JPH01319719A - Objective lens for microscope - Google Patents

Abstract

PURPOSE:To obtain the objective lens for microscopes which can be used in a far UV region by using a positive power meniscus lens made of quartz or fluorite as a 1st group and combining a biconcave lens made of quartz and a biconvex lens made of fluorite to constitute the 2nd group lens. CONSTITUTION:The 1st group lens consisting of the positive power meniscus lens which is made of fluorite and the concave face side of which is directed to an object side and the 2nd group lens 2 parted from the lens 1 via a space on the side opposite to the object side of said lens are disposed. The lens 2 is constituted of the biconcave lens 3 made of quartz and the biconvex lens 4 made of fluorite. This objective lens for microscopes is so constituted as to satisfy the condition equations phi1>0, phi2>0, 0.35phi<phi2<0.92phi, 1.05Lphi<(phi1+phi2)/phi<1.15Lphi, 0.9<¦phi2+/phi2-¦<1.2 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, phi2+: the power of the convex lens constituting the 2nd group lens, phi2-: the power of the concave lens constituting the 2nd group lens.

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 or less.

<Prior Art> Most of the conventionally known objective lenses for igi 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 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. is desired.

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

Presentation Conventional ■ Figure 5 is "LE" by RUDOLF KINGSLAKE.
NS DESIGN FUNDA ENTALS”
(ACADEMIC PRESS 1978)
This is an objective lens for a microscope shown in No. P, 333, 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 the object side cannot be made into a telescopic link. This has the disadvantage that the amount of light decreases due to the shielding, 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, the difference between the multiple objective lenses This has the drawback of a low degree of freedom in design, such as the inability to unify the pupil diameter and parfocal distance at the same time.

Incidentally, fluorite, quartz, lithium fluoride (LiF), barium fluoride (BaFz), and sodium chloride (NaC1) are known as optical materials that can transmit light in the ultraviolet and deep ultraviolet regions. Examples of objective lenses for microscopes using lens 4 are as follows.

Figure 6 of the Kaya-shu-shu-mai group is from ``APPLIE[l] supervised by KINGSLAKE.
OPT[C5AND 0PTICAL ENGINE
ERING III” (ACADEMIC PRES
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 o4 consisting of a third lens 04c made of fluorite with negative power and adjacent to the second lens 04b;
A first reflecting mirror o5 and a second reflecting mirror o having an opening 06
7 and a fourth lens 08 made of quartz that transmits the light passing through the aperture 06.

1st Conventional Figure 7 shows optical technology] Contact magazine Vol. 25 No.
2 (February 1987), P, 137, the objective lens for a microscope is shown as a lens o9 made of fluorite, a concave lens 010a made of quartz, a convex lens 010b made of fluorite,
A second lens 010 sandwiched and cemented with 010c, a concave lens 01la made of quartz, and a convex lens 01 l b made of fluorite, similar to the second lens 010.

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.

The second lens 04a made of quartz is bonded to the second lens 04b made of fluorite, but there is currently no adhesive that can transmit light with wavelengths in the ultraviolet or deep ultraviolet ranges. The bonding surface must be an optical contact so that there is no reflection on the bonding surface, and high precision is required in the processing of the bonding surface, which has the disadvantage of being 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.

1st Main Disaster Team ■ The missing second lens 010 and third lens 011 each consist of concave lenses 010a, 01la made of quartz and two convex lenses 010b, 010c, 011b, 01lc made of fluorite. The convex lens 010b made of fluorite corrects chromatic aberration that cannot be achieved with the concave lenses 010a and 01la alone.
010c, 011b, and 011c, but similarly to the second conventional example, concave lenses 010a and 01la made of quartz and two convex lenses 010b, 010c, and 011b made of fluorite are used in combination. , 01l
(c) The bonding surfaces between each must be made into optical contacts, which requires high precision in machining 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 objective lens for a microscope of the present invention is composed of a positive power meniscus lens made of quartz or fluorite with the concave side facing the object side. a biconcave lens made of quartz disposed on the side opposite to the object side of the first group lens across a space using air as a medium; It is composed of a second lens group consisting of a biconvex lens made of fluorite and a biconvex lens made of fluorite placed apart from a space using air as a medium, and the following conditional formula % formula % φI: power of the first lens group φ2: the second lens group 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. It is characterized in that it is constructed so as to satisfy: the power φ of the convex lens constituting the second group lens, -: the power of the concave 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 2 times and more than 0.35 times. When it becomes 0.92 times or more, the working distance becomes smaller,
On the other hand, if the magnification is 0.35 times or less, the total length of the lens system becomes excessive compared to the focal length.

Power φ1 of the first group lens and power φ2 of the second group lens
The value obtained by dividing the sum of the sum by the total system power φ (φ, +φ, )/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 φ of the entire system, and
It is set to exceed 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 provide one-link characteristics.

Power φ of the biconvex lens made of fluorite that constitutes the second lens group
2. The absolute value of the ratio 1φ2. /φ! -1 is 1.
It is set to be less than 2 and greater than 0.9. Outside this range, it becomes difficult to correct chromatic aberration, and when it exceeds 1.2, spherical aberration becomes insufficiently corrected, and conversely, when it falls below 0.9, it becomes overcorrected and the curvature of the field is distorted. This is because it becomes larger.

According to the above configuration, both the first group lens and the second group lens are made of quartz, fluorite, or a combination of both, and the first group lens, the second group lens, and the second group lens are made of quartz, fluorite, or a combination of both. By not using adhesive between the quartz biconcave lens and the fluorite biconvex lens in the second group lens, light in the ultraviolet region and deep ultraviolet region can be transmitted.
Spherical aberration and chromatic aberration can be corrected by making the second group lens a combination of a biconcave lens made of quartz having negative power and a biconvex lens made of fluorite having positive power.

<Example> Next, embodiments 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 φ of 10.6, and an imaging magnification of 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.

[Composition of the imaging lens] The imaging lens is composed of three lenses: a first lens, a second lens, and a third lens.The material of each lens and the radius of curvature of the surface of the second lens facing away from the second lens are rl, radius of curvature r2 of the surface facing the second lens side, radius r3 of curvature of the surface facing the second lens side of the second lens, radius r4 of curvature of the surface facing the third lens side, The radius of curvature rs of the surface facing the second lens side, the radius of curvature r6 of the surface facing the opposite side from the second lens, the center NdI of the second lens, and the optical axis between the second lens and the second lens. The surface spacing d1□, the center thickness dz of the second lens, and the surface spacing d on the optical axis between the second lens and the third lens! 3s and the center thickness d of the third lens are set as follows.

[Radius of curvature, lens center thickness, lens surface spacing, material] d1
□=2.75 r, =-13,488 This imaging lens also has a combination of only quartz and fluorite lenses, and the second lens and the second lens, and the second lens and the third lens, respectively. are placed separated by a space with air as a medium.

11 stars Figure 1 is a layout diagram of the objective lens of the first embodiment, showing the first group lens 1 made of fluorite and consisting of a positive power meniscus lens with the concave side facing the object side, and its A microscope objective lens is constituted by a second group lens 2 disposed on the opposite side of the object side of the first group lens 1 with a space using air as a medium, and the second group lens 2 includes: It consists of a biconcave lens 3 made of quartz and a biconvex lens 4 made of fluorite placed on the opposite side of the biconcave lens 3 from the object side with a space in which air is used as a medium.

The radius of curvature R1 of the surface of the first group lens 1 facing away from the second group lens 2, the radius of curvature R2 of the surface facing the second group lens 2 side, and the second group lens 2 is configured. The radius of curvature R1 of the surface of the biconcave lens 3 facing the first group lens 1 side,
The radius of curvature R2 of the surface facing the biconvex lens 4 forming the second group lens 2, the biconvex lens 4 forming the second group lens 2
, the radius of curvature R3 of the surface facing the biconcave lens 3 side, and the radius of curvature R of the surface facing the side opposite to the biconcave lens 3.
4, and the center thickness of the first group lens 1,
, the interplanar distance D1□ on the optical axis between the first group lens l and the biconcave lens 3 forming the second group lens 2, the center thickness D2 of the biconcave lens 3, and the biconcave lens 3 forming the second group lens 2. The distance between the surfaces of the biconvex lens 4 on the optical axis. , and the center thickness of the biconvex lens 4 are set as follows.

[Radius of curvature, lens center thickness, lens surface spacing, material] D,
=1. OO made of quartz R, = 5.000 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 second group lens 2.
The power φ2-1 of the biconcave lens 3 constituting the second group lens 2, the power φ20 of the biconvex lens 4 constituting the second group lens 2, the power φ of the entire system, and the distance from the object plane to the image side focal point of the lens system are as follows. It is as follows.

φ+ =0.030513 φ2 =0.02
5630φz-=-0,126829φg,=0.1
23336φ =0.033333 L=45
Based on the above values, 0.35φ=0.011667 0.92φ=0.030667, and it is clear that 0.35φ<0.92φ is satisfied.

Also, (φ, +φ2)/φ=1.6842901.05Lφ−
1,575000 1,15Lφ=1.725000, 1.05Lφ (φ1+φ2)/φ<1.15
It is clear that Lφ is satisfied.

Also, 1φ2 or /φz−1=0.972456, which is 0.9
<lφ2. It is clear that /φ satisfies -1<1.2.

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), 25
When it was determined for light of 3.70 nm (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.

Furthermore, 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,
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 it can be used well in the far ultraviolet region, and it also has reduced aberrations in both astigmatism and distortion. is clear.

Fig. 3 is a layout diagram of the objective lens of the second embodiment, which includes a first lens group 11 made of quartz and a positive power meniscus lens with its concave side facing the object side; It is composed of a second group lens 12 arranged on the opposite side of the first group lens 11 from the object side with a space using air as a medium,
And, the second group lens 12 is a biconcave lens 1 made of quartz.
3, and a biconvex lens 14 made of fluorite, which is placed on the opposite side of the biconcave lens 13 from the object side with a space in which air is used as a medium.

The radius of curvature R8 of the surface of the first group lens 11 facing away from the second group lens 12 and the radius of curvature R2 of the surface facing the second group lens 12 side constitute the second group lens 12. The radius of curvature R2 of the surface of the biconcave lens 13 facing the first group lens 11, the biconvex lens 1 constituting the second group lens 12
The radius of curvature R1 of the surface facing the fourth side, the radius of curvature R1 of the surface facing the biconcave lens 13 side of the biconvex lens 14 constituting the second group lens 12, and the radius of curvature R1 of the surface facing the biconcave lens 13 side, and Each radius of curvature R4 of the surface and the first
Center thickness 3 of group lens 11, surface distance DI on the optical axis between biconcave lens 13 constituting first group lens 11 and second group lens 12! , the center thickness D2 of the biconcave lens 13, the surface distance D0 on the optical axis between the biconcave lens 13 and the biconvex lens 14 constituting the second lens group 12, and the center thickness of the biconvex lens 14, each of which is as follows. is set to .

[Radius of curvature, lens center thickness, lens surface spacing, material] R,
--10,060 In the above objective lens, the power φ8 of the first group lens 11, the power φ2 of the second group lens 12, the power φ of the biconcave lens 13 constituting the second group lens 12, -1 second
The power φ2° of the biconvex lens 14 constituting the group lens 12, the power φ of the entire system, and the distance from the object plane to the image-side focal point of the lens system are as follows.

φl −0,024550φ, =0.030121φ
t-"-0,103851φ!,=O,]16571
φ = 0.033333 L-45 Based on the above values, 0.35φ − 0,011667 0,92φ − = 0.030667, which clearly satisfies 0.35φ<φ2<0.92φ .

Also, (φ−+φ2)/φ−1.6401231.05Lφ−
1,575000 1,15Lφ= 1,725000, 1.05Lφ<(φ1+φ2)/φ<1.15
It is clear that Lφ is satisfied.

Also, 1φ2゜/φz−1=1.122481, which is 0.9
<Iφ2. It is clear that /≠z−l<1.2 is satisfied.

Due to the spherical aberration of the above objective lens, the wavelength is 298.06n.
m (indicated by code 1), 202.54n+a (indicated by code 2
), 398.84 nm (indicated by code 3), 2
When it was determined for light of 53.70 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 the symbol S) and the meridional image plane (indicated by the 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 300r+m for far ultraviolet light (codes 1.2 and 4) with shorter wavelengths than 300r++w.
It is clear that the aberrations as a whole can be reduced compared to that for light in the ultraviolet region with a longer wavelength (code 3), and it can be used well in the far ultraviolet region.It is also possible to reduce aberrations in terms of astigmatism and distortion. It is clear that it is made with less.

The power of the first group lens made of quartz or fluorite is −5, and the power of the second group lens is φ.

, the power φ2 of the quartz biconcave lens constituting the second group lens, the power φ2 of the fluorite biconvex lens constituting the second group lens, the power φ of the entire system, and the power of the lens system from the object plane. If the following conditional formula % formula % is satisfied with respect to the distance to the image side focal point, aberrations can be reduced in terms of spherical aberration, sine condition, astigmatism, and distortion, and even in the ultraviolet and far ultraviolet regions. It was speculated that it is possible to construct an objective lens for a microscope that can be satisfactorily used in the following.

<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. and a space in which air is used as a medium between the first group lens and the second group lens, and the quartz biconcave lens and the fluorite biconvex lens in the second group lens, Since the structure does not use adhesive, 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.

Furthermore, since the second lens group is composed of a biconcave quartz lens with negative power on the object side and a biconvex fluorite lens with positive power on the image side, both chromatic aberration and spherical aberration can be eliminated. A good image can be obtained by correction.

In addition, since a reflective structure is not adopted and the light beam at the center is not blocked, the light at the center of the field of view can be taken in well, and both 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, 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...Biconcave lens 4.14...Biconvex lens included\ Applicant Dainippon Screen Manufacturing Co., Ltd. Agent Patent attorney Tsutomu Sugitani 1 ('') (b) NA: 0.083 NA,,0083Figure (c) (d) M S qt

Claims (1)

[Claims] (1) A first lens group consisting of a positive power meniscus lens made of quartz or fluorite with the concave side facing the object side, and air as a medium on the side opposite to the object side of the first group lens. A second group consisting of a biconcave lens made of quartz arranged with a space between them, and a biconvex lens made of fluorite arranged on the opposite side of the object side of the 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<0.92φ, 1.05Lφ<(φ_1+φ_2)/φ<1.15Lφ
0.9<|φ_2_+/φ_2_-|<1.2 However, φ_1: Power of the first group lens φ_2: Power of the second group lens φ: Power of the entire system L: From the object plane to the image-side focal point of the lens system Distance φ_2_+: power of a convex lens constituting the second group lens φ_2_-: power of a concave lens constituting the second group lens.