Industrial cameras are a key component of machine vision systems, and their most fundamental function is to convert light signals into ordered electrical signals. Choosing the right camera is also a crucial aspect of machine vision system design. The camera selection directly determines not only the resolution and quality of the acquired images but also the overall operating mode of the system.
CCD camera parameters
( 1 ) Resolution: The number of pixels that the camera captures in each image. For digital cameras, it is generally directly related to the number of pixels of the photoelectric sensor. For analog cameras, it depends on the video standard. For PAL , it is 768*576 , and for NTSC , it is 640*480 .
Spatial resolution refers to the minimum distance between two adjacent objects that can be identified in remote sensing imagery. For camera images, it is generally expressed as the number of distinguishable black and white line pairs per unit length (unit: line pairs / mm). Spatial resolution is an important indicator for evaluating sensor performance.
( 2) Pixel depth: that is, the number of bits of data per pixel. 8 bits is commonly used , but digital cameras may also have 10 bits , 12 bits , etc.
( 3 ) Maximum frame rate / line frequency: The rate at which the camera acquires and transmits images. For area scan cameras, it is generally the number of frames acquired per second, and for line scan cameras, it is the number of lines acquired per second.
( 4 ) Exposure mode and shutter speed: Line scan cameras use line-by-line exposure, and can choose between fixed line frequency and external trigger synchronization acquisition modes. The exposure time can be consistent with the line period or a fixed time can be set. Area scan cameras have several common modes such as frame exposure, field exposure, and rolling line exposure. Digital cameras generally provide external trigger image acquisition function. The shutter speed can generally reach 10 microseconds, and high-speed cameras can be even faster.
( 5 ) Pixel size: The size of the pixel and the number of pixels together determine the size of the camera target surface. Currently, the pixel size of digital cameras is generally 3 μm -10 μm . Generally, the smaller the pixel size, the greater the manufacturing difficulty and the more difficult it is to improve the image quality.
( 6 ) Spectral response characteristics: refers to the sensitivity characteristics of the pixel sensor to different light waves. The general response range is 350-1000nm . Some cameras have a filter in front of the target to filter out infrared light. If the system needs to sense infrared light, the filter can be removed.
Advantages of industrial cameras
( 1 ) It has stable performance, is easy to install, has a compact and sturdy structure, is not easily damaged, and can be used in poor industrial environments.
( 2 ) The shutter speed is very short, which can capture fast-moving objects.
( 3 ) The frame rate of industrial cameras is much higher than that of ordinary cameras. Industrial cameras can take 10 to several hundred pictures per second, while ordinary cameras can only take about 2 or 3 pictures per second, which is quite different.
( 4 ) Industrial cameras can work for a long time, such as working 24 hours a day or working continuously for 6 months, while ordinary cameras cannot.
( 5 ) Industrial cameras can be programmed and can be set to take pictures at any time or time interval.
