Posted March 12, 2019 at 3:12 am by by56014904

How optical lenses work

In the application of machine vision in automation, the main goal is to obtain the geometric relationship (size, area, pose, etc.), logical relationship (with or without) of the target by image processing technology, and transmit the information to the robot or the actuator. Control the system and proceed to the next step.

For many machine vision whites, after entering the machine vision industry, learn to master the basics, and then slowly start to do the actual project. After selecting the camera and light source, the choice of high precision ZnS optics is to be considered immediately. Good shots are more expensive, especially when you are just getting started, doing a good job of scratching the liver and buying new ones to pursue higher picture quality, pursuing a greater depth of field and pursuing a broader field of vision. It is appropriate to ignore the mechanical parameters of the optical lens in the visual application, which leads to various unreasonable problems in the subsequent construction of the visual system.

Optical lenses are generally composed of two parts: an optical system and a mechanical device. The optical system consists of a number of lenses (or mirrors) to form the correct object image relationship, ensuring accurate and clear images. It is the core of the lens. The mechanical device includes components for fixing optical components (such as lens holder, aperture, etc.), wholesale large size optical grade sapphire optics adjustment mechanisms (such as aperture adjustment ring, focus ring, etc.), connection mechanisms (such as C, CS interface), and the like. In addition, there are some electronic mechanisms with auto-tuning, auto-focusing or sensing light intensity on the lens.

For optical parameters related to optical lenses, we can consider the focal length f, aperture coefficient (relative aperture), image field of view, and aberrations (such as distortion) as internal parameters of the lens. Usually users build parameters that the vision system cares about, including field of view (FOV), resolution (Resolution), working distance (WD), and depth of field (DOF).
In the machine vision industry, optical lenses are usually divided into zoom lenses, zoom lenses, telecentric lenses, high-precision or megapixel lenses. Of course, these classifications do not have strict boundaries. Each lens has fixed mechanical parameters, including lens mounting dimensions, screw aperture, interface size, weight, working distance, diameter, and length.

In special cases, the visual application has limitations on the mounting size of the camera and the lens, so it is not possible to select a large-sized lens or to select a small-sized lens at will. Therefore, when selecting a lens, certain mechanical parameter objects are also considered in some cases.

When the optical lens is working, the actual working distance is fixed, but the working distance of some custom LiF optics cannot be changed, such as telecentric lenses, microscopes, etc. Generally, the telecentric lens has a working distance of 40 mm, 65 mm, 110 mm, etc., and if it is not equal to the standard working distance, it cannot be clearly imaged. From experience, the longer the length of the lens, the greater the inertia generated during motion, and the weaker the vibration capability during static operation.

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