CN110543005B - Immersion microscope objective - Google Patents

The patent provides an apochromatic immersion microscope objective with all sharp visual images from center to edge at large numerical aperture. The structure is orderly ordered from the object side OBJ as follows: a1 st lens group having a positive refractive power and composed of 2 or more lenses as a whole; the whole lens has positive refractive power, comprises 3 groups of cemented lenses and consists of more than 7 lens groups 2; a 3 rd lens group composed of more than 2 lenses; a4 th lens group having negative refractive power; and a 5 th lens group which is composed of more than 2 lenses and emits parallel light beams. Either the 3 rd lens group or the 5 th lens group is composed of 3 or more lenses. The 3 rd lens group is provided with a bonding surface with a convex surface facing the object side, the 5 th lens group is provided with a bonding surface with a concave surface facing the object side, the maximum image height is Ih, the maximum effective radius of the lens is RDmax, and 0.35 < Ih/RDmax < 2.2 is met.

Immersion microscope objective

Technical Field

The present patent relates to a microscope objective system, and in particular to an infinity system immersion microscope objective at a magnification of from 10 to 20.

Background

The objective lens is the core component of the whole microscope. In a microscope objective system, particularly an immersion microscope objective, a clear image is obtained in the center portion of a screen and the vicinity thereof under a large numerical aperture, but an unclear image is obtained from the middle to the edge region of the screen.

Disclosure of Invention

The patent provides an apochromatic immersion microscope objective with all sharp visual images from center to edge at large numerical aperture.

The technical scheme that this patent adopted is:

In order to achieve the above object, the initial structure of the immersion microscope objective of the present patent is ordered as follows, starting from the object side OBJ: a1 st lens group G1 having a positive refractive power and composed of 2 or more lenses as a whole; the whole lens has positive refractive power, comprises 3 groups of cemented lenses and consists of more than 7 lens groups G2; a 3 rd lens group G3 composed of 2 or more lenses; a4 th lens group G4 having negative refractive power; and a5 th lens group G5 which is composed of more than 2 lenses and emits parallel light beams. Either the 3 rd lens group G3 or the 5 th lens group G5 is composed of 3 or more lenses. The 3 rd lens group G3 has a bonding surface C2 with a convex surface facing the object side, the 5 th lens group G5 has a bonding surface C1 with a concave surface facing the object side, the maximum image height is Ih, the maximum effective radius of the lens is RDmax, and the following condition (1) should be satisfied.

0.35＜Ih/RDmax＜2.2 (1)

The immersion microscope objective is a microscope objective filled with a liquid between the object side OBJ and the 1 st lens group G1.

The condition (1) is a condition in which an appropriate size of the objective lens is specified. If the condition (1) is below the lower limit, the lens diameter becomes too large to be suitable for the actual device, and is not preferable. When the upper limit of the condition (1) is exceeded, the lens diameter becomes too small, and aberration correction becomes difficult, so that it is also undesirable. Further, if the lower limit value is set to 0.45, a better result is obtained, and if it is set to 0.47, a very good result is obtained.

The maximum image height is a value obtained by multiplying the maximum object height of the object OBJ by the magnification of the microscope, and the maximum effective radius of the lens is the radius of the lens when the light flux associated with imaging is the widest.

In the present embodiment, the 5 th lens group G5 is configured to emit a parallel light beam. According to this, it becomes possible to mount on various microscopes, and versatility of the immersion microscope objective increases.

The 4 th lens group G4 is disposed adjacent to the 3 rd lens group G3, and the 5 th lens group G5 is preferably disposed adjacent to the 4 th lens group G4.

When the bonding surface of the concave surface provided in the 5 th lens group G5 toward the object side OBJ is the 1 st bonding surface C1, the refractive power of the 1 st bonding surface C1 is positive, the refractive indexes of the medium on both sides of the 1 st bonding surface C1 are n6 and n7, respectively, the radius of curvature of the 1 st bonding surface C1 is R1, and the focal length of the whole microscope objective lens system is f, the following condition (2) is satisfied.

0.07<| (n6－n7)×f/R1|<1.2 (2)

This condition is a condition for correcting the chromatic coma in the meridian direction well. In addition, in the present specification, the coma aberration means a difference in coma aberration of each wavelength in the visible light domain. If the upper limit of the condition (2) is exceeded, the shape of the lens becomes a shape unfavorable for production, and is therefore undesirable. If the value is less than the lower limit of the condition (2), it is difficult to correct the chromatic coma aberration in the meridian direction, and therefore, it is also unsuitable.

To further improve performance. The 1 st lens group G1 is preferably composed of 4 or more lenses. The 1 st lens group G1 preferably includes a negative lens L11, a biconvex lens L12, a 1 st meniscus lens L13 having a concave surface facing the object side OBJ, and a 2 nd meniscus lens L14 having a concave surface facing the object side OBJ.

When the refractive index of L13 is n3, the following condition (3) is satisfied.

n3＞1.7 (3)

The condition (3) is a condition for well correcting the petzval sum. If this condition (3) is removed, the spherical aberration and the petzval sum cannot be corrected well. The lower limit is set to 1.75, and a better result can be obtained. In addition, this meniscus lens may be either a cemented lens or a separate lens.

In the 1 st lens group G1, when L11 and L12 are cemented together, the following condition (4) is satisfied when the refractive index of L11 is n1 and the refractive index of L12 on the other side is n 2.

n1－n2＞0.10 (4)

The condition (4) is a condition for correcting high-order chromatic spherical aberration well. If it is below the lower limit of the condition (4), it is difficult to correct the higher order chromatic spherical aberration well. If the lower limit value is set to 0.15, better results are obtained.

In the case of the bonding surface C2 between L32 and L33 in the 3 rd lens group G3, it is preferable that the following condition (5) be satisfied when the refractive power of the bonding surface C2 is positive, the refractive indexes of the medium on both sides of the second bonding surface C2 are n4 and n5, the radius of curvature of the second bonding surface C2 is R2, and the focal length of the microscope objective lens system is f.

0.07<| (n4－n5)×f/R2|<1.2 (5)

The condition (5) is for correcting the chromatic coma in the meridian direction well. When the upper limit of the condition (5) is exceeded, the shape of the lens becomes a shape unfavorable for manufacturing, so that it is not suitable. Further, when it is below the lower limit of the condition (5), since it is difficult to correct the chromatic coma in the meridian direction, it is also unsuitable.

The lens surface of the 1 st lens group closest to the object side OBJ is most suitable when it is planar. Is concave, and there is a possibility that air bubbles may be mixed in the actual use. Is convex, and is undesirable in performance because of the large spherical aberration that can be generated.

It is appropriate that the 2 nd lens group G2 includes at least two triple cemented lenses. This can reduce secondary dispersion.

It is preferable that the following condition (6) is satisfied when the radius of curvature of the concave surface C3 having a negative refractive power that initially appears from the object side OBJ is R3 and the distance from the object side OBJ to the concave surface C3 having a negative refractive power that initially appears is d.

－0.3＞d/R3＞－1.5 (6)

The condition (6) is a condition for particularly well correcting spherical aberration. When the upper limit of the condition (6) is exceeded, the total lens length becomes long, and is thus undesirable. If the ratio is less than the lower limit of the condition (6), a large spherical aberration occurs, which is not preferable.

When the distance from the object OBJ surface to the surface of the final lens of the microscope is LL and the angle of the principal ray corresponding to the maximum image height emitted from the microscope objective lens is θ, it is preferable that the following condition (7) be satisfied.

0.00063<tanθ/LL<0.00105 (7)

The condition (7) is a condition for bringing the size of the entire lens into a proper state while maintaining good performance. When the upper limit of the condition (7) is exceeded, since the total lens length becomes short, it is difficult to obtain good performance, which is not desirable. If the total lens length is less than the lower limit of the condition (7), the lens cannot be mounted on a microscope device, and the lens is not suitable.

The 3 rd lens group G3 includes a cemented meniscus lens with a convex surface facing the object side OBJ, and the cemented meniscus lens is composed of 3 lenses cemented together, and can correct aberrations.

In the immersion microscope objective lens, when the radius of curvature of the concave surface C4 of the cemented meniscus lens having the convex surface facing the object side in the 3 rd lens group G3 is R4, the following condition (8) is satisfied.

0.35<|R4|/f<2 (8)

The condition (8) is a condition for maintaining good planarity. It is also a condition that the concave surface C4 has a large refractive power. When the upper limit of the condition (8) is exceeded, since the total lens length becomes short, it is difficult to obtain good performance, which is not desirable. If the total lens length is less than the lower limit of the condition (8), the lens cannot be attached to a microscope device, and the lens is undesirable.

The 5 th lens group G5 includes a cemented meniscus lens having a concave surface facing the object side OBJ, and when the cemented meniscus lens is composed of 3 lenses, aberration can be corrected more favorably.

In the 5 th lens group G5, when the radius of curvature of the concave surface C5 of the meniscus lens, which is cemented to the object side OBJ, is R5, the following condition (9) is preferably satisfied.

0.4<|R5|/f＜2.5 (9)

The condition (9) is a condition for maintaining good planarity of the image plane. Is a condition that the concave surface C5 has a large refractive power. When the upper limit of the condition (9) is exceeded, since the total lens length becomes short, it is difficult to obtain good performance, which is not desirable. If the total lens length is less than the lower limit of the condition (9), the lens is too long, and the lens is difficult to mount on a microscope device, which is undesirable.

When the focal length of the 4 th lens group G4 is f4, the following condition (10) is preferably satisfied.

0.5<|f 4|/f<2 (10)

The condition (10) is a condition for defining an appropriate refractive power of the 4 th lens group. When the upper limit of the condition (10) is exceeded, since the total lens length becomes short, it is difficult to obtain good performance, which is not desirable. If the total lens length is less than the lower limit of the condition (10), the lens length becomes too long, making it difficult to mount the lens on a microscope device, which is undesirable.

The beneficial effects of the technology are that: the objective lens for immersion microscope has excellent flatness over the entire wavelength band used even in the case of a high numerical aperture, and provides a clear image in the middle of the screen and in the periphery of the screen.

Drawings

FIG. 1 is a schematic view showing an objective lens of an immersion microscope according to example 1 of the present patent. In the figure, the 1 st lens group G1 (L11, L12, L13, L14), the 2 nd lens group G2 (L21, L22, L23, L24, L25, L26, L27, L28), the 3 rd lens group G3 (L31, L32, L33), the 4 th lens group G4 (L41), and the 5 th lens group G5 (L51, L52, L53).

Fig. 2 is an aberration diagram.

Fig. 2 (a) is a spherical aberration diagram, the vertical axis is a relative incidence height, and the horizontal axis represents an aberration amount. The g line at 436nm is denoted as g, the F line at 486nm is denoted as F, the d line at 588nm is denoted as d, and the C line at 656nm is denoted as C.

Fig. 2 (B) shows astigmatic aberration, the vertical axis shows object height, the horizontal axis shows aberration amount, the solid line shows meridian image plane (M), and the broken line shows sagittal image plane (S).

Fig. 2 (C) is a distortion aberration diagram, the vertical axis represents object height, and the horizontal axis represents the amount of distortion aberration in percent.

FIG. 3 is a schematic view showing an objective lens of an immersion microscope according to example 2 of the present patent. In the figure, the 1 st lens group G1 (L11, L12, L13, L14), the 2 nd lens group G2 (L21, L22, L23, L24, L25, L26, L27, L28), the 3 rd lens group G3 (L31, L32), the 4 th lens group G4 (L41), and the 5 th lens group G5 (L51, L52, L53).

Fig. 4 is an aberration diagram.

Fig. 4 (a) is a spherical aberration diagram, the vertical axis is a relative incidence height, and the horizontal axis represents an aberration amount. The g line at 436nm is denoted as g, the F line at 486nm is denoted as F, the d line at 588nm is denoted as d, and the C line at 656nm is denoted as C.

Fig. 4 (B) shows astigmatic aberration, the vertical axis shows object height, the horizontal axis shows aberration amount, the solid line shows meridian image plane (M), and the broken line shows sagittal image plane (S).

Fig. 4 (C) is a distortion aberration diagram, the vertical axis represents object height, and the horizontal axis represents the amount of distortion aberration in percent.

FIG. 5 is a schematic view showing an objective lens of an immersion microscope according to example 3 of the present patent. In the figure, the 1 st lens group G1 (L11, L12, L13, L14), the 2 nd lens group G2 (L21, L22, L23, L24, L25, L26, L27, L28), the 3 rd lens group G3 (L31, L32, L33), the 4 th lens group G4 (L41), and the 5 th lens group G5 (L51, L52, L53).

Fig. 6 is an aberration diagram. Fig. 6 (a) is a spherical aberration diagram, the vertical axis is a relative incidence height, and the horizontal axis represents an aberration amount. The g line at 436nm is denoted as g, the F line at 486nm is denoted as F, the d line at 588nm is denoted as d, and the C line at 656nm is denoted as C.

Fig. 6 (B) shows astigmatic aberration, the vertical axis shows object height, the horizontal axis shows aberration amount, the solid line shows meridian image plane (M), and the broken line shows sagittal image plane (S).

Fig. 6 (C) is a distortion aberration diagram, the vertical axis represents object height, and the horizontal axis represents the amount of distortion aberration in percent.

Detailed Description

Example 1:

in this patent 1, the immersion microscope objective (fig. 1) is composed of, in order from the object OBJ side, a1 st lens group G1, a2 nd lens group G2, a 3 rd lens group G3, a 4 th lens group G4, and a 5 th lens group G5. The object side OBJ and the 1 st lens group G1 are filled with water (refractive index nd=1.34, abbe number vd=57.9) with a spacing of 3mm.

The 1 st lens group G1 is composed of, in order, a cemented lens of a plano-concave lens L11 and a biconvex lens L12, a positive meniscus lens L13 having a concave surface facing the object side, and a positive meniscus lens L14 having a concave surface facing the object side.

The 2 nd lens group G2 is composed of, in order, a cemented lens of a biconcave lens L21 and a biconvex lens L22, a cemented lens of a biconcave lens L23 and a three-piece combination of a biconcave lens L24 and a biconvex lens L25, and a cemented lens of a negative meniscus lens L26 with its convex surface facing the object side and a three-piece combination of a biconcave lens L27 and a biconcave lens L28.

The 3 rd lens group G3 is composed of three cemented lenses of a biconvex lens L31, a biconcave lens L32, and a positive meniscus lens L33 with its convex surface facing the object side.

The 4 th lens group G4 is constituted by a negative meniscus lens L41 having a concave surface facing the object side.

The 5 th lens group G5 is composed of a cemented lens composed of three cemented lenses, i.e., a positive meniscus lens L51 with its concave surface facing the object side, a biconcave lens L52, and a biconvex lens L53.

The immersion microscope micromirror of this example has a focal length of 12.4mm, a magnification of 16 times, an object side n.a. of 0.8, a maximum object height of 0.75mm, and a maximum image height Ih of 12.00mm (tube mirror f200mm, the same applies below). The data of this example are shown in Table I. The table shows, in order from the left, the surface number, the radius of curvature (r), the surface spacing (d), the refractive index (nd) at a wavelength of 588nm, and the Abbe number (Vd). The units of radius of curvature r, face spacing d, and other lengths are generally "mm". However, since the optical system can obtain the same optical performance even by scaling up or scaling down, the unit is not limited to "mm".

List one

The following are the condition correspondence values of the present embodiment.

RDmax＝12.13Ih/RDmax＝0.99

|(n6－n7)×f/R1|＝0.37

|(n4－n5)×f/R2|＝0.38

n1－n2＝0.42

(tanθ)/LL＝0.000744

|R4|/f＝0.69

|R5|/f＝1.51

|f4|/f＝1.18

Fig. 2 (a) to (C) show aberration diagrams of the immersion microscope objective of the present embodiment. As can be seen from fig. 2 (a) to (C), the immersion microscope objective of the present embodiment has well corrected chromatic aberration and a good flatness of the image plane.

Example 2:

in the immersion microscope objective (fig. 3) according to embodiment 2, the 1 st lens group G1 is composed of a cemented lens composed of a plano-concave lens L11 and a biconvex lens L12, a positive meniscus lens L13 having a concave surface facing the object side, and a positive meniscus lens L14 having a concave surface facing the object side in this order.

The 2 nd lens group G2 is composed of, in order from the object side OBJ, a cemented lens composed of a biconcave lens L21 and a biconvex lens L22, a cemented lens composed of three of a biconvex lens L23 and a biconcave lens L24 and a biconvex lens L25, and a cemented lens composed of three of a negative meniscus lens L26 with its convex surface facing the object side OBJ and a biconvex lens L27 and a biconcave lens L28.

The 3 rd lens group G3 is constituted by a cemented lens composed of a biconvex lens L31 and a biconcave lens L32.

The 4 th lens group G4 is constituted by a biconcave lens L41.

The 5 th lens group G5 is composed of a cemented lens composed of three positive meniscus lenses L51, a biconcave lens L52, and a biconvex lens L53, the concave surfaces of which face the object side.

In the immersion microscope objective of this example, the magnification was 16.5 times, the object side n.a. was 0.8, the maximum object height was 0.75mm, and the maximum image height Ih was 12.38mm.

Watch II

The following are the condition correspondence values of the present embodiment.

RDmax＝11.29

Ih/RDmax＝1.10

n1－n2＝0.30

(tanθ)/LL＝0.000767

Fig. 4 (a) to (C) show aberration diagrams of the immersion microscope objective of the present embodiment. As can be seen from fig. 4 (a) to (C), the immersion microscope objective of the present embodiment has well corrected chromatic aberration and a good flatness of the image plane.

Example 3:

The immersion microscope objective of example 3 of this patent (FIG. 5). The 1 st lens group G1 is composed of a cemented lens composed of three plano-concave lens L11, a biconvex lens L12, and a positive meniscus lens L13 with its concave surface facing the object side, and a positive meniscus lens L14 with its concave surface facing the object side, in this order.

The 2 nd lens group G2 is composed of a cemented lens composed of a biconcave lens L21 and a biconvex lens L22, a cemented lens composed of three cemented lenses of a biconcave lens L23 and a biconcave lens L24 and a biconvex lens L25, and a cemented lens composed of three cemented lenses of a negative meniscus lens L26 with its convex surface facing the object side and a biconvex lens L27 and a biconcave lens L28 in this order.

The 3 rd lens group G3 is composed of cemented lenses consisting of three of a biconvex lens L31, a biconcave lens L32, and a positive meniscus lens L33 with its convex surface facing the object side.

The 4 th lens group G4 is constituted by a biconcave lens L41.

The 5 th lens group G5 is composed of a cemented lens composed of three positive meniscus lenses L51 with the concave surface facing the object side, a biconcave lens L52, and a biconvex lens L53.

In the immersion microscope objective of this example, the focal length f was 12.5mm, the magnification was 16 times, the object side n.a. was 0.8, the maximum object height was 0.75mm, and the maximum image height Ih was 12.00mm.

Watch III

The following are the condition correspondence values of the present embodiment.

RDmax＝11.99

Ih/RDmax＝1.00

|(n6－n7)×f/R1|＝0.38

|(n4－n5)×f/R2|＝0.39

n1－n2＝0.30

(tanθ)/LL＝0.000747

|R4|/f＝0.61

|R5|/f＝1.49

Fig. 6 (a) to (C) show aberration diagrams of the immersion microscope objective of the present embodiment. As can be seen from fig. 6 (a) to (C), the immersion microscope objective of the present embodiment has well corrected chromatic aberration and a good flatness of the image plane.