Touch-Sensor Display With Pixel Photodetectors
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Solution Overview
Problem
Conventional display devices with optical sensors face challenges in providing an input function independent of light environments due to difficulties in high-speed readout and followability with motion inputs, as well as limitations in determining the lengths and intervals of backlight ON and OFF periods.
Innovation Solution
A display device configuration that includes an active matrix substrate with optical sensors, a sensor driving circuit, an amplifying circuit, and a signal processing circuit, featuring first and second sensor pixel circuits that accumulate and output electric charges corresponding to light received during backlight ON and OFF periods, allowing for independent light environment operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If reset and readout are carried out line-sequentially during backlight ON and OFF periods, then light environment influences can be eliminated, but readout speed becomes too slow for practical implementation
Solution Approach 1:
The sensor pixel circuits are divided into two groups: first sensor pixel circuits that accumulate charges during backlight ON period, and second sensor pixel circuits that accumulate charges during backlight OFF period. This segmentation allows parallel processing of different light condition data, eliminating the need for sequential readout while maintaining the ability to eliminate light environment influences through differential processing.
Solution Approach 2:
The backlight is blinked periodically during one frame period, creating distinct ON and OFF periods. Sensor pixel circuits are configured to accumulate charges during specific periods (ON or OFF), enabling periodic sampling of light conditions. This periodic action facilitates high-speed parallel readout while maintaining the capability to eliminate light environment influences through differential processing of periodically sampled data.
2Use of energy by moving object
If backlight is turned on at once for the entire screen, then power consumption is reduced, but inability to control individual region backlight timing limits light environment adaptation
Solution Approach 1:
The display screen is divided into multiple regions with independently controllable backlight units. Each backlight unit can be controlled individually to turn on or off, allowing selective illumination of different screen regions. This segmentation enables both power saving (by turning off unused regions) and light environment adaptation (by adjusting specific regions based on ambient light conditions).
Solution Approach 2:
The backlight units are designed to be dynamically controllable, allowing real-time adjustment of backlight timing and intensity for different screen regions. This dynamic control enables the system to adapt to varying light environments by adjusting specific regions while maintaining overall power efficiency through selective activation of backlight units based on actual viewing and environmental conditions.
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
Enables high-precision sensor outputs and input functions not dependent on light environments, with improved readout speed and reduced power consumption by allowing individual detection of light during both ON and OFF periods.
Implementation Method 1
a first sensor pixel circuit that, according to the sensor driving signal, accumulates electric charges corresponding to an amount of light received during an accumulation period in an ON time of the light source
Data Source
AI summary
Provided is a display device having a photodetecting element in a pixel, and having an input function that is not dependent on light environments. This is a display device having an optical sensor in a pixel region. The optical sensor includes a first sensor pixel circuit that outputs a sensor signal corresponding to electric charges accumulated during an accumulation period in an ON time of a light source for the sensor; and a second sensor pixel circuit that that outputs a sensor signal corresponding to electric charges accumulated during an accumulation period in an OFF time of the light source. A sensor driving circuit for driving the first sensor pixie circuit and the second sensor pixel circuit supplies reset signals (RST1, RST2) to the first sensor pixel circuit and the second sensor pixel circuit, respectively, during vertical flyback periods in pixel display in the pixel region.