Chromatic Confocal Microscope Spatial Filtering and Dual Sensing
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Solution Overview
Problem
Conventional confocal chromatic microscope systems face limitations in space occupancy, leading to reduced practicality and convenience for surface profile measurements, especially on large objects like 8-inch wafers with LSI chips, due to large system volume and issues with reflection rate variations across different surface colors, which complicates depth measurement and results in decreased image detection resolution.
Innovation Solution
A chromatic confocal microscope system with a pair of color sensing units at different focusing positions and a spatial-filtering optical fiber module to generate distinct RGB intensity signals, reducing cross-talk from stray and unfocused lights, and a signal processing method to build a depth relation curve for accurate surface profiling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional confocal chromatic microscope system is installed on desktop to perform surface profile measurement, then measurement capability is provided, but system volume is large occupying too much space
Solution Approach 1:
The patent merges multiple optical functions (chromatic confocal measurement, color detection, spatial filtering) into a compact integrated optical system. The optical module combines a chromatic confocal objective lens, beam splitter, and color sensing units in a single integrated structure, eliminating the need for separate desktop instruments while maintaining measurement precision.
Solution Approach 2:
The patent transitions from traditional lateral scanning approaches to axial (depth) dimension utilization by employing chromatic confocal technology. Different wavelengths focus at different depths along the optical axis, enabling three-dimensional surface profiling through one-dimensional axial color separation, thus reducing system footprint while enhancing measurement capability.
2Measurement precision
If color sensing units are used to detect RGB intensity signals for surface profiling, then depth information can be obtained, but reflection rate variation with surface color causes measurement errors
Solution Approach 1:
The patent implements feedback through dual color sensing units that simultaneously detect both object light and reference light. The system compares the intensity ratios between object and reference signals, automatically compensating for surface reflection rate variations. This feedback mechanism eliminates the need for manual depth relation curve calibration for different surface colors, improving measurement reliability.
Solution Approach 2:
The patent introduces a reference light path as an intermediary to mediate between the object light and the measurement system. By comparing object light intensity with reference light intensity through color sensing units, the system creates a ratio-based measurement that is insensitive to surface color variations, thus improving measurement accuracy.
3Use of energy by moving object
If a slit structure is used to receive object light in conventional configuration, then light collection is enabled, but cross talk from overlap between neighboring object light, unfocused light, and stray light decreases image detection resolution
Solution Approach 1:
The patent extracts and removes harmful light components (unfocused light and stray light) from the optical path using a spatial filter positioned at the focal plane. The spatial filter selectively blocks out-of-focus light while allowing focused object light to pass through, eliminating cross-talk between neighboring measurement points and improving image detection resolution without sacrificing light collection efficiency.
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 accurate and efficient large-area scanning with improved height resolution, minimizing the impact of surface color variations and vibration during inspection, allowing for precise surface profile measurement on large objects.
Implementation Method 1
chromatic confocal objective lens for focusing the detecting light onto an object surface and for separating a reflected object light into different colors respectively corresponding to different depths
Implementation Method 2
spatial filter for removing unfocused light and stray light from the object light
Implementation Method 3
a color sensing unit is utilized to detect the intensity ratio of the object surface, whereby a surface height or depth can be obtained by calculation according to relationship between color intensity and depth
Data Source
AI summary
A chromatic confocal microscope system and signal process method is provided to utilize a first optical fiber module for modulating a light into a detecting light passing through a chromatic dispersion objective and thereby forming a plurality of chromatic dispersion lights to project onto an object. A second optical fiber module conjugated with the first optical fiber module receives a reflected object light for forming a filtered light, which is split into two filtered lights detected by two color sensing units for generating two sets of RGB intensity signals, wherein one set of RGB intensity signals is adjusted relative to the other set of RGB intensity signals. Then two sets of RGB intensity signals are calculated for obtaining a maximum ratio factor. Finally, according to the maximum ratio factor and a depth relation curve, the surface profile of the object can be reconstructed.