Annular Laser Height Detector for Transparent Workpieces

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

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 is reflected by 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 forming mechanism, a beam splitter, a pinhole mask, and a conical mirror to convert the reflected light into a linear spot shape, allowing the position detector to accurately determine the height position of the upper surface by filtering out light reflected from the lower surface.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a visible laser beam is used for height position detection, then the detection method is simple and cost-effective, but it cannot accurately detect transparent materials like sapphire or quartz because the beam is reflected by both upper and lower surfaces

Engineering Contradiction:

Improvedetection system simplicityVSAvoidheight position detection accuracy for transparent materials

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The detection system segments the reflected light from different surfaces by using an annular spot configuration. The upper surface reflection and lower surface reflection are spatially separated into different radial regions of the annular spot, allowing selective detection of upper surface reflection while filtering out lower surface interference

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system applies local quality by directing different portions of the annular spot to different detection paths. The central region of the annular spot detects upper surface reflection while the outer region detects lower surface reflection, enabling selective measurement based on spatial location

Inventive Principle:

Principle #3Local quality

2Measurement precision

If the laser beam is focused to a small spot for precise measurement, then the measurement precision improves, but the signal from transparent materials becomes weak due to multiple surface reflections

Engineering Contradiction:

Improveheight position detection precisionVSAvoidreflected light intensity from upper surface

Core Design Contradiction:

Measurement precisionVSIllumination intensity

Solution Approach 1:

The system transitions from a point-like spot to an annular spot configuration, adding a radial dimension to the detection. This allows the system to collect reflected light over an extended area while maintaining spatial discrimination between upper and lower surface reflections through radial position filtering

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 secure detection of the height position of the upper surface of works with transparent properties by isolating the reflection from the upper surface, ensuring accurate measurements even for materials like sapphire or quartz.

Implementation Method 1

a beam splitter by which the laser beam with the spot formed into the annular shape by the annular spot forming means is guided into a first path; a pinhole mask disposed in a second path into which the laser beam reflected by the work held on the chuck table is split by the beam splitter

Methodology Applied

Scientific EffectLight reflection: Reflection

Implementation Method 2

a pinhole mask disposed in a second path into which the laser beam reflected by the work held on the chuck table is split by the beam splitter

Methodology Applied

Scientific EffectOptical filtering: Filter (optical)

Implementation Method 3

a conical mirror by which the reflected light with the annular spot shape having passed through the pinhole mask is converted into a linear spot shape

Methodology Applied

Scientific EffectLight reflection and geometric transformation: Reflection

Implementation Method 4

a position detector for detecting the position of the reflected light converted into the linear spot shape by the conical mirror

Methodology Applied

Scientific EffectPhotoelectric detection: Photoelectric Effect

Data Source

PatentUS7564570B2Height position detector for work held on chuck table

Publication Date: 2009.07.21 DISCO CORP

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 a spot of a laser beam oscillated by a laser beam oscillator is formed into an annular shape; a beam splitter by which the laser beam with the spot 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 so as to irradiate the work held on the chuck table therewith; a conical mirror disposed in a second path into which the laser beam reflected by the work is split by the beam splitter, the conical mirror converting the reflected light with the annular spot shape into a linear spot shape; a position detector for detecting the position of the reflected light converted into the linear spot shape by the conical mirror; and a controller by which the height position of the upper surface of the work held on the chuck table is determined based on the position of the reflected light detected by the position detector.