Light source selection
The light source is an important factor affecting the input of the machine vision system, which directly affects the quality of the input data and at least 30% of the application effect. Since there is no general machine vision lighting equipment, for each specific application example, the corresponding lighting device should be selected to achieve the best effect. Balluff provides a variety of high-quality light sources.
The light is directed at the object to get a clear image. This type of light is very effective when it is necessary to obtain high-contrast object images. But when it is used to shine on bright or reflective materials, it will cause mirror-like reflections. General lighting generally uses ring or spot lighting. Ring light is a commonly used general lighting method, which is easy to install on the lens and can provide sufficient illumination for diffuse reflection surfaces.
The formation of coaxial light is the divergence of light from the vertical wall, and it hits a beamsplitter that makes the light downward. The camera looks at the object through the beamsplitter from above. This type of light source is particularly helpful for detecting highly reflective objects, and it is also suitable for detecting objects with inconspicuous areas that are affected by shadows produced by the surrounding environment.
Darkfield illumination is to provide low-angle illumination relative to the surface of the object. Use the camera to shoot the mirror so that it is in its field of view. If the light source can be seen in the field of view, it is considered to illuminate the bright field. On the contrary, if the light source is not visible in the field of view, it is dark field illumination. Therefore, whether the light source is bright field illumination or dark field illumination is related to the position of the light source. Typically, dark field lighting is used to illuminate the raised part of the surface or to illuminate the surface texture change.
Continuous diffuse lighting is applied to the reflectivity of the surface of the object or the surface has a complex angle. Continuous diffuse illumination uses hemispherical uniform illumination to reduce shadows and specular reflections. This lighting method is very useful for fully assembled circuit board lighting. This kind of light source can reach 170 solid angle range of uniform illumination.
Light that shoots from the back of the object with a uniform field of view. The side profile of the object surface can be seen through the camera. Backlight is often used to measure the size and orientation of objects. The backlight produces a strong contrast. When using backlight technology, the surface features of the object may be lost. For example, the backlight technology can be used to measure the diameter of a coin, but the front and back of the coin cannot be judged.