DETERMINATION OF INTERFEROMETRIC MODULATOR MIRROR CURVATURE AND AIRGAP VARIATION USING DIGITAL PHOTOGRAPHS

• US 20090051925A1
• Filed: 05/07/2008
• Published: 02/26/2009
• Est. Priority Date: 06/30/2006
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Djordjev, Kostadin
• Granted Patent: US 7,688,452 B2
• Time in Patent Office: Days
• US Class Current: 356/506
• CPC Class Codes: G02B 26/001 based on interference in an adjustable optical cavity interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26
• CPC Class Codes: G02B 27/0012 Optical design, e.g. procedures, algorithms, optimisation routines
• CPC Class Codes: G02F 1/21 by interference

Abstract

Air gap variation in an interferometric modulator over a two-dimensional spatial map of the modulator is determined by acquiring a digital photograph of the modulator. Color parameters of individual pixels in the photograph are determined and compared to a model of color parameters as a function of air gap distance. The model and individual pixel color parameters may be plotted on a color space plot for comparison. The determined distances may be plotted over a two-dimensional spatial map of the interferometric modulator to visualize the mirror curvature and air gap variation.

Claims

1. A method comprising:

determining, in an electronic device, color parameters for light reflected from a particular location of an interferometer having a first reflective surface and a second reflective surface parallel to the first reflective surface; and

determining, in the electronic device, an estimated distance between the first and second reflective surfaces at the particular location by comparing the determined color parameters with a model stored in a memory.

2. The method of claim 1, wherein the interferometer is an interferometric modulator.

3. The method of claim 1, further comprising repeating the method for a plurality of particular locations of the interferometer.

4. The method of claim 3, further comprising displaying a two-dimensional map of distances between the first and second reflective surfaces as a function of location of the interferometer.

5. The method of claim 3, further comprising determining a tilt, orientation, or curvature of at least one reflective surface of the interferometer.

6. The method of claim 1, further comprising providing an indication of manufacturing defect based at least on the estimated distance.

7. The method of claim 1, further comprising repeating the method for a plurality of interferometers in an array.

8. The method of claim 7, further comprising determining statistical parameters for the plurality of interferometers.

9. The method of claim 8, further comprising providing an indication of manufacturing defect based at least on the determined statistical parameters.

10. A system for identifying a defective display comprising a plurality of interferometers, the system comprising:

a digital photograph acquisition system configured to acquire a digital photograph of the display; and

a computer configured to;

determine color parameters for a plurality of regions in the digital photograph,

compare the determined color parameters with a model to determine distances between a first and second reflective surface of at least one interferometer; and

identify whether the display is defective based on the estimated distances.

11. The system of claim 10, wherein the computer is configured to identify whether the display is defective by comparing the determined distances to a pre-determined specification, wherein the display is identified as defective if the number of interferometers failing to meet the specification is greater than a threshold.

12. The system of claim 10, further comprising an alarm configured to provide an indication of whether the display is defective.

13. The system of claim 10, further comprising a display configured to display a two-dimensional map of determined distances between the first and second reflective surface.

14. The system of claim 10, wherein the computer is further configured to generate the model based on one or more properties of one or more materials in the display, the properties selected from the group consisting of index of refraction, extinction coefficient, and thickness.

15. The system of claim 10, wherein the determined distances correspond to a single distance for each of a plurality of interferometers.

16. A computer-readable medium comprising code which, when executed, causes a processor to perform a method comprising:

determining color parameters for light reflected from a particular location of an interferometer having a first reflective surface and a second reflective surface parallel to the first reflective surface; and

determining an estimated distance between the first and second reflective surfaces at the particular location by comparing the determined color parameters with a model.

17. The computer-readable medium of claim 16, wherein the method further comprises deriving the model based on one or more properties of one or more materials in the interferometer, the properties selected from the group consisting of index of refraction, extinction coefficient, and thickness.

18. The computer-readable medium of claim 16, wherein the method further comprises repeating the method for a plurality of interferometers in an array.

19. The computer-readable medium of claim 18, wherein the method further comprises determining statistical parameters for the plurality of interferometers.

20. The computer-readable medium of claim 19, wherein the method further comprises providing an indication of manufacturing defect based at least on the determined statistical parameters.