Deflectometry Measurement Method for Reflective and Transparent Objects
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Solution Overview
Problem
Existing deflectometry methods are inadequate for accurately measuring the shape of objects with precision close to interferometry, as they either provide only qualitative shape defect measurements or require additional input data and precise alignment, leading to mediocre precision and complexity.
Innovation Solution
A method using a deflectometer with a display showing dynamic fringes and a camera acquiring images of the reflected or transmitted fringes, where the shape and position of the object are calculated by identifying a single common solution among multiple possible solutions obtained in different configurations, without requiring additional input data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional deflectometry is used to measure shape defects, then small defects can be detected, but only qualitative shape defect information is obtained without quantitative shape measurement
Solution Approach 1:
The patent introduces a temporal dimension by capturing images at multiple time points (t1, t2, t3, t4) during display refresh cycles, transforming static fringe pattern analysis into dynamic temporal analysis. This enables reconstruction of both slope information and integration constants, achieving quantitative shape measurement while preserving defect detection capability
Solution Approach 2:
The patent changes the parameter being measured from only slope (first derivative) to include both slope and integration constant (absolute shape). By utilizing temporal variations in fringe patterns across multiple refresh cycles, the system recovers the complete shape information including the previously inaccessible integration constant, transforming qualitative defect detection into quantitative shape measurement
2Measurement precision
If additional input data and precise alignment are used to improve measurement accuracy, then shape can be measured, but device complexity and alignment requirements increase
Solution Approach 1:
The system uses its own temporal refresh cycle and inherent display characteristics to generate the reference information needed for measurement. By capturing images at multiple time points during normal display operation, the system self-calibrates and determines integration constants without requiring external alignment tools or additional input data, eliminating the complexity associated with traditional methods
Solution Approach 2:
The patent exploits the periodic refresh cycle of the display to generate multiple fringe patterns at different phases. This periodic action provides the temporal variation needed to solve for integration constants, replacing the need for additional alignment measurements and auxiliary devices with the display's inherent periodic operation
3Loss of information
If geometric reconstruction by triangulation is used to obtain object shape, then shape information can be obtained, but measurement precision deteriorates due to sensitivity to ray propagation errors
Solution Approach 1:
The patent replaces the geometric triangulation method with a temporal-fringe analysis method. Instead of relying on ray intersection geometry that is sensitive to propagation direction errors, the system uses temporal variations in fringe patterns captured at multiple time points to determine shape and integration constants, achieving higher precision by substituting temporal analysis for spatial triangulation
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 enables the accurate measurement of an object's shape with precision comparable to interferometry, simplifies the measurement process, and reduces approximation errors, while being cost-effective and easy to use.
Implementation Method 1
a camera configured to acquire images of the fringes reflected by the reflective object
Data Source
AI summary
A method for taking a measurement from a reflective object (2) or a transparent object (2) by means of a deflectometer (1) includinga display (10) displaying dynamic fringes; a camera (20) configured to acquire images of the fringes reflected by the reflective object (2) and/or images of the fringes transmitted through the transparent object (2); and a computer (30) configured to run a program in order to perform the measurement based on the images acquired by the camera (20). The method includessuccessively acquiring the images of the fringes reflected and/or transmitted by the object (2) in at least two configurations of an optical system defined by the display (10), the object (2), and the camera (20); based on the acquired images, running the program and calculating possible solutions for the shape of the object (2) and for the position of the object (2) within the optical system defined by the display (10), the object (2), and the camera (20), in each of the configurations; and obtaining a final solution for the shape and position of the object (2) by identifying a single solution common to the previously calculated possible solutions.