RU2547005C1 - Apochromatic lens - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: lens comprises three components on the beam path. The first component is in the form of a positive meniscus, glued from a biconvex and biconcave lens and facing the image plane its concave side. The second component is in the form of a positive meniscus, glued from a first positive lens and a negative lens. The third component is negative and is glued from a biconvex lens and a biconcave lens. The refraction indices and average dispersion coefficients of the materials of the lenses satisfy relationships given in the claim. The lens can be supplemented with a beam-splitter prism placed between the third component and the image plane.

EFFECT: high light-gathering power while maintaining image quality by selecting a combination of glass and aberration correction, which reduces coordinate chromatism and correcting residual astigmatism.

2 cl, 5 dwg, 1 tbl

Description

The invention relates to optical instrumentation and can be used as lenses in various devices, for example, the lenses of a television camera or television rangefinder channel.

Known apochromatic lenses described in patents RU No. 2433432, IPC G02B 9/12, publ. 02/10/2011, RU No. 2331094, IPC G02B 9/28, publ. August 10, 2008. These lenses have a low aperture, which limits their use in television systems at low light levels.

The closest analogue to the claimed technical solution is the apochromatic lens described in patent RU No. 2429508, IPC G02B 9/14, publ. 09/20/2011 This lens consists of three components along the rays: the first component is made in the form of a positive meniscus facing the concave side to the image plane, the second component is in the form of a meniscus glued from biconcave and biconvex lenses, the third component is facing the concave side to image plane and made in the form of closely spaced lenses, the first of which is biconvex, the second is a negative lens. The refractive surfaces of the lenses are spherical. Lenses are made of two brands of optical glasses. The refractive indices and the coefficients of the average dispersion of the lens materials satisfy the ratio: 1.82 <n1 <1.9; 1.57 <n2 <1.65; 21 <ν1 <30; 60 <ν2 <67, in addition, this lens has a low aperture ratio, which is 1: 7.

The objective of the invention is the creation of an apochromatic lens with improved performance.

The technical result is an increase in the aperture of the lens while maintaining image quality by selecting a combination of glasses and correcting aberrations, which reduce the chromaticity of the position and correct residual astigmatism.

This is achieved by the fact that in an apochromatic lens containing three components along the beam, the first of which is made in the form of a positive meniscus with its concave side facing the image plane, the second is in the form of a meniscus glued from two lenses, one of which is positive and the other negative, the third component is negative, containing positive and negative lenses, in contrast to the known one, the meniscus of the first component is made in the form of a glued doublet of biconvex and biconcave lenses, the second component is polo itelny and wherein the first lens is positive, and a third component - of carded biconvex and biconcave lenses, the refractive indices and dispersion medium coefficients materials lenses satisfy the relations:

1.6> n _D1 = n _D3 = n _D5 ≥1.7

50≥υ _D1 = υ _D3 = υ _D5 ≥61

1.65≥n _D2 ≥1.76

26≥υ _D2 ≥33

1.7≥n _D4 ≥1.8

48≥υ _D4 ≥54

1.5≥n _D6 ≥1.6

50≥υ _D6 ≥54

where n _{D1 ... .6} are the refractive indices of the material 1-6 lenses at the wavelength of the corresponding line D of the spectrum;

υ _{D1 ... .6} is the Abbe number of the material 1-6 lenses for the wavelength of the corresponding line D of the spectrum.

In addition, the lens can be supplemented by a beam splitting prism mounted between the third component and the image plane.

Figure 1 presents the optical diagram of the proposed lens, figure 2 shows the optical diagram of the lens with a beam-splitting prism, figure 3 is a graph of the modulation transmission function, figure 4 is a graph of longitudinal chromatic aberration, figure 5 is a graph of the field curvature and distortions.

The apochromatic lens (Fig. 1) consists of three components along the rays: the first component 1, made in the form of a positive meniscus, with its concave side facing the image plane, the second component 2, made in the form of a positive glued meniscus, the third component 3 is made in the form of glued a negative lens facing the concave side to the image plane. The first component 1 consists of a glued doublet of a biconvex lens 4 and a biconcave lens 5. The second component 2 is glued, and the first is a positive lens 6 in the gluing, and the second is a negative lens 7. The third component 3 is glued from a biconvex lens 8 and a biconcave lens 9.

The apochromatic lens (figure 2) is supplemented by a beam splitting prism 10 mounted between the third component and the image plane.

Figure 3-5 shows a graph of the modulation transfer function and the aberration graphs of the calculated apochromatic lens.

The apochromatic lens works as follows:

the light flux emanating from an infinitely distant point of the object enters the first surface of the first component 1 and passes through a glued doublet from a biconvex lens 4 and a biconcave lens 5, and then sequentially through a glued second component 2, where the positive lens 6 is located first in the gluing, and the second is a negative lens 7, and through the third component 3, made in the form of glued biconvex lens 8 and biconcave lens 9, and forms an image of the object in the focal plane of the lens.

When a beam splitting prism 10 is installed, the light flux passes through it and forms an image of an infinitely distant object in two different planes: one that is optically coupled to the face of the beam splitter prism 10, which emits radiation in the spectral sensitivity range of the CCD matrix, and the other that is optically coupled to the beam splitter prisms 10 emitting radiation at a wavelength of laser radiation.

In accordance with the proposed solution, a specific lens is calculated, the design parameters of which are given in the table.

Radius mm Thickness mm Material grade n _D , υ _D Light diameter mm R ₁ = 218.159 73 d ₁ = 12 Tk21 n _D = 1.6569 υ _D = 51.1 R ₂ = -124,483 73 d ₂ = 7.3 TF2 n _D = 1.6727 υ _D = 32.1 R ₃ = 357,020 73 d ₃ = 7.8 R ₄ = 101.296 71 d ₄ = 15 Tk21 n _D = 1.6569 υ _D = 51.1 R ₅ = -101,296 71 d ₅ = 7.1 CTK19 n _D = 1,7441 υ _D = 50,4 R ₆ = 218,159 71 d ₆ = 9.7 R ₇ = 68,747 63 d ₇ = 13 Tk21 n _D = 1.6569 υ _D = 51.1 R ₈ = -182.329 63 d ₈ = 6.1 OF1 n _D = 1.5295 υ _D = 51.7 R ₉ = 43,439 fifty

Characteristics of the calculated lens:

focal length f ′ = 280 mm

relative aperture 1: 4

angle of view 2 ω = 2 °

The proposed apochromatic lens has high image quality, which is confirmed by the graph of the modulation transfer function (Fig. 3) - the modulation transmission coefficient in the spectral range from 0.52 to 0.90 μm per 200 lines / mm is not less than 0.3 for the axis and not less than 0.25 for the edge of the field of view, the graph of longitudinal chromatic aberration (figure 4) - the chromaticity of the position is not more than 70 microns, the curvature of the field and distortion (figure 5) - astigmatism is not more than 15 microns, distortion is not more than 0.02%.

Thus, a technical result was achieved - an apochromatic lens was created with an increased relative aperture, decreased position chromatism and reduced residual astigmatism and increased aperture.

Claims (2)

1. Apochromatic lens containing three components along the beam, the first of which is made in the form of a positive meniscus with the concave side facing the image plane, the second - in the form of a meniscus glued from two lenses, one of which is positive and the other is negative, the third component negative, containing positive and negative lenses, characterized in that the meniscus of the first component is made in the form of a glued doublet of biconvex and biconcave lenses, the second component is positive and the first of the lenses false, and the third component is glued from a biconvex and biconcave lenses, while the refractive indices and the average dispersion coefficients of the lens materials satisfy the relations:
1.6> n _D1 = n _D3 = n _D5 ≥1.7
50≥υ _D1 = υ _D3 = υ _D5 ≥61
1.65≥n _D2 ≥1.76
26≥υ _D2 ≥33
1.7≥n _D4 ≥1.8
48≥υ _D4 ≥54
1.5≥n _D6 ≥1.6
50≥υ _D6 ≥54
where n _{D1 ... .6} are the refractive indices of the material 1-6 lenses at the wavelength of the corresponding line D of the spectrum;
υ _{D1 ... .6} is the Abbe number of the material 1-6 lenses for the wavelength of the corresponding line D of the spectrum. 2. The apochromatic lens according to claim 1, characterized in that it is supplemented by a beam splitting prism mounted between the third component and the image plane.

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