Vertical Chromatic Confocal Scanning with Pinhole Array
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Solution Overview
Problem
Chromatic confocal systems face accuracy issues due to cross-talk effects and stray light, which degrade the precision of depth detection and height measurement, especially in high-resolution applications like semiconductor industries.
Innovation Solution
A confocal scanning method and system utilizing multiple spectral waveforms with overlapping portions, captured by a color camera, to enhance height resolution and scanning speed by modulating the light source with a Lyot filter and pinhole array, suppressing stray light and improving intensity ratio computation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a slit is used instead of a single pinhole point to speed up scanning, then scanning speed is improved, but cross-talk effect becomes severe and accuracy for depth detection deteriorates
Solution Approach 1:
The patent divides the single pinhole aperture into a pinhole array with multiple pinholes arranged in specific patterns. This segmentation allows parallel light collection from multiple points simultaneously, improving scanning speed while maintaining confocality through the pinhole array structure that prevents cross-talk between adjacent measurement points.
Solution Approach 2:
The patent transitions from one-dimensional linear scanning to two-dimensional parallel scanning by arranging pinholes in array patterns (linear, rectangular, or circular arrangements). This dimensional change enables simultaneous measurement of multiple points across the surface, dramatically increasing productivity while the pinhole array geometry maintains depth detection accuracy.
2Device complexity
If maximum intensity ratio computation is used to determine height information, then the system is simple, but accuracy deteriorates due to stray light causing intensity offsets
Solution Approach 1:
The patent applies spectral modulation to the light source before illumination, pre-encoding the light with specific spectral characteristics (sinusoidal, square, triangular, or sawtooth waveforms). This preliminary spectral encoding allows the system to distinguish focused from unfocused light through spectral analysis, eliminating stray light interference before detection and enabling accurate height measurement without complex post-processing.
Solution Approach 2:
The patent changes the spectral parameters of the illumination light by modulating it with specific waveform patterns. By varying the spectral distribution of the light source according to predetermined waveforms, the system creates distinct spectral signatures for different depth positions, enabling accurate depth detection through spectral ratio computation that is insensitive to stray light intensity offsets.
3Device complexity
If conventional chromatic confocal scanning is used, then the system structure is simple, but measurement precision deteriorates due to cross-talk and stray light effects
Solution Approach 1:
The patent applies spectral modulation to the light source before illumination, pre-encoding the light with specific spectral characteristics (sinusoidal, square, triangular, or sawtooth waveforms). This preliminary spectral encoding allows the system to distinguish focused from unfocused light through spectral analysis, eliminating stray light interference before detection and enabling accurate height measurement without complex post-processing.
Solution Approach 2:
The patent divides the single pinhole aperture into a pinhole array with multiple pinholes arranged in specific patterns. This segmentation allows parallel light collection from multiple points simultaneously, improving scanning speed while maintaining confocality through the pinhole array structure that prevents cross-talk between adjacent measurement points.
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
The system achieves higher accuracy and faster measurement speeds by resolving height information from multiple confocal images with enhanced spectral modulation, reducing errors from stray light and enabling cost-effective full-area imaging without the need for a spectrometer.
Implementation Method 1
A confocal scanning method and system utilizing multiple spectral waveforms with overlapping portions, captured by a color camera, to enhance height resolution and scanning speed by modulating the light source with a Lyot filter
Implementation Method 2
modulating the light source with a Lyot filter and pinhole array, suppressing stray light and improving intensity ratio computation
Implementation Method 3
In a chromatic confocal system, light rays with different colors are dispersed along an optical axis, so that only a small range of wavelengths can be reflected from an object of interest and then received by an imaging system
Implementation Method 4
using a camera to capture responsive signals from the object illuminated by the first, second and third spectral waveforms
Data Source
AI summary
A method of scanning a surface of an object using a confocal imaging system comprises the steps of obtaining first, second and third confocal images of the surface of the object when the object is illuminated respectively by light rays having first, second and third spectral waveforms, and using a camera to capture responsive signals from the object illuminated by the first, second and third spectral waveforms. The first, second and third spectral waveforms are distinguishable from one another and each spectral waveform has overlapping portions relative to another spectral waveform. Thereafter, heights of a plurality of points on the surface of the object corresponding to the plurality of points on each confocal image are determined based on said captured responsive signals.