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Effects of defocus on the transfer function of coherence scanning interferometry
Optics Letters
|January 13, 2018
Summary
Defocus in coherence scanning interferometry (CSI) degrades 3D surface measurements. This study extends CSI theory to quantify defocus effects, validating linear systems theory for improved surface topography analysis.
Area of Science:
- Optical metrology
- Surface characterization
- Interferometry
Background:
- Coherence scanning interferometry (CSI) provides high-precision 3D surface topography measurements.
- Defocus in the objective lens is a common issue in CSI, limiting resolution and tilted surface measurement.
- Understanding defocus effects is crucial for accurate CSI performance.
Purpose of the Study:
- To extend the linear theory of CSI to incorporate the impact of defocus.
- To analyze the effects of defocus on the 3D transfer function and point spread function in CSI.
- To compare theoretical predictions with experimental measurements of these functions.
Main Methods:
- Extension of the linear theory of coherence scanning interferometry.
- Mathematical modeling of defocus effects on optical transfer functions.
- Experimental validation using a real CSI instrument.
Main Results:
- Defocus significantly impacts the 3D transfer function and point spread function in CSI.
- Theoretical predictions regarding defocus effects were consistent with experimental measurements.
- The study quantifies the degradation of measurement quality due to defocus.
Conclusions:
- The linear systems theory of CSI is validated for instruments with defocus.
- This work provides a theoretical framework for understanding and potentially mitigating defocus errors in CSI.
- Accurate 3D surface topography measurement requires accounting for optical aberrations like defocus.
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