Concave Cylinder Detection via CGH Interferometry
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Solution Overview
Problem
Current detection technologies for cylindrical optical elements are limited by low precision and high processing costs, as they require high-precision standard cylinders for measurement, which are difficult to process and maintain, and cannot accurately detect asymmetric deviations or large diameters.
Innovation Solution
A method and apparatus using a combination of cylindrical diverging and converging lenses for non-contact interference detection, where wavefront error data is collected using an interferometer to reduce the precision requirements of the lenses and enable mutual detection, allowing for high-precision measurement of concave cylinders and cylindrical lenses without pre-processing high-precision detection tools.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If standard cylinder method is used for detection, then measurement precision can be achieved, but processing difficulty and cost increase significantly due to requirement of high-precision standard cylinders
Solution Approach 1:
The patent uses a computer-generated hologram (CGH) to create a virtual standard cylinder reference instead of requiring a physical high-precision standard cylinder. The CGH encodes the reference wavefront information, allowing the detection system to compare test cylinder wavefronts against this digital reference, thereby eliminating the need to manufacture and maintain expensive physical standard cylinders while preserving measurement precision.
Solution Approach 2:
The patent replaces the mechanical/optical standard cylinder reference system with a computer-generated holographic reference system. Instead of using physical optical elements that require precision machining and alignment, the system uses computationally generated holograms that can be precisely controlled and reproduced, substituting mechanical precision requirements with computational accuracy.
2Ease of operation
If template method or profilometer detection method is used, then detection can be performed, but measurement precision is relatively low and contact detection causes scraping
Solution Approach 1:
The patent replaces contact-based mechanical detection methods (template method, profilometer) with non-contact optical interferometry. By using wavefront sensing and computer-generated holography, the system measures cylinder shape without physical contact, eliminating scraping and wear issues while achieving higher measurement precision through optical wavefront analysis.
Solution Approach 2:
The patent introduces a computer-generated hologram as an intermediary reference that enables non-contact measurement. The CGH serves as a virtual reference that can be digitally stored and reproduced, allowing the test cylinder to be measured without direct physical contact between measurement tools and the test object, thus avoiding scraping while maintaining precision.
3Device complexity
If auxiliary plane method is used, then detection is simplified, but cannot detect asymmetric deviation of cylindrical shape
Solution Approach 1:
The patent replaces the simple auxiliary plane method with computer-generated holographic interferometry. The CGH system can capture complete wavefront information including asymmetric deviations, while maintaining relative simplicity through automated digital processing. The holographic method naturally accommodates asymmetric shapes without requiring complex manual adjustment procedures.
4Adaptability or versatility
If optical fiber method is used, then detection can be performed, but only applicable to cylinders with relatively small diameters
Solution Approach 1:
The patent creates a universal detection system using computer-generated holography that can accommodate cylinders of various diameters. The CGH reference wavefront can be computationally adjusted to match different cylinder sizes and curvature radii, making the same detection apparatus applicable to both small and large diameter cylinders without requiring diameter-specific instrumentation.
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 reduces processing difficulty and measurement errors by eliminating the need for pre-processed high-precision detection tools, enabling accurate detection of cylinders with varying curvature radii and large diameters, thus improving the precision and cost-effectiveness of cylindrical lens detection.
Implementation Method 1
Interference occurs between the detected light wave and the reference light wave to form an interferogram
Implementation Method 2
A beam of parallel light passes through a standard cylindrical lens configured to generate a cylindrical wave
Implementation Method 3
the cylindrical converging lens configured to remodulate diverging light into parallel light
Data Source
AI summary
A method and an apparatus for detecting a concave cylinder and a cylindrical diverging lens are disclosed. In particular, a method for non-contact interference detection of a cylindrical shape is disclosed. A cylindrical converging lens and a cylindrical diverging lens are combined with a to-be-tested concave cylinder respectively. Wavefront error data of the combination of the cylindrical diverging lens and the to-be-tested concave cylinder and wavefront error data of the combination of the cylindrical converging lens and the to-be-tested concave cylinder are obtained through interference measurement respectively. Wavefront error data of a combination of the cylindrical diverging lens and the cylindrical converging lens is then obtained through interference measurement. Shape error data of the to-be-tested concave cylinder, the cylindrical diverging lens, and the cylindrical converging lens is obtained respectively by using a difference algorithm and a wavefront recovery algorithm.