System and method for achieving gray scale DMD operation

• US 5,105,207 A
• Filed: 12/31/1990
• Issued: 04/14/1992
• Est. Priority Date: 12/31/1990
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Nelson, William E.
• Primary Examiner(s): Moses, R. L.
• Application Number:
  US07/636,056
• Time in Patent Office: 470 Days
• Field of Search: 346/160, 346/153.1, 355/233, 355/229, 358/474, 358/475, 101/DIG. 37
• US Class Current: 347/131
• CPC Class Codes: B41J 2/465 using masks, e.g. light-switching masks
• CPC Class Codes: H04N 1/036 for optical reproduction
• CPC Class Codes: H04N 1/40025 Circuits exciting or modulating particular heads for reproducing continuous tone value scales H04N1/401, H04N1/407 take precedence
• CPC Class Codes: H04N 1/40043 using more than one type of modulation, e.g. pulse width modulation and amplitude modulation
• CPC Class Codes: Y10S 101/37 Printing employing electrostatic force

Abstract

There is disclosed a system for enhancing resolution of a xerographic process by submodulation of each individual pixel. The submodulation is achieved by anamorphically reducing the square pixel presentation of light rays to a rectangle having a number of controllable segments within each square pixel scan line. By controlling the presentation of light rays to selected segments within each pixel gray scale an enhanced resolution can be achieved.

Claims

1. A xerographic system where pixel images from a light source are achieved on a moving photoreceptor across a scan row, the system comprising:

a modulator for modulating said light source to establish each of said pixel images within said scan row; and

a segmenter for subdividing each said pixel into segmented time periods;

said segmenter including;

an anamorphic light source optic control for compressing modulated light pixels in the direction of movement of said photoreceptor while allowing said modulated light pixels to impact said photoreceptor across said scan row without compression.

2. The system set forth in claim 1 wherein said anamorphic optics includes an imager lens and an anamorphic lens.

3. The system set forth in claim 1 wherein said imager lens includes an anamorphic configuration integral thereto.

4. The system set forth in claim 2 wherein said segments, are created in the direction of movement of said photoreceptor, and wherein said system further comprises:

control circuitry for providing modulated light during selected ones of said segments of said segmented time period.

5. The system set forth in claim 4 wherein said control circuitry includes:

circuitry for periodically operating said modulator during each pixel modulation time period.

6. The system set forth in claim 2 wherein said modulator is a DMD having at least one row of selectively moveable elements, each controlling a single pixel image at the photoreceptor.

7. The system set forth in claim 6 wherein each said element of said DMD is individually controllable during each said segmented period.

8. The system set forth in claim 6 wherein said light source has selectively controllable light intensity levels.

9. The system set forth in claim 8 wherein said light source is individually controllable with respect to segments of said DMD.

10. The method of creating gray scale on a printed medium using a xerographic process wherein a modulated light source forms individually controllable pixel images on a rotating photoreceptor, said method including the steps of:

presenting said modulated light as individual pixels to said photoreceptor across a row; and

compressing said modulated light pixels in the direction of rotation of said drum while allowing said light pixels to impact said drum across said row without compression.

11. The method set forth in claim 10 wherein said compressing step includes the step of:

focusing said light pixels through an anamorphic lens.

12. The method set forth in claim 11 further comprising the step of:

dividing each said pixel row into a series of segments in the direction of said rotation of said photoreceptor.

13. The method set forth in claim 12 further comprising the step of:

selectively enabling each said pixel during any of said segments.

14. The method set forth in claim 12 further comprising the step of:

selectively enabling said light source during any of said segments.

15. The method set forth in claim 10 wherein said modulating step includes the step of:

presenting said light source to a DMD having individually controllable elements, each element operable to modulate one pixel.

16. A method of creating a xerographic printing process where pixel images from a light source are achieved on a moving photoreceptor across a scan row, the method comprising the steps of:

modulating said light source to establish each of said pixel images in each said scan row; and

subdividing each said pixel into segmented time periods, said segmenter including;

compressing modulated light pixels in the direction of movement of said photoreceptor while allowing said modulated light pixels to impact said photoreceptor across said scan row without compression.

17. The method set forth in claim 16 wherein said compressing step includes the step of:

passing said light pixels through an anamorphic lens.

18. The method set forth in claim 17 wherein said segments are created in the direction of movement of said photoreceptor, and wherein said method further comprises the steps of:

providing modulated light during selected ones of said segments of said segmented time period.

19. The method set forth in claim 18 wherein said method further includes the step of:

periodically operating said modulator during each pixel modulation time period.

20. The method set forth in claim 16 wherein said modulating step includes the step of:

impacting said light source on elements of a DMD having at least one row of selectively moveable elements, each controlling a single pixel.

21. The method set forth in claim 20 wherein each said element of said DMD is individually controllable during each said segmented period.

22. The method set forth in claim 21 wherein said light source has selectively controllable light intensity levels.

23. The method set forth in claim 22 wherein said light source is individually controllable with respect to segments of said DMD.

24. A DMD system comprising:

a light source;

a DMD array of pixels, each pixel being rotatable to focus light from said light source onto a medium for a time period;

a system for dividing each said time period into segments.

25. The system set forth in claim 24 wherein said medium is rotating in a process direction and wherein said dividing system includes:

focusing said DMD pixel elements via an anamorphic lens such that said light from said DMD pixels is compressed at said medium in said process direction while remaining uncompressed with respect to pixels across a row of pixels focused on said medium.

26. The system set forth in claim 25 further comprising:

a system for operating each said pixel for selecting intervals during each said time period.

27. The system set forth in claim 26 wherein said dividing system includes:

a system for varying the timing of said segments.

28. The system set forth in claim 25 wherein said light source has a selectively controllable light level.

29. The system set forth in claim 28 wherein said light source can be illuminated to a selected level during each said segment.

30. A xerographic system where pixel images from a light source are achieved on a moving photoreceptor across a scan row, the system comprising:

a modulator for modulating said light source to establish each of said pixel images within said scan row; and

a segmenter for subdividing each said pixel row into segmented time periods;

said segmenter including a selectable controllable light source operable for changing the light intensity in accordance with said segmented time periods.

31. The system set forth in claim 30 wherein said segments are created in the direction of movement of said photoreceptor.

32. The system set forth in claim 31 further comprising control circuitry for providing modulated light during selected ones of said segments of said segmented time period.

33. The system set forth in claim 32 wherein said control circuitry includes:

circuitry for periodically operating said modulator during each pixel modulation time period.

34. The system set forth in claim 30 wherein said modulator is a DMD having at least one row of selectively moveable elements, each controlling a single pixel image at the photoreceptor.

35. The system set forth in claim 34 wherein each said element of said DMD is individually controllable during each said segmented period.

36. The system set forth in claim 30 wherein said light source is individually controllable with respect to segments of said DMD.

37. The method of creating gray scale on a printed medium using a xerographic process wherein a modulated light source forms individually controllable pixel images on a rotating photoreceptor, said method including the steps of:

presenting said modulated light as individual pixels to said photoreceptor across a row; and

having the intensity of said light source in concert with the rotation of said photoreceptor.

38. The method set forth in claim 37 further comprising the step of:

dividing each said pixel row into a series of segments in the direction of said rotation of said photoreceptor.

39. The method set forth in claim 38 further comprising the step of:

selectively enabling each said pixel during any of said segments.

40. The method set forth in claim 38 further comprising the step of:

selectively enabling said light source during any of said segments.

41. The method set forth in claim 37 wherein said modulating step includes the step of:

presenting said light source to a DMD having individually controllable elements, each element operable to modulate one pixel.