Sensor and Display Device with Segmented Light and Heat Sensing
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Solution Overview
Problem
Conventional LCD devices face challenges in accurately sensing external light due to leakage currents from amorphous silicon photosensors, leading to inefficient power consumption and image degradation, especially under varying light conditions and temperatures.
Innovation Solution
A sensor system comprising a first sensor transistor for external light and a second sensor transistor for external heat, with capacitors to store sensing voltages, and a light blocking member to isolate the heat sensor from light, allowing for precise control of the backlight unit through a sensing signal processor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a photosensor including amorphous silicon is used to sense external light, then the display device can control backlight unit operation, but leakage current is generated leading to inaccurate light sensing and improper operation mode selection
Solution Approach 1:
The sensor is divided into two separate sensor transistors: a first sensor transistor exposed to external light for measuring light intensity, and a second sensor transistor blocked from external light for measuring leakage current. This segmentation allows independent measurement of light signal and leakage current, resolving the accuracy-reliability contradiction by enabling the system to distinguish between actual light sensing and sensor-generated leakage current.
Solution Approach 2:
A light blocking member (black matrix) is introduced as an intermediary to prevent external light from reaching the second sensor transistor. This intermediary structure enables the second transistor to exclusively measure leakage current without light interference, while the first transistor measures total current (light + leakage), allowing the control unit to calculate and compensate for leakage current effects.
2Illumination intensity
If the backlight unit is turned on under strong external light to ensure visibility, then display visibility is maintained, but power consumption increases significantly
Solution Approach 1:
The control unit receives sensing signals from both sensor transistors, calculates the leakage current by comparing their outputs, and uses this feedback to make accurate decisions about backlight unit operation. This feedback mechanism enables the system to distinguish between actual light conditions and sensor leakage, allowing optimal backlight control that maintains visibility while minimizing power consumption under strong external light conditions.
3Adaptability or versatility
If environmental temperature varies, then the display device must adapt to different conditions, but photosensor leakage current changes with temperature leading to sensing errors
Solution Approach 1:
The second sensor transistor, isolated from light by the light blocking member, serves as a self-service reference that automatically measures the temperature-dependent leakage current of the amorphous silicon. The control unit uses this self-measured leakage current information to compensate for temperature effects in the light sensing signal from the first transistor, enabling accurate light measurement across varying environmental temperatures without external calibration.
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 accurate control of the display's luminance, reducing power consumption and maintaining image quality by distinguishing between light and heat sensing, thus optimizing the operation of LCD devices in various environmental conditions.
Implementation Method 1
a first sensor transistor receiving external light and generating a first sensing current based on an amount of the received external light
Implementation Method 2
a second sensor transistor receiving external heat and generating a second sensing current based on an amount of the received external heat
Implementation Method 3
a first capacitor storing a first sensing voltage based on the first sensing current from the first sensor transistor
Implementation Method 4
a second capacitor storing a second sensing voltage based on the second sensing current from the second sensor transistor
Data Source
AI summary
A sensor includes a first sensor transistor receiving external light and generating a first sensing current based on an amount of the received external light, a first capacitor storing a first sensing voltage based on the first sensing current from the first sensor transistor, a second sensor transistor receiving external heat and generating a second sensing current based on an amount of the received external heat, a second capacitor storing a second sensing voltage based on the second sensing current from the second sensor transistor, a light blocking member blocking the second sensor transistor from external light, and an opening exposing the first sensor transistor to external light.