RU2276799C1 - Objective for close infrared area of spectrum - Google Patents

Abstract

FIELD: optics, possible use as objective for night vision devices.

SUBSTANCE: objective contains two components, first of which is force one, consists of flat-convex lens, directed by convexity to subject, double-glued meniscus, directed by convexity towards subject, and flat-concave lens, directed by concavity towards image. Second component - correcting one, consists of flat-convex lens and meniscus, directed by convexities towards subject, while number of glass marks in accordance to nomenclature does not exceed two.

EFFECT: increased technological coefficients due to simplified construction while maintaining high operation characteristics.

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Description

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

Known lenses for night vision devices according to patents RU No. 2047200, IPC G 02 B 13/14, 9/34, 1995, RU No. 2072733, IPC G 02 B 13/14, 9/34, 1997, RU No. 2181207, IPC G 02 B 13/14, 9/60, 2002, RU No. 2105333, IPC G 02 B 9/12, 9/34, 15/22 1998

The main disadvantage of these lenses is their low resolution. The image quality estimated by the modulation transfer coefficient (KPM) for the spectral range of 0.65-0.9 μm at a spatial frequency of N = 30 lin / mm for the center and field edge does not exceed 0.7, which makes these lenses limit the quality when using them in night-vision devices with electron-optical converters (EOFs) of the 2nd, 2+ and 3rd generations.

The closest analogue is the lens for the infrared region of the spectrum according to patent RU No. 22218585, IPC G 02 B 13/14, 9/60, 2003, containing installed along the beam power and correction components, while the power component includes a positive two-lens bonding, positive single meniscus and negative two-lens bonding, and the correction component is made in the form of two menisci, convex to each other, while the refractive indices of the lens material exceed 1.65. The main disadvantages of the analogue are a large number of lenses and a large range of glass brands used.

The objective of the invention is the creation of a lens with high technological performance while maintaining high performance.

The technical result achieved by the invention is to simplify the design.

This is achieved by the fact that in the lens for the near infrared region of the spectrum, made in the form of power and correction components installed along the beam, the power component consists of two positive and negative lenses, and the correction component consists of a single lens and a convex meniscus to the subject, in contrast to the known one, in the power component the first lens is made in the form of a single plane-convex convex to the subject, the second in the form of a double-glued meniscus convex to the subject the third one in the form of a single plane-concave lens facing concavity to the image, and in the correction component the first lens is made in the form of a plane-convex, convex to the object, while the number of glass grades does not exceed two according to the nomenclature.

The invention is illustrated by drawings: in Fig. 1, an optical diagram of a lens is shown, in Fig. 2 is a graph of longitudinal spherical aberration, in Fig. 3 is a graph of curvature and distortion, in Fig. 4 is a graph of polychromatic modulation transmission coefficient (KPM).

The lens for the near infrared region of the spectrum (Fig. 1) contains power and correction components. The power component consists of a plano-convex lens 1, convex to the object, a double-glued positive meniscus 2, convex to the object, and a flat-concave lens 3, facing the concavity to the image. The correction component is made of a plano-convex lens 4, convex to the subject and the meniscus 5, facing the concavity to the image.

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 '= 100 mm is calculated, the design parameters of which are given in the table.

Radii, mm Thickness mm Glass mark 52.72 10 TK21 ∞ one 44.98 eleven TK21 -183.65 4,5 TF5 77.98 7 ∞ four TF5 27.35 51 42.07 5 TK21 ∞ 0.5 18,967 6 TK21 16,293

The lens has a field of view angle of 2ω = 9 ^o , a relative aperture of 1: 2 and high image quality:

- spherical aberration on the pupil area m = 0.707 ΔS '= - 0.027 mm (figure 2),

- meridional curvature ΔX'm = 0,022 mm (figure 3),

- sagittal curvature ΔX's = -0.006 mm (figure 3).

The polychromatic modulation transfer coefficient (CPM) in the image of the sinusoidal world of absolute contrast at a spatial frequency of N = 30 mm ^-1 (Fig. 4) in the spectral range of wavelengths from 660 to 920 nm is

1) for the axial point of the subject - 0.78,

2) for the edge of the field:

the meridional section is 0.74,

sagittal section - 0.75.

The closest analogue of KPM at a frequency of N = 30 mm ^-1 for different examples:

1) for the axial point of the subject - from 0.72 to 0.88

2) for the edge of the field:

meridional section - from 0.58 to 0.69,

sagittal section - 0.63 to 0.78.

As can be seen from a specific calculation example, the lens for the near PC region of the spectrum is made with fewer lenses, with improved manufacturability (three flat surfaces), the range of glass grades used (two glass grades) is reduced while maintaining high image quality.

Thus, a lens was obtained for the near PC region of the spectrum with enhanced technological performance while maintaining high performance.

Claims (1)

The lens for the near infrared region of the spectrum, made in the form of installed along the beam power and correction components, while the power component consists of two positive and negative lenses, and the correction component consists of a single lens and meniscus convex to the object, characterized in that in the power component the first lens is made in the form of a single plane-convex convex to the object, the second in the form of a double-glued meniscus convex to the object, the third in the form of a single pl skovognutoy lens facing concave to the image, and a corrective component of the first lens is formed as a plano-facing convex to the object, wherein the number of stamps according to the nomenclature of glasses does not exceed two.

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