Spatio-temporal light field cameras

• US 9,179,126 B2
• Filed: 10/24/2012
• Issued: 11/03/2015
• Est. Priority Date: 06/01/2012
• Status: Expired due to Fees

• Current Assignee: Ostendo Technologies Inc.
• Original Assignee: Ostendo Technologies Inc.
• Inventors: El-Ghoroury, Hussein S., Alpaslan, Zahir Y., Cai, Jingbo, Maiers, Marty, Warner, Philip, McNeill, Dale A.
• Primary Examiner(s): Giles, Nicholas
• Assistant Examiner(s): Tissire, Abdelaaziz
• Application Number:
  US13/659,776
• Publication Number:
  US 20130321581A1
• Time in Patent Office: 1,105 Days
• US Class Current: 1/1
• CPC Class Codes: G02B 13/0085 employing wafer level optics
• CPC Class Codes: G02B 27/1066 for enhancing image performance, like resolution, pixel numbers, dual magnifications or dynamic range, by tiling, slicing or overlapping fields of view
• CPC Class Codes: G02B 27/1073 characterized by manufacturing or alignment methods
• CPC Class Codes: G02B 27/123 The splitting element being a lens or a system of lenses, including arrays and surfaces with refractive power
• CPC Class Codes: G02B 3/0012 characterised by the manufacturing method
• CPC Class Codes: G02B 3/0056 arranged along two different directions in a plane, e.g. honeycomb arrangement of lenses G02B3/0043 takes precedence; miniaturised objectives for electronic devices employing wafer level optics G02B13/0085
• CPC Class Codes: G02B 30/27 involving lenticular arrays
• CPC Class Codes: G06T 2207/10024 Color image
• CPC Class Codes: G06T 2207/10028 Range image; Depth image; 3D point clouds
• CPC Class Codes: G06T 2207/10052 Images from lightfield camera
• CPC Class Codes: G06T 7/557 from light fields, e.g. from plenoptic cameras
• CPC Class Codes: H04N 13/207 using a single 2D image sensor
• CPC Class Codes: H04N 13/282 for generating image signals corresponding to three or more geometrical viewpoints, e.g. multi-view systems
• CPC Class Codes: H04N 13/286 having separate monoscopic and stereoscopic modes
• CPC Class Codes: H04N 13/289 Switching between monoscopic and stereoscopic modes
• CPC Class Codes: H04N 23/00 Cameras or camera modules comprising electronic image sensors; Control thereof
• CPC Class Codes: H04N 23/16 Optical arrangements associated therewith, e.g. for beam-splitting or for colour correction
• CPC Class Codes: H04N 23/45 for generating image signals from two or more image sensors being of different type or operating in different modes, e.g. with a CMOS sensor for moving images in combination with a charge-coupled device [CCD] for still images
• CPC Class Codes: H04N 23/54 Mounting of pick-up tubes, electronic image sensors, deviation or focusing coils
• CPC Class Codes: H04N 23/57 Mechanical or electrical details of cameras or camera modules specially adapted for being embedded in other devices
• CPC Class Codes: H04N 23/661 : Transmitting camera control signals through networks, e.g. control via the Internet
• CPC Class Codes: H04N 23/667 : Camera operation mode switching, e.g. between still and video, sport and normal or high- and low-resolution modes
• CPC Class Codes: H04N 23/67 : Focus control based on electronic image sensor signals
• CPC Class Codes: H04N 23/68 : for stable pick-up of the scene, e.g. compensating for camera body vibrations
• CPC Class Codes: H04N 23/80 : Camera processing pipelines; Components thereof
• CPC Class Codes: H04N 23/815 : for controlling the resolution by using a single image
• CPC Class Codes: H04N 23/90 : Arrangement of cameras or camera modules, e.g. multiple cameras in TV studios or sports stadiums
• CPC Class Codes: H04N 23/951 : by using two or more images to influence resolution, frame rate or aspect ratio
• CPC Class Codes: H04N 23/957 : Light-field or plenoptic cameras or camera modules
• CPC Class Codes: H04N 25/48 : Increasing resolution by shifting the sensor relative to the scene
• CPC Class Codes: H04N 5/04 : Synchronising for television systems using pulse code modulation H04N7/56

Abstract

Spatio-temporal light field cameras that can be used to capture the light field within its spatio temporally extended angular extent. Such cameras can be used to record 3D images, 2D images that can be computationally focused, or wide angle panoramic 2D images with relatively high spatial and directional resolutions. The light field cameras can be also be used as 2D/3D switchable cameras with extended angular extent. The spatio-temporal aspects of the novel light field cameras allow them to capture and digitally record the intensity and color from multiple directional views within a wide angle. The inherent volumetric compactness of the light field cameras make it possible to embed in small mobile devices to capture either 3D images or computationally focusable 2D images. The inherent versatility of these light field cameras makes them suitable for multiple perspective light field capture for 3D movies and video recording applications.

Claims

1. A light field camera comprising:

a micro photo-detector array device having a light detection surface defining a two dimensional array of pixels, each pixel in the two dimensional array of pixels being a light detector that is individually addressable to output an electrical signal responsive to an intensity of light coupled into an aperture of the respective pixel, the two dimensional array of pixels being subdivided into two dimensional groups of pixels; and

a micro lens array of micro lens elements;

the micro photo-detector array device and the micro lens array being assembled together as a single assembly;

each micro lens element of the micro lens array being associated and aligned relative to a respective group of pixels, with each micro lens element optically mapping light that impinges an aperture of the respective micro lens element from each of a discrete set of directions within a light field, as defined by an angular extent of the respective micro lens element, onto a respective pixel in the respective group of pixels, the discrete set of directions defining an angular resolution between adjacent directions and an angular extent of the discrete set of directions;

the micro photo-detector array device and the micro lens array being mounted to be temporally angularly articulated as a single assembly about two orthogonal axes parallel to a plane of the light detection surface of the micro photo-detector array device and at least through a maximum articulation angle;

the temporal angular articulation having a periodicity selected to enable temporal coverage of the maximum articulation angles within an image frame capture duration;

the temporal angular articulation about the two axes expanding the angular extent and/or the angular resolution in a direction about the axis of the temporal angular articulation; and

,

wherein the temporal angular articulation is either temporally continuous or discrete, and has a repetition rate that is proportional to and synchronized with an image capture frame rate, whereby the maximum angular articulation around each of the two orthogonal axes determines a full angular extent of the light field camera, an angular coverage shape it subtends and an aspect ratio of the angular coverage shape.

2. The light field camera of claim 1 wherein each pixel is individually addressable to output the electrical signal also responsive to the color of light coupled into an aperture of the respective pixel.

3. The light field camera of claim 1 wherein each micro lens element is a Fourier lens system.

4. The light field camera of claim 1 wherein each micro lens element optically maps light that impinges an aperture of the respective micro lens element from a discrete set of directions within a light field defined by an angular extent of the respective micro lens element onto the corresponding pixels within the respective group of pixels.

5. The light field camera of claim 4 wherein the micro lens elements are truncated to each have respective dimensional aspects match that of the respective two dimensional group of pixels, and each have their respective optical center aligned with a center of their respective two dimensional group of pixels.

6. The light field camera of claim 4 wherein the angular articulation temporally expands the angular extent of the respective micro lens element onto the corresponding group of pixels about each axis by a maximum angular articulation, thereby temporally expanding a detectable light field size and increasing the number of directions in the discrete set of directions about each axis by a ratio of said angular extent expansion to the angular extent along the axis of the temporal angular articulation.

7. The light field camera of claim 6 wherein each pixel within each group of pixels, being individually addressable, together with the association of each pixel within each group of pixels with the temporally expanded discrete set of directions allowing the addressability of the pixels over the temporally expanded discrete set of directions, enables the light field camera to detect the light that impinges an aperture of the light field camera from the expanded light field size defined by the discrete set of directions comprising the set of the temporally expanded discrete set of directions.

8. The light field camera of claim 7 wherein each micro photo-detector array device detects individual pixel color and intensity, thereby enabling the light field camera to detect color, intensity and direction of light that impinges the aperture of the light field camera from the expanded light field size defined by a discrete set of directions comprising the temporally expanded discrete set of directions.

9. The light field camera of claim 6 wherein the temporal angular articulation causes any individual directions within the expanded discrete set of directions to be detected during a time interval during which the respective light direction falls within the temporally articulated angular extent.

10. The light field camera of claim 6 wherein each pixel of each of the groups of pixels is individually addressable to detect color, intensity and direction of the light that impinges an aperture of the light field camera, thereby enabling the light field camera to spatially detect the intensity, color and direction of the light that impinges the aperture of the light field camera within the expanded light field size.

11. The light field camera of claim 10 wherein the temporal angular articulation is about two orthogonal axes, and expands the angular extent of the respective micro lens element onto a corresponding group of pixels about each axis by a maximum angular articulation, thereby temporally expanding a detectable light field size and increasing the number of directions to an expanded discrete set of directions about each axis by a ratio of the angular extent expansion to the angular extent along the respective articulation axis, the light field camera having a spatial resolution that is determined by the number of groups of pixels along the respective axis and having a directional resolution that is determined by the number of individual directions within the temporally expanded discrete set of directions.

12. The light field camera of claim 11:

wherein the temporal angular articulation is either temporally continuous or discrete, and has a repetition rate that is proportional to and synchronized with an image capture frame rate, whereby the maximum angular articulation around each of the two orthogonal axes determines the expanded angular extent of the light field camera, an angular coverage shape it subtends and an aspect ratio of the angular coverage shape; and

wherein the temporal angular articulation around each of the two orthogonal axes is at least equal to the image capture frame rate multiplied by a factor that equals a ratio of a size in degrees of the expanded angular extent along each respective axis to a size in degrees of the angular extent about the respective axes;

whereby the light field camera records a light field defined by spatial coordinates, within the groups of pixels, a set of angular directional coordinates defined by the two dimensional array of pixels and temporal values of the articulation angle.

13. The light field camera of claim 11 wherein the spatial resolution and directional resolution of the light field camera are determined by the size of the two dimensional groups of pixels, a resolution and pixel pitch of the micro photo-detector array device, a pitch of the micro lens array, the angular extent and the maximum articulation angle.

14. The light field camera of claim 4:

wherein the micro lens elements are truncated to each have respective dimensional aspects match that of the respective two dimensional group of pixels; and

wherein an optical center of the micro lens element at a center of the micro lens array is aligned with a center of its group of pixels, and the micro lens elements away from a center of the micro lens array have their optical centers offset from the center of their respective group of pixels, with the offset increasing for micro lens elements further away from the center of the micro lens array.

15. The light field camera of claim 1:

wherein the temporal angular articulation is about two orthogonal axes; and

wherein the temporal angular articulation is either temporally continuous or discrete, and has a repetition rate that is proportional to and synchronized with an image capture frame rate, whereby the maximum angular articulation around each of the two axes determines the expanded angular extent of the light field camera, an angular coverage shape it subtends and an aspect ratio of the angular coverage shape;

wherein the temporal angular articulation temporally expands the angular extent of the respective micro lens element onto a corresponding group of pixels about each axis by a maximum angular articulation, thereby temporally expanding a detectable light field size and increasing the number of directions to an expanded discrete set of directions about each axis by a ratio of the angular extent expansion to the angular extent along the respective articulation axis, the light field camera having a spatial resolution that is determined by the number of groups of pixels along the respective axis and having a directional resolution that is determined by the number of individual directions within the temporally expanded discrete set of directions; and

wherein the offset of the optical centers of the micro lens elements enable an increase of directional resolution without sacrificing either the spatial resolution or the full angular extent of the light field camera.

16. The light field camera of claim 1:

wherein the angular articulation around each of the two orthogonal axes is at least equal to the image capture frame rate multiplied by a factor that equals a ratio of a size in degrees of the full angular extent along each respective axis to a size in degrees of the angular extent.

17. The light field camera of claim 1 having an angular resolution defined as an angular separation between individual directions within the temporally expanded discrete set of directions and determined by a fractional value of the angular extent being addressed by each pixel within a pixel group.

18. The light field camera of claim 17:

wherein the temporal angular articulation is about two orthogonal axes; and

wherein the temporal angular articulation temporally expands the angular extent of the respective micro lens element onto the corresponding group of pixels about each axis by a maximum angular articulation, thereby temporally expanding a detectable light field size and increasing the number of directions to an expanded discrete set of directions about each axis by a ratio of an angular extent expansion to the angular extent along the respective articulation axis, the light field camera having a spatial resolution that is determined by the number of groups of pixels along the respective axis and having a directional resolution that is determined by the number of individual directions within the temporally expanded discrete set of directions, and

wherein the maximum angular articulation is selected to affect an increase in the spatial resolution for a given value of the angular resolution.

19. The light field camera of claim 18:

wherein each of the micro lens elements of the micro lens array is an optical system comprising at least one refracting surface whereby the number of said refracting surfaces and their optical characteristics determine the angular extent and affect the angular resolution.

20. The light field camera of claim 19 wherein the optical system of the micro lens elements is a Fourier optical system that is focused at infinity and maps directional aspects of the light field that impinges its aperture within the angular extent onto the two dimensional array of pixels comprising the pixel groups.

21. The light field camera of claim 1 wherein the light field camera is embedded in a mobile device.

22. The light field camera of claim 1 having a temporal angular articulation wherein the light field camera records a curved wavefront of a light field it captures, thus enabling the light field camera to capture curved parallaxes of the light field.

23. The light field camera of claim 22 wherein the curved wavefront recording capability enables the light field camera to record information not only about spatial and directional aspects of the light field, but also about a phase of the wavefront of the light field it captures, thus enabling the light field camera to record a four dimensional spatio-directional space of the light field plus the phase of its wavefront.

24. The light field camera of claim 1 wherein the light field camera captures two dimensional light field images that are then computationally focused at a desired plane or curved surface or computationally focused within a desired depth volume having flat or curved surfaces.

25. The light field camera of claim 1 configured as a three dimensional light field camera with arbitrary spatial and directional resolutions.

26. The light field camera of claim 1 having operational modes for switching between operation as a three dimensional light field camera and operation as a two dimensional light field camera by adapting the desired operational mode.

27. The light field camera of claim 1 wherein the light field camera is embedded in a mobile device and networked to other mobile devices that also have a light field camera embedded therein, the mobile devices being interconnected either through wireless or wireline networks or through bulk data transfer using flash memory modules, thus making it possible to exchange light field camera output data with a multiplicity of such mobile devices that captured a different perspective of a viewing scene, and use such networked light field camera output data to create a collective light field of the viewed scene.

28. The light field camera of claim 27 wherein the networked mobile devices are either cell phones or computers, or alternatively the light field camera is integrated with its own network connectivity interface capabilities.

29. The light field camera of claim 1 configured to record either still or motion video images.

30. The light field camera of claim 1 wherein each micro lens element is truncated to have its respective size match the dimensions of the respective group of pixels, an optical center of the micro lens element at a center of the micro lens array being aligned with a center of its respective pixel group, and the micro lens elements away from the center of the micro lens array having their optical centers offset from the center of their respective pixel group, the offset gradually increasing for micro lens elements further away from the center of the micro lens array.

31. The light field camera of claim 1 wherein the angular articulation temporally expands the angular extent of the respective micro lens element onto the corresponding group of pixels about each axis by a maximum angular articulation, thereby temporally expanding a detectable light field size and increasing the number of directions in the discrete set of directions about each axis by a ratio of said angular extent expansion to the angular extent about each of the two orthogonal axes.