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Optical lens—large size motorized zoom lens

Introduction

The vision is farther, the world is closer; don't you want to know what is happening "thousands of miles away". "Clairvoyance" no longer exists only in mythology. The large zoom electric zoom lens in reality allows you to obtain "clairvoyance" anytime, anywhere.

1. Zoom lens

The zoom lens refers to the continuous change of the focal length of the system by changing the interval between two or more lens groups of the system while the image plane remains still, and the target is found when the zoom is small and the field of view is large. Identify the purpose of the target. In a motorized zoom lens, motorized refers to the use of the DC motor of the lens to achieve functions such as zooming, focusing, and switching between day and night or through fog modes when remotely controlled or programmed.

In the security monitoring industry, the electric zoom lens is the earliest type of zoom lens that can remotely adjust the focal length and focus. Electric zoom lenses can be divided into two variable electric zoom lenses according to the number of variable components; three variable electric zoom lenses. The two variable electric zoom lens means that the focal length and focus can be changed by a motor, and the iris is automatically controlled by the camera drive signal, that is, the automatic iris. The three-variable electric zoom lens means that the three parameters of focal length, focus, and aperture are all driven and changed by an electric motor.

The magnification, zoom ratio, and zoom ratio in a zoom lens refer to the ratio of the focal length at the long focal end to the focal length at the short focal end. Zoom lenses with a magnification of more than 10 times are generally referred to as large zoom lenses; conversely, zoom lenses with a magnification of less than 10 times are generally referred to as small zoom lenses. There are three types of zoom lenses according to the maximum imaging circle size: 1/3”, 1/2” and 1”.

2. Application of zoom lens

The selection principle of the zoom lens is as follows: The maximum imaging circle size of the lens should not be less than the imaging specification of the camera chip, that is to say, 1/2” lens can be used with 1/3” camera; but 1/3” lens cannot It should be used on a 1/2" camera, because the edges of the image will be blurred and vignetting problems will occur.

When the electric zoom lens is used in conjunction with the camera, the functions such as zoom, focus and iris can be controlled artificially through the back-end controller or the control interface of the camera. The magnification of the electric zoom lens is 6 times, 7 times, and 10 times. The focal length of the telephoto end is mostly below 100mm, which is called the short focal length electric zoom lens; 15 times, 16 times, 20 times, 22 times and other medium multiples , The focal length of the telephoto end is mostly between 100mm and 300mm, which are called medium focal length electric zoom lenses; further up, there are 30 times, 33 times, 50 times, 60 times, the general focal length is above 300mm, some even It can reach or exceed 1000mm, and is especially suitable for super long-distance monitoring. It is called a long focal length electric zoom lens. After the choice of the times, the electric zoom lens with the telephoto end focal length below 200mm is basically replaced by the movement lens; the electric zoom lens with the telephoto end focal length in the focal length of 200mm ~ 1000mm, because it is particularly suitable for long-distance and ultra-long-distance monitoring Project use is still widely used.

In rivers, highways, urban commanding heights, railways, forest fire prevention, airports, border defense, coastal defense, ports and other monitoring projects that require large-scale, long-distance, and ultra-long-distance monitoring, large-time long focal length electric zoom lenses are generally used. This type of monitoring project, in the monitoring system, sometimes needs to achieve seamless monitoring in a large area, which is realized through the relay of multiple monitoring points, and the monitoring distance of a single camera generally needs to be about 1-10 kilometers.

In order to be able to achieve 24-hour high-definition day and night monitoring under severe weather conditions such as dust, smog, light rain, etc., it should also have a fog penetration function, that is, a lens with a high transmittance in the infrared band of 700nm~950nm, and is equipped at the same time Through the fog filter, in order to use the principle of near infrared rays to diffract tiny particles in the fog mode, it can shoot very clear, high-contrast black and white images, and improve the effect of long-distance observation.

Common electric zoom lenses will encounter some problems that need to be solved in use:

1.)Since telephoto lenses are mostly used in all-weather monitoring environments, the application of automatic iris technology is essential. The problem that follows is that the depth of field changes continuously with the adjustment of the aperture, especially when the aperture is fully opened at night, so that objects that can be clearly observed during the day may become blurred at this time.

2.)In addition, the telephoto lens has brought us a wider range of observation scenarios. In the same picture, near, medium, and long-range targets may appear at the same time, and targets at different distances can be monitored. Usually, what the monitoring personnel need to do is to continuously adjust the focus of the lens to achieve the ideal observation effect.

3.)In mid-to-long distance monitoring, some scenes will have weather conditions that block the view, such as heavy fog.

Motorized zoom lenses are mostly used in relatively wide outdoor scenes, and generally cover a relatively large focal length range. Since the focal length can be changed by human operation, the key part of the scene can be zoomed in for observation, and the monitoring effect is very good. With the continuous development and improvement of the security industry and the increase of the country’s investment in outdoor infrastructure, such as smart cities, highways, railways and bridges, forest fire prevention, coastal defense, dams, ports, border defense, oil fields and other industries and fields, electric zoom lenses There has been a very large increase in demand.

3. FOCtek's large electric zoom lens

The first large power zoom lens independently developed and designed by Fortek has a long observation distance, high target recognition, strong fog penetration and clear images. The variable frequency motor drive function perfectly solves the problem of conflict between fast focusing and fine focusing. At the same time, the fog penetration function can solve the problem of image sharpness that is easily affected by the weather. The use of multiple ultra-large-diameter, ultra-low-dispersion glass lenses solves the problem that the image at the long focal length of the traditional electric zoom lens is not clear enough.