JPH11231224A - Microscope objective - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the microscope objective which is large in field angle and light and facilitates sampling operation, etc. SOLUTION: The objective consists of a 1st positive group G1, a 2nd meniscus group G2 which is convex to the sample side, a 3rd meniscus group G3 which is concave to the sample side, and a 4th positive group G4 and satisfies the conditions of NA/β>=0.055, WD/f>=0.4, and 0.9>=f/L>=0.5 (f>=40, L>=45). Here, NA is the numerical aperture of the objective, β the magnification of the objective, WD the working distance of the objective, and (f) the focal distance of the whole objective. Consequently, a light lens system which can not be obtained by a conventional objective can be obtained and used for a fluorescent observation of proper magnification and a working distance and a working space which are enough to easily perform sampling operation, etc., are secured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microscope objective lens, and more particularly to a microscope objective lens used for fluorescence observation.

[0002]

2. Description of the Related Art When a low-magnification objective lens is used in fluorescence observation with a microscope, since the observation field of view is wide, when the entire field of view is illuminated, the illuminance of illumination light is reduced and the sample does not emit bright fluorescence. Further, a sufficiently bright fluorescent image cannot be obtained because the numerical aperture of the objective lens is small. Therefore, it has been generally considered that fluorescence observation using a low-magnification objective lens is unsuitable.

[0003] As a conventional example of a microscope objective lens, there is known an objective lens described in Japanese Patent Publication No. 5-67002. This objective lens is an apochromat class lens system having a long working distance, high resolution, a wide field of view, and excellent flatness.

However, the objective lenses described in Examples 1 and 2 in this conventional example have a relatively long working distance as compared with the focal length, but have a short absolute working distance, that is, 15. The working distance is 1 mm and 15.0 mm, and the working distance is insufficient for specimen manipulation under fluorescence observation.

[0005] The objective lens of this prior art embodiment is
Although the numerical aperture is large enough to obtain a high resolution, observing relatively dark fluorescence requires a larger NA than satisfying the high resolution. That is, an NA higher than the NA required to obtain the required resolution is required.

In general, it is easy to design an objective lens having a relatively long working distance by reducing the numerical aperture. However, if the working distance is increased by this method, it is not possible to secure a bright image in fluorescence observation. .

As another means for increasing the working distance of the objective lens, a thick meniscus lens having a convex surface facing the object side is arranged on the side closer to the image, and has the same focal length. There is a method of further increasing the working distance.
However, low magnification objectives with a relatively long focal length
This method is not preferred because the overall length of the lens system becomes too long.

Under the circumstances described above, the objective lens for low magnification observation, which has a long working distance, a wide field of view, and a high NA, which is excellent in fluorescence observation and specimen operability in a macro region,
It did not exist before.

[0009]

In recent years, the need for fluorescence observation at a relatively low magnification has been increasing. Incorporates a protein that emits less fluorescent light such as GFP into a part of the cell under low-magnification fluorescence observation into a part of the cell, and uses it as a marker to observe the behavior of the cell and its screening use when observing its metastasis. There is a demand for a macro application for manually selecting or extracting only a part marked with a fluorescent dye or protein from a set.

As described above, a conventional microscope objective lens has a wide field of view and a low-magnification objective lens cannot obtain sufficient brightness due to a small NA, so that it is difficult to identify the objective lens with a marker or to obtain a specimen. It is not possible to obtain a long working distance that can secure a sufficient working space for performing the operation.

[0011] In addition, a stereo microscope may be used to secure a work space for sample operation or the like. However, the stereo microscope is generally darker in image than a normal microscope due to its structure.
Therefore, there is no known microscope for fluorescence observation that needs to achieve both brightness and a work space.

Also, the objective lens of the stereomicroscope has separate observation optical paths for the left and right, and requires a lens with a sufficiently large diameter so that the left and right optical paths are not shaken. Has the disadvantage of becoming large.

In order to secure a relatively long working distance in a stereomicroscope objective lens having a focal length of about 50 to 100 mm, a thick meniscus lens having a convex surface facing the object side as shown in FIG. Is disposed on the image side. However, in this type of lens system, as can be seen from the drawings, the overall length of the lens system is long, and a microscope equipped with such a type of objective lens has to be large.

The present invention provides a bright and compact microscope objective lens having a large viewing angle.

[0015]

Means for Solving the Problems] microscope objective lens of the present invention, in order from the specimen side, based on the configuration shown in FIG. 1, the first group G ₁ having a power of convex in which the structure, the sample side a second group G ₂ of the meniscus shape with a convex surface, and more become the fourth group G ₄ having a power of the third group G ₃ and the convex meniscus shape with a concave surface facing the specimen side, following conditions (1),
It is characterized by satisfying (2) and (3). (1) NA / β ≧ 0.055 (2) WD / f ≧ 0.4 (3) 0.9 ≧ f / L ≧ 0.5 (f ≧ 40.L ≧ 45) where NA is the objective lens The numerical aperture, β is the magnification of the objective lens, WD is the working distance of the objective lens, and f is the focal length of the entire objective lens system.

The microscope objective lens of the present invention can be formed into a bright lens system, which cannot be obtained by the conventional microscope objective lens, at the time of fluorescence observation at an appropriate magnification, by adopting the above-described configuration, It is possible to secure a sufficient working distance and a work space for easily performing operations and the like.

In the lens system having the above-described lens configuration, if the condition (1) is satisfied, an image brighter than that of the conventional objective lens can be obtained. That is, when the value of NA / β is 0.
If the value is larger than 055, a bright objective lens can be obtained. Conversely, if NA / β is smaller than 0.055, a bright objective lens cannot be obtained. As described above, it is possible to obtain a brighter image as NA / β is larger, but as the value of NA / β becomes larger, the diameter of the light beam emitted from the objective lens becomes larger. Therefore, the diameter of the emitted light beam is limited by the optical path diameter of the main body of the microscope. Therefore, the NA of the objective lens
It is more desirable to satisfy the condition (1) and make the value close to the value of NA / β limited by the diameter of the microscope main body.

The condition (2) is a condition for securing a sufficient working distance for easily performing a sample operation or the like.
When D / f is smaller than 0.4, it is not preferable in terms of operability.

Condition (3) defines the distance L from the microscope mounting surface to the focal position with respect to the focal length f of the entire objective lens system, that is, the distance from the contact surface when the objective lens is mounted on the microscope body to the specimen surface. Is what you do.
This distance L is 45 mm for a conventional general microscope objective lens. In order to secure a wide field of view, it is desirable that the magnification is low, the focal length of the entire system be longer than a certain level, and that L be lengthened to some extent in order to ensure a long working distance WD.

In an objective lens, it is difficult to secure a working distance WD for improving sample operability due to a large NA. In order to ensure a sufficiently long working distance, the focal length f and the length L may be increased. However, if these values are made longer than necessary, the microscope becomes large.

By satisfying the above conditions (2) and (3), it is possible to secure a working distance WD suitable for sample operation while suppressing the overall length of the lens system, so that it is suitable for macro applications under fluorescence observation. An objective lens can be made.

The objective lens of the present invention is a four-group lens system as described above, and has a substantially symmetrical arrangement. In the present invention, it is preferable that the condition (3) is satisfied after satisfying the conditions (1) and (2).
As a result, a lens system having a substantially symmetrical arrangement that can achieve the object of the present invention can be obtained. If the value deviates from the upper limit or the lower limit of the condition (3), the lens configuration must be greatly deviated from the symmetric lens arrangement.
1 has to be adopted. From the above points, it is important to satisfy the condition (3).

In order to obtain an objective lens that can achieve the object of the present invention, it is necessary to efficiently correct aberrations with a relatively simple configuration.

In order to increase the working distance WD with an objective lens whose overall length is slightly longer than the focal length, a symmetrical lens system is desirable. The symmetric lens system includes, in order from the object side (sample side), a lens group having a positive power, a meniscus lens group having a convex surface facing the object side, and a lens group having a meniscus shape facing the object side, like the objective lens of the present invention. The optical system includes a meniscus lens group having a concave surface and a positive power lens group.

In the objective lens according to the present invention having the above-described configuration, it is desirable that the fourth group is composed of one convex lens in order to minimize the number of lenses. Further, if the fourth group is composed of two convex lenses, it is possible to increase the power of the fourth group while suppressing the occurrence of aberration. By increasing the power of the fourth unit in this way, the distance between the lenses, for example, the distance between the third and fourth units can be made variable to efficiently correct aberrations caused by lens manufacturing errors and the like.

In the case where the fourth unit is composed of two lenses as described above, it is preferable that the power of the fourth unit satisfies the following condition (4). (4) 1.3f ≧ f ₄ ≧ 0.75f where f ₄ is the focal length of the fourth lens unit, and f is the focal length of the entire objective lens system.

When the value exceeds the upper limit of 1.3f of the condition (4), the power of the fourth lens unit is weakened, the adjustment amount for aberration correction becomes large, and adjustment becomes difficult. If the lower limit of 0.75f is exceeded, the power of the fourth lens unit becomes too strong to deteriorate the spherical aberration, and the amount of adjustment necessary for aberration correction becomes too small, making it difficult to set the optimum position for adjustment.

In fluorescent observation, in order to obtain a bright and high-contrast image, it is necessary to use a lens having a high NA for the objective lens and a high transmittance for light having a wavelength shorter than the visible light used for the excitation light. It is desirable that the glass material itself emits little fluorescence.

In particular, the selection of the glass material of the convex lens included in the third or fourth group is important in correcting chromatic aberration, and it is desirable to use a low-dispersion glass material for at least one convex lens. Therefore, it is desirable that the third or fourth group includes at least one convex lens having a refractive index of 1.54 or less and an Abbe number of 62 or more. That is, it is desirable to satisfy the following condition (5). (5) n _p ≦ 1.54, ν _p ≧ 62 where n _p and ν _p are the refractive index and Abbe number of the convex lens. The _{n p} is detrimental to [nu _p is 62 or less when the chromatic aberration correction in 1.54 above.

The microscope objective lens of the above-mentioned prior art example is one in which chromatic aberration of the apochromat class is corrected, and the fourth group has an Abbe number of less than 35.8 in order to correct not only axial aberration but also chromatic aberration of magnification. A single positive lens.

However, since the objective lens of the present invention focuses mainly on fluorescence observation and mainly considers an object which emits a single color as an observation object, it does not correct apochromatic-grade chromatic aberration and does not perform light transmittance in the ultraviolet region. And a high NA microscope objective lens can be realized with a simple configuration as much as possible.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described based on examples having the following data.

Example 1 f = 45.00, NA = 0.267, WD = 30.00 r ₁ = 35.3164 d ₁ = 5.2809 n ₁ = 1.51633 ν ₁ = 64.14 r ₂ = -40.0822 d ₂ = 0.5 r ₃ = 14.7646 d ₃ = 4.8525 n ₂ = 1.6779 v ₂ = 55.34 r ₄ = 31.922 d ₄ = 2.2 n ₃ = 1.61656 v ₃ = 36.63 r ₅ = 10.2391 d ₅ = 10.9431 r ₆ = -9.4242 d ₆ = 2.5 n ₄ = 1.61656 v ₄ = 36.63 r _{7 = -30.7191 d 7 = 6.6656 n} 5 = 1.497 ν 5 = 81.54 r 8 = -13.5552 d 8 = 0.5 r 9 = -348.926 d 9 = 3.3819 n 6 = 1.51633 ν 6 = 64.14 r 10 = -36.1128 NA / β = 0.067, WD / f = 0.67, f / L = 0.69 (when L = 65)

Example 2 f = 43.47, NA = 0.265, WD = 26.98 r ₁ = 53.084 d ₁ = 4.3 n ₁ = 1.48749 ν ₁ = 70.23 r ₂ = -40.2552 d ₂ = 0.3 r ₃ = 16.9388 d ₃ = 6.3035 n ₂ = 1.6779 v ₂ = 55.34 r ₄ = −78.748 d ₄ = 1.4954 n ₃ = 1.53172 v ₃ = 48.91 r ₅ = 11.7842 d ₅ = 7.58 r ₆ = -11.4255 d ₆ = 0.9517 n ₄ = 1.59551 v ₄ = 39.21 _{r 7 = 105.4238 d 7 = 7.7345} n 5 = 1.497 ν 5 = 81.54 r 8 = -20.947 d 8 = 0.7 r 9 = -49.1698 d 9 = 4.32 n 6 = 1.48749 ν 6 = 70.23 r 10 = -21.0641 d 10 = _{0.72 r 11 = 112.4636 d 11 =} 3.37 n 7 = 1.48749 ν 7 = 70.23 r 12 = -184.323 NA / β = 0.064, WD / f = 0.62, ( when L = 65) f / L = 0.67 However r _1, r ₂ ,... are the radius of curvature of each lens surface, d
_.. , D ₂ ,...
₁ , n ₂ ,... Are the refractive indices of each lens, ν ₁ , ν ₂ ,.
Is the Abbe number of each lens. The unit of the length of r, d, etc. in the data is mm.

The first embodiment has the structure shown in FIG. 2 and includes a first group G1 composed of a biconvex lens, a second group G2 of a cemented meniscus lens in which a positive lens and a negative lens are cemented, and a negative lens and a positive lens. And a fourth group G4 of a convex meniscus lens and a third group G3 of a cemented meniscus lens, and a four-group six-lens structure.

In this embodiment, the fourth unit is composed of one convex lens, and is a lens system having a small number of lenses.

Embodiment 2 has a lens configuration shown in FIG. 3 and includes a first group G1 of a biconvex lens, a second group G2 of a cemented meniscus lens in which a positive lens and a negative lens are cemented, and a negative lens and a positive lens. And a fourth group G4 including a third group G3 of cemented meniscus lenses and a fourth group G4 of two convex lenses.

In this embodiment, the fourth unit is composed of two lenses, which increases the number of refracting surfaces and can efficiently correct spherical aberration. Power can be strengthened. In addition, the curvature of the surface of the lens other than the fourth group can be reduced, and the lens can be easily processed. Further, by increasing the power of the fourth unit, the inclination of the light beam at the air interval between the third and fourth units is increased, and the aberration generated due to the manufacturing error of each lens is changed by changing the air interval. Efficient cancellation is possible. As described above, the second embodiment is advantageous in terms of manufacturing, although the number of lens components increases.

The third embodiment has the configuration shown in FIG. 4 and the objective of the lens system is the same as that of the second embodiment shown in FIG. the third group and the distance d ₈ of the fourth group is changed to be an embodiment in which so as to correct the aberration.

As described above, the distance (water thickness) D from the water surface to the object when the aberration is corrected by changing the distance d ₈ between the third and fourth units, and the distance when the object is in focus. The distance d ₀ from the water surface to the first surface r ₁ of the objective lens and the value d ₈ of the interval when the third and fourth units are changed for aberration correction are as follows.

D d ₀ d ₈ 0.3 26.7171 0.75 3 24.5675 0.9 6 22.1088 1.15 Each of the objective lenses in the above embodiments is a lens system of infinity design, and is combined with, for example, an imaging lens shown in FIG. 5 and having the following data. Used. _{R 1 = 68.7541 D 1 = 7.7321} N 1 = 1.48749 V 1 = 70.2 R 2 = -37.5679 D 2 = 3.4742 N 2 = 1.8061 V 2 = 40.95 R 3 = -102.848 D 3 = 0.6973 R 4 = 84.3099 D 4 = 6.0238 N ₃ = 1.834 V ₃ = 37.16 R ₅ = -50.71 D ₅ = 3.0298 N ₄ = 1.6445 V ₄ = 40.82 R ₆ = 40.6619 In the data, R ₁ , R ₂ ,... _1, D _2, ··· wall thickness and spacing of the imaging lens, N _1, N _2, ··· is the refractive index at the d-line of the imaging lens, V _1, V _2, ··· are sintered This is the Abbe number of the image lens.

FIGS. 6 and 7 show the aberration states of the first and second embodiments, respectively, and FIGS. 8, 9 and 10 show (1) when the aberration is corrected as described in the above table. , (2),
It is a figure showing the state of aberration in the state of (3).

The aberration curves shown in FIGS. 6 to 10 show the aberrations of the objective lens and the imaging lens as a whole obtained with the imaging lens shown in FIG. 5 at a distance of 120 mm from the objective lens in each embodiment. Is shown.

In the microscope objective lens of the present invention, the following lens system can achieve the object of the invention in addition to the constitution described in the claims.

(1) A microscope according to claim 3, wherein an aberration due to a manufacturing error is corrected by changing a distance between the third and fourth groups. Objective lens.

(2) In the lens system according to the third aspect of the present invention, by changing the distance between the third unit and the fourth unit, aberrations due to the thickness of the liquid in front of the sample (on the lens system side) can be reduced. A microscope objective lens for correcting deterioration.

[0047]

According to the objective lens of the present invention, unprecedented brightness can be obtained, a relatively dark fluorescent image can be observed in a wide field of view at a low magnification, and the efficiency of the screening operation under fluorescent observation can be improved. obtain.

Also, it is possible to secure a sufficient working distance while suppressing the total length of the objective lens, so that it can be mounted on a microscope in combination with a conventional objective lens whose distance from the microscope mounting surface to the focal position is about 45 mm. Thus, the size of the entire microscope can be prevented from increasing, and a working space around the specimen can be secured. This facilitates manual operations such as selection of a sample using fluorescence as a marker and extraction of a specific site. In addition, by using a high-magnification objective lens whose distance from the microscope mounting surface to the focal point is about 45 mm, it is possible to switch the objective lens by simple switching means. Detailed observation with the lens can be done quickly.

[Brief description of the drawings]

FIG. 1 is a diagram showing a basic configuration of an objective lens of the present invention.

FIG. 2 is a cross-sectional view of Embodiment 1 of the present invention.

FIG. 3 is a sectional view of a second embodiment of the present invention.

FIG. 4 is a sectional view of a third embodiment of the present invention.

FIG. 5 is a sectional view of an imaging lens used in combination with the objective lens of the present invention.

FIG. 6 is an aberration curve diagram according to the first embodiment of the present invention.

FIG. 7 is an aberration curve diagram according to the second embodiment of the present invention.

FIG. 8 is an aberration curve diagram according to the third embodiment of the present invention.

FIG. 9 is an aberration curve diagram according to the third embodiment of the present invention.

FIG. 10 is an aberration curve diagram according to the third embodiment of the present invention.

FIG. 11 shows an example of a conventional objective lens.

Claims (3)

[Claims] 1. A first power source having a convex power in order from the specimen side.
A second group having a meniscus shape having a convex surface facing the specimen side, a third group having a meniscus shape having a concave surface facing the sample side, and a fourth group having a convex power.
A microscope objective lens that satisfies (2) and (3). (1) NA / β ≧ 0.055 (2) WD / f ≧ 0.4 (3) 0.9 ≧ f / L ≧ 0.5 (f ≧ 40.L ≧ 45) where NA is the objective lens The numerical aperture, β is the magnification of the objective lens, WD is the working distance of the objective lens, and f is the focal length of the entire objective lens system. 2. The microscope objective according to claim 1, wherein at least one convex lens satisfying the following condition (5) is included in each of the third and fourth groups. (5) n _p ≦ 1.54, ν _p ≧ 62 where n _p is the refractive index of the convex lens, and ν _p is the Abbe number of the convex lens. 3. The fourth group includes at least two convex lenses, and satisfies the following condition (4), and is capable of correcting the aberration by changing the air gap between the third and fourth groups. Item 1
Microscope objective lens. (4) 1.3f ≧ f ₄ ≧ 0.75f where f ₄ is the focal length of the fourth lens unit, and f is the focal length of the entire objective lens system.