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size, angle, offset brightness, color and position of the components, etc.) and outputs the images
with the comparison results exceeding the rated error threshold through the display, and displays
the specific positions of the images on the circuit board.
5.4 Principle of color extraction
Any color can be mixed with red, green and blue in a certain proportion. A
three-dimensional color cube is formed with red, green and blue. Color extraction is to cut a
small color cube that we need from a set of color cubes. In other words, the color range is
selected according to needs. Then, whether the ratio of the color in the inspected image that
meets the color in the cube to the total number of colors in the image meets the setting range
required. Under the red, green and blue light, this method is most suitable for the inspection of
soldering tin such as resistance and capacitance.
5.5 Principle of gray scale operation
The target image is converted into gray scale image according to certain method. Then, a
certain brightness threshold is selected for image processing. The image below the threshold is
directly turned into black, and the image above the threshold is directly turned into white. In this
way, the concerned regions, such as characters and IC short circuits, are directly separated from
the original image.