JP2018010218A - Eyepiece optical system, optical instrument, and eyepiece optical system manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an eyepiece optical system, optical instrument and eyepiece optical system manufacturing method that are high in variable magnification and have excellent optical efficiency.SOLUTION: An eyepiece optical system EL includes at least two lens groups GF1 and GF2 that have positive refractive power, in which upon varying a magnification from a high magnification end state to a low magnification end state, an interval between lens groups adjacent to each of the two lens groups GF1 and GF2 having the positive refractive power is changed, and a lens surface on the most eyepoint side of the lens group on the most eyepoint side is a concave surface directed at the eyepoint side, and the eyepiece optical system satisfies a condition of a prescribed conditional expression.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an eyepiece optical system, an optical apparatus, and a method for manufacturing an eyepiece optical system.

  Conventionally, an eyepiece optical system that changes the observation magnification has been proposed (see, for example, Patent Document 1). However, Patent Document 1 has a problem that further improvement in optical performance is desired.

JP-A-9-189868

The eyepiece optical system according to the first aspect of the present invention includes at least two lens groups having positive refractive power, and has two positive refractive powers when zooming from a high magnification end state to a low magnification end state. The distance between each adjacent lens group and the adjacent lens group is changed, and the most eye point side lens surface of the most eye point side lens group is a concave surface facing the eye point side. It is characterized by satisfaction.
0.45 <f1 / f2 <0.90
However,
f1: The focal length of the lens group on the object side among the two lens groups having positive refractive power f2: The focal length of the lens group on the eye point side among the lens groups having two positive refractive powers The lens component refers to a single lens or a cemented lens.

A method for manufacturing an eyepiece optical system according to the first aspect of the present invention is a method for manufacturing an eyepiece optical system including a lens group having at least two positive refractive powers, from a high magnification end state to a low magnification end. When changing the state, the distance between each of the two lens groups having positive refractive power and the adjacent lens group is changed, and the most eye point side lens group of the most eye point side lens group is arranged. The surface is disposed so as to be a concave surface facing the eye point side, and is disposed so as to satisfy the condition of the following expression.
0.45 <f1 / f2 <0.90
However,
f1: The focal length of the lens group on the object side among the two lens groups having positive refractive power f2: The focal length of the lens group on the eye point side among the lens groups having two positive refractive powers The lens component refers to a single lens or a cemented lens.

It is sectional drawing which shows the lens structure of the eyepiece optical system which concerns on 1st Example. FIG. 6 is a diagram illustrating various aberrations of the eyepiece optical system according to Example ¹ when the diopter is ⁻¹ m ⁻¹ , where (W) indicates a high magnification end state, (M) indicates an intermediate magnification state, and (T) Indicates a low magnification end state. It is sectional drawing which shows the lens structure of the eyepiece optical system which concerns on 2nd Example. FIG. 6 is a diagram illustrating various aberrations of the eyepiece optical system according to Example 2 when the diopter is ⁻¹ m ⁻¹ , where (W) indicates a high magnification end state, (M) indicates an intermediate magnification state, and (T) Indicates a low magnification end state. It is sectional drawing which shows the lens structure of the eyepiece optical system which concerns on 3rd Example. FIG. 6 is a diagram illustrating various aberrations of the eyepiece optical system according to Example 3 when the diopter is ⁻¹ m ⁻¹ , where (W) indicates a high magnification end state, (M) indicates an intermediate magnification state, and (T) Indicates a low magnification end state. It is sectional drawing which shows the lens structure of the eyepiece optical system which concerns on 4th Example. FIG. 9A is a diagram illustrating various aberrations of the eyepiece optical system according to Example 4 when the diopter is ⁻¹ m ⁻¹ , where (W) indicates a high magnification end state, (M) indicates an intermediate magnification state, and (T) Indicates a low magnification end state. It is sectional drawing which shows the lens structure of the eyepiece optical system which concerns on 5th Example. FIG. 7A is a diagram illustrating various aberrations of the eyepiece optical system according to Example 5 when the diopter is ⁻¹ m ⁻¹ , where (W) indicates a high magnification end state, (M) indicates an intermediate magnification state, and (T) Indicates a low magnification end state. It is sectional drawing which shows the lens structure of the eyepiece optical system which concerns on 6th Example. FIG. 11 is a diagram illustrating various aberrations of the eyepiece optical system according to Example 6 at a diopter of ⁻¹ m ⁻¹ , where (W) represents a high magnification end state, (M) represents an intermediate magnification state, and (T) Indicates a low magnification end state. It is sectional drawing which shows the lens structure of the eyepiece optical system which concerns on 7th Example. FIG. 11 is a diagram illustrating various aberrations of the eyepiece optical system according to Example 7 when the diopter is ⁻¹ m ⁻¹ , where (W) represents a high magnification end state, (M) represents an intermediate magnification state, and (T) Indicates a low magnification end state. It is sectional drawing of the camera carrying the said eyepiece optical system. It is a flowchart for demonstrating the manufacturing method of the said eyepiece optical system.

  Hereinafter, preferred embodiments will be described with reference to the drawings. As shown in FIG. 1, the eyepiece optical system EL according to the present embodiment includes at least two lens groups having positive refractive power, and two lens groups (for example, the lens groups having positive refractive power (for example, 1, the first lens group G1 and the second lens group G2, and hereinafter the lens group on the observation object (simply referred to as “object”) side is referred to as a first variable magnification lens group GF1, The lens group is called a second variable magnification lens group GF2) and an interval between adjacent lens groups is changed when changing magnification from the high magnification end state to the low magnification end state. Good optical performance can be obtained by changing the distance between each of the first variable magnification lens group GF1 and the second variable magnification lens group GF2 and the adjacent lens group at the time of zooming.

  In the eyepiece optical system EL according to this embodiment, the first variable power lens group GF1 and the second variable power lens group GF2 move in the optical axis direction when zooming from the high magnification end state to the low magnification end state. It is desirable to be configured.

  When only one lens group having a positive refractive power among the lens groups moved during zooming is used, the refractive power (power) of the lens group having a positive refractive power is increased. For this reason, the amount of aberration generated becomes large, and it becomes difficult to achieve high zooming. On the other hand, by moving the two lens units having positive refractive power at the time of zooming, the refractive power (power) of the moving lens group having positive refractive power becomes relatively weak, and the amount of aberration generated is reduced. Get smaller. For this reason, even if the amount of movement of the two lens groups having the first refractive power (the first variable magnification lens group GF1 and the second variable magnification lens group GF2) is increased, the aberrations are not deteriorated and high magnification can be achieved. is there. In particular, when two lens groups having positive refractive power are moved in the same direction, a space required for zooming is reduced, which is advantageous for high zooming. In particular, it is possible to reduce the fluctuation of coma during zooming.

  Further, the eyepiece optical system EL according to the present embodiment has the most eye point side lens surface (for example, the ninth surface in FIG. 1) of the most eye point side lens group (for example, the third lens group G3 in FIG. 1). Is configured to be a concave surface facing the eye point side. When the zoom ratio is increased, the lens surface closest to the eye point of the lens unit closest to the eye point is made concave, so that the declination of a light beam having a large angle of view is reduced and coma aberration is improved.

  Moreover, it is desirable that the eyepiece optical system EL according to the present embodiment satisfies the following conditional expression (1).

0.45 <f1 / f2 <0.90 (1)
However,
f1: Focal length of the first variable magnification lens group GF1 f2: Focal length of the second variable magnification lens group GF2

  Conditional expression (1) is the first lens group on the object side in a lens group having two positive refractive powers that move during zooming in order to suppress the occurrence of spherical aberration and field curvature over the entire zoom range. It defines the refracting power (power) of the variable power lens group GF1 and the second variable power lens group GF2 that is the eye point side lens group. If the lower limit of conditional expression (1) is not reached, the refractive power (power) of the first variable magnification lens group GF1 becomes relatively strong, so that a large curvature of field occurs during zoom magnification, which is not preferable. In order to secure the effect of conditional expression (1), it is desirable to set the lower limit of conditional expression (1) to 0.455. If the upper limit value of conditional expression (1) is exceeded, the refractive power (power) of the second variable magnification lens group GF2 becomes relatively strong, so that a large amount of spherical aberration occurs during zoom magnification, which is not preferable. . In order to secure the effect of the conditional expression (1), it is desirable that the upper limit value of the conditional expression (1) is 0.89.

  In addition, when the eyepiece optical system EL according to the present embodiment changes the magnification from the high magnification end state to the low magnification end state, the first variable magnification lens group GF1 and the second variable magnification lens group GF2 described above have diopters. It is desirable to be configured to move so as to keep constant. Here, “move so as to keep the diopter constant” of the eyepiece optical system EL means that the first change is made so that the distance between the object point (object or intermediate image) and the image point (eye point) is kept constant. It shows that the magnification lens group GF1 and the second variable magnification lens group GF2 move. By appropriately selecting the amount of movement of each of the first variable magnification lens group GF1 and the second variable magnification lens group GF2, it is possible to perform variable magnification while keeping the diopter constant.

  Moreover, it is desirable that the eyepiece optical system EL according to the present embodiment satisfies the following conditional expression (2).

νEP <63.00 (2)
However,
νEP: Abbe number for the d-line of the lens medium closest to the eye point

  Conditional expression (2) defines the Abbe number of the lens medium closest to the eye point in order to correct axial chromatic aberration and lateral chromatic aberration. Since the lens surface closest to the eye point in the lens group closest to the eye point is a concave surface, exceeding the upper limit value of the conditional expression (2) is not preferable because axial chromatic aberration and lateral chromatic aberration are deteriorated. In order to secure the effect of the conditional expression (2), it is more desirable to set the upper limit value of the conditional expression (2) to 59.00, further 55.00. In order to secure the effect of the conditional expression (2), it is desirable that the lower limit value of the conditional expression (3) is 25.00.

  Moreover, it is desirable that the eyepiece optical system EL according to the present embodiment satisfies the following conditional expression (3).

0.00 <ΔD1 / ΔD2 (3)
However,
ΔD1: Amount of movement of the first variable magnification lens group GF1 when changing magnification from the high magnification end state to the low magnification end state ΔD2: Change of the second variable magnification lens group GF2 from the high magnification end state to the low magnification end state Here, the amount of movement is doubled from the object side to the eye point side.

  Conditional expression (3) allows the first variable power lens group GF1 and the second variable power lens group GF2, which are two lens groups having positive refractive power that move during zooming, to enable high zooming. The amount is specified. If the lower limit of conditional expression (3) is not reached, the first variable magnification lens group GF1 and the second variable magnification lens group GF2 move in the opposite direction, so that the space required for variable magnification becomes large and high magnification is reduced. Doing so will worsen the aberrations. In order to secure the effect of conditional expression (3), it is desirable to set the lower limit of conditional expression (3) to 0.29. In order to secure the effect of the conditional expression (3), it is desirable to set the upper limit value of the conditional expression (3) to 7.60.

  Moreover, it is desirable that the eyepiece optical system EL according to the present embodiment satisfies the following conditional expression (4). Conditional expression (4) defines an optimum zoom ratio of the eyepiece optical system EL.

1.26 <fT / fW (4)
However,
fT: focal length of the entire system in the low magnification end state fW: focal length of the entire system in the high magnification end state

  It is more desirable to set the lower limit value of conditional expression (4) to 1.30, more preferably 1.32. Moreover, it is more desirable to set the upper limit value of conditional expression (4) to 1.60, further 1.53.

  Further, the eyepiece optical system EL according to the present embodiment has sufficient aberration correction capability even when an image inverting member (for example, the image inverting member PR shown in FIG. 3) is inserted. When observing a real image formed by the objective lens (for example, real image O in FIG. 1), an erect image can be observed by inserting an image inverting member. Further, it is possible to reduce the size as compared with a case where an erect image is formed in the relay system.

  In the eyepiece optical system EL according to the present embodiment, the lens component closest to the eye point of the first variable power lens group GF1 that is a lens group that moves on the object side among the lens groups that move during zooming is as follows. It is desirable to satisfy the conditional expression (5) shown below.

-1.45 <(R1Ef-R1Er) / (R1Ef + R1Er) <4.40 (5)
However,
R1Ef: radius of curvature of the lens surface closest to the object side of the lens component closest to the eye point of the first variable magnification lens group GF1 R1Er: the lens component closest to the eye point of the lens component closest to the eye point of the first variable magnification lens group GF1 Radius of curvature of lens surface

  Conditional expression (5) defines the shape of the lens component closest to the eye point of the first variable magnification lens group GF1. If the lens component closest to the eye point of the first variable magnification lens group GF1 is a biconvex shape within the range of the conditional expression (5), it is effective for correcting curvature of field, astigmatism, and coma. is there. In order to satisfactorily correct field curvature, astigmatism, and coma, the lens component on the most eyepoint side of the first variable magnification lens group GF1 that is the object-side lens group that moves at the time of zooming is substantially omitted. It is preferable to become telecentric. Conditional expression (5) prescribes that the declination of the light ray is minimized in a substantially telecentric state. In order to secure the effect of the conditional expression (5), it is desirable to set the lower limit value of the conditional expression (5) to −1.41. In order to ensure the effect of conditional expression (5), it is desirable to set the upper limit of conditional expression (5) to 4.34.

  Further, in the eyepiece optical system EL according to the present embodiment, in addition to the conditional expression (5), it is corrected that the most object side lens surface of the lens unit closest to the object side is a concave surface facing the object side. Is preferred.

  In addition, the eyepiece optical system EL according to the present embodiment includes a high refractive index glass material having a refractive index higher than 1.8 for the d-line in each of the lens groups constituting the eyepiece optical system EL. Can be realized. When each lens group includes a high refractive index glass material, the curvature becomes loose, and it is possible to obtain a group interval necessary for high zooming. Particularly, by disposing the high refractive index glass material on the most object side and the most eye point side in each lens group, the group interval required for high zooming can be obtained. Further, by using a high refractive index glass material, it is possible to suppress the amount of occurrence of various aberrations. The high refractive index glass material included in the first variable magnification lens group GF1 and the second variable magnification lens group GF2 is effective in correcting astigmatism and field curvature. In particular, inclusion of a high refractive index glass material in the negative lens in the cemented lens is advantageous for correcting astigmatism and field curvature. Further, a high refractive index glass material included in a lens group other than the first variable magnification lens group GF1 and the second variable magnification lens group GF2 (for example, the third lens group G3 in FIG. 1) is effective in correcting coma aberration.

  Moreover, it is desirable that the eyepiece optical system EL according to the present embodiment satisfies the following conditional expression (6).

1.70 <NG1 <1.92 (6)
However,
NG1: Average refractive index of the lens medium included in the first variable magnification lens group GF1

  When this conditional expression (6) is satisfied, it is effective for increasing the zoom ratio and correcting various aberrations for the above reason. In order to secure the effect of the conditional expression (6), it is more desirable to set the lower limit value of the conditional expression (6) to 1.75, further 1.80. In order to secure the effect of the conditional expression (6), it is desirable to set the upper limit value of the conditional expression (6) to 1.90.

  Moreover, it is desirable that the eyepiece optical system EL according to the present embodiment satisfies the following conditional expression (7).

1.70 <NG2 <1.95 (7)
However,
NG2: Average refractive index of the lens medium included in the second variable magnification lens group GF2

  When this conditional expression (7) is satisfied, it is effective for high zooming and correction of various aberrations for the above reason. In order to secure the effect of the conditional expression (7), it is more desirable to set the lower limit value of the conditional expression (7) to 1.75, further 1.80. In order to ensure the effect of the conditional expression (7), it is more desirable to set the upper limit value of the conditional expression (7) to 1.92, further 1.90.

  In addition, the eyepiece optical system EL according to this embodiment corrects chromatic aberration satisfactorily by providing a cemented lens in at least one of the first variable magnification lens group GF1 and the second variable magnification lens group GF2 that moves at the time of zooming. can do. It is desirable that the cemented lens is included in the first variable magnification lens group GF1 that is the object side lens group among the variable magnification lens groups that move. Further, the cemented lens is advantageous in correcting distortion by adopting a negative lens configuration on the object side and a sacred lens configuration on the eye point side.

  In addition, the eyepiece optical system EL according to this embodiment has a meniscus shape in which the lens component closest to the eye point of the second variable magnification lens group GF2 has a concave surface facing the eye point, thereby declination of off-axis light. Can be reduced, and coma correction can be improved.

  Note that the conditions and configurations described above each exhibit the above-described effects, and are not limited to satisfying all the conditions and configurations. The above-described effects can be obtained even if the combination of the above conditions or configurations is satisfied.

  Next, a camera that is an optical apparatus including the eyepiece optical system EL according to the present embodiment will be described with reference to FIG. This camera 1 is a so-called mirrorless camera with an interchangeable lens provided with an objective lens (photographing lens) OL. In the camera 1, light from an object (subject) (not shown) is collected by the objective lens OL, and then on the imaging surface of the imaging unit C via an OLPF (Optical low pass filter) (not shown). A subject image is formed on the screen. Then, the subject image is photoelectrically converted by the photoelectric conversion element provided in the imaging unit C, and an image of the subject is generated. This image is displayed on an electronic viewfinder EVF (Electronic view finder) provided in the camera 1. Here, the electronic viewfinder EVF includes an image display element (observation object) O such as a liquid crystal display element, and an eyepiece optical system EL for magnifying and observing an image displayed on the image display element O. The Thus, the photographer can observe the image of the object (subject) formed by the objective lens OL via the eyepiece optical system EL by positioning the eye at the eye point EP.

  Further, when a release button (not shown) is pressed by the photographer, an image photoelectrically converted by the imaging unit C is stored in a memory (not shown). In this way, the photographer can shoot the subject with the camera 1. In this embodiment, an example of a mirrorless camera has been described. However, the eyepiece optical system EL according to this embodiment is provided in a single-lens reflex type camera that has a quick return mirror in the camera body and observes a subject with a finder optical system. Even when mounted, the same effects as the camera 1 can be obtained.

  The contents described below can be appropriately adopted as long as the optical performance is not impaired.

  In the present embodiment, the eyepiece optical system EL having the second group, the third group, and the fourth group configuration is shown. However, the above-described configuration conditions and the like can be applied to other group configurations such as the fifth group, the sixth group, and the like. Further, a configuration in which a lens or a lens group is added closest to the object side, or a configuration in which a lens or a lens group is added closest to the eye point may be used. Specifically, a configuration in which a lens group whose position relative to the image plane is fixed at the time of zooming or diopter adjustment on the most eyepoint side is conceivable. The lens group refers to a portion having at least one lens separated by an air interval that changes during zooming or diopter adjustment. The lens component refers to a single lens or a cemented lens in which a plurality of lenses are cemented.

  Further, the diopter adjustment may be performed on the entire eyepiece optical system. Moreover, it is good also as a diopter adjustment lens group which moves diopter adjustment by moving an individual or several lens group or a partial lens group to an optical axis direction. In particular, it is preferable that at least a part of the second lens group G2 is a diopter adjustment lens group, and other lenses are fixed in position relative to the image plane during diopter adjustment. Considering the load applied to the motor, it is preferable that the diopter adjustment lens group is composed of a single lens.

  In addition, the lens group or partial lens group is moved so as to have a displacement component perpendicular to the optical axis, or rotated (swinged) in the in-plane direction including the optical axis to correct image blur caused by camera shake. An anti-vibration lens group may be used. In particular, it is preferable that at least a part of the second lens group G2 is an anti-vibration lens group.

  Further, the lens surface may be formed as a spherical surface, a flat surface, or an aspheric surface. When the lens surface is a spherical surface or a flat surface, lens processing and assembly adjustment are facilitated, and optical performance deterioration due to errors in processing and assembly adjustment can be prevented. Further, even when the image plane is deviated, it is preferable because there is little deterioration in drawing performance. When the lens surface is an aspheric surface, the aspheric surface is an aspheric surface by grinding, a glass mold aspheric surface made of glass with an aspheric shape, or a composite aspheric surface made of resin with an aspheric shape on the glass surface. Any aspherical surface may be used. The lens surface may be a diffractive surface, and the lens may be a gradient index lens (GRIN lens) or a plastic lens.

  Further, each lens surface may be provided with an antireflection film having high transmittance in a wide wavelength region in order to reduce flare and ghost and achieve high optical performance with high contrast.

  The eyepiece optical system EL of the present embodiment has a zoom ratio of about 1.2 to 3 times.

  Hereinafter, an outline of a method of manufacturing the eyepiece optical system EL according to the present embodiment will be described with reference to FIG. First, each lens is arranged to prepare a lens group including a first variable magnification lens group GF1 and a second variable magnification lens group GF2 which are lens groups having at least two positive refractive powers (step S100). When changing the magnification from the high magnification end state to the low magnification end state, the first variable magnification lens group GF1 and the second variable magnification lens group GF2 are arranged so as to change the interval between the adjacent lens groups (steps). S200). Further, the lens surface closest to the eye point in the lens group closest to the eye point is disposed so as to be a concave surface facing the eye point (step S300). Furthermore, it arrange | positions so that the conditions by predetermined | prescribed conditional expression (For example, conditional expression (1) mentioned above) may be satisfied (step S400).

  Specifically, in the present embodiment, for example, as shown in FIG. 1, a cemented positive lens in which a biconcave negative lens L11 and a biconvex positive lens L12 are cemented in order from the object side, and a biconvex positive lens L13 are provided. The first lens group G1 is disposed, the biconvex positive lens L21 is disposed as the second lens group G2, and the negative meniscus lens L31 having a concave surface facing the eye point is disposed as the third lens group G3. In this example, the first lens group G1 corresponds to the first variable power lens group GF1, and the second lens group G2 corresponds to the second variable power lens group GF2. The lens groups prepared in this way are arranged according to the above-described procedure to manufacture the eyepiece optical system EL.

  With the configuration described above, an eyepiece optical system EL having a high zoom ratio and good optical performance, an optical apparatus having the eyepiece optical system EL, and a method for manufacturing the eyepiece optical system EL can be provided.

  Hereinafter, each example of the present application will be described with reference to the drawings. 1, 3, 5, 7, 9, 11, and 13 are sectional views showing the configuration and refractive power distribution of the eyepiece optical system EL (EL1 to EL7) according to each example. It is. Further, in the lower part of the cross-sectional views of these eyepiece optical systems EL1 to EL7, each lens group when changing magnification from the high magnification end state (W) to the intermediate magnification state (M) to the low magnification end state (T). The moving direction along the optical axis of G1 to G3 (or G4) is indicated by an arrow. A lens group to which no arrow is added is fixed at the time of zooming.

In the seventh embodiment, the height of the aspheric surface in the direction perpendicular to the optical axis is y, and the distance along the optical axis from the tangent plane of the apex of each aspheric surface to each aspheric surface at height y ( When the sag amount is S (y), the radius of curvature of the reference sphere (paraxial radius of curvature) is r, the conic constant is K, and the n-th aspherical coefficient is An, the following equation (a) expressed. In the following examples, “E−n” indicates “× 10 ⁻ⁿ ”.

S (y) = (y ² / r) / {1+ (1−K × y ² / r ² ) ^1/2 }
+ A4 × y ⁴ + A6 × y ⁶ + A8 × y ⁸ (a)

  In each embodiment, the secondary aspheric coefficient A2 is zero. In the table of each example, an aspherical surface is marked with * on the right side of the surface number.

[First embodiment]
FIG. 1 is a diagram illustrating a configuration of an eyepiece optical system EL1 according to the first example. The eyepiece optical system EL1 has, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, a negative refractive power, and the most eyepoint side. And a third lens group G3 having a concave surface.

  In the eyepiece optical system EL1, the first lens group G1 includes, in order from the object side, a cemented positive lens in which a biconcave negative lens L11 and a biconvex positive lens L12 are cemented, and a biconvex positive lens L13. . The second lens group G2 is composed of a biconvex positive lens L21. The third lens group G3 includes a negative meniscus lens L31 having a concave surface directed toward the eye point.

  In the eyepiece optical system EL1, the first lens group G1 is a first variable magnification lens group GF1, and the second lens group G2 is a second variable magnification lens group GF2, which changes from a high magnification end state to a low magnification end state. At the time of doubling, the distance between the object O and the first lens group G1 increases, the distance between the first lens group G1 and the second lens group G2 increases, and the distance between the second lens group G2 and the third lens group G3. Is performed by moving each of the first variable magnification lens group GF1 and the second variable magnification lens group GF2 to the eye point side along the optical axis. With this configuration, it is possible to reduce the lens movement space necessary for zooming. Further, since the two lens units having positive refractive power are moved and changed in magnification, the refractive power (power) of the first variable magnification lens group GF1 and the second variable magnification lens group GF2 becomes relatively weak, and aberration correction is performed. Is excellent. The third lens group G3 is fixed at the time of zooming. At this time, by appropriately selecting the movement amounts of the first variable magnification lens group GF1 and the second variable magnification lens group GF2, the magnification can be changed while keeping the diopter constant.

  The diopter adjustment in the eyepiece optical system EL1 is performed by moving the second lens group G2 alone in the optical axis direction.

Table 1 below lists values of specifications of the eyepiece optical system EL1. In Table 1, f shown in the overall specifications is the focal length of the entire system, h is the maximum object height, TL is the total length value, the high magnification end state when the diopter is ⁻¹ m ⁻¹ , the intermediate magnification state, Shown for each low magnification end state. Here, the total length TL indicates the distance on the optical axis from the observation object O to the lens surface (9th surface) closest to the eye point of the eyepiece optical system EL1, and is the longest of the eyepiece optical system EL1 from the observation object O. The distance to the lens surface (first surface) on the observation object side indicates the air equivalent length. In the lens data, the first column m indicates the order (surface number) of the lens surfaces from the object side along the traveling direction of the light beam, the second column r indicates the curvature radius of each lens surface, and the third column. d is the distance on the optical axis from each optical surface to the next optical surface (surface interval). The fourth column nd and the fifth column νd are the refractive index and Abbe number for the d-line (λ = 587.6 nm). Is shown. The radius of curvature of 0.0000 indicates a plane, and the refractive index of air of 1.0000 is omitted. The lens group focal length indicates the number of the starting surface and the focal length of each of the first to third lens groups G1 to G3. The object plane indicates the object O, and the image plane indicates the eye point EP. In addition, for the diopter unit “m ⁻¹ ”, the diopter X [m ⁻¹ ] means that the image by the eyepiece optical system EL is 1 / X [m (meter)] from the eye point EP onto the optical axis. This indicates that the position can be achieved (the sign is positive when the image is closer to the viewer than the eyepiece optical system EL).

  Here, the focal length f, the radius of curvature r, the surface interval d, and other length units listed in all the following specification values are generally “mm”, but the optical system is proportionally enlarged or proportional. Since the same optical performance can be obtained even if the image is reduced, the present invention is not limited to this. The description of these symbols and the description of the specification table are the same in the following embodiments.

(Table 1) First Example [Overall Specifications]
High magnification end state Medium magnification state Low magnification end state f = 20.532 to 24.802 to 31.199
h = 6.35 to 6.35 to 6.35
TL (air equivalent length) = 67.210-67.211-67.211

[Lens data]
m r d nd νd
Object ∞ D0
1 -71.0648 9.0000 1.90200 25.26
2 36.2748 10.2376 1.72826 54.64
3 -32.4915 0.3000
4 166.1448 4.9329 1.73096 54.35
5 -69.3628 D1
6 35.9752 7.2180 1.72916 54.61
7 -370.3918 D2
8 33.9569 1.2000 1.80662 27.94
9 16.8531 D3
Image plane ∞

[Lens focal length]
Lens group Start surface Focal length 1st lens group 1 39.502
Second lens group 6 45.309
Third lens group 8 -42.822

In the eyepiece optical system EL1, the on-axis air distance D0 between the object O and the first lens group G1, the on-axis air distance D1 between the first lens group G1 and the second lens group G2, and the second lens group G2. As described above, the axial air distance D2 between the third lens group G3 and the third lens group G3 changes during zooming, and the axial air distance D3 between the third lens group G3 and the eye point EP does not change during zooming. The third lens group G3 is fixed during zooming. The following table 2, diopter -1 m ^-1, the high magnification end state in each of -2m ^-1 and 1 m ^-1 (W), each of the intermediate magnification state (M) and low magnification end state (T) The variable interval in the focal length state is shown. Note that D0 indicates the distance from the most object-side surface (first surface) of the eyepiece optical system EL1 to the object O, f indicates the focal length, h indicates the object height, and TL indicates the total length (hereinafter referred to as the following). The same applies to the examples).

(Table 2)
[Variable interval data]
Diopter -1m ^-1 -2m ^-1
W M T W M T
f 20.532 24.802 31.199 22.267 26.761 33.668
h 6.35 6.35 6.35 6.35 6.35 6.35
D0 14.937 16.420 19.150 14.937 16.420 19.150
D1 2.705 7.878 12.619 5.522 10.344 14.878
D2 16.679 10.024 2.553 13.862 7.557 0.294
D3 17.000 17.000 17.000 17.000 17.000 17.000
TL 67.210 67.211 67.211 67.210 67.210 67.211

Diopter 1m ^-1
W M T
f 19.180 23.222 29.195
h 6.35 6.35 6.35
D0 14.937 16.420 19.150
D1 0.278 5.698 10.611
D2 19.107 12.204 4.561
D3 17.000 17.000 17.000
TL 67.211 67.211 67.211

  Table 3 below shows values corresponding to the conditional expressions in the eyepiece optical system EL1. In Table 3, f1 is the focal length of the first variable magnification lens group GF1, f2 is the focal length of the second variable magnification lens group GF2, and νEP is the Abbe number of the lens medium closest to the eyepoint with respect to the d-line. , ΔD1 is the amount of movement of the first variable magnification lens group GF1 when zooming from the high magnification end state to the low magnification end state, and ΔD2 is from the high magnification end state of the second variable magnification lens group GF2 to the low magnification end state. FT is the focal length of the entire system in the low magnification end state, fW is the focal length of the entire system in the high magnification end state, and R1Ef is the most eye point of the first variable magnification lens group GF1. R1Er is the radius of curvature of the lens surface closest to the object side of the first variable magnification lens group GF1, and NG1 is the first radius of curvature of the lens surface closest to the eyepoint of the lens component of the first variable magnification lens group GF1. Included in variable magnification lens group GF1 The average refractive index of the medium that lens, NG2 is an average refractive index of the medium of lens in the second lens group GF2, represents respectively. The description of the reference numerals is the same in the following embodiments. In the first embodiment, the lens closest to the eye point corresponds to the negative meniscus lens L31 (νEP is the Abbe number of the eighth surface), f1 corresponds to the focal length of the first lens group G1, and f2 The focal length of the second lens group G2 corresponds, ΔD1 corresponds to the amount of movement of the first lens group G1, ΔD2 corresponds to the amount of movement of the second lens group G2, and the most eye of the first variable magnification lens group GF1. The lens component on the point side corresponds to a biconvex positive lens L13 (R1Ef is the curvature radius of the fourth surface and R1Er is the curvature radius of the fifth surface).

(Table 3)
ΔD1 = 4.213
ΔD2 = 14.126
[Values for conditional expressions]
(1) f1 / f2 = 0.872
(2) νEP = 27.94
(3) ΔD1 / ΔD2 = 0.298
(4) fT / fW = 1.520
(5) (R1Ef−R1Er) / (R1Ef + R1Er) = 2.433
(6) NG1 = 1.787
(7) NG2 = 1.729

  Thus, this eyepiece optical system EL1 satisfies the conditional expressions (1) to (5).

The ocular optical system EL1 has a spherical aberration diagram, an astigmatism diagram, a distortion in a high magnification end state (W), an intermediate magnification state (M), and a low magnification end state (T) when the diopter is -1m ^-1 . An aberration diagram and a coma aberration diagram are shown in FIG. The spherical aberration diagram shows the value of the incident height, the astigmatism diagram and the distortion diagram show the object height value, and the coma diagram shows the value of each object height. The unit of the horizontal axis of the spherical aberration diagram and the astigmatism diagram is “m ⁻¹ ”, which is indicated by “D” in the figure. Further, “′” in the coma aberration diagram indicates the minute in the angle unit, and “″” indicates the second in the angle unit. D represents the d-line (λ = 587.6 nm), and g represents the g-line (λ = 435.8 nm). In the astigmatism diagram, the solid line indicates the sagittal image plane, and the broken line indicates the meridional image plane. Further, the spherical aberration diagram and the coma aberration diagram show aberration diagrams assuming an eyepoint diameter of 4 mm. Also, the same reference numerals as in this example are used in the aberration diagrams of the examples shown below. From these respective aberration diagrams, it can be seen that in this eyepiece optical system EL1, various aberrations are satisfactorily corrected in all the areas, although the zoom ratio is large.

[Second Embodiment]
FIG. 3 is a diagram illustrating a configuration of the eyepiece optical system EL2 according to the second example. The eyepiece optical system EL2 includes, in order from the object side, a condenser lens group Gc having a positive refractive power, an image inverting member PR, a first lens group G1 having a positive refractive power, and a first lens group having a positive refractive power. The second lens group G2 includes a second lens group G2 and a third lens group G3 having negative refractive power and having a concave surface closest to the eye point.

  In the eyepiece optical system EL2, the condenser lens group Gc includes, in order from the object side, a substantially parallel flat plate Lc1 and a planoconvex positive lens Lc2 having a plane facing the object side. The first lens group G1 includes, in order from the object side, a cemented positive lens in which a planoconcave negative lens L11 having a plane facing the object side and a biconvex positive lens L12 are cemented, and a positive surface having a convex surface facing the object side. It is composed of a meniscus lens L13. The second lens group G2 includes a positive meniscus lens L21 having a convex surface directed toward the object side. The third lens group G3 includes a negative meniscus lens L31 having a concave surface directed toward the eye point.

  In this eyepiece optical system EL2, the first lens group G1 is a first variable magnification lens group GF1, and the second lens group G2 is a second variable magnification lens group GF2, which changes from a high magnification end state to a low magnification end state. At the time of magnification, the distance between the image inverting member PR and the first lens group G1 is increased, the distance between the first lens group G1 and the second lens group G2 is decreased, and the second lens group G2 and the third lens group G3 The first variable power lens group GF1 and the second variable power lens group GF2 are moved along the optical axis so that the distance between the third lens group G3 and the eye point EP increases. By moving to the side. With this configuration, it is possible to reduce the lens movement space necessary for zooming. Further, since the two lens units having positive refractive power are moved and changed in magnification, the refractive power (power) of the first variable magnification lens group GF1 and the second variable magnification lens group GF2 becomes relatively weak, and aberration correction is performed. Is excellent. The third lens group G3 is fixed at the time of zooming. At this time, by appropriately selecting the movement amounts of the first variable magnification lens group GF1 and the second variable magnification lens group GF2, the magnification can be changed while keeping the diopter constant.

  The diopter adjustment in the eyepiece optical system EL2 is performed by moving the second lens group G2 alone in the optical axis direction. At the time of diopter adjustment, if the second lens group G2 is moved in the optical axis direction by a certain amount, the same diopter adjustment amount can be obtained at all magnifications.

  Table 4 below lists values of specifications of the eyepiece optical system EL2.

(Table 4) Second Example [Overall Specifications]
High magnification end state Medium magnification state Low magnification end state f = 51.781 to 61.504 to 71.930
h = 13.518 to 17.297 to 21.188
TL (air equivalent length) = 101.133 to 101.133 to 101.133

[Lens data]
m r d nd νd
Object ∞ 0.8000
1 0.0000 1.0000 1.51680 63.88
2 0.0000 0.3000
3 0.0000 5.5000 1.60311 60.69
4 -60.5319 0.4000
5 0.0000 97.2770 1.51680 63.88
6 0.0000 D1
7 0.0000 1.2000 1.90200 25.26
8 28.4179 4.1000 1.75500 52.33
9 -123.9036 0.2000
10 35.3708 2.7000 1.90265 35.72
11 155.9624 D2
12 29.2335 2.1000 1.90366 31.27
13 65.8951 D3
14 61.9986 1.2000 1.88300 40.66
15 18.7248 D4
Image plane ∞

[Lens focal length]
Lens group Start surface Focal length 1st lens group 7 47.212
Second lens group 12 56.607
Third lens group 14 -30.782

In the eyepiece optical system EL2, the axial air distance D1 between the image reversing member PR and the first lens group G1, the axial air distance D2 between the first lens group G1 and the second lens group G2, and the second lens group G2. As described above, the axial air gap D3 between the third lens group G3 and the axial air gap D4 between the third lens group G3 and the eye point EP changes during zooming. The third lens group G3 is fixed during zooming. The following Table 5 shows each of the high magnification end state (W), the intermediate magnification state (M), and the low magnification end state (T) when the diopter is ^-1 m ^-1 , 0 m ^-1 and -2 m ^-1. The variable interval in the focal length state is shown.

(Table 5)
[Variable interval data]
Diopter -1m ^-1 0m ^-1
W M T W M T
f 51.781 61.504 71.930 50.575 59.847 69.778
h 13.518 17.297 21.188 13.518 17.297 21.188
D1 0.300 7.500 14.300 0.300 7.500 14.300
D2 13.610 7.810 1.640 12.510 6.670 0.500
D3 3.590 2.190 1.560 4.690 3.330 2.700
D4 16.000 16.500 17.000 14.500 15.000 15.500
TL 101.133 101.133 101.133 101.133 101.133 101.133

Diopter -2m ^-1
W M T
f 53.142 63.325 74.318
h 13.518 17.297 21.188
D1 0.300 7.500 14.300
D2 14.860 9.060 2.890
D3 2.340 0.940 0.310
D4 16.000 16.500 17.000
TL 101.133 101.133 101.133

  Table 6 below shows values corresponding to the conditional expressions in the eyepiece optical system EL2. In the second embodiment, the lens closest to the eye point corresponds to the negative meniscus lens L31 (νEP is the Abbe number of the 14th surface), f1 corresponds to the focal length of the first lens group G1, and f2 The focal length of the second lens group G2 corresponds, ΔD1 corresponds to the amount of movement of the first lens group G1, ΔD2 corresponds to the amount of movement of the second lens group G2, and the most eye of the first variable magnification lens group GF1. The lens component on the point side corresponds to a positive meniscus lens L13 (R1Ef is the radius of curvature of the tenth surface and R1Er is the radius of curvature of the eleventh surface).

(Table 6)
ΔD1 = 14,000
ΔD2 = 2.030
[Values for conditional expressions]
(1) f1 / f2 = 0.833
(2) νEP = 40.66
(3) ΔD1 / ΔD2 = 6.897
(4) fT / fW = 1.389
(5) (R1Ef−R1Er) / (R1Ef + R1Er) = − 0.630
(6) NG1 = 1.853
(7) NG2 = 1.904

  Thus, this eyepiece optical system EL2 satisfies the conditional expressions (1) to (7).

The ocular optical system EL2 has spherical aberration diagrams, astigmatism diagrams, and distortions in the high magnification end state (W), the intermediate magnification state (M), and the low magnification end state (T) when the diopter is -1m- ¹ . Aberration diagrams and coma aberration diagrams are shown in FIG. From these aberration diagrams, it can be seen that the eyepiece optical system EL2 has various aberrations well corrected in all the regions, despite the large zoom ratio.

[Third embodiment]
FIG. 5 is a diagram showing a configuration of the eyepiece optical system EL3 according to the third example. The eyepiece optical system EL3 includes, in order from the object side, a condenser lens group Gc having a positive refractive power, an image inverting member PR, a first lens group G1 having a positive refractive power, and a first lens group having a positive refractive power. The lens unit G2 includes a second lens group G2, a third lens group G3 having negative refractive power and having a concave surface closest to the eye point, and a substantially parallel plate PL.

  In the eyepiece optical system EL3, the condenser lens group Gc includes, in order from the object side, a substantially parallel flat plate Lc1 and a planoconvex positive lens Lc2 having a plane facing the object side. The first lens group G1 includes, in order from the object side, a cemented positive lens in which a planoconcave negative lens L11 having a plane facing the object side and a biconvex positive lens L12 are cemented, and a positive surface having a convex surface facing the object side. It is composed of a meniscus lens L13. The second lens group G2 includes a positive meniscus lens L21 having a convex surface directed toward the object side. The third lens group G3 is composed of a biconcave negative lens L31.

  In this eyepiece optical system EL3, the first lens group G1 is a first variable magnification lens group GF1, and the second lens group G2 is a second variable magnification lens group GF2, which changes from a high magnification end state to a low magnification end state. At the time of magnification, the distance between the image inverting member PR and the first lens group G1 is increased, the distance between the first lens group G1 and the second lens group G2 is decreased, and the second lens group G2 and the third lens group G3 Each of the first variable magnification lens group GF1 and the second variable magnification lens group GF2 is arranged on the eye point side along the optical axis so that the distance between the first and second variable magnification lens groups GF1 and GF2 increases and the distance between the substantially parallel plate PL and the eye point EP increases. By moving to. With this configuration, it is possible to reduce the lens movement space necessary for zooming. Further, since the two lens units having positive refractive power are moved and changed in magnification, the refractive power (power) of the first variable magnification lens group GF1 and the second variable magnification lens group GF2 becomes relatively weak, and aberration correction is performed. Is excellent. Note that the third lens group G3 and the substantially parallel plate PL are fixed at the time of zooming. At this time, by appropriately selecting the movement amounts of the first variable magnification lens group GF1 and the second variable magnification lens group GF2, the magnification can be changed while keeping the diopter constant.

  The diopter adjustment in the eyepiece optical system EL3 is performed by moving the second lens group G2 alone in the optical axis direction. At the time of diopter adjustment, if the second lens group G2 is moved in the optical axis direction by a certain amount, the same diopter adjustment amount can be obtained at all magnifications.

  Table 7 below provides values of specifications of the eyepiece optical system EL3.

(Table 7) Third Example [Overall Specifications]
High magnification end state Medium magnification state Low magnification end state f = 53.321 to 65.984 to 70.682
h = 13.518 to 17.297 to 21.188
TL (Air equivalent length) = 100.603 to 100.603 to 100.603

[Lens data]
m r d nd νd
Object ∞ 0.8000
1 0.0000 1.0000 1.51680 63.88
2 0.0000 0.1500
3 0.0000 5.5000 1.65844 50.83
4 -60.5319 0.4000
5 0.0000 97.2770 1.51680 63.88
6 0.0000 D1
7 0.0000 1.2000 1.90200 25.26
8 29.9235 3.6500 1.76684 46.78
9 -133.2823 0.2000
10 36.7781 2.7000 1.79952 42.09
11 471.1611 D2
12 42.3803 2.1000 1.88300 40.66
13 465.8572 D3
14 -288.3886 1.2000 1.72916 54.61
15 23.6824 1.2200
16 0.0000 1.0000 1.51680 63.88
17 0.0000 D4
Image plane ∞

[Lens focal length]
Lens group Start surface Focal length 1st lens group 7 46.353
Second lens group 12 52.677
Third lens group 14 -29.966

In the eyepiece optical system EL3, the axial air distance D1 between the image reversing member PR and the first lens group G1, the axial air distance D2 between the first lens group G1 and the second lens group G2, and the second lens group G2. As described above, the axial air distance D3 between the third lens group G3 and the axial air distance D4 between the third lens group G3 and the substantially parallel flat plate PL and the eye point EP changes during zooming. The third lens group G3 and the substantially parallel plate PL are fixed during zooming. The following Table 8 shows each of the high magnification end state (W), the intermediate magnification state (M), and the low magnification end state (T) when the diopter is ^-1 m ^-1 , 0 m ^-1 and -2 m ^-1. The variable interval in the focal length state is shown.

(Table 8)
[Variable interval data]
Diopter -1m ^-1 0m ^-1
W M T W M T
f 53.321 65.984 70.682 52.134 64.329 68.843
h 13.518 17.297 21.188 13.518 17.297 21.188
D1 0.300 9.200 12.170 0.300 9.200 12.170
D2 11.850 4.300 1.550 10.800 3.250 0.500
D3 3.200 1.850 1.630 4.250 2.900 2.680
D4 15.000 16.000 17.000 13.500 14.500 15.200
TL 100.603 100.603 100.603 100.603 100.603 100.603

Diopter -2m ^-1
W M T
f 54.617 67.807 72.713
h 13.518 17.297 21.188
D1 0.300 9.200 12.170
D2 13.010 5.460 2.710
D3 2.040 0.690 0.470
D4 15.000 16.000 17.000
TL 100.603 100.603 100.603

  Table 9 below shows values corresponding to the conditional expressions in the eyepiece optical system EL3. In the third embodiment, the substantially parallel flat plate PL is provided closest to the eye point. However, the substantially parallel flat plate PL closest to the eye point is not subject to the conditional expression (2). The lens closest to the substantially parallel plate PL is the target of conditional expression (2). That is, in the third embodiment, the most eye point side lens corresponds to the biconcave negative lens L31 (νEP is the Abbe number of the 14th surface). F1 corresponds to the focal length of the first lens group G1, f2 corresponds to the focal length of the second lens group G2, ΔD1 corresponds to the amount of movement of the first lens group G1, and ΔD2 corresponds to the second lens group. The amount of movement of G2 corresponds, and the lens component closest to the eye point in the first variable magnification lens group GF1 corresponds to the positive meniscus lens L13 (R1Ef is the curvature radius of the tenth surface and R1Er is the curvature radius of the eleventh surface). .

(Table 9)
ΔD1 = 11.870
ΔD2 = 1.570
[Values for conditional expressions]
(1) f1 / f2 = 0.880
(2) νEP = 54.61
(3) ΔD1 / ΔD2 = 7.561
(4) fT / fW = 1.326
(5) (R1Ef−R1Er) / (R1Ef + R1Er) = − 0.855
(6) NG1 = 1.823
(7) NG2 = 1.883

  Thus, this eyepiece optical system EL3 satisfies the conditional expressions (1) to (7).

The ocular optical system EL3 has a spherical aberration diagram, an astigmatism diagram, and a distortion in a high magnification end state (W), an intermediate magnification state (M), and a low magnification end state (T) when the diopter is −1m ⁻¹ . An aberration diagram and a coma aberration diagram are shown in FIG. From these respective aberration diagrams, it can be seen that in this eyepiece optical system EL3, various aberrations are satisfactorily corrected in all the areas, although the zoom ratio is large.

[Fourth embodiment]
FIG. 7 is a diagram illustrating a configuration of the eyepiece optical system EL4 according to the fourth example. The eyepiece optical system EL4 has, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, a negative refractive power, and the most eyepoint side. And a third lens group G3 having a concave surface.

  In the eyepiece optical system EL4, the first lens group G1 includes, in order from the object side, a cemented positive lens in which a biconcave negative lens L11 and a biconvex positive lens L12 are cemented, and a biconvex positive lens L13. . The second lens group G2 includes, in order from the object side, a positive meniscus lens L21 having a convex surface facing the object side, and a positive meniscus lens L22 having a convex surface facing the object side. The third lens group G3 includes a negative meniscus lens L31 having a concave surface directed toward the eye point.

  In this eyepiece optical system EL4, the first lens group G1 is a first variable magnification lens group GF1, and the second lens group G2 is a second variable magnification lens group GF2, which changes from a high magnification end state to a low magnification end state. At the time of doubling, the distance between the object O and the first lens group G1 increases, the distance between the first lens group G1 and the second lens group G2 changes, and the distance between the second lens group G2 and the third lens group G3. Is performed by moving each of the first variable magnification lens group GF1 and the second variable magnification lens group GF2 to the eye point side along the optical axis. With this configuration, it is possible to reduce the lens movement space necessary for zooming. Further, since the two lens units having positive refractive power are moved and changed in magnification, the refractive power (power) of the first variable magnification lens group GF1 and the second variable magnification lens group GF2 becomes relatively weak, and aberration correction is performed. Is excellent. The third lens group G3 is fixed at the time of zooming. At this time, by appropriately selecting the movement amounts of the first variable magnification lens group GF1 and the second variable magnification lens group GF2, the magnification can be changed while keeping the diopter constant.

  The diopter adjustment in the eyepiece optical system EL4 is performed by moving the second lens group G2 alone in the optical axis direction. At the time of diopter adjustment, if the second lens group G2 is moved in the optical axis direction by a certain amount, the same diopter adjustment amount can be obtained at all magnifications.

  Table 10 below lists values of specifications of the eyepiece optical system EL4.

(Table 10) Fourth Example [Overall Specifications]
High magnification end state Medium magnification state Low magnification end state f = 19.220 to 23.202 to 29.238
h = 6.35 to 6.35 to 6.35
TL (air equivalent length) = 59.972 to 59.972 to 59.973

[Lens data]
m r d nd νd
Object ∞ D0
1 -75.9474 9.0000 1.90200 25.26
2 27.6207 9.0000 1.72764 54.66
3 -42.7959 0.3000
4 63.8476 9.0000 1.67810 56.54
5 -39.9336 D1
6 35.2881 3.4769 1.75849 50.74
7 81.9082 0.3000
8 20.3062 3.3000 1.86509 41.7
9 28.3235 D2
10 57.6080 1.2000 1.77118 35.45
11 13.4716 D3
Image plane ∞

[Lens focal length]
Lens group Start surface Focal length 1st lens group 1 31.590
Second lens group 6 37.028
Third lens group 10 -23.074

In the eyepiece optical system EL4, the axial air gap D0 between the object O and the first lens group G1, the axial air gap D1 between the first lens group G1 and the second lens group G2, the second lens group G2 and the third lens group G2. As described above, the on-axis air gap D2 between the lens group G3 changes during zooming, and the on-axis air gap D3 between the third lens group G3 and the eye point EP does not change during zooming. The third lens group G3 is fixed during zooming. The following table 11, diopter -1 m ^-1, the high magnification end state in each of -2m ^-1 and 1 m ^-1 (W), each of the intermediate magnification state (M) and low magnification end state (T) The variable interval in the focal length state is shown.

(Table 11)
[Variable interval data]
Diopter -1m ^-1 -2m ^-1
W M T W M T
f 19.220 23.202 29.238 19.837 24.053 30.544
h 6.35 6.35 6.35 6.35 6.35 6.35
D0 15.227 17.893 21.830 15.227 17.893 21.830
D1 0.850 1.569 0.955 1.459 2.178 1.563
D2 8.318 4.933 1.611 7.709 4.325 1.003
D3 17.000 17.000 17.000 17.000 17.000 17.000
TL 59.972 59.972 59.973 59.972 59.973 59.973

Diopter 1m ^-1
W M T
f 18.679 22.461 28.115
h 6.35 6.35 6.35
D0 15.227 17.893 21.830
D1 0.292 1.011 0.396
D2 8.876 5.492 2.169
D3 17.000 17.000 17.000
TL 59.972 59.973 59.972

  Table 12 below shows values corresponding to the conditional expressions in the eyepiece optical system EL4. In the fourth example, the lens closest to the eye point corresponds to the negative meniscus lens L31 (νEP is the Abbe number of the tenth surface), f1 corresponds to the focal length of the first lens group G1, and f2 The focal length of the second lens group G2 corresponds, ΔD1 corresponds to the amount of movement of the first lens group G1, ΔD2 corresponds to the amount of movement of the second lens group G2, and the most eye of the first variable magnification lens group GF1. The lens component on the point side corresponds to a biconvex positive lens L13 (R1Ef is the curvature radius of the fourth surface and R1Er is the curvature radius of the fifth surface).

(Table 12)
ΔD1 = 6.602
ΔD2 = 6.707
[Values for conditional expressions]
(1) f1 / f2 = 0.853
(2) νEP = 35.45
(3) ΔD1 / ΔD2 = 0.984
(4) fT / fW = 1.521
(5) (R1Ef−R1Er) / (R1Ef + R1Er) = 4.340
(6) NG1 = 1.769
(7) NG2 = 1.812

  Thus, the eyepiece optical system EL4 satisfies the conditional expressions (1) to (5) and (7).

The ocular optical system EL4 has a spherical aberration diagram, an astigmatism diagram, and a distortion in a high magnification end state (W), an intermediate magnification state (M), and a low magnification end state (T) when the diopter is −1m ⁻¹ . An aberration diagram and a coma aberration diagram are shown in FIG. From these respective aberration diagrams, it can be seen that in this eyepiece optical system EL4, various aberrations are satisfactorily corrected in all the areas, although the zoom ratio is large.

[Fifth embodiment]
FIG. 9 is a diagram showing a configuration of an eyepiece optical system EL5 according to the fifth example. The eyepiece optical system EL5 includes, in order from the object side, a first lens group G1 having a positive refractive power and a second lens group G2 having a positive refractive power and having a concave surface closest to the eye point. Configured.

  In the eyepiece optical system EL5, the first lens group G1 includes, in order from the object side, a negative meniscus lens L11 having a concave surface directed toward the object side, and a biconvex positive lens L12. The second lens group G2 includes, in order from the object side, a cemented negative lens in which a biconcave negative lens L21 and a biconvex positive lens L22 are cemented, a positive meniscus lens L23 having a convex surface on the object side, and a convex surface on the object side. And a negative meniscus lens L25 having a concave surface facing the eye point.

  In the eyepiece optical system EL5, the first lens group G1 is a first variable magnification lens group GF1, and the second lens group G2 is a second variable magnification lens group GF2, which changes from a high magnification end state to a low magnification end state. At the time of doubling, the distance between the object O and the first lens group G1 decreases, the distance between the first lens group G1 and the second lens group G2 increases, and the distance between the second lens group G2 and the eye point EP increases. In this manner, the first variable magnification lens group GF1 is moved to the object side along the optical axis, and the second variable magnification lens group GF2 is moved to the eye point side along the optical axis. Since the lens group having two positive refractive powers is moved to change the magnification, the refractive power (power) of the first variable power lens group GF1 and the second variable power lens group GF2 becomes relatively weak, and is excellent in aberration correction. ing. At this time, by appropriately selecting the movement amounts of the first variable magnification lens group GF1 and the second variable magnification lens group GF2, the magnification can be changed while keeping the diopter constant.

  The diopter adjustment in the eyepiece optical system EL5 is performed by moving the first lens group G1 alone in the optical axis direction.

  Table 13 below provides values of specifications of the eyepiece optical system EL5.

(Table 13) Fifth Example [Overall Specifications]
High magnification end state Medium magnification state Low magnification end state f = 19.430 to 23.111 to 28.518
h = 6.35 to 6.35 to 6.35
TL (equivalent air length) = 34.941 to 48.828 to 61.803

[Lens data]
m r d nd νd
Object ∞ D0
1 -8.9702 2.7141 1.88300 40.66
2 -10.9861 0.3000
3 559.7292 4.0695 1.88300 40.66
4 -26.4857 D1
5 -26.0578 1.2000 1.90200 25.26
6 21.4466 5.1847 1.72930 54.59
7 -30.8103 0.3000
8 20.9116 2.3926 1.88300 40.66
9 40.0111 0.3000
10 12.6320 2.9459 1.88300 40.66
11 19.3209 0.3000
12 11.8148 1.2000 1.78732 46.70
13 7.7753 D2
Image plane ∞

[Lens focal length]
Lens group Start surface Focal length 1st lens group 1 29.734
Second lens group 5 64.590

In the eyepiece optical system EL5, the on-axis air distance D0 between the object O and the first lens group G1, the on-axis air distance D1 between the first lens group G1 and the second lens group G2, and the second lens group G2. As described above, the axial air distance D2 from the eye point EP changes upon zooming. The following table 14, diopter -1 m ^-1, the high magnification end state in each of -2m ^-1 and 1 m ^-1 (W), each of the intermediate magnification state (M) and low magnification end state (T) The variable interval in the focal length state is shown.

(Table 14)
[Variable interval data]
Diopter -1m ^-1 -2m ^-1
W M T W M T
f 19.430 23.111 28.518 19.514 23.294 29.022
h 6.35 6.35 6.35 6.35 6.35 6.35
D0 13.307 11.450 8.668 12.882 10.796 7.498
D1 0.727 16.471 32.228 1.152 17.125 33.398
D2 17.000 18.000 19.000 17.000 18.000 19.000
TL 34.941 48.828 61.803 34.941 48.828 61.803

Diopter 1m ^-1
W M T
f 19.348 22.940 28.088
h 6.35 6.35 6.35
D0 13.721 12.069 9.699
D1 0.313 15.852 31.197
D2 17.000 18.000 19.000
TL 34.941 48.828 61.803

  Table 15 below shows values corresponding to the conditional expressions in the eyepiece optical system EL5. In this fifth example, the lens closest to the eye point corresponds to the negative meniscus lens L25 (νEP is the Abbe number of the twelfth surface), f1 corresponds to the focal length of the first lens group G1, and f2 The focal length of the second lens group G2 corresponds, ΔD1 corresponds to the amount of movement of the first lens group G1, ΔD2 corresponds to the amount of movement of the second lens group G2, and the most eye of the first variable magnification lens group GF1. The lens component on the point side corresponds to a biconvex positive lens L12 (R1Ef is the curvature radius of the third surface and R1Er is the curvature radius of the fourth surface).

(Table 15)
ΔD1 = -4.6383
ΔD2 = 26.862
[Values for conditional expressions]
(1) f1 / f2 = 0.460
(2) νEP = 46.70
(3) ΔD1 / ΔD2 = −0.173
(4) fT / fW = 1.468
(5) (R1Ef−R1Er) / (R1Ef + R1Er) = 1.0099
(6) NG1 = 1.883
(7) NG2 = 1.837

  Thus, this eyepiece optical system EL5 satisfies the above conditional expressions (1), (2), and (4) to (7).

The ocular optical system EL5 has a spherical aberration diagram, an astigmatism diagram, and a distortion in a high magnification end state (W), an intermediate magnification state (M), and a low magnification end state (T) when the diopter is −1m ⁻¹ . An aberration diagram and a coma aberration diagram are shown in FIG. From these respective aberration diagrams, it can be seen that in this eyepiece optical system EL5, various aberrations are satisfactorily corrected in all the areas, although the zoom ratio is large.

[Sixth embodiment]
FIG. 11 is a diagram illustrating a configuration of an eyepiece optical system EL6 according to the sixth example. The eyepiece optical system EL6 includes, in order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a positive refractive power. And a fourth lens group G4 having negative refractive power and having a concave surface closest to the eye point.

  In the eyepiece optical system EL6, the first lens group G1 includes, in order from the object side, a negative meniscus lens L11 having a concave surface facing the object side, and a positive meniscus lens L12 having a concave surface facing the object side. The second lens group G2 includes, in order from the object side, a cemented positive lens in which a negative meniscus lens L21 having a convex surface facing the object side and a biconvex positive lens L22 are cemented, and a biconvex positive lens L23. Yes. The third lens group G3 includes a positive meniscus lens L31 having a convex surface directed toward the object side. The fourth lens group G4 includes a negative meniscus lens L41 having a concave surface directed toward the eye point.

  In the eyepiece optical system EL6, the second lens group G2 is a first variable magnification lens group GF1, and the third lens group G3 is a second variable magnification lens group GF2, which changes from a high magnification end state to a low magnification end state. At the time of magnification, the distance between the first lens group G1 and the second lens group G2 increases, the distance between the second lens group G2 and the third lens group G3 decreases, and the third lens group G3 and the fourth lens group G4 The first variable power lens group GF1 and the second variable power lens group GF2 are moved along the optical axis so that the distance between the fourth lens group G4 and the eye point EP increases. By moving to. With this configuration, it is possible to reduce the lens movement space necessary for zooming. Further, since the two lens units having positive refractive power are moved and changed in magnification, the refractive power (power) of the first variable magnification lens group GF1 and the second variable magnification lens group GF2 becomes relatively weak, and aberration correction is performed. Is excellent. The first lens group G1 and the fourth lens group G4 are fixed at the time of zooming. At this time, by appropriately selecting the movement amounts of the first variable magnification lens group GF1 and the second variable magnification lens group GF2, the magnification can be changed while keeping the diopter constant.

  The diopter adjustment in the eyepiece optical system EL6 is performed by moving the third lens group G3 alone in the optical axis direction.

  Table 16 below provides values of specifications of the eyepiece optical system EL6.

(Table 16) Sixth Example [Overall specifications]
High magnification end state Medium magnification state Low magnification end state f = 19.262 to 23.203 to 29.256
h = 6.35 to 6.35 to 6.35
TL (air equivalent length) = 67.815 to 67.815 to 67.815

[Lens data]
m r d nd νd
Object ∞ D0
1 -19.6063 9.0000 1.88307 40.57
2 -25.7127 0.3000
3 -56.4713 9.0000 1.73090 54.36
4 -37.6432 D1
5 658.1338 3.5439 1.90200 25.26
6 33.1576 8.2601 1.72362 54.80
7 -57.1690 0.3000
8 39.8517 5.6904 1.72073 54.90
9 -234.4271 D2
10 21.9997 3.5796 1.73163 54.25
11 41.0860 D3
12 29.4163 1.2000 1.89449 29.64
13 13.1263 D4
Image plane ∞

[Lens focal length]
Lens group Start surface Focal length 1st lens group 1 154.011
Second lens group 5 33.278
Third lens group 10 59.976
Fourth lens group 12 -27.454

In the eyepiece optical system EL6, the axial air distance D1 between the first lens group G1 and the second lens group G2, the axial air distance D2 between the second lens group G2 and the third lens group G3, and the third lens group G3. As described above, the axial air distance D3 between the first lens group G4 and the fourth lens group G4, and the axial air distance D4 between the fourth lens group G4 and the eye point EP change during zooming, so The axial air distance D0 from the lens group G1 does not change during zooming. The first lens group G1 and the fourth lens group G4 are fixed during zooming. The following table 17, diopter -1 m ^-1, the high magnification end state in each of -2m ^-1 and 1 m ^-1 (W), each of the intermediate magnification state (M) and low magnification end state (T) The variable interval in the focal length state is shown.

(Table 17)
[Variable interval data]
Diopter -1m ^-1 -2m ^-1
W M T W M T
f 19.262 23.203 29.256 19.858 24.061 30.671
h 6.35 6.35 6.35 6.35 6.35 6.35
D0 8.000 8.000 8.000 8.000 8.000 8.000
D1 5.798 10.252 16.331 5.798 10.252 16.331
D2 5.712 4.650 1.255 6.673 5.658 2.309
D3 7.431 4.039 1.355 6.470 3.030 0.300
D4 17.000 18.000 19.000 17.000 18.000 19.000
TL 67.815 67.815 67.815 67.815 67.814 67.814

Diopter 1m ^-1
W M T
f 18.735 22.452 28.044
h 6.35 6.35 6.35
D0 8.000 8.000 8.000
D1 5.798 10.252 16.331
D2 4.836 3.733 0.299
D3 8.306 4.955 2.311
D4 17.000 18.000 19.000
TL 67.814 67.814 67.815

  Table 18 below shows values corresponding to the conditional expressions in the eyepiece optical system EL6. In the sixth example, the lens closest to the eye point corresponds to the negative meniscus lens L41 (νEP is the Abbe number of the twelfth surface), f1 corresponds to the focal length of the second lens group G2, and f2 The focal length of the third lens group G3 corresponds, ΔD1 corresponds to the amount of movement of the second lens group G2, ΔD2 corresponds to the amount of movement of the third lens group G3, and the most eye of the first variable magnification lens group GF1. The lens component on the point side corresponds to a biconvex positive lens L23 (R1Ef is the curvature radius of the eighth surface and R1Er is the curvature radius of the ninth surface).

(Table 18)
ΔD1 = 10.533
ΔD2 = 6.076
[Values for conditional expressions]
(1) f1 / f2 = 0.555
(2) νEP = 29.64
(3) ΔD1 / ΔD2 = 1.734
(4) fT / fW = 1.519
(5) (R1Ef-R1Er) / (R1Ef + R1Er) =-1.410
(6) NG1 = 1.784
(7) NG2 = 1.732

  Thus, this eyepiece optical system EL6 satisfies the above conditional expressions (1), (2), and (4).

The ocular optical system EL6 has a spherical aberration diagram, an astigmatism diagram, and a distortion in a high magnification end state (W), an intermediate magnification state (M), and a low magnification end state (T) when the diopter is -1m- ¹ . Aberration diagrams and coma aberration diagrams are shown in FIG. From these respective aberration diagrams, it can be seen that in this eyepiece optical system EL6, various aberrations are satisfactorily corrected in all the areas, although the zoom ratio is large.

[Seventh embodiment]
FIG. 13 is a diagram illustrating a configuration of an eyepiece optical system EL7 according to the seventh example. The eyepiece optical system EL7 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, a positive refractive power, and the most eyepoint side. And a third lens group G3 having a concave surface.

  In the eyepiece optical system EL7, the first lens group G1 includes a biconvex positive lens L11. The second lens group G2 includes a negative meniscus negative lens L21 having an aspheric lens surface on the object side and a concave surface facing the object side. The third lens group G3 is composed of a cemented positive lens in which, from the object side, a positive lens L31 having a biconvex lens shape having an aspheric lens surface on the object side and a biconcave negative lens L32 are cemented. ing.

  In the eyepiece optical system EL7, the first lens group G1 is a first variable magnification lens group GF1, and the third lens group G3 is a second variable magnification lens group GF2, which changes from a high magnification end state to a low magnification end state. At the time of doubling, the distance between the object O and the first lens group G1 decreases, the distance between the first lens group G1 and the second lens group G2 increases, and the distance between the second lens group G2 and the third lens group G3 increases. The first variable magnification lens group GF1 is moved to the object side along the optical axis so that the distance between the third lens group G3 and the eye point EP increases, and the second variable magnification lens group GF2 is moved along the optical axis. This is done by moving to the eye point side. Since the lens group having two positive refractive powers is moved to change the magnification, the refractive power (power) of the first variable power lens group GF1 and the second variable power lens group GF2 becomes relatively weak, and is excellent in aberration correction. ing. The second lens group G2 is fixed at the time of zooming. At this time, by appropriately selecting the movement amounts of the first variable magnification lens group GF1 and the second variable magnification lens group GF2, the magnification can be changed while keeping the diopter constant.

  The diopter adjustment in the eyepiece optical system EL7 is performed by moving the whole eyepiece optical system in the optical axis direction.

  Here, by making the lens surface closest to the object side of the second lens group G2 concave, astigmatism and curvature of field can be favorably corrected over the entire zooming region. Further, the coma aberration can be favorably corrected by making the lens surface closest to the eye point of the second lens group G2 convex.

  In addition, it is desirable for correcting astigmatism and field curvature that the lens surface closest to the object side of the second lens group G2 is a concave surface and satisfies the following conditional expression (8).

0.60 <H / (-RG2O) <0.90 (8)
However,
H: Maximum object height of observation object O RG2O: Radius of curvature of lens surface closest to object in second lens group G2

  If the lower limit value of conditional expression (8) is not reached, the negative refractive power (power) with respect to light rays with a high angle of view becomes small, and it is difficult to effectively correct astigmatism and field curvature. In order to further secure the effect of the conditional expression (8), it is desirable to set the lower limit value of the conditional expression (8) to 0.65. If the upper limit of conditional expression (8) is exceeded, the lens surface becomes close to a hemisphere, making processing difficult. In order to further secure the effect of the conditional expression (8), it is more desirable to set the upper limit value of the conditional expression (8) to 0.85, and further to 0.80.

  In the second lens group G2, astigmatism and curvature of field can be favorably corrected by making the concave surface with the most curvature as an aspherical surface. Directing the concave surface, which is an aspherical surface, to the object side is more desirable for correcting astigmatism and field curvature.

  Further, it is possible to improve coma aberration correction by making the convex surface of the third lens group G3 an aspherical surface. Directing the aspherical surface to the object side is more desirable for correcting coma.

  Further, by providing a cemented lens in the third lens group G3, correction of chromatic aberration can be improved.

  Table 19 below provides values of specifications of the eyepiece optical system EL7.

(Table 19) Seventh Example [Overall specifications]
High magnification end state Medium magnification state Low magnification end state f = 19.370 to 22.729 to 28.432
h = 6.34 to 6.34 to 6.34
TL (air equivalent length) = 28.112 to 34.058 to 37.841

[Lens data]
m r d nd νd
Object ∞ D0
1 105.1350 3.7973 1.72916 54.61
2 -18.0276 D1
3 * -8.7512 4.6248 1.92286 20.88
4 -14.2746 D2
5 * 22.8977 4.7283 1.88300 40.66
6 -19.5745 0.7000 1.80518 25.45
7 85.0633 D3
Image plane ∞

[Lens focal length]
Lens group Start surface Focal length 1st lens group 1 21.383
Second lens group 5 -40.972
Third lens group 10 29.622

  In the eyepiece optical system ZL7, the third surface and the fifth surface are formed in an aspheric shape. Table 20 below shows the aspheric data, that is, the values of the conic constant K and the aspheric constants A4 to A8. In Table 20, m represents a surface number.

(Table 20)
[Aspherical data]
m K A4 A6 A8
3 0.64380 -8.25302E-06 1.07951E-06 -5.76676E-09
5 -0.54230 2.26208E-06 -2.69432E-07 1.46998E-09

In this eyepiece optical system EL7, the axial air gap D0 between the object O and the first lens group G1, the axial air gap D1 between the first lens group G1 and the second lens group G2, the second lens group G2 and the third lens group G1. As described above, the axial air gap D2 between the lens group G3 and the axial air gap D3 between the third lens group G3 and the eye point EP changes during zooming. The second lens group G2 is fixed during zooming. Table 21 below shows the variable intervals in each of the focal length states in the high magnification end state (W), the intermediate magnification state (M), and the low magnification end state (T) when the diopter is ⁻¹ m ⁻¹ .

(Table 21)
[Variable interval data]
Diopter -1m ^-1
W M T
f 19.370 22.729 28.432
h 6.34 6.34 6.34
D0 11.762 7.961 3.000
D1 2.200 6.001 10.962
D2 0.300 6.246 10.029
D3 17.000 20.000 25.000
TL 28.112 34.058 37.841

  Table 22 below shows values corresponding to the conditional expressions in the eyepiece optical system EL7. Here, H represents the maximum object height of the observation object O, and RG2O represents the radius of curvature of the lens surface closest to the object of the second lens group G2. In the seventh embodiment, the most eye point side lens corresponds to the biconcave negative lens L32 (νEP is the Abbe number of the sixth surface), f1 corresponds to the focal length of the first lens group G1, and f2 Is equivalent to the focal length of the third lens group G3, ΔD1 is equivalent to the moving amount of the first lens group G1, ΔD2 is equivalent to the moving amount of the third lens group G3, and is the most of the first variable magnification lens group GF1. The lens component on the eye point side corresponds to a biconvex positive lens L11 (R1Ef is the curvature radius of the first surface and R1Er is the curvature radius of the second surface). The most object side lens surface of the second lens group G2 is the third surface.

(Table 22)
ΔD1 = -8.762
ΔD2 = 9.729
[Values for conditional expressions]
(1) f1 / f2 = 0.722
(2) νEP = 25.45
(3) ΔD1 / ΔD2 = −0.901
(4) fT / fW = 1.468
(5) (R1Ef−R1Er) / (R1Ef + R1Er) = 1.414
(6) NG1 = 1.729
(7) NG2 = 1.844
(8) H / (-RG2O) = 0.724

  Thus, this eyepiece optical system EL7 satisfies the conditional expressions (1), (2), (4), (5), (7), and (8).

The ocular optical system EL7 has a spherical aberration diagram, an astigmatism diagram, and a distortion in a high magnification end state (W), an intermediate magnification state (M), and a low magnification end state (T) when the diopter is −1m ⁻¹ . An aberration diagram and a coma aberration diagram are shown in FIG. From these respective aberration diagrams, it can be seen that in the eyepiece optical system EL7, various aberrations are well corrected in all the areas, although the zoom ratio is large.

EL (EL1 to EL7) Eyepiece optical system GF1 First variable lens group GF2 Second variable lens group 1 Camera (optical device)

Claims (15)

Including a lens group having two positive refractive powers;
When changing from the high magnification end state to the low magnification end state, the distance between each of the two lens groups having positive refractive power and the adjacent lens group is changed,
The lens surface closest to the eye point of the lens group closest to the eye point is a concave surface facing the eye point.
An eyepiece optical system characterized by satisfying the following condition:
0.45 <f1 / f2 <0.90
However,
f1: Focal length of the object-side lens group among the two lens groups having positive refractive power f2: Of the two lens groups having positive refractive power, the focal length of the lens group on the eyepoint side The lens component means a single lens or a cemented lens.   2. The eyepiece optical system according to claim 1, wherein the two lens groups having positive refractive power move in the optical axis direction when zooming from a high magnification end state to a low magnification end state.   The lens group having the two positive refractive powers moves so as to keep the diopter constant when zooming from the high magnification end state to the low magnification end state. The eyepiece optical system described. The eyepiece optical system according to claim 1, wherein the condition of the following formula is satisfied.
νEP <63.00
However,
νEP: Abbe number for the d-line of the lens medium closest to the eye point The eyepiece optical system according to any one of claims 1 to 4, wherein a condition of the following formula is satisfied.
0.00 <ΔD1 / ΔD2
However,
ΔD1: A movement amount of the lens group on the object side among the two lens groups having positive refractive power when zooming from the high magnification end state to the low magnification end state ΔD2: The two positive refractive powers The amount of movement of the lens group on the eye point side when zooming from the high magnification end state to the low magnification end state is the normal movement from the object side to the eye point side. And The eyepiece optical system according to claim 1, wherein the condition of the following formula is satisfied.
1.26 <fT / fW
However,
fT: focal length of the entire system in the low magnification end state fW: focal length of the entire system in the high magnification end state The eyepiece optical system according to claim 1, wherein a condition of the following formula is satisfied.
-1.45 <(R1Ef-R1Er) / (R1Ef + R1Er) <4.40
However,
R1Ef: radius of curvature of the lens surface closest to the object side of the lens component closest to the appointment side of the lens group having the positive refractive power among the two lens groups having positive refractive power R1Er: having the two positive refractive powers The radius of curvature of the lens surface closest to the eye point of the lens component closest to the appointment side of the lens group on the object side of the lens group   The eyepiece optical system according to claim 1, wherein a lens surface closest to the object side of the lens group closest to the object side is a concave surface facing the object side. The eyepiece optical system according to claim 1, wherein a condition of the following formula is satisfied.
1.70 <NG1 <1.92
However,
NG1: Average refractive index of a lens medium included in the object-side lens group among the two lens groups having positive refractive power The eyepiece optical system according to claim 1, wherein the condition of the following formula is satisfied.
1.70 <NG2 <1.95
However,
NG1: Average refractive index of a lens medium included in the lens group on the eye point side among the two lens groups having positive refractive power   The eyepiece optical system according to any one of claims 1 to 10, wherein at least one of the two lens groups having positive refractive power includes a cemented lens.   2. The lens component closest to the eye point in the lens group on the eye point side of the two lens groups having positive refractive power is a meniscus shape having a concave surface facing the eye point side. The eyepiece optical system according to any one of ˜11.   The eyepiece optical system according to claim 1, further comprising an image reversal member.   An optical apparatus comprising the eyepiece optical system according to claim 1. A method of manufacturing an eyepiece optical system including a lens group having at least two positive refractive powers,
When changing the magnification from the high magnification end state to the low magnification end state, the distance between each of the two lens groups having positive refractive power and the adjacent lens group is changed,
The lens surface on the most eyepoint side of the lens group on the most eyepoint side is arranged so as to be a concave surface facing the eyepoint side,
A method of manufacturing an eyepiece optical system, wherein the eyepiece optical system is arranged so as to satisfy the condition of the following formula.
0.45 <f1 / f2 <0.90
However,
f1: Focal length of the object-side lens group among the two lens groups having positive refractive power f2: Of the two lens groups having positive refractive power, the focal length of the lens group on the eyepoint side The lens component means a single lens or a cemented lens.