JPH0476453B2 - - Google Patents

Description

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

<Prior Art> Most of the conventionally known objective lenses for microscopes are used in the visible region or infrared region.

This means that most optical glasses have a wavelength of 300nm.
This is because it cannot transmit light in the ultraviolet region or deep ultraviolet region with shorter wavelengths.

By the way, even if the numerical aperture (NA) is the same, as the wavelength becomes shorter, the resolution limit increases and more details can be observed. In order to obtain a large amount of information in response to changes in the optical properties of a sample, it is desired that the device can be used in the ultraviolet and deep ultraviolet regions.

Conventional objective lenses for microscopes have not adopted a light transmission configuration, but instead have adopted a reflection configuration using a reflecting mirror.

First conventional example Figure 5 is “LENS DESIGN FUNDAMETALS” by RUDOLF KINGSLAKE.
(ACADEMIC PRESS 1978) This is the microscope objective lens shown on page 333, and the reflection configuration described above is adopted.

That is, a first reflecting mirror 02 having an opening 01,
It is composed of a second reflecting mirror 03 that reflects light incident from the aperture 01 to a first reflecting mirror 02.

According to this first conventional example, two reflecting mirrors 02,
Since only 03 is used, there is no chromatic aberration, and if there are no problems with the reflectance of mirrors 02 and 03, it can be used even in the ultraviolet region, and has excellent performance.

However, an objective lens with such a configuration has drawbacks such as a decrease in the amount of light at the periphery of the field of view and a change in magnification due to the unevenness of the sample because it cannot be made telecentric, and the light beam at the center is blocked. This has the drawback that the amount of light decreases due to the turret-like structure, and the resolution decreases due to diffraction.Furthermore, if you try to change the magnification by switching multiple objective lenses arranged in a turret type, the pupil will change between the multiple objective lenses. Just as the diameter and parfocal distance cannot be unified at the same time, there is a drawback of a low degree of freedom in design.

By the way, fluorite, quartz, lithium fluoride (LiF), barium fluoride (BaF ₂ ), and sodium chloride (NaCl) are known as optical materials that can transmit light in the ultraviolet and deep ultraviolet regions. Examples of microscope objective lenses constructed using these materials are as follows.

2nd conventional example Figure 6 shows “APPLIED” supervised by KINGSLAKE.
OPTICS AND OPTICAL ENGINEERING”
(ACADEMIC PRESS1965) A catadioptric type microscope objective lens described on page 173 includes a first lens 04a made of quartz with negative power, and a lens with positive power cemented to this first lens 04a. A refractive lens system 04 consisting of a second lens 04b made of fluorite and a third lens 04c of negative power made of fluorite adjacent to the second lens 04b.
, a first reflecting mirror 05, and a second reflecting mirror 05 having an aperture 06.
, and a fourth lens 08 made of quartz that transmits the light passing through the aperture 06.

Third conventional example Figure 7 shows the optical technology contact magazine Vol. 25 No. 2.
(February 1987) P. 137 shows the objective lens for a microscope, and the first lens 09 made of fluorite,
The concave lens 010a made of quartz is replaced with the convex lens 0 made of fluorite.
2nd lens 0 sandwiched and bonded with 10b and 010c
10, and like the second lens 010, a concave lens 011a made of quartz is replaced with a convex lens 011b made of fluorite,
It is composed of a third lens 011 which is sandwiched and cemented by lenses 011c and 011c.

<Problems to be Solved by the Invention> However, the second and third conventional examples described above each have the following drawbacks.

Disadvantages of the second conventional example: Although the first lens 04a made of quartz and the second lens 04b made of fluorite are bonded together, there is currently no adhesive that can transmit light with wavelengths in the ultraviolet region or deep ultraviolet region. Therefore, the bonding surface must be an optical contact so that there is no reflection at the bonding surface, and this has the drawback of requiring high precision in processing the bonding surface, resulting in high costs.

Furthermore, since the central light beam is blocked, there is a drawback that both the resolution and the amount of light are reduced, similar to the first conventional example described above.

Disadvantages of the third conventional example The second lens 010 and the third lens 011 are each made of concave lenses 010a, 011a made of quartz and two convex lenses 010b, 010c, 01 made of fluorite.
1b, 011c, and the convex lenses 010b, 010c, 0 made of fluorite correct the chromatic aberration that cannot be achieved with only the concave lenses 010a, 011a made of quartz.
11b, 011c, but similarly to the second conventional example, concave lenses 010a, 011a made of quartz and two convex lenses 010b, 010c, 011 made of fluorite are used.
The bonding surfaces between the bonding surfaces b and 011c must be optical contacts, which requires high accuracy in processing the bonding surfaces, resulting in high costs.

The present invention has been made in view of these circumstances, and uses a combination of a quartz lens and a fluorite lens to correct chromatic aberration and improve the performance in the ultraviolet and deep ultraviolet regions without adopting a reflective configuration. The purpose of the present invention is to provide a microscope objective lens that can be used in a wide range of areas at a low cost.

<Means for Solving the Problems> In order to achieve the above object, the microscope objective lens of the present invention includes a first biconcave lens made of quartz or a negative lens made of quartz with the convex side facing the object side. Consisting of a meniscus lens of high power and a first biconvex lens made of quartz or fluorite disposed on the opposite side of the object side of the first biconcave lens or meniscus lens with a space using air as a medium. a first group lens made of quartz, and a second group lens made of quartz disposed on the opposite side of the object side of the first group lens with a space using air as a medium.
and a second biconvex lens made of fluorite, which is disposed on the opposite side of the object side of the second biconcave lens with a space in which air is used as a medium. and the following conditional expressions φ ₁ >0, φ ₂ <0, 0.35φ<φ ₂ <0.9φ, 1.05φ<(φ ₁ +φ ₂ )/φ<1.15Lφ 1.45<|φ ₁₊ /φ _{1 -} ｜＜1.65 0.8＜｜φ ₂₊ /φ _2- ｜＜1.1 However, φ ₁ : Power of 1st group lens φ ₂ : Power of 2nd group lens φ : Power of entire system L : Lens system from object plane Distance to the image-side focal point φ ₁₊ : Power of the positive lens forming the first group lens φ _1- : Power of the negative lens forming the first group lens φ ₂₊ : Power of the second lens forming the second group lens The power of the positive lens φ _2- is characterized by being configured to satisfy the power of the second negative lens constituting the second lens group.

The power φ ₂ of the second group lens is the power φ of the entire system
It is set to be less than 0.9 times and more than 0.35 times. This is because when the magnification is 0.9 times or more, the working distance becomes small, and conversely, when the magnification is 0.35 times or less, the total length of the lens system becomes excessive compared to the focal length.

The value obtained by dividing the sum of the power φ ₁ of the first group lens and the power φ ₂ of the second group lens by the power φ of the entire system (φ ₁
+φ ₂ )/φ is the distance L from the object plane to the image-side focal point of the lens system multiplied by the power of the entire system φ.
It is set to be less than 1.15 times and more than 1.05 times. When the magnification is 1.15 times or more, the Petzval sum becomes large and the curvature of the field becomes too large, and the total length of the lens system becomes too large compared to the focal length. This is because it becomes difficult to carry.

The positive lens power φ ₁₊ of the first biconvex lens made of quartz or fluorite forming the first group lens and the first biconcave lens made of quartz or a meniscus lens with negative power forming the first group lens Absolute value of the ratio of the negative lens power φ _1- by |φ ₁₊ /φ _1- |
is set to be less than 1.65 and greater than 1.45. If it falls outside this range, it becomes difficult to correct chromatic aberration, and if it exceeds 1.65, spherical aberration will not be corrected enough, and if it falls below 1.45, it will be overcorrected and the curvature of the field will increase. It is.

Also, the absolute value of the ratio between the power φ ₂₊ of the second positive lens made of fluorite that makes up the second group lens and the power φ _2- of the second negative lens made of quartz that makes up the second group lens. |φ ₂₊ /φ ₂₋ | is set to be less than 1.1 and greater than 0.8. Outside this range,
This is because it becomes difficult to correct chromatic aberration, and if the value exceeds 1.1, the correction of spherical aberration will be insufficient, while if it becomes less than 0.8, it will be overcorrected and the curvature of the field will become large.

In the above absolute values, there is a difference in the range between the first group lens and the second group lens because the height of the ray passing through the first group lens on the object side is lower than the height of the ray through the second group lens, and the aberration correction This is because it is necessary to change the state, and it is better to correct aberrations by combining the first group lens and the second group lens.

As the positive lens with positive power in the first group lens, it is better to use a convex lens made of fluorite in order to correct chromatic aberration.
Since the group lens has a low ray height and has a small effect on chromatic aberration, it is not necessarily necessary to correct chromatic aberration, and a convex lens made of quartz may be used instead of made of fluorite, which is difficult to process.

<Function> According to the above configuration, the basic idea is to separate the cemented surfaces of the Lister type, which is the basic type of low-magnification objective lenses, and the first group lens and the second group lens are separated. Both are made of quartz, fluorite, or a combination of both, and
A first biconcave lens made of quartz or a meniscus lens made of quartz and a first biconvex lens made of quartz or fluorite in the first group lens, the first biconvex lens and a second biconvex lens made of quartz in the second group lens. By providing an air gap between the biconcave lens and the second biconvex lens made of fluorite in the second lens group, and eliminating the need for adhesive, ultraviolet rays can be removed. By making both the first group lens and the second group lens a combination of a negative lens with negative power and a positive lens with positive power, By making at least the second group lens a combination of a second biconcave lens made of quartz and a second biconvex lens made of fluorite, chromatic aberration can be corrected.

<Example> Next, an example of the present invention will be described using the drawings.

The microscope objective lenses of both the first and second examples below have specifications of a numerical aperture (NA) of 0.083, an image size of 10.6, and an imaging magnification of -10 times.

In addition, when configuring a microscope, we use a so-called infinity correction system, considering that it will be used with epi-illumination that illuminates the sample through the objective lens. It is assumed that it will be used in combination with an image lens.

[Imaging lens configuration]

The imaging lens is composed of three types: a first lens, a second lens, and a third lens, and the materials of each lens,
Radius of curvature r ₁ of the surface of the first lens facing away from the second lens, radius of curvature of the surface facing the second lens
r ₂ , radius of curvature r ₃ of the surface of the second lens facing the first lens side, radius of curvature r ₄ of the surface facing the third lens side,
Radius of curvature of the surface of the third lens facing the second lens side
r ₅ and the radius of curvature r ₆ of the surface facing away from the second lens, the center thickness d ₁ of the first lens, and the distance between the surfaces of the first lens and the second lens on the optical axis. d ₁₂ , the center thickness of the second lens d ₂ , the distance between the second lens and the third lens on the optical axis d ₂₃ , and
The center thickness _d3 of each third lens is set as follows.

[Radius of curvature, lens center thickness, lens surface spacing, material]

r ₁ = 23.000 d ₁ = 7.00 Fluorite r ₂ = -31.540 d ₁₂ = 2.75 r ₃ = -23.180 d 2 = 7.00 Quartz r ₄ = 33.710 d ₂₃ = 86.40 _{r 5} = -10.530 d ₃ = 7.00 Quartz made r ₆ = −13.488 This imaging lens is also composed of a combination of quartz and fluorite lenses, and the first
lens and second lens, and second lens and third lens
Each of the lenses is arranged separated by a space using air as a medium.

First Embodiment FIG. 1 is a layout diagram of the objective lens of the first embodiment. is composed of a second lens group 2 arranged on the opposite side with a space using air as a medium.

The first group lens 1 is a negative power meniscus lens 3 made of quartz and whose convex side faces the object side.
and a first biconvex lens 4 made of quartz, which is placed on the opposite side of the meniscus lens 3 from the object side with a space in which air is used as a medium.

Further, the second lens group 2 includes a biconcave lens (second concave lens) 5 made of quartz, and a biconcave lens 5 made of quartz.
A second biconvex lens 6 made of fluorite is placed on the side opposite to the object side of the lens 6 with a space in which air is used as a medium.

The radius of curvature R ₁ of the surface of the meniscus lens 3 facing the object side, the radius of curvature R ₂ of the surface facing the first biconvex lens 4 side, and the radius of curvature R 2 of the surface of the first biconvex lens 4 facing the meniscus lens 3 side. radius of curvature R ₃ of the surface facing the second group lens 2 side, radius of curvature R ₄ of the surface facing the second group lens 2 side,
The radius of curvature R 5 of the surface facing the first group lens 1 side of the biconcave lens ₅ constituting the group lens 2, the radius of curvature R 6 of the surface facing the second biconvex lens 6 side, and the radius of curvature R ₆ of the surface facing the second biconvex lens 6 side. The radius of curvature R ₇ of the surface facing the biconcave lens 5 side, the radius of curvature R ₈ of the surface facing the opposite side from the biconcave lens 5, the center thickness D ₁ of the meniscus lens 3, and the meniscus lens 3. Surface spacing on the optical axis with the first biconvex lens 4
D ₁₂ , center thickness of the first biconvex lens 4 D ₂ , distance between the first biconvex lens 4 and the biconcave lens 5 forming the second lens group 2 on the optical axis D ₂₃ , center of the biconcave lens 5 Thickness D ₃ , biconcave lens 5 and second biconvex lens 6
The surface distance D ₃₄ on the optical axis and the center thickness D ₄ of the second biconvex lens 6 are set as follows.

[Radius of curvature, lens center thickness, lens surface spacing, material]

R ₁ = 17.430 D ₁ = 3.50 Quartz R ₂ = 5.200 D ₁₂ = 0.10 R ₃ = 22.800 D ₂ = 1.00 Quartz R ₄ = -7.260 D ₂₃ = 20.50 R ₅ = -17.550 D ₃ = 0.90 Quartz R ₆ = 5.300 D ₃₄ = 0.20 R ₇ = 5.700 D ₄ = 3.60 Fluorite R ₈ = -7.600 In addition, in the above objective lens, the power φ ₁ of the first group lens 1, the power φ 2 of the second group lens 2, the power φ ₂ of the second group lens 2, The power φ _1- of the meniscus lens 3 forming the first group lens 1 , the power φ ₁₊ of the first biconvex lens 4 forming the first group lens 1 , the power φ of the biconcave lens 5 forming the second group lens 2 _2- , the power φ ₂₊ of the second biconvex lens 6 constituting the second group lens 2, the power φ of the entire system, and the distance L from the object plane to the image-side focal point of the lens system are as follows. be.

φ ₁ =0.025453 φ ₂ =0.029426 φ _1- =−0.059710 φ ₁₊ =0.087720 φ _2- =0.121523 φ ₂₊ =0.127712 φ=0.033333 L=45 Based on the above values, 0.35φ=0.011 667 0.9φ=0.030000 , 0.35φ<φ ₂ <0.9φ.

Furthermore, (φ ₁ +φ ₂ )/φ=1.646370 1.05Lφ=1.575000 1.15Lφ=1.725000, and it is clear that 1.05Lφ<(φ ₁ + _φ2 )/φ<1.15Lφ is satisfied.

Also, |φ ₁₊ /φ _1- |=1.469101, and it is clear that 1.45<|φ ₁₊ /φ _1- |<1.65 is satisfied.

Also, |φ ₂₊ /φ _2- |=1.050929, which clearly satisfies 0.8<|φ ₂₊ /φ _2- |<1.1.

Due to the spherical aberration of the above objective lens, the wavelength
298.06nm (indicated by code 1), 202.54nm (indicated by code 2)
), 398.84nm (indicated by code 3), 253,70n
When calculated for light of m (indicated by code 4),
The diagram shown in FIG. 2a was obtained.

Further, when the sine condition of the objective lens was determined for the wavelengths of light indicated by the same reference numerals 1 to 4 as described above, the diagram shown in FIG. 2b was obtained.

In addition, regarding the astigmatism of the objective lens, the sagittal image plane (indicated by the symbol S) and the meridional image surface (indicated by the symbol M) were obtained.
A diagram shown in FIG. 2c was obtained.

Further, when the distortion aberration of the objective lens was determined, the diagram shown in d of FIG. 2 was obtained.

As a result, it is possible to reduce aberrations for both ultraviolet and far ultraviolet light due to spherical aberration and sine conditions, and moreover, it is possible to reduce aberrations for both ultraviolet and far ultraviolet light (codes 1, 2, and 4) with wavelengths shorter than 300 nm. ), it has less aberrations as a whole than for light in the ultraviolet region with a wavelength longer than 300 nm (code 3), and it is clear that it can be used well in the far ultraviolet region, and it also reduces astigmatism and distortion. It is clear that each aberration can be reduced.

Second Embodiment FIG. 3 is a layout diagram of an objective lens according to a second embodiment, in which the microscope objective lens includes a first lens group 11 located on the object side, and It is composed of a second lens group 12 arranged on the opposite side with a space using air as a medium.

The first group lens 11 includes a negative power meniscus lens 13 made of quartz with a convex side facing the object side, and a space using air as a medium on the opposite side of the meniscus lens 13 from the object side. and a first biconvex lens 14 made of fluorite.

The second lens group 12 includes a biconcave lens (second concave lens) 15 made of quartz, and a fluorite crystal disposed on the opposite side of the biconcave lens 15 from the object side with a space using air as a medium. It is composed of a second biconvex lens 16 made of.

The radius of curvature R ₁ of the surface of the meniscus lens 13 facing the object side, the radius of curvature R 2 of the surface facing the first biconvex lens 14 side, and the radius of curvature R ₂ of the surface facing the first biconvex lens 14 side.
The radius of curvature of the surface facing the meniscus lens 13 side of
R ₃ , radius of curvature of the surface facing the second group lens 12 side
R ₄ , biconcave lens 1 constituting the second group lens 12
The radius of curvature of the surface facing the first group lens 11 of No. 5
R ₅ , radius of curvature R ₆ of the surface facing the second biconvex lens 16 side, radius of curvature R ₇ of the surface of the second biconvex lens 16 facing the biconcave lens 15 side, and the biconcave lens 15 is on the opposite side. Radius of curvature R of the surface facing ₈
and the center thickness D ₁ of the meniscus lens 13, the surface spacing D ₁₂ on the optical axis between the meniscus lens 13 and the first biconvex lens 14, the center thickness D ₂ of the first biconvex lens 14, and the first biconvex lens 14, respectively. Double convex lens 14
and the biconcave lens 15 constituting the second lens group 12 on the optical axis; the center thickness D ₃ of the biconcave lens 15; the biconcave lens ₁₅ and the second biconvex lens 16.
The surface distance D ₃₄ on the optical axis and the center thickness D ₄ of the second biconvex lens 16 are set as follows.

[Radius of curvature, lens center thickness, distance between lens surfaces, material] R ₁ = 49.692 D ₁ = 3.00 Quartz R ₂ = 6.062 D ₁₂ = 0.10 R ₃ = 6.062 D ₂ = 5.00 Fluorite R ₄ = -11.980 D ₂₃ = 17.75 R ₅ = -12.992 D ₃ = 1.00 R ₆ made of quartz = 6.328 D ₃₄ = 0.45 R ₇ = 7.288 D ₄ = 6.00 R ₈ made of fluorite = -9.253 In addition, in the above objective lens, the first group lens 11 power φ ₁ , power φ ₂ of the second group lens 12,
Meniscus lens 1 constituting the first lens group 11
3, the power φ _1- of the first biconvex lens 14 constituting the first lens group 11, the power φ ₁₊ of the biconcave lens 15 constituting the second group lens 12, the power φ _2- of the biconcave lens 15 constituting the second group lens 12, The second biconvex lens 16
The power φ ₂₊ of , the power φ of the entire system, and the distance L from the object plane to the image-side focal point of the lens system are as follows.

φ ₁ =0.041662 φ ₂ =0.013444 φ _1- =−0.069139 φ ₁₊ =0.103115 φ _2- =−0.116715 φ ₂₊ =0.098827 φ=0.033333 L=45 Based on the above values, 0.35φ=0.01 1667 0.9φ=0.030000 It is clear that 0.35φ<φ ₂ <0.9φ is satisfied.

Further, (φ ₁ +φ ₂ )/φ=1.653180 1.05Lφ=1.575000 1.15Lφ=1.725000, and it is clear that 1.05Lφ<(φ ₁ + _φ2 )/φ<1.15Lφ is satisfied.

Also, |φ ₁₊ /φ _1- |=1.491416, which clearly satisfies 1.45<φ ₂₊ /φ _2- |<1.65.

Also, |φ ₂₊ /φ _2- |=0.846738, which clearly satisfies 0.8<|φ ₂₊ /φ _2- |<1.1.

Due to the spherical aberration of the above objective lens, the wavelength
298.06nm (indicated by code 1), 202.54nm (indicated by code 2)
), 398.84nm (indicated by code 3), 253.70nm
(indicated by reference numeral 4), the figure shown in a of FIG. 4 was obtained.

Further, the sine condition of the objective lens was determined for the wavelengths of light indicated by the same reference numerals 1 to 4 as described above, and the diagram shown in FIG. 4b was obtained.

In addition, regarding the astigmatism of the objective lens, the sagittal image plane (indicated by the symbol S) and the meridional image surface (indicated by the symbol M) were obtained.
A diagram shown in FIG. 4c was obtained.

Further, when the distortion aberration of the objective lens was determined, the diagram shown in d of FIG. 4 was obtained.

As a result, it is possible to reduce aberrations for both ultraviolet and far ultraviolet light due to spherical aberration and sine conditions, and moreover, it is possible to reduce aberrations for both ultraviolet and far ultraviolet light (codes 1, 2, and 4) with wavelengths shorter than 300 nm. ), it has less aberrations as a whole than for light in the ultraviolet region with a wavelength longer than 300 nm (code 3), and it is clear that it can be used well in the far ultraviolet region, and it also reduces astigmatism and distortion. It is clear that each aberration can be reduced.

In the present invention, a first biconcave lens made of quartz may be used instead of the negative power meniscus lenses 3 and 13 in the first group lenses 1 and 11.

Then, the power φ ₁ of the first group lens, the power φ ₂ of the second group lens, and the power φ _1- of the first biconcave lens made of quartz or the negative power meniscus lens made of quartz constituting the first group lens. , power φ ₁₊ of the first biconvex lens made of quartz or fluorite forming the first group lens, power φ ₂₋ of the biconcave quartz lens forming the second group lens, For the power φ ₂₊ of the biconvex lens made of fluorite, the power φ ₂ of the second group lens, the power φ of the entire system, and the distance L from the object plane to the image-side focal point of the lens system, the following conditional expression is satisfied. φ ₁ >0, φ ₂ >0, 0.35φ<φ ₂ <0.9φ, 1.05Lφ<(φ ₁ +φ ₂ )/φ<1.15Lφ 1.45<|φ ₁₊ /φ _1- |<1.65 0.8<|φ A microscope objective that can reduce spherical aberration, sine condition, astigmatism, and distortion when satisfying ₂₊ /φ _2- |<1.1, and can be used well in the ultraviolet and far ultraviolet regions. It was speculated that it could be used to form a lens.

<Effects of the Invention> As explained above, according to the microscope objective lens of the present invention, the first group lens and the second group lens are made of only quartz or fluorite that can transmit light in the ultraviolet region or deep ultraviolet region. constitutes either of the above, and
In the first group lens, a first biconcave lens made of quartz or a negative power meniscus lens made of quartz, a first biconvex lens made of fluorite or quartz, a first group lens, a second group lens, and a second group lens. A second biconcave lens made of quartz and a second lens made of fluorite in the second group lens.
Since the space between each of the biconvex lenses is made using air as a medium and no adhesive is used, it is possible to provide a microscope objective lens that can be used well in the ultraviolet region and deep ultraviolet region.

Moreover, not only does it not use adhesive, but it also eliminates the need for optical contact on the bonding surface.
Precision is not required for machining the joint surfaces, and construction can be made at low cost.

Moreover, since the second group lens is composed of a second biconcave lens made of quartz having negative power and a second biconvex lens made of fluorite having positive power,
A good image can be obtained by correcting both chromatic aberration and spherical aberration.

In addition, since a reflective configuration is not adopted and the central light beam is not blocked, light at the center of the field of view can be taken in well, the resolution and the amount of light can be increased, and a clear image can be obtained.

[Brief explanation of the drawing]

The drawings show an embodiment of the objective lens for a microscope according to the present invention. FIG. 1 is a layout diagram of the lens of the first embodiment, and a, b, c, and d of FIG. 2 are the arrangement of the lens of the first embodiment. Spherical aberration diagram, sine condition diagram, astigmatism diagram and distortion aberration diagram; FIG. 3 is a lens arrangement diagram of the second embodiment; a, b, c, and d in FIG. 4 are diagrams of the second embodiment. Spherical aberration diagram, sine condition diagram, astigmatism diagram and distortion aberration diagram, FIG. 5 is a layout diagram of a reflecting mirror in the first conventional example, and FIG. 6 is a layout diagram of a lens and a reflecting mirror in a second conventional example. , FIG. 7 is a layout diagram of lenses of a third conventional example. 1, 11...first group lens, 2,12...second lens
Group lens, 3, 13...meniscus lens, 4,
14...First biconvex lens, 5, 15... Second biconcave lens, 6, 16... Second biconvex lens.

Claims (1)

[Scope of Claims] 1. A first biconcave lens made of quartz or a negative power meniscus lens made of quartz with a convex side facing toward the object side, and the object side of the first biconcave lens or meniscus lens is opposite to the object side. a first lens group consisting of a first biconvex lens made of quartz or fluorite disposed with a space in which air is used as a medium on the side; a second biconcave lens made of quartz disposed across a space using air as a medium; and a fluorite disposed on a side opposite to the object side of the second biconcave lens across a space using air as a medium. and _a second lens group consisting of a _second double _{- convex} lens made of +φ ₂ )／φ＜1.15Lφ 1.45＜| ₁₊ /φ _1- |＜1.65 0.8＜｜φ ₂₊ /φ _2- |＜1.1 However, φ ₁ : Power of the first group lens φ ₂ : Second group Power of the lens φ: Power of the entire system L: Distance from the object plane to the image-side focal point of the lens system φ ₁₊ : Power of the positive lens that makes up the first group lens φ _1- : Negative lens that makes up the first group lens A microscope objective lens characterized in that it is configured to satisfy the power of the lens φ ₂₊ : the power of the positive lens constituting the second group lens φ ₂₋ : the power of the negative lens constituting the second group lens.