certain range. An imaging lens having an exit pupil outside this range may underfill the image sensor 168 (i.e. the generated image will be vignetted) or overfill the image sensor (i.e. there may be considerable light loss.

In the embodiment shown in Figure 2, the image recorder 102 includes an image sensor 168 disposed at the image plane 106 for recording the image. The image sensor 168 may be a Charge Coupled Device (CCD) or a CMOS active pixel device, for example. Alternatively, the image may be recorded by any other suitable image recording medium or device, such as photosensitive film. The image recorder 102 also includes a controller 170, which is in communication with the image sensor 168 for controlling image recording operations of the image sensor 168. The controller 170 is also configured to control other functions of the image recorder such as focusing, exposure, and aperture control. In some embodiments the interface 112 provides for electrical and/or mechanical drive coupling between the image recorder 102 and the lens 104 in order to provide for automatic focusing of the lens. For example, in the double Gauss lens arrangement shown, the plurality of lenses 150 and 152 may be coupled to a mechanical actuator (not shown) for moving the lenses along the central axis 154 to facilitate focusing.

The 3D imaging system 100 of Figure 1 is shown in top view in Figure 3. Referring to Figure 3, for 3D imaging the adaptor 108 is directly coupled to the first interface 112 of the image recorder 102 and the imaging lens 104 is coupled to the second interface 114 of the adaptor. The first relay lens 116 images the exit pupil 158 to the aperture plane location 118 (at a point where the chief ray 160 crosses the central axis 154). The image modulator 120 is located as close as possible to the aperture plane location 118. In the embodiment shown the aperture plane location 118 falls within lens element 128 of the second relay lens 122, and thus it is not possible to locate the image modulator 120 exactly at the aperture plane. However, as long as the image modulator 120 is located at least proximate to the aperture plane location 118, significant vignetting of the images is unlikely to occur. For any specific lens configuration, an optical tolerancing of the lens design may be performed to determine an acceptable displacement of the modulator from the aperture plane location 118. Note that in this embodiment the image modulator 120 extends beyond the marginal ray 162 so that the image modulator does not un-intentionally become an aperture for the system. The image modulator 120 includes an input 200 for receiving a drive signal operable to cause the image modulator 120 to selectively transmit light through respective first and second regions 202 and 204 of the image modulator. The image modulator 120 will be described in greater detail later herein.

The adaptor 108 also includes a controller 206 for controlling operation of the image modulator 120. The controller 206 may be located within the housing 110 or in a separate housing attached to the housing 110 (not shown). Alternatively, the functions of the controller 206 may be provided by the controller 170 of the image recorder 102.

The controller 206 includes an output 208 for generating the image modulator drive signal or signals. The controller 206 also has an output 210 for producing a synchronization signal. The output 210 is in communication with the controller 170 of the image recorder 102 for controlling image recording operations of the image sensor 168 in synchronism with the actuation of the image modulator 120. Alternatively, an image modulator synchronization signal may be derived from an internal synchronization signal produced by the controller 170 and provided to the controller 206 via an input (not shown) for synchronizing actuation of the image modulator 120.

The operation of the adaptor 108 in generating 3D image information is described further with reference to Figure 4 and 5. In Figure 4, a first light ray bundle 220 emanating from a first point 222 on the object 132 is captured by the imaging lens 104 and impinges on the first region 202 of the image modulator 120 and a second light ray bundle 224 from a second point 226 on the object 132 is captured by the imaging lens and impinges on the second region 204 of the image modulator. The first region 202 of the image modulator 120 is actuated to permit light from a first portion of the single imaging path to be transmitted through the second relay lens 122 to the image plane 106. At the same time the second region 204 of the image modulator 120 is actuated to prevent light from a first portion of the single imaging path from being transmitted. When the image modulator 120 is actuated as shown in Figure 4, light is thus transmitted through a first portion of the single image path of the imaging lens 104 corresponding to the first region 202 of the image modulator 120 and a first image is formed at the image plane 106. When the image modulator 120 is actuated to cause the first region 202 to prevent light transmission and to actuate the second region 204 for transmission, light is transmitted through a second portion of the single image path of the imaging lens 104 corresponding to the second region 204 of the image modulator 120 and a second image is formed at the image plane 106.

Referring to Figure 5, representative first and second images of the object 132 are shown generally at 250 and 252. Since the first portion of the single imaging path is offset from the central axis 154, the first image 250 has a perspective viewpoint from one side of the object 132 and is offset toward the left from an image center 254. When the second region 204 of the image modulator 120 is actuated to transmit light, the second image 252 having a perspective viewpoint from the other side of the object 132 is formed offset toward the right from the image center 254. When the first and second images 250 and 252 are selectively directed to respective right and left eyes of a user, the user will be able to discern 3D information from the images, in much the same way that the user would be able to discern 3D information when viewing the actual object. In one embodiment, the first and second images 250, 252 may be alternately displayed as separate video fields on a display monitor. Various types of active and passive eyewear are available for directing such displayed first and second images 250 and 252 to the user's eyes. Passive types of eyewear generally rely on additional wavelength or polarization processing of the images to enable passive filter elements in the eyewear to separate the images. Active types of eyewear generally include a receiver for receiving a synchronization signal from a display to alternatively permit transmission of the first and second images 250, 252 to the respective left and right eyes. Alternatively, the first and second images 250 and 252 may be processed to match up identifiable features in the respective images and to determine lateral shifts between the identified features. The determined lateral shifts along with a knowledge of the imaging parameters of the imaging system 100 may be used to calculate a difference in depth between points on an object or between objects at different depths.

In this embodiment, the respective first and second regions 202 and 204 have approximately the same extent (i.e. 50% of the extent of image modulator

120). In other embodiments the first and second portions may be greater than or less than 50% of the extent of the image modulator 120. The level of 3D depth discernment provided by the images is generally greater when the perspective viewpoints for each of the first and second images 250 and 252 are spaced apart by a greater distance from the central axis 54.

Advantageously, the single image path through the imaging lens 104 produces first and second images 250 and 252 from which 3D information can be perceived and/or extracted without requiring any special alignments other than would normally be required in assembling the lenses at the time of manufacture. In contrast, stereoscopic imaging systems that use separate image paths to form separated first and second images may cause eyestrain or other uncomfortable effects for users if there is even a minor misalignment between the separated image paths.

Image modulator

In one embodiment the image modulator 120 may be implemented using a liquid crystal device (LCD), which alternately actuates the first and second regions 202 and 204 to transmit light in response to the drive signal received at the input 200. Referring to Figure 6, an LCD image modulator is shown generally at 300. The LCD modulator 300 includes a liquid crystal material layer 302 disposed between a first glass plate 304 and a second glass plate 306. The first glass plate 304 includes a plurality of transparent electrodes 308 arranged in columns. Each electrode 308 has an associated connector 310, which may be a wire-bonded or flexible circuit connection, for example. The connectors 310 connect to a header 312, which in turn facilitates connection to the output 210 of the controller 206 shown in Figure 3. The second glass plate 306 includes a transparent area electrode (not shown) which extends across a surface of the second glass plate and acts as a common electrode. Each transparent electrode 308 defines an element between the electrode and the transparent area electrode, thus defining a plurality of elements 318 that may be separately actuated by providing a drive potential between the corresponding electrode 308 and the area electrode.

The LCD image modulator 300 also includes a first polarizer 314, having a first linear polarization property (in this case vertical polarization). The first polarizer 314 overlays the plurality of transparent electrodes 308. The modulator 300 further includes a second polarizer 316 overlaying the second electrode and having a second linear polarization property (in this case horizontal polarization). In Figure 6 the various layers are not necessarily shown to scale.

The controller 206 (shown in Figure 3) is shown in greater detail in Figure 7. The controller 206 includes the output 210 for producing the synchronization signal (SYNC), which typically comprises a time separated pulse train. The controller 206 further includes a modulator driver 212 for generating the drive signals at the output 208. In the embodiment shown, the modulator driver is configured to drive the LCD modulator shown in Figure 6, and the output 208 thus has "n" output channels corresponding to the number of elements 318 of the modulator 120. In one embodiment the controller 206 may be implemented using a processor circuit such as a micro-controller, for example. ln the embodiment shown, the output 208 of the controller 206 is operably configured to provide an individual drive signal for each electrode 308. The drive signals are coupled to the respective electrodes 308 via the header 312 and connectors 310, with the common electrode acting as a ground connection. In one embodiment the drive voltage may be a 50% duty cycle square wave varying between a voltage V* and V, where the voltages are selected within a range of safe operating voltages to provide sufficient contrast between transmission and blocking of light impinging on the LCD modulator 300. In the embodiment shown, the plurality of columnar elements 318 facilitate changes to the extent of the regions 202 and 204 shown in Figure 1 and 3. However in other embodiments, the LCD modulator 300 may be configured to include only two columnar elements, each element having an extent of approximately 50% of the front surface of the LCD modulator 300. Alternatively, the columnar elements 318 may alternatively be sub-divided into a plurality of pixels that may be individually actuated to provide the desired extent of the first and second regions 202 and 204.

In operation, the first polarizer 314 transmits light having a vertical polarization. In this embodiment the liquid crystal material 302 is selected so that in its relaxed phase (un-actuated) the polarization of light passing through the crystal is unaffected and the second polarizer 316 thus blocks the light. When actuated by the drive voltage applied to any of the electrodes 308, a portion of the liquid crystal material layer 302 underlying the electrode causes light transmitted through the layer to undergo a 90° change in polarization, thus passing through the second polarizer 316 and the modulator 300. By alternately generating drive signals for first and second pluralities of the electrodes 308, the modulator 300 thus alternates between blocking and transmitting light at the first and second regions 202 and 204 respectively.

In an alternative embodiment the polarizers 314 and 316 may both be vertically polarized, such that the LCD Modulator is transmissive when no actuation voltage is applied. In this case, when an element is actuated, the liquid crystal material causes the light to undergo a 90° change in polarization thus causing elements 318 to block transmission of light. In another embodiment, the electrodes 308 of the modulator 300 may be divided into a plurality of pixels (shown in broken line at 320) and connector 310 and header 312 may be configured to individually drive each pixel 320. In operation, column of elements 318 may be actuated by actuating each of the pixels 320 in the column. Alternatively, it may be desired to actuate pixels in other than columnar patterns. For example, pixels 320 may be actuated to cause aperturing of the image at the aperture plane 614 by actuating pixels in a circular or semi-circular pattern.

Mechanical image modulator

In an alternative embodiment the modulator 120 shown in Figure 3 may be implemented using a spatial modulator shown generally at 380 in Figure 8. Referring to Figure 8, the spatial modulator 380 includes an opaque shutter blade 382 having a slot 383 mounted on an arm 384. The arm 384 is mounted on a pivot 386 to provide for side-to-side motion of the arm. The arm 384 also includes a magnet 390 mounted partway along the arm. The magnet 390 is disposed between first and second electromagnets 392 and 394. The arm 384, pivot 386, and the electromagnets 392 and 394, together make up a mechanical actuator operable to produce a force for moving the shutter blade 382 from side-to-side in the direction of the arrow 388 between a pair of stops 414 and 416, which respectively define first and second positions of the arm and the slot 383. The stops 414 and 416 each comprise a threaded portion 420 that provides for adjustment for aligning the slot 383 to selectively permit light from respective first and second portions of the imaging path to be directed toward the imaging plane 106. In one embodiment the stops 414 and 416 may be coupled to an electrical actuator (not shown), thus facilitating alignment of the slot 383 without requiring access to the modulator 380.

For driving the spatial modulator 380, the controller 206 may be replaced by the modulator controller 400 shown in Figure 8. The modulator controller 400 includes a first pair of outputs 402 for driving a coil 404 of the first electromagnet 392 and a second pair of outputs 406 for driving a coil 408 of the second electromagnet 394. The modulator controller 400 also includes an output 412 for producing a synchronization signal (SYNC) for synchronizing operation of the camera 102, as described above in connection with Figure 3.

Alternatively, the output 412 may be configured as an input for receiving a synchronization signal generated by the controller 170 of the camera 102.

In operation, the modulator controller 400 either generates the SYNCH signal internally, or receives the SYNC signal at 412. In response to the SYNCH signal, the modulator generates current waveforms at the outputs 402 and 406 for driving the respective coils 404 and 408. The current through the respective coils 404 and 408 cause forces to be exerted on the arm 384 to move toward a desired stop 414 or 416. Advantageously, the modulator controller 400 may be implemented as a push-pull controller where one of the electromagnets 392 and 394 provides an attractive force on the magnet 390, while the other of the electromagnets provides a repulsion force.

Exemplary waveforms of a current drive provided to the coils 404 and 408 to cause the arm 384 to move toward the first electromagnet 392 are shown graphically in Figure 9. The current waveform through the coil 404 is shown at 440 and the current waveform through the coil 408 is shown at 442. The SYNCH signal pulse waveform is shown at 446. A rising edge of the SYNCH signal 446 defines a start time of a first time period 444, in which the current 440 rises rapidly to produce an attractive force on the arm 384. The attractive force overcomes the inertia of the arm 384 and causes the arm to accelerate away from the stop 414 and the second electromagnet 394. During the first time period 444 the current 442 is initially at zero and once the arm 384 begins to accelerate, the current 442 increases rapidly to provide a decelerating force as the arm approaches the stop 416, thereby damping the motion of the arm to prevent bouncing of the arm when engaging the stop.

The arm 384 comes to rest at the stop 416 and the currents 440 and 442 reduce to a small holding current in each of the coils 404 and 408 to hold the arm at the stop 416. A second time period 448 during which the arm 384 is held at the stop 416 provides sufficient time to complete capture of the first image.

Similarly, a subsequent rising edge of the SYNCH signal 446 defines a start time of a third time period 450, in which the current 442 causes an attractive force and the current 440 a repulsion force on the arm 384 to cause the arm to move toward the stop 414. A time period 452 during which the arm 384 is at rest at the stop 414 defines a fourth time period 452, which provides sufficient time to complete capture of the second image.

Referring to Figure 10, an alternative embodiment of the actuator portion of the spatial modulator 380 (shown in Figure 10) is shown generally at 500.

The actuator 500 includes a motor 502 having a rotor shaft 506 extending through the motor. The arm 384 carries the shutter blade 382 and is mounted to the shaft 506 for side-to-side motion between stops 414 and 416. In this embodiment, the motor 502 is implemented using a pair of magnets 508 and 510 and the shaft 506 supports an actuator coil 516 between the magnets.

The actuator coil 516 may be coupled to the modulator output 402 for receiving a drive current, which causes a torque to be generated on the shaft 506. In general, the actuator 500 operates in a manner similar to an analogue meter movement and provides movement between stops 414 and 416. In other embodiments, the motor portion 502 may be configured such that the shaft 506 is magnetized and the coil is wound around pole pieces (i.e. 508 and 510).

Alternative adapter embodiment

Referring to Figure 11 , an alternative adaptor embodiment is shown generally at 600. The adaptor 600 includes a housing 602 having a first interface 604 for mounting to the image recorder 102 and a second interface 606 for mounting an imaging lens 608. The imaging lens 608 has an exit pupil 610. The adaptor 600 further includes a first relay lens 612. The adaptor 600 further includes an image modulator 616 located at or proximate to the aperture plane location 614.

In this embodiment the first relay lens 612 comprises a relay lens pair 618, including relay lenses 620 and 622 for imaging exit pupil of the imaging lens 608 to the aperture plane location 614. The first relay lens 612 also includes a lens group 624 that is configured to adapt an image size or format produced by the imaging lens 608 to the adaptor 600. In one embodiment the embodiment the lens group 624 is implemented using a zoom lens triplet (lenses 626, 628, and 630) in which at least lenses 628 and 630 are moveable to vary the focal length of the lens group. In other embodiments the lenses in the lens group 624 may be fixed in place in the housing 602, in which case the adaptor 600 would be configured for a single image size/format. The adaptor 600 also includes a second relay lens 631 for forming corresponding first and second images at the image plane 106. The second relay lens 631 includes a relay lens pair 632 including relay lenses 634 and 636 for forming an image at the image plane 106. The second relay lens 631 also includes a lens group 638, which is configured to produce an image at the image plane 106 that is sized in accordance with the size of the image sensor 168. In this embodiment the lens group 638 is implemented using a zoom lens triplet (lenses 640, 642, and 644) in which at least lenses 642 and 644 are moveable to vary the focal length of the lens group. Again, in an embodiment where the adaptor 600 is intended for use with a specific image recorder 102, the lenses in the lens group 624 may be fixed in place in the housing 602.

In this embodiment the adaptor 600 also includes an optional moveable focusing lens 646 for adjusting image focus at the image plane 106. In operation, the moveable elements 626 and 628 of the lens group 624 permit adjustment of the focal length of the lens group 624 to configure the adaptor for use with lenses 608 have varying image formats, while the relay lens pair 618 images the an exit pupil 610 of the imaging lens 608 to the aperture plane location 614. Advantageously, the provided adjustments allow a wider variety of lenses to be used in combination with the adaptor, and also facilitates use of lenses that are not strictly compatible with the format of the image recorder 102. The lenses 628 and 630 may be moved using a mechanical actuator ring (not shown) to change an overall focal length of the relay lens 612 to image the exit pupil 610 of the lens 608 to the aperture plane location 614.

Similarly, moving lenses 642 and 644 of the lens group 638 configures the adaptor 600 for operation with the image recorder 102 such that the image at the image plane 106 is correctly formatted for the sensor 168. Advantageously, the lens group 638 facilitates adjustment of the adaptor to match a larger range of image recoding devices without overfilling or underfilling the sensor 168.

The imaging lens 608 will generally include provisions for adjustment of focus so that that the image formed at the image plane 106 is correctly focused.

Such adjustment may be provided in the form of a manual mechanical actuator ring (not shown) on the outside of the housing for manual focusing or by in the form of a motorized actuator for automatic focusing. The focusing lens 646 additionally allows the focus range of the lens 608 to be optionally offset should the focus range of the imaging lens 608 not be sufficient to permit focusing of the image at the image plane 106.

Once the relay lenses 612 and 639 are adjusted for operation with the lens 608 and image recorder 102, the operation of the adaptor 600 in generating 3D images is generally as described above in connection with Figure 4 and Figure s.

Other embodiments

In another embodiment of the image modulator 300 shown in Figure 6, the second polarizer 316 may be omitted to configure the modulator to selectively change the polarization of the transmitted light rather than to selectively block transmission of light. Portions of the liquid crystal material layer 302 underlying un-actuated electrodes 308 would thus have no effect on the polarization of the light, which would be transmitted as vertically polarized light due to the action of the first polarizer 314. Portions the liquid crystal material 350 underlying actuated electrodes 308 would cause the light to undergo a

90° change in polarization, thus causing transmitted light to have a horizontal polarization. In this alternative embodiment, the image modulator 300 would thus result in first and second images having respective vertical and horizontal polarization states being simultaneously formed at the image plane 106. Alternatively, the liquid crystal material layer 302 of the LCD modulator 300 may be configured to produce a first image having right circular polarized light and a second image having left circular polarized light. The sensor 168 may be configured to simultaneously receive the respective first and second images by adding polarizing elements in front of individual sensor array elements. For example, adjacent sensor pixels may be alternately horizontally polarized and vertically polarized to provide polarization selective pixels that are sensitive to only one polarization orientation. The sensor would thus permit both the first and second images to be simultaneously received. The first and second images may be separated during readout of the array or in a separate processing step.

The above adaptor embodiments facilitate adaptation of a wide range of 2D imaging lenses and 2D image recorders for producing 3D image information. Advantageously, since the images are captured using the single image path of the imaging lens, the adaptor facilitates generation of 3D images without any further requirement for alignment of imaging paths.

While specific embodiments of the invention have been described and illustrated, such embodiments should be considered illustrative of the invention only and not as limiting the invention as construed in accordance with the accompanying claims.

Claims

What is claimed is:

1. An adapter apparatus for generating three-dimensional image information at an image plane of an image recorder in response to receiving light captured by an imaging lens having a single imaging path with an associated field of view, the apparatus comprising: a housing having a first interface for mounting to the image recorder and a second interface for mounting the imaging lens; a first relay lens for imaging an exit pupil of the imaging lens to an aperture plane location within said housing; an image modulator located at or proximate to said aperture plane location within said housing and operably configured to selectively permit light from respective first and second portions of the single imaging path to be directed toward said imaging plane; and a second relay lens for forming corresponding first and second images at the image plane, said first and second images together being operable to represent three dimensional spatial attributes of objects within the field of view of the imaging lens.

2. The apparatus of claim 1 wherein said first relay lens comprises a plurality of lenses.

3. The apparatus of claim 2 wherein said first relay lens further comprises a lens group operably configured to cause light captured by said imaging lens to be formatted for said adaptor.

The apparatus of claim 3 wherein said lens group comprises at least one moveable lens element.

The apparatus of claim 1 wherein said image modulator is operably configured to selectively transmit light from respective first and second portions of the single imaging path.

The apparatus of claim 5 wherein said image modulator is operably configured to selectively transmit light by alternately: blocking said first portion of the single imaging path while permitting light to be received through said second portion of the single imaging path; and blocking said second portion of the single imaging path while permitting light to be received through said first portion of the single imaging path.

The apparatus of claim 6 wherein said image modulator comprises a blocker disposed in the single imaging path and operably configured to move between first and second positions.

The apparatus of claim 6 wherein said image modulator comprises an optical element having first and second regions, said first and second regions operably configured to be selectively actuated to block said first and second portions of the single imaging path.

The apparatus of claim 8 wherein said image modulator comprises an optical element having a plurality of individually actuated elements and wherein said first and second regions comprise first and second selectively actuated groups of said plurality of elements.

The apparatus of claim 9 wherein said image modulator is operably configured to selectively vary an actuation pattern of said plurality of elements to cause the image modulator to reduce light transmission through each of the first and second regions.

The apparatus of claim 1 wherein said image modulator is operably configured to selectively change a state of polarization of light from at least one of the first and second portions of the single imaging path.

12. The apparatus of claim 1 wherein said image modulator is operably configured to selectively transmit light from respective first and second portions of the single imaging path in response to a synchronization signal.

13. The apparatus of claim 1 wherein said second relay lens comprises a plurality of lenses.

14. The apparatus of claim 13 wherein said second relay lens further comprises a lens group operably configured to produce an image at the image plane having a format corresponding to a format of an image recorder disposed to record said image at said image plane.

15. The apparatus of claim 14 wherein said lens group comprises at least one moveable lens element.

16. The apparatus of claim 1 wherein said image sensor is operably configured to generate electrical signals representing said first and second images formed at the image plane.

17. A method for generating three-dimensional image information at an image plane of an image recorder in response to receiving light captured by an imaging iens having a single imaging path with an associated field of view, the method comprising: imaging an exit pupil of the imaging lens to an aperture plane location within a housing, said housing having a first interface for mounting to the image recorder and a second interface for mounting the imaging lens; causing an image modulator located at or proximate to said aperture plane location within said housing to selectively permit light from respective first and second portions of the single imaging path to be directed toward said imaging plane; and forming corresponding first and second images at the image plane, said first and second images together being operable to represent three dimensional spatial attributes of objects within the field of view of the imaging lens.

18. The method of claim 17 wherein imaging said exit pupil comprises disposing a first relay lens within the housing to image said exit pupil to said aperture plane location.

19. The method of claim 18 wherein disposing said first relay lens comprises disposing a lens group to cause light captured by said imaging lens to be formatted for receipt by said first relay lens.

20. The method of claim 18 wherein disposing said lens group comprises disposing at least one moveable lens element within said housing.

21. The method of claim 17 wherein causing said image modulator to selectively permit light from respective first and second portions of the single imaging path to be directed toward said imaging plane comprises causing said image modulator to selectively transmit light from respective first and- second portions of the single imaging path.

22. The method of claim 21 wherein causing said image modulator to selectively transmit light comprises alternately: blocking said first portion of the single imaging path while permitting light to be received through said second portion of the single imaging path; and blocking said second portion of the single imaging path while permitting light to be received through said first portion of the single imaging path.

23. The method of claim 22 wherein alternately blocking said first and second portions of the single imaging path comprises causing a blocker disposed in the single imaging path to move between first and second positions.

24. The method of claim 22 wherein alternately blocking said first and second portions of the single imaging path comprises selectively actuating first and second regions of an optical element to selectively block said first and second portions of the single imaging path.

25. The method of claim 24 wherein the image modulator comprises a plurality of elements and wherein alternately blocking said first and second portions of the single imaging path comprises selectively actuating elements in first and second regions to selectively block said first and second portions of the single imaging path.

26. The method of claim 25 further comprising selectively varying an actuation pattern of said plurality of elements to cause the image modulator to reduce light transmission through each of the first and second regions.

27. The method of claim 17 wherein causing said image modulator to selectively permit light from respective first and second portions of the single imaging path to be directed toward said imaging plane comprises causing said image modulator to selectively change a state of polarization of light from at least one of the first and second portions of the single imaging path.

The method of claim 17 wherein causing said image modulator to selectively permit light from respective first and second portions of the single imaging path to be directed toward said imaging plane comprises causing said image modulator to selectively transmit light from respective first and second portions of the single imaging path in response to a synchronization signal.

The method of claim 17 wherein forming corresponding first and second images at the image plane comprises disposing a second relay lens within the housing to form corresponding first and second images at the image plane.

30. The method of claim 29 wherein disposing said second relay lens comprises disposing a plurality of lenses to form corresponding first and second images at the image plane.

31. The method of claim 30 wherein disposing said second relay lens comprises: disposing at least one moveable lens element within said housing; and positioning said at least one moveable lens element to cause to form corresponding first and second images at the image plane.

32. The method of claim 31 wherein forming said corresponding first and second images at the image plane further comprises disposing at least one moveable focus lens within said housing and positioning said focus element to focus said corresponding first and second images at the image plane.

33. The method of claim 17 wherein forming corresponding first and second images at the image plane comprises forming first and second images at an image sensor operable to generate electrical signals representing said first and second images.

34. An adapter apparatus for generating three-dimensional image information at an image plane of an image recorder in response to receiving light captured by an imaging lens having a single imaging path with an associated field of view, the apparatus comprising: a housing having a first interface for mounting to the image recorder and a second interface for mounting the imaging lens; means for imaging an exit pupil of the imaging lens to an aperture plane location within said housing; means for selectively permitting light from respective first and second portions of the single imaging path to be directed toward said imaging plane, said means for permitting being located at or proximate to said aperture plane location within said housing; and means for forming corresponding first and second images at the image plane, said first and second images together being operable to represent three dimensional spatial attributes of objects within the field of view of the imaging lens.

35. The apparatus of claim 34 wherein said means for imaging said exit pupil comprises: at least one moveable lens element within said housing; and means for positioning said at least one moveable lens element to cause said exit pupil to be imaged to said aperture plane location.

36. The apparatus of claim 34 wherein said means for selectively permitting light to be directed toward said imaging plane comprises means for selectively transmitting light from respective first and second portions of the single imaging path.

37. The apparatus - of claim 36 wherein said means for selectively transmitting light comprises means for alternately: blocking said first portion of the single imaging path while permitting light to be received through said second portion of the single imaging path; and blocking said second portion of the single imaging path while permitting light to be received through said first portion of the single imaging path.

38. The apparatus of claim 37 wherein said means for alternately blocking said first and second portions of the single imaging path comprises means for causing a blocker disposed in the single imaging path to move between first and second positions.

39. The apparatus of claim 37 wherein said means for alternately blocking said first and second portions of the single imaging path comprises an optical element operably configured to selectively block said first and second portions of the single imaging path.

40. The apparatus of claim 34 wherein said means for causing said image modulator to selectively permit light from respective first and second portions of the single imaging path to be directed toward said imaging plane comprises means for causing said image modulator to selectively change a state of polarization of light from at least one of the first and second portions of the single imaging path.

41. The apparatus of claim 34 wherein said means for forming corresponding first and second images at the image plane comprises: at least one moveable lens element within said housing; and means for positioning said at least one moveable lens element to cause to form corresponding first and second images at the image plane.

42. The apparatus of claim 41 wherein said means for forming said corresponding first and second images at the image plane further comprises means for focusing said corresponding first and second images at the image plane. The apparatus of claim 34 further comprising means for generating electrical signals representing said first and second images formed at the image plane.