Optical Touch System Using Polarizing Elements to Block Hot Spots
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Solution Overview
Problem
Conventional touch rear projection systems face challenges in accurately determining touch positions due to overexposed hot spots caused by infrared beams, leading to increased system volume and energy waste, and higher costs from multiple IR-LEDs and image detectors.
Innovation Solution
An optical touch system utilizing non-visible light sources, a screen, a first polarizing element, and a second polarizing element, where the second polarizing element blocks part of the non-visible beam causing hot spots, enhancing accuracy and reducing system volume and energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the infrared beam is emitted at a larger angle to avoid hot spots, then the hot spot issue is reduced, but the system volume becomes larger
Solution Approach 1:
A polarizing element is introduced as an intermediary component between the IR-LED and the screen. This polarizing element selectively blocks the reflected infrared beam that would otherwise create hot spots on the image detector, while allowing the transmitted beam to pass through. By using this intermediary polarizing element, the system can emit infrared beams at larger angles without increasing system volume, as the hot spot problem is solved optically rather than geometrically.
2Illumination intensity
If multiple IR-LEDs or higher energy IR-LEDs are adopted to compensate for insufficient illumination, then the illumination intensity is improved, but energy consumption increases
Solution Approach 1:
The patent changes the polarization parameter of the infrared beam using a polarizing element. This parameter change allows the system to maintain sufficient illumination intensity with a single IR-LED by optimizing the beam's polarization state, rather than increasing energy output or using multiple LEDs. The polarizing element ensures that the reflected beam is blocked while allowing the transmitted beam to maintain adequate intensity for touch detection.
3Illumination intensity
If multiple IR-LEDs are adopted to improve illumination, then the illumination intensity is improved, but the number of image detectors and image capture lenses increases, enhancing cost
Solution Approach 1:
The polarizing element serves as an intermediary that enables a single IR-LED to provide sufficient illumination intensity by controlling the polarization state of the beam. This eliminates the need for multiple IR-LEDs and consequently reduces the number of required image detectors and image capture lenses, simplifying the overall system structure and reducing cost while maintaining adequate illumination for touch position detection.
4Object-affected harmful factors
If the infrared beam is emitted at a larger angle to avoid hot spots, then the hot spot issue is reduced, but the illumination becomes insufficient
Solution Approach 1:
The patent applies parameter changes by introducing a polarizing element that modifies the polarization state of the infrared beam. This allows the system to emit beams at larger angles to avoid hot spots while maintaining sufficient illumination intensity through the polarizing element's selective transmission properties. The polarizing element ensures that the transmitted beam retains adequate energy for effective touch detection despite the larger emission angle.
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
The system effectively enhances touch position accuracy, reduces system size, and improves light efficiency by eliminating hot spots and minimizing the need for additional IR-LEDs and image detectors.
Implementation Method 1
The first polarizing element is disposed in the light path of the non-visible beam and located between the non-visible light source and the screen. The second polarizing element is disposed in the light path of the object beam passing through the screen and located between the screen and the optical detector.
Data Source
AI summary
An optical touch system includes a non-visible light source, a screen, a first and second polarizing elements, and an optical detector. The non-visible light source emits a non-visible beam. A part of the non-visible beam passes through the screen disposed in a light path of the non-visible beam. The touch object reflects the part of the non-visible beam into an object beam when a touch object approaches or touches the screen, and the object beam passes through the screen. The first polarizing element is disposed in the light path of the non-visible beam and between the non-visible light source and the screen. The optical detector is disposed in a light path of the object beam, and senses the object beam. The second polarizing element is disposed in the light path of the object beam passing through the screen and between the screen and the optical detector.