Spatial light modulator printer and method of operation

• US 5,041,851 A
• Filed: 12/21/1989
• Issued: 08/20/1991
• Est. Priority Date: 12/21/1989
• Status: Expired due to Fees

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Nelson, William E.
• Primary Examiner(s): Fuller, Benjamin R.
• Assistant Examiner(s): Gibson, Randy W.
• Application Number:
  US07/454,568
• Time in Patent Office: 607 Days
• Field of Search: 346/1.1, 346/96 L, 346/154, 346/155, 346/160, 346/160.1, 346/108
• US Class Current: 347/134
• CPC Class Codes: B41J 2/44 using single radiation source per colour, e.g. lighting beams or shutter arrangements B41J2/475 takes precedence
• CPC Class Codes: B41J 2/465 using masks, e.g. light-switching masks
• CPC Class Codes: G03G 15/043 with means for controlling illumination or exposure G03G15/041 takes precedence
• CPC Class Codes: G03G 15/326 by application of light, e.g. using a LED array

Abstract

A printing system and method which uses an unmodulated light focused on a spatial light modulator (SLM) device. The light modulator device, in one embodiment, can be a deformable set of mirrors monolithically integrated onto a semiconductor substrate which act, under control of data signals, to selectively modulate light onto a focusing lens which in turn images the light to the drum of the xerographic printing process. The deformable mirrors are formed in one or more parallel rows and the selective timing of the rows is controllable in order to compensate for variations in xerographic process speed. A stepped light baffle removes the unmodulated light further enhancing the dark field effect.

Claims

1. A printing system having an exposure unit and a contact reproductive unit, said contact reproductive unit operative in response to presentation of images for representing said images on a print transfer medium and for subsequently transferring said represented image to a final printed surface, said exposure unit comprising

a source of light;

an array of spatial light modulator elements arranged in a line and in a same plane as, but opposed to said light source;

at least one lens for focusing light from said light source onto said array;

an imager lens for accepting light imagers modulated from selected ones of said modulator elements of said array and for presenting said accepted light images to said contact reproductive unit said imager lens being on a same side of said array as is said light source;

circuitry for controlling said individual array elements such that light is modulated to said imager lens from certain of said elements and unmodulated to said imager lens from others of said elements;

said light source and lenses arranged to create an optical axis for said modulated and unmodulated light so as to take advantage of a dark field effect with respect to light modulated from said array; and

a light baffle constructed between said array of spatial light modulator elements and said imager lens, said light baffle having a plurality of concentric, sloped walls for changing an angle of said light which said spatial light modulator elements do not modulate to said imager lens, said walls constructed perpendicular to said optical axis of said modulated and unmodulated light, said walls interconnected by a series of sloping steps, the slope of which is substantially parallel to said optical axis.

2. The printing system set forth in claim 1 wherein said light from said light source impacts said spatial light modulator elements in a horizontal plane and wherein said optical axis, which is defined by the optical axis of said spatial light modulator array and said imaging lens, slopes downward from said horizontal plane.

3. The printing system set forth in claim 1, wherein said array and said control circuitry are both constructed on the same substrate.

4. The printing system set forth in claim 1, wherein said array consists of deformable mirrors constructed on a substrate.

5. The printing system set forth in claim 4, wherein said array has a double row of said deformable mirrors, said double row enabled cooperatively to form images.

6. The printing system set forth in claim 1, wherein said light source is a light bulb mounted adjacent to a first end of said exposure unit, said array is mounted adjacent a second end of said exposure unit, said imager lens and said focusing lens mounted between said light source and said array.

7. The printing system set forth in claim 1, wherein said light baffle has the shape of a bee thorax, and wherein said imager lens is mounted within said thorax.

8. The printing system set forth in claim 7, wherein said exposure unit includes a slot therein, and wherein said presented images are reflected through said slot to said contact reproductive unit.

9. An exposure unit for use in generating optical images, said images comprising a plurality of individual bits each controlled by an off/on data signal, said exposure unit comprising:

a source of light;

an exit for passing light out of said exposure unit;

an array of spatial light modulator elements positioned opposite to, but in a same plane as, said light source a focusing lens such that light from said source travels in a substantially horizontal plane and falls on said array elements;

imaging lens for accepting light selectively modulated from selected ones of said array elements and for communicating said modulated light to said exit;

circuitry for selecting said array elements in accordance with said on/off data signals; and

a sloped light baffle interposed between said array and said imaging lens, said light baffle sloped in a plane at an angle to said horizontal plane, said sloped plane substantially parallel to an optical axis formed by said spatial light modulator and said imaging lens mounted at an end of said light baffle in said sloped plane.

10. The exposure unit set forth in claim 9 wherein said steps each have walls perpendicular to said sloped plane and wherein a top of each wall is connected to a base of an adjacent wall by a surface which is substantially parallel to said sloped plane.

11. The exposure unit set forth in claim 9, wherein said array elements are deformable mirrors arranged to change a light reflective angle upon being addressed by a data signal.

12. The exposure unit set forth in claim 11, wherein said array is contained on a substrate in conjunction with circuitry for controlling said addressing.

13. The exposure unit set forth in claim 12, wherein said imager lens is on a same side of said array as is said light source and wherein said control circuitry takes advantage of a dark field effect with respect to light reflected from said array.

14. The exposure unit set forth in claim 10, wherein said array elements are deformable mirrors arranged to change their light reflective angle upon being addressed by a data signal.

15. The exposure unit set forth in claim 10, wherein said light source is a light bulb mounted adjacent a first end of said exposure unit, said array is mounted adjacent a second end of said exposure unit, said imager lens and said focusing lens mounted between said light source and said array.

16. The exposure unit set forth in claim 10, wherein said exit includes a slot and, wherein said communicated images are reflected through said slot to said reproductive unit.

17. A printing system having an exposure unit, a contact reproductive unit and a paper feeder unit, said paper feeder unit operative to supply paper surfaces for contact with said contact reproductive unit, said contact reproductive unit operative in response to presentation of images for representing said images on a print transfer medium and for subsequently transferring said represented image to a supplied paper surface, said exposure unit comprising:

a source of light;

an exit for passing light out of said exposure unit;

an array of spatial light modulator elements positioned opposite to, but in a same plane as, said light source and a focusing lens such that light from said source travels in a substantially horizontal plane and falls on said array elements;

imaging lens for accepting light selectively modulated from selected ones of said array elements and for communicating said modulated light to said exit;

circuitry for selecting said array elements in accordance with said on/off data signals; and

a sloped light baffle interposed between said array and said imaging lens, said light baffle sloped in a plane at an angle to said horizontal plane, said sloped plane substantially parallel to optical axis formed by said spatial light modulator, said imaging lens mounted at an end of said light baffle in said sloped plane.

18. The printing system set forth in claim 17 wherein said steps each have walls perpendicular to said sloped plane and wherein a top of each wall is connected to a base of an adjacent wall by a surface which is substantially parallel to said sloped plane.

19. The printing system set forth in claim 18, wherein said array elements are deformable mirrors arranged to change a light reflective angle upon being addressed by a data signal.

20. The printing system set out in claim 19, wherein said array is contained on a substrate in conjunction with circuitry for controlling said addressing.

21. The printing system set forth in claim 17, wherein said array elements are deformable mirrors arranged to change a light reflective angle upon being addressed by a data signal.

22. A printing method having an exposure process and a contact reproductive process, said contact reproductive process operative in response to presentation of images for representing said images on a print transfer medium and for subsequently transferring said represented image to a final printed surface, said printing method comprising the steps of:

accepting light from a light source;

focusing light from said light source onto an array of spatial light modulator elements;

selectively accepting through an imager lens images modulated from said array, presenting said accepted light images to said contact reproductive process;

controlling said individual array elements such that light is modulated to said imager lens in one mode and not modulated to said imager lens in a second mode; and

said controlling step further including the step of bouncing the light from said second mode away from said imager lens by using a series of sloping steps, a wall of each step being constructed substantially perpendicular to the path of said second mode light.

23. A ticket printing system comprising:

a printer remote from a central computer, said printer adapted to receive transmitted event information from said central computer through said transmission circuitry,

a source of coupon stock, internal to said printer;

said printer arranged to print said received event information on said coupon stock, said printer including;

a xerographic system wherein said printing is created on said coupon in response to a series of electrical signals representative of said printing information, said electrical signals operative for modulating light energy through a deformable mirror device spatial light modulator array into a series of modulated light pulses representative of said printing, said light pulses in turn operative for presentation to a drum of said xerographic system, said printer further including;

a reproductive unit for accepting said light pulses and for converting said light pulses to said printing by said drum;

a light modulation unit for accepting said electrical signals and for converting unmodulated light from a light source into modulated light pulses in accordance with said accepted electrical signals by a deformable mirror device spatial light modulator array; and

a positioning device for mating said reproductive unit and said modulation unit together so as to effect alignment between said modulated light pulses and said drum.

24. The system set forth in claim 23 wherein said light modulator unit further comprises:

a box having a horizontal partition dividing said box into a lower portion and an upper portion, said lower portion communicating directly with one end of an exit passage, said lower portion also including a pair of mirrors for accepting rays of modulated light from said upper portion and for redirecting said accepted rays of light for presentation to said exit passage, said exit passage integral to a flexible lower cover;

said box upper portion having a spatial light modulation device positioned at one end to modulate light along a longitudinal axis divided in said horizontal partition, said longitudinal axis defining a semi-circular indentation sloped into said partition and away from a modulating device, said indentation ending in a passage through said partition; and

an imaging lens positioned within said indentation for communicating said modulated light from said spatial light modulation device to said pair of mirrors in said lower portion of said box.

25. The system set forth in claim 24 wherein said indentation further includes a plurality of semi-circular saw-tooth steps positioned in sides of said indentation, said steps each having a first surface for reflecting light backward along said longitudinal light axis and a second surface for reflecting light from said backward direction at an angle substantially perpendicular to said longitudinal axis.

26. The system set forth in claim 23 wherein said coupon stock is stored internal to said printer prior to printing.

27. The system set forth in claim 26 wherein printed ones of said coupons are stored internal to said printer.

28. The system set forth in claim 26 wherein said coupon stock source is a plurality of different selectable coupons.

29. The system set forth in claim 28 wherein one of said selectable coupons is obtained external to said printer at the time of printing.