APPARATUS AND METHOD FOR IMAGE SUPER-RESOLUTION USING INTEGRAL SHIFTING OPTICS

• US 20150098013A1
• Filed: 10/09/2013
• Published: 04/09/2015
• Est. Priority Date: 10/09/2013
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Gray, Daniel Curtis, Harding, Kevin George, Wheeler, Frederick Wilson, Abramovich, Gil
• Granted Patent: US 9,025,067 B2
• Time in Patent Office: Days
• US Class Current: 348/369
• CPC Class Codes: G02B 5/3083 Birefringent or phase retarding elements G02B5/3008, G02B5/3016 take precedence; systems for polarisation control G02B27/286; manufacturing phase modulating patterns by lithographic processes G03F7/001
• CPC Class Codes: G02F 1/0136 for the control of polarisation, e.g. state of polarisation [SOP] control, polarisation scrambling, TE-TM mode conversion or separation G02F1/0353 takes precedence
• CPC Class Codes: G02F 1/09 based on magneto-optical elements, e.g. exhibiting Faraday effect
• CPC Class Codes: G02F 1/1313 specially adapted for a particular application
• CPC Class Codes: G06V 10/147 Details of sensors, e.g. sensor lenses fingerprint or palmprint sensors G06V40/13; vascular sensors G06V40/145; eye sensors G06V40/19
• CPC Class Codes: G06V 40/1312 direct reading, e.g. contactless acquisition

Abstract

An image capture device includes an electro-optics arrangement having an arrangement of polarizers, polarization sensitive optical elements, and polarization modulating elements. First and second polarization sensitive optical elements are provided having an edge displaced relative to a plane normal to an optical axis of the electro-optics arrangement. A control system coupled to the electro-optics arrangement controls the application of voltages to the polarization modulating elements to control the polarization rotation of the light input to the polarization sensitive optical elements, such that the optical path length of the polarization sensitive optical elements is changed to provide for capture of the object images at each of the different focal planes. The first and second polarization sensitive optical elements generate lateral image shifts between respective object images captured at the different focal planes responsive to the polarization rotation of the light input thereto.

Claims

1. An image capture device configured to capture images of an object, the image capture device comprising:

an imaging camera lens system;

an electro-optics arrangement positioned between the object and the imaging camera, the electro-optics arrangement including;

one or more polarizers configured to orient a polarization of light passing therethrough;

a plurality of polarization sensitive optical elements having an optical path length that changes with different polarization states so as to provide for capture of the object images at each of a plurality of different focal planes; and

a plurality of polarization modulating elements configured to selectively control a polarization rotation of light input to the plurality of polarization sensitive optical elements responsive to voltages applied thereto;

wherein the plurality of polarization sensitive optical elements comprises at least a first polarization sensitive optical element and a second polarization sensitive optical element, with the first polarization sensitive optical element and the second polarization sensitive optical element having an edge displaced relative to a plane normal to an optical axis of the electro-optics arrangement; and

a control system coupled to the electro-optics arrangement and being configured to control the application of voltages to each of the plurality of polarization modulating elements to control the polarization rotation of the light input to the plurality of polarization sensitive optical elements, such that the optical path length of the plurality of polarization sensitive optical elements is changed to provide for capture of the object images at each of the plurality of different focal planes;

wherein the first and second polarization sensitive optical elements generate lateral image shifts between respective object images captured at the plurality of different focal planes responsive to the polarization rotation of the light input thereto.

2. The image capture device of claim 1 wherein each of the first polarization sensitive optical element and the second polarization sensitive optical element is mechanically tilted from the plane normal to the optical axis such that the edge thereof is displaced relative to the plane normal to the optical axis.

3. The image capture device of claim 1 wherein each of the first polarization sensitive optical element and the second polarization sensitive optical element comprises a wedge element constructed such that the edge thereof is displaced relative to the plane normal to the optical axis.

4. The image capture device of claim 1 wherein the edges of the first polarization sensitive optical element and the second polarization sensitive optical element are displaced relative to the plane normal to the optical axis such that the edge of the first polarization sensitive optical element and the edge of the second polarization sensitive optical element are oriented in planes 90 degrees in rotation about the optical axis relative to each other.

5. The image capture device of claim 1 wherein the edges of the first polarization sensitive optical element and the second polarization sensitive optical element are displaced relative to the plane normal to the optical axis such that the edge of the first polarization sensitive optical element and the edge of the second polarization sensitive optical element are in planes relative to each other at an angle other than 90 degrees, so as to impart non-orthogonal lateral image shifts between respective object images captured at the plurality of different focal planes responsive to the polarization rotation of the light input thereto.

6. The image capture device of claim 1 wherein the lateral images shifts comprise sub-pixel shifts between respective object images captured at the plurality of different focal distances.

7. The image capture device of claim 1 wherein the tilted first and second polarization sensitive optical elements provide a square shift pattern at the plurality of different focal distances comprising four sub-pixel image shift locations.

8. The image capture device of claim 1 where each object image has a depth-of-focus that overlaps with a depth-of-focus of object images at adjacent focal planes such that redundant depth data is captured.

9. The image capture device of claim 8 wherein the control system is configured to:

input the object images into a super-resolution algorithm, such that the redundant depth data and lateral image shifts of the object images are provided to the super-resolution algorithm; and

generate a composite image from the super-resolution algorithm, such that the spatial resolution of the composite image is increased from a first image resolution level at which the object images are acquired to a second higher image resolution level.

10. The image capture device of claim 8 wherein each object image is separated in focal distance from other object images by a set focus step, and wherein the depth-of-focus of each object image is approximately equal to a size of the focus step.

11. The image capture device of claim 1 wherein the control system is configured to apply de-convolution to the acquired object images to correct for out of focus light.

12. The image capture device of claim 1 wherein the polarization modulating elements comprise at least one of Faraday rotators, optoelectric crystals, wave plates, and liquid crystal panels (LCPs) and wherein the polarization sensitive optical elements comprise at least one of birefringent windows and birefringent lenses.

13. The image capture device of claim 1 wherein the image capture device is configured to capture object images at 1 to 32 different focal planes, including at 4 different focal planes, 8 different focal planes or 16 different focal planes.

14. The image capture device of claim 1 wherein the image capture device further comprises a voltage source controlled by the control system to apply voltage to the plurality of polarization modulating elements to change orientation states thereof, so as to control the polarization rotation of light input to the plurality of polarization sensitive optical elements to vary an optical path length thereof.

20. The image capture device of claim 1 wherein the at least one birefringent window comprises a wedge element constructed such that the edge thereof is displaced relative to the plane normal to the optical axis.

15. A method for acquiring images of an object via an image capture device, the method comprising:

providing an image capture device comprising an image forming optical lens and an electro-optic lens section, the electro-optics lens section further including;

one or more polarizers configured to orient a polarization of light passing therethrough;

birefringent windows that exhibit a different index of refraction depending on an input polarization of light passing therethrough, wherein at least one of the birefringent windows has an edge displaced relative to a plane normal to an optical axis of the electro-optic lens section; and

liquid crystal polarization rotators configured to selectively rotate an axis of the input polarization of light provided to the birefringent windows; and

capturing an image of at least a portion of the object at each of a plurality of fixed focus positions by way of the image capture device, wherein capturing the object images at the plurality of fixed focus positions comprises;

selectively applying a voltage to the liquid crystal polarization rotators in the electro-optics lens section to rotate the axis of the input polarization of light provided to the birefringent windows; and

capturing an image of at least a portion of the object at each of the plurality of fixed focus positions responsive to the voltage applied to the liquid crystal polarization rotators, with images being captured at each of the plurality of fixed focus positions based on differing indexes of refraction of the birefringent windows;

wherein each object image acquired at a respective fixed focus position has a sub-pixel lateral image shift as compared to object images acquired at adjacent fixed focus positions responsive to the axis rotation of the input polarization of light provided to the at least one birefringent window having the edge displaced relative to the plane normal to the optical axis of the electro-optic lens section.

16. The method of claim 15 wherein the at least one birefringent window comprises a first birefringent window and a second birefringent window, with the first and second tilted birefringent windows providing a square shift pattern of sub-pixel lateral image shifts at the fixed focus positions comprising four sub-pixel image shift locations.

17. The method of claim 15 further comprising:

registering the images captured at the plurality of fixed focus positions to create pixel correspondence between the images;

determining a 3D shape of at least a portion of the hand using one of a depth from focus and a depth from defocus algorithm;

inputting the registered images and the 3D shape into a super-resolution algorithm; and

generating the composite image from the super-resolution algorithm, with the composite image having a second spatial resolution level that is increased from a first image resolution level at which the object images are acquired.

18. The method of claim 15 wherein capturing object images at the plurality of fixed focus positions comprises capturing object images at between 1 and 32 different fixed focus positions.

19. The method of claim 15 wherein the at least one birefringent window is mechanically tilted from the plane normal to the optical axis, such that the edge thereof is displaced relative to the plane normal to the optical axis.

21. An electro-optics lens section for use in an image capture device configured to capture objects of an image at a plurality of different focal planes, the electro-optics lens section comprising:

one or more polarizers configured to orient a polarization of light passing therethrough;

a plurality of polarization sensitive optical elements having an optical path length that changes with different polarization states so as to provide for capture of the object images at each of a plurality of different focal planes, the plurality of polarization sensitive optical elements including at least a first polarization sensitive optical element and a second polarization sensitive optical element, with the first polarization sensitive optical element and the second polarization sensitive optical element being tilted relative to a plane normal to an optical axis of the electro-optics lens section and tilted in planes 90 degrees in rotation about the optical axis relative to each other; and

a plurality of polarization modulating elements configured to selectively control a polarization rotation of light input to the plurality of polarization sensitive optical elements responsive to voltages applied thereto, so as to enable capture of object images at a plurality of different focal planes;

wherein the tilted first and second polarization sensitive optical elements generate lateral image shifts between respective object images captured at the plurality of different focal planes responsive to varying of the polarization rotation of the light input to the plurality of polarization sensitive optical elements resulting from the voltages applied to the plurality of polarization modulating elements, such that no mechanical motion of the electro-optics lens section is needed in generating the lateral image shifts.

22. The electro-optics lens section of claim 21 wherein the tilted first and second polarization sensitive optical elements provide a square shift pattern at the plurality of different focal distances comprising four sub-pixel image shift locations.