RU2549915C1 - Four-element lens - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: lens consists of two components separated by an air gap. The first component on the beam path is glued from a biconvex and a biconcave lens, the second component consists, on the beam path, of a separate biconcave lens and a separate biconvex lens. The radii of the optical surfaces of the biconvex lens of the second component are equal in magnitude and the following relationships hold: 1.63<n₁=n₄<1.7; 1.7<n₂<1.9; where n₁, n₂, n₄ are refraction indices of the material on the beam path of the first, second and fourth lenses for the spectral line D.

EFFECT: high aperture ratio, larger field angle in the object space and high technological effectiveness.

1 dwg, 2 tbl

Description

The present invention relates to optical instrumentation and can be used as a photographic lens.

Petzval’s four-lens portrait photographic portrait lens is known, described in the publication of M. Berek “Fundamentals of Practical Optics”, translation from German, ed. Acad. S.I. Vavilova, State Technical and Theoretical Publishing House, Moscow, Leningrad, 1933, Fig. 31, 38, p. 35, 36, 59, 60, 61, Table 1, consisting of two components separated by an air gap, the first of which along the rays - glued from a biconvex and biconcave lenses, the second - consisting along the rays of a single negative meniscus, turned concavity to the image and a single biconvex lens, and there are relations:

n ₁ = n ₄ = 1.517;

n ₂ = 1,575;

where n ₁ , n ₂ , n ₄ are the refractive indices of the material along the rays of the first, second and fourth lenses.

However, this lens has an insufficient relative aperture of 1: 3.4; insufficient angular field in the space of objects with the passage of the main beam 2W = 24 degrees. and lack of manufacturability, since all the radii of the optical surfaces of this lens are different and there are no flat optical surfaces. In addition, for this lens, the entrance pupil, the aperture diaphragm, is spaced L = 0.102f, where f is the focal length in front of the first optical surface to correct the second Seidel sum, which increases the longitudinal dimensions of the entire lens.

The four-lens photographic portrait lens of Petzval is known, described in the reference book “Computational Optics” under the general ed. M.M. Rusinova, Leningrad, “Mechanical Engineering”, Leningrad Branch, 1984, Fig. 34.1, Table 34.1, p. 355, 356, consisting of two components separated by an air gap, the first of which is glued from biconvex and biconcave along the rays lenses, the second - consisting along the rays of a single negative meniscus, facing concavity to the image, and a biconvex lens, and there are relations:

n ₁ = n ₄ = 1.5181;

n ₂ = 1.5783,

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

Entrance pupil - the aperture diaphragm in the given lens coincides with the first surface of the lens. However, this lens has an insufficient relative aperture of 1: 3, an insufficient angular field in the space of objects 2W = 30 degrees. and lack of manufacturability, since all the radii of the optical surfaces of this lens are different and there are no flat optical surfaces.

The objective of the invention is to provide a lens with enhanced performance.

The technical result is an increase in the relative aperture, an increase in the angular field in the space of objects and an increase in manufacturability.

This is achieved by the fact that in a four-lens lens, consisting along the rays of two components separated by an air gap, the first of which is glued from a biconvex and negative lenses, the second one consists of a single negative lens and a single biconvex lens, in contrast to the known negative lens in the first component is made concave flat, the negative lens in the second component is biconcave, the radii of the optical surfaces of the biconvex lens of the second component are equal in magnitude and and eyut following relations:

1.63 <n ₁ = n ₄ <1.7;

1.7 <n ₂ <1.9,

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

The drawing shows an optical diagram of a four-lens.

The four-lens lens consists of two components along the rays, the first of which is glued from a biconvex lens 1 and a concave plane lens 2; the second - consisting of a single biconcave lens 3 and a single biconvex lens 4. The aperture diaphragm is located at a distance of 3 mm in front of the lens 3.

Four-lens works as follows.

The luminous flux emanating from the plane of objects at infinity passes through a four-lens lens and is displayed in the plane of the best setting in which the photodetector (not shown) is located.

As a specific example of the invention, a four-lens lens is calculated, corrected in the spectral range from 435 nm to 656 nm with the structural data presented in table 1.

The calculated four-lens lens has the following characteristics:

The focal length of the lens f ' 84.01 mm Relative hole 1: 2.2 Angular field in the space of objects 32 deg. Linear field in image space 2U '= 43.26 mm Back focal length 43.22 mm

For this lens, there are relations:

1.63 <(n ₁ = n ₄ = 1.6568) <1.7;

1.7 <(n ₂ = 1.755) <1.9.

Table 1 Radii, mm Thickness mm Glass mark Refractive index, n _D Coeff. variance, ν _D Light diameter mm R ₁ = 43.05 37.5 d ₁ = 13 Tk21 1.6568 51.11 R ₂ = -66.53 35,2 d ₂ = 4 TF5 1,755 27.52 R ₃ = ∞ 33,2 d ₃ = 21 one R ₄ = -45.29 23.1 d ₄ = 8 LF5 1,5749 41.3 R ₅ = 26.3 21.5 d ₅ = 3.4 one R ₆ = 42.17 22.4 d ₆ = 8.8 Tk21 1.6568 51.11 R ₇ = -42.17 22.4 one

table 2 Type of aberration The proposed four-lens lens (no more) Transverse spherical aberration for a point on the axis with a relative aperture of 1: 2.2 0.03 mm Transverse aberration of a wide inclined beam in the meridional section for an angular field of 2W = 32 deg. 01479 mm Transverse aberration of a wide inclined beam in a sagittal section for an angular field of 2W = 32 deg. 0.0244 mm The meridional astigmatic segment X _m for the angular field 2W = 32 degrees. -2.364 mm Sagittal astigmatic segment X _s for an angular field 2W = 32 deg. 0.2449 mm Distortion for the angular field 2W = 32 deg. 2.34%

Table 2 shows the aberrations for λ = 0.54607 μm for the proposed four-lens objective according to a specific embodiment.

The proposed lens has one flat optical surface in the first component and the radii of the spherical optical surfaces of the biconvex lens of the second component with the same modulus, which characterizes its high manufacturability. Thus, a technical result is obtained: a four-lens lens with a higher relative aperture, an angular field in the space of objects with increased adaptability is created.

Claims (1)

A four-lens lens consisting of two components separated by an air gap, the first of which along the rays is glued from a biconvex and negative lenses, the second is consisting of a single negative lens and a single biconvex lens along the rays, characterized in that the negative lens in the first component is made concave, the negative lens in the second component is biconcave, the radii of the optical surfaces of the biconvex lens of the second component are equal in magnitude and osheniya:
1.63 <n ₁ = n ₄ <1.7;
1.7 <n ₂ <1.9,
where n ₁ , n ₂ , n ₄ are the refractive indices of the material along the rays of the first, second and fourth lenses for the spectrum line D.