Overlapping response separation and extraction method for ultra-thin sample thickness measurement in chromatic...

Area of Science:

• Metrology
• Optical Sensing
• Materials Science

Background:

• Chromatic confocal sensors are used for thickness measurement.
• Overlapping spectral responses limit accuracy for ultra-thin samples.
• Existing algorithms struggle with separating these overlapping responses.

Purpose of the Study:

• To develop an improved method for separating and extracting overlapping chromatic confocal responses.
• To enhance the thickness measurement accuracy of ultra-thin transparent samples.
• To overcome limitations of conventional algorithms in peak extraction.

Main Methods:

• Proposed a novel method based on second-order numerical differentiation for initial peak estimation.
• Employed generalized Gaussian fitting and iterative optimization.
• Incorporated false response suppression to improve accuracy.

Main Results:

• Achieved a minimum measurable thickness of 25.53 μm for wedge air gaps.
• Maintained a relative standard deviation below 1%.
• Demonstrated a performance improvement exceeding 60% compared to conventional methods.

Conclusions:

• The proposed method effectively separates overlapping responses in chromatic confocal sensing.
• Significantly enhances the measurable thickness range for ultra-thin transparent samples.
• Offers a more precise and reliable approach for metrology applications.