Glass Substrate Inspection via Interferometric Phase Shifting
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Solution Overview
Problem
Existing inspecting apparatuses for glass substrates struggle to detect blurs, such as butterfly blurs, caused by thickness differences or overlays of pigments in LCD manufacturing, especially in color filter and TFT layers, leading to production losses and increased costs due to the need for separate sampling and metal-deposited glass substrates.
Innovation Solution
An inspecting apparatus with a first illumination unit for reflective light and a second illumination unit for transmissive light, combined with a rear plate and driving interferometer system that generates a phase difference between the lights, allowing for the detection of blurs by creating hologram light through optical interference, enabling the detection of defects on the surface and within the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional illumination methods are used for inspecting glass substrates, then the inspection process is simple, but blurs such as butterfly blurs caused by pigment thickness differences or overlays cannot be detected
Solution Approach 1:
The illumination system is divided into multiple independent illumination units, each providing light from different directions and angles. This segmentation allows each unit to target specific defect types, with the combined effect enabling comprehensive detection of blurs and other defects that single-direction illumination cannot detect.
Solution Approach 2:
The inspection system transitions from single-direction illumination to multi-directional illumination by adding spatial dimensions to light sources. By positioning illumination units at various angles and heights, the system creates three-dimensional lighting coverage that reveals depth information and optical path differences caused by blurs and overlay defects.
2Measurement precision
If sampling inspection with metal-deposited glass substrates is performed, then blurs can be detected, but production costs increase and production time is lost due to separate fabrication
Solution Approach 1:
The inspection method is integrated into the existing manufacturing process flow, allowing defects to be detected during normal production rather than requiring separate sampling and testing. The illumination system is configured to inspect substrates at stages where they are already present in the manufacturing line, eliminating the need for additional fabrication steps.
Solution Approach 2:
The inspection system is designed to handle multiple defect types and multiple substrate stages using the same apparatus. The multi-directional illumination units can detect various defect types (blurs, overlays, pigment thickness variations) across different manufacturing stages, making the system universally applicable throughout the production process.
3Reliability
If conventional single-direction illumination is used, then the inspection apparatus is simple, but defects affecting viewing angle characteristics cannot be detected
Solution Approach 1:
Different illumination units are positioned to provide specialized lighting for detecting specific defect types. Each illumination unit is optimized for particular viewing angles and defect characteristics, with local adjustments in light direction, intensity, and angle to highlight specific defect features that affect viewing angle properties.
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
Enhances the detection of mura defects and blurs, allowing for earlier detection of issues like butterfly blurs, reducing production losses and costs by integrating the detection process into the existing manufacturing line without the need for separate sampling or metal-deposited substrates, thereby improving the yield and quality of LCD production.
Implementation Method 1
a first illumination unit supplying reflective light to a surface of the substrate to inspect whether the surface of the substrate is defective or not
Implementation Method 2
a second illumination unit supplying transmissive light from a rear side of the substrate to inspect whether the interior of the substrate is defective or not
Implementation Method 3
a driving guide disposed on a rear surface of the rear plate and generating a phase difference between the light provided from the first illumination unit and the light provided from the second illumination unit
Data Source
AI summary
An inspecting apparatus for a glass substrate detects blurs of a green color filter layer, a blue color filter layer, a column spacer layer, a pixel layer of a thin film transistor, or the like, which are generally hardly inspected. The inspecting apparatus for a glass substrate includes: a first illumination unit supplying reflective light to a surface of the substrate to inspect whether the surface of the substrate is defective or not; a second illumination unit supplying transmissive light from a rear side of the substrate to inspect whether the interior of the substrate is defective or not; a latticed rear plate provided on a rear surface of the substrate; and a driving interferometer system generating a phase difference of light by driving such that a driving guide is moved along the rear plate or the rear plate itself is moved.