Deflectometry Phase Mapping With Dithered Binary Illumination
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Solution Overview
Problem
Conventional phase-shifting deflectometry methods face issues with phase jumps, non-linearity, contrast problems, and complexity due to oblique-incidence configurations, leading to longer analysis times and reduced accuracy in surface characterization.
Innovation Solution
A method and system using binarized luminous images obtained through dithering and normal-incidence configuration, with imaging optics perpendicular to the surface, to determine a bijective object absolute phase function, reducing non-linearity and enabling faster, more accurate surface analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oblique-incidence configuration is used to enable reflection imaging, then the surface can be characterized, but phase jumps and non-linearity occur leading to reduced measurement precision
Solution Approach 1:
The patent inverts the conventional oblique-incidence configuration by using normal-incidence configuration where the display and detector are positioned perpendicular to the surface. This inversion eliminates the phase jumps and non-linearity issues inherent in oblique-incidence methods, thereby resolving the contradiction between reliability and measurement precision.
Solution Approach 2:
The patent changes the geometric parameter of the imaging configuration from oblique-incidence to normal-incidence. This parameter change fundamentally alters the optical path and eliminates the phase wrapping problems, achieving both high reliability and precision in surface characterization.
2Reliability
If conventional phase-shifting deflectometry is used, then surface analysis can be performed, but analysis time increases due to processing complexity
Solution Approach 1:
The patent extracts and eliminates the complex phase-shifting processing steps from the conventional method. By using normal-incidence configuration with binarized images, the method removes the need for multi-step phase unwrapping and non-linearity correction algorithms, significantly reducing analysis time while maintaining surface analysis capability.
3Measurement precision
If dithering is applied to create binarized images, then non-linearity is reduced, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical or optical phase-shifting mechanisms with a computational dithering approach. By using software-based dithering algorithms to generate binarized images, the method achieves linear response characteristics without requiring complex hardware modifications, thus reducing overall device complexity while improving measurement precision.
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
The method achieves faster and more accurate surface characterization by eliminating phase jumps and non-linearity, maintaining contrast, and focusing on the entire surface, enhancing measurement sensitivity and dynamic range.
Implementation Method 1
A display Disp arranged such that luminous images displayed on the display are reflected from the reflective surface S
Data Source
AI summary
A method is provided for analyzing a reflective surface through deflectometry, with a system including a display and imaging optics. The method includes the following steps: successively displaying n luminous images on the display, a luminous image having a binarized luminous intensity that is obtained by dithering the pattern M(x−xi), detecting, on the matrix detector, n images obtained by reflection of the n luminous images from the reflective surface, determining a function, referred to as object absolute phase function, based on the n detected images, the function g also satisfying the relationship: g(k·M)=g(M), with k being any real value, comparing the object absolute phase function with a reference absolute phase function, and deducing therefrom information about the shape of the surface.