Large-diaphragm monitoring camera

Abstract

The invention discloses a large-diaphragm monitoring camera. From an object along an optical axis, the large-diaphragm monitoring camera comprises a first lens system with a retro focus, an automatic diaphragm and a second lens system with a positive focus, wherein the second lens system comprises at least three lenses; the first lens and the last lens are plastic aspheric lenses, the first lens has the positive focus, and the last lens has the retro focus; and the focus between the first lens and the last lens satisfies the condition of 2.0<|fa / fb|<4.0, wherein fa is the focus of the first lens, and fb is the focus of the last lens. By using two complementary aspherical lenses, the invention does not influence the imaging quality and well corrects the effect of aberration on the premise of ensuring high light flux. Meanwhile, by replacing glass with plastics, the invention can reduce the weight of the overall system and the total length of the mechanism, thereby effectively lowering the cost.

Description

(1) Technical field: [0001] The invention relates to a variable magnification lens applied to a monitoring image capturing device. (two) background technology: [0002] The rapid development of the economy has made the monitoring system widely used in many industries. With the development of major projects such as "National Emergency System", "Safe City", "Safe Construction", and "Strengthening Police with Science and Technology" across the country, the nighttime application of monitoring systems is becoming more and more frequent. How to correctly select the lens according to the environment of the monitored site is very important, because the lens determines the quality of the camera, which also directly affects the monitoring effect. At present, most of the lenses used in domestic surveillance systems are composed of all-glass spherical lenses, with an aperture value of FNo. Due to the low brightness of the outside world, there are certain limitations in recognition. I...

AI Technical Summary

Problems solved by technology

At present, most of the lenses used in domestic surveillance systems are composed of all-glass spherical lenses, with an aperture value of FNo. Due to the low brightness of the outside world, there are certain limitations in recognition

If a large aperture value is used, the aberration of this lens is obvious, the definition is insufficient, and the size is large

Some foreign manufacturers have tried to add glass aspheric lenses, but the production precision of glass aspheric lenses is high and the production cost is high, which makes the whole lens expensive. This expensive high-end surveillance lens discourages many domestic users.

Moreover, due to technical and other reasons, it is difficult for domestic lens manufacturers to produce high-precision glass aspheric lenses. This type of glass aspheric lenses mostly relies on imports, so the market share of high-end surveillance lenses is definitely occupied by foreign lens manufacturers.

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