Transparent Work Height Detection Using Annular Laser Spot
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Solution Overview
Problem
Existing height position detection methods fail to accurately measure the upper surface of works made from transparent materials like sapphire or quartz, as the laser beam reflects from both the upper and lower surfaces, making it impossible to distinguish the reflection from the upper surface alone.
Innovation Solution
A height position detector system that uses an annular spot of laser beam, a pinhole mask, and dual light receiving elements to isolate and measure the reflection from the upper surface by intercepting the lower surface reflection, allowing accurate detection of the upper surface height even in transparent materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a laser beam is used to detect the height position of a work made from transparent material, then the detection can be performed, but the laser beam reflects from both upper and lower surfaces making it impossible to distinguish the reflection from the upper surface alone
Solution Approach 1:
The patent segments the reflected light into two distinct paths using a beam splitter: one path for upper surface reflection and another path for lower surface reflection. This segmentation allows the system to separately detect and identify reflections from each surface, resolving the ambiguity of mixed reflections from transparent materials.
Solution Approach 2:
The patent extracts the lower surface reflection from the mixed reflection signal by using a beam splitter to separate the light paths. The upper surface reflection is isolated and detected independently, allowing accurate height position measurement without interference from lower surface reflections.
2Measurement precision
If the laser beam is transmitted through transparent work, then the back-side surface reflection occurs, but this makes it impossible to measure only the quantity of light reflected by the face-side surface
Solution Approach 1:
The beam splitter extracts the harmful back-side surface reflection from the detection path, separating it from the useful face-side surface reflection signal. This allows the system to measure only the face-side surface reflection quantity needed for accurate height position detection.
Solution Approach 2:
The patent converts the harmful effect of back-side surface reflection into a beneficial separation mechanism. By using the beam splitter to divide the light paths, the system uses the reflected light from both surfaces to create distinct detection channels, where the previously harmful back-side reflection becomes a separable and manageable component.
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 precise detection of the upper surface height of transparent materials by distinguishing and measuring the reflection from the upper surface, ensuring accurate machining processes.
Implementation Method 1
laser beam oscillating means for oscillating a laser beam
Implementation Method 2
the quantity of light corresponding to the area of reflection by the face-side surface (upper surface) of the work
Implementation Method 3
a light receiving element for receiving the reflected light and for generating an electrical signal corresponding to the quantity of received light
Data Source
AI summary
A height position detector for detecting the height position of an upper surface of a work held on a chuck table, including: an annular spot forming part by which the spot shape of a laser beam oscillated by a laser beam oscillator is formed into an annular shape; a first beam splitter by which the laser beam with the spot shape formed into the annular shape is guided into a first path; a light condenser by which the laser beam guided into the first path is condensed to irradiate the work therewith; a second beam splitter for splitting the reflected light reflected by the work; a first light receiving element for receiving the reflected light transmitted through the second beam splitter; a second light receiving element for receiving the reflected light reflected by the second beam splitter; a light reception region restricting part for restricting the light reception region for the reflected light received by the second light receiving element; and a controller for determining the height position of the upper surface of the work on the basis of the ratio between the quantity of light received by the first light receiving element and the quantity of light received by the second light receiving element.