JPS6323119A - Objective lens for microscope - Google Patents

Abstract

PURPOSE:To obtain an objective lens for microscope having a long working range, by refracting rays of light diverged by the 1st group in an object-side plane after they are transformed to almost parallel or nearly parallel rays of light and correcting the spherical aberration of the color produced by the 4th group and, at the same time, compensating insufficiently corrected spherical aberration. CONSTITUTION:This objective lens for microscope is composed of the divergent 1st group which has a concave surface and contains a positive and negative lens components on the object side and Abbe's numbers of whose image-side and object-side lenses are respectively v1 and v2, 2nd group which is placed on the object side of the 1st group and composed of a positive lens having a focal range F2, 3rd group which is provided on the object side of the 2nd group and contains a cemented lens block composed of a concave and convex lenses whose refractive indexes are respectively nc and nr, and 4th group which is provided on the object side of the 3rd group and has a strong convex surface on the image side. Each optical constant is caused to satisfy the formulae. The F1 and d3 of the formulae are the focal range of the 1st group lens and range between the 1st- and 2nd-group lenses, respectively.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an objective lens for a microscope, and more particularly to a so-called infinite correction type microscope equilength working blank apochromat objective lens that forms an image using an imaging lens.

[Conventional technology]

Generally, in order to improve the operability of a microscope, it is necessary to increase the working distance of the objective lens, but conventional microscope objective lenses with a magnification of about 50x do not have a sufficient working distance and are difficult to operate. It had the problem of being bad. That is, when trying to obtain a long working distance in an objective lens, secondary spectralization increases and chromatic aberration and spherical aberration become large, so conventionally, the working distance had to be shortened by 1λ. On the other hand, designing an apochromatic objective lens with a large numerical aperture NA requires appropriate and effective use of glass materials and appropriate power distribution of each lens, which is one of the most difficult types of lens design. It was one. (Problems to be Solved by the Invention) The present invention has been made to solve the above-mentioned conventional problems. It is an object of the present invention to provide an infinity-corrected microscope objective lens in which various aberrations and other aberrations are well corrected.

[Means to solve the problem]

The present invention provides a microscope objective lens with a diverging first group, which has a concave surface facing the object side, includes a positive lens component and a negative lens component, and has Abbe numbers of the image side and object side lenses of ν1 and ν2, respectively. A second group is arranged on the object side of this first group and consists of a positive lens with a focal length of F2, and a concave lens and a convex lens are arranged on the object side of this second group and each has a refractive index of 'C1nr. A third lens block including a cemented lens block consisting of
and a fourth group consisting of a positive lens disposed on the object side of the third group and having a stronger convex surface on the image side. and second
When the distance between the lenses of the group is d3, each optical constant has the following relationship S2-S1〉15... (1) 0.8
(lF+l+d3)<F2...(2)<2.
0 (IFl 1+d 3) tic nr>0.05...(3)
The above objective has been achieved by satisfying the following.

[Effect]

Here, the above-mentioned equation (1) is a necessary condition for correcting the lateral chromatic aberration by the objective lens itself. In addition, the above equation (2) shows the relationship between the power of the first group and the second group, and the light rays diverged by the first group are changed to almost parallel or close to parallel, and in particular, This is to ensure that spherical aberration is under-corrected by refraction at the object-side surface. Furthermore, the equation (3) above corrects the chromatic spherical aberration that mainly occurs in the fourth group under the condition that the cemented surface has negative power, and at the same time corrects the chromatic spherical aberration that occurs under the condition of the equation (2) above. This is to cancel out the spherical aberration that is insufficiently corrected.

【Example】

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described in detail below with reference to the drawings. As shown in FIG. 1, the first embodiment of the present invention has a concave surface facing the object side, and includes a positive lens LI and a negative lens L2, and the numbers of the image side and object side lenses are ν1 and ν2, respectively. A first group G1 having a certain diverging property, and a second group G disposed on the object side of the first group G1 and consisting of a positive lens L3 having a focal length of F2.
2, and a second cemented lens block disposed on the object side of the second group G2 and including two cemented lens blocks consisting of concave lenses Ls, Lm and convex lenses L4, L(, 1L7, F9, respectively, with refractive indexes of nC and II1). 3 R\G s, and a fourth R\04 consisting of two positive lenses L+ 0% L+ + which are disposed on the object side of the third group G3 and have a stronger convex surface on the edge side.
It consists of With the above configuration, when an image is formed with an imaging lens with a focal length of 200 mm, the magnification is 50 times, the numerical aperture on the object side is 0.42, and the focal length is 4.00 mm. By satisfying the relationships of equations (1) to (3) and setting the optical constants of each lens as shown in Table 1 below, we found that the distance from the center of the final lens to the object surface (1fJJ distance w
li) WD Ka22. On. That is, it was 5.5 times the focal length @f, and a long working distance could be obtained. Here, rl...F17 is the radius of curvature of each lens surface,
dl...(Its is the thickness of each lens and the lens interval, nl...n1g is the refractive index of each lens, ν1...
ν16 is the Abbe number 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 11
The image height when combining with a 1120 On imaging lens is not shown. As is clear from the figure, various aberrations are well corrected despite having an extremely long working path MWD and a large numerical aperture NA. Table 1 1'+= -13, 20d+= 2. On+-1,7
8474LL+-25,60r 2=-3
, 65d 2-1. On2- 1.786
49 v2- 49.97r 3= 12.0
06 a= 33.6r4= -91,38d
4 = 3,8 n 4- 1.4
5570 ν<-90, 42rs=-18,
30ds=0.4ra=700. Ods+=
6.3 ns= 1.45590 L/a-90,46
ry=-17,9d7=1. On7=1.56
471 Shear 53,27ra= 22,5 da
= 6.3 na = 1.455901. Ja = 90
．． 46r s=-52,68d *= 0.4r
1o = 70.00 d 1 (1-6, 3n 16-
1,45590ν, o -90,46r ++= -2
0,96d ++-1, On11-1, 56471 L
/++=53.27r +2- 18.83 d 12
-6,3 n 12-1.45590 L/12=90
．． 46r + 3= 107.2 d l 3-0.4
r 14- 25.11 d 14=3.5014=
1.497071/14-81.75r+s=295
．． Od+s=0.2 r, 6- 18.36 d+a-3,50,a-1,6
5831L/, 5=57.44r I7=51.
20 [Effects of the Invention] As explained above, according to the present invention, it is possible to obtain a lens with an A8 ratio of about 50 It can be used as a microscope objective lens. Therefore, the operability of the microscope can be greatly improved, and it has the excellent effect of being extremely useful as a microscope objective lens.

[Brief explanation of the drawing]

FIG. 1 is a V diagram showing the lens configuration of a first embodiment of the objective lens for a microscope according to the present invention, and FIG. 2 is a diagram showing various aberrations of the first embodiment. G1...1st group, G2...28th group, G3...3rd group, G4...4th group, L1~L++ river lens. Agent Kei Matsuyama Ya Cantaka Theory Figure 1 Figure 2 Ball I! ] @Jk lμd Nobuhata Sakazuki Li Colored Buddha 1988
April 27th

Claims (1)

[Claims] (1) A diverging first group having a concave surface facing the object side, including a positive lens component and a negative lens component, and having Abbe numbers of the image side and object steel lenses ν_1 and ν_2, respectively;
A second group is arranged on the object side of the group and consists of a positive lens with a focal length of F_2, and a cemented lens is arranged on the object side of this second group and consists of a concave lens and a convex lens with refractive indices of n_c and n_r, respectively. It consists of a third group that includes a block, and a fourth group that is disposed on the object side of this third group and consists of a positive lens that has a stronger convex surface on the image side. F_1, when the distance between the lenses of the first group and the second group is d_3, each optical constant has the following relationship ν_2-ν_1>15 0.8(|F_1|+d_3)<F_2 <2.0(|F_1 |+d_3) n_c−n_r>0.05 An objective lens for a microscope, characterized in that it satisfies the following.