Chiopt Classroom | How to do the industrial lens selection?
Industrial lens selection is a very important and key link, because industrial lens selection is related to the imaging quality of machine vision. Let's learn about the basic parameters, formula and examples of lens selection.
1. basic parameters of lens selection
Field of view (FOV)
Working distance (WD)
2. model selection formula
focal length f=WD × CCD Chip size ( H or V) / FOV( H or V)
3-1. Example of industrial lens selection - area array lens
Disc screw Identification & tooth burrs
Lens type: FA;
Camera model: 1/2.5 "500W Basler;
Chip diagonal 6.4mm;
Fov:150*150mm, diagonal 210mm;
Optical magnification =6.4/210=0.03x;
The working distance is not required, but the closer it is, the better; WD is better between 2-4 times of the field of vision, so 2x is selected here; Focal length ≈ optical magnification *wd ≈ 0.03 × 420 ≈12mm； The final model selection is fa1201c.
3-2. Example of industrial lens selection telecentric lens
Field of vision 40mm*35mm;
Magnification = chip / field of view =12.8/40=0.32x;
Find an image plane equal to or greater than 1 "; The magnification is slightly less than 0.32x; According to the lens specification, tc0527a meets the requirements.
When to use telecentric lens?
① High precision measurement
② Very small vision or close working distance
3-3. Example of industrial lens selection - line scan lens
So find an image plane equal to or greater than Φ 56, the magnification can support 0.093x; When 0.16x, WD is 256mm; When calculating 0.093x, WD ≈ 256 × (0.16/0.093)=440mm； According to the lens specification, ls4005a meets the requirements.
When 0167x, WD is 404mm; When calculating 0.093x, WD ≈ 404 × (0.167/0.093)=725mm。 For similar parameters, the shorter the working distance, the more expensive the lens is, and the choice shall be weighed according to the actual demand.
4. selection process of line scan lens
Chip: determine camera chip size and resolution
Determine the flange distance and interface of the camera
Magnification: calculated lens magnification = chip length / field length
Find lenses with similar magnification in the product manual
Connecting ring: confirm whether the lens o/i distance and working distance meet the requirements
Through the above cases, we can roughly solve some problems encountered in the selection of industrial lens. If you have any questions, you are welcome to leave a message for consultation. Xiaobian will make every effort to answer them for you!