Defect Inspection Apparatus Using Laser and Incoherent Light
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Solution Overview
Problem
Conventional defect inspection apparatuses using laser interferometry face challenges in performing both surface layer defect inspection and appearance inspection effectively due to image quality deterioration caused by speckle interference, making it difficult to conduct both inspections with a single apparatus.
Innovation Solution
A defect inspection apparatus is designed with a displacement unit, a first irradiation unit for emitting laser light, a second irradiation unit for emitting incoherent light, a control unit for managing irradiation, and an imaging unit that captures both interfered laser light and incoherent light, allowing for the generation of surface layer inspection images based on laser light intensity patterns and appearance inspection images based on incoherent light intensity patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If laser light is used for surface layer defect inspection, then measurement precision is improved, but image quality deteriorates due to speckle interference
Solution Approach 1:
The patent segments the inspection process into two distinct modes: surface layer defect inspection using laser interferometry and appearance inspection using incoherent light. By separating the inspection functions and using different light sources for each, the system avoids speckle interference in appearance images while maintaining measurement precision in defect detection.
Solution Approach 2:
The defect inspection apparatus is designed with multi-functionality to perform both surface layer defect inspection and appearance inspection using a single system. The control unit manages two irradiation units (laser and incoherent light) and the imaging unit to execute different inspection types, making the apparatus universal and eliminating the need for separate inspection devices.
2Device complexity
If a single apparatus is used for both surface layer defect inspection and appearance inspection, then device complexity is reduced, but image quality deteriorates due to speckle
Solution Approach 1:
The apparatus integrates multiple inspection functions into a single system by incorporating both laser irradiation and incoherent light irradiation units. The control unit manages the switching between different inspection modes, enabling the single apparatus to perform both surface layer defect inspection and appearance inspection without requiring separate devices.
Solution Approach 2:
The control unit acts as an intermediary that manages the operation of multiple irradiation units and coordinates the imaging process. It controls the switching between laser irradiation for defect inspection and incoherent light irradiation for appearance inspection, ensuring that the appropriate light source is used for each inspection type while maintaining system integration.
3Loss of information
If incoherent light is used for appearance inspection, then image quality is improved, but measurement precision for defect detection decreases
Solution Approach 1:
The inspection process is segmented into two distinct functions: surface layer defect inspection requiring high measurement precision and appearance inspection requiring high image quality. By assigning different light sources to different inspection functions (laser for defect detection, incoherent light for appearance), the system optimizes performance for each specific inspection type without compromise.
Solution Approach 2:
The apparatus achieves universality by incorporating both laser irradiation and incoherent light irradiation capabilities in a single system. The control unit manages the switching between these different light sources based on the inspection type required, enabling the system to deliver both high measurement precision for defects and high image quality for appearance inspection.
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
Enables the simultaneous performance of surface layer defect inspection and appearance inspection without speckle interference, using a single apparatus, thereby improving image quality and inspection accuracy.
Implementation Method 1
an interference unit configured to cause interference of the laser light reflected at the measurement region by laser interferometry
Implementation Method 2
a second irradiation unit configured to emit incoherent light defined as light which is incoherent to the measurement region
Data Source
AI summary
A defect inspection apparatus generates a surface layer inspection image which is an image representing displacement of an inspection target in a measurement region based on an intensity pattern of interfered laser light. The defect inspection apparatus is configured to generate an appearance inspection image which is an image of an outer surface of the measurement region based on an intensity pattern of incoherent light.