Image Inspection Apparatus for Moving Workpieces
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Solution Overview
Problem
Conventional image inspection apparatuses using photometric stereo methods are limited in inspecting moving workpieces due to the assumption of stationary workpieces, leading to inaccurate results from varying illumination conditions and installation errors, and struggle to effectively detect three-dimensional shape and printed character information.
Innovation Solution
An image inspection apparatus with multiple illumination sections that can be turned on sequentially or simultaneously, capturing partial illumination images from different directions, and using a tracking target image to estimate corresponding pixel positions across images, enabling accurate inspection of moving workpieces by generating inspection images for photometric stereo processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If photometric stereo method is used on moving workpieces, then three-dimensional shape information can be obtained, but position changes during image capture cause inaccurate results
Solution Approach 1:
The patent captures a reference image of the workpiece position before photometric stereo imaging, and uses this reference image to correct position deviations in subsequently captured images. This preliminary action of recording the initial position enables accurate alignment of multiple images captured during workpiece movement.
Solution Approach 2:
The patent implements feedback by comparing the positions of workpieces in reference images and photometric stereo images, calculating position deviations, and using these deviations to correct the captured images. This feedback mechanism ensures that even when workpieces move during imaging, the final three-dimensional measurement remains accurate.
2Measurement precision
If multiple illumination directions are used for photometric stereo, then surface normal information can be extracted, but illumination condition variations cause erroneous inspection
Solution Approach 1:
The patent captures a reference image under simultaneous illumination from all light sources before performing photometric stereo imaging. This reference image serves as a baseline for correcting position and illumination variations, enabling reliable extraction of surface normal vectors even when illumination conditions vary during the imaging process.
Solution Approach 2:
The patent uses reference images as an intermediary between the actual captured images and the photometric stereo processing. By comparing captured images with reference images and applying correction based on position deviations, the system eliminates errors caused by illumination condition variations and workpiece movement.
3Productivity
If sequential illumination is used for moving workpieces, then position changes can be tracked, but corresponding pixel positions across images become difficult to determine
Solution Approach 1:
The patent captures reference images that record the workpiece position at specific time points before photometric stereo imaging. These reference images serve as a basis for determining corresponding pixel positions in sequentially captured images, enabling accurate tracking of moving workpieces and correct alignment of images taken at different times.
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 solution allows for stable and accurate inspection of moving workpieces by compensating for position changes and illumination variations, effectively detecting flaws and printed characters, even when partial illumination images of the same position cannot be captured simultaneously.
Implementation Method 1
three or more illumination sections for illuminating a workpiece from mutually different illumination directions
Implementation Method 2
an imaging section for capturing an image of the workpiece from a certain direction at illumination timing
Data Source
AI summary
An inspection apparatus includes: an imaging section for capturing a first reference image by simultaneously turning on three or more illumination sections, and a second reference image at imaging timing temporally after the first reference image; a tracking target image designating section for designating a tracking target image in the first reference image and is used for tracking a position of the workpiece; a corresponding position estimating section for searching a position of the tracking target image designated by the tracking target image designating section from the second reference image, and specifying a position including the tracking target image in the second reference image, to estimate a corresponding relation of pixels that correspond among each of the partial illumination images; and an inspection image generating section for generating an inspection image for photometric stereo based on the corresponding relation of each of the pixels of the partial illumination images.