Optical Interfacial Position Measurement Using Inclined Light-Convergent Points
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Solution Overview
Problem
Conventional interfacial position measuring apparatuses for optical discs are inefficient in achieving high-speed measurement due to the need to move the sample vertically, which limits their ability to accurately measure multiple interfacial positions within transparent substrates with high precision.
Innovation Solution
The method involves emitting light to a substrate with laminated optically transparent layers and placing multiple light-convergent points at specific coordinates to measure light intensities, determining interfacial positions based on threshold values, and using a diffraction grating to enhance measurement accuracy and speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional confocal optical microscope is used to measure interfacial positions by moving sample vertically, then measurement precision can be achieved, but measurement speed is slow
Solution Approach 1:
The patent transitions from vertical scanning (Z-axis movement) to horizontal scanning (X-axis movement) of the laser beam across the sample surface. By projecting multiple light-convergent points in the X direction and detecting reflected light at different Z positions simultaneously, the system achieves high-speed measurement while maintaining precision through the optical detection of interface reflections.
Solution Approach 2:
The patent enables continuous measurement by scanning the laser beam horizontally across the entire sample surface without interruption, rather than moving the sample vertically through discrete steps. This continuous scanning approach with simultaneous multi-point detection significantly increases measurement speed while maintaining interface position detection accuracy.
2Productivity
If multiple light-convergent points are placed at different coordinates to measure multiple interfaces simultaneously, then measurement speed increases, but measurement precision may deteriorate due to overlapping light paths
Solution Approach 1:
The patent divides the measurement task into multiple independent light-convergent points positioned at different coordinates in the X direction. Each light-convergent point independently measures interfaces at its specific location, and the results are combined to provide comprehensive interface position data. This segmentation allows simultaneous measurement of multiple interfaces without path interference.
Solution Approach 2:
The patent introduces a diffraction grating as an intermediary element that separates and organizes the light paths from multiple light-convergent points. The grating ensures that light from different X positions is properly directed to the detector, preventing overlap and interference between measurement paths while maintaining the speed benefits of multi-point simultaneous measurement.
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 approach allows for high-speed and accurate measurement of interfacial positions within transparent substrates, reducing errors and improving measurement precision by correcting for inclination and preventing light noise, enabling efficient layer thickness control in optical disc manufacturing.
Implementation Method 1
a light source (1) that emits light so as to form a plurality of light-convergent points (7, 8) on a substrate (5)
Implementation Method 2
a diffraction grating (32) that is inclined with respect to an optical axis (15) of the emitted light, for diffracting the emitted light so as to form the plurality of light-convergent points (7, 8)
Implementation Method 3
measuring light intensities of reflected light of the emitted light and reflected within the substrate
Data Source
AI summary
An interfacial position measuring method for a substrate internally having a plurality of interfaces parallel to one another. A light-convergent line which has converged in only a one-axis direction out of parallel light having an optical axis vertical to the substrate surface is formed so as to be inclined with respect to the substrate surface, and the light-convergent line is made to intersect with the substrate. Out of reflected light of the light-convergent line reflected by the substrate, a position having a light intensity peak is taken as an interface, by which a plurality of interfaces inside the substrate can be measured simultaneously and high-speed interfacial position measurement can be achieved.