Printing system exposure module alignment method and apparatus of manufacture

• US 5,105,369 A
• Filed: 12/21/1989
• Issued: 04/14/1992
• Est. Priority Date: 12/21/1989
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Nelson, William E.
• Primary Examiner(s): Lall, Parshotam S.
• Assistant Examiner(s): PIPALA, EDWARD J
• Application Number:
  US07/454,657
• Time in Patent Office: 845 Days
• Field of Search: 364/550, 364/559, 364/551.01, 364/571.01, 364/525, 364/468, 358/480, 358/481, 250/201.9, 250/201.4, 355/228, 355/229, 355/232, 355/53, 355/61, 355/55, 350/6.1, 350/6.5, 350/518, 350/531, 346/76 L, 346/108
• US Class Current: 250/201.4
• CPC Class Codes: B41J 2/465 using masks, e.g. light-switching masks
• CPC Class Codes: G06K 15/12 by photographic printing , e.g. by laser printers
• CPC Class Codes: G06K 15/1252 using an array of light modulators, e.g. a linear array

Abstract

There is disclosed a manufacturing method and apparatus which allows for the efficient assembly of the exposure module of a xerographic reproduction system. The system uses an array of deformable mirrors fabricated in one embodiment, on a monolithic silicon substrate as a light modulation element. The substrate package is positioned with respect to a set of molded support brackets such that a multi-axis adjustment of this single element allows for the alignment of the entire optical set. A system of cameras is used, in conjunction with a computer, to control the substrate positioning and to determine optimum efficiency of the system. The computer adjusts the package around the various rotational axis in sequential fashion.

Claims

1. The method of aligning a light modulation device in a reproduction exposure module unit comprising the steps of:

prealigning the optic elements contained within said exposure module to form a path extending from a source of light to a position representative of where a reproductive surface would reside in an operational printing system;

positioning a light modulation device within said prealigned exposure module along said path;

sending light from said light source through said aligned optics to said representative position;

substituting at said representative position at least one light sensitive detector for said reproduction surface; and

adjusting the rotational and translational position of said light modulation device with respect to said unit in accordance with outputs from said detector.

2. The method set forth in claim 1 wherein said light modulation device includes a plurality of addressable elements;

and

wherein said sending step includes the step of periodically addressing certain of said light modulation elements to cause a modulated light signal to be received by said detector.

3. The method set forth in claim 1 wherein said light sending step comprises the step of:

activating certain elements of said modulation device depending upon the step in the alignment process under consideration.

4. The method set forth in claim 2 wherein said adjusting step is performed in six axes of rotation/translation.

5. The method set forth in claim 4 wherein said six axes of rotation steps include:

adjusting first the X and Y axis, where the X axis is perpendicular to the base upon which said modulation device is mounted and Y is the axis along the longitudinal length of said modulation device;

adjusting next the roll angle Theta, where Theta is the rotational angle around the Z axis, where said Z axis is along said optical path;

adjusting next the pitch angle Epsilon, where Epsilon is the rotational angle around said Y axis;

checking next the outside end elements of said modulation device along said Y axis;

adjusting next the Y axis angle Psi, where Psi is the rotational angle around said X axis; and

adjusting next the focus along said Z axis.

6. The method set forth in claim 5 wherein said light sending step comprises the step of:

activating certain elements of said modulation device depending upon the step in the alignment process.

7. The method set forth in claim 4 further comprising a device for positioning said modulation element with respect to said six axes under control of externally applied signals.

8. The method set forth in claim 7 wherein said external signals are generated from said detector outputs.

9. The method set forth in claim 1 wherein said detector outputs are applied to an algorithm in a computer for subsequent control of said positioning device.

10. The method set forth in claim 9 wherein said algorithm includes the steps of:

determining relative energy levels at certain locations from activated ones of said elements; and

comparing said determined energy levels against pre-established energy levels.

11. The method set forth in claim 2 wherein said adjusting step includes the step of permanently fastening said light modulation device to said exposure module.

12. The method set forth in claim 1 wherein said adjusting step includes holding said light modulation device by a multi-axis control system separate from said unit such that said modulation device is free to move with respect to said unit;

and

controlling the movement of said control system from said detector signals via a controller following one or more pre-established algorithms.

13. The invention set forth in claim 1 wherein said receptor is an electronic camera selectively viewing all light from said modulation device along said optic path.

14. The method set forth in claim 1 wherein said light modulation device includes a plurality of addressable elements arranged in a row;

and

wherein said receptor is a pair of electronic cameras focused on either end of said row.

15. The method set forth in claim 1 wherein said aligning step includes the added step of sending a collimated light beam through said optic path from said representative position to said source of light, reflecting off of a surface simulating the ideal location and action of said light-modulation element.

16. A system for aligning a light modulation device in a xerographic reproduction exposure module unit comprising:

an aligning mechanism for aligning the optics into a line extending from a source of light to a position representative of where a reproductive surface would reside in an operational system;

positioning circuitry for positioning within said aligned optics a light modulation device;

sending circuitry for sending light from said light source through said aligned optics to said representative position;

a light sensitive receptor adapted for substituting at said representative position for said reproductive surface; and

adjusting circuitry for precisely adjusting the relative position of said light modulation device with respect to said unit in accordance with outputs from said receptor.

17. The system set forth in claim 16 wherein said light modulation device includes a plurality of addressable elements;

and

circuitry for periodically addressing certain of said light modulation elements to cause a modulated light signal to be received by said receptors.

18. The system set forth in claim 16 further comprising a system of multi-axis servos for holding said light modulation device separate from said unit such that said device is free to move with respect to said unit, and wherein said servo is controlled from said receptor signals.

19. The system set forth in claim 18 further comprising:

circuitry for accepting said receptor signals and iteratively processing said signals to control said servo until said alignment is achieved.

20. The system set forth in claim 16 wherein said receptor is an electronic camera.

21. The system set forth in claim 16 wherein said light modulation device includes a plurality of addressable elements arranged in a row;

and

wherein said receptor is a pair of electronic cameras focused on either end of said row.

22. The system set forth in claim 16 wherein said aligning mechanism includes optics for sending a collimated light beam through said optic path from said representative position to said source of light.

23. A computer system for positioning a light modulation device in an exposure unit of a reproductive system, said exposure unit having a light source, an optic path, including mirrors, and an imaging lens within said optic path for focusing light modulated by said modulation device, said system comprising:

a positioning device for holding and positioning said light modulation device with respect to said optical path;

circuitry for controlling said positioned modulation device to produce selected modulated light output along said optical path, said modulated light being reflected from said light modulation device; and

a computer for driving said positioning device through a plurality of rotational and translational axes in response to said modulated light signals.

24. The system set forth in claim 23 wherein said system further includes an optic receptor positioned at a location corresponding to a plane at which modulated light from said modulation device would fall upon a reproductive surface of a xerographic process if said modulated light were following said optical path;

and

circuitry for communicating signals from said optic receptor to said computer in order to control said positioning device.

25. The system set forth in claim 24 wherein said positioning device moves said modulation device through at least six rotational/translational axes.

26. The system set forth in claim 25 wherein said computer drives said positioning device along said six axes under control of a system comprising:

circuitry for adjusting the X and Y axis, where the X axis is perpendicular to the base upon which said modulation device is mounted and Y is the axis along the longitudinal length of said modulation device;

circuitry for adjusting the roll angle Theta, where Theta is the rotational angle around the Z axis, where said Z axis is along said optical path;

circuitry for adjusting the pitch angle Epsilon, where Epsilon is the rotational angle around said Y axis;

circuitry for checking the outside end elements of said modulation device along said Y axis;

circuitry for adjusting the Y axis angle Psi, where Psi is the rotational angle around said X axis; and

circuitry for adjusting next the focus along said Z axis.

27. The system set forth in claim 26 wherein said selected light modulation output includes:

circuitry for activating certain elements of said modulation device depending upon the axis in the alignment process being manipulated.

28. The system set forth in claim 26 wherein said positioning control circuitry includes:

circuitry for determining relative energy levels at certain locations from activated ones of said elements; and

circuitry for comparing said determined energy levels against pre-established energy levels.

29. The method of checking optic path alignment in an optic modulation unit of a xerographic reproduction system, said method comprising the steps of:

positioning an optic receptor at a position corresponding to a light source in said modulation unit;

positioning a source of light at a position corresponding to a plane at which modulated light from said modulated unit would fall upon a reproductive surface of the xerographic process if said modulated light were following said optic path; and

inserting a reflective surface in said modulation unit at a location therein corresponding to the location where a modulation element would be located so that light from said light source would pass along said optic path and impact upon said positioned optic receptor as an indication that said optic path is properly aligned.

30. The method set forth in claim 29 further comprising the steps of:

substituting a light modulation unit for said reflective surface; and

reversing said optic receptor and said light source.