Side-Emitting Illumination for Accurate Edge Extraction
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Solution Overview
Problem
Conventional image measurement devices using epi-illumination struggle with stable edge extraction, particularly when measuring workpieces with steps or surfaces having low photographing magnification, as textures can be erroneously extracted as edges, leading to inaccurate dimension measurements.
Innovation Solution
An image measurement device employing a side-emitting illumination device with a light amount distribution that sharply changes in the photographing axis direction, allowing localized irradiation and preventing the influence of distant textures, along with a relative position adjustment mechanism to identify optimal illumination positions for accurate edge extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If epi-illumination is used to photograph the workpiece, then the workpiece surface can be illuminated from the same side as the camera, but textures on the workpiece surface are erroneously extracted as edges, making dimension measurement unstable
Solution Approach 1:
The patent applies local quality by making the illumination light amount distribution non-uniform in the photographing axis direction. The side-emitting illumination device creates a sharp change in light intensity at specific depths, illuminating only the targeted surface region while leaving other regions in shadow. This localized illumination quality prevents textures from regions outside the measurement target from being erroneously extracted as edges, thereby improving edge extraction accuracy while maintaining ease of operation.
2Area of stationary object
If a camera with low photographing magnification is used, then a larger area can be captured, but the depth of field increases causing both upper and lower ends of vertical planes to be in focus, making correct edge extraction difficult
Solution Approach 1:
The patent resolves this contradiction by applying local quality through depth-selective illumination. The side-emitting illumination device creates a sharp light amount distribution in the photographing axis direction, illuminating only the specific depth region corresponding to the measurement target. Even though the camera's large depth of field keeps multiple regions in focus, the illumination selectively highlights only the target region, allowing correct edge extraction while maintaining the advantage of a large field of view.
Solution Approach 2:
The patent applies segmentation by spatially separating the illumination regions in the photographing axis direction. The side-emitting illumination device divides the workpiece surface into illuminated and non-illuminated regions based on depth position. This segmentation allows the system to capture a large area with low magnification while selectively processing only the illuminated region for edge extraction, preventing interference from out-of-focus regions.
3Measurement precision
If the light amount distribution is made sharp in the photographing axis direction, then localized irradiation is achieved and distant textures are prevented from influencing measurement, but the device complexity increases
Solution Approach 1:
The patent applies mechanics substitution by replacing complex mechanical positioning systems with an optical field control approach. Instead of mechanically moving the camera or workpiece to achieve depth-selective measurement, the side-emitting illumination device creates a sharp light amount distribution in the photographing axis direction. This optical field segmentation achieves localized irradiation and prevents distant textures from influencing measurement, improving edge extraction accuracy without significantly increasing device complexity.
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
The solution enables stable and accurate edge extraction, suppressing erroneous texture extraction and correctly identifying steps, even with low-magnification cameras, by localizing irradiation and adjusting relative positions for optimal illumination.
Implementation Method 1
a side-emitting illumination device that has a light amount distribution sharply changing in a photographing axis direction of the camera, and irradiates the workpiece on the stage with illumination light from a side
Implementation Method 2
a camera that photographs the workpiece on the stage and generates a workpiece image
Data Source
AI summary
The image measurement device includes: a side-emitting illumination device that has a light amount distribution sharply changing in a photographing axis direction of a camera, and irradiates a workpiece on a movable stage with illumination light from a side; a measurement target place specifying part that specifies a measurement target place on a workpiece image; an illumination position adjusting part that moves the side-emitting illumination device in the photographing axis direction, to adjust a relative position of the side-emitting illumination device to the movable stage; a relative position identifying part that obtains a change in luminance in the measurement target place with respect to two or more of the workpiece images photographed by making the relative position different, to identify a relative position; an imaging control part that controls the illumination position adjusting part based on the identified relative position and drives the side-emitting illumination device.