RU2478996C1 - Three-element lens - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: three-element lens consists of three separate lenses arranged in series on the beam path, the first of which is a negative meniscus whose convex surface faces the object, the second is a positive lens whose first surface is convex and the third element is a negative meniscus whose convex surface faces the object. The second lens on the beam path can be biconvex.

EFFECT: longer focal distance and high image quality.

3 cl, 1 dwg, 2 tbl

Description

The invention relates to optical instrumentation and can be used in various optical systems, for example, in receiving channels operating with CCD arrays.

The well-known three-lens photographic telephoto lens “Tair-3” (D.S. Volosov, “Photographic Optics”, publishing house “Art”, Moscow, 1971, p. 461, table V.6, p. 466, Fig. V .12, a) containing two components, the first of which (along the rays) is positive, consisting of two single lenses - biconvex and negative, and the second component - negative single meniscus, convex to the object. This lens has a focal length of 300 mm and a relative aperture of 1: 4.5. However, this telephoto lens has an insufficient relative aperture and significant geometric vignetting - 40%.

The closest analogue to the claimed technical solution is a telescope lens (US patent No. 2158507, 88-57, publ. 1939, example 1, figure 1), containing two components, the first of which along the rays - two-lens, glued from biconvex and biconcave lenses, the second component is a single negative meniscus convex to the subject. In this lens, for the spectral line D, the refractive index of a biconvex lens is 1.5209; a biconcave lens - 1,6646 and a negative meniscus - 1,5163. However, this lens has an insufficient focal length of 96.3 mm and image quality. So, for a relative aperture of 1: 4.29 and an angular field in the space of objects 2W = 4 deg 10 min, the lens has a transverse aberration for a point on the axis minus 0.083 mm, a transverse aberration in the sagittal section minus 0.09 mm, a transverse aberration in the meridional section minus 0.1471 mm, for the spectrum line D.

The task of the invention is to increase the operational characteristics of a three-lens.

The technical result is an increase in focal length and improved image quality.

This is achieved by the fact that in a three-lens lens containing two components, the first of which along the rays is a two-lens one, which includes a negative and a positive lens, the first surface of a positive lens convex, the second component a single negative meniscus convex to the object, in unlike the known lenses of the first component are single, and the first of them is a negative meniscus convex to the subject

In addition, the second single lens along the rays of the first component can be made biconvex.

In addition, for the spectrum line D, the refractive index of a single negative lens of the first component can be more than 1.67 and less than 1.79, a single positive lens of the first component, respectively, more than 1.3 and less than 1.5 and a negative meniscus of the second component, respectively, more than 1, 6 and less than 1.71.

The drawing shows an optical diagram of the proposed three-lens.

A three-lens lens consists of two components sequentially located along the rays - a two-lens one, consisting of a single negative meniscus 1, convex to the object, and a single positive lens 2. The second component is a single negative meniscus 3, convex to the object. The aperture diaphragm is located at a distance of 35.72 mm behind lens 2, but can be located in another place.

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).

In accordance with the proposed solution, a three-lens lens was calculated, corrected in the spectral range from 589 nm to 800 nm. The basic calculated wavelength is 706.52 nm.

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

Characteristics of the calculated lens:

focal length 300.33 mm relative hole 1: 4.29 angular field in the space of objects 4 deg 10 min back focal length 49.29 mm

In the proposed lens for the line of the spectrum D, the refractive index of a single negative lens of the first component is equal to 1.6709; a single positive lens of the first component is equal to 1,447303; the negative meniscus of the second component is 1.6594.

Table 2 shows the aberrations for a wavelength of 589.3 nm for the lens of the closest analogue and for the proposed lens for a wavelength of 706.52 nm.

The proposed lens has an increased focal length of 300.33 mm compared to the closest analogue and enhanced image quality (especially for wide field inclined beams), which follows from Table 2.

Directly, this apochromat lens is designed to operate in the infrared range of the spectrum, which allows you to take pictures in a digital camera with special effects such as "Winter landscape with hoarfrost" under any weather conditions. The proposed lens in terms of the visible range of the spectrum can also be used as a photographic lens for a frame format of 24 × 18 mm ² , including for digital cameras.

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

Table 1 Radii, mm Thickness, m Glass mark Refractive index n _e Coeff. variances ν _e Light diameter mm R ₁ = 99.772 70 d ₁ = 6.2 Bf16 1.674385 47 R ₂ = 60,269 70 d ₂ = 0.4 one R ₃ = 59,295 70 d ₃ = 15 Ok4 1,4485 91.53 R ₄ = -2310,307 69.8 d ₄ = 223.15 one R ₅ = 22.03 28,2 d ₅ = 3.05 STK3 1.662237 57.09 R ₆ = 19.725 26.2

table 2 Type of aberration The closest analogue Proposed lens (no more) one 2 3 Transverse spherical aberration for a point on the axis for a relative aperture of 1: 4.29 -0.083 mm 0, 073 mm Transverse aberration of a wide inclined beam in the meridional section for the angular field in the space of objects 2W = 4 deg 10 min -0.1471 mm 0.072 mm Transverse aberration of a wide inclined beam in a sagittal section for an angular field in the space of objects 2W = 4 deg 10 min -0.09 mm 0.036 mm The meridional astigmatic segment X ' _m for the angular field in the space of objects 2W = 4 deg 10 min 0.0352 mm -0.021 mm Sagittal astigmatic segment X ' _s for the angular field in the space of objects 2W = 4 deg 10 min 0.01 mm -0.054 mm Distortion for the angular field in the space of objects 2W = 4 deg 10 min 0.086% 0.977%

Claims (3)

1. A three-lens lens containing two components, the first of which is a two-lens lens along the rays, including a negative and a positive lens, the first surface of a positive lens convex, the second component a single negative meniscus convex to the object, characterized in that the lens The first component is made single and the first of them is a negative meniscus convex to the subject. 2. The three-lens lens according to claim 1, characterized in that the second single lens of the first component along the rays is biconvex. 3. The three-lens lens according to claim 1, characterized in that for the line of spectrum D the refractive index of a single negative lens of the first component is more than 1.67 and less than 1.79, a single positive lens of the first component is more than 1.3 and less than 1.5, negative the meniscus of the second component is more than 1.6 and less than 1.71.