Disk-Shaped Graduation Plate Defect Detection via Polar Coordinate Transformation
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Solution Overview
Problem
Existing inspection methods for dial gauges cannot distinguish between indication errors caused by the internal mechanism and defects in the disk-shaped graduation plate, making it difficult to accurately identify and address defects in the graduation plate.
Innovation Solution
An inspection method that acquires image data of the graduation plate, transforms it into polar coordinates, and detects defects by calculating the center of gravity and pitch of graduations, allowing for precise identification of defects such as scratches, dirt, or distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional inspection methods are used to check dial gauge indication errors, then measurement capability is maintained, but the ability to distinguish defects in the graduation plate from internal mechanism errors is lost
Solution Approach 1:
The inspection system segments the dial gauge into two independent inspection targets: the graduation plate and the internal mechanism. By using a camera to capture images of the graduation plate and comparing them with reference images, the system can identify defects such as scratches, dirt, or distortion on the graduation plate separately from indication errors caused by internal mechanism issues. This segmentation allows precise localization of defects while maintaining overall measurement capability.
2Measurement precision
If manual inspection of graduation plates is performed, then defect identification capability is maintained, but inspection efficiency and productivity are reduced
Solution Approach 1:
The system replaces manual visual inspection with an automated image processing system. A camera captures images of the graduation plate, and computer algorithms automatically compare these images with reference images to detect defects. This substitution of mechanical/manual inspection with automated optical and computational methods maintains high defect detection accuracy while dramatically increasing inspection throughput and productivity.
3Reliability
If comprehensive inspection of both graduation plate and internal mechanism is performed using conventional methods, then all potential defects are detected, but inspection time and operational complexity increase
Solution Approach 1:
The system performs preliminary inspection of the graduation plate using image capture and comparison before proceeding to indication error measurement. By pre-identifying and flagging graduation plate defects, the system can quickly determine whether subsequent indication error measurements are relevant or if the defect is already visible on the graduation plate. This preliminary action reduces unnecessary measurement steps and shortens the overall inspection cycle time while maintaining comprehensive defect detection.
Data Source
AI summary
An inspection method includes an image-data acquisition step of acquiring data about an image of a disk-shaped graduation plate as disk-shaped graduation-plate image data, and a polar-coordinate transformation step of transforming the disk-shaped graduation-plate image data into polar coordinates using a center of the disk-shaped graduation plate as a reference to generate polar-coordinate graduation image data. A defect detection step includes a processing-region setting step of setting a processing region for each of graduation line on a polar-coordinate angle display axis, a center-of-gravity calculation step of calculating a center of gravity for each processing region, and a center-of-gravity pitch calculation step of calculating a pitch of the center of gravity calculated in the center-of-gravity calculation step. the defect detection is executed by comparing a pitch of graduations in the polar-coordinate graduation image data with a predetermined reference value