JPH08292374A - Liquid immersion microscope objective lens - Google Patents

Abstract

PURPOSE: To provide a liquid immersion microscope objective lens for which a magnification is set about from 40 times to 60 times, operating distance is comparatively long, the flatness of an image is improved as well, the number of openings is large about from 0.8 to 0.95 and the diameter of an objective lens top end is made fine ans sharp while maintaining satisfactory image formation performance. CONSTITUTION: This objective lens is composed of a 1st lens group G1 of positive refracting power, which is arranged on the most-object side and provided with the joint lens of a positive lens component and a meniscus lens component turning its concave surface toward the object side, and a 2nd lens group G2 of negative refracting power and satisfies the conditions as follows; d2 <|r2 |<4.5F and |r1 /F|>7. In this case, F is the focal distance of an entire system, r1 and r2 are the curvature radius of the lens surface on the most-object side of the joint lens and the curvature radius of a joint surface, and d2 is the central thickness of the meniscus lens component arranged on the image side of the joint lens.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an immersion microscope objective lens, and in particular, it has a magnifying power of 40 to 60 times and a numerical aperture of 0.8 to 0.95 and maintains excellent imaging performance. However, it relates to an immersion microscope objective lens having a relatively large working distance.

[0002]

2. Description of the Related Art Many proposals have been made in the past for an immersion microscope objective lens, especially for a high numerical aperture microscope objective lens using an oil immersion liquid. For example, Japanese Patent Laid-Open No. 6-1
No. 60720 has a magnification of about 40 times and a numerical aperture of about 1.0, and JP-A No. 54-79053 has a magnification of 100 times and a numerical aperture of about 1.25, both of which are apochromat. There is disclosed a technique for forming an immersion microscope objective lens in which aberration correction is performed in a class. The common point of these techniques is to have a cemented lens of a plano-convex lens closest to the object side and a meniscus lens having a strong concave surface toward the object side in order to secure the flatness of the image.

On the other hand, in order to observe a sample in an aqueous solution,
As a so-called water immersion objective lens in which the tip portion of the objective lens is directly immersed in an aqueous solution, the technique disclosed in Japanese Utility Model Laid-Open No. 3-31712 and German Utility Model No. 930353.7 is known. Further, in the technique disclosed in Japanese Patent Laid-Open No. 60-260016, when a dry objective lens has a relatively long working distance, a parallel flat plate is attached or incorporated as a waterproof glass at the tip of the objective lens to obtain a solution in an aqueous solution. It is noted that the sample can be observed.

[0004]

In recent years, in the field of biology, the focus is shifting from the conventional cell morphological observation to the investigation of the information transmission mechanism between cells. Along with this, needs for higher performance of microscopes and objective lenses are also expanding. For example, a patch clamp method, in which a minute glass electrode with a diameter of about several μm is brought into close contact with the cell membrane surface to examine the electrical characteristics of the ion channel of the cell membrane, which plays an important role in intracellular and intercellular information transmission The so-called method has been widely used recently. When attempting to perform this patch clamp method with an upright microscope, cells are often placed in a culture solution in order to maintain a state close to that in the living body. Since it is difficult to operate the electrodes, the influence of fluctuations on the surface of the culture solution is generally eliminated by using a water immersion objective lens in which the objective lens is directly immersed in the culture solution.

Next, when a water immersion objective lens is used, as shown in FIG.
As shown in, the micro glass electrode 4 is inserted between the objective lens 1 and the sample 2 in the culture medium 3, that is, in the space formed by the working distance of the objective lens 1 and is brought into close contact with the cell membrane surface. In order to improve the operability of the fine glass electrode 4 at this time, the objective lens 1 should have a long working distance, the tip should be as thin and sharp as possible, and the cell membrane surface should be made wider and clearer. It is desired to have a high numerical aperture for observation and to have good image flatness. The magnification of the objective lens 1 is preferably about 40 to 60 times, depending on the size of the cell of the observation target 2.

However, the above-mentioned Japanese Patent Laid-Open No. 6-1607.
The techniques disclosed in JP-A No. 20 and JP-A-54-79053 have a high numerical aperture of 1.0 and a numerical aperture of 1.25 and 40, respectively. Since the working distance is very short and the diameter of the tip of the objective lens is large,
It must be said that it is almost impossible to insert the micro glass electrode into the sample as described above.

Next, Japanese Utility Model Application No. 3-31712 and German Utility Model No. 930353.7 have almost the same purpose as that of the present invention described later, that is, when the patch clamp method is performed by an upright microscope. Regarding the technology of the water immersion microscope objective lens used, the one of Jitsukaihei 3-31712 is mainly used for the optical performance by the replacement of the inexpensive tip member against the alteration or damage of the lens surface caused by the culture solution or the like. In order to prevent the objective lens barrel part from being corroded by the acid or salt in the culture solution, the objective lens barrel This is a technique related to covering a portion with resin from the outside.

[0008] Therefore, in these techniques, in order to improve the operability of the micro glass electrode, the demand has recently been increased, the working distance is increased, and the tip diameter is made as thin and sharp as possible. Cannot have an immersion microscope objective lens having a high numerical aperture and a good image flatness. In addition, JP-A-60-260016
As described in No. 1), when a dry objective lens has a relatively long working distance, a parallel plane plate is attached or incorporated as a waterproof glass at the tip of the objective lens to observe a sample in an aqueous solution. However, with this technique, the numerical aperture is as small as 0.55 and the resolution cannot be said to be sufficient. Even if the numerical aperture can be made larger than 0.55, if the air layer is interposed between the waterproof glass and the first surface of the objective lens, the sample to the first surface of the lens are all filled with the liquid. In comparison, the angle of incidence of the axial aperture ray on the first surface of the lens is equal to the refractive index of the liquid, specifically about 1.33 times when the liquid is water, and about 1.52 when the liquid is an oil immersion liquid. It is about twice as large, and the diameter of the tip of the objective lens cannot be made thin and sharp.

The present invention has been made in view of such a situation of the prior art, and its object is to increase the magnification from 40 times to 6 times.
About 0 times, the working distance is relatively long, the flatness of the image is good, and the numerical aperture is as large as 0.8 to 0.95. An object of the present invention is to provide an immersion microscope objective lens having a small diameter and a sharpened diameter.

[0010]

An immersion microscope objective according to the present invention that achieves the above object is a meniscus lens having a positive lens component and a concave surface facing the object side, which are arranged in order from the object side to the most object side. The first lens group having a positive refracting power and a second lens group having a negative refracting power, each of which has a cemented lens with a component, are characterized by satisfying the following conditions. (1) d ₂ <| r ₂ | <4.5F (2) | r ₁ / F |> 7 where F is the focal length of the entire system and r ₁ and r ₂ are the most object side of the cemented lens. The radius of curvature of the lens surface, the radius of curvature of the cemented surface, and d ₂ are the central thicknesses of the meniscus lens components arranged on the image side of the cemented lens.

In this case, it is desirable that the following condition is further satisfied. (3) 0.8 <d ₀ / d ₁ <5 (4) n ₂ −n ₁ > 0.1 where d ₀ is the distance from the object plane to the first lens surface, d
₁ is the center wall thickness of the positive lens component arranged on the object side of the cemented lens, n ₁ and n ₂ are the refractive indices of the positive lens component arranged on the object side of the cemented lens, and are arranged on the image side. It is the refractive index of the meniscus lens component.

Further, it is preferable that the cemented lens has a chamfered portion which is inclined in a direction of an axial aperture ray incident on the cemented lens from the object surface.

[0013]

The reason why the above structure is adopted and the operation thereof will be described below. In the immersion microscope objective lens of the present invention, the first lens group having a positive refractive power is disposed on the most object side, and includes a positive lens component directly immersed in the liquid and a meniscus lens component having a concave surface facing the object side. With the cemented lens, the luminous flux is guided to the second lens group while balancing the occurrence of spherical aberration, field curvature, etc. with the ray angle of the axial aperture ray emerging from this cemented lens and keeping the ray height low. It has become. The second lens group corrects spherical aberration, field curvature, and coma that are undercorrected in the first lens group due to its negative refracting power, and at the same time, makes the entire length of the objective lens a predetermined value, that is, the so-called parfocal distance. Plays a role in keeping in. Generally, in the design of an objective lens, maintaining a long working distance and a high numerical aperture is contradictory to making the diameter of the tip of the objective lens thin and sharp, but in the present invention, these The functions of the first and second lens groups constitute an immersion microscope objective lens having a sharp and sharp tip diameter of the objective lens while maintaining good imaging performance as the entire objective lens.

Each conditional expression will be described below. Conditional expression (1) defines the radius of curvature of the cemented surface between the positive lens component arranged closest to the object side in the first lens unit and the meniscus lens component having a concave surface facing the object side, and the spherical aberration These are conditions provided for correction of field curvature and coma. If the lower limit d ₂ of this conditional expression is not satisfied, the radius of curvature of this cemented surface becomes tight and the negative refractive power at that cemented surface becomes large, which is advantageous for correction of field curvature, but The effect of converging the light flux becomes weaker, and it is not possible to keep the ray angle and height of the axial aperture ray exiting this cemented lens low, but also the higher ray height causes higher-order spherical aberration. , The second lens group cannot be completely corrected. At this time, the ray angle of the on-axis aperture ray,
Although it is possible to suppress the ray height to a low level by shortening the working distance, it cannot be said to be an appropriate means in the present invention which also aims at maintaining a long working distance. On the other hand, when the upper limit of 4.5F in this conditional expression is exceeded, the radius of curvature of the cemented surface becomes gentle, and the ray angle and ray height of the axial aperture ray emerging from this cemented lens can be suppressed to a low level, but the image The surface curvature is large and the correction is insufficient. In order to correct this with the second lens group, a strong negative refractive power surface must be provided in the second lens group, but due to this strong negative refractive power surface, high-order spherical aberration and coma aberration occur, It becomes impossible to maintain good imaging performance as the entire objective lens.

Conditional expression (2) defines the radius of curvature of the first surface of the lens which is closest to the object side among the cemented lenses arranged closest to the object side in the first lens group and which is directly immersed in the liquid. It is a thing. When the radius of curvature of the first lens surface is negative, this cemented lens becomes a meniscus lens, which is preferable for correction of spherical aberration and field curvature. However, when the lower limit of 7 of these conditions is not satisfied, this cemented lens is emitted. It becomes impossible to keep the ray angle and ray height of the axial aperture ray low. If you try to force the ray angle and ray height low,
As in the case where the lower limit of the condition (1) is not satisfied, the working distance becomes extremely short, which is not preferable. When the radius of curvature of the first lens surface is positive, this cemented lens becomes a biconvex lens,
Since the converging action becomes strong, the ray angle and the ray height of the axial aperture ray emerging from this cemented lens can be kept low. However, if the converging action becomes too strong beyond the lower limit of 7 of this condition, not only the field curvature but also the spherical aberration and the coma will be largely undercorrected, and the second lens group will not be able to fully correct. Further, regardless of whether the radius of curvature of the first surface of the lens is positive or negative, if the radius of curvature is out of the lower limit of this condition, the immersion liquid will enter the peripheral portion of the lens and will not be wiped off or air will enter. Operational problems such as a higher possibility will occur.

Further, in the present invention, it is desirable to satisfy the conditional expressions (3) and (4) in order to perform the aberration correction better. Conditional expression (3) is the distance from the object surface to the first lens surface, that is, the working distance and the center of the positive lens component arranged on the object side of the cemented lens arranged on the most object side in the first lens group. The ratio to the wall thickness is determined. If the lower limit of 0.8 of this condition is not satisfied, the center wall thickness of the positive lens component becomes relatively thick, and the ray angle of the axial aperture ray and the ray height are It cannot be kept low. On the other hand, when the upper limit of 5 to this condition is exceeded, the center thickness of the positive lens component becomes thin, and the shape becomes close to the so-called embedded lens shape that is often used for a front lens cemented lens of an oil immersion microscope objective lens. There is an unavoidable increase in costs.

Conditional expression (4) is defined by the refractive index of the positive lens component arranged on the object side of the cemented lens arranged on the most object side in the first lens group and the refraction of the meniscus lens component arranged on the image side. It defines the relationship of the ratios and relates to the correction of the field curvature. The lower limit of this conditional expression is 0.1
If the value is out of the range, the divergent power at the cemented surface of this cemented lens becomes weak, and the field curvature is largely undercorrected. For the same reason as when the upper limit of conditional expression (1) is exceeded, the second lens group corrects I can't run out.

In the present invention, the cemented lens arranged closest to the object side in the first lens group has a chamfered portion which is inclined in the direction of the axial aperture ray incident on the cemented lens from the object plane. It is desirable to make the tip of the objective lens as thin and sharp as possible.

In order to satisfactorily correct the axial chromatic aberration, the first lens group includes a cemented lens arranged closest to the object side, a divergent cemented surface, and a positive lens and a negative lens. It is desirable to have a cemented lens and to satisfy the following conditions. (5) ν _1P −ν _1N > 20 where ν _1P and ν _1N are the cemented lenses having a divergent cemented surface other than the cemented lens arranged closest to the object side in the first lens group, respectively, At least one positive lens Abbe number and negative lens Abbe number.

If the lower limit of 20 to condition (5) is not satisfied, axial chromatic aberration will be large and correction will remain insufficient. If this is attempted to be forcibly corrected, the curvature of the divergent cemented surface will become tight and high-order spherical aberration will occur.

Further, in order to more favorably correct the field curvature and the chromatic aberration of magnification, the second lens unit having negative refracting power has a cemented meniscus lens component having a convex surface facing the object side and a concave surface facing the object side. It is desirable to have a so-called Gauss type, which is composed of a cemented meniscus lens component.

[0022]

EXAMPLES Examples 1 to 4 of the immersion microscope objective lens of the present invention will be described below.

Although the lens data of each example will be described later, FIGS. 2 to 4 are sectional views showing the lens configurations of Examples 1 to 3, respectively. The fourth embodiment is almost the same as the first embodiment, and is not shown.

In Examples 1 and 4, as shown in FIG. 2, the first lens group G1 is cemented with a positive meniscus lens having a gentle concave surface facing the object side and a positive meniscus lens having a concave surface facing the object side. The second lens group G2 includes a positive meniscus lens, a positive meniscus lens having a concave surface facing the object side, and a double-convex lens, and a double-concave lens and a double-convex lens. The second lens group G2 includes a negative meniscus lens, a biconvex lens, and a negative meniscus lens. And a cemented meniscus lens of a biconvex lens and a biconcave lens, and a cemented meniscus lens of a biconcave lens and a biconvex lens.

In the second embodiment, as shown in FIG. 3, the first lens group G1 is a cemented positive lens including a biconvex lens having a gentle convex surface facing the object side and a positive meniscus lens having a concave surface facing the object side. It is composed of a positive meniscus lens with a concave surface facing toward the side, a double-convex lens, a double-concave lens, and a double-convex lens, and a second lens group G2 includes a negative meniscus lens, a double-convex lens, and a negative meniscus lens. lens,
It is composed of a cemented meniscus lens of a biconvex lens and a biconcave lens, and a cemented meniscus lens of a biconcave lens and a biconvex lens.

In the third embodiment, as shown in FIG. 4, the first lens group G1 is a cemented positive lens composed of a plano-convex lens and a positive meniscus lens having a concave surface facing the object side, and a positive meniscus having a concave surface facing the object side. The second lens group G2 includes a double-convex lens, a double-concave lens, a double-concave lens, and a double-convex lens, and a double-convex lens. The second lens group G2 includes a negative meniscus lens, a double-convex lens, a double-concave lens, and a double-convex lens. It is composed of a cemented meniscus lens with a concave lens and a cemented meniscus lens with a biconcave lens and a biconvex lens.

The lens data of each example are shown below. In addition to the above, the symbols are F, the focal length of the entire objective lens system, β is the magnification, NA is the numerical aperture, and d ₀ is the working distance (sample surface). To the top of the lens on the most object side). In addition, r ₁ , r ₂ ... Are the radii of curvature of the respective lens surfaces shown in order from the object side, d ₁ , d ₂ ... _Are the intervals between the lens surfaces shown in order from the object side, and n _d1 , n _d2 . The d-line refractive index of each lens shown in order from the side, v _d1 , v _d2, ... Are Abbe numbers of each lens shown in order from the object side. Further, water is used as the immersion liquid, and the d-line has a refractive index of n _d = 1.33304,
The Abbe number is ν _d = 55.79.

Example 1 F = 4.5, β = 40 ×, NA = 0.8, d ₀ = 3.3 r ₁ = -50.0000 d ₁ = 1.7142 n _d1 = 1.51633 ν _d1 = 64.15 r ₂ =- 14.9837 d ₂ = 2.9404 n _d2 = 1.78650 ν _d2 = 50.00 r ₃ = -6.4578 d ₃ = 0.2000 r ₄ = -18.4075 d ₄ = 2.2000 n _d3 = 1.49700 ν _d3 = 81.61 r ₅ = -9.0329 d ₅ = 0.2000 r ₆ = 10.9628 d ₆ = 3.7000 n _d4 = 1.43875 ν _d4 = 94.97 r ₇ = -43.3236 d ₇ = 1.0000 n _d5 = 1.78650 ν _d5 = 50.00 r ₈ = 12.8380 d ₈ = 4.0000 n _d6 = 1.49700 ν _d6 = 81.61 r ₉ = -18.9597 d ₉ = 0.2000 r ₁₀ = 20.7312 d ₁₀ = 0.9000 n _d7 = 1.59551 ν _d7 = 39.29 r ₁₁ = 9.7690 d ₁₁ = 5.7000 n _d8 = 1.43875 ν _d8 = 94.97 r ₁₂ = -7.1490 d ₁₂ = 1.0000 _nd9 = 1.78650 ν _d9 = 50.00 r ₁₃ = -23.0774 d ₁₃ = 0.2000 r ₁₄ = 6.6879 d ₁₄ = 5.4198 n _d10 = 1.49700 ν _d10 = 81.61 r ₁₅ = -10.8851 d ₁₅ = 2.9732 n _d11 = 1.52944 ν _d11 = 51.72 r ₁₆ = 5.9666 d ₁₆ = 4.8172 r ₁₇ = -3.2410 d ₁₇ = 5.3712 n _d12 = 1.50378 ν _d12 = 66 .81 r ₁₈ = 77.5188 d ₁₈ = 3.2885 n _d13 = 1.58144 ν _d13 = 40.75 r ₁₉ = -9.0743 ｜ r ₁ / F ｜ = 11.11 d ₀ / d ₁ = 1.93 n ₂ −n ₁ = 0.27 ν _1P −ν _1N = 31.61.

Example 2 F = 4.5, β = 40 ×, NA = 0.8, d ₀ = 3.3 r ₁ = 80.0000 d ₁ = 1.6912 n _d1 = 1.51633 ν _d1 = 64.15 r ₂ = -8.8752 d ₂ = 2.5950 n _d2 = 1.78650 ν _d2 = 50.00 r ₃ = -6.0510 d ₃ = 0.2000 r ₄ = -15.4999 d ₄ = 2.3337 n _d3 = 1.49700 ν _d3 = 81.61 r ₅ = -9.1373 d ₅ = 0.2000 r ₆ = 10.5626 d ₆ = 3.7112 n _d4 = 1.43875 ν _d4 = 94.97 r ₇ = -71.3466 d ₇ = 1.0000 n _d5 = 1.78650 ν _d5 = 50.00 r ₈ = 15.0752 d ₈ = 3.9298 n _d6 = 1.49700 ν _d6 = 81.61 r ₉ =- 22.3245 d ₉ = 0.2000 r ₁₀ = 20.1621 d ₁₀ = 1.3847 n _d7 = 1.59551 ν _d7 = 39.29 r ₁₁ = 8.9947 d ₁₁ = 5.6341 n _d8 = 1.43875 ν _d8 = 94.97 r ₁₂ = -6.6141 d ₁₂ = 0.9018 n _d9 = 1.78650 ν _d9 = 50.00 r ₁₃ = -19.8617 d ₁₃ = 0.3000 r ₁₄ = 6.6746 d ₁₄ = 5.4724 n _d10 = 1.49700 ν _d10 = 81.61 r ₁₅ = -10.8419 d ₁₅ = 2.9912 n _d11 = 1.52944 ν _d11 = 51.72 r ₁₆ = 6.5021 d ₁₆ = 4.7029 r ₁₇ = -3.2522 d ₁₇ = 4.9352 n _d12 = 1.50378 ν _d12 = 66.8 1 r ₁₈ = 30.1585 d ₁₈ = 3.6414 n _d13 = 1.58144 ν _d13 = 40.75 r ₁₉ = -9.3897 ｜ r ₁ / F ｜ ＝ 17.78 d ₀ / d ₁ = 1.95 n ₂ −n ₁ ＝ 0.27 ν _1P −ν _1N ＝ 31.61.

Example 3 F = 3, β = 60 ×, NA = 0.95, d ₀ = 2 r ₁ = ∞ d ₁ = 1.6786 n _d1 = 1.51633 ν _d1 = 64.15 r ₂ = -4.7504 d ₂ = 2.8313 n _d2 = 1.78650 ν _d2 = 50.00 r ₃ = -4.8697 d ₃ = 0.2000 r ₄ = -22.9988 d ₄ = 2.3000 n _d3 = 1.56907 ν _d3 = 71.30 r ₅ = -8.8777 d ₅ = 0.2500 r ₆ = 14.0213 d ₆ = 4.5000 n _d4 = 1.49700 ν _d4 = 81.10 r ₇ = -8.3387 d ₇ = 1.0000 n _d5 = 1.78650 ν _d5 = 50.00 r ₈ = 38.5186 d ₈ = 3.8257 n _d6 = 1.43875 ν _d6 = 94.97 r ₉ = -15.0470 d ₉ = 0.1500 r ₁₀ = 11.7026 d ₁₀ = 3.5500 n _d7 = 1.56907 ν _d7 = 71.30 r ₁₁ = -55.5525 d ₁₁ = 0.4583 r ₁₂ = 11.7215 d ₁₂ = 1.6666 n _d8 = 1.78650 ν _d8 = 50.00 r ₁₃ = 4.9117 d ₁₃ = 5.2000 n _d9 = 1.43875 ν _d9 = 94.97 r ₁₄ = -7.0332 d ₁₄ = 1.0000 n _d10 = 1.59551 ν _d10 = 39.29 r ₁₅ = 29.9783 d ₁₅ = 0.9834 r ₁₆ = 10.2367 d ₁₆ = 4.0000 n _d11 = 1.49700 ν _d11 = 81.10 r ₁₇ = -4.0244 d ₁₇ = 4.5641 n _d12 = 1.52944 ν _d12 = 51.72 r ₁₈ = 3. 2217 d ₁₈ = 1.6475 r ₁₉ = -2.8800 d ₁₉ = 4.4943 n _d13 = 1.50378 ν _d13 = 66.81 r ₂₀ = 52.3711 d ₂₀ = 2.5000 n _d14 = 1.58144 ν _d14 = 40.75 r ₂₁ = -6.2506 ｜ r ₁ / F ｜ = ∞ d ₀ / d ₁ = 1.19 n ₂ −n ₁ = 0.27 ν _1P −ν _1N = 31.61.

Example 4 F = 4.5, β = 40 ×, NA = 0.8, d ₀ = 3.7 r ₁ = -50.0000 d ₁ = 1.2003 n _d1 = 1.51633 ν _d1 = 64.15 r ₂ =- 8.9713 d ₂ = 3.3118 n _d2 = 1.78650 ν _d2 = 50.00 r ₃ = -6.3181 d ₃ = 0.2000 r ₄ = -15.6224 d ₄ = 2.2000 n _d3 = 1.49700 ν _d3 = 81.61 r ₅ = -9.3413 d ₅ = 0.2000 r _{6 = 11.1102 d 6 = 3.7000 n d4} = 1.43875 ν d4 = 94.97 r 7 = -43.2426 d 7 = 1.0000 n d5 = 1.78650 ν d5 = 50.00 r 8 = 19.2603 d 8 = 4.0000 n d6 = 1.49700 ν d6 = 81.61 r 9 = -18.8109 d ₉ = 0.2000 r ₁₀ = 16.7250 d ₁₀ = 0.9000 n _d7 = 1.59551 ν _d7 = 39.29 r ₁₁ = 8.2417 d ₁₁ = 5.7000 n _d8 = 1.43875 ν _d8 = 94.97 r ₁₂ = -7.0879 d ₁₂ = 1.0000 n _d9 = 1.78650 ν _d9 = 50.00 r ₁₃ = -31.8041 d ₁₃ = 0.2000 r ₁₄ = 6.5196 d ₁₄ = 5.3629 n _d10 = 1.49700 ν _d10 = 81.61 r ₁₅ = -10.9160 d ₁₅ = 2.8938 n _d11 = 1.52944 ν _d11 = 51.72 r ₁₆ = 5.7419 d ₁₆ = 4.6506 r ₁₇ = -3.1185 d ₁₇ = 4.7817 n _d12 = 1.50378 ν _d12 = 66. 81 r ₁₈ = 81.3310 d ₁₈ = 3.9234 n _d13 = 1.58144 ν _d13 = 40.75 r ₁₉ = -8.8477 ｜ r ₁ / F ｜ = 11.11 d ₀ / d ₁ = 3.08 n ₂ −n ₁ = 0.27 ν _1P −ν _1N = 31.61.

Each of the first to fourth embodiments is an infinity correction type objective lens in which the light emitted from the objective lens becomes a parallel light beam, and does not form an image by itself. Therefore, for example, it is used in combination with the imaging lens having the lens data shown below and having the lens cross section shown in FIG. However, in the lens data, r ₁ ′, r ₂ ′ ... Are the radii of curvature of the respective lens surfaces shown in order from the object side, d ₁ ′, d ₂ ′ ... are the intervals between the lens surfaces shown in order from the object side, n _d1 ', n _d2 ' ... are d-line refractive indices of the lenses shown in order from the object side, and v _d1 ', v _d2 ' ... are Abbe numbers of the lenses shown in order from the object side.

R ₁ '= 68.7541 d ₁ ' = 7.7321 n _d1 '= 1.48749 ν _d1 ' = 70.20 r ₂ '= -37.5679 d ₂ ' = 3.4742 n _d2 '= 1.80610 ν _d2 ' = 40.95 r ₃ '= -102.8477 d ₃ '= 0.6973 r ₄ ' = 84.3099 d ₄ '= 6.0238 n _d3 ' = 1.83400 ν _d3 '= 37.16 r ₅ ' = -50.7100 d ₅ '= 3.0298 n _d4 ' = 1.64450 ν _d4 '= 40.82 r ₆ ' = 40.6619.

In this case, the distance between the objective lens of Examples 1 to 4 and the imaging lens of FIG. 5 may be any position between 50 mm and 170 mm, but Example 1 when this distance is 120 mm Aberration diagrams of 4 to 4 are shown in FIGS. 6 to 9, respectively. However, in these aberration diagrams, (a) shows spherical aberration, (b) shows coma, and (c) shows astigmatism. In these aberration diagrams, IM. H indicates the image height. It should be noted that substantially the same aberration situation is exhibited at positions other than 120 mm when the distance is between 50 mm and 170 mm.

[0035]

As is apparent from the above description, according to the present invention, the magnification is about 40 to 60 times, the working distance is relatively long, the flatness of the image is good, and the aperture is large. The number is as large as 0.8 to 0.95, and it is possible to provide an immersion microscope objective lens in which the diameter of the objective lens tip is thin and sharpened while maintaining excellent imaging performance.

[Brief description of drawings]

FIG. 1 is a diagram for explaining requirements required for a water immersion microscope objective lens when performing a patch clamp method.

FIG. 2 is a lens sectional view of Example 1 of the immersion microscope objective lens of the present invention.

FIG. 3 is a lens cross-sectional view of Example 2.

FIG. 4 is a lens cross-sectional view of Example 3.

FIG. 5 is a lens cross-sectional view of an example of an imaging lens used with the immersion microscope objective lens of each example.

FIG. 6 is an aberration diagram showing spherical aberration, coma and astigmatism of Example 1.

FIG. 7 is an aberration diagram showing spherical aberration, coma aberration, and astigmatism of Example 2.

FIG. 8 is an aberration diagram showing spherical aberration, coma and astigmatism of Example 3.

FIG. 9 is an aberration diagram showing spherical aberration, coma and astigmatism of Example 4.

[Explanation of symbols]

 G1 ... 1st lens group G2 ... 2nd lens group 1 ... Water immersion microscope objective lens 2 ... Sample 3 ... Culture liquid 4 ... Micro glass electrode

Claims (3)

[Claims] 1. A first lens unit having a positive refracting power, which is arranged on the most object side in order from the object side and has a cemented lens of a positive lens component and a meniscus lens component having a concave surface facing the object side, and a negative refracting power. And a second lens group of No. 2, which satisfies the following conditions. (1) d ₂ <| r ₂ | <4.5F (2) | r ₁ / F |> 7 where F is the focal length of the entire system and r ₁ and r ₂ are the most object side of the cemented lens. The radius of curvature of the lens surface, the radius of curvature of the cemented surface, and d ₂ are the central thicknesses of the meniscus lens components arranged on the image side of the cemented lens. 2. The immersion microscope objective lens according to claim 1, wherein the following conditions are satisfied. (3) 0.8 <d ₀ / d ₁ <5 (4) n ₂ −n ₁ > 0.1 where d ₀ is the distance from the object plane to the first lens surface, d
₁ is the center wall thickness of the positive lens component arranged on the object side of the cemented lens, n ₁ and n ₂ are the refractive indices of the positive lens component arranged on the object side of the cemented lens, and are arranged on the image side. It is the refractive index of the meniscus lens component. 3. The immersion microscope objective lens according to claim 1, wherein the cemented lens has a chamfered portion that is inclined in a direction of an axial aperture ray incident on the cemented lens from an object plane. .