Fizeau Interferometer Objective Common Path Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Tilted Wave Interferometers face instability in phase differences due to separate reference and object wave paths, leading to measurement instability and susceptibility to thermal changes and oscillations, and require custom interferometer objectives, which are costly and not commercially available.
Innovation Solution
Each sample produces its own reference wave, using a Fizeau objective to create a common path design with minimal optical component differences between object and reference waves, allowing for a compact and stable interferometer setup with movable stops to select the reference wave for each measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If separate reference and object wave paths are used in Tilted Wave Interferometers, then the interferometer can be configured with distinct beam paths, but phase difference instability occurs due to thermal changes and refractive index fluctuations
Solution Approach 1:
The patent merges the reference wave path and object wave path into a common path configuration. The reference wave and object wave travel through the same optical components (collimator, interferometer objective, beam splitter, imaging optics) and share the same physical path between the Fizeau surface and the specimen, eliminating phase instability caused by separate paths.
2Manufacturing precision
If custom interferometer objectives are manufactured for Tilted Wave Interferometers, then the interferometer can achieve proper wave front compensation, but the cost increases significantly and commercial availability is reduced
Solution Approach 1:
The patent makes the interferometer objective universal by using a standard Fizeau objective that serves dual purposes: it provides the Fizeau surface for reference wave generation and functions as the interferometer objective for wave front compensation. This eliminates the need for custom-designed objectives, enabling the use of commercially available components.
3Reliability
If a common path design with Fizeau objective is used, then calibration stability and measurement speed improve, but the optical path configuration becomes more constrained
Solution Approach 1:
The Fizeau objective serves itself by generating the reference wave through its own Fizeau surface rather than requiring a separate reference wave generation system. The same objective that compensates for wave front deviations also provides the reference wave, eliminating the need for additional reference wave generation components and simplifying the overall system.
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 design enhances calibration stability, reduces the impact of refractive index fluctuations, and allows for faster measurement with improved sensitivity and reduced oscillation susceptibility, using commercially available Fizeau objectives and enabling phase shifting or carrier frequency methods for evaluation.
Implementation Method 1
produce the reference wave by means of beam-splitting Fizeau surface
Implementation Method 2
a collimator, an optional interferometer objective... arranged downstream of the PLSA within the optical path of light emanating from the PLSA
Implementation Method 3
uses a set of mutually tilted wave fronts in order to locally compensate for the specimen's deviation from the sphere of best fit
Implementation Method 4
produce their interferograms by superimposing the object wave fronts reflected by the specimen onto a reference wave that is coherent with all the object wave fronts
Data Source
AI summary
An interferometer for areally measuring an optically smooth surface is presented, including means for illuminating a surface region with a plurality of discrete object waves from different directions and comprising means which, on a detector, superimpose object waves reflected at the surface onto a reference wave that is coherent with a plurality of object waves in order to form an interferogram. The interferometer is distinguished by virtue of it being configured to illuminate the surface with a plurality of object waves at the same time and produce the reference wave by way of a Fizeau beam splitter plate or a Fizeau objective, and by virtue of the interferometer including an interferometer stop that is arranged in the beam path upstream of the detector, and imaging optics, wherein the interferometer stop is situated within, or slightly outside of, the Fourier plane of the imaging optics and said interferometer stop filters the object waves reflected by the surface.