Industrial lens selection needs to pay attention to these issues

In the entire machine vision system, the machine vision industrial lens is an important imaging component of the image acquisition part, so the correct selection of the machine vision industrial lens is very important. From the following seven aspects, let's talk about the considerations of machine vision industrial lens selection: 1. Customer's special requirements Generally, the customer's special requirements for machine vision lenses should be considered first, such as whether other devices (lenses, reflective lenses, glass) and the working environment of the machine vision lens are added before the machine vision lens and the workpiece. The following points need to be confirmed first: 1. There are restrictions on the installation space: the size, length and other parameters of the machine vision lens; 2. Fix the camera suspension lens: For example, some cameras cannot hang a heavier machine vision lens; 3. The camera system needs to move: if the speed is too fast, the camera system may shift due to inertia; 4. There are special requirements for the spectral response: For example, for the ultraviolet environment, an ordinary glass lens will absorb almost all ultraviolet light; 5. Do you need to add a light source to the machine vision lens: According to the scene environment, for the need to increase the brightness, you need to add a light source. If it is a coaxial lens, a point light source can be installed; 6. Price requirements; 7. The working environment of the machine vision lens; 8. Whether there are other special components; 2. Do you need to use a telecentric lens? For precision measurement systems, you need to use a telecentric lens. The main function of the telecentric lens is to overcome the effect of perspective phase difference (the phenomenon of inconsistent magnification due to different distances during imaging), so that the size data obtained when the detection target moves within a certain range is almost unchanged. In general, telecentric lenses are fixed focal length and working distance, and some telecentric lenses are very large, and some weigh more than ten kilograms. It is necessary to understand the customer’s field of view size, working distance, space restrictions, and The requirements of motion control can only determine the required lens model specifications. When there are no strict requirements on the image of the object in general surface defect detection and judgment, choose a telecentric lens with small distortion. Third, the depth of field of machine vision industrial lens Some vision systems with special requirements require a lens with a relatively large depth of field. For example, in some inspections or measurements, the industrial camera must be at a certain angle and the entire object must be imaged clearly; the measured target is not on the same plane, which requires consideration of the depth of field of the lens. The shorter the focal length, the greater the depth of field; the smaller the aperture, the greater the depth of field; the farther the lens is from the object, the greater the depth of field; small aperture and good light make focusing easier, but a small aperture will lose the fine structure of the object. The larger the pixel of the camera chip, the greater the depth of field. Fourth, the chip size of the machine vision lens Each machine vision lens can only be compatible with cameras with a chip not exceeding a certain size. Therefore, when choosing a machine vision lens, you must first determine the chip size of the industrial camera. In order to ensure the quality of the entire image, the maximum adaptable chip size of the machine vision lens must be larger than the chip size matched with it, otherwise it will cause serious distortion and phase difference. . 5. Machine vision lens interface Machine vision lens interface and camera interface are divided into C, CS, F and other larger size interface types. The camera and lens are complementary, that is, a C-mount camera can only use a C-mount lens. Sixth, the focal length of the machine vision lens The focal length of the lens mainly has a greater impact on the field of view and working distance. Before determining the focal length of a machine vision lens, factors such as the field of view, working distance, and camera chip size must be determined. 7. Distortion of machine vision industrial lens is the image distortion caused by the inconsistency of local magnification in the field of view. Due to the influence of the production process, lens distortion is inevitable, the better the lens, the smaller the distortion. Generally, in the case of high precision requirements such as precision measurement systems, the distortion of the machine vision lens must be considered. These lens parameters must be d according to the actual project.