JPH046510A - Objective lens for microscope - Google Patents

Abstract

PURPOSE:To obtain the objective lens which is usable in the ultraviolet ranges and far ultraviolet range at low cost by arraying 1st - 5th specific lenses at specific air intervals from the object side to the image side in this order. CONSTITUTION:The 1st - 5th lenses are arrayed at the specific air intervals from the object side to the image side in this order. The 1st lens 11 is a meniscus-lens which is made of quartz or fluorite and has a concave surface 11a on the object side and the 2nd lens 12 is a meniscus lens which is made of quartz and has negative power and a convex surface 12a on the object side; and the 3rd and 5th lenses 13 and 15 are both made of fluorite and have positive power and the 4th lens 14 is made of quartz and has negative power. Consequently, light in the ultraviolet range or far ultraviolet range can be transmitted through the objective and the lens is usable in the ultraviolet range and far ultraviolet range. Further, the respective lenses are isolated mutually across the specific air intervals, so the need for optical contact is eliminated and the objective lens can be obtained at low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an objective lens for a microscope that can be used even in the ultraviolet region, particularly in the far ultraviolet region with a wavelength of 300 ns or less.

(Prior art and its problems) As is well known, in a microscope, if the numerical aperture (NA) of the objective lens is the same, the resolution limit increases as the wavelength becomes shorter, and the resolution limit of the sample increases. You can observe every detail. Furthermore, when a sample is irradiated with ultraviolet rays, more intense fluorescence is often emitted than when irradiated with visible light. Therefore, in order to obtain more information by observing a sample using a microscope, it is desired to provide a microscope that can be used even in the ultraviolet region. For this purpose, an objective lens that can be used in the ultraviolet and deep ultraviolet regions is required.

Therefore, for example, a microscope objective lens shown in FIG. 6 has been employed as an objective lens usable in the ultraviolet region or deep ultraviolet region. FIG. 6 is a diagram showing the configuration of this objective lens 70 for a microscope. This objective lens 70 is
Light Wave Jutsu] Contact Magazine Vol. 1.25 No. 2 (1987
(February 2013) P, 137.

As shown in the figure, the objective lens 70 includes a first lens 71 made of fluorite, a second lens 71, and a second lens 71 made of fluorite, which are arranged sequentially from the object side (left side in the figure) to the imaging side (right side in the figure). It is composed of three lens groups 72 and 73. The second lens group 72 includes a concave lens 72a made of quartz and convex lenses 72b and 72b made of fluorite.
2c and sandwiched together. Similarly to the second lens group 72, the third lens group 73 is made by joining a concave lens 73a made of quartz with convex lenses 73b and 73c made of fluorite.

This objective lens 70 includes each lens 71.72a to 72.
c and 73a to 73c are all made of quartz or fluorite, so they can transmit ultraviolet rays and far ultraviolet rays. Therefore, the objective lens 70 can be used even in the ultraviolet region and deep ultraviolet region.

Moreover, the second lens group 72 includes a concave lens 72a made of quartz and convex lenses 72b, 72c made of fluorite, and the third lens group 73 includes a concave lens 73a made of quartz and convex lenses 73b, 73c made of fluorite. Since it is composed of
It is also possible to correct chromatic aberration.

By the way, in the second lens group 72, the convex lens 72
b, the concave lens 72a and the convex lens 72C are in optical contact with each other.

Also in the third lens group 73, convex lenses 73b,
The concave lens 73a and the convex lens 73c are in optical contact with each other. This is because, at present, there is no practical adhesive that transmits deep ultraviolet rays. Therefore, the only way to prevent total reflection at the lens cementation surface is to make optical contact with the cementation surface. Therefore, each cemented surface is required to be processed with high precision, and there is a problem in that the manufacturing cost of the objective lens 70 increases.

Therefore, the inventor of the present invention developed an objective lens for a microscope that solved the above problem in an earlier application (Japanese Unexamined Patent Publications No. 1-319719 and 1-319720, hereinafter simply referred to as the "earlier application"). Proposed. FIG. 7 is a diagram showing an example of the objective lens for a microscope according to this proposal.

According to this proposed example, the microscope objective lens 60 is composed of lenses 61 to 63 made of quartz or fluorite. And these first to third lenses 61 to 63
As shown in the figure, they are arranged in this order from the object side (left side in the figure) to the image side (right side in the figure) with a predetermined air interval. Therefore, this microscope objective lens 6
0 can be used in the ultraviolet region and deep ultraviolet region. Furthermore, the lenses 61 to 63 are spaced apart from each other; in other words, the objective lens 60 has no bonding surface. Therefore, this microscope objective lens 60 is
It becomes unnecessary to use optical contact, and the above problem is solved.

By the way, the objective lens 60 shown in FIG. 7 cooperates with an imaging lens (the detailed structure of which will be described later) to form an image of an object with a predetermined imaging magnification M on the focal plane of the imaging lens. It is configured in such a way that

The imaging magnification M at this time is the ratio of the focal length f2 of the imaging lens and the focal length f1 of the objective lens 60.

That is, the imaging magnification M is M--f2/f1...(1).

Furthermore, in a microscope, the imaging lens is usually fixed and the objective lens is replaced to change the imaging magnification M.
Therefore, it is necessary to prepare objective lenses with mutually different focal lengths.

For example, consider a case where the objective lens 60 shown in FIG. 7 is replaced with a certain objective lens to double the imaging magnification.

In this case, as can be seen from equation (1), in order to double the imaging magnification, it is necessary to prepare an objective lens with a focal length of (f1/2). Here, simply set the focal length (f,
/2), for example, the objective lens 60
All you have to do is reduce it proportionally.

However, when the objective lens 60 is replaced with an objective lens with a magnification of 1/2, as long as the position of the pupil is fixed, the distance from the objective lens to the object must also be increased by a factor of 172. After that, you will need to refocus. This significantly reduces the operability of the microscope and is not preferable. On the other hand, if the object position is fixed, the position of the pupil will move, so a fixed illumination system will change the illumination state, which is undesirable.

Also, by replacing the objective lens mentioned above, the pupil size can be increased to 17mm.
This will double the amount of light used in a fixed illumination system.

Therefore, when doubling the imaging magnification by replacing the objective lens, the replaced objective lens (1) has a focal length l/2 times that of the objective lens 60, and (2) replaces the objective lens. After that, there is no need to refocus, that is, it is parfocal with the objective lens 60, and (3) the position and size of the pupil are approximately equal to that of the objective lens 60. It will be done.

(Object of the invention) This invention has been made in view of the above problems, and provides a microscope objective lens that can be used even in the ultraviolet region and deep ultraviolet region, with a different configuration from the objective lens according to the above-mentioned earlier application. The primary objective is to provide the following at low cost.

In addition, the present invention has a focal length that is approximately 1/2 that of the objective lens of the above-mentioned earlier application, which cooperates with an imaging lens to form an image of an object on a focal plane with a predetermined imaging magnification. A second object of the present invention is to provide an objective lens for a microscope which is magnified and parfocal, and whose pupil position and size are approximately equal.

(Means for Achieving the Object) In order to achieve the above-mentioned first object, the invention as claimed in claim 1 includes the first to fifth lenses arranged in this order with a predetermined air interval from the object side to the image side. Arranged. These first
Of the to fifth lenses, the first lens is a meniscus lens made of quartz or fluorite with a concave surface facing the object side, and the second lens is a negative power lens made of quartz with a convex surface facing the object side. The third and fifth lenses are both made of fluorite and have positive power, and the fourth lens is made of quartz and has negative power.

In order to better achieve the first object, in addition to the invention of claim 1, the powers of the second to fifth lenses are respectively φ, φ, φ, φ, and a composite composed of the second and third lenses. The power of the system is φ, the fourth and fifth
When the power of the composite system consisting of lenses is φ and the power of the entire system is φ, for the objective lens, 2.1 < lφ / φ2 | < 2.7 0.85 < I φ5/φ4 | < (1, 451,85
< lφ23/φ l<2.250.83< l
The inequality expressed as φ45/φ l<0.89 is satisfied.

Further, the invention according to claim 3 cooperates with the imaging lens,
It is replaceable with an objective lens that forms an image of an object on the focal plane of the imaging lens with a predetermined imaging magnification, and when used in combination with the imaging lens instead of the objective lens, It is intended for a microscope objective lens that almost doubles the image magnification.

In order to achieve the second objective, the first to fifteenth lenses are arranged in this order from the object side to the image side with a predetermined air interval. Among these first to fifth lenses, the first lens is a meniscus lens made of quartz or fluorite and has a concave surface facing the object side, and the second lens is a negative lens made of quartz and has a convex surface facing the object side. The third and fifth lenses are both made of fluorite and have positive power, and the fourth lens is made of quartz and has negative power.

Furthermore, the powers of the second to fifth lenses are set to φ, φ8, . φ4. φ5, the power of the composite system consisting of the second and third lenses is φ23, the power of the composite system consisting of the fourth and fifth lenses is φ, the power of the entire system is φ
When, for the objective lens, 2.1 < l φ / φ2 | < 2.7 0.35 < l φ / φ4 | < 0.451.8
5< 1-φ23/φ l<2.250, [i3<
The inequality shown by l φ45/φ l<0.69 is satisfied.

(Function) According to the invention of claim 1, the second and fourth lenses are both made of quartz, the third and fifth lenses are both made of fluorite, and the first lens is made of quartz or fluorite. Made in Japan. Therefore, light in the ultraviolet region or deep ultraviolet region can pass through the objective lens, and it can be used in the ultraviolet region and deep ultraviolet region.

Further, the first to fifth lenses are spaced apart from each other by a predetermined air gap. Therefore, there is no need for an optical contact, and the objective lens can be provided at low cost.

In particular, the powers of the second to fifth lenses are each φ
, φ3. φ4. φ5, the power of the composite system consisting of the second and third lenses is φ, the power of the composite system consisting of the j114 and the fifth lens is φ, the power of the entire system is φ
When, the objective lens is 2.1 < Iφ /φ2|<2.7...
・(2) 0.15< I φ /φ4 | <0.4
5...(3) 1.85< l φ2
3/φ l<2.25 (4) 0.
68< l φ45/φ l < 0.69
...If the inequality shown in (5) is satisfied, there is spherical aberration.

Chromatic aberration etc. become more favorable.

The reason for this is that when the value 1φ 2 /φ21 becomes larger than 2.7, the aberration correction becomes insufficient. Conversely, if the value Iφ8/φ21 becomes smaller than 2.1, the aberration correction becomes excessive.

Further, if the value 1φ 2 /φ41 becomes larger than 0.45, the aberration correction will be insufficient (under). vice versa,
This is because if the value 1φ/φ41 becomes smaller than 0.35, the aberration correction becomes excessive.

Further, if the value Iφ23/φ1 becomes larger than 2.25, the aberration correction will be insufficient (under). Conversely, if the value 1φ23/φ1 becomes smaller than 1.85, the aberration correction becomes excessive.

Furthermore, if the value 1φ45/φ1 becomes larger than 0.69, the aberration correction becomes excessive.

Conversely, if the value 1φ45/φI is smaller than 0.63, the aberration correction will be insufficient (under).

According to the invention of claim 3, since the objective lens is of a so-called modified amici type, the focal length of the objective lens can be changed from that of the objective of the earlier application to be replaced without changing the pupil diameter. It is possible to reduce the size of the lens by almost half, and as a result, the imaging magnification can be doubled. Here, the objective lens is different from a pure Amici type in that the lens (first lens) disposed closest to the object side is a meniscus lens. This is because this meniscus lens has an abrasive character and a field flattener character to actively correct aberrations. In addition,
Particularly when the objective lens is a teleceletric system, it is desirable to set the meniscus lens to have negative power.

Further, when the objective lens satisfies the inequalities (2) to (5), spherical aberration and the like become better. Note that the reason is the same as above.

Furthermore, as mentioned above, the focal length of the objective lens is approximately half that of the objective lens of the earlier application to be replaced;
Corresponding to the shortened focal length, the distance between the principal points of the objective lens is larger than that of the objective lens of the previous application,
If the objective is designed, the parfocal length of the objective matches the objective of the previous application. The distance between the principal points is approximately 1/3 of the parfocal distance, which is the same as the focal length, and is a small value. Therefore, according to the objective lens according to the third aspect of the invention, it is easy to make the objective lens and the objective lens of the previous application confocal.

(Embodiments) A. First Embodiment FIG. 1 is a diagram showing a first embodiment of a microscope objective lens according to the present invention. As shown in the figure, this objective lens 10 is composed of first to fifth lenses 11 to 15. These first to fifth lenses 11 to 15 are
They are arranged in this order from the object side (left side in the figure) to the image side (right side in the figure) with a predetermined air interval.

The second lens 12 is a meniscus lens with a concave surface 11a facing the object side. Further, the second lens 12 is a meniscus lens having a negative power with a convex surface 12a facing the object side. Furthermore, the third and fifth lenses 13.15 both have positive power, while the fourth lens 14 has negative power.

Table 1 shows lens data of the objective lens 10 configured as described above.

Table 1 In addition, in the same table (and Table 3, which will be explained later), r
l is the radius of curvature of the i-th lens surface (i-1 to 10) counting from the object side, and dl is the radius of curvature of the i-th (i-1 to 10) counting from the object side.
It shows the inter-lens distance on the optical axis Z between the lens surfaces i-1 to 9) and the (i+1)th lens surface. Also,
As shown in the same table, 1. 2nd and 4th lens 1
1, 12, and 14 are all made of quartz, and the third and fifth lenses 13.15 are both made of fluorite.

Further, the focal length f of the objective lens 1o is 15, the numerical aperture (N^) is 1/6, and the image size is 10.8.

Also, the powers φ, φ2. φ3゜φ
, φ5 are as follows.

φ, −−0,04544,<62−0.08247
φ3-0.2142, φ4--0.2507
φ5-0.1005 In addition, the power φ23 of the composite system consisting of the second and third lenses 12.13, the power φ45 of the composite system consisting of the fourth and fifth lenses 14.15, and the total system (objective lens 10
) are respectively φ2s-0, 1436 and φ
45−0.04325°φ −0,08867.

Therefore, from the above data, φ /φ21-2.597 φ5/φ41-0.4010 φ23/φ l-2,154 φ45/φ l -0,6487 are found, respectively, and the objective lens 1o is determined by the inequality (2) to (
It is clear that each of 5) is satisfied.

By the way, this objective lens 1o has a so-called infinity correction system in consideration of its application to an epi-illumination type microscope. That is, in combination with the imaging lens described below,
It is configured to form an image of the object on a predetermined imaging plane.

<Imaging Lens> FIG. 2 is a diagram showing the configuration of an imaging lens, which is the same as the imaging lens shown in the previous application. As shown in the figure, the imaging lens 5o is composed of first to third lenses 51 to 53. These first to third lenses 51 to 53 are arranged in this order from the object side (left side in the figure) to the image side (right side in the figure) with a predetermined air interval.

Table 2 shows lens data of the imaging lens 50 configured as described above.

Table 2 In the same table, R is the first one (counting from the object side).
The radius of curvature of the lens surface i-1 to 6), and Dl is the radius of curvature of the lens surface of the i-th (1-1 to 5) counting from the object side and (i+
1) It shows the distance between the lens surfaces on the optical axis Z with the th lens surface. Further, as can be seen from the table, the third lens 52 is made of fluorite, and the second and third lenses 52.5
3 is made of quartz. Further, the focal length f' of this imaging lens 50 is 300 mm.

Therefore, the imaging magnification M of the microscope composed of this imaging lens 50 and the objective lens 10 according to the first embodiment 1 is as follows: M--f'/f--300/15--20.
It becomes 0.

FIGS. 3A and 3B are diagrams showing the spherical aberration and sine conditions of a lens system combining the objective lens 10 and the imaging lens 50, respectively. In addition, in both figures (and FIGS. 5A and 5B, which will be explained later), symbols A to D each indicate a wavelength of 298.08 (nm).

202.54 (r+m), 398.84 (nm),
The results are shown for light of 253.70 (nm).

Figures 3C and 3D each have a wavelength of 298°0.
It is a figure showing astigmatism and distortion aberration about 6 (na). In FIG. 2C (and FIG. 5C, which will be explained later), a solid line S indicates a sagittal image plane, and a broken line M indicates a meridional image plane.

It can be seen from FIGS. 3A and 3B that this objective lens 10 has little aberration for light in the ultraviolet region and deep ultraviolet region. Therefore, it is clear that this objective lens 10 can be used in the ultraviolet region and deep ultraviolet region. Also, from FIG. 3C and FIG. 3D, the objective lens 1
It is clear that the astigmatism and distortion aberration of the lens system using 0 is also small.

B. Second Embodiment FIG. 4 is a diagram showing a second embodiment of the objective lens for a microscope according to the present invention. The objective lens 20 according to the second embodiment has basically the same configuration as the objective lens 10. That is, the objective lens 20 includes first to fifth lenses 21 to 2 arranged sequentially from the object side (left side in the figure) to the image side (right side in the figure) with a predetermined air interval.
5.

Table 3 shows lens data of this objective lens 20.

Table 3: As shown in the table, the second and fourth lenses 2
2.24 are all made of quartz, and the first, third, and fifth lenses 21, 23.25 are both made of fluorite.

Further, the focal length f of the objective lens 10 is 15, the numerical aperture (NA) is 1/6, and the image size is 1018.

Also, the powers φ, φ3, . φ4φ5 are as follows.

φ, −−0,02242, φ2−0.09068φ
-0,2075, φ4--0.2208φ5-0.0
8927 Also, the power φ of the composite system consisting of the second and third lenses 22.23, the power φ45 of the composite system consisting of the fourth and fifth lenses 24.25, and the entire system (objective lens 20)
The power φ of is φ = 0.1304, respectively.
φ45−0.04466φ−0,013667.

Therefore, from the above data, φ /φ21-2.288 φ /φ41-0.4043 φ23/φ l-1,956 φ45/φ l -0,6[i99 are found, respectively, and the objective lens 20 is determined by the inequality (2). ~(
It is clear that each of 5) is satisfied.

Regarding this objective lens 20, similarly to the first embodiment,
It is combined with an imaging lens 50 shown in FIG. 2 as a so-called infinity correction system. Therefore, this imaging lens 50
The imaging magnification M of the microscope consisting of the objective lens 20 according to the second embodiment is also M −−f ′ / f −−8
00/15--20.0.

FIGS. 5A and 5B are diagrams showing the spherical aberration and sine conditions of a lens system combining the objective lens 20 and the imaging lens 50, respectively. Also, Figures 5C and 5D
The figure shows astigmatism and distortion at a wavelength of 298.06 (nw), respectively.

From FIG. 5A and FIG. 5B, it can be seen that this objective lens 20 has little aberration for light in the ultraviolet region and deep ultraviolet region. Therefore, it is clear that this objective lens 20 can be used in the ultraviolet region and deep ultraviolet region. Also, from FIG. 5C and FIG. 5D, it is clear that the objective lens 2
It is clear that the lens system using 0 has less astigmatism and distortion.

C6 Effects of the first and second embodiments As described above, the objective lenses 10.20 according to the first and second embodiments can be used in the ultraviolet region and deep ultraviolet region, and have excellent characteristics in these wavelength regions. have. Furthermore, in any of the embodiments, the first to fifth lenses are spaced apart from each other. Therefore, there is no need for an optical contact, and the objective lens can be provided at low cost.

Although not specifically explained above, all examples have little aberration in both the visible and infrared regions, and each objective lens 10.20 can be used in the range from the infrared region to the far ultraviolet region. It was confirmed that

By the way, the objective lens 60 (FIG. 7) according to the earlier application previously disclosed by the present inventor is combined with the imaging lens 50 to constitute a lens system with an imaging magnification M of 110 times. . That is, the focal length of the objective lens 60 is 30.

On the other hand, the objective lens 10.2 according to the above embodiment
The focal length of 0 is 15 in both cases. Therefore, by keeping the imaging lens 50 fixed and replacing the objective lens 10 of the first embodiment with the objective lens 60, for example, the imaging magnification M can be changed from 110 times to 120 times.

Furthermore, objective lenses 10 and 20 are both objective lenses 6 and 6.
It is parfocal with 0. As a result, even after replacing the objective lens (for example, replacing the objective lens 6o with the objective lens 10), there is no need to refocus, and the operability of the microscope is improved.

Moreover, the pupil diameter of each objective lens 10.20 is
It is almost the same as 0. Therefore, even when the lens is replaced, there is no significant change in the amount of light illuminating the object, and the object can be observed in good condition.

That is, the objective lenses 10 and 20 according to the above embodiments can all be said to be objective lenses that meet the second objective of the present application.

(Effect of the invention) As described above, according to the invention of claim 1, the first lens made of quartz or fluorite, the second lens made of quartz, the third lens made of fluorite, and the first lens made of quartz or fluorite. The fourth lens is made of fluorite, and the fifth lens is made of fluorite.
Since the lenses are arranged in this order from the object side to the image side with a predetermined air interval, the objective lens can be used in the ultraviolet region or deep ultraviolet region.

Furthermore, since the lenses are separated from each other by a predetermined air interval, there is no need for optical contacts, and the objective lens can be provided at low cost.

In particular, in the invention of claim 2, the objective lens has the inequality (
Since conditions 2) to (5) are satisfied, spherical aberration, chromatic aberration, etc. can be improved.

According to the invention of claim 3, since the objective lens is of a so-called modified amici type, the focal length of the objective lens can be changed to almost the same as that of the objective lens of the earlier application to be replaced, without changing the pupil diameter. It can be halved and the imaging magnification can be doubled.

Further, although the focal length of the objective lens is approximately half that of the objective lens of the earlier application to be replaced, the objective lens can easily be made parfocal with the objective lens of the earlier application.

[Brief explanation of the drawing]

FIG. 1 shows the first objective lens for a microscope according to the present invention.
FIG. 2 is a diagram showing the configuration of the imaging lens, and FIG. 3A, FIG. 3B, FIG. 3c, and FIG.
FIG. 4 is a diagram showing the spherical aberration, sine condition, astigmatism, and distortion of a lens system that combines the objective lens shown in the figure and the above-mentioned imaging lens, and FIG. 4 shows the objective lens for a microscope according to the present invention. FIG. 5A, FIG. 5B, FIG. 5c, and FIG. 5D are diagrams showing the spherical aberration of a lens system that combines the objective lens shown in FIG. 4 and the above-mentioned imaging lens, respectively. , a sine condition, astigmatism, and distortion aberration, and FIGS. 6 and 7 are diagrams each showing the configuration of a conventional objective lens for a microscope. 10.20... Objective lens, 11.21... First lens, 11a, 21a... Concave surface, 12.22... Second lens, 12a, 22B... Convex surface, 13.23...・Third lens, 14.24...Fourth lens, 15.25...Fifth lens, 50...Imaging lens, 60...Objective lens

Claims (1)

[Scope of Claims] (1) First to fifth lenses are arranged in this order with a predetermined air interval from the object side to the image side,
The lens is a meniscus lens made of quartz or fluorite and has a concave surface facing the object side, the second lens is a meniscus lens made of quartz and has a negative power with a convex surface facing the object side, and the third and An objective lens for a microscope, wherein both the fifth lenses are made of fluorite and have positive power, and the fourth lens is made of quartz and has negative power. (2) The powers of the second to fifth lenses are each φ
_2, φ_3, φ_4, φ_5, the power of the composite system consisting of the second and third lenses is φ_2_3, the power of the composite system consisting of the fourth and fifth lenses is φ_4_5,
When the power of the entire system is φ, 2.1<|φ_3/φ_
2|<2.7 0.35<|φ_5/φ_4|<0.45 1.85<|φ_2_3/φ|<2.25 0.63<|φ_4_5/φ|<0.69 1. The microscope objective lens described in 1. (3) It can be replaced with an objective lens that cooperates with the imaging lens to form an image of an object on the imaging plane with a predetermined imaging magnification, and can be combined with the imaging lens instead of the objective lens. An objective lens for a microscope that almost doubles the imaging magnification when used as The first lens is a meniscus lens made of quartz or fluorite and has a concave surface facing the object side, the second lens is a meniscus lens made of quartz and has a negative power with a convex surface facing the object side; The third and fifth lenses are both made of fluorite and have positive power, the fourth lens is made of quartz and has negative power, and the powers of the second to fifth lenses are respectively φ_2,
φ_3, φ_4, φ_5, when the power of the composite system consisting of the second and third lenses is φ_2_3, the power of the composite system consisting of the fourth and fifth lenses is φ_4_5, and the power of the entire system is φ, 2. 1<|φ_3/φ_2|<2.7 0.35<|φ_5/φ_4|<0.45 1.85<|φ_2_3/φ|<2.25 0.63<|φ_4_5/φ|<0.69 An objective lens for a microscope characterized by satisfying the following.