Observation optical system and optical device

Abstract

The present application provides an observation optical system that takes into account both miniaturization and high magnification of a viewfinder magnification, and an optical device provided with the observation optical system. The observation optical system is provided with a display element and an eyepiece disposed on an eye point side of the display element. The eyepiece includes, in order from the display element side toward the eye point side, a first lens having positive refractive power, a second lens having negative refractive power, and a third lens having positive refractive power. A predetermined conditional expression is satisfied.

Description

Technical Field

[0001] This invention relates to an observation optical system and optical device. Background Technology

[0002] Conventionally, viewfinders in imaging devices such as digital cameras use an observation optical system for viewing images displayed on display elements such as liquid crystal displays with the naked eye. Lens systems that can be used as observation optical systems are described in Patent Documents 1 to 7 below.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2015-135471

[0004] Patent Document 2: Japanese Patent No. 5745186

[0005] Patent Document 3: Japanese Patent Application Publication No. 2019-133055

[0006] Patent Document 4: Japanese Patent Application Publication No. 2011-085872

[0007] Patent Document 5: Japanese Patent No. 6436680

[0008] Patent Document 6: Japanese Patent Application Publication No. 2016-166969

[0009] Patent Document 7: Japanese Patent No. 5886707

[0010] In recent years, there has been a demand for a smaller observation optical system that can enable high magnification of the viewfinder. Summary of the Invention

[0011] The present invention was made in view of the above circumstances, and its object is to provide an observation optical system that combines miniaturization and high magnification of viewfinder, as well as an optical device having the observation optical system.

[0012] The observation optical system of the present invention includes a display element and an eyepiece disposed on the eye point side of the display element. The eyepiece includes, in sequence from the display element side toward the eye point side, a first lens with positive refractive power, a second lens with negative refractive power, and a third lens with positive refractive power. When the longest diameter of the display area in the display element is set to H and the focal length of the eyepiece is set to fA, the condition (1) expressed by the following is satisfied.

[0013] 0.7 < H / fA < 0.8 (1)

[0014] Furthermore, in the observation optical system of the present invention, it is preferable to satisfy the following conditional expression (1-1), and more preferably to satisfy the following conditional expression (1-2).

[0015] 0.72 < H / fA < 0.78 (1-1)

[0016] 0.735 < H / fA < 0.77 (1-2)

[0017] Furthermore, in the observation optical system of the present invention, when the distance on the optical axis from the display element side surface of the first lens to the eye point side surface of the third lens is set to TL, it is preferable to satisfy the following condition (2), and more preferably to satisfy the following condition (2-1).

[0018] 1.075 < TL / fA < 1.16 (2)

[0019] 1.085 < TL / fA < 1.15 (2-1)

[0020] Furthermore, in the observation optical system of the present invention, when the average value of the refractive index of the first lens relative to the d-line and the refractive index of the third lens relative to the d-line is set to NdA, it is preferable to satisfy the following condition (3), and more preferably to satisfy the following condition (3-1).

[0021] 1.64 < NdA < 1.8 (3)

[0022] 1.65 < NdA < 1.79 (3-1)

[0023] Furthermore, in the observation optical system of the present invention, when the focal length of the first lens is set to f1, it is preferable to satisfy the following condition (4), and more preferably to satisfy the following condition (4-1).

[0024] 0.63 < f1 / fA < 0.75 (4)

[0025] 0.64 < f1 / fA < 0.74 (4-1)

[0026] Furthermore, in the observation optical system of the present invention, when the focal length of the second lens is set to f2, it is preferable to satisfy the following condition (5), and more preferably to satisfy the following condition (5-1).

[0027] 0.62 < -f2 / fA < 0.77 (5)

[0028] 0.63 < -f2 / fA < 0.76 (5-1)

[0029] Furthermore, in the observation optical system of the present invention, it is preferable that the first lens, the second lens, and the third lens are each a single lens.

[0030] Furthermore, in the observation optical system of the present invention, the first lens is preferably a biconvex lens.

[0031] Furthermore, in the observation optical system of the present invention, the second lens is preferably a biconcave lens.

[0032] Furthermore, in the observation optical system of the present invention, the third lens is preferably a biconvex lens.

[0033] Furthermore, in the observation optical system of the present invention, it is preferable that at least one surface of the first lens is aspherical.

[0034] Furthermore, in the observation optical system of the present invention, it is preferable that at least one surface of the second lens is aspherical.

[0035] Furthermore, in the observation optical system of the present invention, it is preferable that at least one surface of the third lens is aspherical.

[0036] The optical device of the present invention includes the observation optical system of the present invention.

[0037] In addition, the phrases “composed of” and “composed of” in this specification indicate that, in addition to the constituent elements listed, it may also substantially include lenses that do not have refractive power, as well as optical elements other than lenses such as apertures, filters and cover glass, and lens flanges, lens barrels, etc.

[0038] Furthermore, in this specification, "single lens" refers to a single, unbonded lens. However, compound aspherical lenses (lenses in which a spherical lens and an aspherical film formed on the spherical lens are integrated, functioning as a single aspherical lens as a whole) are not considered as bonded lenses, but rather as a single lens. Regarding lenses including aspherical surfaces, unless otherwise specified, the sign of refractive power and the surface shape of the lens surface will be considered in the paraxial region.

[0039] Furthermore, in this specification, the "focal length" used in the conditional expressions refers to the paraxial focal length. The values ​​of the conditional expressions are based on the d-line. The "d-line," "C-line," and "F-line" described in this specification are bright lines, with the wavelength of the d-line being 587.56 nm, the wavelength of the C-line being 656.27 nm, and the wavelength of the F-line being 486.13 nm.

[0040] Invention Effects

[0041] According to the present invention, an observation optical system that combines miniaturization and high magnification of the viewfinder, and an optical device having the observation optical system, can be provided. Attached Figure Description

[0042] Figure 1 This is a cross-sectional view showing the structure and optical path of an observation optical system (the observation optical system of Embodiment 1) according to one embodiment.

[0043] Figure 2These are the spherical aberration diagram, astigmatism diagram, distortion aberration diagram, and magnification chromatic aberration diagram of the observation optical system in Example 1.

[0044] Figure 3 This is a lateral aberration diagram of the observation optical system in Example 1.

[0045] Figure 4 This is a cross-sectional view showing the structure and optical path of the observation optical system of Embodiment 2.

[0046] Figure 5 These are the spherical aberration diagram, astigmatism diagram, distortion aberration diagram, and magnification chromatic aberration diagram of the observation optical system in Example 2.

[0047] Figure 6 This is a lateral aberration diagram of the observation optical system in Example 2.

[0048] Figure 7 This is a cross-sectional view showing the structure and optical path of the observation optical system of Example 3.

[0049] Figure 8 These are the spherical aberration diagram, astigmatism diagram, distortion aberration diagram, and magnification chromatic aberration diagram of the observation optical system in Example 3.

[0050] Figure 9 This is a lateral aberration diagram of the observation optical system in Example 3.

[0051] Figure 10 This is a diagram illustrating the hardware structure of an optical device according to one embodiment.

[0052] Figure 11 This is a diagram showing an example of a correction table.

[0053] Figure 12 This is a diagram illustrating the functional structure of an optical device according to one embodiment. Detailed Implementation

[0054] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Figure 1 This is a diagram showing the structure and optical path of the observation optical system 5 according to an embodiment of the present invention in a cross section including the optical axis Z, corresponding to the lens structure of Embodiment 1 described later. Figure 1 In the example shown, display element 1 is used as the object of observation, and the light beam from the point and the highest point on the optical axis of display element 1 toward the eye point EP is also shown. Additionally, Figure 1 The eyepoint EP shown does not represent size or shape, but rather its position along the optical axis. Figure 1 In the diagram, the left side is the side of the observed object, and the right side is the side of the eye point.

[0055] The observation optical system 5 of this embodiment includes a display element 1 and an eyepiece 3 disposed on the eyepoint side of the display element 1. The display element 1 includes a display area 1a on which an image is displayed. Examples of display elements 1 include liquid crystal displays and organic EL (Electroluminescence) displays. The eyepiece 3 is used for observation by magnifying the image displayed in the display area 1a of the display element 1. Furthermore, in Figure 1 In the example, optical components 2 and 4, which do not have parallel incident and exit surfaces, are respectively arranged between the display element 1 and the eyepiece 3 and between the eyepiece 3 and the eye point EP. Optical components 2 and 4 are envisioned as protective cover glass or various filters, etc. In this embodiment, structures other than optical components 2 and 4 may also be used.

[0056] The eyepiece 3, along the optical axis Z from the object side towards the eyepoint side, includes 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. By arranging the eyepiece 3 with these three lenses, a triple structure is created, making it easier to control various aberrations. Furthermore, compared to structures with four or more lenses, the triple structure of the eyepiece 3 shortens the length of the optical axis from the lens surface closest to the object side to the lens surface closest to the eyepoint side, thus facilitating miniaturization.

[0057] Preferably, the first lens L1, the second lens L2, and the third lens L3 are all single lenses. This structure increases design freedom and is therefore beneficial for correcting various aberrations.

[0058] Preferably, the first lens L1 is a biconvex lens. By making the first lens L1 a biconvex lens, the refractive power can be enhanced, which is beneficial for miniaturization. Furthermore, by making the eye-point side surface of the first lens L1 convex, it is beneficial to correct distortion aberrations generated in lenses further from the eye-point side than the first lens L1. Also, preferably, at least one surface of the first lens L1 is aspherical. By making at least one surface of the first lens L1 aspherical, astigmatism, higher-order spherical aberrations, and distortion aberrations can be easily corrected.

[0059] Preferably, the second lens L2 is a biconcave lens. By making the second lens L2 a biconcave lens, it can have a strong negative refractive power, thus helping to ensure a sufficient field of view and facilitating the correction of various aberrations such as coma and image plane curvature. Furthermore, it is preferable that at least one surface of the second lens L2 is aspherical. By making at least one surface of the second lens L2 aspherical, astigmatism, higher-order spherical aberrations, and distortion aberrations can be easily corrected.

[0060] Preferably, the third lens L3 is a biconvex lens. Making the third lens L3 a biconvex lens enhances refractive power and facilitates miniaturization. Furthermore, making the eyepoint side surface of the third lens L3 convex facilitates the correction of spherical aberration. Also preferably, at least one surface of the third lens L3 is aspherical. Making at least one surface of the third lens L3 aspherical allows for easy correction of astigmatism, higher-order spherical aberrations, and distortion aberrations.

[0061] The observation optical system 5 of the present invention is configured such that, with the longest diameter of the display area 1a in the display element 1 set to H and the focal length of the eyepiece 3 set to fA, the following conditional expression (1) is satisfied. By avoiding the conditional expression (1) from falling below its lower limit, the observed size of the image displayed in the display area 1a in the display element 1 can be suppressed from decreasing, thus facilitating a higher magnification of the viewfinder. By avoiding the conditional expression (1) from falling above its upper limit, coma aberration can be easily corrected. Furthermore, to obtain even better characteristics, it is preferable to satisfy the following conditional expression (1-1), and more preferably to satisfy the following conditional expression (1-2).

[0062] 0.7 < H / fA < 0.8 (1)

[0063] 0.72 < H / fA < 0.78 (1-1)

[0064] 0.735 < H / fA < 0.77 (1-2)

[0065] Furthermore, "the longest diameter of the display area 1a in the display element 1" refers to twice the distance between the point furthest from the optical axis Z in the radial direction within the display area 1a, whose centroid is aligned with the optical axis Z. For example, if the display area 1a is rectangular, the length of the diagonal of the display area 1a can be set to H. Also, for example, if the display area 1a is a perfect circle, the diameter of the display area 1a can be set to H; if the display area 1a is an ellipse, the longest diameter (major axis) of the diameters of the display area 1a can be set to H.

[0066] Furthermore, display area 1a refers to the area where the image is actually displayed. For example, if display element 1 has a display section with an aspect ratio of 4:3 and a plurality of pixels are arranged therein, and a portion of the display section displays an image with an aspect ratio of 3:2, then display area 1a refers to the area where the image with an aspect ratio of 3:2 is displayed. Therefore, the diameter of display element 1 and the longest diameter H of display area 1a are not limited to, for example... Figure 1 The same approach as in the examples can also be different.

[0067] Furthermore, when the distance on the optical axis from the display element side of the first lens L1 to the eyepoint side of the third lens L3 is set to TL, the observation optical system 5 of the present invention preferably satisfies the following conditional expression (2). By avoiding conditions below the lower limit of conditional expression (2), it is beneficial to ensure the refractive power adjustment width and correct coma aberration. By avoiding conditions above the upper limit of conditional expression (2), it is beneficial to miniaturize the optical axis in the Z direction. In addition, to obtain better characteristics, it is preferable to satisfy the following conditional expression (2-1).

[0068] 1.075 < TL / fA < 1.16 (2)

[0069] 1.085 < TL / fA < 1.15 (2-1)

[0070] Furthermore, when the average value of the refractive index of the first lens L1 relative to the d-line and the refractive index of the third lens L3 relative to the d-line is set to NdA, the observation optical system 5 of the present invention preferably satisfies the following conditional expression (3). By avoiding conditions falling below the lower limit of conditional expression (3), the Petzvar sum can be reduced, which is beneficial for suppressing image plane curvature. By avoiding conditions falling above the upper limit of conditional expression (3), materials with appropriate Abbe numbers can be selected, which is beneficial for correcting chromatic aberration. In addition, to obtain better characteristics, it is preferable to satisfy the following conditional expression (3-1).

[0071] 1.64 < NdA < 1.8 (3)

[0072] 1.65 < NdA < 1.79 (3-1)

[0073] Furthermore, when the focal length of the first lens L1 is set to f1, the observation optical system 5 of the present invention preferably satisfies the following conditional expression (4). By avoiding the conditional expression (4) from falling below its lower limit, the refractive power of the first lens L1 can be suppressed from becoming too strong, which is beneficial for correcting distortion aberrations. By avoiding the conditional expression (4) from falling above its upper limit, the refractive power of the first lens L1 can be suppressed from weakening, thus suppressing the increase in the gap between the first lens L1 and the second lens L2, which is beneficial for miniaturization in the Z-direction of the optical axis. In addition, to obtain better characteristics, it is preferable to satisfy the following conditional expression (4-1).

[0074] 0.63 < f1 / fA < 0.75 (4)

[0075] 0.64 < f1 / fA < 0.74 (4-1)

[0076] Furthermore, when the focal length of the second lens is set to f2, the observation optical system 5 of the present invention preferably satisfies the following conditional expression (5). By avoiding the conditional expression (5) from falling below its lower limit, the refractive power of the second lens L2 can be suppressed from becoming too strong, which is beneficial for correcting coma, astigmatism, and image plane curvature. By avoiding the conditional expression (5) from falling above its upper limit, the refractive power of the second lens L2 can be suppressed from weakening, which is beneficial for ensuring a sufficient field of view. In addition, to obtain better characteristics, it is preferable to satisfy the following conditional expression (5-1).

[0077] 0.62 < -f2 / fA < 0.77 (5)

[0078] 0.63 < -f2 / fA < 0.76 (5-1)

[0079] The above-mentioned preferred structures and possible structures can be combined arbitrarily, and are preferably adopted selectively and appropriately according to the required specifications.

[0080] Next, a numerical embodiment of the observation optical system 5 of the present invention will be described.

[0081] [Example 1]

[0082] Figure 1 A cross-sectional view showing the structure and optical path of the observation optical system 5 of Embodiment 1 is shown, and the illustration method is as described above, so a repetition of the description is omitted here. Regarding the observation optical system 5 of Embodiment 1, the basic lens data is shown in Table 1, the variable surface spacing is shown in Table 2, the specifications are shown in Table 3, and the aspherical coefficients are shown in Table 4.

[0083] In Table 1, the Sn column shows the surface of display element 1 on the viewing object side (the surface with display area 1a) as the first surface, with the surface numbers increasing sequentially towards the eye point side. Table 1 also lists display element 1, optical components 2 and 4, and the eye point EP. The Sn column for the surface corresponding to the eye point EP lists the surface number and the statement (EP). The R column shows the radius of curvature for each surface. Regarding the sign of the radius of curvature, the radius of curvature of the surface shape with the convex surface facing the viewing object side is set to positive, and the radius of curvature of the surface shape with the convex surface facing the eye point side is set to negative. Additionally, an asterisk (*) is added to the surface number of aspherical surfaces, and the paraxial radius of curvature value is listed in the radius of curvature column for aspherical surfaces.

[0084] Furthermore, in Table 1, the column for D shows the surface spacing along the optical axis Z of each surface and the surface adjacent to it on the eyepoint side. For variable surface spacing during diopter adjustment, the notation dd[] is used, with the object-side surface number of that spacing appended in the brackets. The column for Nd shows the refractive index of each component relative to the d-line. The column for νd shows the Abbe number of each component based on the d-line reference.

[0085] Table 2 shows the values ​​of the variable surface interval for each diopter. "dpt" in Table 2 refers to diopter. Furthermore, the observation optical system 5 of Example 1 can adjust the diopter within the range of -4dpt to +2dpt by moving the eyepiece 3 integrally along the optical axis Z.

[0086] Table 3 shows the focal length fA of eyepiece 3, the longest diameter H of display area 1a in display element 1, and the viewfinder magnification. The values ​​shown in Table 3 are for a diopter of -1 dpt. Furthermore, the viewfinder magnification is the magnification relative to a full-size (24 mm × 36 mm) imaging element when an imaging lens with a focal length of 50 mm is installed.

[0087] Table 4 shows the aspheric surface number in the Sn column. The aspheric coefficient values ​​for each aspheric surface are shown in the KA and Am columns (where m is an integer greater than 3, varying depending on the surface). The aspheric coefficient value "E±n" (where n is an integer) refers to "×10" ±n KA and Am are the aspheric coefficients in the aspheric formula expressed by the following equation.

[0088] Zd=C×h 2 / {1+(1-KA×C 2 ×h 2 ) 1 / 2}+∑Am×h m

[0089] in,

[0090] Zd: Aspherical depth (the length of the perpendicular line drawn from a point on the aspherical surface at height h to the plane perpendicular to the optical axis touched by the vertex of the aspherical surface).

[0091] h: Height (distance from the optical axis to the lens surface)

[0092] C: Paraxial curvature

[0093] KA, Am: Aspherical coefficients. In the aspherical form, ∑ refers to the summation related to m.

[0094] In the following tables and figures, degrees are used as the unit for angles and millimeters as the unit for lengths. However, optical systems can be used even when scaling up or down, so other appropriate units can also be used. Furthermore, the values ​​rounded to a predetermined number of decimal places are shown in the tables below.

[0095] [Table 1]

[0096] Example 1

[0097]

[0098]

[0099] [Table 2]

[0100] Example 1

[0101] Diopters +2 dpt -1 dpt -4 dpt dd[4] 2.4893 1.4873 0.4854 dd

[10] 0.9980 2.0000 3.0020

[0102] [Table 3]

[0103] Example 1

[0104] fA 17.05 H 12.81 Magnification of viewfinder 0.83

[0105] [Table 4]

[0106] Example 1

[0107] Sn 5 6 KA 1.0000000E+00 1.0000000E+00 A3 6.9216316E-04 4.8506862E-04 A4 -3.2171020E-04 1.0056522E-04 A5 -3.2993820E-05 -7.3476840E-05 A6 1.5313698E-05 2.0929413E-05 A7 -1.4947398E-06 -1.8972398E-06 A8 -1.5590193E-07 -6.9349964E-08 A9 -6.3861916E-09 -2.2661059E-08 A10 4.6034657E-09 6.5489130E-09 A11 -8.0493375E-11 1.8478622E-10 A12 -6.5592997E-11 2.1377768E-12 A13 9.6124067E-12 -5.6211993E-12 A14 1.5079980E-12 -2.5420101E-13 A15 -2.6005121E-14 -5.5311989E-14 A16 -3.5918844E-14 2.8423269E-15 A17 -1.1490078E-15 -1.3915850E-16 A18 4.4197799E-17 8.4020502E-17 A19 2.7174300E-18 2.0061156E-17 A20 3.3240781E-18 -2.1682810E-18

[0108] Sn 7 8 9 10 KA 1.0000000E+00 1.0000000E+00 1.0000000E+00 1.0000000E+00 A4 1.3899615E-04 -2.7023970E-05 -4.9310076E-05 2.1362106E-05 A6 -1.8644415E-06 1.1995181E-06 1.7542443E-07 2.2724185E-09 A8 4.9573857E-08 -2.3734790E-08 8.6803823E-09 2.4857547E-09 A10 1.3976821E-09 -3.0549515E11 5.7656500E-11 -1.6958512E-11 A12 -2.0973660E-11 3.5870389E-12 -6.5413266E-13 -1.8228669E-13 A14 -5.6454084E-13 4.3983495E-14 -7.1906207E-15 4.2807141E-15 A16 -3.4110745E-15 -1.1538080E-15 5.9862936E-17 -6.2535493E-18 A18 4.2433336E-16 2.1087573E-18 -1.6643714E-19 -2.4082303E-19 A20 -4.0821887E-18 2.9593585E-20 1.0560399E-21 1.3492906E-21

[0109] Regarding the observation optical system 5 involved in Example 1, Figure 2 This diagram shows the spherical aberration, astigmatism, distortion aberration, and chromatic aberration diagrams for a refractive power of -1.00 diopters. In the spherical aberration diagram, aberrations along the d-line, C-line, and F-line are shown using solid, short, and long dashed lines, respectively. In the astigmatism diagram, aberrations along the sagittal d-line are shown using solid lines, and aberrations along the meridional d-line are shown using short dashed lines. In the distortion aberration diagram, aberrations along the d-line are shown using solid lines. In the chromatic aberration diagram, aberrations along the C-line and F-line are shown using short and long dashed lines, respectively. The horizontal axis of the spherical aberration and astigmatism diagrams is in diopters. In the spherical aberration diagram, φ refers to the diameter of the eyepoint when the unit is mm (millimeters), and ω in the other aberration diagrams refers to the field of view at half the angle of view.

[0110] Regarding the observation optical system 5 involved in Example 1, Figure 3 The image shows the lateral aberration diagram for a refractive power of -1.00 diopter. For each viewing angle, the left column shows the aberrations in the meridional direction, and the right column shows the aberrations in the sagittal direction. Figure 3 In the diagram, the aberrations on the d-line, C-line, and F-line are represented by solid lines, short dashed lines, and long dashed lines, respectively. Figure 3 ω refers to the field of view angle at half the angle of view.

[0111] Unless otherwise specified, the labeling, meaning and recording method of the data related to Embodiment 1 above are the same in the following embodiments, so repeated descriptions are omitted below.

[0112] [Example 2]

[0113] Regarding the observation optical system 5 of Example 2, a cross-sectional view of its structure and optical path is shown below. Figure 4 The aberrations are plotted on the graph. Figure 5 The lateral aberration is plotted on Figure 6 Furthermore, regarding the observation optical system 5 of Embodiment 2, the basic lens data is shown in Table 5, the variable surface spacing is shown in Table 6, the specifications are shown in Table 7, and the aspherical coefficients are shown in Table 8.

[0114] [Table 5]

[0115] Example 2

[0116] Sn R D Nd νd 1 ∞ 0.7000 1.51680 64.20 2 ∞ 4.3000 3 ∞ 0.5000 1.49023 57.49 4 ∞ dd[4] *5 27.0386 6.0000 1.69569 56.72 *6 -11.2818 0.9960 *7 -10.9914 2.0824 1.67775 31.59 *8 42.2252 0.9000 *9 63.8196 9.1762 1.63648 59.68 *10 -12.0790 dd

[10] 11 ∞ 1.2000 1.49023 57.50 12 ∞ 20.6000 13 (EP) ∞

[0117] [Table 6]

[0118] Example 2

[0119] Diopters +2 dpt -1 dpt -4 dpt dd[4] 2.5239 1.5279 0.5320 dd

[10] 1.0040 2.0000 2.9960

[0120] [Table 7]

[0121] Example 2

[0122] fA 16.98 H 12.81 Magnification of viewfinder 0.84

[0123] [Table 8]

[0124] Example 2

[0125] Sn 5 6 KA 1.0000000E+00 1.0000000E+00 A3 6.7931360E-04 2.0130397E-04 A4 -4.1911342E-04 1.5418747E-04 A5 -2.1370564E-05 -8.2575975E-05 A6 1.4238223E-05 2.0586825E-05 A7 -1.4947398E-06 -1.8972398E-06 A8 -1.5590193E-07 -6.9349964E-08 A9 -6.3861916E-09 -2.2661059E-08 A10 4.6034657E-09 6.5489130E-09 A11 -8.0493375E-11 1.8478622E-10 A12 -6.5592997E-11 2.1377768E-12 A13 9.6124067E-12 -5.6211993E-12 A14 1.5079980E-12 -2.5420101E-13 A15 -2.6005121E-14 -5.5311989E-14 A16 -3.5918844E-14 2.8423269E-15 A17 -1.1490078E-15 -1.3915850E-16 A18 4.4197799E-17 8.4020502E-17 A19 2.7174300E-18 2.0061156E-17 A20 3.3240781E-18 -2.1682810E-18

[0126] Sn 7 8 9 10 KA 1.0000000E+00 1.0000000E+00 1.0000000E+00 1.0000000E+00 A4 7.0044628E-05 -7.7986421E-06 2.8165078E-05 4.2191814E-05 A6 -2.3381040E-06 1.5668618E-06 7.3739130E-08 8.4131994E-09 A8 4.9581629E-08 -1.3911791E-08 4.8409282E-10 3.0131724E-09 A10 1.7415233E-09 -1.0757491E-10 2.1303049E-12 -1.4451463E-11 A12 -1.3582433E-11 -1.1385447E-12 -3.4556919E-13 -1.1184443E-13 A14 -6.0419383E-13 6.8962261E-14 1.8448391E-15 3.9140013E-15 A16 -5.7000808E-15 6.4888121E-16 5.8675879E-17 -3.4307541E-18 A18 3.5240227E-16 1.3440670E-18 -7.2609314E-19 2.6591309E-19 A20 2.7050338E-18 3.4577392E-21 2.3539422E-21 1.8020909E-21

[0127] [Example 3]

[0128] Regarding the observation optical system 5 of Example 3, a cross-sectional view of its structure and optical path is shown below. Figure 7 The aberrations are plotted on the graph. Figure 8 The lateral aberration is plotted on Figure 9 Furthermore, regarding the observation optical system 5 of Embodiment 3, the basic lens data is shown in Table 9, the variable surface spacing is shown in Table 10, the specifications are shown in Table 11, and the aspherical coefficients are shown in Table 12.

[0129] [Table 9]

[0130] Example 3

[0131]

[0132]

[0133] [Table 10]

[0134] Example 3

[0135] Diopters +2 dpt -1 dpt -4 dpt dd[4] 2.5532 1.5384 0.5236 dd

[10] 0.9852 2.0000 3.0148

[0136] [Table 11]

[0137] Example 3

[0138] fA 17.16 H 12.81 Magnification of viewfinder 0.83

[0139] [Table 12]

[0140] Example 3

[0141] Sn 5 6 KA 1.0000000E+00 1.0000000E+00 A3 -1.1861428E-04 7.6654943E-05 A4 -1.5861301E-05 2.1292211E-04 A5 -5.9580393E-05 -8.2176597E-05 A6 1.5625272E-05 2.0216333E-05 A7 -1.4947398E-06 -1.8972398E-06 A8 -1.5590193E-07 -6.9349964E-08 A9 -6.3861916E-09 -2.2661059E-08 A10 4.6034657E-09 6.5489130E-09 A11 -8.0493375E-11 1.8478622E-10 A12 -6.5592997E-11 2.1377768E-12 A13 9.6124067E-12 -5.6211993E-12 A14 1.5079980E-12 -2.5420101E-13 A15 -2.6005121E-14 -5.5311989E-14 A16 -3.5918844E-14 2.8423269E-15 A17 -1.1490078E-15 -1.3915850E-16 A18 4.4197799E-17 8.4020502E-17 A19 2.7174300E-18 2.0061156E-17 A20 3.3240781E-18 -2.1682810E-18

[0142] Sn 7 8 9 10 KA 1.0000000E+00 1.0000000E+00 1.0000000E+00 1.0000000E+00 A4 4.3615015E-05 -2.0827493E-06 3.2182451E-05 3.2975141E-05 A6 -2.6473691E-06 1.5588570E-06 -7.0586880E-08 1.3760120E-07 A8 5.7554797E-08 -1.4878102E-08 -2.1748428E-10 3.2318971E-09 A10 1.9221272E-09 -1.2314097E-10 -4.9473924E-12 -2.2134047E-11 A12 -1.6737736E-11 -1.4547032E-12 -3.9078466E-13 -1.3438702E-13 A14 -6.8547955E-13 7.1265945E-14 1.9500532E-15 5.0198175E-15 A16 -6.0994352E-15 -6.2218036E-16 6.6150477E-17 -6.6093657E-18 A18 4.1064370E-16 1.4048183E-18 -6.5371577E-19 -3.1112633E-19 A20 -3.2773775E-18 1.7234307E-21 1.6465746E-21 2.0029872E-21

[0143] Table 13 shows the corresponding values ​​of conditional equations (1) to (5) for the observation optical system 5 of Examples 1 to 3. The values ​​shown in Table 13 are based on the d-line.

[0144] [Table 13]

[0145] Formula number Condition formula Example 1 Example 2 Example 3 (1) H / fA 0.7515 0.7546 0.7465 (2) TL / fA 1.1337 1.1284 1.0977 (3) NdA 1.771795 1.666083 1.681150 (4) f1 / fA 0.6505 0.7203 0.7311 (5) -f2 / fA 0.6442 0.7462 0.6884

[0146] As can be seen from the above data, the observation optical system 5 of Examples 1 to 3 respectively satisfies the conditions (1) to (5), is small and has a viewfinder magnification of 0.8 times or more, and is constituted as a high magnification system.

[0147] Furthermore, the present invention is not limited to the above-described embodiments and examples, and various modifications are possible. For example, the radius of curvature, interplanar spacing, refractive index, Abbe number, and aspherical coefficient of each lens are not limited to the values ​​shown in the numerical embodiments above, and other values ​​can be used.

[0148] Next, a camera 10 will be described as an example of an optical device having the observation optical system 5 according to an embodiment of the present invention. The camera 10 according to this embodiment is a camera device equipped with an EVF (Electronic View Finder), which is configured to include the observation optical system 5 having the display element 1 and eyepiece 3 according to the present invention. Furthermore, the camera 10 has the function of correcting the image displayed on the display element 1 to reduce the influence of the optical characteristics of the observation optical system 5 on the image observed by the user through the observation optical system 5 (i.e., the image displayed on the display element 1). Through such image correction, the user can observe an image with reduced influence from the optical characteristics of the observation optical system 5. In addition to various aberrations such as chromatic aberration and distortion aberration, the optical characteristics of the observation optical system 5 also include the degree of reduction in peripheral light.

[0149] First, refer to Figure 10 The hardware structure of the camera 10 according to this embodiment will be described. For example... Figure 10 As shown, the camera 10 includes the observation optical system 5, imaging lens LO, imaging element 11, and diopter adjustment mechanism 18 of the present invention inside the camera body 30. Furthermore, the camera 10 includes an eyecup 24 and a diopter adjustment unit 26. The diopter adjustment unit 26 is a rotary or similar operating unit for adjusting the diopter of the observation optical system 5. The camera 10 also includes a CPU (Central Processing Unit) 12, a memory 13 serving as a temporary storage area, and a non-volatile storage unit 14. The display element 1, imaging element 11, CPU 12, memory 13, storage unit 14, and diopter adjustment mechanism 18 are connected to a bus 19.

[0150] In camera 10, the image of the subject is imaged onto the imaging surface of imaging element 11 through imaging lens LO. Imaging element 11 outputs an image displaying the image of the subject. Various image corrections are performed on the image captured by imaging element 11, and the corrected image is displayed on display element 1. The user observes the EVF through eyecup 24 and the image displayed on display element 1 through observation optical system 5. Furthermore, based on the operation of diopter adjustment unit 26 by the user, diopter adjustment mechanism 18 moves the position of eyepiece 3 along the optical axis Z. Thus, the focus can be adjusted according to the user's diopter, such as myopia or hyperopia.

[0151] The storage unit 14 is implemented using HDD (Hard Disk Drive), SSD (Solid State Drive), and flash memory, etc. The storage unit 14 stores the calibration table 15 and the image processing program 16. After the CPU 12 reads the image processing program 16 from the storage unit 14, it opens it in the memory 13 and executes the opened image processing program 16.

[0152] refer to Figure 11 An example of calibration table 15 will be explained. In calibration table 15, calibration data for correcting the image observed by the user through the observation optical system 5 is stored according to each combination of conditions such as the type of EVF provided by the camera 10, the type of camera body 30, the type of eyecup 24, and the diopter adjustment amount of the observation optical system 5.

[0153] exist Figure 11 In the examples, E1 and E2 are shown as examples of different types of EVFs. Regarding each EVF, such as E1 and E2, the optical characteristics of the observation optical system 5 included in the EVF differ.

[0154] Furthermore, in Figure 11In the examples, C1 and C2 are shown as examples of different types of camera bodies 30. For example, the imaging lens LO differs between each camera body 30, such as C1 and C2. If the imaging lens LO is different, the optical characteristics of various aberrations of the imaging lens LO will also differ. Similar to the optical characteristics of the observation optical system 5, the optical characteristics of the imaging lens LO, for example, include various aberrations such as magnification chromatic aberration and distortion aberration, as well as the degree of reduction in peripheral light. In the camera 10, the image displayed on the display element 1 is acquired through the imaging lens LO and the imaging element 11; therefore, the optical characteristics of the imaging lens LO also affect the image displayed on the display element 1. Thus, the image observed by the user through the observation optical system 5 is affected not only by the optical characteristics of the observation optical system 5 but also by the optical characteristics of the imaging lens LO.

[0155] Furthermore, in Figure 11 In the examples, eye1 and eye2 are shown as examples of different types of eyecups 24. Each eyecup 24, such as eye1 and eye2, differs in, for example, its thickness along the Z-axis of the observation optical system 5 and the size of the opening for the user to observe the EVF. Due to these differences, the manner in which distortion aberrations and chromatic aberration occur in the image observed by the user through the observation optical system 5, as well as the degree of reduction in peripheral light, also change. Thus, the image observed by the user through the observation optical system 5 is affected not only by the optical characteristics of the observation optical system 5 but also by the type of eyecup 24.

[0156] Furthermore, in Figure 11 In the examples, +2dpt, -1dpt, and -4dpt are shown as examples of diopter adjustment amounts. When the diopter adjustment amount changes, the position of the eyepiece 3 relative to the display element 1 changes, and therefore, for example, the path of light relative to the observation optical system 5 changes. Due to this change, the manner in which distortion aberrations and chromatic aberration, as well as the degree of reduction in peripheral light, appear in the image observed by the user through the observation optical system 5 also change. Thus, the image observed by the user through the observation optical system 5 is affected not only by the optical characteristics of the observation optical system 5 but also by the diopter adjustment amount.

[0157] As described above, the image observed by the user through the optical system 5 is affected by various conditions. Therefore, depending on each combination of conditions, the manner in which distortion aberrations and chromatic aberration occur, as well as the degree of reduction in peripheral light, also change. Therefore, the correction table 15 of this embodiment stores correction data that varies according to each combination of conditions and can appropriately correct the image observed by the user through the optical system 5. The correction data defines how to change the pixel value for each pixel of the image to be corrected, in order to reduce various aberrations such as distortion aberrations and chromatic aberration, as well as the reduction in peripheral light.

[0158] exist Figure 11 In the example, d1 to d24 are shown as examples of correction data. For example, correction data d1 is the correction data when the EVF is E1, the camera body 30 is C1, the eyecup 24 is eye1, and the diopter adjustment is "+2dpt".

[0159] refer to Figure 12 The functional structure of the camera 10 according to this embodiment will be described. For example... Figure 12 As shown, the camera 10 includes an image acquisition unit 21, a conditional acquisition unit 22, and an image processing unit 23. The camera functions as the image acquisition unit 21, the conditional acquisition unit 22, and the image processing unit 23 by executing the image processing program 16 via the CPU 12.

[0160] The image acquisition unit 21 acquires the image output from the imaging element 11. The condition acquisition unit 22 acquires information related to each condition defined in the calibration table 15. Information related to each condition, such as the type of EVF (E1 and E2, etc.), the type of camera body (C1 and C2, etc.), and the type of eyecup (eye1 and eye2, etc.), is stored in the storage unit 14 in advance, for example, during the manufacturing of the camera 10. Information related to the condition of the diopter adjustment amount, such as the current value set by the user, is stored in the storage unit 14. At this time, the condition acquisition unit 22 acquires information related to the combination of each condition from the storage unit 14.

[0161] The image processing unit 23 reads the correction data corresponding to each condition from the correction table 15 based on the conditions acquired by the condition acquisition unit 22, and performs image correction on the image based on the read correction data. Then, the image processing unit 23 outputs the corrected image to the display element 1. The corrected image is displayed on the display element 1. Furthermore, the image processing unit 23 can perform various image processing operations on the image, such as white balance correction, brightness correction, and contrast adjustment.

[0162] As explained above, the camera 10 of this embodiment performs image correction on an image generated from an image acquired by the imaging element 11, and then displays the corrected image on the display element 1. This image correction reduces the influence on the image caused by the optical characteristics of the observation optical system 5, etc. The image correction is performed based on correction data that takes into account factors that affect the image observed by the user through the observation optical system 5. The correction data used for image correction is selected from a combination of conditions including conditions that limit the optical characteristics of the observation optical system 5, conditions that limit the optical characteristics of the imaging lens LO, the type of eyecup 24, and the amount of diopter adjustment. Therefore, even in a camera 10 that has an observation optical system 5 that balances miniaturization and high magnification of the viewfinder, the influence on the image caused by the optical characteristics of the observation optical system 5, etc., can be appropriately corrected according to the various components constituting the camera 10.

[0163] Furthermore, the aforementioned correction table 15 is merely an example and can be modified in various ways. For instance, among the conditions mentioned above, one can selectively use any condition, or one can use other conditions.

[0164] For example, if the eyecup 24 can be attached to or detached from the camera body 30 and the user can choose whether to use it, the calibration data can be changed based on the presence or absence of the eyecup 24. In this case, the information about the presence or absence of the eyecup 24 can be input by the user through an input unit (not shown) provided in the camera 10, and the input information is stored in the storage unit 14 as a condition of the eyecup 24.

[0165] Furthermore, the type of eyecup 24 and its presence or absence are examples of conditions that limit the position of the eyepoint EP of the observation optical system 5. Therefore, alternatively, a mechanism for acquiring the position of the eyepoint EP can be provided in the camera 10, and the position of the eyepoint EP acquired by this mechanism can be used as a condition for selecting correction data. For example, the mechanism for acquiring the position of the eyepoint EP could be an input unit or similar device provided in the camera 10 that accepts input manually operated by the user. Alternatively, a sensor for optically detecting the user's pupil position can be provided in the eyepiece unit or similar device of the camera body 30, and this sensor can be used as a mechanism for acquiring the position of the eyepoint EP.

[0166] Furthermore, the diopter adjustment amount is one example of a condition that limits the diopter of the observation optical system 5. Therefore, in addition to this, or instead, the diopter of the diopter adjustment lens when the detachable diopter adjustment lens is installed can also be used as a condition for selecting the correction data. In this case, the information on the diopter adjustment lens diopter can be input by the user through an input unit (not shown) provided in the camera 10, and the input information is stored in the storage unit 14 as a condition for the diopter adjustment lens diopter.

[0167] and, Figure 10 The hardware structure of the camera 10 shown is only one example. The observation optical system 5 of the camera 10 can include optical components 2 and 4. Furthermore, the imaging optical system can include an aperture and a mechanism for controlling the imaging lens LO and the aperture. Alternatively, it can be a structure that omits the diopter adjustment mechanism 18, the eyecup 24, and the diopter adjustment section 26. Figure 10 An example of a viewfinder built into camera 10 is shown, but the invention can also be applied to external viewfinders.

[0168] Furthermore, in the above embodiments, for example, the hardware structure of the processing unit that performs various processes such as the image acquisition unit 21, the condition acquisition unit 22, and the image processing unit 23 can be adapted to various processors as described below. As mentioned above, among the various processors described above, in addition to the general-purpose processor that executes software (program) and functions as various processing units, namely the CPU, processors such as FPGA (Field Programmable Gate Array) whose circuit structure can be changed after manufacturing, i.e., programmable logic devices (PLDs), and processors such as ASIC (Application Specific Integrated Circuit) with circuit structures specially designed to perform specific processes, i.e., dedicated circuits, etc.

[0169] A processing unit can be composed of one of these various processors, or it can be composed of a combination of two or more processors of the same or different types (e.g., a combination of multiple FPGAs or a combination of a CPU and an FPGA). Furthermore, a single processor can also constitute multiple processing units. As examples of a single processor constituting multiple processing units, firstly, as exemplified by client and server computers, a processor is composed of a combination of one or more CPUs and software, which functions as multiple processing units. Secondly, as exemplified by System-on-Chip (SoC), a processor is used to implement the overall system functionality including multiple processing units using a single IC (Integrated Circuit) chip. Thus, various processing units are constructed using one or more of the aforementioned processors as hardware structures.

[0170] Moreover, as the hardware structure of these various processors, more specifically, it is possible to use circuits that combine circuit elements such as semiconductor elements.

[0171] Based on the above explanation, one can master the optical devices described in the following notes.

[0172] Note 1

[0173] An optical device comprising:

[0174] An imaging element that outputs an image of the subject captured by an imaging lens;

[0175] An observation optical system comprising: a display element for displaying an image output from the imaging element; and an eyepiece for observing the image displayed on the display element; and

[0176] The processor performs image correction on the image displayed on the display element.

[0177] The processor performs image correction on the image displayed on the display element based on correction data that takes into account factors that affect the image observed by the user through the observation optical system and corresponds to a combination of conditions selected from a plurality of conditions including conditions that define the optical characteristics of the observation optical system, conditions that define the optical characteristics of the imaging lens, the type of eyecup, and the amount of diopter adjustment.

[0178] Furthermore, the observation optical system 5 of the present invention is not only applicable to the camera 10 according to this embodiment, but also applicable to optical devices that do not involve processing to correct the image displayed on the display element 1. Moreover, the observation optical system 5 of the present invention can also be applied to optical devices such as film cameras, video cameras, and head-mounted displays.

[0179] Symbol Explanation

[0180] 1-Display element, 1a-Display area, 2, 4-Optical components, 3-Eyepiece, 5-Observation optical system, 10-Camera, 11-Imaging element, 12-CPU, 13-Memory, 14-Storage unit, 15-Calibration table, 16-Image processing program, 18-Diopter adjustment mechanism, 19-Bus, 21-Image acquisition unit, 22-Conditional acquisition unit, 23-Image processing unit, 24-Eyecup, 26-Diopter adjustment unit, 30-Camera body, EP-Eyepoint, H-Longest diameter of display area, L1-First lens, L2-Second lens, L3-Third lens, LO-Imaging lens, Z-Optical axis.

Claims

1. An observation optical system comprising a display element and an eyepiece disposed on the eyepoint side of the display element. The eyepiece, from the display element side toward the eye point side, consists of a first lens with positive refractive power, a second lens with negative refractive power, and a third lens with positive refractive power. Let the longest diameter of the display area in the display element be H, and the focal length of the eyepiece be fA. Let the average of the refractive index of the first lens relative to the d-line and the refractive index of the third lens relative to the d-line be NdA. Set the focal length of the first lens to f1. When the focal length of the second lens is set to f2, the following conditions (1), (3), (4) and (5) are satisfied. 0.7 < H / fA < 0.8 (1) 1.64 < NdA < 1.8 (3) 0.63 < f1 / fA < 0.75 (4) 0.62<-f2 / fA<0.77 (5).

2. The observation optical system according to claim 1, wherein, When the distance on the optical axis from the display element side of the first lens to the eye point side of the third lens is set to TL, the condition (2) expressed below is satisfied. 1.075<TL / fA<1.16 (2).

3. The observation optical system according to claim 1 or 2, wherein, The first lens, the second lens, and the third lens are all single lenses.

4. The observation optical system according to claim 1 or 2, wherein, The first lens is a biconvex lens.

5. The observation optical system according to claim 1 or 2, wherein, The second lens is a biconcave lens.

6. The observation optical system according to claim 1 or 2, wherein, The third lens is a biconvex lens.

7. The observation optical system according to claim 1 or 2, wherein, At least one surface of the first lens is aspherical.

8. The observation optical system according to claim 1 or 2, wherein, At least one surface of the second lens is an aspherical surface.

9. The observation optical system according to claim 1 or 2, wherein, At least one surface of the third lens is aspherical.

10. The observation optical system according to claim 1, which satisfies the condition (1-1) expressed below. 0.72<H / fA<0.78 (1-1).

11. The observation optical system according to claim 1, which satisfies the conditional expressions (1-2) expressed below. 0.735<H / fA<0.77 (1-2).

12. The observation optical system according to claim 2, which satisfies the condition (2-1) expressed below. 1.085<TL / fA<1.15 (2-1).

13. The observation optical system according to claim 1, which satisfies the condition (3-1) expressed below. 1.65<NdA<1.79 (3-1).

14. The observation optical system according to claim 1, which satisfies the condition (4-1) expressed below. 0.64<f1 / fA<0.74 (4-1).

15. The observation optical system according to claim 1, which satisfies the condition (5-1) expressed below. 0.63<-f2 / fA<0.76 (5-1).

16. The observation optical system according to claim 1 or 2, which satisfies the condition (3-2) expressed below. 1.64<NdA≤1.771795 (3-2).

17. The observation optical system according to claim 1 or 2, which satisfies the condition (4-2) expressed below. 0.63<f1 / fA≤0.7311 (4-2).

18. The observation optical system according to claim 1, which satisfies the condition (5-2) expressed below. 0.62<-f2 / fA≤0.7462 (5-2).

19. An optical device comprising the observation optical system according to any one of claims 1 to 18.

Images