JP6436680B2 - Viewfinder optical system, observation apparatus having the same, and imaging apparatus - Google Patents

Description

  The present invention relates to a viewfinder optical system and an observation apparatus and an imaging apparatus having the same, and is suitable for observing an image displayed on an image display element in an electronic viewfinder used in, for example, a video camera, a still camera, and a broadcast camera. It is a thing.

  2. Description of the Related Art Conventionally, electronic viewfinders used in optical devices such as video cameras and broadcast cameras are equipped with a finder optical system for magnifying and observing an image displayed on a liquid crystal screen provided inside the camera.

  2. Description of the Related Art In recent years, electronic viewfinders that have a wide field of view and can display a large image have been demanded with the enhancement of functions of imaging devices. As a method for realizing such a demand, there are a method of enlarging an image display surface such as a liquid crystal screen and a method of increasing the observation magnification of the finder optical system.

  Here, when the image display surface is enlarged, the size of the finder is increased. Therefore, in order to reduce the size of the finder as a whole, it is preferable to increase the observation magnification of the finder optical system. In order to increase the observation magnification of the finder optical system, it is necessary to increase the positive refractive power in the finder optical system. Here, if the finder optical system is configured with only a lens having a positive refractive power (positive lens), many axial chromatic aberrations, lateral chromatic aberrations and the like are generated, and it is difficult to correct them. Therefore, in order to obtain a high-definition observation image while increasing the observation magnification of the finder optical system, it is possible to configure the finder optical system using a lens having a negative refractive power (negative lens) in addition to the positive lens. preferable. Thereby, an observation image in which the longitudinal chromatic aberration and the lateral chromatic aberration are corrected well can be obtained.

  There is also a need for a finder with a long eye relief that can be used even when the user is wearing glasses.

  Patent Document 1 discloses a finder optical system including a positive lens, a negative lens, and a positive lens in order from the image display surface side to the observation side (eye point side). By appropriately setting the shape of the positive lens arranged on the observation side, a finder optical system in which coma and distortion are satisfactorily corrected is achieved.

JP 2010-175895 A

  As described above, in order to realize a finder optical system having a long eye relief and a wide viewing angle, a positive lens, a negative lens, and a positive lens are sequentially arranged from the image display surface side to the observation side (eye point side). A viewfinder optical system is known.

  In the finder optical system of Patent Document 1, the distance between the positive lens closest to the image display surface and the image display surface is widened in order to increase the magnification during observation. As a result, the viewfinder optical system tends to be enlarged.

  An object of the present invention is to provide a finder optical system having a long eye relief, a wide viewing angle, a small size, and high optical performance, and an observation apparatus and an imaging apparatus having the same.

The finder optical system according to the present invention includes 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 order from the image display surface side to the observation side. A finder optical system having a radius of curvature of the surface on the observation side of the first lens of R12, a radius of curvature of the surface of the second lens on the image display surface of R21, and a diopter of -1.0 diopter. When the distance on the optical axis from the image display surface to the image display surface side of the first lens is D1, the focal length of the entire finder optical system is f , and the focal length of the third lens is f3 ,
2.00 <(R21 + R12) / (R21-R12) <100.00
0.15 <D1 / f <1.00
1.04 ≦ f3 / f <1.50
The following conditional expression is satisfied.

  According to the present invention, a finder optical system having a long eye relief, a wide viewing angle, a small size, and high optical performance can be obtained.

Sectional view of the lens of the finder optical system of Example 1 of the present invention Each aberration diagram of the finder optical system of Example 1 of the present invention Sectional view of the lens of the finder optical system of Example 2 of the present invention Each aberration diagram of the finder optical system according to Example 2 of the present invention Sectional view of the lens of the finder optical system of Example 3 of the present invention Each aberration diagram of the finder optical system according to Example 3 of the present invention Sectional view of a finder optical system according to a fourth embodiment of the present invention Each aberration diagram of the finder optical system according to Example 4 of the present invention Sectional view of the finder optical system of Reference Example 1 of the present invention Each aberration diagram of the finder optical system of Reference Example 1 of the present invention Schematic diagram of main parts of an imaging apparatus of the present invention

  Hereinafter, a finder optical system of the present invention, an observation apparatus having the same, and an imaging apparatus will be described in detail with reference to the accompanying drawings. In the finder optical system of the present invention, a first lens G1 having a positive refractive power, a second lens G2 having a negative refractive power, and a third lens having a positive refractive power are sequentially arranged from the image display surface side to the observation side (eye point side). Consists of G3.

  FIG. 1 is a lens cross-sectional view of the finder optical system of Example 1 at a diopter of −1.0 diopter (reference state). FIG. 2 is an aberration diagram in the reference state of the finder optical system according to Example 1. FIG. 3 is a lens cross-sectional view of the finder optical system of Example 2 at a diopter of −1.0 diopter (reference state). FIG. 4 is an aberration diagram of the finder optical system of Example 2 in the reference state.

  FIG. 5 is a lens cross-sectional view of the finder optical system of Example 3 at a diopter of −1.0 diopter (reference state). FIG. 6 is an aberration diagram of the finder optical system according to Example 3 in the reference state. FIG. 7 is a lens cross-sectional view of the finder optical system of Example 4 at a diopter of −1.0 diopter (reference state). FIG. 8 is an aberration diagram of the finder optical system according to Example 4 in the reference state.

FIG. 9 is a lens cross-sectional view of the finder optical system of Reference Example 1 at a diopter of −1.0 diopter (reference state). FIG. 10 is an aberration diagram of the finder optical system of Reference Example 1 in the reference state.

  FIG. 11 is a schematic diagram of a main part of an image pickup apparatus including the finder optical system according to the present invention.

  The finder optical system of each embodiment is used for an electronic view finder 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. DP is an image display element such as a liquid crystal element or an organic EL element. CG is a protective plate for the image display element DP. PG is a protective plate for protecting the finder optical system. EP is an eye point for a user to observe an image displayed on the image display element. Here, the eye point EP may be moved in the optical axis direction as long as the off-axis light beam emitted from the image display element DP can pass through the pupil of the observer.

  Each aberration diagram shows an aberration that occurs in the finder optical system of each example when the finder diopter is in the reference state.

  In the spherical aberration diagram, spherical aberrations with respect to d-line (wavelength 587.6 nm) and g-line (wavelength 435.8 nm) are shown. In the astigmatism diagram, ΔS is a sagittal image plane, and ΔM is a meridional image plane. Distortion is shown for the d-line. The chromatic aberration diagram shows the chromatic aberration at the g-line.

  Here, when an attempt is made to realize a finder optical system having a long eye relief and a wide viewing angle, there is a possibility that an observation image becomes unclear. In the present invention, by forming a finder optical system using two positive lenses and one negative lens, it is possible to obtain a high-definition observation image in which axial chromatic aberration and lateral chromatic aberration are well corrected.

  As described above, in the present invention, the first lens G1 having a positive refractive power, the second lens G2 having a negative refractive power, and the third lens G3 having a positive refractive power are sequentially arranged from the image display surface side to the observation side. Is configured.

  Further, the present invention is configured such that the positive refractive power of the first lens G1 is stronger than the positive refractive power of the third lens G3. Thereby, the height of the light beam incident on the second lens G2 can be lowered, and the coma aberration generated in the second lens G2 can be reduced. Also, by using two positive lenses, off-axis rays can be gently refracted, and as a result, the occurrence of coma and higher-order aberrations can be suppressed.

  In each embodiment, the first lens G1 is a biconvex lens, the second lens G2 is a biconcave lens, and the third lens G3 is a biconvex lens. By making the shape of each lens in this way, the refractive power of each lens can be increased, and as a result, the total lens length can be shortened.

  Here, in the finder optical system of each embodiment, diopter adjustment can be performed by integrally moving all the lenses from the first lens G1 to the third lens G3 in the optical axis direction. By moving each lens integrally, fluctuations in coma due to diopter changes can be reduced.

Further, the finder optical system of each example satisfies the following conditional expression.
2.00 <(R21 + R12) / (R21−R12) <100.00 (1)
0.15 <D1 / f <1.00 (2)

  Here, the curvature radius (paraxial curvature radius) of the surface on the observation side of the first lens G1 is R12, and the curvature radius (paraxial curvature radius) of the image display surface side of the second lens G2 is R21. . Further, the distance on the optical axis from the image display surface to the image display surface side surface of the first lens G1 when the diopter is -1.0 diopter is D1, and the focal length of the entire finder optical system is f. .

  Conditional expression (1) defines the shape of the air lens formed by the first lens G1 and the second lens G2. Conditional expression (1) indicates that the air lens has a concave meniscus shape on the screen display surface side.

  Exceeding the upper limit value of conditional expression (1) is not preferable because the curvature of the surface on the observation side of the first lens G1 becomes too small and it becomes difficult to sufficiently correct coma.

  Exceeding the lower limit value of conditional expression (1) is not preferable because the curvature of the observation side surface of the first lens G1 becomes too large and a large amount of spherical aberration and astigmatism occur. Further, the height of the light beam incident on the second lens G2 becomes too low, and it is necessary to increase the refractive power of the second lens G2 in order to lengthen the eye relief. As a result, many spherical aberrations and astigmatism occur in the second lens G2, which is not preferable.

  Exceeding the upper limit of conditional expression (2) is preferable because the distance on the optical axis from the image display surface to the image display surface side of the first lens G1 becomes too wide and the total length of the finder optical system increases. Absent. Further, the width of the light beam incident on the first lens G1 is widened, and the effective diameter of the first lens G1 is increased, which is not preferable. If the lower limit of conditional expression (2) is exceeded, the distance on the optical axis from the image display surface to the image display surface side of the first lens G1 becomes too narrow, and the diopter adjustment in the minus direction is appropriately performed. This is not preferable because it is difficult to perform.

In each embodiment, it is preferable to set the numerical ranges of conditional expressions (1) and (2) as follows.
2.10 <(R21 + R12) / (R21−R12) <20.00 (1a)
0.20 <D1 / f <0.80 (2a)

More preferably, the numerical ranges of the conditional expressions (1) and (2) are set as follows.
2.20 <(R21 + R12) / (R21−R12) <10.00 (1b)
0.28 <D1 / f <0.70 (2b)

Furthermore, in each embodiment, it is more preferable to satisfy one or more of the following conditional expressions.
0.30 <f1 / f <1.00 (3)
−1.10 <f2 / f <−0.50 (4)
0.50 <f3 / f <2.50 (5)
5.0 <νd2 <32.0 (6)
−1000.00 <(R31 + R22) / (R31−R22) <10.00 (7)

  Here, the curvature radius (paraxial curvature radius) of the surface on the observation side of the second lens G2 is R22, and the curvature radius (paraxial curvature radius) of the image display surface side of the third lens G3 is R31. . The focal length of the first lens G1 is f1, the focal length of the second lens G2 is f2, and the focal length of the third lens G3 is f3. Further, the Abbe number based on the d-line of the material of the second lens G2 is denoted by νd2.

The Abbe number νd is NF, NC, Nd when the refractive indices of the materials for the F line (486.1 nm), C line (656.3 nm), and d line (587.6 nm) are respectively
νd = (Nd−1) / (NF−NC)
It is a numerical value represented by

  If the upper limit of conditional expression (3) is exceeded and the focal length f1 of the first lens G1 becomes longer, the refractive power of the first lens G1 becomes too weak and it becomes difficult to sufficiently correct coma. It is not preferable.

  If the lower limit of conditional expression (3) is exceeded and the focal length f1 of the first lens G1 becomes shorter, the refractive power of the first lens G1 becomes too strong, and the optical axis of the off-axis light incident on the second lens G2 The height from is lowered. As a result, it becomes difficult to realize a finder optical system having a wide viewing angle, which is not preferable.

  If the upper limit of conditional expression (4) is exceeded and the focal length f2 of the second lens G2 is shortened, the refractive power of the second lens G2 becomes too strong and the coma aberration is excessively corrected. It is not preferable. Further, the height of the light beam incident on the third lens G3 is increased, and the diameter of the third lens G3 is increased, which is not preferable.

  If the lower limit of conditional expression (4) is exceeded and the focal length f2 of the second lens G2 becomes longer, the refractive power of the second lens G2 becomes too weak, and the coma aberration is sufficiently corrected in the second lens G2. Is not preferable because it becomes difficult.

  If the upper limit of conditional expression (5) is exceeded and the focal length f3 of the third lens G3 becomes longer, the refractive power of the third lens G3 becomes too weak and it is difficult to realize a finder optical system with a wide viewing angle. Therefore, it is not preferable.

  If the lower limit of conditional expression (5) is exceeded and the focal length f3 of the third lens G3 becomes shorter, the refractive power of the third lens G3 becomes too strong, and it becomes difficult to ensure a sufficiently long eye relief. Therefore, it is not preferable.

  If the Abbe number νd2 with reference to the d-line of the material of the second lens G2 exceeds the upper limit value of the conditional expression (6), it is difficult to sufficiently correct chromatic aberration, which is not preferable.

  If the Abbe number ν2 with respect to the d-line of the material of the second lens G2 exceeds the lower limit of the conditional expression (6), the chromatic aberration is excessively corrected, which is not preferable. Moreover, since the material which can be selected as a lens material will be limited, it is not preferable.

  Conditional expression (7) defines the shape of the air lens formed by the second lens G2 and the third lens G3. When the upper limit value of conditional expression (7) is exceeded, the curvature of the surface of the third lens G3 on the image display surface side becomes too small, and it is difficult to realize a finder optical system with a wide viewing angle. Absent.

  When the lower limit value of conditional expression (7) is exceeded, the curvature of the surface on the observation side of the second lens G2 becomes too small, and it becomes difficult to sufficiently correct coma in the second lens G2. .

In each embodiment, it is preferable to set the numerical ranges of conditional expressions (3) to (7) as follows.
0.50 <f1 / f <0.90 (3a)
−1.05 <f2 / f <−0.60 (4a)
0.60 <f3 / f <2.00 (5a)
10.0 <νd2 <30.5 (6a)
−500.00 <(R31 + R22) / (R31−R22) <5.00 (7a)

More preferably, the numerical ranges of the conditional expressions (3) to (7) are set as follows.
0.60 <f1 / f <0.86 (3b)
−1.04 <f2 / f <−0.65 (4b)
0.70 <f3 / f <1.50 (5b)
20.0 <νd2 <30.3 (6b)
−350.00 <(R31 + R22) / (R31−R22) <4.00 (7b)

Furthermore, when the finder optical system of each embodiment is used in an observation apparatus that observes an image displayed on the image display surface, it is preferable that one or more of the following conditional expressions are satisfied.
0.20 <H / D13 <0.80 (8)
0.20 <H / f <0.80 (9)

  Here, the diagonal length of the image display surface is H, and the distance on the optical axis from the image display surface side surface of the first lens G1 to the observation side surface of the third lens G3 at a diopter of −1.0 diopter. Let D13 be the focal length of the entire finder optical system.

  If the upper limit of conditional expression (8) is exceeded and the image display surface becomes too large, the height of the light beam incident on the first lens G1 increases and the effective diameter of the first lens G1 increases, which is not preferable.

  If the lower limit of conditional expression (8) is exceeded and the image display surface becomes too small, it is necessary to increase the magnification of the finder optical system in order to display a large image. In order to increase the magnification of the finder optical system, increasing the refractive power of the entire finder optical system is not preferable because it is difficult to correct various aberrations satisfactorily. If the lower limit of conditional expression (8) is exceeded, the distance D13 on the optical axis from the image display surface side surface of the first lens G1 to the observation side surface of the third lens G3 becomes too large, and the viewfinder This is not preferable because the optical system becomes large.

  If the upper limit of conditional expression (9) is exceeded and the image display surface becomes too large, the height of the light beam incident on the first lens G1 increases and the effective diameter of the first lens G1 increases, which is not preferable. If the upper limit of conditional expression (9) is exceeded and the focal length f of the entire finder optical system becomes shorter, the refractive power of the entire finder optical system becomes too strong, and various aberrations are corrected favorably. This is not preferable because it becomes difficult.

  If the lower limit of conditional expression (9) is exceeded and the image display surface becomes too small, it is necessary to increase the magnification of the finder optical system in order to display a large image. In order to increase the magnification of the finder optical system, increasing the refractive power of the entire finder optical system is not preferable because it is difficult to correct various aberrations satisfactorily. If the focal length f of the entire finder optical system exceeds the lower limit of conditional expression (9), it is difficult to realize a finder optical system with a wide viewing angle, which is not preferable.

In each embodiment, the numerical ranges of conditional expressions (8) and (9) are preferably set as follows.
0.25 <H / D13 <0.60 (8a)
0.30 <H / f <0.60 (9a)

More preferably, the numerical ranges of conditional expressions (8) and (9) should be set as follows.
0.30 <H / D13 <0.50 (8b)
0.33 <H / f <0.50 (9b)

Next, Numerical Examples 1 to 4 corresponding to Embodiments 1 to 4 of the present invention and Numerical Reference Example 1 corresponding to Reference Example 1 will be shown. In each numerical example, i indicates the order of the optical surfaces from the image display surface side. ri is the radius of curvature of the i-th optical surface (i-th surface), di is the distance between the i-th surface and the i + 1-th surface, and ndi and νdi are the refractions of the material of the i-th optical member with respect to the d-line, respectively. Indicates the rate and Abbe number. r1 represents the image display surface, and r2 represents the surface on the observation side of the protective plate for protecting the image display surface. The most observing surface shows an eye point EP.

Further, when K is the eccentricity, A4, A6, and A8 are aspherical coefficients, and the displacement in the optical axis direction at the position of the height h from the optical axis with respect to the surface vertex is x, the aspherical surface. The shape is
x = (h ² / R) / [1+ [1− (1 + K) (h / R) ² ] ^1/2 ] + A4h ⁴ + A6h ⁶ + A8h ⁸
Is displayed. Where R is the paraxial radius of curvature. A surface with * on the right side of the surface number indicates an aspheric surface. The display of “e-Z” means “10 ^−Z ”.

[Numerical Example 1]
Unit mm
Surface data surface number rd nd νd
1 (Image display surface)
2 ∞ 0.70 1.51633 64.1
3 ∞ (variable)
4 * 8.357 5.10 1.49171 57.4
5 * -6.143 1.80
6 * -8.542 1.00 1.58500 30.2
7 10.376 0.30
8 10.307 3.62 1.49171 57.4
9 * -10.456 (variable)
10 ∞ 1.00 1.49 171 57.4
11 ∞ 11.00
12 (Eyepoint)
Aspheric data 4th surface
K = -5.45607e + 000
5th page
K = -1.03996e + 000 A 4 = 3.92745e-004 A 6 = -3.00145e-006 A 8 = 2.12118e-008
6th page
K = -9.64168e-001 A 4 = 9.25026e-004 A 6 = -1.74638e-006
9th page
K = -2.06489e + 000 A 4 = 1.55012e-004 A 6 = 5.96927e-006
Various data diopters [diopter] -1.0 -3.0 3.0
Focal length 10.76 10.76 10.76
d 3 6.76 6.52 7.21
d 9 0.92 1.16 0.46

[Numerical Example 2]
Unit mm
Surface data surface number rd nd νd
1 (Image display surface)
2 ∞ 0.70 1.51633 64.1
3 ∞ (variable)
4 * 7.370 5.10 1.53160 55.8
5 * -7.506 1.11
6 * -15.562 1.00 1.63550 23.9
7 9.481 1.50
8 16.347 3.62 1.53160 55.8
9 * -9.931 (variable)
10 ∞ 1.00 1.49 171 57.4
11 ∞ 11.00
12 (Eyepoint)
Aspheric data 4th surface
K = -5.36454e + 000 A 4 = -4.01790e-005
5th page
K = -9.80945e-001 A 4 = 5.59152e-004 A 6 = -2.49735e-006 A 8 = 3.04155e-008
6th page
K = -1.05481e + 000 A 4 = 9.39317e-004 A 6 = -2.62140e-006
9th page
K = -2.12145e + 000 A 4 = -9.53563e-005 A 6 = 1.27891e-006
Various data diopters [diopter] -1.0 -3.0 3.0
Focal length 10.73 10.73 10.73
d 3 5.34 5.10 5.79
d 9 2.34 2.58 1.89

[Numerical Example 3]
Unit mm
Surface data surface number rd nd νd
1 (Image display surface)
2 ∞ 0.70 1.51633 64.1
3 ∞ (variable)
4 * 8.368 3.50 1.53160 55.8
5 * -8.076 1.50
6 * -10.064 1.00 1.63550 23.9
7 17.581 1.00
8 32.576 4.00 1.53160 55.8
9 * -7.391 (variable)
10 ∞ 1.00 1.49 171 57.4
11 ∞ 11.00
12 (Eyepoint)
Aspheric data 4th surface
K = -5.36684e + 000 A 4 = 3.97666e-004
5th page
K = -1.07584e + 000 A 4 = 7.50887e-004 A 6 = 8.20911e-006 A 8 = 1.81876e-009
6th page
K = -9.91174e-001 A 4 = 3.62930e-004 A 6 = 5.02784e-006
9th page
K = -2.11528e + 000 A 4 = -4.90386e-004 A 6 = 3.52245e-006
Various data diopters [diopter] -1.0 -3.0 3.0
Focal length 10.73 10.73 10.73
d 3 5.14 4.90 5.60
d 9 1.54 1.77 1.08

[Numerical Example 4]
Unit mm
Surface data surface number rd nd νd
1 (Image display screen)
2 ∞ 0.70 1.51633 64.1
3 ∞ (variable)
4 * 6.916 5.10 1.53160 55.8
5 * -6.660 1.28
6 * -16.531 1.00 1.63550 23.9
7 10.360 1.50
8 20.120 3.62 1.53160 55.8
9 * -9.671 (variable)
10 ∞ 1.00 1.49 171 57.4
11 ∞ 11.00
12 (Eyepoint)
Aspheric data 4th surface
K = -5.51942e + 000 A 4 = 1.78189e-004
5th page
K = -8.51736e-001 A 4 = 4.66404e-004 A 6 = -3.24636e-006 A 8 = 4.16130e-008
6th page
K = -8.97278e-002 A 4 = 4.62514e-004 A 6 = -6.03029e-006
9th page
K = -2.11657e + 000 A 4 = -2.11200e-004 A 6 = -2.28052e-007
Various data diopters [diopter] -1.0 -3.0 3.0
Focal length 9.80 9.80 9.80
d 3 4.57 4.37 4.95
d 9 1.11 1.31 0.73

[Numerical reference example 1 ]
Unit mm
Surface data surface number rd nd νd
1 (Image display surface)
2 ∞ 0.70 1.51633 64.1
3 ∞ (variable)
4 * 18.060 5.10 1.49171 57.4
5 * -7.031 3.00
6 * -9.227 1.00 1.58500 30.2
7 12.518 1.51
8 10.062 3.62 1.49171 57.4
9 * -8.190 (variable)
10 ∞ 1.00 1.49 171 57.4
11 ∞ 10.00
12 (Eyepoint)
Aspheric data 4th surface
K = -5.47962e + 000
5th page
K = -1.26681e + 000 A 4 = 7.56145e-004 A 6 = 7.52290e-006 A 8 = -2.65773e-007
6th page
K = -1.01572e + 000 A 4 = 9.90874e-004 A 6 = 1.33541e-005
9th page
K = -2.07154e + 000 A 4 = 3.51837e-005 A 6 = 1.07947e-005
Various data diopters [diopter] -1.0 -3.0 3.0
Focal length 13.0 13.0 13.0
d 3 3.83 3.49 4.50
d 9 1.54 1.88 0.87

  Subsequently, the numerical values of the conditional expressions described above in the respective numerical examples are shown in Table 1.

  Next, an embodiment of an imaging apparatus using the finder optical system shown in each example will be described with reference to FIG. The object image formed by the imaging optical system 101 is converted into an electric signal by the imaging element 102 which is a photoelectric conversion element. As the imaging element 102, a CCD sensor, a CMOS sensor, or the like is used.

  An output signal from the image sensor 102 is processed by the image processing circuit 103 to form an image. The formed image is recorded on a recording medium such as a semiconductor memory, a magnetic tape, or an optical disk. The image formed in the image processing circuit 103 is displayed on the finder unit 105. The finder unit 105 includes an image display element 1051 and a finder optical system 1052 of each embodiment. The image display element 1051 includes a liquid crystal display element LCD, a CRT, or the like.

  In this way, by applying the finder optical system of the present invention to an imaging apparatus such as a digital camera or a video camera, an imaging apparatus having a wide viewing angle, a small size, and high optical performance can be obtained.

G1 1st lens G2 2nd lens G3 3rd lens EP Eye point DP Image display element CG Image display element protection plate PG Viewfinder optical system protection plate

Claims (10)

A finder optical system that is arranged in order from the image display surface side to the observation side, and includes 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,
The radius of curvature of the surface on the observation side of the first lens is R12, the radius of curvature of the surface on the image display surface side of the second lens is R21, and the first lens from the image display surface when the diopter is −1.0 diopter. When the distance on the optical axis to the image display surface side is D1, the focal length of the entire finder optical system is f , and the focal length of the third lens is f3 ,
2.00 <(R21 + R12) / (R21-R12) <100.00
0.15 <D1 / f <1.00
1.04 ≦ f3 / f <1.50
A finder optical system characterized by satisfying the following conditional expression: When the focal length of the first lens is f1,
0.30 <f1 / f <1.00
The finder optical system according to claim 1, wherein the following conditional expression is satisfied. When the focal length of the second lens is f2,
−1.10 <f2 / f <−0.50
The finder optical system according to claim 1, wherein the following conditional expression is satisfied. When the Abbe number based on the d-line of the material of the second lens is νd2,
5.0 <νd2 <32.0
The finder optical system according to any one of claims 1 to 3 , wherein the following conditional expression is satisfied. When the curvature radius of the observation side surface of the second lens is R22, and the curvature radius of the image display surface side of the third lens is R31,
−1000.00 <(R31 + R22) / (R31−R22) <10.00
Finder optical system according to any one of claims 1 to 4, characterized by satisfying the conditional expression. Wherein the first lens is a biconvex shape and the second lens is a biconcave shape, the third lens according to any one of claims 1 to 5, characterized in that a biconvex Viewfinder optical system. The viewfinder optical system according to any one of claims 1 to 6 , wherein the first lens, the second lens, and the third lens move together in diopter adjustment. An image display element that displays an image, and an observation apparatus that observes an image displayed on the image display surface of the image display element using the finder optical system according to any one of claims 1 to 7 ,
The diagonal length of the image display surface is H, and the distance on the optical axis from the image display surface side surface of the first lens to the observation side surface of the third lens at a diopter of −1.0 diopter is D13. When
0.20 <H / D13 <0.80
An observation apparatus that satisfies the following conditional expression: An image display element that displays an image, and an observation apparatus that observes an image displayed on the image display surface of the image display element using the finder optical system according to any one of claims 1 to 7 ,
When the diagonal length of the image display surface is H,
0.20 <H / f <0.80
An observation apparatus that satisfies the following conditional expression: An image sensor;
An imaging optical system for forming an object image on the imaging device;
An image display element for displaying the object image;
Imaging apparatus characterized by having a finder optical system according to any one of claims 1 to 7 used for observing the image displayed by the image display device.

Images