JP2018189879A - Eyepiece optical system and observation device having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an eyepiece optical system that is easily manufactured and facilitates an observation in a large view field, while well suppressing various aberrations and ensuring high optical performance.SOLUTION: The eyepiece optical system is to be used for an observation of an image displayed on an image display screen, and the system is constituted by, successively arranged from the image display screen side to an observation side, a first lens having a positive refractive power, a second lens having a negative refractive power, a third lens, and a fourth lens having positive refractive power. An average value Nda of refractive indices of the lens materials for the first lens to the fourth lens with respect to d-line, a radius of curvature L1R2 of a lens surface on the observation side of the first lens, a radius of curvature L2R1 of a lens surface on the image display screen side of the second lens, a composite focal distance f34 of the third lens and the fourth lens, and a focal distance f of the eyepiece optical system are each appropriately set.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an eyepiece optical system and an observation apparatus having the eyepiece optical system. For example, in an electronic viewfinder used for a video camera, a still camera, and a broadcast camera, an image displayed on an image display surface of an image display element is observed. Is preferred.

  2. Description of the Related Art Conventionally, in an electronic viewfinder (observation apparatus) used in an imaging apparatus (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.

  Furthermore, in order to reduce the size of the observation apparatus, an image display element used in the observation apparatus 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 comprising 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 to satisfactorily correct various aberrations while reducing the size of the entire system. Is used.

  Patent Document 2 discloses an eyepiece for an endoscope that includes a lens group having a negative refractive power and a lens group having a positive refractive surface.

  Further, in Patent Document 3, in order from the image display element side to the observation side, a biconvex shape, a first lens having a positive refractive power, a second lens having a negative refractive power, a third lens having a positive refractive power, 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 favorably corrected while having a high observation magnification.

JP 2001-066652 A JP 05-313073 A JP, 2015-075713, A

  In an eyepiece optical system used in an observation apparatus, in order to ensure 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 a small image display surface is used, 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 lens 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, although optical performance and specifications are easy to ensure, manufacturing tends to be difficult.

  The eyepiece for endoscope disclosed in Patent Document 2 uses a high refractive index material lens and an aspherical lens to reduce the number of lenses and ensure a high observation magnification. However, since many high refractive index materials 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, the curvatures of the lens surfaces of the first lens surface and the second lens surface that jump up the light beam to increase the magnification become tight, and the light beam changes abruptly. For this reason, field curvature tends to occur.

  In addition, since a lot of aspheric surfaces are used to facilitate correction of various aberrations, manufacturing tends to be complicated.

  An object of the present invention is to provide an eyepiece optical system that can be easily manufactured and that can be easily observed in a high field of view while satisfactorily suppressing various aberrations and ensuring high optical performance.

An eyepiece optical system of the present invention is an eyepiece optical system for observing an image displayed on an image display surface, and is arranged in order from the image display surface side to the observation side, a first lens having a positive refractive power, It is composed of a second lens having a negative refractive power, a third lens, and a fourth lens having a positive refractive power, and the average value of the refractive index at the d-line of each lens material of the first lens to the fourth lens is represented by Nda. The curvature radius of the lens surface on the observation side of the first lens is L1R2, the curvature radius of the lens surface on the image display surface side of the second lens is L2R1, and the combined focal length of the third lens and the fourth lens is f34. When the focal length 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 following conditional expression.

  According to the present invention, it is possible to obtain an eyepiece optical system that can be easily manufactured and that can be easily observed 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 Example 1 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 Example 2 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 Example 3 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 Example 4 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 Example 5 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 Example 6 of the present invention

  Hereinafter, the eyepiece optical system of the present invention and the observation apparatus 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 includes 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 lens sectional view of Example 1 of the eyepiece optical system of the present invention. FIG. 2 is an aberration diagram for Example 1 of the eyepiece optical system according to the present invention when the diopter is −1.0 diopter (standard diopter).

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

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

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

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

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

  The eyepiece optical system of each embodiment is used in an electronic viewfinder (observation apparatus) of an imaging apparatus such as a digital camera or a video camera. In the lens cross-sectional view, the left side is the image display surface side, and the right side is the observation side (exit pupil side). In the lens cross-sectional view, 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 or organic EL. EP is an observation surface (eye point) (exit pupil) for observation. CG1 is a cover glass.

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

  In order to observe a small image display surface (display panel) having 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 refracting power (power). For this purpose, each lens constituting the eyepiece optical system needs to have strong positive refractive power and negative refractive power. If so, in many cases, curvature of field and lateral chromatic aberration 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, the eyepiece optical system is configured by four lens groups in order from the image display surface IP side (object side) to the observation surface (eyepoint) EP side. Yes. Specifically, the first lens L1 having a positive refractive power, the second lens L2 having a negative refractive power, the third lens L3 having a positive or negative refractive power, and the fourth lens L4 having a positive refractive power are included. Yes.

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

  In the eyepiece L0 of the present invention, the average value of the refractive index at the d-line of the material of each lens of the first lens L1 to the fourth lens L4 is Nda. The curvature radius of the lens surface on the observation side of the first lens L1 is L1R2, and the curvature radius of the lens surface on the image display surface side of the second lens L2 is L2R1. The combined focal length of the third lens L3 and the fourth lens L4 is 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)
This satisfies the conditional expression

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

  Conditional expression (1) prescribes the average value of the refractive index at the d-line of the material of each lens of the first lens L1 to the fourth lens L4. If the refractive index of the material of each lens increases beyond the upper limit of 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 manufacture difficult. Further, if 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.

  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 the curvature of field while maintaining a high observation magnification. In each embodiment, in order to obtain a high observation magnification, the light beam emitted from the first lens L1 is bounced up by the second lens L2. If the lower limit of conditional expression (2) is not reached, 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, particularly the field curvature. If the upper limit is exceeded, the light beam will not jump up sufficiently, making it difficult to obtain a high observation magnification.

  Conditional expression (3) defines the combined focal length of the combined system composed of the third lens L3 and the fourth lens L4 and the focal length of the entire system. If the upper limit of conditional expression (3) is exceeded, the positive refractive power of the synthesis system becomes weak, making it difficult to obtain a high observation magnification. If the lower limit value of conditional expression (3) is not reached, the positive refractive power of the composite system becomes strong, and it becomes difficult to secure a sufficiently long eye relief, making it difficult to observe the image display surface satisfactorily. .

Preferably, the numerical ranges of conditional expressions (1) to (3) are set 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 ranges of the conditional expressions (1a) to (3a) are 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, an eyepiece optical system optimum for an electronic viewfinder having high optical performance at a high observation magnification can be obtained.

  In each embodiment, it is more preferable to satisfy one or more of the following conditional expressions. The distance on the optical axis between the first lens L1 and the second lens L2 is d3, and the distance on the optical axis between the second lens group L2 and the third lens L3 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 is Half is PN. 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 is defined as d1.

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 conditional expression will be described. 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. Conditional expression (4) is for satisfactorily correcting the chromatic aberration of magnification while obtaining a large observation magnification.

  If the upper limit of conditional expression (4) is exceeded and the distance between the second lens L2 and the third lens L3 is increased, it will be difficult to correct lateral chromatic aberration. In addition, when the distance between the first lens L1 and the second lens L2 is narrowed, the ray angle of the light beam incident on the second lens L2 becomes tight, and the curvature of field particularly at a high image height increases. If the distance between the first lens L1 and the second lens L2 is less than the lower limit value, the height of the light ray incident on the second lens is lowered, so that it is difficult to jump up the light beam and obtain a high observation field magnification.

  Conditional expression (5) defines the ratio of the half of the diagonal length of the image display surface of the image display element and the focal length of the entire system. 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 conditional expression (5), it is advantageous for high observation magnification, but it is difficult to ensure high optical performance. If the lower limit of conditional expression (5) is not reached, the refractive power of the entire system becomes weak, and it becomes difficult to ensure a high observation magnification.

  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 is widened, making it difficult to downsize the entire system.

Preferably, the numerical ranges of conditional expressions (4) to (6) are set 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 ranges of the conditional expressions (4a) to (6a) are set as follows.
0.0 ≦ d5 / d3 ≦ 0.5 (4b)
0.25 <PN / f <0.45 (5b)
0.00 ≦ d1 / f <0.55 (6b)
As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

  Numerical data corresponding to each embodiment of the present invention will be shown below. In the numerical data, ω represents an apparent field of view (half angle of view) when the diopter is −1 diopter (standard diopter). In the order from the image display surface IP to the viewing side EP, “ri” indicates the paraxial radius of curvature of the i-th surface. “Di” indicates an axial upper surface distance between the i-th surface and the (i + 1) -th surface in order from the image display surface IP. Furthermore, “Ndi” represents the refractive index of the i-th material with respect to the d-line (wavelength = 578.6 nm), and “νdi” represents 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 numerical data, the unit of length described is [mm] unless otherwise specified. However, since the optical system can obtain the same optical performance even when proportionally enlarged or reduced, the unit is not limited to [mm], and other appropriate units can be used. In the numerical data, the surface in which the suffix “*” is written in the paraxial radius of curvature column is an aspherical shape defined by the following equation (1).

In (Expression 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 paraxial radius of curvature at the apex of the lens surface, and k is The conic constants c ₂ , c ₄ and c ₆ are polynomial coefficients. In the aspheric coefficient, “E−i” represents an exponential expression with 10 as the base, that is, “10 ⁻ⁱ ”.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

[Numeric data 1]

Overall focal length Image display surface diagonal length 2ω [°]
18.97 12.6 35.0

Lens data Surface Paraxial radius of curvature Axis surface 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

Aspheric 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


[Numeric data 2]

Overall focal length Image display surface diagonal length 2ω [°]
13.37 9.9 40.6

Lens data surface Paraxial radius of curvature Axis surface 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

Aspheric 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


[Numeric data 3]

Overall focal length Image display surface diagonal length 2ω [°]
17.96 9.9 29.1

Lens data surface Paraxial radius of curvature Axis surface 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

Aspheric 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


[Numeric data 4]

Overall focal length Image display surface diagonal length 2ω [°]
16.50 9.9 32.0

Lens data Surface Paraxial radius of curvature Axis surface 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

Aspheric 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


[Numeric data 5]

Overall focal length Image display surface diagonal length 2ω [°]
25.22 16.8 35.1

Lens data Surface Paraxial radius of curvature Axis surface 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

Aspheric 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



[Numeric data 6]

Overall focal length Image display surface diagonal length 2ω [°]
20.46 12.6 33.1

Lens data Surface Paraxial radius of curvature Axis surface 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

Aspheric 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 first lens L2 second lens L3 third lens L4 fourth lens IP image display surface EP observation surface

Claims (5)

An eyepiece optical system for observing an image displayed on an image display surface, which is arranged in order from the image display surface side to the observation side, a first lens having a positive refractive power and a second lens having a negative refractive power , A third lens, and a fourth lens having a positive refractive power. The average value of the refractive index at the d-line of each lens material of the first lens to the fourth lens 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 length of the third lens and the fourth lens is f34, and the focal length of the eyepiece optical system Let f be
1.520 ≦ Nda ≦ 1.730
−15.0 ≦ (L2R1 + L1R2) / (L2R1−L1R2) ≦ 0.0
0.68 ≦ f34 / f ≦ 1.30
An eyepiece optical system satisfying the following conditional expression: When the distance on the optical axis between the first lens and the second lens is d3, and the distance on the optical axis between the second lens and the third lens is d5,
0.00 ≦ d5 / d3 ≦ 0.75
The eyepiece optical system according to claim 1, wherein the following conditional expression is satisfied.   An observation apparatus comprising: an image display element that displays an image; and an eyepiece optical system according to claim 1 that is used to observe 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 apparatus according to claim 3, wherein the following conditional expression is satisfied. 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 apparatus according to claim 3, wherein the following conditional expression is satisfied.