JPS6070412A - Objective lens for microscope - Google Patents

Abstract

PURPOSE:To obtain a lens of an infinite correction type, which has a long operating distance, and whose chromatic aberration and other various aberrations have been corrected satisfactorily by an objective lens itself, by constituting it with lenses of five groups so that each optical constant satisfies a specified condition. CONSTITUTION:A titled objective lens is constituted of the first group G1 consisting of a negative meniscus lens L1 in which radiuses of curvature of surface of image and object sides are r1 and r2, respectively, the second group G2 having a diverging property, which contains a positive lens L2 and a negative lens L3, and in which Abbe numbers of lenses of the image side and the object side are nu3 and nu4, respectively, the third group G3 consisting of joint positive meniscus lenses L4, L5, the fourth group G4 consisting of concave lenses L6, L9 and L12, and convex lenses L7, L3, L10 and L11, whose refractive indexes are (nc) and (nr), respectively, and the fifth group G5 consisting of two positive lenses L13, L14, so that a conditional expression is satisfied, when a composite focal distance of lenses of the first group and the second group, and an inter- lens distance of the second group and the third group are denoted as F12 and d5, respectively. According to such a constitution, a long operation distance can be obtained without sacrificing a chromatic aberration and various chromatic aberrations.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an objective lens for a microscope, and particularly to an objective lens for forming an image using an imaging lens. This invention relates to a so-called infinity-corrected microscope circumference operating plan apochromatic objective lens.

Generally, in order to improve the operability of a microscope, it is necessary to increase the working distance of the objective lens, but conventional objective lenses for microscopes with a magnification of about 10 to 50 times do not have a sufficient working distance, especially at high magnifications. However, there was a problem in that the operability was poor. That is, when attempting to obtain a long working distance in an objective lens, the amount of secondary spectrum increases and chromatic aberration and spherical aberration become large, so conventionally, the working distance had to be shortened at the expense of sacrifice. On the other hand, the numerical aperture N
Designing an apochromatic objective lens with a large A requires appropriate and effective use of glass materials and appropriate power distribution for each lens, which is one of the most difficult aspects of lens design.

The present invention was made to solve the above-mentioned conventional problems, and has a very long working distance of about 1.5 to 4 times the focal length, and the objective lens itself eliminates chromatic aberration and other various aberrations. It is an object of the present invention to provide a well-corrected, infinitely corrected microscope objective lens.

The present invention provides a first objective lens for a microscope consisting of a negative meniscus lens, which is disposed on the image side with its concave surface facing divergently, and whose image-side and object-side surfaces have radii of curvature r, , and r2', respectively. a positive lens component and a negative lens component disposed on the object side of the first group with a concave surface facing the object side,
The Atsube numbers of the image side and object side lenses are ν3 and ν4, respectively.
a diverging second group with a concave surface facing the image side;
A third group consisting of a positive meniscus lens with a focal length of F3 arranged on the object side of the group, and a concave lens with refractive indices of II C and II r, respectively arranged on the object side of the third group. The fourth group includes a cemented lens block made of a convex lens, and the fifth group is disposed on the object side of the fourth group and consists of a positive lens having a stronger convex surface on the image side. When the combined focal length of the lens group and the second lens is F12, and the distance between the lenses of the second group and the third group is d5, each optical constant has the following relationship 1 < (r z / r + ) < 2・
... (1) C4-C3 〉10... (2) 0, 8 (l F+ 2 l+d s) <F3<2
．． 0 (l F+ 2 l+d s) ... (3
)n C-n rho, 05- (4) The above objective is achieved by satisfying the following.

Here, Equation (1) above defines the shape and power of the first lens group, which is a negative meniscus lens with a concave surface facing the image side, and if this condition is violated, astigmatism and frame loss will occur. It becomes difficult to correct aberrations. Furthermore, the above equation (2) is a necessary condition for correcting chromatic aberration of magnification with the objective lens itself, and if this condition is violated, it becomes difficult to correct chromatic aberration of magnification with the objective lens itself, especially at high magnifications. It becomes difficult. Also, mentioned above (3
) formula shows the relationship between the power of the first group, second group, and third group, and changes the light rays diverged by the first and second groups to almost parallel or close to parallel. , in particular, to ensure that spherical aberration is under-corrected by refracting only on the object-side surface.

Furthermore, the equation (4) above corrects the chromatic spherical aberration that mainly occurs in the fifth lens group under the conditions that the cemented surface can have negative power, and at the same time allows light generation under the conditions of the equation (3) above. This is to cancel out the spherical aberration that is insufficiently corrected.

Further, in an actual aspect of the present invention, the positive meniscus lens of the third group is constituted by a cemented positive meniscus lens, so that the function of the third group can be easily satisfied.

Furthermore, in another embodiment of the present invention, the 48f cemented lens block is configured with two to three cemented lens blocks, so that the low performance of the fourth group can be easily satisfied. It is something.

Further, in still another embodiment of the present invention, the positive lens of the fifth group can be composed of one or two positive lenses, so that the functions of the fifth group can be performed with a simple configuration. It has been made possible.

Embodiments 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 image side and is disposed on the image side, and the radius of curvature of the image side and object side surfaces is r, C2. A first group G1 consisting of a negative meniscus lens L1, and a first group G1 with a concave surface facing the object side.
A positive lens L2 and a negative lens L are arranged on the object side of 1.
3, and the Abbe numbers of the image-side and object-side lenses are ν3 and ν4, respectively; In addition, there is a third group G3 consisting of cemented positive meniscus lenses La and Ls with a focal length of F3, and concave lenses Ls, Ls, and Lt with refractive indices of nc and nf, respectively, arranged on the object side of the third group G3.
2 and convex angle 'Lf, L+1, L+ as Lt +
A fourth group G4 includes three cemented lens blocks, and a fifth lens group G4 includes two positive lenses L+ 3 and L+ 4, which are disposed on the object side of the fourth group G4 and have a stronger convex surface on the edge side. It consists of group G5.

With the above configuration, when an image is formed with an imaging lens with a focal length of 200 inches, the magnification is 50 times, the numerical aperture NA on the object side is 0.55, and the focal side li! The optical constants of each lens were set as shown in Table 1 below, satisfying the relationships of formulas (1) to (4) above so that f was 4.00.
Distance from the center of the final lens to the object plane (working distance) W
D is 1! :l, Oin, i.e. focal length [of 3.75
It is now possible to obtain a longer working distance.

Here, 1゛1...1゛22 is the radius of curvature of each lens surface, dl... (121 is the 19 length of each lens and the lens interval, [11...1121 is the refraction of each lens. rate,
ν1...ν21 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 the rays from the edge toward the object surface (')' - is an imaging lens with a focal length of 200 mm (') represents the image height when combined. As is clear from the figure, despite having an extremely long working distance WD and a large numerical aperture NA, various aberrations are well corrected. (1+=1.5 nt=1.
78472 L11= 25.7r 2= -23,0
9d 2= 0.2r3= 65.67 (la= 2
．． Ons= 1.76182 1/3= 2(3,6r
<= -5,74 (14= 1.0114= 1.74
33 ν<= 49.2r s= 8,45 d s=
32.01゛s=-45,27d6=1. Ons
= 1.565 νg-53,0r7= 35,95
(17= 8.Or+7= 1,456 Schiff=90
．． 3r8= 217.23 d s = 0.2rg=
-110,0dg=1. Orls=i, 565
L/g=53.0r1o-26,6d+o=6. On
, 1o=1.456 shi10=90,3r 11=-
47.5d 1. = 0.2r+2= 110. Od+
2=6.31+2=1.456 ν12=90.31'
13=-21,5d+a=1. OIl+3=1.56
5 ν+a=53.0 "14= 21.5 d to"
-6,3014= 1.456 1/14=90,3r
+ 5= -110, Od t s= 0.21'+6
= 31.66 d1g=6.811+s=1,497
1/16=81.6r+7=-40,22(117
=1. On17-1.6125 Si17=44,9r
, 6= 1750 d + g= 0.2r1e= 2
4.126+e=4.01+1s=1.497 L/+
5=81.6r2o=149. Od 2 o=
0.21' 21- 13・29d2+44.0 ro2
1 = 1.6583 C2. Yo51.3r2z-23
, 08 In this example, the third group G3 is composed of a cemented positive meniscus lens, the fourth group G4 is composed of three cemented lens blocks, and the fifth group G5 is composed of two positive lenses. ζ′, the efficiency of each group can be easily satisfied.

Next, a second embodiment of the present invention will be described in detail.

As shown in FIG. 3, this second embodiment has a first group G1. @2nd group G2 and 3rd group G3,
A fourth group G4 is arranged on the object side of the third group G3 and includes two cemented lens blocks consisting of a concave lens 17, L+o, and convex lenses L6.1a and L9, each having a refractive index of II C and II j. , two positive lenses L+ having a stronger convex surface on the edge side are arranged E1 on the object side of the fourth group G4.
+, and a fifth group G5 consisting of L12.

The configuration as described above - (゛, magnification when imaging with an imaging lens with a focal length of 200 mz is 20@, and the number of entrances on the object side is N.
So that A is 0.45 and the focal length is 10.01u, satisfy the relationships of formulas (1) to (4) above, and set the optical constants of each lens as shown in the $2 table below. When set, the operating button 1i1WD becomes 16°6■, that is, 1.66 times the focal length f, and a long working distance can be obtained.

FIG. 4 shows the measurement results of spherical aberration, astigmatism, distortion, and chromatic aberration of magnification in this example.

As is clear from the figure, it can be seen that various aberrations are well corrected despite the extremely long operating button 11WD and the large frontage number NA.

In this embodiment, the fourth group G4 is composed of two cemented lenses, so it is a relatively small group.
78472 ν1= 25,7r 2= -26,7d
2 = 0,2+゛3= 31.9 d3= 3.0
113= 1.76182 ν3= 26.6r4=
-20,0 (14=i, O114=1.7433
))4=49,2r,,=i9.4 cl 5
= 27.01'6--49,9 16= 1.0 1
1s= 1.565 ν(,-!13.0r7= 49
．． 9 d7= 8.0 117= 1.456 v7=
90.3r a--18,3! lds=0.2
1・g= iIO,of+9= 6.3 119=
1.456 ν9=90.31”, o=-2L5
d+o=1. On+0=1.5G5 ν+ O=! 13
．． 01'11= 21,5 dl, =6,3 11++
=1.456 1+=90.3r+ 2=-110,
Od 12= 0.2r, 3= 45.7 (1+3=
6.8 Il+3=L497 Shi+3=8I, 61'+
q=-20, 4d+4=+, OIl+4=L6125
ν+ 4 = 44.9r 1s= 1060 (1,
5=0.2r+6=23.9d+6=4. O11
+6=1.497 s =81,131'+7=
257. Od+7=0.21”+g=14.27 d
+a=4. o n+8=1. G583 L/+a-b7
．． Third, a third embodiment of the present invention will be explained in detail.

As shown in FIG. 5, this third embodiment includes a first group G1 and a second group G2 similar to those of the first embodiment, and a concave surface of the second group G2 facing the image side. One positive meniscus lens with a focal length of F3 [3rd group G consisting of 4]
3, and a fourth group including two cemented lenses arranged on the object side of the third group G3 and consisting of concave lenses Ls and La and convex lenses L6 and L7 with refractive indexes II Q and II j, respectively. G4, and a fifth group G5 consisting of one positive lens L9 disposed on the object side of the fourth group G4 and having a convex surface that is stronger on the image side.

With the configuration described above, when an image is formed with a focusing lens with a focal length of 200 mm, the magnification is 10 times, the numerical aperture on the object side is 0.28, and the focal length 11f is 20.0 Ol[I]. When the optical constants of each lens were set as shown in Table 3 below by satisfying the relationships of Tateyama formulas (1) to (4), the working distance WD was 33.8■, that is, the focal length f The distance was 1.69 times that of the previous one, and a long working distance could be obtained.

Table 3 r, = -14,5d, = 2,0 11+= 1.7
0154 '91= 41.21・2= -19,0(
+. = 0.2r3= 44.2 c13= 3.0
113= 1.76182 ν3= 213. Cil・
4=-44,2d 4=1. b n 4=-1,7
433ν4=49.21・5−16.08 d5=T
9.541'5--57.3 (+6= 5.b r+
6= 1.497 ν et al.= 81.61・7−-18,
18 d7=0.21゛ε-190,0(+8=
1.5 r+, = 1. C1125νa= 44
．． 91'g= 29.62 (Ig= 6.0 119
= 1.456 'bJ9= 90,3r + o=
b5.4 [+ 10= 0.21'++= 69.7
d4. =7.0 11++=1.45(i Shu1=
90.31・, 2--22.75 [1+ 2= 4.
! + 11 + 2= 1. 'G125νI 2 =4
4.9r+3=405. Od+3=0.41'
+ 4 = 23.5 d+*=5. oll+q=1
．． 497 L'+ 4 = 8+, 6 In this example, the measurement results of spherical aberration, astigmatism, distortion, and chromatic aberration of magnification are shown in FIG.

As is clear from the figure, various aberrations are well corrected despite the extremely long working distance WD and large numerical aperture NA.

In this example, the third group G3 and the fifth group G5 are both composed of one lens, and the fourth group G4 is composed of two cemented lens blocks, so the vA configuration is simple. Yes, it is small and lightweight.

As explained above, according to the present invention, a very long working distance of 1.5 to 4 times the focal length can be obtained without sacrificing chromatic aberration and other aberrations. Therefore, the operability of the microscope can be greatly improved, and it has the excellent effect of being extremely useful as an objective lens for a microscope.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the lens configuration of the first embodiment of the objective lens for a microscope according to invention A, FIG. 2 is a diagram showing various aberrations of the first embodiment, and FIG. FIG. 4 is a diagram showing the structure of the second embodiment of the objective lens for a microscope according to the present invention. FIG. 5 is a diagram showing the configuration of the third embodiment of the objective lens for a microscope according to the present invention, and FIG. Diagram showing aberration G1...1st B leather, G2...2nd
k, G3...Third liver, G4...Fourth e+, G5
...5th stroke, 1~m+4...lens. Agent Naoya Ron (and 1 other person) Figure 1 Figure 3 Figure 4

Claims (1)

[Scope of Claims] (1) A negative meniscus lens arranged on the image side with its concave surface facing the image side and having a radius of curvature of 1.1.1゛2 on the image side and object side surfaces, respectively. 1 group, and a positive lens component and a negative lens component disposed on the object side of the first group with the concave surface facing the object side, and the Atbe numbers of the gap and the object side lens are ν3 and ν4, respectively. , a diverging second group, a third lens consisting of a positive meniscus lens with a focal length of F3, which is disposed on the object side of the second group with its concave surface facing the image side;
placed on the object side of the group, with refractive indexes of 11c and n, respectively.
@4 group including a cemented lens block consisting of an r concave lens and a convex lens, and a 5th group consisting of a positive lens with a stronger convex surface on the image side, which is disposed on the object side of the fourth group.
When the combined focal length of the first lens group and the second lens group 2'M is F12, and the distance between the lenses of the second group and third group is 65, each optical constant has the following relationship 1 < ( r 2./'I' + ) <2 4 - ν3
〉10 0.8(lFtzl+ds)-F3<2.0(lF+21yo(15)IIC-IIrho,05 A microscope objective lens characterized in that it has a vortex-like shape. 2. The objective lens for a microscope according to claim 1, wherein the third group of positive meniscus lenses is a cemented positive meniscus lens. (3) The number of cemented lens blocks in the fourth group is 2 to 1.
The objective lens for a microscope according to claim 1, which is constituted by a cemented lens block of la1. (4) The objective lens for a microscope according to claim 1, wherein the positive lens of the fifth group is composed of one or two positive lenses.