Polarizing Reference Surface for Fizeau Interferogram Contrast
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Solution Overview
Problem
Existing Fizeau interferometers face challenges in maintaining optimal beam intensity ratios and interferogram contrast due to varying reflectivity of test and reference surfaces, requiring multiple reference surfaces and ND filters, increasing cost and measurement time, and risking contamination.
Innovation Solution
Employ a polarizing reference surface with different polarization angles for the reference and test light beams, and use a variable angle polarizer to adjust the polarization angle to optimize the beam ratio and contrast of the interferogram.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple reference surfaces and ND filters are used to control beam ratio, then interferogram contrast is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies a single polarizing reference surface that can function as both a beam splitter and a polarizer, eliminating the need for separate ND filters and multiple reference surfaces. This multi-functional component achieves beam ratio control and interferogram contrast optimization without increasing device complexity
Solution Approach 2:
The patent changes the polarization state parameter of the reference light beam using a polarizing reference surface, allowing control of beam ratio by adjusting polarization angles rather than physically replacing components. This parameter-based control reduces the number of physical components needed
2Measurement precision
If multiple reference surfaces and ND filters are used to optimize beam ratio, then interferogram contrast is improved, but measurement time increases
Solution Approach 1:
The patent introduces a variable angle polarizer that can dynamically adjust the polarization angle of the reference light beam in real-time during measurements. This dynamic adjustment allows optimal beam ratio control without the need to physically replace components between measurements, reducing measurement time
Solution Approach 2:
The polarizing reference surface is pre-configured with specific polarization characteristics that enable immediate beam ratio control upon illumination. This preliminary configuration eliminates the need for time-consuming component replacement and realignment operations
3Illumination intensity
If reference surface and test surface reflectivity differ significantly, then beam ratio becomes unbalanced, but interferogram contrast decreases
Solution Approach 1:
The polarizing reference surface acts as an intermediary element that introduces polarization-dependent intensity modulation between the reference and test beams. By controlling the polarization angle, it mediates the intensity difference caused by varying surface reflectivity, achieving balanced beam ratios even when surface properties differ
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
Improves interferogram contrast and optical performance by aligning polarization angles, allowing for better measurement accuracy without the need for multiple components or realignment, reducing contamination risks and measurement time.
Implementation Method 1
the reference surface is a polarizing partially reflective reference surface, so that the reference light beam is formed by the reference surface through partially reflection and polarization of the light beam
Implementation Method 2
the first polarizer is configured to allow light of a third polarization angle to pass towards the imaging system
Implementation Method 3
an interference pattern, called an interferogram, may be formed by interference of a reference light beam and a test light beam
Data Source
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AI summary
The invention relates to the field of interferometry, in particular to Fizeau interferometers for improving a contrast of an interferogram. The Fizeau interferometer comprises a light source, a reference surface, a test surface positioned in on a support of the Fizeau interferometer and an imaging system. The Fizeau interferometer utilizes a polarizing reference surface to improve the contrast of the interferogram. The invention further relates to a method for using the Fizeau interferometer of the invention for improving contrast of an interferogram obtained by the Fizeau interferometer.