Infrared Touch Screen Band Pass Filter for Outdoor Light Interference
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Solution Overview
Problem
Infrared touch screens with thin bezels suffer from increased noise and malfunction due to external light interference, leading to reduced touch recognition and accuracy, especially in outdoor environments where sunlight exposure is significant.
Innovation Solution
The implementation of a band pass filter that only allows specific wavelength bands of infrared signals to pass through, combined with high pass filters and a unique installation groove shape, significantly reduces external light interference by filtering out unwanted wavelengths and improving the interception efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the size of touch screen is increased, then the display area is improved, but the interference of external light becomes larger
Solution Approach 1:
A band pass filter is introduced as an intermediary component between the infrared light emitting elements and light receiving elements. The filter selectively transmits only the specific wavelength band (e.g., 900-1000 nm) used by the infrared LEDs while blocking other wavelengths including sunlight interference. This mediator allows the large display area to function properly even in outdoor environments by eliminating the harmful external light frequencies.
Solution Approach 2:
The patent changes the optical parameter by implementing a band pass filter with specific wavelength transmission characteristics. Instead of using a conventional high pass filter that blocks only certain frequencies, the band pass filter is designed to transmit only the narrow wavelength range emitted by the infrared LEDs (e.g., 900-1000 nm). This parameter change in filter characteristics dramatically reduces external light interference while maintaining infrared signal transmission.
2Device complexity
If conventional high pass filter is used, then the structure is simple, but the external light removal performance is insufficient
Solution Approach 1:
The patent transitions from a conventional high pass filter to a band pass filter with specifically optimized wavelength transmission parameters. The band pass filter is designed to transmit only the narrow wavelength range (e.g., 900-1000 nm) corresponding to the infrared LED emission, while blocking all other wavelengths including visible sunlight. This parameter optimization in the filter's spectral characteristics provides superior external light rejection compared to conventional filters.
3Length of stationary object
If thin bezel structure is adopted, then the device thickness is reduced, but the touch recognition accuracy deteriorates due to increased noise
Solution Approach 1:
The band pass filter serves as an intermediary that cleans the optical signal before it reaches the light receiving elements. By blocking external light wavelengths and transmitting only the infrared signal wavelengths, the filter reduces noise in the received signal. This allows the thin bezel structure to maintain adequate signal-to-noise ratio for accurate touch recognition, even with reduced structural space for signal processing.
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 solution reduces external light interference by more than five times, enabling stable outdoor operation, improving touch velocity and accuracy, and reducing manufacturing costs through enhanced productivity and reduced material usage.
Implementation Method 1
the band pass filter which makes only the infrared of specific wavelength band among the infrared transmitted from the above transmission unit to be received to the above multiple numbers of light receiving elements
Implementation Method 2
the band pass filter which passes only the signal of specific wavelength band
Implementation Method 3
the transmission unit including multiple numbers of light transmitting elements which transmit infrared forward
Implementation Method 4
the reception unit including multiple numbers of light receiving elements installed at two bezels of the above bezels to receive the infrared transmitted from the above transmission unit
Data Source
AI summary
Provided is an infrared touch screen device including the transmission unit which contains the rectangular bezel which is constituted so that the touch screen panel is to be installed, and the multiple numbers of light transmitting elements which are installed in the lengthwise direction of corresponding bezel to one horizontal bezel and one vertical bezel respectively among the bezels and transmitting the infrared rays forward, and the reception unit which is further configured to have the multiple numbers of light receiving elements which are installed at two bezels among the bezels so that the infrared rays transmitted from the transmission unit is to be received and contain the band pass filter which makes only the infrared rays of specific wavelength band among the infrared rays transmitted from the transmission unit to be received by the multiple numbers of light receiving elements.