Method and system for cancellation of ambient light using light frequency

• US 20060091288A1
• Filed: 10/29/2004
• Published: 05/04/2006
• Est. Priority Date: 10/29/2004
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Wilson, Andrew D., Gillett, Donald M., Keam, Nigel S.
• Granted Patent: US 7,359,564 B2
• Time in Patent Office: Days
• US Class Current: 250/208.1
• CPC Class Codes: G06F 2203/04108 Touchless 2D- digitiser, i.e. digitiser detecting the X/Y position of the input means, finger or stylus, also when it does not touch, but is proximate to the digitiser's interaction surface without distance measurement in the Z direction
• CPC Class Codes: G06F 3/04182 Filtering of noise external to the device and not generated by digitiser components
• CPC Class Codes: G06F 3/0425 using a single imaging device like a video camera for tracking the absolute position of a single or a plurality of objects with respect to an imaged reference surface, e.g. video camera imaging a display or a projection screen, a table or a wall surface, on which a computer generated image is displayed or projected tracking a projected light spot to determine a position on a display surface G06F3/0386
• CPC Class Codes: G06V 10/145 Illumination specially adapted for pattern recognition, e.g. using gratings
• CPC Class Codes: H04N 23/745 Detection of flicker frequency or suppression of flicker wherein the flicker is caused by illumination, e.g. due to fluorescent tube illumination or pulsed LED illumination

Abstract

Compensation of the effects of uncontrolled light in an imaging system using a controlled light source. Light from the controlled light source reflected by an object and uncontrolled light are detected in a plurality of frequency ranges. Intensity of the uncontrolled light is determined based on the varying sensitivity of an image sensor to light in the different frequency ranges and known emission characteristics of the controlled light source in the frequency ranges. Once the intensity of the uncontrolled light is determined, the total light detected at each point is adjusted to reduce the effects of the uncontrolled light in the resulting imaging data produced by the imaging system.

Claims

1. A method for reducing effects of uncontrolled light in imaging data, comprising the steps of:

(a) illuminating a region of interest with controlled light generated by a controlled light source emitting light having known intensities in a plurality of frequency ranges;

(b) positioning an image sensing system to receive light from the region of interest, the image sensor system being configured to detect an intensity of light in each of the plurality of frequency ranges;

(c) acknowledging different sensitivities of the image sensing system to light received in each of the plurality of frequency ranges;

(d) detecting the intensity of received light from the region of interest in each of the plurality of frequency ranges, the received light including the uncontrolled light and a portion of the controlled light that has been reflected from the region of interest; and

(e) computing an intensity of the uncontrolled light included in the received light based on the known intensities of the controlled light source and the intensity of light intensity detected in each of the plurality of frequency ranges; and

(f) adjusting the imaging data as a function of the computed intensity of the uncontrolled light to compensate for a contribution of the uncontrolled light to the imaging data.

2. The method of claim 1, wherein the controlled light source emits light in at least one of:

(a) an infrared spectrum;

(b) a visible spectrum; and

(c) an ultraviolet spectrum.

3. The method of claim 1, further comprising configuring the controlled light source such that the controlled light source emits light of approximately equal intensity in each of the plurality of frequency ranges.

4. The method of claim 1, wherein the steps of detecting the intensity of the received light, computing the intensity of the uncontrolled light, and adjusting the imaging data is performed for each of a plurality of portions comprising the region of interest.

5. The method of claim 4, wherein the portions of the region of interest include each of the points in the region of interest.

6. The method of claim 5, wherein the step of adjusting the imaging data comprises the step of adjusting the imaging data based on the computed intensity of the uncontrolled light by subtracting the computed intensity of the uncontrolled light from an intensity of the received light at each point within the region of interest.

7. The method of claim 1, wherein the image sensing system includes one of:

(a) a detector fitted with a mosaic filter, the detector having a plurality of positions each being correlated with filter elements, each of the filter elements being configured to allow a selected frequency range of light to pass at each of the plurality of positions;

(b) a plurality of image detectors, each of the detectors being adapted to receive light in a different frequency range; and

(c) a detector fitted with a cycling filter having a plurality of filter elements allowing a particular frequency range to pass during each cycle of the cycling filter; and

(d) a composite color image detector having a plurality of detecting cells at each of a plurality of positions, each of the detecting cells being configured to detect a particular frequency range.

8. The method of claim 7, wherein the filter elements are configured to pass one of:

(a) a red frequency range;

(b) a blue frequency range; and

(c) a green frequency range.

9. The method of claim 7, wherein the detector comprises a digital camera and the mosaic filter includes a Bayer filter that passes predefined frequency ranges of light at each of the plurality of positions, each of the plurality of positions corresponding to a pixel of the digital camera.

10. A method for reducing effects of uncontrolled light in imaging data, comprising the steps of:

(a) illuminating a region of interest with controlled light generated by a controlled light source emitting light having a consistent intensity over a plurality of frequency ranges;

(b) positioning an image sensing system to receive light from the region of interest at each of a plurality of positions, the image sensor system being configured to detect an intensity of light in each of the plurality of frequency ranges at each of the plurality of positions;

(c) acknowledging different sensitivities of the image sensing system to light received in each of the plurality of frequency ranges;

(d) detecting the intensity of received light from the region of interest in each of the plurality of frequency ranges at each of the plurality of positions, the received light including the uncontrolled light and a portion of the controlled light that has been reflected from the region of interest;

(e) computing an intensity of the uncontrolled light included in the received light based at each of the plurality of positions based on the consistent intensity of the controlled light source and the intensity of light intensity detected in each of the plurality of frequency ranges at each of the plurality of positions; and

(f) adjusting the imaging data for each of the plurality of positions as a function of the computed intensity of the uncontrolled light at each of the plurality of positions to compensate for a contribution of the uncontrolled light to the imaging data.

11. The method of claim 10, wherein the controlled light source emits light in at least one of:

(d) an infrared spectrum;

(e) a visible spectrum; and

(f) an ultraviolet spectrum.

12. The method of claim 10, wherein the image sensing system includes one of:

(a) a detector fitted with a mosaic filter, the sensor having a plurality of positions each being correlated with filter elements, each of the filter elements being configured to allow a selected frequency range of light to pass at each of the plurality of positions;

(b) a plurality of image sensors, each of the sensors being adapted to receive light in a different frequency range; and

(c) a sensor fitted with a cycling filter having a plurality of filter elements allowing a particular frequency range to pass during each cycle of the cycling filter; and

(d) a composite color image sensor having a plurality of detecting cells at each of a plurality of positions, each of the detecting cells being configured to detect a particular frequency range.

13. The method of claim 12, wherein the filter elements are configured to pass one of:

(a) a red frequency range;

(b) a blue frequency range; and

(c) a green frequency range.

14. The method of claim 12, wherein the sensor comprises a digital camera and the mosaic filter includes a Bayer filter that passes predefined frequency ranges of light at each of the plurality of positions, each of the plurality of positions corresponding to a pixel of the digital camera.

15. The method of claim 10, wherein the step of adjusting the imaging data comprises the step of adjusting the imaging data for each of the plurality of positions within the region of interest by subtracting the computed intensity of the uncontrolled light for each position of the region of interest from an intensity of the received light at each position within the region of interest.

16. The method of claim 10, wherein the step of adjusting the imaging data comprises the step of subtracting the computed intensity of the uncontrolled light from an intensity of the received light at each position within the region of interest.

17. A system for reducing effects of uncontrolled light in imaging data, comprising:

(a) a display surface adjacent to which an object having a marking thereon can be disposed, said display surface displaying images determined by the software application

(b) a controlled light source disposed to illuminate an object disposed adjacent the interactive display surface, the controlled light source being configured to emit controlled light having known intensities in a plurality of frequency ranges;

(c) an image sensing system disposed to receive light from the region of interest, the image sensor system being configured to detect an intensity of light in each of the plurality of frequency ranges and having differing sensitivities to light received in each of the plurality of frequency ranges, the received light including the uncontrolled light and a portion of the controlled light that has been reflected from the region of interest;

(d) a processor in communication with the image sensing system;

(d) a memory in communication with the processor, the memory storing data and machine instructions that cause the processor to carry out a plurality of functions, including;

(i) computing an intensity of the uncontrolled light included in the received light based on the known intensities of the controlled light source and the intensity of light intensity detected in each of the plurality of frequency ranges; and

(ii) adjusting the imaging data as a function of the computed intensity of the uncontrolled light to compensate for a contribution of the uncontrolled light to the imaging data.

18. The system of claim 17, wherein the controlled light is configured to emit light in at least one of:

(g) an infrared spectrum;

(h) a visible spectrum; and

(i) an ultraviolet spectrum.

19. The system of claim 17, wherein the controlled light source is configured to emit light of approximately equal intensity in each of the frequency ranges.

20. The system of claim 17, wherein the intensity of the received light is detected, computing intensity of the uncontrolled light is computed, and the imaging data is adjusted for each plurality of portions comprising the region of interest.

21. The system of claim 20, wherein the portions of the region of interest include each of the points in the region of interest.

22. The system of claim 21, wherein adjusting the imaging data comprises adjusting the imaging data based on the computed intensity of the uncontrolled light by subtracting the computed intensity of the uncontrolled light from an intensity of the received light at each point within the region of interest.

23. The system of claim 17, wherein the image sensing system includes one of:

(a) a sensor fitted with a mosaic filter, the sensor having a plurality of positions each being correlated with filter elements, each of the filter elements being configured to allow a selected frequency range of light to pass at each of the plurality of positions;

(b) a plurality of image sensors, each of the sensors being adapted to receive light in a different frequency range; and

(c) a sensor fitted with a cycling filter having a plurality of filter elements allowing a particular frequency range to pass during each cycle of the cycling filter; and

(d) a composite color image sensor having a plurality of detecting cells at each of a plurality of positions, each of the detecting cells being configured to detect a particular frequency range.

24. The system of claim 23, wherein the filter elements are configured to pass one of:

(a) a red frequency range;

(b) a blue frequency range; and

(c) a green frequency range.

25. The system of claim 23, wherein the sensor comprises a digital camera and the mosaic filter includes a Bayer filter that passes predefined frequency ranges of light at each of the plurality of positions, each of the plurality of positions corresponding to a pixel of the digital camera.

26. A system for reducing effects of uncontrolled light in imaging data, comprising:

(a) a display surface adjacent to which an object having a marking thereon can be disposed, said display surface displaying images determined by the software application

(b) a controlled light source disposed to illuminate an object disposed adjacent the interactive display surface, the controlled light source being configured to emit controlled light having a consistent intensity across a plurality of frequency ranges;

(c) an image sensing system disposed to receive light from the region of interest, the image sensor system being configured to detect an intensity of light in each of the plurality of frequency ranges at each of a plurality of positions, the received light including the uncontrolled light and a portion of the controlled light that has been reflected from the region of interest;

(d) a processor in communication with the image sensing system;

(d) a memory in communication with the processor, the memory storing data and machine instructions that cause the processor to carry out a plurality of functions, including;

(i) computing an intensity of the uncontrolled light included in the received light at each of the plurality of positions based on the consistent intensity of the controlled light source and the intensity of light intensity detected in each of the plurality of frequency ranges at each of the plurality of positions; and

(ii) adjusting the imaging data as a function of the computed intensity of the uncontrolled light to compensate for a contribution of the uncontrolled light to the imaging data at each of the plurality of positions.

27. The system of claim 26, wherein the controlled light is configured to emit light in at least one of:

(j) an infrared spectrum;

(k) a visible spectrum; and

(l) an ultraviolet spectrum.

28. The system of claim 26, wherein the image sensing system includes one of:

(a) a sensor fitted with a mosaic filter, the sensor having a plurality of positions each being correlated with filter elements, each of the filter elements being configured to allow a selected frequency ranges of light to pass at each of the plurality of positions;

(b) a plurality of image sensors, each of the sensors being adapted to receive light in a different frequency range; and

(c) a sensor fitted with a cycling filter having a plurality of filter elements allowing a particular frequency range to pass during each cycle of the cycling filter; and

(d) a composite color image sensor having a plurality of detecting cells at each of a plurality of positions, each of the detecting cells being configured to detect a particular frequency range.

29. The system of claim 28, wherein the filter elements are configured to pass one of:

(a) a red frequency range;

(b) a blue frequency range; and

(c) a green frequency range.

30. The system of claim 28, wherein the sensor comprises a digital camera and the mosaic filter includes a Bayer filter that passes predefined frequency ranges of light at each of the plurality of positions, each of the plurality of positions corresponding to a pixel of the digital camera.