RU2304795C1 - Objective - Google Patents

Abstract

FIELD: optics.

SUBSTANCE: objective has two serial components disposed in the direction of paths of beams. First component has to be positive one made of two glued lenses; one lens is biconvex and the other one is negative concave flat lens. Second component is made of two singular lenses, namely, negative meniscus which is turned with its concavity to object and convex flat lens disposed behind negative meniscus. There can be prism or prisms either flat parallel plate or plates between singular lenses of second component. Relations among width of second air gap, focal length of whole objective, radiuses of second, fourth and fifth optical surfaces, thickness of third lens and refractivity factors and dispersion coefficients for line d of materials of lenses are given in description of invention. Air gap between third and fourth lenses in increased to give ability of installing additional optical members.

EFFECT: increased relative aperture; higher adaptability to manufacture; higher quality of image.

5 cl, 2 dwg

Description

The present invention relates to optical instrumentation and can be used in various optical, including infrared optical systems.

A known lens (US patent No. 2703037, NKI 359-748, publ. 1955), consisting of four single lenses, divided into two components, two lenses in each, the first component along the rays is positive and includes a biconvex the lens and the biconcave glued with it, and the second component is negative and consists along the rays of the negative meniscus and the positive meniscus, facing concavity to the object and separated by a small air gap.

However, this lens has an insufficiently high relative aperture of 1: 4.5 and insufficient manufacturability, since it does not contain flat surfaces.

The closest analogue to the claimed technical solution is a photo lens (US patent No. 2631497, NKI 359-748, publ. 1953), consisting of four single lenses, divided into two components, two lenses each, with the first component along the rays is positive and includes a biconvex lens and a biconcave glued with it, and the second component is negative and consists in the direction of the rays from the negative meniscus, facing concavity to the object, and a plano-convex lens separated by a small air gap tkom; these two components are separated by an air gap equal to more than 0.2 and less than 0.5 of the focal length of the lens; the radius of the front surface of the first lens is more than 0.23 of the focal length of the lens, the radius of the glued surfaces of the first two lenses is about 0.4 of the focal length of the lens, the radius of the rear surface of the second lens is about 0.7 of the focal length of the lens, the radius of the front surface of the third lens is 0, 1-0.2 focal length of the lens, the radius of the rear surface of the third lens is equal to more than 0.2 of the focal length of the lens and less than infinity, the radius of the front surface of the fourth lens is much larger than the focal length the lens, and the radius of the rear surface of the fourth lens is equal to 1/4 of the focal length of the lens; the total axial thickness of the first two lenses plus the gap between the opposite surfaces of the second and third lenses is at least 0.37 of the focal length of the lens.

Characteristics of this lens:

focal length f ' 100 mm relative hole 1: 4,5

The relations are satisfied:

d _b2 / f '= 0,0003

| R ₂ | / f '= 0.408

| R ₄ | / f '= 0.13395

R ₄ / R ₅ = 0.1372

d ₃ / f '= 0.0079

n ₁ = 1,62398

n ₂ = 1.74066

n ₃ = 1.61008

n ₄ = 1.72719

ν ₁ = 47

ν ₂ = 27.2

ν ₃ = 46

ν ₄ = 28,

where d _B2 is the magnitude of the second air gap;

f 'is the focal length of the entire lens;

R ₂ , R ₄ , R ₅ - the radii of the second, fourth and fifth optical surfaces;

d ₃ is the thickness of the third lens;

n ₁ , ν ₁ - refractive index and dispersion coefficient for line d of the material of the first lens;

n ₂ , ν ₂ - refractive index and dispersion coefficient for line d of the material of the second lens;

n ₃ , ν ₃ - refractive index and dispersion coefficient for line d of the material of the third lens;

n ₄ , ν ₄ - refractive index and dispersion coefficient for the line d of the fourth lens material.

This lens has a relatively large relative aperture, a small second air gap, which does not allow a prism (or prism) with a significant ray path in the glass (large) to be placed behind the third lens in front of the fourth lens of the lens, and lack of manufacturability, since it contains only one flat optical surface. When processing the lenses of this lens, test glasses and a processing tool should be made on each spherical optical surface, and test glasses and a processing tool are always available on flat surfaces. In addition, when monitoring flat surfaces, an interferometer can be used instead of a test glass, which allows to increase the cleanliness class of a flat surface.

The objective of the invention is the creation of a lens with improved performance and high adaptability with high image quality.

The technical result is an increase in the relative aperture, an increase in the air gap between the third and fourth lenses brought to air in order to be able to install additional optical elements and to increase manufacturability with high image quality.

This is achieved by the fact that in a lens containing two components, the first of which (along the rays) is positive, consisting of two glued lenses - the first is biconvex and the second is negative, the second component consists of two single lenses - the third - negative meniscus, facing concavity to the object, and the fourth positive lens located behind it, containing a flat optical surface, the two components being separated by a first air gap equal to a value in the range of more than 0.2 and less than 0.5 f the ocular distance of the lens, and the radius of the front surface of the first lens is more than 0.23 of the focal length of the lens; in contrast to the known second component - positive, the negative lens of the first component is made concave, the fourth lens faces the image plane, while between the third and fourth lenses there is an optical refractive element with flat surfaces, in addition, the following conditions are met:

0.19 <d _B2 / f '<0.8

0.7 <| R ₂ | / f '<1

0.2 <| R ₄ | / f '<0.4

0.3 <R ₄ / R ₅ <0.6

0.01 <d ₃ / f '<0.1

1.42 <n ₁ <1.5

1.6 <n ₂ <1.68

1.42 <n ₃ <1.54

1.42 <n ₄ <1.63

48 <ν ₁ <98

31 <ν ₂ <36

47 <ν ₃ <98

56 <ν ₄ <98,

where d _B2 is the magnitude of the second air gap reduced to air along the optical axis;

f 'is the focal length of the entire lens;

R ₂ , R ₄ , R ₅ - the radii of the second, fourth and fifth optical surfaces;

d ₃ is the thickness of the third lens;

n ₁ , ν ₁ - refractive index and dispersion coefficient for line d of the material of the first lens;

n ₂ , ν ₂ - refractive index and dispersion coefficient for line d of the material of the second lens;

n ₃ , ν ₃ - refractive index and dispersion coefficient for line d of the material of the third lens;

n ₄ , ν ₄ - refractive index and dispersion coefficient for the line d of the fourth lens material.

In addition, the optical refractive element can be made in the form of a prism (or prisms) or plane-parallel plate (or plates).

Figure 1 and 2 presents the optical scheme of the proposed lens.

The lens (figures 1 and 2) consists of two components sequentially located along the rays from the object, the first of which (along the rays) is positive, consisting of two glued lenses: biconvex 1 and negative - concave plane 2; the second component, consisting of two single lenses - a negative meniscus 3, facing concavity to the object, and a convex lens 4 located behind it. Moreover, Fig. 1 shows an optical diagram of a lens with a plane-parallel plate 5 located between 3 and 4 lenses, and in Fig. .2 shows an optical diagram of a lens with a prism 6 located between 3 and 4 lenses; a plane-parallel plate can be located behind the lens.

The proposed optical system works as a lens collecting from infinity, that is, the light flux from an object located at infinity enters the lens, where it passes through lenses 1, 2, 3, plane-parallel plate 5 or prism 6, and then through lens 4 and forms an image of the object in the plane of the best setup in which the optical radiation receiver (not shown) is installed.

The proposed optical system can also work as a collimator lens in the reverse ray path.

In accordance with the proposed solution, the lens is calculated, corrected for a wavelength of 900 nm.

The design parameters of the lens are given in table 1.

Characteristics of the calculated lens:

focal length f ' 101.69 mm relative hole 1: 2.5 field of view angle 40 min back focal length 1.79 mm

The conditions are met:

d _B2 / f '= 0.6542

| R ₂ | / f '= 0.8293

| R ₄ | / f '= 0.2665

R ₄ / R ₅ = 0.5034

d ₃ / f '= 0.0295

n ₁ = 1.487464

n ₂ = 1,664262

n ₃ = 1,516373

n ₄ = 1,516373

ν ₁ = 70.03

ν ₂ = 35.44

ν ₃ = 64.07

ν ₄ = 64.0,

where d _B2 - the value of the second air gap;

f 'is the focal length of the entire lens;

R ₂ , R ₄ , R ₅ - the radii of the second, fourth and fifth optical surfaces;

d ₃ is the thickness of the third lens;

n ₁ , ν ₁ - refractive index and dispersion coefficient for line d of the material of the first lens;

n ₂ , ν ₂ - refractive index and dispersion coefficient for line d of the material of the second lens;

n ₃ , ν ₃ - refractive index and dispersion coefficient for line d of the material of the third lens;

n ₄ , ν ₄ - refractive index and dispersion coefficient for the line d of the fourth lens material.

Table 1
Lens design Radii, mm Thickness mm Glass mark Refractive index n _d Coeff. variance ν _d Light diameter mm R ₁ = 41.69 40 d ₁ = 11 LK3 1.487464 70.03 R ₂ = -84.33 40 d ₂ = 4 Bf28 1,664262 35.44 R ₃ = ∞ 38 d ₃ = 47.4 one R ₄ = -27.1 21 d ₄ = 3 K8 1,516373 64.07 R ₅ = -53.83 22 d ₅ = 9.7 one R ₆ = ∞ twenty d ₆ = 81 K8 1,516373 64.07 R ₇ = ∞ twenty d ₇ = 2 one R ₈ = 6,699 6 d ₈ = 1.7 K8 1,516373 64.07 R ₉ = ∞ 6 d ₉ = 1.6 one R ₁₀ = ∞ 6 D ₁₀ = 1.6 K8 1,516373 64.07 R ₁₁ = ∞ 6

Table 2 shows the aberrations for λ = 900 nm of the calculated lens variant.

table 2 Type of aberration The proposed fast lens (no more) Transverse spherical aberration for a point on the axis with a relative aperture of 1: 2.5 0.014 mm Transverse aberration of a wide inclined beam in the meridional section for the field of view 2W = 40 min 0.016 mm Transverse aberration of a wide inclined beam in a sagittal section for a field of view 2W = 40 min 0.013 mm Meridional astigmatic segment X _m for the field of view 2W = 40 min 0.063 mm Sagittal astigmatic segment X _s for the field of view 2W = 40 min 0.056 mm Distortion for the field of view 2W = 40 min -0.055%

Thus, as a result of the proposed solution, a technical result is obtained: a lens is created with an increased relative aperture, an enlarged air gap between the third and fourth lenses brought to air, and high adaptability with high image quality.

Claims (5)

1. A lens containing two components, the first of which (along the rays) is positive, consisting of two glued lenses - the first is biconvex and the second is negative, the second component consists of two single lenses - the third - negative meniscus, facing concavity to an object, and a fourth positive lens located behind it, containing a flat optical surface, the two components being separated by a first air gap equal to a value in the range of more than 0.2 and less than 0.5 focal length the lens, and the radius of the front surface of the first lens is more than 0.23 of the focal length of the lens, characterized in that the second component is positive, the negative lens of the first component is made concave, the fourth lens faces the image with a plane, and an optical refractive element is located between the third and fourth lenses with flat surfaces, in addition, the conditions are met 0.19 <d _B2 / f '<0.8, 0.7 <| R ₂ | / f '<1, 0.2 <| R ₄ | / f '<0.4, 0.3 <R ₄ / R ₅ <0.6, 0.01 <d ₃ / f '<0.1, 1.42 <n ₁ <1.5, 1.6 <n ₂ <1.68, 1.42 <n ₃ <1.54, 1.42 <n ₄ <1.63, 48 <ν ₁ <98, 31 <ν ₂ <36, 47 <ν ₃ <98, 56 <ν ₄ <98, where d _B2 is the magnitude of the second air gap reduced to air along the optical axis; f 'is the focal length of the entire lens; R ₂ , R ₄ , R ₅ - the radii of the second, fourth and fifth optical surfaces; d ₃ is the thickness of the third lens; n ₁ , ν ₁ - refractive index and dispersion coefficient for line d of the material of the first lens; n ₂ , ν ₂ refractive index and dispersion coefficient for the line d of the material of the second lens; n ₃ , ν ₃ - refractive index and dispersion coefficient for line d of the material of the third lens; n ₄ , ν ₄ - refractive index and dispersion coefficient for the line d of the fourth lens material. 2. The lens according to claim 1, characterized in that the optical refractive element is made in the form of a prism. 3. The lens according to claim 1, characterized in that the optical refractive element is made in the form of prisms. 4. The lens according to claim 1, characterized in that the optical refractive element is made in the form of a plane-parallel plate. 5. The lens according to claim 1, characterized in that the optical refractive element is made in the form of plane-parallel plates.

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