RU2412455C1 - Four-element lens - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: proposed device comprises four separate lenses. First element is biconvex lens, second element is concave-plane lens with plane facing the image, third element is convex-plane with plane facing the image, or a positive meniscus with convex facing the object, and the fourth element is a negative meniscus with convex facing the object. Behind negative meniscus, there may be located one or several prisms and/or plane parallel plates. For radii of optical surfaces, index of refraction and coefficient of dispersion of lens material, thickness of negative meniscus and focal distance, relations are observed specified in claims.

EFFECT: higher polychromatic coefficient of modulation transmission.

3 cl, 2 dwg, 4 tbl

Description

The invention relates to optical instrumentation and can be used in various optical systems, for example, in visual and infrared systems.

Known four-lens photographic telephoto lens (Swiss patent No. 339753, NKI 42 N, 4/10, publ. 1959, figure 5), containing two components, the first of which (along the rays) is positive, consisting of two bonded lenses - biconvex and biconcave, and a positive single meniscus, convex to the subject; and the second component is a single negative meniscus facing concavity to the subject. This lens has a focal length of 135 mm and a relative aperture of 1: 4.

However, this telephoto lens, recalculated to a focal length of 220 mm with a relative aperture of 1: 5.5 and an angular field in the space of objects 2W = 2.6 degrees, has insufficient image quality (for example, for a wavelength of 546 nm, transverse aberration for a point on the axis, it is 0.0122 mm, and for the edge of the angular field, the transverse aberration in the meridional section is 0.0236 mm and in the sagittal section 0.0122 mm, the meridional astigmatic segment is 0.178 mm, and the sagittal astigmatic segment is 0.053 mm).

The closest analogue to the claimed technical solutions is the lens (RF patent No. 2239212, G02B 9/12, publ. 2004), containing three components, the first of which is two-lens, glued from a biconvex and plano-concave lenses, the plane facing to the image, the second and third components are the positive and negative menisci, convex to the subject, and there are relations:

;

;

;

;

0.45 <R ₄ / R ₅ <0.6;

n ₁ = 1.615506;

n ₂ = 1.723166;

n ₃ = 1.615506;

n ₄ = 1.518294;

ν _i = 60.34;

ν ₂ = 29.29;

ν ₃ = 60.34;

ν ₄ = 63.83;

,

,

where: R ₁ , R ₂ , R ₄ , R ₅ are the radii of the first, second, fourth and fifth optical surfaces along the rays;

n ₁ , n ₂ , n ₃ , n ₄ - the refractive indices of the material for the line e of the first, second, third and fourth lenses along the rays;

ν ₁ , ν ₂ , ν ₃ , ν ₄ - the dispersion coefficients of the material for the line e of the first, second, third and fourth lenses along the rays;

d is the thickness of the negative meniscus;

f ^' is the focal length of the entire lens for line e.

However, this lens, recalculated to a focal length of 220 mm with a relative aperture of 1: 5.5 and an angular field in the space of objects 2W = 2.6 deg., Has insufficient image quality (for example, for a wavelength of 546 nm, transverse aberration for a point on the axis is 0.0006 mm, and for the edge of the angular field, the transverse aberration in the meridional section is 0.0165 mm, and in the sagittal section 0.00164 mm, the meridional astigmatic segment is 0.065 mm, and the sagittal astigmatic segment is 0.015 mm). The modulation transmission coefficients for this lens for the above focal length, relative aperture, and angular field are also insufficient, which indicates a corresponding insufficient image quality (for example, the polychromatic modulation transmission coefficient for a spatial frequency of 120 mm ^-1 in the spectral range from 435 nm up to 656 nm with weight coefficients for wavelengths equal to one, for a point on the axis 0.231; and for an angular field W = 1.3 degrees in the worst section, it is 0.103.

The objective of the invention is to increase the operational characteristics of the lens.

The technical result is an increase in image quality.

This is achieved by the fact that in a four-lens lens containing three components, the first of which along the rays is a two-lens one, consisting of a biconvex and plano-concave lenses, the plane facing the image, the second component being a single positive lens with one convex surface facing the subject, the third component is a single negative meniscus convex to the object, and the ratio of the radius of the first optical surface along the rays of the biconvex lens from the first component to the radius of its second ited modulus greater than 0.9 and less than 1.8; in contrast to the known component, both lenses are single in the first component, and the radius of the second optical surface along the rays of the biconvex lens from the first component is larger in absolute value than the radius of the first optical surface of the flat-concave lens, the radius of the first optical surface along the rays of the flat-concave lens from the first component is larger in absolute value the radius of the first optical surface of the second component, in addition,

1.4 <n ₁ <1.6;

1.47 <n ₂ <1.6;

1.4 <n ₃ <1.6;

63 <ν ₁ <95;

60 <ν ₂ <71;

63 <ν ₃ <95;

,

,

where: n ₁ , n ₂ , n ₃ , are the refractive indices of the material for line e of the first, second, and third lenses along the rays;

ν ₁ , ν ₂ , ν ₃ , are the dispersion coefficients of the material for line e of the first, second, and third lenses along the rays;

d is the thickness of the negative meniscus;

- фокусное расстояние всего объектива для линии е.

is the focal length of the entire lens for line e.

In this case, the second component can be made in the form of a convex-flat lens, and the relations

1.63 <n ₄ <1.68;

46 <ν ₄ <58,

where n ₄ , ν ₄ is the refractive index and the dispersion coefficient of the material for line e of the fourth lens along the rays;

In addition, the second component can be made in the form of a positive meniscus, in which the ratio of the radius of the first optical surface along the rays to the radius of its second optical surface is more than 0.2 and less than 0.45.

Figure 1 presents the optical diagram of the proposed lens with a convex-flat lens in the second component, figure 2 - with a meniscus.

The four-lens lens (Fig. 1) consists of four single lenses sequentially located along the rays from the subject, the first of which is a biconvex lens 1, the second is a flat-concave lens 2 facing the image, the third is a convex-flat lens 3 facing the plane image, in the second embodiment (figure 2) is a positive meniscus 5, convex to the subject; the fourth is negative meniscus 4, convex to the subject. Behind the negative meniscus 4 there may be one or more prisms and (or) plane-parallel plates. In this case, the aperture diaphragm is located at a distance of 0.1 mm behind the lens 3, but can be located in another place.

In the second embodiment of FIG. 2, the third lens is made in the form of a positive meniscus 5, convex to the object. In this case, the aperture diaphragm is located at a distance of 0.1 mm behind the lens 5, but can be located in another place.

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, 4 (in the second case, 1, 2, 5, 4) and forms image of an object in the plane of the best setup in which an optical radiation receiver (not shown) is installed.

In accordance with the proposed solution, lenses were calculated for both versions corrected in the spectral range from 435 nm to 656 nm. The main calculated wavelength is 546 nm (line e).

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

Characteristics of the calculated lens:

focal length 220.14 mm relative hole 1: 5.5 angular field in the space of objects 2.6 degrees back focal length 63.43 mm back focal length without plane parallel plate 156.47 mm

For this lens, the ratio of the radius of the first optical surface along the rays of the biconvex lens from the first component to the radius of its second surface is equal to 1.4456 in absolute value.

Table 1 Radii, mm Thickness mm Glass mark Refractive index n _e Coeff. variances ν _e Light diameter mm R ₁ = 143.56 40 d ₁ = 8 Ok4 1,4485 91.53 R ₂ = -99,306 39.8 d ₂ = 0.9 one R ₃ = -87.324 39.6 d ₃ = 4 K8 1,518294 63.83 R ₄ = ∞ 39.5 d ₄ = 0.85 one R ₅ = 66.83 39,4 d ₅ = 7 Ok4 1,4485 91.53 R ₆ = ∞ 38.6 d ₆ = 23 one R ₇ = 64,712 31,2 d ₇ = 3 TK21 1.659961 50.81 R ₈ = 41.6 29.8 d ₈ = 20 one R ₉ = ∞ 27.6 d ₉ = 112.64 BK6 1,542136 59.38 R ₁₀ = ∞ 18.2

The relations are satisfied:

n ₁ = 1.4485;

n ₂ = 1.518294;

n ₃ = 1.4485;

n ₄ = 1.659961;

ν ₁ = 91.53;

ν ₂ = 63.83;

ν ₃ = 91.53;

ν ₄ = 50.81;

.

.

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

Characteristics of the calculated lens:

focal length 220.34 mm relative hole 1: 5.5 angular field in the space of objects 2.6 degrees back focal length 62.94 mm back focal length without plane parallel plate 159.28 mm

For this lens, the ratio of the radius of the first optical surface along the rays of the biconvex lens from the first component to the radius of its second surface is modulo 1. The ratio of the radius of the first optical surface along the rays of the second component to the radius of its second optical surface is 0.3542. The relations are satisfied:

n ₁ = 1.4485;

n ₂ = 1.518294;

n ₃ = 1.4485;

ν ₁ = 91.53;

ν ₂ = 63.83;

ν ₃ = 91.53;

.

.

table 2 Radii, mm Thickness mm Mark
glass Indicator
refraction n _e Coeff.
variances ν _e Light diameter mm R ₁ = 74.818 40 d ₄ = 7.85 Ok4 1,4485 91.53 R ₂ = -74,718 39.7 d ₂ = 4.6 one R ₃ = -64,428 37.6 d ₃ = 3 K8 1,518294 63.83 R ₄ = ∞ 37.1 d ₄ = 0.5 one R ₅ = 35.319 36,4 d ₅ = 7 Ok4 1,4485 91.53 R ₆ = 99.772 34.8 d ₆ = 5.5 one R ₇ = 68,554 31,2 d ₇ = 3 K8 1,518294 63.83 R ₈ = 27.983 29.4 d ₈ = 23.3 one R ₉ = ∞ 27 d ₉ = 112.64 BK6 1,542136 59.38 R ₁₀ = ∞ 17.9

Table 3 shows the aberrations for the wavelength of 546 nm of the calculated lens options in comparison with the closest analogue.

Table 4 shows the polychromatic modulation transmission coefficients for a spatial frequency of 120 mm ^-1 for the spectral range from 435 nm to 656 nm, calculated at weighting coefficients at wavelengths equal to unity of the calculated lens options in comparison with the closest analogue. Lens - the closest analogue is counted at a focal length of 220 mm with a relative aperture of 1: 5.5.

Table 3 Type of aberration The closest analogue The proposed lens according to the first embodiment, (no more) The proposed lens according to the second option, (no more) Transverse spherical aberration for a point on the axis -0,0006 mm -0.0029 mm -0.0029 mm Transverse aberration of a wide inclined beam in the meridional section for the angular field in the space of objects 2W '= 2.6 deg. -0.0165 mm -0.01 mm -0.004 mm Transverse aberration of a wide inclined beam in a sagittal section for an angular field in the space of objects 2W '= 2.6 degrees. -0.00164 mm -0.0046 mm -0.00365 mm The meridional astigmatic segment X ' _m for the angular field in the space of objects 2W' = 2.6 degrees. - 0,065 mm -0.0159 mm -0.00857 mm Sagittal astigmatic segment X ' _s for the angular field in the space of objects 2W' = 2.6 degrees. - 0.015 mm -0.0268 mm - 0.0147 mm Distortion for the angular field in the space of objects 2W '= 2.6 degrees. 0.075% 0.019% 0.022%

Table 4 Corner points of the field in the space of objects Modulation Gain The closest analogue The proposed lens in the first embodiment The proposed lens according to the second option Center W = 0 deg. 0.231 0.521 0.526 Inclined beam W = 1.3 deg. 0.103 0.475 0.513

Thus, as a result of the proposed solution, a technical result is obtained: a four-lens lens with improved image quality is created.

Claims (3)

1. A four-lens lens containing three components, the first of which is a two-lens lens along the rays, consisting of a biconvex and plano-concave lenses, the plane facing the image, the second component being a single positive lens with one convex surface facing the subject, and the third component being a single the negative meniscus convex to the object and the ratio of the radius of the first optical surface along the rays of the biconvex lens from the first component to the radius of its second surface modulo more than 0.9 and less than 1.8, characterized in that in the first component both lenses are single, and the radius of the second optical surface along the rays of the biconvex lens from the first component is modulo larger than the radius of the first optical surface of the plano-concave lens, the radius of the first optical surface along the rays of the plano-concave lens the modulus of the first component is greater than the radius of the first optical surface of the second component, in addition,
1.4 <n ₁ <1.6,
1.47 <n ₂ <1.6,
1.4 <n ₃ <1.6,
63 <ν ₁ <95,
60 <ν ₂ <71,
63 <ν ₃ <95,
0.005 <d / f '<0.1,
where n ₁ , n ₂ , n ₃ , are the refractive indices of the material for line e of the first, second, and third lenses along the rays;
ν ₁ , ν ₂ , ν ₃ , are the dispersion coefficients of the material for line e of the first, second, and third lenses along the rays;
d is the thickness of the negative meniscus;
f 'is the focal length of the entire lens for line e. 2. The four-lens lens according to claim 1, characterized in that the second component is made in the form of a convex-flat lens and there are relations:
1.63 <n ₄ <1.68,
46 <ν ₄ <58,
where n ₄ , ν ₄ is the refractive index and the dispersion coefficient of the material for the line e of the fourth lens along the rays. 3. The four-lens lens according to claim 1, characterized in that the second component is made in the form of a positive meniscus, in which the ratio of the radius of the first optical surface along the rays to the radius of its second optical surface is more than 0.2 and less than 0.45.

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