Curved Reflective Surface Testing Using Photon Count Measurements
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Solution Overview
Problem
Current methods for testing reflective coatings on curved optical elements are inadequate, as defects in the coatings cannot be accurately assessed without visual inspection, and these defects can lead to costly rework or rejection of optical elements, especially when operating outside the visual spectrum.
Innovation Solution
A method and system for calculating reflectance values by emitting radiation at different intensities and angles to determine the quality metric of a reflective coating on a curved surface, using a detector to receive and analyze the reflected radiation, and comparing it to a conforming region, allowing for direct testing of curved reflective surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If visual inspection is used to assess defects in curved reflective surface coatings, then the inspection process is simple, but the assessment is inaccurate for non-visual spectra and cannot provide quantitative reflectance measurements
Solution Approach 1:
The patent replaces manual visual inspection with an automated optical measurement system that uses radiation sources and detectors to measure reflectance. This substitution enables quantitative measurements across non-visual spectra while eliminating the limitations of human visual inspection.
Solution Approach 2:
The patent introduces a flat witness sample as an intermediary reference object with known reflectance properties. This witness sample serves as a mediator to calibrate and validate the measurement system, enabling accurate reflectance measurements of the curved optical element by comparing measurements against the known reference.
2Reliability
If flat witness samples are used to infer reflectance properties of curved optics, then the testing process is simple, but defects specific to curved surfaces are not detected
Solution Approach 1:
The patent applies local quality by making the measurement process adaptable to the specific geometry being tested. The system can measure both flat witness samples and curved optical elements directly, with the measurement approach tailored to the local surface geometry, ensuring defects specific to curved surfaces are detected.
Solution Approach 2:
The patent creates a universal measurement system that can handle multiple types of surfaces (flat and curved) and multiple spectral ranges (visual and non-visual) using the same fundamental apparatus. This multi-functional system eliminates the need for separate testing procedures for different surface types.
3Measurement precision
If extensive rework or analysis is performed to assess defect impact, then defect assessment is thorough, but manufacturing time and cost increase significantly
Solution Approach 1:
The patent performs preliminary reflectance measurements during the manufacturing process rather than after completion. By measuring the curved optical element directly with the automated system, defect impact is assessed early, allowing immediate decisions about whether rework is needed, thus avoiding time-consuming post-manufacturing analysis.
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 enables accurate assessment of reflective coating quality on curved surfaces, reducing the likelihood of defects and associated rework costs by providing a quantitative measure of reflectance, thereby improving manufacturing efficiency and reducing waste.
Implementation Method 1
emitting, by an extended radiation source, first radiation at a first intensity along a first optical axis
Implementation Method 2
reflecting, along a second optical axis separated from the first optical axis by a predetermined angle, the first radiation from a region of a curved surface of an optical element having a reflective coating
Implementation Method 3
receiving, by a detector, the reflected first radiation, determining a first count from the received first radiation
Data Source
AI summary
Methods and systems for calculating a reflectance value of a reflective coating on a curved surface of an optical element include calculating the reflectance value by taking a series of photon count measurements of an extended radiation source over a range of values of emitted radiation reflected from the curved surface into a detector. A combination of the measurements and a known value of accepted or conforming reflectance for the reflective coating is used to calculate the reflectance value of the reflective coating on the curved surface.