Optical Waveguide Input System with Periodic Radiation Switching
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Solution Overview
Problem
Interactive input systems face challenges in accurately detecting pointers due to detrimental light sources such as sunlight and external glare, which degrade the signal-to-noise ratio and lead to false pointer detections.
Innovation Solution
The system employs an optical waveguide with a diffusion layer and a radiation source configuration where the first radiation source is turned off when the second source is on, and vice versa, with the imaging device's exposure time reduced to minimize ambient light capture while increasing the intensity of the radiation source during exposure, enhancing the signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the imaging device captures images for a longer exposure time to improve pointer detection, then more ambient light is captured, but the signal-to-noise ratio deteriorates due to detrimental light sources
Solution Approach 1:
The system uses periodic action by alternating between two radiation sources in a time-division multiplexing scheme. The first radiation source illuminates during the first exposure period, then turns off while the second radiation source turns on for the second exposure period. This periodic switching allows the imaging device to capture images at different illumination conditions sequentially, improving pointer detection accuracy while managing ambient light interference through temporal separation of illumination events.
2Illumination intensity
If the radiation source intensity is increased to improve signal capture, then the desired light signal is enhanced, but the detrimental light interference is also amplified
Solution Approach 1:
The system applies periodic action by switching between two radiation sources with different characteristics. During the first exposure period, the first radiation source operates at optimal intensity for signal capture. During the second exposure period, the second radiation source operates, allowing the system to compare images taken under different illumination conditions. This periodic switching enables the system to enhance desired light signal while managing detrimental light interference through differential processing of the two image sets.
3Object-affected harmful factors
If ambient light capture is reduced by shortening exposure time, then detrimental light interference is minimized, but the total image frame capture time increases due to multiple exposure periods
Solution Approach 1:
The system uses periodic action with two radiation sources to capture images during separate exposure periods within a single frame capture cycle. By alternating illumination sources and capturing images during each period, the system minimizes ambient light interference in each individual exposure while maintaining efficient overall frame capture throughput through parallel processing of the two image sets.
Solution Approach 2:
The system applies preliminary action by pre-coordinating the switching between two radiation sources and the imaging device exposure timing. The controller synchronizes the radiation source transitions with the image capture periods, ensuring that each source is ready to illuminate at the precise moment needed. This preliminary coordination optimizes the use of available time and reduces overhead, minimizing the total frame capture time while still achieving reduced ambient light interference through the dual-period approach.
4Measurement precision
If two radiation sources are used alternately to improve signal-to-noise ratio, then pointer detection accuracy is enhanced, but the device complexity increases
Solution Approach 1:
The system uses periodic action with two radiation sources to capture images under different illumination conditions, then processes these images to improve pointer detection accuracy. The controller manages the periodic switching between sources and coordinates the imaging device to capture frames during each period. This approach enhances measurement precision through differential image analysis while keeping device complexity manageable by using a systematic, time-division based control strategy rather than more complex spatial or spectral multiplexing methods.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly improves pointer detection accuracy by reducing detrimental light capture and increasing desired light capture, resulting in a higher signal-to-noise ratio and more robust image processing.
Implementation Method 1
a first radiation source directing radiation into the optical waveguide, the radiation undergoing total internal reflection within the optical waveguide
Implementation Method 2
a diffusion layer adjacent to and on one side of the optical waveguide, totally internally reflected light being frustrated and escaping the optical waveguide in response to the pointer contacts on the diffusion layer
Data Source
AI summary
An input panel for an interactive input system comprises an optical waveguide; a 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 on one side of the optical waveguide, totally internally reflected light being frustrated and escaping the optical waveguide in response to pointer contacts on the diffusion layer; a second radiation source directing radiation towards another side of the optical waveguide that is opposite the one side; and at least one imaging device having a field of view looking at the optical waveguide and capturing image frames, wherein said first and second radiation sources are turned on and off in succession and wherein said first radiation source is turned off when said second radiation source is on and wherein said first radiation source is turned on when said second radiation source is off.