In machine vision systems, obtaining a high-quality and processable image is crucial for success. The failure of a machine vision project is mostly due to poor image quality and unclear features. To ensure good images, it is necessary to choose a suitable light source. What are the basic elements of light source selection?
Contrast is very important for machine vision. The most important task of the lighting applied in machine vision is to produce the highest contrast between features that need to be observed and features that need to be ignored, making feature differentiation easier.
Contrast is defined as the sufficient difference in grayscale between features and their surrounding regions. Good lighting should ensure that the features to be detected stand out from the background.
When machine vision chooses between two light sources, the brighter one is the best choice. When the light source is not bright enough, three bad situations may occur. First, the camera's signal-to-noise ratio is not sufficient. If the brightness of the machine vision light source is not enough, the contrast of the image is inevitably insufficient, and the possibility of noise appearing in the image increases accordingly. Secondly, if the light source is not bright enough, the aperture must be enlarged, reducing the depth of field. In addition, when the light source is not bright enough, the impact of natural and random light on the machine vision measurement system will be the greatest.
Another way to test a good light source is to see if the light source is the least sensitive to the position of the component. When the light source is placed in different areas or angles of the camera's field of view, the resulting image should not change.
A directional light source increases the probability of specular reflection in bright areas, which is not conducive to subsequent feature extraction. A good light source should make the features you are looking for very clear, produce the maximum contrast, have sufficient brightness, and be insensitive to the position change of the components in addition to being able to be shot by the camera.
Once the machine vision light source is selected, the remaining work becomes much easier. The specific method of selecting a light source still depends on practical experience from experiments.
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