Optical Fixture for Simultaneous Thickness and Profile Metrology
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Solution Overview
Problem
Existing metrology methods for measuring object thickness and surface profiles, particularly for thin or tapered parts like razor blades, face challenges in accuracy and speed, requiring immediate determination of part quality for retention or disposal.
Innovation Solution
A specialized fixture with mirrors redirects light from a 3D profiling system to opposing sides of the object, using reference surfaces for calibration and image analysis to establish object edge location and thickness profiles, suitable for use with 3D interference microscopes or other optical metrology systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional metrology methods are used to measure object thickness and surface profiles, then measurement can be performed, but measurement accuracy and speed are insufficient for immediate quality control determination
Solution Approach 1:
The measurement system is segmented into multiple independent optical paths, each equipped with its own detector array. This allows simultaneous measurement of multiple parameters (thickness, surface profile, edge location) without sequential scanning, thereby improving both accuracy and speed for quality control applications.
Solution Approach 2:
The invention transitions from conventional 2D surface profiling to 3D volumetric measurement by capturing interference patterns from multiple depths simultaneously. This dimensional enhancement enables accurate thickness measurement alongside surface profile analysis, resolving the contradiction between comprehensive measurement accuracy and measurement speed.
2Loss of information
If conventional single-sided measurement is used, then measurement setup is simple, but complete spatial information including opposing surfaces cannot be obtained simultaneously
Solution Approach 1:
The invention merges multiple measurement functions (front surface profiling, back surface profiling, thickness measurement, edge location detection) into a single integrated optical system. By combining these functions simultaneously through multiple optical paths sharing common infrastructure, complete spatial information is obtained without proportionally increasing system complexity.
Solution Approach 2:
The invention introduces reference surfaces as intermediaries between the measurement object and detectors. These reference surfaces enable accurate determination of spatial relationships and thickness by providing known reference points for calibration, thereby completing spatial information while maintaining manageable system complexity through standardized reference elements.
3Measurement precision
If fixture position drift occurs during measurement, then measurement may be completed, but accuracy deteriorates due to location variations
Solution Approach 1:
The invention incorporates real-time feedback through reference surface measurements. The system continuously monitors the positions of reference surfaces attached to the fixture, detects any drift or movement, and automatically compensates for these variations during measurement calculations. This feedback mechanism maintains measurement accuracy despite fixture position instability.
Solution Approach 2:
The invention performs preliminary calibration by measuring reference surfaces before actual object measurement. This preliminary action establishes baseline position information and calibration factors that are used to correct subsequent measurements, thereby preventing accuracy deterioration from fixture drift without requiring continuous active stabilization during the measurement process.
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 accurate and rapid measurement of spatial information, including thickness and surface profiles, effectively sorting parts based on quality control criteria, ensuring precise determination of part retention or disposal.
Implementation Method 1
a specialized fixture with mirrors which redirect light from a 3D profiling system to opposing sides of the object simultaneously
Implementation Method 2
using an adaptation of a 3D interference microscope or other 3D optical metrology system
Data Source
AI summary
Determining spatial information about a part includes positioning the part in a fixture having two reference surfaces, where the part is positioned between the two reference surfaces, imaging the two reference surfaces and opposing surfaces of the part to different locations of a multi-element detector, simultaneously acquiring images of the opposing sides of the part and the two reference surfaces using the multi-element detector, and determining spatial information about the part based on the simultaneously acquired images.