White Light Interferometric Microscope Phase Control
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Solution Overview
Problem
Conventional light-interference measuring apparatuses face challenges in measuring objects with parts of different reflectances, as they require adjusting light quantities, leading to lower throughput due to the need for separate measurements and potential saturation issues.
Innovation Solution
A light-interference measuring apparatus with a phase difference control member, such as a thin film with a dielectric multilayer film, is used to generate destructive interference fringes at positions where the optical path difference is zero, allowing for the detection of minimum luminance positions without saturation, enabling simultaneous measurement of high and low reflectance parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If light quantity is adjusted based on high reflectance part, then measurement of high reflectance part is adequate, but luminance of interference fringes in low reflectance part becomes low and maximum luminance positions become difficult to detect
Solution Approach 1:
The patent inverts the conventional approach by generating destructive interference fringes instead of constructive interference fringes. By making the zero-order fringe a dark fringe (minimum luminance) rather than a bright fringe (maximum luminance), the system enables detection of minimum luminance positions instead of maximum luminance positions. This inversion allows adequate measurement of both high and low reflectance parts without saturation issues.
2Measurement precision
If light quantity is adjusted based on low reflectance part, then measurement of low reflectance part is adequate, but luminance of high reflectance part may exceed the tolerance of imaging device causing saturation
Solution Approach 1:
The patent inverts the conventional approach by generating destructive interference fringes instead of constructive interference fringes. By making the zero-order fringe a dark fringe (minimum luminance) rather than a bright fringe (maximum luminance), the system enables detection of minimum luminance positions instead of maximum luminance positions. This inversion allows adequate measurement of both high and low reflectance parts without saturation issues.
3Measurement precision
If separate measurements are carried out for high and low reflectance parts with different light quantities, then measurement precision is improved, but throughput is lowered
Solution Approach 1:
The patent merges the measurement process for both high and low reflectance parts into a single simultaneous measurement by using destructive interference fringes. The phase difference control member enables both types of parts to be measured at the same time with the same light quantity settings, eliminating the need for separate measurements and data synthesis, thereby improving throughput while maintaining measurement precision.
4Ease of operation
If conventional light-interference measuring apparatus is used, then simple measurement process is available, but processing of carrying out measurement twice and synthesizing data is necessary for objects with different reflectances
Solution Approach 1:
The patent merges the measurement process for both high and low reflectance parts into a single simultaneous measurement by using destructive interference fringes. The phase difference control member enables both types of parts to be measured at the same time with the same light quantity settings, eliminating the need for separate measurements and data synthesis, thereby improving throughput while maintaining measurement precision.
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 allows for easy measurement of objects with varying reflectances by detecting minimum luminance positions without causing saturation, improving measurement efficiency and reducing the need for multiple measurements.
Implementation Method 1
a phase difference control member (34) which controls a phase difference between the reference light and the object light to generate destructive interference fringes at a position at which an optical path difference between the reference optical path and the measuring optical path is zero
Implementation Method 2
a light passing through the measuring optical path transmits through the phase difference control member (34) twice and thereby a phase of the transmitted light is reversed by 180°
Implementation Method 3
a beam splitter (35) to branch the optical path of the broad band light output from the light source into the reference optical path and the measuring optical path
Implementation Method 4
reflected light from the reference mirror (reference light) and reflected light from the measuring object (object light) are superposed
Data Source
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AI summary
A light-interference measuring apparatus including: a light source of a broad band light; an objective lens section to branch an optical path of the broad band light into a reference optical path including a reference mirror and a measuring optical path including a measuring object and to output a superposed wave of two branched lights; and an optical path length changing section to change an optical path length of either the reference optical path or the measuring optical path; wherein the objective lens section includes a phase difference control member to control a phase difference between the reference light and the object light to generate destructive interference fringes at a position of zero-path difference between the reference optical path and the measuring optical path, and a minimum luminance position detecting section to detect minimum luminance position of the destructive interference fringes.