Spinning Laser Beam Inspection for Spherical Surfaces
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Solution Overview
Problem
Current methods for inspecting optical components with curved surfaces lack the sensitivity and throughput to detect small imperfections, relying on subjective human observation and being inadequate for high-quality standards, especially for spherical, near-spherical, and aspherical surfaces.
Innovation Solution
A method and apparatus utilizing a spinning laser beam with constant incidence angle and controlled motion to scan spherical surfaces, collecting and classifying scattered radiation for precise defect detection and classification, enabling high-speed and high-accuracy inspection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If automated inspection systems are implemented, then productivity and measurement precision are improved, but device complexity increases
Solution Approach 1:
The inspection system is divided into independent functional modules: illumination source, beam shaping optics, scanning mechanism, detection system, and control unit. Each module performs a specific function and can be independently optimized or replaced, reducing overall system complexity while maintaining high productivity.
Solution Approach 2:
The system uses variable parameters such as beam width, scanning speed, and detection sensitivity that can be adjusted based on the specific inspection requirements. This allows the same apparatus to handle different defect sizes and surface types without requiring complete system redesign, thereby improving productivity without proportionally increasing complexity.
2Measurement precision
If high sensitivity detection is used to detect small imperfections, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The illumination system provides localized high-intensity lighting at the beam spot on the workpiece surface, concentrating optical energy only where needed for detection. This local quality approach enables high measurement precision for small defects without requiring the entire system to be overly complex or energy-intensive.
Solution Approach 2:
A beam shaping element is introduced as an intermediary component between the illumination source and the workpiece surface. This element conditions the light beam to achieve optimal spot size and intensity distribution, enabling high defect detection sensitivity while using a relatively simple and cost-effective illumination source.
3Measurement precision
If constant angle of incidence is maintained during scanning, then measurement consistency is improved, but ease of operation deteriorates
Solution Approach 1:
The system is designed to work with spherical or curved workpiece surfaces by maintaining the beam incident angle constant relative to the local surface normal at each scan position. This geometric approach ensures measurement consistency across curved surfaces without requiring complex real-time angle adjustment mechanisms, thereby preserving ease of operation.
Solution Approach 2:
The control unit receives position information from the scanning mechanism and automatically adjusts the illumination and detection angles to maintain constant incidence relative to the surface normal. This feedback mechanism ensures measurement consistency while automating the alignment process, reducing the operational burden on the user.
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 approach enhances defect detectability and classification on curved surfaces, providing consistent and objective inspection results comparable to flat wafer inspection systems, improving the quality control of optical components.
Implementation Method 1
A method is disclosed wherein an inspected surface of an object is scanned with a beam of electromagnetic radiation in the result of spinning the beam about a spin axis, the spin axis being directed normally towards the surface and passing through a center of a sphere making up the inspected spherical surface so that an angle of incidence of the beam at the surface is constant during the scanning
Implementation Method 2
A portion of electromagnetic radiation scattered at the surface features and imperfections is collected by an optical system set in a fixed mechanical relationship with the beam and also spinning about the spin axis
Data Source
AI summary
Disclosed are a method and an apparatus for inspection of workpieces and products having curved and, in particular, spherical surfaces. The method is based on scanning inspected objects with a narrow probing beam of electromagnetic radiation and concurrently measuring the radiation scattered on the surface. The method and apparatus improve the detectability of features and imperfections on inspected surfaces by providing invariable parameters and conditions of scanning, robust mechanical stability of scanning systems, high positioning accuracy of the probing electromagnetic beam and efficient collection of the scattered radiation. The apparatus allows surface defect classification, determining defect dimensions and convenient automation of inspection.