JP2009075281A - Microscope objective lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microscope objective lens which has a magnification of about 60 times, and a high numerical aperture and in which various kinds of aberration including chromatic aberration are successfully corrected. <P>SOLUTION: The microscope objective lens is provided with; a first lens group G1 which includes a first lens component L1, which comprises a cemented lens comprising a plano-convex lens L11 whose plane faces the object side and a negative meniscus lens L12 whose concave surface faces the object side, and has positive refractive power; a second lens group G2 which includes a cemented lens whose connection surfaces have negative refractive power; and a third lens group G3 comprising an L7, which comprises a positive lens L71 and a negative lens L72, and an L8 comprising a negative lens L81 and a positive lens L82, and has negative refractive power. The lens groups G1-G3 are arranged in this order from the object side. In this case, the following inequalities are satisfied: 1.8<n12<1.85, 1.8<n34<1.85, 35<ν12<50, and 35<ν34<50, wherein n12 and ν12 represent the refractive index to the d-line and Abbe number of the L12, respectively, and n34 and ν34 represent the refractive index to the d-line and Abbe number of the L82, respectively. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a microscope objective lens, and more particularly to a microscope objective lens for immersion fluorescence that has a high chromatic aberration performance of apochromat and can be excited by ultraviolet rays.

  In recent years, fluorescent microscopes that can observe the movement and activity of specific sites in living cells with high sensitivity have been widely used particularly in the field of biological research (see, for example, Patent Documents 1 to 3).

JP-A-7-230039 JP 2000-35541 A JP 2002-148519 A

  By the way, recently, with the advent of various fluorescent proteins and quantum dots, the excitation wavelength in fluorescence observation has also expanded, but near ultraviolet excitation using i-line (wavelength 365 nm) as a typical excitation wavelength is still widely used. It has been. For this reason, the objective lens of a fluorescent microscope has not only excellent imaging performance, but also sufficient transmittance from the near infrared region to the near ultraviolet region, particularly i-line, and the fluorescence emitted from the specimen is weak. Therefore, it is low auto-fluorescence so that the contrast of the fluorescence observation image is not significantly deteriorated, and the fluorescence generated in the specimen is generally weak as described above. In order to obtain a good image that is easy to observe, it is required to have a large numerical aperture.

  However, the objective lens described in Patent Document 1 has a very high transmittance in the near ultraviolet region and a large numerical aperture, but has a large field curvature and sufficient imaging performance. I can't say that. In addition, the objective lenses described in Patent Document 2 and Patent Document 3 have a large numerical aperture and excellent imaging performance, but do not sufficiently satisfy the near-ultraviolet transmittance of the glass material used.

  The present invention has been made in view of such a problem, and has a high numerical aperture and high transmittance from the near infrared region to the near ultraviolet region (i-line), but various aberrations including chromatic aberration are good. The objective of the present invention is to provide a microscope objective lens that is corrected to the above and has high imaging performance and image flatness.

  In order to achieve such an object, the microscope objective lens of the present invention is composed of a cemented lens of a plano-convex lens having a plane facing the object side and a negative meniscus lens having a concave surface facing the object side, which are arranged in order from the object side. A first lens group including a first lens component and converting a divergent light beam from an object into a convergent light beam, and having a positive refractive power as a whole, and a second lens group including a cemented lens whose cemented surface has a negative refractive power A front group including a cemented meniscus lens having a concave surface facing the image side (for example, the seventh lens component L7 in the present embodiment), a negative lens, and a positive lens. And a rear lens group (for example, the eighth lens component L8 in the present embodiment) including a cemented meniscus lens having a concave surface directed to the side, and a third lens group having a negative refractive power as a whole, The negative meniscus lens constituting the first lens component of the lens group has a refractive index and an Abbe number with respect to d-line of n12 and ν12, respectively, and the positive meniscus constituting the cemented meniscus lens included in the rear group of the third lens group. When the refractive index and Abbe number for the d-line of the lens are n34 and ν34, respectively, the following expressions 1.8 <n12 <1.85, 1.8 <n34 <1.85, 35 <ν12 <50 and 35 <ν34 <50 conditions are satisfied.

  In the present invention, the radius of curvature of the cemented surface of the cemented lens constituting the first lens component is r12, the focal length of the entire objective lens system is F, and the negative meniscus lens constituting the first lens component is When the refractive index for the d-line is n12 and the refractive index for the d-line of the plano-convex lens constituting the first lens component is n11, the following expression 0.65 <| r12 / F | × n12 <0.75 and 0 .27 <| n12−n11 | <0.40 is preferably satisfied.

  In the present invention, it is preferable that the condition of the following expression ν2n> 50 is satisfied, where ν2n is the Abbe number of the negative lens included in the cemented lens of the second lens group.

  Further, the radius of curvature of the concave surface facing the image side in the cemented meniscus lens included in the front group of the third lens group is set to r3A, and the cemented meniscus lens included in the rear group of the third lens group is directed toward the object side. When the radius of curvature of the concave surface is r3B, it is preferable to satisfy the condition of the following formula 2.4 <(r3A−r3B) / F <2.8.

  As described above, according to the present invention, it is possible to excite ultraviolet rays (particularly i-line) and to correct various aberrations satisfactorily at a magnification of about 60 times and a high numerical aperture (about 1.4). A microscope objective lens having excellent imaging performance can be realized.

  Hereinafter, preferred embodiments of the present application will be described. The microscope objective lens of the present application is an immersion system, and is a first lens component composed of a cemented lens of a plano-convex lens having a plane facing the object side and a negative meniscus lens having a concave surface facing the object side, which are arranged in order from the object side. A first lens group having a positive refractive power as a whole, a second lens group including a cemented lens whose cemented surface has a negative refractive power, a positive lens and a negative lens, and a concave surface on the image side A third lens having a negative refracting power as a whole, including a front group including a facing meniscus lens and a rear group including a cemented meniscus lens having a concave surface facing the object side, and a negative lens and a positive lens With a group. Then, the divergent light beam from the object is converted into a convergent light beam by the first lens group, then gently bent by the second lens group, converted into a parallel light beam by the third lens group, and sent to the imaging lens. It is led with.

  In the microscope objective lens configured as described above, the refractive index and Abbe number for the d-line of the negative meniscus lens constituting the first lens component of the first lens group are n12 and ν12, respectively, and are included in the rear group of the third lens group. When the refractive index and Abbe number for the d-line of the positive lens constituting the meniscus lens are n34 and ν34, respectively, the following expressions (1) to (4) are satisfied.

1.8 <n12 <1.85 (1)
1.8 <n34 <1.85 (2)
35 <ν12 <50 (3)
35 <ν34 <50 (4)

  The above conditional expressions (1) to (4) are used to select appropriate refractions when selecting glass materials for the negative meniscus lens constituting the first lens component of the first lens group and the positive lens constituting the rear group of the third lens group. It defines the rate and Abbe number.

  By satisfying conditional expressions (1) and (2), it is possible to efficiently correct the Petzval sum while ensuring the transmittance in the near ultraviolet region (i-line) in these lenses. However, if the upper limit of conditional expressions (1) and (2) is exceeded, the Petzval sum can be satisfactorily corrected in these lenses, but the transmittance in the near ultraviolet region (i-line) is ensured due to the composition of the glass material. This is not preferable because the glass material cannot be selected. On the other hand, if the lower limit value of the conditional expressions (1) and (2) is not reached, it is not preferable because the glass material selection cannot effectively correct the Petzval sum in these lenses.

  Further, if the upper and lower limits of the conditional expressions (3) and (4) are deviated, these lenses can secure the transmittance in the near ultraviolet region (i-line), but are necessary for effective chromatic aberration correction. The Abbe number cannot be obtained.

  As described above, in the first lens group of the present application, the first lens component consisting of a cemented lens of a plano-convex lens having a plane facing the object side and a negative meniscus lens having a concave surface facing the object side is the most so-called embedded lens. Arranged on the object side. As a result, due to the difference in refractive index between the planoconvex lens and the negative meniscus lens constituting the first lens component, the joint surface of the lens component has a strong negative refractive power, thereby reducing the Petzval sum and reducing the image plane. Flatness is ensured.

  Further, in the first lens group, the plano-convex lens located closest to the object side has a refractive index substantially equal to the refractive index of the immersion liquid (oil) in order to prevent the occurrence of spherical aberration at the boundary surface between the immersion liquid (oil) and the lens. The glass material which has a rate is used. Therefore, the refractive power of the surface having negative refractive power in the first lens group is determined by the negative meniscus lens constituting the first lens component together with the plano-convex lens, and the conditional expressions (1) and (3) are The preferable conditions for selecting the glass material of this lens are defined.

  In the present application, the third lens group has a pair of concave surfaces (front group and rear group) facing each other, and effectively reduces the Petzval sum by its strong negative refracting power. By doing so, the image plane is further flattened.

  Generally, in an objective lens, the larger the numerical aperture, the greater the amount of spherical aberration and axial chromatic aberration generated. If these are corrected preferentially, it becomes difficult to suppress the occurrence of lateral chromatic aberration. For this reason, it is important to correct lateral chromatic aberration with a positive lens close to the final group of the objective lens. Furthermore, if the refractive index of the positive lens close to the final group or the final group is small, the curvature of the lens surface has to be increased, and the amount of spherical aberration, axial chromatic aberration, coma and astigmatism increases, It becomes difficult to carry out balanced aberration correction.

  Therefore, in the present application, in the third lens group, a glass material having a large chromatic dispersion (small Abbe number) and a high refractive index (so-called flint type) is selected for the positive lens constituting the rear group, and the rear group is configured. By selecting a negative lens material having a small chromatic dispersion (large Abbe number) and a low refractive index (so-called crown type), a chromatic aberration opposite to the chromatic aberration generated in the first lens group and the second lens group can be obtained. It is possible to correct chromatic aberration of magnification well and correct other aberrations in a well-balanced manner. The conditional expressions (2) and (4) define preferable conditions in selecting the glass material of the positive lens constituting the rear group of the third lens group.

  Further, in the present application, in the first lens group, the curvature radius of the cemented surface of the cemented lens constituting the first lens component is r12, the focal length of the entire objective lens system is F, and the first lens component is configured as described above. When the refractive index with respect to the d-line of the negative meniscus lens is n12 and the refractive index with respect to the d-line of the plano-convex lens constituting the first lens component is n11, it is preferable that the following expressions (5) and (6) are satisfied. .

0.65 <| r12 / F | × n12 <0.75 (5)
0.27 <| n12-n11 | <0.40 (6)

  Conditional expression (5) indicates that the radius of curvature of the cemented surface of the cemented lens that constitutes the first lens component of the first lens group, the focal length of the entire objective lens system, and the refraction of the negative meniscus lens that constitutes the first lens component. It defines the appropriate relationship between rates. By satisfying conditional expression (5), it is possible to achieve good correction of Petzval sum while correcting spherical aberration. If the upper limit of conditional expression (5) is exceeded, the radius of curvature of the joint surface becomes large, the Petzval sum cannot be corrected, and the spherical aberration remains negative. On the other hand, if the lower limit of conditional expression (5) is not reached, Petzval sum can be corrected, but higher-order bending occurs in spherical aberration, resulting in an aberrationally unstable optical system.

  Conditional expression (6) defines an appropriate refractive index difference between the plano-convex lens to be embedded and the negative meniscus lens to be embedded in the first lens component of the first lens group. Since the refractive index of the plano-convex lens is substantially the same as that of the immersion liquid used as described above, this condition substantially defines the refractive index of the negative meniscus lens. If the upper limit of conditional expression (6) is exceeded, the refractive index difference between the plano-convex lens and the negative meniscus lens becomes large, and sufficient negative refractive power can be given to the cemented surface, but the refractive power of the immersion liquid. A plano-convex lens having a lower refractive power must be selected, and there is no realistic glass. On the other hand, if the lower limit of conditional expression (6) is not reached, the refractive index difference between the plano-convex lens and the negative meniscus lens becomes small, and sufficient negative refractive power cannot be given to the cemented surface. It becomes difficult to correct.

  In the present application, it is preferable that the following expression (7) is satisfied when the Abbe number of the negative lens included in the cemented lens of the second lens group is ν2n.

  ν2n> 50 (7)

  Since the second lens group of the present application plays a role of correcting chromatic aberration, particularly axial chromatic aberration, the cemented lens is an achromatic lens including a positive lens and a negative lens. Here, when trying to correct chromatic aberration satisfactorily while sufficiently securing a sufficient transmittance in the near ultraviolet region (for example, i-line), as a glass material usable for a positive lens, a crown glass having anomalous dispersion is used. Or it is limited to using fluorite. For this reason, in the negative lens constituting the cemented lens of the second lens group, it is necessary to select a glass material that is as close to the partial dispersion ratio as possible while ensuring an Abbe number difference with respect to the positive lens. Conditional expression (7) indicates that chromatic aberration (particularly the secondary spectrum of longitudinal chromatic aberration) is secured while ensuring the transmittance in the near ultraviolet region (i-line) in all negative lenses constituting the cemented lens of the second lens group. This prescribes the selection conditions for glass materials that can efficiently correct the above. If the lower limit of conditional expression (7) is not reached, realistic glass will no longer exist.

  In the present application, the radius of curvature of the concave surface facing the image side in the cemented meniscus lens included in the front group of the third lens group G3 is r3A, and the object side in the cemented meniscus lens included in the rear group of the third lens group It is preferable that the following equation (8) is satisfied, where r3B is the radius of curvature of the concave surface facing the surface.

  2.4 <(r3A-r3B) / F <2.8 (8)

  The conditional expression (8) defines a condition for satisfactorily correcting coma aberration that has a great influence on the imaging performance of the objective lens. The negative refractive power of the third lens group is mainly borne by a pair of concave surfaces facing each other arranged in the front group and the rear group. However, if the upper limit value of the conditional expression (8) is exceeded, the radius of curvature of the concave surface is increased. As a result, the refractive index becomes large and sufficient refractive power cannot be secured, and the Petzval sum cannot be corrected efficiently. On the other hand, if the lower limit value of conditional expression (8) is not reached, the radius of curvature of the concave surface becomes excessively small, the asymmetric component of coma increases rapidly, and correction becomes difficult.

  Embodiments of the microscope objective lens according to the present application will be described below with reference to the accompanying drawings.

  In each example, the microscope objective lens has an oil immersion type design. The immersion liquid (oil) has a refractive index nd = 1.5154 and an Abbe number νd = 41.4, and the cover glass C has a refractive index nd = 1.5222. It is assumed that an Abbe number νd = 58.8 and a thickness t = 0.17 are used.

(First embodiment)
The microscope objective lens according to the first example of the present application will be described with reference to FIGS. FIG. 1 is a cross-sectional view showing a lens configuration of a microscope objective lens according to the first example. As shown in FIG. 1, the microscope objective lens according to the first example includes a first lens group G1 having a positive refractive power as a whole, and a cemented surface having a negative refractive power, arranged in order from the object side. A second lens group G2 including a lens and a third lens group G3 having a negative refractive power as a whole are provided.

  The first lens group G1 includes a first lens component L1 which is a cemented lens of a planoconvex lens L11 having a plane facing the object side and a negative meniscus lens L12 having a concave surface facing the object side, arranged in order from the object side, A second lens component L2 that is a positive meniscus lens having a concave surface facing side, a third lens component L3 that is a cemented lens of a biconcave lens L31 and a biconvex lens L32, a biconvex lens L41, a biconcave lens L42, and a biconvex lens L43. And a fourth lens component L4 which is a cemented lens.

  The second lens group G2 includes a fifth lens component L5 that is a cemented lens of a negative meniscus lens L51 (corresponding to the negative lens according to claim 3) having a convex surface directed toward the object side and a biconvex lens L52, and a biconvex lens L61. And a sixth lens component L6 that is a cemented lens with a biconcave lens L62 that is a negative lens (corresponding to the negative lens according to claim 3).

  The third lens group G3 is a cemented lens of a positive lens L71 and a negative lens L72. The seventh lens component L7 (front group) having a meniscus shape with the concave surface facing the image side as a whole, the negative lens L81, and a positive lens This is a cemented lens with the lens L82, and is composed of an eighth lens component L8 (rear group) having a meniscus shape with the concave surface facing the object as a whole. Here, the positive lens L71 constituting the seventh lens component L7 is a biconvex lens, and the negative lens L71 is a biconcave lens. The negative lens L81 constituting the eighth lens component L8 is a biconcave lens, and the positive lens L82 is a biconvex lens.

  A cover glass C is disposed on the object side of the first lens group G1, and the space between the cover glass C and the lens (plano-convex lens L11) disposed closest to the object side of the first lens group G1 is immersed. Filled with liquid (oil).

  Table 1 shows a table of specifications of each lens constituting the microscope objective lens according to the first example. In Table 1, F is the focal length of the objective lens, NA is the numerical aperture, β is the magnification, and d0 is the distance on the optical axis from the object surface to the first surface of the lens system. The transmittance of i-line (wavelength 365 nm) and A'-line (wavelength 768 nm) is the i-line transmittance of the entire system when a single layer film coat optimized at 500 nm is attached to the front surface (excluding the bonding surface). And the transmittance | permeability of A 'line is shown. Further, the surface numbers are the order of the lens surfaces from the object side along the direction in which the light beam travels (hereinafter referred to as surface numbers. Note that the surface numbers 1 to 24 in Table 1 are the surface numbers 1 to 24 shown in FIG. The distance between the surfaces indicates the distance on the optical axis from each optical surface to the next optical surface (or image surface), and the refractive index indicates a value for the d-line (wavelength 587.6 nm). In Table 1, values corresponding to the conditional expressions (1) to (8) (namely, condition corresponding values) are also shown.

  In the table, “mm” is generally used as a unit of focal length F, radius of curvature, surface interval, and other lengths. However, since the optical system can obtain the same optical performance even when proportionally enlarged or proportionally reduced, the unit is not limited to “mm”, and other appropriate units can be used. In the table, the radius of curvature “0.0000” indicates a plane, and the description of the refractive index “1.00000” of air is omitted.

  The description of the above table is the same in other embodiments.

(Table 1)
[Overall specifications]
F = 3.33, NA = 1.4, β = −60, d0 = 0.15
i-line transmittance = 44%, A'-line transmittance = 69%
[Lens specifications]
Surface number Curvature radius Surface spacing Refractive index Abbe number Lens name 1 0.00000 0.65 1.51823 58.89 L11
2 -1.27500 3.10 1.83481 42.72 L12
3 -3.15888 0.10
4 -10.08883 3.55 1.59240 68.33 L2
5 -6.21419 0.15
6 -105.42021 1.10 1.57501 41.49 L31
7 22.33430 7.20 1.49782 82.56 L32
8 -12.66434 0.15
9 30.36810 4.50 1.49782 82.56 L41
10 -32.12572 1.00 1.78800 47.38 L42
11 17.35533 8.40 1.43385 95.25
12 -15.28941 0.15
13 32.20991 1.10 1.73400 51.47 L52
14 11.70124 7.60 1.43385 95.25
15 -20.39512 0.15
16 13.47997 5.40 1.43385 95.25 L62
17 -24.68351 1.20 1.72916 54.66 L63
18 13.41725 0.20
19 7.55485 5.00 1.59240 62.33 L71
20 -18.54275 4.40 1.75500 52.32 L72
21 4.44359 3.20
22 -4.39478 2.80 1.69680 55.52 L81
23 62.27168 3.00 1.80440 39.59 L82
24 -7.85083 120.00
[Conditional value]
n12 = 1.83481
n34 = 1.80440
ν12 = 42.72
ν34 = 39.59
r12 = -1.27500
F = 3.33
n11 = 1.51823
ν2n = 51.47 (negative lens L51), 54.66 (negative lens L62)
r3A = 4.44359
r3B = -4.39478
Conditional expression (1) n12 = 1.83481
Conditional expression (2) n34 = 1.80440
Conditional expression (3) ν12 = 42.72
Conditional expression (4) ν34 = 39.59
Conditional expression (5) | r12 / F | × n12 = 0.703
Conditional expression (6) | n12−n11 | = 0.317
Conditional expression (7) ν2n = 51.47, 54.66
Conditional expression (8) (r3A-r3B) /F=2.65

  As can be seen from the table of specifications shown in Table 1, it can be seen that the microscope objective lens according to the present example satisfies all the conditional expressions (1) to (8).

  2A and 2B are graphs showing various aberrations of the microscope objective lens according to Example 1. FIG. 2A shows spherical aberration, FIG. 2B shows astigmatism, FIG. 2C shows chromatic aberration of magnification, FIG. e) shows distortion aberration, respectively. In the astigmatism diagram of (c), the solid line represents the sagittal image plane, and the broken line represents the meridional image plane. Further, in the distortion diagram of (e), the aberration with respect to the d-line as the reference wavelength is shown. In FIG. 2, NA indicates the numerical aperture, and y indicates the image height (mm). The solid line indicates the d line (wavelength 587.6 nm), the broken line indicates the C line (wavelength 656.3 nm), the alternate long and short dash line indicates the F line (wavelength 486.1 nm), and the two-dot chain line indicates the g line (wavelength 435.8 nm). ing. The explanation of the above aberration diagrams is the same in the other examples.

  As is apparent from the respective aberration diagrams shown in FIG. 2, it can be seen that in the microscope objective lens according to the first example, various aberrations are satisfactorily corrected and excellent imaging performance is secured.

(Second embodiment)
2nd Example of this application is described using FIG. 3, FIG. 4 and Table 2. FIG. The microscope objective lens according to the second example includes a first lens group G1 having a positive refractive power as a whole, and a cemented lens whose cemented surface has a negative refractive power, arranged in order from the object side. G2 and a third lens group G3 having negative refractive power as a whole are provided.

  The first lens group G1 includes a first lens component L1 which is a cemented lens of a planoconvex lens L11 having a plane facing the object side and a negative meniscus lens L12 having a concave surface facing the object side, arranged in order from the object side, A second lens component L2 that is a positive meniscus lens having a concave surface facing side, a third lens component L3 that is a cemented lens of a biconcave lens L31 and a biconvex lens L32, and a cemented lens of a biconcave lens L41 and a biconvex lens L42. The lens includes a fourth lens component L4 and a fifth lens component L5 that is a cemented lens of a biconcave lens L51 and a negative meniscus lens L52 having a convex surface facing the image side.

  The second lens group G2 includes a negative meniscus lens L61 having a convex surface directed toward the object side (corresponding to the negative lens according to claim 3), a biconvex lens L62, and a biconcave lens L63 (corresponding to the negative lens according to claim 3). And a sixth lens component L6 that is a cemented lens.

  The third lens group G3 is a cemented lens of a positive lens L71 and a negative lens L72. The seventh lens component L7 (front group) having a meniscus shape with the concave surface facing the image side as a whole, the negative lens L81, and a positive lens This is a cemented lens with the lens L82, and is composed of an eighth lens component L8 (rear group) having a meniscus shape with the concave surface facing the object as a whole. Here, the positive lens L71 constituting the seventh lens component L7 is a biconvex lens, and the negative lens L71 is a biconcave lens. The negative lens L81 constituting the eighth lens component L8 is a biconcave lens, and the positive lens L82 is a biconvex lens.

  A cover glass C is disposed on the object side of the first lens group G1, and the space between the cover glass C and the lens (plano-convex lens L11) disposed closest to the object side of the first lens group G1 is immersed. Filled with liquid (oil).

  Table 2 shows a table of specifications in the second embodiment. The surface numbers 1 to 24 in Table 2 correspond to the surfaces 1 to 24 shown in FIG.

(Table 2)
[Overall specifications]
F = 3.33, NA = 1.4, β = −60, d0 = 0.15
i-line transmittance = 47%, A'-line transmittance = 70%
[Lens specifications]
Surface number Curvature radius Surface spacing Refractive index Abbe number Lens name 1 0.00000 0.65 1.51823 58.89 L11
2 -1.27500 3.00 1.83481 42.72 L12
3 -3.00050 0.10
4 -11.85681 3.55 1.59240 68.33 L2
5 -6.34946 0.15
6 -137.67065 1.10 1.61334 44.27 L31
7 17.62769 7.50 1.49782 82.56 L32
8 -11.70286 0.15
9 -29.74857 1.00 1.78800 47.38 L41
10 22.33206 9.00 1.43385 95.25 L42
11 -12.47212 0.15
12 16.77957 8.70 1.43385 95.25 L51
13 -14.04003 1.10 1.51823 58.96 L52
14 -77.40080 0.15
15 17.26929 1.40 1.73400 51.47 L61
16 9.15332 6.80 1.43385 95.25 L62
17 -12.33305 1.10 1.73400 51.47 L63
18 44.89891 0.20
19 7.34853 5.00 1.59240 68.33 L71
20 -27.11446 4.20 1.75500 52.32 L72
21 4.01471 3.20
22 -4.48427 2.70 1.69680 55.52 L81
23 50.56600 3.00 1.80440 39.59 L82
24 -7.76194 120.0
[Conditional value]
n12 = 1.83481
n34 = 1.80440
ν12 = 42.72
ν34 = 39.59
r12 = -1.27500
F = 3.33
n11 = 1.51823
ν2n = 51.47 (negative lens L61), 51.47 (negative lens L63)
r3A = 4.01471
r3B = -4.48427
Conditional expression (1) n12 = 1.83481
Conditional expression (2) n34 = 1.80440
Conditional expression (3) ν12 = 42.72
Conditional expression (4) ν34 = 39.59
Conditional expression (5) | r12 / F | × n12 = 0.703
Conditional expression (6) | n12−n11 | = 0.317
Conditional expression (7) ν2n = 51.47, 51.47
Conditional expression (8) (r3A-r3B) /F=2.55

  As can be seen from the table of specifications shown in Table 2, it can be seen that the microscope objective lens according to the present example satisfies all the conditional expressions (1) to (8).

  4A and 4B are graphs showing various aberrations of the microscope objective lens according to Example 2. FIG. 4A is spherical aberration, FIG. 4B is astigmatism, FIG. 4C is chromatic aberration of magnification, FIG. e) shows distortion aberration, respectively. As is apparent from the respective aberration diagrams shown in FIG. 4, it can be seen that in the microscope objective lens according to the second example, various aberrations are satisfactorily corrected and excellent imaging performance is secured.

  In addition, since the microscope objective lens according to each embodiment is an infinity correction lens, an imaging lens is arranged on the image side of the microscope objective lens, and a combination of the microscope objective lens and the imaging lens is used. A finite optical system is formed. Here, the imaging lens used in the above embodiment will be described with reference to FIG. 5 and Table 3.

  FIG. 5 is a configuration diagram of an image forming lens used in combination with the microscope objective lens in each of the above-described embodiments, and a first joint formed by bonding a biconvex lens M11 and a biconcave lens M12 arranged in order from the object side. The lens M1 is composed of a second cemented lens M2 formed by bonding a biconvex lens M21 and a biconcave lens M22. Table 3 shows the specification values of this imaging lens. In Table 3, the surface number is the order of the lens surfaces from the object side (hereinafter referred to as surface number) along the direction in which the light beam travels, and the surface interval is from each optical surface to the next optical surface (or image surface). ) On the optical axis, the refractive index indicates the refractive index with respect to the d-line (wavelength 587.6 nm) of the glass constituting each lens, and F ′ indicates the focal length of the entire imaging lens system.

(Table 3)
[Lens specifications]
F '= 200
Surface number Curvature radius Surface spacing Refractive index Abbe number Lens name 1 75.043 5.1 1.62801 57.03 M11
2 -75.043 2.0 1.74950 35.19 M12
3 1600.580 7.5
4 50.260 5.1 1.66755 41.96 M21
5 -84.541 1.8 1.61266 44.41 M22
6 36.911

  As described above, according to the present application, it has a high numerical aperture (NA 1.4), high transparency from the near ultraviolet region to the near infrared region, various aberrations including chromatic aberration are sufficiently corrected, and high results. A microscope objective lens in which image performance and image surface flatness are ensured can be provided.

  The present invention as described above is not limited to the above-described embodiment, and can be appropriately improved as long as it does not depart from the gist of the present invention.

It is a lens block diagram of the microscope objective lens which concerns on 1st Example of this invention. FIG. 6 is a diagram illustrating various aberrations of the microscope objective lens according to the first example of the present invention. It is a lens block diagram of the microscope objective lens which concerns on 2nd Example of this invention. FIG. 6 is various aberration diagrams of the microscope objective lens according to the second example of the present invention. It is a lens block diagram of the imaging lens used in combination with the microscope objective lens which concerns on the said 1st Example and 2nd Example.

Explanation of symbols

G1 1st lens group G2 2nd lens group G3 3rd lens group Ln nth lens component (n = 1-8)
L11 Plano-convex lens constituting the first lens component L12 Negative meniscus lens constituting the first lens component L71 Positive lens constituting the seventh lens component L72 Negative lens constituting the seventh lens component L81 Negative constituting the eighth lens component Lens L82 Positive lens constituting the eighth lens component

Claims (4)

Arranged in order from the object side,
Includes a first lens component consisting of a cemented lens of a plano-convex lens with a plane facing the object side and a negative meniscus lens with a concave surface facing the object side, and converts the divergent light beam from the object into a convergent light beam as a whole as a positive refraction A first lens group having power;
A second lens group including a cemented lens having a cemented surface having negative refractive power;
From a front group including a cemented meniscus lens having a positive lens and a negative lens and having a concave surface facing the image side, and a rear group including a cemented meniscus lens having a negative lens and a positive lens having a concave surface facing the object side And a third lens group having negative refractive power as a whole,
The negative meniscus lens constituting the first lens component of the first lens group has a refractive index and an Abbe number for the d-line of n12 and ν12, respectively, and the cemented meniscus lens included in the rear group of the third lens group When the refractive index and Abbe number for the d-line of the constituting positive lens are n34 and ν34, respectively, the following expression 1.8 <n12 <1.85
1.8 <n34 <1.85
35 <ν12 <50
35 <ν34 <50
A microscope objective lens characterized by satisfying the following conditions. The curvature radius of the cemented surface of the cemented lens that constitutes the first lens component is r12, the focal length of the entire objective lens system is F, and the refractive index with respect to the d-line of the negative meniscus lens that constitutes the first lens component is When n12 is set and the refractive index with respect to the d-line of the plano-convex lens constituting the first lens component is set to n11, the following expression 0.65 <| r12 / F | × n12 <0.75
0.27 <| n12-n11 | <0.40
The microscope objective lens according to claim 1, wherein the following condition is satisfied. When the Abbe number of the negative lens included in the cemented lens of the second lens group is ν2n, the following equation ν2n> 50
The microscope objective lens according to claim 1 or 2, wherein the following condition is satisfied. In the cemented meniscus lens included in the front group of the third lens group, the radius of curvature of the concave surface facing the image side is r3A, and in the cemented meniscus lens included in the rear group of the third lens group, the concave surface facing the object side is set. When the curvature radius is r3B, the following formula 2.4 <(r3A−r3B) / F <2.8
The microscope objective lens according to claim 1, wherein the following condition is satisfied.

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