Optical Interferometric Apparatus for Real-Time Thickness Inspection
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Solution Overview
Problem
Current thickness measurement techniques for transparent materials, such as glass substrates in TFT-LCDs, face challenges in achieving rapid online inspection with high accuracy and wide-area coverage due to the need for phase shift and optical components that restrict measurement area and increase costs.
Innovation Solution
An optical interferometric apparatus that uses a high-coherence point-expanded spherical-wavefront light beam incident at an oblique angle, eliminating the need for optical lens groups and phase shift, allowing for instantaneous and wide-area full-field thickness measurement through a single interference fringe pattern image analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional optical interferometric methods using optical lens groups and phase shift are employed, then measurement precision can be maintained, but device complexity and cost increase, and measurement area is restricted
Solution Approach 1:
The patent extracts and removes the optical lens groups and phase shift components from the traditional interferometric measurement system. By eliminating these complex optical elements, the system achieves wide-area full-field measurement capability while maintaining thickness measurement precision through direct analysis of interference fringe patterns captured by the imaging device.
Solution Approach 2:
The patent transitions from point-by-point or limited-area measurement to wide-area full-field measurement by capturing the entire interference fringe pattern simultaneously with an imaging device. This dimensional change from sequential measurement to parallel full-field capture enables comprehensive thickness distribution analysis across large areas without requiring complex optical scanning components.
2Measurement precision
If phase shift technique is used for thickness analysis, then measurement accuracy is improved, but measurement time increases due to multiple image capture requirements
Solution Approach 1:
The patent performs preliminary action by directly capturing the complete interference fringe pattern in a single shot without requiring sequential phase shift steps. The interference pattern is recorded with sufficient information content that allows direct thickness calculation through fringe analysis, eliminating the time-consuming multi-step phase shift process while maintaining measurement accuracy.
Solution Approach 2:
The patent skips the intermediate phase shift steps traditionally required in interferometric measurement. By using direct fringe pattern analysis methods, the system rushes through the measurement process in a single capture, achieving rapid thickness mapping without sacrificing precision through the elimination of multi-temporal sampling requirements.
3Measurement precision
If traditional interferometric optical paths with special optical elements are used, then interference patterns can be generated, but measurement area is restricted and cost increases
Solution Approach 1:
The patent makes the measurement system universal by using a simple optical path configuration that can measure large-area objects without requiring specialized optical elements. The simplified setup with basic imaging components achieves both good interference pattern quality and wide measurement area coverage, making the system adaptable to various large-scale transparent material inspection applications.
Solution Approach 2:
The patent segments the measurement function from the complex optical components, using a simplified optical path that generates interference patterns through geometric arrangement rather than specialized elements. This segmentation allows the system to cover large measurement areas while maintaining pattern quality through direct optical geometry rather than component-based interference generation.
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 real-time, low-cost, and non-contact thickness measurement across large areas without the limitations of traditional optical components, providing precise thickness distribution data for transparent materials like glass substrates, suitable for production line inspections.
Implementation Method 1
a high-coherence point-expanded spherical-wavefront light beam is propagating to an object in an oblique angle for an instantaneous and wide-area full-field thickness measurement; phase shift is not necessary
Data Source
AI summary
A device for real-time thickness inspection is provided. An optical interferometric technique is used. Measurement requirements in rapid online thickness inspection can be satisfied. An object is measured in a non-contact and non-destructive way. For measuring, an optical spherical wavefront is radiated on the object in an oblique angle. The interference fringe pattern (IFP) thus imaged on a screen is directly related to the thickness distribution of the object. The phase difference on the same horizontal cross section in the IFP monotonically decreases from the light source side to the other side. Accordingly, phase unwrapping can be effectively performed without using phase shift. The present invention achieves rapid on-line thickness inspection through the optical path of interference without using optical lens groups and special optical elements. The present invention radiates a high-coherence point-expanded spherical-wavefront light beam in an oblique angle for an instantaneous and wide-area full-field thickness measurement.