RU2545465C1 - Large-aperture lens - Google Patents

Abstract

FIELD: physics, optics.

SUBSTANCE: large-aperture lens can be used in devices together with matrix receivers. The lens contains located consistently along the beam path the biconcave lens, the unit of two positive meniscuses facing by cambers to each other, the biconvex lens and the component comprising biconvex and biconcave lenses which are glued together to each other. The single biconvex lens is made from optical glass with the dispersion coefficient greater than 90. Relative aperture of the lens is 1:1.4, the angular field of vision is 88°.

EFFECT: expansion of working area of spectral range from 0,4 up to near infrared (1 mcm) with image quality saving.

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Description

The invention relates to optical devices and can be used to create aperture lenses with an extended spectral range, working with matrix receivers.

Known lenses used in night vision devices operating in the visible and near infrared spectral range, for example, fast lens according to the patent of the Russian Federation No. 2178194, publ. January 10, 2002. The lens contains five components, the first of which is the negative meniscus facing the concave surface to the image, the second is the biconvex lens, the third is the biconcave lens, the fourth is the biconvex lens and the fifth is the positive meniscus facing the convex surface to the subject. The relative aperture of the lens is 1: 2, the angular field of view in the space of objects is 48 °, the working spectral range is 0.6 ... 1.0 μm. As you can see, the spectral range is quite narrow and the lens does not solve the task.

The closest in design to the proposed is a fast lens with an enlarged rear focal segment according to ed. testimonial. USSR No. 781732, publ. 11/23/1980, containing four components, the first of which is negative in the form of a glued meniscus facing inwardly toward the subject, the second is a concave-convex meniscus, the third is a convex-concave positive meniscus, and the fourth is a positive meniscus facing concavity to the image. The second component is located from the first one at a distance of 0.3-0.4 of the focal length of the lens, and each of the subsequent components relative to its previous one is located at a distance of not more than 0.01 of the focal length of the lens. The second and third components (menisci) are a common unit, designed for a minimum of spherical aberration. The lens has an increased relative aperture and angle of field of view, but their specific values are not indicated. The region of the spectral range in which the lens is intended to operate is also not indicated, but it is obvious that this is the visible spectral range.

The technical result of the invention is to expand the working region of the spectrum from 0.4 μm to near infrared (1 μm), increase the relative aperture to 1: 1.4 and increase the angle of the field of view in the space of objects to 88 ° while maintaining high image quality in the specified spectral range .

The technical result is achieved by the fact that in a fast lens comprising a negative component, a block of two positive menisci, convex to each other, and a positive meniscus, convex to the object, in contrast to the known, the negative component is made in the form of a biconcave lens, a positive meniscus - in the form of biconvex and biconcave lenses glued to each other, in front of which a biconvex lens made of glass with a dispersion coefficient of more than 90 is additionally introduced.

The implementation of the first component in the form of a biconcave lens provides an increase in the angle of the field of view while maintaining high image quality throughout the field. A group of the last two components — a biconvex lens and a positive two-glued meniscus — and a biconvex lens made of glass with a dispersion coefficient of more than 90 provide an extension of the working spectral range of the lens from visible to near infrared (1 μm). The aperture diaphragm is located between a biconvex lens made of glass with a dispersion coefficient of more than 90 and a double-glued component and provides a large value of the relative aperture - 1: 1.4.

The optical scheme of the lens is illustrated in the drawing and diagrams, where:

chart 1 - frequency-contrast characteristic;

chart 2 - secondary spectrum and residual chromatism of the lens.

The proposed lens is shown in the drawing and contains a biconcave lens 1, a positive meniscus 2, convex to the image, a positive meniscus 3, convex to the object, a biconvex lens 4 and a positive component glued from a biconvex lens 5 and a biconcave lens 6. Lens 4 and component of lenses 5 and 6 are separated by an aperture diaphragm 7 and form a group 8.

As a specific example of the invention, a lens with the following characteristics is designed:

focal length of the lens f ′ = 5.58 mm;

posterior focal length S ′ _{F ′} = 6.24 mm;

relative aperture - 1: 1.4;

angular field in the space of objects - 88 °;

spectral range - (0.4 ... 1) microns;

the length of the optical system is 6.21f ′.

Radius mm Thickness mm Refractive index for λ = 0.546 μm The dispersion coefficient for λ = 0.546 μm Glass mark Light diameter mm R ₁ = -71.94 d ₁ = 1 1,617772 39.76 Bf21 11.3 R ₂ = 6.02 d ₂ = 7.9 8.6 R ₃ = -32.43 d ₃ = 5.5 1,746231 27.94 TF4 7.9 R ₄ = -16.368 d ₄ = 0.78 9.9 R ₅ = 9.954 d ₅ = 4, l 1.761712 27.32 TF5 10,4 R ₆ = 6,607 d ₆ = l, 04 8.7 R ₇ = 7.87 d ₇ = 6.5 1,4485 91.53 OK4 9.5 R ₈ = -11.108 d ₈ = 0.8 9,4 R ₉ = 10.814 d ₉ = 4,2 1,615506 60.33 TK14 8.4 R ₁₀ = -6.637 d ₁₀ = 2.9 1.761712 27.32 TF5 8.1 R ₁₁ = 83.56 7.9

The lens works as follows: the parallel light flux from an object located at infinity enters the lens, where it passes sequentially through components 1-6 and forms an image of the object in the plane of the best setting in which the optical image receiver (not shown) is installed.

The frequency-contrast characteristic of this lens in the spectral range: 0.4-1 μm, is presented in diagram 1.

From diagram 1 it follows that the lens has a high value of the contrast transfer coefficient (CPC) at a frequency of 62 mm ^-1 for both the axial beam of rays (0.6 - the second curve from above) and off-axis beams (more than 0.3), which confirms the high image quality obtained by the lens.

The secondary spectrum and residual chromatism of the presented lens is shown in diagram 2.

Diagram 2 shows that the residual chromaticity of the presented lens does not exceed 0.011f ′, which indicates a good correction of chromatic aberrations in the entire spectral range of the lens.

Thus, as a result of the proposed solution, a technical result is obtained in comparison with the closest analogue: the spectral range of operation is expanded to 0.4 ... 1.0 μm instead of 0.6 ... 1.0 μm (with good image quality, points on the axis and field ), the relative aperture of the lens 1: 1.4 and the angular field of view in the space of objects 88 were obtained.

Claims (1)

A fast lens comprising a negative component, a block of two positive meniscuses convex to each other, and a positive meniscus convex to the object, characterized in that the negative component is made in the form of a biconcave lens, and the positive meniscus is in the form of biconvex glued together and biconcave lenses, and in front of them is additionally introduced a biconvex lens made of optical glass with a dispersion coefficient of more than 90.

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