Correction of lens distortion
Manufacturer of spherical lens introduce to you：This is a problem in the field of optics, which has its own standard definition. Images taken with a camera will deform. To take an extreme example, we all have the experience of taking pictures with ordinary household cameras. There is a kind of lens called "wide-angle lens", a bit more ruthless simply called "fish eye lens". When you take a picture with this kind of lens, you will find that the image on the four sides of the picture is curved. This phenomenon is caused by "lens distortion". The extreme example of "fish eye lens" is because "fish eye lens" is a kind of large distortion lens.
Manufacturer of spherical lens introduce to you：If the lens is distorted, the only difference is that the distortion is large or small. For the visual inspection system, of course, the smaller the lens distortion, the better. This is because when the vision system detects, it always detects on the image of the camera. If the camera imaging is "crooked", the result detected by the system is not "positive" - which means that the upper beam is not straight and the lower beam is crooked.
Manufacturer of spherical lens introduce to you：There are two ways to correct lens distortion in vision system: hardware or software. The way to start with hardware is simple: use a lens with very small distortion. This kind of lens is called telecentric imaging lens, which is expensive, more than 6 or 7 times of the price of ordinary lens. This kind of lens distortion is less than 1%, some can reach 0.1%. Most high-precision vision measurement systems use this kind of lens: the second method is to start with software. In the process of "camera calibration", the dot matrix on the calibration standard module is used to calculate. The specific method is: after the "camera calibration" is completed, the size of each point in the lattice is obtained according to the known measurement, and the size of the point in the periphery of the lattice is analyzed, which is different from the size of the point in the inner circle of the lattice. Through comparison, we can get a ratio, which is the lens distortion. With this ratio, distortion can be corrected in actual measurement.
