Nowadays, with the advent of Industry 4.0, machine vision technology is gradually playing a very important position in industrial automation. The continuous innovation of machine vision technology has promoted the progress of industrial automation, smart security and artificial intelligence. Development has brought more development potential and opportunities to the fields where this technology can be applied.
Everyone says that 80% of the information that humans perceive from the outside world is obtained through the eyes, and the amount of information contained in the image is the largest. Then the emergence of machine vision technology is to install eyes that perceive the outside world for machinery and equipment, so that the machine has visual functions like humans, so as to realize various detection, judgment, identification, measurement and other functions.
Today, let’s experience the charm of machine vision technology.
Five typical architectures of machine vision
I still remember that when I was attending a conference on machine vision technology, a technologist specially emphasized the importance of lighting in machine vision. It is understood that lighting is an important factor that affects the input of the machine vision system, and it directly affects the quality of the input data and the application effect.
The light source can be divided into visible light and invisible light. Several commonly used visible light sources are white flag lamps, fluorescent lamps, mercury lamps and sodium lamps. The disadvantage of visible light is that the light energy cannot be kept stable. How to keep the light energy stable to a certain extent is an urgent problem that needs to be solved in the course of practice. On the other hand, ambient light may affect the quality of the image, so a protective screen can be used to reduce the impact of ambient light.
lighting system can be divided into back lighting, forward lighting, structured light and stroboscopic lighting according to its illumination method. Among them, the back lighting is the object to be measured is placed between the light source and the camera, and its advantage is that it can obtain high-contrast images. The forward illumination is that the light source and the camera are located on the same side of the object under test, which is convenient for installation. Structured light illumination is to project a grating or a line light source onto the measured object, and demodulate the three-dimensional information of the measured object according to the distortion produced by them. Stroboscopic lighting is to irradiate high-frequency light pulses on the object, and the camera shooting requires synchronization with the light source.
The lens is equivalent to the existence of the human eye. It is mainly responsible for light beam modulation in the machine vision system and completes signal transmission. It is understood that most of the lenses on the market so far can meet the needs of machine vision applications, but more professional machine vision systems may require customized lenses and coatings. Fortunately, many lens manufacturers with in-house production capabilities are ready to customize lenses to meet these application needs. Of course, these custom lenses are more expensive, so they are usually only used in specific imaging systems that are not cost-sensitive (such as military applications), or in the production line of high-volume consumer products.
3. Industrial camera
The most essential function of an industrial camera in a machine vision system is to convert optical signals into electrical signals. Compared with ordinary cameras, it has higher transmission power, anti-interference power and stable imaging capabilities. According to different standards, there are multiple classifications: according to the output signal mode, it can be divided into analog industrial cameras and digital industrial cameras; according to different chip types, it can be divided into CCD industrial cameras and CMOS industrial cameras.
4. Frame grabber
Although the frame grabber is only a part of a complete machine vision system, it plays a very important role and directly determines the interface of the camera: black and white, color, analog, digital, etc. The typical ones are PCI capture card, 1394 capture card, VGA capture card and GigE gigabit network capture card. Some of these capture cards have built-in multi-channel switches, which 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 automatic processing in a machine vision system. According to specific application requirements, the software package is re-developed to automatically complete image acquisition, display, storage and processing. Through the early transmission to the dedicated image processing software, according to the pixel distribution, brightness, color and other information, it is transformed into a digital signal; the machine vision software then performs various operations on these signals to extract the characteristics of the target, and then controls the scene according to the results of the discrimination. Device action.
Five common application areas
Machine vision can be said to be the soul window of industrial automation systems. From object/barcode identification, product inspection, appearance size measurement to robotic arm/transmission equipment positioning, it is a stage where machine vision technology can be used, so its application range is very wide. Extensive, the industry application fields are even more dazzling.
1. Image recognition application
Image recognition is the use of machine vision to process, analyze and understand images to identify targets and objects in various modes. The most typical application of image recognition in the field of machine vision industry is the recognition of two-dimensional codes. Two-dimensional codes are the most common one of our usual barcodes. Store a large amount of data information in this small two-dimensional code, and track and manage the product through the barcode. Through the machine vision system, it is convenient to identify and read the barcode on the surface of various materials, which greatly improves the efficiency of modern production. .
2. Image detection application
Inspection is one of the most important applications in the machine vision industry. Almost all products need to be inspected. Manual inspection has many drawbacks. The accuracy of manual inspection is low. If you work for a long time, the accuracy cannot be guaranteed. The slow speed easily affects the efficiency of the entire production process. Therefore, machine vision is also widely used in image detection, such as the detection of characters on the edge of a coin. In the fifth set of RMB issued in October 2000, the side of the one-yuan coin has an enhanced anti-counterfeiting function. In view of the strict control requirements of the production process, a visual inspection system is installed in the last process of coinage; during the printing process Color registration and color matching inspection, printing quality inspection of beverage bottle caps in the packaging process, barcode and character recognition on product packaging, etc.; defect detection of glass bottles. The defect detection of glass bottles by the machine vision system also includes the category of medicinal glass bottles. That is to say, machine vision also involves the medical field. Its main inspections include size inspection, bottle body appearance defect detection, bottle shoulder defect detection, bottle Mouth detection, etc.
3. Visual positioning application
Visual positioning requires the machine vision system to quickly and accurately find the tested part and confirm its position. In the field of semiconductor packaging, equipment needs to adjust the pickup head according to the chip position information obtained by machine vision, accurately pick up the chip and bind it. This is the most basic application of vision positioning in the machine vision industry.
4. Object measurement application
The biggest feature of machine vision industrial applications is its non-contact measurement technology, which also has high-precision and high-speed performance, but non-contact and wear-free, eliminating the hidden danger of secondary damage that may be caused by contact measurement. Common measurement applications include gears, connectors, auto parts, IC component pins, twist drills, and Luoding thread testing.
5. Object sorting application
In fact, the application of object sorting is based on a link after recognition and detection, and the image is processed through a machine vision system to achieve sorting. In machine vision industrial applications, it is often used for food sorting, automatic sorting of surface defects on parts, and cotton fiber sorting.
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