JP5605309B2 - Observation zoom optical system - Google Patents

Description

  The present invention relates to an observation zoom optical system, for example, an observation zoom optical system used for medical loupes (surgical loupes, etc.), binoculars, telescopes and the like.

  In observation optical systems used in loupes, binoculars, telescopes, etc., the inverted image formed by the objective optical system is inverted to an erect image by a reversal optical system such as a prism, and the image is observed by an eyepiece optical system. A so-called Kepler type (real image type) has been generally employed. In addition, since a zoom optical system having a zoom ratio of about 2 times can be easily downsized, a type in which zooming is performed by an eyepiece optical system is generally adopted as proposed in Patent Documents 1 to 3. ing.

  In the observation zoom optical system described in Patent Document 1, approximately five optical elements are arranged by sequentially arranging a movable negative lens group, a movable positive lens group, and a fixed positive lens group with an image forming plane sandwiched from the object side. Zooming with a small number of lenses. In the observation zoom optical system described in Patent Document 2, the group closest to the primary imaging plane of the objective lens group is moved, and diopter correction associated therewith is corrected at the position of the most object-side group or prism. Thereby, the change in the apparent field of view due to the zoom is reduced. In the observation zoom optical system described in Patent Document 3, the positive lens is arranged on the pupil side of the reversal optical system, thereby suppressing the light flux passing through the reversal optical system. Thereby, the inversion optical system is made compact, and the observation zoom optical system is miniaturized.

Japanese Patent Laid-Open No. 62-134617 JP 2000-214384 A JP 2003-315687 A

  The observation zoom optical system described in Patent Document 1 is a type that is used for orthodox as an eyepiece zoom. However, since the negative power lens group is disposed on the object side of the primary image plane, the objective optical system is used. It has the effect of enlarging the image formed by Therefore, the focal length of the lens group arranged on the pupil side becomes longer than that, and it becomes difficult to make the entire length of the optical system compact.

  In recent years, observation optical systems used in loupes, binoculars, telescopes, etc. have been used for a long time not only outdoors but also at manufacturing sites, inspection processes, medical sites, etc., and there is an increasing need for miniaturization and weight reduction. . In addition, severe conditions are often required in the above usage conditions, and waterproof / dustproof functions are often required. On the other hand, in the observation zoom optical system described in Patent Document 2, the front lens of the objective optical system moves, so that there is a problem that the configuration becomes complicated if an attempt is made to realize a waterproof / dustproof function.

  In the observation zoom optical system described in Patent Document 3, the positive lens arranged on the pupil side of the reversal optical system is fixed during zooming. For this reason, in order to correct aberration fluctuations when zoomed, it is necessary to use only a lens arranged on the pupil side of the positive lens. This is a cause of increasing the size of the entire optical system.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an observation zoom optical system that has good matching with a waterproof / dustproof mechanism, is small and lightweight, and has good optical performance.

To achieve the above object, an observation zoom optical system according to a first aspect of the present invention is formed of an objective optical system, a reversal optical system that erects an inverted image formed by the objective optical system, and the reversal optical system. An eyepiece optical system that allows an erect image to be observed at the pupil, wherein the objective optical system includes, in order from the object side, a first group having positive power, A second group having power, and a third group having negative power. The eyepiece optical system includes, in order from the object side, a fourth group having positive power, and a fifth group having positive power. And the reversal optical system is located between the first group and the second group, and zooming is performed by changing each group interval, and in zooming from the low magnification end to the high magnification end, both the fourth group is moved from the object side to the pupil side, the said first group of third Wherein the fifth group is Oite stationary during zooming and.

Observation zoom optical system of the second aspect of the invention related to the first invention, the fifth unit, in order from the object side, it made a meniscus lens having a concave surface on the object side, a lens having a positive power, It is characterized by.

An observation zoom optical system according to a third aspect of the invention is characterized in that, in the first or second aspect of the invention, the following conditional expression (1) is satisfied.
−0.5 <FL2 / FLt <−0.1 (1)
However,
FL2: focal length of the second group,
FLt: focal length of the entire system at the high magnification end,
It is.

An observation zoom optical system according to a fourth invention is characterized in that, in any one of the first to third inventions, the following conditional expression (2) is satisfied.
0.2 <| FL23w / FL23t | <3.2 (2)
However,
FL23t: the combined focal length of the second group and the third group at the high magnification end,
FL23w: the combined focal length of the second group and the third group at the low magnification end,
It is.

An observation zoom optical system according to a fifth invention is characterized in that, in any one of the first to fourth inventions, the second group is composed of a positive single lens, and satisfies the following conditional expression (3). And
0.6 <(Rb + Ra) / (Rb−Ra) <1.7 (3)
However,
Ra: radius of curvature of the object side surface of the second lens unit,
Rb: radius of curvature of the pupil side surface of the second lens unit
It is.

An observation zoom optical system according to a sixth aspect of the present invention is the observation zoom optical system according to any one of the first to fifth aspects, wherein the fourth group is composed of a positive meniscus lens that is concave on the object side and a positive lens that is biconvex. And

An observation zoom optical system according to a seventh aspect of the invention is characterized in that, in the sixth aspect of the invention, the following conditional expression (4) is satisfied.
0 <| νd1-νd2 | <20 (4)
However,
νd1: Abbe number of a positive meniscus lens concave on the object side,
νd2: Abbe number of a biconvex positive lens,
It is.

An observation zoom optical system according to an eighth invention is characterized in that, in any one of the first to seventh inventions, the second group has at least one aspheric surface.

An observation zoom optical system according to a ninth invention is characterized in that, in any one of the first to eighth inventions, the fifth group has at least one aspheric surface.

  According to the present invention, in zooming from the low magnification end to the high magnification end, both the second group and the fourth group move from the object side to the pupil side across the third group with a fixed zoom position. Therefore, it is possible to realize an observation zoom optical system that has good matching with the waterproof / dustproof mechanism, is small and lightweight, and has good optical performance.

The optical block diagram of 1st Embodiment (Example 1). The optical block diagram of 2nd Embodiment (Example 2). The optical block diagram of 3rd Embodiment (Example 3). The optical block diagram of 4th Embodiment (Example 4). The optical path figure of 1st Embodiment (Example 1). The optical path figure of 2nd Embodiment (Example 2). The optical path figure of 3rd Embodiment (Example 3). The optical path figure of 4th Embodiment (Example 4). FIG. 6 is an aberration diagram of Example 1. FIG. 6 is an aberration diagram of Example 2. FIG. 6 is an aberration diagram of Example 3. FIG. 6 is an aberration diagram of Example 4. The schematic diagram which shows the example of schematic structure of the observation zoom optical system which mounts the Schmitt prism as a reversal optical system.

  The observation zoom optical system according to the present invention will be described below. In the observation zoom optical system according to the present invention, an objective optical system, a reversal optical system that erects an inverted image formed by the objective optical system, and an erect image formed by the reversal optical system are observed at the pupil. An eye observation optical system, wherein the objective optical system is in order from the object side, a first group having a positive power, a second group having a positive power, and a negative A third group having power, and the eyepiece optical system includes, in order from the object side, a fourth group having positive power and a fifth group having positive power, and the inversion optical system is the first group. It is located between the first group and the second group (power: an amount defined by the reciprocal of the focal length). Then, zooming is performed by changing each group interval. In zooming from the low magnification end to the high magnification end, both the second group and the fourth group move from the object side to the pupil side, and the third group is It is characterized by its fixed position during zooming.

  The objective optical system and the eyepiece optical system are configured with positive, negative, positive, and positive five-group zooms, and both the second group and the fourth group of positive power are moved from the object side to the pupil side as the magnification changes from low to high. By moving along the optical axis, the real-image visual observation optical system can have a zoom function with good optical performance. A general configuration of the first group includes a cemented lens having positive power. In the observation optical system, the first group is often constituted by a cemented lens. However, an aberration correction effect may be improved by adding one positive lens or adding an aspheric lens thereto. .

  When at least one of the first group and the fifth group is zoomed and fixed in position, the matching with the waterproof / dustproof mechanism is further improved, and the observation zoom optical system can be easily provided with a waterproof / dustproof function. It becomes. Therefore, the first group and the fifth group are preferably fixed in position during zooming. When a diopter adjustment mechanism is required, an appropriate waterproof structure such as packing and a diopter adjustment mechanism may be used in combination.

  By arranging the second group having positive power on the pupil side of the inverting optical system, it is possible to reduce the width of the light beam passing through the inverting optical system composed of a prism and the like, and to reduce the volume of the inverting optical system. It becomes. As a result, since the space occupied by the reversing optical system is reduced, it is possible to contribute to miniaturization of the observation zoom optical system. Further, by moving the second group in the optical axis direction during zooming, the region through which the light beam passes in the second group to the fifth group changes between low magnification and high magnification. Correction can be made in the second group to the fifth group.

  According to the above characteristic configuration, in zooming from the low magnification end to the high magnification end, both the second group and the fourth group move from the object side to the pupil side across the third group with a fixed zoom position. Therefore, it is possible to realize an observation zoom optical system that has good matching with a waterproof / dustproof mechanism, is small and light, and has good optical performance. The conditions for achieving such effects in a well-balanced manner and achieving higher optical performance, downsizing, etc. will be described below.

It is desirable to satisfy the following conditional expression (1).
−0.5 <FL2 / FLt <−0.1 (1)
However,
FL2: focal length of the second group,
FLt: focal length of the entire system at the high magnification end,
It is.

  When the lower limit of conditional expression (1) is exceeded, the power of the second group becomes weak and the amount of movement during zooming increases, making it difficult to downsize the entire optical system. On the other hand, if the upper limit of conditional expression (1) is exceeded, the power of the second group becomes strong, and various aberrations (for example, spherical aberration, astigmatism, etc.) are likely to occur. It will be difficult to achieve. Therefore, by satisfying conditional expression (1), it is possible to achieve a good balance between light weight reduction and high performance of the observation optical system.

It is more desirable to satisfy the following conditional expression (1a).
−0.4 <FL2 / FLt <−0.2 (1a)
The conditional expression (1a) defines a more preferable condition range based on the above viewpoints, etc., among the condition ranges defined by the conditional expression (1). Therefore, the above effect can be further enhanced preferably by satisfying conditional expression (1a).

  If the upper limit of conditional expression (1a) is exceeded, the power of the second group becomes weak, which tends to be disadvantageous in reducing the outer diameter of the lens. On the other hand, when the lower limit of conditional expression (1a) is exceeded, the power of the second group becomes strong, and the error sensitivity such as one-sided blur that occurs at the time of eccentricity tends to increase. Even though it is a mobile group, tight tolerances are required, which increases the difficulty of manufacturing and may lead to deterioration in productivity and cost increase.

It is desirable to satisfy the following conditional expression (2).
0.2 <| FL23w / FL23t | <3.2 (2)
However,
FL23t: the combined focal length of the second group and the third group at the high magnification end,
FL23w: the combined focal length of the second group and the third group at the low magnification end,
It is.

  If the upper limit of the conditional expression (2) is exceeded, the ratio of the second group and the third group contributing to zoom increases, and various aberrations (for example, spherical aberration, astigmatism, coma aberration in the second group and the third group). Etc.) are likely to occur. This increases the burden of aberration correction of other lenses, which is disadvantageous for performance improvement. On the other hand, if the lower limit of conditional expression (2) is exceeded, the ratio of the second group and the third group contributing to zoom decreases, and the amount of movement of the second group increases, making it difficult to achieve downsizing. Become. Therefore, by satisfying conditional expression (2), it is possible to achieve a good balance between light weight reduction and high performance of the observation optical system.

It is desirable that the second group is composed of a positive single lens and satisfies the following conditional expression (3).
0.6 <(Rb + Ra) / (Rb−Ra) <1.7 (3)
However,
Ra: radius of curvature of the object side surface of the second lens unit,
Rb: radius of curvature of the pupil side surface of the second lens unit
It is.

  In order to reduce the size and weight, it is desirable to configure the second group with a positive single lens. If the lower limit of conditional expression (3) is exceeded, various aberrations (eg, spherical aberration, astigmatism, etc.) are likely to occur, increasing the burden of aberration correction with other lenses, making it difficult to achieve miniaturization. It becomes. On the other hand, if the upper limit of conditional expression (3) is exceeded, the power of the positive lens in the second group becomes weak, and the amount of movement during zooming becomes large, making it difficult to achieve miniaturization. Or, since the number of lenses increases, it is difficult to reduce the weight. Therefore, by satisfying conditional expression (3), it is possible to achieve a reduction in weight and size and performance of the observation optical system in a balanced manner. The surface shape is a notation based on paraxial curvature.

It is more desirable to satisfy the following conditional expression (3a).
0.8 <(Rb + Ra) / (Rb−Ra) <1.5 (3a)
This conditional expression (3a) defines a more preferable condition range based on the above viewpoints, etc., among the condition ranges defined by the conditional expression (3). Therefore, the above effect can be further increased preferably by satisfying conditional expression (3a).

  When the lower limit of conditional expression (3a) is exceeded, the curvature radius Rb of the pupil side surface increases (that is, the curvature becomes loose), and aberration correction is borne only by the object side surface of the curvature radius Ra. As a result, the performance tends to be disadvantageous. Conversely, if the upper limit of conditional expression (3a) is exceeded, the power will be weakened, the effective diameter of the lens will be increased, and the width of the light beam passing through the prism placed immediately beside will be expanded, reducing the size of the optical system. This is a disadvantageous trend.

  It is desirable that the second group has at least one aspheric surface. By disposing an aspherical surface in the second group, it is possible to obtain further correction effects such as field curvature and spherical aberration.

  The third group is preferably composed of a single lens in consideration of reduction in size and weight. In addition, by providing an aspheric surface there, it is possible to improve the aberration correction effect for field curvature, spherical aberration, and the like. An aberration correction effect can also be obtained by arranging a cemented lens instead of an aspherical surface as in Example 4 described later.

  The fourth group preferably includes a positive meniscus lens that is concave on the object side and a positive lens that is biconvex. Generally, chromatic aberration correction is often performed with a positive / negative configuration. However, when the fourth group is configured and arranged as described above, the effective diameter of the lens is suppressed by increasing the power of the fourth group, and the entire optical system. Can be miniaturized. It is also possible to satisfactorily correct various aberrations (coma aberration, astigmatism, curvature of field, etc.) while increasing the power.

It is desirable that the fourth group includes a positive meniscus lens that is concave on the object side and a biconvex positive lens that satisfies the following conditional expression (4).
0 <| νd1-νd2 | <20 (4)
However,
νd1: Abbe number of a positive meniscus lens concave on the object side,
νd2: Abbe number of a biconvex positive lens,
It is.

  If the condition range of the conditional expression (4) is not met, an Abbe number difference occurs between adjacent lenses having positive power, which is disadvantageous for correction of axial chromatic aberration. If the refractive indexes for the d, F, and C lines are nd, nF, and nC, respectively, the Abbe number νd is expressed by the definition formula: νd = (nd−1) / (nF−nC). In addition, since the resin material used for the composite aspherical lens (the lens formed by applying a thin resin material on the spherical glass material to be a substrate) has only an additional function of the substrate glass material, It is not handled as an optical member, but is handled in the same way as when the substrate glass material has an aspheric surface, and the number of lenses is considered to be one. At this time, the lens refractive index is also defined as the refractive index of the glass material serving as the substrate.

  In the fourth group, a negative lens may be used as a meniscus lens having a concave surface facing the object side. By disposing the negative lens and the positive lens adjacent to each other, it is possible to effectively correct aberrations such as axial chromatic aberration and lateral chromatic aberration.

  It is desirable that the fifth group includes, in order from the object side, a meniscus lens having a concave surface directed toward the object side, and a lens having positive power. By disposing the fifth group in this way, it becomes possible to effectively correct aberrations such as distortion and astigmatism. It is desirable that the fifth group has at least one aspheric surface. Aberration correction can be performed more effectively by disposing an aspherical surface in the fifth group as in Example 2 described later.

  In the observation zoom optical system according to the present invention, the glass lens having an aspherical surface may be molded by a mold or may of course be a composite type of a glass material and a resin material. The mold type is suitable for mass production, but the glass material is limited. On the other hand, the composite type has the advantage that the glass material that can serve as the substrate is very large and the degree of freedom in design is high. Since an aspherical lens using a high refractive material is generally difficult to mold, in the case of a single-sided aspherical surface, the advantages of the composite type can be maximized.

  In the observation zoom optical system according to the present invention, it is desirable that the lens closest to the object side and the lens closest to the pupil be made of a glass material. In the outdoors, manufacturing sites, inspection processes, medical sites, etc., the lens surface exposed to the outside is often exposed, and frequent attachment / detachment tends to put a burden on the lens on the most object side / most pupil side. . From these points, it is desirable that the lens on the most object side / most pupil side, which requires robustness, chemical resistance, waterproofness, etc., be made of a glass material.

  Next, the specific optical configuration of the observation zoom optical system will be described in more detail with reference to the first to fourth embodiments. 1 to 4 are lens configuration diagrams respectively corresponding to the observation zoom optical system LZ constituting the first to fourth embodiments, and lenses at a low magnification end (W) and a high magnification end (T). The arrangement is shown in optical section. 5 to 8 are optical path diagrams corresponding to the observation zoom optical systems LZ constituting the first to fourth embodiments, respectively, at the low magnification end (W) and the high magnification end (T). The optical path is shown.

  The observation zoom optical system LZ has a positive / negative / positive / positive five-group zoom configuration, and includes an objective optical system LO composed of a first group Gr1, a second group Gr2, and a third group Gr3, a fourth group Gr4, and a fourth group Gr4. The eyepiece optical system LE composed of the fifth group Gr5 constitutes a substantially afocal real-image observation optical system. The reversal optical system PR positioned between the first group Gr1 and the second group Gr2 A statue is observed. Then, the second group Gr2 and the fourth group Gr4 move along the optical axis AX with the third group Gr3 having a fixed zoom position interposed therebetween to change the distance between the groups, thereby performing zooming (ie, zooming). The pupil EP (FIGS. 5 to 8) is configured to observe the object image IM (PT: protective glass). In addition, arrows m2, m3, and m4 in FIGS. 1 to 4 indicate movements of the second group Gr2, the third group Gr3, and the fourth group Gr4 during zooming from the low magnification end (W) to the high magnification end (T). Are shown schematically, and a broken-line arrow m3 indicates that the zoom position of the third lens group Gr3 is fixed.

  In the first embodiment (FIG. 1), in order from the object side, a first group Gr1 composed of a cemented lens of a positive lens and a negative lens, a reversing optical system PR, and a second lens composed of an object-side convex positive lens. A group Gr2, a third group Gr3 composed of a biconcave negative lens, a fourth group Gr4 composed of an object-side concave positive meniscus lens and a biconvex positive lens, an object-side concave negative meniscus lens, and a biconvex positive And a fifth group Gr5 composed of lenses. During zooming from the low magnification end (W) to the high magnification end (T), both the second group Gr2 and the fourth group Gr4 move from the object side to the pupil EP side, and the third group Gr3 and the fourth group Gr4. The image IM is formed by the objective optical system LO. All the lenses from the first group Gr1 to the fifth group Gr5 are spherical lenses made of glass, and the reversal optical system PR positioned between the first group Gr1 and the second group Gr2 is constituted by a prism, for example. FIG. 13 shows an example of a zoom observation optical system LZ equipped with a Schmitt prism as the reversal optical system PR.

  In the second embodiment (FIG. 2), in order from the object side, a first group Gr1 composed of a cemented lens of a positive lens and a negative lens, a reversing optical system PR, and a positive meniscus lens convex on the object side. A second group Gr2, a third group Gr3 composed of a biconcave negative lens, a fourth group Gr4 composed of an object side concave positive meniscus lens and a biconvex positive lens, an object side concave negative meniscus lens and a biconvex lens And a fifth lens unit Gr5 composed of a positive lens. During zooming from the low magnification end (W) to the high magnification end (T), both the second group Gr2 and the fourth group Gr4 move from the object side to the pupil EP side, and the third group Gr3 and the fourth group Gr4. The image IM is formed by the objective optical system LO. All the lenses from the first group Gr1 to the fifth group Gr5 are made of glass, and the reversal optical system PR positioned between the first group Gr1 and the second group Gr2 is constituted by a prism, for example. The object side surface of the biconcave lens of the third group Gr3 and the pupil side surface of the negative meniscus lens of the fifth group Gr5 are aspherical.

  In the third embodiment (FIG. 3), in order from the object side, a first group Gr1 composed of a cemented lens of a positive lens and a negative lens, a reversing optical system PR, and a positive meniscus lens convex on the object side. 2 group Gr2, 3rd group Gr3 which consists of a biconcave negative lens, 4th group Gr4 which consists of an object side concave positive meniscus lens and a biconvex positive lens, a biconcave negative lens, and a biconvex positive lens And a fifth lens unit Gr5 composed of a cemented lens. During zooming from the low magnification end (W) to the high magnification end (T), both the second group Gr2 and the fourth group Gr4 move from the object side to the pupil EP side, and the third group Gr3 and the fourth group Gr4. The image IM is formed by the objective optical system LO. All the lenses from the first group Gr1 to the fifth group Gr5 are made of glass, and the reversal optical system PR positioned between the first group Gr1 and the second group Gr2 is constituted by a prism, for example. The object-side surface of the biconcave lens in the third group Gr3 and the object-side surface of the positive meniscus lens in the fourth group Gr4 are aspherical surfaces.

  In the fourth embodiment (FIG. 4), in order from the object side, a first group Gr1 composed of a cemented lens of a positive lens and a negative lens, a reversing optical system PR, and a positive meniscus lens convex on the object side. The second group Gr2, the third group Gr3 composed of a cemented lens of a negative lens and a positive lens, the fourth group Gr4 composed of an object side concave positive meniscus lens and a biconvex positive lens, a biconcave negative lens and both And a fifth lens unit Gr5 composed of a cemented lens with a convex positive lens. During zooming from the low magnification end (W) to the high magnification end (T), both the second group Gr2 and the fourth group Gr4 move from the object side to the pupil EP side, and the third group Gr3 and the fourth group Gr4. The image IM is formed by the objective optical system LO. All the lenses from the first group Gr1 to the fifth group Gr5 are spherical lenses made of glass, and the reversal optical system PR positioned between the first group Gr1 and the second group Gr2 is constituted by a prism, for example.

  Hereinafter, the configuration and the like of the observation zoom optical system embodying the present invention will be described more specifically with reference to the construction data of the examples. Examples 1 to 4 (EX1 to 4) listed here are numerical examples corresponding to the first to fourth embodiments, respectively, and are optical configuration diagrams showing the first to fourth embodiments. (FIGS. 1 to 4) and optical path diagrams (FIGS. 5 to 8) respectively show lens configurations, optical paths, and the like of the corresponding first to fourth embodiments.

In the construction data of each embodiment, as surface data, in order from the left column, the surface number, the radius of curvature r (mm), the on-axis surface distance d (mm), and the refractive index with respect to the d-line (wavelength 587.56 nm). The Abbe number vd regarding the nd and d lines is shown. A surface with * in the surface number is an aspheric surface, and the surface shape is defined by the following expression (AS) using a local orthogonal coordinate system (x, y, z) with the surface vertex as the origin. . As aspheric data, an aspheric coefficient or the like is shown. It should be noted that the coefficient of the term not described in the aspherical data of each example is 0, and E−n = × 10 ⁻ⁿ for all data.
z = (c · h ² ) / [1 + √ {1− (1 + K) · c ² · h ² }] + A · h ⁴ + B · h ⁶ + C · h ⁸ + D · h ¹⁰ (AS)
However,
h: height in the direction perpendicular to the z axis (optical axis AX) (h ² = x ² + y ² ),
z: displacement in the direction of the optical axis AX at the position of the height h (based on the surface vertex),
c: curvature at the surface vertex (the reciprocal of the radius of curvature r),
K: conic constant,
A, B, C, D: 4th order, 6th order, 8th order, 10th order aspheric coefficients,
It is.

  As various data, magnification (times), object distance (mm), imaging range (mm), diopter (diopt), and variable surface distances D1 to D4 (mm) are shown for each magnification state. Table 1 shows values corresponding to the conditional expressions of the respective examples, and related data is shown in Table 2 (FL1 to FL5: focal lengths of the first group to the fifth group, FLw: focal point of the entire system at the low magnification end. distance).

  9 to 12 are aberration diagrams corresponding to Examples 1 to 4 (EX1 to EX4), respectively. Various aberrations (spherical surfaces in order from the left) at the low magnification end (W) and the high magnification end (T). Aberration, distortion and astigmatism) are shown (vertical axis: pupil radius). In the spherical aberration diagram, the solid line represents the e line, the two-dot chain line represents the g line, and the broken line represents the spherical aberration (diopt) with respect to the c line. In the distortion diagram, the solid line represents the distortion (%). In the astigmatism diagram, the broken line represents the meridional surface, and the solid line represents each astigmatism (diopt) on the sagittal surface.

Example 1
Unit: mm
Surface data surface number rd nd vd
1 49.457 3.279 1.48749 70.40
2 -35.262 1.126 1.84666 23.80
3 -71.661 20.870
4 ∞ 25.000 1.72000 50.20
5 ∞ 0.100
6 ∞ 30.000 1.72000 50.20
7 ∞ D1 (variable)
8 22.425 2.000 1.83400 37.30
9 -410.539 D2 (variable)
10 -20.764 1.626 1.72916 54.70
11 17.334 D3 (variable)
12 -24.800 3.188 1.71736 29.50
13 -14.199 0.199
14 82.384 9.000 1.88300 40.80
15 -20.058 D4 (variable)
16 -10.135 5.974 1.83500 43.00
17 -13.325 0.100
18 421.362 5.500 1.77250 49.60
19 -43.711 11.000
20 (Eye position) ∞

Various data Magnification (times) 2.5 6
Object distance (mm) 400 400
Shooting range (mm) φ74 φ64
Diopter -1 -1

D1 2.559 7.319
D2 14.279 9.519
D3 2.397 12.954
D4 14.962 4.406

Example 2
Unit: mm
Surface data surface number rd nd vd
1 35.552 3.729 1.48749 70.40
2 -34.580 1.000 1.84666 23.80
3 -94.252 9.847
4 ∞ 25.000 1.72000 50.20
5 ∞ 0.100
6 ∞ 30.000 1.72000 50.20
7 ∞ D1 (variable)
8 21.453 2.000 1.80610 33.30
9 280.567 D2 (variable)
10 * -12.489 1.000 1.48749 70.40
11 16.649 D3 (variable)
12 -60.016 4.186 1.88300 40.80
13 -14.510 0.139
14 160.248 2.981 1.84666 23.80
15 -33.493 D4 (variable)
16 -9.616 4.997 1.74400 44.90
17 * -12.515 0.100
18 105.421 2.022 1.62041 60.30
19 -26.462 11.000
20 (Eye position) ∞

Aspheric data 10th surface
K = 0.000
A = 1.329E-04
B = 1.256E-06
C = 6.786E-09
D = -1.764E-09

17th page
K = 0.000
A = 5.054E-06
B = -3.021E-09
C = -3.631E-10
D = -1.071E-11

Various data Magnification (times) 2.5 6
Object distance (mm) 400 400
Shooting range (mm) φ74 φ64
Diopter -1 -1

D1 2.084 6.843
D2 15.950 11.192
D3 2.460 12.901
D4 14.514 4.074

Example 3
Unit: mm
Surface data surface number rd nd vd
1 43.108 3.500 1.48749 70.40
2 -41.500 1.000 1.84666 23.80
3 -141.052 28.429
4 ∞ 25.000 1.72000 50.20
5 ∞ 0.100
6 ∞ 30.000 1.72000 50.20
7 ∞ D1 (variable)
8 20.378 2.000 1.88300 40.80
9 121.008 D2 (variable)
10 * -17.499 1.049 1.72000 50.20
11 31.174 D3 (variable)
12 * -24.665 3.692 1.84666 23.80
13 -14.460 0.300
14 44.529 4.964 1.80518 25.50
15 -45.133 D4 (variable)
16 -26.469 5.000 1.59551 39.20
18 130.000 5.500 1.83500 43.00
19 -22.205 11.000
20 (Eye position) ∞

Aspheric data 10th surface
K = 0.000
A = 2.776E-05
B = 8.665E-10
C = -6.157E-09
D = -1.609E-10

12th page
K = 0.000
A = -7.993E-06
B = -1.648E-07
C = -3.634E-10

Various data Magnification (times) 2.5 6
Object distance (mm) 400 400
Shooting range (mm) φ74 φ64
Diopter -1 -1

D1 4.545 10.000
D2 18.095 12.639
D3 4.823 17.483
D4 17.795 5.134

Example 4
Unit: mm
Surface data surface number rd nd vd
1 47.385 3.112 1.48749 70.40
2 -35.211 1.388 1.84666 23.80
3 -89.974 14.145
4 ∞ 30.000 1.56883 56.00
5 ∞ 0.100
6 ∞ 30.000 1.56883 56.00
7 ∞ D1 (variable)
8 21.485 1.997 1.83500 43.00
9 422.187 D2 (variable)
10 -17.856 1.000 1.75700 47.80
11 13.604 1.014 1.84666 23.80
12 20.731 D3 (variable)
13 -32.095 5.000 1.84666 23.80
14 -14.718 0.114
15 90.682 7.244 1.88300 40.80
16 -25.223 D4 (variable)
18 -10.925 5.293 1.69350 50.80
19 -13.885 0.100
20 -667.883 5.311 1.70000 48.10
21 -29.318 11.000
22 (Eye position) ∞

Various data Magnification (times) 2.5 6
Object distance (mm) 400 400
Shooting range (mm) φ74 φ64
Diopter -1 -1

D1 0.309 5.044
D2 17.110 12.375
D3 1.820 12.265
D4 14.011 3.565

LZ observation zoom optical system LO objective optical system LE eyepiece optical system Gr1 first group Gr2 second group Gr3 third group Gr4 fourth group Gr5 fifth group PR reversal optical system IM image EP pupil AX optical axis

Claims (9)

An objective optical system, an inversion optical system that erects an inverted image formed by the objective optical system, and an eyepiece optical system that allows an erect image formed by the inversion optical system to be observed by a pupil A visual observation optical system,
The objective optical system includes, in order from the object side, a first group having positive power, a second group having positive power, and a third group having negative power, and the eyepiece optical system is from the object side. Sequentially, a fourth group having positive power and a fifth group having positive power are provided, and the inversion optical system is located between the first group and the second group, and each group interval is changed. In the zooming from the low magnification end to the high magnification end, both the second group and the fourth group move from the object side to the pupil side, and the first group, the third group, and the fifth group are moved . observation zoom optical system, wherein the group is Oite stationary during zooming. The fifth unit, in order from the object side, a meniscus lens having a concave surface on the object side, the observation zoom optical system according to claim 1, characterized in that it consists of a lens, having a positive power. The following conditional expressions (1) according to claim 1 or 2, wherein the observation optical zoom system, characterized by satisfying the;
−0.5 <FL2 / FLt <−0.1 (1)
However,
FL2: focal length of the second group,
FLt: focal length of the entire system at the high magnification end,
It is. The following conditional expression (2) observation zoom optical system according to any one of claims 1 to 3, characterized by satisfying the;
0.2 <| FL23w / FL23t | <3.2 (2)
However,
FL23t: the combined focal length of the second group and the third group at the high magnification end,
FL23w: the combined focal length of the second group and the third group at the low magnification end,
It is. The second group is composed of a positive single lens, the following conditional expression (3) Observation zoom optical system according to any one of claims 1 to 4, characterized in that satisfies;
0.6 <(Rb + Ra) / (Rb−Ra) <1.7 (3)
However,
Ra: radius of curvature of the object side surface of the second lens unit,
Rb: radius of curvature of the pupil side surface of the second lens unit
It is. The fourth group, the observation zoom optical system according to any one of claims 1 to 5, characterized in that it consists of a concave to the object side positive meniscus lens and a biconvex positive lens. The observation zoom optical system according to claim 6, wherein the following conditional expression (4) is satisfied:
0 <| νd1-νd2 | <20 (4)
However,
νd1: Abbe number of a positive meniscus lens concave on the object side,
νd2: Abbe number of a biconvex positive lens,
It is. Observation zoom optical system according to any one of claims 1 to 7, characterized in that the second unit has at least one aspherical surface. Observation zoom optical system according to any one of claims 1-8, characterized in that the fifth group has at least one aspherical surface.

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