In the machine vision system, the light source plays a very important role. Choosing the right light source becomes the key factor to determine the success of the whole system. The main purpose of the light source is to distinguish the measured object from the background as clearly as possible to obtain high-quality, high-contrast images. Let's take you through the selection strategy of machine vision light source color.
In general, if you use a black and white camera, and there is no special requirement for the color of the object to be measured, red is a more suitable choice. Because the red LED has a long life, stability, and low price, more importantly, the wavelength of the red LED is closer to the sensitivity peak of the sensor, and the usual CCD is less sensitive to purple and blue light than red light.
If imaging in color, a white light source is usually considered. There are several ways to manufacture white LED light sources. One is to use white LEDs. There are blue light-emitting chips inside the light-emitting tube and phosphors that emit yellow after being excited. The light emitted is superimposed in a certain proportion, which seems to form white, which is the most common form.
Another method is to use red, green and blue LEDs of three different colors, arrange them on the light source in a certain order or way, and control the intensity of each color separately, which is relatively convenient to use. This method usually uses four monochromatic RGGB particles for arrangement, so the green component is usually relatively sufficient. The reason why one more green G flux is added is that the human eye is most sensitive to green light sources (wavelength 555nm).
We see an object as a certain color because it reflects the corresponding spectrum. When we shoot an object, if we want to make a certain color white, we must use a light source that is the same or similar to the color (the wavelength of light is the same or close to it), and if you want to make it black, you need to choose a light source with a large wavelength difference from the target color.
In color images, except black and gray are not obvious, others such as white, purple, blue, green, yellow, orange, red, and brown are very obvious, and the colors are full and gorgeous. In the large-scale imaging of black and white cameras with multi-color cables under a white light source, it can be found that white, yellow, green, and orange are brighter, indicating that the camera is more sensitive to these wavelengths.
When imaging under red light, the colors of white, red, orange, and yellow are more obvious, and the other colors are very dark, which means that when red light illuminates an object, the object itself can only reflect red light when it has a red component. Under the black and white camera Shown as red features. Under a green light source, white, green, and yellow are bright, while others are dim. Under the blue light source of machine vision, white, purple, blue, etc. are brighter and can effectively reflect blue light.
It can also be found that white, no matter what light it is in, is obviously white, because it does not absorb the spectrum itself, and any spectrum irradiated on its surface will be reflected; on the contrary, no matter what light is irradiated on, black materials will not reflect black.
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