RU2346312C1 - Large-aperture lens - Google Patents

Abstract

FIELD: physics; optics.

SUBSTANCE: lens consists of two components installed in succession along the beam path. The first component is double-lens, which consists of a double-convex lens and a negative meniscus lens glued together; convex side of the latter is at the image side. The second component is a single positive meniscus lens with its concave side to the image. |R₂|/|R₄|=1, |R₃|/|R₅|=1, where R₂, R₃, R₄, R₅ - radii of curvature of the 2^nd, the 3^rd, the 4^th and the 5^th optical faces, respectively, along the beam path.

EFFECT: increased focal distance, aperture ratio and enhanced producibility together with high image quality.

3 cl, 1 dwg

Description

The present invention relates to optical instrumentation and can be used in various visual and other optical systems.

Known fast lens (US patent No. 4753524, G02B 9/06, 9/12, NKI 350/480, publ. 1989), containing two components. The first component along the rays is a positive two-lens one, glued from a biconvex lens and a negative plano-concave lens, the plane facing the image. The second component is a single positive meniscus facing concavity to the image.

This lens has insufficient image quality for a point on the axis (transverse spherical aberration for a focal length of 100 mm is 0.04 mm); insufficient angular field of view 2W = 1.4 deg., and lack of manufacturability, since the lens has different radii of the optical surfaces, and therefore, it is necessary to manufacture its own test glass and processing tool on each optical surface.

The closest analogue to the claimed technical solution is a fast lens (G. G. Slyusarev. “Calculation of optical systems”, Leningrad, “Engineering”, Leningrad branch, 1975, p. 110, table I. 34), containing two components . The first component along the rays is a positive two-lens one glued from a biconvex lens and a negative meniscus convex to the image. The second component is a single positive meniscus facing concavity to the image.

For this lens, the ratio is:

| R ₃ | / | R ₁ | = 2.54

n ₂ = 1.7398

where R ₁ is the radius of curvature of the first optical surface along the rays;

R ₃ is the radius of curvature of the third optical surface along the rays;

n ₂ is the refractive index of the material of the second lens.

The refractive index n ₂ corresponds to the refractive index of the TF 4 glass for line D, and for line e, the refractive index is 1.746231.

However, the known fast lens has a small focal length equal to 64 mm, a small relative aperture of 1: 2.6, and a lack of manufacturability, since all its radii of the optical surfaces are of different sizes and, therefore, require the manufacture of a test glass and a processing tool for each optical surface.

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

The technical result is an increase in focal length, relative aperture and increased manufacturability with high image quality.

This is achieved by the fact that in a fast lens consisting of two components, the first component along the rays is a positive one glued from a biconvex lens and a negative meniscus convex to the image, the second component is a single positive meniscus facing concavity to the image, unlike known, there are relations:

| R ₂ | / | R ₄ | = 1

| R ₃ | / | R ₅ | = 1

| R ₃ | / | R ₁ | <1

1.75 <n ₂ <1.78

where R ₁ is the radius of curvature of the first optical surface along the rays;

R ₂ is the radius of curvature of the second optical surface along the rays;

R ₃ is the radius of curvature of the third optical surface along the rays;

R ₄ is the radius of curvature of the fourth optical surface along the rays;

R ₅ is the radius of curvature of the fifth optical surface along the rays;

n ₂ is the refractive index of the material of the second lens for line e.

The drawing shows an optical diagram of the proposed aperture lens.

A fast lens consists of two components sequentially located along the rays from the subject. The first component is positive, glued from a biconvex lens 1 and a negative meniscus 2, convex to the image; the second component is a single positive meniscus 3, facing concavity to the image. Behind the meniscus 3, a light filter, a plane-parallel plate (or plates) and a prism (or prisms) can be located.

The entrance pupil in the lens coincides with the first surface.

The proposed optical system works as a lens collecting from infinity, i.e., the light flux from an object located at infinity enters the lens, where it passes through lenses 1, 2, 3 and forms an image of the object in the plane of the best setup in which the optical radiation detector is installed ( not shown).

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

In accordance with the proposed solution, a fast lens was calculated, corrected for λ = 546 nm and achromatic for λ = 486 nm and λ = 656 nm.

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

Table 1 Radius mm Thickness mm Glass mark Refractive index n _e Coeff. variances ν _e Light diameter mm R ₁ = 382,426 41.7 d ₁ = 6.5 TK16 1,615192 58.09 R ₂ = -61.843 41.6 d ₂ = 3,5 TF5 1.761712 27.32 R ₃ = -197,359 41.7 d ₃ = 0.2 one R ₄ = 61.843 41.1 d ₄ = 4,5 TK16 1,615192 58.09 R ₅ = 197.359 40.5

Characteristics of the calculated lens:

focal length f ′ 100 mm back focal length 95.82 mm relative hole 1: 2.4 angular field of view 5 deg.

There is a ratio:

| R ₃ | / | R ₁ | = 0.516

Table 2 shows the aberration values for λ = 546 nm of the calculated version of the fast lens.

table 2 Type of aberration The value of aberration in the proposed lens (no more) Transverse spherical aberration for a point on the axis 0.008 mm with a relative aperture of 1: 2.4 Transverse aberration of a wide inclined beam in 0.079 mm meridional section for the field of view 2W = 5 deg. Transverse aberration of a wide inclined beam in 0.026 mm sagittal section for the field of view 2W = 5 deg. Meridional astigmatic segment X _m for -0.346 mm field of view 2W = 5 deg. Sagittal astigmatic segment X _s for the field -0.157 mm view 2W = 5 deg. Distortion for the field of view 2W = 5 deg. -0.019%

In the proposed lens there is a pairwise equality of the values of the radii of the optical surfaces on four surfaces, which increases the manufacturability of the lens, in addition, there is a large focal length and relative aperture.

Thus, as a result of the proposed solution, a technical result is obtained: a fast lens with an increased focal length of 100 mm, with an increased relative aperture of 1: 2.4 and increased manufacturability with high image quality is created.

Claims (3)

1. A fast lens consisting of two components, the first component along the rays - a positive, glued from a biconvex lens and a negative meniscus convex to the image, the second component - a single positive meniscus, facing concavity to the image, characterized in that there are relations
| R ₂ | / | R ₄ | = 1, | R ₃ | / | R ₅ | = 1,
where R ₂ is the radius of curvature of the second optical surface along the rays;
R ₃ is the radius of curvature of the third optical surface along the rays;
R ₄ is the radius of curvature of the fourth optical surface along the rays;
R ₅ is the radius of curvature of the fifth optical surface along the rays. 2. A fast lens according to claim 1, characterized in that there is a ratio
| R ₃ | / | R ₁ | <1,
where R ₁ is the radius of curvature of the first optical surface along the rays;
R ₃ is the radius of curvature of the third optical surface along the rays. 3. A fast lens according to claim 1 or 2, characterized in that the ratio
1.75 <n ₂ <1.78,
where n ₂ is the refractive index of the material of the second lens for the line e.