RU2357274C1 - Objective - Google Patents

Abstract

FIELD: instrument making.

SUBSTANCE: invention relates to optical instrument making and can be used in various optical devices, including, TV cameras incorporating a reception matrix. The objective consists of four lenses arranged along the beam, i.e. the first making the biconvex lens, the second making a biconcave lens, the third making a convexo-plane lens, the fourth making a convex-plane lens. The convexo-plane lens thickness-to-objective focal length ratio varies from 0.09 to 0.15. The following ratios exist in this case, i.e. 1.61 < n₁ = n₃ = n₄ <1.63, 1.6 < n₂ <1.673, where n₁, n₂, n₃, n₄ are the parametres of refraction of the material of the first, second, third and fourth lenses for line D. The third air interval-to-objective focal length ratio can make vary 0.001 to 001.

EFFECT: higher-quality image and ease of manufacture.

2 cl, 1 dwg

Description

The present invention relates to optical instrumentation and can be used in various optical devices, including in cameras operating with a receiving matrix.

A four-lens photographic lens is known (German patent No. 403706, 42h 4/05, publ. 1924), in which the first lens along the beam is biconvex, the second is biconcave, the third is biconvex and the fourth lens is a positive meniscus convex to the image .

However, this lens, calculated at a focal length of 78.05 mm, has a relative aperture of 1: 2.6 and a field of view angle of 2W = 9 degrees. It doesn’t have a high enough image quality (for example, the transverse spherical aberration for a point on the axis reaches 0.215 mm, and for wide inclined beams in the meridional and sagittal sections, it reaches 0.218 mm and 0.224 mm, respectively).

The closest analogue to the claimed technical solution is a photographic lens (German patent No. 440229, 42h 4/05, figure 2, publ. 1927), consisting of four single lenses, in which the first along the beam is a biconvex lens, the second biconcave, the third is a positive meniscus convex to the image, and the fourth lens is biconvex. The ratio of the thickness of the third lens to the focal length of the entire lens is 0.07; and the ratio of the size of the third air gap to the focal length of the entire lens is 0.015. In addition, there are equalities:

n ₁ = n ₃ = n ₄ = 1.60958,

n ₂ = 1.6733,

where n ₁ , n ₂ , n ₃ , n ₄ are the refractive indices of the material of the first, second, third and fourth components for line D.

The lens has a higher image quality than the lens according to German patent No. 403706.

This lens is close in design to the claimed one, however, calculated for a focal length of 78.05 mm, with a relative aperture of 1: 2.6 and a field of view angle of 2W = 9 degrees. it has insufficiently high image quality (for example, the transverse spherical aberration for a point on the axis reaches 0.0571 mm, and for wide inclined beams in the meridional and sagittal sections - 0.0431 mm and 0.0642 mm, respectively, astigmatism is significant - 0 , 11 mm) and lack of manufacturability, since it does not have flat optical surfaces.

The task of the invention is to create a lens with high image quality at a high level of manufacturability.

The technical result is determined by the task and represents an increase in image quality with a high level of adaptability of the lens.

This is achieved by the fact that in the lens, consisting of four single lenses, sequentially installed along the beam: biconvex, biconcave and two positive lenses, the equality n ₁ = n ₃ = n ₄ is observed. Moreover, the first of the two mentioned positive lenses is plano-convex, the second is convex. The ratio of the thickness of a plano-convex lens to the focal length of the entire lens is from 0.09 to 0.15. The relations are:

1.61 <n ₁ = n ₃ = n ₄ <1.63,

1,6 <n ₂ <1.673,

where n ₁ , n ₂ , n ₃ , n ₄ are the refractive indices of the material of the first, second, third and fourth lenses for line D.

In addition, the ratio of the size of the third air gap to the focal length of the entire lens can be from 0.001 to 0.01.

The drawing shows an optical diagram of the proposed lens.

The lens consists of four single lenses along the rays: the first is a biconvex lens 1, the second is a biconcave lens 2, the third is a convex lens 3, and the fourth is a convex lens 4. Behind lens 4 there can be a light filter and one or more plane-parallel plates or one or several prisms.

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 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 lens can also work in the reverse direction of the rays as a collimator.

In accordance with the proposed solution, a lens is calculated that is corrected in the spectral range from 480 to 660 nm.

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

Characteristics of the calculated lens:

focal length 78.05 mm relative hole 1: 2.6 field of view angle 9 deg. back focal length 67.98 mm

the entrance pupil coincides with the first surface.

Table 1 Radius mm Thickness mm Glass mark Refractive index
n _D Coeff. variance ν _D Light diameter mm R ₁ = 61.8 thirty d ₁ = 6.2 Tk14 1,613 60.57 R ₂ = -389.9 29.3 d ₂ = 17.9 one R ₃ = -33.11 24.1 d ₃ = 2.1 TF1 1.6475 33.86 R ₄ = 68.55 24.8 d ₄ = 7.8 one R ₅ = ∞ 27.9 d ₅ = 10.1 Tk14 1,613 60.57 R ₆ = -32.81 thirty d ₆ = 0.3 one R ₇ = 87.3 29.6 d ₇ = 4.7 Tk14 1,613 60.57 R ₈ = ∞ 29th

In the proposed lens, the ratio of the thickness of the third lens to the focal length of the entire lens is 0.1294; and the ratio of the magnitude of the third air gap to the focal length of the entire lens is 0.003844. In addition, the following equations are satisfied in the lens:

n ₁ = n ₃ = n ₄ = 1,613,

n ₂ = 1.6475,

where n ₁ , n ₂ , n ₃ , n ₄ are the refractive indices of the material of the first, second, third and fourth lenses for line D.

Table 2 shows the aberrations for the wavelength of 589.3 nm of the closest analogue, calculated at the focal length of 78.05 mm, and the proposed lens.

table 2 Aberration value Type of aberration The closest analogue Proposed lens Transverse spherical aberration for a point on the axis with a relative aperture of 1: 2.6 0.0571 mm 0.024 mm Transverse aberration of a wide inclined beam in the meridional section for the field of view 2W = 9 deg. 0.0431 mm 0.019 mm Transverse aberration of a wide inclined beam in a sagittal section for a field of view 2W = 9 deg. 0.0642 mm 0.028 mm The meridional astigmatic segment X ' _m for the field of view 2W = 9 deg. 0.0331 mm - 0,077 mm Sagittal astigmatic segment X ' _s for the field of view 2W = 9 degrees. -0.0766 mm - 0,094 mm Astigmatism for the field of view 2W = 9 deg. 0.11 mm 0.0167 mm Distortion for the field of view 2W = 9 deg. -0.0028% - 0,092%

In addition, the proposed lens has two flat optical surfaces, which provides it with high technology. The proposed lens has a higher image quality, which follows from table 2.

Thus, as a result of the proposed solution, a technical result is obtained: a lens is created for the spectral range from 480 to 660 nm with enhanced image quality with high technology.

Claims (2)

1. A lens consisting of four single lenses sequentially mounted along the beam: biconvex, biconcave, and two positive lenses, and n ₁ = n ₃ = n ₄ , characterized in that the first positive lens is plano-convex, the second is convex, the thickness ratio flat convex lens to the focal length of the entire lens is from 0.09 to 0.15; in addition, there are relations:
1.61 <n ₁ = n ₃ = n ₄ <1.63,
1.6 <n ₂ <1.673,
where n ₁ , n ₂ , n ₃ , n ₄ are the refractive indices of the material of the first, second, third and fourth lenses for line D. 2. The lens according to claim 1, characterized in that the ratio of the magnitude of the third air gap to the focal length of the entire lens is from 0.001 to 0.01.