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       Ground light sourceHow is it good? How to choose? What are the requirements for color? Generally speakingGround light source selection criteria are as follows:

　　1. The ground light source uniformity is good, and the standard deviation of gray value is small in the effective irradiation range.

　　The spectral range should be wide, and objects of different materials can be detected.

　　3. The light intensity should be sufficient to improve the signal-to-noise ratio and facilitate image processing.

　　4. Long service life and high stability. It is necessary to ensure that the lighting environment can be provided continuously and stably under long-term operation.

5. Low cost, easy to customize special shape light source according to on-site conditions.

In visual inspection,Ground light sourceThe use of directly determines the detection effect. How to choose the right ground light source? Mainly from the following aspects.

　　1. Characteristics of the measured object

The purpose of lighting is to highlight the detected object and improve the contrast, so the feature of the detected object is the selected reference point. This requires a lot of experimentation and experience. For example, scratches on a smooth surface require low-angle grazing, so that light reflected from the surface cannot enter the lens, and flaws such as scratches will change the direction of light, thus forming prominent features on a black background, with high contrast and easy handling.

　　2. Focus distance

　　It is obviously impossible to use the same light source at a distance of 5mm and 500mm. The distance between the ground light source and the blocked object determines many indicators of the light source. For LED particles, the illuminance is inversely proportional to the square of the distance. General illumination can be approximated by this law.

　　3. Vision size

The light sources used to form a uniform field of view with a diameter of 50mm and 500mm will not be the same. Moreover, the same field size, for different measurement targets, the selection is also different. If you are only measuring a circular object, then perhaps a circular light source will do, and if you want to measure an object on a surface and want uniform illumination, then perhaps a light source with no shadows on all sides is a better choice.

　　4. Installation method

How to install the light source on the mechanical structure, how much installation space? At this time, it is necessary to consider the installation of visual light source.

　　5. The color of the light source

Generally speaking, machine vision projects are dominated by black and white cameras, because image processing functions play a much more important role in grayscale and binary images than in color images. Some projects do not require much in terms of camera color. Therefore, if there is no special need, the black and white camera can meet the requirements, you can consider the use of red, green and blue and other monochromatic light sources. Because the monochromatic light source has a single spectrum, it is almost achromatic, and its imaging is better than the white light source used in color cameras.

Among themGround light sourceThe color choices are as follows:

　　1. White light source: usually defined by color temperature. The color with high color temperature is blue (cool color, color temperature 500k), and the color with low color temperature is red (warm color, color temperature 3300k), which is called the intermediate color between 3300k and 5000k. White light has wide applicability and high brightness, especially when shooting color images.

　　2. Red light source: The wavelength is relatively long, and it can transmit some darker objects, such as the hole position of the black transparent soft board of the substrate, the circuit detection of the green circuit board, and the thickness detection of the transparent film. Use a red light source to better improve contrast.

　　3. Green light source: the wavelength is between red and blue, mainly for products: red background products and silver background products (such as silver and gold, machined parts, etc.).

　　4. Blue light source: widely used in metal products, such as steel rails, cold-rolled strip steel, ship processing parts, mobile phone shells, etc.

　　Infrared light: the general wavelength is 780-1400. Infrared light is invisible and highly transmissive. In general, the LCD detection and video surveillance industry is widely used.

6. Ultraviolet rays: mainly use ultraviolet rays with a wavelength of 385, which are short in wavelength and strong in penetration. It is mainly used for document detection, touch screen ITO detection, cloth surface damage detection, dispensing overflow detection, metal surface scratch detection, etc.