What are the hardware components of machine vision?

Machine vision is a rapidly developing branch of artificial intelligence. Simply put, machine vision is to use machines to replace human eyes for measurement and judgment. The machine vision system uses machine vision products (i.e. image acquisition devices, divided into CMOS and CCD) to convert the captured target into image signals, transmit them to a dedicated image processing system, obtain the morphological information of the captured target, and convert them into digital signals based on pixel distribution, brightness, color and other information; the image system performs various operations on these signals to extract the characteristics of the target, and then controls the equipment action on site based on the judgment results.

With the widespread application of Industry 4.0 in the industrial field, the supply, manufacturing, and sales information in production are digitized and intelligentized, ultimately achieving fast, efficient, and personalized product supply. The Industry 4.0 system is applicable to intelligent production technology and industrial manufacturing. It is not a simple production process, but the communication between products and machines.

Machine vision is a comprehensive technology that includes image processing, mechanical engineering technology, control, electric light source lighting, optical imaging, sensors, analog and digital video technology, computer software and hardware technology (image enhancement and analysis algorithms, image cards, I/O cards, etc.).

A typical machine vision application system includes image capture, light source system, image digitization module, digital image processing module, intelligent judgment and decision module and mechanical control execution module.

Machine vision inspection equipment is a machine developed in recent years that can replace human eyes to inspect relevant parts of products. If it is widely used, there will be surface defect detection of products. What parts does the machine vision inspection equipment system accessories consist of?

Machine vision inspection equipment system accessories:

1. Industrial cameras: CMOS cameras, CCD color cameras, area array cameras, CAMERA-LINK cameras, line array cameras, infrared cameras, high-speed cameras, 1394 interface cameras;

Smart Camera is a highly integrated miniature machine vision system. It integrates image acquisition, processing and communication functions into a single camera, thus providing a multifunctional, modular, highly reliable and easy-to-implement machine vision system. At the same time, due to the application of the latest DSP/GPU, FPGA and large-capacity storage technology, its intelligence level is constantly improving, which can meet the application requirements of various machine vision.

CCD cameras can provide good image quality and noise immunity. Although the size of the system becomes larger and the replication is improved due to the addition of external circuits, circuit designers can be more flexible and better improve certain performances of CCD cameras that are of particular concern. CCD is more suitable for applications that require very high camera performance but are not very strict in cost control, such as astronomy, high-definition medical X-ray imaging, and other applications that require long exposure and strict requirements on image noise.

The working principle of CCD camera: the image of the object to be tested is focused on the CCD chip through the optical lens; the timing generation circuit module provides horizontal driving pulses to help the CCD chip complete the conversion, storage, transfer and reading of photoelectric charges, and convert the optical signal into an electrical signal output; the signal processing circuit module receives the electrical signal from the CCD chip, collects and holds the pulses, and performs pre-processing such as automatic gain control and video signal synthesis to convert the electrical signal output by the CCD chip into the required video format, i.e., video output. The machine vision inspection system uses a CCD camera to convert the target object to be inspected into an image signal, which is transmitted to a dedicated image processing system and converted into a digital signal based on pixel distribution, brightness, color and other information. The image processing system performs various operations on these signals to extract the characteristics of the target, such as area, quantity, position, length, and then outputs the results according to the preset tolerance and other conditions, including size, angle, number, qualified/unqualified, presence/absence, etc., to achieve automatic recognition and judgment functions.

Area array camera: It realizes pixel matrix shooting. In the image captured by the camera, the image details are not determined by the number of pixels, but by the resolution. The resolution is determined by the focal length of the selected lens. The same camera has different resolutions when using lenses with different focal lengths. The number of pixels does not determine the resolution (clarity) of the image, so what are the benefits of a large pixel camera? There is only one answer: reduce the number of shots and increase the test speed.

Linear array camera: As the name implies, it is in the shape of a "line". Although it is also a two-dimensional image, it is extremely long. The length is several K, and the width is only a few pixels. Generally, this camera is only used in two situations: 1. The field of view to be measured is a long and thin strip, which is mostly used for problems on rollers.

2. Camera interface

CameraLink interface: specially designed for high-end machine vision applications, with high speed, high resolution and good noise immunity.

IEEE 1394 (FireWire) interface: Plug-and-play serial interface that can support 63 cameras at the same time, each 4.5 meters apart, up to 72 meters away. Supports transmission speeds of 800Mbits/s or even 3200Mbits/s.

USB interface: It is a widely used serial interface with a transmission rate of up to 480Mbits/s and can be used by up to 127 devices at the same time.

Gigabit Ethernet interface: Based on the network connection protocol Ethernet, plug and play, continuous high-speed data transmission.

3. Lens

Cameras and lenses are usually matched. The selection of lenses mainly considers the viewing distance of the image. The steps for lens selection are:

1) Calculate the number of pixels corresponding to the short side E = B / C. The number of pixels on both the long and short sides of the camera must be greater than E;

2) Pixel size = product short side size B / number of pixels on the short side of the selected camera

3) Magnification = selected camera chip short film size / camera short side field of view

4) Resolvable product accuracy = pixel size/magnification (determine whether it is less than C)

5) Focal length of objective lens = working distance/(1+1/magnification) Unit: mm

6) The resolution of the image plane must be greater than 1/(2×0.1×magnification) Unit: lp/mm

The supported CCD size of the selected lens should be greater than or equal to the size of the camera's CCD sensor chip. In addition, the mounting seat should also match the C, CS or F type interface. At the same time, consider the working distance of the lens, whether there is enough space, etc. If you are still unsure about the choice of lens, you can consult the manufacturer's technical support and let the manufacturer recommend a suitable lens based on your application scenario.

4. Image acquisition card

Although the image acquisition card is only a part of the complete machine vision system, it is also very important and directly determines the interface of the camera: black and white, color, analog, digital, etc. Typical ones include PCI acquisition cards, 1394 acquisition cards, VGA acquisition cards and GigE Gigabit Ethernet acquisition cards. Some of these acquisition cards have built-in multi-way switches that can connect multiple cameras and capture multiple channels of information at the same time.

5. Machine Vision Software

Machine vision software is a key component of automated processing in machine vision systems. According to specific application requirements, secondary development of the software package can automatically complete image acquisition, display, storage and processing. When purchasing machine vision software, you must pay attention to the development hardware environment, development operating system, development language, etc. to ensure that the software runs stably and facilitates secondary development.

6. Light source: LED light source, xenon lighting system, ultraviolet lighting system, infrared light source, fiber optic lighting system, fluorescent lighting system.

As an important part of the machine vision system input, the quality of the light source directly affects the quality of the input data and the application effect. Since there is no universal machine vision light source equipment, the corresponding visual light source should be selected for each specific application instance to achieve the best effect. Common light sources include: LED ring light source, low-angle light source, backlight source, strip light source, coaxial light source, cold light source, point light source, linear light source, parallel light source, etc.