Workpiece Inspection via Synchronized Image Differential
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Solution Overview
Problem
Existing workpiece inspecting apparatuses require significant time for image pickup and inspection due to the need for precise stopping of rotating workpieces and high processing loads, often leading to overlooked defects, especially when images are picked up under fixed illumination directions.
Innovation Solution
A workpiece inspecting apparatus that uses a workpiece rotating mechanism to output reference pulses at a fixed interval, synchronizing image pickup with the rotation to capture images without stopping the workpiece, and employs an illuminating device with an oblique optical axis to reduce brightness unevenness and enhance defect detection precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the workpiece is stopped at each image pickup position to capture images, then image quality and inspection accuracy are improved, but the time required for image pickup and inspection increases significantly
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing reference images of the workpiece at various rotational positions before actual inspection. During inspection, the system compares captured images against these pre-prepared references, eliminating the need to stop the workpiece for each measurement and significantly reducing inspection time while maintaining accuracy
Solution Approach 2:
The patent creates copies of the workpiece images at different rotational positions and stores them as reference data. Instead of capturing images during rotation stops, the system uses these pre-captured copies for comparison, allowing continuous rotation during inspection and thereby reducing time loss
2Manufacturing precision
If the workpiece rotation is stopped frequently for image pickup, then precise image alignment is achieved, but the productivity and inspection efficiency decrease
Solution Approach 1:
The patent replaces the mechanical stopping mechanism with a computational approach. Instead of physically stopping the workpiece rotation to align images, the system uses image processing algorithms and reference image comparison to achieve precise alignment computationally, thereby maintaining continuous rotation and improving productivity
Solution Approach 2:
The system performs preliminary image capture and alignment work by creating reference images at various rotational positions before the actual inspection process. This preliminary preparation allows the main inspection to proceed without stopping, maintaining both alignment precision and high productivity
3Measurement precision
If images are processed individually for defect detection, then detection accuracy is maintained, but the processing load and time consumption increase
Solution Approach 1:
The patent merges multiple image processing operations into a single comparative operation. By capturing images at different rotational positions and comparing them simultaneously against reference images, the system achieves comprehensive defect detection without the need for separate processing of each image, thereby reducing total processing time while maintaining accuracy
Solution Approach 2:
The system performs preliminary comparison operations by establishing reference images in advance. During actual inspection, the captured images are compared against these pre-established references, which reduces the computational burden during real-time processing and decreases overall processing time while maintaining detection accuracy
4Device complexity
If illumination is provided from a fixed direction, then the lighting setup is simple, but defects may be overlooked due to insufficient contrast
Solution Approach 1:
The patent applies dynamics by making the illumination direction variable rather than fixed. The illumination source can change its angle and position dynamically during the inspection process, allowing light to interact with surface defects from multiple angles and improving detection reliability without significantly increasing system complexity
Solution Approach 2:
The illumination system performs periodic scanning or oscillation, changing the illumination angle in a periodic manner during inspection. This periodic variation in lighting direction enhances the visibility of different types of defects while maintaining a relatively simple illumination setup, thereby improving detection reliability
Data Source
AI summary
A workpiece inspecting apparatus for rotating a workpiece having a shape portion containing a convex portion and a concave portion which are periodically and repetitively formed on the workpiece and picking up images of the shape portion of the workpiece to inspect the workpiece, including a workpiece rotating mechanism that outputs reference pulses at a fixed interval while rotating the workpiece at a fixed rotational speed, an image pickup mechanism that picks up images of the shape portions of the workpiece every image pickup timing based on the reference pulses, an image pickup controller that synchronizes each of the shape portions of the workpiece with the image pickup timing, and an inspection controller that executes image processing of taking a difference between a pickup k-th (k represents an integer) image and a pickup (k+1)-th image and detects a defect on the basis of differential data representing the difference.