Field diode detection of excess light conditions for spatial light modulator

• US 20030123123A1
• Filed: 12/23/2002
• Published: 07/03/2003
• Est. Priority Date: 12/27/2001
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Huffman, James D.
• Granted Patent: US 7,116,459 B2
• Time in Patent Office: Days
• US Class Current: 359/248
• CPC Class Codes: G02B 26/0841 the reflecting element being moved or deformed by electrostatic means
• CPC Class Codes: G09G 2330/04 Display protection
• CPC Class Codes: G09G 3/346 based on modulation of the reflection angle, e.g. micromirrors micromirrors devices per se G02B26/0833

Abstract

An improved SLM that is capable of detecting when light incident on the SLM exceeds a predetermined threshold. A diode is fabricated around, or within the pixel array. Light incident on the array (and the diode) results in a current increase through the diode, which may detected and used to initiate a disable signal to control circuitry of the SLM.

Claims

1. An improved spatial light modulator (SLM) having an array of pixel elements and control circuitry, the improvement comprising:

a diode placed around at least a portion of the perimeter of the pixel array, the diode operable to conduct current in response to light incident on the pixel array; and

a disable circuit operable to receive the current from the diode and to deliver a disable signal to the control circuitry when the current exceeds a predetermined amplitude.

2. The improved SLM of claim 1, wherein the SLM is a DMD and the pixel array is an array of micro-mirror elements.

3. The improved SLM of claim 1, wherein the SLM is a LCD and the pixel array is an array of liquid crystal elements.

4. The improved SLM of claim 1, wherein the diode is an n−

well diode.

5. The improved SLM of claim 1, wherein the diode is reverse biased.

6. The improved SLM of claim 1, wherein the diode is biased in electrical connection with an operating voltage of the SLM.

7. An improved spatial light modulator (SLM) having an array of pixel elements and control circuitry, the improvement comprising:

at least one diode fabricated within the pixel array, the diode operable to conduct current in response to light incident on the pixel array; and

a disable circuit operable to receive the current from the diode and to deliver a disable signal to the control circuitry when the current exceeds a predetermined amplitude.

8. The improved SLM of claim 7, wherein the SLM is a DMD and the pixel array is an array of micro-mirror elements.

9. The improved SLM of claim 7, wherein the SLM is a LCD and the pixel array is an array of liquid crystal elements.

10. The improved SLM of claim 7, wherein the diode is an n−

well diode.

11. The improved SLM of claim 7, wherein the diode is reverse biased.

12. The improved SLM of claim 7, wherein the diode is biased in electrical connection with an operating voltage of the SLM.

13. A method of detecting light incident on a spatial light modulator (SLM), the SLM having an array of pixel elements and control circuitry, the improvement comprising:

placing a diode proximate to pixels of the pixel array, the diode operable to conduct current in response to light incident on the pixel array; and

providing electrical connection between current through the diode and a sensing circuit; and

detecting the current through the diode using the sensing circuit.

14. The method of claim 13, further providing the step of determining whether the current exceeds a predetermined amplitude.

15. The method of claim 14, further comprising the step of providing an electrical connection from the sensing circuit to a control circuit of the SLM, and of disabling the SLM when the current exceeds a predetermined threshold.

16. The method of claim 13, wherein the placing step is performed by providing a field diode around at least a portion of the perimeter of the array.

17. The method of claim 13, wherein the placing step is performed by providing at least one diode within the array.

18. The method of claim 13, wherein the SLM and the diode are fabricated using semiconductor fabrication techniques.

19. The method of claim 13, wherein the SLM is a DMD and the pixel array is an array of micro-mirror elements.

20. The method of claim 13, wherein the SLM is a LCD and the pixel array is an array of liquid crystal elements.

21. An array of digital micromirror pixel elements, comprising:

a mirror layer having a reflective mirror associated with each pixel element;

a hinge layer spaced under the mirror layer, the hinge layer having a torsion hinge under each mirror and attached to the mirror such that the mirror may tilt above the hinge layer;

an address layer spaced under the hinge layer, the address layer having circuitry for controlling operation of the pixel elements;

a diode placed around at least a portion of the perimeter of the pixel elements, the diode operable to conduct current in response to light incident on the mirrors; and

a disable circuit operable to receive the current from the diode and to disable operation of the pixel elements when the current exceeds a predetermined amplitude.

22. An array of digital micromirror pixel elements, comprising:

a mirror layer having a reflective mirror associated with each pixel element;

a hinge layer spaced under the mirror layer, the hinge layer having a torsion hinge under each mirror and attached to the mirror such that the mirror may tilt above the hinge layer;

an address layer spaced under the hinge layer, the address layer having circuitry for controlling operation of the pixel elements;

at least one diode fabricated within the mirror layer, the diode operable to conduct current in response to light incident on the mirrors; and

a disable circuit operable to receive the current from the diode and to disable operation of the pixel elements when the current exceeds a predetermined amplitude.