RU2384868C1 - Doublet objective lens - Google Patents

Abstract

FIELD: physics, optics.

SUBSTANCE: lens can be used in different optical systems, in visual and infrared systems. The objective lens consists of two lenses. The first lens is biconvex and the second is in form of a negative meniscus, whose convex side faces the image. Three relationships hold: |R₁|=|R₃|; |R₁|<|R₂|; 1.41<n₁<1.619; 1.54<n₂<1.79; where: R₁, R₂, R₃ are radii of the first, second and third optical surfaces on the beam path; n₁, n₂ are refractive indices of the material of the first and second lenses on the beam path for line e.

EFFECT: increased focal distance with increase in technological effectiveness and high image quality.

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Description

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

A well-known two-lens lens - achromat (French Application No. 2025476, class G02B 13/14, publ. 1970), operating in the infrared range from 8 to 14 microns, consisting of a separate biconvex lens and a negative meniscus convex to the image. The lenses of the lens are made of CsBr and ZnS materials with refractive indices of 1.66251 and 2.1986. The lens has a small focal length of 100 mm and lack of manufacturability, as The use of different reference test glasses for each optical surface is required.

The closest analogue to the claimed technical solution is a two-lens lens (Russian Patent No. 2316795, class G02B 9/10, publ. 2008), consisting of a biconvex lens located along the beam and a negative meniscus convex to the image, in which the ratio the first along the rays of the radius of the meniscus lens to its second radius is less than 0.8, and there are relations:

1.46 <n ₁ <1.63;

1.66 <n ₂ <1.78;

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

This lens has a small focal length of 150.75 mm.

The task of the invention is the creation of a technologically advanced two-lens lens with enhanced performance characteristics.

The technical result is an increase in focal length with high adaptability and high image quality.

This is achieved by the fact that in a two-lens lens, consisting of a biconvex lens located along the rays and a negative meniscus convex to the image, in contrast to the known relation,

| R ₁ | = | R ₃ |;

| R ₁ | <| R ₂ |;

1.41 <n ₁ <1.619;

1.54 <n ₂ <1.79;

where R ₁ , R ₂ , R ₃ are the radii of the first, second and third optical surfaces along the rays;

n ₁ , n ₂ are the refractive indices of the material of the first and second lenses along the rays for line e.

The drawing shows an optical diagram of the proposed lens.

A two-lens lens consists of biconvex lens 1 located along the rays and a negative meniscus 2 convex to the image. The radius of the first along the rays of the optical surface of the biconvex lens 1 is equal in absolute value to the radius of the first along the rays of the optical surface of the negative meniscus 2, in addition, the radius of the first along the rays of the optical surface of the lens 1 is less than the radius of curvature of its second optical surface.

The lens works as follows: the light flux from an object located at infinity enters the lens, where it passes through lenses 1, 2 and forms an image of the object in the plane of the best setup in which the optical radiation receiver (not shown) is installed.

In accordance with the proposed solution, two two-lens lenses are designed.

The first lens is corrected for λ = 520 nm and for λ = 900 nm and achromatized for these wavelengths. The lens can work as a collimator. The lens operates in the visible and near infrared spectral range.

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

The entrance pupil is located at a distance of 208.7 mm in front of the first optical surface, but may be in another place.

Characteristics of the calculated first lens:

focal length 1002.45 mm relative hole 1: 19.2 field of view angle 1 degree 36 minutes

The lens has the following aberrations for λ = 520 nm:

- transverse spherical aberration for a point on the axis no more than 0,0028 mm - transverse aberration of a wide inclined beam in the meridional section for the field of view 2W = 1 deg. 36 minutes no more than 0,016 mm - transverse aberration of a wide inclined beam in the sagittal section for the field of view 2W = 1 deg. 36 minutes no more than 0,0068 mm - meridional astigmatic segment X _m no more than 0,357 mm - sagittal astigmatic segment X _s no more than 0,153 mm - distortion no more than 0,0066%

In the present invention:

| R ₁ | = | R ₃ | = 530.9;

n ₁ -1.615506;

n ₂ = 1.723166;

where R ₁ , R ₃ are the radii of the first and third optical surfaces along the rays;

n ₁ , n ₂ are the refractive indices of the material of the first and

the second lens along the rays for the line e.

The second lens is corrected for λ = 580 nm and for λ = 900 nm and achromatized for these wavelengths and can also work as a collimator. The lens operates in the visible and near infrared spectral range.

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

The entrance pupil is located at a distance of 188 mm in front of the first optical surface of the second lens, but can be located in another place.

Characteristics of the calculated second lens:

focal length 899.84 mm relative hole 1:18 field of view angle 1 degree 40 min

The lens has the following aberrations for λ = 580 nm:

- transverse spherical aberration for a point on the axis no more than 0,0061 mm - transverse aberration of a wide inclined beam in the meridional section for the field of view 2W = 1 deg. 40 min no more than 0,031 mm - transverse aberration of a wide inclined beam in the sagittal section for the field of view 2W = 1 deg. 40 min no more than 0,011 mm - meridional astigmatic segment X _m no more than 0, 423 mm - sagittal astigmatic segment X _s no more than 0,187 mm - distortion no more than 0,0003%

In the present invention:

| R ₁ | = | R ₃ | = 358,198;

n ₁ = 1.44754;

n ₂ = 1.575568;

where R ₁ , R ₃ are the radii of the first and third optical surfaces along the rays;

n ₁ , n ₂ are the refractive indices of the material of the first and second lenses along the rays for line e.

Thus, as a result of the proposed solution, a technical result is obtained: a two-lens lens with an increased focal length with increased adaptability with high image quality is created.

Claims (1)

A two-lens lens consisting of biconvex lenses located along the path and a negative meniscus convex to the image, characterized in that there are relations
| R ₁ | = | R ₃ |;
| R ₁ | <| R ₂ |
1.41 <n ₁ <1.619;
1.54 <n ₂ <1.79;
where R ₁ , R ₂ , R ₃ are the radii of the first, second and third optical surfaces along the rays;
n ₁ , n ₂ are the refractive indices of the material of the first and second lenses along the rays for line e.