Wavelength-Selective Optical Inspection for BRDF Surface Identification
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Solution Overview
Problem
Existing optical inspection methods struggle to accurately acquire surface information of objects in a non-contact state, particularly in distinguishing surface properties and shapes, without spectrally dividing illumination into R, G, and B.
Innovation Solution
An optical inspection method utilizing an image sensor that discriminately receives light components of multiple predetermined wavelengths, performing color count estimation and scattered light distribution identification to determine the Bidirectional Reflectance Distribution Function (BRDF) of the object surface, using a wavelength selection portion and a processing device to analyze the surface state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If spectrally divided light beams (R, G, B) are used for illumination, then surface information acquisition capability is improved, but device complexity and measurement precision requirements increase
Solution Approach 1:
The patent segments the spectral information acquisition by using multiple wavelength selection portions (first, second, third wavelength selection portions) that selectively pass different wavelength bands. Each wavelength selection portion corresponds to specific color channels in the image sensor, enabling spectral information to be acquired through spatial segmentation rather than temporal or complex spectral division methods.
Solution Approach 2:
The patent introduces a wavelength selection portion as an intermediary component between the illumination source and the image sensor. This intermediary selectively transmits specific wavelength components while blocking others, simplifying the overall system by replacing complex spectrally divided illumination with a single illumination source combined with wavelength-selective filtering.
2Measurement precision
If color channels are used to estimate number of colors, then surface state identification accuracy is improved, but processing complexity increases
Solution Approach 1:
The patent utilizes color channel intensity ratios from the image sensor to estimate the number of colors present in each pixel. By analyzing the relative intensities of different color channels (which correspond to different wavelength selections), the system can infer surface properties such as BRDF characteristics without requiring complex spectral analysis, thus maintaining processing simplicity while improving measurement precision.
3Measurement precision
If BRDF analysis is performed from scattered light distribution, then three-dimensional shape identification is improved, but measurement time and processing load increase
Solution Approach 1:
The patent performs preliminary action by capturing scattered light distribution information across multiple wavelength bands simultaneously in a single imaging operation. The wavelength selection portions and color channels are configured to collect BRDF-related information beforehand, allowing the processing device to subsequently extract three-dimensional shape information through computational analysis of the already-captured data, rather than requiring additional measurement time.
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
Enables accurate acquisition of surface information and three-dimensional shape of objects without spectrally divided illumination, allowing for precise identification of surface properties and shapes, including defects, through the use of color channels and BRDF analysis.
Implementation Method 1
an imaging element acquires each spectrally divided image
Implementation Method 2
using light from a surface of an object, which passes through a wavelength selection portion configured to selectively pass light components of a plurality of predetermined wavelengths
Implementation Method 3
performing at least one of scattered light distribution identification processing configured to identify a scattered light distribution as Bidirectional Reflectance Distribution Function (BRDF)
Data Source
AI summary
According to the embodiment, an optical inspection method includes: acquiring an image by capturing the image, using light from a surface of an object, which passes through a wavelength selection portion configured to selectively pass light components of a plurality of predetermined wavelengths different from each other, the image sensor including color channels configured to discriminately receive the light components of the plurality of predetermined wavelengths, performing color count estimation processing configured to estimate the number of colors based on the intensity ratio of the color channels that have received the light in each pixel of the image, and performing scattered light distribution identification processing configured to identify a scattered light distribution as BRDF from the surface of the object based on the number of colors or surface state identification processing configured to identify a state of the surface of the object based on the number of colors.