In machine vision, it's important to get a high-quality, processable image. The success of the machine vision system is to ensure that the image quality is good and the features are obvious. Conversely, if the image quality is not good and the features are not obvious, the machine vision system will become unreliable or robust, and even lead to project failure. Therefore, spherical/aspherical/cylindrical/paraboloid optical lens selection skills are necessary, the following introduces the basic elements of light source selection:
Good visual source color selection can produce a large contrast between the features that need to be observed and the image features that need to be ignored, that is, there is enough gray-scale difference between the features and the surrounding area, so that the features can be easily distinguished. . In order to distinguish the object to be observed and the background to a greater extent, a complementary color source is usually selected. For example, when the object to be observed is green, selecting a background of the red source can improve the contrast.
When the observed matter is mixed with impurities that we do not want to see, the background light source color is usually selected to be the same color as the magazine, so that the impurity interference can be visually filtered out.
Ultraviolet light is a good choice when detecting tiny dust particles. For example, in the detection of wafer dust particles, ultraviolet light is usually used.
Good lighting should ensure that features that need to be detected stand out from other backgrounds. There are many lighting methods, such as wholesale high efficiency laser grade optical filter, back lighting, coaxial lighting, etc. Depending on the application background, different lighting methods are directly related to the success or failure of the project.
When it is desired to highlight the contour of the object, back illumination is usually employed, that is, the object to be observed is located between the visual source and the high speed camera.
In addition, the flexibility to use custom lighting is also important in some special applications. For example, in order to save the space of the [visual light source] and the high-speed camera while achieving the effect of the light source from a certain angle, a mirror can be used, and the high-speed camera and the laser line emitter can be fixed by the seam tracking system independently developed by Ke Tianjian. In a small box, the direction of the laser line is changed by a mirror so that the laser line and the high-speed camera are at a large angle to the laser axis for laser triangulation of the weld.
The brightness and robustness of the light source are also non-negligible elements in the selection of the light source.
Brightness: When choosing two sources, the best choice is to choose the brighter one. When the light source is not bright enough, there may be three bad conditions. First, the signal-to-noise ratio of the high-speed camera is not enough; because the brightness of the light source is not enough, the contrast of the image is not enough, and the possibility of noise appearing on the image increases. Secondly, the brightness of the light source is not enough, and the aperture must be increased, thereby reducing the depth of field. In addition, when the brightness of the light source is insufficient, random light such as natural light will have a greater influence on the system.
Robustness: refers to whether the light source is sensitive to the position of the component. When the light source is placed in different areas of the camera's field of view or at different angles, the resulting image should not change. A highly directional light source increases the likelihood of specular reflections in the highlighted area, which is detrimental to subsequent feature extraction.
A good wholesale BBO nonlinear crystal needs to be able to make the features you need to look very obvious. In addition to being able to capture parts with a high-speed camera, a good light source should be able to produce greater contrast, brightness and insensitivity to changes in the position of the part. The light source is chosen, and the rest of the work is much easier. Of course, the specific method of light source selection lies in the practical experience of the test.