Light source of machine vision

For the machine vision industry. The performance of detecting system effect lies in the processing, discrimination and optimization of the algorithm. The basis of algorithm processing lies in the good and difference of imaging, and for the imaging effect, the decisive factor lies in the collocation and choice of light source.

The classification of light sources is also varied:

1. According to the color, there are: red light, green light, warm white light, cold white light, etc.

2. According to the shape, it is divided into: bar light, ring light, dome light, etc.

3. According to its characteristics, it can be divided into point light source, line light source, shadowless light source, combination light source, etc.

Large to different industries, small to different products, will have their own selection criteria.

01 For flexible packaging products

Mainly detect some printing defects, then dome light is the best choice, high brightness, good uniformity. The best imaging results are for printed matter.

02 For filter film or aluminized film products

The product is characterized by strong reflective properties. Pay more attention to the choice of light source. As a result of product reflection is stronger, imaging will be dark, from the external performance often give a person light source brightness insufficient judgment. In fact, the main reason is that the trajectory of the light source and the trajectory of the camera image are not on the same trajectory, which leads to the dimmer image.

If a light is used, most of the light path is outside the track of the scan line of the camera, resulting in a dimmer image, as shown below:

If dome light is used, because the light source is scattered in the dome, a small part of the light trace will be in the scan line trace of the camera, and the brightness will be slightly improved, as shown in the figure below:

But in the actual production activities, the above two methods can not achieve good imaging results. In actual production, dome and Angle are often used. The diagram below:

When there is a certain Angle between the scan line of the camera and the material direction of the product, part of the optical path trajectory of the dome light must coincide with the trajectory of the scan line, so as to get a better image.

In fact, this scheme is also a compromise scheme, mainly in order to test the mechanical design of the equipment and installation convenience, in this scheme, a lot of the light path of the dome light is wasted.

Regardless of the cost and difficulty of mechanical design and installation, the imaging scheme for products with aluminized film or pure aluminum film should be shown below.

This scheme makes full use of the brightness of the strip light, but has great requirements for the size of the machine and the difficulty of the design.

03 For glass products

The reflectivity of glass products almost reached the state of full reflection, for the choice of light source and greater requirements for the scheme, most of the current scheme is to use coaxial light source or combination light source.

There are also dome light and coaxial light combination form of the scheme, some manufacturers called universal light source.

Light source plays an important role in machine vision imaging. Choosing a good light source is crucial for imaging.

Good imaging light source system is one of the keys to the success of the whole detection system, plays a very important role, it is not simply to illuminate the object. First of all, the light source should be able to reproduce the color of the product, without causing color distortion. This requires the light source spectrum to be close to daylight, while ensuring sufficient brightness and uniform brightness in the entire illumination area. Followed by light source lighting system design to avoid the high reflectivity area on some of the products of precision is reduced, the last sample image quality of high and low, and the subsequent testing ability depends on the strength of the light source of light intensity, homogeneity and stability, and reliability of the detection system with life, also greatly depends on the reliability of the light source and life.