Fizeau Interferometer Optical Delay Apparatus Surface Shape Measurement
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Solution Overview
Problem
Conventional methods for measuring and manufacturing optical elements with flat parallel or spherical surfaces struggle with precision, particularly in analyzing interference patterns from three interfering beams and determining surface thickness accurately, due to complexity in wavelength control and aberration issues.
Innovation Solution
The integration of an optical delay apparatus with a Fizeau interferometer system, utilizing a short coherence length light source and beam splitters, allows for adjustable optical path lengths to isolate specific surface contributions to the interference pattern, reducing aberrations and enabling precise measurement of surface shapes and thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional Fizeau interferometer is used to measure optical surfaces, then measurement capability is provided, but interference patterns from multiple surfaces cannot be sufficiently analyzed to determine shape errors with desired accuracy
Solution Approach 1:
The patent changes the parameter of light coherence length by using a superluminescent diode instead of conventional laser sources. This parameter change allows the system to achieve high measurement precision for shape errors while avoiding the complexity of wavelength control, as the short coherence length inherently suppresses interference from unwanted surfaces.
Solution Approach 2:
The patent replaces the conventional laser-based interferometric system with a superluminescent diode-based system. This substitution eliminates the need for complex wavelength tuning mechanisms and control systems, while maintaining or improving measurement capability for optical surface shape errors.
2Measurement precision
If conventional interferometer methods are used, then optical surface measurement is achieved, but thickness determination of optical element cannot be performed with desired accuracy
Solution Approach 1:
The patent extracts or isolates the interference signal from the front surface of the optical element by using the short coherence length property of the superluminescent diode. This allows the system to selectively measure the front surface shape and thickness without being contaminated by interference patterns from the back surface, thereby achieving accurate thickness determination.
3Measurement precision
If wavelength tunable light source is used to suppress unwanted surface contributions, then measurement precision is improved, but device complexity and control requirements increase
Solution Approach 1:
The patent changes the coherence length parameter of the light source by using a superluminescent diode with inherently short coherence length. This parameter change provides the same surface-selective measurement capability as wavelength tuning, but without the need for complex wavelength control mechanisms, thereby reducing device complexity while maintaining measurement precision.
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
This approach enhances the accuracy of surface shape and thickness determination in optical elements, allowing for high-precision manufacturing and processing of optical components by isolating surface contributions and reducing aberrations in interference patterns.
Implementation Method 1
utilizing a short coherence length light source
Implementation Method 2
beam splitters, allows for adjustable optical path lengths
Implementation Method 3
measuring light reflected from both surfaces will be incident on the detector to interfere
Implementation Method 4
The light reflected from the Fizeau surface and the light reflected from the reference surface generate an interference pattern on the camera
Data Source
AI summary
A method of manufacturing an optical element involves an interferometric test of the optical element using an interferometer system of a Fizeau type combined with principles of white-light interferometry. The optical element is disposed in a cavity between a Fizeau surface and a mirror, and an optical path difference between a back surface of the optical element and the mirror is determined for determining parameters of the optical element, such as a thickness thereof. Measuring light from an optical delay apparatus can be supplied to the Fizeau interferometer through an optical fiber.