The purpose of the telecentric lens design is to eliminate the inconsistency of the distance between the measured object (or CCD chip) and the lens, resulting in different magnifications. According to the classification of the telecentric lens, the design principle is as follows:

　　 1. The design principle and function of the object-side telecentric light path: the main ray of the object side is parallel to the optical axis and the convergence center of the main ray is located The image side is infinitely far away, which is called: the object side telecentric light path. Its function is: it can eliminate the reading error caused by the inaccurate focusing of the object.

　　2. The design principle and function of the image-side telecentric light path: the main ray of the image side is parallel to the optical axis and the convergent center of the main ray is located infinitely far away from the object, which is called: image Fang Yuanxin optical path. Its function is: it can eliminate the measurement error caused by the inaccurate focusing of the image side.

　　3. The design principle and function of the telecentric light path on both sides: it integrates the dual functions of object-side/image-side telecentricity. Mainly used in the field of vision measurement and inspection. It can be seen from the above design principles of various types of telecentric lenses that the telecentric lens is a high-precision lens designed to make full use of optical imaging characteristics and fully consider the influence of light in imaging. At present, it is used in machine vision precision measurement and high-precision inspection. The field has been widely used.

　　The photographic lens is generally composed of two parts: an optical system and a mechanical device. The main lens of the optical system is designed to include several lenses or cemented lenses, as well as mirrors and other components. The contact surface between the component and the space is generally plated with an anti-reflection coating to increase the light transmittance of the lens.

　　The mechanical device mainly includes parts for fixing optical components (such as lens barrel, lens holder, connecting ring, etc.), lens adjustment mechanism (such as aperture adjustment ring, focus ring, zoom Ring, etc.), lens adjustment mechanisms (such as aperture blades), and preview depth-of-field mirrors, etc. Some photographic lenses are also equipped with electronic devices (such as automatic focus, automatic zoom, aperture value sensing elements, etc.).

　　 There is no big difference in the basic structure of the photographic lenses currently used in cameras and video cameras. It is just that with the development of science and technology and the continuous innovation in the field of optics, The optical system of the photographic lens is more complete, and some automatic devices are designed in the mechanical part, which provides more convenience for photographers and ensures the technical quality of the picture.

　　 The imaging quality of a photographic lens directly affects the technical quality of the captured image, because it is related to the sharpness, contrast, color reproduction and distortion of the image In order to ensure the imaging quality of the lens, correct use and maintenance methods should be followed.

　　 Correctly attach and unload the photographic lens

　　 The structure of the photographic lens and optical lens is very sophisticated. When attaching and unloading the lens, pay attention to the correct rotation Direction, so as not to damage the lens coupling mechanism.

　　When removing the lens, some lenses require reverse rotation, while others require forward rotation. When removing the lens from the camera body, the lens lock should be released first Otherwise, the lens cannot be removed. For example, the lens on an Ali movie camera. To remove the lens, you only need to squeeze the two lock buttons, and you can directly pull the lens out.

　　 When installing the lens, the mounting marks (usually red dot marks) on the rear end of the lens and the body lens should be aligned with each other, and the rear end of the lens should be inserted into the lens mount Insert it to the end, and then rotate to the end according to the required direction. When you hear a 'click' sound, it is locked.

　　 When attaching and unloading the lens, you should hold the photographic lens in your hand to operate, instead of holding the focus ring, zoom ring, or iris adjustment ring to rotate the lens, because these parts Should not be too strong, otherwise it is easy to damage the photographic lens.

　　Some photographic lenses are equipped with mounting rings. When attaching and removing the lens, you only need to hold the photographic lens mounting ring and loosen it to easily unscrew the mounting ring. , Carry out the loading and unloading of the lens.

　　 When attaching and unloading a photographic lens with an inter-lens shutter, you should generally wind the shutter before attaching and unloading the lens.