WO2006038266A1

WO2006038266A1 - Microscope zoom objective lens

Info

Publication number: WO2006038266A1
Application number: PCT/JP2004/014397
Authority: WO
Inventors: Kunio Shimada
Original assignee: Kunio Shimada
Priority date: 2004-09-30
Filing date: 2004-09-30
Publication date: 2006-04-13
Also published as: JPWO2006038266A1

Abstract

Microscope objective lenses (10, 20, 30) of a telecentric system and having a high zoom ratio. The objective lenses comprises two or three lens groups, and each of the lens groups (101, 102; 201, 202, 203; 301, 302, 303) has positive refraction power. In the arrangement of the lens groups, a variable magnification lens group is arranged at a position that is closest to an object to be observed. A first lens group (101, 201, 301) having a variable magnification function comes closest to the object at the maximum magnification and positioned farthest from the object at the minimum magnification.

Description

Specification

Microscope zoom objective lens

TECHNICAL FIELD OF THE INVENTION

[0001] The present invention is a microscope objective lens for imaging an object (specimen) positioned on an object point to an image point separated by a predetermined distance on the optical axis, which is a telecentric system and has a high zoom ratio. The present invention relates to a technique of a microscopic zoom objective lens.

Background of the Invention

[0002] In general, an optical system of a microscope is divided into an finite correction optical system and an infinite correction optical system from an imaging system. The former finite correction optical system is an optical system in which an object lens that first passes light from an object forms an image of the object alone. The latter infinite correction optical system has an imaging lens behind the objective lens. Light from the object passes through the objective lens and becomes afocal (parallel to the optical axis), and the afocal light is imaged. Image is formed behind the lens. Therefore, as a method of zooming the microscope, the concept of zooming the imaging lens and the concept of zooming the objective lens are known.

[0003] Patent Document 1 and Patent Document 2 are examples in which an imaging lens in an infinite correction optical system is zoomed. A zoomed imaging lens usually has at least three or more lens groups, and there is also an objective lens, which tends to increase the optical tube length of the entire microscope. Patent Document 1: Japanese Patent Publication No. 2-54925

Patent Document 2: JP-A-11-271644

[0004] Patent Document 3 is an example in which an objective lens in a finite correction optical system is zoomed, and a zoom ratio of 5 is obtained by four lens groups.

Patent Document 3: Japanese Patent Publication No. 4 65364

Disclosure of the invention

Problems to be solved by the invention

[0005] When the two optical systems described above are compared, the objective lens in the finite correction optical system also functions as an imaging lens, so that a microscope with a shorter optical tube length can be obtained. However, regardless of the optical system, the zoom objective lens used so far has a zoom ratio It is not possible to find one satisfying both the requirements of a sufficiently large and a telecentric system required for a microscope.

[0006] Therefore, a main object of the present invention is to provide a novel microscope zoom objective lens that can respond to having a high zoom ratio and enabling a telecentric system.

Still another object of the present invention will become apparent from the following description.

Means for solving the problem

[0007] In the present invention, a telecentric system can be realized even when the zoom ratio is increased by using a lens unit having a positive refractive power as each lens group. Telecentric systems are the most important requirement for microscopes that are optical instruments. In that regard, in conventional zoom microscopes, it has been very common to use a lens with negative refractive power as a variable power lens. For this reason, when the zoom ratio was increased, the negative refractive power of the variable power lens (lens group) became stronger, making it impossible to achieve a telecentric system essential for microscopes. For telecentric systems, it is possible to perform differential interference using a Nomarski prism, to perform specular observation, to be advantageous for measurement, for example, to observe the bottom surface of a processed groove by etching. There are many advantages such as being able to design and easy design of the illumination optical system.

[0008] Further, according to the present invention, in terms of the arrangement of the lens or the lens group, a variable configuration (magnification change) lens (lens group) is arranged at a position closest to the object to be observed. Use. The first lens group that faces the object and has a zooming function is closest to the tele end (that is, at the maximum magnification) and is farthest from the object at the wide end (that is, at the minimum magnification). This is a characteristic required for a microscope objective lens, that is, a large aperture is required at the maximum magnification, and aberration correction is easier as the force is closer to the object. Conversely, a long working distance is required at the minimum magnification. It matches the characteristic that

[0009] The microscope zoom objective lens of the present invention based on the basic concept as described above has a two-group or three-group configuration, and includes a first lens group close to the object side and a rear side of the first lens group. And one or two other lens groups positioned in the. Each of these lens groups has the following features (A), (B), and (C). (A) The first lens group has positive refractive power

(B) The first lens group moves in the direction of the optical axis and functions as a variable magnification lens, and the lens also forms a first image of the object in front of the other lens groups.

(C) The other lens groups move according to the change in the position of the first image, and the image plane correction function that corrects the image plane and the function as the imaging lens that finally forms the first image With

[0010] Here, the other lens groups having the image plane correction function and the Z or imaging lens function generate the respective functions, and at the same time, the magnification by the first lens group is obtained in order to obtain the specified magnification. Of course, it is necessary to compensate (so that only the first lens group can obtain an insufficient magnification) and to carry out magnification amplification.

[0011] As shown in the features (A) and (B), the greatest feature of the present invention is the first feature having a positive refractive power.

The first image of the object is formed between one lens group force S and another lens group located behind it. The first lens group is the lens group closest to the object, and the lens also functions as a variable power lens. Therefore, it is necessary to cope with aberrations at each position during zooming only with aberrations as an objective lens. In order to cope with such aberrations, the first lens unit having a positive refractive power is composed of a large number of lenses. In this regard, by forming the first image before the final image is formed, the first lens group can be configured with a large number of lenses without difficulty.

In a preferred embodiment, the other lens group following the first lens group is one lens group having a positive refractive power, that is, the second lens group. Therefore, the entire objective lens is composed of two lens groups, a first lens group and a second lens group, both having positive refractive power. I will explain this form a little more using mathematical formulas. Among the zooming functions of the first lens group, if the magnification between the object and the first image at the minimum magnification (wide) is Blw, and the magnification at the maximum magnification (tele) is Bit, it depends on the first lens group. For the scaling ratio M, we obtain M = Blt / Bl w. For the first lens group, if the movement amount from the minimum magnification to the maximum magnification is Vt, the focal length F1 of the first lens group is obtained by Fl = VtxBlwxMZ (M−l). Furthermore, if the object side principal plane force of the first lens group at the minimum magnification is S1 w, the distance to the object surface is S1 w, and the object side principal plane force of the first lens group at the maximum magnification is Sit , They are Slw = Fl (-1 + 1 / Blw) and Slt = Fl (—1 + 1 / Blt) = S lw — Vt. These two expressions show the positional relationship between the first lens group and the object plane or object point. The first lens group is closest to the object plane at the maximum magnification and is furthest away from the object plane at the minimum magnification. Each magnification Blw and Bit by the first lens group satisfies the condition of 0−—Blw <l <—B It.

Furthermore, the positional relationship between the first lens group and the second lens group is as follows. Bw = BlwxB2w, where B2w is the magnification between the first image at the minimum magnification and the final image from the second lens group, and Bw is the final image magnification of the entire system at the minimum magnification. Therefore, B2w = BwZBlw is obtained by a simple equation transformation. This B2w is the amplification value of the multiplication function by the second lens group. Therefore, the image side main plane force of the first lens group at the minimum magnification can also be obtained by the following equation as the distance Dw to the object side main plane of the second lens group.

Dw = Fl (l-Blw) + F2 (l-l / B2w)

This Dw is too small to avoid contact between the first lens group and the second lens group by increasing F2. S2Bw = F2 (l−B2w) where S2Bw is the position of the final image by the second lens group, that is, the distance from the second lens group to the image side principal plane force final image.

[0014] Further, the other lens group can be composed of two lens groups. That is, the entire lens has a positive refracting power and is located further behind the second lens group having the image surface correction function and the second and first lens groups, and has a positive refracting power as a whole. This is a two-group configuration with a 2-2 lens group that functions as an imaging lens for finally forming the first image. In that case, the objective lens is composed of three lens groups as a whole. When the other lens groups have a two-group configuration, it is possible to easily modify the optical system, such as making the 2-1 lens group force diffractive to the 2-2 lens group.

Brief Description of Drawings

FIG. 1A is a configuration diagram of a lens that is a first embodiment of the present invention and shows a minimum magnification (wide).

FIG. 1B is a configuration diagram of a lens that represents the first embodiment of the present invention and shows an intermediate time.

FIG. 1C is a configuration diagram of a lens, showing a maximum magnification (tele), according to the first embodiment of the present invention. FIG. 2 is an aberration characteristic diagram showing chromatic aberration and spherical aberration in the first example.

[3] FIG. 3 is an aberration characteristic diagram showing astigmatism of the first example.

FIG. 4 is an aberration characteristic diagram showing distortion in the first example.

[5A] This is a second embodiment of the present invention, and is a lens configuration diagram showing the minimum magnification (wide).

圆 5B] This is a second embodiment of the present invention, and is a configuration diagram of a lens showing an intermediate time.

[5C] This is a second embodiment of the present invention, and is a lens configuration diagram showing the maximum magnification (tele).

FIG. 6 is an aberration characteristic diagram showing chromatic aberration and spherical aberration in the second example.

FIG. 7 is an aberration characteristic diagram showing astigmatism of the second example.

8] Aberration characteristic diagram showing distortion in the second example.

FIG. 9A is still another example of the present invention, and is a configuration diagram of a lens showing a minimum magnification (wide).

FIG. 9B is a structural diagram of a lens showing an intermediate time in still another example of the present invention.

FIG. 9C is a structural diagram of a lens showing the maximum magnification (tele) in still another example of the present invention.

Explanation of symbols

10 Zoom objective (first example)

101 1st lens group

102 Second lens group

LI—L16 lens

20 Zoom objective lens (second embodiment)

201 1st lens group

202 2nd lens group (2nd-1 lens group)

203 3rd lens group (2nd and 2nd lens groups)

L21— L40

30 Zoom objective (further examples)

301 1st lens group 302 Second lens group (2-1st lens group)

303 3rd lens group (2nd and 2nd lens groups)

BEST MODE FOR CARRYING OUT THE INVENTION

First Example: Zoom Objective Lens Composed of Two Lens Group Forces (see FIGS. 1A to 1C) The zoom objective lens 10 according to the first example includes a first lens group 101 and a second lens group 102. The two lens group forces are also constructed. The entire lens group is two, which is very different from the conventional three or more groups. The first lens group 101 includes eleven lenses L1 to Lll, and the second lens group 102 includes five lenses L12 to L16. These two lens groups 101 and 102, and the individual lenses L1 and L16 constituting each lens group, of course, have the same optical axis, but a radius of curvature R (mm) for specifying them. , Thickness or spacing t (mm) between adjacent ones, refractive index N with respect to e-line (wavelength 546. lnm), and specifications of Abbe number v are as follows. In the first lens group 101, the lenses L1, L5, and L11 are a single lens, whereas the lenses L2, L3, and L4 and the lenses L6, L7, and L8 are each a combination of three lenses. Lenses L9 and L10 are two lenses.

[First lens group 101]

R t N

REN: L1 -40. 9961 5. 3000 1. 80642 34.7

-17. 6574

0. 3000 (Lens: Distance between L1 and L2)

Lens L2 66. 6800 11. 0000 1. 43985 94. 6

-12. 9288

Lens L3 -12. 9288. 4000 ―. 61669 44. 0

-45. 1204

Lens L4 -45. 1204 7. 3000 ―. 43985 94. 6

-27. 9493

0. 3000 (Distance between lens 4 and L5)

Lens L5 30. 9633 8. 8000 1. 43985 94. 6

-41. 1725 0. 3000 (Distance between lens L5 and L6) Lens L6 22. 2584 3. 3000 1. 72538 34.5

11. 3525

Lens L7 11. 3525 14. 0000 1. 43985 94. 6

-17. 3439

Lens L8 -17. 3439 2. 0000 1. 72538 34.5

199. 8884

18. 0000 (Distance between lens L8 and L9) Lens L9 27. 9557 3. 5000 1. 76859 26.3

-6. 9830

Lens L10 -6. 9830 1. 0000 1. 59 143 61. 0

24. 1608

3. 5000 (Lens: Distance between L10 and L11) Lens L 11 -6. 8090 1. 0000 1. 72794 37. 7

-25. 9548

(Second lens group 102)

R t N

Lens L12 -96. 4469 3. 2000 1. 62032 63. 1

-8. 3475

0. 5000 (Lens: Distance between L12 and 13) Lens L13 16. 5838 4. 0000 1. 62032 63. 1

-11.0015

1. 0000 (Lens: Distance between L13 and 14) Lens L14 -7. 5596 1. 2000 1. 72538 34. 5

25. 5602

6. 5000 (Lens: Distance between L14 and L15) Lens L15 7. 6413 3. 5000 1. 59143 61. 0

-12. 7882 1. 0000 (Lens: Distance between L15 and 16)

Lens L16 -8. 1431 1. 0000 1. 59911 39. 0

12. 9992

Each of the lens groups 101 and 102 described above has a positive refractive power. The combined focal length of each of the first lens group 101 is 7.0273 mm, and that of the second lens group 102 is 10. It is 0000mm. The theoretical distance between the first lens group 101 and the second lens group 102 (the distance between the image side main plane of the first lens group 101 and the object side main plane of the second lens group 102) is a multiplication factor X5 At the time of wide-angle [Koo! /, 19.8819mm, magnification X16.86, medium time [koo, 24.647 9mm, magnification X50, tele at 39.8819mm. Furthermore, the distance between the first lens group 101 and the second lens group 102 (the distance between the rear surface of the lens 11 and the front surface of the lens 12) is 1.4257 mm for wide, 6.1917 mm for intermediate, and 21.4257 mm for tele. It is.

In the optical system of the microscope, the object to be observed is at an object point O on the front side of the lens L1 of the first lens group 101, and the object point is fixed during zooming. The first lens group 101 having a zooming function moves in a predetermined manner during zooming, for example, by a guide action of a pin fitted in a linear cam groove. Such a first lens group 101 forms an image of an object on the object point O as a first image in front of the second lens group 102. The second lens group 102 located behind the first lens 101 on the optical axis functions as an imaging lens that finally forms an image of the first image at a predetermined position behind the second lens group 102. The distance between the object point O and the image point by the imaging lens (that is, the distance between the object images) is 294.0006 mm, and is constant during zooming. In this case, the second lens group 102, which is an imaging lens, moves in accordance with a change in the position of the first image, and has an image plane correction function for correcting the image plane (that is, the plane including the image point). Have. Therefore, the second lens group 102 moves according to the guide action of a pin that fits into a U-shaped curved groove, for example.

[0022] Here, focusing on the distance from the object point O to the front surface of the lens L1 of the first lens group 101 (that is, the object distance), the object distance is 34.383 mm when the magnification is X5 wide. Has a sufficiently large working distance. By the way, the object distance is 19.188mm in the middle and 14.383mm in tele at X50 magnification.

Next, FIGS. 2 to 4 clearly show aberrations of the zoom objective lens 10 according to the first embodiment. To do. Those skilled in the art will understand from these aberration data that the zoom objective 10 is sufficiently practical. Figure 2 shows the chromatic aberration and spherical aberration at wide, intermediate, and telephoto. The vertical axis is the numerical aperture (NA), and the symbol attached to the aberration curve is the display based on the Flanhofer line. F is the F-line with a wavelength of 486.lnm, e is the e-line with a wavelength of 546.lnm, and d is the wavelength. 587. 5 nm d-line, C is 65.6 nm wavelength C-line. For chromatic aberration, the aberration with respect to e-line is plotted. Figure 3 shows astigmatism at wide, intermediate, and telephoto. The vertical axis shows the height of the image, the display DS attached to the aberration curve is spherical aberration, and DM is meridian aberration. In addition, Fig. 4 shows distortion in wide, intermediate, and telephoto directions, with the vertical axis representing the image height.

Second Example: Zoom Objective Lens Consisting of Three Lens Groups (see Figs. 5A-5C) The zoom objective lens 20 of the second example is an image that the second lens group 102 in the first example combines. This lens configuration separates the two functions of the surface correction function and the imaging lens function. That is, the zoom objective lens 20 of the second example includes the first lens group 201 having the same function as the first lens group 101 of the first example, and the second lens behind the first lens group 201. Two lens groups of a group 202 and a third lens group 203 are provided. The second lens group 202 can be referred to as a 2-1 lens group in which the second lens group is separated from the viewpoint that it performs the image plane correction function of the second lens 102 of the first embodiment. Similarly, the third lens group 203 may be referred to as a second or second lens group separated from the second lens group in that it performs the imaging lens function of the second lens 102 of the first embodiment. it can. In this way, by making the second lens group 102 of the first example separated for each function, according to the zoom objective lens 20 of the second example, in addition to the advantages of the first example, Further advantages can be obtained. One of the additional advantages is that the knock focus can be reduced. For example, the back focus (when wide) 155.3 mm in the first embodiment can be reduced to 80.1 mm. In addition, the third lens group 203 can be fixed, and an advantage of facilitating correction of aberrations, such as correction of common aberrations in wide, intermediate, and telephoto modes, is obtained. Further, in the second embodiment, an intermediate or afocal part can be provided between the second lens group 202 and the third lens group 203 without causing a problem of aberration in the afocal part. If you can insert a lighting system! [0025] Specifications, curvature radius R (mm), thickness or distance between adjacent ones t (mm), refractive index N with respect to e-line (wavelength 546. Inm), and Abbe number v in the second embodiment are: It is as follows.

[First lens group 201]

R t N

Lenth: L21 41. 2442 3. 9000 1. 74706 27. 6

-26. 5441

0. 5000 (Distance between lens 21 and L22)

Lens L22 644. 3724 5. 0000 1. 49845 81.2

-12. 6583

Lens L23 -12. 6583 1. 5000 1. 72538 34.5

25. 9185

Lens L24 25. 9185 5. 0000 1. 43985 94. 6

-20. 7559

0. 4000 (Distance between lens 24 and L25)

Lens L25 64. 7337 7. 0000 1. 43985 94. 6

-15. 5339

Lens L26 -15. 5339 1. 8000 1. 72538 34.5

-83. 7746

Lens L27 -83. 7746 4. 5000 1. 48915 70. 0

-36. 2468

0. 4000 (distance between lenses 27 and 28)

Lens L28 26. 2297 5. 5000 1. 49845 81. 2

-114. 0953

12. 0000 (Lens 28 and 29)

Lens L29 25. 4514 3. 8000 1. 81 264 25. 2

57. 4200

2. 0000 (distance between lenses 29 and 30) Lens L30 13.4657 1.5000 1.48915 70.0

7. 1153

4.0000 (Distance between lens 30 and L31) Lens L31 16.6901 1.5000 1.48915 70.0

18.7119

[Second lens group 202]

R t N

Lens L32 23.8097 3.0000 1.62032 63.1

-13.2876

0.5000 (Distance between lenses 32 and 33) Lens L33 28.7044 4.0000 1.62032 63.1

-16.0739

1.0000 (Distance between lenses 33 and 34) Lens L34 -10.3611 1.2000 1.72538 34.5

162.8997

7.0000 (Distance between lenses 34 and 35) Lens L35 14.9463 2.0000 1.59143 61.0 Plane

1.0000 (Distance between lenses 35 and 36) Lens L36 -12.8543 1.0000 1.59911 39.0

112.554

[Third lens group 203]

R t N

Lens L37 14.7579 3.5000 1.62032 63.1

-13.8696

1.5000 (Distance between lenses 37 and 38) Lens L38 -9.7790 1.5000 1.59911 39.0

22.6743 22. 0000 (Lens 38 and 39)

Lens L39 -27. 0717 1. 5000 1. 48915 70. 0

122. 819

[0029] Also in the second embodiment, each of the lens groups 201, 202, and 203 has a positive refractive power, and the combined focal length of each of the first lens group 201 is 17.5682mm. In group 202, it is 12.0000 mm, and in third lens group 203 it is 189.7400 mm. The theoretical distance between the first lens group 201 and the second lens group 202 (the distance between the image side main plane of the first lens group 201 and the object side main plane of the second lens group 202) is X5 When wide is 35.1238mm, magnification is XI5.8, and when it is XI5.8, it is 47.1364mm and when magnification is X50, it is 85.1238mm. Further, the distance between the first lens group 201 and the second lens group 202 is 6.3963 mm for wide, 18.4089 mm for intermediate, and 56.3963 mm for tele. In addition, the distance between the second lens group 202 and the third lens group 203 is 20.0000 mm for wide, 45.9746 mm for intermediate, and 20.0000 mm for tele. Note that the object-image distance between the object point O and the image point formed by the imaging lens (third lens group 203) in the second column f is 281.4464 mm. In addition, each object distance (working distance in other words) at wide, intermediate, and tele time (in other words, the working distance) is small (13. 978 mm) when tele (13.978 mm) and large (63. 978mm) o

Next, aberrations of the zoom objective lens 20 according to the second embodiment will be clarified in FIGS. 6 to 8. FIG. Each figure is the same as FIG. 2 to FIG. 4 in the first embodiment. From these aberration data, it can be said that the zoom objective lens 210 in the second embodiment also has sufficient practicality.

[0031] It should be noted that those skilled in the art can modify the second embodiment so that the zooming function is provided not only in the first lens group but also in the third lens group, so as to form a so-called double zoom form. It can be done easily. The zoom objective lens 30 shown in FIGS. 9A to 9C is a modified example including the first lens group 301, the second lens group 302, and the third lens group 303. The zoom lens 30 includes the first lens group 301, the third lens group 303, and the like. Each of the two groups has a scaling function.

Claims

The scope of the claims

[1] A microscope objective lens that forms an object located on an object point at an image point separated by a predetermined distance on the optical axis,

The objective lens includes a first lens group close to the object side and one or two other lens groups located on the rear side of the first lens group, and each of these lens groups has the following characteristics. Microscope zoom objective lens.

(A) The first lens group has positive refractive power

(B) The first lens group moves in the direction of the optical axis and functions as a variable power lens, and forms a first image of the object in front of the other lens group.

(C) The other lens group moves in accordance with a change in the position of the first image, and an image plane correction function for correcting the image plane, and finally the first image is connected to the image point. Functions as an imaging lens for imaging

[2] The microscope zoom objective lens according to claim 1, wherein the first lens group moves closer to the object at a maximum magnification and away from the object at a minimum magnification.

3. The microscope zoom objective lens according to claim 1, wherein the first lens group is a lens group closest to the object.

[4] The other lens group is a second lens group that is a single lens group and has a positive refractive power. Therefore, the total power of the objective lens is two of the second lens group and the first lens group. The microscope zoom objective according to claim 1, comprising:

[5] The other lens group is located behind the first lens group, has a positive refractive power as a whole, and has the image plane correcting function, and the second lens group. 2. A second and second lens group that is positioned further rearward of the lens group and has a positive refractive power as a whole and functions as an imaging lens that forms the first image on the image point. 1 microscope zoom objective lens.

6. The microscope zoom objective lens according to claim 5, wherein the directional light is afocal from the 2-1 lens group to the 2-2 lens group.

7. The microscope zoom objective according to claim 5, wherein the second and second lens groups have a function as a variable power lens, and have a double zoom function in combination with the variable power lens function of the first lens group. Lens.