Conic Optical Surface Testing via Retro Ball Alignment
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Solution Overview
Problem
Existing techniques for testing conic optical surfaces are inadequate due to high costs and tolerance buildup in test jigs, which affect the accuracy of reflective optical surfaces like paraboloids and ellipsoids.
Innovation Solution
A test apparatus using a 5-axis support mechanism and an interferometer with a sequence of operations involving flat and spherical waves, along with a retro ball, to accurately align and verify the conic optical surfaces by ensuring reflections travel perpendicular to the interferometer's axis, thereby detecting any aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional test jigs or fixtures are used to align the optical surface with the interferometer, then mechanical alignment is achieved, but the cost increases and tolerance buildup reduces measurement accuracy
Solution Approach 1:
The patent replaces the mechanical test jig system with an optical alignment system. Instead of using mechanical fixtures to physically position and align the workpiece, the invention uses optical references (retro-reflector and spherical reference surface) combined with interferometer feedback to achieve precise alignment. This substitution eliminates the mechanical tolerance buildup inherent in test jigs while maintaining alignment accuracy.
Solution Approach 2:
The patent introduces optical intermediary elements - specifically a retro-reflector and spherical reference surface - that mediate between the workpiece and the interferometer. These intermediaries provide precise optical alignment references without requiring complex mechanical fixtures. The retro-reflector establishes the optical axis alignment, and the spherical reference surface provides focal point registration, serving as intermediaries that simplify the alignment process while improving precision.
2Measurement precision
If precise test jigs are manufactured to achieve accurate alignment, then alignment accuracy improves, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive, precision-machined mechanical test jigs with simpler optical alignment components. The retro-reflector and spherical reference surface can be manufactured with standard precision and then used to establish high-precision alignment through optical feedback, rather than requiring the test jig itself to be manufactured with extreme precision.
Solution Approach 2:
The patent uses optical copying principles where the interferometer creates and analyzes light wave patterns that replicate the ideal conic surface geometry. By comparing the actual surface reflections against these optical copies of the desired geometry, the system achieves precise measurement without requiring physical test jigs that replicate the same geometry mechanically.
3Ease of operation
If mechanical alignment methods are used, then alignment is achieved, but tolerance buildup reduces testing accuracy
Solution Approach 1:
The patent replaces mechanical alignment methods that accumulate tolerances through multiple mechanical interfaces with a direct optical alignment system. The interferometer directly measures the optical path differences caused by misalignment, and the control system directly adjusts the workpiece position based on these optical measurements, eliminating the tolerance buildup that occurs in mechanical alignment chains.
Solution Approach 2:
The patent implements closed-loop feedback control for alignment. The interferometer continuously monitors the optical alignment status by analyzing reflected light patterns, and this feedback information is used to adjust the workpiece position until optimal alignment is achieved. This feedback mechanism eliminates tolerance buildup by continuously correcting alignment errors rather than relying on precision mechanical fixtures.
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 method allows for precise and cost-effective testing of conic optical surfaces by accurately determining their alignment and machining accuracy, reducing errors and aberrations, and providing a reliable assessment of surface accuracy.
Implementation Method 1
the interferometer is then used to generate spherical waves and to monitor reflections from the spherical reference surface and the retro ball
Data Source
AI summary
According to one aspect, a part has two reflective surfaces, one being a conic surface portion having an axis with a focus thereon, and the other being part of a spherical surface with a centerpoint at the focus. According to a different aspect, a method includes fabricating a part with first and second reflective surfaces, the first being a conic surface portion with an axis and a focus on the axis, and the second being a spherical surface portion with a centerpoint at the focus. The second surface is used to position the part so that the focus coincides with the centerpoint of a spherical wave from an interferometer. Then, a reflective further spherical surface portion on a member is used with the interferometer to position a centerpoint of the further surface at the focus. The interferometer then evaluates the first surface for accuracy.