This is a problem in the field of optics, and it has its own standard definition.The image taken with the camera will be deformed.To take an extreme example, we all have experience in taking pictures with ordinary home cameras.There is a lens called a “wide-angle lens”, and a more ruthless lens is called a “fisheye lens”.When you take pictures with this lens, you will find that the images on all sides of the photo are curved.This phenomenon is caused by ”lens distortion".An extreme example of a fisheye lens is that a fisheye lens is a large distortion lens.

Optical lenses have distortion, but the difference is that the distortion varies in size.Of course, for visual inspection systems, we hope that the smaller the lens distortion, the better.This is because the detection of the vision system is carried out on the image of the camera.If the camera image is ”tilted“, the result detected by the system is not ”positive", that is, the upper beam is not correct, and the lower beam is tilted.

In the vision system, there are two ways to correct the distortion of the lens: hardware or software.The way to start with hardware is simple: just use a lens with a small distortion.This kind of lens is called a telecentric imaging lens and is expensive, more than 6 or 7 times that of ordinary lenses.The distortion rate of this lens is less than 1%, and some can reach 0.1%.Most high-precision vision measurement systems use this lens: the second method is to start with software.When the camera is calibrated, the lattice on the calibration standard module is used for calculation.The specific method is: after completing the "camera calibration”, according to the known measurement value to obtain the size value of each point in the lattice, analyze the size of the surrounding points of the lattice, and the size of the inner circle points of the lattice.Through comparison, we can get a ratio, that is, the distortion rate of the lens.Using this ratio, the distortion can be corrected in the actual measurement.