Interactive input system with improved signal-to-noise ratio (SNR) and image capture method

1. An input panel for an interactive input system comprising:

an optical waveguide;

a first radiation source that is turned on and off, when on said first radiation source directing radiation into said optical waveguide, said radiation undergoing total internal reflection within said optical waveguide;

a diffusion layer adjacent to and disposed on one major outer side of the optical waveguide, totally internally reflected radiation within said optical waveguide being frustrated and escaping the optical waveguide in response to one or more pointer contacts on the diffusion layer;

at least one second radiation source that is turned on and off, when on said at least one second radiation source directing radiation towards an opposite major outer side of the optical waveguide; and

at least one imaging device having a field of view looking at the opposite major outer side of the optical waveguide and capturing image frames, wherein during image frame capture operation, image frames are captured at least when (i) the first radiation source is on and the at least one second radiation source is off (ii) the first radiation source is off and the at least one second radiation source is on and (iii) the first radiation source is off and the at least one second radiation source off.

2. The input panel of claim 1 , wherein said at least one imaging device comprises a first imaging device and a second imaging device, wherein said first imaging device is timed to capture image frames when said first radiation source is on and said at least one second radiation source is off and wherein said second imaging device is timed to capture image frames when said first radiation source is off and said at least one second radiation source is on and when said first radiation source is off and said at least one second radiation source is off.

3. The input panel of claim 2 further comprising processing structure processing the image frames captured by said first and second imaging devices to identify the location of one or more pointer contacts on the diffusion layer.

4. The input panel of claim 3 , further comprising a projector receiving image data from said processing structure and projecting images based on said image data for presentation on said diffusion layer.

5. The input panel of claim 4 , further comprising an infrared reflective film above the diffusion layer.

6. The input panel of claim 2 , wherein the first radiation source directs radiation at a first wavelength and the at least one second radiation source directs radiation at a second wavelength different from the first wavelength.

7. The input panel of claim 6 , wherein the processing structure compares image frames captured by the first imaging device with image frames captured by the second imaging device to filter out tracing artifacts.

8. The input panel of claim 1 further comprising processing structure processing the image frames captured by said at least one imaging device to identify the location of one or more pointer contacts on the diffusion layer.

9. The input panel of claim 8 , further comprising a projector receiving image data from said processing structure and projecting images based on said image data for presentation on said diffusion layer.

10. The input panel of claim 1 , wherein the exposure time of the at least one imaging device is less than a total image frame capture time.

11. The input panel of claim 1 , wherein said first and at least one second radiation sources comprise infrared light emitting diodes.

12. The input panel of claim 1 , wherein the diffusion layer is a weave material that, when depressed, frustrates the totally internally reflected radiation within the optical waveguide.

13. The input panel of claim 1 , wherein the diffusion layer is formed of a projection screen material.

14. The input panel of claim 1 , further comprising an infrared reflective film above the diffusion layer.

15. The input panel of claim 1 , wherein said at least one imaging device during normal image frame capture operation is timed to capture image frames when the first radiation source is on and the at least one second radiation source is off and wherein when one or more pointer contacts on the diffusion layer are detected, the normal image frame operation is interrupted and image frames are captured by the at least one imaging device with the first radiation source off and the at least one second radiation source on and with the first radiation source off and the at least one second radiation source off.

16. An interactive input system comprising:

at least one Imaging device capturing image frames of a region of interest, wherein the exposure time for each captured image frame is less than a total image frame capture time;

at least first and second radiation sources that are turned on and off, when on each of the at least first and second radiation sources emitting radiation into the region of interest during the exposure time; and

processing structure processing images captured by said at least one imaging device to determine the presence of one or more pointers within the region of interest, wherein during image frame capture operation, image frames are captured at least when (i) the first radiation source is on and the second radiation source is off (ii) the first radiation source is off and the second radiation source is on and (iii) the first radiation source is off and the second radiation source off.

17. The interactive input system of claim 16 , wherein the exposure time is 40% of the total image frame capture time.

18. The interactive input system of claim 16 , wherein the at least one imaging device comprises a first imaging device and a second imaging device.

19. The interactive input system of claim 18 , wherein the processing structure triangulates the position of the one or more pointers using triangulation based on image frames captured by the first and second imaging devices.

20. The interactive input system of claim 18 , wherein the first and second radiation sources each comprise a current control module that receives a control signal from a respective one of the first and second imaging devices to emit radiation during respective exposure times.

21. The interactive input system of claim 16 , further comprising a projector receiving image data from said processing structure and projecting images based on said image data for presentation on a display surface.

22. The interactive input system of claim 16 , further comprising one or more reflective bezel segments associated with the region of interest for reflecting radiation emitted by the first and second radiation sources back to the at least one imaging device.

23. The interactive input system of claim 22 , wherein the processing structure detects presence of a pointer within the region of interest based on detecting occlusion of reflected radiation in captured image frames.

24. The interactive input system of claim 16 , wherein the processing structure detects presence of one or more pointers within the region of interest based on detecting one or more bright spots corresponding to the pulsed radiation emitted by the one of more pointers.