Touch Screen Sensor Accuracy via Backlight Periodic Switching
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Solution Overview
Problem
The detection accuracy of sensors in touch screen display devices is compromised by external light and backlight or light from spontaneous light-emitting elements, which affects the ability to accurately detect touch inputs.
Innovation Solution
Implementing a control mechanism that turns off the backlight or displays the panel in black during sensor output scans to reduce the influence of external light and spontaneous light-emitting elements, thereby enhancing touch detection accuracy while minimizing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the backlight is kept on continuously, then the display remains visible and provides good user experience, but the sensor detection accuracy deteriorates due to interference from backlight light
Solution Approach 1:
The patent implements periodic switching of the backlight between on and off states. During touch detection periods, the backlight is turned off to eliminate interference and improve sensor accuracy. During display periods, the backlight is turned on to maintain visibility. This periodic action resolves the contradiction by alternating between the two opposing requirements at different time intervals.
Solution Approach 2:
The patent performs preliminary actions by turning off the backlight before touch detection begins and turning it back on after detection completes. This preliminary control of the backlight state ensures that no interference is present during the critical detection phase, thereby maintaining high measurement precision without requiring continuous backlight suppression.
2Measurement precision
If the backlight is turned off during sensor scan, then touch detection accuracy improves, but power consumption increases due to extended backlight control cycles
Solution Approach 1:
The patent uses periodic switching to minimize power consumption while maintaining detection accuracy. By alternating between detection mode (backlight off) and display mode (backlight on), the system ensures the backlight is off only during brief detection intervals rather than continuously, thereby reducing energy use while preserving touch detection precision.
3Use of energy by moving object
If external light is utilized for touch detection, then power consumption is reduced by eliminating separate illumination sources, but detection accuracy deteriorates due to noise from external light variations
Solution Approach 1:
The patent converts the harmful effect of external light variations into a beneficial measurement signal. By using the ambient light that would normally cause noise as the illumination source for touch detection, the system eliminates the need for separate illumination sources and reduces power consumption. The external light, instead of being purely detrimental, becomes the useful illumination needed for detecting touch-induced changes.
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 increases touch detection accuracy by eliminating the interference from external and backlight light sources, making it suitable for various liquid crystal display devices such as cellular phones, PDAs, and TVs, and organic ELs, while reducing power consumption.
Implementation Method 1
a system for building optical sensors into a liquid crystal display panel... the sensor receives not only external light but also backlight from its rear surface
Data Source
AI summary
A display device with a touch screen having display pixels and optical sensors each arranged in a matrix. In the display device, a backlight controller controls a backlight unit to be turned ON in a data display duration and controls the backlight unit to be turned OFF in a sensor detection duration other than the data display duration. Consequently, the influence of backlight on a touch part when the shade of the touch part is to be detected, can be reduced and an accuracy in the detection of an optical sensor can be increased.