Built-in Photo Detecting Module for LCD Signal-to-Noise Ratio

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Solution Overview

Problem

Conventional ambient light sensors in display devices suffer from poor signal-to-noise ratio due to dark current, which is exacerbated by temperature variations, leading to increased complexity and cost in circuit design and fabrication.

Innovation Solution

A liquid crystal display panel with a built-in photo detecting module comprising thin film transistors, storage capacitors, and light sensitive elements, which outputs a multi-bit digital signal corresponding to light intensity, eliminating the need for additional sensor modules and sophisticated amplification circuits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional ambient light sensors with photodiodes are used, then light detection function is achieved, but dark current generates poor signal-to-noise ratio

Engineering Contradiction:

Improvesignal-to-noise ratioVSAvoiddark current

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The patent merges the photo detecting module with the display panel by integrating photo detecting units into the same substrate and using shared thin film transistor circuits. This integration eliminates the need for separate sensor modules and their associated dark current problems, while maintaining light detection functionality through the display panel's own structure.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent changes the detection parameter from analog photo current to digital signal by using the thin film transistor's threshold voltage shift caused by trapped charges in the insulating layer. This parameter transformation eliminates dark current interference because the measurement is based on voltage threshold changes rather than direct current measurement, significantly improving signal-to-noise ratio.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If additional sensor modules are composed onto display device, then ambient light sensing function is enabled, but number of parts and fabrication cost increase

Engineering Contradiction:

Improveambient light sensing functionVSAvoidnumber of parts

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The display panel serves multiple functions: it acts as both the display device and the ambient light sensor. The thin film transistor circuit in the display panel is dual-used for both display driving and light intensity detection, eliminating the need for separate sensor modules and reducing overall device complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The photo detecting module is merged with the display panel by integrating photo detecting units into the same substrate and using shared thin film transistor circuits. This integration eliminates the need for separate sensor modules and their associated dark current problems, while maintaining light detection functionality through the display panel's own structure.

Inventive Principle:

Principle #5Merging (Combining)

3Measurement precision

If sophisticated amplification and ADC conversion circuits are added, then dark current compensation is achieved, but fabrication cost increases

Engineering Contradiction:

Improvelight signal detection accuracyVSAvoidfabrication cost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces complex analog amplification and ADC conversion circuits with a simpler digital detection method using thin film transistor threshold voltage characteristics. This substitution maintains detection accuracy while dramatically reducing circuit complexity and fabrication cost.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 the number of components and design complexity, enhances signal quality, and allows for efficient light intensity adjustment without increasing fabrication costs, while maintaining slimness and energy efficiency in display devices.

Implementation Method 1

The conventional ambient light sensor generates a photo current under photo excitement by means of photodiode

Methodology Applied

Scientific EffectPhotoelectric Effect: Photoelectric Effect

Data Source

PatentUS8390607B2Liquid crystal display panel, liquid crystal display device, photo detecting device and light intensity adjustment method

Publication Date: 2013.03.05 ACER INC

AI summary

The present invention discloses a liquid crystal display panel, liquid crystal display device, photo detecting device and light intensity adjustment method. The liquid crystal display panel comprises a plurality of first scan lines, a plurality of first data lines, a plurality of first thin film transistors, a plurality of liquid crystal pixel units and a built-in photo detecting module. The plurality of first thin film transistors are respectively disposed at intercrosses of the plurality of first scan lines and the plurality of first data lines, and each of the first thin film transistors is connected to the first data line and the first scan line. Each of the first thin film transistors is used to drive a liquid crystal pixel unit. The built-in photo detecting module detects light and outputs a multi-bit digital signal corresponding to the intensity of the light.