JP4660873B2 - Parallel system stereo microscope objective lens - Google Patents

Description

図２は、本実施例の諸収差を示す図である。諸収差はいずれも観察光学系側（物体より遠い側）より光線を入射させて追跡したもので、観察光学系の光軸を通る光線を基準にして表示してある。また、非点収差と歪曲収差はズーム低倍時、横収差はズーム高倍時の収差図である。なお、以下、全ての実施例の諸収差図は、本実施例の諸収差と同様の条件のものを示し、同様の符号を用いる。図からも明らかなように諸収差が良好に補正されていることがわかる。
【００２５】
（第２実施例）
図３は、本実施例にかかる平行系実体顕微鏡対物レンズのレンズ構成を示す図である。物体から遠い側より順に、正の屈折力を有し、レンズＬ１とレンズＬ２とからなる両凸形状の接合レンズを含む第１レンズ群Ｇ１と、複数の接合レンズ又は単レンズからなり、少なくとも２群の接合レンズを含む第２レンズ群Ｇ２とを有している。また、第２レンズ群Ｇ２は、物体から最も遠い側に、レンズＬ３とレンズＬ４とからなり、凹面を物体から遠い側に向けたメニスカス形状の第1の接合レンズを有している。
【００２６】
表２に本実施例の諸元値を掲げる。なお、観察光学系の光軸間距離は22ｍｍ、観察光学系の入射瞳位置はズーム低倍時41ｍｍ、ズーム高倍時165ｍｍである。
【００２７】
【表２】

図４は本実施例の諸収差を示す図である。図から明らかなように良好に諸収差が補正されていることがわかる。
【００２８】
（第３実施例）
図５は、本実施例にかかる平行系実体顕微鏡対物レンズのレンズ構成を示す図である。物体から遠い側より順に、正の屈折力を有し、レンズＬ１とレンズＬ２とからなる両凸形状の接合レンズを含む第１レンズ群Ｇ１と、複数の接合レンズ又は単レンズからなり、少なくとも２群の接合レンズを含む第２レンズ群Ｇ２とを有している。また、第２レンズ群Ｇ２は、物体から最も遠い側に、レンズＬ３とレンズＬ４とからなる凹面を物体から遠い側に向けたメニスカス形状の第1の接合レンズを有している。
【００２９】
表３に本実施例の諸元値を掲げる。なお、観察光学系の光軸間距離は22ｍｍ、観察光学系の入射瞳位置はズーム低倍時41ｍｍ、ズーム高倍時165ｍｍである。
【００３０】
【表３】

図６は本実施例の諸収差を示す図である。図から明らかなように良好に諸収差が補正されていることがわかる。
【００３１】
（第４実施例）
図７は、本実施例にかかる平行系実体顕微鏡対物レンズのレンズ構成を示す図である。物体から遠い側より順に、正の屈折力を有し、レンズＬ１とレンズＬ２とからなる両凸形状の接合レンズを含む第１レンズ群Ｇ１と、複数の接合レンズ又は単レンズからなり、少なくとも２群の接合レンズを含む第２レンズ群Ｇ２とを有している。また、第２レンズ群Ｇ２は、物体から最も遠い側に、レンズＬ３とレンズＬ４とからなる凹面を物体から遠い側に向けたメニスカス形状の第1の接合レンズを有している。
【００３２】
表４に本実施例の諸元値を掲げる。なお、観察光学系の光軸間距離は22ｍｍ、観察光学系の入射瞳位置はズーム低倍時41ｍｍ、ズーム高倍時165ｍｍである。
【００３３】
【表４】

図８は本実施例の諸収差を示す図である。図から明らかなように良好に諸収差が補正されていることがわかる。
【００３４】
（第５実施例）
図９は、本実施例にかかる平行系実体顕微鏡対物レンズのレンズ構成を示す図である。物体から遠い側より順に、正の屈折力を有し、レンズＬ１とレンズＬ２とからなる両凸形状の接合レンズを含む第１レンズ群Ｇ１と、複数の接合レンズ又は単レンズからなり、少なくとも２群の接合レンズを含む第２レンズ群Ｇ２とを有している。また、第２レンズ群Ｇ２は、物体から最も遠い側に、レンズＬ３とレンズＬ４とからなる凹面を物体から遠い側に向けたメニスカス形状の第1の接合レンズを有している。
【００３５】
表５に本実施例の諸元値を掲げる。なお、観察光学系の光軸間距離は22ｍｍ、観察光学系の入射瞳位置はズーム低倍時41ｍｍ、ズーム高倍時165ｍｍである。
【００３６】
【表５】

図１０は本実施例の諸収差を示す図である。図から明らかなように良好に諸収差が補正されていることがわかる。
【００３７】
【発明の効果】
以上説明したように、本発明によれば、高倍率、高ＮＡでアポクロマート級の性能を有する平行系実体顕微鏡対物レンズを提供することができる。
【図面の簡単な説明】
【図１】第1実施例のレンズ構成及び光路を示す図である。
【図２】第１実施例の諸収差を示す図である。
【図３】第２実施例のレンズ構成及び光路を示す図である。
【図４】第２実施例の諸収差を示す図である。
【図５】第３実施例のレンズ構成及び光路を示す図である。
【図６】第３実施例の諸収差を示す図である。
【図７】第４実施例のレンズ構成及び光路を示す図である。
【図８】第４実施例の諸収差を示す図である。
【図９】第５実施例のレンズ構成及び光路を示す図である。
【図１０】第５実施例の諸収差を示す図である。
【図１１】従来の平行系実体顕微鏡レンズの構成を示す図である。
【符号の説明】
Ｇ１ 第１レンズ群
Ｇ２ 第２レンズ群
Ｌ１〜Ｌ８ 各レンズ成分[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an objective lens for a parallel single-objective binocular stereomicroscope that has an apochromat class performance that suppresses the occurrence of chromatic aberration as much as possible and that has excellent image flatness. In particular, the present invention relates to a high-magnification objective lens for a parallel stereomicroscope having a focal length of about 50 mm.
[0002]
[Prior art]
With a stereomicroscope, when an uneven object is observed, it can be observed with a three-dimensional effect in the same way as when viewed with both eyes. For this reason, when working under a microscope, it is possible to easily grasp the distance relationship between a tool such as tweezers and an object. Therefore, it is particularly effective in fields requiring fine treatment such as precision machine industry, biological dissection, and surgery. In a stereomicroscope, in order to obtain a parallax for a stereoscopic effect of an object, the optical systems of light beams incident on the left and right eyes are at least partially independent so that their optical axes intersect on the object plane. Then, a magnified image of the object viewed from different directions is created, and the object is viewed through an eyepiece lens, thereby stereoscopically viewing the minute object. As a typical method for obtaining stereoscopic vision of a stereomicroscope, there is a parallel stereo microscope (parallel single objective binocular microscope). The parallel system stereomicroscope has one objective lens system and two observation optical systems for the right eye and for the left eye arranged in parallel to the optical axis of the objective lens system.
[0003]
[Problems to be solved by the invention]
In the parallel system stereomicroscope, one objective lens whose focal position coincides with the object plane plays a role of guiding an afocal light beam to the subsequent variable power optical system for both eyes. That is, the optical axis of the objective lens is different from the optical axis of the zoom optical system for the left and right eyes actually used for observation. Thus, since the light beam passing through the objective lens is decentered with respect to the center of rotation of the objective lens, the lens system has a very high degree of difficulty in optical design.
[0004]
In the case of a stereomicroscope, the NA of an objective lens that determines the brightness and resolution of an observation image is usually relatively small, around 0.1. This is because the overall observation magnification is as low as 10 to 500 times, and a long working distance has been regarded as important in consideration of operability rather than resolving power. In the case of an objective lens of a single objective binocular stereomicroscope, it is necessary to correct aberrations with a double NA since a single objective lens guides light of the necessary NA for both eyes.
[0005]
In recent years, research on manipulating smaller objects such as fertilized eggs and cells has been actively conducted, and the need for high-magnification and high-NA stereomicroscopes is increasing. There is also a need for an apochromatic objective lens with good chromatic aberration correction performance in order to obtain high resolution over a wide wavelength region. In addition, since it is also necessary to take a photograph of a specimen, a high-magnification and high-NA apochromatic objective lens is required for a parallel single objective binocular stereomicroscope with high system characteristics.
[0006]
In addition, since the zoom ratio of the variable magnification optical system is increased by observing from the whole image to the partially magnified image with one microscope, the image by the objective lens tends to be magnified to a higher magnification. As examples of the objective lens of such a single objective binocular stereomicroscope, the lens systems disclosed in Japanese Utility Model Publication Nos. 7-60218 and 10-26729 are known.
[0007]
FIG. 11 is a diagram showing a configuration of a lens system disclosed in Japanese Utility Model Publication No. 7-60218. In the embodiment described in the above publication, the spherical aberration of a light beam having a short wavelength with respect to the reference wavelength is excessively corrected in the periphery. Further, when enlarging at a high magnification by the subsequent variable magnification optical system, the chromatic aberration becomes conspicuous and the resolution is poor.
[0008]
The present invention has been made in view of the above problems, and an object of the present invention is to provide an apochromat-type parallel stereomicroscope objective lens that has a high magnification and a high NA, and has thoroughly eliminated chromatic aberration.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, the present invention includes, in order from the side farther from the object, a first lens group having a positive refractive power and composed of a biconvex cemented lens;
A second lens group including at least two cemented lenses;
Have
While satisfying the following conditions , the light from the object is substantially parallel to the optical axes of the second lens group and the first lens group via the second lens group and the first lens group. A parallel stereomicroscope objective lens is provided that emits light toward at least two observation optical systems each having an optical axis .
(1) 0.1 <| r11 / f1 | <1.0
here,
r11: radius of curvature of the cemented surface of the cemented lens of the first lens group,
f1: focal length of the first lens group.
[0011]
Conditional expression (1) defines the amount of axial chromatic aberration. The on-axis light beam that gives a large NA first passes through the first lens group, where it is bent into a convergent light beam. Therefore, it is desirable that the first lens group has an axial aberration correcting action. However, if only the cemented lens of the first lens group has the above correction action, the spherical aberration on the long wavelength side is insufficiently corrected and the spherical aberration on the short wavelength side is excessively corrected with respect to the reference wavelength. In particular, chromatic aberration becomes conspicuous at zoom high magnification.
[0012]
If the upper limit value of conditional expression (1) is exceeded, axial aberration correction becomes difficult, and the bending of the change in spherical aberration due to the increase in brightness becomes large. On the other hand, if the lower limit of conditional expression (1) is not reached, it becomes difficult to correct chromatic aberration, and color misregistration at the time of zoom high magnification becomes conspicuous. More preferably, the upper limit value is 0.42 and the lower limit value is 0.15.
[0013]
According to the present invention, the first cemented lens of the two groups of cemented lenses in the second lens group is disposed on the side farthest from the object, and has a meniscus shape with the concave surface facing the side far from the object. It is desirable to satisfy the following conditions.
(2) 0.5 <| r21 / f | <80
here,
r21: radius of curvature of the cemented surface of the first cemented lens,
f: The focal length of the entire system of the parallel stereomicroscope objective lens.
[0014]
Conditional expression (2) defines the amount of the secondary spectrum and distortion. The secondary spectrum is a case where the other two wavelengths are achromatic with respect to the reference wavelength, but the achromaticity is not complete and insufficient for the other wavelengths, and the image point is on the optical axis. Is a phenomenon that occurs in a folded form with a certain wavelength as a minimum. Since an apochromatic objective lens corrects chromatic aberration in the wavelength region of visible light, it is necessary to correct the secondary spectrum.
[0015]
Also, when distortion remains, especially when zooming is low, the objective lens passes through the left and right beams of the image, causing asymmetric distortion between the beam passing through the periphery and the beam passing near the center. . As a result, the depth perception of the observer is disturbed, and the illusion that a planar object is convex is generated. Furthermore, observation over a long period of time has been shown to cause a phenomenon similar to seasickness.
[0016]
Now, the light with a large angle of view at the time of zoom low magnification is bent substantially parallel to the optical axis by the positive refractive power of the first lens group, and jumped up away from the optical axis by the first concave surface of the second lens group. . At that time, it contributes to the generation of large positive distortion. The parallel stereomicroscope objective lens has a pupil outside the lens system, and the entire lens has a positive refractive power. For this reason, a negative distortion aberration occurs as it is. In particular, a high-magnification objective lens has a large negative distortion due to its short focal length, that is, its strong refractive power. This is corrected by generating a positive aberration by the concave surface.
[0017]
However, the concave surface also bounces large NA light. Therefore, it is necessary to balance the subsequent joint surfaces so as to correct chromatic aberration, particularly the secondary spectrum, and not to deteriorate the distortion.
[0018]
If the upper limit of conditional expression (2) is exceeded, the secondary spectrum cannot be corrected, and color misregistration becomes conspicuous at zoom magnification. Conversely, if the lower limit of conditional expression (2) is not reached, negative distortion occurs, and the distortion becomes asymmetric on the left and right sides of the image. More preferably, the upper limit value is 15 and the lower limit value is 0.7.
[0019]
In the present invention, it is desirable that the second cemented lens of the two groups of cemented lenses in the second lens group satisfies the following conditions.
(3) 0.1 <| r22 / f | <1.0
here,
r22: radius of curvature of the cemented surface of the second cemented lens of the second lens group,
f: The focal length of the entire system of the parallel stereomicroscope objective lens.
[0020]
Conditional expression (3) balances astigmatism at the time of zoom low magnification and axial aberration at the time of zoom high magnification. If the upper limit of conditional expression (3) is exceeded, the achromatic power of the joint surface will be weakened and the secondary spectrum will be poor. On the other hand, if the lower limit of conditional expression (3) is not reached, a surface with a tight radius of curvature exists relatively near the image surface, and astigmatism at the time of zoom low magnification cannot be corrected. More preferably, the upper limit value is 0.75 and the lower limit value is 0.4.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, numerical examples of a parallel stereomicroscope objective lens according to the present invention will be described with reference to the accompanying drawings.
[0022]
(First embodiment)
FIG. 1 is a diagram illustrating a lens configuration of a parallel stereomicroscope objective lens according to the present embodiment. In order from the side farthest from the object, the first lens group G1 including a biconvex cemented lens having a positive refractive power and including a lens L1 and a lens L2, and a plurality of cemented lenses or a single lens, and at least 2 And a second lens group G2 including a cemented lens of the group. The second lens group G2 has a meniscus first cemented lens having a concave surface composed of the lens L3 and the lens L4 facing away from the object on the side farthest from the object.
[0023]
Table 1 lists the specification values of this example. In the overall specifications, f represents the focal length of the entire objective lens system, WD represents the working distance, and f1 represents the focal length of the first lens group G1. In the lens data, s is the order of the lens surfaces counted from the side far from the object, r is the radius of curvature of each lens surface, d is the surface interval, nd and vd are the d lines (λ of the glass used for each lens) = 587.56 nm) and the Abbe number, respectively. Units such as length and radius of curvature are mm. The distance between the optical axes of the observation optical system is 22 mm, and the entrance pupil position of the observation optical system is 41 mm when the zoom is low and 165 mm when the zoom is high. Further, in the specification values of all the examples below, the same symbols as those of the specification values of this example are used.
[0024]
[Table 1]

FIG. 2 is a diagram showing various aberrations of this example. All the aberrations are tracked by entering light rays from the observation optical system side (the side farther from the object) and are displayed with reference to the light rays passing through the optical axis of the observation optical system. Further, astigmatism and distortion are aberration diagrams at zoom low magnification, and lateral aberration is at zoom high magnification. In the following, the aberration diagrams of all the examples show the same conditions as the aberrations of the present example, and the same reference numerals are used. As is apparent from the figure, it can be seen that various aberrations are well corrected.
[0025]
(Second embodiment)
FIG. 3 is a diagram illustrating a lens configuration of a parallel system stereomicroscope objective lens according to the present embodiment. In order from the side farthest from the object, the first lens group G1 including a biconvex cemented lens having a positive refractive power and including a lens L1 and a lens L2, and a plurality of cemented lenses or a single lens, and at least 2 And a second lens group G2 including a cemented lens of the group. The second lens group G2 includes a lens L3 and a lens L4 on the side farthest from the object, and a first meniscus cemented lens having a concave surface facing the side far from the object.
[0026]
Table 2 lists the specification values of this example. The distance between the optical axes of the observation optical system is 22 mm, and the entrance pupil position of the observation optical system is 41 mm when the zoom is low and 165 mm when the zoom is high.
[0027]
[Table 2]

FIG. 4 is a diagram showing various aberrations of this embodiment. As can be seen from the figure, various aberrations are corrected satisfactorily.
[0028]
(Third embodiment)
FIG. 5 is a diagram showing a lens configuration of the parallel system stereomicroscope objective lens according to the present embodiment. In order from the side farthest from the object, the first lens group G1 including a biconvex cemented lens having a positive refractive power and including a lens L1 and a lens L2, and a plurality of cemented lenses or a single lens, and at least 2 And a second lens group G2 including a cemented lens of the group. In addition, the second lens group G2 has a meniscus first cemented lens with a concave surface made up of the lens L3 and the lens L4 facing away from the object on the side farthest from the object.
[0029]
Table 3 lists the specification values of this example. The distance between the optical axes of the observation optical system is 22 mm, and the entrance pupil position of the observation optical system is 41 mm when the zoom is low and 165 mm when the zoom is high.
[0030]
[Table 3]

FIG. 6 is a diagram showing various aberrations of this embodiment. As can be seen from the figure, various aberrations are corrected satisfactorily.
[0031]
(Fourth embodiment)
FIG. 7 is a diagram showing a lens configuration of the parallel-system stereomicroscope objective lens according to the present example. In order from the side farthest from the object, the first lens group G1 including a biconvex cemented lens having a positive refractive power and including a lens L1 and a lens L2, and a plurality of cemented lenses or a single lens, and at least 2 And a second lens group G2 including a cemented lens of the group. The second lens group G2 has a first meniscus cemented lens having a concave surface composed of the lens L3 and the lens L4 facing away from the object on the side farthest from the object.
[0032]
Table 4 lists the specification values of this example. The distance between the optical axes of the observation optical system is 22 mm, and the entrance pupil position of the observation optical system is 41 mm when the zoom is low and 165 mm when the zoom is high.
[0033]
[Table 4]

FIG. 8 is a diagram showing various aberrations of this embodiment. As can be seen from the figure, various aberrations are corrected satisfactorily.
[0034]
(5th Example)
FIG. 9 is a diagram illustrating a lens configuration of the parallel-system stereomicroscope objective lens according to the present example. In order from the side farthest from the object, the first lens group G1 includes a biconvex cemented lens having a positive refractive power and composed of a lens L1 and a lens L2, and a plurality of cemented lenses or a single lens. And a second lens group G2 including a cemented lens of the group. In addition, the second lens group G2 has a meniscus first cemented lens with a concave surface made up of the lens L3 and the lens L4 facing away from the object on the side farthest from the object.
[0035]
Table 5 lists the specification values of this example. The distance between the optical axes of the observation optical system is 22 mm, and the entrance pupil position of the observation optical system is 41 mm when the zoom is low and 165 mm when the zoom is high.
[0036]
[Table 5]

FIG. 10 is a diagram showing various aberrations in this embodiment. As can be seen from the figure, various aberrations are corrected satisfactorily.
[0037]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a parallel stereomicroscope objective lens having a high magnification, high NA, and apochromat class performance.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a lens configuration and an optical path of a first example.
FIG. 2 is a diagram showing various aberrations of the first example.
FIG. 3 is a diagram illustrating a lens configuration and an optical path of a second example.
FIG. 4 is a diagram illustrating various aberrations of the second example.
FIG. 5 is a diagram illustrating a lens configuration and an optical path of a third example.
FIG. 6 is a diagram showing various aberrations of the third example.
FIG. 7 is a diagram illustrating a lens configuration and an optical path of a fourth example.
FIG. 8 is a diagram showing various aberrations of the fourth example.
FIG. 9 is a diagram illustrating a lens configuration and an optical path of a fifth example.
FIG. 10 is a diagram showing various aberrations of the fifth example.
FIG. 11 is a diagram showing a configuration of a conventional parallel stereomicroscope lens.
[Explanation of symbols]
G1 First lens group G2 Second lens group L1 to L8 Each lens component

Claims (3)

A first lens group having a positive refractive power and a biconvex cemented lens in order from the side farthest from the object;
A second lens group including at least two cemented lenses;
Have
While satisfying the following conditions , the light from the object is substantially parallel to the optical axes of the second lens group and the first lens group via the second lens group and the first lens group. A parallel stereomicroscope objective lens, characterized by being emitted toward at least two observation optical systems each having an optical axis .
(1) 0.1 <| r11 / f1 | <1.0
here,
r11: radius of curvature of the cemented surface of the cemented lens of the first lens group,
f1: focal length of the first lens group. The first cemented lens among the two groups of cemented lenses in the second lens group is arranged on the side farthest from the object, has a meniscus shape with the concave surface facing the side far from the object, and the following conditions The parallel stereomicroscope objective lens according to claim 1, wherein:
(2) 0.5 <| r21 / f | <80
here,
r21: radius of curvature of the cemented surface of the first cemented lens,
f: Focal length of the entire system of the parallel stereomicroscope objective lens. 3. The parallel-system stereomicroscope objective lens according to claim 1, wherein a second cemented lens among the two groups of cemented lenses in the second lens group satisfies the following condition.
(3) 0.1 <| r22 / f | <1.0
here,
r22: radius of curvature of the cemented surface of the second cemented lens,
f: Focal length of the entire system of the parallel stereomicroscope objective lens.

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