RU2384870C1 - Objective lens for near infrared spectrum - Google Patents

Abstract

FIELD: physics, optics.

SUBSTANCE: objective lens can be used in night vision devices (NVD). The objective lens has four components. The first and third components are biconvex lenses. The second component is in form of two meniscuses glued together, with the convex side facing the object and consisting of a biconvex and a biconcave lens. The fourth component is a biconcave lens. The first component, the first lens of the second component and the fourth component are made from glass with density of not more than 2.6 g/cm³.

EFFECT: reduced weight and higher image quality.

2 dwg, 1 tbl

Description

The invention relates to optical instrumentation and can be used in night vision devices (NVD).

Known lenses for night vision devices in accordance with RU No. 22218585, IPC G02B 13/14, 9/60, 2003, RU No. 2276799, IPC G02B 13/14, 9/60, 2004. They consist of six lenses, have significant weight, which significantly reduces the consumer properties of portable devices in which they are used. The relative weight characteristic, characterized by the reduced weight and equal to the value of the weight related to the value of the entrance pupil, for these lenses exceeds 3 g / mm.

The closest analogue is the lens for the infrared region of the spectrum according to patent RU No. 2072733, IPC G02B 13/14, 9/34, 1997, containing four components installed along the beam, the first of which is made in the form of a positive meniscus, convex to an object, the second in the form of a double-glued meniscus, consisting of a biconvex and biconcave lens, convex to the object, the third in the form of a negative meniscus, convex to the object, and the fourth in the form of a biconvex lens. This lens also has a large value of the reduced weight of 3 g / mm and low image quality - polychromatic modulation transfer coefficient (KPM) in the image of a sinusoidal measure of absolute contrast at a frequency of N = 30 mm ^-1 in the spectral range of wavelengths from 660 to 920 nm is:

1) for the axial point of the item - 0.50 *

2) for the edge of the field (ω = 4.3 °):

meridional section - 0.37 *,

sagittal section - 0.28 *,

where: * - KPM is designed for lenses with a 5.6 mm thick glass plate mounted in the rear focal segment and simulating the glass substrate of the photocathode of the electron-optical converter.

The objective of the invention is to provide a lens with enhanced performance.

The technical result achieved by the implementation of the invention is the reduction of weight characteristics, while improving image quality.

This is achieved by the fact that in the lens for the near infrared region of the spectrum, which consists of four components installed along the beam, the first of which is made in the form of a positive lens, the second is in the form of a double-glued meniscus, the third and fourth are in the form of single lenses, in contrast from the known, in the first and third components - the lenses are biconvex, and in the fourth - biconcave, while the lens of the first component, one of the lenses of the second component and the lens of the fourth component are made of glass with a density of not more than 2.6 g / cm ³ .

The invention is illustrated by drawings: in Fig.1 shows an optical diagram of the lens, Fig.2 is a graph of a polychromatic modulation transfer coefficient (KPM).

The lens for the near infrared region of the spectrum (Fig. 1) contains four components, the first of which is made in the form of a biconvex lens 1, the second is a double-glued meniscus convex to the object and consists of a biconvex 2 and biconcave 3 lenses, and the third is a biconvex lens 4 and the fourth component is a biconcave lens 5.

The lens works as follows. The light from an object located at an infinitely large distance from the first component, refracting, passes through lenses 1, 2, 3, 4, 5 and forms an image of the object in the focal plane of the lens.

In accordance with the proposed technical solution, the lens variant for the focal length f '= 120 mm is calculated, the design parameters of which are given in the table.

The lens has a field of view angle of 2ω = 8.6 °, a relative aperture of 1: 2 and high image quality - polychromatic KPM in the image of the sinusoidal world of absolute contrast at a spatial frequency of N = 30 mm ^-1 (figure 2) in the spectral range of wavelengths from 660 to 920 nm is:

1) for the axial point of the subject - 0.67 *,

2) for the edge of the field (ω = 4.3 °):

meridional section - 0.68 *,

sagittal section - 0.65 *.

Note: * - KPM is designed for lenses with a 5.6 mm thick glass plate mounted in the rear focal segment and simulating the glass substrate of the photocathode of the electron-optical converter.

Three of the five lenses are made of K8 glass, lighter and cheaper than in the closest analogue. The mass of the optical parts of the lens is 154 g, which provides a value of weight reduced to the size of the entrance pupil equal to 2.57 g / mm

As can be seen from a specific calculation example, the lens for the near infrared region of the spectrum is made with a lower weight indicator and higher image quality, which indicates that the proposed set of distinctive features provides the desired result.

Thus, the obtained lens for the near infrared region of the spectrum with enhanced performance.

Claims (1)

A lens for the near infrared region of the spectrum containing four components, the first of which is a positive single lens, the second is a double-glued meniscus convex to the subject and consisting of a biconvex and biconcave lenses, the third and fourth components are single lenses, characterized in that the first and the third component is a biconvex lens, the fourth component is a biconcave lens, and in addition, the first component, the first lens of the second component and the fourth component are made of glass with a density of not more than 2.6 g / cm ³ .

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