System and Method for Varying Exposure Time for Different Parts of a Field of View While Acquiring an Image

• US 20070216794A1
• Filed: 11/06/2006
• Published: 09/20/2007
• Est. Priority Date: 12/31/2001
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Neidrich, Jason
• Granted Patent: US 7,782,389 B2
• Time in Patent Office: Days
• US Class Current: 348/335
• CPC Class Codes: G02B 23/02 involving prisms or mirrors G02B23/14 takes precedence
• CPC Class Codes: G02F 1/31 Digital deflection, i.e. optical switchingG02F1/33 takes precedence
• CPC Class Codes: H04N 23/55 Optical parts specially adapted for electronic image sensors; Mounting thereof
• CPC Class Codes: H04N 23/75 by influencing optical camera components

Abstract

A system and method for exposing different parts of a single field of view for various and differing lengths of time while capturing an image is provided. For astrophotography, unwanted light pollution or over-saturation bleeding from nearby or obtrusive stars may be greatly reduced or eliminated while still capturing the image of the nearby brighter star in the same field of view. Also, a system and method for real-time contrast control while capturing an image to optimize signal-to-noise ratio for various parts of the captured image, is provided. An embodiment of the present invention provides such techniques by using spatial light modulator devices, such as a digital micro-mirror device, to controllably mask different portions of light from an image that expose film or a charge-coupled device. A system and method for a way to use a spatial light modulator device as an active and controllable mask for photolithography, is provided.

Claims

1. A device for masking one or more selected areas of a field of view while capturing an image, comprising:

an image aperture formed in the device;

a first spatial light modulator (SLM) comprising an array of movable reflective elements, the first SLM being positioned at a first angle with respect to a central axis of image light rays entering the device through the image aperture, and the first SLM positioned such that the image light rays will hit at least some of the reflective elements on the first SLM;

a second SLM comprising an array of movable reflective elements, the second SLM being positioned apart from the first SLM such that, when at least some of the first SLM reflective elements are in a first position, at least some of the image light rays reflected from the first SLM reflective elements positioned in the first position of the first SLM will hit at least part of the second SLM; and

an image capturing device for use in recording an image, the image capturing device being located in a position such that, when at least some of the second SLM reflective elements are in a first position, at least some of the image light rays reflected from the second SLM reflective elements positioned in the first position of the second SLM will eventually hit at least part of the image capturing device.

2. The device of claim 1, wherein at least the first or the second SLM comprises a digital micro-mirror device.

3. The device of claim 1, wherein at least the first or the second SLM comprises an anti-reflective membrane device.

4. The device of claim 1, wherein at least the first or the second SLM comprises a deformable film modulator device.

5. The device of claim 1, wherein the image capturing device comprises a digital light sensor.

6. The device of claim 1 wherein the image capturing device comprises a charge-coupled device.

7. The device of claim 1, wherein the image capturing device comprises photographic film.

8. The device of claim 1, wherein the image capturing device comprises a photo-reactive material that is formed on a semiconductor wafer.

9. The device of claim 1, further comprising:

a lens located in the image aperture.

10. The device of claim 1, further comprising:

a lens located within an image reflection path between the second SLM and the image capturing device.

11. The device of claim 1, wherein the device is a camera.

12. The device of claim 1, wherein the device is part of a video camera.

13. The device of claim 1, wherein the device is adapted to be optically coupled to a telescope.

39. The device of claim 1 wherein the second SLM is shifted relative to the first SLM so that image rays reflected from a given position of a movable element of the first SLM will hit a location at a differing position of a respective movable element of the second SLM.

40. The device of claim 39 wherein the differing position is one-half a distance of a dimension of each movable element of the first SLM.

41. The device of claim 1:

wherein the device comprises a plurality of SLMs;

wherein the plurality of SLMs includes the second SLM; and

wherein each SLM in the plurality of SLMs comprises a respective array of movable reflective elements and is positioned apart from another SLM in the plurality of SLMs such that, when at least some of the reflective elements of a given SLM in the plurality of SLMs are in a first position, at least some of the image light rays reflected from the given SLM reflective elements will hit either at least part of another SLM in the plurality of SLMs or at least part of the image capturing device.

14. A device for masking one or more selected areas of a field of view while capturing an image, comprising:

an image aperture formed in the device;

a first digital micro-mirror device (DMD) comprising an array of movable mirror elements, the first DMD being positioned at a first angle with respect to a central axis of image light rays entering the device through the image aperture, and the first DMD being positioned such that the image light rays will hit at least some of the mirror elements on the first DMD;

a second DMD comprising an array of movable mirror elements, the second DMD being positioned apart from the first DMD such that, when at least some of the first DMD mirror element are in a first position, at least some of the image light rays reflected from the first DMD mirror elements positioned in the first position of the first DMD will hit at least part of the second DMD; and

a charge-coupled device (CCD) comprising an array of photon sensing elements, the CCD being locate in a position so that, when at least some of the second DMD mirror elements are in a first position, at least some of the image light rays reflected from the second DMD mirror elements positioned in the second DMD first position will eventually hit at least some of the CCD elements.

15. The device of claim 14, further comprising:

a shutter adapted to block the image light rays from striking the first DMD when the shutter is closed and to allow at least some of the image light rays to strike the first DMD when the shutter is open.

16. The device of claim 14, further comprising:

a controller electrically coupled to the first DMD and the second DMD, the controller being adapted to selectively send signals to the first DMD and the second DMD for causing one or more movable mirror elements in a respective DMD to be actuated.

17. The device of claim 14, further comprising:

an electrical circuit electrically coupled to the first DMD and the second DMD and the CCD.

42. The device of claim 14 wherein the second DMD is shifted relative to the first DMD so that image rays reflected from a given position of a movable mirror element of the first DMD will hit a location at a differing position of a respective movable mirror element of the second DMD.

43. The device of claim 42 wherein the differing position is one-half a distance of a dimension of each movable mirror element of the first DMD.

44. The device of claim 14:

wherein the device comprises a plurality of DMDs;

wherein the plurality of DMDs includes the second DMD; and

wherein each DMD in the plurality of DMDs comprises a respective array of movable mirror elements and is positioned apart from another DMD in the plurality of DMDs such that, when at least some of the movable mirror elements of a given DMD in the plurality of DMDs are in a first position, at least some of the image light rays reflected from the given DMD mirror elements will hit either at least part of another DMD in the plurality of DMDs or at least part of the image capturing device.

18. (canceled)

19. A device for masking one or more selected areas of a field of view while capturing an image, comprising:

an image aperture formed in the device;

a first digital micro-mirror device (DMD) comprising a first array of electrically controllable and movable mirror elements, the first DMD being positioned at a first angle with respect to a central axis of image light rays entering the device through the image aperture, and the first DMD being positioned such that the image light rays will hit at least some of the mirror elements on the first DMD;

a second DMD comprising a second array of electrically controllable and movable mirror elements, the second DMD being positioned at a first spaced distance from the first DMD, the second array of mirror elements facing in an opposite direction than the first array of mirror elements, and the second DMD being positioned so that, when at least some of the first DMD mirror elements are in a first position, at least some of the image light rays reflected from the first DMD mirror elements positioned in the first position will hit at least some of the second DMD mirror elements; and

a charge-coupled device (CCD) comprising an array of photon sensing elements, the CCD being located in a position so that, when at least some of the second DMD mirror elements are in a first position, at least some of the image light rays reflected from the second DMD mirror elements positioned in the first position will eventually hit at least some of the CCD elements.

20. The device of claim 19, wherein the second DMD position is offset relative to the first DMD position such that image light rays reflecting from the center of at least some of the first DMD mirrors at the first position hit a location on the second DMD where two or more second DMD mirror elements meet.

21. The device of claim 19, wherein the second DMD position is offset relative to the first DMD position such that image light rays reflecting from the center of at least some of the first DMD mirrors at the first position hit a location on the second DMD where two or more second DMD mirror elements meet.

22. The device of claim 19, wherein the second DMD is substantially parallel to the first DMD.

23. The device of claim 19, further comprising:

a third DMD comprising a third array of electrically controllable and movable mirror elements, the third DMD being positioned at a second spaced distance from the second DMD, the third DMD being substantially parallel to the second DMD, the third array of mirror elements facing in an opposite direction than the second array of mirror elements, and the third DMD being positioned so that, when at least some of the second DMD mirror elements are in a first position, at least some of the image light rays reflected from the second DMD mirror elements positioned in the first position will hit at least some of the third DMD mirror elements; and

the CCD also being located in a position so that, when at least some of the third DMD mirror elements are in a first position, at least some of the image light rays reflected from the third DMD mirror elements positioned in the first position will eventually hit at least some of the CCD elements.

24. The device of claim 23, further comprising:

a fourth DMD comprising a fourth array of electrically controllable and movable mirror elements, the fourth DMD being positioned at a third spaced distance from the third DMD, the fourth DMD being substantially parallel to the third DMD, the fourth array of mirror elements facing in an opposite direction than the third array of mirror elements, and the fourth DMD being positioned so that, when at least some of the third DMD mirror elements are in a first position, at least some of the image light rays reflected from the third DMD mirror elements positioned in the first position will hit at least some of the fourth DMD mirror elements; and

the CCD also being located in a position so that, when at least some of the fourth DMD mirror elements are in a first position, at least some of the image light rays reflected from the fourth DMD mirror elements positioned in the first position will hit at least some of the CCD elements.

25-27. -27. (canceled)

28. A method of astrophotography, comprising the steps of:

during a first period of time, reflecting a first part of an image off of a first spatial light modulator (SLM) at a first angle toward a second SLM;

also during the first period of time, reflecting a second part of the image off of the first SLM at a second angle that directs the second part of the image to a first location where the second part of the image will not go to the second SLM;

also during the first period of time, reflecting a third part of the image off of the second SLM at a third angle so that at least some of the third part of the image will eventually strike the image capturing device, wherein the third part of the image comprises a portion of the first part of the image;

also during the first period of time, reflecting a fourth part of the image off of the second SLM at a fourth angle that directs the fourth part of the image to a second location where the fourth part of the image will not go to the image capturing device, wherein the fourth part of the image comprises another portion of the first part of the image;

also during the first period of time, striking at least part of the image capturing device with at least some of the third part of the image; and

during a second period of time, reflecting a fifth part of the image off of the first SLM at a fifth angle so that at least some of the fifth part of the image will eventually strike the image capturing device, wherein the fifth part of the image comprises at least some of the second part of the image, and wherein the fifth angle is about the same as the first angle.

29. The method of 28, further comprising the steps of:

also during the first period of time, reflecting a sixth part of the image off of a third SLM at a sixth angle so that at least some of the sixth part of the image will eventually strike the image capturing device, wherein the sixth part of the image comprises a portion of the third part of the image; and

also during the first period of time, reflecting a seventh part of the image off of the third SLM at a seventh angle that directs the seventh part of the image to a third location where the seventh part of the image will not go to the image capturing device, wherein the seventh part of the image comprises another portion of the third part of the image.

30. The method of 29, further comprising the steps of:

also during the first period of time, reflecting an eighth part of the image off of a fourth SLM at an eighth angle so that at least some of the eighth part of the image will eventually strike the image capturing device, wherein the eighth part of the image comprises a portion of the sixth part of the image; and

also during the first period of time, reflecting a ninth part of the image off of the fourth SLM at a ninth angle that directs the ninth part of the image to a fourth location where the ninth part of the image will not go to the image capturing device, wherein the ninth part of the image comprises another portion of the sixth part of the image.

31-36. -36. (canceled)

37. A method of astrophotography, comprising the steps of:

during a first period of time, reflecting a first part of an image off of a first digital micro-mirror device (DMD) at a first angle to a second DMD;

also during the first period of time, reflecting a second part of the image off of the first DMD at a second angle that directs the second part of the image to a first light absorption location so that the second part of the image does not go to the second DMD;

also during the first period of time, reflecting a third part of the image off of the second DMD at a third angle so that at least some of the third part of the image will eventually strike a charge-coupled device (CCD), wherein the third part of the image comprises a portion of the first part of the image; and

also during the first period of time, reflecting a fourth part of the image off of the second DMD at a fourth angle that directs the fourth part of the image to a second light absorption location so that the fourth part of the image does not go to the CCD, wherein the fourth part of the image comprises another portion of the first part of the image.

38. The method of claim 37, further comprising the steps of:

during a second period of time, reflecting a fifth part of an image off of the first DMD at the first angle to the second DMD;

also during the second period of time, reflecting a sixth part of the image off of the first DMD at the second angle that directs the sixth part of the image to the first light absorption location so that the sixth part of the image does not go to the second DMD;

also during the second period of time, reflecting a seventh part of the image off of the second DMD at the third angle so that at least some of the seventh part of the image will eventually strike the CCD, wherein the seventh part of the image comprises a portion of the sixth part of the image; and

also during the second period of time, reflecting an eighth part of the image off of the second DMD at the fourth angle that directs the eighth part of the image to the second light absorption location so that the eighth part of the image does not go to the CCD, wherein the eighth part of the image comprises another portion of the sixth part of the image.