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Glossary
[H]
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Halogen lamp
Light source with halogen gas in the bulb. When a halogen lamp is lit, the halogen gas and vaporized
tungsten combine. When the filament is heated, these combined particles reattach to the tungsten, in
stead of being deposited on the glass bulb, so that the original brightness of the lamp is maintained
throughout its life span.
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High frequency lighting
If a fluorescent lamp is powered by commercial electricity, it will flicker at 50 Hz or 60 Hz. Since the CCD
scans images at 60 Hz, the brightness of the image may fluctuated due to the flickering of the fluorescent
lamp.
By increasing frequency sued to power the fluorescent lamp (employing a high frequency light), this type
interference is eliminated and a stable image can be obtained.
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Gray scale processing (gray image processing)
This is a process used to handle the unmodified captured image data, obtained from the CCD camera. In
other words, the image data is not converted to binary values.
- This process produces more precise results than binary image processing (one pixel = one bit) by using
8 bits (one pixel = 256 gray levels) to represent each pixel in a gray scale image.
[Advantage]
Theoretically, better precision and reliability can be offered because the image contains
more information about the brightness of each pixel in the image.
[Disadvantage] More processing time is required because this approach must handle a large amount of
data.
Positional deviation measurement
(Output)
(Application)
Maximum matching level value
Shape inspection
The center coordinates where the highest
level of matching is obtained
[Procedures]
1
Store the reference image as a gray scale image with 256 levels of gray.
2
Capture the workpiece image to be measured.
3
Move the captured image of the object so that the upper left corner of the captured image is right
on top of the upper left edge of the reference image. Calculates the level of matching between
the two images, based on the stored gray scale image data.
4
If the match is G, slide the reference image over one pixel width and then measure the level of
matching at that position.
5
Repeat step
4
above for the whole workpiece image until a good match is found.
Reference image
Search range in the image
Detected image
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Gray scale search (corrected gray scale search)
The "gray scale search" function is a system for detecting a point where the input image and the refer-
ence image match, after calculating the matching levels in the input image and the reference image.
