One-shot colored reflectance direction field imaging system for optical inspection

Area of Science:

• Materials Science
• Optical Engineering
• Surface Metrology

Background:

• Conventional cameras struggle to detect microscale surface defects.
• Microscale defects significantly alter a surface's bidirectional reflectance distribution function (BRDF).

Purpose of the Study:

• To propose a simple, effective imaging system for detecting microscale surface defects.
• To utilize color mapping of light reflectance to quantify BRDF changes caused by defects.

Main Methods:

• Development of a novel imaging system incorporating a multicolor filter in front of an imaging lens.
• Color mapping of light rays passing through different filter regions to analyze reflectance direction field.
• Experimental validation using a plastic surface with a micrometer-depth scratch.

Main Results:

• The proposed system successfully detected microscale defects on a plastic surface.
• Color variations directly correlated with the broadening of the BRDF, indicating defect presence.
• Demonstrated effectiveness for optical inspection of surfaces with shallow defects.

Conclusions:

• The multicolor filter imaging system offers a simple and effective solution for detecting microscale surface defects.
• This method provides a quantitative measure of BRDF changes, crucial for quality control.
• The system shows promise for various industrial optical inspection applications.