JP4685399B2 - Objective lens with correction mechanism - Google Patents

Description

    The present invention relates to a microscope objective lens having a correction ring with a wide real field of view and good operability.

    Conventionally, a stereomicroscope has been used to perform observation in a wide real field of view. As an example, there is a single-objective stereomicroscope configured as shown in FIG. The stereomicroscope shown in FIG. 34 includes a single objective lens 11, left and right variable magnification optical systems 12, and left and right eyepieces 13, and the stereoscopic observation is performed with the left and right eyes 14 of the observer. . Although this stereomicroscope has a large objective lens diameter, the image side of the objective lens has a plurality of imaging optical systems that only use a part of the light beam of the pupil to form a parallax image. Used. Therefore, there is a problem that the image becomes dark. In order to solve this problem and obtain a bright image, a microscope that uses all of the light flux from the objective lens and obtains a bright fluorescent image is desired.

    As described above, an optical system that uses a large luminous flux has a large NA.

    An objective lens of a stereomicroscope, a high magnification lens system has a focal length of 40 to 60 nm and an NA exceeding 0.4. In such an objective lens, when an object in a liquid such as water is observed, an aberration due to the liquid is generated, and the image is significantly deteriorated. In such an objective lens, an aberration correction mechanism for suppressing image deterioration is desired.

As conventional objective lenses having such an aberration correction mechanism, objective lenses described in the following documents are known.
Japanese Patent Publication No. 4-26448 Among the above documents, the objective lens described in Patent Document 1 has a meniscus example lens with a concave surface facing the object side in order from the object side, and has a positive refractive power. It consists of one lens group, a second lens group having a positive refractive power, and a third lens group having a cemented surface and a combined negative refractive power, and aberration caused by a transparent object between the object and the objective lens. The third lens group is moved for correction.

    In addition, the objective lens described in Patent Document 2 includes, in order from the object side, a first lens group having a positive refractive power and a positive, negative, and positive three-piece cemented lens from the object side, and has a small refractive power. The lens is composed of a second lens group and a third lens group having a negative refractive power, and aberration correction is performed by moving the second lens group in the optical axis direction.

    The disadvantages of these conventional examples are that the focal position changes and the focus is adjusted when aberration correction is performed, so that two operations are performed to compare the quality of the images, so that the workability is poor.

    The present invention provides an objective lens having an aberration correction mechanism that is capable of correcting aberrations and has good operability with a wide real field of view compared to an objective lens having the same magnification.

    The objective lens of the present invention emits a light beam from an object as an afocal light beam. When the maximum real field diameter is 15 mm or more, the maximum numerical aperture is NAmax, the focal length of the entire system is FLob, and the total length is Dob. In a lens system that satisfies the following conditions (1) and (2), in order from the object side, a first group that includes a plurality of lenses and has a positive refractive power, a second group that includes a meniscus cemented lens, and an image A third lens unit having a positive refractive power from the side and a meniscus lens component with a strong concave surface facing the image side and having a positive refractive power, the focal length of the second unit being FL2, and the relay magnification of the second unit being β2. This second group satisfies the following conditions (3) and (4), and the second group is moved in the optical axis direction to change the amount of aberration generated.

(1) NAmax × FLob ≧ 15 (mm)
(2) 0.3 ≦ FLob / Dob ≦ 0.6
(3) FL2 / FLob ≧ 10
(4) 0.9 ≦ β2 ≦ 1.1
In the above description, a lens component such as a meniscus lens component refers to a single lens or a cemented lens in which the front and rear thereof are separated by an air interval, and will be used in the same meaning later.

    The objective lens of the present invention is used for a microscope described below. In other words, an image is formed by an imaging optical system including an objective lens that receives a light beam from an object and emits an afocal light beam and a zoom optical system that forms an afocal light beam emitted from the objective lens. This is an objective lens used in a stereomicroscope that images an image by magnifying it with an eyepiece lens or that images an image by placing an image-receiving element on the imaging surface. The objective lens of the present invention is an optical system having the above configuration.

    In the objective lens of the present invention configured as described above, if the condition (1) is not satisfied, that is, if the value of NAmax × Flob is below the lower limit of 15 of the condition (1), sufficiently bright fluorescence cannot be obtained. In the condition (2), if the value of FLob / Dob is less than the lower limit of 0.3, the entire length of the objective lens becomes long, and it becomes difficult to maintain the same focus with other objective lenses. If the upper limit of 0.6 is exceeded, the total length of the objective lens becomes short, making it difficult to arrange a plurality of lenses necessary for correction, and as a result, sufficient aberration correction cannot be performed.

    Conditions (3) and (4) are conditions for defining the focal length and magnification of the second group to be moved to change the amount of spherical aberration generated.

    Among these conditions, if the value is outside the range of condition (3), that is, if the value of FL2 / Flob is less than 10, the amount of movement of the second group becomes large, so the range in which the lens in the objective lens can be arranged becomes narrow. Since a sufficient number of lenses cannot be arranged, good resolution cannot be obtained.

    Condition (4) defines the magnification of the second group. If the condition (4) is out of the range of condition (4), the magnification β2 is less than the lower limit value 0.9 of condition (4) or the upper limit value. If the ratio exceeds 1.1, the amount of movement of the image plane when correcting spherical aberration increases, and adjustment to the best image becomes difficult.

    In the objective lens of the present invention described above, when the correction is performed by the movement of the second group, the amount of movement of the second group is reduced, the movement of the image plane during spherical aberration correction is reduced, and the correction during spherical aberration correction is performed. In order to make it possible to consider that the image plane movement is practically constant, the second group cemented meniscus lens has a shape with a convex surface facing the object side, and instead of the conditions (3) and (4), the following conditions are satisfied. It is desirable to satisfy (3-1) and (4-1).

(3-1) FL2 / Flob ≧ 20
(4-1) 0.96 ≦ β2 ≦ 1.02
Further, in the objective lens of the present invention, in order to satisfactorily correct various aberrations, particularly chromatic aberration, the third lens unit is composed of three lens components in order from the object side: a positive cemented lens, a meniscus lens, and a convex lens. Desirably, the following conditions (5), (6), and (7) are satisfied.

(5) 0.6 ≦ | r32i / Flob | ≦ 1.1
(6) 0.6 ≦ | r31c / Flob | ≦ 1.3
(7) | ν31o−ν31i | ≧ 37
Here, r31c is the radius of curvature of the cemented surface of the cemented lens on the object side of the third group, r32i is the radius of curvature of the image side surface of the meniscus lens that is the second lens from the object side of the third group, and ν31o and ν31i are It is the Abbe number of the glass material in the object side lens and the image side lens of the third group object side cemented lens, respectively.

    Condition (5) is a condition that defines the radius of curvature of the image side surface of the second lens (meniscus lens component) of the third group, and the value of | r32i / Flob | is the lower limit of condition (5). When the value is less than 0.6, the generation of higher-order aberrations of spherical aberration becomes large, making it difficult to correct aberrations, and at the same time, the entire lens becomes large and the operability becomes poor. If the value of | r32i / Flob | exceeds the upper limit of 1.1 of the condition (5), it is difficult to correct spherical aberration.

    Condition (6) defines the radius of curvature of the cemented surface of the third group cemented lens. When the value of | r31c / Flob | is less than the lower limit of 0.6 in condition (6), the cemented surface And the thickness of the cemented lens is increased. As a result, in order to dispose the lens within the desired overall length of the objective lens, the number of lenses must be reduced, making it difficult to correct aberrations satisfactorily. If the upper limit of 1.3 is exceeded, it will be difficult to correct longitudinal chromatic aberration.

    Condition (7) defines the Abbe number of both lenses of the cemented lens on the object side. If the value of | ν31o−ν31i | is below the lower limit of 37, it is difficult to correct axial chromatic aberration.

    Furthermore, in the objective lens of the present invention, in order to correct off-axis aberration satisfactorily, the first group is composed of a positive lens and a cemented lens in order from the object side, and the following conditions (8), (9) , (10) is preferably satisfied.

(8) FL12 / FLob ≧ 4
(9) 0.9 ≦ | r12c / Flob | ≦ 2
(10) | ν12o−ν12i | ≧ 37
Where FL12 is the focal length of the cemented lens disposed on the image side of the first group, r12c is the radius of curvature of the cemented surface of the cemented lens, and ν12o and ν12i are the object side lens and the image side lens of the cemented lens, respectively. Abbe number of glass material.

    Among these conditions, the condition (8) defines the focal length of the cemented lens disposed on the image side of the first group. If the condition (8) is not satisfied, the value of FL12 / Flob is the lower limit value. If it is less than 4, correction of curvature of field becomes difficult.

Condition (9) is a condition that defines the radius of curvature of the cemented surface of the cemented lens on the image side of the first group. Under this condition (9), if the value of | r12c / Flob | is less than the lower limit of 0.9, the thickness of the lens increases, and the number of lenses that can be disposed within the desired overall length of the objective lens decreases, resulting in aberrations. Correction becomes difficult. When the upper limit of 2 of the condition (9) is exceeded, the condition (10) further defines the difference in the Abbe number of the glass material of the object side image lens and the image side lens of the first group. If the range of (10) is exceeded, that is, if the value of | ν12o−ν12i | is less than the upper limit of 37 in the condition (10), it is difficult to correct chromatic aberration of magnification.

    The objective lens according to the present invention is a bright lens system with a wide real field of view, a large NA, and the occurrence of spherical aberration when there is a transparent liquid between the object and the objective lens by moving the second group. It is possible to correct the above, and the operability is good.

    The objective lens of the present invention is used in a microscope having a configuration as shown in FIG. In FIG. 31, 1 is a stereomicroscope, 2 is an objective lens, 3 is an afocal variable magnification optical system, and 4 is an imaging optical system. In the illustrated example, the eyepiece 5 is used for performing magnified observation from the viewpoint. It has been. However, an image pickup device may be arranged on the image forming surface of the image forming optical system without using the eyepiece lens 5.

    In the microscope 1 shown in FIG. 31, a light beam from an object is emitted as an afocal light beam by an objective lens 2, is incident on an afocal variable magnification optical system, and is imaged by an imaging optical system 4 to form an eyepiece 5 Observe the object image.

    The afocal zoom optical system used here has a configuration as shown in FIG. In other words, in order from the objective lens side, the first lens group AG1, the second lens group AG2, the third lens group AG3, the fourth lens group AG4, the fifth lens group AG5, and the sixth lens group AG6 are composed of six lens groups. ), (B), and (C), zooming is performed by moving the second group AG2, the third group AG3, and the fourth group AG4 along the optical axis.

    Further, for example, an object image is formed by disposing an imaging optical system configured as shown in FIG. 33 behind the afocal zoom optical system.

    The objective lens of the present invention is used in such a microscope, and is an optical system having a configuration shown in each example described later.

    As described above, the embodiment of the present invention is used by arranging the afocal zoom optical system and the imaging optical system shown in FIGS. 2 and 3 on the image side.

An example of the afocal zoom optical system and the imaging optical system used here is an optical system having the following data.

Afocal zoom optical system R ₁ = 143.584 D ₁ = 6.5 N ₁ = 1.43875 V ₁ = 94.93
R ₂ = -151.471 D ₂ = 4.5 N ₂ = 1.67300 V ₂ = 38.15
R ₃ = -406.964 D ₃ = 0.5
R ₄ = 86.266 D ₄ = 7 N ₃ = 1.43875 V ₃ = 94.93
_{R 5 = -182.860 D 5 = 4} N 4 = 1.67300 V 4 = 38.15
R ₆ = -627.529 D ₆ (variable)
R ₇ = 289.274 D ₇ = 5.6 N ₅ = 1.73800 V ₅ = 32.26
_{R 8 = -40.355 D 8 = 3} N 6 = 1.77250 V 6 = 49.60
R ₉ = 42.167 D ₉ = 3.2
_{R 10 = -172.814 D 10 = 2.8} N 7 = 1.77250 V 7 = 49.60
R ₁₁ = 22.430 D ₁₁ = 4.5 N ₈ = 1.73800 V ₈ = 32.26
R ₁₂ = 267.473 D ₁₂ (variable)
R ₁₃ = -38.998 D ₁₃ = 2.8 N ₉ = 1.67790 V ₉ = 55.34
R ₁₄ = -112.304 D ₁₄ (variable)
R ₁₅ = -104.447 D ₁₅ = 4.5 N ₁₀ = 1.43875 V ₁₀ = 94.93
R ₁₆ = -37.846 D ₁₆ (variable)
R ₁₇ = 86.418 D ₁₇ = 4.5 N ₁₁ = 1.43875 V ₁₁ = 94.93
R ₁₈ = -96.570 D ₁₈ (variable)
R ₁₉ = -62.848 D ₁₉ = 3.5 N ₁₂ = 1.67790 V ₁₂ = 55.34
R ₂₀ = -174.072

Imaging optical system R ₂₁ = 69.845 D ₂₁ = 9.98 N ₁₃ = 1.49700 V ₁₃ = 81.54
R ₂₂ = -54.633 D ₂₂ = 4.65 N ₁₄ = 1.80610 V ₁₄ = 40.92
R ₂₃ = -172.571 D ₂₃ = 9.58
R ₂₄ = 60.898 D ₂₄ = 11.43 N ₁₅ = 1.83400 V ₁₅ = 37.16
R ₂₅ = -82.872 D ₂₅ = 5.76 N ₁₆ = 1.65412 V ₁₆ = 39.68
R ₂₆ = 31.904 D ₂₆ = 126.94

FL 56.0 177.0 560.0
D ₆ 6.000 49.684 65.362
D ₁₂ 63.114 19.430 3.752
D ₁₄ 33.132 30.751 4.429
D ₁₆ 27.652 25.599 8.000
D ₁₈ 3.200 7.634 51.555

However, R _1, R _2, ··· is the radius of curvature of each lens surface, D _1, D _2, ··· wall thickness and lens distance of each lens, N _1, N _2, ··· each lens , V ₁ , V ₂ ,... Are Abbe numbers of the respective lenses.

FL is the combined focal length of the afocal zoom optical system and the imaging optical system. The variable distances D ₆ , D ₁₂ , D _{14 of the} afocal zoom optical system when the focal length FL is 56 mm, 177 mm, 560 mm. , D ₁₆ , D ₁₈ are as shown in the above data. Here, (A), (B), and (C) of FIG. 32 correspond to the case where the focal length FL is the above value.
The unit of length in the data is mm.

    The distance between the afocal zoom optical system and the imaging optical system used together with the objective lens of the present invention is preferably set to a value between 50 mm and 100 mm so that the objective lens can maintain the peripheral light amount during this period. In the objective lenses of the following embodiments, the interval is set to 80 mm.

    The objective lens of Example 1 of the present invention has a configuration as shown in FIGS. 1A, 1B, 1C, and 1D. Among these figures, FIG. 1A shows the case where the focal length FL = 56 mm of the combined afocal zoom optical system and imaging optical system, FIG. 1B shows the case where the combined focal length FL = 177 mm of the optical system, and FIG. It is a figure in case the synthetic | combination focal distance FL = 560mm of a system. Also, FIG. 1D corrects the deterioration of spherical aberration when the thickness is the maximum when water L, which is a transparent liquid, exists between the object and the objective lens with the combined focal length FL = 560 mm of the optical system. It is a figure which shows a structure when the 2nd group is moved in order to do.

As shown in these drawings, the objective lens of Example 1 is a cemented lens in which a positive lens (r _{1 to} r ₂ ), a negative lens (r _{3 to} r ₄ ), and a positive lens (r _{4 to} r ₅ ) are cemented. A meniscus shape having a convex surface facing the object side in which the first group G1 composed of the components (r _{3 to} r ₅ ), the positive lens (r _{6 to} r ₇ ) and the negative lens (r _{7 to} r ₈ ) are bonded together. Positive cemented lens component (r ₉ ) obtained by bonding the second lens group G2 composed of the cemented lens components (r _{6 to} r ₈ ), the positive lens (r _{9 to} r ₁₀ ), and the negative lens (r _{10 to} r ₁₁ ). ˜r ₁₁ ), a positive lens (r ₁₂ ˜r ₁₃ ), and a negative lens (r ₁₃ ˜r ₁₄ ), and a meniscus cemented lens component (r ₁₂ ˜r ₁₄ ) having a strong concave surface facing the image side. And a third lens group G3 composed of convex lenses (r _{15 to} r ₁₆ ). Then, the deterioration of spherical aberration due to the transparent liquid is corrected by moving the second group G2.

Example 1 has the following configuration and the following data.

r ₁ = ∞ d ₁ = 14.1 n ₁ = 1.48749 ν ₁ = 70.23
r ₂ = −32.668 d ₂ = 0.5
r ₃ = −157.804 d ₃ = 5.5 n ₂ = 1.673 ν ₂ = 38.15
r ₄ = 59.000 d ₄ = 17.9 n ₃ = 1.43875 ν ₃ = 94.93
r ₅ = -49.931 d ₅ (variable)
r ₆ = 71.717 d ₆ = 9.6 n ₄ = 1.497 ν ₄ = 81.54
r ₇ = ∞ d ₇ = 5.5 n ₅ = 1.6134 ν ₅ = 44.27
r ₈ = 90.764 d ₈ (variable)
r ₉ = ∞ d ₉ = 11.7 n ₆ = 1.43875 ν ₆ = 94.93
r ₁₀ = -52.032 d ₁₀ = 5.5 n ₇ = 1.673 ν ₇ = 38.15
r ₁₁ = -97.657 d ₁₁ = 0.5
r ₁₂ = 61.047 d ₁₂ = 15.5 n ₈ = 1.738 ν ₈ = 32.26
r ₁₃ = 116.067 d ₁₃ = 7.3 n ₉ = 1.8061 ν ₉ = 40.92
r ₁₄ = 53.243 d ₁₄ = 7.5
r ₁₅ = ∞ d ₁₅ = 5.2 n ₁₀ = 1.48749 ν ₁₀ = 70.23
r ₁₆ = -77.238

Water depth d ₅ d ₈
0 1.2 13.5
5 mm 8.77 5.93

WD = 21mm
FLob = 55mm
Number of fields = 22
NAmax = 0.4
Dob = 121mm
FL2 = 1582.63mm
β2 = 0.9997
FL12 = 655.3mm
NAmax × Flob = 22
FLob / Dob = 0.45
FL2 / Flob = 28.8
| R32i / Flob | = 0.97
| R31c / Flob | = 0.946
| Ν31o−ν31i | = 56.8
FL12 / FLob = 11.91
| R12c / Flob | = 1.07
| Ν12o−ν12i | = 56.8

However, r _1, r _2, ··· is the radius of curvature of each lens surface, d _1, d _2, ··· wall thickness and lens distance of each lens, n _1, n _2, ··· each lens , Ν ₁ , ν ₂ ,... Are Abbe numbers of the respective lenses. WD is a working distance.

In the first embodiment, the second group G2 is moved to change the distances d ₅ and d ₈ as shown in the data to correct the deterioration of the spherical aberration due to the presence of the transparent liquid. There is almost no movement of the paraxial image plane due to the movement of the second group G2. Further, the second group G2 has a simple configuration consisting of only one cemented lens, and the operability during correction is very good.

    Further, in order to reduce color bleeding by the objective lens, it is desirable to use anomalous dispersion glass for the convex lens. Therefore, it is desirable to use at least one anomalous dispersion glass for the third group G3, one for the first group G1 for off-axis correction, and one or more anomalous dispersion glass for the moving second group G2. The anomalous dispersion glass of Example 1 is a third lens, a fourth lens, and a sixth lens when counted from the object side.

    In Example 1, as described in the data, the conditions (1), (2), (3), (4), (3-1), (4-1), (5), (6) , (7), (8), (9), and (10) are satisfied.

    The aberration status of Example 1 is as shown in FIGS. 6, 7, 8, 9, and 10. Among these aberration diagrams, FIG. 6 shows spherical aberration, FIG. 7 shows coma aberration, FIG. 8 shows field curvature, and FIG. 9 shows chromatic aberration of magnification. Of these figures, (A) shows the focal length FL = 56 mm of the combined afocal zoom optical system and imaging optical system, (B) shows the combined focal length FL = 177 mm of the optical system, and (C) shows the same optical system. FIG. 6 is an aberration diagram when a combined focal length FL is 560 mm. Further, FIG. 10 shows the spherical aberration when the water depth is maximum when the combined focal length FL = 560 mm of the afocal zoom optical system and the imaging optical system and a transparent liquid (water) exists between the object and the objective lens. is there. In FIG. 10, (A0) is the spherical aberration before correction, and (A1) is the spherical aberration after correction.

    Each of these aberration diagrams is obtained when an afocal zoom optical system and an imaging optical system arranged with an interval of 80 mm are used.

    6 to 9, the aberration of the objective lens of Example 1 is corrected well, and the spherical aberration deteriorates due to the presence of water between the object and the objective lens from FIG. The spherical aberration deteriorated by moving the second group is corrected well.

    The objective lens according to Example 2 of the present invention has a configuration as shown in FIGS. 2A, 2B, 2C, and 2D. FIG. 2A shows a focal length FL = 56 mm of the synthesis of the afocal zoom optical system and the imaging optical system. FIG. 2B shows a state when the synthetic focal length FL of the optical system is 177 mm, and FIG. 2C shows a state when the synthetic focal length FL of the optical system is 560 mm. FIG. 2D shows a case where water L, which is a transparent liquid, exists between the object and the objective lens with the combined focal length FL = 560 mm of the optical system, and the spherical aberration is corrected by moving the second group 2G. It is the state of time.

The objective lens of Example 2 has the same lens configuration as that of Example 1 as shown in FIGS. 2A to 2D and has the following data.

r ₁ = ∞ d ₁ = 13.7 n ₁ = 1.48749 ν ₁ = 70.23
r ₂ = -33.032 d ₂ = 0.5
r ₃ = -205.305 d ₃ = 5.5 n ₂ = 1.738 ν ₂ = 32.26
r ₄ = 62.678 d ₄ = 17.8 n ₃ = 1.497 ν ₃ = 81.54
r ₅ = -48.3451 d ₅ (variable)
r ₆ = 62.4329 d ₆ = 9.6 n ₄ = 1.497 ν ₄ = 81.54
r ₇ = ∞ d ₇ = 5.5 n ₅ = 1.6134 ν ₅ = 44.27
r ₈ = 77.1944 d ₈ (variable)
r ₉ = ∞ d ₉ = 13.1 n ₆ = 1.43875 ν ₆ = 94.93
r ₁₀ = −49.702 d ₁₀ = 5.5 n ₇ = 1.673 ν ₇ = 38.15
r ₁₁ = -92.883 d ₁₁ = 0.5
r ₁₂ = 57.78 d ₁₂ = 15 n ₈ = 1.738 ν ₈ = 32.26
r ₁₃ = 143.193 d ₁₃ = 6.7 n ₉ = 1.7725 ν ₉ = 49.6
r ₁₄ = 48.408 d ₁₄ = 7
r ₁₅ = 412.397 d ₁₅ = 5.3 n ₁₀ = 1.43875 ν ₁₀ = 94.93
r ₁₆ = -96.299

Water depth d ₅ d ₈
0 1.8 9.32
5mm 13.5 5.98

WD = 21mm
FLob = 50mm
Number of fields = 22
NAmax = 0.45
Dob = 121mm
FL2 = 1573.11mm
β2 = 0.9997
FL12 = 261.2mm
NAmax x FLob = 22.5
FLob / Dob = 0.41
FL2 / FLob = 31.5
| R32i / Flob | = 0.97
| R31c / Flob | = 0.994
| Ν31o−ν31i | = 56.8
FL12 / FLob = 5.22
| R12c / Flob | = 1.25
| Ν12o−ν12i | = 49.3

In the objective lens of Example 2, the variation of spherical aberration is corrected by moving the second group G2 to change the distances d ₅ and d ₈ .

    The objective lens of Example 2 has the same lens configuration as that of Example 1, but has a shorter focal length and higher magnification than Example 1. For this reason, the deterioration of spherical aberration is greater when a transparent liquid exists between the object and the objective lens. However, the spherical aberration can be favorably corrected by the movement of the second group G2. Further, there is almost no movement of the paraxial image plane due to the movement of the second group G2. In Example 2, in order to prevent color bleeding, anomalous dispersion glass is provided in each group in the same manner as in Example 1. In particular, two anomalous dispersion glasses are used for the third group G3. The anomalous dispersion glass of Example 2 is a third lens, a fourth lens, a sixth lens, and a tenth lens, counted from the object side.

    In the objective lens of Example 2, as shown in the data, the conditions (1), (2), (3), (4), (3-1), (4-1), (5), ( 6), (7), (8), (9), (10) are all satisfied.

    Also in the second embodiment, an afocal zoom optical system and an imaging optical system having the data shown in FIGS. 32 and 33 are arranged and used on the image side.

    The aberration status of Example 2 is as shown in FIGS. 11, 12, 13, 14, and 15. Among these aberration diagrams, FIG. 11 shows spherical aberration, FIG. 12 shows coma, FIG. 13 shows field curvature, and FIG. 14 shows chromatic aberration of magnification. 11, FIG. 12, FIG. 13 and FIG. 14, (A) is the combined focal length FL = 56 mm of the afocal zoom optical system and the imaging optical system, and (B) is the combined focal length FL of the same optical system. = 177 mm, (C) is an aberration diagram when the combined focal length FL of the same optical system is 560 mm. FIG. 15 is a spherical aberration when a transparent liquid (water) exists between the object and the objective lens at a combined focal length FL = 560 mm of the afocal zoom optical system and the imaging optical system, and (A0) is Spherical aberration deteriorated by water when the water depth is maximum, (A1) shows spherical aberration corrected by the second group G2.

    These aberration diagrams are also obtained when the afocal zoom optical system and the imaging optical system are arranged on the image side of the objective lens, and the distance between the afocal zoom optical system and the imaging lens is 80 mm.

    As shown in FIGS. 11 to 14, the objective lens of Example 2 has its aberration corrected well. Further, as shown in FIG. 15, the spherical aberration that is deteriorated due to the presence of water between the object and the objective lens is favorably corrected by the movement of the second group G2.

    The objective lens of Example 3 of the present invention has a configuration as shown in FIGS. 3A, 3B, 3C, and 3D. Of these figures, FIG. 3A shows the combined focal length FL = 56 mm of the afocal zoom optical system and the imaging optical system, FIG. 3B shows the combined focal length FL = 177 mm of the optical system, and FIG. 3C shows the combined focal length of the optical system. The distance FL = 560 mm, and FIG. 3D shows the case where the combined focal length FL = 560 mm of the afocal zoom optical system and the imaging optical system, and there is a transparent liquid (water) L between the object and the objective lens. The configuration when the second group G2 is moved in order to correct the deterioration of the spherical aberration at that time is shown.

The third embodiment has the same lens configuration as the first and second embodiments as shown in the figure, and the data is as follows.

r ₁ = −612.777 d ₁ = 12.5 n ₁ = 1.58913 ν ₁ = 61.14
r ₂ = −34.804 d ₂ = 0.5
r ₃ = -229.065 d ₃ = 5.5 n ₂ = 1.738 ν ₂ = 32.26
r ₄ = 67.361 d ₄ = 17.9 n ₃ = 1.497 ν ₃ = 81.54
r ₅ = -48.375 d ₅ (variable)
r ₆ = 55.44 d ₆ = 9.65 n ₄ = 1.497 ν ₄ = 81.54
r ₇ = ∞ d ₇ = 5.5 n ₅ = 1.6134 ν ₅ = 44.27
r ₈ = 67.172 d ₈ (variable)
r ₉ = 523.772 d ₉ = 13.1 n ₆ = 1.43875 ν ₆ = 94.93
r ₁₀ = -41.9 d ₁₀ = 5.5 n ₇ = 1.673 ν ₇ = 38.15
r ₁₁ = -89.561 d ₁₁ = 0.5
r ₁₂ = 55.292 d ₁₂ = 14.6 n ₈ = 1.738 ν ₈ = 32.26
r ₁₃ = 186.57 d ₁₃ = 8.1 n ₉ = 1.7725 ν ₉ = 49.6
r ₁₄ = 44.624 d ₁₄ = 7.05
r ₁₅ = 232.844 d ₁₅ = 5.2 n ₁₀ = 1.43875 ν ₁₀ = 94.93
r ₁₆ = −112.321

Water depth d ₅ d ₈
0 1.8 9.21
5mm 13.5 6.19

WD = 21.1mm
FLob = 45.5mm
Number of fields = 22
NAmax = 0.5
Dob = 120.9mm
FL2 = 1563.22mm
β2 = 0.9910
FL12 = 228.181mm
NAmax x FLob = 22.5
FLob / Dob = 0.376
FL2 / Flob = 34.4
| R32i / Flob | = 0.98
| R31c / Flob | = 0.922
| Ν31o−ν31i | = 56.8
FL12 / FLob = 5.01
| R12c / Flob | = 1.48
| Ν12o−ν12i | = 49.3

As is apparent from the above data, the third embodiment of the present invention corrects spherical aberration by moving the second group G2 and changing the distances d ₅ and d ₈ as shown in the data.

    The third embodiment is a lens system having a shorter focal length and higher magnification than the second embodiment. However, the movement of the second group G2 corrects the deterioration of the spherical aberration, and there is almost no movement of the on-axis image plane due to the movement. Further, the most object-side surface is concave for correcting coma aberration.

    In Example 3, as shown in the data, the conditions (1), (2), (3), (4), (3-1), (4-1), (5), (6), ( 7), (8), (9), and (10) are satisfied.

    The objective lens of Example 3 also has the configuration shown in FIGS. 32 and 33 and uses the afocal zoom optical system and the imaging optical system having the data described above arranged on the image side.

    The aberration status of Example 3 is as shown in FIG. 16, FIG. 17, FIG. 18, FIG. Of these aberration diagrams, FIG. 16 shows spherical aberration, FIG. 17 shows coma, FIG. 18 shows field curvature, and FIG. 19 shows chromatic aberration of magnification. Of these figures, (A) shows the focal length FL = 56 mm of the combined afocal zoom optical system and imaging optical system, (B) shows the combined focal length FL = 177 mm of the optical system, and (C) shows the same optical system. FIG. 6 is an aberration diagram when a transparent liquid is not present between the object and the objective lens at a combined focal length FL of 560 mm. FIG. 20 is a spherical aberration diagram when the combined focal length of the afocal zoom optical system and the imaging optical system is 560 mm, transparent liquid (water) exists between the object and the objective lens, and the water depth is maximum. . In FIG. 20, (A0) is the spherical aberration before correction when water is present, and (A1) is the spherical aberration after correction by the second group G2.

    These aberration diagrams (FIGS. 16, 17, 18, 19, and 20) are also aberration diagrams when the afocal zoom optical system and the imaging optical system are arranged on the image side of the objective lens. The distance between the system and the imaging lens is 80 mm.

    As shown in these figures, the objective lens of Example 3 of the present invention has various aberrations corrected well. Further, as shown in FIG. 20, by moving the second group, it is possible to satisfactorily correct the deterioration of spherical aberration due to the presence of water between the object and the objective lens. Also in Example 3, an anomalous dispersion glass is used to satisfactorily correct chromatic aberration. The anomalous dispersion glass is a third lens, a fourth lens, a sixth lens, and a tenth lens, counted from the object side.

    The objective lens of Example 4 of the present invention has a configuration as shown in FIGS. 4A, 4B, 4C, and 4D. Of these figures, FIG. 4A shows the combined focal length FL = 56 mm of the afocal zoom optical system and the imaging optical system, FIG. 4B shows the combined focal length FL = 177 mm of the optical system, and FIG. 4C shows the combined focal length of the optical system. When the distance is FL = 560 mm, both show the state when no liquid exists between the object and the objective lens. FIG. 4D shows the case where the composite focal length FL of the optical system is FL = 560 mm and there is a transparent liquid L between the object and the objective lens, and the second group is used to correct the spherical aberration generated at that time. It is a figure when G2 is moved.

As shown in these drawings, the objective lens of Example 4 has lens components (r ₁ to r) in which a plane parallel plate (r _{1 to} r ₂ ) that is a cover glass and a plano-convex lens (r _{2 to} r ₃ ) are bonded together. ₃ ), a negative lens (r _{4 to} r ₅ ), a positive lens (r _{5 to} r ₆ ) and a cemented lens component (r _{4 to} r ₆ ), and a first lens group G1 and a positive lens (r ₇ ˜r ₈ ) and the negative lens (r ₈ ˜r ₉ ) and the second lens group G2 of the meniscus cemented lens component (r ₇ ˜r ₉ ) having a convex object side and the positive lens (r ₁₀ ˜r _11). ) And a negative lens (r _{11 to} r ₁₂ ), a cemented lens component (r _{10 to} r ₁₂ ), a positive lens (r _{13 to} r ₁₄ ), and a negative lens (r _{14 to} r ₁₅ ) a third group G3 a cemented lens component of strong concave surface of a meniscus shape an object side (r ₁₃ ~r ₁₅₎ consisting of a convex lens (r ₁₆ ~r ₁₇₎ A lenses system configuration Te. In the objective lens of this embodiment, as shown in FIG. 4D, the second group G2 is moved to correct the variation of spherical aberration due to the transparent liquid.

The data of the objective lens of Example 4 is shown below.

r ₁ = ∞ d ₁ = 1 n ₁ = 1.51633 ν ₁ = 64.14
r ₂ = ∞ d ₂ = 13.1 n ₂ = 1.497 ν ₂ = 81.54
r ₃ = -34.091 d ₃ = 0.5
r ₄ = -327.131 d ₄ = 5.5 n ₃ = 1.738 ν ₃ = 32.26
r ₅ = 69.411 d ₅ = 17.6 n ₄ = 1.497 ν ₄ = 81.54
r ₆ = -49.142 d ₆ (variable)
r ₇ = 56.124 d ₇ = 9.65 n ₅ = 1.497 ν ₅ = 81.54
r ₈ = ∞ d ₈ = 5.5 n ₆ = 1.6134 ν ₆ = 44.27
r ₉ = 67.348 d ₉ (variable)
r ₁₀ = 367.241 d ₁₀ = 12.9 n ₇ = 1.43875 ν ₇ = 94.99
r ₁₁ = −42.204 d ₁₁ = 5.5 n ₈ = 1.673 ν ₈ = 38.15
r ₁₂ = -86.888 d ₁₂ = 0.5
r ₁₃ = 52.08 d ₁₃ = 15 n ₉ = 1.738 ν ₉ = 32.26
r ₁₄ = −10000 d ₁₄ = 6.7 n ₁₀ = 1.7859 ν ₁₀ = 44.2
r ₁₅ = 42.599 d ₁₅ = 7.05
r ₁₆ = 238.505 d ₁₆ = 5.2 n ₁₁ = 1.43875 ν ₁₁ = 94.93
r ₁₇ = -127.05

Water depth d ₆ d ₉
0 1 5.9
5mm 10.3 5.4

WD = 21mm
FLob = 45.5mm
Number of fields = 22
NAmax = 0.5
Dob = 121mm
FL2 = 1843.69mm
β2 = 0.9814
FL12 = 195.43mm
NAmax x FLob = 22.5
FLob / Dob = 0.376
FL2 / FLob = 40.5
| R32i / Flob | = 0.936
| R31c / Flob | = 0.828
| Ν31o−ν31i | = 56.8
FL12 / FLob = 4.3
| R12c / Flob | = 1.52
| Ν12o−ν12i | = 49.3

In the objective lens of Example 4, the second group G2 is moved to change the distances d ₆ and d ₉ , thereby reducing the spherical aberration when a transparent liquid (water) exists between the object and the objective lens. It is corrected.

    Further, in this Example 4, as shown in the data, the conditions (1), (2), (3), (4), (3-1), (4-1), (5), (6) , (7), (8), (9), and (10) are satisfied.

    In the objective lens of Example 4, since the color of the g-line on the axis is large, it can be seen that there is a slight color blur in the case of photography. In order to remove this, it is preferable to use anomalous dispersion glass. However, since anomalous dispersion glass has low resistance, it is desirable to provide a cover glass on the object side. The anomalous dispersion glass of Example 4 is a second lens, a fourth lens, a fifth lens, a seventh lens, and an eleventh lens, counted from the object side.

    In Example 4, the paraxial image plane position at the time of aberration correction is set 4 mm away from the object side. As a result, when the maximum aberration is generated, the best image position in a state where no aberration correction is performed is different from the paraxial image plane. In this embodiment, in consideration of this point, the best image position does not fluctuate when the aberration correction is performed by the second group G2 when the transparent liquid exists.

    The aberration status of Example 4 is as shown in FIG. 21, FIG. 22, FIG. 23, FIG. 24, and FIG. FIG. 21 shows spherical aberration, FIG. 22 shows coma, FIG. 23 shows field curvature, and FIG. 24 shows chromatic aberration of magnification. Of these aberration diagrams, (A) is when the combined focal length FL = 56 mm of the afocal zoom optical system and the imaging optical system, and (B) is (C) when the combined focal length FL of the optical system is 177 mm. ) Is an aberration diagram when the combined focal length FL of the same optical system is 560 mm. FIG. 25 shows spherical aberration when a transparent liquid (water) exists between the object and the objective lens when the combined focal length of the afocal zoom optical system and the imaging optical system is 560 mm. In FIG. 25, (A0) is the spherical aberration when the water depth is maximum, and (A1) is the spherical aberration after correction due to the movement of the second group G2 at that time.

    The above aberration diagrams are obtained when the afocal zoom optical system and the imaging optical system are arranged on the image side of the objective lens. At that time, the distance between the afocal zoom optical system and the imaging lens is 80 mm.

    As apparent from the aberration diagrams of FIGS. 21 to 24, the objective lens of Example 4 of the present invention has various aberrations corrected satisfactorily. Also, from FIG. 25, when a transparent liquid exists between the object and the objective lens, the spherical aberration can be favorably corrected by the movement of the second group G2.

    The objective lens of Example 5 of the present invention has a configuration as shown in FIGS. 5A, 5B, 5C, and 5D. Of these figures, FIG. 5A shows the combined focal length FL = 56 mm of the afocal zoom optical system and the imaging optical system, FIG. 5B shows the combined focal length FL = 177 mm of the optical system, and FIG. 5C shows the combined focal length of the optical system. It is a figure which shows the state in distance FL = 560mm. FIG. 5D shows the combined focal length FL = 560 mm of the afocal zoom optical system and the imaging optical system, and a transparent liquid L exists between the object and the objective lens, and the spherical aberration caused thereby is corrected. It is a figure which shows the state which moved 2nd group G2.

As shown in these drawings, the objective lens of Example 5 of the present invention is a cemented lens (r ₁ ) in which a negative lens (r _{1 to} r ₂ ) and a positive lens (r _{2 to} r ₃ ) are cemented in order from the object side. ˜r ₃ ), a negative lens (r ₄ ˜r ₅ ), and a cemented lens (r ₄ ˜r ₆ ) obtained by bonding the positive lens (r ₅ ˜r ₆ ) together and G1, a positive lens (r ₇ ~r ₈₎ and a negative lens (r ₈ ~r ₉₎ and a bonded cemented lens (r ₇ ~r ₉₎ in the cemented lens component having a meniscus shape with the convex surface and the object a second group G2, a positive lens (r ₁₀ ~r ₁₁₎ and a negative lens (r ₁₁ ~r ₁₂₎ and the junction with the cemented lens (r ₁₀ ~r _12), and a positive lens (r ₁₃ ~r ₁₄₎ a negative lens (r ₁₄ ~r ₁₅₎ and the junction with the cemented lens (r ₁₃ ~r _15), a cemented lens component having a strong concave surface facing the image side and a convex lens Are composed of a third unit G3 consists in (r ₁₆ ~r ₁₇₎ and.

The data of the objective lens of Example 5 is shown below.

r ₁ = ∞ d ₁ = 4 n ₁ = 1.6779 ν ₁ = 55.34
r ₂ = 81.396 d ₂ = 21.1 n ₂ = 1.603 ν ₂ = 65.44
r ₃ = −36.366 d ₃ = 0.5
r ₄ = -340.848 d ₄ = 4.3 n ₃ = 1.6134 ν ₃ = 44.27
r ₅ = 45.418 d ₅ = 16.8 n ₄ = 1.497 ν ₄ = 81.54
r ₆ = -78.468 d ₆ (variable)
r ₇ = 49.61 d ₇ = 10.8 n ₅ = 1.497 ν ₅ = 81.54
r ₈ = ∞ d ₈ = 4.9 n ₆ = 1.6134 ν ₆ = 44.27
r ₉ = 57.831 d ₉ (variable)
r ₁₀ = 176.375 d ₁₀ = 13.5 n ₇ = 1.43875 ν ₇ = 94.93
r ₁₁ = −44.438 d ₁₁ = 5 n ₈ = 1.673 ν ₈ = 38.15
r ₁₂ = −102.463 d ₁₂ = 0.5
r ₁₃ = 45.86 d ₁₃ = 11.1 n ₉ = 1.738 ν ₉ = 32.26
r ₁₄ = ∞ d ₁₄ = 5 n ₁₀ = 1.79952 ν ₁₀ = 42.22
r ₁₅ = 39.134 d ₁₅ = 7.4
r ₁₆ = 2075.463 d ₁₆ = 4.8 n ₁₁ = 1.43875 ν ₁₁ = 94.93
r ₁₇ = -103.994

Water depth d ₆ d ₉
0 1 5.79
5mm 10.3 5.51

WD = 20mm
FLob = 45.5mm
Number of fields = 20
NAmax = 0.5
Dob = 121mm
FL2 = 1996.54mm
β2 = 0.9695
FL12 = 437.71mm
NAmax x FLob = 22.5
FLob / Dob = 0.376
FL2 / FLob = 43.9
| R32i / Flob | = 0.86
| R31c / Flob | = 0.998
| Ν31o−ν31i | = 56.8
FL12 / FLob = 9.62
| R12c / Flob | = 1.52
| Ν12o−ν12i | = 37.3

In the objective lens according to Example 5 of the present invention, the second group G2 is moved to change the lens distances d ₆ and d ₉ as shown in the data, so that a spherical surface made of a transparent liquid is formed between the object and the objective lens. Aberration fluctuations are corrected.

    Further, in the objective lens of Example 5, as shown in the data, the conditions (1), (2), (3), (4), (3-1), (4-1), (5) , (6), (7), (8), (9), (10) are satisfied.

    In Example 5, axial chromatic aberration was further reduced as compared with Example 4. Therefore, the lens on the most object side was a cemented lens. By using anomalous dispersion glass for the convex lens of this cemented lens, curvature of field and coma are slightly worsened, but axial chromatic aberration is corrected more satisfactorily. The anomalous dispersion glass of Example 5 is a fourth lens, a fifth lens, a seventh lens, and an eleventh lens, counted from the object side.

    In the fifth embodiment, the optical system having the configuration shown in FIGS. 32 and 33, the afocal zoom optical system having the data as described above, and the imaging optical system are arranged on the image side and used.

    The aberration status of Example 5 is as shown in FIG. 26, FIG. 27, FIG. 28, FIG. 29, and FIG. In these figures, FIG. 26 shows spherical aberration, FIG. 27 shows coma, FIG. 28 shows field curvature, and FIG. 29 shows chromatic aberration of magnification. In these drawings, (A) shows the combined focal length FL = 56 mm of the afocal zoom optical system and the imaging optical system shown in FIGS. 32 and 33, and (B) shows the combined focal length FL = 177 mm of the same optical system. (C) is a diagram showing a state of the optical system at a combined focal length FL = 560 mm. FIG. 30 is a spherical aberration when the combined focal length of the afocal zoom optical system and the imaging optical system is 560 mm and there is a transparent liquid (water) between the object and the objective lens, and (A0) is Before correction of the variation of the spherical aberration due to the presence of water, (A1) shows after correction. The aberration diagrams in FIGS. 26, 27, 28, 29, and 30 are obtained when the afocal zoom optical system and the imaging optical system are arranged on the image side of the objective lens of Example 5. In this case, the distance between the afocal zoom optical system and the imaging lens at that time is 80 mm.

    From these aberration diagrams, the objective lens of Example 5 of the present invention has various aberrations corrected well. Even if a transparent liquid exists between the object and the objective lens, the spherical aberration can be corrected sufficiently well by the movement of the second group G2.

    As described above, the objective lenses of the above embodiments are used together with the afocal zoom optical system having a large entrance pupil diameter and the imaging light beam that forms an image of the light beam, and the image formed by the imaging optical system. Is used for magnifying observation using an eyepiece.

    If each embodiment of the present invention is used as this objective lens, it is easy to increase the exit pupil diameter of the eyepiece, and in particular, when the magnification is reduced, it is possible to make the pupil diameter more than twice that of the human pupil. . If such an image is observed, the viewing direction of the object can be changed by moving the head of the observer, so that motion parallax can be obtained. Therefore, three-dimensional information can be obtained even by observation with one eye.

    Furthermore, when light is split by a half mirror before the light beam enters the eyepiece, changing the eye width creates a difference from the position determined by the human pupil, thereby creating parallax. Is possible.

    In this case, when the eye width is changed, the solid is reversed depending on the direction.

    The objective lens according to the present invention is used together with an afocal zoom optical system and an imaging optical system, and thus enables imaging and entity observation.

    The objective lens of the present invention has a wide real field of view, is bright with a high NA, and can easily correct aberrations by moving the second group consisting of only one cemented lens even when a transparent liquid exists between the objective lens and the object.

    Further, when used together with the above optical system, stereoscopic observation can be easily performed because observation with a wide field of view is possible.

The figure which shows the structure of Example 1 at the time of synthetic | combination focal distance 56mm. The figure which shows the structure of Example 1 at the time of synthetic | combination focal distance 177mm. The figure which shows the structure of Example 1 at the time of synthetic | combination focal distance 560mm. The figure which shows the structure of Example 1 in the state which moved 2nd group for the aberration correction at the time of synthetic | combination focal distance 560mm. The figure which shows the structure of Example 2 at the time of synthetic | combination focal distance 56mm. The figure which shows the structure of Example 2 at the time of synthetic | combination focal distance 177mm. The figure which shows the structure of Example 2 at the time of synthetic | combination focal distance 560mm. The figure which shows the structure of Example 2 in the state which moved 2nd group for the aberration correction at the time of synthetic | combination focal distance 560mm. The figure which shows the structure of Example 3 at the time of synthetic | combination focal distance 56mm. The figure which shows the structure of Example 3 at the time of synthetic | combination focal distance 177mm. The figure which shows the structure of Example 3 at the time of synthetic | combination focal distance 560mm. The figure which shows the structure of Example 3 in the state which moved 2nd group for the aberration correction at the time of synthetic | combination focal distance 560mm. The figure which shows the structure of Example 4 at the time of synthetic | combination focal distance 56mm. The figure which shows the structure of Example 4 at the time of synthetic | combination focal distance 177mm. The figure which shows the structure of Example 4 at the time of synthetic | combination focal distance 560mm. The figure which shows the structure of Example 4 in the state which moved 2nd group for the aberration correction at the time of synthetic | combination focal distance 560mm. The figure which shows the structure of Example 5 at the time of synthetic | combination focal distance 56mm. The figure which shows the structure of Example 5 at the time of synthetic | combination focal distance 177mm. The figure which shows the structure of Example 5 at the time of synthetic | combination focal distance 560mm. The figure which shows the structure of Example 5 in the state which moved 2nd group for the aberration correction at the time of synthetic | combination focal distance 560mm. Spherical aberration diagram of Example 1 Comatic aberration diagram of Example 1 Field curvature diagram of Example 1 Chromatic aberration diagram of magnification in Example 1 Spherical aberration diagram before and after correction by the second lens group in Example 1 Spherical aberration diagram of Example 2 Comatic aberration diagram of Example 2 Field curvature diagram of Example 2 Chromatic aberration diagram of magnification in Example 2 Spherical aberration diagram before and after correction by the second lens group in Example 2 Spherical aberration diagram of Example 3 Comatic aberration diagram of Example 3 Field curvature diagram of Example 3 Magnification Aberration Diagram of Example 3 Spherical aberration diagram before and after correction by the second lens group in Example 3 Spherical aberration diagram of Example 4 Comatic aberration diagram of Example 4 Field curvature diagram of Example 4 Magnification Aberration Diagram of Example 4 Spherical aberration diagram before and after correction by the second lens group in Example 4 Spherical aberration diagram of Example 5 Comatic aberration diagram of Example 5 Field curvature diagram of Example 5 Magnification Aberration Diagram of Example 5 Spherical aberration diagram before and after correction by the second lens group in Example 5 The figure which shows the structure of the stereomicroscope using the objective lens of this invention The figure which shows the structure of the afocal zoom optical system used with the objective lens of this invention The figure which shows the structure of the imaging lens used with the objective lens of this invention The figure which shows the structure of the optical system of the conventional single objective stereomicroscope

Claims (4)

An objective lens that emits a luminous flux from an object as an afocal luminous flux and has a maximum actual field diameter of 15 mm or more and satisfies the following conditions (1) and (2). It consists of a plurality of lenses in order from the object side. A first group having a positive refractive power, a second group consisting of a meniscus cemented lens, and a third group having a positive refractive power from the image side and a meniscus lens having a strong concave surface facing the image side from the image side An objective lens with a correction mechanism that satisfies the following conditions (3) and (4) and moves the second group in the optical axis direction to change the aberration generation amount.
(1) NAmax × FLob ≧ 15 (mm)
(2) 0.3 ≦ FLob / Dob ≦ 0.6
(3) FL2 / FLob ≧ 10
(4) 0.9 ≦ β2 ≦ 1.1
Where NAmax is the maximum numerical aperture of the objective lens, FLob is the focal length of the objective lens, Dob is the total length of the objective lens, FL2 is the focal length of the second group, and β2 is the magnification of the second group. The correction of claim 1, wherein the second group meniscus cemented lens has a convex surface facing the object side, and satisfies the following conditions (3-1) and (4-1) instead of the conditions (3) and (4): Objective lens with mechanism.
(3-1) FL2 / Flob ≧ 20
(4-1) 0.96 ≦ β2 ≦ 1.02 The third group is composed of three lens components of a positive cemented lens, a meniscus lens component, and a convex lens in order from the object side, and satisfies the following conditions (5), (6), and (7): Objective lens with 2 correction mechanism.
(5) 0.6 ≦ | r32i / Flob | ≦ 1.1
(6) 0.6 ≦ | r31c / Flob | ≦ 1.3
(7) | ν31o−ν31i | ≧ 37
Here, r32i is the radius of curvature of the image side surface of the meniscus lens that is the second lens from the object side in the third group, r31c is the radius of curvature of the cemented surface of the cemented lens on the object side of the third group, and ν31o and ν31i are These are the Abbe numbers of the object-side lens and the image-side lens of the third-group object-side cemented lens, respectively. The objective lens with a correction mechanism according to claim 3, wherein the first group includes a positive lens component and a cemented lens in order from the object side, and satisfies the following conditions (8), (9), and (10).
(8) FL12 / FLob ≧ 4
(9) 0.9 ≦ | r12c / Flob | ≦ 2
(10) | ν12o−ν12i | ≧ 37
Where FL12 is the focal length of the cemented lens of the second lens component of the first group, r12c is the radius of curvature of the cemented surface of the cemented lens of the first group, and ν12o and ν12i are the object side of the cemented lens of the first group. The Abbe number of the lens and the image side lens.

Images