An optical lens with back focus compensation

Abstract

The invention discloses an optical lens with back focal compensation. A front lens group with negative focal power and a rear lens group with positive focal power are arranged from an object side to an image side in sequence; the front lens group is a crescent-shaped first lens with negative focal power; the rear lens group consists of four lens units; a second lens and a fifth lens are biconvex lenses with positive focal power; a third lens is a biconcave lens with negative focal power; a fourth lens is a positive meniscus lens with positive focal power, of which a concave face faces the object side; a diaphragm of each optical lens is positioned in front of or behind the second lens; at least one element of the fourth lens or the fifth lens is used as a rear focal compensation lens; and the formulas that Vd is greater than 72 and dn / dt is less than minus 5*10<-6> are met, wherein Vd is abbe constant of the lens material, and dn / dt indicates variation of the refractive index of the lens along with temperature variation. The lens keeps perfect imaging definition in a temperature range of minus 40 DEG C to plus 85 DEG C.

Description

technical field [0001] The invention designs a wide-angle lens with new functions, which is especially suitable for monitoring or vehicle-mounted front-view lenses with back focus compensation technology. Background technique [0002] Ordinary lenses do not have the function of suppressing thermal drift of the lens. When the temperature rises or falls, the optical back focus of the lens will also change with the change of temperature. The mechanical back focus of the lens must be adjusted to compensate in order to maintain a good resolution. picture. However, the current application of fixed-focus lenses such as vehicles requires a wider operating temperature range, and it can work normally within the temperature range of -40°C to +85°C. On the one hand, as the temperature changes, the lens module expands and contracts with the heat of the lens base, causing the distance between the image plane and the lens (FFL) to change, causing the lens to deviate from the optimal image...

AI Technical Summary

Problems solved by technology

Such as Japanese Patent No. 1998300905 (A), Japanese Patent No. JP2002228925 (A), Japanese Patent No. JP1991063613 (A), Japanese Patent No. JP2008-8960A, because the fourth lens and the fifth lens of the rear group do not use special dn / The dt material cannot maintain a good resolution in the working temperature range of -40°C to 85°C

The overall length of these lenses is also long, which cannot meet the customer's requirements for small size, low price and high performance

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