Projection display with screen compensation

• US 20070115440A1
• Filed: 11/21/2005
• Published: 05/24/2007
• Est. Priority Date: 11/21/2005
• Status: Abandoned Application

• Current Assignee: Microvision, Inc.
• Original Assignee: Microvision, Inc.
• Inventors: Wiklof, Christopher
• Application Number:
  US11/284,043
• Publication Number:
  US 20070115440A1
• Time in Patent Office: Days
• US Class Current: 353/69
• CPC Class Codes: G03B 21/14 Details
• CPC Class Codes: G03B 21/26 Projecting separately subsidiary matter simultaneously with main image
• CPC Class Codes: H04N 5/74 Projection arrangements for image reproduction, e.g. using eidophor
• CPC Class Codes: H04N 9/31 Projection devices for colour picture display , e.g. using electronic spatial light modulators [ESLM]
• CPC Class Codes: H04N 9/3194 including sensor feedback

Abstract

A control system for a projection display includes means for compensating for spatial variations or artifacts in light scattered by a projection screen. According to embodiments, a sensor produces a signal corresponding to the amount of light scattered to a viewer on a region-by-region or pixel-by-pixel basis. A screen map is created from the sensor signal. Input display data is convolved with the screen map to produce a compensated display signal. The compensated display signal drives a projection display engine. The projected light driven by the compensated display signal convolves with the display screen to produce a viewable image having reduced artifacts. According to one embodiment, a relatively fixed screen map is produced during a calibration routine. According to another embodiment the screen map is updated dynamically during a display session.

Claims

1. A method for compensating for patterns on a display surface in a front-projection display comprising:

A) providing a screen compensation map, including;

projecting a first pixel onto a display surface;

measuring the brightness of the first pixel;

storing the brightness of the first pixel in a screen compensation map; and

repeating the projecting, measuring, and storing until a representative plurality of pixels have been projected, measured, and stored to produce the screen compensation map; and

B) projecting a compensated image onto the display surface, including;

receiving a video image signal comprising pixels;

reading the screen compensation map;

modifying the grayscale values of the pixels in the video image signal according to corresponding values in the screen compensation map to produced a compensated video image signal; and

projecting a compensated video image corresponding to the compensated video image signal onto the display surface.

2. The method for compensating for patterns on a display surface in a front-projection display of claim 1 wherein the representative plurality of pixels comprises substantially all the pixels.

3. The method for compensating for patterns on a display surface in a front-projection display of claim 1 wherein the representative plurality of pixels comprises less than substantially all the pixels and wherein providing the screen compensation map further includes interpolating between projected and measured pixels to provide additional interpolated pixels that, taken together with the projected and measured pixels, comprise substantially all the pixels of the display.

4. The method for compensating for patterns on a display surface in a front-projection display of claim 3 further comprising:

determining pairs of measured pixels between which there are relatively large changes in measured screen response; and

for at least one additional pixel between such pairs of measured pixels, repeating the steps of projecting, measuring, and storing to provide the screen compensation map with a more accurate representation of the projection surface.

5. The method for compensating for patterns on a display surface in a front-projection display of claim 1 wherein the steps of repeating the projecting and measuring of the brightness of a pixel on the display surface are performed serially.

6. The method for compensating for patterns on a display surface in a front-projection display of claim 1 wherein the steps of repeating the projecting and measuring of the brightness of a pixel on the display surface are performed substantially simultaneously.

7. A projection display comprising;

a housing;

a projection display engine disposed in the housing and aligned to an external field of view and operable to project pixels onto the external field of view;

a light sensor carried by the housing and aligned to receive energy from the external field of view and operable to detect at least a portion of light energy projected by the projection display engine and scattered by the external field of view and produce a detection signal corresponding to the received scattered energy; and

an interface coupled to the display engine and the light sensor operable to receive from an image source a signal corresponding to an image for display by the projection display engine and further operable to transmit to the image source the detection signal;

whereby the signal corresponding to the image for display may include compensation for the light scattering characteristics of the external field of view.

8. The projection display of claim 7 wherein the projection display engine comprises a scanned beam projection display engine.

9. The projection display of claim 7 wherein the projection display engine comprises a projection implementation selected from the group consisting of an LCD, an LCOS display, a deformable mirror array display, a CRT display, a field emission display, and a plasma display.

10. The projection display of claim 7 wherein the light sensor comprises a non-imaging light sensor.

11. The projection display of claim 10 wherein the light sensor comprises at least one detector selected from the group consisting of a PIN photodiode, an avalanche photodiode, and a photomultiplier tube.

12. The projection display of claim 7 wherein the light sensor comprises an imaging light sensor.

13. The projection display of claim 12 wherein the light sensor is selected from the group consisting of a Bayer-filtered charged coupled device array, a charge coupled device array, three filtered charge coupled device arrays, a Bayer-filtered complementary metal-oxide semiconductor array, a complementary metal-oxide semiconductor array, and three filtered complementary metal-oxide semiconductor arrays.

14. A projection display comprising;

a housing;

a projection display engine disposed in the housing and aligned to an external field of view and operable to project pixels onto the external field of view;

a light sensor carried by the housing and aligned to receive energy from the external field of view and operable to detect at least a portion of light energy projected by the projection display engine and scattered by the external field of view and produce a detection signal corresponding to the received scattered energy;

an interface coupled to the display engine and operable to receive from an image source a signal corresponding to an image for display by the projection display engine; and

a controller operatively coupled to the interface, the projection display engine, and the light sensor;

wherein the controller is operable to modify the received image for display responsive to the detection signal to produce a signal for driving the projection display engine.

15. The projection display of claim 14 wherein the controller comprises a screen memory and wherein the controller is operable to:

drive the projection display engine to project at least one pixel onto the field of view;

receive a signal from the light sensor responsive to light scattered from the at least one projected pixel; and

store at least one compensation value corresponding to the at least one projected pixel in the screen memory.

16. The projection display of claim 15 wherein the controller is operable to receive signals from the light sensor and store compensation values in screen memory during a screen calibration routine.

17. The projection display of claim 15 wherein the controller is operable to receive signals from the light sensor and store compensation values in screen memory substantially during projection of video images by the display engine.

18. A method for projecting an image comprising the steps of:

receiving an input video image;

for a plurality of pixels in the input video image, determining a corresponding screen compensation value; and

transmitting an output video image comprising at least one pixel value modified according to its corresponding screen compensation value to be different than the corresponding pixel value received in the input video image.

19. The method for projecting an image of claim 18 further comprising driving a display engine with the output video image to display a compensated video image.

20. The method for projecting an image of claim 18 wherein receiving an input video image comprises reading an input video image from memory.

21. The method for projecting an image of claim 18 wherein transmitting an output video image comprises writing an output video image to memory.

22. The method for projecting an image of claim 18 wherein determining a corresponding screen compensation value comprises reading the corresponding screen compensation value from memory.

23. The method for projecting an image of claim 18 further comprising calculating a modified pixel value from the corresponding input pixel value and screen compensation value.

24. The method for projecting an image of claim 23 wherein calculating a modified pixel value comprises performing an operation selected from the group consisting of adding, subtracting, multiplying, and dividing.

25. The method for projecting an image of claim 24 wherein performing the operation comprises executing an operation selected from the list consisting of a digital logic function, an analog logic function, and a fuzzy logic function.

26. An apparatus for generating a compensated image comprising:

an image buffer operable to receive an input image signal;

a screen memory operable to hold a screen compensation map; and

an electronic processor operable to read the image buffer and the screen memory, and determine a compensated image signal corresponding to the input image signal and the screen compensation map.

30. The apparatus of claim 26 wherein the electronic processor comprises a device selected from the group consisting of a digital integrated circuit, an analog integrated circuit, a mixed-signal integrated circuit, a fuzzy logic circuit, discrete circuitry, a microprocessor, a microcontroller, a gate array, a programmable gate array, a field programmable gate array, an application specific integrated circuit, a custom application specific integrated circuit, a standard cell application specific integrated circuit, a programmable logic device, a programmable array logic device, a generic array logic device, a shared controller, and an optical processor.

31. The apparatus for generating a compensated image of claim 26 further comprising a display engine operable to receive the compensated image signal and display a corresponding compensated image.

32. The apparatus for generating a compensated image of claim 31 further comprising a light sensor operable to receive light scattered from the displayed compensated image and generate a sensor signal corresponding to the received light.

33. The apparatus for generating a compensated image of claim 32 wherein the electronic controller is further operable to receive the sensor signal from the light sensor and responsively generate the screen compensation map.

34. The apparatus for generating a compensated image of claim 26 further comprising a video source operable to generate the input image signal.

35. The apparatus for generating a compensated image of claim 26 further comprising an interface operable to receive the input image signal.

27. The apparatus for generating a compensated image wherein the electronic processor is further operable to write the compensated image signal to a buffer.

28. The apparatus for generating a compensated image of claim 27 further comprising an output buffer operable to receive the compensated image signal written by the electronic processor.

29. The apparatus for generating a compensated image of claim 27 wherein the input buffer is further operable to receive the compensated image signal written by the electronic processor.

36. A method for displaying an image comprising:

receiving a first signal corresponding to an image for display;

receiving a second signal corresponding to a response characteristic of a screen, the response characteristic including at least one of an image portion displacement and an image portion brightness variation; and

combining the first and second signals to produce a third signal that includes an image signal modified according to the response characteristic.

37. The method of claim 36 further comprising driving a projection engine with the third signal to project a displayed image onto the screen.

38. The method of claim 37 wherein the displayed image includes a reduced artifact corresponding to the characteristic of the screen.

39. The method of claim 38 wherein the artifact comprises brightness non-uniformity.

40. The method of claim 38 wherein the artifact comprises geometric distortion.

41. The method of claim 36 wherein the first signal comprises a video image.

42. The method of claim 36 wherein the first signal comprises a bitmapped image.

43. The method of claim 36 wherein the second signal comprises a bitmapped image.

44. The method of claim 36 wherein combining the first and second signals comprises adding corresponding pixel values to produce summed pixel values.

45. The method of claim 44 wherein combining the first and second signals further comprises scaling the summed pixel values to produce summed and scaled pixel values.

46. The method of claim 36 wherein combining the first and second signals comprises multiplying corresponding pixel values to produce multiplied pixel values.

47. The method of claim 46 wherein combining the first and second signals further comprises scaling the summed pixel values to produce multiplied and scaled pixel values.

48. The method of claim 36 further comprising detecting an image produced by the screen to produce the screen response signal.

49. The method of claim 48 further comprising comparing the detected image to an input video image to produce the screen response signal.

50. The method of claim 48 wherein detecting the image produced by the screen includes measuring the amount of light scattered by the screen across a plurality of screen locations and across a plurality of color channels.

51. The method of claim 48 wherein the detecting is performed during a calibration.

52. The method of claim 48 wherein the detecting is performed a plurality of times.

53. The method of claim 52 wherein the detecting is performed substantially continuously and the third compensated signal includes compensation for screen response variations that occur dynamically.

54. The method of claim 48 wherein the detecting is performed by a calibration device.

55. The method of claim 48 wherein the detecting is performed by a sensor that is integral to a projection display.