RU2554274C1 - High-magnification plan-apochromatic microlens with increased working distance - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: microlens can be used in microscopes for visual observation, output to a TV camera or photographing low-contrast microscopic structures at the resolution limit of optical microscopes. The microlens comprises four components. The first component comprises n frontal separate positive lenses. The second component comprises a triple-glued lens made of two biconvex lenses with a biconcave lens in between, and two double-glued positive lenses, facing each other by positive lenses. The third positive component is double-glued and consists of a biconvex lens and a negative lens. The fourth component comprises a double-glued lens consisting of a biconvex lens and a biconcave lens, and an additional lens.

EFFECT: longer working distance while achieving plan-apochromatic correction.

4 cl, 1 dwg, 1 app, 2 tbl

Description

The present invention relates to optical instrumentation, namely, microscope lenses with an increased working distance, and can be used for visual observation, output to a TV camera and photographing low-contrast microscopic structures that are at the limit of the resolution of light microscopes in natural light, luminescence light, in polarized light, by the method of bright field, dark field, phase contrast, when assessing the quality of manufacturing and certification in industrial production of microelectronics products, etc.

Known immersion micro-lens of large magnification with an increased working distance [1], containing the front component located along the optical axis in the form of a meniscus, convex in the image space, the second single positive component, the third positive component double-glued from the negative and positive lenses, the fourth double-glued from the negative and positive lens component, the fifth in the form of single menisci facing concavity into the image space.

The lens has an increased working distance, improved correction of mono and chromatic aberrations (achromatic), the observed area of the object is increased at the same time.

But the micro-lens has an insufficient linear image field (20 mm), achromatic correction, and residual chromaticity of magnification.

The closest technical solution to the claimed technical solution is a micro lens with an increased working distance [2]. The lens consists of four components, the first of which contains “n” frontal single positive lenses, the second contains two double-glued lenses facing with positive lenses facing each other, the third component contains a positive single lens, the fourth contains a double-lensed lens from a positive meniscus turned concave into space object, and a biconcave negative lens.

The lens has a linear image field of 25 mm, improved correction of spherochromatic aberrations, astigmatism and curvature, fixed chromaticity magnification.

But the lens does not have enough working distance, achromatic correction and residual astigmatism and image curvature.

The main task, the solution of which the invention is directed, is to increase the working distance when achieving planochromatic correction.

The problem is solved using the proposed planochromatic micro-lens of large magnification, which, like the prototype, contains four components in series, the first of which is made in the form of n positive lenses, the second component is made in the form of two double-glued lenses, facing the positive lenses facing each other, the third the positive component, the fourth component is made in the form of a double-glued lens, consisting of a positive lens and a biconcave negative lens.

Unlike the prototype, in the second component, in front of two double-glued lenses facing the positive lenses facing each other, a triple-glued lens is placed made of two positive biconvex lenses with a negative biconcave lens placed between them, the third positive component is double-glued of biconvex positive and negative lenses, and in the fourth component, in the double-glued lens, the positive lens is biconvex and an additional lens is placed behind it.

An additional lens of the fourth component can be made in the form of a meniscus facing concavity into the space of the object, and can also be glued from a positive meniscus and a negative biconcave lens.

In addition, the refractive index of the positive lenses of the triple-bonded lens of the second component has a value of 1.42≤n _d ≤1.45, and its dispersion coefficient is 90≤ν _d ≤95, the refractive index of the first positive lens of the first component has a value of 1.85≤n _d ≤1.93, and its coefficient variance 30≤ν _d ≤33.

The essence of the invention lies in the fact that the addition of a three-glued lens in the second component, the implementation of the third component double-glued from a positive biconvex lens and a negative meniscus facing concavity into the space of the object, placing an additional lens in the fourth component, allowed for the first time to increase the working distance to two focal lengths in a lens with a large increase, improve the planned correction, and the implementation of lenses with the above refractive indices and coefficients The dispersion elements made it possible to provide apochromatic correction with corrected chromaticity of magnification.

Based on the foregoing, we can conclude that the new set of essential features of the invention allowed to obtain a technical result, which consists in increasing the working distance by more than 2 times, to provide apochromatic correction and improve aberration of off-axis beams.

According to the proposed scheme, micro lenses are implemented:

1) an increase of 100 times, an input aperture of 0.7, a linear image field of 25 mm, a working distance of 4.1 mm;

2) an increase of 250 times, an input aperture of 0.85, a linear image field of 25 mm, a working distance of 0.8 mm, exceeding the focal length of the micro lens.

The proposed planochromatic micro lens of large magnification with an increased working distance is illustrated by the drawing, which shows its optical scheme, as well as by the Appendix, which gives the design parameters and aberration releases.

The inventive planochromatic micro lens of large magnification with an increased working distance contains four components.

The first component I contains a positive meniscus 1, convex in the image space, and a positive biconvex lens 2.

The second component II consists of two glued lenses, the first of which is glued from the negative meniscus 3, convex into the space of the object, and a biconvex positive lens 4, the second gluing consists of a biconvex 5 and a biconcave 6 lenses.

The third component III contains a glued lens of a positive biconvex 7 and a negative biconcave 8 lenses.

The fourth component IV is glued from a positive biconvex lens 9 and a negative biconcave lens 10.

In the second component II and in front of the two bonded lenses 1 and 2, 3 and 4, a triple bonded lens is additionally placed, consisting of two positive biconvex lenses 11 and 12 with a negative biconcave lens 13 located between them.

In the fourth component IV, behind the double-glued lens, lens 14 is additionally placed.

Additional lens 14 of the fourth component IV can be made in the form of a positive meniscus facing concavity into the space of the object, as well as glued from a positive meniscus and a negative biconcave lens.

In addition, the refractive index of the positive lenses of the triple-bonded lens of the second component has a value of 1.42≤n _d ≤1.45, and its dispersion coefficient is 90≤ν _d ≤95, the refractive index of the first positive lens of the first component has a value of 1.85≤n _d ≤1.93, and its coefficient variance 30≤ν _d ≤33.

The proposed lens works as follows.

The lens works with a tube lens f ′ = 200 mm.

Rays from the object of observation located in the front focal plane of the micro-lens pass through the first component I - the positive meniscus 1 and the biconvex lens 2, forming an imaginary enlarged image, introducing negative spherochromatic aberration, chromaticity of position and magnification, to whom.

Components II and III of lens 11, 13, 12, 3, 4, 5, 6, 7, and 8 create an imaginary enlarged image in the focal plane of component IV, correcting spherochromatic aberration and coma.

Next, the IV component of the lens 9, 10 and 14 transfers the image of the object to infinity, forming a planochromatic high-contrast image of the object.

The annex contains a micro lens with a magnification of 100 ^x , a numerical aperture of 0.7, a linear image field of 25 mm and a working distance increased by more than 2 times compared with the prototype (1.5 mm in the prototype, 4.1 mm in the claimed technical solution).

Table 1 presents the Strehl number, which characterizes the image quality of the micro-lens for the relative values of the image values.

Table 1 Rel image value Strehl number one 0.77 0.866 0.84 0.707 0.87 0.5 0.87 0 0.84

Table 2 shows the Strehl number of a micro lens with an increase of 250 ^x , an input aperture of 0.85, a linear image field of 25 mm, and a working distance of 0.8 mm.

table 2 Rel image value Strehl number one 0.89 0.866 0.92 0.707 0.93 0.5 0.94 0 0.945

Information sources

1. Russian Federation, patent for invention No. 2176804, IPC: G02B 21/02, publ. December 10, 2001

2. Russian Federation, patent for invention No. 2097810, IPC: G02B 21/02, publ. November 27, 1997 - a prototype.

Claims (4)

1. Plano-chromatic micro-lens of large magnification with an increased working distance, containing four components in series, the first of which contains “n” frontal single positive lenses, the second - two double-bonded positive lenses facing the positive lenses facing each other, the third positive component and the fourth component, made in the form of a double-glued lens, consisting of a positive and biconcave negative lenses, characterized in that in the second component before being able to use double-glued lenses, facing positive lenses facing each other, a triple-glued lens is placed made of two positive biconvex lenses with a negative biconcave lens placed between them, the third positive component is double-glued of biconvex positive and negative lenses, and the fourth component has a double-glued lens made biconvex and an additional lens is placed behind it. 2. Plano-chromatic micro-lens of large magnification with an increased working distance according to claim 1, characterized in that the additional lens of the fourth component is made in the form of a meniscus, turned concavity into the space of the object. 3. Plano-chromatic micro-lens of large magnification with an increased working distance according to claim 1, characterized in that the additional lens of the fourth component is glued from a positive meniscus and a negative biconcave lens. 4. A large-magnification plano-chromatic micro lens with an increased working distance according to claim 1, characterized in that the refractive index of the positive lenses of the triple-bonded lens of the second component is 1.42≤n _d ≤1.45, and its dispersion coefficient is 90≤ν _d ≤95, the refractive index of the first the positive lens of the first component has a value of 1.85≤n _d ≤1.93, and its dispersion coefficient is 30≤ν _d ≤33.

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