As a critical component of the machine vision system, the industrial camera is usually installed on the machine assembly line to replace human eyes to do measurement and judgment. Thus, choosing the proper camera is also an essential part of machine vision system design. How should we select the proper industrial camera? What problems should be paid attention to when choosing an industrial camera lens? Let's learn about it.
Choosing CCD or CMOS camera according to different applications.
The CCD industrial camera is mainly used in the image extraction of moving objects. Of course, with CMOS technology development, the CMOS industrial camera is also applied for many chip mounters. The CCD industrial camera is widely used in vision automatic inspection. CMOS industrial cameras are widely used because of their low cost and low power consumption.
The selection of resolution
Firstly, by considering the object's accuracy to be observed or measured to select the resolution accordingly. If camera pixel accuracy = single direction field of view size/camera single direction resolution, then the camera's resolution in one direction = the size of the field of view in one direction / the theoretical accuracy.
If the single field of view is 5mm and the theoretical accuracy is 0.02mm, the single direction resolution is 5 / 0.02 = 250. However, to increase the stability of the system, not only one-pixel unit is used to correspond to one measurement/observation accuracy value. Generally, multiple four or higher can be selected. In this way, the camera needs a single direction resolution of 1000 and 1.3 million pixels.
Secondly, considering an industrial camera's output, high resolution is helpful for posture observation or machine software analysis and recognition. If it is the VGA or USB output, It should be observed on display; thus, it also depends on the resolution of the display. No matter how high the resolution of an industrial camera lens is, it isn't very meaningful if the resolution of the display is not enough. If you use the memory card or the photo-taking function, the high resolution of an industrial camera also helps.
The selection of camera frame number
When the measured object is moving, the industrial camera lens with high frame number should be selected. But generally speaking, the higher the resolution, the lower the number of frames.
The match of the lens
The size of the sensor chip should be less than or equal to the lens size, and the C or CS mount should also match.
C interface or CS interface. The interface distance of the C interface is 17.5mm, while that of the CS interface is 12.5mm. Only right interface could lead to focus.
The lens should be selected according to the size of the photosensitive device. For a 2/3-inch photosensitive chip, the lens corresponding to the imaging coil should be selected. If 1/3"or 1/2" is selected, there will be a large dark angle.
Select the focal length; that is, select the lens whose field of view is slightly larger than the observation range.
Depth of field and light environment should match. For areas with enough light or light source illumination, a small aperture can be chosen to increase the depth of field, thereby improving the shooting clarity. Where there is not enough light, a slightly larger aperture or a sensitive chip with high sensitivity would be selected.