Multi-Surface Specular Reflection Inspector for Transparent Samples
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Solution Overview
Problem
The inspection of transparent solids is complicated by the difficulty in separating specular reflection from the top surface from the bottom surface, especially when only a single scan is allowed, which hinders the detection of defects in display and touch screen devices.
Innovation Solution
An optical inspector with a time varying beam reflector, radiating source, and telecentric scan lens is used to direct radiation onto both surfaces of a transparent sample, employing detectors and polarizing elements to separate and measure top and bottom surface specular reflections, determining the location of defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single scan is performed at any given location on the transparent sample, then the inspection speed is improved, but the ability to separate top surface specular reflection from bottom surface specular reflection deteriorates
Solution Approach 1:
The patent employs a time-varying beam reflector (such as a rotating polygon mirror or resonant galvanometer) that dynamically changes the angle of incident radiation on the transparent sample during a single scan. By varying the incident angle over time, the system can selectively direct specular reflections from the top surface and bottom surface to different detectors at different moments, enabling separation of the two reflections without requiring multiple scans. This dynamic approach maintains high inspection speed while solving the separation problem.
2Measurement precision
If multiple scans are performed to separate top and bottom surface reflections, then the measurement precision is improved, but the inspection time increases
Solution Approach 1:
The system uses a time-varying beam reflector that operates periodically (such as a rotating polygon mirror that repeats its rotation cycle) to modulate the incident angle in a predictable, periodic manner. This periodic variation in incident angle creates a temporal signature for reflections from different surfaces, allowing the system to distinguish and separate top surface and bottom surface reflections by analyzing the periodic signal patterns at the detectors. This enables precise defect location identification within a single periodic cycle, avoiding the need for multiple separate scans.
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 effectively differentiates between top and bottom surface defects, enabling accurate detection of defects on transparent samples, such as particles, stress fields, and pits, improving the quality and reliability of display devices by identifying issues before further processing.
Implementation Method 1
separating specular reflection from the top surface of a transparent sample from specular reflection from the bottom surface of a transparent sample
Implementation Method 2
a first polarizing element that receives the top surface specular reflection, where the first detector receives at least a portion of polarized top surface specular reflection that passed through the first polarizing element
Data Source
AI summary
An optical inspector includes a time varying beam reflector, a radiating source that irradiates the time varying beam reflector, a telecentric scan lens configured to direct the radiation reflected by the time varying beam reflector onto a first surface of a transparent sample, a first detector that receives at least a portion of top surface specular reflection, a second detector that receives at least a portion of the bottom surface specular reflection. A turning mirror may also be included. The turning mirror is a switchable mirror that can be adjusted to a first position where the turning mirror reflects the top and bottom surface specular reflection, and can be adjusted to a second position where the turning mirror does not reflect the top or the bottom surface specular reflection. A first and second polarizing element may also be included to detect additional types of defects on either surface.