Cylindrical Light Guide for High-Accuracy Optical Inspection
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Solution Overview
Problem
Conventional optical inspection methods using oblique-incidence ring lighting face challenges in achieving high accuracy due to wide light distribution angles, which affect the precision of inspections regardless of the object's azimuth direction.
Innovation Solution
An optical inspection apparatus featuring a cylindrical light guide with a total reflecting surface and a mirror surface, combined with a limited number of light sources arranged symmetrically around the optical axis, narrows the light distribution angle by using the Etendue conservation law to ensure precise illumination and imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If oblique-incidence ring lighting is used to inspect objects irrespective of azimuth direction, then inspection coverage is improved, but light distribution angle becomes wide which deteriorates measurement precision
Solution Approach 1:
The light guide is divided into multiple independent light source positions (first, second, third, and fourth light sources) arranged at different angular positions. Each light source independently illuminates the object from a specific azimuth direction, allowing comprehensive coverage while maintaining narrow light distribution angles for high precision measurement at each position.
Solution Approach 2:
The light guide employs asymmetric surface structures with different optical properties: the outer surface has a mirror surface for directional light reflection, while the inner surface has a diffuse reflecting surface. This asymmetric design enables precise control of light distribution angles while maintaining versatility in inspecting objects from multiple azimuth directions.
2Adaptability or versatility
If multiple light sources are arranged to achieve comprehensive inspection coverage, then adaptability is improved, but device complexity increases
Solution Approach 1:
Multiple light sources are integrated into a single cylindrical light guide structure that rotates around the optical axis. This merging of multiple light sources into one unified rotating component reduces device complexity compared to using separate fixed light sources, while still achieving comprehensive inspection coverage through rotational positioning.
Solution Approach 2:
The cylindrical light guide serves multiple functions: it houses multiple light sources, provides rotational movement for azimuth coverage, maintains narrow light distribution angles through its mirror surface, and enables comprehensive inspection of objects from all directions. This multi-functionality reduces the need for separate components, simplifying the overall device structure.
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 configuration allows for high-accuracy inspections by reducing the light distribution angle, enabling more precise imaging and reducing the number of light sources required, thus lowering manufacturing costs and improving cooling efficiency while maintaining high inspection accuracy.
Implementation Method 1
a total reflecting surface formed on an inner surface of the light guide to totally internally reflect light struck into the light guide from the end face
Implementation Method 2
a mirror surface formed on an outer surface of the light guide to reflect light struck into the light guide from the one or more light sources, toward the inspection target
Data Source
AI summary
According to one embodiment, an optical inspection apparatus including: an imaging optical system; one or more light sources; a light guide which extends cylindrically along an optical axis of the imaging optical system and whose end face is opposed to the one or more light sources; a total reflecting surface formed on an inner surface of the light guide to totally internally reflect light struck into the light guide from the end face; a mirror surface formed on an outer surface of the light guide to reflect light struck into the light guide from the one or more light sources, toward the inspection target; and a transmission surface formed on the inner surface of the light guide to transmit the light reflected by the mirror surface, toward the inspection target.