Single-Frame Tilted-Wave Interferometer for Freeform Surface Measurement
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Solution Overview
Problem
Existing interferometric methods for measuring aspherical and freeform surfaces are slow, costly, and prone to environmental disturbances due to the need for sequential measurements and specialized null lenses, lacking a flexible and rapid measurement technique for high precision optics production.
Innovation Solution
A tilted wave interferometer using multiple color channels or wavelengths illuminates the test object simultaneously from different directions, allowing spectral decomposition of interferograms to determine phase information from a single camera exposure, eliminating the need for sequential switching and specialized lenses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sequential scanning measurement is used, then measurement precision can be maintained, but measurement time increases significantly and productivity decreases
Solution Approach 1:
The measurement process is segmented into multiple wavelength channels, each capturing different spatial frequencies of the surface. By dividing the measurement into spectral segments rather than temporal sequences, the system achieves areal measurement without sacrificing precision.
Solution Approach 2:
The patent transitions from temporal sequencing (sequential scanning) to spectral dimensioning (multi-wavelength simultaneous capture). By adding the wavelength dimension as a parallel measurement pathway, the system measures entire surfaces simultaneously rather than point-by-point or region-by-region in sequence.
2Measurement precision
If null lenses are used for aspheric surface measurement, then measurement accuracy improves, but device complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates the null lens component from the optical system. Instead of using specialized null lenses to measure aspheric surfaces, the system uses multi-wavelength interferometry with computational algorithms to achieve the same measurement capability without the complex optical elements.
Solution Approach 2:
The patent replaces the mechanical/optical null lens system with a computational approach. By using multi-wavelength interferometric data and processing algorithms, the system substitutes physical optical complexity with computational complexity, achieving aspheric surface measurement without specialized lenses.
3Measurement precision
If sequential illumination configurations are used, then complete surface coverage is achieved, but measurement time increases and environmental stability requirements increase
Solution Approach 1:
The patent merges multiple illumination configurations into a single simultaneous measurement. By capturing interferograms from different wavelengths and angles at the same time rather than sequentially, the system achieves complete surface coverage while eliminating time-related environmental instability issues.
Solution Approach 2:
The patent maintains continuous measurement action across the entire surface simultaneously. Instead of discontinuous sequential scanning that requires the system to pause and reposition between measurements, the multi-wavelength interferometer continuously captures all surface information in one exposure, eliminating gaps and time delays.
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
Enables precise, high-accuracy measurement of aspherical and freeform surfaces in a single exposure, reducing measurement time and environmental interference, and integrating seamlessly into production processes.
Implementation Method 1
When a known reference wave is superimposed on an object wave which is coherent thereto and which is typically deformed by the surface of a test object, regions with extinction and regions with light amplification arise. The resulting intensity image, the interferogram, contains information about the deviation of the test object from the desired shape
Implementation Method 2
The image capture device is configured to spectrally decompose the interferograms produced by the superposition into wavelength-specific partial interferograms
Data Source
AI summary
An interferometer for the measurement of a surface or an optical thickness of an optically smooth test object is provided, wherein the interferometer is configured to illuminate the optically smooth test object simultaneously with a plurality of object waves, which have different wavelengths from one another, and to superimpose the object waves deformed by the illuminated test object onto coherent reference waves on an image capture device, and to spectrally decompose the interferograms resulting from the superposition into wavelength-specific partial interferograms.