JPH01319720A - Objective lens for microscope - Google Patents

Abstract

PURPOSE:To obtain the objective lens fro microscope which can be used in a far UV region by constituting the lens of a 1st group lens disposed on an object side and the 2nd group lens disposed apart a space on the opposite side thereof. CONSTITUTION:The 1st group lens is constituted of a meniscus lens of a negative power made of quartz the convex face side of which is directed to an object and a biconvex lens 4 made of quartz on the opposite side and the 2nd group lens 2 is constituted of a biconcave lens made of quartz and a biconvex lens 6 made of fluorite. This objective lens is so constituted as to satisfy the condition equations phi1>0, phi2>0, 0.35phi<phi2<0.9phi, 1.05Lphi<(phi1+phi2)/phi<1.15Lphi, 1.45<¦phi1+/phi1-¦<1.65, 0.8<¦phi2+/phi2-¦<1.1 where phi1: the power of the 1st group lens, phi2: the power of the 2nd group lens, phi: the power of the entire system, L: the distance from the object face to the image side focus of the lens system, phi1+: positive lens power of the 1st group, phi2+: the positive lens power of the 2nd group, phi2-: the negative lens power of the 2nd group.

Description

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

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

This is because most optical glasses cannot transmit light in the ultraviolet region or deep ultraviolet region with wavelengths shorter than 300 nm.

By the way, even if the numerical aperture (NA) is the same, the shorter the wavelength, the higher the resolution limit and the more details can be observed.
It can also be used in the ultraviolet and deep ultraviolet regions to obtain a lot of information in response to changes in the optical properties of the sample, such as by irradiating the sample with ultraviolet light and observing the ultraviolet light or fluorescence emitted from the sample. It is hoped that it will be possible.

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

1 Saturday Conventional■ Figure 5 is "LE" written by RUDOLF KINGSLAKE.
NS DESIGN FUNDAMENTALS” (A
CADEMIC PRESS 1978) P, 333
This is the objective lens for a microscope shown in , which employs the above-mentioned reflection configuration.

That is, a first reflecting mirror 02 having an aperture 01;
and a second reflecting mirror 03 that reflects the light incident thereon to the first reflecting mirror 02.

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

However, an objective lens with such a configuration has disadvantages 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 used as a telescopic link, and the light beam at the center is blocked. This has the disadvantage that the amount of light decreases due to the presence of light, and the resolution decreases due to diffraction.
Furthermore, if you try to change the magnification by switching multiple objective lenses arranged in a turret style, there is a drawback due to the design, such as the inability to unify the pupil diameter and parfocal distance among the multiple objective lenses at the same time. The disadvantage was that the degree of freedom was low.

Incidentally, fluorite, quartz, lithium fluoride (LiF), barium fluoride (BaFz), and sodium chloride (NaCj) are known as optical materials that can transmit light in the ultraviolet and deep ultraviolet regions. Examples of microscope objective lenses constructed using materials include the following.

11 Conventional Flame Figure 6 is supervised by KTNGSLAXE ``APPLIED''
0PTIC5AND 0PTICAL ENGINEE
RING I[['“ (ACADEMTCPRES
S1965) P, 173 shows a catadioptric type microscope objective lens, and a negative power quartz lens 04a.
a second lens 04b made of positive power fluorite bonded to;
and a refractive lens system 04 consisting of a third lens 04c made of fluorite with a negative power and adjacent to the second lens 04b;
A first reflecting mirror 05 and a second reflecting mirror 0 having an aperture 06
7 and a fourth lens 08 made of quartz that transmits the light passing through the aperture 06.

[No.]" CE box Fig. 7 is Photonic Technology] Contact Magazine Vol. 25 No.
2 (February 1987), P, 137, the fourth lens 08 made of fluorite,
The concave lens 010a made of quartz is replaced with the convex lens 010b made of fluorite.
, 010c and a concave lens 01la made of quartz and a convex lens 01 l b 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.

A second lens 010 made of quartz and a second lens 04b made of fluorite are placed at the tip of the point.
However, as there is currently no adhesive that can transmit light in the ultraviolet and deep ultraviolet wavelengths, the bonding surface must be an optical contact to prevent reflections on the bonding surface. This method has the drawback of requiring high precision in machining the joint surfaces, making it expensive.

Further, 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.

The second lens 010 and the third lens 011 each consist of concave lenses 0IOa, 01la made of quartz and two convex lenses 010b, 010c, 011b, 01lc made of fluorite. Convex lens 010b made of fluorite corrects chromatic aberration that cannot be achieved with 010a and 01la alone.
010c, 011b, 01lc, but as in the second conventional example, concave lenses 010a, 01la made of quartz and two convex lenses 010b, 010c, 011b made of fluorite are used. 01lc
The bonding surfaces between each must be optically contacted, which has the disadvantage of requiring high precision in machining the bonding surfaces, making them expensive.

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. The first
A group lens, a second biconcave lens made of quartz disposed on the opposite side from the object side of the first group lens across a space using air as a medium, and an object side of the second biconcave lens. It is composed of a second lens group made up of a second biconvex lens made of fluorite placed on the opposite side with a space in which air is used as a medium, and the following conditional formula % formula % φ, : 1st Group lens power φ! : Power of the second group lens φ : Power of the entire system L : Distance from the object plane to the image-side focal point of the lens system φ1. :Power of the positive lens forming the first group lens φ1-:Power of the negative lens forming the first group lens φ0. : The power of the second positive lens constituting the second lens group; and the power of the second negative lens constituting the second group lens.

The power φ2 of the second group lens is 0.9 of the power φ of the entire system.
It is set to be less than 0.35 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.

Value obtained by dividing the sum of the power φ1 of the first lens group and the power φ of the 29th lens by the power φ of the entire system (φ8 + φ8)/φ
is less than 1.15 times the distance from the object plane to the image-side focal point of the lens system multiplied by the power of the entire system, and 1
．． It is set to exceed 0.05 times. If it 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 excessive compared to the focal length. Conversely, if it becomes 1.05 times or less, the telecentering This is because it becomes difficult to provide drink characteristics.

The power of the positive lens by the first biconvex lens made of quartz or fluorite constituting the first group lens is φ1. The absolute value lφ1°/φ1-1 of the ratio of the power φ1− of the negative lens formed by the first biconcave lens made of quartz or the meniscus lens with negative power constituting the first group lens is less than 1.65, Moreover, it is set to exceed 1.45. Outside this range, it becomes difficult to correct chromatic aberration, and 1.6
If the value is 5 or more, the correction of spherical aberration will be insufficient, and conversely, 1.
This is because if the value is less than 45, overcorrection will occur and the curvature of the field will become large.

Further, the power of the second positive lens made of fluorite constituting the second group lens is φ2. and a second lens made of quartz that constitutes the second lens group.
The absolute value of the ratio of the power of the negative lens to φ2- is 1φ2°/φ
, -1 is set to be less than 1.1 and greater than 0.8". Outside this range, it becomes difficult to correct chromatic aberration, and when it exceeds 1.1, spherical aberration This is because if the correction is insufficient and, conversely, the angle is less than 0°8, the correction will be excessive 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 a 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, but in the first group lens close to the object side, the ray height is low and chromatic aberration Since the effect on the lens is small, 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.

<Operation> 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 the first lens in the first group lens is made of quartz.
A biconcave lens or a meniscus lens made of quartz, a first biconvex lens made of quartz or fluorite, the first biconvex lens and a second biconcave lens made of quartz in the second lens group,
And, by providing an air gap between the second biconcave lens and the second biconvex lens made of fluorite in the second lens group, and eliminating the need for adhesive, it is possible to It can transmit light, and 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, spherical aberration can be corrected. , 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, embodiments of the present invention will be described using the drawings.

Both of the following microscope objective lenses in the first and second examples have a numerical aperture (NA) of 0.083 and an image size of 1.
0.6, and the imaging magnification is 110 times.

In addition, when constructing a microscope, consider using it with epi-illumination that illuminates the sample through the objective lens.
This is a so-called infinity correction system, and it is assumed that the objective lens does not form an image alone, but is used in combination with, for example, the following imaging lens.

[Imaging lens configuration]

The imaging lens is composed of three types of lenses: a first lens, a second lens, and a third lens. radius of curvature rz of the surface facing the second lens, radius of curvature r3 of the surface facing the second lens side of the second lens, radius of curvature ra of the surface facing the third lens side, surface of the third lens facing the second lens side radius of curvature r5, and radius of curvature r6 of the surface facing away from the second lens, respectively, the center thickness dl of the first lun, and the interplanar distance d1 on the optical axis between the second lens and the second lens. , the center thickness d2 of the second lens, the interplanar distance d0 between the second lens and the third lens on the optical axis, and the center thickness d of the third lens are set as follows.

[Radius of curvature, lens center thickness, lens surface spacing, material] r,
--13,488 This imaging lens is also composed of a combination of lenses made of quartz and fluorite, and the first lens and the second lens, and the second lens and the third lens, are made of air. They are placed across a space that serves as a medium.

Presentation 1 Figure 1 is a layout diagram of the objective lens of the first embodiment.
and a second lens group 2 disposed on the opposite side of the object side of the first lens group 1 with a space using air as a medium.

The first group lens 1 includes a negative power meniscus lens 3 made of quartz whose convex surface is aligned with the object side, and a space using air as a medium on the opposite side of the meniscus lens 3 from the object side. A first biconvex lens 4 made of quartz is arranged.

The second group lens 2 includes a biconcave lens (second concave lens) 5 made of quartz, and a fluorite crystal disposed on the opposite side of the biconcave lens 5 from the object side with a space using air as a medium. It is composed of a second biconvex lens 6 made of

The radius of curvature R1 of the surface of the meniscus lens 3 facing the object side, the radius of curvature Rt of the surface facing the first biconvex lens 4 side, and the radius of curvature of the surface of the first biconvex lens 4 facing the meniscus lens 3 side. radius R3, radius of curvature R4 of the surface facing the second group lens 2, biconcave lens 5 constituting the second group lens 2;
radius of curvature RS of the surface facing the first group lens 1 side, radius of curvature R8 of the surface facing the second biconvex lens 6 side, curvature of the surface of the second biconvex lens 6 facing the biconcave lens 5 side. Radius R
1 and the radius of curvature R6 of the surface facing away from the biconcave lens 5, the center thickness D+ of the meniscus lens 3, and the distance between the surfaces of the meniscus lens 3 and the first biconvex lens 4 on the optical axis. DI□, center thickness Dt of the first biconvex lens 4, surface distance Dt3 on the optical axis between the first biconvex lens 4 and the biconcave lens 5 constituting the second lens group 2, center thickness Ds of the biconcave lens 5 , a biconcave lens 5 and a second biconvex lens 6
The interplanar distance D34 on the optical axis and the center thickness D4 of the second biconvex lens 6 are set as follows.

[Radius of curvature, lens center thickness, lens surface spacing, material] D3
=0.90 Nanao fissure R, =-7,60
0 In addition, in the above objective lens, the power φ1 of the first group lens 1, the power φ2 of the second group lens 2, and the power φ2 of the first group lens 1
The power φ of the meniscus lens 3 constituting the -1 power φl of the first biconvex lens 4 constituting the first group lens 1 and the power φ2 of the biconcave lens 5 constituting the second group lens 2
-1 The power φ20 of the second biconvex lens 6 constituting the second group lens 2, the power φ of the entire system, and the distance ML from the object plane to the image-side focal point of the lens system are as follows.

φ, =0.025453 φ, -0,02
9426φ, -1=-0,059710φ1. Ta 0.0
87720φz-=-0,121523φ2. Mi0.
127712φ -0,033333L=45 Based on the above values, 0.35φ=0.011667 0.9 φ=0.030000, which clearly satisfies 0.35φ<0.9φ .

Also, (φ1+φ2)/φ=1.6463701.05Lφ=
1.575000 1.15Lφ=1.725000, 1.05Lφ<(φ1+φ2)/φ<1.15
It is clear that Lφ is satisfied.

Also, 1φ. /φ+-1-1,469101, which is 1.4
5<lφ1. It is clear that /φ, -1<1.65 is satisfied.

Also, 1φ2. /φz-1=1.050929, which is 0.8
<lφ2. It is clear that /φg-1<1.1 is satisfied.

Due to the spherical aberration of the above objective lens, the wavelength is 298.060
I11 (indicated by code 1), 202.54 nm (indicated by code 2), 398.84 nm (indicated by code 3),
When the calculation was performed for light of 253.70 nn (indicated by reference numeral 4), the diagram shown in FIG. 2(a) was obtained.

In addition, regarding the sine condition of the objective lens, when it was found for light of wavelengths indicated by the same symbols 1 to 4 as above, the second
A diagram shown in Figure (b) was obtained.

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

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

From these results, spherical aberration and sine conditions, respectively,
It is possible to reduce aberrations for both ultraviolet and far ultraviolet light, and it is possible to reduce aberrations for both ultraviolet and far ultraviolet light (codes 1.2 and 4) with wavelengths shorter than 300nm. It is clear that the aberrations as a whole are reduced compared to those for light in the deep ultraviolet region (code 3), and it is clear that it can be used well in the far ultraviolet region.It is also possible to reduce aberrations in both astigmatism and distortion. is clear.

Figure 3 is a layout diagram of the objective lens of the second embodiment, in which the microscope layer objective lens includes the first group lens 1 located on the object side and the first group lens 11. A second lens group 12 is arranged on the opposite side from the object side with a space using air as a medium.
It is composed of.

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

Further, the second group lens 12 is a biconcave lens made of quartz (
A second biconvex lens 16 made of fluorite is arranged on the opposite side of the object side of the biconcave lens 15 with a space in which air is used as a medium.

The radius of curvature R7 of the surface of the meniscus lens 13 facing the object side, the radius of curvature Rz of the surface facing the first biconvex lens 14, and the meniscus lens 1 of the first biconvex lens 14.
radius of curvature Rs of the surface facing the 3rd group side, radius of curvature R4 of the surface facing the 2nd group lens 12 side, curvature of the surface of the biconcave lens 15 that forms the 2nd group lens 12 facing the 1st group lens ll side. radius R7, radius of curvature R8 of the surface facing the second biconvex lens 16 side, radius of curvature R1 of the surface of the second biconvex lens 16 facing the biconcave lens 15 side, and the side opposite to the biconcave lens 15. The radius of curvature R8 of each facing surface, the center thickness DI of the meniscus lens 13, and the interplanar distance D between the meniscus lens 13 and the first biconvex lens 14 on the optical axis
I! , the center thickness D2 of the first biconvex lens 14, and the biconcave lens 1 constituting the first biconvex lens 14 and the second lens group 12.
5 on the optical axis, the center thickness D3 of the biconcave lens 15, the spacing D1 on the optical axis between the biconcave lens 15 and the second biconvex lens 16, and the spacing D1 on the optical axis of the second biconvex lens 16. Each center thickness D4 is set as follows.

[Radius of curvature, lens center thickness, lens surface spacing, material] R,
=49.692D, =3. OO made of quartz R, = 6.062 In addition, in the above objective lens, the power φ1 of the first group lens 11, the power φ2 of the second group lens 12, and the power φ1− of the meniscus lens 13 constituting the first group lens 11.
1 Power φ1 of the first biconvex lens 14 constituting the first lens group 11. , the power φ2 of the biconcave lens 15 constituting the second group lens 12, and the power φ2 . , the power φ of the entire system, and the distance from the object surface to the image-side focal point of the lens system are as follows.

φ, =0.041662 4g =0.013
444φ, −= −0,069139φ1. =0.10
3115φ! -=-0, 116715φ2 or =0.09
8827φ =0.033333 L=4
5 Based on the above values, 0.35φ=0.011667 0.9φ=0.030000, and it is clear that 0.35φ<0.9φ is satisfied.

Also, (φ1+φ2)/φ=1.6531801.05Lφ−
1,575000 1,15Lφ=1.725000, 1.05Lφ<(φ1+φ,)/φ<1.15
It is clear that Lφ is satisfied.

Also, 1φ, or /φ+-l −1,491416, 1.
It is clear that 45<lφ1/φ and −1<1.65 are satisfied.

Also, 1φ2. /φ, -1-0,846738, which is 0.8
<lφ! ,/φ! It is clear that -1<1.1 is satisfied.

Due to the spherical aberration of the above objective lens, the wavelength is 298.06n.
m (indicated by code 1), 202.54 nm (indicated by code 2), 398.84 nm (indicated by code 3),
When it was determined for light of 253.70 nm (indicated by reference numeral 4), the diagram shown in FIG. 4(a) was obtained.

In addition, regarding the sine condition of the objective lens, when it was found for light of wavelengths indicated by the same symbols 1 to 4 as described above, the 4th
A diagram shown in Figure (b) was obtained.

Regarding the astigmatism of the objective lens, the sagittal image plane (indicated by symbol S) and the meridional image plane (indicated by symbol M) were determined, and the diagram shown in FIG. 4(C) was obtained.

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

From these results, spherical aberration and sine conditions, respectively,
Aberrations can be reduced for both ultraviolet and far ultraviolet light, and in addition, for far ultraviolet light (codes 1.2 and 4) with wavelengths shorter than 300 nm, it is possible to reduce aberrations for both ultraviolet and far ultraviolet light. It is clear that the aberrations are reduced overall compared to the light (code 3), and it can be used well in the far ultraviolet region.It is also clear that the aberrations of astigmatism and distortion are reduced. it is obvious.

In the present invention, a first biconcave lens made of quartz may be used in place of the negative power meniscus lens 3.13 in the first lens group 1.11.

The power φ1 of the first group lens, the power φ2 of the second group lens, and the power φ1-1 of the first biconcave lens made of quartz or the negative power meniscus lens made of quartz constituting the first group lens. The power of the first biconvex lens made of quartz or fluorite that makes up the group lens is φ1°, the power of the biconcave quartz lens that makes up the second group lens is φ2-1, the power of the biconcave lens made of fluorite that makes up the second group lens is Power of biconvex lens φ21,
The power φ2 of the second group lens, the power φ of the entire system, and
For the distance from the object plane to the image-side focal point of the lens system,
The following conditional expression φ2 〉0. 0.35φ×φZ < 0.9φ, 1.05Lφ<(φ, +φ2)/φ<1.15Lφ1.
45<l φ1゜/φ, -1<1.650.8<l
φ2. /φ2-1<1.1, a microscope objective lens that can reduce aberrations in all of spherical aberration, sine condition, astigmatism, and distortion, and can be used well in the ultraviolet region and deep ultraviolet region. It was speculated that it could be configured.

<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 far ultraviolet region. a first biconcave lens made of quartz or a negative power meniscus lens made of quartz and a first biconvex lens made of fluorite or quartz in the first group lens;
An adhesive is applied between the first group lens and the second group lens, and between the second biconcave lens made of quartz and the second biconvex lens made of fluorite in the second group lens, using air as a medium. Since the structure is such that it is not used, it is possible to provide a microscope objective lens that can be used satisfactorily in the ultraviolet region and deep ultraviolet region.

Moreover, since not only no adhesive is used, but also there is no need to make the joint surface an optical contact, precision is not required in the machining of the joint surface, and the construction can be made at low cost.

Moreover, the second group lens is composed of a second biconcave lens made of quartz having negative power and a second biconcave lens made of fluorite having positive power.
Since it is constructed with a biconvex lens, it is possible to correct both chromatic aberration and spherical aberration and obtain a good image.

In addition, since a reflective configuration is not adopted and the central light beam is not blocked, the light at the center of the field of view can be taken in well, the resolution and the sight can be improved, 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, and FIG. 1 is a layout diagram of the lens of the first embodiment, and FIG. ) are spherical aberration diagrams, sine condition diagrams, astigmatism diagrams, and distortion aberration diagrams of the first embodiment, FIG. 3 is a lens arrangement diagram of the second embodiment, and FIG.
a), (b), (c) and (d) are spherical aberration diagrams, sine condition diagrams, astigmatism diagrams and distortion aberration diagrams of the second example,
FIG. 5 is a layout diagram of a reflecting mirror in a first conventional example, FIG. 6 is a layout diagram of a lens and a reflecting mirror in a second conventional example, and FIG. 7 is a layout diagram of a lens in a third conventional example. . 1.11...First group lens 2.12...Second group lens 3.13...Meniscus lens 4.14...First biconvex lens 5.15...Second biconcave lens 6.16...Second biconvex lens

Claims (1)

[Claims] (1) A first biconcave lens made of quartz or a negative-power meniscus lens made of quartz whose convex side faces the object side, and air on the side opposite to the object side of the first biconcave lens or meniscus lens. A first lens group consisting of a first biconvex lens made of quartz or fluorite placed apart from a space serving as a medium, and using air as a medium on the side opposite to the object side of the first group lens. a second biconcave lens made of quartz arranged with a space between them; and a second biconcave lens made of fluorite disposed with a space in which air is used as a medium on the opposite side of the object side of the second biconcave lens. and a second lens group consisting of a biconvex lens, and the following conditional expressions 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−|<1.650.8
<|φ_2_+/φ_2_-|<1.1 However, φ_1: Power of the first group lens φ_2: Power of the second group 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 forming the first group lens φ_1_-:Power of the negative lens forming the first group lens φ_2_+:Power of the positive lens forming the second group lens φ_2_-:Negative lens forming the second group lens An objective lens for a microscope characterized by being configured to satisfy the power of the lens.