RU2778445C1 - Lens for night vision devices - Google Patents

Abstract

FIELD: optical technology.

SUBSTANCE: lens can be used in conjunction with electron-optical converters in night vision devices operating in low light conditions in active and passive modes. The lens consists of a biconvex lens, a complex lens, glued together from biconvex and biconcave lenses, a negative meniscus, facing the concave surface to the image plane, and a biconvex lens. A biconcave lens and a positive meniscus, facing the convex surface to the plane of the object are introduced, installed sequentially one after another between the complex glued lens and a negative meniscus. The aperture diaphragm is located between the complex glued lens and the biconcave lens. A plane-parallel plate is installed behind a biconvex lens in front of the image plane. The lenses are made of two brands of glass.

EFFECT: increase in the rapidity and focal length, an increase in image quality within the entire angular field of the lens, an increase in the rear vertex segment.

1 cl, 2 tbl, 4 dwg

Description

The invention relates to the field of optical instrumentation, and in particular to lenses used in conjunction with image intensifier tubes in night vision devices operating in low light in both active and passive modes.

A lens lens of a night vision device is known according to the patent of the Russian Federation No. 2218585, IPC G02B 9/60, 13/14, published in 2003. It is made with a focal length f'=80 mm, a relative aperture of 1:1.5, a linear field in the image space 2y'=18 mm. The lens contains power and correction components installed along the beam. The force component includes a positive two-lens splice and a single meniscus, as well as a negative two-lens splice installed after the single meniscus. The correction component is made in the form of two menisci, facing each other with bulges, and a plane-parallel plate. However, this lens has an insufficiently large relative aperture and focal length, which leads to an increase in the aiming error on the ground, as well as a narrow spectral interval (0.68-0.88) nm and a shortened rear vertex segment, which does not allow to place a turret with interchangeable light filters designed to operate in passive, active and alignment modes when using an image intensifier tube with a protective glass 5.6 mm thick, which worsens the output parameters of the devices.

The closest analogue of the proposed technical solution is a high-aperture lens described in the utility model patent RU No. 37844, published on May 10, 2004, application No. 2003134804, IPC G02B 9/34, G02B 11/20. The lens consists of a positive biconvex lens installed in series along the beam, a composite lens glued from a positive biconvex lens and a negative biconcave lens, a glued positive meniscus with its convex side facing the object plane, a negative meniscus with its convex side facing the object plane, and a positive biconvex lens . This lens is designed to work with image intensifier tubes and has the following characteristics: focal length f'=50 mm, aperture ratio 1:1, linear field in image space equal to 17 mm. However, this lens has a small entrance pupil diameter and focal length, which makes it impossible to use it at long ranges due to the deterioration of energy and accuracy characteristics, as well as a small back focal length, which does not allow placing replaceable filters when working with modern electronic cameras. optical converters with protective glass 5.6 mm thick. In addition, the lens has a low image quality within the specified field with the introduction of replaceable light filters and protective glass of the electron-optical converter into the path of the rays.

The objective of the claimed invention is to create a lens for night vision devices with improved technical and operational characteristics.

EFFECT: creation of a lens for night vision devices with increased luminosity and focal length, with improved image quality within the entire angular field of the lens, with an increased rear vertex segment, which allows the placement of replaceable light filters when working with image intensifier tubes having a protective glass with a thickness of 5 .6 mm.

This is achieved by the fact that in the lens for night vision devices, consisting of a positive biconvex lens sequentially located along the beam, a complex lens glued from a positive biconvex lens and a negative biconcave lens, a negative meniscus, facing the concave surface to the image plane, and a positive biconvex lens , unlike the known one, a negative biconcave lens and a positive meniscus are introduced, facing the object plane with a convex surface, installed sequentially one after another along the beam between the complex glued lens and the negative meniscus, while the aperture diaphragm is located between the complex glued lens and the negative biconcave lens , and a plane-parallel plate is installed along the beam behind a positive biconvex lens in front of the image plane, and the objective lenses are made of two grades of glass.

In FIG. 1 shows an optical diagram of the proposed lens for night vision devices, Fig. 2 shows the graphs of the modulation transfer coefficients of the lens in the meridional and sagittal sections, in Fig. 3 and 4 are plots of lens aberrations for night vision devices.

The lens for night vision devices (Fig. 1) consists along the rays of a positive biconvex lens 1, a complex lens glued from a positive biconvex lens 2 and a negative biconcave lens 3, a negative biconcave lens 4, a positive meniscus 5, facing the concave surface to the image plane , a negative meniscus 6, facing the concave surface to the image plane, a positive biconvex lens 7 and a plane-parallel plate 8. The plane-parallel plate 8, installed in front of the image plane, imitates the total thickness of the protective glass of the electron-optical converter and a replaceable light filter that highlights a certain region of the spectrum corresponding to different modes device operation. The aperture diaphragm with a maximum diameter of 49.3 mm is located between the negative biconcave lens 3 and the negative biconcave lens 4 at a distance of 5.5 mm from the negative biconcave lens 3. The diameter of the aperture diaphragm can be changed if it is necessary to reduce the illumination of the image of objects observed on the ground.

The lens for night vision devices works as follows. The light flux emanating from the plane of objects, which is at infinity, passes through the lens for night vision devices in a certain sequence. First, the light flux passes through the positive biconvex lens 1, the positive biconvex lens 2, the negative biconcave lens 3, the negative biconcave lens 4, through the positive meniscus 5, the negative meniscus 6 and the positive biconvex lens 7, then the light flux passes through the optical elements located behind the lens 7 of a lens that forms an image of an object in the focal plane.

As a specific example of the implementation of the invention, a lens for night vision devices is designed, operating in the spectral range from 520 nm to 925 nm, calculated taking into account a plane-parallel plate and with the design data presented in table. one.

The calculated lens for night vision devices has the following characteristics:

Lens focal length f' 100.2 mm Relative hole 1:1.25 Entrance pupil diameter 80 mm Angular field in object space 2β=8.5 deg. Linear field in image space 15 mm Posterior focal length S' _F 22.8mm

The lens for night vision devices has high values of polychromatic modulation transfer coefficients for a spatial frequency of 15 lines/mm within the entire image field, taking into account the spectral distribution of night channel actinic fluxes operating with an image intensifier tube having a plate with a total thickness of 7.8 mm in front of the cathode , taking into account the thickness of 5.6 mm of the protective glass of the electron-optical converter and light filter, in this particular case 2.2 mm. The values of the modulation transfer coefficients for the interval from 5 to 30 lines/mm are given in Table 2.

In the proposed lens for night vision devices, the lenses are made of two types of glass, which can be ordinary or low-darkening under the influence of ionizing radiation. In addition, the combination of the biconvex lens 1, the positive biconvex lens 2, the negative biconcave lens 3, and the negative biconcave lens 4 provides correction for spherical aberration. The positive meniscus 5 and the negative meniscus 6 ensure the elimination of the residual curvature of the image field, and the biconvex lens 7 is a power component to ensure a given focal length.

Thus, the technical result is obtained: a lens for night vision devices with increased aperture ratio and focal length, with improved image quality within the entire angular field of the lens image, and with the possibility of placing replaceable light filters when working with image intensifier tubes having a protective glass 5.6 mm thick.

Claims (1)

Objective for night vision devices, consisting of a positive biconvex lens sequentially arranged along the beam, a composite lens glued from a positive biconvex lens and a negative biconcave lens, a negative meniscus with its concave surface facing the image plane, and a positive biconvex lens, characterized in that a negative biconcave lens and a positive meniscus facing the plane of the object with a convex surface, installed sequentially one after another along the beam between the complex glued lens and the negative meniscus, while the aperture diaphragm is located between the complex glued lens and the negative biconcave lens, and the plane-parallel plate is installed along the beam beam behind a positive biconvex lens in front of the image plane, and the objective lenses are made of two grades of glass.

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