JPS5846311A - Photomicrographic lens - Google Patents

Abstract

PURPOSE:To make a photomicrography possible with good pictures of less distortion, by constituting a lens system with the first-group lens of a positive lens, the second-group lens of a negative compound lens, and the third-lens group of a biconvex compound lens and satisfying specific conditions. CONSTITUTION:A lens system consists of the first-group lens of a positive meniscus lens whose convex faces to an object lens, the second-group lens of a cemented negative meniscus lens whose convex faces to the object lens, and the third-group lens of a biconvex compound lens. When the focal length of the whole of the system, the focal length of the first-group lens, and the radius of curvature of the first-group lens, the resultant focal length of second and third- group lenses, thicknesses of respective lenses of the second-group lens, and refractive indexes of respective lenses of the second-group lens are denoted as f, f1, r1, f23, d3, d4, n2, and n3 respectively, conditions (1)-(4) are satisfied. Thus, the distortion is restrained within 0.5%, and a good-image photomicrography is possible.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention' relates to a microscopic photographic lens for photographing the ear wings by re-imaging an object image formed by an objective lens of a microscope on a film surface.

For example, when a photographic lens of this kind is used in a gold phase microscope to take a photograph, the image becomes distorted due to distortion aberration. It is difficult to correct this defect with microscope objectives. This is because most objective lenses have positive distortion, and most eyepiece lenses also have positive distortion. For this reason, pictures taken with a microscope have pincushion distortion. In order to eliminate this drawback, it is necessary to use a microphotography lens with distortion that is close to O (even if it is positive, it is extremely small) or has negative distortion.

As a conventional lens for microscopic photography of this type, JP-A-54
There is one described in Japanese Patent No.-11754. In this conventional example, the distortion aberration is about 10.3% at the extreme periphery.Also, since it is a lens system composed of four groups (2), there is a lot of surface reflection, which causes some problems in terms of contrast. Furthermore, spherical aberration is slightly larger.

The present invention eliminates the drawbacks of the conventional ones as described above,
To provide a microphotography lens which is a lens system having a distortion aberration close to zero or negative, and which enables photographing with a good image with little distortion.

The lens system of the present invention includes a first lens group consisting of a positive meniscus lens with a convex surface facing the objective lens, a second lens group consisting of a cemented negative meniscus lens with a convex surface facing the objective lens, and a second lens group consisting of a double-convex cemented lens. This lens system is composed of three lens groups, and is further characterized in that it satisfies the following conditions.

12) 0.345 ≦ −≦ 0.39t41
0.01 ≦ l3 - n2, ≦ 0.05 (3) where f is the focal length of the entire system, f] is the focal length # of the first group lens (front group), fz3 is the focal length of the second group lens and the third group The composite focal length of the lens (rear group), rl is the radius of curvature of the objective/z side surface of the first group lens, d3+d4 is the thickness s of both lenses of the second group lens, n2+n3 is the thickness of both lenses of the second group lens is the refractive index of

The above conditions will be explained below.

In a lens system like the present invention, distortion is almost determined by the power distribution of each group in the entire system. conditions(
1) is a condition set in order to make the distortion aberration a value close to zero or a slightly negative value, which is the purpose of the present application, and to correct various aberrations in a well-balanced manner.

If the lower limit of this condition (1) is exceeded, the distortion cannot be a positive value, and moreover, cannot be made to be a value close to zero. Also, the condition (1
) is undesirable because the distortion becomes too large, although it is a negative value.

Condition (2) is a condition provided to further correct distortion aberration satisfactorily within the framework of the basic configuration defined in condition (1) and to balance it with other aberrations.

If this condition is not satisfied, when the distortion aberration is set to a desired value (4), other aberrations will worsen and it will not be possible to correct them completely. In other words, if the lower limit of condition (2) is exceeded, the lower rays of the frame will be insufficiently corrected and astigmatism at the periphery of the screen will not be fully corrected. Furthermore, if the upper limit of condition (2) is exceeded, the lower rays of the frame will be overcorrected and it will be difficult to correct astigmatism around the screen.

Condition (3) is necessary for correcting the Petzval sum to maintain flatness of the image and for balancing coma aberration. If the lower limit of this condition is exceeded, the field curvature will be under-corrected and the lower ray of the frame will be over-corrected. If the upper limit is exceeded, the field curvature will be over-corrected, and the upper rays of the frame will be over-corrected.

Condition (4) defines the refractive index of both lenses of the second group lens, and is related to the cemented surface r4 of the second group lens to correct the astigmatism difference, and is also related to the thickness of both lenses of the second group lens. This is to correct coma aberration.

If the lower limit of this condition is exceeded, the curvature of surface r4 becomes strong, the lower ray of the coma becomes over-corrected, 6m becomes over-corrected, and the astigmatism difference becomes large. When the upper limit is exceeded, T4 becomes loose, and the upper ray of the frame becomes over-corrected (5), while 6 m becomes under-corrected.

Next, embodiments of the microscope photography lens of the present invention described above will be shown.

Example 1 rl = 0.3810 d+ = 0.1125 1+ = 1.755 ν
r = 52.33r2 = 0.5114 d2-7 = 0.7978 r3 = 0.5258 d3 = 0.1065 n2 = 1.5231
92 = 50.84r4 = -0,1882 d4 = 0.0245 13 = 1.54771 1
'3 = 62.83rs = 0.2-762 ds = 0.0679 re = 0.5154 d6 = Oo, 1085 n4 = 1.734 1'
4 = 51.49r7 = -0,1568 d7 = 0.0241 n5 = 1.71736
I's = 29.51rB = -0,5307 f = 1.000 (6) fa = 1,443 fb = 0.546 fB/
fb = 2.64 Example 2 rl = 0.3797 d+ = 0.1123 nt = 1.755 1
/+ = 52.33r2 = 0.5103 d2= o, 7963 ra = 0.5503 d3 = 0.1063 n2 = 1.51118
1/2 = 51.02r4 = -0,1707 d4 = 0.0245 n3 = 1.52542
1'3 = 64.55rs = 0.2696 dS = 0.0678 ra = o, 5063 d6 = 0.1083 n4 = 1,741 1'
4 = 52.68rf = -0,1616 dy" 0.0241 ns = 1.71736
I's = 29.51rs = -0,5658 f = 1.000 fB = 1.434 fb = 0.545 fB
/fb= 2.63 Example 3 (7) r+ =' 0.3619 d+ = 0.1125 nt = 1,75
5 νt = 52.33r2 = 0.4669 d2 = 0.7975 ra = 0.4977 d3 = 0.1065 n2 = 1.53172
1'2 = 48.9r4 = -0,,1721 d+ = -0,0245n3 = 1.55232
L's = 63.75rs = 0.2645 ds = 0.0679 ra = 0.5015 d6 = fl, 1085 n4 = 1,741 1
'4 = 52.68r7 = -0,1534 d7 = 0.024Ins = 1.71736
ν5=29.51rs=-0,5632 f=1.000 fB=1,459 fb=01546 fa
/fb = 2.67 Example 4 rH = 0.3837 d+ = 0.1205 nt = 1.755
ν, = 52.33(8) rz = 0.5056 d2 = 0.8015 rs = 0.5290 da = 0.1145 n2 = 1.51118
ν2 = 51.02rn = -0,1867 d4 = 0.0305 n3 = 1.53113
1'3 = 62.44rs = 0.2583 ds = 0.0599 ra = 0.4625 da = 0.1105 n4 = 1.72916
1'4 = 54.68ry --0,1613 dt = 0.0241 ns = 1.69895
1's = 30.12r@ = -0,5709 f = 1.000 fB = 1,479 fb = 0.545 fB
/fb=2.7 where rl+r2+...+r8 is the radius of curvature of each lens surface, dl+d2+...,...+d7 is the wall thickness and air gap of each lens, n 1 + 12 +
... + n 5 is the refractive index of each lens, shi! , C2.・
..., ν5 is the Atsube number of each lens.

Among the above embodiments, Examples 1, 2.4 each have a positive value of distortion (9). 75. L 005% or less, which is extremely close to zero (if) compared to the conventional lens of this type, which is generally about 3%.

With this level of distortion, good photographic performance can be obtained even when used with a general microscope objective lens.
.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the photographing lens according to the present invention, and FIGS. 2 to 5 are aberration curve diagrams of Examples 1 to 4 of the present invention, respectively. Applicant: Agent of Orinokus Optical Industry Co., Ltd.
Hiroshi Mukai (10) Spherical aberration Astigmatism Distortion aberration Coma aberration It surface M Astigmatism Distortion aberration Coma aberration Spherical aberration Non-Ω] Distortion aberration Romani aberration Figure 5 Spherical aberration Non-reflective aberration Distortion aberration Comatic aberration

Claims (1)

[Claims] A first group lens of a positive meniscus lens with a convex surface facing the objective lens side, a cemented lens second group lens of a negative meniscus lens with a convex surface facing the objective lens side, and a biconvex cemented lens. A microscopic photography lens that satisfies each of the following conditions. 1 (2) 0.345 ≦ −≦ 0.39 (4)
0.01 ≦ n3-n2 ≦ 0.05 but f
is the focal length of the entire system, f is the focal length of the first group lens (front group), f23 is the combined focal length of the second group lens and third group lens (rear group), and rt is the objective of the first group lens Radius of curvature of the surface on the lens side* d3+d4 is the thickness of each lens in the second group lens, n2+n3 is the refractive index of each lens in the second (1) group lens6