JP2021005111A - Eyepiece optical system and observation device having the same - Google Patents

Abstract

To provide an eyepiece optical system which suppresses aberrations well, secures high optical performance, is easy to manufacture, and facilitates observation over a wide field of view.SOLUTION: An eyepiece optical system for observing an image displayed on an image display surface is provided, the eyepiece optical system comprising, in order from an image display surface side to an observation side, a first lens L1 having positive refractive power, a second lens L2 having negative refractive power, a third lens L3, and a fourth lens L4 having positive refractive power. The eyepiece optical system satisfies following conditional expressions: 1.520≤Nda≤1.730, -15.0≤(L2R1+L1R2)/(L2R1-L1R2)≤0.0, 0.68≤f34/f≤1.30, where Nda represents an average refractive index of materials of the first through fourth lenses for a d-ray, L1R2 represents a curvature radius of an observation-side surface of the first lens, L2R1 represents a curvature radius of an image display-side surface of the second lens, f34 represents a composite focal length of the third and fourth lenses, and f represents a focal length of the eyepiece optical system.SELECTED DRAWING: Figure 1

Description

The present invention relates to an eyepiece optical system and an observation device having the same, for observing an image displayed on an image display surface of an image display element, for example, in an electronic viewfinder used in a video camera, a still camera, or a broadcasting camera. It is suitable.

Conventionally, in an electronic viewfinder (observation device) used in an imaging device (camera) such as a video camera or a still camera, an eyepiece optical system is used for magnifying and observing an image displayed on a liquid crystal screen or the like. .. In the electronic viewfinder, in order to make the image display surface highly visible and easy to see, it is necessary to have a high observation magnification and a long eye relief.

Further, from the demand for miniaturization of the observation device, the image display element used in the observation device is required to have a small size (for example, a diagonal length of 20 mm or less).

Conventionally, various eyepiece optical systems having a high observation magnification have been proposed (Patent Documents 1 to 3).

In Patent Document 1, from the image display element side toward the observation side, a first lens having a positive refractive power, a second lens having a negative refractive power, a third lens having a positive or negative refractive power, and a positive refractive power. An eyepiece optical system including a fourth lens is disclosed.

In Patent Document 1, at least two lenses having a positive refractive power, at least one lens having a negative refractive power, and a diffractive optical element are used in order to satisfactorily correct various aberrations while reducing the size of the entire system. Is used.

Further, Patent Document 2 discloses an eyepiece for an endoscope including a lens group having a negative refractive power and a lens group having a positive refracting surface.

Further, in Patent Document 3, in order from the image display element side to the observation side, a biconvex first lens having a positive refractive power, a second lens having a negative refractive power, and a third lens having a positive refractive power are used. An eyepiece optical system including a fourth lens having a positive refractive power is disclosed. Patent Document 3 discloses an eyepiece optical system in which various aberrations are satisfactorily corrected while having a high observation magnification.

Japanese Unexamined Patent Publication No. 2001-066522 Japanese Unexamined Patent Publication No. 05-313073 Japanese Unexamined Patent Publication No. 2015-07513

In the eyepiece optical system used for the observation device, in order to secure a high observation magnification and a long eye relief, it is important to appropriately set the lens configuration of the eyepiece optical system and the refractive power of each lens. .. In addition, when using a small image display surface, it is important to appropriately set the ratio of the refractive power of the eyepiece optical system to the size of the image display surface.

The eyepiece for an image display device disclosed in Patent Document 1 uses a curved panel, a diffractive optical element, and a high refractive index material to correct various aberrations while ensuring a high observation magnification. Therefore, it is easy to secure the optical performance and specifications, but it tends to be difficult to manufacture.

The eyepiece for an endoscope disclosed in Patent Document 2 reduces the number of lenses by using a lens made of a high refractive index material and an aspherical lens, and secures a high observation magnification. However, since many materials having a high refractive index are used, the production tends to be difficult.

The eyepiece optical system disclosed in Patent Document 3 uses a material having a relatively low refractive index to ensure a high observation magnification. However, in order to increase the magnification, the curvatures of the lens surfaces of the first lens surface and the second lens surface that bounce off the light rays become tight, and the light rays change rapidly. For this reason, curvature of field is likely to occur.

Further, since the correction of various aberrations is facilitated by using a large number of aspherical surfaces, the manufacturing tends to be complicated.

An object of the present invention is to provide an eyepiece optical system that is easy to manufacture and easy to observe in a high field of view while satisfactorily suppressing various aberrations and ensuring high optical performance.

The eyepiece optical system of the present invention is an eyepiece optical system for observing an image displayed on an image display surface, and is a first lens having a positive refractive force arranged in order from the image display surface side to the observation side. It is composed of a second lens with a negative refractive force, a third lens, and a fourth lens with a positive refractive force, and the average value of the refractive index in the d line of the material of each lens of the first lens to the fourth lens is Nda. The radius of curvature of the lens surface on the observation side of the first lens is L1R2, the radius of curvature of the lens surface of the second lens on the image display surface side is L2R1, and the combined focal distance between the third lens and the fourth lens is f34. When the focal distance of the eyepiece optical system is f,
1.520 ≤ Nda ≤ 1.730
-15.0 ≦ (L2R1 + L1R2) / (L2R1-L1R2) ≦ 0.0
0.68 ≤ f34 / f ≤ 1.30
It is characterized by satisfying the conditional expression.

According to the present invention, it is possible to obtain an eyepiece optical system that is easy to manufacture and easy to observe in a high field of view while satisfactorily suppressing various aberrations and ensuring high optical performance.

Sectional drawing which shows the lens structure of the eyepiece optical system which concerns on Example 1 of this invention. Each aberration diagram of the eyepiece optical system according to the first embodiment of the present invention. Sectional drawing which shows the lens structure of the eyepiece optical system which concerns on Example 2 of this invention. Each aberration diagram of the eyepiece optical system according to the second embodiment of the present invention. Sectional drawing which shows the lens structure of the eyepiece optical system which concerns on Example 3 of this invention. Each aberration diagram of the eyepiece optical system according to the third embodiment of the present invention. Sectional drawing which shows the lens structure of the eyepiece optical system which concerns on Example 4 of this invention. Each aberration diagram of the eyepiece optical system according to the fourth embodiment of the present invention. Sectional drawing which shows the lens structure of the eyepiece optical system which concerns on Example 5 of this invention. Each aberration diagram of the eyepiece optical system according to the fifth embodiment of the present invention. Sectional drawing which shows the lens structure of the eyepiece optical system which concerns on Example 6 of this invention. Each aberration diagram of the eyepiece optical system according to the sixth embodiment of the present invention.

Hereinafter, the eyepiece optical system of the present invention and an observation device having the same will be described. The eyepiece optical system of the present invention is an eyepiece optical system for observing an image displayed on an image display surface. The eyepiece optical system is composed of a first lens having a positive refractive power, a second lens having a negative refractive power, a third lens, and a fourth lens having a positive refractive power, which are arranged in order from the image display surface side to the observation side. ing.

FIG. 1 is a cross-sectional view of a lens of Example 1 of the eyepiece optical system of the present invention. FIG. 2 is an aberration diagram when the diopter of Example 1 of the eyepiece optical system of the present invention is −1.0 diopter (standard diopter).

FIG. 3 is a cross-sectional view of the lens of Example 2 of the eyepiece optical system of the present invention. FIG. 4 is an aberration diagram when the diopter of Example 2 of the eyepiece optical system of the present invention is −1.0 diopter.

FIG. 5 is a cross-sectional view of the lens of Example 3 of the eyepiece optical system of the present invention. FIG. 6 is an aberration diagram when the diopter of Example 3 of the eyepiece optical system of the present invention is −1.0 diopter.

FIG. 7 is a cross-sectional view of the lens of Example 4 of the eyepiece optical system of the present invention. FIG. 8 is an aberration diagram when the diopter of Example 4 of the eyepiece optical system of the present invention is −1.0 diopter.

FIG. 9 is a cross-sectional view of the lens of Example 5 of the eyepiece optical system of the present invention. FIG. 10 is an aberration diagram when the diopter of Example 5 of the eyepiece optical system of the present invention is −1.0 diopter.

FIG. 11 is a cross-sectional view of the lens of Example 6 of the eyepiece optical system of the present invention. FIG. 12 is an aberration diagram when the diopter of Example 6 of the eyepiece optical system of the present invention is −1.0 diopter.

The eyepiece optical system of each embodiment is used as an electronic viewfinder (observation device) of an imaging device such as a digital camera or a video camera. In the cross-sectional view of the lens, the left side is the image display surface side, and the right side is the observation side (exit pupil side). In the cross-sectional view of the lens, L0 is an eyepiece optical system. Li is the i-th lens. IP is an image display surface of an image display element made of liquid crystal, organic EL, or the like. EP is an observation surface (eye point) (exit pupil) for observation. CG1 is a cover glass.

In the spherical aberration diagram of each aberration diagram, the solid line d indicates the d line (wavelength 587.6 nm), and the dotted line F indicates the F line (wavelength 486.1 nm). In the astigmatism diagram, ΔSd indicates the sagittal image plane of the d line, and ΔMd indicates the meridional image plane of the d line. ΔSF indicates the sagittal image plane of the F line, and ΔMF indicates the meridional image plane of the F line. The distortion is shown for the d line. Chromatic aberration of magnification is shown for the F line. H is half the diagonal length of the image display surface (maximum image height). The numerical value is a value when the numerical data described later is expressed in millimeters.

In order to observe a small image display surface (display panel) with a diagonal length of about 20 mm or less on the image display surface of the image display element with a large observation field of view (viewing angle of about 30 degrees or more), the entire eyepiece optical system is strongly positive. It is necessary to have the refractive power (power) of. For that purpose, each lens constituting the eyepiece optical system needs a strong positive refractive power and a negative refractive power. Then, in many cases, curvature of field and chromatic aberration of magnification increase, and it becomes difficult to correct these various aberrations.

Therefore, in the eyepiece optical system according to each embodiment, as shown in each lens cross-sectional view, four lens groups are configured in order from the image display surface IP side (object side) to the observation surface (eye point) EP side. There is. Specifically, it is composed of a first lens L1 having a positive refractive power, a second lens L2 having a negative refractive power, a third lens L3 having a positive or negative refractive power, and a fourth lens L4 having a positive refractive power. There is.

In each embodiment, the observation surface EP may move in the optical axis direction as long as the light rays from the outermost periphery of the image display surface IP pass through the observer's pupil. Further, the distance from the final surface of the lens (the surface on the observation side of the fourth lens L4) to the observation surface EP is defined as the eye relief. The cover glass is a plate that protects the image display surface IP and the lens, and may or may not be provided between the image display surface IP and the lens or between the lens and the observation surface EP.

In the eyepiece L0 of the present invention, the average value of the refractive indexes of the materials of the first lens L1 to the fourth lens L4 on the d line is Nda. The radius of curvature of the lens surface on the observation side of the first lens L1 is L1R2, and the radius of curvature of the lens surface of the second lens L2 on the image display surface side is L2R1. Let the combined focal length of the third lens L3 and the fourth lens L4 be f34. Let f be the focal length of the eyepiece optical system.

At this time,
1.520 ≤ Nda ≤ 1.730 ... (1)
-15.0 ≦ (L2R1 + L1R2) / (L2R1-L1R2) ≦ 0.0 ・ ・ ・ (2)
0.68 ≤ f34 / f ≤ 1.30 ... (3)
Satisfy the conditional expression.

Next, the technical meaning of each of the above conditional expressions will be described.

The conditional expression (1) defines the average value of the refractive indexes of the materials of the first lens L1 to the fourth lens L4 on the d-line. When the refractive index of the material of each lens increases beyond the upper limit of the conditional expression (1), the power of the entire system can be increased, and it becomes easy to obtain a high observation magnification (high viewing angle). However, as a material having a high refractive index, for example, glass or the like must be frequently used, which makes production difficult. Further, when the refractive index of the material of each lens becomes lower than the lower limit value, the refractive power of the entire system becomes weak and it becomes difficult to increase the viewing angle.

The conditional expression (2) defines the shape of the air lens formed between the first lens L1 and the second lens L2. Conditional expression (2) is for satisfactorily correcting curvature of field while maintaining a high observation magnification. In each embodiment, the light beam emitted from the first lens L1 is bounced up by the second lens L2 in order to obtain a high observation magnification. If it is less than the lower limit of the conditional expression (2), the bending of the light beam between the first lens L1 and the second lens L2 becomes too steep, so that it becomes difficult to correct various aberrations, especially the aberration of curvature of field. If the upper limit is exceeded, the bounce of light rays becomes insufficient, and it becomes difficult to obtain a high observation magnification.

The conditional expression (3) defines the composite focal length of the synthetic system including the third lens L3 and the fourth lens L4 and the focal length of the entire system. If the upper limit of the conditional expression (3) is exceeded, the positive refractive power of the synthetic system becomes weak and it becomes difficult to obtain a high observation magnification. If it falls below the lower limit of the conditional expression (3), the positive refractive power of the synthetic system becomes strong, it becomes difficult to secure an eye relief of a sufficient length, and it becomes difficult to observe the image display surface well. ..

It is preferable to set the numerical range of the conditional expressions (1) to (3) as follows.
1.550 ≤ Nda ≤ 1.730 ... (1a)
-12.0 ≦ (L2R1 + L1R2) / (L2R1-L1R2) ≦ 0.0 ... (2a)
0.68 ≤ f34 / f ≤ 1.25 ... (3a)
More preferably, the numerical range of the conditional expressions (1a) to (3a) is set as follows.
1.550 ≤ Nda ≤ 1.700 ... (1b)
-10.0 ≦ (L2R1 + L1R2) / (L2R1-L1R2) ≦ 0.0 ... (2b)
0.70 ≦ f34 / f ≦ 1.25 ・ ・ ・ (3b)
As described above, according to the present invention, it is possible to obtain an optimal eyepiece optical system for an electronic viewfinder having high observation magnification and high optical performance.

More preferably, one or more of the following conditional expressions is satisfied in each embodiment. The distance between the first lens L1 and the second lens L2 on the optical axis is d3, and the distance between the second lens group L2 and the third lens L3 on the optical axis is d5. In an observation device having an image display element for displaying an image and an eyepiece optical system used for observing an image displayed on the image display surface IP of the image display element, the diagonal length of the image display surface of the image display element Let half be PN. Let d1 be the distance on the optical axis from the image display surface IP to the lens surface on the image display surface side of the first lens L1.

At this time, it is preferable to satisfy one or more of the following conditional expressions.
0.00≤d5 / d3≤0.75 ... (4)
0.25 <PN / f <0.55 ... (5)
0.0 ≦ d1 / f <0.8 ・ ・ ・ (6)
Next, the technical meaning of each of the above conditional expressions will be described. The conditional expression (4) defines the ratio of the distance between the first lens L1 and the second lens L2 to the distance between the second lens L2 and the third lens L3. The conditional expression (4) is for satisfactorily correcting the chromatic aberration of magnification while obtaining a large observation magnification.

If the distance between the second lens L2 and the third lens L3 becomes larger than the upper limit of the conditional expression (4), it becomes difficult to correct the chromatic aberration of magnification. Further, when the distance between the first lens L1 and the second lens L2 becomes narrower, the light angle of the light beam incident on the second lens L2 becomes tighter, and the curvature of field increases particularly at a high image height. When the distance between the first lens L1 and the second lens L2 becomes wider than the lower limit value, the height of the light beam incident on the second lens becomes low, so that it becomes difficult to bounce the light ray and obtain a high observation field magnification.

The conditional expression (5) defines the ratio of half the diagonal length of the image display surface of the image display element to the focal length of the entire system. The conditional expression (5) is for ensuring a high observation magnification while ensuring a long eye relief. If the focal length of the entire system becomes shorter than the upper limit of the conditional expression (5), it is advantageous for a high observation magnification, but it becomes difficult to secure high optical performance. If it falls below the lower limit of the conditional expression (5), the refractive power of the entire system becomes weak, and it becomes difficult to secure a high observation magnification.

The conditional expression (6) defines the length on the optical axis from the image display surface of the image display element to the lens surface on the image display surface side of the first lens L1 and the focal length of the entire system. If the upper limit is exceeded, the distance from the image display surface to the lens surface on the image display surface side of the first lens increases, which makes it difficult to reduce the size of the entire system.

It is preferable to set the numerical range of the conditional expressions (4) to (6) as follows.
0.0 ≦ d5 / d3 ≦ 0.6 ・ ・ ・ (4a)
0.25 <PN / f <0.50 ... (5a)
0.00≤d1 / f <0.60 ... (6a)
More preferably, the numerical range of the conditional expressions (4a) to (6a) is set as follows.
0.0 ≤ d5 / d3 ≤ 0.5 ... (4b)
0.25 <PN / f <0.45 ... (5b)
0.00≤d1 / f <0.55 ... (6b)
Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and modifications can be made within the scope of the gist thereof.

Numerical data corresponding to each embodiment of the present invention is shown below. In the numerical data, ω indicates the apparent field of view (half angle of view) when the diopter is -1 diopter (standard diopter). From the image display surface IP to the observation side EP, "ri" indicates the paraxial radius of curvature of the i-th surface. “Di” indicates the axis upper surface distance between the i-th surface and the i + 1th surface in order from the image display surface IP. Further, "Ndi" indicates the refractive index of the i-th material with respect to the d-line (wavelength = 578.6 nm), and "νdi" indicates the Abbe number of the i-th material with respect to the d-line. r0 is an image display surface IP, and r9 and r10 are cover glasses.

In the numerical data, the unit of the described length is [mm] unless otherwise specified. However, since the same optical performance can be obtained even if the optical system is proportionally expanded or decreased, the unit is not limited to [mm], and other appropriate units can be used. In the numerical data, the surface on which the subscript "*" is written in the column of the radius of curvature of the paraxial axis is an aspherical shape defined by the following equation (1).

In (Equation 1), x is the distance in the optical axis direction from the apex of the lens surface, h is the height in the direction perpendicular to the optical axis, R is the radius of curvature of the near axis at the apex of the lens surface, and k is. The cone constants c2, c4 and c6 are polynomial coefficients. In the aspherical coefficient, "Ei" represents an exponential notation with a base of 10, that is, "10-i".

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and modifications can be made within the scope of the gist thereof.

[Numerical data 1]
Overall focal length Image display surface Diagonal length 2ω [°]
18.97 12.6 35.0

Lens data Paraxial radius of curvature Axis top spacing Refractive index (Nd) Abbe number (νd)
r0 display panel d1 variable
r1 553.90 d2 3.30 1.821 42.7
* r2 -14.37 d3 2.84
* r4 -7.18 d4 1.65 1.636 23.9
r5 -50.31 d5 0.62
* r6 -31.65 d6 2.63 1.592 67.0
r7 -16.79 d7 0.22
r8 50.42 d8 6.50 1.535 55.7
* r9 -13.05 d9 variable
r10 0.00 d10 0.80 1.492 57.4
r11 0.00 d11 23.00
EP

Aspherical coefficient k C2 C4 C6 C8
r2 0.00E + 00 0.00E + 00 3.88E-05 3.65E-08 0.00E + 00
r3 -8.22E-01 0.00E + 00 -9.72E-05 -9.34E-07 0.00E + 00
r5 0.00E + 00 0.00E + 00 1.10E-05 0.00E + 00 0.00E + 00
r8 -2.30E + 00 0.00E + 00 -4.87E-05 2.14E-07 -2.73E-10

Variable interval diopter [dpt] 0 -3 +1 -1
d1 7.76 6.66 8.15 7.42
d9 1.51 2.60 1.12 1.85

[Numerical data 2]
Overall focal length Image display surface Diagonal length 2ω [°]
13.37 9.9 40.6

Lens data plane Paraxial radius of curvature Axis top spacing Refractive index (Nd) Abbe number (νd)
r0 display panel d1 variable
* r1 13.421 d2 6.14 1.535 56.0
* r2 -8.334 d3 2.15
* r3 -5.637 d4 1.48 1.636 23.9
r4 -15.213 d5 0.17
r5 -34.833 d6 2.11 1.535 56.0
r6 -17.151 d7 0.15
r7 -152.436 d8 3.31 1.535 56.0
* r8 -11.013 d9 Variable
r9 0.000 d10 0.70 1.492 57.4
r10 0.000 d11 18.00
EP

Aspherical coefficient
k C2 C4 C6
r1 -6.34E + 00 0.00E + 00 0.00E + 00 0.00E + 00
r2 -1.68E + 00 0.00E + 00 -9.39E-05 0.00E + 00
r3 -9.67E-01 0.00E + 00 0.00E + 00 0.00E + 00
r8 -2.34E + 00 0.00E + 00 3.69E-06 3.31E-07

Variable interval diopter [dpt] 0 -3 +1 -1
d1 5.74 5.14 5.91 5.55
d9 0.67 1.26 0.50 0.86

[Numerical data 3]
Overall focal length Image display surface Diagonal length 2ω [°]
17.96 9.9 29.1

Lens data plane Paraxial radius of curvature Axis top spacing Refractive index (Nd) Abbe number (νd)
r0 display panel d1 variable
r1 24.08 d2 4.02 1.532 55.8
* r2 -9.64 d3 3.62
* r3 -5.70 d4 1.50 1.636 23.9
r4 -35.58 d5 1.30
r5 -16.99 d6 3.32 1.532 55.8
* r6 -9.80 d7 0.33
r7 39.45 d8 3.23 1.532 55.8
* r8 -16.38 d9 Variable
r9 0.00 d10 1.00 1.516 64.1
r10 0.00 d11 21.00
EP

Aspherical coefficient
k C2 C4 C6
r2 0.00E + 00 0.00E + 00 2.28E-04 0.00E + 00
r3 -4.72E-01 0.00E + 00 1.67E-04 0.00E + 00
r6 0.00E + 00 0.00E + 00 1.67E-05 0.00E + 00
r8 0.00E + 00 0.00E + 00 6.95E-05 5.15E-08

Variable interval diopter [dpt] 0 -3 +1 -1
d1 5.95 4.88 6.24 5.59
d9 0.79 1.86 0.50 1.15

[Numerical data 4]
Overall focal length Image display surface Diagonal length 2ω [°]
16.50 9.9 32.0

Lens data Paraxial radius of curvature Axis top spacing Refractive index (Nd) Abbe number (νd)
r0 display panel d1 variable
r1 21.75 d2 4.95 1.535 55.7
* r2 -10.27 d3 2.39
* r3 -5.62 d4 1.75 1.636 23.9
r4 -18.39 d5 0.22
* r5 -22.78 d6 2.62 1.535 55.7
r6 -11.84 d7 0.22
r7 105.20 d8 3.87 1.535 55.7
* r8 -13.85 d9 Variable
r9 0.00 d10 0.80 1.492 57.4
r10 0.00 d11 21.00
EP

Aspherical coefficient k C2 C4 C6 C8
r2 0.00E + 00 0.00E + 00 1.57E-04 8.64E-07 0.00E + 00
r3 -7.62E-01 0.00E + 00 8.52E-05 0.00E + 00 0.00E + 00
r5 0.00E + 00 0.00E + 00 -7.94E-05 0.00E + 00 0.00E + 00
r8 0.00E + 00 0.00E + 00 1.27E-04 -3.08E-07 3.21E-09

Variable interval diopter [dpt] 0 -3 +1 -1
d1 7.10 6.25 7.35 6.83
d9 1.05 1.90 0.80 1.32

[Numerical data 5]
Overall focal length Image display surface Diagonal length 2ω [°]
25.22 16.8 35.1

Lens data Paraxial radius of curvature Axis top spacing Refractive index (Nd) Abbe number (νd)
r0 display panel d1 variable
r1 49.56 d2 6.43 1.535 55.7
* r2 -17.25 d3 4.39
* r3 -8.84 d4 1.95 1.636 23.9
r4 -30.05 d5 0.22
r5 266.69 d6 5.26 1.531 55.9
r6 -27.75 d7 0.22
r7 235.81 d8 5.82 1.535 55.7
* r8 -18.98 d9 Variable
r9 0.00 d10 0.80 1.492 57.4
r10 0.00 d11 30.00
EP

Aspherical coefficient k C2 C4 C6
r1 0.00E + 00 0.00E + 00 2.91E-05 0.00.E + 00
r2 -1.33E + 00 0.00E + 00 -1.12E-04 0.00.E + 00
r8 -2.17E + 00 0.00E + 00 1.01E-05 1.04E-08

Variable interval diopter [dpt] 0 -3 +1 -1
d1 10.39 8.38 11.02 9.74
d9 2.04 4.05 1.41 2.69

[Numerical data 6]
Overall focal length Image display surface Diagonal length 2ω [°]
20.46 12.6 33.1

Lens data Paraxial radius of curvature Axis top spacing Refractive index (Nd) Abbe number (νd)
r0 display panel d1 variable
r1 59.97 d2 5.95 1.694 53.2
* r2 -11.68 d3 2.38
* r3 -6.74 d4 1.67 1.636 23.9
r4 -28.97 d5 0.00
r5 -28.97 d6 3.09 1.535 56.0
r6 -35.80 d7 0.25
r7 61.73 d8 5.49 1.535 56.0
* r8 -12.03 d9 Variable
r9 0.00 d10 0.80 1.492 57.4
r10 0.00 d11 24.00
EP

Aspherical coefficient
k C2 C4 C6
r2 0.00E + 00 0.00E + 00 1.15E-04 2.75E-07
r3 -9.93E-01 0.00E + 00 0.00E + 00 0.00E + 00
r8 -5.80E-01 0.00E + 00 6.48E-05 8.67E-08

Variable interval diopter [dpt] 0 -3 +1 -1
d1 9.47 8.06 9.85 9.01
d9 0.87 2.28 0.50 1.34

L0 Eyepiece optical system L1 1st lens L2 2nd lens L3 3rd lens L4 4th lens IP image display surface EP observation surface

The eyepiece optical system of the present invention is composed of a first lens having a positive refractive force, a second lens having a negative refractive force, a third lens, and a fourth lens having a positive refractive force arranged in order from the object side to the observation side. a ocular optical system that consists, Nda the average value of the refractive index at the d-line of the material of each lens of the first lens to the fourth lens, the radius of curvature of the lens surface on the viewing side of the first lens When L1R2, the radius of curvature of the lens surface of the second lens on the object side is L2R1, the combined focal distance between the third lens and the fourth lens is f34, and the focal distance of the eyepiece optical system is f.
1.520 ≤ Nda ≤ 1.730
-15.0 ≦ (L2R1 + L1R2) / (L2R1-L1R2) ≦ 0.0
0.68 ≤ f34 / f ≤ 1.30
It is characterized by satisfying the conditional expression.

Claims (5)

An eyepiece optical system for observing an image displayed on an image display surface, the first lens having a positive refractive force and the second lens having a negative refractive force arranged in order from the image display surface side to the observation side. , A third lens and a fourth lens having a positive refractive force, and the average value of the refractive index of the material of each lens of the first lens to the fourth lens on the d line is Nda, and the observation side of the first lens. The radius of curvature of the lens surface is L1R2, the radius of curvature of the lens surface on the image display surface side of the second lens is L2R1, the combined focal distance between the third lens and the fourth lens is f34, and the focal distance of the eyepiece optical system. When is f
1.520 ≤ Nda ≤ 1.730
-15.0 ≦ (L2R1 + L1R2) / (L2R1-L1R2) ≦ 0.0
0.68 ≤ f34 / f ≤ 1.30
An eyepiece optical system characterized by satisfying the conditional expression. When the distance between the first lens and the second lens on the optical axis is d3, and the distance between the second lens and the third lens on the optical axis is d5,
0.00≤d5 / d3≤0.75
The eyepiece optical system according to claim 1, wherein the eyepiece optical system satisfies the conditional expression. An observation device comprising an image display element for displaying an image and an eyepiece optical system according to claim 1 or 2, which is used for observing an image displayed on an image display surface of the image display element. When half of the diagonal length of the image display surface of the image display element is PN,
0.25 <PN / f <0.55
The observation device according to claim 3, wherein the observation device satisfies the conditional expression. When the distance on the optical axis from the image display surface to the lens surface on the image display surface side of the first lens is d1
0.0 ≦ d1 / f <0.8
The observation device according to claim 3 or 4, wherein the observation device satisfies the conditional expression.

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