Liquid Crystal Modulator for Substrate Defect Detection
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Solution Overview
Problem
Current display device inspection methods fail to effectively detect defects in substrates during manufacturing, particularly in liquid crystal display devices, due to limitations in accurately differentiating between normal and defective pixels based on transmittance and reflectance.
Innovation Solution
An inspection apparatus incorporating a liquid crystal modulator with a hybrid aligned nematic liquid crystal layer, alignment layers, and a polarizer, which operates in either normally black or normally white mode, utilizing a quarter wave plate and beam splitter to differentiate defective pixels by varying transmittance and reflectance based on applied voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional inspection methods are used to detect substrate defects, then the inspection process is simple, but the ability to differentiate between normal and defective pixels is insufficient
Solution Approach 1:
The inspection apparatus segments the light path into multiple channels using beam splitters, creating separate measurement paths for different polarization states. This allows simultaneous measurement of multiple optical properties (transmittance and reflectance) through divided light paths, improving defect detection capability without requiring a single complex measurement system
Solution Approach 2:
A liquid crystal modulator is introduced as an intermediary component between the light source and the substrate under test. This modulator controls the polarization state of incident light and the state of reflected light, enabling differentiation between normal and defective pixels through polarization-dependent optical responses
2Measurement precision
If high driving voltage is applied to achieve clear differentiation between normal and defective pixels, then the detection accuracy is improved, but the operational cost increases
Solution Approach 1:
The liquid crystal modulator changes optical parameters (polarization state) rather than relying on high voltage to achieve pixel differentiation. By controlling the polarization state of incident and reflected light, the system achieves clear differentiation between normal and defective pixels through optical parameter modulation at low driving voltages
Solution Approach 2:
The system replaces high-voltage electrical actuation with optical field control using polarized light and liquid crystal modulation. This substitution allows differentiation of pixel states through optical properties rather than requiring high electrical fields, reducing energy consumption while maintaining detection accuracy
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
The apparatus enables clear differentiation between normal and defective pixels with a lower driving voltage, reducing operational costs and improving manufacturing quality by accurately identifying defects through distinct black and white outputs.
Implementation Method 1
a liquid crystal layer, an electrode, and a polarizer. The reflection layer may be configured to reflect the plurality of lights provided from the beam splitter. The liquid crystal layer may be provided on the reflection layer and may include a hybrid aligned nematic liquid crystal
Implementation Method 2
The polarizer may be configured to receive light and provide polarization component therefrom
Implementation Method 3
The liquid crystal layer may delay a phase of one of polarization components of light incident to the liquid crystal layer by a quarter wavelength
Implementation Method 4
The beam splitter may be configured to divide the light emitted from the light emitting unit into a plurality of lights and to provide the plurality of lights to the liquid crystal modulator
Implementation Method 5
The measurement unit may be configured to sense a plurality of lights output from the liquid crystal modulator
Data Source
AI summary
An inspection apparatus for detecting a defect of a substrate is provided. The inspection apparatus includes a liquid crystal modulator, a light emitting unit, a beam splitter, and a measurement unit. The liquid crystal modulator includes a reflection layer, a liquid crystal layer, an electrode, and a polarizer. The reflection layer reflects a light. The sensor layer includes a hybrid aligned nematic liquid crystal. The electrode is provided on the liquid crystal layer. The polarizer is provided on the electrode.