JP2011118159A - Zoom lens for microscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive zoom lens for a microscope having a variable power ratio exceeding 5 times, and having the number of lenses which is small to the utmost. <P>SOLUTION: The zoom lens has in due order from the sample side, a first lens group G1 having a positive refractive power, a second lens group G2 in which a positive refractive power performing zoom action is moved, and a third lens group G3 in which a positive refractive power performing zoom action is moved, and satisfies following conditional formulas (1), (2) and (3): (1) 0.8<f2/f3<1.3; (2) 0.3<f1/(f2+f3)<1.4; and (3) 0.4<(f2+f3)/L<1.1; wherein f1 is a focal distance of the first lens group G1; f2 is a focal distance of the second lens group G2; f3 is a focal distance of the third lens group G3; and L is a distance from the sample to an image. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a zoom lens for a microscope, and more particularly to a zoom lens suitable for a microscope that performs magnification conversion by zooming at an enlargement ratio of about 1 to 10 times excluding an eyepiece.

  Conventionally, for example, a lens described in Patent Document 1 is known as a zoom lens for a microscope. This is a zoom lens of about 5 to 8 times having two moving lens groups having the same power (refractive power).

  Further, Patent Document 2 proposes a zoom lens having a moving lens group of about 13 times composed of two lens groups of a negative lens group and a positive lens group. Further, Patent Document 3 discloses a zoom lens of about 4 times in which the moving lens group is composed of two lens groups, a negative refractive power lens group and a positive refractive power lens group.

JP 2004-145351 A Japanese Patent Laid-Open No. 11-95099 Japanese Patent No. 3990126

Since the zoom lens described in Patent Document 1 is a concave lens, the light beam diverges. For this reason, an image cannot be formed unless convex lenses are added to the front and rear. This increases the number of lenses.
The zoom lenses described in Patent Document 2 and Patent Document 3 have a large number of lenses.
As described above, in the conventional configuration of the combination of the negative refracting power lens and the positive refracting power lens, there is a problem that the number of lenses increases when the zoom ratio is increased.

  The present invention has been made in view of the above, and an object of the present invention is to provide an inexpensive zoom lens for a microscope having a zoom ratio exceeding 5 times, the number of lenses being as small as possible.

In order to solve the above-mentioned problems and achieve the object, according to the present invention,
In order from the sample side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power that performs a zoom action, and a third lens group G3 having a positive refractive power that performs a zoom action. Have
A microscope zoom lens characterized by satisfying the following conditional expressions (1), (2), and (3) can be provided.
0.8 <f2 / f3 <1.3 (1)
0.3 <f1 / (f2 + f3) <1.4 (2)
0.4 <(f2 + f3) / L <1.1 (3)
here,
f1 is the focal length of the first lens group G1,
f2 is the focal length of the second lens group G2,
f3 is the focal length of the third lens group G3,
L is the distance from the specimen to the image,
It is.

According to a preferred aspect of the present invention, the fourth lens group G4 having a negative refractive power is further provided between the third lens group G3 and the image plane.
It is preferable that the following conditional expression (4) is satisfied.
0.3 <| 2 · f4 / (f2 + f3) | (4)
here,
f4 is the focal length of the fourth lens group G4,
It is.

According to a preferred aspect of the present invention, the first lens group G1 includes, in order from the sample side, a lens group G1t having a positive refractive power and a lens group having a negative refractive power arranged at a distance d0 from the lens group G1t. It is preferable that the following conditional expressions (5) and (6) are satisfied.
0.7 <| f1t / f1o | <1 (5)
d0 / f1t <0.5 (6)
here,
f1t is a focal length of the lens unit G1t having a positive refractive power,
f1o is a focal length of the lens unit G1o having a negative refractive power,
It is.

According to a preferred aspect of the present invention, the fourth lens group G4 is composed of a negative refractive power lens group G4o and a positive refractive power lens group G4t in this order from the sample side.
It is preferable that the following conditional expression (7) is satisfied.
1 <| f4t / f4o | (7)
here,
f4o is a focal length of the lens unit G4o having a negative refractive power,
f4t is a focal length of the lens unit G4t having a positive refractive power,
It is.

  The present invention has an effect of providing a zoom lens for a microscope that has a zoom ratio exceeding 5 times, has as few lenses as possible, and is inexpensive.

Lens cross section at high magnification (9.8 times) (a), medium magnification (2.65 times) (b), and low magnification (0.72 times) (c) of Example 1 of the zoom lens for a microscope of the present invention FIG. FIG. 5 is aberration diagrams of Example 1 at high magnification (a), medium magnification (b), and low magnification (c). The lens cross section at high magnification (3.75 times) (a), medium magnification (1.38 times) (b), and low magnification (0.75 times) (c) of Example 2 of the zoom lens for a microscope of the present invention. FIG. FIG. 6 is aberration diagrams of Example 2 at high magnification (a), medium magnification (b), and low magnification (c). FIG. 6 is a lens cross-sectional view at a high magnification (9 ×) (a), a medium magnification (3 ×) (b), and a low magnification (1 ×) (c) of Example 3 of a zoom lens for a microscope according to the present invention. FIG. 6 is aberration diagrams of Example 3 at high magnification (a), medium magnification (b), and low magnification (c). FIG. 4 is a lens cross-sectional view at a high magnification (10 ×) (a), a medium magnification (2.7 ×) (b), and a low magnification (0.74 ×) (c) of Example 4 of a zoom lens for a microscope according to the present invention. is there. FIG. 6 is aberration diagrams of Example 4 at high magnification (a), medium magnification (b), and low magnification (c). Example 5 of the zoom lens for a microscope according to the present invention at high magnification (9.3 times) (a), medium magnification (2.5 times) (b), and low magnification (0.68 times) (c) FIG. FIG. 6 is aberration diagrams of Example 5 at high magnification (a), medium magnification (b), and low magnification (c). Lens cross section at high magnification (9.3 times) (a), medium magnification (2.5 times) (b), and low magnification (0.68 times) (c) of Example 6 of a zoom lens for a microscope of the present invention FIG. FIG. 6 is aberration diagrams of Example 6 at high magnification (a), medium magnification (b), and low magnification (c). FIG. 6 is a lens cross-sectional view at a high magnification (9 ×) (a), a medium magnification (2.4 ×) (b), and a low magnification (0.66 ×) (c) of Example 7 of a zoom lens for a microscope according to the present invention. is there. FIG. 8 is aberration diagrams of Example 7 at high magnification (a), medium magnification (b), and low magnification (c). It is a figure explaining the concept of this invention.

Embodiments of a zoom lens for a microscope according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.
First, prior to the description of the embodiments, the operational effects of the microscope zoom lens will be described.

  The zoom lens for a microscope according to the embodiment has two moving groups as a minimum configuration. The first moving group is a lens group (variator) that moves to change the projection magnification. The second moving group is a lens group (compensator) that corrects the shift of the imaging position accompanying the movement of the variator.

  The magnification also changes in accordance with the movement of the lens group that corrects the deviation of the imaging position. For this reason, in practice, the role of the variator and the role of the compensator cannot be clearly distinguished, or the main role may be switched during zooming.

  A zoom lens having two moving groups usually comprises a positive refractive power group and a negative refractive power group. If you try to increase the zoom ratio, the number of lenses increases. In this embodiment, the movable lens unit is composed of two movable groups of a positive refractive power lens group and a positive refractive power lens group. Therefore, a desired zoom magnification ratio can be achieved with a small number of lenses.

  The operation and effect of this embodiment will be described with reference to FIG. FIG. 15A shows a lens arrangement with a magnification of 2X. FIG. 15B shows a lens arrangement with a magnification of 0.5X in which the arrangement of FIG. When the movable groups G1 and G2 are both positive groups, it can be seen that the arrangement of the magnification 2X and the magnification 0.5X can be continuously connected paraxially.

  On the other hand, when the movable groups G1 and G2 are composed of two positive and negative groups, it is impossible to connect them in this way. For this reason, the positive group is more advantageous for the two groups with respect to the fact that a large zoom ratio can be obtained.

  Further, when only the second group G1, G2 is viewed, the lens arrangement is symmetric with respect to the magnification 1X. For this reason, the absolute magnification cannot be increased. In order to increase the magnification as a microscope, a lens group with a fixed positive refractive power for enlarging the image and increasing the NA is arranged on the front side, and an image of the image at low magnification is further increased behind the movable group. In order to secure a circle, a lens group having a negative refractive power may be arranged.

  If the positive lens group fixed on the front side is composed of a convex lens and a concave lens, the distance between the two lenses is close to afocal. For this reason, focusing can be performed by moving the convex lens. The concave lens can correct spherical aberration and field curvature by improving Petzval sum. The negative lens group behind the movable group also has a large effect of correcting curvature of field by improving the Petzval sum. Moreover, the exit pupil position can be adjusted by configuring the rear negative lens group with a convex lens and a concave lens. This makes it possible to make the incident angle of light rays on an image pickup device such as a CCD closer to telecentricity.

And according to this embodiment,
In order from the sample side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power that performs a zoom action, and a third lens group G3 having a positive refractive power that performs a zoom action. Have
A microscope zoom lens characterized by satisfying the following conditional expressions (1), (2), and (3) can be provided.
0.8 <f2 / f3 <1.3 (1)
0.3 <f1 / (f2 + f3) <1.4 (2)
0.4 <(f2 + f3) / L <1.1 (3)
here,
f1 is the focal length of the first lens group G1,
f2 is the focal length of the second lens group G2,
f3 is the focal length of the third lens group G3,
L is the distance from the specimen to the image,
It is.

Conditional expression (1) defines the ratio of the focal lengths of the two lens groups that move with zoom. Since the two lens groups that move by zooming have the same power, the lens configuration is symmetric and a zoom ratio can be achieved. In the sixth and seventh embodiments, the two lens groups are the same lens.
If the lower limit of conditional expression (1) is not reached, it is impossible to secure a visual field at low magnification.
If the upper limit of conditional expression (1) is exceeded, the NA at high magnification cannot be increased. In order to ensure NA, the power of the first lens group G1 may be increased. However, in this case, coma aberration around the visual field at the time of low magnification deteriorates.

If the lower limit value of conditional expression (2) is not reached, the power of the first lens group G1 becomes strong, and the coma aberration at the periphery of the field of view at the time of low magnification deteriorates.
If the upper limit of conditional expression (2) is exceeded, the NA at high magnification cannot be increased.

If the lower limit value of conditional expression (3) is not reached, the power of the second lens group G2 and the third lens group G3 becomes strong, and the number of lenses increases for aberration correction.
If the upper limit of conditional expression (3) is exceeded, the zoom ratio cannot be increased.

According to a preferred embodiment of the present invention, the fourth lens group G4 having a negative refractive power is further provided between the third lens group G3 and the image plane.
It is preferable that the following conditional expression (4) is satisfied.
0.3 <| 2 · f4 / (f2 + f3) | (4)
here,
f4 is the focal length of the fourth lens group G4,
It is.

  If the lower limit value of conditional expression (4) is not reached, the exit pupil approaches the image position and coma increases.

According to a preferred embodiment of the present invention, the first lens group G1 includes, in order from the sample side, a positive refractive power lens group G1t, and a negative refractive power lens disposed at a distance d0 from the lens group G1t. It is preferable to satisfy the following conditional expressions (5) and (6).
0.7 <| f1t / f1o | <1 (5)
d0 / f1t <0.5 (6)
here,
f1t is the focal length of the lens group G1t,
f1o is the focal length of the lens group G1o,
It is.

If the lower limit of conditional expression (5) is not reached, coma will increase when zooming is reduced.
If the upper limit of conditional expression (5) is exceeded, the NA at high magnification cannot be increased.
If the upper limit of conditional expression (6) is exceeded, spherical aberration at the time of high magnification deteriorates. In addition, the field curvature at the time of low magnification deteriorates.

According to a preferred embodiment of the present invention, the fourth lens group G4 is composed of a negative refractive power lens group G4o and a positive refractive power lens group G4t in this order from the sample side.
It is preferable that the following conditional expression (7) is satisfied.
1 <| f4t / f4o | (7)
here,
f4o is the focal length of the lens unit G4o having negative refractive power,
f4t is a focal length of the lens unit G4t having a positive refractive power,
It is.

  If the lower limit of conditional expression (7) is not reached, coma will increase.

Next, a microscope zoom lens according to embodiment 1 of the present invention will be described. 1A and 1B are cross-sectional views along an optical axis showing an optical configuration of a microscope zoom lens according to Example 1 of the present invention. FIG. 1A is a high magnification (9.8 ×), and FIG. 1B is a medium magnification (2. (65 times) and (c) are cross-sectional views at a low magnification (0.72 times).
In this embodiment, a fixed magnification of 1.39 times is applied to the fixed first lens group G1, and 1.9 times is applied to the fixed fourth lens group G4, and the entire zoom lens is 0.72 to 9.8 times. This is a zoom lens for a microscope with a zoom ratio of 13.6 times.

  FIG. 2 is a diagram illustrating spherical aberration (SA), field curvature (AS, S is sagittal, T is tangential), and distortion (DT) when the zoom lens according to the first embodiment is focused on an object point at infinity. (A) is a high magnification, (b) is a medium magnification, and (c) is a low magnification state. NA represents the numerical aperture, FNO represents the F number, and FIY represents the image height. The symbols in the aberration diagrams are the same in the examples described later.

As shown in FIG. 1, the zoom lens of Example 1 includes, in order from the sample side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a positive refractive power. And a fourth lens group G4 having negative refracting power.
In all of the following examples, I indicates an imaging plane (an imaging plane of an electronic imaging device).

  The first lens group G1 includes a positive meniscus lens L1 having a convex surface directed toward the image surface side, and has a positive refractive power as a whole. The second lens group G2 includes, in order from the sample side, a cemented lens of a negative meniscus lens L2 having a convex surface facing the sample side and a biconvex positive lens L3, and has a positive refractive power as a whole. . The third lens group G3 includes, in order from the sample side, a cemented lens of a negative meniscus lens L4 having a convex surface facing the sample side and a biconvex positive lens L5, and has a positive refractive power as a whole. . The fourth lens group G4 includes a biconcave negative lens L6, and has a negative refracting power as a whole.

  When zooming from high magnification to low magnification, the first lens group G1 is fixed. The second lens group G2 moves to the image plane side. The third lens group G3 moves to the image plane side. The fourth lens group G4 is fixed.

  The aspheric surface is provided on one surface of the sample side of the positive meniscus lens L1 of the first lens group G1.

Next, a microscope zoom lens according to embodiment 2 of the present invention will be described. 3A and 3B are cross-sectional views along the optical axis showing the optical configuration of the microscope zoom lens according to Example 2 of the present invention. FIG. 3A is a high magnification (3.75 times), and FIG. 3B is a medium magnification (1. (38 times) and (c) are cross-sectional views at a low magnification (0.75 times).
The present embodiment is a microscope zoom lens having a zoom ratio of 5.times., Which is 1.68 times for the fixed first lens group G1 and 0.75 times to 3.75 times for the entire zoom lens. By suppressing the zoom ratio, the fourth lens group G4 can be omitted, and the third lens group G3 can be simplified to a single lens.

  FIG. 4 is a diagram illustrating spherical aberration (SA), field curvature (AS, S is sagittal, T is tangential), and distortion (DT) when the zoom lens according to the second embodiment is focused on an object point at infinity. (A) is a high magnification, (b) is a medium magnification, and (c) is a low magnification state.

  As shown in FIG. 3, the zoom lens of Example 2 includes, in order from the sample side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a positive refractive power. And a third lens group G3.

  The first lens group G1 includes a biconvex positive lens L1, and has a positive refractive power as a whole. The second lens group G2 includes, in order from the sample side, a cemented lens of a negative meniscus lens L2 having a convex surface facing the sample side and a biconvex positive lens L3, and has a positive refractive power as a whole. . The third lens group G3 is composed of a biconvex positive lens L4, and has a positive refractive power as a whole.

  When zooming from high magnification to low magnification, the first lens group G1 is fixed. The second lens group G2 moves to the image plane side. The third lens group G3 moves to the image plane side.

Next, a microscope zoom lens according to embodiment 3 of the present invention will be described. 5A and 5B are cross-sectional views along the optical axis showing the optical configuration of the microscope zoom lens according to Example 3 of the present invention, in which FIG. 5A is a high magnification (9 ×), FIG. 5B is a medium magnification (3 ×), (C) is a cross-sectional view at a low magnification (1 ×).
In this embodiment, a fixed magnification of 1.63 times is applied to the fixed first lens group G1, and 1.83 times is applied to the fixed fourth lens group G4, and a zoom ratio of 1 to 9 times in the entire zoom lens is 9 times. This is a microscope zoom lens. By suppressing the zoom ratio, the third lens group G3 can be simplified to a single lens.

  FIG. 6 is a diagram illustrating spherical aberration (SA), field curvature (AS, S is sagittal, T is tangential), and distortion (DT) when the zoom lens according to the third embodiment is focused on an object point at infinity. (A) is a high magnification, (b) is a medium magnification, and (c) is a low magnification state.

  As shown in FIG. 5, the zoom lens of Example 3 includes, in order from the sample side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a positive refractive power. A third lens group G3 having a negative refractive power and a fourth lens group G4 having a negative refractive power.

  The first lens group G1 includes a positive meniscus lens L1 having a convex surface directed toward the image surface side, and has a positive refractive power as a whole. The second lens group G2 includes, in order from the sample side, a cemented lens of a biconcave negative lens L2 and a biconvex positive lens L3, and has a positive refractive power as a whole. The third lens group G3 is composed of a biconvex positive lens L4, and has a positive refractive power as a whole. The fourth lens group G4 includes a negative meniscus lens L5 having a convex surface directed toward the sample side, and has a negative refracting power as a whole.

  When zooming from high magnification to low magnification, the first lens group G1 is fixed. The second lens group G2 moves to the image plane side. The third lens group G3 moves to the image plane side. The fourth lens group G4 is fixed.

Next, a microscope zoom lens according to embodiment 4 of the present invention will be described. 7A and 7B are cross-sectional views along the optical axis showing the optical configuration of the microscope zoom lens according to Example 4 of the present invention. FIG. 7A is a high magnification (10 times), and FIG. 7B is a medium magnification (2.7 times). ) And (c) are cross-sectional views at a low magnification (0.74 times).
In this embodiment, a fixed magnification of 1.4 times is applied to the fixed first lens group G1, and 1.93 times is applied to the fixed fourth lens group G4, and a zoom ratio of 0.74 times to 10 times is applied to the entire zoom lens. This is a 13.5 times zoom lens for a microscope. The fourth lens group G4 is made into two groups, negative and positive, to correct the exit pupil position.

  FIG. 8 is a diagram illustrating spherical aberration (SA), field curvature (AS, S is sagittal, T is tangential), and distortion (DT) when the zoom lens according to the fourth embodiment is focused on an object point at infinity. (A) is a high magnification, (b) is a medium magnification, and (c) is a low magnification state.

  As shown in FIG. 7, the zoom lens of Example 4 includes, in order from the sample side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a positive refractive power. A third lens group G3 having a negative refractive power and a fourth lens group G4 having a negative refractive power.

  The first lens group G1 includes a positive meniscus lens L1 having a convex surface directed toward the image surface side, and has a positive refractive power as a whole. The second lens group G2 includes, in order from the sample side, a cemented lens of a negative meniscus lens L2 having a convex surface facing the sample side and a biconvex positive lens L3, and has a positive refractive power as a whole. . The third lens group G3 includes, in order from the sample side, a negative meniscus lens L4 having a convex surface facing the sample side and a biconvex positive lens L5, and has a positive refractive power as a whole. The fourth lens group G4 includes, in order from the sample side, a biconcave negative lens L6 and a biconvex positive lens L7, and has a negative refracting power as a whole.

  When zooming from high magnification to low magnification, the first lens group G1 is fixed. The second lens group G2 moves to the image plane side. The third lens group G3 moves to the image plane side. The fourth lens group G4 is fixed.

Next, a microscope zoom lens according to embodiment 5 of the present invention will be described. 9A and 9B are cross-sectional views along the optical axis showing the optical configuration of the microscope zoom lens according to Example 5 of the present invention. FIG. 9A is a high magnification (9.3 times), and FIG. 9B is a medium magnification (2. 5x) and (c) are cross-sectional views at a low magnification (0.68 times).
In this embodiment, a fixed magnification of 1.07 times is applied to the fixed first lens group G1, and 2.34 times is applied to the fixed fourth lens group G4. The entire zoom lens is 0.68 to 9.3 times. This is a zoom lens for a microscope with a zoom ratio of 13.7 times.

  FIG. 10 is a diagram illustrating spherical aberration (SA), field curvature (AS, S is sagittal, T is tangential), and distortion (DT) when the zoom lens according to Example 5 is focused on an object point at infinity. (A) is a high magnification, (b) is a medium magnification, and (c) is a low magnification state.

  As shown in FIG. 9, the zoom lens of Example 5 includes, in order from the sample side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a positive refractive power. A third lens group G3 having a negative refractive power and a fourth lens group G4 having a negative refractive power.

  The first lens group G1 includes, in order from the sample side, a biconvex positive lens L1 and a biconcave negative lens, and has a positive refractive power as a whole. The second lens group G2 includes, in order from the sample side, a cemented lens of a negative meniscus lens L3 having a convex surface facing the sample side and a biconvex positive lens L4, and has a positive refractive power as a whole. . The third lens group G3 includes a cemented lens which is formed by a biconvex positive lens L5 and a negative meniscus lens L6 having a convex surface directed toward the image side, and has a positive refracting power as a whole. The fourth lens group G4 includes a biconcave negative lens L7, and has a negative refracting power as a whole.

  When zooming from high magnification to low magnification, the first lens group G1 is fixed. The second lens group G2 moves to the image plane side. The third lens group G3 moves to the image plane side. The fourth lens group G4 is fixed.

Next, a microscope zoom lens according to embodiment 6 of the present invention will be described. 11A and 11B are cross-sectional views along the optical axis showing the optical configuration of the microscope zoom lens according to Example 6 of the present invention. FIG. 11A is a high magnification (9.3 times), and FIG. 11B is a medium magnification (2. 5x) and (c) are cross-sectional views at a low magnification (0.68 times).
In this embodiment, a fixed magnification of 1.07 times is applied to the fixed first lens group G1, and 2.34 times is applied to the fixed fourth lens group G4, and the entire zoom lens is 0.68 times to 9.3 times. This is a zoom lens for a microscope with a zoom ratio of 13.7 times.

  FIG. 12 is a diagram illustrating spherical aberration (SA), field curvature (AS, S is sagittal, T is tangential), and distortion (DT) when the zoom lens according to Example 6 is focused on an object point at infinity. (A) is a high magnification, (b) is a medium magnification, and (c) is a low magnification state.

  As shown in FIG. 11, the zoom lens of Example 6 includes, in order from the sample side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a positive refractive power. A third lens group G3 having a negative refractive power and a fourth lens group G4 having a negative refractive power.

  The first lens group G1 includes, in order from the sample side, a biconvex positive lens L1 and a biconcave negative lens, and has a positive refractive power as a whole. The second lens group G2 includes, in order from the sample side, a cemented lens of a negative meniscus lens L3 having a convex surface facing the sample side and a biconvex positive lens L4, and has a positive refractive power as a whole. . The third lens group G3 is composed of, in order from the sample side, a cemented lens of a biconvex positive lens L5 and a negative meniscus lens L6 having a convex surface facing the image surface, and has a positive refractive power as a whole. Yes. The fourth lens group G4 includes, in order from the sample side, a cemented lens of a biconcave negative lens L7 and a positive meniscus lens L8 having a convex surface facing the sample side, and has a negative refractive power as a whole. .

  When zooming from high magnification to low magnification, the first lens group G1 is fixed. The second lens group G2 moves to the image plane side. The third lens group G3 moves to the image plane side. The fourth lens group G4 is fixed.

Next, a microscope zoom lens according to embodiment 7 of the present invention will be described. 13A and 13B are cross-sectional views along the optical axis showing the optical configuration of the microscope zoom lens according to Example 7 of the present invention. FIG. 13A is a high magnification (9 ×), and FIG. 13B is a medium magnification (2.4 ×). ) And (c) are cross-sectional views at a low magnification (0.66 times).
This embodiment is a microscope zoom lens having a configuration in which the specimen-side positive lens of the fixed first lens group G1 is extended by 5 mm compared to the sixth embodiment. In this embodiment, the distance between the biconvex positive lens L1 and the biconcave negative lens L2 of the first lens group G1 is not perfect afocal. For this reason, the magnification and the aberration are slightly changed, but focusing is possible.

  FIG. 14 is a diagram illustrating spherical aberration (SA), field curvature (AS, S is sagittal, T is tangential), and distortion (DT) when the zoom lens according to the seventh embodiment is focused on an object point at infinity. (A) is a high magnification, (b) is a medium magnification, and (c) is a low magnification state.

  As shown in FIG. 13, the zoom lens of Example 7 includes, in order from the sample side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a positive refractive power. A third lens group G3 having a negative refractive power and a fourth lens group G4 having a negative refractive power.

  The first lens group G1 includes, in order from the sample side, a biconvex positive lens L1 and a biconcave negative lens L2, and has a positive refractive power as a whole. The second lens group G2 includes, in order from the sample side, a cemented lens of a negative meniscus lens L3 having a convex surface facing the sample side and a biconvex positive lens L4, and has a positive refractive power as a whole. . The third lens group G3 is composed of, in order from the sample side, a cemented lens of a biconvex positive lens L5 and a negative meniscus lens L6 having a convex surface facing the image surface, and has a positive refractive power as a whole. Yes. The fourth lens group G4 includes, in order from the sample side, a cemented lens of a biconcave negative lens L7 and a positive meniscus lens L8 having a convex surface facing the sample side, and has a negative refractive power as a whole. .

  When zooming from high magnification to low magnification, the first lens group G1 is fixed. The second lens group G2 moves to the image plane side. The third lens group G3 moves to the image plane side. The fourth lens group G4 is fixed.

  Next, numerical data of optical members constituting the zoom lens of each of the above embodiments will be listed. In the numerical data of each embodiment, r1, r2,... Are the radius of curvature of each lens surface, d1, d2,... Are the thickness or air spacing of each lens, and nd1, nd2,. Are the Abbe number of each lens, Fno. Is the F number, f is the focal length of the entire system, and D0 is the distance from the sample to the first surface. * Indicates an aspherical surface.

The aspherical shape is expressed by the following equation (I) where z is the optical axis direction, y is the direction orthogonal to the optical axis, K is the conic coefficient, and A4, A6, A8, and A10 are the aspheric coefficients. expressed.
z = (y ² / r) / [1+ {1− (1 + K) (y / r) ² } ^1/2 ]
+ A2y ² + A4y ⁴ + A6y ⁶ + A8y ⁸ + A10y ¹⁰ (I)
E represents a power of 10. The symbols of these specification values are common to the numerical data of the examples described later.

Numerical example 1
Unit mm

Surface data surface number rd nd νd
Sample surface ∞ 13.20
1 * -27.467 4 1.51633 64.14
2 -16.094 2.06
3 40.324 1.8 1.74 28.3
4 15.421 4 1.56384 60.67
5 -35.209 2
6 40.278 1.8 1.7495 35.28
7 15.802 4 1.56384 60.67
8 -35.070 87.96
9 -21.299 1.7 1.497 81.54
10 201.232 34.02
11 ∞ (image plane)

Aspheric data first surface
K = 0.
A2 = 0.0000E + 00, A4 = -1.1670E-05, A6 = 1.1352E-06, A8 = -1.0241E-08, A10 = 0.0000E + 00

Zoom data surface spacing High magnification 9.8x Medium magnification 2.65x Low magnification 0.72x
d2 2.06 19.33 82.97
d5 2.00 48.51 2.16
d8 87.96 24.18 6.90

Numerical example 2
Unit mm

Surface data surface number rd nd νd
Object ∞ 20.27
1 917.818 4 1.58913 61.14
2 -34.303 1.11
3 45.424 1.8 1.7552 27.51
4 16.516 4 1.497 81.54
5 -34.625 2
6 92.859 3 1.51633 64.14
7 -39.148 96.52
8 ∞ (image plane)

Zoom data surface interval Wide angle 3.75x Medium magnification 1.38x Low magnification 0.75x
d2 1.11 24.66 56.03
d5 2.00 21.81 2.00
d7 96.52 53.16 41.61

Numerical Example 3
Unit mm

Surface data surface number rd nd νd
Object ∞ 10.12
1 -17.229 4 1.717 47.92
2 -11.923 1.11
3 -82.897 1.8 1.74077 27.79
4 14.317 4 1.62299 58.16
5 -16.099 2
6 21.729 3 1.497 81.54
7 -872.193 67.40
8 -15.378 1.7 1.697 48.52
9 -40.356 28.94
10 ∞ (image plane)

Zoom data surface interval High magnification 9x Medium magnification 3x Low magnification 1x
d2 1.1 15.3 57.9
d5 2.0 30.5 2.2
d7 67.4 24.7 10.4

Numerical Example 4
Unit mm

Surface data surface number rd nd νd
Object ∞ 13.20
1 * -27.091 4 1.51633 64.14
2 -15.896 2.06
3 38.432 1.8 1.74 28.3
4 15.181 4 1.56384 60.67
5 -36.868 2
6 38.335 1.8 1.7495 35.28
7 15.506 4 1.56384 60.67
8 -36.709 91.21
9 -16.533 1.7 1.58913 61.14
10 102.418 10
11 500.000 2 1.51742 52.43
12 -41.893 20.02
13 ∞ (image plane)

Aspheric data first surface
K = 0.
A2 = 0.0000E + 00, A4 = 1.3484E-06, A6 = -5.9922E-07, A8 = 8.7842E-09, A10 = 0.0000E + 00

Zoom data surface interval High magnification 10x Medium magnification 2.7x Low magnification 0.74x
d2 2.06 19.33 82.97
d5 2.00 48.51 2.16
d8 91.21 27.43 10.15

Numerical Example 5
Unit mm

Surface data surface number rd nd νd
Surface ∞ 17.92
1 86.258 4.5 1.57135 52.95
2 -15.782 1.5
3 -23.743 2 1.48749 70.23
4 28.552 2.42
5 45.504 1.8 1.74 28.28
6 19.740 4 1.55963 61.17
7 -36.008 2
8 36.008 4 1.55963 61.17
9 -19.740 1.8 1.74 28.28
10 -45.504 95.20
11 -24.965 1.7 1.55232 63.46
12 19.375 25.73
13 ∞ (image plane)

Zoom data surface interval High magnification 10x Medium magnification 2.7x Low magnification 0.74x
d4 2.42 19.80 83.84
d7 2.00 48.80 2.16
d10 95.20 31.02 13.63

Numerical Example 6
Unit mm

Surface data surface number rd nd νd
Surface ∞ 17.88
1 86.21 4.5 1.57135 52.95
2 -15.776 2.17
3 -23.754 2 1.48749 70.23
4 28.579 2.42
5 45.504 1.8 1.74 28.28
6 19.74 4 1.55963 61.17
7 -36.008 2
8 36.008 4 1.55963 61.17
9 -19.74 1.8 1.74 28.28
10 -45.504 95.23
11 -11.591 1.2 1.48749 70.23
12 8.317 3 1.7552 27.51
13 16.683 23.19
14 ∞ (image plane)

Zoom data surface interval High magnification 10x Medium magnification 2.7x Low magnification 0.74x

d4 2.42 19.80 83.84
d7 2.00 48.80 2.16
d10 98.45 34.27 16.88

Numerical Example 7
Unit mm

Surface data surface number rd nd νd
Surface ∞ 17.78
1 86.21 4.5 1.57135 52.95
2 -15.776 7.17
3 -23.754 2 1.48749 70.23
4 28.579 2.42
5 45.504 1.8 1.74 28.28
6 19.74 4 1.55963 61.17
7 -36.008 2
8 36.008 4 1.55963 61.17
9 -19.74 1.8 1.74 28.28
10 -45.504 95.23
11 -11.591 1.2 1.48749 70.23
12 8.317 3 1.7552 27.51
13 16.683 23.19
14 ∞ (image plane)

Zoom data surface interval High magnification 10x Medium magnification 2.7x Low magnification 0.74x
d4 2.42 19.80 83.84
d7 2.00 48.80 2.16
d10 98.45 34.27 16.88

The values corresponding to the conditional expressions of the respective examples are listed below.

Conditional Example Example 1 Example 2 Example 3 Example 4
f1 67.2 56.2 41.1 66.4
f1t----
f1o----
f2 44.3 65.3 42.6 44.3
f3 44.3 53.8 42.7 44.3
f4 -38.66--36.7 -46.5
f4o----24
f4t---74.8
d0----
L 156.6 132.7 124.08 157.8

(1) f2 / f3 1.00 1.21 0.998 1.00
(2) f1 / (f2 + f3) 0.76 0.47 0.48 0.75
(3) (f2 + f3) / L 0.57 0.90 0.69 0.56
(4) | 2 ・ f4 / (f2 + f3) | 0.87-0.86 1.05
(5) | f1t / f1o |----
(6) d0 / f1t----
(7) | f4t / f4o |---3.12

Conditional Example 5 Example 6 Example 7
f1 122.6 107.8 107.8
f1t 23.7 23.7 23.7
f1o -26.3 -26.3 -26.3
f2 44.9 44.9 44.9
f3 44.9 44.9 44.9
f4 -19.5 -17.8 -17.8
f4o--9.74-
f4t-19.03-
d0 1.5 2.17 7.17
L 164.6 165.2 170.2

(1) f2 / f3 1.00 1.00 1.00
(2) f1 / (f2 + f3) 1.37 1.20 1.20
(3) (f2 + f3) / L 0.55 0.54 0.53
(4) | 2 ・ f4 / (f2 + f3) | 0.43 0.40 0.40
(5) | f1t / f1o | 0.90 0.90 0.90
(6) d0 / f1t 0.06 0.09 0.30
(7) | f4t / f4o |-1.95-

  As described above, the present invention is useful for a zoom lens, and is particularly suitable for a zoom lens for a microscope.

G1 First lens group G2 Second lens group G3 Third lens group G4 Fourth lens group L1 to L8 Each lens I Image surface

Claims (4)

In order from the sample side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power that performs a zoom action, and a third lens group G3 having a positive refractive power that performs a zoom action. Have
A zoom lens for a microscope, which satisfies the following conditional expressions (1), (2), and (3):
0.8 <f2 / f3 <1.3 (1)
0.3 <f1 / (f2 + f3) <1.4 (2)
0.4 <(f2 + f3) / L <1.1 (3)
here,
f1 is the focal length of the first lens group G1,
f2 is the focal length of the second lens group G2,
f3 is the focal length of the third lens group G3,
L is the distance from the specimen to the image,
It is. Between the third lens group G3 and the image plane, further has a fourth lens group G4 having a negative refractive power,
The zoom lens for a microscope according to claim 1, wherein the following conditional expression (4) is satisfied.
0.3 <| 2 · f4 / (f2 + f3) | (4)
here,
f4 is the focal length of the fourth lens group G4,
It is. The first lens group G1 includes, in order from the sample side, a lens group G1t having a positive refractive power, and a lens group G1o having a negative refractive power arranged at an interval d0 from the lens group G1t.
3. The microscope zoom lens according to claim 1, wherein the following conditional expressions (5) and (6) are satisfied.
0.7 <| f1t / f1o | <1 (5)
d0 / f1t <0.5 (6)
here,
f1t is the focal length of the lens group G1t,
f1o is the focal length of the lens group G1o,
It is. The fourth lens group G4 is composed of a negative refractive power lens group G4o and a positive refractive power lens group G4t in this order from the sample side.
The zoom lens for a microscope according to claim 2, wherein the following conditional expression (7) is satisfied.
1 <| f4t / f4o | (7)
here,
f4o is the focal length of the lens group G4o having negative refractive power,
f4t is a focal length of the lens group G4t having a positive refractive power,
It is.

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