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The principle of machine vision technology
The principle of machine vision technology
The machine vision system refers to the conversion of the target into the image signal through the machine vision products (that is, the image pickup device, CMOS and CCD two), and transfer it to the special image processing system, which is converted into digital signal according to the information of pixel distribution, brightness and color, and the image system carries out various kinds of transportation to these signals. It extracts the characteristics of the target, and then controls the action of the scene based on the result of the discrimination.
machine vision
The machine vision system is characterized by improving the flexibility and automation of production. The machine vision is used to replace artificial vision in some dangerous working environment or artificial vision which is not suitable for manual work. At the same time, in large batch industrial production, the quality efficiency of the product is low and the precision is not high. The method of machine vision detection can greatly improve the production efficiency. The degree of automation and the degree of automation of production. Moreover, machine vision is easy to implement information integration, and is the basic technology of computer integrated manufacturing. It is precisely because the machine vision system can quickly obtain a large amount of information, and is easy to automatically handle, and easy to integrate with the design information and processing control information. Therefore, in the process of modern automation, the machine vision system is widely used in the field of monitoring, product inspection and quality control.
Basic structure
A typical industrial machine vision system includes: light source, lens, camera (including CCD camera and COMS camera), image processing unit (or image capture card), image processing software, monitor, communication / input and output unit and so on.
The system can be divided into: Host Computer, image capture card (Frame Grabber) and image processor, image camera, CCT lens, microlens, lighting equipment, Halogen light source, LED light source, high frequency light source, flash source, other special light source, image display, LC mechanism and control system. PLC, PC-Base controller, precision table, servo movement machine.
Working principle
The machine vision detection system uses the CCD camera to convert the detected target into the image signal and transmit it to a special image processing system. According to the information of pixel distribution and brightness, color and other information, the image processing system performs various operations on these signals to extract the features of the target, such as the area and quantity. The position, length, and the output of the presupposed permissible degree and other conditions, including size, angle, number, qualified / unqualified, / no and so on, can be realized automatically.
lighting
Lighting is an important factor that affects the input of machine vision system. It directly affects the quality and application effect of input data. Since there is no general machine vision lighting device, for each specific application case, the corresponding lighting device should be selected to achieve the best effect. The light source can be divided into visible and invisible light. Several commonly used visible light sources are white indicator, fluorescent lamp, mercury lamp and sodium lamp. The shortcoming of visible light is that the light can not remain stable. How to maintain the stability of light energy to a certain extent is a pressing problem in the practical process. On the other hand, ambient light may affect the quality of the image. Therefore, the protective screen can be used to reduce the influence of ambient light. Lighting system can be divided into back lighting, forward lighting, structured light and frequency flash lighting according to its illumination method. Among them, the back lighting is placed between the light source and the camera, and its advantage is that it can get high contrast images. Forward illumination is the light source and the camera located on the same side of the tested object, which is convenient for installation. Structured light illumination is the projection of grating or line light source to the object, and the three-dimensional information of the object is demodulated according to the distortion produced by them. Frequency flash illumination is to irradiate high frequency light pulses onto objects, and the camera is required to synchronize with the light source.
Camera lens
FOV (Field Of Vision) = resolution * subpixel * camera size /PRTM (part measurement tolerance ratio) lens selection should be paid attention to: (1) focal length, target height, image height, magnification, image to target
camera
According to different standards, it can be divided into: standard resolution digital camera and analog camera. Different cameras and high resolution cameras should be selected according to different practical applications: line scanning CCD and area array CCD, monochromatic camera and color camera.
Image acquisition card
Image acquisition card is only a component of the complete machine vision system, but it plays a very important role. The image acquisition card directly determines the interface of the camera: black and white, color, analog, digital and so on.
Typically, PCI or AGP compatible capture cards can quickly transmit images to computer memory for processing. Some of the acquisition cards have a built-in multiple switch. For example, you can connect 8 different cameras and tell the capture card to capture the information captured by that camera. Some acquisition cards have built-in digital input to trigger the capture card to capture. When the capture card grabs the image, the digital output triggers the gate.
Visual processor
The visual processor integrates the acquisition card with the processor. In the past, when the computer was slower, visual processors were used to accelerate visual processing tasks. Now that the acquisition card can transmit images to memory quickly, and computers are much faster, visual processors are now using less.
application area
The application of machine vision mainly includes two aspects: detection and robot vision.
One
machine vision
The machine vision system is characterized by improving the flexibility and automation of production. The machine vision is used to replace artificial vision in some dangerous working environment or artificial vision which is not suitable for manual work. At the same time, in large batch industrial production, the quality efficiency of the product is low and the precision is not high. The method of machine vision detection can greatly improve the production efficiency. The degree of automation and the degree of automation of production. Moreover, machine vision is easy to implement information integration, and is the basic technology of computer integrated manufacturing. It is precisely because the machine vision system can quickly obtain a large amount of information, and is easy to automatically handle, and easy to integrate with the design information and processing control information. Therefore, in the process of modern automation, the machine vision system is widely used in the field of monitoring, product inspection and quality control.
Basic structure
A typical industrial machine vision system includes: light source, lens, camera (including CCD camera and COMS camera), image processing unit (or image capture card), image processing software, monitor, communication / input and output unit and so on.
The system can be divided into: Host Computer, image capture card (Frame Grabber) and image processor, image camera, CCT lens, microlens, lighting equipment, Halogen light source, LED light source, high frequency light source, flash source, other special light source, image display, LC mechanism and control system. PLC, PC-Base controller, precision table, servo movement machine.
Working principle
The machine vision detection system uses the CCD camera to convert the detected target into the image signal and transmit it to a special image processing system. According to the information of pixel distribution and brightness, color and other information, the image processing system performs various operations on these signals to extract the features of the target, such as the area and quantity. The position, length, and the output of the presupposed permissible degree and other conditions, including size, angle, number, qualified / unqualified, / no and so on, can be realized automatically.
lighting
Lighting is an important factor that affects the input of machine vision system. It directly affects the quality and application effect of input data. Since there is no general machine vision lighting device, for each specific application case, the corresponding lighting device should be selected to achieve the best effect. The light source can be divided into visible and invisible light. Several commonly used visible light sources are white indicator, fluorescent lamp, mercury lamp and sodium lamp. The shortcoming of visible light is that the light can not remain stable. How to maintain the stability of light energy to a certain extent is a pressing problem in the practical process. On the other hand, ambient light may affect the quality of the image. Therefore, the protective screen can be used to reduce the influence of ambient light. Lighting system can be divided into back lighting, forward lighting, structured light and frequency flash lighting according to its illumination method. Among them, the back lighting is placed between the light source and the camera, and its advantage is that it can get high contrast images. Forward illumination is the light source and the camera located on the same side of the tested object, which is convenient for installation. Structured light illumination is the projection of grating or line light source to the object, and the three-dimensional information of the object is demodulated according to the distortion produced by them. Frequency flash illumination is to irradiate high frequency light pulses onto objects, and the camera is required to synchronize with the light source.
Camera lens
FOV (Field Of Vision) = resolution * subpixel * camera size /PRTM (part measurement tolerance ratio) lens selection should be paid attention to: (1) focal length, target height, image height, magnification, image to target
camera
According to different standards, it can be divided into: standard resolution digital camera and analog camera. Different cameras and high resolution cameras should be selected according to different practical applications: line scanning CCD and area array CCD, monochromatic camera and color camera.
Image acquisition card
Image acquisition card is only a component of the complete machine vision system, but it plays a very important role. The image acquisition card directly determines the interface of the camera: black and white, color, analog, digital and so on.
Typically, PCI or AGP compatible capture cards can quickly transmit images to computer memory for processing. Some of the acquisition cards have a built-in multiple switch. For example, you can connect 8 different cameras and tell the capture card to capture the information captured by that camera. Some acquisition cards have built-in digital input to trigger the capture card to capture. When the capture card grabs the image, the digital output triggers the gate.
Visual processor
The visual processor integrates the acquisition card with the processor. In the past, when the computer was slower, visual processors were used to accelerate visual processing tasks. Now that the acquisition card can transmit images to memory quickly, and computers are much faster, visual processors are now using less.
application area
The application of machine vision mainly includes two aspects: detection and robot vision.
One