TFT Optical Sensor Brightness Control for Sudden Light Changes
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Solution Overview
Problem
Existing liquid crystal display devices face delays in brightness control when the peripheral environment suddenly changes from dark to bright, due to the inefficiency of optical sensors formed by TFTs in detecting illumination, leading to delayed backlight adjustments.
Innovation Solution
A display device with an optical sensor formed by a TFT and a capacitor, where the optical sensor controller measures illumination by monitoring the voltage of the capacitor and turns on the charging switch after a predetermined time, allowing for immediate detection of illumination changes and adjusting brightness accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an optical sensor formed by a TFT is used to detect external light, then the number of manufacturing processes is reduced, but the detection speed decreases when the environment suddenly changes from dark to bright
Solution Approach 1:
The capacitor is charged in advance during the dark state before the bright state occurs. When the environment suddenly becomes bright, the pre-charged capacitor can immediately discharge through the optical sensor, enabling rapid detection without waiting for charging to complete from scratch.
Solution Approach 2:
The system dynamically switches between charging and discharging modes of the capacitor based on ambient light conditions. The control unit adjusts the timing of charge and discharge operations to optimize both manufacturing simplicity and detection speed response.
2Measurement precision
If the capacitor is charged before detecting illumination changes, then detection precision is improved, but the response time to sudden brightness changes increases
Solution Approach 1:
The capacitor is charged in advance during the dark state before the bright state occurs. When the environment suddenly becomes bright, the pre-charged capacitor can immediately discharge through the optical sensor, enabling rapid detection without waiting for charging to complete from scratch.
Solution Approach 2:
The system performs periodic charging operations during dark states and immediately discharges when bright states are detected. This periodic charge-discharge cycle optimizes both measurement precision and response time by maintaining the capacitor in a ready state for rapid discharge.
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 enables quick and accurate brightness adjustments, ensuring the display screen is comfortable to view without delays, even when the environment suddenly becomes brighter, while also reducing the number of manufacturing processes and maintaining detection precision.
Implementation Method 1
an optical sensor formed by a TFT simultaneously formed with a TFT for driving the liquid crystal display panel is used as the optical sensor. The optical sensor formed by the TFT functions as an optical conductive element in which a leakage current caused by optical leakage increases in accordance with an increase of illumination
Data Source
AI summary
A display device includes: a display panel; an optical detector which includes an optical sensor formed by a thin film transistor for detecting external light and a capacitor connected between a pair of electrodes of the optical sensor; a switch which turns on or off a charging operation of the capacitor; an optical sensor controller which controls the switch to be turned on or off and measures illumination of the external light on the basis of a time period during which the switch is turned off and a voltage of the capacitor becomes a value not more than a threshold value; and a controller which controls brightness of the display panel on the basis of an output of the optical sensor controller, wherein after the optical sensor controller detects a fact that the voltage of the capacitor becomes the value not more than the threshold value, the optical sensor controller turns on the switch after a predetermined time.