RU2328022C2 - Objective lens with outrigger entrance pupil - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: objective lens includes five components. First component, single meniscus lens with concavity directed to an object, and second component, a single convex-convex lens, form first optic unit I; third component, two single negative meniscus lenses with their convexities directed to each other, form second optic unit II; fourth component, a single convex-convex lens, and fifth component, a single negative meniscus lens with concavity directed the image, form third optic unit III. Optical powers of lenses, units and objective lens correlate according to the invention formula.

EFFECT: wider functional capabilities due to the maintenance of operation in UV spectrum with simultaneous support of telecentric ray path in the image space.

2 cl, 1 dwg, 1 app

Description

The invention relates to optical instrumentation and can be used in the optical industry and, in particular, for the control of surface microdefects.

The main requirements for the lens are:

- UV region of the spectrum;

- remote entrance pupil at a distance of at least 0.5 f ', where

f 'is the focal length of the lens;

- telecentric ray path in the image space;

- rear working distance of more than 0.5 ÷ 0.6f ';

- linear field of the image 2y '> 0.25f';

- relative aperture of more than 1: 2;

- diffraction-limited image quality;

- distortion - less than 0.2%.

Known fast lens with a remote entrance pupil [1], containing four components, the first of which is a single positive lens, the second contains positive and negative menisci facing concavity to the subject, the third is a single biconvex lens, and the fourth component is positive.

To increase the relative aperture and improve the image quality of the lens, the first component is made in the form of a meniscus facing concavity to the object, the second component is made of single menisci, the fourth component is glued from biconvex and biconcave lenses.

A long-focus lens with a remote entrance pupil [2] is known, containing four components, of which the first component is glued from a biconcave and positive lenses, the second component is a single positive lens, and the third and fourth components are glued.

To improve the image quality and increase the exit pupil extension to the value s ₁ = 0.6-0.7 f ', the positive lens of the first component is made biconvex, the second component is made as a biconvex lens, the third component is glued from a biconvex lens and a negative meniscus, and the fourth component consists of a biconcave and positive lens, where f 'is the focal length of the lens.

Known fast lens with a remote entrance pupil [3], containing four positive components, the first and second of which are double-glued, the third is a biconvex lens, the fourth is glued from the positive and negative lenses.

An increase in the relative aperture, an increase in the extension of the entrance pupil, and an increase in image quality are achieved by the fact that the first component has positive and negative menisci convex to the object, the first component is made of a biconvex lens and negative meniscus, the second is made of biconcave and biconvex lenses, in the fourth the positive lens component is biconvex, and the negative lens is biconcave.

A known lens with a remote entrance pupil [4], which relates to optical instrumentation and can be used to build television surveillance systems.

The lens contains five components, the first of which is made in the form of a positive double-glued lens, the second is in the form of a single biconcave lens, the third is in the form of a single positive lens, the fourth is in the form of a positive lens, and the fifth is in the form of a positive lens and glued from a biconvex and biconcave lenses.

The entrance pupil of the lens is made relative to its first surface and the aperture diaphragm is placed in it.

The specified construction of the lens provides an increase in its relative aperture while increasing the angular field and maintaining high image quality.

A common drawback of these lenses is:

- the inability to work in the UV region of the spectrum with wavelengths less than 300 nm;

- lack of telecentric ray path in the image space;

- small back working segment;

- image quality does not match the diffraction-limited system.

Closest to the claimed technical solution is a fast lens with a remote entrance pupil [5], containing five components, the first of which is a single-lens component, the second is a single-lens positive, the third is a two-lens negative component, the fourth is a single biconvex lens and the fifth is a single negative lens . In this case, the total optical power of the first and second components is positive, the third component is negative, the fourth and fifth are negative.

The disadvantages of the lens adopted for the prototype are:

- the inability to work in the UV region of the spectrum due to the use of conventional brands of lens glasses;

- lack of telecentric ray path in the image space;

- a small rear working segment, less than 0.2f ', which limits its use.

The main objective to which the invention is directed is to expand the functionality of the lens by ensuring its operation in the ultraviolet region of the spectrum for wavelengths less than 300 nm while ensuring the telecentric path of the rays in the image space, high image quality and minimal distortion.

To solve this problem, a lens with a remote entrance pupil is proposed, which, like the prototype, contains the first single-lens component, the second positive single-lens component, the third negative two-lens component, the fourth component made in the form of a single biconvex lens and the fifth component in the form of a single negative lens .

Unlike the prototype, the first and second components form the first optical node I, the third component forms the second optical node II, while the optical forces of the first and second optical nodes φ _I and φ _II satisfy the condition:

φ _I = -φ _II = (0.6 ÷ 0.7) φ,

φ _I + φ _II <0,06φ, where φ is the optical power of the entire lens, the distance between nodes d satisfies the condition:

d = (0.3 ÷ 0.4) / φ, while in the first optical node I, the first lens is made in the form of a meniscus facing the concavity to the object, and the second lens is in the form of a biconvex, with the optical powers of the lenses φ _I1 and φ _I2 satisfy the condition:

φ _I1 = - (1,5 ÷ 1,65) φ,

φ _I2 = (0.5 ÷ 0.65) φ,

the second optical node is made of two single negative menisci, convex to each other, while the optical power of the lenses satisfy the condition:

φ _{II, 1} = - (0.01 ÷ 0.02) φ,

φ _{II, 2} = - (0.5 ÷ 0.6) φ,

the fourth and fifth components form the third optical node III, with a third optical power, with φ _III = (1 ÷ 1.1) φ, in addition, the III optical node is made of a biconvex lens and a negative meniscus facing concavity to the image, the optical power of the lenses satisfy the condition:

φ _{III, 1} = φ,

φ _{III, 2} = - (0.12 ÷ 0.2) φ.

In addition, all lenses are made of quartz glass.

The essence of the invention lies in the fact that, thanks to the proposed design of the lens, consisting of three optical nodes, each of which is made of two single lenses, the optical forces of which satisfy the condition:

φ _I = -φ _II = (0.6 ÷ 0.7) φ,

φ _I + φ _II <0.06φ,

d = (0.3 ÷ 0.4) / φ,

φ _III = (1 ÷ 1,1) φ.

the entrance pupil is extended to a distance of more than 0.5 f ', the value of the posterior segment is more than 0.5-0.6 f' and the telecentric course of the main rays in the image space.

This is achieved due to the fact that I and II optical nodes form a system close to the afocal (φ _I + φ _II <0.06φ) telescopic system of the Gallileum type with an increase of about - 1.

In this case, the optical power of the entire lens is provided by the third node, for which φ _III ≃φ.

Close to the afocal system of I and II optical nodes, the system performs two main functions:

1. Moves the front focus of the third optical node into the space of objects in front of the first optical node at a distance of not less than 0.5 f '. The entrance pupil of the lens is combined with this plane, which ensures telecentric, i.e. parallel, optical axis ray path in the image space.

2. It is a corrector for aberrations of the third node.

The third node with the entrance pupil, combined with the front focus, introduces a positive wave spherical negative coma and positive astigmatism.

Whereas a system consisting of I and II optical nodes has aberrations equal in magnitude and opposite in sign.

The choice of the optical powers of the lenses I and II of the optical nodes and their configurations provides the necessary removal of the main planes and foci of the nodes, which provides an afocal system with an increase close to unity, and the necessary value of aberrations in magnitude and sign for the correction of aberrations of the III optical node. The choice of optical forces and lens configurations of the III optical node provides a large value of the rear working segment.

To ensure the operation of the lens in the UV spectral region, the lens material is quartz glass. To correct chromatic aberrations in a narrow UV spectral range, the optical forces of the lenses satisfy the condition:

those. the algebraic sum of optical forces is close to zero.

Thus, the combination of the above features allows us to solve the problem.

The essence of the proposed utility model is illustrated by the drawing, which shows the optical scheme of the lens with a remote entrance pupil and the Appendix, which shows the design parameters and optical characteristics of the lens.

The proposed optical system of the lens contains six lenses.

The first and second lenses form the I optical node, the third and fourth lenses form the II optical node and the fifth and sixth - III optical node.

I optical node has an optical power of φ _I = -φ _II = (0.6 ÷ 0.7) φ, consists of a meniscus 1 facing the concave object of a biconvex lens 2, while their optical forces satisfy the condition:

φ _I1 = - (1,5 ÷ 1,65) φ,

φ _I2 = (0.5 ÷ 0.65) φ.

II optical node has optical power - φ _II = (0.6 ÷ 0.7) φ, consists of negative menisci 3 and 4, convex to each other, while their optical forces satisfy the condition:

φ _{II, 1} = - (0.01 ÷ 0.02) φ,

φ _{II, 2} = - (0.5 ÷ 0.6) φ.

III optical node has an optical power φ _III = (1 ÷ 1,1) φ, consists of a biconvex lens 5 and a negative meniscus 6, facing a concavity to the image, while their optical forces satisfy the condition:

φ _{III, 1} = φ,

φ _{III, 2} = - (0.12 ÷ 0.2) φ.

All lenses are made of quartz glass.

The proposed lens works as follows.

The lens is located at infinity.

The optical nodes I and II (lenses 1, 2, 3, and 4) depict the object at a great distance from the last surface of the lens 4.

The optical node III (lenses 5 and 6) redesign it into a plane close to the focal plane of the optical node III.

The entrance pupil is located at a distance of more than 0.5 f 'in front of the first surface of the lens, and the image of the infinitely distant lens is in the focal plane of the lens, located at a distance of 0.5 ÷ 0.6 f' from the last surface of the lens.

The advantages of the proposed lens include the expansion of its functionality by ensuring its operation in the UV spectral region with wavelengths less than 300 nm while providing a telecentric path of rays in the image space.

Providing the removal of the entrance pupil to a distance of more than 0.5f 'allows you to install optical scanning elements, masks, phase and amplitude filters, etc. in its plane.

With the rear working distance of more than 0.5 ÷ 0.6 f ', it is possible to install lighting devices between the object and the lens when working in reflected light or when working in the reverse direction of rays, receivers, the sensitive surface of which is located deep inside its structure, etc. .

In addition, the proposed lens achieved diffraction-limited image quality and distortion of less than 0.2% for a linear image field of at least 0.25 f 'with a relative aperture of at least 1: 2.

INFORMATION SOURCES

1. Russian Federation, copyright certificate No. 1642426, IPC: 5 G02B 11/34, 1991

2. Russian Federation, copyright certificate No. 1615659, IPC: 5 G02B 9/34, 1991

3. Russian Federation, copyright certificate No. 1578679, IPC: 5 G02В 9/64, 11/32, 1990

4. Russian Federation patent No. 2053530, IPC: 6 G02B 9/60, 1996

5. Russian Federation, patent No. 2053531, IPC: 6 G02B 9/60, 1996 - prototype.

Claims (2)

1. The lens with a remote entrance pupil, containing the first single-lens component, and the second single-lens positive component, the third two-lens negative component, the fourth component made in the form of a single biconvex lens, and the fifth component in the form of a single negative lens, characterized in that the first and the second components form the first optical node I, the third component forms the second optical node II, while the optical forces of the first and second optical nodes φ _I and φ _II satisfy the condition: φ _I = -φ _II = (0.6 ÷ 0.7) φ, φ _I + φ _II <0.06φ, where φ is the optical power of the entire lens, the distance between nodes d satisfies the condition: d = (0.3 ÷ 0.4) / φ, at the same time, in the first optical node I, the first lens is made in the form of a meniscus facing concavity to the object, and the second lens is in the form of a biconvex, while the optical forces of the lenses φ _I1 and φ _I2 satisfy the condition: φ _I1 = - (1,5 ÷ 1,65) φ, φ _I2 = (0.5 ÷ 0.65) φ, the second optical node is made of two single negative menisci, convex to each other, while the optical power of the lenses satisfy the condition: φ _{II, 1} = - (0.01 ÷ 0.02) φ, φ _{II, 2} = - (0.5 ÷ 0.6) φ, the fourth and fifth components form the third optical node III, with optical power φ _III , while φ _III = (1 ÷ 1,1) φ, in addition, the III optical unit is made of a biconvex lens and a negative meniscus facing concavity to the image, while the optical forces of the lenses satisfy the condition: φ _{III, 1} = φ, φ _{III, 2} = - (0.12 ÷ 0.2) φ. 2. The lens according to claim 1, characterized in that all the lenses of the lens are made of quartz glass.