RU2290675C1 - Gauss type objective - Google Patents

Abstract

FIELD: optical tool-making, namely, engineering of objectives, possible use in various optical systems such as photo and video cameras.

SUBSTANCE: objective consists of first component - positive single meniscus, directed by its convex surface to object, second component - negative meniscus glued together using two single lenses - positive and negative, directed by convex surface to the object, third component - negative meniscus, glued together from two single lenses - negative and positive, directed by convex surface towards the image and of fourth component - single, biconvex lens. In the formula of invention mathematical relations are given, connecting distance between convex surfaces of second and third components, radiuses of optical surfaces, focal distance of objective, lens material refraction coefficients and their dispersion coefficients.

EFFECT: increased manufacturability, increased back focal portion of Gauss type objective while maintaining high image quality.

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Description

The present invention relates to optical instrumentation, namely to lenses, and can be used in various optical systems, for example, in cameras and video cameras.

A known Gaussian type lens [US Patent No. 2532751, NKI 350-222, publ. 1950], which consists of four components: the first component is a positive single meniscus convex to the object, the second component is a complex negative meniscus facing the convex side of the object, glued from two single lenses, along the rays - positive and negative, the third component - a complex negative meniscus, facing the convex side of the image, glued from two single lenses, in the direction of the rays - negative and positive; and the fourth component is a single biconvex lens.

The following conditions exist in the lens:

0.5F <λ <0.65F

0,1λ <T '<0,4λ

0,1λ <T '' <0,325λ

0.3λ <R ₅ <0.45λ

0.31λ <R ₆ <0.5λ

where λ is the distance between the external, convex surfaces of two complex negative menisci;

T 'is the thickness of the first in the direction of the rays of the complex negative meniscus;

T '' is the thickness of the second downstream complex negative meniscus;

R ₅ , R ₆ - the radii of the fifth and sixth optical surfaces along the rays;

F is the focal length of the entire lens.

However, this lens has low manufacturability, since almost all the radii of the optical surfaces are steep; insufficient image quality when converted to a focal length of 52.2 mm; relative aperture 1: 2 and angular field of view 2W = 46 deg. and a small rear focal segment with a focal length of 52.2 mm (not more than 33.1 mm).

The closest analogue to the claimed technical solution is a Gaussian type lens [US Patent No. 2532752, NKI 350-222, publ. 1950], which consists of four components: the first component is a positive single meniscus convex to the object, the second component is a complex negative meniscus facing the convex side of the object, glued from two single lenses, along the rays - positive and negative, the third component - a complex negative meniscus, facing the convex side of the image - glued from two single lenses, along the rays - negative and positive, and the fourth component - single second lenticular lens.

The following conditions exist in the lens:

0.5F <λ <0.65F

0.1 <T '<0.4λ

0.1λ <T '' <0.325λ

0.31 <R ₆ <0.5λ

0.76R ₆ <R ₅ <0.95R ₆

R ₈ / λ <1

R ₈ / λ <5

R ₁₀ / λ + 1,192 · R ₈ / λ-2,542 · R ₈ / λ · R ₁₀ / λ <0, in addition, R ₁₀ / λ is more than R ₈ / λ less than 5 times.

where λ is the distance between the external, convex surfaces of two complex negative menisci;

T 'is the thickness of the first in the direction of the rays of the complex negative meniscus;

T '' is the thickness of the second downstream complex negative meniscus;

R ₅ , R ₆ , R ₈ , R ₁₀ are the radii of the fifth, sixth, eighth and tenth optical surfaces along the rays;

F is the focal length of the entire lens.

This lens has a higher image quality than a Gaussian type lens described in US Pat. No. 2,532,751.

However, this lens has low manufacturability, since almost all the radii of optical surfaces are steep, which does not allow, when processing optical surfaces, to attach a large number of lenses to the block at the same time; and a small rear focal segment with a focal length of 52.2 mm (no more than 31.6 mm), which does not allow it to be used in SLR cameras.

The task of the invention is the creation of a Gaussian type lens with improved performance and high adaptability.

The technical result is an increase in manufacturability and an increase in the back focal length of a Gaussian type lens with very high image quality.

This is achieved by the fact that in a Gaussian-type lens, consisting of four components along the rays: the first component is a positive single meniscus facing a convex surface to the object, the second component is a negative meniscus glued from two single lenses - positive and negative facing a convex surface to the subject, the third component - the negative meniscus glued from two single lenses - negative and positive, with a convex surface facing the image, and the fourth component that of a single biconvex lens, in addition, the conditions are:

1.64 <n ₁ , n ₂ , n ₅ , n ₆ <1.68

46 <ν ₁ , ν ₂ <53

46 <ν ₅ , ν ₆ <58

1.6 <n ₃ <1.649

1.6 <n ₄ <1.617

0≤f '/ | R ₄ | <0.5

0≤f '/ | R ₇ | <0.5,

in contrast to the known conditions are:

33.83 <ν ₃ <38

33.83 <ν ₄ <35

0.5L <| R ₆ | <0.7L

1,02 | R ₆ | <R ₅ <1,2 | R ₆ |,

in addition, the lens of the fourth component and the positive lens of the third component can be made of lanthanum glass, and there can also be equality:

R ₁ = | R ₁₀ |,

where L is the distance between the convex surfaces of the second and third components;

R ₁ , R ₄ , R ₅ , R ₆ , R ₇ , R ₁₀ are the radii of the first, fourth, fifth, sixth, seventh and tenth optical surfaces;

f 'is the focal length of the entire lens;

n ₁ , n ₂ , n ₃ , n ₄ , n ₅ , n ₆ are the refractive indices of the materials of the first, second, third, fourth, fifth and sixth lenses for line D;

ν ₁ , ν ₂ , ν ₃ , ν ₄ , ν ₅ , ν ₆ - dispersion coefficient for the line D of the material of the first, second, third, fourth, fifth and sixth lenses.

Figure 1 presents the optical diagram of the proposed lens in the first embodiment of a specific embodiment, and figure 2 presents the optical diagram of the proposed lens in the second embodiment of a specific embodiment.

The lens consists of four components along the rays: the first component is the positive single meniscus 1 facing the convex surface of the object, the second component is the negative meniscus glued from two single lenses - positive 2 and the negative 3 facing the convex surface to the object, the third component is a negative meniscus glued from two single lenses - negative 4 and positive 5, with a convex surface facing the image, and the fourth component - a single biconvex lens 6 .

The proposed optical system works like a lens collecting from infinity.

The lens works as follows: the light flux from an object located at infinity enters the lens, where it passes through lenses 1, 2, 3, 4, 5, 6 and forms an image of the object in the plane of the best setting in which the optical radiation detector or film is installed (not shown).

In accordance with the proposed solution, two specific versions of a Gaussian type lens were calculated, corrected in the spectral range from 400 to 700 nm.

The design parameters of the lens according to the first embodiment are given in table 1.

Characteristics of the calculated lens:

focal length 52.2 mm relative hole 1: 2 field of view angle 46 deg. back focal length 38.15 mm

Table 1 Radii, mm Thickness mm Glass mark Refractive Index n _D Coeff. variance ν _D Light diameter mm R ₁ = 44,264 26 d ₁ = 2.7 Tk21 n ₁ = 1.6568 ν ₁ = 51.11 R ₂ = 143.56 25.7 d ₂ = 2.2 one R ₃ = 23.879 24.2 d ₃ = 5.8 Tk21 n ₂ = 1.6568 ν ₂ = 51.11 R ₄ = 220,274 22.5 d ₄ = 4.45 Bf24 n ₃ = 1,6344 ν ₃ = 36.76 R ₅ = 15.74 18.1 d ₅ = 9.35 one R ₆ = -15.17 17.5 d ₆ = 2.25 F19 n ₄ = 1,613369 ν ₄ = 34.28 R ₇ = 311.937 19.6 d ₇ = 5.6 STK3 n ₅ = 1.6594 ν ₅ = 57.33 R ₈ = -21.23 20.7 d ₈ = 0.2 one R ₉ = 115.61 23.6 d ₉ = 3.75 Tk21 n ₆ = 1.6568 ν ₆ = 51.11 R ₁₀ = -44,264 24.2

the aperture diaphragm is located behind the lens 3 at a distance of 4.3 mm

In the proposed embodiment of the invention, there are equalities:

| R ₆ | = 0.5526L

R ₅ = 1,0376 | R ₆ |

f '/ | R ₄ | = 0.2372

f '/ | R ₇ | = 0.1675

R ₁ = | R ₁₀ |,

where L is the distance between the convex surfaces of the second and third components;

R ₁ , R ₄ , R ₅ , R ₆ , R ₇ , R ₁₀ are the radii of the first, fourth, fifth, sixth, seventh and tenth optical surfaces;

f 'is the focal length of the entire lens.

The design parameters of the lens according to the second embodiment are given in table 2.

Characteristics of the calculated lens:

focal length 52.2 mm relative hole 1: 2 field of view angle 46 deg. back focal length 38.11 mm

the aperture diaphragm is located behind the lens 3 at a distance of 4.3 mm

In the proposed embodiment of the invention, there are equalities:

| R ₆ | = 0,543L

R ₅ = 1.1023 | R ₆ |

f '/ | R ₄ | = 0

f '/ | R ₇ | = 0

where L is the distance between the outer, convex surfaces of two complex negative menisci;

R ₄ , R ₅ , R ₆ , R ₇ - the radii of the fourth, fifth, sixth and seventh optical surfaces;

f 'is the focal length of the entire lens.

As follows from Tables 1 and 2, the negative lens 4 of the third component is made of glass grade F19 or F9, which has a special dispersion. Materials differing in v by more than ± 3 units from glasses with the usual dispersion course for equal values of relative partial dispersions p _F'g = (n _g -n _{F '} ) / (n _F' -n _{C '} ), it is considered to be special (see §2 Optical materials with a special dispersion ..., Ivanova T.A., Kirillovsky V.K. Design and control of the optics of microscopes. - L., Mechanical Engineering, Leningrad. Department, 1984. p.11. ), and the positive lens 5 of the third component is made of STK3 lanthanum glass. Similarly, the lens 6 of the fourth component can be made of lanthanum glass.

Table 3 shows the aberrations for λ = 0.589 μm of the proposed Gaussian type lens according to the first and second variants of a specific design.

The proposed lens has a very high image quality. Photographic resolution of the proposed lens for a point on the axis of at least 70 mm ^-1 and within the field of view of at least 45 mm ^-1 .

In the proposed lens of 10 optical surfaces 9 are more gentle than in the closest analogue, so the proposed lens is more technological, since when processing the surfaces of the lenses, you can place more lenses on the block.

Thus, as a result of the proposed solution, a technical result is obtained: a Gaussian type lens with increased adaptability and an increased rear focal length with a very high image quality is created.

table 2 Radii, mm Thickness mm Brand glass Refractive Index n _D Coeff. variance ν _D Light diameter mm R ₁ = 48.028 26 d ₁ = 3.71 Tk21 n ₁ = 1.6568 ν ₁ = 51.11 R ₂ = 157.192 25.5 d ₂ = 2.36 one R ₃ = 24.36 24.2 d ₃ = 9.16 Tk21 n ₂ = 1.6568 ν ₂ = 51.11 R ₄ = ∞ 20.7 d ₄ = 1.5 Bf24 n ₃ = 1,6344 ν ₃ = 36.76 R ₅ = 16.142 18.1 d ₅ = 9.03 one R ₆ = -14.644 17.5 d ₆ = 1.99 F9 n ₄ = 1.6137 ν ₄ = 34.57 R ₇ = ∞ 19.7 d ₇ = 5.29 STK3 n ₅ = 1.6594 ν ₅ = 57.33 R ₈ = -20,363 20.7 d ₈ = 0.15 one R ₉ = 116,416 23.3 d ₉ = 4.53 Tk21 n ₆ = 1.6568 ν ₆ = 51.11 R ₁₀ = -42.205 24.2

Table 3 Type of aberration The proposed lens according to the first embodiment (no more) The proposed lens for the second var. (no more) Transverse spherical aberration for a point on the axis with a relative aperture of 1: 2 0.02 mm 0.03 mm Transverse aberration of a wide inclined beam in the meridional section for the field of view 2W = 46 deg. 0.019 mm 0.021 mm Transverse aberration of a wide inclined beam in a sagittal section for a field of view 2W = 46 deg. 0.1 mm 0.08 mm The meridional astigmatic segment X ' _m for the field of view 2W = 46 deg. 0.345 mm -0.387 mm Sagittal astigmatic segment X ' _s for the field of view 2W = 46 deg. -0.097 mm -0.1 mm Distortion for the field of view 2W = 46 deg. -2.1% -2%

Claims (4)

1. A Gaussian type lens, consisting of four components along the rays: the first component is a positive single meniscus with a convex surface facing the object, the second component is a negative meniscus glued from two single lenses - a positive and negative facing with a convex surface to the object, third the negative meniscus component, glued from two single lenses - negative and positive, with a convex surface facing the image, and the fourth component - a single, bicuspid cloy lenses, in addition, there are conditions: 1.64 <n ₁ , n ₂ , n ₅ , n ₆ <1.68, 46 <ν ₁ , ν ₂ <53, 46 <ν ₅ , ν ₆ <58, 1.6 <n ₃ <1.649, 1.6 <n ₄ <1.617, 0≤f '/ | R ₄ | <0.5 0≤f '/ | R ₇ | <0.5, characterized in that the conditions are: 33.83 <ν ₃ <38 33.83 <ν ₄ <35 0.5L <| R ₆ | <0.7L, 1,02 | R ₆ | <R ₅ <1,2 | R ₆ |, where L is the distance between the convex surfaces of the second and third components; R ₄ , R ₅ , R ₆ , R ₇ - the radii of the fourth, fifth, sixth and seventh optical surfaces; f 'is the focal length of the entire lens; n ₁ , n ₂ , n ₃ , n ₄ , n ₅ , n ₆ are the refractive indices of the materials of the first, second, third, fourth, fifth and sixth lenses for line D; ν ₁ , ν ₂ , ν ₃ , ν ₄ , ν ₅ , ν ₆ are the dispersion coefficients for the line D of the material of the first, second, third, fourth, fifth, and sixth lenses. 2. A Gaussian type lens according to claim 1, characterized in that the condition R ₁ = | R ₁₀ | where R ₁ , R ₁₀ are the radii of the first and tenth optical surfaces. 3. A Gaussian type lens according to claim 1, characterized in that the positive lens of the third component is made of lanthanum glass. 4. A Gaussian type lens according to claim 1, characterized in that the lens of the fourth component is made of lanthanum glass.

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