JP5278558B2 - Microscope zoom lens, microscope - Google Patents

Description

  The present invention relates to a zoom lens for a microscope used in a microscope, and a microscope having the same.

  Conventionally, a microscope zoom lens used in a microscope and a microscope having a microscope zoom lens have been proposed (for example, Japanese Patent Laid-Open Nos. 6-18784 and 2006-178440).

  In recent years, in microscopes, stereo microscopes, digital microscopes, etc., there is an object-side telecentric microscope zoom lens that does not change the size of the image even when defocused due to the measurement function such as measuring the size of the test object. It is desired. Such a zoom lens for a microscope is further required to have a high zoom ratio and high imaging performance, and to be small in size.

  However, it has been difficult for conventional zoom lenses for microscopes to satisfy all of these requirements.

  The present invention has been made in view of the above problems, and has a zoom lens for a microscope that ensures object-side telecentricity and is small and has a high zoom ratio and high imaging performance, and a microscope having the zoom lens for the microscope. The issue is to provide.

In order to solve the above problems, the present invention provides:
Receiving a flat row light from the objective lens, a microscope zoom lens for forming on an imaging surface of the imaging device,
In order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens having a negative refractive power It consists of a group,
The fourth lens group includes, in order from the object side, an eleventh positive lens, a twelfth negative lens, and a thirteenth positive lens.
Upon zooming from the low magnification end state to the high magnification end state, the second lens group and the third lens group move along the optical axis direction,
A zoom lens for a microscope characterized by satisfying the following conditions.
0.4 <d1W / | f2 | <0.7
0.9 <d11 / d12 <1.2
However,
d1W: Distance between the most image side lens surface of the first lens group and the most object side lens surface of the second lens group in the low magnification end state f2: Focal length of the second lens group d11: The eleventh distance between the most object side lens surface of the most image side lens surface and the twelfth negative lens of the positive lens d12: the most object side of the most image side lens surface of the twelfth negative lens and the thirteenth positive lens Distance from lens surface

The zoom lens for a microscope according to the present invention preferably further satisfies the following conditions.
0.05 <d11 / | f4 | <0.2
However,
d11: Distance between the most image side lens surface of the eleventh positive lens and the most object side lens surface of the twelfth negative lens f4: Focal length of the fourth lens group

Furthermore, the zoom lens for a microscope according to the present invention preferably satisfies the following conditions.
| F1 / f2 |> 4.5
However,
f1: Focal length of the first lens group

In the zoom lens for a microscope of the present invention, it is preferable that the following conditions are further satisfied.
Z ^0.5 <V2 <Z ^0.6
However,
Z: Zoom ratio of the microscope zoom lens V2: Variable magnification of the second lens group

In the zoom lens for a microscope according to the present invention, it is preferable that the most object side lens surface of the second lens group has a concave shape.

In the zoom lens for a microscope according to the present invention, the second lens group moves only from the object side to the image side and the third lens group moves from the image side to the object side during zooming from the low magnification end state to the high magnification end state. It is preferable to move only to the side.

According to another aspect of the present invention, there is provided a microscope comprising the objective lens and the zoom lens for a microscope according to the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the zoom lens for microscopes which ensures object side telecentricity, is small, has a high zoom ratio, and high image formation performance, and a microscope which has this zoom lens for microscopes can be provided.

1A and 1B are diagrams showing a basic configuration and zoom movement locus of a zoom lens for a microscope according to an embodiment of the present invention. These are figures which show the lens structure of the zoom lens for microscopes concerning 1st Example of this application. 3A to 3C are graphs showing various aberrations of the microscope zoom lens according to the first example in an infinitely focused state. FIG. 3A is a low magnification end state, FIG. 3B is an intermediate focal length state, and FIG. Each aberration diagram in the state is shown. These are figures which show the lens structure of the zoom lens for microscopes concerning 2nd Example of this application. FIGS. 5A to 5C are graphs showing various aberrations of the microscope zoom lens according to the second example in the infinite focus state. FIG. 5A is a low magnification end state, FIG. 5B is an intermediate focal length state, and FIG. Each aberration diagram in the state is shown. These are figures which show the lens structure of an example of the objective lens used in combination with the zoom lens for microscopes concerning embodiment of this invention. These are figures which show the optical system of the microscope provided with the zoom lens for microscopes concerning embodiment of this invention.

  Hereinafter, a zoom lens for a microscope according to an embodiment of the present invention will be described. The following embodiments are only for facilitating understanding of the invention, and exclude additions and substitutions that can be performed by those skilled in the art without departing from the technical idea of the present invention. Is not intended.

The zoom lens for a microscope according to this embodiment includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power. And a fourth lens group having a negative refractive power, the lens surface closest to the object side of the second lens group has a concave shape, and upon zooming from the low magnification end state to the high magnification end state, The second lens group and the third lens group move along the optical axis direction, and the following conditional expressions (1), (2), and (3) are satisfied.
(1) 0.4 <d1W / | f2 | <0.7
(2) | f1 / f2 |> 4.5
(3) ^Z0.5 <V2 < ^Z0.6
Here, d1W is the distance between the most image side lens surface of the first lens group and the most object side lens surface of the second lens group in the low magnification end state, f2 is the focal length of the second lens group, and f1. Is the focal length of the first lens group, Z is the zoom ratio of the zoom lens for microscope, and V2 is the magnification of the second lens group.

  With such a configuration, the zoom lens for this microscope can reduce the angle formed by the principal ray and the optical axis at about 70% of the field of view (object height) in the low magnification end state to 0.013 ° or less. It is possible to achieve a zoom lens for a microscope that secures object-side telecentricity, has a high zoom ratio of 15 times or more, and is small and has high imaging performance.

  Conditional expression (1) is the distance between the most image side lens surface of the first lens group and the most object side lens surface of the second lens group in the low magnification end state, that is, the first lens group and the second lens group. An appropriate range of the ratio between the distance in the optical axis direction and the focal length of the second lens group is defined. By satisfying conditional expression (1), the entrance pupil position in the low magnification end state can be moved away from the object plane, and the object side telecentricity in the low magnification end state can be ensured.

  When the upper limit of conditional expression (1) is exceeded, the outer diameter of the objective lens becomes large, and the fluctuation of coma aberration at the time of zooming becomes large.

  If the lower limit value of conditional expression (1) is not reached, the entrance pupil position in the low magnification end state is close to the object plane, and the rate of change of the image size at the time of defocusing becomes large, so the object side telecentricity cannot be ensured. .

  In this zoom lens for a microscope, since the lens surface closest to the object side of the second lens group has a concave shape, the lens having the concave shape reasonably bends the light beam and satisfies the conditional expression (1). The occurrence of coma from the two lens units is suppressed.

  Conditional expression (2) defines an appropriate range of the ratio of the focal lengths of the first lens group and the second lens group. By satisfying conditional expression (2), a zoom lens for a microscope having a high zoom ratio of 15 times or more and having a small zoom lens with high imaging performance while keeping the entrance pupil position in the low magnification end state away from the object plane Can be achieved.

  When the lower limit value of conditional expression (2) is not reached, the distance between the first lens group and the second lens group in the optical axis direction is narrowed, and the first lens group and the second lens group interfere with each other. The zoom ratio cannot be reduced, and as a result, a high zoom ratio cannot be obtained. In addition, if an attempt is made to obtain a high zoom ratio in a state where the lower limit value of conditional expression (2) is not reached, the distance between the first lens group and the second lens group becomes wide, making it impossible to achieve downsizing. In addition, if the zoom ratio is increased by increasing the refractive power of the third lens group and the fourth lens group in a state where the lower limit of conditional expression (2) is not reached, a high zoom ratio of 15 times or more is obtained. Absent.

  Conditional expression (3) defines an appropriate range of the magnification of the second lens group. By satisfying conditional expression (3), it is possible to achieve a zoom lens for a microscope having high imaging performance while maintaining the overall length of the zoom lens for microscope compact. In the present specification, the “magnification ratio” indicates the “burden amount” with respect to the “zoom ratio” of the microscope zoom lens.

  When the upper limit of conditional expression (3) is exceeded, the refractive power of the second lens group increases and the “burden amount” of the second lens group increases, which is advantageous for downsizing the zoom lens for a microscope. . However, in this case, an increase in distortion, an increase in astigmatism due to the deterioration of Petzval sum, an increase in coma at the time of zooming, especially an increase in fluctuation of the lower coma, etc. occur in the low magnification end state. Increases spherical aberration and the like.

  If the lower limit value of conditional expression (3) is not reached, an attempt to obtain a high zoom ratio increases the zoom ratio of the third lens group, and the amount of movement of the third lens group during zooming increases. As a result, it is necessary to increase the distance between the second lens group and the third lens group in order to prevent interference between the second lens group and the third lens group, and the overall length of the zoom lens for the microscope is increased. Cannot be achieved.

  In this zoom lens for a microscope, the fourth lens group has, in order from the object side, an eleventh lens group having a positive refractive power, a twelfth lens group having a negative refractive power, and a positive refractive power. The thirteenth lens group is preferable. With such a configuration, various aberrations can be corrected favorably, and downsizing of the zoom lens for a microscope can be achieved.

  When the lens closest to the image side of the fourth lens group is configured as a positive lens, the back focus can be shortened compared to when the lens closest to the image side is configured as a negative lens, and the overall length of the zoom lens is reduced.

  In addition, since the zoom lens for a microscope has the first to fourth lens groups, the case of a four-group configuration is included. In general, a zoom lens having a four-group configuration includes a focusing lens (first group: focus and focus adjustment), a variator lens (second group: variable magnification lens), a compensator lens (third group: correction lens), a relay lens ( 4th group: imaging lens), and each group has an independent role.

  The first group (focusing lens) has a function to focus on the subject, and the second group (variator lens) has a function to change the size of the image by changing the power distribution in the front and back, and the third group (compensator). The lens) works in conjunction with the variator lens and has a function of correcting the focus shift. The fourth group is called a relay lens or a master lens, and corrects aberrations generated in the zoom unit including the focusing lens, the variator lens, and the compensator lens of the first group to the third group, and is formed by the zoom unit. It has the function of returning the virtual image to a real image.

  As described above, the fourth group plays a role of forming an image formed by the zoom unit composed of the first group to the third group, so that the light flux passing through the fourth group at the time of zooming is substantially constant, and the fourth group In the zoom lens having the configuration, the fourth group acts as an independent lens. For this reason, various aberrations can be favorably corrected by configuring the fourth group to have a positive and negative triplet structure.

In addition, it is preferable that the zoom lens for the microscope satisfies the following conditional expression (4).
(4) 0.9 <d11 / d12 <1.2
Here, d11 is the distance between the most image side lens surface of the eleventh lens group and the most object side lens surface of the twelfth lens group, and d12 is the most image side lens surface of the twelfth lens group and the thirteenth lens group. The distance from the most object side lens surface of the 13 lens group is shown.

  Conditional expression (4) defines an appropriate range of the ratio between the distance between the twelfth lens group and the thirteenth lens group and the distance between the eleventh lens group and the twelfth lens group. By satisfying conditional expression (4), in the fourth lens group, the distance between the eleventh lens group and the twelfth lens group and the distance between the twelfth lens group and the thirteenth lens group become substantially equal. It is possible to satisfactorily correct aberrations, particularly spherical aberrations and coma.

  If the upper limit value of conditional expression (4) is exceeded, the distance between the eleventh lens group and the twelfth lens group becomes too large, and the field curvature deteriorates.

  When the lower limit value of conditional expression (4) is not reached, coma and spherical aberration are deteriorated.

In addition, it is preferable that the zoom lens for the microscope satisfies the following conditional expression (5).
(5) 0.05 <d11 / | f4 | <0.2
Here, d11 is the distance between the most image side lens surface of the eleventh lens group and the most object side lens surface of the twelfth lens group, and f4 is the focal length of the fourth lens group.

  Conditional expression (5) defines the focal length of the fourth lens group and the distance between the eleventh lens group and the twelfth lens group in the fourth lens group. By satisfying conditional expression (5), an appropriate back focus can be secured and the exit pupil position can be moved away from the image plane.

  An image pickup device such as a CCD has an element structure, for example, a color filter or a light receiving portion located behind a light shielding portion of a charge transfer path. When an image sensor such as a CCD is placed on the image plane to change the amount of peripheral light (shading), the exit pupil position is set as far as possible from the image formation position, and the light beam is designed to enter the element almost perpendicularly. There is a need. In addition, when an eyepiece is placed behind the image plane and the image is viewed through the eyepiece, it is easier to observe the image when the exit pupil position is far from the image plane, and the optical performance of the microscope itself is prevented from deteriorating. Can do.

  When the upper limit value of conditional expression (5) is exceeded, the back focus becomes too short, for example, even if an image pickup device such as a CCD is arranged on the image plane, the space cannot be secured, or optical adjustment after the lens is assembled. There is a possibility that the range of the movable image plane cannot be secured sometimes.

  If the lower limit value of conditional expression (5) is not reached, the exit pupil position approaches the image plane and the back focus becomes longer. As a result, the entire length of the zoom lens for a microscope becomes large, and it becomes impossible to achieve downsizing.

  In the zoom lens for a microscope, the second lens group moves only from the object side to the image side and the third lens group moves from the image side to the object side when zooming from the low magnification end state to the high magnification end state. It is preferable to move only to. With such a configuration, the moving mechanism of the lens unit at the time of zooming can be simplified.

  In addition, the microscope of the present application includes the microscope zoom lens having the above-described configuration. As a result, it is possible to realize a compact microscope having high image-forming performance while ensuring object-side telecentricity and having a high zoom ratio.

  Hereinafter, numerical examples of the microscope zoom lens according to the present embodiment will be described with reference to the accompanying drawings.

  FIG. 1A and FIG. 1B are diagrams showing a basic configuration and zoom movement locus of a zoom lens for a microscope common to each numerical example.

The zoom lens for a microscope according to each example includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a third lens having a positive refractive power. The lens group G3 includes a fourth lens group G4 having negative refractive power, and the lens surface closest to the object side of the second lens group G2 has a concave shape.
1A and 1B, I indicates an image plane.

  The zoom lens for this microscope is designed so that the air gap between the second lens group G2 and the third lens group G3 is reduced upon zooming from the low magnification end state (FIG. 1A) to the high magnification end state (FIG. 1B). The second lens group G2 moves only from the object side to the image side, and the third lens group G3 moves only from the image side to the object side. In this way, the zoom lens for this microscope can take a trajectory that the second lens group and the third lens group move only in one direction and return in the middle when zooming from the low magnification end state to the high magnification end state. Absent.

(First embodiment)
FIG. 2 is a diagram illustrating a lens configuration of the zoom lens for a microscope according to the first example.

  The zoom lens for a microscope according to the first example includes a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, an aperture stop S, and a positive lens in order from the object side. It is composed of a third lens group G3 having a refractive power and a fourth lens group G4 having a negative refractive power.

  The first lens group G1 includes, in order from the object side, a cemented positive lens composed of a negative meniscus lens L11 having a convex surface facing the object side and a biconvex positive lens L12, and a positive meniscus having a convex surface facing the object side. It consists of a lens L13.

  The second lens group G2 includes, in order from the object side, a negative biconcave lens L21, a negative cemented lens formed by cementing a biconcave negative lens L22 and a positive meniscus lens L23 having a convex surface facing the object side. Has been.

  The third lens group G3 includes, in order from the object side, a biconvex positive lens L31, and a cemented positive lens formed by cementing a negative meniscus lens L32 having a convex surface toward the object side and a biconvex positive lens L33. Has been.

  The fourth lens group G4 includes, in order from the object side, an eleventh lens group G4a having a positive refractive power, a twelfth lens group G4b having a negative refractive power, and a thirteenth lens group G4c having a positive refractive power. It is composed of

  The eleventh lens group G4a includes, in order from the object side, a cemented positive lens formed by cementing a biconvex positive lens L41 and a biconcave negative lens L42.

  The twelfth lens group G4b includes, in order from the object side, a cemented negative lens formed by cementing a planoconvex lens L43 having a convex surface toward the image surface I side and a biconcave negative lens L44.

  The thirteenth lens group G4c is composed of a biconvex positive lens L45.

  Table 1 below shows specification values of the zoom lens for a microscope according to the first example.

  In (lens data), the object surface is the object surface, the surface number is the order of the lens surfaces counted from the object side, r is the radius of curvature of each lens surface, d is the surface spacing of the lens surfaces, and nd is the d-line (wavelength λ = The refractive index is 587.6 nm), νd is the Abbe number for the d-line (wavelength λ = 587.6 nm), (variable) is the variable surface separation, (diaphragm) is the aperture stop S, and the image plane is the image plane I. ing. Note that “∞” of the radius of curvature r indicates a plane, and the refractive index of air nd = 1.00000 is omitted.

  In (various data), f represents a focal length, FNO represents an F number, Y represents an image height, Bf represents a back focus, and di (i: integer) represents a variable surface interval value at a surface number i. (Conditional expression corresponding value) indicates the corresponding value of each conditional expression. Note that β represents the total magnification of the entire system when an objective lens shown in Table 4 described later is attached to the microscope zoom lens of each of the following examples.

  It should be noted that “mm” is generally used as a unit of focal length f, radius of curvature r, and other lengths listed in all the following specification values. However, the optical system is not limited to this because the same optical performance can be obtained even when proportionally enlarged or reduced. Further, the unit is not limited to “mm”, and other appropriate units may be used. Further, these symbols are the same in the other embodiments described below, and the description thereof is omitted.

(Table 1) First Example

(Lens data)
Surface number r d nd νd
Object ∞
1) 90.853 2.0 1.80440 39.58
2) 40.963 3.7 1.49782 82.52
3) -93.816 0.2
4) 35.739 2.5 1.49782 82.52
5) 57.591 (variable)
6) -46.767 1.5 1.77250 49.61
7) 26.174 2.5
8) -41.406 1.0 1.60300 65.47
9) 15.6205 2.2 1.75520 27.51
10) 148.037 (variable)
11> (Aperture) ∞ (Variable)
12) 58.572 2.0 1.60300 65.47
13) -58.572 0.2
14) 42.396 1.5 1.74950 35.33
15) 19.005 2.6 1.49782 82.52
16) -363.441 (variable)
17) 13.3198 3.0 1.48749 70.41
18) -331.203 1.5 1.65844 50.89
19) 22.4254 14.8
20) ∞ 2.0 1.62004 36.26
21) -10.484 1.5 1.77250 49.61
22) 10.484 15.7
23) 25.847 2.7 1.72916 54.66
24) -471.548
Image plane ∞

(Various data)
Zoom ratio (Z) 20.0
Low magnification end state Intermediate focal length state High magnification end state β 0.445 2.0 8.9
f 22.25 100 445
FNO 10.93 13.86 22.44
Y 4.45 4.45 4.45
Bf 17.22 17.22 17.22
d5 7.84782 38.30537 50.90242
d10 45.92459 15.46704 2.86999
d11 45.12076 30.05941 2.87356
d16 2.52033 17.58168 44.76753

(Zoom lens group data)
Group start surface f
1 1 82.1
2 6 -17.3
3 12 37.75
4 17 -135.2
11 17 101.15
12 20 -11.2
13 23 33.7

(Values for conditional expressions)
(1) d1W / | f2 | = 0.454
(2) | f1 / f2 | = 4.75
(3) Z ^0.5 = 4.472 <V2 = 5.884 <Z ^0.6 = 6.034
(4) d11 / d12 = 0.944
(5) d11 / | f4 | = 0.11

  3A to 3C are graphs showing various aberrations in the infinitely focused state of the microscope zoom lens according to the first example. FIG. 3A is a low magnification end state, FIG. 3B is an intermediate focal length state, and FIG. Each aberration diagram in the end state is shown. When actually used as a microscope, it is used in combination with an objective lens shown in Table 3 to be described later. In this example, in order to show the performance of the microscope zoom lens well, aberrations of only the microscope zoom lens are used. Figure (ie ray tracing from infinity) is shown.

  In each aberration diagram, FNO represents an F number, and Y represents an image height. D is a d-line (wavelength λ = 587.56 nm), C is a C-line (wavelength λ = 656.27 nm), F is an F-line (wavelength λ = 486.13 nm), and g is a g-line (wavelength λ = 435). .84 nm) aberration curve.

  In the astigmatism diagram, the solid line represents the sagittal image plane, and the dotted line represents the meridional image plane.

  In addition, in the various aberration diagrams of the following examples, the same reference numerals as those of the present example are used.

  From the various aberration diagrams, the zoom lens for a microscope according to the first example corrects various aberrations well in each of the low magnification end state, the intermediate focal length state, and the high magnification end state, and has excellent imaging. It can be seen that it has performance. While having a high zoom ratio of 20 times, the object side telecentricity at the low magnification end state is ensured.

(Second embodiment)
FIG. 4 is a diagram illustrating a lens configuration of a zoom lens for a microscope according to the second example.

  The zoom lens for a microscope according to the second example includes a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, an aperture stop S, and a positive lens in order from the object side. It is composed of a third lens group G3 having a refractive power and a fourth lens group having a negative refractive power.

  The first lens group G1 includes, in order from the object side, a cemented positive lens composed of a negative meniscus lens L11 having a convex surface facing the object side and a biconvex positive lens L12, and a positive meniscus having a convex surface facing the object side. It consists of a lens L13.

  The second lens group G2 includes, in order from the object side, a biconcave negative lens L21, a cemented negative lens formed by cementing a biconcave negative lens L22 and a positive meniscus lens L23 having a convex surface facing the object side. It is configured.

  The third lens group G3 includes, in order from the object side, a biconvex positive lens L31, and a cemented positive lens formed by cementing a negative meniscus lens L32 having a convex surface toward the object side and a biconvex positive lens L33. It is configured.

  The fourth lens group G4 includes, in order from the object side, an eleventh lens group G4a having a positive refractive power, a twelfth lens group G4b having a negative refractive power, and a thirteenth lens group G4c having a positive refractive power. It is composed of

  The eleventh lens group G4a includes, in order from the object side, a cemented positive lens formed by cementing a positive meniscus lens L41 having a convex surface toward the object side and a negative meniscus lens L42 having a convex surface toward the object side.

  The twelfth lens group G4b includes, in order from the object side, a cemented negative lens formed by cementing a positive meniscus lens L43 having a convex surface toward the image plane I side and a biconcave negative lens L44.

  The thirteenth lens group G4c is composed of a positive meniscus lens L45 having a convex surface directed toward the image plane I side.

  Table 2 below shows specification values of the zoom lens for a microscope according to the second example.

(Table 2) Second Example

(Lens data)
Surface number r d nd νd
Object ∞
1) 91.226 2.0 1.80454 39.58
2) 40.601 3.7 1.49782 82.52
3) -87.866 0.2
4) 35.309 2.5 1.49782 82.52
5) 57.954 (variable)
6) -80.849 1.5 1.83481 42.72
7) 22.652 2.5
8) -109.856 1.0 1.67025 57.53
9) 13.908 2.2 1.80518 25.41
10) 69.587 (variable)
11> (Aperture) ∞ (Variable)
12) 65.818 2.0 1.59319 67.87
13) -189.737 0.2
14) 35.488 1.5 1.80384 33.89
15) 19.685 2.6 1.49782 82.52
16) -68.032 (variable)
17) 12.935 3.0 1.48749 70.41
18) 337.055 1.5 1.74810 52.30
19) 22.591 18.866
20) -70.712 2.0 1.62004 36.27
21) -5.747 1.5 1.80411 46.55
22) 10.889 16.529
23) -161.088 2.7 1.61720 54.01
24) -17.582
Image plane ∞

(Various data)
Zoom ratio (Z) 15.0
Low magnification end state Intermediate focal length state High magnification end state β 0.7 2.7 10.5
f 35 135 525
FNO 11.65 14.56 25.09
Y 4.45 4.45 4.45
Bf 16.00 16.00 16.00
d5 10.69191 35.75734 47.15302
d10 39.83384 14.76841 3.37273
d11 42.85259 28.38675 3.34255
d16 2.47741 16.94325 41.98745


(Zoom lens group data)
Group start surface f
1 1 79.0
2 6 -17.5
3 12 38.0
4 17 -120.41
11 17 112.41
12 20 -8.43
13 23 31.75

(Values for conditional expressions)
(1) d1W / | f2 | = 0.611
(2) | f1 / f2 | = 4.51
(3) Z ^0.5 = 3.873 <V2 = 4.969 <Z ^0.6 = 5.078
(4) d11 / d12 = 1.141
(5) d11 / | f4 | = 0.157

  FIGS. 5A to 5C are graphs showing various aberrations of the microscope zoom lens according to the second example in the infinite focus state. FIG. 5A is a low magnification end state, FIG. 5B is an intermediate focal length state, and FIG. Each aberration diagram in the end state is shown.

  From the various aberration diagrams, the zoom lens for a microscope according to the second example corrects various aberrations well in each of the low magnification end state, the intermediate focal length state, and the high magnification end state, and has excellent imaging. It can be seen that it has performance. While having a high zoom ratio of 15 times, the object side telecentricity at the low magnification end state is ensured.

  The zoom lens for a microscope according to the present embodiment can be used in combination with, for example, an objective lens having specifications shown in FIG. 6 and Table 3 below.

  FIG. 6 is a diagram showing the lens configuration of the objective lens.

(Table 3)

(Lens data)
Surface number r d nd νd
Object ∞
1) -14.400 1.60 1.65412 39.68
2) -19.900 0.10
3) 24.500 4.30 1.72342 37.95
4) 423.036 1.20 1.61340 44.27
5) 39.904 2.10
6) 296.026 1.20 1.83481 42.72
7) 20.657 8.10 1.43425 95.00
8) -32.011 0.35
9) 101.559 3.80 1.49782 82.52
10) -40.270
Image plane ∞

(Various data)
Focal length = 50
Maximum NA = 0.2
Working distance = 30.28

  FIG. 7 is a diagram illustrating an optical system of a microscope including the microscope zoom lens according to the embodiment.

  The light from the object 1 is converted into parallel light by the objective lens 2 as shown in FIG. 6, and then zoomed by the zoom lens 3 and simultaneously forms an image of the object on the image plane I. Then, for example, an observer observes this image through an eyepiece (not shown), or an imaging unit such as an imaging device I such as a CCD is arranged on the image plane and observed through a monitor. When an imaging means such as a CCD is disposed on the image plane, a relatively large object such as a metal specimen or a mechanical part (for example, a gear) can be observed well with a wide field of view.

Claims (7)

Receiving a flat row light from the objective lens, a microscope zoom lens for forming on an imaging surface of the imaging device,
In order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and a fourth lens having a negative refractive power It consists of a group,
The fourth lens group includes, in order from the object side, an eleventh positive lens, a twelfth negative lens, and a thirteenth positive lens.
Upon zooming from the low magnification end state to the high magnification end state, the second lens group and the third lens group move along the optical axis direction,
A zoom lens for a microscope characterized by satisfying the following conditions.
0.4 <d1W / | f2 | <0.7
0.9 <d11 / d12 <1.2
However,
d1W: Distance between the most image side lens surface of the first lens group and the most object side lens surface of the second lens group in the low magnification end state f2: Focal length of the second lens group d11: The eleventh distance between the most object side lens surface of the most image side lens surface and the twelfth negative lens of the positive lens d12: the most object side of the most image side lens surface of the twelfth negative lens and the thirteenth positive lens Distance from lens surface The zoom lens for a microscope according to claim 1, wherein the following condition is satisfied.
0.05 <d11 / | f4 | <0.2
However,
d11: Distance between the most image side lens surface of the eleventh positive lens and the most object side lens surface of the twelfth negative lens f4: Focal length of the fourth lens group The zoom lens for a microscope according to claim 1, wherein the following condition is satisfied.
| F1 / f2 |> 4.5
However,
f1: Focal length of the first lens group The zoom lens for a microscope according to claim 1, wherein the following condition is satisfied.
Z0.5 <V2 <Z0.6
However,
Z: Zoom ratio of the microscope zoom lens V2: Variable magnification of the second lens group   The zoom lens for a microscope according to claim 1 or 2, wherein a lens surface closest to the object side of the second lens group has a concave shape.   In zooming from the low magnification end state to the high magnification end state, the second lens group moves only from the object side to the image side, and the third lens group moves only from the image side to the object side. The zoom lens for microscopes according to claim 1 or 2.   A microscope comprising: an objective lens; and the zoom lens for a microscope according to claim 1.

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