JPS6098417A - Objective lens for microscope - Google Patents

Abstract

PURPOSE:To correct satisfactorily a magnification chromatic aberration and other various aberrations by constituting a titled lens of the first group consisting of a positive single lens, the second group consisting of a cemented meniscus lens, the third group consisting of a meniscus lens, and the fourth group consisting of a cemented positive lens, and constituting it so that a specified optical constant is satisfied. CONSTITUTION:A titled lens is constituted of the first group G1 consisting of a positive single lens L1, the second group G2 provided on an object side of the first group G1 and consisting of a cemented meniscus lens which contains a positive lens L2 and a negative lens L3, and whose radius of curvature of an object side face is r5, the tird group G3 provided on the object side of the second group G2 and consisting of a meniscus lens L4 whose radius of curvature of an image side face is r6 and whose lens center thickness is d6, and the fourth group G4 provided on the object side of the third group G3 and consisting of a cemented positive lens containing a positive lens L5 and a negative lens L6 whose Abbe numbers are nu8, nu9, respectively, and when a focal distance of the whole system is denoted as (f), this lens is constituted so that each optical constant satisfies nu8-nu9>10, f/8<d6, 0.15f<r5<0.3f, and 0.15f<-r6<0.3f, by which a chromatic aberration and other various chromatic aberrations are corrected, and a long working distance is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a microscope objective lens, and more particularly to a so-called infinitely corrected microscope circumference-operated blank apochromat objective lens that forms an image using an imaging lens.

Generally, in order to improve the operability of a microscope, it is necessary to increase the working distance of the objective lens, but the working distance of a conventional objective lens for a microscope with a magnification of about 5 times is 0.2 to 0.2 of the focal length. It was about 0.5 times, which was not sufficient, and the operability was poor. Further, many of them have a numerical aperture NA of about 0.1 to 0.13, and there is a problem that there are few that have a flat image plane over a sufficiently wide field of view. In other words, when trying to obtain a long working distance with an objective lens, the amount of secondary spectra increases and chromatic aberration and spherical aberration become large. .

On the other hand, in order to design an objective lens that has a large numerical aperture NA and is highly efficient, it is necessary to use glass materials appropriately and effectively, and to appropriately distribute the power of each lens. It was one of the difficult ones.

The present invention has been made to solve the above-mentioned conventional problems, and has a large numerical aperture NA of about 0.14, a long working distance of about 0.8 times the focal length, and a wide field of view. It is an object of the present invention to provide an objective lens for an infinity correction type microscope, in which the image plane is flat over the entire range, and lateral chromatic aberration and other various aberrations are well corrected by the objective lens itself.

The present invention provides a microscope objective lens arranged on the image side.
A first group consisting of a positive single lens and a radius of curvature of the object side surface arranged on the object side of the first group with the convex surface facing the edge side are r.
A second group consisting of a cemented meniscus lens with a diameter of 5 and a meniscus lens with a radius of curvature of r6 on the image side surface and a thickness of d6 at the center of the lens, which is disposed on the object side of the second group with its concave surface facing the image side. It consists of a third group, and a fourth group consisting of a cemented positive lens including a positive lens and a negative lens with Abbe numbers of ν8 and ν9, respectively, arranged on the object side of the third group. When the focal length is f, each optical constant has the following relationship ν8-ν, 〉10 (1) f/8<
d 6 ・・・・・・・・・(2) 0, 15f <r
s <0.3f ・-------<3>0, 15r
<-r a <0.3f -------- (4) is satisfied, thereby achieving the above object.

Here, the above equation (1) defines the difference between the Atsube number ν8 of the positive lens and the Atsube number ν9 of the negative lens included in the fourth group, and it corrects the longitudinal chromatic aberration and also corrects the lateral chromatic aberration. This is for good correction by the objective lens itself.

Further, the above-mentioned equation (2) defines the center thickness d6 of the meniscus lens of the third group, and if this condition is violated, it becomes difficult to correct comatic aberration and field curvature at the same time.

In addition, Equations (3) and (4) above define the radius of curvature r5 of the object side surface of the cemented meniscus lens in the second group and the radius of curvature r6 of the image side surface of the meniscus lens in the third group, and the Petzval sum is This is to improve the image quality and correct field curvature.

Embodiments of the present invention will be described in detail below with reference to the drawings.

As shown in FIG. 1, in this embodiment, a 1111'G+ consisting of a positive single lens L1 is arranged on the edge side, and a lens 1111'G+ is arranged on the object side of the first group G1 with its convex surface facing the image side. a second group G2 consisting of a cemented meniscus lens including a positive lens L2 and a negative lens L3 and having a radius of curvature of r5 on the object side; was done,
a third group G3 consisting of a meniscus lens L4 having an image side surface radius of curvature r6 and a lens center wall thickness do;
The fourth group G4 includes a positive lens L5 having an Abbe number of 6 and 9, and a cemented positive lens including a negative lens 1-6, which are disposed on the object side of the lens.

With the above configuration, when an image is formed with an imaging lens with a focal length of 200 IIm, the magnification is 5 times, and the numerical aperture NA on the object side is 0.
．． 14. Set the optical constants of each lens as shown in Table 1 below, satisfying the relationships of equations (1) to (4) above so that the focal length of the entire system is 40.01 mm. As a result, the distance WD from the vertex of the R-lens to the object surface (operating button 1 m) was 32.3 square meters, that is, 0.81 times the focal length t, and a long working distance could be obtained.

Here, rbi=r+o is the radius of curvature of each lens surface, dbead d9 is the center thickness of each lens or lens interval, nbi・
n9 is the refractive index of each lens, and ν1...ν9 are the Abbe numbers of each lens.

FIG. 2 shows the measurement results of spherical aberration, astigmatism, distortion, and chromatic aberration of magnification in this example.

This figure 2 was obtained by tracing rays from the image side toward the object plane, and Y- is the focal length 2.
It represents the image height when combined with a 00■ imaging lens. As is clear from the figure, the operating button 111 is extremely long.
It can be seen that various aberrations are well corrected despite having a WD and a large numerical aperture NA.

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As explained above, according to the present invention, it is possible to achieve high performance and zero focal length without sacrificing chromatic aberration and other chromatic aberrations.
．． A very long working distance of about 8 times can be obtained. Therefore, the operability of the microscope can be greatly improved, and it has an excellent effect of being extremely useful as an objective lens for a microscope.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the lens configuration of an example of the objective lens for a microscope according to the present invention, and FIG. 2 is a diagram showing various aberrations of the example. G1...first group, G2...second group, G3...third group, G4...fourth group, L1 to L6...lens. Agent Takaya Ron (1 idiot)

Claims (1)

[Claims] (1) A first group consisting of a positive single lens arranged on the image side, and a junction meniscus with a radius of curvature r5 on the object side, arranged on the object side of the W11 group with the convex surface facing the edge side. a second group consisting of a lens, and a third group consisting of a meniscus lens with a radius of curvature of the image side surface r6 and a lens center thickness da, which is disposed on the object side of the second group with the concave surface facing the edge side. , arranged on the object side of the third group, each having an Atsube number of ν8,
ν. and a fourth group consisting of a cemented positive lens including a positive lens and a negative lens, and when the focal length of the entire system is f, each optical constant has the following relationship ν8-ν9>10 f/8< An objective lens for a microscope, characterized in that it satisfies the following: da0.15f<rs<0.3fO, 15f<-rs<0.3f.