Spatial light modulator based phase contrast image projection system

• US 5,508,841 A
• Filed: 01/09/1995
• Issued: 04/16/1996
• Est. Priority Date: 09/15/1993
• Status: Expired due to Term

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Leddy, Michael, Boysel, Mark, Florence, James M., Lin, Tsen-Hwang
• Primary Examiner(s): Lee, John D.
• Application Number:
  US08/369,979
• Time in Patent Office: 463 Days
• Field of Search: 359/259, 359/263, 359/276, 359/277, 359/559-562, 359/577, 359/316, 359/318, 382/31, 382/42, 382/43, 382/278-280, 382/284
• US Class Current: 359/318
• CPC Class Codes: G02B 26/06 for controlling the phase of light G02B26/08 takes precedence , measuring optical phase difference G01J9/00
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G02B 27/52 Phase contrast optics in microscopes G02B21/14

Abstract

A phase-contrast DMD based image system 36 for projecting an amplitude and phase modulated image. A flexure beam DMD array 34 is used to allow analog phase modulation of reflected light 38. The phase modulation is converted to amplitude modulation by the phase-contrast imaging optics including a phase plate 42. The resulting amplitude modulated wave is flicker-free and does not need to be synchronized to optical image sensors.

Claims

1. A method of amplitude modulation of visible and non-visible light comprising:

providing a coherent incident beam of light having a selected frequency;

deflecting at least one selected element of an array of deflectable micro-mirror elements;

reflecting said incident beam of light from said deflected micro-mirror element to form a reflected beam of light, wherein the path of said reflected light is lengthened by said deflecting step, thereby altering the phase of said reflected light;

focusing said reflected beam to separate the zeroth-order components from the other components; and

altering the relative phase of said reflected beam to cause interference between said zeroth-order component and said other components.

2. The method of claim 1 wherein said zeroth order is retarded π

/2 radians.

3. The method of claim 1 wherein said selected frequency of said incident beam of light is an infrared frequency.

4. The method of claim 1 further comprising the step of separating said reflected beam from said incident beam;

5. The method of claim 1 wherein each of said elements of said array of deflectable micro-mirror elements comprises a mirror suspended over an electrode by flexure hinges.

6. The method of claim 1 further comprising the step of attenuating said zeroth-order component.

7. An image display system comprising:

a source of coherent light to project incident light along a light path;

a micro-mirror device array having addressable mirror elements located in said light path for reflecting said incident light so as to shift the phase of said reflected light;

a lens for focusing said reflected light, said focusing to separate said reflected light into a zeroth-order component and higher-order components; and

a phase plate for altering the relative phase of said focused reflected light thereby causing interference between said zeroth-order component and said higher order components to produce amplitude modulated light.

8. The display system of claim 7 wherein said source is an infrared source.

9. The display system of claim 7 wherein said source is a visible source.

10. The display system of claim 7 wherein said source is an ultra-violet source.

11. The display system of claim 7 wherein said phase plate retards the zeroth-order of said reflected light by π

/2 radians.

12. The display system of claim 7 wherein said phase plate attenuates the zeroth-order of said reflected light.

13. The display system of claim 7 further comprising a beamsplitter for separating said incident light from said reflected light.

14. An image display system comprising:

an array having addressable modulator elements positioned to phase-modulate an incident beam of coherent light;

means for separating said phase-modulated beam into a zeroth-order component and higher-order components;

means for altering the relative phases of said components; and

means for recombining said phase altered components so as to cause interference between said zeroth-order component and said higher order components.

15. The display system of claim 14 wherein said incident beam of coherent light is an infrared beam of coherent light.

16. The display system of claim 14 wherein said incident beam of coherent light is a visible beam of coherent light.

17. The display system of claim 14 wherein said incident beam of coherent light is an ultra-violet beam of coherent light.

18. The display system of claim 14 wherein said means for altering retards the zeroth-order of said separated light by π

/2 radians.

19. The display system of claim 14 wherein said means for altering attenuates the zeroth-order of said separated light.

20. The display system of claim 14 further comprising a beamsplitter for separating said incident beam of coherent light from said phase-modulated beam.