JP2003156691A - Condenser lens for microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a lens having a long working distance and a high numerical aperture while keeping a focal distance constant. SOLUTION: The condenser lens having the long working distance and the high numerical aperture while keeping the focal distance short is realized by making the lens a retrofocus type one consisting of a 1st lens group being a doublet negative meniscus lens whose concave surface faces to a light source side and a 2nd lens group consisting of a plurality of single positive lenses in order from the light source side to a sample side. Assuming that the focal distance of the single lens nearest to the sample side is f0 and the synthetic focal distance of the 1st and the 2nd lens groups is (f), they satisfy a condition (1). (1) 1<f0/f<1.8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a condenser lens used in an illumination optical system of a microscope.

[0002]

2. Description of the Related Art A transmission illumination optical system of a microscope has a structure as shown in FIG.

In FIG. 7, 1 is a light source, 2 is a collector lens, 3 is a field stop, 4 is a field lens, 5 is an aperture stop, 6 is a condenser lens, and 7 is a sample.

This illumination optical system is configured to illuminate the sample 1 by condensing the light from the light source 1 through the collector lens 2, the field lens 4 and the condenser lens 6.

In the illumination optical system having such a configuration, when a plane parallel plate 8 such as a slide glass or a petri dish is arranged between the condenser lens 6 and the sample 7, the illumination light passes through the plane parallel plate and reaches the sample 7. Collected.

Conventionally, in an inverted microscope, a condenser lens having a long working distance has been preferred so that work on a stage can be easily performed.

As a conventional example of a condenser lens for a microscope having a long working distance, a condenser lens described in Japanese Patent Laid-Open No. 2000-292708 is known.

The conventional condenser lens is composed of a first lens group having a negative refractive power and a second lens group having a positive refractive power in order from the light source side toward the sample. The aperture stop can be arranged between the second lens group and the second lens group.

As another conventional example, Japanese Patent Laid-Open No. 10-3
A condenser lens described in Japanese Patent No. 9225 is known. This condenser lens is a condenser lens for a microscope, which is composed of a first lens group having a negative refractive power and a second lens group having a positive refractive power in order from the light source side.

[0010]

In recent years, using an inverted microscope, operations such as injection and screening with cells, eggs and the like have been carried out on a stage. In such work, various instruments are placed on the stage. Therefore, the condenser lens is required to have a long working distance so that a wide working space can be secured.

However, in order to increase the working distance of the condenser lens, it is necessary to secure a numerical aperture (NA) on the illumination light side, that is, on the condenser lens side.

Although the resolving power of the microscope is improved in proportion to the numerical aperture (NA), simply increasing the NA of the objective lens does not improve the resolving power. This is because the effective NA on the objective lens side does not become large unless the NA on the illumination light side is made large.

In order to solve such a problem, it is conceivable to increase the focal length of the condenser lens.
However, if the illumination optical system is configured to maintain an appropriate NA and illumination field, the device becomes large. In addition to the aperture stop, apertures such as phase-difference ring slits, dark-field ring slits, modulation contrast apertures, and optical elements such as differential interference prisms and polarizing plates are placed near the front focus position of the condenser lens. To be done. Then, using these apertures and optical elements, a phase difference spectroscope, a differential interference spectroscope, a dark field speculum, a modulation contrast spectroscope, and a polarization spectroscope are performed. However, when the focal length of the condenser lens is increased as described above, the diameter of each of the optical elements and the aperture becomes large. Therefore, the turrets and sliders that hold these large-sized optical elements and the openings also become large. As a result, the work space is narrowed, which hinders the work related to injection and the work related to screening. Further, if the diameter of the optical element or the aperture becomes large, for example, in the case of a differential interference microscope, it becomes difficult to maintain the surface accuracy of the differential interference prism having the large diameter. Therefore, a good differential interference image cannot be obtained.

In the case of a modulation contrast microscope, the modulator 10 shown in FIG. 8 is arranged at the pupil position of the objective lens, and the modulation contrast aperture 11 (hereinafter referred to as MC aperture) shown in FIG. 9 is a condenser lens. It is placed at the front focal position of and the speculum is performed. Here, in the modulator 10, the region 10
Areas A, 10B, and 10C have different transmittances.
The magnitude relationship of the transmittance values is usually 10A <10B <10.
It has a C relationship. Further, the opening 11A of the MC opening 11 is provided at a position where the light passing through the opening 11A passes through the region 10C. Also, the opening 11
B is provided at a position where the light passing through the opening 11B passes through the region 10B.

With such a configuration, when the size of the opening of the opening 11A or the opening 11B becomes large, the distortion aberration generated in proportion to the cube of the image height becomes extremely large. for that reason,
Accurate projection cannot be performed on the modulator around the aperture, and good modulation contrast microscopy cannot be performed.

Further, if the focal length of the condenser lens is increased and the NA is increased, it becomes difficult to correct the aberration of the image of the field stop. In particular, spherical aberration and chromatic aberration tend to be large. Therefore, if these aberrations cannot be corrected sufficiently, it becomes difficult to understand the optimal focus position of the field stop, and it becomes difficult to adjust the focus of the field stop.

Japanese Patent Laid-Open No. 2000-2927, which is the conventional example.
The condenser lens disclosed in Japanese Patent Publication No. 08 has a relatively short focal length and can secure a long working distance and high NA. However, this conventional condenser lens is configured such that the front focal position of the second lens group having a positive refractive power is located between the first lens group and the second lens group. In this case, the light beam from the field stop does not become a parallel light beam at the front focus position of the positive second lens group. Therefore, for example, in a differential interference microscope, a differential interference prism is arranged in a non-parallel light beam. Then, the difference in retardation amount between the axial ray and the marginal ray becomes large, so that a good differential interference image cannot be obtained.

Further, in the case of the polarization microscope, the polarizing plate is arranged in the non-parallel light flux. In this case, the incident angle of the off-axis ray that enters the polarizing plate is not vertical. Therefore, the optimum polarized light cannot be obtained.

Further, the conventional example disclosed in Japanese Patent Laid-Open No. 10-39225 includes a correction ring for moving a part of the lens group in the condenser lens. The correction ring is used to optimize the image forming characteristics of the condenser lens when the thickness or the refractive index of the plane-parallel plate changes. However, there is a drawback that the working distance is short with respect to the focal length of the condenser lens and the working space cannot be wide.

The present invention provides a condenser lens having a long working distance and a high numerical aperture while keeping the focal length constant. Further, the present invention provides a condenser lens having a good imaging performance of the field stop. Another object of the present invention is to obtain a good image in a spectroscopic method in which a condenser lens and an optical element (or an aperture) are combined, such as a differential interference spectroscope and a polarization spectroscope.

[0021]

A microscope condenser lens according to the present invention comprises, in order from a light source side toward a sample, a first lens group of a cemented negative meniscus lens having a concave surface facing the light source side and a plurality of positive single lenses. And a second lens unit configured to satisfy the following condition (1). (1) 1 <f0 / f <1.8 where f0 is the focal length of the single lens closest to the sample, and f is the combined focal length of the first lens group and the second lens group.

In the microscope condenser lens of the present invention,
By using a retrofocus type composed of a first lens group having a negative refractive power and a second lens group having a positive refractive power,
A lens system having a long working distance and a high numerical aperture can be obtained while keeping the focal length short.

Since the focal length of the microscope condenser lens of the present invention is shorter than the working distance, the condenser lens and the entire illuminating device can be made compact. For example, when the front focal position of the condenser lens is matched with the sample position, the light flux on the light source side of the condenser lens becomes a parallel light flux. In the present invention, since the focal length of the condenser lens is short, the diameter of this parallel light flux becomes small. Therefore, an optical element having a small diameter (small area) or an aperture can be arranged in this parallel light flux. As a result, it is possible to prevent the turret and the slider that hold these optical elements and the aperture from increasing in size, and it is possible to realize a compact illumination device.

Further, as described above, the differential interference prism is
If the diameter becomes large, it becomes difficult to maintain the surface accuracy of the prism, which leads to deterioration in performance. However, in the present invention, since the light beam diameter at the position where the differential interference prism is arranged can be made fine, it is possible to use a differential interference prism having a small diameter (high surface accuracy). Therefore, a good differential interference contrast image can be obtained.

The diameter of the MC opening can also be reduced. Therefore, the distortion aberration generated in the image of the MC aperture projected at the pupil position of the objective lens can be reduced. That is, the MC aperture can be accurately projected onto the modulator arranged near the pupil position of the objective lens. This allows
A good modulation contrast image can be obtained.

In the microscope condenser lens of the present invention, a cemented negative meniscus lens is arranged in the first lens group. Thus, the chromatic aberration is corrected by utilizing the difference in dispersion of the glass material before and after the cemented surface of the cemented lens. In particular, the chromatic aberration occurring in the image of the field stop arranged in the illumination optical system is well corrected. As a result, no color blur occurs in the image of the field stop projected on the sample. Therefore, the focus of the image of the field stop can be easily adjusted.

Further, as described above, since the first lens group is composed of the cemented negative meniscus lens,
Due to the negative refracting power of the lens group, spherical aberration generated in the second lens group composed of a plurality of positive single lenses can be canceled. Furthermore, by arranging the concave surface of the cemented negative meniscus lens of the first lens group toward the light source side, the position where the marginal ray passes can be made higher than when the concave surface is directed toward the sample surface. This makes it possible to achieve a long working distance and a high numerical aperture while keeping the focal length short.

The microscope condenser lens of the present invention is characterized by satisfying the condition (1) as described above.

In the condenser lens, the height of the axial marginal ray on the first surface on the sample side is substantially determined by the working distance and the numerical aperture. Therefore, when the working distance is long and the numerical aperture is high, the height of the marginal ray on the lens surface closest to the sample is high. Also, the angle formed by this marginal ray and the optical axis becomes tight. Therefore, if it is attempted to realize a condenser lens having a high numerical aperture with a long working distance while keeping the focal length short by using the first lens unit having a negative refractive power and the second lens unit having a positive refractive power, The second lens group having a refracting power and the first lens group having a negative refracting power have to be converted into a parallel light flux that is kept small in diameter.

Therefore, the power of the second lens unit having a positive refractive power must be made stronger than that of the conventional condenser lens having a short working distance. In that case, increasing the power of the positive lens on the sample side is advantageous in correcting spherical aberration.

For the above reason, the condition (1) defines the focal length of the positive single lens closest to the sample in the condenser lens of the present invention.

In the condition (1), when f0 / f becomes the upper limit of 1.8 or more, the refractive power of the positive single lens closest to the sample becomes weak, and the refractive power of other positive single lenses becomes too strong. . As a result, the spherical aberration generated by the other positive single lens cannot be completely corrected by the cemented negative meniscus lens of the first lens group.

When f0 / f is equal to or smaller than the lower limit of 1 of the condition (1), the refractive power of the positive single lens closest to the sample becomes too strong. Therefore, the spherical negative aberration generated by this lens cannot be completely corrected by the cemented negative meniscus lens of the first lens group.

In the microscope condenser lens of the present invention, it is desirable that the following condition (2) is satisfied. (2) 1.5 <| r ₁ / (n ₁ −1) / f | × f 0 /f<4.6 where r ₁ is the radius of curvature of the lens surface closest to the light source, and n ₁ is the radius closest to the light source. The refractive index of the lens.

The microscope condenser lens of the present invention comprises the first lens group of the negative cemented meniscus lens with the concave surface facing the light source side, and the second lens group of a plurality of positive single lenses. While keeping the focal length short,
This is a condenser lens with a long working distance and a high numerical aperture. In order to increase the working distance without changing the focal length, the negative refracting power of the first lens group, especially the most negative refracting power of the first lens group on the light source side, diverges the light incident on the first lens group. Need to let. This makes it possible to increase the height of the marginal ray and make it enter the second lens group. Then, the marginal ray having a high ray height is directed to the center of the sample by the positive refractive power of the second lens group.

Therefore, the condition (2) defines the negative refractive power of the concave surface of the first lens group closest to the light source and the positive power of the lens closest to the sample.

In this condition (2), when the upper limit of 4.6 or more is reached, the negative refractive power of the concave surface of the cemented negative meniscus lens with the concave surface facing the light source side of the first lens group and the positive single lens closest to the sample side. The positive refractive power of the lens becomes too weak. Therefore, the height of the marginal ray cannot be increased, and it becomes impossible to configure a condenser lens having a high numerical aperture with a long working distance while maintaining a short focal length.

When the lower limit of the condition (2) is not more than 1.5, the negative refractive power of the concave surface of the cemented negative meniscus lens with the concave surface facing the light source side of the first lens unit and the positive single lens on the most sample side. The positive refractive power of the lens becomes too strong. Therefore, the spherical aberration generated in each lens becomes too large, and it becomes difficult to satisfactorily correct this.

In the microscope condenser lens of the present invention, it is desirable that the following condition (3) is satisfied. _{(3) 0.5 <| r 1} / (n 1 -1) | / f0 <2

When the value exceeds the upper limit of 2 in the above condition (3), the negative refractive power of the concave surface of the cemented negative meniscus lens with the concave surface facing the light source side of the first lens group is the positive refractive index of the most sample side. Too strong compared to the power of the lens. Therefore, the spherical aberration generated in the second lens group is excessively corrected by the concave surface on the light source side of the first lens group.

In the condition (3), the lower limit value of 0.
When it is less than 5, the negative refractive power of the concave surface of the cemented negative meniscus lens with the concave surface facing the light source side of the first lens group becomes too weak compared to the power of the positive single lens closest to the sample side. Therefore, the spherical aberration generated in the second lens group cannot be completely corrected by the concave surface on the light source side of the cemented negative meniscus lens.

In the microscope condenser lens of the present invention, it is preferable that the following condition (4) is satisfied. (4) 1 <WD / f <2 where WD is the distance (working distance) from the surface of the condenser lens closest to the sample to the sample.

As described above, the microscope condenser lens of the present invention comprises the first lens group having the negative refracting power and the second lens group having the positive refracting power in order from the light source side. While keeping the distance short, a condenser lens with a long working distance and a high numerical aperture can be formed. As a result, it is possible to secure a wide working space for performing operations such as injection and screening.

The condition (4) defines the working distance. In this condition (4), if the value of WD / f is less than the lower limit value of 1, the working space cannot be sufficiently secured. When the value of WD / f is equal to or more than the upper limit of 2 in the condition (4), the distance between the rear principal point position of the condenser lens and the lens surface closest to the sample (first surface on the sample side) is too large. Therefore, when the first lens group having a negative refractive power and the second lens group having a positive refractive power are used as in the present invention, the negative power of the first lens group is made extremely strong, The positive power of the second lens group must be increased. However, in this case, it becomes difficult to correct spherical aberration.

Further, in the microscope condenser lens of the present invention, it is desirable that the cemented lens of the first lens group is composed of a concave lens and a convex lens from the light source side, and the following condition (5) is satisfied. (5) │ν ₁ -ν ₂ │> 25 where ν ₁ and ν ₂ are the Abbe numbers of the concave lens and the convex lens of the cemented negative meniscus lens, respectively.

As described above, in the microscope condenser lens of the present invention, the first lens group is composed of a cemented negative meniscus lens. Then, the difference in dispersion of the glass materials before and after the cemented surface in this cemented negative meniscus lens is used to satisfactorily correct the chromatic aberration with respect to the image of the field stop disposed in the illumination optical system. That is, the difference in Abbe number between the convex lens and the concave lens before and after the cemented surface of the cemented negative meniscus lens is defined as shown in the condition (5) so that the chromatic aberration is corrected well.

In the condition (5), when the difference between the Abbe numbers is 25 or less, which is the lower limit value, the difference in dispersion is too small, and it becomes difficult to sufficiently correct chromatic aberration.

Further, in the present invention, it is preferable that the second lens group is composed of two single lenses. At this time, the single lens on the light source side is preferably a biconvex lens. Further, it is preferable that the single lens on the sample side is constituted by a positive meniscus lens having a concave surface facing the sample side, or a plano-convex lens having a flat surface on the sample side.

If the second lens group is composed of three or more positive single lenses, the total length of the condenser lens becomes long. In addition, the entire illuminating device becomes large, and it becomes impossible to obtain a sufficiently compact illuminating device. In addition, the number of lenses increases, which is not preferable in terms of cost.

If the positive single lens on the sample side is concave on the sample side or has a flat surface on the sample side, this surface approaches the aplanatic condition with respect to the sample surface, and spherical aberration is improved. Can be corrected.

[0051]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the microscope condenser lens of the present invention will be described based on each example.

Each of the examples (Examples 1 to 3) of the microscope condenser lens of the present invention has a configuration as shown in FIGS. 1 to 3 and has the following data.

Example 1 f = 25, NA = 0.55, OH = 2.75 R ₀ = ∞ D ₀ = 108.0000 R ₁ = ∞ D ₁ = 4.0000 N ₁ = 1.71999 V ₁ = 50.22 R ₂ = -84.7780 D ₂ = 52.9103 _{r 0 = ∞ d 0 = 8.3163} r 1 = -36.7215 d 1 = 4.1973 n 1 = 1.80518 ν 1 = 25.42 r 2 = 30.0104 d 2 = 12.9916 n 2 = 1.51633 ν 2 = 64.14 r 3 = -38.8636 d 3 = 0.25 _{r 4 = 86.2726 d 4 = 6.5147} n 3 = 1.71999 ν 3 = 50.22 r 5 = -82.7421 d 5 = 0.25 r 6 = 28.6170 d 6 = 8.7741 n 4 = 1.78650 ν 4 = 50.00 r 7 = 170.5435 d 7 = 26.7956 r _{8 = ∞ d 8 = 2.0000 n} 5 = 1.33304 ν 5 = 55.79 r 9 = ∞ f0 = 42.5633 f0 / f = 1.703 | r 1 / (n 1 -1) /f|×f0/f=3.112 | r 1 / (N ₁ −1) | /f0=1.07 WD / f = 1.132 | ν _t −ν ₀ | = 38.72

Example 2 f = 27.2294, NA = 0.55, OH = 2.75 R ₀ = ∞ D ₀ = 108.0000 R ₁ = ∞ D ₁ = 4.0000 N ₁ = 1.71999 V ₁ = 50.22 R ₂ = -84.7780 D ₂ = 50.6222 r ₀ = ∞ d ₀ = 10.8389 r ₁ = -58.8881 d ₁ = 4.1879 n ₁ = 1.80518 ν ₁ = 25.42 r ₂ = 27.4220 d ₂ = 13.0167 n ₂ = 1.51633 ν ₂ = 64.14 r ₃ -46.5948 d ₃ = 0.25 _{r 4 = 55.6077 d 4 = 6.5016} n 3 = 1.71999 ν 3 = 50.22 r 5 = -181.8504 d 5 = 0.25 r 6 = 27.5660 d 6 = 8.8853 n 4 = 1.65844 ν 4 = 50.88 r 7 = 249.5378 d 7 = 26.4475 r _{8 = ∞ d 8 = 2.0000 n} 5 = 1.33304 ν 5 = 55.79 r 9 = ∞ f0 = 46.3284 f0 / f = 1.701 | r 1 / (n 1 -1) /f|×f0/f=4.57 | r 1 / (N ₁ −1) | /f0=1.58 WD / f = 1.026 | ν _t −ν ₀ | = 38.72

Example 3 f = 36.4, NA = 0.5, OH = 2.75 R ₀ = ∞ D ₀ = 111.7770 R ₁ = 309.9940 D ₁ = 6.7371 N ₁ = 1.58913 V ₁ = 61.14 R ₂ = -86.1104 D ₂ = 12.33853 _{r 0 = ∞ d 0 = 10.7420} r 1 = -40.0100 d 1 = 5.1000 n 1 = 1.84666 ν 1 = 23.78 r 2 = 48.0199 d 2 = 19.4592 n 2 = 1.51742 ν 2 = 52.43 r 3 = -40.6490 d 3 = 0.4000 _{r 4 = 207.9072 d 4 = 9.4994} n 3 = 1.65844 ν 3 = 50.88 r 5 = -91.5256 d 5 = 0.3000 r 6 = 42.2090 d 6 = 12.6000 n 4 = 1.65844 ν 4 = 50.88 r 7 = ∞ d 7 = 44.0000 r _{8 = ∞ d 8 = 2.0000 n} 5 = 1.33304 ν 5 = 55.79 r 9 = ∞ f0 = 64.1045 f0 / f = 1.761 | r 1 / (n 1 -1) /f|×f0/f=2.286 | r 1 / (N ₁ −1) | /f0=0.737 WD / f = 1.25 | ν _t −ν ₀ | = 28.65

However, R ₁ , R ₂ , ..., R ₀ , r ₁ , ...
.. is the radius of curvature of each surface of the field lens, condenser lens, etc., D ₁ , D ₂ , ..., d ₀ , d ₁ , ... Is the surface spacing of the field lens, condenser lens, etc.,
N ₁ , n ₁ , n ₂ , ... Are the refractive indices of the field lens and condenser lens for the d-line, V ₁ ,
ν ₁ , ν ₂ , ... Are Abbe numbers for the d-line of each lens of the field lens and the condenser lens. Again O
H is the height of the object (sample) on the sample surface illuminated by the condenser lens. Focal length f in these data,
The radius of curvature r ₁ , r _2, ... And other units of length are mm.

In the above-mentioned embodiments, Embodiment 1 has the structure as shown in FIG. 1, in which F is a field lens and C is a condenser lens of the present invention.

The condenser lens C of the present invention comprises, from the light source side (field lens F side), a first lens group G1 having a negative refractive power and a second lens group G2 having a positive refractive power.

Here, the field lens F is composed of a positive single lens and is arranged so as to project the image of the field stop at infinity. Therefore, the light between the field lens F and the condenser lens C becomes a parallel light flux. Therefore, by combining the field lens F and the condenser lens C, a single body serves as a condenser lens that focuses an infinite light flux. Also, the field lens F
At the same time, it also has the function of forming an image of the field stop near the sample surface.

The first lens group G of the condenser lens
Reference numeral 1 denotes a cemented negative meniscus lens having a concave surface facing the light source side, the second lens group G2 is composed of two positive single lenses, of which the light source side lenses (r _{4 to} r ₅ ) are biconvex lenses, The lenses (r _{6 to} r ₇ ) on the other sample side are the surfaces (r 6
₇ ) is a positive meniscus lens with a concave surface.

The front focal position of the condenser lens C is r ₀ between the field lens F and the condenser lens C in the drawings and data. An aperture stop, an optical element, an aperture, etc. can be installed in the vicinity of the front focal position.

Although a parallel light beam is formed between the field lens F and the condenser lens C, a good image can be obtained even if an optical element for differential interference is arranged there because of a small light beam diameter. .

Further, in FIG. 1, r _{8 to} r ₉ and n ₅ and ν ₅ in the data are aqueous solutions of the sample. In the case of an inverted microscope, it is assumed that a culture solution is put in a petri dish and the cultured cells are often observed, and therefore, a part between the cells and the condenser lens is covered with water. .

The second embodiment has a structure as shown in FIG. 2, which is substantially the same as that of the first embodiment shown in FIG.

The third embodiment is shown in FIG. 3, in which the second lens group G2 of the condenser lens C of the present invention has a biconvex lens on the light source side and a plano-convex lens with its plane facing the sample side on the sample side. The configuration is different from the first and second embodiments.

As shown in the data, the condenser lenses of Examples 1 to 3 have the above-mentioned conditions (1), (2),
All the conditions (3), (4), and (5) are satisfied.

The aberrations of the image of the field stop projected on the sample surface when the field lens and condenser lens of Examples 1, 2, and 3 are combined are as shown in FIGS. In these aberration diagrams, FIY is the height of the sample.

In Examples 1, 2, and 3 described above, the NA was 0.5.
Spherical aberration, axial chromatic aberration, etc., which is about 0.55, are well corrected.

The microscope condenser lens of the present invention has the constitution as described in detail above, and in addition to the lens system having the constitution described in the claims, the condenser lens as shown in each of the following items is also included in the present invention. Can achieve the purpose.

(1) A microscope condenser lens characterized by satisfying the following condition (3) in a lens system according to claim 2 of the invention. _{(3) 0.5 <| r 1} / (n 1 -1) | / f0 <2

(2) A microscope condenser lens characterized by satisfying the following condition (5) in the lens system described in claim 1, 2 or 3 or in the above item (1). (5) │ν ₁ -ν ₂ │> 25 where ν ₁ and ν ₂ are the Abbe numbers of the convex lens and the concave lens of the cemented negative meniscus lens, respectively.

(3) In the lens system according to claim 1, 2 or 3 of the claims, or (1) or (2), the second lens group is a biconvex lens in order from the light source side. A microscope condenser lens comprising a single positive meniscus lens having a concave surface facing the sample surface or a plano-convex single lens having a flat surface on the sample side.

[0073]

According to the present invention, a retrofocus type lens unit having a first lens unit having a negative power and a second lens unit having a positive power is used, whereby a long working distance is maintained while keeping the focal length short. Can realize a microscope condenser lens with a high numerical aperture. Further, since the light flux at the front focus position of the condenser lens is a parallel light flux and the light flux diameter is small, a good image can be obtained even when an optical element or an aperture is inserted at the front focus position and a microscope is performed. Also, because the chromatic aberration of the image of the field stop is corrected well,
The image of the field stop can be adjusted well.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a first embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a second embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a third embodiment of the present invention.

FIG. 4 is an aberration diagram of Example 1.

5 is an aberration diagram of Example 2. FIG.

6 is an aberration diagram of Example 3. FIG.

FIG. 7 is a diagram showing a configuration of an entire microscope illumination optical system.

FIG. 8 is a schematic diagram of a modulator for modulation contrast.

FIG. 9 is a schematic view of an aperture for modulation contrast.

Claims (3)

[Claims] 1. A first lens group consisting of a cemented negative meniscus lens having a concave surface facing the light source side and a second lens group consisting of a plurality of single positive lenses in this order from the light source side toward the sample side. A microscope condenser lens that satisfies the following condition (1). (1) 1 <f0 / f <1.8 where f0 is the focal length of the single lens closest to the sample, and f is the combined focal length of the first lens group and the second lens group. 2. A first lens group consisting of a cemented negative meniscus lens having a concave surface facing the light source side and a second lens group consisting of a plurality of single positive lenses in order from the light source side toward the sample side. A microscope condenser lens that satisfies the following condition (2). (2) 1.5 <| r ₁ / (n ₁ −1) / f | × f 0 /f<4.6 where r ₁ is the radius of curvature of the lens surface closest to the light source, and n ₁ is the radius closest to the light source. The refractive index of the lens, f0 is the focal length of the single lens closest to the sample, and f is the combined focal length of the first lens group and the second lens group. 3. The microscope condenser lens according to claim 1, which satisfies the following condition (4). (4) 1 <WD / f <2 where WD is the distance from the surface of the condenser lens closest to the sample to the sample.