WO2014028904A1 - Stereoscopic image capture - Google Patents

Abstract

An exemplary optical system may include a rig including capture devices and may address linearly and/or elliptically polarized light entering the rig. Embodiments may include capture devices disposed proximate to output ports of a beam splitting element. The lens optical axes of the capture devices may point in generally orthogonal directions to one another. The optical system may further include a polarization manipulating element disposed in a light path entering or exiting the beam splitting element.

Description

Stereoscopic image capture

Cross-reference to Related Application

[0001] This application relates and claims priority to commonly-assigned U.S. Provisional Patent Application No. 61/684,548, filed August 17, 2012, and entitled "Reduction of polarized light artifacts in stereoscopic image capture" and to commonly-assigned U.S. Provisional Patent Application No.61/684, 557, filed August 17, 2012, and entitled "Stereoscopic image capture with spatially-multiplexed aperture," all of which are incorporated herein by reference for all purposes.

Technical Field

[0002] The present disclosure generally relates to display technology and image capture, and more specifically, to two dimensional and three dimensional display technologies and image capture.

Background

[0003] Generally, current stereoscopic technologies may include functionality to capture, deploy, view and/or display three dimensional ("3D") content. 3-D or stereoscopic image presentation is enabled by presenting independent left and right eye views to a person. The independent left and right eye views have slight disparities in image location and scene which create the illusion of a three-dimensional volume.

Summary

[0004] An embodiment of a stereoscopic imaging system may comprise a beam splitting element operable to split incident light along an input light path and output light along at least two output light paths. The imaging system may further comprise capture devices disposed in the output light paths and a polarization manipulating element disposed in the input light path, the polarization manipulating element operable to manipulate the polarization of the incident light in the input light path such that an intensity difference between light in the output light paths is reduced. [0005] Another embodiment of a stereoscopic imaging system may comprise a beam splitting element operable to split incident light along an input light path and output light along at least two output light paths. The imaging system may also include capture devices disposed in the output light paths and quarter wave plates optically preceding the capture devices and disposed in the output light paths, the quarter wave plates being oriented at substantially 45 degrees relative to a horizontal direction or a vertical direction.

[0006] An embodiment of a method of manufacturing a stereoscopic imaging system may comprise providing a beam splitting element operable to split incident light along an input light path and output light along at least two output light paths. The method may also include disposing capture devices in the output light paths and disposing a polarization manipulating element in the input light path, the polarization manipulating element operable to manipulate the polarization of incident light in the input light path such that an intensity difference between light in the output light paths is reduced.

[0007] Another embodiment of a method of manufacturing a stereoscopic imaging system may comprise providing a beam splitting element operable to split incident light along an input light path and output light along at least two output light paths. The method may also include disposing capture devices in the output light paths and disposing quarter wave plates optically preceding the capture devices in the output light paths, the quarter wave plates being oriented at substantially 45 degrees relative to a horizontal direction or a vertical direction.

Brief Description of the Drawings

[0008] Embodiments are illustrated by way of example in the accompanying figures, in which like reference numbers indicate similar parts, and in which:

[0009] FIGURE 1 is a schematic diagram illustrating a top view of a side-by-side rig including cameras;

[0010] FIGURE 2 A is a schematic diagram illustrating a side view of a beam splitter rig including cameras;

[0011] FIGURE 2B is a schematic diagram illustrating a perspective-back view of a beam splitter rig of FIGURE 2A; [0012] FIGURE 3 is a schematic diagram illustrating a side view of an exemplary imaging system having a polarization manipulating element, in accordance with the present disclosure;

[0013] FIGURE 4 is a schematic diagram illustrating an embodiment of the polarization manipulating element shown in FIGURE 3, in accordance with the present disclosure;

[0014] FIGURE 5 is a schematic diagram illustrating another embodiment of the polarization manipulating element shown in FIGURE 3, in accordance with the present disclosure;

[0015] FIGURE 6 is a schematic diagram illustrating yet another embodiment of the polarization manipulating element shown in FIGURE 3, in accordance with the present disclosure;

[0016] FIGURE 7 is a schematic diagram illustrating another exemplary embodiment of the polarization manipulating element shown in FIGURE 3, in accordance with the present disclosure;

[0017] FIGURE 8 is a schematic diagram illustrating another exemplary embodiment of the polarization manipulating element shown in FIGURE 3, in accordance with the present disclosure; and

[0018] FIGURE 9 is a schematic diagram illustrating a side view of an exemplary imaging system, in accordance with the present disclosure.

Detailed Description

[0019] To capture live scenes for stereoscopic imaging, two cameras may be used for the independent views. The cameras are physically offset from one another, with their separation, termed interaxial separation or IA, and rotation in the horizontal plane, termed vergence or convergence, controlling the depth and location of the scene volume (respectively) as the imagery is displayed to the viewer.

[0020] Generally, two broad categories of stereoscopic camera systems or rigs include side -by- side rigs or beam splitter rigs. FIGURE 1 is a schematic diagram illustrating a top view of a side -by-side rig 100. The side-by-side rig 100 as illustrated in FIGURE 1 may include two cameras 102a and 102b having respective optical axes 104a and 104b defined through respective camera lenses 106a and 106b. The cameras 102a and 102b may be affixed to a mechanical rail 101 with optical axes 104a and 104b pointing generally in the same direction.

[0021] As previously discussed, the cameras 102a and 102b are physically offset from one another, with the separation referred to herein as an interaxial separation, or "IA.' he IA may be the distance between the centers of the camera lenses 106a and 106b; stated differently the IA may be generally determined by the separation of the optical axes 104a and 104b of the camera lenses 106a and 106b. The rotation in the horizontal plane, or convergence, may be determined by the angle of the camera lenses 106a and 106b with respect to one another in the horizontal plane. It is to be appreciated that the horizontal plane is the plane of the page, and rotation in the horizontal plane referred to herein may be a rotation about axis that is normal to the page. The minimum IA for side-by-side rigs may be determined by the physical size of the camera and/or lens. For close-up scenes, the minimum IA in the rig 100 may produce too large a disparity in the stereoscopic imagery for comfortable viewing.

[0022] FIGURE 2A is a schematic diagram illustrating a side view of a beam splitter rig 200, and FIGURE 2B is a schematic diagram illustrating a back view of the beam splitter rig 200. The beam splitter rig 200 may include two cameras 202a and 202b. Cameras 202a and 202b may have respective optical axes 204a and 204b defined by respective camera lenses 206a and 206b. The cameras 202a and 202b may be affixed to a mechanical support (not shown) such that the optical axes 204a and 204b point in approximately orthogonal directions to one another. A beam splitting element 201 may be placed in the overlapping frustums formed by the fields of view 208a and 208b of the two cameras 202a and 202b. The beam splitting element 201 may be any suitable beam splitter known in the art, including but not limited to a cube, a prism, or a mirror such as a half-silvered plate mirror. One of the cameras 202a and 202b may capture an image reflected by the beam splitting element 201, while the other may capture an image transmitted by the beam splitting element 201.

[0023] The IA of the beam splitter rig 200 may be adjusted by sliding the cameras 202a and 202b along rails (not shown) substantially perpendicular to the optical axes 204a and 204b. The convergence of the beam splitter rig 200 may be determined by the angular rotation of the lenses 206a and 206b in their respective horizontal planes. Unlike the rig 100, the beam splitter rig 200 does not have a minimum IA, as the two cameras 202a and 202b do not physically occupy the same space. In an embodiment, the beam splitter rig 200 may however have a maximum IA, which may be determined by the size of the beam splitting element 201 and/or the mechanical support rails (not shown).

[0024] When capturing two images, filmmakers may employ various shooting methods such as parallel or converged shooting methods. Parallel shooting may include locating both cameras such that the optical axes of the cameras are approximately parallel when viewing the scene. In one embodiment, the beam splitter rig 200 may be used for parallel shooting, and the optical axes 204a and 204b of the cameras 202a and 202b, respectively, may be approximately perpendicular in physical space, and optically parallel as one optical axis is reflected by the beam splitting element 201. When parallel shooting is used on the set, the amount of IA determines scene volume. Convergence or locating the scene volume relative to the viewing screen may then be determined by horizontally translating the images, an operation termed HIT, in post-production.

[0025] Converged shooting may be enabled by adjusting the IA and/or convergence of the capture cameras. Converged shooting may provide more subtle viewing around objects in a scene which may result in a better sense of "roundness" in the stereoscopic image. Converging the cameras may induce keystone distortion, of opposite sense, in the captured left and right eye imagery, and the keystone distortion may be addressed with geometric correction or image warping in post-production. Parallel shooting theoretically requires little to no correction of keystone distortion in the two images. Converged shooting can also utilize HIT in post- production to fine tune the convergence.

[0026] In some embodiments, the beam splitter rig 200 may produce both local and global color and luminance mismatches between the two camera views, which may lead to post-production correction of the two images. Optical wavefront errors in the beam splitting element 201 can induce asymmetric distortions in the two images. Linearly polarized light, such as a reflection from a water surface, or elliptically polarized light (e.g. reflected from a vehicle window), may be split unequally in the two optical paths, thus creating undesirable differences in the two images. These errors may result in time consuming fixes in post-production, becoming costly and slowing down the workflow and degrading the final stereoscopic image quality.

[0027] FIGURE 3 is a schematic diagram illustrating a side view of a system 300 in an exemplary embodiment. The system 300 may include capture devices 302a and 302b, and may be configured to address above discussed issues associated with the linearly and/or elliptically polarized light entering the rig 200. Similar to the embodiments of FIGURES 2 A and 2B, capture devices 302a and 302b may include cameras affixed to mechanical support (not shown) such that the optical axes point in generally orthogonal directions to one another. It is to be appreciated that the optical axes may point in general orthogonal directions while deviating from relative orthogonal alignment to allow for converged shooting as discussed above. The system 300 may include a beam splitting element 301 disposed in the overlapping frustums formed by the fields of view of the capture devices 302a and 302b. The beam splitting element 301 may be operable to split incident light along an input light path 308 and output light along at least two output light paths 304a and 304b.The input light path 308 may pass through an input port 306 and the output light paths 304a and 304b may pass through output ports 307a and 307b, respectively. It is to be appreciated that the beam splitting element 301 may be configured as a plate, a cube, a wire grid polarizing beam splitter, or any other configuration suitable for the embodiments discussed herein, and the input port 308 and output ports 307a and 307b may be defined physically by a physical portion of the beam splitting element 301 or optically by the functionalities of the of the beam splitting element 301.

[0028] The system 300 may further include a polarization manipulating element 303 proximate to an input port 306 of the beam splitting element 301 in the input light path 308. In an exemplary embodiment, the polarization manipulating element 303 may be configured to manipulate the polarization of light in the light path such that an intensity difference between light in the output light paths 304a and 304b is reduced. In an embodiment, the polarization manipulating element 303 may be a combination of static wave plates, an electronically driven liquid-crystal modulator and/or polarizers, or any combination thereof, as described below.

[0029] Light reflecting from a horizontal surface such as a pool of water is attenuated in approximately the vertical direction and substantially not attenuated in the horizontal direction, resulting in substantially horizontally polarized light. Horizontally polarized light (p) and vertically polarized light (s) may have different transmission and reflection properties at the beam splitter reflecting face, and may cause undesirable intensity differences in the left and right eye images. [0030] FIGURE 4 is a schematic diagram of an embodiment of the polarization manipulating element 400. The configuration of polarization manipulating element 400 may be incorporated into similar elements disclosed in the present disclosure, including the polarization manipulating element 303 in FIGURE 3. Referring to FIGURES 3 and 4, in one embodiment, the polarization manipulating element 400 may comprise a quarter-wave retarder 402 oriented at substantially 45 degrees to the horizontal or vertical direction. In an embodiment, the quarter-wave retarder 308 may be a quarter wave plate and disposed at or near a surface of the polarization manipulating element 400. In this embodiment, linearly polarized light that is substantially horizontally or vertically aligned may be manipulated by the polarization manipulating element 400 to become circularly polarized light. The circularly polarized light may have approximately equal components of s-polarized light and p-polarized light at the beam splitter reflecting face of the beam splitting element 301, and thereby split the light intensity substantially equally between the reflected and transmitted paths. In an embodiment, the quarter-wave retarder 400 may be made achromatic to better circularize the most of or the entire spectrum of available light.

[0031] FIGURE 5 is a schematic diagram of another embodiment of the polarization manipulating element 500. The configuration of polarization manipulating element 500 may be incorporated into similar elements disclosed in the present disclosure, including the polarization manipulating element 303 in FIGURE 3. Referring to FIGURES 3 and 5, in one embodiment, the polarization manipulating element 500 may comprise a linear polarizer 502 oriented at substantially 45 degrees to the horizontal plane. The linear polarizer 502 may be disposed at or near a surface of the polarization manipulating element 500. The linear polarizer 502 at the substantial 45 degrees orientation may reduce the incoming light to approximately a single linear state, having approximately equal components of s-polarization and p-polarization. The sums of the s-components and p-components reaching each camera may then be approximately equal, thus substantially minimizing intensity differences in the images. Since the linear polarizer 502 is a static optical component, the reduction of intensity differences may be achieved statically, which allows for calibration of the capture equipments to further reduce any residual intensity difference. This static reduction may be achieved with any embodiments of the present disclosure using no active elements.

[0032] FIGURE 6 is a schematic diagram of another embodiment of the polarization manipulating element 600. The configuration of polarization manipulating element 600 may be incorporated into similar elements disclosed in the present disclosure, including the polarization manipulating element 303 in FIGURE 3. Referring to FIGURES 3 and 6, in one embodiment, the polarization manipulating element 600 may comprise may comprise a circular polarizer 602 disposed at or near a surface of the polarization manipulating element 600. The circular polarizer 602 may include a linear polarizer 604 and a quarter wave retarder 606 optically following the linear polarizer 604. Incoming linearly polarized light may again become circularly polarized by passing through the quarter wave retarder 606. Like the quarter wave retarder 402, the quarter wave retarder 606 may also be achromatic. The linear polarizer 604 which may be oriented at substantially 45 degrees like the linear polarizer 502 in FIGURE 5.

[0033] FIGURE 7 is a schematic diagram of another embodiment of the polarization manipulating element 700. The configuration of polarization manipulating element 700 may be incorporated into similar elements disclosed in the present disclosure, including the polarization manipulating element 303 in FIGURE 3. Referring to FIGURES 3 and 7, in one embodiment, the polarization manipulating element 700 may comprise an active liquid-crystal (LC) element 702. The LC element 702 may be disposed at or near a surface of the polarization manipulating element 700. Not all of the problematic light splitting in a beam splitter is due to linearly polarized light. Elliptical states that may be input to the beam splitter can also have different left and right eye intensities after the beam splitter. An active liquid-crystal cell is one possible solution to this issue. The LC element 702 of the polarization manipulating element 700 may include an active liquid-crystal (LC) cell or multiple LC cells, and the LC element 702 may be driven substantially randomly or deterministically through a range of approximately zero to full- wave or half- wave at a rate faster than the capture rate of the capture devices 302a and 302b. The active LC element 702 may scramble the incoming polarization, providing randomly polarized light to the beam splitting element 301 for most or substantially all input states, such as linear, circular or elliptical and facilitating approximately equal intensity splitting between the two outputs of the beam splitting element 301. In an embodiment, to allow for linear polarization, the polarization manipulating element 700 may optionally include a polarizing element 704 disposed optically before the LC element 702 as shown in FIGURE 7, and the polarizing element 320 may include the linear polarizer 502 shown in FIGURE 5. In an embodiment, to provide circular polarization outputs, the polarization manipulating element 700 may optionally include a polarizing element 704 configured to include the quarter wave retarder 402 shown in FIGURE 4 or the circular polarizer 602 shown in FIGURE 6. It is to be appreciated that the polarizing element 704 may be disposed optically following the LC element 702 instead of before the LC element 702 in any of the embodiments discussed above. It is to be further appreciated that the LC element 702 may include any liquid crystal-based polarization switch known in the art, including but not limited to, a push-pull modulator as described in commonly-owned U.S. Pat. Nos. 4,792,850, and 7,477,206, a pi-cell as described in commonly- owned U.S. Pat. App. Ser. No. 12/156,683, a ferro-electric LC modulator as described in commonly-owned U.S. Pat. No. 6,078,374, a twisted nematic cell as described in commonly- owned U.S. Pat. No. 6,172,722, or an achromatic polarization switch as described in commonly- owned U.S. Pat. No. 7,528,906, all of which are incorporated by reference herein in their entirety.

[0034] FIGURE 8 is a schematic diagram of another embodiment of the polarization manipulating element 800. The configuration of polarization manipulating element 800 may be incorporated into similar elements disclosed in the present disclosure, including the polarization manipulating element 303 in FIGURE 3. Referring to FIGURES 3 and 8, in one embodiment, the polarization manipulating element 800 may comprise a spinning retarder or rotator 802 which may relieve issues with elliptical states entering the beam splitter. The spinning retarder or rotator 802 may act as a continuously variable rotator, rotating the incoming polarization state through a range angles in a single capture frame. If the spinning retarder or rotator 802 is spun at a rate higher than the capture rate of the capture devices 302a and 302b, then the time-averaged polarization state reaching the beam splitter may be effectively random, allowing for substantially equal splitting of intensities at the beam splitting element 301. An exemplary embodiment of the spinning retarder or rotator 802 is described in the commonly -owned U.S. Pat. No. 8,408,708, entitled, "Polarization modulation wheel," which is herein incorporated by reference in its entirety.

[0035] FIGURE 9 is a schematic diagram illustrating a side view of an imaging system 900 in an exemplary embodiment. The system 900 may include capture devices 902a and 902b affixed to a mechanical support (not shown) such that the optical axes 904a and 904b point in generally orthogonal directions to one another. The system 900 may include a beam splitting element 901 disposed in the overlapping frustums formed by the fields of view of the capture devices 902a and 902b. The beam splitting element 901 may be operable to split incident light along an input light path 908 and output light along at least two output light paths 904a and 904b. The input light path 908 may pass through an input port 906 and the output light paths 904a and 904b may pass through output ports 907a and 907b, respectively. It is to be appreciated that the beam splitting element 901 may be configured as a plate, a cube, or any other configuration suitable for the embodiments discussed herein, and the input port 908 and output ports 907a and 907b may be defined physically by a physical portion of the beam splitting element 901 or optically by the functionalities of the of the beam splitting element 901.

[0036] The system 900 may further include quarter wave retarders 940a and 940b disposed proximate to output ports 907a and 907b and in the output light paths 904a and 904b, respectively. The quarter wave retarders 940a and 940b may optically precede the capture devices 902a and 902b. Linearly or elliptically polarized light at the camera sensor (not shown) of the capture devices 902a and 902b may cause a different electro-optical response based on the rotation angle of the polarization axis. Quarter wave retarders 940a and 940b may be disposed in the output light paths exiting the output ports 907a and 907b, respectively, with an orientation of substantially 45 degrees relative to the horizontal or vertical. The quarter wave retarders may function to circularize light exiting the output ports 907a and 907b, and induce a more uniform response between capture devices. In an embodiment, the quarter wave retarders 940a and 940b may comprise static quarter wave plates and may be oriented at substantially 45 degrees to the vertical or horizontal (i.e. +/- 45 degrees to the sagittal or tangential ray fans through the beam splitting element). In an embodiment, the quarter wave retarders 940a and 940b may be substantially achromatic.

[0037] It is to be appreciated that in some embodiments, the system 900 may further include the polarization manipulating element 903 disposed proximate to an input port 906 of the beam splitting element 901 and configured as discussed above with respect to FIGURES 3-8. As such, the quarter wave retarders 940a and 940b may work in cooperation with any combination of the quarter wave retarder 400, linear polarizer 500, circular polarizer 600, the LC element 700, and or the spinning retarder/rotator 800 to reduce intensity differences.

[0038] It is to be further appreciated that in any of the above discussed embodiments, the beam splitting element 301 or 901 may be provided by a polarizing beam splitter (PBS), which may also assist with creating an approximately even split of light into the two optical paths. For example, a dichroic or wire grid polarizing beam splitter may have better uniformity of operation over varying incoming ray angles of incidence than a non-polarizing half-mirror or dichroic beam splitter. The PBS 301 or 901 may be used in cooperation with the polarization manipulating elements 400, 500, 600, 700, or 800 discussed above.

[0039] It should be noted that embodiments of the present disclosure may be used in a variety of optical capture systems. Aspects of the present disclosure may be used with practically any apparatus related to optical image capture and electrical devices, optical systems, capture systems or any apparatus that may contain any type of optical system. Accordingly, embodiments of the present disclosure may be employed in optical systems, devices used in visual and/or optical presentations, capture peripherals and so on and in a number of environments including consumer devices, still and video cameras, camera phones, smart phones, webcams, commercial-grade cameras, security cameras, vehicle-based cameras, and so on.

[0040] Additionally, it should be understood that the embodiment is not limited in its application or creation to the details of the particular arrangements shown, because the embodiment is capable of other variations. Moreover, aspects of the embodiments may be set forth in different combinations and arrangements to define embodiments unique in their own right. Also, the terminology used herein is for the purpose of description and not of limitation.

[0041] As may be used herein, the terms "substantially" and "approximately" provide an industry-accepted tolerance for its corresponding term and/or relativity between items. Such an industry-accepted tolerance ranges from zero percent to ten percent and corresponds to, but is not limited to, component values, angles, et cetera. Such relativity between items ranges between approximately zero percent to ten percent.

[0042] While various embodiments in accordance with the principles disclosed herein have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of this disclosure should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with any claims and their equivalents issuing from this disclosure. Furthermore, the above advantages and features are provided in described embodiments, but shall not limit the application of such issued claims to processes and structures accomplishing any or all of the above advantages. [0043] Additionally, the section headings herein are provided for consistency with the suggestions under 37 CFR 1.77 or otherwise to provide organizational cues. These headings shall not limit or characterize the embodiment(s) set out in any claims that may issue from this disclosure. Specifically and by way of example, although the headings refer to a "Technical Field," the claims should not be limited by the language chosen under this heading to describe the so-called field. Further, a description of a technology in the "Background" is not to be construed as an admission that certain technology is prior art to any embodiment(s) in this disclosure. Neither is the "Summary" to be considered as a characterization of the embodiment(s) set forth in issued claims. Furthermore, any reference in this disclosure to "invention" in the singular should not be used to argue that there is only a single point of novelty in this disclosure. Multiple embodiments may be set forth according to the limitations of the multiple claims issuing from this disclosure, and such claims accordingly define the embodiment(s), and their equivalents, that are protected thereby. In all instances, the scope of such claims shall be considered on their own merits in light of this disclosure, but should not be constrained by the headings set forth herein.

Claims

Claims What is claimed is:

1. A stereoscopic imaging system comprising:

a beam splitting element operable to split incident light along an input light path and output light along at least two output light paths;

capture devices disposed in the output light paths; and

a polarization manipulating element disposed in the input light path, the polarization manipulating element operable to manipulate the polarization of the incident light in the input light path such that an intensity difference between light in the output light paths is reduced.

2. The stereoscopic imaging system of claim 1, wherein the polarization manipulating

element comprises a quarter wave plate oriented at substantially 45 degrees to a horizontal direction or a vertical direction.

3. The stereoscopic imaging system of claim 2, wherein the quarter wave plate is

substantially achromatic.

4. The stereoscopic imaging system of claim 1, wherein the polarization manipulating

element comprises a linear polarizer oriented at substantially 45 degrees to a horizontal direction or a vertical direction.

5. The stereoscopic imaging system of claim 1, wherein the polarization manipulating

element comprises circular polarizer.

6. The stereoscopic imaging system of claim 5, wherein the circular polarizer comprises a linear polarizer oriented at substantially 45 degrees to a horizontal direction or a vertical direction and a quarter wave plate optically following the linear polarizer.

7. The stereoscopic imaging system of claim 1, wherein the polarization manipulating

element comprises a liquid-crystal element operable to be driven substantially at a rate faster than a capture rate of the capture devices.

8. The stereoscopic imaging system of claim 1, wherein the system further comprises

quarter wave plates disposed in the output light paths.

9. The stereoscopic imaging system of claim 1, wherein the beam splitting element

comprises a polarizing beam splitter.

10. The stereoscopic imaging system of claim 8, wherein the polarizing beam splitter comprises a wire grid polarizing beam splitter or a dichroic polarizing beam splitter.

11. A stereoscopic imaging system comprising:

a beam splitting element operable to split incident light along an input light path and output light along at least two output light paths;

capture devices disposed in the output light paths; and

quarter wave plates optically preceding the capture devices and disposed in the output light paths, the quarter wave plates being oriented at substantially 45 degrees relative to a horizontal direction or a vertical direction.

12. The stereoscopic imaging system of claim 11, wherein the quarter wave plates are

substantially achromatic.

13. The stereoscopic imaging system of claim 11, wherein the beam splitting element

comprises a polarizing beam splitter.

14. The stereoscopic imaging system of claim 14 wherein the polarizing beam splitter comprises a wire grid polarizing beam splitter or a dichroic polarizing beam splitter.

15. A method of manufacturing a stereoscopic imaging system, comprising:

providing a beam splitting element operable to split incident light along an input light path and output light along at least two output light paths;

disposing capture devices in the output light paths; and

disposing a polarization manipulating element in the input light path, the polarization manipulating element operable to manipulate the polarization of incident light in the input light path such that an intensity difference between light in the output light paths is reduced.

16. The method of claim 15, wherein the polarization manipulating element comprises a quarter wave plate, and the method comprises orienting the quarter wave plate at substantially 45 degrees to a horizontal direction or a vertical direction.

17. The method of claim 15, wherein the polarization manipulating element comprises a linear polarizer, and the method comprises orienting the linear polarizer at substantially 45 degrees to a horizontal direction or a vertical direction.

18. The method of claim 15, wherein the polarization manipulating element comprises a circular polarizer, the circular polarizer comprising a linear polarizer and a quarter wave plate optically following the linear polarizer, and wherein the method comprises orienting the linear polarizer at substantially 45 degrees to a horizontal direction or a vertical direction.

19. The method of claim 15, wherein the polarization manipulating element comprises a liquid-crystal element operable to be driven substantially at a rate faster than a capture rate of the capture devices.

20. A method of manufacturing a stereoscopic imaging system, comprising:

providing a beam splitting element operable to split incident light along an input light path and output light along at least two output light paths;

disposing capture devices in the output light paths; and

disposing quarter wave plates optically preceding the capture devices in the output light paths, the quarter wave plates being oriented at substantially 45 degrees relative to a horizontal direction or a vertical direction.