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Category Cars
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Created 2019-03-11
Owner xzbbvfvbh
Title 11 key points for choosing an optical lens
Description Optical lenses have a higher advantage in image stability, anti-interference ability and data transmission. They are a key part of the machine vision system. The performance of the purchasing BIBO nonlinear crystal determines the stability of the machine vision system. First determine the project requirements, determine the resolution of the camera according to the field of view and detection accuracy, determine whether to use the CCD or COMS according to the speed of the object being photographed, or determine the camera frame rate according to the unit time requirement of the captured image. Determine what connection method to use (USB or Gigabit, etc.) based on the project site environment. Therefore, choosing customized large size and special shape CaF2 optics suitable for an automated vision project is critical to the success of the entire project. Summarize the following points: 1. Items that require testing, such as size, or yo! 2, the state of the workpiece, the movement is still still! 3. Product size and detection speed. 5. What is the background color of the workpiece! 6, product reflective is good, product batch consistency is the same! The parameters to be noted when selecting the camera: 1, camera type For still detection or general low speed detection, the area array camera is preferred, and linear array cameras are considered for special applications such as large-format high-speed motion or roller motion. Depending on the speed of detection, the frame rate of the selected camera must be greater than the speed of the object's motion, and must be completed within the exposure and transmission time of the camera. 2, camera resolution If the measurement accuracy of the project and the field of view size, then the selected camera pixel calculation relationship is as follows: Camera resolution (L/W) ≥ field of view (L/W) / accuracy. If the project requires a field of view of 100mm*75mm and an accuracy requirement of 0.05mm, the camera's pixel length is 100/0.05=2000PIX, which is a camera that requires 2000*1500=3000000=3 million pixels. This is just the pixel accuracy of the camera, it does not mean that the accuracy of the entire system is so high, there are other precisions to consider, such as the resolution of the lens, the jitter of the system, the wavelength of the light source, and so on. The pixel precision of the purchase plano/spherical/aspherical/cylindrical CaF2 optics must be higher than the precision required by the system, so that the actual measurement significance can be realized. The accuracy improvement of the sub-pixel does not have much influence in the actual measurement, and the problem of insufficient precision cannot be fundamentally solved. In general, if conditions permit, we will require an increase in the resolution of the camera by an order of magnitude or an increase in the pixel accuracy of the camera by an order of magnitude. 3, camera frame rate The camera's frame rate determines the measurement efficiency of the device. If the camera's frame rate is 30FPS, it will take 30 shots per second. And if the speed of the camera is 120FPS, if the algorithm is fast enough, then 120 products can be detected every second. In general, the lower the resolution of the camera, the higher the frame rate of the same interface, and the higher the resolution, the lower the frame rate. Frame rate * resolution ≤ bus bandwidth, that is, when the interface is certain (bus bandwidth has been determined), the frame rate also has a large value when the resolution is constant. That is, if the resolution of the camera is fast and the frame rate of the camera is high, then it is necessary to find a bus with a larger bandwidth, that is, an output interface of the camera. 4, camera output interface Under the same pixel condition, the camera frame rate of the bus of various interfaces is different. Generally, Camera Link>USB3>GIGE>1394B>USB2, 1394A. Now the Camera Link bus is fast. The theoretical speed of USB3 is 5Gbps or 640MB. In actual performance, there should be 80% effective bandwidth, that is, the total bandwidth of 512M is available for actual transmission, so if a 5 megapixel The camera, 5M per image, can reach 100 frames per second, and the speed is not fast. For the GIGE Gigabit network camera, the 5 megapixel camera can achieve 23FPS faster. 1394B's 5 megapixel camera can do 13FPS, USB2, 1394A is generally 5 to 6 frames.
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