JPH06281865A - Photographic lens for microscope - Google Patents

Abstract

PURPOSE:To excellently compensate aberrations such as a curvature of image surface, an astigmatic aberration, a distortion aberration and a coma aberration with a small number of lems groups and lenses by making the refractive power of the joined surface of the cemented lens of a second lens group negative. CONSTITUTION:This lens is composed of a first lens group G1 comprising a meniscus-shaped cemented lens whose convex surface confronts the objestive lens side and a second lens group G2 including a cemented lens whose negatice lens and a positive lens are joined together through an intermediate position in the order from the objective lens side. The condition in the equation is satisfied. Here, (f) represents the focal distance of the whole system, f1 the focal distance of the first lens group, n3, n4 the refractive indice for d-line of the negative lens and the positive lens of the cemented lens of the second lens group G2, respectively, r5, r6 the radii of curvature of the surface on the objective side and the joined surface of the cemented lens of the second lens group G2, respectively, and nu3, nu4 the Abbe numbers of the negative lens and the positive lens of the cemented lens of the second lens group G2, respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microscope photographic lens for re-imaging an object image formed by a microscope objective lens on a film surface for photographing.

[0002]

2. Description of the Related Art As a conventional example of a microscope photography lens, there is a lens system disclosed in Japanese Patent Publication No. 61-25127. This lens system is composed of a positive first lens group, a positive second lens group through an intermediate image position, a negative third lens group, and a positive fourth lens group in order from the object side. Has been done.

As another conventional example of the microscope photography lens, there is a lens system described in JP-A-58-95314. This conventional lens system includes a first lens group including a cemented lens in which a positive lens and a negative lens are cemented in order from the object side, and a first lens group including a meniscus lens having a convex surface directed toward the object side through an intermediate image position. It is composed of two lenses and a third lens group including a cemented lens in which a negative lens and a positive lens are cemented.

[0004]

Of the above-mentioned conventional examples,
The former (Japanese Patent Publication No. 61-25127) has a lens system of 4
The lens system of the fifth group has a constitution, and the latter lens system (Japanese Patent Laid-Open No. 58-95314) has a constitution of five groups of three groups. Each of the conventional examples has a drawback that the number of groups and the number of lenses are large.

An object of the present invention is to provide a photographic lens which is used by mounting an objective lens and an eyepiece lens on the image side of a microscope objective lens which independently corrects field curvature, and which is a small group, An object of the present invention is to provide a microscope photography lens in which various aberrations such as field curvature, astigmatism, distortion, and coma are corrected very well with a small number of lenses.

[0006]

The microscope photography lens of the present invention is used by being mounted on the image side of the microscope objective lens as described above, and the convex surface is directed in order from the objective lens side to the objective lens side. A lens system that includes a first lens group including a meniscus-shaped cemented lens and a second lens group that includes a cemented lens in which a negative lens and a positive lens are cemented via an intermediate image position, and that satisfies the following conditions. is there.

(1) | f / f ₁ | <0.5 (2) 0 <{(n ₃ −1) / r ₅ } · f <4 (3) −4 <{(n ₄ −n ₃ ). / R ₆ } · f <0 (4) ν ₄ −ν ₃ > 10 where f is the focal length of the entire system, f ₁ is the focal length of the first lens group, and n ₃ and n ₄ are the second lens group, respectively. D-line refractive index of the negative and positive lenses of the cemented lens inside, r ₅ ,
r ₆ is the radius of curvature of the cemented surface and the object side surface of the cemented lens in the second lens group, and ν ₃ and ν ₄ are the Abbe numbers of the negative and positive lenses of the cemented lens in the second lens group, respectively. .

In order to obtain a wide-field microscopic photographic lens, the present invention arranges the first lens group, which is a field lens, closer to the objective lens side than the position where an image can be formed by the objective lens, so that the light flux has an appropriate size. I tried to squeeze it. This narrowed light flux is once condensed at the intermediate image position and then spread again to make the second
The second lens group has a cemented lens composed of a negative lens and a positive lens, and has a lens system having the above-described configuration.

In such a lens system of the present invention, the first lens group is a meniscus cemented lens having a convex surface facing the objective lens side as described above, thereby reducing Petzval's sum and chromatic aberration of magnification. Was corrected. Further, a cemented lens is arranged in the second lens group, the object side surface of the negative lens on the object side thereof has a weak positive refractive power, and the cemented surface has a weak negative refractive power, whereby spherical aberration And off-axis aberrations are well balanced. Further, the axial chromatic aberration is corrected by setting the Abbe numbers of the negative lens and the positive lens of the cemented lens of the second lens group to appropriate values.

For the reasons described above, the present invention satisfies the above conditions (1) to (4).

The condition (1) defines the refractive power of the first lens group, and is for reducing the Petzval sum. In order to reduce the Petzval sum, it is necessary to prevent the refractive power from becoming larger than that shown in the condition (1). If the upper limit of 0.5 of the condition (1) is not satisfied, the refractive power becomes too large and the Petzval sum cannot be made small, so that it becomes difficult to correct various aberrations of the lens system in a well-balanced manner.

Conditions (2) and (3) define the refracting powers of the cemented surface and the object side surface of the cemented lens of the second lens group, respectively, in order to correct spherical aberration and off-axis aberration in a well-balanced manner. belongs to. These conditions (2), (3)
Are determined so as to weaken the refracting power of each surface, and if the upper limit of 4 in the condition (2) is exceeded, the positive refracting power of the object side surface of the cemented lens becomes too strong. Further, in the condition (3), when the lower limit of -4 is exceeded, the negative refractive power of the cemented surface of the cemented lens becomes too strong. Therefore,
When the upper limit of the condition (2) or the lower limit of the condition (3) is exceeded, the spherical aberration and the off-axis aberration cannot be balanced.
If the lower limit of the condition (2) is exceeded, the object-side surface of the cemented lens in the second lens group will have a negative refractive power, and spherical aberration and off-axis aberration cannot be corrected in good balance. If the upper limit of condition (3) is exceeded, the cemented surface of the cemented lens will have a positive refractive power, and spherical aberration and off-axis aberration cannot be corrected in a well-balanced manner.

The condition (4) defines the difference in Abbe number between the negative lens and the positive lens of the cemented lens of the second lens group, and is for correcting the axial chromatic aberration. If the Abbe number difference is smaller than the lower limit of 10 in this condition (4), it becomes difficult to correct the axial chromatic aberration.

In the prior art example of Japanese Patent Laid-Open No. 58-95314, the cemented lens arranged on the film surface side is a combination of a negative lens and a positive lens, but the cemented surface has a refractive power. Since it is positive, a meniscus lens with a convex surface facing the objective lens is placed between the cemented lens and the intermediate image position in front of this cemented lens to ensure negative refracting power and correct the overall aberration. ing.

In the present invention, the refractive power of the cemented surface of the cemented lens of the second lens group is made negative as described above, so that the aberration can be favorably corrected with a small number of groups and a small number of lenses. ing.

[0016]

EXAMPLES Examples of the microscope photography lens of the present invention will be described below. Example 1 β = −4 ×, NA = −0.04, IH = −25, OB = 17.83, EP = 1328 f = 32.234 r ₁ = 11.5433 d ₁ = 6.5000 n ₁ = 1.78650 ν ₁ = 50.00 r ₂ = -17.3065 d ₂ = 1.8000 n ₂ = 1.80100 ν ₂ ＝ 34.97 r ₃ ＝ 9.8963 d ₃ ＝ 4.8000 r ₄ ＝ ∞ (intermediate image position) d ₄ ＝ 20.6033 r ₅ = 11.1609 d ₅ ＝ 2.0000 n ₃ = 1.80518 ν ₃ ＝ 25.43 r _{6 = 6.4173 d 6 = 5.0000 n} 4 = 1.51454 ν 4 = 54.69 r 7 = -19.1579 f 1 = 82.706, | f / f 1 | = 0.389, {(n 3 -1) / r 5} · f = 2.325 { (N ₄ −n ₃ ) / r ₆ } · f = −1.46, ν ₄ −ν ₃ = 29.26 Example 2 β = −4 ×, NA = −0.04, IH = −25, OB = 17.83, EP = 1577 _{f = 31.934 r 1 = 11.6184 d} 1 = 6.5000 n 1 = 1.78650 ν 1 = 50.00 r 2 = -17.2887 d 2 = 1.8000 n 2 = 1.80100 ν 2 = 34.97 r 3 = 9.8019 d 3 = 4.8000 r 4 = ∞ ( intermediate Image position) d ₄ = 20.7721 r ₅ = 1.3098 d ₅ = 2.0000 n ₃ = 1.80518 ν _{3 = 25.43 r 6 = 6.7749 d} 6 = 5.0000 n 4 = 1.54739 ν 4 = 53.55 r 7 = -20.6377 f 1 = 91.342, | f / f 1 | = 0.35, {(n 3 -1) / r 5} · f = 2.089 {(n ₄ −n ₃ ) / r ₆ } f = −1.215, ν ₄ −ν ₃ = 28.12 Example 3 β = −5 ×, NA = −0.04, IH = −25, OB = 17.83 , EP = 456.5 f = 24.725 r 1 = 8.5561 d 1 = 5.0000 n 1 = 1.53256 ν 1 = 45.91 r 2 = -46.4055 d 2 = 2.0000 n 2 = 1.80100 ν 2 = 34.97 r 3 = 10.3276 d 3 = 6.3000 r 4 = ∞ (intermediate image _{position) d 4 = 18.1435 r 5 =} 24.4687 d 5 = 2.0000 n 3 = 1.80518 ν 3 = 25.43 r 6 = 6.7484 d 6 = 5.0000 n 4 = 1.73520 ν 4 = 41.08 r 7 = -20.1156 f 1 _{= 1268.64, | f / f 1} | = 0.019 {(n 3 -1) / r 5} · f = 0.814 {(n 4 -n 3) / r 6} · f = -0.256, ν 4 -ν 3 = 15.65 Example 4 β = −5 ×, NA = −0.04, IH = −25, OB = 17.83, EP = 1017 f = 26.189 _{1 = 9.6691 d 1 = 6.5000 n} 1 = 1.51633 ν 1 = 64.15 r 2 = -158.4859 d 2 = 1.8000 n 2 = 1.78300 ν 2 = 36.15 r 3 = 13.4794 d 3 = 5.0000 r 4 = ∞ ( intermediate image position) d ₄ = 17.3797 r ₅ = 11.4885 d ₅ = 2.0000 n ₃ = 1.72825 ν ₃ = 28.46 r ₆ = 5.7 515 d ₆ = 5.0000 n ₄ = 1.57439 ν ₄ = 53.55 r ₇ = -17.7903 f ₁ = 96.465, | f / f ₁ ｜ = 0.27, 0.1 / f = 0.0041 {(n ₃ -1) / r ₅ } ・ f = 1.66 {(n ₄ −n ₃ ) / r ₆ } ・ f = −0.824, ν ₄ −ν ₃ = 25.09 r ₁ , r ₂ , ... Are the radii of curvature of the respective lens surfaces, d
_1, d _2, ··· wall thickness of each lens, n _1, n _2, ··· is the refractive index of each lens, ν _1, ν _2, ··· is the Abbe number of each lens. Β is the magnification, NA is the numerical aperture, IH is the image height,
OB is the object point position measured from the first surface, and EP is the entrance pupil position measured from the first surface.

In each of Examples 1 to 4 described above, the lens configuration shown in FIG. 1 is used. The first lens group G ₁ is composed of one cemented lens in which a biconvex lens and a biconcave lens are cemented, and an intermediate image position (r ₄ ). The second lens group G ₂ arranged via the lens is composed of one cemented lens in which a negative meniscus lens having a convex surface facing the objective lens image and a biconvex lens are cemented.

The aberration curve diagrams of Examples 1 to 4 shown in FIGS. 2 to 5 are obtained when the tracing back is performed from the film surface to the objective image position.

[0019]

The microphotographing lens of the present invention is used in a microscope in which an objective lens and an eyepiece lens independently correct the field curvature, and the field curvature can be achieved with a small number of groups and a small number of lenses. Various aberrations such as astigmatism, distortion, and coma are corrected very well.

[Brief description of drawings]

FIG. 1 is a sectional view of a microscope photography lens of the present invention.

FIG. 2 is an aberration curve diagram of Example 1 of the present invention.

FIG. 3 is an aberration curve diagram of Example 2 of the present invention.

FIG. 4 is an aberration curve diagram of Example 3 of the present invention.

FIG. 5 is an aberration curve diagram of Example 4 of the present invention.

Claims (1)

[Claims] 1. A lens system mounted and used on the image side of a microscope objective lens, wherein a first lens group consisting of a meniscus-shaped cemented lens with a convex surface facing the objective lens and an intermediate image position are arranged in order from the object side. A second lens group including a cemented lens in which a negative lens and a positive lens are cemented to each other, which satisfy the following conditions. (1) | f / f ₁ | <0.5 (2) 0 <{(n ₃ −1) / r ₅ } · f <4 (3) −4 <{(n ₄ −n ₃ ) / r ₆ } · F <0 (4) ν ₄ −ν ₃ > 10 where f is the focal length of the entire system, f ₁ is the focal length of the first lens group, and n ₃ and n ₄ are cemented lenses of the second lens group, respectively. Refractive indices of the negative lens and the positive lens of d-line, r ₅ and r ₆ are the radii of curvature of the object-side surface and the cemented surface of the cemented lens of the second lens group, and ν ₃ and ν ₄ are the second lens group, respectively. Is the Abbe number of the negative lens and the positive lens of the cemented lens.