If the machine vision system can't capture clear and accurate images, there is no guarantee that the subsequent series of operations are correct or meaningful, so image acquisition is a vital part of the entire machine vision system. The machine vision lens is an important component for realizing the measurement and judgment of the machine vision system using the machine instead of the human eye. The quality of the machine directly affects whether the whole system can obtain high-quality images, whether it can be automated and intelligent. In the following, the machine vision lens is understood by interpreting and analyzing the main parameters of the optical lens.
Parameter one: focal length. The focal length is the distance from the center point of the lens to the focus of the clear image. The focal length is an important performance indicator of the machine vision lens. The length determines the size of the image, the size of the angle of view, and the depth of field. The shorter the focal length, the larger the viewing angle, the larger the range that can be observed; conversely, the more often the focal length, the smaller the viewing angle, and the smaller the range that can be observed. In order to achieve better image acquisition, the lens is divided into two categories: fixed focus and zoom.
Parameter two: aperture. The aperture is a mechanical device that changes the size of the middle hole in the lens, and its size is determined by the ratio of the focal length to the aperture. The smaller the ratio, the larger the aperture, the greater the amount of light per unit time; conversely, the larger the ratio, the smaller the aperture and the smaller the amount of light.
Parameter three: depth of field. The machine vision lens captures the clear range of the measured object with a certain limit, and the depth of field refers to the range that can be clearly displayed within a certain distance before and after the object is focused. The depth of field is closely related to the aperture, focal length, and shooting distance. (1) The larger the aperture, the smaller the depth of field; the smaller the aperture, the greater the depth of field. (2 The longer the focal length, the smaller the depth of field; the shorter the focal length, the greater the depth of field; (3) The farther the shooting distance is, the greater the depth of field; the closer the distance, the smaller the depth of field.
Parameter four: shooting distance. As the name suggests, the distance from the working surface of the lens to the object being measured is the so-called shooting distance.
In addition to the above four main parameters that affect each other, the parameters of the machine vision lens include the size of the CCD, the interface with the camera, the resolution, the field of view, the optical magnification, and so on. It is these parameters that influence whether the machine vision lens can play its role. When selecting a lens, it must be based on the principle of suitable detection. Therefore, it is essential to understand its parameters.