JP2007328014A - Microscope objective lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microscope objective lens having a correction ring that corrects deterioration in imaging performance caused by a change in the thickness of a transparent parallel flat plate such as a cover glass, the objective lens which is designed so as to ensure a space for a moving mechanism by the correction ring. <P>SOLUTION: The microscope objective lens includes: a first lens group with positive refractive power; a second lens group with positive refractive power, which is movable along an optical axis; a third lens group having at least one cemented lens; and a fourth lens group having a convex face which is located closest to an object. The microscope objective lens satisfies conditions described below, ensures the moving mechanism by means of the correction ring, is compact and has satisfactory imaging performance. The conditions are (1) 6<f<SB>2</SB>/f<16, (2) 0.2<f<SB>2</SB>/f<SB>3</SB><1.2, and (3) ¾R<SB>3</SB>¾/¾R<SB>4</SB>¾>4. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

    The present invention relates to a microscope objective lens, and in particular, a microscope objective with a correction ring that can obtain good imaging performance even when the thickness of a transparent plane parallel plate such as a cover glass disposed on the object side changes. It relates to lenses.

    In general, when the thickness of a plane parallel plate such as a cover glass differs greatly from a design value, the imaging performance of the microscope objective lens deteriorates. This tendency becomes more prominent as the numerical aperture (NA) of the objective lens increases.

    Conventionally, a so-called correction ring objective lens that corrects aberration fluctuations by changing the lens interval in the objective lens according to the change in the thickness of the cover glass is known.

As a conventional example of such a correction ring objective lens, a lens system disclosed in the following document is known.
Japanese Patent Laid-Open No. 10-142510 Among these conventional examples, the objective lens described in Patent Document 1 has, in order from the object side, a lens having a negative refractive power with a concave surface facing the object side and a convex surface on the image side. A first lens group composed of a cemented lens with a lens having a positive refractive power directed to the second lens group, a second lens group of a cemented lens having a cemented surface having a negative refractive power, and a third lens group that converts a divergent light beam into a convergent light beam And a fourth lens group having a negative refractive power whose surface closest to the image side is a concave surface, and the second lens group is moved along the optical axis to correct aberration by changing the thickness of the cover glass. Is doing.

    Patent Document 2 discloses a first lens group having a positive meniscus lens component having a concave surface directed toward the object side in order from the object side and having a positive refractive power for converting light from the object into a substantially parallel light beam. A second lens group that includes a divergent cementing surface and has a combined refractive power of positive refractive power, a third lens group that has a negative refractive surface having a strong diverging action, and a fourth lens having negative refractive power. With the objective lens configured by the lens group, the second lens group is moved along the optical axis, thereby correcting the aberration by changing the thickness of the cover glass.

    In recent years, there are an increasing number of products that carry wiring under transparent parallel flat plates such as glass and electronic devices incorporating optical elements. Through transparent parallel flat plates, such as those found in liquid crystal substrate inspection, etc. There is an increasing demand for devices capable of inspecting objects.

    The microscope objective lens used in such an apparatus is required to have a high numerical aperture and a long working distance, and the correction ring objective lens also has a high numerical aperture and a long working distance. Is required. The correction ring objective lens is required to be compact so that it can be easily incorporated into an object inspection apparatus through a transparent plane-parallel plate.

    However, the objective lens has a high NA, and the lens diameter tends to increase as the working distance increases.

    The objective lens of Patent Document 1 has a large NA, suppressed aberrations, high resolution and high contrast, but cannot sufficiently suppress the ray height of the group behind the moving group, and the maximum ray height of the objective lens. In other words, the overall diameter of the objective lens is large and it is difficult to incorporate it into the apparatus.

    The objective lens of Patent Document 2 has a large NA, chromatic aberration is corrected by a cemented lens, high resolution and high contrast, but the moving group has a high beam height, and a space for arranging the moving mechanism of the correcting group. If the moving mechanism is disposed, the diameter of the entire objective lens including the moving mechanism becomes large, and it is difficult to incorporate it into the apparatus.

    The present invention has been made in order to solve the above-described problems of the conventional example, and provides a compact objective lens having good imaging performance and ensuring a space for a moving mechanism by a correction ring. Is.

    The microscope objective lens according to the present invention includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a positive refractive power and movable along the optical axis, and at least one joint. A third lens group having a lens, and a fourth lens group having a negative refractive power as a whole with the most object side surface convex to the object side, and the following conditions (1), (2), (3) is satisfied.

(1) 6 <f ₂ / f <16
(2) 0.2 <f ₂ / f ₃ <1.2
(3) | R ₃ | / | R ₄ |> 4
Where f ₂ is the focal length of the second lens group, f ₃ is the focal length of the third lens group, f is the focal length of the entire objective lens system, and R ₃ is the radius of curvature of the most image side surface of the third lens group. , R ₄ is the radius of curvature of the surface of the fourth lens group closest to the object side.

    The objective lens according to the present invention is a lens system having the above-described configuration, wherein the focal length of the entire system satisfies the following condition (5), and further satisfies the condition (4).

(4) −10 <f ₄ / f <−2
(5) 1 <f <5
Here, f ₄ is the focal length of the fourth lens group.

The microscope objective lens according to the present invention is a lens system that includes the lens configuration, that is, the first, second, third, and fourth lens groups, and satisfies the conditions (1), (2), and (3). The focal length f ₄ ′ of the fourth lens group satisfies the condition (6) within the range where the focal length f of the entire system satisfies the following condition (7).

(6) −40 <f ₄ ′ / f <−20
(7) 8 <f <11
In the microscope objective lens of the present invention, it is desirable that the first lens group satisfies the following condition (8).

(8) 1 <f ₁ / f <5
Here, f ₁ is the focal length of the first lens group.

In the microscope objective lens, that is, an objective lens configured by the first lens group, the second lens group, and the third lens group and satisfying the conditions (1), (2), and (3), It is desirable to satisfy the following condition (9), where H ₂ is the highest ray height in the lens group and H ₃ is the highest ray height in the third lens group.

(9) H ₂ / H ₃ <1
In the objective lens of the present invention, it is desirable that the refractive index N ₁ of the lens closest to the object side in the first lens group be within a range satisfying the following condition (10).

(10) N ₁ > 1.7
In the microscope objective lens, when the radius of curvature of the object side surface of the first lens unit is R ₁ and the radius of curvature of the image side surface is R ₂ , the following condition (11) is preferably satisfied.

(11) | R ₁ | / | R ₂ |> 1
In the objective lens of the present invention, when the fourth lens group includes a cemented lens in which a convex lens and a concave lens are cemented, and the Abbe number of the convex lens is ν _(4p) , it is preferable that the following condition (12) is satisfied. .

(12) ν _(4p) <35
In the microscope objective lens according to the present invention, it is preferable that the following condition (13) is satisfied, where D is an air space between the third lens group and the fourth lens group.

(13) 0 <D <3
Although the microscope objective lens of the present invention is as described above, the following lens system can also achieve the object of the present invention.

    That is, as described above, the objective lens of the present invention includes the first lens group having positive refractive power and the second lens group having positive refractive power and movable along the optical axis in order from the object side. And a third lens group having at least one cemented lens and a fourth lens group in which the most object-side surface is a convex surface on the object side, and the conditions (1), (2), (3 ) Satisfying the condition (4) in which the focal length f of the entire system is within the range shown in the above (5), or the focal length f of the entire system is the above (7). In the objective lens satisfying the condition (6), at least one of the conditions (8), (9), (10), (11), (12), and (13) is satisfied. A satisfactory lens system can also achieve the object of the present invention.

    Next, the lens configuration of the present invention and the reason for setting each condition will be described.

    As described above, the microscope objective lens according to the present invention includes the positive first lens group, the positive second lens group, the positive third lens group including at least one cemented lens component, and the most object-side surface. Consists of a negative fourth lens unit having a convex surface on the object side, and satisfies the conditions (1), (2), and (3).

    The objective lens of the present invention has an action of reducing the opening angle of a high NA light beam emitted from an object by the positive first lens group.

    Then, the spread of the beam diameter is suppressed by the next second lens group. Thereby, spherical aberration and chromatic aberration are effectively corrected. In addition, the second lens group adjusts the variation in spherical aberration due to the change in the thickness of a transparent plane parallel plate such as glass by being moved along the optical axis.

    Further, the second lens group defines its refractive power so as to satisfy the condition (1).

Under this condition (1), when f ₂ / f is smaller than the lower limit of 6, the refractive power of the second lens group becomes too strong and negative spherical aberration occurs, and a spherical surface generated in the first lens group. It is difficult to correct aberrations. On the other hand, if the value exceeds the upper limit of 16 in the condition (1), the refractive power of the second lens group becomes weak, the beam diameter cannot be suppressed, and the maximum ray height of the next third lens group becomes too high. The diameter of the entire objective lens becomes large.

    Next, the light flux from the second lens group is converged by the third lens group.

    Since the objective lens of the present invention moves the second lens group, it is necessary to secure a space for the moving mechanism of the moving group. Therefore, it is characterized by balancing the beam height.

    If the light beam height of the moving lens group is smaller than the maximum light beam height of the entire objective lens, the mechanical mechanism of the moving lens group can be arranged without increasing the diameter of the entire objective lens including the mechanical mechanism. .

    In order to achieve such a relationship, the ratio of the refractive powers of the second lens group and the third lens group needs to satisfy the condition (2).

(2) 0.2 <f ₂ / f ₃ <1.2
This condition (2) defines the ratio of the refractive powers to be converged in the second lens group and the third lens group, so that the convergence of the second lens group and the third lens group is balanced. .

    If the focal length of the second lens group is smaller than or close to the focal length of the third lens group, it is possible to balance convergence by both lens groups.

If the value of f ₂ / f ₃ is larger than the upper limit of 1.2 of the condition (2), the ray height of the lens group behind the moving lens group (second lens group) becomes too high, and the objective lens The overall diameter increases. In addition, high-order aberrations occur in light rays having a high ray height.

On the other hand, when the value of f ₂ / f ₃ is smaller than the lower limit of 0.2, the height of the light beam of the second lens group, which is the moving lens group, becomes too high, and there is no space for the mechanical mechanism of the moving group.

    Furthermore, the objective lens of the present invention corrects chromatic aberration by the third lens group including a cemented lens component.

    The lens diameter of the present invention has a large refractive power in the first lens group, the second lens group, and the third lens group. For this purpose, the fourth lens group has its most object-side surface convex toward the object side, the entire lens group has negative refractive power, and the third lens group has the most image-side surface. It is necessary to determine the relationship of the radius of curvature of the surface closest to the object side of the fourth lens group so as to satisfy the condition (3).

(3) | R ₃ | / | R ₄ |> 4
If the value of | R ₃ | / | R ₄ | deviates from this condition (3) and becomes smaller than 4, the light beam cannot be lowered sufficiently from the third lens group to the fourth lens group, and sufficient negative refraction is caused. Unable to gain power, the Petzval sum cannot be controlled to an appropriate value.

In the objective lens of the present invention, when the focal length f of the whole system is a lens system within the range of the following condition (5), the focal length f ₄ of the fourth lens group satisfies the following condition (4). ing.

(4) −10 <f ₄ / f <−2
(5) 1 <f <5
In the condition (4), if the value of f ₄ / f is larger than the upper limit value −2, coma is generated, which is not preferable. If the value of f ₄ / f is smaller than the lower limit of −10, the negative refractive power of the fourth lens group becomes small, and the Petzval sum cannot be maintained at an appropriate value.

When the focal length f of the entire objective lens system of the present invention is within the range of the following condition (7), it is desirable that the focal length f ₄ ′ of the fourth lens group satisfies the following condition (6).

(6) −40 <f ₄ ′ / f <−20
(7) 8 <f <11
Also in this case, if the value of f ₄ ′ / f is larger than the upper limit value −20 of the condition (6), coma is generated, which is not preferable. If the value of f ₄ ′ / f becomes smaller than the lower limit value of −40, the negative refractive power of the fourth lens group becomes small, and the Petzval sum cannot be maintained at an appropriate value.

As described above, the objective lens of the present invention reduces the opening angle of the high NA light beam emitted from the object in the first lens group. The refractive power f ₁ of the first lens group is desirably set so as to satisfy the following condition (8).

(8) 1 <f ₁ / f <5
This condition (8) defines the refractive power of the first lens group, and is a condition for correcting spherical aberration, coma aberration, and chromatic aberration, and for controlling the beam height.

In this condition (8), if f ₁ / f is smaller than the lower limit of 1, the refractive power of the first lens group becomes too strong, and the spherical aberration, coma aberration, and chromatic aberration are greatly corrected, and this Correction in the lens group after the first lens group becomes difficult.

On the other hand, if f ₁ / f is larger than the upper limit of 5, the refractive power of the first lens group becomes too weak, and the beam diameter cannot be sufficiently reduced, and the beam height becomes higher in the next second lens group. The space for the mechanical mechanism for moving the second lens group, which is the moving group, can be secured. Furthermore, higher-order spherical aberration occurs due to an increase in the height of light rays in the second lens group.

    In the microscope objective lens of the present invention described above, it is preferable that the following condition (9) is satisfied.

(9) H ₂ / H ₃ <1
Under this condition (9), if the value of H ₂ / H ₃ is larger than the upper limit value 1, the height of the light beam of the second lens group becomes high, the lens diameter becomes large, and the space for the mechanical mechanism of the moving group is eliminated. .

    Furthermore, in the objective lens of the present invention, it is preferable that the following condition (10) is satisfied.

(10) N ₁ > 1.7
This is a condition for satisfactorily correcting spherical aberration and coma aberration under the condition relating to the refractive index N ₁ of the lens closest to the object side of the first lens group. By making this refractive index N ₁ a large value, the curvature of the image side surface of this lens can be relaxed to prevent the occurrence of spherical aberration and coma. If the N ₁ value condition (10) is less than the lower limit of 1.7, spherical aberration and coma occur, making it difficult to correct with the subsequent lens group.

    In the microscope objective lens of the present invention, it is more desirable if the following condition (11) is satisfied.

(11) | R ₁ | / | R ₂ |> 1
Here, R ₁ and R ₂ are the radius of curvature of the object side surface and the radius of curvature of the image side surface of the lens closest to the object side in the first lens group, respectively.

    This condition (11) is an objective lens having a long working distance, and relates to spherical aberration, coma aberration, flare and the like.

    The objective lens with a long working distance increases the radius of curvature of the surface closest to the object side of the first lens unit to reduce flare, and decreases the radius of curvature of the surface on the image side to prevent the occurrence of spherical aberration and coma. Like that.

    In this condition (11), if the lower limit value is smaller than 1, flare occurs, spherical aberration and coma occur, and the lens after this lens cannot be corrected.

In the objective lens of the present invention, it is desirable that the Abbe number ν _(4p) of the convex lens of the cemented lens in the fourth lens group satisfies the following condition (12).

(12) ν _(4p) <35
The condition (12) is for correcting chromatic aberration. When the Abbe number ν _{(4p) of the} convex lens is larger than 35, the chromatic aberration is insufficiently corrected.

    Furthermore, in the microscope objective lens of the present invention, it is desirable to set the axial air distance D between the third lens group and the fourth lens group within a range that satisfies the following condition (13).

(13) 0 <D <3
When the air distance D becomes 3 or more, which is the upper limit value, the space of the fourth lens group that is high in the third lens group becomes too small. Alternatively, the negative refracting power of the fourth lens group has to be increased, and coma is generated.

    The objective lens of the present invention has a sufficiently good imaging performance, secures a space for a moving mechanism by a correction ring, and has a compact configuration, and favors aberration fluctuation due to a change in the thickness of a transparent plane parallel plate. It can be corrected.

    Next, examples of the microscope objective lens according to the present invention will be described.

Example 1 of the microscope objective lens of the present invention has a configuration as shown in FIG. 1 and has the following data.
NA = 0.45, WD = 7.7, β = −20, f = 9
r ₁ = 511.7622 d ₁ = 2.8337 n ₁ = 1.75500 ν ₁ = 52.32
r ₂ = -10.6395 d ₂ = 1.6761
r ₃ = 786.4951 d ₃ = 1.4031 n ₂ = 1.63775 ν ₂ = 42.41
r ₄ = 11.7157 d ₄ = 4.0224 n ₃ = 1.43875 ν ₃ = 94.93
r ₅ = -13.7840 d ₅ = 1.2031
r ₆ = 20.4811 d ₆ = 3.8894 n ₄ = 1.43875 ν ₄ = 94.93
r ₇ = -9.9917 d ₇ = 1.4079 n ₅ = 1.63775 ν ₅ = 42.41
r ₈ = -63.5867 d ₈ = 2.5875
r ₉ = 6.9516 d ₉ = 6.0001 n ₆ = 1.43875 ν ₆ = 94.93
r ₁₀ = -12.8237 d ₁₀ = 1.9998 n ₇ = 1.51633 ν ₇ = 64.14
r ₁₁ = 6.2806 d ₁₁ = 6.4514
r ₁₂ = -3.9606 d ₁₂ = 2.1830 n ₈ = 1.51633 ν ₈ = 64.14
r ₁₃ = −340.3705 d ₁₃ = 3.7868 n ₉ = 1.74100 ν ₉ = 52.64
r ₁₄ = -9.3379

Cover glass thickness (mm) 0 0.7 2
WD 8.119 7.698 6.921
d ₂ 2.19 1.676 0.65
d ₅ 0.69 1.203 2.229

(1) f ₂ /f=6.537
_{(2) f 2 / f 3} = 0.707
(3) | R ₃ | / | R ₄ | = 9.147
(6) f ₄ ′ /f=−19.172
(7) f = 8.954
(8) f ₁ /f=1.546
(9) H ₂ / H ₃ = 0.992
(10) N ₁ = 1.755
(11) | R ₁ | / | R ₂ | = 48.100
(12) ν _(4p) = 52.640
(13) D = 2.588

In the above data, r ₁ , r ₂ ,... Are the radius of curvature of each lens surface, d ₁ , d ₂ ,... Are the thickness and air spacing of each lens, and n ₁ , n ₂ ,. Refractive index of each lens, ν ₁ , ν ₂ ,... NA is the numerical aperture, WD is the working distance, β is the magnification, and f is the focal length of the entire system. In the above values, the unit of length is mm.

In the first embodiment, as shown in FIG. 1, a first lens group G1 including a single biconvex lens (r _{1 to} r ₂ ) and a negative meniscus lens (r _{3 to} r ₄ ) having a convex surface facing the object side. ) And a biconvex lens (r _{4 to} r ₅ ) and a cemented lens (r _{3 to} r ₅ ), a biconvex lens (r _{6 to} r ₇ ), and a convex surface facing the image side. negative meniscus lens (r ₇ ~r ₈₎ and the third lens group G3 composed of a cemented junction lens (r ₆ ~r _8), biconvex lens (r ₉ ~r ₁₀₎ and a biconcave lens (r ₁₀ ~r ₁₁₎ a bonded cemented meniscus lens (r ₉ ~r ₁₁₎ and a negative meniscus lens having a concave surface on the object side (r ₁₂ ~r ₁₃₎ and a positive meniscus lens having a convex surface directed toward the image side (r ₁₃ ˜r ₁₄ ) and a cemented meniscus lens (r ₁₂ ˜r ₁₄ ) and a fourth lens group It is an objective lens composed of G4.

The objective lens of Example 1 performs correction by moving the second lens group G2 along the optical axis in accordance with the thickness of the cover glass to be used. That is, correction is performed by changing the distances d ₂ and d ₅ .

The working distance WD with respect to the thickness of the cover glass and the amount of movement of the second lens group (the amount of change in d ₂ and d ₅ ) are shown in the data.

    In the first embodiment, as shown in the data, the focal length of the entire system is f = 9, which is a value within the range shown in the condition (7). Therefore, the fourth lens group G4 satisfies the condition (6). As shown in the data, the conditions (1), (2), (3), (8), (9), (10), (11), (12), and (13) are satisfied.

    The aberration states at each position of the second lens group in Example 1, that is, the aberration states when the cover glass thickness is 0 mm, 0.7 mm, and 2 mm are shown in FIGS. 10, 11, and 12, respectively. As shown in

    The objective lens of Example 1 is an infinity correction type, and is used in combination with the imaging lens shown in FIG. Therefore, the aberration diagram is also in a state where the imaging lens is mounted.

    As is clear from FIGS. 10, 11, and 12, all the aberrations are well corrected, and the variation in aberration due to the change in the cover glass thickness is well corrected by the movement of the second lens group. Yes.

Example 2 of the microscope objective lens of the present invention has a configuration as shown in FIG. 2 and has the following data.

NA = 0.45, WD = 7.7, β = −20, f = 9
r ₁ = 351.0865 d ₁ = 2.8152 n ₁ = 1.75500 ν ₁ = 52.32
r ₂ = -10.6513 d ₂ = 1.5666
r ₃ = 281.3200 d ₃ = 1.3969 n ₂ = 1.63775 ν ₂ = 42.41
r ₄ = 11.6679 d ₄ = 4.0041 n ₃ = 1.43875 ν ₃ = 94.93
r ₅ = -13.9484 d ₅ = 1.8755
r ₆ = 20.3507 d ₆ = 3.8962 n ₄ = 1.43875 ν ₄ = 94.93
_{r 7 = -9.5944 d 7 = 1.3983} n 5 = 1.63775 ν 5 = 42.41
r ₈ = -82.6239 d ₈ = 2.5950
r ₉ = 6.8783 d ₉ = 6.0035 n ₆ = 1.43875 ν ₆ = 94.93
r ₁₀ = -12.1962 d ₁₀ = 2.0045 n ₇ = 1.51633 ν ₇ = 64.14
r ₁₁ = 6.6924 d ₁₁ = 6.4612
r ₁₂ = -3.8209 d ₁₂ = 2.1906 n ₈ = 1.51633 ν ₈ = 64.14
r ₁₃ = 121.4062 d ₁₃ = 3.7920 n ₉ = 1.74100 ν ₉ = 52.64
r ₁₄ = -9.3348

Cover glass thickness (mm) 0 0.7 2
WD 8.117 7.692 6.913
d ₂ 2.027 1.567 0.556
d ₅ 1.417 1.878 2.888

(1) f ₂ /f=6.207
_{(2) f 2 / f 3} = 0.518
(3) | R ₃ | / | R ₄ | = 12.012
(6) f ₄ ′ /f=−37.237
(7) f = 8.992
(8) f ₁ /f=1.528
_{(9) H 2 / H 3} = 0.996
(10) N ₁ = 1.755
(11) | R ₁ | / | R ₂ | = 32.962
(12) ν _(4p) = 52.640
(13) D = 2.950

In Example 2, as shown in FIG. 2, a first lens group G1 composed of a single biconvex lens (r _{1 to} r ₂ ) and a negative meniscus lens (r _{3 to} r ₄ ) having a convex surface facing the object side. ) And a biconvex lens (r _{4 to} r ₅ ) and a cemented lens (r _{3 to} r ₅ ), a second lens group G2, a biconvex lens (r _{6 to} r ₇ ), and a convex surface facing the image side and a negative meniscus lens (r ₇ ~r ₈₎ the third lens group G3 composed of a cemented junction lens (r ₆ ~r _8), biconvex lens (r ₉ ~r ₁₀₎ and a biconcave lens (r ₁₀ ~ r ₁₁₎ of the bonded cemented meniscus lens (r ₉ ~r ₁₁₎ and a biconcave lens (r ₁₂ ~r ₁₃₎ and a biconvex lens (r ₁₃ ~r ₁₄₎ and a bonded cemented meniscus lens (r ₁₂ ~r ₁₄ ) and a fourth lens group G4.

    In the second embodiment, the second lens group G2 is moved along the optical axis to correct the aberration due to the change in the thickness of the cover glass.

The amount of movement of the second lens group in accordance with the value of the cover glass used by the change in the distances d ₂ and d ₅ due to the movement of the second lens group G2 is as shown in the data.

    In Example 2, the focal length of the entire system is f = 9, which is a value within the range shown in the condition (7). Therefore, the fourth lens group G4 is a lens system that satisfies the condition (6). That is, in the second embodiment, as described in the data, the conditions (1), (2), (3), (6), (7), (8), (9), (10), (11 ), (12), and (13) are satisfied.

    In addition, the aberration states at the respective positions of the second lens group are as shown in FIGS. 13, 14, and 15, respectively, and are corrected satisfactorily. That is, the variation in aberration due to the change in the thickness of the cover glass is favorably corrected by the movement of the second lens group.

Example 3 of the microscope objective lens of the present invention has a configuration as shown in FIG. 3 and has the following data.

NA = 0.45, WD = 7.6, β = −17, f = 10.4
r ₁ = 590.8302 d ₁ = 2.7526 n ₁ = 1.75500 ν ₁ = 52.32
r ₂ = -10.8634 d ₂ = 1.6914
r ₃ = 188.935 d ₃ = 1.4109 n ₂ = 1.63775 ν ₂ = 42.41
r ₄ = 11.804 d ₄ = 4.0068 n ₃ = 1.43875 ν ₃ = 94.93
r ₅ = -15.7728 d ₅ = 1.1681
r ₆ = 27.4571 d ₆ = 3.8801 n ₄ = 1.43875 ν ₄ = 94.93
r ₇ = -9.9939 d ₇ = 1.3337 n ₅ = 1.60562 ν ₅ = 43.7
r ₈ = -42.8394 d ₈ = 2.4607
r ₉ = 7.131 d ₉ = 5.9995 n ₆ = 1.43875 ν ₆ = 94.93
r ₁₀ = -17.6713 d ₁₀ = 1.99938 n ₇ = 1.51823 ν ₇ = 58.9
r ₁₁ = 6.2859 d ₁₁ = 6.4885
r ₁₂ = -3.9297 d ₁₂ = 2.1174 n ₈ = 1.51742 ν ₈ = 52.43
r ₁₃ = −95.1977 d ₁₃ = 3.7247 n ₉ = 1.755 ν ₉ = 52.32
r ₁₄ = -8.7085

Cover glass thickness (mm) 0 0.7 2
WD 8.0039 7.619 6.849
d ₂ 2.175 1.691 0.629
d ₅ 0.684 1.168 2.231

(1) f ₂ /f=6.292
_{(2) f 2 / f 3} = 0.882
(3) | R ₃ | / | R ₄ | = 6.007
(6) f ₄ '/f=-39.501
(7) f = 10.3359
(8) f ₁ /f=1.367
(9) H ₂ / H ₃ = 0.986
(10) N ₁ = 1.775
(11) | R ₁ | / | R ₂ | = 54.311
(12) ν _(4p) = 52.32
(13) D = 2.461

In Example 3, as shown in FIG. 3, a first lens group G1 including a single biconvex lens (r _{1 to} r ₂ ) in order from the object side, and a negative meniscus lens (r having a convex surface facing the object side) _{3 to} r ₄ ) and a biconvex lens (r _{4 to} r ₅ ) and a cemented lens (r _{3 to} r ₅ ), a second lens group G2, and a biconvex lens (r _{6 to} r ₇ ) and the image side. convex surface and negative meniscus lens (r ₇ ~r ₈₎ a bonded cemented lens (r ₆ ~r ₈₎ the third lens group G3 composed of towards a biconvex lens (r ₉ ~r ₁₀₎ and a biconcave lens ( r ₁₀ ~r ₁₁₎ a bonded cemented meniscus lens (r ₉ ~r ₁₁₎ and a negative meniscus lens having a concave surface on the object side (r ₁₂ ~r ₁₃₎ and a positive meniscus having a convex surface directed toward the image side lens (r ₁₃ ~r ₁₄₎ and a bonded cemented meniscus lens (r ₁₂ ~r ₁₄₎ Tona A fourth lens group G4.

    In the third embodiment, the second lens group is moved to correct the aberration due to the change in the thickness of the cover glass or the like.

In the data, the position (d ₂ , d ₅ ) and the like of the second lens group corresponding to the thickness of the cover glass are shown.

    In Example 3, as shown in the data, the focal length of the entire system is f = 9, which is a value within the range shown in the condition (7). Therefore, the fourth lens group G4 satisfies the condition (6). As shown in the data, the conditions (1), (2), (3), (8), (9), (10), (11), (12), and (13) are satisfied.

    The aberration state at each position indicated in the data by the second lens group in Example 3 is as shown in FIG. 16, FIG. 17, and FIG. As is clear from these figures, the aberration is corrected well, and the variation of the aberration due to the thickness of the cover glass is corrected well.

Example 4 of the present invention has a lens configuration as shown in FIG. 4 and has the following data.

NA = 0.7, WD = 3.3, β = −50, f = 3.6
r ₁ = −7.1161 d ₁ = 3.9842 n ₁ = 1.74100 ν ₁ = 52.64
r ₂ = -5.3759 d ₂ = 0.2017
r ₃ = 30.4018 d ₃ = 3.6526 n ₂ = 1.49700 ν ₂ = 81.54
r ₄ = −8.3706 d ₄ = 1.4000 n ₃ = 1.72047 ν ₃ = 34.71
r ₅ = -14.5668 d ₅ = 1.1749
r ₆ = 31.0081 d ₆ = 1.3300 n ₄ = 1.78590 ν ₄ = 44.2
r ₇ = 13.6781 d ₇ = 4.5217 n ₅ = 1.49700 ν ₅ = 81.54
r ₈ = -13.6781 d ₈ = 1.2763
r ₉ = -13.3810 d ₉ = 1.3500 n ₆ = 1.72047 ν ₆ = 34.71
r ₁₀ = 17.8619 d ₁₀ = 3.7416 n ₇ = 1.49700 ν ₇ = 81.54
r ₁₁ = -20.0357 d ₁₁ = 0.3057
r ₁₂ = 19.6054 d ₁₂ = 3.7698 n ₈ = 1.43875 ν ₈ = 94.93
r ₁₃ = -17.6832 d ₁₃ = 1.4107 n ₉ = 1.83400 ν ₉ = 37.16
r ₁₄ = -48.3594 d ₁₄ = 0.3058
r ₁₅ = 28.4034 d ₁₅ = 3.4387 n ₁₀ = 1.61800 ν ₁₀ = 63.33
r ₁₆ = -16.2132 d ₁₆ = 1.6859 n ₁₁ = 1.61340 ν ₁₁ = 44.27
r ₁₇ = -71.1011 d ₁₇ = 1.4457
r ₁₈ = 8.1527 d ₁₈ = 3.1866 n ₁₂ = 1.80518 ν ₁₂ = 25.42
r ₁₉ = 73.3349 d ₁₉ = 1.4016 n ₁₃ = 1.61340 ν ₁₃ = 44.27
r ₂₀ = 3.8916 d ₂₀ = 3.3130
r ₂₁ = -11.7951 d ₂₁ = 0.9147 n ₁₄ = 1.56384 ν ₁₄ = 60.67
r ₂₂ = 13.2420

Cover glass thickness (mm) 0 0.7 1.2
WD 3.832 3.333 2.974
d ₅ 2.038 1.175 0.409
d ₈ 0.413 1.276 2.042

(1) f ₂ /f=6.985
_{(2) f 2 / f 3} = 0.590
(3) | R ₃ | / | R ₄ | = −8.721
(4) f ₄ /f=−2.927
(5) f = 3.601
(8) f ₁ /f=2.590
_{(9) H 2 / H 3} = 0.918
(10) N ₁ = 1.741
(11) | R ₁ | / | R ₂ | = 1.324
(12) ν _(4p) = 25.420
(13) D = 1.446

In Example 4, as shown in FIG. 4, in order from the object side, a single positive meniscus lens (r _{1 to} r ₂ ) and a biconvex lens (r _{3 to} r ₄ ) having a convex surface facing the image surface side. and a negative meniscus lens (r ₄ ~r ₅₎ a bonded cemented lens (r ₃ ~r ₅₎ more becomes the first lens group G1 having a convex surface directed toward the image side, a negative having a convex surface directed toward the object side a meniscus lens (r ₆ ~r ₇₎ and a biconvex lens (r ₇ ~r ₈₎ a bonded cemented lens (r ₆ ~r ₈₎ the second lens group G2 composed of a biconcave lens (r ₉ ~r ₁₀₎ a biconvex lens (r ₁₀ ~r ₁₁₎ a bonded cemented meniscus lens (r ₉ ~r ₁₁₎ and a biconvex lens (r ₁₂ ~r ₁₃₎ and a negative meniscus lens having a convex surface directed toward the image side (r ₁₃ ~ r ₁₄₎ and a bonded cemented lens (r ₁₂ ~r ₁₄₎ and a biconvex lens (r ₁₅ ~r ₁₆₎ and convex on the image side A negative meniscus lens (r ₁₆ ~r ₁₇₎ and a bonded cemented lens (r ₁₅ ~r ₁₇₎ the third lens group G3 composed of a directed and a convex surface directed toward the object side positive meniscus lens (r ₁₈ ~r ₁₉₎ and the image side and a concave negative meniscus lens (r ₁₉ ~r ₂₀₎ a bonded cemented meniscus lens (r ₁₈ ~r ₂₀₎ and a single double-concave lens (r ₂₁ ~r ₂₂₎ And a fourth lens group G4.

    Example 4 is a lens system in which f = 3.6 and the focal length f of the entire system is within the range indicated by the condition (5). Therefore, Example 4 satisfies the conditions (1) to (5) and the conditions (8) to (13).

In the lens system of Example 4, the second lens group G2 is moved to correct aberration variation due to a change in the thickness of the cover glass. That is, d ₅ and d ₈ are changed in the data according to the thickness of the cover glass.

    The aberration status of Example 4 is corrected well as shown in FIGS. 19, 20, and 21. FIG. That is, the aberration variation is corrected by moving the second lens group in accordance with the thickness of the cover glass.

Example 5 of the present invention is an objective lens as shown in FIG. 5 and has the following data.

NA = 0.65, WD = 3.3, β = −50, f = 3.6
r ₁ = -6.6412 d ₁ = 3.5687 n ₁ = 1.74100 ν ₁ = 52.64
r ₂ = -5.0534 d ₂ = 0.4356
r ₃ = 23.6979 d ₃ = 3.5505 n ₂ = 1.49700 ν ₂ = 81.54
r ₄ = -8.1019 d ₄ = 1.5638 n ₃ = 1.72047 ν ₃ = 34.71
r ₅ = -11.7521 d ₅ = 1.5309
r ₆ = 78.7455 d ₆ = 1.4746 n ₄ = 1.778590 ν ₄ = 44.2
r ₇ = 19.2598 d ₇ = 2.4362 n ₅ = 1.49700 ν ₅ = 81.54
r ₈ = -15.8295 d ₈ = 1.9591
r ₉ = -10.1039 d ₉ = 1.4738 n ₆ = 1.72047 ν ₆ = 34.71
r ₁₀ = 21.3847 d ₁₀ = 3.1322 n ₇ = 1.49700 ν ₇ = 81.54
r ₁₁ = -14.3025 d ₁₁ = 0.3869
r ₁₂ = 36.9212 d ₁₂ = 3.5375 n ₈ = 1.43875 ν ₈ = 94.93
r ₁₃ = -32.2728 d ₁₃ = 2.9110 n ₉ = 1.83400 ν ₉ = 37.16
r ₁₄ = -66.6984 d ₁₄ = 0.2023
r ₁₅ = 16.2178 d ₁₅ = 5.7735 n ₁₀ = 1.61800 ν ₁₀ = 63.33
r ₁₆ = -9.5268 d ₁₆ = 2.9318 n ₁₁ = 1.61340 ν ₁₁ = 44.27
r ₁₇ = 34.5869 d ₁₇ = 2.2517
r ₁₈ = 8.6250 d ₁₈ = 3.6906 n ₁₂ = 1.80518 ν ₁₂ = 25.42
r ₁₉ = -4963.6686 d ₁₉ = 1.8920 n ₁₃ = 1.61340 ν ₁₃ = 44.27
r ₂₀ = 3.7707 d ₂₀ = 2.3770
r ₂₁ = -13.6585 d ₂₁ = 1.4756 n ₁₄ = 1.56384 ν ₁₄ = 60.67
r ₂₂ = 52.7443

Cover glass thickness (mm) 0 0.7 1.2
WD 3.846 3.335 2.968
d ₅ 2.661 1.531 0.617
d ₈ 0.829 1.959 2.873

(1) f ₂ /f=10.486
_{(2) f 2 / f 3} = 0.300
(3) | R ₃ | / | R ₄ | = 4.010
(4) f ₄ /f=−4.643
(5) f = 3.601
(8) f ₁ /f=2.260
_{(9) H 2 / H 3} = 0.862
(10) N ₁ = 1.741
(11) | R ₁ | / | R ₂ | = 1.314
(12) ν _(4p) = 25.420
(13) D = 2.252

As shown in FIG. 5, the fifth embodiment includes a single positive meniscus lens (r _{1 to} r ₂ ) and a biconvex lens (r _{3 to} r ₄ ) with a convex surface facing the image surface side in order from the object side. and a negative meniscus lens (r ₄ ~r ₅₎ a bonded cemented lens (r ₃ ~r ₅₎ more becomes the first lens group G1 having a convex surface directed toward the image side, a negative having a convex surface directed toward the object side a meniscus lens (r ₆ ~r ₇₎ and a biconvex lens (r ₇ ~r ₈₎ a bonded cemented lens (r ₆ ~r ₈₎ the second lens group G2 composed of a biconcave lens (r ₉ ~r ₁₀₎ a biconvex lens (r ₁₀ ~r ₁₁₎ a bonded cemented meniscus lens (r ₉ ~r ₁₁₎ and a biconvex lens (r ₁₂ ~r ₁₃₎ and a negative meniscus lens having a convex surface directed toward the image side (r ₁₃ ~ r ₁₄₎ and the a bonded cemented lens (r ₁₂ ~r ₁₄₎ and a biconvex lens (r ₁₅ ~r ₁₆₎ biconcave lens (R ₁₆ ~r ₁₇₎ and a bonded cemented meniscus lens and (r ₁₅ ~r ₁₇₎ the third lens group G3 composed of a biconvex lens (r ₁₈ ~r ₁₉₎ and a biconcave lens (r ₁₉ ~r ₂₀₎ Is a lens system composed of a cemented meniscus lens (r _{18 to} r ₂₀ ) and a fourth lens group G4 including a single biconcave lens (r _{21 to} r ₂₂ ).

    The fifth embodiment is a lens system in which the focal length f of the entire system is f = 3.6 as shown in the data, and is in the range shown in the condition (5). Therefore, Example 5 is an objective lens that satisfies the conditions (1) to (5) and the conditions (8) to (13).

Also in the lens system of Example 5, the second lens group G2 is moved to correct the aberration variation due to the change in the thickness of the cover glass. That is, as shown in the data, aberration variation is corrected by changing d ₅ and d ₈ corresponding to the thickness of the cover glass.

    The aberration state of Example 5 is corrected as shown in FIGS. 22, 23, and 24. That is, the variation in aberration due to the change in the thickness of the cover glass is corrected.

Example 6 of the present invention is an objective lens as shown in FIG. 6 and has the following data.

NA = 0.65, WD = 3.49, β = −50, f = 3.6
r ₁ = -6.6651 d ₁ = 3.9041 n ₁ = 1.74100 ν ₁ = 52.64
r ₂ = -5.3303 d ₂ = 0.2960
r ₃ = 20.5175 d ₃ = 3.6703 n ₂ = 1.49700 ν ₂ = 81.54
r ₄ = -8.6224 d ₄ = 1.6318 n ₃ = 1.72047 ν ₃ = 34.71
r ₅ = -12.5643 d ₅ = 1.1662
r ₆ = 186.6075 d ₆ = 1.4671 n ₄ = 1.78590 ν ₄ = 44.2
r ₇ = 32.0895 d ₇ = 4.3406 n ₅ = 1.49700 ν ₅ = 81.54
r ₈ = -17.0960 d ₈ = 1.5963
r ₉ = -10.8824 d ₉ = 1.5113 n ₆ = 1.72047 ν ₆ = 34.71
r ₁₀ = 15.1231 d ₁₀ = 3.7860 n ₇ = 1.49700 ν ₇ = 81.54
r ₁₁ = -18.3524 d ₁₁ = 0.3896
_{r 12 = 17.6826 d 12 = 5.0208} n 8 = 1.43875 ν 8 = 94.93
r ₁₃ = -17.1958 d ₁₃ = 2.7453 n ₉ = 1.83400 ν ₉ = 37.16
r ₁₄ = -49.0717 d ₁₄ = 0.2018
r ₁₅ = 19.5170 d ₁₅ = 4.0367 n ₁₀ = 1.61800 ν ₁₀ = 63.33
r ₁₆ = -11.2916 d ₁₆ = 1.8551 n ₁₁ = 1.61340 ν ₁₁ = 44.27
r ₁₇ = -124.4000 d ₁₇ = 1.4947
r ₁₈ = 7.5168 d ₁₈ = 3.2427 n ₁₂ = 1.80518 ν ₁₂ = 25.42
r ₁₉ = 21.8154 d ₁₉ = 1.4959 n ₁₃ = 1.61340 ν ₁₃ = 44.27
r ₂₀ = 3.5464 d ₂₀ = 3.1412
r ₂₁ = -13.9111 d ₂₁ = 0.8932 n ₁₄ = 1.56384 ν ₁₄ = 60.67
r ₂₂ = 11.1115

Cover glass thickness (mm) 0 0.7 1.2
WD 4 3.491 3.126
d ₅ 2.158 1.166 0.405
d ₈ 0.605 1.596 2.358

(1) f ₂ /f=11.286
(2) f ₂ / f ₃ = 1.190
(3) | R ₃ | / | R ₄ | = −16.550
(4) f ₄ /f=−2.856
(5) f = 3.601
(8) f ₁ /f=2.309
(9) H ₂ / H ₃ = 0.839
(10) N ₁ = 1.741
(11) | R ₁ | / | R ₂ | = 1.250
(12) ν _(4p) = 25.420
(13) D = 1.495

In Example 6, as shown in FIG. 6, in order from the object side, a single positive meniscus lens (r _{1 to} r ₂ ) and a biconvex lens (r _{3 to} r ₄ ) having a convex surface facing the image surface side. and a negative meniscus lens (r ₄ ~r ₅₎ a bonded cemented lens (r ₃ ~r ₅₎ more becomes the first lens group G1 having a convex surface directed toward the image side, a negative having a convex surface directed toward the object side a meniscus lens (r ₆ ~r ₇₎ and a biconvex lens (r ₇ ~r ₈₎ a bonded cemented lens (r ₆ ~r ₈₎ the second lens group G2 composed of a biconcave lens (r ₉ ~r ₁₀₎ a biconvex lens (r ₁₀ ~r ₁₁₎ a bonded cemented meniscus lens (r ₉ ~r ₁₁₎ and a biconvex lens (r ₁₂ ~r ₁₃₎ and a negative meniscus lens having a convex surface directed toward the image side (r ₁₃ ~ r ₁₄₎ and a bonded cemented lens (r ₁₂ ~r ₁₄₎ and a biconvex lens (r ₁₅ ~r ₁₆₎ and convex on the image side A negative meniscus lens (r ₁₆ ~r ₁₇₎ and a bonded cemented lens (r ₁₅ ~r ₁₇₎ the third lens group G3 composed of a directed and a convex surface directed toward the object side positive meniscus lens (r ₁₈ ~r ₁₉₎ and a negative meniscus lens (r ₁₉ ~r ₂₀₎ a bonded cemented meniscus lens (r ₁₈ ~r ₂₀₎ and single biconcave lens having a concave surface on the image side (r ₂₁ ~r ₂₂₎ And a fourth lens group G4.

    The sixth embodiment is a lens system in which the focal length f of the entire system is f = 3.6 and the focal length is in the range of the condition (5).

    In Example 6, as shown in the data, the conditions (1) to (5) and the conditions (8) to (13) are satisfied.

Further, by moving by changing d ₅ and d ₈ to show the second lens group G2 to the data, and correcting the aberration fluctuation due to changes in the thickness of the cover glass.

    The aberration status of Example 6 is corrected well as shown in FIGS. 25, 26, and 27. FIG. That is, the variation in aberration due to the change in the thickness of the cover glass is corrected satisfactorily.

Example 7 of the present invention is an objective lens as shown in FIG. 7 and has the following data.

NA = 0.8, WD = 1.5, β = -100, f = 1.8
r ₁ = -6.4131 d ₁ = 1.8872 n ₁ = 1.88300 ν ₁ = 40.76
r ₂ = -3.5144 d ₂ = 0.15
r ₃ = 116.8536 d ₃ = 1.7485 n ₂ = 1.72047 ν ₂ = 34.71
r ₄ = 9.8301 d ₄ = 3.99577 n ₃ = 1.49700 ν ₃ = 81.54
r ₅ = -6.0797 d ₅ = 1.1614
r ₆ = 14.897 d ₆ = 2.7659 n ₄ = 1.43875 ν ₄ = 94.93
r ₇ = -10.2282 d ₇ = 1.1828
r ₈ = -7.8385 d ₈ = 1.6088 n ₅ = 1.75500 ν ₅ = 52.32
r ₉ = 20.1451 d ₉ = 3.8246 n ₆ = 1.43875 ν ₆ = 94.93
r ₁₀ = −7.1339 d ₁₀ = 1.3945 n ₇ = 1.65412 ν ₇ = 39.68
r ₁₁ = -14.5872 d ₁₁ = 0.1
_{r 12 = 28.1671 d 12 = 3.7541} n 8 = 1.56907 ν 8 = 71.3
r ₁₃ = -14.8567 d ₁₃ = 0.2
r ₁₄ = 14.172 d ₁₄ = 1 n ₉ = 1.72916 ν ₉ = 54.68
r ₁₅ = 8.8213 d ₁₅ = 3.5586 n ₁₀ = 1.43875 ν ₁₀ = 94.93
r ₁₆ = -15.6932 d ₁₆ = 1.0289 n ₁₁ = 1.72047 ν ₁₁ = 34.71
r ₁₇ = -292.431 d ₁₇ = 0.1
r ₁₈ = 10.3581 d ₁₈ = 3.928 n ₁₂ = 1.60300 ν ₁₂ = 65.44
r ₁₉ = 15 d ₁₉ = 3.4576 n ₁₃ = 1.51633 ν ₁₃ = 64.14
r ₂₀ = 3.222 d ₂₀ = 5.0454
r ₂₁ = 4.7959 d ₂₁ = 2.0368 n ₁₄ = 1.80518 ν ₁₄ = 25.42
r ₂₂ = -13.4523 d ₂₂ = 0.4 n ₁₅ = 1.75500 ν ₁₅ = 52.32
r ₂₃ = 5.0917 d ₂₃ = 1.2
r ₂₄ = -9.9082 d ₂₄ = 1.2 n ₁₆ = 1.80518 ν ₁₆ = 25.42
r ₂₅ = 28.8646

Cover glass thickness (mm) 0 0.4 0.7
WD 1.78 1.499 1.287
d ₅ 1.621 1.161 0.737
d ₇ 0.724 1.183 1.609

(1) f ₂ /f=7.946
_{(2) f 2 / f 3} = 0.238
(3) | R ₃ | / | R ₄ | = 28.232
(4) f ₄ /f=−4.647
(5) f = 1.8
(8) f ₁ /f=3.039
_{(9) H 2 / H 3} = 0.748
(10) N ₁ = 1.883
(11) | R ₁ | / | R ₂ | = 1.825
(12) ν _(4p) = 25.42.
(13) D = 0.1

In the lens system of Example 7, in order from the object side, a single positive meniscus lens (r _{1 to} r ₂ ) having a convex surface facing the image surface side and a negative meniscus lens (r ₃ to r ₂ ) having a convex surface facing the object side. r ₄₎ and a biconvex lens (r ₄ ~r ₅₎ and more becomes the first lens group G1 and the cemented cemented lens (r ₃ ~r _5), a single double-convex lens (r ₆ ~r ₇₎ first and the second lens group G2, 3 sheets obtained by bonding a biconcave lens (r ₈ ~r ₉₎ and a biconvex lens (r ₉ ~r ₁₀₎ and a negative meniscus lens having a convex surface directed toward the image side (r ₁₀ ~r ₁₁₎ cemented lens (r ₈ ~r ₁₁₎ and a single biconvex lens (r ₁₂ ~r ₁₃₎ and a negative meniscus lens having a convex surface directed toward the object side (r ₁₄ ~r ₁₅₎ and a biconvex lens of (r ₁₅ ~r ₁₆ ) And a negative meniscus lens (r _{16 to} r ₁₇ ) having a convex surface facing the image side, a cemented three-piece lens (r ₁₄ ˜r ₁₇ ), a positive meniscus lens (r ₁₈ ˜r ₁₉ ) having a convex surface facing the object side, and a negative meniscus lens (r ₁₉ ˜r ₂₀ ) having a concave surface facing the image side. the bonded cemented meniscus lens (r ₁₈ ~r ₂₀₎ and a biconvex lens (r ₂₁ ~r ₂₂₎ and a biconcave lens (r ₂₂ ~r ₂₃₎ and a bonded cemented meniscus lens and (r ₂₁ ~r ₂₃₎ a lens system which is constituted by a single double-concave lens (r ₂₄ ~r ₂₅₎ and become more fourth lens group G4.

    In the lens system of Example 7, as shown in the data, the focal length f of the entire system is f = 1.8, and the focal length is within the range of the condition (5). Therefore, the fourth lens group satisfies the condition (4). That is, Example 7 satisfies the conditions (1) to (5) and the conditions (8) to (13) as shown in the data.

In Example 7, the second lens group G2 is moved, that is, the distances d ₅ and d ₇ are changed corresponding to the change in the thickness of the cover glass, as shown in the data, Aberration fluctuation due to thickness change is corrected.

    The aberration status of Example 7 is corrected as shown in FIGS. 28, 29, and 30. That is, the variation in aberration due to the change in the thickness of the cover glass is corrected satisfactorily.

The optical system of Example 8 of the present invention has the following data with the configuration shown in FIG.

NA = 0.85, WD = 1.28, β = −100, f = 1.8
r ₁ = -10.1037 d ₁ = 1.5759 n ₁ = 1.88300 ν ₁ = 40.76
r ₂ = -5.4838 d ₂ = 0.15
r ₃ = 73.2387 d ₃ = 2.278 n ₂ = 1.74951 ν ₂ = 35.33
r ₄ = 14.3381 d ₄ = 4.6437 n ₃ = 1.49700 ν ₃ = 81.54
r ₅ = -6.6845 d ₅ = 1.273
r ₆ = 473.0632 d ₆ = 2.3126 n ₄ = 1.58913 ν ₄ = 61.14
r ₇ = -16.3646 d ₇ = 1.5111
r ₈ = 66.6774 d ₈ = 4.8207 n ₅ = 1.43875 ν ₅ = 94.93
r ₉ = -8.7946 d ₉ = 1.35 n ₆ = 1.65412 ν ₆ = 39.68
r ₁₀ = -31.5482 d ₁₀ = 0.1
r ₁₁ = 27.0709 d ₁₁ = 2.473 n ₇ = 1.49700 ν ₇ = 81.54
r ₁₂ = -29.8881 d ₁₂ = 0.2
r ₁₃ = 18.2202 d ₁₃ = 1.4 n ₈ = 1.72916 ν ₈ = 54.68
r ₁₄ = 9.0694 d ₁₄ = 5.7345 n ₉ = 1.43875 ν ₉ = 94.93
r ₁₅ = -7.7731 d ₁₅ = 1.2 n ₁₀ = 1.61340 ν ₁₀ = 44.27
r ₁₆ = 118.3338 d ₁₆ = 0.1
r ₁₇ = 6.0069 d ₁₇ = 3.5034 n ₁₁ = 1.49700 ν ₁₁ = 81.54
r ₁₈ = 100.0715 d ₁₈ = 2.5178 n ₁₂ = 1.61340 ν ₁₂ = 44.27
r ₁₉ = 3.9277 d ₁₉ = 3.1927
r ₂₀ = 4.5166 d ₂₀ = 2.4729 n ₁₃ = 1.80518 ν ₁₃ = 25.42
r ₂₁ = −9.4524 d ₂₁ = 0.62 n ₁₄ = 1.72916 ν ₁₄ = 54.68
r ₂₂ = 3.66 d ₂₂ = 1.5328
r ₂₃ = -2.9476 d ₂₃ = 1.0016 n ₁₅ = 1.69895 ν ₁₅ = 30.13
r ₂₄ = -6.9668

Cover glass thickness (mm) 0 0.4 0.7
WD 1.454 1.282 1.161
d ₅ 2.148 1.273 0.499
d ₇ 0.637 1.511 2.286

(1) f ₂ /f=4.244
(2) f ₂ / f ₃ = 14.942
(3) | R ₃ | / | R ₄ | = 19.7
(4) f ₄ /f=−9.087
(5) f = 1.8
(8) f ₁ /f=4.244
_{(9) H 2 / H 3} = 0.956
(10) N ₁ = 1.883
(11) | R ₁ | / | R ₂ | = 1.842
(12) ν _(4p) = 25.42.
(13) D = 0.1

In the lens system of Example 8, in order from the object side, a single positive meniscus lens (r _{1 to} r ₂ ) having a convex surface facing the image surface side and a negative meniscus lens (r ₃ having a convex surface facing the object side). ˜r ₄ ) and a biconvex lens (r ₄ ˜r ₅ ) and a cemented lens (r ₃ ˜r ₅ ), a first lens group G1, and a single biconvex lens (r ₆ ˜r ₇ ). a second lens group G2, a double convex lens (r ₈ ~r ₉₎ and a negative meniscus lens having a convex surface directed toward the image side (r ₉ ~r ₁₀₎ and a bonded cemented lens (r ₈ ~r ₁₀₎ A single biconvex lens (r _{11 to} r ₁₂ ), a negative meniscus lens (r _{13 to} r ₁₄ ) having a convex surface facing the object side, a biconvex lens (r _{14 to} r ₁₅ ), and a biconcave lens (r _{15 to} r ₁₆ ) towards DOO a third lens group G3 composed of a bonded three cemented lenses (r ₁₃ ~r _16), a convex surface on the object side Positive meniscus lens (r ₁₇ ~r ₁₈₎ and a negative meniscus lens having a concave surface on the image side (r ₁₈ ~r ₁₉₎ and a bonded cemented meniscus lens (r ₁₇ ~r ₁₉₎ biconvex lens (r ₂₀ ~r ₂₁₎ and a biconcave lens (r ₂₁ ~r ₂₂₎ cemented meniscus lens (r ₂₀ bonding the ~r ₂₂₎ and a single negative meniscus lens having a concave surface on the object side (r ₂₃ ~r ₂₄ ) And the fourth lens group G4.

    The focal length f of the entire objective lens of Example 8 is f = 1.8, which is a value within the range of the condition (5). Therefore, this Example 8 satisfies the condition (4). That is, the objective lens of Example 8 satisfies the conditions (1) to (5) and the conditions (8) to (13).

In the eighth embodiment, the second lens group G2 is moved to correct the aberration variation due to the change in the cover glass thickness. For example, as shown in the data, the aberration variation is corrected by moving the second lens group in accordance with the thickness of the cover glass and changing the distances d ₅ and d ₇ before and after the second lens group.

    The aberration status of Example 8 is as shown in FIGS. 31, 32, and 33, and all are well corrected. That is, the variation in aberration due to the change in the thickness of the cover glass is corrected satisfactorily.

Example 9 of the present invention is an objective lens as shown in FIG. 9 and has the following data.

NA = 0.8, WD = 1.5, β = -100, f = 1.8
r ₁ = -11.0153 d ₁ = 1.25 n ₁ = 1.88300 ν ₁ = 40.76
r ₂ = -4.7398 d ₂ = 0.15
r ₃ = 75.4804 d ₃ = 1.834 n ₂ = 1.74951 ν ₂ = 35.33
r ₄ = 12.2874 d ₄ = 5.2782 n ₃ = 1.49700 ν ₃ = 81.54
r ₅ = -6.7073 d ₅ = 1.3145
r ₆ = -460.618 d ₆ = 2.2185 n ₄ = 1.58913 ν ₄ = 61.14
r ₇ = -15.4389 d ₇ = 1.3144
r ₈ = -315.987 d ₈ = 4.6485 n ₅ = 1.43875 ν ₅ = 94.93
r ₉ = -7.6277 d ₉ = 1.5 n ₆ = 1.65412 ν ₆ = 39.68
r ₁₀ = -22.2502 d ₁₀ = 0.1
r ₁₁ = 25.6319 d ₁₁ = 2.6017 n ₇ = 1.49700 ν ₇ = 81.54
r ₁₂ = -122.917 d ₁₂ = 0.2
r ₁₃ = 11.0415 d ₁₃ = 1.2 n ₈ = 1.72916 ν ₈ = 54.68
r ₁₄ = 7.2433 d ₁₄ = 6.1973 n ₉ = 1.43875 ν ₉ = 94.93
r ₁₅ = -10.786 d ₁₅ = 1 n ₁₀ = 1.61340 ν ₁₀ = 44.27
r ₁₆ = 25 d ₁₆ = 0.1
r ₁₇ = 5.4163 d ₁₇ = 3.262 n ₁₁ = 1.49700 ν ₁₁ = 81.54
r ₁₈ = -226.993 d ₁₈ = 3.1635 n ₁₂ = 1.61340 ν ₁₂ = 44.27
r ₁₉ = 2.8676 d ₁₉ = 4.6293
r ₂₀ = 4.1817 d ₂₀ = 1.9386 n ₁₃ = 1.80518 ν ₁₃ = 25.42
r ₂₁ = -14.5209 d ₂₁ = 0.5 n ₁₄ = 1.755 ν ₁₄ = 52.32
r ₂₂ = 3.9555 d ₂₂ = 1.4401
r ₂₃ = -3.4982 d ₂₃ = 0.6 n ₁₅ = 1.80518 ν ₁₅ = 25.42
r ₂₄ = -5.8209

Cover glass thickness (mm) 0 0.4 0.7
WD 1.593 1.499 1.358
d ₅ 2.18 1.314 0.546
d ₇ 0.449 1.314 2.083

(1) f ₂ /f=15.711
_{(2) f 2 / f 3} = 0.704
(3) | R ₃ | / | R ₄ | = 4.74
(4) f ₄ /f=−9.017
(5) f = 1.8
(8) f ₁ /f=3.791
(9) H ₂ / H ₃ = 0.942
(10) N ₁ = 1.883
(11) | R ₁ | / | R ₂ | = 2.324
(12) ν _(4p) = 25.42.
(13) D = 0.1

In Example 9, in order from the object side, a single positive meniscus lens (r _{1 to} r ₂ ) having a convex surface facing the image side and a negative meniscus lens (r _{3 to} r ₄ ) having a convex surface facing the object side. ) And a biconvex lens (r _{4 to} r ₅ ) and a cemented lens (r _{3 to} r ₅ ), and a single positive meniscus lens (r ₆ having a convex surface facing the image side). a second lens group G2 composed of ~r _7), a concave surface directed toward the object side positive meniscus lens (r ₈ ~r ₉₎ and a negative meniscus lens having a convex surface directed toward the image side (r ₉ ~r ₁₀₎ A cemented lens (r _{8 to} r ₁₀ ), a single biconvex lens (r _{11 to} r ₁₂ ), a negative meniscus lens (r _{13 to} r ₁₄ ) with a convex surface facing the object side, and a biconvex lens (r ₁₄ ~r ₁₅₎ and a biconcave lens (r ₁₅ ~r ₁₆₎ of the bonded cemented triplet (r ₁₃ ~r ₁₆₎ And Li Cheng the third lens group G3, biconvex lens (r ₁₇ ~r ₁₈₎ and a biconcave lens (r ₁₈ ~r ₁₉₎ a bonded cemented meniscus lens (r ₁₇ ~r ₁₉₎ and a biconvex lens (r ₂₀ ~r ₂₁ ) and a bi-concave lens (r _{21 to} r ₂₂ ) bonded together, a cemented meniscus lens (r _{20 to} r ₂₂ ), and a single negative meniscus lens (r _{23 to} r ₂₄ ) with the concave surface facing the object side. And a fourth lens group G4.

    The objective lens of Example 9 is a lens system in which the focal length f of the entire system is f = 1.8 and within the range of the condition (5), and satisfies the condition (4). That is, Example 9 satisfies the conditions (1) to (5) and the conditions (8) to (13).

In the lens system of Example 9, aberration variation due to a change in the thickness of a transparent plane-parallel plate such as a cover glass is corrected by moving the second lens group G2. As shown in the data, in Example 9, aberration variation is corrected by moving the second lens group G2 (changing the distances d ₅ and d ₇ ) according to the thickness of the cover glass.

    The aberration status of Example 9 is as shown in FIGS. 34, 35, and 36, and all are well corrected. That is, the variation in aberration due to the change in the thickness of the cover glass is corrected satisfactorily.

    As with the first embodiment, the second to ninth embodiments are also infinity-corrected lens systems, and are used with an imaging lens as shown in FIG. 37, for example.

The imaging lens shown in FIG. 37 has the following data.

F = 180
R ₁ = 68.754 D ₁ = 7.732 N ₁ = 1.487 V ₁ = 70.2
R ₂ = −37.567 D ₂ = 3.474 N ₂ = 1.806 V ₂ = 40.9
R ₃ = -102.847 D ₃ = 0.697
R ₄ = 84.309 D ₄ = 6.023 N ₃ = 1.834 V ₃ = 37.1
_{R 5 = -50.710 D 5 = 3.029} N 4 = 1.644 V 4 = 40.8
R ₆ = 40.661
_{Wherein, R 1, R 2, ···} R 6 is the radius of curvature of each lens surface of the imaging _{lens, D 1, D 2, ···} D 5 is the thickness and air space of the lens of the imaging lens , N ₁ , N ₂ , N ₃ , and N ₄ are the refractive indexes of the lenses of the imaging lens, V ₁ , V ₂ , V ₃ , and V ₄ are Abbe numbers of the lenses of the imaging lens, and F is the imaging lens Is the focal length.

    The objective lenses of Examples 1 to 9 are used in an arrangement in which the distance between the objective lens and the imaging lens shown in FIG. 37 is 50 mm to 170 mm.

    The aberration diagrams of the respective examples are obtained when the distance between the objective lens and the imaging lens is 119 mm. However, if the distance is within the above range other than 119 mm, the aberration situation is almost the same as that shown in the aberration diagram.

    The objective of the present invention is a microscope objective lens with a correction ring, which can respond to changes in the thickness of a transparent plane parallel plate such as a cover glass, and can easily correct aberration variations due to thickness changes, and is always good. It is possible to observe an object with excellent imaging performance.

Sectional drawing of Example 1 of this invention Sectional drawing of Example 2 of this invention Sectional drawing of Example 3 of this invention Sectional drawing of Example 4 of this invention Sectional drawing of Example 5 of this invention Sectional drawing of Example 6 of this invention Sectional drawing of Example 7 of this invention Sectional drawing of Example 8 of this invention Sectional drawing of Example 9 of this invention Aberration diagram when the thickness of the cover glass of Example 1 of the present invention is 0 mm Aberration diagram when the thickness of the cover glass of Example 1 of the present invention is 0.7 mm. Aberration diagram when the thickness of the cover glass of Example 1 of the present invention is 1.2 mm Aberration diagram when the thickness of the cover glass of Example 2 of the present invention is 0 mm Aberration diagram when the thickness of the cover glass of Example 2 of the present invention is 0.7 mm Aberration diagram when the thickness of the cover glass of Example 2 of the present invention is 1.2 mm. Aberration diagram when the thickness of the cover glass of Example 3 of the present invention is 0 mm Aberration diagram when the thickness of the cover glass of Example 3 of the present invention is 0.7 mm Aberration diagram when the thickness of the cover glass of Example 3 of the present invention is 1.2 mm. Aberration diagram when the thickness of the cover glass of Example 4 of the present invention is 0 mm Aberration diagram when the thickness of the cover glass of Example 4 of the present invention is 0.7 mm Aberration diagram when the thickness of the cover glass of Example 4 of the present invention is 1.2 mm Aberration diagram when the thickness of the cover glass of Example 5 of the present invention is 0 mm Aberration diagram when thickness of cover glass of Example 5 of the present invention is 0.7 mm Aberration diagram when the thickness of the cover glass of Example 5 of the present invention is 1.2 mm Aberration diagram when the thickness of the cover glass of Example 6 of the present invention is 0 mm Aberration diagram when the thickness of the cover glass of Example 6 of the present invention is 0.7 mm. Aberration diagram when the thickness of the cover glass of Example 6 of the present invention is 1.2 mm. Aberration diagram when the thickness of the cover glass of Example 7 of the present invention is 0 mm Aberration diagram when the thickness of the cover glass of Example 7 of the present invention is 0.4 mm Aberration diagram when thickness of cover glass of Example 7 of the present invention is 0.7 mm Aberration diagram when the thickness of the cover glass of Example 8 of the present invention is 0 mm Aberration diagram when the thickness of the cover glass of Example 8 of the present invention is 0.4 mm Aberration diagram when the thickness of the cover glass of Example 8 of the present invention is 0.7 mm Aberration diagram when the thickness of the cover glass of Example 9 of the present invention is 0 mm Aberration diagram when the thickness of the cover glass of Example 9 of the present invention is 0.4 mm Aberration diagram when the thickness of the cover glass of Example 9 of the present invention is 0.7 mm Sectional drawing of the imaging lens used in combination with the objective lens of each of the above embodiments

Explanation of symbols

G1 First lens group G2 Second lens group G3 Third lens group G4 Fourth lens group

Claims (9)

In order from the object side, the first lens group having a positive refractive power, the second lens group having a positive refractive power and movable along the optical axis, and at least one cemented lens component as a whole are positive. The third lens group having refractive power and the fourth lens group having a negative refractive power as a whole with the most object-side surface facing the object side, and the following conditions (1), (2), A microscope objective lens satisfying (3).
(1) 6 <f ₂ / f <16
(2) 0.2 <f ₂ / f ₃ <1.2
(3) | R ₃ | / | R ₄ |> 4
Where f ₂ is the focal length of the second lens group, f ₃ is the focal length of the third lens group, f is the focal length of the entire objective lens system, and R ₃ is the radius of curvature of the most image side surface of the third lens group. , R ₄ is the radius of curvature of the surface of the fourth lens group closest to the object side. The microscope objective lens according to claim 1, wherein the focal length f of the entire system satisfies the following condition (4) within the range of the following (5).
(4) −10 <f ₄ / f <−2
(5) 1 <f <5
Here, f ₄ is the focal length of the fourth lens group. The microscope objective lens according to claim 1, wherein the focal length f of the entire system satisfies the following condition (6) within the range of the following (7).
(6) −40 <f ₄ ′ / f <−20
(7) 8 <f <11
Here, f ₄ ′ is the focal length of the fourth lens group. The microscope objective lens according to claim 1, 2 or 3, which satisfies the following condition (8).
(8) 1 <f ₁ / f <5
Here, f ₁ is the focal length of the first lens group. The microscope objective lens according to claim 1, 2, 3, or 4, which satisfies the following condition (9).
(9) H ₂ / H ₃ <1
However, H ₂ is the highest beam height of the second lens group, and H ₃ is the highest beam height of the third lens group. The microscope objective lens according to claim 1, 2, 3, 4 or 5, which satisfies the following condition (10).
(10) N ₁ > 1.7
N ₁ is the refractive index of the lens closest to the object side in the first lens group. The microscope objective lens according to claim 1, 2, 3, 4, 5, or 65 satisfying the following condition (11).
(11) | R ₁ | / | R ₂ |> 1
Here, R ₁ and R ₂ are the radii of curvature of the object-side surface and the image-side surface of the most object-side lens of the first lens group, respectively. The microscope objective lens according to claim 1, wherein the fourth lens group includes a cemented lens in which a convex lens and a concave lens are cemented, and satisfies the following condition (12).
(12) ν _(4p) <35
Where ν _(4p) is the Abbe number of the convex lens of the cemented lens of the fourth lens group. The microscope objective lens according to claim 1, 2, 3, 4, 5, 6, 7 or 8, which satisfies the following condition (13).
(13) 0 <D <3
Here, D is the air space (mm) on the optical axis of the third lens group and the fourth lens group.

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