What five parts does a machine vision system include?

Machine vision is the use of machines instead of human eyes for measurement and judgment.

The machine vision system refers to converting the ingested target into an image signal through machine vision products (ie image capture device, divided into CMOS and CCD), and sending it to a dedicated image processing system. , into a digital signal;

The image system performs various calculations on these signals to extract the characteristics of the target, and then controls the on-site equipment actions according to the results of the discrimination.

A typical machine vision system consists of the following five parts:

1. Lighting

Lighting is an important factor affecting the input of machine vision systems, which directly affects the quality and application effect of input data. Since there is no general machine vision light source lighting equipment, it is necessary to select a corresponding lighting device for each specific application instance in order to achieve the best effect.

Light sources can be divided into visible light and invisible light. Common visible light sources include incandescent lamps, fluorescent lamps, mercury lamps, and sodium lamps. The disadvantage of visible light is that the light energy is not stable. Therefore, how to keep the light energy stable to a certain extent is an urgent problem to be solved at present; on the other hand, ambient light may affect the quality of the image, so in this case, the method of adding a protective screen can be used to reduce the ambient light. The effect of light.

According to the lighting method, the lighting system can be divided into: backlighting, forward lighting, structured light and stroboscopic lighting.

Among them, backlighting is to place the object under test between the light source and the camera, which has the advantage of obtaining a high-contrast image;

The forward lighting is to place the light source and the camera on the same side of the object under test, which is more convenient for installation;

Structured light illumination is to project a grating or light source onto the object to be measured, so as to mediate the three-dimensional information of the object to be measured. Strobe lighting is to irradiate high-frequency light pulses onto objects, while camera shooting requires synchronization with the light source.

2. Lens

FOV (Field Of Vision) = required resolution * sub-pixel * camera size/PRTM (part measurement tolerance) When selecting a lens, you need to pay attention to: ① focal length ② target height ③ image height ④ magnification ⑤ distance from image to target ⑥ center point / Node ⑦ Distortion

3. Camera

According to different standards, it can be divided into: standard resolution digital camera and analog camera. However, different cameras and high-resolution cameras such as line scan CCD and area array CCD, monochrome cameras and color cameras need to be selected according to different practical applications.

4. Frame grabber

Although the frame grabber is only a part of the complete visual positioning system, it plays a very important role; the frame grabber directly determines the interface of the camera:

Black and white, color, analog, digital, etc. The more typical ones are PCI or AGP compatible capture cards, which can quickly transfer images to computer memory for processing, and some capture cards have built-in multiplex switches. For example, you can connect 8 different cameras, and then tell the capture card to use the information captured by that camera.

And some capture cards have built-in digital input to trigger the capture card to capture, and the digital output port triggers the gate when the capture card captures an image.

5. Vision processor

The vision processor integrates the acquisition card and the processor into one. In the past, when the computer was slow, the visual processor was used to speed up the visual processing tasks. Now, because the capture card can quickly transfer the image to the memory, and the computer is much faster, the visual processor is used less now.

Machine vision system is to use machines instead of human eyes to make various measurements and judgments. It is an important branch of computer science, which integrates technologies in optics, mechanics, electronics, computer software and hardware, etc. . The rapid development of technologies such as image processing and pattern recognition has also greatly promoted the development of machine vision.