Concepts and Classification
1, front light/incident light: camera and light source in the same measurement.
Typical coaxial light, annular light, strip light source, etc.
2. Backlight/transmitted light: the camera and light source are located on both sides of the detected object.
The typical light source is the backlight;
3, bright field lighting: the light source and the measured object is at a certain Angle, so that most of the light reflected to the camera;
Typical high Angle annular light source, strip light source, etc.
4, dark field lighting: the light source and the measured object is at a certain Angle, so that most of the light source can not be reflected to the camera, so that a small part of the light or specific light reflected to the camera;
Typical light source is low Angle light source;
Practical application cases (in actual use, for reference only, in the selection of light source, first select coaxial light or annular light according to the conventional routine, and then select the color of light source, the conventional routine is not good, is to do a lot of tests on the basis of the conventional)
(summed up in their own use of the experience) in practical use is commonly used in four kinds of coaxial light source, annular light source, strip light source and backlight;
1, backlight: generally used for size contour detection, if the use of positive irradiation, reflection will cause virtual shadow, loss of pixels, thereby reducing the accuracy;
2. Strip light source: most of the time, it is generally not used alone, but used for several combinations together to form Angle light, which has more flexible advantages. With arch smooth top surface can be made into dome light source, uniformity is better.
3, ring light: generally used for positioning and detection of specific defects, it is difficult to detect a product with many kinds of defects, ring light is relatively limited.
4, coaxial light: when the product defects are more, the use of coaxial light is more appropriate, for example, the surface of the product is yellow, oil, scratches (deep). The disadvantage is also very obvious, is that the light source in a certain area has attenuation, mainly because of the principle of coaxial light using spectroscopic refraction, far from the light source is relatively dark, near the light source is relatively bright; Generally, if it is necessary to use, according to my personal experience, choose a relatively large coaxial light, the detected object is relatively small, can choose a more uniform position detection
