JP2582918B2 - Microscope objective lens - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an objective lens for a microscope which can be used in an ultraviolet region, particularly in a deep ultraviolet region having a wavelength of 300 nm or less.

(Conventional technology and its problems) As is well known, in a microscope, when the numerical aperture (NA) of the objective lens is the same, the resolution limit increases as the wavelength decreases, and the It can be observed in detail. In addition, when the sample is irradiated with ultraviolet light, fluorescent light having higher intensity is often emitted as compared with the case where visible light is irradiated. Therefore, it is desired to provide a microscope that can be used even in the ultraviolet region in order to obtain more information by observing a sample with a microscope. For that purpose, an objective lens that can be used in the ultraviolet region or the far ultraviolet region is required.

Therefore, conventionally, for example, an objective lens for a microscope as shown in FIG. 6 has been adopted as an objective lens usable in an ultraviolet region or a far ultraviolet region. FIG. 6 is a view showing the configuration of the objective lens 70 for a microscope. This objective lens 70
Is Optical Technology Contact Magazine Vol.25 No.2 (February 1987) P.1
37.

As shown in the figure, the objective lens 70 is composed of a first fluorite lens 71, a second lens 71, and a second lens sequentially arranged from the object side (the left side in the figure) to the imaging side (the right side in the figure). Third lens group 7
It consists of 2,73. The second lens group 72 is formed by joining a concave lens 72a made of quartz and convex lenses 72b and 72c made of fluorite. The third lens group 73 is a second lens group.
Similarly to the lens 72, the concave lens 73a made of quartz is replaced with the convex lens 7 made of fluorite.
It is the one sandwiched between 3b and 73c.

In this objective lens 70, each lens 71, 72a to 72c, 73a to 7
Since 3c is made of quartz or fluorite, it can transmit ultraviolet rays and far ultraviolet rays. Therefore, the objective lens 70
Can also be used in the ultraviolet or far ultraviolet region.

In addition, the second lens group 72 is composed of a concave lens 72a made of quartz and convex lenses 72b and 72c made of fluorite, and the third lens group 73 is a concave lens 73a made of quartz and convex lenses 73b and 73c made of fluorite.
Therefore, chromatic aberration can be corrected.

By the way, in the second lens group 72, the convex lens 72b,
Optical contact is made between the concave lens 72a and the convex lens 72c. Also in the third lens group 73, the convex lens 73b, the concave lens 73a, and the convex lens 73c are in optical contact with each other. The reason is that, at present, there is no adhesive that transmits far ultraviolet rays. Therefore, the only way to prevent reflection at the lens joint surface is to make optical contact at the joint surface. Therefore, it is required to process each joint surface with high precision, and there is a problem that the manufacturing cost of the objective lens 70 increases.

The inventor of the present application proposed an objective lens for a microscope in which the above-mentioned problem was solved in an earlier application (JP-A-1-319719 and JP-A-1-319720, hereinafter simply referred to as “an earlier application”). did. FIG. 7 is a view showing one example of a microscope objective lens according to this proposal. According to this proposal, the microscope objective lens 60 is formed of quartz or fluorite lenses 61 to 63. These first to third lenses 61 to 63 are, as shown in FIG.
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 gap. Therefore, the microscope objective lens 60 can be used in an ultraviolet region or a far ultraviolet region. Moreover, the lenses 61 to 63 are separated from each other. In other words, in this objective lens 60,
There is no bonding surface. As a result, in the microscope objective lens 60, it is not necessary to use an optical contact, and the above problem is solved.

Incidentally, the objective lens 60 shown in FIG. 7 forms an image of an object on the focal plane of the imaging lens with a predetermined imaging magnification M in cooperation with an imaging lens (the detailed configuration thereof will be described later). It has a configuration that looks like an image. The imaging magnification M at this time is
The focal length f ₂ and the ratio between the focal length f ₁ of the objective lens 60 of the imaging lens. That is, the imaging magnification M is as follows: M = −f ₂ / f ₁ (1)

In a microscope, the imaging lens is usually fixed,
The imaging magnification M is changed by appropriately changing the objective lens. In order to change the imaging magnification M, it is necessary to prepare objective lenses having mutually different focal lengths.

For example, consider a case in which the objective lens 60 shown in FIG. 7 is replaced with a certain objective lens and the imaging magnification is doubled.

In this case, as can be seen from equation (1), in order to the image magnification M is doubled, it is necessary to have a focal length to provide the objective lens of (f _1/2). Where simply the focal length (f ₁ /
If only 2) is set, for example, the objective lens 60 may be reduced in proportion.

However, when the objective lens 60 is replaced with an objective lens with a 1/2 magnification, as long as the position of the pupil is fixed,
The distance from the objective lens to the object also needs to be reduced by half, and after the objective lens is replaced, it is necessary to refocus. This significantly reduces the operability of the microscope and is not preferable. In addition, the size of the pupil is reduced by half by replacing the objective lens, and in a fixed illumination system, the amount of light for proving an object changes greatly simultaneously with the replacement of the lens.

Therefore, by changing the objective lens, the imaging magnification becomes 2
When the magnification is doubled, the objective lens after the exchange is (1) the focal length is 1/2 times that of the objective lens 60, and (2) it is not necessary to refocus after the exchange of the objective lens. (3) It is required to satisfy the condition that the pupil size is almost equal to that of the objective lens 60.

(Object of the Invention) The present invention has been made in view of the above-mentioned problems, and has a configuration different from the objective lens according to the above-mentioned prior application, whereby an objective lens for a microscope that can be used in an ultraviolet region or a far ultraviolet region is provided. It is a first object to provide at low cost.

Also, the present invention provides an objective lens of the prior application, which forms an image of an object on a focal plane of the imaging lens at a predetermined imaging magnification in cooperation with the imaging lens, has a focal length substantially equal to that of the objective lens. It is a second object of the present invention to provide a microscope objective lens which is 1/2 times and is confocal and has almost the same pupil size.

(Means for Achieving the Object) According to the first aspect of the present invention, in order to achieve the first object, the first to sixth lenses are arranged in this order from the object side to the image side with a predetermined air gap. They are arranged. Among these first to sixth lenses, the first lens is made of quartz and has a negative power, the second lens is made of quartz or fluorite and has a positive power, and the third lens is made of quartz. The fourth lens is made of fluorite and has a positive power, the fifth lens is made of quartz and has a negative power, and the sixth lens is made of fluorite and made of positive. And the powers of the first to sixth lenses are φ ₁ ,
When φ ₂ , φ ₃ , φ ₄ , φ ₅ , φ ₆ , the objective lens has | φ ₂ / φ ₁ | <0.92 1.1 <| φ ₄ / φ ₃ | <8.8 | φ ₆ / φ ₅ | The inequality shown by <0.85 is satisfied.

The invention according to claim 2 is interchangeable with an objective lens that forms an image of an object on a focal plane of the imaging lens at a predetermined imaging magnification in cooperation with the imaging lens. The present invention is directed to a microscope objective lens whose imaging magnification is almost doubled when used in combination with the above-mentioned imaging lens instead of the objective lens.

In order to achieve the second object, the first to sixth lenses are arranged in this order from the object side to the image side with a predetermined air gap. Among the first to sixth lenses, the first lens is made of quartz and has a negative power, the second lens is made of quartz or fluorite and has a positive power, and the third lens is made of quartz. With negative power,
The fourth lens is made of fluorite and has a positive power.
The lens is made of quartz and has a negative power, and the sixth lens is made of fluorite and has a positive power. In addition, the powers of the first to sixth lenses are respectively φ ₁ , φ ₂ , φ ₃ , φ ₄ , φ
_5, when the phi _6, wherein the objective lens _{is, | φ 2 / φ 1 |} <0.92 1.1 <| φ 4 / φ 3 | <8.8 | φ 6 / φ 5 | inequalities represented by <0.85 is satisfied I have.

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

The first to sixth lenses are separated from each other with a predetermined air gap. Therefore, there is no need for an optical contact, and the objective lens can be provided at low cost.

Moreover, while the second, fourth and sixth lenses have positive power, the first, third and fifth lenses have negative power, and the power φ of the first through sixth lenses
When the objective lens is ₁ , φ ₂ , φ ₃ , φ ₄ , φ ₅ , φ ₆ , the objective lens is | φ ₂ / φ ₁ | <0.92 (2) 1.1 <| φ ₄ / φ ₃ | <8.8. (3) | φ ₆ / φ ₅ | <0.85 (4) Since the inequality expression (4) is satisfied, the spherical aberration is improved.

The reason is that when the value | φ ₂ / φ ₁ | becomes larger than 0.92, the correction becomes insufficient (under).

When the value | φ ₄ / φ ₃ | is smaller than 1.1, the correction of spherical aberration and chromatic aberration is excessive (over), and when the value is larger than 8.8, the correction is insufficient (under). is there.

Further, when the value | φ ₆ / φ ₅ | becomes larger than 0.85, the correction becomes insufficient (under).

According to the second aspect of the present invention, three lens systems (hereinafter, referred to as “concave and concave pairs”) each including a convex lens and a concave lens are provided, and the focal length of the objective lens can be changed without changing the pupil diameter. About half of the objective lens of the earlier application. As a result, the imaging magnification is doubled.

By the way, in consideration of achromatism, it is desirable that each concave-convex pair is composed of a quartz lens and a fluorite lens, and it is desirable that chromatic aberration is corrected for each concave-convex pair. However, this objective lens is a system that disperses power and sequentially refracts an incident light beam, and the object point distance is different for each concave-convex pair.
Therefore, the amount of correction of the spherical aberration in each concave-convex pair is also different, and the ray height becomes lower toward the object side. Therefore, it is not necessary to achromatize the concavo-convex pair located closest to the object side by using a quartz lens and a fluorite lens. Can be corrected by the concave-convex pair. That is, when the objective lens satisfies the inequalities (2) to (4), the spherical aberration and the like become better. In addition,
The reason is the same as above.

Further, as described above, since the focal length of the objective lens is almost half that of the objective lens of the earlier application to be replaced,
Corresponding to the shorter focal length, the principal point spacing of the objective lens is larger than the objective lens of the earlier application,
If the objective lens is designed, the parfocal length of the objective lens matches the objective lens of the earlier application. The amount of the principal point interval is about 1/3 of the focal length, and is a small value. Therefore, according to the objective lens according to the second aspect of the present invention, it is easy to make the objective lens and the objective lens of the prior application confocal.

(Embodiment) A. First Embodiment FIG. 1 shows a first embodiment of a microscope objective lens according to the present invention.
It is a figure showing an example. As shown in FIG. 1, the objective lens 10 includes first to sixth lenses 11 to 16. The first to sixth lenses 11 to 16 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 gap. In addition, the first and third
The fifth lens 11, 13, and 15 both have negative power. On the other hand, the second, fourth and sixth lenses 12, 14, 16 all have positive power.

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

In the table (and in Table 3 described later),
r _i is the radius of curvature of the i-th (i = 1 to 12) lens surface counted from the object side, and d _i is the i-th radius (i =
3 shows the distance between the lens surfaces 1 to 11) and the (i + 1) -th lens surface on the optical axis Z. As can be seen from the table, the first to third lenses 11 to 13 and the fifth
The lens 15 is made of quartz, and the fourth and sixth lenses 14, 16 are both made of fluorite.

The focal length f of the objective lens 10 is 15, the numerical aperture (NA) is 1/6, and the image size is 10.8.

Further, for the wavelength 298.06 (nm), the power phi ₁ of the first to sixth lenses _{11~16, φ 2, φ 3,} φ 4, φ 5, φ 6 is as follows.

φ ₁ = -0.2890, φ ₂ = 0.2607 φ ₃ = -0.2189, φ ₄ = 0.2431 φ ₅ = -0.2625, φ ₆ = 0.1097 Therefore, from the above data, | φ ₂ / φ ₁ | = 0.902 | φ ₄ / φ ₃ | = 1.111 | φ ₆ / φ ₅ | = 0.418, respectively, and the objective lens 10 is inequality (2) ~
It is clear that each of (4) is satisfied.

Incidentally, this objective lens 10 is a so-called infinity correction system in consideration of application to an epi-illumination type microscope. That is, in combination with the imaging lens described below,
The image of the object is formed on a predetermined image plane.

<Imaging Lens> FIG. 2 is a view showing the configuration of the imaging lens, which is the same as the imaging lens disclosed in the earlier application (Japanese Patent Application Laid-Open Nos. 1-319719 and 1-319720). Things.
As shown in the figure, the imaging lens 50 is composed of first to third lenses 51 to 53. The 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 gap.

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

Incidentally, in the table, R _i is the radius of curvature of the lens surface of i-th counted from the object side (i = 1 to 6), also D _i is the i-th counted from the object side (i = 1 to 5) The lens surface and (i +
1) shows the distance between the lens surface on the optical axis Z and the first lens surface. As can be seen from the table, the first lens 51 is made of fluorite, and the second and third lenses 52 and 53 are made of quartz. The focal length f 'of the imaging lens 50 is
300.

Therefore, the imaging magnification M of the microscope including the imaging lens 50 and the objective lens 10 according to the first embodiment is M = −f ′ / f = −300 / 15 = −20.0.

3A and 3B are diagrams showing the spherical aberration and the sine condition of a lens system in which the objective lens 10 and the imaging lens 50 are combined, respectively. Note that both figures (and the later-described
In FIGS. 5A and 5B), reference numerals A to D indicate wavelengths 29, respectively.
8.06 (nm), 202.54 (nm), 398.84 (nm), 253.70 (nm)
3 shows the results for the light.

3C and 3D are diagrams respectively showing astigmatism and distortion at a wavelength of 298.06 (nm). In FIG. 3C (and FIG. 5C described later), a solid line S indicates a sagittal image plane, and a broken line M indicates a meridional image plane.

From FIGS. 3A and 3B, it can be seen that the objective lens 10 has less aberration with respect to light in the ultraviolet region and the far ultraviolet region. Therefore, it is clear that this objective lens 10 can be used in the ultraviolet region or the far ultraviolet region.
3C and 3D that the lens system using the objective lens 10 has less astigmatism and distortion.

B. Second Embodiment FIG. 4 shows a second embodiment of the microscope objective lens according to the present invention.
It is a figure showing an example. 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 is constituted by first to sixth lenses 21 to 26 which 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 3 shows lens data of the objective lens 20 configured as described above.

As can be seen from the table, the first, third and fifth lenses 2
1, 23 and 25 are all made of quartz, and the second, fourth and sixth
The lenses 22, 24, 26 are all made of fluorite.

The focal length f of the objective lens 10 is 15, the numerical aperture (NA) is 1/6, and the image size is 10.8.

Further, for the wavelength 298.06 (nm), the power phi ₁ of the first to sixth lenses _{21~26, φ 2, φ 3,} φ 4, φ 5, φ 6 is as follows.

φ ₁ = -0.2419, φ ₂ = 0.1275 φ ₃ = -0.0380, φ ₄ = 0.2047 φ ₅ = -0.2140, φ ₆ = 0.0781 Therefore, from the above data, | φ ₂ / φ ₁ | = 0.527 | φ ₄ / φ ₃ | = 5.388 | φ ₆ / φ ₅ | = 0.365, respectively, and the objective lens 20 is inequality (2) ~
It is clear that each of (4) is satisfied.

Also for this objective lens 20, as in the above embodiment,
An imaging lens shown in FIG. 2 as a so-called infinity correction system
Combined 50. Therefore, the imaging magnification M of the microscope including the imaging lens 50 and the objective lens 20 according to the second embodiment is also M = -f '/ f = -300 / 15 = -20.0.

5A and 5B are diagrams showing the spherical aberration and the sine condition of a lens system in which the objective lens 20 and the imaging lens 50 are combined, respectively. FIGS. 5C and 5D are diagrams respectively showing astigmatism and distortion at a wavelength of 298.06 (nm).

From FIGS. 5A and 5B, it can be seen that the objective lens 20 has a small aberration with respect to light in the ultraviolet region and the far ultraviolet region. Therefore, it is clear that this objective lens 20 can be used in the ultraviolet region or the far ultraviolet region.
5C and 5D show that the lens system using the objective lens 20 has less astigmatism and distortion.

C. Effects of First and Second Embodiments As described above, the objective lenses 10 and 20 according to the first and second embodiments can be used in an ultraviolet region or a deep ultraviolet region, and are excellent in these wavelength regions. Has characteristics. Also, in any of the embodiments, the first to sixth
The lenses are spaced from each other. Therefore, there is no need for an optical contact, and an objective lens can be provided at low cost.

Although not particularly described in the above, any of the examples has a small aberration in both the visible range and the infrared range, and each of the objective lenses 10 and 20 can be used in the range from the infrared range to the far ultraviolet range. Was confirmed.

By the way, the objective lens 60 (FIG. 7) according to the earlier application disclosed by the inventor of the present application is combined with the imaging lens 50 to constitute a lens system having an imaging magnification M of −10 ×. . That is, the focal length of the objective lens 60 is 30. On the other hand, the focal lengths of the objective lenses 10 and 20 according to the above embodiment are both 15. Therefore, the imaging magnification M can be changed from -10 times to -20 times by fixing the imaging lens 50 and replacing the objective lens 10 of the first embodiment with the objective lens 60, for example.

In addition, both the objective lenses 10 and 20 are confocal with the objective lens 60. As a result, after replacement of the objective lens (for example, replacement of the objective lens 60 to the objective lens 10),
There is no need to refocus, and the operability of the microscope is improved.

In addition, the pupil diameter of each of the objective lenses 10 and 20 is substantially the same as that of the objective lens 60. Therefore, even when the lens is replaced, a large change in the amount of light illuminating the object is not recognized, and the object can be observed in a good state.

That is, it can be said that the objective lenses 10 and 20 according to the above-described embodiments are both objective lenses that meet the second object of the present invention.

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

In addition, since the lenses are separated from each other with a predetermined air gap, there is no need for an optical contact, and the objective lens can be provided at a low cost.

Moreover, while the first, third and fifth lenses have a positive power, the second, fourth and sixth lenses have a negative power, and the objective lenses have inequalities (2) to (4). ) Is satisfied, so that spherical aberration and the like can be made favorable.

According to the invention of claim 2, a pair of a first lens having negative power and a second lens having positive power, and a pair of a third lens having negative power and a fourth lens having positive power. And a pair of a fifth lens having a negative power and a sixth lens having a positive power are provided, so that the focal length of the objective lens can be changed without changing the pupil diameter. It can be reduced to almost half of the objective lens of the prior application, and the imaging magnification can be doubled.

Although the objective lens has a focal length that is almost half of that of the objective lens of the earlier application to be replaced, the objective lens can be easily made to have the same focal point as the objective lens of the earlier application.

[Brief description of the drawings]

FIG. 1 is a first view of a microscope objective lens according to the present invention.
FIG. 2 is a diagram showing an embodiment, FIG. 2 is a diagram showing a configuration of an imaging lens, and FIGS. 3A, 3B, 3C, and 3D each show a first example.
FIG. 4 is a diagram showing spherical aberration, sine condition, astigmatism, and distortion of a lens system obtained by combining the objective lens shown in the figure and the above-mentioned imaging lens. FIG. 4 is a diagram showing a microscope objective lens according to the present invention. 2
FIGS. 5A, 5B, 5C, and 5D each show an embodiment.
FIGS. 6 and 7 are diagrams showing spherical aberration, sine condition, astigmatism and distortion of a lens system in which the objective lens shown in FIG. 1 and the above-mentioned imaging lens are combined. FIGS. FIG. 3 is a diagram illustrating a configuration of a lens. 10,20 ... objective lens, 11,21 ... first lens, 12,22 ... second lens, 13,23 ... third lens, 14,24 ... fourth lens, 15,25 ... second 5 lenses, 16,26 ... 6th lens, 50 ... imaging lens, 60 ... objective lens

Claims (2)

(57) [Claims] 1. A first to a sixth lens are arranged in this order from the object side to the image side with a predetermined air interval, the first lens is made of quartz, has a negative power, and the second lens has a negative power. The lens is made of quartz or fluorite and has a positive power. The third lens is made of quartz and has a negative power. The fourth lens is made of fluorite and has a positive power. The lens is made of quartz and has a negative power, the sixth lens is made of fluorite and has a positive power, and the powers of the first to sixth lenses are φ1, φ2,
An objective lens for a microscope characterized by satisfying | φ2 / φ1 | <0.92 1.1 <| φ4 / φ3 | <8.8 | φ6 / φ5 | <0.85 when φ3, φ4, φ5, φ6. 2. An imaging lens which is interchangeable with an objective lens for forming an image of an object on an imaging surface at a predetermined imaging magnification in cooperation with an imaging lens, and wherein said objective lens is replaced with said objective lens. A microscope objective lens for substantially doubling the imaging magnification when used in combination with a first to sixth lenses arranged in this order from the object side to the image side with a predetermined air gap. The first lens is made of quartz and has a negative power, the second lens is made of quartz or fluorite and has a positive power, the third lens is made of quartz and has a negative power, The fourth lens is made of fluorite and has a positive power, the fifth lens is made of quartz and has a negative power, and the sixth lens is made of fluorite and has a positive power. Or the power of the sixth lens is φ1, φ2,
An objective lens for a microscope characterized by satisfying | φ2 / φ1 | <0.92 1.1 <| φ4 / φ3 | <8.8 | φ6 / φ5 | <0.85 when φ3, φ4, φ5, φ6.