JP7746064B2 - Eyepiece optical system, and observation device and imaging device having the same - Google Patents

Description

The present invention relates to an eyepiece optical system and is suitable for imaging devices such as digital video cameras, digital still cameras, broadcast cameras, and cameras for silver halide film.

In the field of eyepiece optical systems, to improve visibility, eyepiece optical systems are required that have a sufficiently wide field of view (high magnification), long eye relief, and good correction of various aberrations.

A specific configuration of an eyepiece optical system is known, which includes, from the image display element side toward the pupil plane (aperture plane) on the observer side (observation side), a first lens with positive refractive power, a second lens with negative refractive power, and a third lens with positive refractive power (Patent Document 1).

Japanese Patent Application Laid-Open No. 2020-91340

In the eyepiece optical system disclosed in Patent Document 1, the refractive power of the second lens is strong in order to correct aberrations. In this eyepiece optical system, the second lens has a strongly concave shape facing the object side, which tends to increase the refractive power of the adjacent first lens. When the refractive power of the first lens is strong, the light rays emerging from the image display element are bent more strongly by the first lens. In this case, it may become necessary to increase the angle of emergence of the light rays from the image display element.

However, if the exit angle of the light rays from the image display element becomes large, color inconsistency and a decrease in light intensity can occur. To solve these problems, the eyepiece optical system must be designed to reduce the exit angle from the image display surface (telecentricity must be ensured). However, on the other hand, increasing telecentricity makes it difficult to increase the refractive power of the entire optical system, making it difficult to achieve high magnification.

The present invention therefore aims to provide an eyepiece optical system that has high magnification while maintaining telecentricity.

The eyepiece optical system of the present invention is an eyepiece optical system for observing an image displayed on an image display element, and comprises, in order from the image display element to the observation side, a first lens having positive refractive power, a second lens having negative refractive power, and a third lens having positive refractive power, wherein when the focal length of the eyepiece optical system is f, the focal length of the first lens is f1, the focal length of the third lens is f3, the radius of curvature of the first lens on the observation side is G1R2, the radius of curvature of the second lens on the image display element side is G2R1, the distance from the image display element to the lens surface of the first lens on the image display element side at standard diopter is sk [mm] , the distance between the first lens and the second lens is d3, and the distance between the second lens and the third lens is d5, then:
0.80<f1/f<1.19
0.78<f3/f<1.80
-3.90<(G2R1+G1R2)/(G2R1-G1R2)<-1.00
3.00<sk<7.00
3.00<d3/d5<50.0
1.01≦f1/f3<1.60
The present invention is characterized in that the following conditional expression is satisfied:

The present invention makes it possible to realize a high-magnification eyepiece optical system while maintaining telecentricity.

FIG. 1 is a cross-sectional view of an eyepiece optical system according to a first embodiment. 4A to 4C are aberration diagrams of the eyepiece optical system of Example 1. FIG. 10 is a cross-sectional view of an eyepiece optical system according to a second embodiment. 10A and 10B are aberration diagrams of the eyepiece optical system of Example 2. FIG. 10 is a cross-sectional view of an eyepiece optical system according to a third embodiment. 10A and 10B are aberration diagrams of the eyepiece optical system of Example 3. FIG. 10 is a cross-sectional view of an eyepiece optical system according to a fourth embodiment. 10A and 10B are aberration diagrams of the eyepiece optical system of Example 4. FIG. 10 is a cross-sectional view of an eyepiece optical system according to a fifth embodiment. 10A and 10B are aberration diagrams of the eyepiece optical system of Example 5. FIG. 10 is a cross-sectional view of an eyepiece optical system according to a sixth embodiment. 13A to 13C are aberration diagrams of the eyepiece optical system of Example 6. FIG. 13 is a cross-sectional view of an eyepiece optical system according to a seventh embodiment. 13A to 13C are aberration diagrams of the eyepiece optical system of Example 7. FIG. 13 is a cross-sectional view of an eyepiece optical system according to an eighth embodiment. 13A to 13C are aberration diagrams of the eyepiece optical system of Example 8. FIG. 13 is a cross-sectional view of an eyepiece optical system according to a ninth embodiment. 13A to 13C are aberration diagrams of the eyepiece optical system of Example 9. FIG. 20 is a cross-sectional view of an eyepiece optical system according to a tenth embodiment. 13A to 13C are aberration diagrams of the eyepiece optical system of Example 10. FIG. 1 is a schematic diagram showing an imaging device.

Below, embodiments of the eyepiece optical system of the present invention and an imaging device (observation device) incorporating the same will be described with reference to the accompanying drawings.

Figures 1, 3, 5, 7, 9, 11, 13, 15, 17, and 19 are cross-sectional views showing the lens configuration of the eyepiece optical system L0 of Examples 1 to 10.

In each cross-sectional view, IP is the image display surface of the image display element. Li indicates the ith lens (i is the lens number counted from the image display surface IP toward the viewing side). Additionally, CGI1 indicates the protective member for the image display element, CGI2 indicates the dustproof member for the image display element, CG indicates the protective member for the eyepiece optical system, and EP indicates the eyepoint position on the viewing side. An image display element is an element capable of displaying an image, and can be constructed, for example, from an organic EL panel or a liquid crystal panel.

2, 4, 6, 8, 10, 12, 14, 16, 18, and 20 are aberration diagrams of the eyepiece optical system L0 of Examples 1 to 10. Each aberration diagram shows the amount of aberration when the viewfinder diopter is −1 m ⁻¹ (dpt, diopter), which is the standard diopter.

The spherical aberration diagram shows spherical aberration for the d-line (wavelength 587.56 nm) and F-line (wavelength 486.13 nm). In the astigmatism diagram, S indicates the sagittal image plane, and M indicates the meridional image plane. Distortion aberration is shown for the d-line. The chromatic aberration diagram shows chromatic aberration for the F-line (wavelength 486.13 nm) when the d-line (wavelength 587.56 nm) is used as the reference.

To observe a small image display element (for example, with a diagonal length of approximately 10-20 mm) at a magnification of approximately 35-50 degrees, the eyepiece optical system requires a strong positive refractive power. However, as you move away from the center of the subject (image display element), field curvature and astigmatism become more likely to occur, degrading optical performance.

To improve this field curvature and astigmatism, the eyepiece optical system L0 in each embodiment is configured to have, in order from the image display element side, a first lens L1 with positive refractive power, a second lens L2 with negative refractive power, and a third lens L3 with positive refractive power.

In this case, by appropriately setting the refractive power, lens arrangement, and radius of curvature of each lens, it is possible to realize an eyepiece optical system L0 with high magnification while ensuring telecentricity. Specifically, the eyepiece optical systems of each embodiment are configured to satisfy the following conditional expressions:
0.80<f1/f<1.19 (1)
0.78<f3/f<1.80 (2)
-3.90<(G2R1+G1R2)/(G2R1-G1R2)<-1.00 (3)
3.00<sk<7.00 (4)
3.00<d3/d5<50.0 (5)

Here, f is the focal length of the entire eyepiece optical system L0. f1 is the focal length of the first lens L1. f3 is the focal length of the third lens. G1R2 is the radius of curvature of the lens surface on the observation side of the first lens L1. G2R1 is the radius of curvature of the lens surface on the image display element side of the second lens L2. sk is the distance from the image display element to the lens surface of the first lens L1 on the image display element side at standard diopter (-1 dpt). d3 is the distance between the first lens L1 and the second lens L2. d5 is the distance between the second lens L2 and the third lens L3.

Conditional formula (1) defines the focal length of the first lens L1 and is a condition for achieving both high magnification and telecentricity. If the value of f1/f is below the lower limit of conditional formula (1), the refractive power of the first lens L1 becomes too strong, making it impossible to ensure sufficient telecentricity. If the value of f1/f is above the upper limit of conditional formula (1), the refractive power of the first lens L1 becomes too weak, making it difficult to achieve high magnification.

Conditional formula (2) defines the focal length of the third lens L3 and is a condition for achieving good aberration correction. If the value of f3/f falls below the lower limit of conditional formula (2), the refractive power of the third lens L3 becomes too strong, making aberration correction difficult. If the value of f3/f exceeds the upper limit of conditional formula (2), the refractive power of the third lens L3 becomes too weak, making it difficult to achieve high magnification.

Conditional formula (3) defines the shape of the air lens between the first and second lenses, and is a condition for achieving both field curvature correction and high magnification. If the value of conditional formula (3) falls below the lower limit, the air lens shape becomes closer to symmetry, making it difficult to correct field curvature. If the value of conditional formula (3) exceeds the upper limit, the curvature of the second lens L2 on the image display element side becomes stronger, making it difficult to achieve high magnification.

Conditional formula (4) defines the distance between the image display element and the first lens L1 at standard diopter, and is a condition for achieving both aberration correction and high magnification. If the value of sk is below the lower limit of conditional formula (4), the distance between the image display element and the first lens L1 becomes too short, making it difficult to achieve good aberration correction. If the value of sk is above the upper limit of conditional formula (4), the distance between the image display element and the first lens L1 becomes too wide, making it difficult to ensure sufficient magnification.

Conditional formula (5) defines the relationship between the distance between the first lens L1 and the second lens L2, and the distance between the second lens L2 and the third lens L3. If the value of d3/d5 falls below the lower limit of conditional formula (5), the distance between the second lens L2 and the third lens L3 becomes too large, making it difficult to ensure sufficient magnification. If the value of d3/d5 exceeds the upper limit of conditional formula (5), the distance between the second lens L2 and the third lens L3 becomes too small, making it easier for the lenses to interfere with each other due to assembly errors during manufacturing, which is undesirable.

The above configuration makes it possible to realize a high-magnification eyepiece optical system while ensuring telecentricity.

It is more preferable that at least one of the upper limit and lower limit of the numerical range of conditional expressions (1) to (5) be set as in the following conditional expressions (1a) to (5a), and it is even more preferable that at least one of the upper limit and lower limit be set as in the following conditional expressions (1b) to (5b).
0.83<f1/f<1.17 (1a)
0.79<f3/f<1.60 (2a)
-3.88<(G2R1+G1R2)/(G2R1-G1R2)<-1.50 (3a)
3.50<sk<6.90 (4a)
5.00<d3/d5<48.0 (5a)
0.85<f1/f<1.16 (1b)
0.85<f3/f<1.40 (2b)
-3.86<(G2R1+G1R2)/(G2R1-G1R2)<-1.90 (3b)
4.40<sk<6.80 (4b)
7.00<d3/d5<47.0 (5b)

Next, conditions that the eyepiece optical system L0 of each embodiment should preferably satisfy will be described. It is preferable that the eyepiece optical system L0 of each embodiment should preferably satisfy one or more of the following conditional expressions.
0.30<H/f<0.45 (6)
-1.10<f2/f<-0.50 (7)
-2.00<f1/f2<-0.80 (8)
0.60<f1/f3<1.60 (9)
0.70<(f1/f+|f2|/f+f3/f)/3<1.20 (10)
-1.00<(G1R2+G1R1)/(G1R2-G1R1)<0.50 (11)
1.00<(G2R2+G2R1)/(G2R2-G2R1)<4.00 (12)
19.0<Vd2<26.0 (13)

Here, H is half the diagonal length of the image display surface IP of the image display element. f2 is the focal length of the second lens L2. G1R1 is the radius of curvature of the lens surface of the first lens L1 on the image display element side. G2R2 is the radius of curvature of the lens surface of the second lens L2 on the observation side. Vd2 is the Abbe number of the second lens L2.

Conditional formula (6) defines the relationship between half the diagonal length of the image display surface IP and the focal length of the eyepiece optical system L0. If the value of H/f falls below the lower limit of conditional formula (6), the angle of view when observing the image display surface IP through the eyepiece optical system L0 becomes small, making it difficult to configure the eyepiece optical system L0 with a sufficiently high magnification. If the value of H/f exceeds the upper limit of conditional formula (6), the refractive power of the eyepiece optical system L0 becomes too large relative to the size of the image display element, making it difficult to achieve sufficient aberration correction.

Conditional formula (7) defines the focal length of the second lens L2. If the value of f2/f falls below the lower limit of conditional formula (7), the refractive power of the second lens L2, which has negative refractive power, becomes too strong, making it difficult to achieve a sufficiently high magnification. If the value of f2/f exceeds the upper limit of conditional formula (7), the refractive power of the second lens L2 becomes too weak, making it difficult to perform sufficient aberration correction.

Conditional formula (8) defines the relationship between the focal length of the first lens and the focal length of the second lens. If the value of f1/f2 falls below the lower limit of conditional formula (8), the refractive power of the first lens L1 becomes too large compared to the refractive power of the second lens L2, making it difficult to perform sufficiently good field curvature correction. If the value of f1/f2 exceeds the upper limit of conditional formula (8), the refractive power of the second lens L2 becomes too large compared to the refractive power of the first lens L1, which may result in excessive field curvature correction.

Conditional formula (9) defines the relationship between the focal length of the first lens L1 and the focal length of the third lens L3. If the value of f1/f3 falls below the lower limit of conditional formula (9), the refractive power of the first lens L1 becomes too large, making it difficult to ensure sufficient telecentricity. If the value of f1/f3 exceeds the upper limit of conditional formula (9), the refractive power of the third lens L3 becomes too large compared to the refractive power of the first lens L1. As a result, the balance with the surface of the second lens L2 facing the first lens L1 (the image display element side) becomes poor, making it difficult to achieve sufficiently good aberration correction.

Conditional formula (10) defines the relationship between the focal length of the first lens, the focal length of the second lens, and the focal length of the third lens. If the value of conditional formula (10) is below the lower limit, the refractive power of each lens will be too weak, making it difficult to configure the eyepiece optical system L0 with a sufficiently high magnification. If the value of conditional formula (10) is above the upper limit, lenses with significantly high refractive power will exist from the first lens L1 to the third lens L3, making it difficult to achieve sufficiently good aberration correction.

Conditional expression (11) defines the relationship between the radius of curvature of the first lens L1 on the image display element side and the radius of curvature on the observation side. If the value of conditional expression (11) is below the lower limit, it becomes difficult to perform sufficiently good aberration correction. If the value of conditional expression (11) is above the upper limit, it becomes difficult to ensure sufficient telecentricity.

Conditional expression (12) defines the relationship between the radius of curvature of the second lens L2 on the image display element side and the radius of curvature on the observation side. If the value of conditional expression (12) falls below the lower limit, it becomes difficult to perform sufficiently good aberration correction. If the value of conditional expression (12) exceeds the upper limit, it becomes difficult to configure the eyepiece optical system L0 with a sufficiently high magnification.

Conditional expression (13) defines the Abbe number of the second lens. If the value of Vd2 is below the lower limit of conditional expression (13), chromatic aberration may be overcorrected. If the value of Vd2 is above the upper limit of conditional expression (13), chromatic aberration may be undercorrected.

It is more preferable that at least one of the upper limit and lower limit of the conditions (6) to (13) be set to a value defined by the following conditions (6a) to (13a).
0.30<H/f<0.44 (6a)
-1.07<f2/f<-0.55 (7a)
-1.90<f1/f2<-0.85 (8a)
0.70<f1/f3<1.53 (9a)
0.74<(f1/f+|f2|/f+f3/f)/3<1.17 (10a)
-0.97<(G1R2+G1R1)/(G1R2-G1R1)<0.40 (11a)
1.03<(G2R2+G2R1)/(G2R2-G2R1)<3.60 (12a)
20.0<Vd2<25.0 (13a)

It is more preferable that at least one of the upper limit and lower limit of the conditions (6) to (13) be set to a value defined by the following conditions (6b) to (13b).
0.30<H/f<0.43 (6b)
-1.05<f2/f<-0.60 (7b)
-1.80<f1/f2<-0.90 (8b)
0.80<f1/f3<1.45 (9b)
0.78<(f1/f+|f2|/f+f3/f)/3<1.14 (10b)
-0.94<(G1R2+G1R1)/(G1R2-G1R1)<0.30 (11b)
1.05<(G2R2+G2R1)/(G2R2-G2R1)<3.20 (12b)
21.0<Vd2<24.0 (13b)

In the optical systems of each embodiment, it is preferable to configure the eyepiece optical system L0 with the first lens L1 to the third lens L3, as this allows the eyepiece optical system to be made more compact. However, it is also possible to add another lens to the eyepiece optical system L0. For example, by adding a fourth lens with positive refractive power, the degree of freedom in optical design can be further improved, making it possible to improve the performance of the eyepiece optical system L0.

Next, we will show numerical examples 1 to 10 corresponding to examples 1 to 10, respectively.

In each numerical example, the surface number i (i is a natural number) from the image display surface side is assigned. r is the radius of curvature of each surface (mm), d is the lens thickness or distance (air gap) on the optical axis between the surface with surface number i and the surface with surface number (i+1) (mm), nd is the refractive index for the d-line of the material of the optical element that makes up each surface. νd is the Abbe number for the d-line of the material of the optical element that makes up each surface.

In each numerical example, the surface shape marked with an asterisk in the paraxial radius of curvature column is an aspheric shape defined by the following formula:

Here, x is the distance from the vertex of the lens surface in the direction of the optical axis, h is the height in the direction perpendicular to the optical axis, R is the paraxial radius of curvature at the vertex of the lens surface, k is the conic constant, and A4, A6, ... are polynomial coefficients. In Table 1 and other tables showing aspherical coefficients, "E-zz" represents an exponential expression with base 10, i.e., "10 ^-zz ."

In addition, in each numerical example, the diagonal length of the image display element refers to the diagonal length of the image display element, and is twice the maximum image height on the object surface (image display surface).

[Numerical Example 1]
Unit: mm
At standard diopter focal length f=16.18 Pupil diameter 11
Diagonal length of image display element: 10.2 Maximum image height: 5.1

Surface data surface number rd nd νd
1 ∞ 0.70 1.52100 65.1
2∞2.88
3 ∞ 0.50 1.68000 30.0
4 ∞ (variable)
5 31.117 6.00 1.53500 55.7
6* -8.916 2.66
7* -4.414 2.00 1.63550 23.9
8* -10.903 0.30
9 30.958 6.08 1.53500 55.7
10* -9.971 (variable)
11 ∞ 0.80 1.49171 57.4
12 ∞ 19.00
13 (eye point)

Aspherical data No. 6
K=-1.04134e-001 A 4=-9.74800e-006 A 6= 2.76580e-006

Side 7
K =-7.27616e-001 A 4= 3.10400e-004 A 6= 9.38116e-006

Side 8
K = 2.34021e-002 A 4= 4.21201e-004 A 6= 1.41603e-009

Side 10
K=-6.05374e-001 A 4= 1.10626e-004 A 6= 9.63785e-008

Variable interval 0m-1 -4 +1 -1 (standard diopter)
d 4 2.08 1.00 2.37 1.86
d10 1.28 2.36 0.99 1.50

[Numerical Example 2]
Unit: mm
At standard diopter focal length f=18.42 pupil diameter 12
Diagonal length of image display element: 12.8 Maximum image height: 6.4

Surface data surface number rd nd νd
1 ∞ 0.70 1.52100 65.1
2∞1.35
3 ∞ 0.50 1.68000 30.0
4 ∞ (variable)
5 216.542 7.08 1.53500 55.7
6* -9.041 2.95
7* -4.900 2.00 1.63550 23.9
8* -16.661 0.30
9 81.585 5.57 1.59323 67.0
10* -12.373 0.30
11 -673.142 3.37 1.53514 55.7
12* -24.294 (variable)
13 ∞ 0.80 1.49171 57.4
14 ∞ 23.00
15 (eye point)

Aspherical data No. 6
K =-8.87604e-002 A 4= 4.46088e-004 A 6=-7.20395e-006 A 8= 8.10800e-008

Side 7
K =-9.82045e-001 A 4= 4.84235e-004 A 6=-8.42219e-006 A 8= 6.31210e-008

Side 8
K =-1.17028e+000 A 4= 1.10635e-004 A 6= 1.41603e-009

Side 10
K =-3.80443e-001 A 4= 2.51795e-004 A 6=-1.80937e-006 A 8= 6.78570e-009

Side 12
K = 0.00000e+000 A 4=-6.75556e-005 A 6= 8.97306e-007 A 8=-3.54309e-009

Variable interval 0m-1 -4 +2 -1 (standard diopter)
d 4 2.56 1.00 3.30 2.20
d12 1.73 3.29 1.00 2.09

[Numerical Example 3]
Unit: mm
At standard diopter focal length f=17.51 pupil diameter 11
Diagonal length of image display element: 12 Maximum image height: 6

Surface data surface number rd nd νd
1 ∞ 0.70 1.52100 65.1
2∞3.44
3 ∞ 0.50 1.65100 30.0
4 ∞ (variable)
5 24.066 6.27 1.53500 55.7
6* -12.111 4.23
7* -4.331 2.00 1.65100 21.5
8* -8.694 0.20
9 25.156 5.58 1.53500 55.7
10* -11.855 (variable)
11 ∞ 0.80 1.49171 57.4
12 ∞ 19.00
13 (eye point)

Aspherical data No. 6
K=-1.04134e-001 A 4=-2.42540e-005 A 6= 5.46788e-007

Side 7
K =-9.01627e-001 A 4= 2.06998e-004 A 6= 5.08870e-006 A 8=-3.28321e-008

Side 8
K=-6.22846e-001 A 4= 3.15216e-004 A 6=-5.51616e-007

Side 10
K=-9.75687e-001 A 4= 1.60280e-004 A 6=-2.28236e-007

Variable interval 0m-1 -4 +1 -1 (standard diopter)
d 4 2.32 1.00 2.65 2.03
d10 1.32 2.65 1.00 1.62

[Numerical Example 4]
Unit: mm
Standard diopter focal length f=16.23 Pupil diameter 11
Diagonal length of image display element: 10.2mm, maximum image height: 5.1mm

Surface data surface number rd nd νd
1 ∞ 0.70 1.52100 65.1
2∞2.01
3 ∞ 0.50 1.68000 30.0
4 ∞ (variable)
5 29.282 7.36 1.55130 71.0
6* -8.778 2.53
7* -4.582 2.00 1.63550 23.9
8* -13.088 0.30
9 28.933 6.27 1.53659 49.2
10* -9.698 (variable)
11 ∞ 0.80 1.49171 57.4
12 ∞ 19.00
13 (eye point)

Aspherical data No. 6
K =-1.04134e-001 A 4= 1.06352e-005 A 6= 3.03805e-006

Side 7
K=-7.01845e-001 A 4= 2.53069e-004 A 6= 9.59282e-006

Side 8
K = 5.66191e-001 A 4= 3.84526e-004 A 6= 1.41603e-009

Side 10
K=-9.97732e-001 A 4= 5.64229e-005 A 6= 1.19996e-008

Variable interval 0m-1 -4 +1 -1 (standard diopter)
d 4 2.22 1.01 2.47 1.97
d10 1.25 2.46 0.99 1.49

[Numerical Example 5]
Unit: mm
Standard diopter focal length f=16.24 Pupil diameter 11
Diagonal length of image display element: 10.2mm, maximum image height: 5.1mm

Surface data surface number rd nd νd
1 ∞ 0.70 1.52100 65.1
2∞2.02
3 ∞ 0.50 1.68000 30.0
4 ∞ (variable)
5 19.140 7.70 1.85232 40.1
6* -30.502 4.17
7* -4.003 2.00 1.63550 23.9
8* -7.802 0.09
9 21.628 5.51 1.55431 71.0
10* -11.410 (variable)
11 ∞ 0.80 1.49171 57.4
12 ∞ 19.00
13 (eye point)

Aspherical data No. 6
K=-1.04134e-001 A 4=-2.67246e-005 A 6= 5.76301e-007

Side 7
K =-7.73760e-001 A 4= 8.38429e-004 A 6= 8.87723e-006

Side 8
K =-3.62476e-001 A 4= 7.50661e-004 A 6= 1.41603e-009

Side 10
K =-1.00343e+000 A 4= 1.13945e-004 A 6=-3.64090e-008

Variable interval 0m-1 -4 +1 -1 (standard diopter)
d 4 2.48 1.02 2.60 2.16
d10 1.12 2.57 0.99 1.43

[Numerical Example 6]
Unit: mm
Standard diopter focal length f=16.2 Pupil diameter 11
Diagonal length of image display element: 10.2mm, maximum image height: 5.1mm

Surface data surface number rd nd νd
1 ∞ 0.70 1.52100 65.1
2∞2.00
3 ∞ 0.50 1.68000 30.0
4 ∞ (variable)
5 44.515 5.91 1.49704 81.6
6* -8.757 2.96
7* -4.632 2.00 1.63550 23.9
8* -13.486 0.20
9 58.859 5.74 1.69357 53.2
10* -10.195 (variable)
11 ∞ 0.80 1.49171 57.4
12 ∞ 19.00
13 (eye point)

Aspherical data No. 6
K =-1.04134e-001 A 4= 1.41202e-005 A 6= 1.23699e-006

Side 7
K=-8.64180e-001 A 4=-1.14021e-004 A 6= 1.64058e-006

Side 8
K = 2.80276e-002 A 4= 2.72192e-004 A 6= 1.41603e-009

Side 10
K =-1.00272e+000 A 4= 2.31219e-005 A 6=-8.95421e-008

Variable interval 0m-1 -4 +1 -1 (standard diopter)
d 4 2.13 1.00 2.44 1.88
d10 1.31 2.44 1.00 1.56

[Numerical Example 7]
Unit: mm
Standard diopter focal length f=18.53 Pupil diameter 12
Diagonal length of image display element: 12.8 Maximum image height: 6.4

Surface data surface number rd nd νd
1 ∞ 0.70 1.52100 65.1
2∞1.99
3 ∞ 0.50 1.68000 30.0
4 ∞ (variable)
5 24.883 5.07 1.49079 81.0
6* -14.440 3.64
7* -5.715 2.00 1.63550 23.9
8* -22.418 0.20
9 81.634 3.41 1.53590 55.7
10* -18.766 0.20
11 87.864 4.71 1.69425 53.2
12* -17.235 (variable)
13 ∞ 0.80 1.49171 57.4
14 ∞ 23.00
15 (eye point)

Aspherical data No. 6
K =-9.67157e-001 A 4=-1.54092e-004 A 6=-1.56282e-007 A 8= 7.51010e-009

Side 7
K =-6.37451e-001 A 4= 1.48514e-006 A 6= 2.77128e-006 A 8= 3.72321e-008

Side 8
K =-1.02148e+000 A 4= 1.92202e-005 A 6= 1.41603e-009

Side 10
K =-9.99975e-001 A 4= 1.21897e-004 A 6= 8.14415e-009 A 8= 4.01517e-010

Side 12
K = 0.00000e+000 A 4= 4.77748e-005 A 6=-6.97641e-009 A 8=-2.65928e-010

Variable interval 0m-1 -4 +2 -1 (standard diopter)
d 4 2.91 1.29 3.62 2.53
d12 1.70 3.32 1.00 2.07

[Numerical Example 8]
Unit: mm
At standard diopter focal length f=19.31 pupil diameter 12
Diagonal length of image display element: 16 Maximum image height: 8

Surface data surface number rd nd νd
1 ∞ 0.70 1.52100 65.1
2∞0.09
3 ∞ 0.50 1.68000 30.0
4 ∞ (variable)
5 68.876 3.72 1.53788 55.7
6* -11.313 4.04
7* -6.648 2.00 1.63550 23.9
8* -212.262 0.30
9 -284.386 8.17 1.59997 67.0
10* -10.158 0.30
11 44.210 5.29 1.54012 55.7
12* -55.777 (variable)
13 ∞ 0.80 1.49171 57.4
14 ∞ 23.00
15 (eye point)

Aspherical data No. 6
K =-1.94993e+000 A 4= 4.32216e-004 A 6=-5.29833e-006 A 8= 2.29891e-008

Side 7
K =-5.49467e-001 A 4= 3.50805e-004 A 6=-5.33604e-006 A 8= 4.36609e-008

Side 8
K = 1.00005e+000 A 4=-2.03890e-005 A 6= 1.41603e-009

Side 10
K =-4.58806e-001 A 4= 7.59205e-005 A 6=-1.76954e-007 A 8= 3.73986e-009

Side 12
K = 0.00000e+000 A 4=-5.39967e-005 A 6= 7.59519e-009 A 8= 5.10223e-010

Variable interval 0m-1 -4 +2 -1 (standard diopter)
d 4 2.56 0.79 3.28 2.10
d12 1.57 3.35 0.93 2.00

[Numerical Example 9]
Unit: mm
At standard diopter focal length f=18.51 pupil diameter 12
Diagonal length of image display element: 12.8 Maximum image height: 6.4

Surface data surface number rd nd νd
1 ∞ 0.70 1.52100 65.1
2∞1.29
3 ∞ 0.50 1.68000 30.0
4 ∞ (variable)
5 70.066 6.02 1.49010 81.0
6* -11.907 3.51
7* -6.442 2.00 1.63550 23.9
8* -47.976 0.10
9 85.738 5.59 1.76813 49.2
10* -13.015 0.10
11 -58.256 3.52 1.53506 55.7
12* -18.774 (variable)
13 ∞ 0.80 1.49171 57.4
14 ∞ 23.00
15 (eye point)

Aspherical data No. 6
K = 2.39678e-001 A 4=-2.60035e-005 A 6= 6.07258e-007 A 8=-4.98512e-009

Side 7
K =-1.01159e+000 A 4=-3.90531e-004 A 6=-8.39438e-007 A 8= 2.92836e-008

Side 8
K =-1.00082e+000 A 4= 9.16494e-006 A 6= 1.41603e-009

Side 10
K =-9.87266e-001 A 4= 1.24519e-005 A 6= 3.49982e-007 A 8= 4.56903e-010

Side 12
K = 0.00000e+000 A 4=-6.12252e-006 A 6= 5.28987e-009 A 8=-6.45945e-010

Variable interval 0m-1 -4 +2 -1 (standard diopter)
d 4 2.56 1.00 3.29 2.20
d12 1.72 3.29 1.00 2.08

Numerical Example 10
Unit: mm
At standard diopter focal length f=18.52 pupil diameter 12
Diagonal length of image display element: 12.8 Maximum image height: 6.4

Surface data surface number rd nd νd
1 ∞ 0.70 1.52100 65.1
2∞2.19
3 ∞ 0.50 1.68000 30.0
4 ∞ (variable)
5 23.866 5.77 1.53554 55.7
6* -11.281 2.96
7* -6.376 2.00 1.63550 23.9
8* -36.228 0.87
9 -35.267 4.32 1.53588 55.7
10* -8.979 0.30
11 206.429 4.26 1.53540 55.7
12* -26.041 (variable)
13 ∞ 0.80 1.49171 57.4
14 ∞ 23.00
15 (eye point)

Aspherical data No. 6
K =-1.00765e+000 A 4= 4.54474e-005 A 6=-1.08092e-006 A 8= 5.02629e-009

Side 7
K =-6.49957e-001 A 4=-7.02238e-005 A 6= 2.61162e-006 A 8= 1.81818e-008

Side 8
K = 1.00585e+000 A 4=-1.63746e-005 A 6= 1.41603e-009

Side 10
K =-9.99999e-001 A 4= 1.99139e-005 A 6= 3.70553e-007 A 8= 6.15468e-009

Side 12
K = 0.00000e+000 A 4=-9.44136e-005 A 6= 3.81756e-007 A 8=-1.30067e-009

Variable interval 0m-1 -4 +2 -1 (standard diopter)
d 4 2.78 1.19 3.53 2.45
d12 1.75 3.33 1.00 2.08

The table below shows the various values for each example.

[Imaging device]
Next, an embodiment of an imaging device using an observation device having the eyepiece optical system L0 shown in each example will be described with reference to Fig. 21. Fig. 21 is a schematic diagram of the main parts of an imaging device equipped with the eyepiece optical system L0 of each example. An object image formed by the imaging optical system 101 is converted into an electrical signal by an imaging element 102, which is a photoelectric conversion element. A CCD sensor, a CMOS sensor, or the like is used as the imaging element 102.

The output signal from the image sensor 102 is processed in the image processing circuit 103 to form an image. The formed image is recorded on a recording medium 104, such as a semiconductor memory, magnetic tape, or optical disk. The image formed in the image processing circuit 103 is displayed on a viewfinder optical system unit (observation device) 105. The observation device 105 includes an image display element 1051 and an eyepiece optical system 1052 in each embodiment. The image display element 1051 is composed of a liquid crystal display element (LCD), organic EL, or the like.

By applying an observation device having the eyepiece optical system of the present invention to an imaging device such as a digital camera or video camera, it is possible to obtain an imaging device equipped with a high-magnification observation device with little color unevenness or loss of light intensity.

The above describes preferred embodiments of the present invention, but the present invention is not limited to these embodiments, and various modifications and variations are possible within the scope of the invention.

L0 Eyepiece optical system L1 First lens L2 Second lens L3 Third lens

Claims (10)

An eyepiece optical system for observing an image displayed on an image display element,
a first lens having a positive refractive power, a second lens having a negative refractive power, and a third lens having a positive refractive power, which are arranged in this order from the image display element to the observation side;
When the focal length of the eyepiece optical system is f, the focal length of the first lens is f1, the focal length of the third lens is f3, the radius of curvature of the first lens on the observation side is G1R2, the radius of curvature of the second lens on the image display element side is G2R1, the distance from the image display element to the lens surface of the first lens on the image display element side at standard diopter is sk [mm] , the distance between the first lens and the second lens is d3, and the distance between the second lens and the third lens is d5,
0.80<f1/f<1.19
0.78<f3/f<1.80
-3.90<(G2R1+G1R2)/(G2R1-G1R2)<-1.00
3.00<sk<7.00
3.00<d3/d5<50.0
1.01≦f1/f3<1.60
An eyepiece optical system characterized by satisfying the following conditional expression: When the focal length of the second lens is f2,
-1.10<f2/f<-0.50
2. The eyepiece optical system according to claim 1, wherein the following condition is satisfied: When the focal length of the second lens is f2,
-2.00<f1/f2<-0.80
3. The eyepiece optical system according to claim 1, wherein the following condition is satisfied: When the focal length of the second lens is f2,
0.70<(f1/f+|f2|/f+f3/f)/3<1.20
4. The eyepiece optical system according to claim 1 , wherein the following condition is satisfied: When the radius of curvature of the first lens on the image display element side is G1R1,
-1.00<(G1R2+G1R1)/(G1R2-G1R1)<0.50
5. The eyepiece optical system according to claim 1 , wherein the following condition is satisfied: When the radius of curvature of the second lens on the observation side is G2R2,
1.00<(G2R2+G2R1)/(G2R2-G2R1)<4.00
6. The eyepiece optical system according to claim 1 , wherein the following condition is satisfied: When the Abbe number of the second lens is Vd2,
19.0<Vd2<26.0
7. The eyepiece optical system according to claim 1, wherein the following condition is satisfied: an image display element for displaying an image;
An observation device comprising the eyepiece optical system according to any one of claims 1 to 7 for observing an image displayed on the image display element. When half the diagonal length of the image display surface of the image display element is H,
0.30<H/f<0.45
9. The observation device according to claim 8 , wherein the following condition is satisfied: An imaging element;
An imaging device comprising the observation device according to claim 8 or 9.