JP2015075593A - Eyepiece lens and optical equipment including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an eyepiece lens that has a high observation magnification and is adjustable for a diopter.SOLUTION: An eyepiece lens EL for the observation of an image formed by an objective lens via an erecting optical system is provided. The eyepiece lens comprises, successively arranged from an object side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a negative refractive power. The first lens group G1 comprises a single negative meniscus lens L1; the third lens group G3 comprises a single biconcave lens L3; and the eyepiece lens satisfies the following conditional expressions (1) to (3). They are (1):1.35<f1/f3<2.50, (2):1.50<|(R12+R11)/(R12-R11)|<10.00, and (3):0.30<|(R32+R31)/(R32-R31)|<0.90.

Description

  The present invention relates to an eyepiece used in a single-lens reflex camera or the like.

  In recent years, eyepiece lenses capable of adjusting diopter have been proposed (see, for example, Patent Document 1).

JP 2000-171731 A

  However, with conventional eyepieces, the observation magnification is not sufficient.

  The present invention has been made in view of such a problem, and an object thereof is to provide an eyepiece having a high observation magnification and capable of adjusting diopter, and an optical apparatus including the eyepiece.

  In order to achieve such an object, an eyepiece according to the present invention is an eyepiece for observing an image formed by an objective lens through an erecting optical system, and is arranged in order from the object side. A first lens group having a refractive power, a second lens group having a positive refractive power, and a third lens group having a negative refractive power, and the first lens group is a single negative meniscus lens. The third lens unit is composed of one biconcave lens, and satisfies the following conditional expression.

1.35 <f1 / f3 <2.50
1.50 <| (R12 + R11) / (R12-R11) | <10.00
0.30 <| (R32 + R31) / (R32-R31) | <0.90
However,
f1: the focal length of the first lens group,
f3: focal length of the third lens group,
R11: radius of curvature of the object side surface of the negative meniscus lens,
R12: radius of curvature of the side surface of the eye point of the negative meniscus lens,
R31: radius of curvature of the object side surface of the biconcave lens,
R32: radius of curvature of the side surface of the eye point of the biconcave lens.

  In the eyepiece according to the present invention, it is preferable that the following conditional expression is satisfied.

0.30 <(− f3) / f <0.70
However,
f: Focal length of the entire system when the diopter is −1.0 [1 / m].

  In the eyepiece according to the present invention, it is preferable that the following conditional expression is satisfied.

0.20 <f2 / f <0.40
However,
f2: focal length of the second lens group,
f: Focal length of the entire system when the diopter is −1.0 [1 / m].

  In the eyepiece according to the present invention, it is preferable that the following conditional expression is satisfied.

0.80 <(− f1) / f <2.00
However,
f: Focal length of the entire system when the diopter is −1.0 [1 / m].

  In the eyepiece according to the present invention, it is preferable to adjust the diopter by moving the second lens group along the optical axis.

  An optical apparatus according to the present invention includes an objective lens that forms an image of an object on a predetermined surface, and an eyepiece lens for observing the image formed by the objective lens through an erecting optical system. And the eyepiece is any one of the eyepieces described above.

  According to the present invention, it is possible to provide an eyepiece having a high observation magnification and capable of adjusting diopter, and an optical apparatus including the eyepiece.

It is a block diagram of the eyepiece which concerns on 1st Example. FIG. 4 is a diagram illustrating various aberrations (spherical aberration, astigmatism, coma aberration, distortion, and lateral chromatic aberration) of the eyepiece according to the first example, and (a) illustrates various aberrations when the diopter is −1.0 [m ⁻¹ ]. Aberration diagram, (b) shows various aberration diagrams when the diopter is -1.7 [m ^-1 ], and (c) shows various aberration diagrams when the diopter is +0.5 [m ^-1 ]. It is a block diagram of the eyepiece which concerns on 2nd Example. FIG. 6 is various aberration diagrams (spherical aberration, astigmatism, coma aberration, distortion aberration, and chromatic aberration of magnification) of the eyepiece according to the second example, and (a) shows various aberrations when the diopter is −1.0 [m ⁻¹ ]. Aberration diagram, (b) shows various aberration diagrams when the diopter is -1.7 [m ^-1 ], and (c) shows various aberration diagrams when the diopter is +0.5 [m ^-1 ]. It is a block diagram of the eyepiece which concerns on 3rd Example. FIG. 6 is various aberration diagrams (spherical aberration, astigmatism, coma aberration, distortion aberration, and chromatic aberration of magnification) of the eyepiece according to the third example, and (a) shows various aberrations when the diopter is −1.0 [m ⁻¹ ]. Aberration diagram, (b) shows various aberration diagrams when the diopter is -1.7 [m ^-1 ], and (c) shows various aberration diagrams when the diopter is +0.5 [m ^-1 ]. It is a block diagram of the eyepiece which concerns on 4th Example. FIG. 10 is a diagram illustrating various aberrations (spherical aberration, astigmatism, coma aberration, distortion, and lateral chromatic aberration) of the eyepiece according to the fourth example, and (a) illustrates various aberrations when the diopter is −1.0 [m ⁻¹ ]. Aberration diagram, (b) shows various aberration diagrams when the diopter is -1.7 [m ^-1 ], and (c) shows various aberration diagrams when the diopter is +0.5 [m ^-1 ]. It is a schematic block diagram of a single-lens reflex camera.

  Hereinafter, the present embodiment will be described with reference to the drawings. The eyepiece lens EL according to the present embodiment is an eyepiece lens for observing an image formed by the objective lens OL through the erecting optical system P as described later (see FIG. 9), and is shown in FIG. As described above, the first lens group G1 having negative refractive power, the second lens group G2 having positive refractive power, and the third lens group G3 having negative refractive power, which are arranged in order from the object side, The first lens group G1 includes a single negative meniscus lens L1, and the third lens group G3 includes a single biconcave lens L3.

  With this configuration, it is possible to obtain an eyepiece having good optical performance while ensuring a desired observation magnification.

  Based on the above configuration, the eyepiece EL according to the present embodiment satisfies the following conditional expressions (1) to (3).

1.35 <f1 / f3 <2.50 (1)
1.50 <| (R12 + R11) / (R12-R11) | <10.00 (2)
0.30 <| (R32 + R31) / (R32-R31) | <0.90 (3)
However,
f1: Focal length of the first lens group G1
f3: focal length of the third lens group G3,
R11: radius of curvature of the object side surface of the negative meniscus lens L1,
R12: radius of curvature of the side surface of the eye point of the negative meniscus lens L1,
R31: radius of curvature of object side surface of biconcave lens L3,
R32: radius of curvature of the side surface of the eye point of the biconcave lens L3.

  Conditional expression (1) defines the ratio between the refractive power of the first lens group G1 and the refractive power of the third lens group G3. If the lower limit value of conditional expression (1) is not reached, the refractive power of the first lens group G1 becomes large, and it becomes difficult to correct spherical aberration and coma aberration while securing a desired observation magnification, which is not preferable. If the upper limit of conditional expression (1) is exceeded, the refractive power of the third lens group G3 will increase, and it will be easy to increase the magnification, but it will be difficult to correct spherical aberration and curvature of field, which is not preferable.

  In order to ensure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (1) to 1.60. In order to ensure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (1) to 2.00. Thereby, the refractive power of the first lens group G1 and the refractive power of the third lens group G3 can be set more appropriately.

  Conditional expression (2) defines the lens shape of the negative meniscus lens L1 in the first lens group G1. If the lower limit value of conditional expression (2) is not reached, the meridional image plane becomes excessively negative, which is not preferable because good image plane correction cannot be performed. If the upper limit of conditional expression (2) is exceeded, the meridional image plane becomes excessive on the plus side, which is not preferable because good image plane correction cannot be performed.

  In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (2) to 1.70. In order to ensure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (2) to 6.00. Thereby, the lens shape of the negative meniscus lens L1 can be set more appropriately.

  Conditional expression (3) defines the lens shape of the biconcave lens L3 in the third lens group G3. If the lower limit value of conditional expression (3) is not reached, the radius of curvature of the side surface of the eye point becomes tight, and external light is reflected and easily enters the eyes of the observer. If the upper limit of conditional expression (3) is not reached, the radius of curvature of the object side surface becomes tight, and it becomes difficult to correct spherical aberration and coma aberration within the diopter adjustment range, which is not preferable.

  In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (3) to 0.40. In order to ensure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (3) to 0.80. Thereby, the lens shape of the biconcave lens L3 can be set more appropriately.

  In the eyepiece lens EL according to this embodiment, it is preferable that the following conditional expression (4) is satisfied.

0.30 <(− f3) / f <0.70 (4)
However,
f: Focal length of the entire system when the diopter is −1.0 [1 / m].

  Conditional expression (4) defines the refractive power of the third lens group G3. If the lower limit value of conditional expression (4) is not reached, the refractive power of the third lens group G3 becomes large, and it is easy to increase the magnification, but it becomes difficult to correct spherical aberration and curvature of field, which is not preferable. Exceeding the upper limit of conditional expression (4) is not preferable because the refractive power of the third lens group G3 becomes small and it is difficult to ensure sufficient eye relief.

  In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (4) to 0.40. In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (4) to 0.55. Thereby, the refractive power of the third lens group G3 can be set appropriately.

  In the eyepiece lens EL according to this embodiment, it is preferable that the following conditional expression (5) is satisfied.

0.20 <f2 / f <0.40 (5)
However,
f2: focal length of the second lens group G2,
f: Focal length of the entire system when the diopter is −1.0 [1 / m].

  Conditional expression (5) defines the refractive power of the second lens group G2. If the lower limit of conditional expression (5) is not reached, the refractive power of the second lens group G2 becomes too large, and it becomes difficult to correct spherical aberration and coma aberration, which is not preferable. If the upper limit of conditional expression (5) is exceeded, aberration fluctuations due to movement of the second lens group G2 can be suppressed, but the required movement amount of the second lens group G2 accompanying diopter adjustment becomes large, which is not preferable.

  In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (5) to 0.25. In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (5) to 0.37. Thereby, the refractive power of the second lens group G2 can be set more appropriately.

  In the eyepiece lens EL according to this embodiment, it is preferable that the following conditional expression (6) is satisfied.

0.80 <(− f1) / f <2.00 (6)
However,
f: Focal length of the entire system when the diopter is −1.0 [1 / m].

  Conditional expression (6) defines the refractive power of the first lens group G1. If the lower limit value of conditional expression (6) is not reached, the refractive power of the first lens group G1 becomes large, and it becomes difficult to correct spherical aberration and coma aberration while securing a desired observation magnification. Exceeding the upper limit of conditional expression (6) is not preferable because the refractive power of the first lens group G1 becomes small and it becomes difficult to correct lateral chromatic aberration.

  In order to secure the effect of the present embodiment, it is preferable to set the lower limit of conditional expression (6) to 0.81. In order to secure the effect of the present embodiment, it is preferable to set the upper limit of conditional expression (6) to 1.50. Thereby, the refractive power of the first lens group G1 can be set appropriately.

  In the eyepiece EL according to the present embodiment, it is preferable to adjust the diopter by moving the second lens group G2 along the optical axis.

  With this configuration, an eyepiece with good optical performance can be obtained within a desired diopter adjustment range.

  According to the zoom lens EL according to the present embodiment having the above-described configuration, it is possible to provide an eyepiece having a high observation magnification and adjustable diopter, and an optical apparatus including the eyepiece.

  Next, the configuration of the single-lens reflex camera CAM shown in FIG. 9 will be described as an optical apparatus having the eyepiece lens EL according to the present embodiment. The single-lens reflex camera CAM includes an objective lens OL, a mirror M, an imaging device CCD for photographing, and a finder optical system VF.

  The viewfinder optical system VF includes a focusing screen F, a condenser lens C, a pentaprism P as an erecting optical system, and the eyepiece EL described above, which are arranged along the optical axis in order from the object side. The image formed on the focusing screen F by the objective lens OL can be observed by the eyepiece lens EL. It should be noted that an eye point E.E. P is provided.

  The objective lens OL forms a subject image on the image sensor CCD or the focusing screen F. The mirror M is inserted at an angle of 45 degrees with respect to the optical axis passing through the objective lens OL, and in a normal state (in a shooting standby state), light from a subject (not shown) passing through the objective lens OL is received. The light is reflected and imaged on the focusing screen F. When the shutter is released, the mirror is raised and jumps up, and light from a subject (not shown) passing through the objective lens OL forms an image on the image sensor CCD. ing. That is, the image sensor CCD and the focusing screen F are disposed at optically conjugate positions.

  The pentaprism P inverts the subject image (inverted image) on the focusing screen F formed by the objective lens OL into an upright image by inverting the image vertically. The pentaprism P allows the observer to observe the subject image as an erect image, and allows the finder optical system VF to be configured in a compact manner. A condenser lens C is provided between the focusing screen F and the pentaprism P, and the subject image on the focusing screen F is guided to the pentaprism P. The condenser lens C has a positive refractive power that suppresses the divergence of the light beam, and the spread of the light beam increases as the distance from the exit pupil of the objective lens OL increases. Therefore, the upright optical system and the eyepiece optical system increase in size. In order to prevent this, it is disposed near the imaging position of the subject image formed by the objective lens OL (for example, between the focusing screen F and the pentaprism P as in the present embodiment).

  In the single-lens reflex camera CAM having such a configuration, light from a subject (not shown) passes through the objective lens OL, is reflected by the mirror M toward the focusing screen F, and a subject image is formed on the focusing screen F. The In the finder optical system VF, the light beam from the subject image on the focusing screen F passes through the condenser lens C, the pentaprism P, and the eyepiece EL described above, and the eye point E.E. Eye point E. At P, the observer can observe a real image of a subject (not shown). At the time of shutter release, light from a subject (not shown) that has passed through the objective lens OL is imaged on the image sensor CCD because the mirror M is in a mirror-up state.

  According to the single-lens reflex camera CAM provided with such an eyepiece lens EL, a high observation magnification can be ensured while having a diopter-adjustable configuration.

  Hereinafter, each example according to the present embodiment will be described with reference to the drawings. Tables 1 to 4 are shown below, but these are tables of specifications in the first to fourth examples.

  In addition, each reference code with respect to FIG. 1 according to the first embodiment is used independently for each embodiment in order to avoid complication of explanation due to an increase in the number of digits of the reference code. Therefore, even if the same reference numerals as those in the drawings according to the other embodiments are given, they are not necessarily in the same configuration as the other embodiments.

  In each embodiment, d-line (wavelength 587.5620 nm) and g-line (wavelength 435.8350 nm) are selected as the calculation targets of the aberration characteristics.

  In [Overall specifications] in the table, Y indicates the object height, and TL indicates the total lens length.

  In [Lens Specifications] in the table, the surface number is the focal plane I formed on the focusing screen F, and the order of the optical surfaces from the object side along the light traveling direction is defined as R. A radius of curvature, D is a surface interval that is a distance on the optical axis from each optical surface to the next optical surface (or image surface), nd is a refractive index with respect to the d-line (wavelength 587.56 nm) of the lens material, νd is the Abbe number based on the d-line (wavelength 587.56 nm) of the lens material, “∞” in the column of curvature radius R is the plane, P indicates an eye point. When the lens surface is an aspherical surface, the surface number is marked with *, and the column of curvature radius R indicates the paraxial curvature radius.

[Aspherical data] in the table shows the shape of the aspherical surface shown in [Lens Specification] by the following equation (a). X (y) is the distance along the optical axis direction from the tangential plane at the apex of the aspheric surface to the position on the aspheric surface at height y, R is the radius of curvature of the reference sphere (paraxial radius of curvature), and κ is Ai represents the i-th aspherical coefficient. “E-n” indicates “× 10 ⁻ⁿ ”. For example, 1.234E-05 = 1.234 × 10 ⁻⁵ .

X (y) = y ² / [R × {1+ (1−κ × y ² / R ² ) ^1/2 }] + A4 × y ⁴ + A6 × y ⁶ (a)

  In [Variable surface interval data] in the table, f indicates the focal length of the eyepiece lens, and Di (where i is an integer) indicates the variable surface interval of the i-th surface.

  In [Lens Group Data] in the table, G represents the group number, the first group surface represents the surface number closest to the object in each group, and the group focal length represents the focal length of each group.

  In [Conditional Expression] in the table, values corresponding to the conditional expressions (1) to (6) are shown.

  Hereinafter, in all the specification values, “mm” is generally used for the focal length f, curvature radius R, surface distance D, and other lengths, etc. unless otherwise specified, but the optical system is proportionally enlarged. Alternatively, the same optical performance can be obtained even by proportional reduction, and the present invention is not limited to this. The unit is not limited to “mm”, and other suitable units can be used.

The unit of diopter is “m ⁻¹ ”. Diopter X “m ⁻¹ ” indicates a state in which an image by an eyepiece lens can be located at a position of 1 / X [m (meter)] on the optical axis from the eye point (however, the sign is the image from the eye point) Negative if it is on the object side).

  The description of the table so far is common to all the embodiments, and the description below is omitted.

(First embodiment)
A first embodiment will be described with reference to FIGS. 1 and 2 and Table 1. FIG. In FIG. 1, illustration of the condenser lens C and the pentaprism P is omitted, and for the focusing screen F, only the focal plane I formed on the focusing screen F is shown.

  As shown in FIG. 1, the eyepiece lens EL (EL1) according to the first example includes a first lens group G1 having negative refractive power and a second lens having positive refractive power, which are arranged in order from the object side. It consists of a group G2 and a third lens group G3 having negative refractive power, and is configured to adjust diopter by moving the second lens group G2 along the optical axis.

  The first lens group G1 includes a negative meniscus lens L1 having a convex surface directed toward the object side. The second lens group G2 is composed of a biconvex lens L2. The third lens group G3 is composed of a biconcave lens L3.

  The eye point side surface of the negative meniscus lens L1, the both side surfaces of the biconvex lens L2, and the both side surfaces of the biconcave lens L3 are each formed of an aspherical surface.

  In the present embodiment, as described above, in the vicinity of the focal plane I along the optical axis in order from the real image plane of the objective lens (not shown), that is, the focal plane I side, between the focal plane I and the first lens group G1. A condenser lens C and a pentaprism P are arranged. Therefore, in the eyepiece lens EL1 according to the first example, an image on the focal plane I (formed by an objective lens (not shown)) is converted into an erect image through the condenser lens C and the pentaprism P in this order. The eyepiece E1 is enlarged by the eyepiece lens EL1 composed of the first lens group G1 to the third lens group G3. It can be observed at P.

  Table 1 below shows the values of each item in the first example. Surface numbers 1 to 7 in Table 1 correspond to the optical surfaces m1 to m7 shown in FIG.

  In this embodiment, the diopter is set to -1.7 to +0.5 [1 / m], and the eye point E.E. The pupil diameter of P is φ10 mm, and the eye point E.E. The lens design is performed with the position of P (that is, the distance from the eyepiece lens EL1 along the optical axis) being 15.7 to 21.0 mm and the number of fields of view being 26.4.

(Table 1)
[Overall specifications]
Y 21.30
TL 13.23

[Lens specifications]
Surface number R D nd νd
1 ∞ 76.964 1.00000
2 47.792 2.000 1.58276 30.34
* 3 18.092 D3 (variable) 1.00000
* 4 14.024 7.300 1.52444 56.21
* 5 -27.877 D5 (variable) 1.00000
* 6 -58.560 2.500 1.49108 57.10
* 7 20.000 D7 (variable) 1.00000
EP

[Aspherical data]
3rd surface κ = -0.4305, A4 = -3.85363E-06, A6 = 1.92535E-08
4th surface κ = -0.2257, A4 = -7.48438E-07, A6 = -1.06606E-08
5th surface κ = -7.1789, A4 = -8.01318E-06, A6 = 1.05971E-08
6th surface κ = -70.0000, A4 = 2.56100E-05, A6 = 0.00000E + 00
7th surface κ = 3.0123, A4 = 1.40408E-05, A6 = -3.79525E-08

[Variable surface interval data]
f 62.200 61.178 70.726
Diopter -1.027 -1.680 0.503
D3 1.30 0.50 5.20
D5 8.20 9.00 4.30
D7 18.00 15.70 21.00

[Lens group data]
Group number Group first surface Group focal length G1 2 -51.230
G2 4 18.926
G3 6 -30.043

[Conditional expression]
Conditional expression (1) f1 / f3 = 1.71
Conditional expression (2) | (R12 + R11) / (R12-R11) | = 2.22
Conditional expression (3) | (R32 + R31) / (R32-R31) | = 0.49
Conditional expression (4) (−f3) /f=0.48
Conditional expression (5) f2 / f = 0.30
Conditional expression (6) (−f1) /f=0.82

  From the table of specifications shown in Table 1, it can be seen that the eyepiece EL1 according to the first example satisfies the conditional expressions (1) to (6).

FIG. 2 is a diagram showing various aberrations (spherical aberration, astigmatism, coma aberration, distortion aberration, and lateral chromatic aberration) of the eyepiece EL1 according to the first example, and (a) is a diopter −1.0 [m ^{−. 1} ] shows various aberration diagrams, (b) shows various aberration diagrams at a diopter of −1.7 [m ⁻¹ ], and (c) shows various aberration diagrams at a diopter +0.5 [m ⁻¹ ]. .

In each aberration diagram, Y1 is an eye point E.E. The ray height at P and Y0 the object height on the focal plane F. In the astigmatism diagram, the solid line indicates the sagittal image plane and the broken line indicates the meridional image plane. The coma aberration diagram is displayed in degrees / seconds, and the distortion diagram is displayed in percentage. In the spherical aberration diagram and the astigmatism diagram, the unit of the horizontal axis is [m ⁻¹ ], and is indicated by “D” in the drawing. Further, d represents an aberration curve for the d line, and g represents an aberration curve for the G line. The description of the aberration diagrams is the same in the other examples.

  As is apparent from the respective aberration diagrams, the eyepiece lens EL1 according to the first example is well corrected for various aberrations within the diopter adjustment range, and has excellent optical performance.

  As a result, according to the eyepiece lens EL1 according to the first example, an eyepiece lens with high observation magnification and adjustable diopter can be obtained. Moreover, according to the single-lens reflex camera CAM provided with such an eyepiece lens EL1, a high observation magnification can be ensured even though the diopter can be adjusted.

(Second embodiment)
The second embodiment will be described with reference to FIGS. 3 and 4 and Table 2. FIG. In FIG. 3, illustration of the condenser lens C and the pentaprism P is omitted, and for the focusing screen F, only the focal plane I formed on the focusing screen F is shown.

  As shown in FIG. 3, the eyepiece EL (EL2) according to the second example includes a first lens group G1 having negative refractive power and a second lens having positive refractive power, which are arranged in order from the object side. It consists of a group G2 and a third lens group G3 having negative refractive power, and is configured to adjust the diopter by moving the second lens group G2 along the optical axis.

  The first lens group G1 includes a negative meniscus lens L1 having a convex surface directed toward the object side. The second lens group G2 is composed of a biconvex lens L2. The third lens group G3 is composed of a biconcave lens L3.

  The eye point side surface of the negative meniscus lens L1, the both side surfaces of the biconvex lens L2, and the both side surfaces of the biconcave lens L3 are each formed of an aspherical surface.

  In the present embodiment, as described above, in the vicinity of the focal plane I along the optical axis in order from the real image plane of the objective lens (not shown), that is, the focal plane I side, between the focal plane I and the first lens group G1. A condenser lens C and a pentaprism P are arranged. Therefore, in the eyepiece EL2 according to the second example, after the image on the focal plane I (formed by an objective lens (not shown)) is an erect image through the condenser lens C and the pentaprism P in order, The eyepiece E1 is enlarged by the eyepiece lens EL1 composed of the first lens group G1 to the third lens group G3. It can be observed at P.

  Table 2 below shows the values of each item in the second embodiment. Surface numbers 1 to 7 in Table 2 correspond to the optical surfaces m1 to m7 shown in FIG.

  In this embodiment, the diopter is set to -1.7 to +0.5 [1 / m], and the eye point E.E. The pupil diameter of P is φ10 mm, and the eye point E.E. The lens design is performed by setting the position of P (that is, the distance from the eyepiece lens EL2 along the optical axis) to 15.7 to 21.0 mm and the number of fields of view to 26.0.

(Table 2)
[Overall specifications]
Y 21.4
TL 13.02

[Lens specifications]
Surface number R D nd νd
1 ∞ 76.964 1.00000
2 50.182 2.000 1.58276 30.34
* 3 18.500 D3 (variable) 1.00000
* 4 14.200 7.300 1.52444 56.21
* 5 -27.681 D5 (variable) 1.00000
* 6 -60.457 2.500 1.49108 57.10
* 7 20.000 D7 (variable) 1.00000
EP

[Aspherical data]
3rd surface κ = -0.2957, A4 = -6.42005E-06, A6 = 1.84727E-08
4th surface κ = -0.1293, A4 = -3.74246E-06, A6 = -1.06606E-08
5th surface κ = -7.3292, A4 = -8.01318E-06, A6 = 1.05971E-08
6th surface κ = -70.0000, A4 = 2.56100E-05, A6 = 0.00000E + 00
7th surface κ = -3.7483, A4 = 1.11103E-04, A6 = 7.93451E-08

[Variable surface interval data]
f 62.300 61.297 70.047
Diopter -1.028 -1.679 0.503
D3 1.30 0.50 5.00
D5 8.30 9.10 4.60
D7 18.00 16.00 20.00

[Lens group data]
Group number Group first surface Group focal length G1 2 -51.479
G2 4 19.038
G3 6 -30.293

[Conditional expression]
Conditional expression (1) f1 / f3 = 1.70
Conditional expression (2) | (R12 + R11) / (R12-R11) | = 2.17
Conditional expression (3) | (R32 + R31) / (R32-R31) | = 0.50
Conditional expression (4) (−f3) /f=0.49
Conditional expression (5) f2 / f = 0.31
Conditional expression (6) (−f1) /f=0.83

  From the table of specifications shown in Table 2, it can be seen that the eyepiece lens EL2 according to the second example satisfies the conditional expressions (1) to (6).

FIG. 4 is a diagram illustrating various aberrations (spherical aberration, astigmatism, coma aberration, distortion aberration, and chromatic aberration of magnification) of the eyepiece lens EL <b> 2 according to the second example, and (a) is a diopter −1.0 [m ^{−. 1} ] shows various aberration diagrams, (b) shows various aberration diagrams at a diopter of −1.7 [m ⁻¹ ], and (c) shows various aberration diagrams at a diopter +0.5 [m ⁻¹ ]. . As is apparent from the respective aberration diagrams, the eyepiece lens EL2 according to the second example has various aberrations corrected well within the diopter adjustment range, and excellent optical performance is ensured.

  As a result, according to the eyepiece lens EL2 according to the second embodiment, an eyepiece lens with high observation magnification and adjustable diopter can be obtained. In addition, according to the single-lens reflex camera CAM provided with such an eyepiece lens EL2, a high observation magnification can be secured even though the diopter can be adjusted.

(Third embodiment)
A third embodiment will be described with reference to FIGS. 5 and 6 and Table 3. FIG. In FIG. 5, illustration of the condenser lens C and the pentaprism P is omitted, and for the focusing screen F, only the focal plane I formed on the focusing screen F is shown.

  As shown in FIG. 5, the eyepiece lens EL (EL3) according to the third example includes a first lens group G1 having negative refractive power and a second lens having positive refractive power, which are arranged in order from the object side. It consists of a group G2 and a third lens group G3 having negative refractive power, and is configured to adjust the diopter by moving the second lens group G2 along the optical axis.

  The first lens group G1 includes a negative meniscus lens L1 having a convex surface directed toward the object side. The second lens group G2 is composed of a biconvex lens L2. The third lens group G3 is composed of a biconcave lens L3.

  The eye point side surface of the negative meniscus lens L1, both side surfaces of the biconvex lens L2, and the object side surface of the biconcave lens L3 are each formed of an aspherical surface.

  In the present embodiment, as described above, in the vicinity of the focal plane I along the optical axis in order from the real image plane of the objective lens (not shown), that is, the focal plane I side, between the focal plane I and the first lens group G1. A condenser lens C and a pentaprism P are arranged. Therefore, in the eyepiece EL3 according to the third example, an image on the focal plane I (formed by an objective lens (not shown)) is converted into an erect image through the condenser lens C and the pentaprism P in this order, The eyepiece E1 is enlarged by the eyepiece lens EL1 composed of the first lens group G1 to the third lens group G3. It can be observed at P.

  Table 3 below shows values of various specifications in the third example. Surface numbers 1 to 7 in Table 3 correspond to the optical surfaces m1 to m7 shown in FIG.

  In this embodiment, the diopter is set to -1.7 to +0.5 [1 / m], and the eye point E.E. The pupil diameter of P is φ10 mm, and the eye point E.E. The lens design is performed by setting the position of P (that is, the distance from the eyepiece lens EL3 along the optical axis) to 15.7 to 21.0 mm and the number of fields of view to 26.0.

(Table 3)
[Overall specifications]
Y 21.46
TL 13.02

[Lens specifications]
Surface number R D nd νd
1 ∞ 76.764 1.00000
2 28.366 2.400 1.63550 23.89
* 3 16.159 D3 (variable) 1.00000
* 4 14.741 6.600 1.52444 56.21
* 5 -35.791 D5 (variable) 1.00000
* 6 -115.486 2.500 1.49108 57.10
7 20.000 D7 (variable) 1.00000
EP

[Aspherical data]
3rd surface κ = -0.2678, A4 = -8.41135E-07, A6 = 6.57225E-08
4th surface κ = -0.2484, A4 = -7.30745E-06, A6 = 1.24645E-07
5th surface κ = -2.8827, A4 = 1.19825E-05, A6 = 1.38819E-08
6th surface κ = -10.0000, A4 = 2.64218E-05, A6 = -1.92590E-07

[Variable surface interval data]
f 62.224 60.968 72.934
Diopter -1.033 -1.686 0.489
D3 1.45 0.50 6.40
D5 8.51 9.46 3.56
D7 18.00 15.00 23.00

[Lens group data]
Group number Group first surface Group focal length G1 2 -63.972
G2 4 20.846
G3 6 -34.505

[Conditional expression]
Conditional expression (1) f1 / f3 = 1.85
Conditional expression (2) | (R12 + R11) / (R12-R11) | = 3.65
Conditional expression (3) | (R32 + R31) / (R32-R31) | = 0.70
Conditional expression (4) (−f3) /f=0.55
Conditional expression (5) f2 / f = 0.34
Conditional expression (6) (−f1) /f=1.03

  From the table of specifications shown in Table 3, it can be seen that the eyepiece lens EL3 according to the third example satisfies the conditional expressions (1) to (6).

FIG. 6 is a diagram showing various aberrations (spherical aberration, astigmatism, coma aberration, distortion aberration, and chromatic aberration of magnification) of the eyepiece lens EL3 according to Example 3, wherein (a) is a diopter of −1.0 [m ^{−. 1} ] shows various aberration diagrams, (b) shows various aberration diagrams at a diopter of −1.7 [m ⁻¹ ], and (c) shows various aberration diagrams at a diopter +0.5 [m ⁻¹ ]. . As is apparent from the respective aberration diagrams, the eyepiece lens EL3 according to the third example has various aberrations well corrected within the diopter adjustment range, and excellent optical performance is ensured.

  As a result, according to the eyepiece lens EL3 according to the third example, an eyepiece lens with high observation magnification and adjustable diopter can be obtained. Moreover, according to the single-lens reflex camera CAM provided with such an eyepiece lens EL3, a high observation magnification can be ensured even though the diopter can be adjusted.

(Fourth embodiment)
A fourth embodiment will be described with reference to FIGS. 7 and 8 and Table 4. FIG. In FIG. 7, illustration of the condenser lens C and the pentaprism P is omitted, and for the focusing screen F, only the focal plane I formed on the focusing screen F is shown.

  As shown in FIG. 7, the eyepiece lens EL (EL4) according to the fourth example includes a first lens group G1 having negative refractive power and a second lens having positive refractive power, which are arranged in order from the object side. It consists of a group G2 and a third lens group G3 having negative refractive power, and is configured to adjust the diopter by moving the second lens group G2 along the optical axis.

  The first lens group G1 includes a negative meniscus lens L1 having a convex surface directed toward the object side. The second lens group G2 is composed of a biconvex lens L2. The third lens group G3 is composed of a biconcave lens L3.

  The eye point side surface of the negative meniscus lens L1, the both side surfaces of the biconvex lens L2, and the both side surfaces of the biconcave lens L3 are each formed of an aspherical surface.

  In the present embodiment, as described above, in the vicinity of the focal plane I along the optical axis in order from the real image plane of the objective lens (not shown), that is, the focal plane I side, between the focal plane I and the first lens group G1. A condenser lens C and a pentaprism P are arranged. Therefore, in the eyepiece lens EL4 according to the fourth example, after the image on the focal plane I (formed by an objective lens (not shown)) is made into an erect image through the condenser lens C and the pentaprism P in this order, The eyepiece E1 is enlarged by the eyepiece lens EL1 composed of the first lens group G1 to the third lens group G3. It can be observed at P.

  Table 4 below shows values of various specifications in the fourth embodiment. Surface numbers 1 to 7 in Table 4 correspond to the optical surfaces m1 to m7 shown in FIG.

  In this embodiment, the diopter is set to -1.7 to +0.5 [1 / m], and the eye point E.E. The pupil diameter of P is φ10 mm, and the eye point E.E. The lens design is performed with the position of P (that is, the distance from the eyepiece lens EL4 along the optical axis) being 15.7 to 21.0 mm and the number of fields of view being 26.0.

(Table 4)
[Overall specifications]
Y 22.10
TL 13.02

[Lens specifications]
Surface number R D nd νd
1 ∞ 76.863 1.00000
2 65.593 2.000 1.58276 30.34
* 3 20.462 D3 (variable) 1.00000
* 4 13.693 7.500 1.52444 56.21
* 5 -29.719 D5 (variable) 1.00000
* 6 -86.474 2.500 1.49108 57.10
* 7 17.220 D7 (variable) 1.00000
EP

[Aspherical data]
3rd surface κ = 0.0595, A4 = 1.04041E-06, A6 = -3.98928E-08
4th surface κ = -0.0086, A4 = -4.91358E-07, A6 = -6.41921E-08
5th surface κ = -3.2470, A4 = 3.92439E-06, A6 = -2.20318E-08
6th surface κ = 4.8374, A4 = 6.31796E-05, A6 = 0.00000E + 00
7th surface κ = 0.0595, A4 = 9.71530E-05, A6 = 4.92708E-07

[Variable surface interval data]
f 60.001 58.886 68.947
Diopter -1.021 -1.724 0.480
D3 1.30 0.45 5.30
D5 8.80 9.65 4.80
D7 17.80 16.00 20.00

[Lens group data]
Group number Group first surface Group focal length G1 2 -51.878
G2 4 19.005
G3 6 -29.013

[Conditional expression]
Conditional expression (1) f1 / f3 = 1.79
Conditional expression (2) | (R12 + R11) / (R12-R11) | = 1.91
Conditional expression (3) | (R32 + R31) / (R32-R31) | = 0.67
Conditional expression (4) (−f3) /f=0.48
Conditional expression (5) f2 / f = 0.32
Conditional expression (6) (−f1) /f=0.86

  From the table of specifications shown in Table 4, it can be seen that the eyepiece lens EL4 according to the fourth example satisfies the conditional expressions (1) to (6).

FIG. 8 is a diagram showing various aberrations (spherical aberration, astigmatism, coma aberration, distortion aberration, and lateral chromatic aberration) of the eyepiece EL4 according to Example 4, and (a) shows a diopter of −1.0 [m ^{−. 1} ] shows various aberration diagrams, (b) shows various aberration diagrams at a diopter of −1.7 [m ⁻¹ ], and (c) shows various aberration diagrams at a diopter +0.5 [m ⁻¹ ]. . As is apparent from the respective aberration diagrams, it is understood that the eyepiece lens EL4 according to the fourth example has various aberrations well corrected within the diopter adjustment range, and excellent optical performance is ensured.

  As a result, according to the eyepiece lens EL4 according to the fourth example, an eyepiece lens having a high observation magnification and adjustable diopter can be obtained. In addition, according to the single-lens reflex camera CAM provided with such an eyepiece lens EL4, a high observation magnification can be secured even though the diopter can be adjusted.

  In order to make the present invention easier to understand, the configuration requirements of the embodiment have been described, but it goes without saying that the present invention is not limited to this.

  For example, the eyepiece according to the present embodiment is not limited to an eyepiece used in a finder optical system of a single-lens reflex camera, but can be widely used as a finder eyepiece in a real image optical system.

  Further, in the above-described embodiment, the diopter adjustment can be performed by moving the second lens L2 along the optical axis, but is not limited thereto. For example, the diopter adjustment may be performed by moving the first lens L1, or by moving both the first lens L1 and the second lens L2, and the first lens L1 and the second lens L2. In addition, it is only necessary that the diopter adjustment can be performed by moving at least one of the third lens L3 along the optical axis.

G1 First lens group G2 Second lens group G3 Third lens group L1 Negative meniscus lens in the first lens group L2 Biconvex lens in the second lens group L3 Biconcave lens in the third lens group EL (EL1 to EL4) Eyepiece Lens CAM single-lens reflex camera (optical equipment)

Claims (6)

An eyepiece for observing an image formed by an objective lens through an erecting optical system,
A first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a negative refractive power, arranged in order from the object side,
The first lens group includes one negative meniscus lens,
The third lens group includes one biconcave lens,
An eyepiece that satisfies the following conditional expression:
1.35 <f1 / f3 <2.50
1.50 <| (R12 + R11) / (R12-R11) | <10.00
0.30 <| (R32 + R31) / (R32-R31) | <0.90
However,
f1: the focal length of the first lens group,
f3: focal length of the third lens group,
R11: radius of curvature of the object side surface of the negative meniscus lens,
R12: radius of curvature of the side surface of the eye point of the negative meniscus lens,
R31: radius of curvature of the object side surface of the biconcave lens,
R32: radius of curvature of the side surface of the eye point of the biconcave lens. The eyepiece according to claim 1, wherein the following conditional expression is satisfied.
0.30 <(− f3) / f <0.70
However,
f: Focal length of the entire system when the diopter is −1.0 [1 / m]. The eyepiece according to claim 1, wherein the following conditional expression is satisfied.
0.20 <f2 / f <0.40
However,
f2: focal length of the second lens group,
f: Focal length of the entire system when the diopter is −1.0 [1 / m]. The eyepiece according to claim 1, wherein the following conditional expression is satisfied.
0.80 <(− f1) / f <2.00
However,
f: Focal length of the entire system when the diopter is −1.0 [1 / m].   The eyepiece lens according to claim 1, wherein diopter adjustment is performed by moving the second lens group along an optical axis. An objective lens that forms an image of an object on a predetermined surface;
In an optical apparatus configured to include an eyepiece for observing an image formed by the objective lens through an erecting optical system,
An optical apparatus, wherein the eyepiece is the eyepiece according to any one of claims 1 to 5.

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