Eyepiece optical system, optical apparatus, and observation method

Abstract

The eyepiece optical system (EL) is provided with a first positive lens (Lp1) having a positive refractive power and a second positive lens (Lp2) having a positive refractive power, and satisfies the following conditional expressions: 1.700 < Np1 < 2.050 and 1.700 < Np2 < 2.050, where Np1 is the refractive index of the first positive lens (Lp1) with respect to the d-line, and Np2 is the refractive index of the second positive lens (Lp2) with respect to the d-line.

Description

Technical Field

[0001] The present invention relates to an eyepiece optical system for viewing an image displayed on an image display element, suitable for electronic viewfinders (so-called EVFs) and the like. Background Technology

[0002] An eyepiece optical system capable of observing an image displayed on an image display element at high magnification has been proposed (for example, see Patent Document 1). In such an eyepiece optical system, it is difficult to correct various aberrations, especially astigmatism and distortion, to obtain good optical performance.

[0003] Priority Technology Documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2013-88632 Summary of the Invention

[0006] The eyepiece optical system of the first invention comprises a first positive lens having positive optical power and a second positive lens having positive optical power, and satisfies the following condition: 1.700 < Np1 < 2.050 1.700 < Np2 < 2.050 Wherein, Np1: the refractive index of the first positive lens for the d-line. Np2: The refractive index of the second positive lens for the d-line.

[0007] The second eyepiece optical system of the present invention has at least five lenses and satisfies the following condition: 0.400 < h / fe < 0.500 Wherein, fe: the composite focal length of the eyepiece optical system. h: The maximum height of the object being observed in the eyepiece optical system.

[0008] The third eyepiece optical system of the present invention observes the image displayed on the image display element, wherein the eyepiece optical system has at least five lenses.

[0009] The optical device of the present invention comprises: an objective lens; an imaging element for capturing an image formed by the objective lens; an image display element for displaying the image captured by the imaging element; and an eyepiece optical system for observing the image displayed on the image display element, wherein the eyepiece optical system is any of the eyepiece optical systems described above.

[0010] The observation method of the present invention observes the observed object via any of the above-described eyepiece optical systems. Attached Figure Description

[0011] Figure 1 This is a structural diagram of the eyepiece optical system of the first embodiment.

[0012] Figure 2 The diopter of the eyepiece optical system in the first embodiment is -1 [m] -1 Aberration diagrams at different times.

[0013] Figure 3 This is a structural diagram of the eyepiece optical system of the second embodiment.

[0014] Figure 4 The eyepiece optical system of the second embodiment has a diopter of -1 [m]. -1 Aberration diagrams at different times.

[0015] Figure 5 This is a structural diagram of the eyepiece optical system of the third embodiment.

[0016] Figure 6 The eyepiece optical system of the third embodiment has a diopter of -1 [m]. -1 Aberration diagrams at different times.

[0017] Figure 7 This is a structural diagram of the eyepiece optical system of the fourth embodiment.

[0018] Figure 8 The eyepiece optical system of the fourth embodiment has a diopter of -1 [m]. -1 Aberration diagrams at different times.

[0019] Figure 9 This is a structural diagram of the eyepiece optical system of the fifth embodiment.

[0020] Figure 10 The eyepiece optical system of embodiment 5 has a diopter of -1 [m] -1 Aberration diagrams at different times.

[0021] Figure 11 This is a structural diagram of the eyepiece optical system of the sixth embodiment.

[0022] Figure 12 The eyepiece optical system of embodiment 6 has a diopter of -1 [m] -1 Aberration diagrams at different times.

[0023] Figure 13 This is a structural diagram of the eyepiece optical system of the 7th embodiment.

[0024] Figure 14 The eyepiece optical system of embodiment 7 has a diopter of -1 [m] -1 Aberration diagrams at different times.

[0025] Figure 15 It is a cross-sectional view of a digital camera. Detailed Implementation

[0026] The preferred embodiments of the present invention will be described below. First, in Figure 15 The diagram illustrates a digital camera CAM (optical device) as an optical device equipped with an eyepiece optical system EL in various embodiments. The digital camera CAM is configured to include an objective lens OL, an imaging element C such as a CCD or CMOS, and an electronic viewfinder EVF. The electronic viewfinder EVF is configured to include an image display element (observed object) Op such as a liquid crystal display element, and an eyepiece optical system EL for magnifying and observing the image displayed on the image display element Op.

[0027] In the digital camera CAM with the above-described structure, light from an object (subject) not shown is focused on the objective lens OL and imaged on the imaging element C to form an image of the subject. The image of the subject formed on the imaging element C is captured by the imaging element C, and the image of the subject captured by the imaging element C is displayed on the image display element Ob. By positioning their eye at the viewpoint EP, the photographer can magnify and observe the image of the object (subject) formed by the objective lens OL via the eyepiece optical system EL.

[0028] Furthermore, when the photographer presses the release button (not shown), the image captured by the imaging element C at that moment (i.e., the image displayed on the image display element Ob as observed through the eyepiece optical system EL) is recorded as an image of the object (subject) in a memory (not shown). Thus, the photographer can perform photography of the object (subject) using a digital camera CAM. Additionally, Figure 15 The eyepiece optical system EL shown is a schematic diagram of the eyepiece optical system of a digital camera CAM. The lens structure of the eyepiece optical system EL is not limited to this structure.

[0029] Next, the eyepiece optical system of the first embodiment will be described. For example... Figure 1 As shown, the eyepiece optical system EL (EL1), which is an example of the eyepiece optical system EL in the first embodiment, includes a first positive lens Lp1 with positive optical power and a second positive lens Lp2 with positive optical power.

[0030] Under the above structure, the eyepiece optical system EL of the first embodiment satisfies the following conditional expressions (1) and (2).

[0031] 1.700<Np1<2.050···(1)

[0032] 1.700<Np2<2.050···(2)

[0033] Where Np1: the refractive index of the first positive lens Lp1 for the d-line.

[0034] Np2: The refractive index of the second positive lens Lp2 for the d-line.

[0035] According to the first embodiment, an eyepiece optical system with good optical performance that corrects various aberrations, especially astigmatism and distortion, and an optical device equipped with the eyepiece optical system can be obtained. The zoom optical system ZL of the first embodiment can be... Figure 3 The eyepiece optical system EL (EL2) shown can also be Figure 5 The eyepiece optical system EL (EL3) shown can also be Figure 7 The eyepiece optical system EL (EL4) shown can also be Figure 9 The eyepiece optical system EL (EL5) shown can also be Figure 11 The eyepiece optical system EL (EL6) shown can also be Figure 13 The eyepiece optical system shown is EL (EL7).

[0036] Condition (1) specifies the refractive index of the first positive lens Lp1 for the d-line within an appropriate range. By satisfying condition (1) with the positive lens Lp1, astigmatism can be well corrected.

[0037] If the corresponding value of condition (1) exceeds the upper limit, the refractive index of the positive lens Lp1 increases, the petzia deteriorates, and it becomes difficult to correct astigmatism. By setting the upper limit of condition (1) to 1.960, and further to 1.890, the effect of this embodiment can be made more reliable.

[0038] If the corresponding value of condition (1) is lower than the lower limit, the refractive index of the positive lens Lp1 decreases, the petzia deteriorates, and it becomes difficult to correct astigmatism. By setting the lower limit of condition (1) to 1.750, and further to 1.810, the effect of this embodiment can be made more reliable.

[0039] Condition (2) specifies the refractive index of the second positive lens Lp2 for the d-line within an appropriate range. By satisfying condition (2) with the positive lens Lp2, astigmatism can be well corrected.

[0040] If the corresponding value of condition (2) exceeds the upper limit, the refractive index of the positive lens Lp2 increases, the petzia deteriorates, and it becomes difficult to correct astigmatism. By setting the upper limit of condition (2) to 1.960, and further to 1.890, the effect of this embodiment can be made more reliable.

[0041] If the corresponding value of condition (2) is lower than the lower limit, the refractive index of the positive lens Lp2 decreases, the petzia deteriorates, and it becomes difficult to correct astigmatism. By setting the lower limit of condition (2) to 1.750, and further to 1.810, the effect of this embodiment can be made more reliable.

[0042] In the eyepiece optical system EL of the first embodiment, it is preferable that the first positive lens Lp1 has the strongest positive power in the eyepiece optical system EL and satisfies the following condition (3).

[0043] 0.90<Np2 / Np1<1.10···(3)

[0044] Condition (3) specifies the appropriate relationship between the refractive index of the second positive lens Lp2 and the refractive index of the first positive lens Lp1 on the d-line. By satisfying condition (3), astigmatism can be well corrected.

[0045] If the corresponding value of condition (3) exceeds the upper limit, the refractive index of the first positive lens Lp1, which has the strongest positive optical power relative to the second positive lens, becomes too small for the d-line and deteriorates, making it difficult to correct astigmatism. By setting the upper limit of condition (3) to 1.05, and further to 1.01, the effect of this embodiment can be made more reliable.

[0046] If the corresponding value of condition (3) is lower than the lower limit, the refractive index of the first positive lens Lp1 relative to the second positive lens becomes too large for the d line, resulting in patellar degradation and making it difficult to correct astigmatism. By setting the lower limit of condition (3) to 0.92, 0.94, 0.95, and further to 0.96, the effectiveness of this embodiment can be made more reliable.

[0047] In the eyepiece optical system EL of the first embodiment, it is preferable that the first positive lens Lp1 has the strongest positive power in the eyepiece optical system EL and satisfies the following condition (4).

[0048] 0.70<fLp1 / fe<1.30···(4)

[0049] Where fLp1: the focal length of the first positive lens Lp1.

[0050] fe: Combined focal length of the eyepiece optical system EL

[0051] Condition (4) specifies the appropriate relationship between the focal length of the entire eyepiece optical system EL and the focal length of the first positive lens Lp1. By satisfying condition (4), image plane curvature can be well corrected.

[0052] If the corresponding value of condition (4) exceeds the upper limit, the optical power of the first positive lens Lp1 will weaken, and the petzia and deterioration will become difficult to correct the image plane curvature. By setting the upper limit of condition (4) to 1.28, 1.24, 1.22, 1.20, and further setting it to 1.10, the effect of this embodiment can be made more reliable.

[0053] If the corresponding value of condition (4) is lower than the lower limit, the optical power of the first positive lens Lp1 becomes stronger, and the petzia deteriorates, making it difficult to correct the image plane curvature. By setting the lower limit of condition (4) to 0.720, 0.740, 0.750, 0.800, and further setting it to 0.900, the effect of this embodiment can be made more reliable.

[0054] In the eyepiece optical system EL of the first embodiment, it is preferable that the second positive lens Lp2 has the second strongest positive power in the eyepiece optical system EL and satisfies the following condition (5).

[0055] 0.90<fLp2 / fe<1.70···(5)

[0056] Where fLp2: the focal length of the second positive lens Lp2.

[0057] fe: Combined focal length of the eyepiece optical system EL

[0058] Condition (5) specifies the appropriate relationship between the focal length of the entire eyepiece optical system EL and the focal length of the second positive lens Lp2. By satisfying condition (5), image plane curvature can be well corrected.

[0059] If the corresponding value of condition (5) exceeds the upper limit, the optical power of the second positive lens Lp2 will weaken, and the petzia and deterioration will make it difficult to correct the image plane curvature. By setting the upper limit of condition (5) to 1.68, 1.58, 1.55, 1.35, and further setting it to 1.30, the effect of this embodiment can be made more reliable.

[0060] If the corresponding value of condition (5) is lower than the lower limit, the optical power of the second positive lens Lp2 becomes stronger, and the petzia and deterioration become more difficult to correct for the image plane curvature. By setting the lower limit of condition (5) to 0.95, 1.00, and further to 1.10, the effect of this embodiment can be made more reliable.

[0061] In the eyepiece optical system EL of the first embodiment, it is preferable to have a first negative lens Ln1, which has the strongest negative optical power in the eyepiece optical system EL and satisfies the following conditional expressions (6) and (7).

[0062] 1.500<Nn1<1.700···(6)

[0063] 16.000<νn1<36.000···(7)

[0064] Where Nn1: the refractive index of the first negative lens Ln1 for the d-line.

[0065] νn1: The Abbe number of the first negative lens Ln1 relative to the d-line.

[0066] Condition (6) specifies the refractive index of the first negative lens Ln1, which has the strongest negative optical power in the eyepiece optical system EL, to the d-line within an appropriate range. By satisfying condition (6) with the negative lens Ln1, astigmatism can be well corrected.

[0067] If the corresponding value of condition (6) exceeds the upper limit, the refractive index of the negative lens Ln1 increases, and the petzia and astigmatism deteriorate, making it difficult to correct. By setting the upper limit of condition (6) to 1.650, and further to 1.640, the effect of this embodiment can be made more reliable.

[0068] If the corresponding value of condition (6) is lower than the lower limit, the refractive index of the negative lens Ln1 decreases, and the petzvar deteriorates, making it difficult to correct astigmatism. By setting the lower limit of condition (6) to 1.530, 1.550, and further to 1.600, the effect of this embodiment can be made more reliable.

[0069] Condition (7) specifies the Abbe number of the first negative lens Ln1, which has the strongest negative optical power in the eyepiece optical system EL, within an appropriate range. By satisfying condition (7) with the Abbe number of the negative lens Ln1, chromatic aberration can be well corrected.

[0070] If the corresponding value of condition (7) exceeds the upper limit, the dispersion based on the negative lens Ln1 becomes smaller, and the correction of chromatic aberration becomes insufficient, which is therefore not preferred. By setting the upper limit of condition (7) to 30.000, and further setting it to 25.000, the effect of this embodiment can be made more reliable.

[0071] If the corresponding value of condition (7) is lower than the lower limit, the dispersion based on the negative lens Ln1 increases, and the chromatic aberration correction becomes excessive, which is not preferred. By setting the lower limit of condition (7) to 18.000, and further setting it to 20.000, the effect of this embodiment can be made more reliable.

[0072] In the eyepiece optical system EL of the first embodiment, it is preferable to have a second negative lens Ln2, which has the second strongest negative optical power in the eyepiece optical system EL, and satisfies the following conditional expression (8).

[0073] 1.500<Nn2<1.700···(8)

[0074] Where Nn2: the refractive index of the second negative lens Ln2 for the d-line.

[0075] Condition (8) specifies the refractive index of the second negative lens Ln2, which has the second strongest optical power in the eyepiece optical system EL, within an appropriate range for the d-line. By satisfying condition (8) with the negative lens Ln2, astigmatism can be well corrected.

[0076] If the corresponding value of condition (8) exceeds the upper limit, the refractive index of the negative lens Ln2 increases, the petzia deteriorates, and it becomes difficult to correct astigmatism. By setting the upper limit of condition (8) to 1.650, and further to 1.640, the effect of this embodiment can be made more reliable.

[0077] If the corresponding value of condition (8) is lower than the lower limit, the refractive index of the negative lens Ln2 decreases, the petzia deteriorates, and it becomes difficult to correct astigmatism. By setting the lower limit of condition (8) to 1.530, 1.550, and further to 1.600, the effect of this embodiment can be made more reliable.

[0078] In the eyepiece optical system EL of the first embodiment, it is preferable to have a first negative lens Ln1 with the strongest negative optical power and satisfy the following condition (9).

[0079] 8.000<νp1-νn1<35.000···(9)

[0080] Wherein, νp1: the Abbe number of the first positive lens Lp1 relative to the d-line.

[0081] νn1: The Abbe number of the first negative lens Ln1 relative to the d-line.

[0082] Condition (9) specifies the difference between the Abbe numbers of the first positive lens Lp1 and the first negative lens Ln1 within an appropriate range. By satisfying condition (9), chromatic aberration can be well corrected.

[0083] If the corresponding value of condition (9) exceeds the upper limit, the dispersion of the negative lens Ln1 becomes larger relative to the first positive lens Lp1, and the correction of chromatic aberration becomes excessive, which is not preferred. By setting the upper limit of condition (9) to 30.000, and further setting it to 25.000, the effect of this embodiment can be made more reliable.

[0084] If the corresponding value of condition (9) is lower than the lower limit, the dispersion of the negative lens Ln1 becomes smaller relative to the first positive lens Lp1, and the chromatic aberration correction becomes insufficient, which is not preferred. By setting the lower limit of condition (9) to 10.000, 12.000, 15.000, and further to 20.000, the effect of this embodiment can be made more reliable.

[0085] In the eyepiece optical system EL of the first embodiment, it is preferable to have a first negative lens Ln1 with the strongest negative optical power, and to satisfy the following conditional expression (10).

[0086] 8.000<νp2-νn1<35.000···(10)

[0087] Wherein, νp2: the Abbe number of the second positive lens Lp2 with reference to the d-line.

[0088] νn1: The Abbe number of the first negative lens Ln1 relative to the d-line.

[0089] Condition (10) specifies the difference between the Abbe numbers of the second positive lens Lp2 and the first negative lens Ln1 within an appropriate range. By satisfying condition (10), chromatic aberration can be well corrected.

[0090] If the corresponding value of condition (10) exceeds the upper limit, the dispersion of the negative lens Ln1 becomes larger relative to the second positive lens Lp2, and the correction of chromatic aberration becomes excessive, which is not preferred. By setting the upper limit of condition (10) to 30.000, and further setting it to 25.000, the effect of this embodiment can be made more reliable.

[0091] If the corresponding value of conditional expression (10) is lower than the lower limit, the dispersion of negative lens Ln1 becomes smaller relative to the second positive lens Lp2, and the chromatic aberration correction becomes insufficient, which is not preferred. By setting the lower limit of conditional expression (10) to 10.000, 12.000, 15.000, and further to 20.000, the effect of this embodiment can be made more reliable.

[0092] In the eyepiece optical system EL of the first embodiment, it is preferable that the following condition (11) is satisfied.

[0093] 0.400<h / fe<0.500···(11)

[0094] Where fe: the composite focal length of the eyepiece optical system EL

[0095] h: Maximum height of the observed object Ob in the eyepiece optical system EL

[0096] Condition (11) defines the size of the image obtained by the eyepiece optical system EL by the maximum height of the observed object Ob relative to the overall focal length of the eyepiece optical system EL. By satisfying condition (11), aberrations can be well corrected even with a large field of view.

[0097] If the corresponding value of condition (11) exceeds the upper limit, the field of view becomes too large, and the correction of off-axis aberrations becomes difficult, which is not preferred. By setting the upper limit of condition (11) to 0.480, 0.470, 0.460, and further setting it to 0.450, the effect of this embodiment can be made more reliable.

[0098] If the corresponding value of condition (11) is lower than the lower limit, the magnification of the eyepiece optical system EL becomes higher, and the correction of various aberrations becomes more difficult. By setting the lower limit of condition (11) to 0.420, 0.430, and further to 0.440, the effect of this embodiment can be made more reliable.

[0099] In the eyepiece optical system EL of the first embodiment, it is preferable to have at least one lens with an aspherical surface formed on the lens surface that satisfies the following condition (12).

[0100] 0.000≤Daspe / ΣD<0.200···(12)

[0101] Where Daspe is the distance along the optical axis from the aspherical surface closest to the viewpoint to the lens surface closest to the viewpoint in the eyepiece optical system EL.

[0102] ΣD: The distance along the optical axis from the lens surface closest to the observed object (Ob) to the lens surface closest to the viewpoint (EP).

[0103] Condition (12) specifies the ratio of the distance on the optical axis from the aspherical surface closest to the viewpoint EP to the lens surface closest to the viewpoint EP to the distance on the optical axis from the lens surface closest to the observed object Ob to the lens surface closest to the viewpoint EP within an appropriate range. By satisfying condition (12), spherical aberration and coma generated on the viewpoint EP side can be well corrected.

[0104] If the corresponding value of condition (12) exceeds the upper limit, the position of the aspherical surface located on the side closest to the viewpoint EP moves away from the viewpoint EP, making it difficult to correct spherical aberration and coma generated on the viewpoint EP side. By setting the upper limit of condition (12) to 0.190, and further setting it to 0.170, the effectiveness of this embodiment can be made more reliable. In addition, the lower limit of condition (12) represents the lens surface closest to the viewpoint EP.

[0105] In the eyepiece optical system EL of the first embodiment, it is preferable to have at least one lens with an aspherical surface formed on the lens surface that satisfies the following condition (13).

[0106] 0.000≤Daspо / ΣD<0.200···(13)

[0107] Where Dasp0: the distance on the optical axis from the lens surface of the eyepiece optical system EL closest to the ob side of the observed object to the aspherical surface closest to the ob side of the observed object.

[0108] ΣD: The distance along the optical axis from the lens surface closest to the observed object (Ob) to the lens surface closest to the viewpoint (EP).

[0109] Condition (13) specifies the ratio of the distance on the optical axis from the lens surface closest to the ob side of the observed object to the aspherical surface closest to the ob side of the observed object to the distance on the optical axis from the lens surface closest to the ob side of the observed object to the lens surface closest to the viewpoint EP side within an appropriate range. By satisfying condition (13), distortion generated on the ob side of the eyepiece optical system EL can be well corrected.

[0110] If the corresponding value of condition (13) exceeds the upper limit, the position of the aspherical surface located closest to the ob side of the observed object moves away from the ob side, making it difficult to correct the distortion generated on the ob side of the observed object. By setting the upper limit of condition (13) to 0.190, and further to 0.170, the effectiveness of this embodiment can be made more reliable. In addition, the lower limit of condition (13) of 0.000 represents the lens surface closest to the ob side of the observed object.

[0111] In the eyepiece optical system EL of the first embodiment, it is preferable to have at least one lens La with an aspherical surface formed on the lens surface and an inflection point on the aspherical surface where the radius of curvature reverses from positive to negative or from negative to positive, and to satisfy the following conditional expression (14).

[0112] 0.20<y / Ry<0.85···(14)

[0113] Where y: the distance between the optical axis and the inflection point in the direction perpendicular to the optical axis of lens La.

[0114] Ry: Radius of lens La

[0115] Condition (14) specifies the ratio of the distance between the optical axis and the position of the inflection point in the direction perpendicular to the optical axis in lens La to the radius of lens La within an appropriate range. By satisfying condition (14), an inflection point is provided at the periphery of the optical axis within the effective aperture of lens La, and distortion can be well corrected by the inflection point. The inflection point is the position where the radius of curvature reverses, and the radius of curvature reverses from positive to negative or from negative to positive with this position as the boundary. Furthermore, it is preferable to configure the lens La with the inflection point as the lens having the aspherical surface closest to the ob side of the observed object. With such a structure, distortion can be well corrected. Furthermore, lens La is configured as a lens with positive optical power paraxially and an inflection point at the periphery, thereby improving the telecentricity of the ob side of the observed object.

[0116] If the corresponding value of condition (14) exceeds the upper limit, the distortion of the intermediate image height will worsen and it will not be preferred. By setting the upper limit of condition (14) to 0.700, and further setting it to 0.500, the effect of this embodiment can be made more reliable.

[0117] If the corresponding value of condition (14) is lower than the lower limit, the image plane curvature deteriorates and is not preferred. By setting the lower limit of condition (14) to 0.250, and further to 0.300, the effect of this embodiment can be made more reliable.

[0118] In the eyepiece optical system EL of the first embodiment, it is preferable to have at least five lenses. With this structure, various aberrations can be well corrected. If the number of lenses is four or less, the optical power of each individual lens becomes stronger, making aberration correction more difficult.

[0119] In the eyepiece optical system EL of the first embodiment, it is preferable that both the first positive lens Lp1 and the second positive lens Lp2 are lenses with spherical lens surfaces. The spherical lens surfaces of the positive lenses Lp1 and Lp2 reduce performance degradation due to eccentricity. Furthermore, performance degradation caused by aspherical shape errors, which have a greater impact on high-refractive-index lenses, can be avoided.

[0120] Next, the eyepiece optical system of the second embodiment will be described. For example... Figure 1 As shown, the eyepiece optical system EL (EL1), which is an example of the eyepiece optical system EL in the second embodiment, has at least 5 lenses.

[0121] Under the above structure, the eyepiece optical system EL of the second embodiment satisfies the following conditional expression (11).

[0122] 0.400<h / fe<0.500···(11)

[0123] Where fe: the composite focal length of the eyepiece optical system EL

[0124] h: Maximum height of the observed object Ob in the eyepiece optical system EL

[0125] According to the second embodiment, an eyepiece optical system with good optical performance that corrects various aberrations, especially astigmatism and distortion, and an optical device equipped with the eyepiece optical system can be obtained. The zoom optical system ZL of the second embodiment can be... Figure 3 The eyepiece optical system EL (EL2) shown can also be Figure 5 The eyepiece optical system EL (EL3) shown can also be Figure 7 The eyepiece optical system EL (EL4) shown can also be Figure 9 The eyepiece optical system EL (EL5) shown can also be Figure 11 The eyepiece optical system EL (EL6) shown can also be Figure 13 The eyepiece optical system shown is EL (EL7).

[0126] By configuring the eyepiece optics system (EL) with at least five lenses, various aberrations can be effectively corrected. If the number of lenses is four or fewer, the optical power of each individual lens becomes stronger, making aberration correction more difficult.

[0127] Condition (11) is the same as that in the first embodiment, and the same effect can be obtained. If the corresponding value of condition (11) exceeds the upper limit, the field of view becomes too large, and the correction of off-axis aberrations becomes difficult, so it is not preferred. By setting the upper limit of condition (11) to 0.480, 0.470, 0.460, and further setting it to 0.450, the effect of this embodiment can be made more reliable.

[0128] If the corresponding value of condition (11) is lower than the lower limit, the magnification of the eyepiece optical system EL becomes higher, and the correction of various aberrations becomes more difficult. By setting the lower limit of condition (11) to 0.420, 0.430, and further to 0.440, the effect of this embodiment can be made more reliable.

[0129] In the eyepiece optical system EL of the second embodiment, it is preferable that the following condition (11) is satisfied.

[0130] 0.400<h / fe<0.500···(11)

[0131] Where fe: the composite focal length of the eyepiece optical system EL

[0132] h: Maximum height of the observed object Ob in the eyepiece optical system EL

[0133] Condition (11) is the same as that in the first embodiment, and the same effect can be obtained. If the corresponding value of condition (11) exceeds the upper limit, the field of view becomes too large, and the correction of off-axis aberrations becomes difficult, so it is not preferred. By setting the upper limit of condition (11) to 0.480, 0.470, 0.460, and further setting it to 0.450, the effect of this embodiment can be made more reliable.

[0134] If the corresponding value of condition (11) is lower than the lower limit, the magnification of the eyepiece optical system EL becomes higher, and the correction of various aberrations becomes more difficult. By setting the lower limit of condition (11) to 0.420, 0.430, and further to 0.440, the effect of this embodiment can be made more reliable.

[0135] In the eyepiece optical system EL of the second embodiment, it is preferable to have at least one lens with an aspherical surface formed on the lens surface that satisfies the following condition (12).

[0136] 0.000≤Daspe / ΣD<0.200···(12)

[0137] Where Daspe is the distance along the optical axis from the aspherical surface closest to the viewpoint to the lens surface closest to the viewpoint in the eyepiece optical system EL.

[0138] ΣD: The distance along the optical axis from the lens surface closest to the observed object (Ob) to the lens surface closest to the viewpoint (EP).

[0139] Condition (12) is the same as that in the first embodiment, and the same effect can be obtained. By satisfying condition (12), spherical aberration and coma generated at the viewpoint EP can be well corrected by aspherical surface.

[0140] If the corresponding value of condition (12) exceeds the upper limit, the position of the aspherical surface located on the side closest to the viewpoint EP moves away from the viewpoint EP, making it difficult to correct spherical aberration and coma generated on the viewpoint EP side. By setting the upper limit of condition (12) to 0.190, and further setting it to 0.170, the effectiveness of this embodiment can be made more reliable. In addition, the lower limit of condition (12) represents the lens surface closest to the viewpoint EP.

[0141] In the eyepiece optical system EL of the second embodiment, it is preferable to have at least one lens with an aspherical surface formed on the lens surface that satisfies the following condition (13).

[0142] 0.000≤Daspо / ΣD<0.200···(13)

[0143] Where Dasp0: the distance on the optical axis from the lens surface of the eyepiece optical system EL closest to the ob side of the observed object to the aspherical surface closest to the ob side of the observed object.

[0144] ΣD: The distance along the optical axis from the lens surface closest to the observed object (Ob) to the lens surface closest to the viewpoint (EP).

[0145] Condition (13) is the same as that in the first embodiment, and the same effect can be obtained. By satisfying condition (13), the distortion generated on the ob side of the observed object in the eyepiece optical system EL can be well corrected by the aspherical surface.

[0146] If the corresponding value of condition (13) exceeds the upper limit, the position of the aspherical surface located closest to the ob side of the observed object moves away from the ob side, making it difficult to correct the distortion generated on the ob side of the observed object. By setting the upper limit of condition (13) to 0.190, and further to 0.170, the effectiveness of this embodiment can be made more reliable. In addition, the lower limit of condition (13) represents the lens surface closest to the ob side of the observed object.

[0147] In the eyepiece optical system EL of the second embodiment, it is preferable to have at least one lens La with an aspherical surface formed on the lens surface and an inflection point on the aspherical surface where the radius of curvature reverses from positive to negative or from negative to positive, and to satisfy the following conditional expression (14).

[0148] 0.20<y / Ry<0.85···(14)

[0149] Where y: the distance between the optical axis and the inflection point in the direction perpendicular to the optical axis of lens La.

[0150] Ry: Radius of lens La

[0151] Condition (14) is the same as in the first embodiment, and the same effect can be obtained. By satisfying condition (14), an inflection point is provided at the periphery of the optical axis within the effective aperture of lens La, and distortion can be well corrected by the inflection point. The inflection point is the position where the radius of curvature reverses, and the radius of curvature reverses from positive to negative or from negative to positive with this position as the boundary. In addition, it is preferable to configure the lens La with the inflection point as the lens having the aspherical surface closest to the ob side of the observed object. By setting it with such a structure, distortion can be well corrected. Furthermore, lens La is configured as a lens with positive optical power paraxially and an inflection point at the periphery, thereby improving the telecentricity of the ob side of the observed object.

[0152] If the corresponding value of condition (14) exceeds the upper limit, the distortion of the intermediate image height will worsen and it will not be preferred. By setting the upper limit of condition (14) to 0.700, and further setting it to 0.500, the effect of this embodiment can be made more reliable.

[0153] If the corresponding value of condition (14) is lower than the lower limit, the image plane curvature deteriorates and is not preferred. By setting the lower limit of condition (14) to 0.250, and further to 0.300, the effect of this embodiment can be made more reliable.

[0154] In the eyepiece optical system EL of the second embodiment, it is preferable to have at least five lenses. This structure allows for good correction of various aberrations. If the number of lenses is four or less, the optical power of each individual lens becomes stronger, making aberration correction more difficult.

[0155] Next, the eyepiece optical system of the third embodiment will be described. For example... Figure 1 , Figure 15 As shown, the eyepiece optical system EL (EL1), which is an example of the eyepiece optical system EL in the third embodiment, is an eyepiece optical system for observing an image displayed on an image display element and has at least 5 lenses.

[0156] According to the third embodiment, an eyepiece optical system with good optical performance that corrects various aberrations, especially astigmatism and distortion, and an optical device equipped with the eyepiece optical system can be obtained. The zoom optical system ZL of the second embodiment can be... Figure 3 The eyepiece optical system EL (EL2) shown can also be Figure 5 The eyepiece optical system EL (EL3) shown can also be Figure 7 The eyepiece optical system EL (EL4) shown can also be Figure 9 The eyepiece optical system EL (EL5) shown can also be Figure 11 The eyepiece optical system EL (EL6) shown can also be Figure 13 The eyepiece optical system shown is EL (EL7).

[0157] By configuring the eyepiece optics system (EL) with at least five lenses, various aberrations can be effectively corrected. If the number of lenses is four or fewer, the optical power of each individual lens becomes stronger, making aberration correction more difficult.

[0158] In the eyepiece optical system EL of the third embodiment, it is preferable that the following condition (11) is satisfied.

[0159] 0.400<h / fe<0.500···(11)

[0160] Where fe: the composite focal length of the eyepiece optical system EL

[0161] h: Maximum height of the observed object Ob in the eyepiece optical system EL

[0162] Condition (11) is the same as that in the first and second embodiments, and the same effect can be obtained. By satisfying condition (11), even with a large field of view, various aberrations can be well corrected.

[0163] If the corresponding value of condition (11) exceeds the upper limit, the field of view becomes too large, and the correction of off-axis aberrations becomes difficult, which is not preferred. By setting the upper limit of condition (11) to 0.480, 0.470, 0.460, and further setting it to 0.450, the effect of this embodiment can be made more reliable.

[0164] If the corresponding value of condition (11) is lower than the lower limit, the magnification of the eyepiece optical system EL becomes higher, and the correction of various aberrations becomes more difficult. By setting the lower limit of condition (11) to 0.420, 0.430, and further to 0.440, the effect of this embodiment can be made more reliable.

[0165] In the eyepiece optical system EL of the third embodiment, it is preferable to have at least one lens with an aspherical surface formed on the lens surface that satisfies the following condition (12).

[0166] 0.000≤Daspe / ΣD<0.200···(12)

[0167] Where Daspe is the distance along the optical axis from the aspherical surface closest to the viewpoint to the lens surface closest to the viewpoint in the eyepiece optical system EL.

[0168] ΣD: The distance along the optical axis from the lens surface closest to the observed object (Ob) to the lens surface closest to the viewpoint (EP).

[0169] Condition (12) is the same as that in the first and second embodiments, and the same effect can be obtained. By satisfying condition (12), spherical aberration and coma generated at the viewpoint EP can be well corrected by aspherical surface.

[0170] If the corresponding value of condition (12) exceeds the upper limit, the position of the aspherical surface located on the side closest to the viewpoint EP moves away from the viewpoint EP, making it difficult to correct spherical aberration and coma generated on the viewpoint EP side. By setting the upper limit of condition (12) to 0.190, and further setting it to 0.170, the effectiveness of this embodiment can be made more reliable. In addition, the lower limit of condition (12) represents the lens surface closest to the viewpoint EP.

[0171] In the eyepiece optical system EL of the third embodiment, it is preferable to have at least one lens with an aspherical surface formed on the lens surface that satisfies the following condition (13).

[0172] 0.000≤Daspо / ΣD<0.200···(13)

[0173] Where Dasp0: the distance on the optical axis from the lens surface of the eyepiece optical system EL closest to the ob side of the observed object to the aspherical surface closest to the ob side of the observed object.

[0174] ΣD: The distance along the optical axis from the lens surface closest to the observed object (Ob) to the lens surface closest to the viewpoint (EP).

[0175] Condition (13) is the same as in the first and second embodiments, and the same effect can be obtained. By satisfying condition (13), the distortion generated on the ob side of the observed object in the eyepiece optical system EL can be well corrected by the aspherical surface.

[0176] If the corresponding value of condition (13) exceeds the upper limit, the position of the aspherical surface located closest to the ob side of the observed object moves away from the ob side, making it difficult to correct the distortion generated on the ob side of the observed object. By setting the upper limit of condition (13) to 0.190, and further to 0.170, the effectiveness of this embodiment can be made more reliable. In addition, the lower limit of condition (13) represents the lens surface closest to the ob side of the observed object.

[0177] In the eyepiece optical system EL of the third embodiment, it is preferable to have at least one lens La with an aspherical surface formed on the lens surface and an inflection point on the aspherical surface where the radius of curvature reverses from positive to negative or from negative to positive, and to satisfy the following conditional expression (14).

[0178] 0.20<y / Ry<0.85···(14)

[0179] Where y: the distance between the optical axis and the inflection point in the direction perpendicular to the optical axis of lens La.

[0180] Ry: Radius of lens La

[0181] Conditional expression (14) is the same as in the first and second embodiments, and the same effect can be obtained. By satisfying conditional expression (14), an inflection point is provided at the periphery of the optical axis within the effective aperture of lens La, and distortion can be well corrected by the inflection point. The inflection point is the position where the radius of curvature reverses, and the radius of curvature reverses from positive to negative or from negative to positive with this position as the boundary. In addition, it is preferable to configure the lens La with the inflection point as the lens having the aspherical surface closest to the ob side of the observed object. By setting it to such a structure, distortion can be well corrected. Furthermore, lens La is configured as a lens with positive optical power paraxially and an inflection point at the periphery, thereby improving the telecentricity of the ob side of the observed object.

[0182] If the corresponding value of condition (14) exceeds the upper limit, the distortion of the intermediate image height will worsen and it will not be preferred. By setting the upper limit of condition (14) to 0.700, and further setting it to 0.500, the effect of this embodiment can be made more reliable.

[0183] If the corresponding value of condition (14) is lower than the lower limit, the image plane curvature deteriorates and is not preferred. By setting the lower limit of condition (14) to 0.250, and further to 0.300, the effect of this embodiment can be made more reliable.

[0184] In the eyepiece optical system EL of the first to third embodiments described above, it is preferable that the following conditional expression (15) is satisfied.

[0185] 20.000[mm]<De<30.000[mm]···(15)

[0186] Where De: the distance on the optical axis from the lens surface of the eyepiece optical system EL closest to the viewpoint EP to the viewpoint EP.

[0187] Condition (15) specifies the distance on the optical axis from the lens surface closest to the viewpoint EP in the eyepiece optical system EL to the viewpoint EP. By satisfying condition (15), various aberrations such as distortion, spherical aberration, and coma can be well corrected.

[0188] If the corresponding value of condition (15) exceeds the upper limit, a convex lens with strong positive power is placed at a position away from the aperture arranged outside the eyepiece optical system EL, making distortion correction difficult and therefore not preferred. By setting the upper limit of condition (15) to 28.000, and further to 26.000, the effect of this embodiment can be made more reliable.

[0189] If the corresponding value of condition (15) is lower than the lower limit, the separation between the on-axis beam and the off-axis beam on the viewpoint EP side becomes smaller, making it difficult to correct spherical aberration and coma, which is therefore not preferred. By setting the lower limit of condition (15) to 21.000, and further to 22.000, the effect of this embodiment can be made more reliable.

[0190] In the eyepiece optical system EL of the first to third embodiments described above, it is preferable that the following conditional expression (16) is satisfied.

[0191] 1.100<De / fe<1.500···(16)

[0192] Where De: the distance on the optical axis from the lens surface of the eyepiece optical system EL closest to the viewpoint EP to the viewpoint EP.

[0193] fe: Combined focal length of the eyepiece optical system EL

[0194] Condition (16) specifies the ratio of the distance on the optical axis from the lens surface closest to the viewpoint EP of the eyepiece optical system EL to the overall focal length of the eyepiece optical system EL within an appropriate range. By satisfying condition (16), various aberrations such as distortion, spherical aberration, and coma can be well corrected.

[0195] If the corresponding value of condition (16) exceeds the upper limit, a convex lens with strong positive power is placed at a position away from the aperture arranged outside the eyepiece optical system EL, making distortion correction difficult and therefore undesirable. By setting the upper limit of condition (16) to 1.450, 1.400, and further to 1.350, the effect of this embodiment can be made more reliable.

[0196] If the corresponding value of condition (16) is lower than the lower limit, the separation between the on-axis beam and the off-axis beam on the viewpoint EP side becomes smaller, making it difficult to correct spherical aberration and coma, which is therefore not preferred. By setting the lower limit of condition (16) to 1.200, 1.240, 1.280, and further to 1.300, the effectiveness of this embodiment can be made more reliable.

[0197] In the eyepiece optical system EL of the first to third embodiments described above, it is preferable that the lens disposed on the side closest to the observed object (Ob) has positive optical power. By adopting such a structure, distortion can be well corrected. On the other hand, if a lens with negative optical power is disposed on the side closest to the observed object (Ob), the lens becomes larger in the radial direction, which is not preferable.

[0198] In the eyepiece optical system EL of the first to third embodiments described above, it is preferable that the following conditional expression (17) is satisfied.

[0199] 0.250<D0 / fe<0.500···(17)

[0200] Where D0: from a viewpoint of 0 [m] -1 The distance on the optical axis from the observed object Ob to the lens surface closest to the observed object Ob.

[0201] fe: Combined focal length of the eyepiece optical system EL

[0202] Conditional expression (17) will reduce the visibility to 0 [m] -1 The ratio of the distance on the optical axis from the observed object Ob to the lens surface closest to the observed object Ob to the overall focal length of the eyepiece optical system EL is specified within an appropriate range. By satisfying condition (17), various aberrations such as image plane curvature and distortion can be well corrected, and the telecentricity on the side of the observed object Ob can be maintained.

[0203] If the corresponding value of condition (17) exceeds the upper limit, the lens surface closest to the observed object Ob moves away from the observed object Ob, making it difficult to correct image plane curvature and distortion. By setting the upper limit of condition (17) to 0.480, 0.460, 0.440, and further to 0.420, the effectiveness of this embodiment can be made more reliable.

[0204] If the corresponding value of condition (17) is lower than the lower limit, the lens surface closest to the observed object Ob is too close to the observed object Ob, thereby destroying the centrifugality of the observed object Ob side, which is not preferred. By setting the lower limit of condition (17) to 0.300, 0.350, and further to 0.400, the effect of this embodiment can be made more reliable.

[0205] In the eyepiece optical system EL of the first to third embodiments described above, it is preferable that the following conditional expression (18) is satisfied.

[0206] 0.120<D0 / TL<0.250···(18)

[0207] Where D0: from a viewpoint of 0 [m] -1 The distance on the optical axis from the observed object Ob to the lens surface closest to the observed object Ob.

[0208] TL: From a viewpoint of 0 [m] -1 The distance on the optical axis from the observed object Ob to the lens surface closest to the viewpoint EP.

[0209] Conditional expression (18) will reduce the visibility to 0 [m] -1 The distance along the optical axis from the observed object Ob to the lens surface closest to the observed object Ob is equal to the distance from the lens surface with a diopter of 0 [m]. -1 The ratio of the distance on the optical axis from the observed object Ob to the lens surface closest to the viewpoint EP is specified within an appropriate range. By satisfying condition (18), various aberrations such as image plane curvature and distortion can be well corrected, ensuring telecentrism on the side of the observed object Ob.

[0210] If the corresponding value of condition (18) exceeds the upper limit, the lens surface closest to the observed object Ob moves away from the observed object Ob, making it difficult to correct image plane curvature and distortion. By setting the upper limit of condition (18) to 0.240, and further to 0.230, the effectiveness of this embodiment can be made more reliable.

[0211] If the corresponding value of condition (18) is lower than the lower limit, the lens surface closest to the observed object Ob is too close to the observed object Ob, making it difficult to ensure the centrifugality of the observed object Ob side, which is therefore not preferred. By setting the lower limit of condition (18) to 0.125, 0.150, and further to 0.200, the effect of this embodiment can be made more reliable.

[0212] In the eyepiece optical system EL of the first to third embodiments described above, it is preferable that the following conditional expression (19) is satisfied.

[0213] 0.080<ΣDair / ΣD<0.200···(19)

[0214] Wherein, ΣDair: the sum of the air gaps between lenses from the lens closest to the observed object Ob to the lens closest to the viewpoint EP.

[0215] ΣD: The distance along the optical axis from the lens surface closest to the observed object (Ob) to the lens surface closest to the viewpoint (EP).

[0216] Condition (19) specifies the ratio of the sum of the air gaps between the lenses from the lens closest to the observed object Ob to the lens closest to the viewpoint EP to the distance on the optical axis from the lens surface closest to the observed object Ob to the lens surface closest to the viewpoint EP to an appropriate range. By satisfying condition (19), various aberrations can be well corrected. Furthermore, optical elements without optical power, such as prisms, can be used before and after the eyepiece optical system EL. Preferably, when using optical elements without optical power, such as prisms, in the eyepiece optical system EL, ΣDair is the equivalent air length from the lens closest to the observed object Ob to the lens closest to the viewpoint EP. That is, ΣDair is the equivalent air length including optical elements without optical power, such as prisms.

[0217] If the corresponding value of condition (19) exceeds the upper limit, the distance between the lenses becomes larger, and the correction of each aberration becomes difficult. By setting the upper limit of condition (19) to 0.180, 0.170, 0.160, and further to 0.150, the effect of this embodiment can be made more reliable.

[0218] If the corresponding value of condition (19) is lower than the lower limit, it is necessary to reduce the difference in the radius of curvature of the convex and concave surfaces of adjacent lenses, making aberration correction at the convex and concave surfaces difficult. By setting the lower limit of condition (19) to 0.085, 0.090, 0.100, and further to 0.110, the effectiveness of this embodiment can be made more reliable.

[0219] In the eyepiece optical system EL of the first to third embodiments described above, it is preferable that the lens disposed on the side closest to the observed object Ob has positive optical power, and the lens disposed adjacent to the lens on the viewpoint side of the lens closest to the observed object has positive optical power. By adopting such a structure, it becomes easy to balance the correction of distortion and spherical aberration.

[0220] In the eyepiece optical system EL of the first to third embodiments described above, it is preferable that the number of lenses having positive optical power is four. By arranging it in this way, the convex optical power of each lens can be reduced, and therefore the correction of each aberration is good.

[0221] In the eyepiece optical system EL of the first to third embodiments described above, it is preferable that the following conditional expression (20) is satisfied.

[0222] 1.00<f1 / fe<2.50···(20)

[0223] Where f1: the focal length of the lens positioned closest to the object being observed.

[0224] fe: the composite focal length of the eyepiece optical system

[0225] Condition (20) specifies the ratio of the focal length of the lens positioned closest to the observed object to the overall focal length of the eyepiece optical system EL within an appropriate range. By satisfying condition (20), various aberrations can be well corrected.

[0226] If the corresponding value of condition (20) exceeds the upper limit, the positive optical power of the lens closest to the observed object weakens, thus the distortion worsens and aberration correction becomes difficult. By setting the upper limit of condition (20) to 2.00, 2.10, and further to 2.30, the effect of this embodiment can be made more reliable.

[0227] If the corresponding value of condition (20) is lower than the lower limit, the positive optical power of the lens closest to the observed object becomes stronger, thus the image plane curvature worsens and aberration correction becomes difficult. By setting the lower limit of condition (20) to 1.10, 1.20, and further to 1.25, the effect of this embodiment can be made more reliable.

[0228] In the eyepiece optical system EL of the first to third embodiments described above, it is preferable that the following conditional expression (21) is satisfied.

[0229] 1.50<fep / fe<5.00···(21)

[0230] Where, fep: the focal length of the lens positioned closest to the viewpoint.

[0231] fe: the composite focal length of the eyepiece optical system

[0232] Condition (21) specifies the ratio of the focal length of the lens located on the viewpoint side to the overall focal length of the eyepiece optical system EL within an appropriate range. By satisfying condition (21), various aberrations can be well corrected.

[0233] If the corresponding value of condition (21) exceeds the upper limit, the positive optical power of the lens closest to the viewpoint weakens, making it difficult to increase the magnification while maintaining the curvature of the image plane. By setting the upper limit of condition (21) to 4.10, 4.20, and further to 4.30, the effectiveness of this embodiment can be made more reliable.

[0234] If the corresponding value of condition (21) is lower than the lower limit, the positive optical power of the lens closest to the viewpoint becomes stronger, thus worsening spherical aberration / coma and making aberration correction difficult. By setting the lower limit of condition (21) to 1.60, 1.65, and further to 1.70, the effect of this embodiment can be made more reliable.

[0235] Based on the above-described embodiment, an eyepiece optical system with good optical performance that corrects various aberrations, especially astigmatism and distortion, and an optical device equipped with the eyepiece optical system can be obtained.

[0236] Example

[0237] Hereinafter, the observation optical system EL of this embodiment will be described based on the accompanying drawings. Figure 1 , Figure 3 , Figure 5 , Figure 7 , Figure 9 , Figure 11 , Figure 13 These are cross-sectional views showing the structure and power distribution of the observation optical system EL{EL(1)~EL(7)} in embodiments 1 to 7. Figure 1 , Figure 3 , Figure 5 , Figure 7 , Figure 9 , Figure 13 In this embodiment, each lens is represented by a combination of the symbol L and a number. To prevent complexity caused by an increase in the types and number of symbols and numbers, each embodiment uses a separate combination of symbols and numbers to represent lens groups, etc. Therefore, even if the same combination of symbols and numbers is used between embodiments, it does not mean that they are the same structure. Furthermore, the (+) or (-) appended to the designation of each lens group indicates the optical power of each lens group, which is also the case in all the embodiments below.

[0238] Tables 1 through 7 are shown below, where Table 1 shows the first embodiment, Table 2 shows the second embodiment, Table 3 shows the third embodiment, Table 4 shows the fourth embodiment, Table 5 shows the fifth embodiment, Table 6 shows the sixth embodiment, and Table 7 shows the parameter data in the seventh embodiment. In each embodiment, the d-line (wavelength λ = 587.6 nm) and the g-line (wavelength λ = 435.8 nm) are selected as the objects for calculating aberration characteristics.

[0239] In the table's [Overall Parameters], fe represents the overall focal length of the eyepiece optical system EL, and TL represents the total length of the eyepiece optical system EL (from 0 m). -1ΣD represents the distance along the optical axis from the lens surface closest to the ob side of the observed object to the lens surface closest to the viewpoint EP. ΣDair represents the total air gap between the lenses from the lens closest to the ob side of the observed object to the lens surface closest to the viewpoint EP. Daspe represents the distance along the optical axis from the lens surface closest to the ob side of the eyepiece optical system EL to the aspherical surface closest to the ob side of the observed object. Dasp0 represents the distance from the lens surface closest to the ob side of the eyepiece optical system EL to the aspherical surface closest to the ob side of the observed object. The distance along the optical axis from the aspherical surface closest to the observed object (Ob), where Np1 represents the refractive index of the first positive lens Lp1 with respect to the d-line, Np2 represents the refractive index of the second positive lens Lp2 with respect to the d-line, Nn1 represents the refractive index of the first negative lens Ln1 with respect to the d-line, Nn2 represents the refractive index of the second negative lens Ln2 with respect to the d-line, fLp1 represents the focal length of the first positive lens Lp1, fLp2 represents the focal length of the second positive lens Lp2, νp1 represents the Abbe number of the first positive lens Lp1 with respect to the d-line, νp2 represents the Abbe number of the second positive lens Lp2 with respect to the d-line, and νn1 represents the Abbe number of the first negative lens Ln1 with respect to the d-line.

[0240] In the [Lens Parameters] table, the surface number indicates the order of the optical surfaces from the Ob side of the observed object along the direction of light travel; r represents the radius of curvature of each optical surface; D represents the distance on the optical axis from each optical surface to the next optical surface (or viewpoint EP), i.e., the surface spacing; νd represents the Abbe number of the lens material relative to the d-line; nd represents the refractive index of the lens material relative to the d-line; "∞" in the radius of curvature r column indicates a plane; and EP represents the viewpoint. The refractive index of air, "1.0000", is omitted. When the optical surface is aspherical, an additional value is added to the surface number. The paraxial radius of curvature is indicated in the column for radius of curvature r.

[0241] The [Aspherical Data] in the table shows the shape of the aspherical surface shown in the [Lens Parameters] using the following equation (a). X(y) represents the distance along the optical axis from the tangent plane at the vertex of the aspherical surface to the position on the aspherical surface at height y, r represents the radius of curvature (paraxial radius of curvature) of the reference sphere, κ represents the conic constant, and Ai represents the aspherical coefficient of the i-th order. "En" indicates "×10 -n For example, 1.234E-05 = 1.234 × 10⁻⁵ -5 .

[0242] X(y)=(y 2 / r) / {1+(1-κ y 2 / r2 ) 1 / 2}+A4×y 4 +A6×y 6 +A8×y 8 ···(a)

[0243] [Variable Interval Data] shows the changes in D0 and De as indicated in the [Lens Parameters], which vary by adjusting the diopter. D0 represents the change from diopter 0 [m] -1 De represents the distance along the optical axis from the lens surface closest to the observed object (Ob) to the viewpoint (EP) of the eyepiece optical system EL. TL represents the total length of the eyepiece optical system EL (from the diopter 0m). -1 The distance along the optical axis from the ob surface of the observed object to the lens surface closest to the viewpoint EP (when viewed from a distance). The unit of diopter is "m". -1 "Viewpoint Xm" -1 "This indicates that the image formed by the eyepiece optical system EL is located at a position of 1 / X [m (meters)] on the optical axis from the viewpoint EP (where the sign is positive when the image is formed on the observer side of the eyepiece optical system EL).

[0244] In all the parameter values ​​listed below, the focal length f, radius of curvature r, interplanar spacing D, and other lengths are generally expressed in "mm" unless otherwise specified. However, since optical systems can achieve equivalent optical performance even when magnified or reduced proportionally, this is not a limitation. Furthermore, the unit is not limited to "mm" and other appropriate units may be used.

[0245] The table descriptions up to this point are general in all embodiments, and the following descriptions are omitted.

[0246] (First embodiment)

[0247] use Figure 1 , Figure 2 Table 1 illustrates the first embodiment. For example... Figure 1 As shown, the eyepiece optical system EL (EL1) of the first embodiment consists of a first lens L1 with positive optical power, a second lens L2 with positive optical power, a third lens L3 with negative optical power, a fourth lens with negative optical power, a fifth lens with positive optical power, and a sixth lens with positive optical power, arranged sequentially along the optical axis from the side of the observed object (image display element) Ob.

[0248] The first lens L1 is a biconvex positive lens. The lens surfaces of the first lens on the object-observed side (Ob) and the viewpoint side (EP) are formed aspherical. On the aspherical surface, there are inflection points where the curvature changes from positive to negative or from negative to positive in the periphery within the effective aperture.

[0249] The second lens, L2, is a meniscus-shaped positive lens with its concave surface facing the side of the observed object, Ob.

[0250] The third lens, L3, is a meniscus-shaped negative lens with its concave surface facing the ob side of the observed object. The lens surface of the third lens L3 on the ob side of the observed object is formed aspherical.

[0251] Lens L4 is a negative lens with a biconcave shape. The lens surface of lens L4 on the ob side of the observed object is aspherical.

[0252] The fifth lens, L5, is a biconvex positive lens.

[0253] Lens L6 is a meniscus positive lens with its convex surface facing the ob side of the observed object. Aspherical surfaces are formed on both sides of lens L6.

[0254] Diopter adjustment is performed by moving the first lens L1 to the sixth lens L6 as a single unit along the optical axis.

[0255] In this embodiment, the fifth lens L5 constitutes the first positive lens Lp1, and the second lens L2 constitutes the second positive lens Lp2. Furthermore, the third lens L3 constitutes the first negative lens Ln1, and the fourth lens L4 constitutes the second negative lens Ln2. Additionally, the first lens L1 constitutes a lens La with an inflection point on an aspherical surface. Furthermore, the lens positioned closest to the observed object is the first lens L1, and the lens positioned closest to the viewpoint is the sixth lens L6.

[0256] Table 1 below shows the values ​​of each parameter in the first embodiment. The face numbers in Table 1 are... Figure 1 Each optical surface corresponds to another optical surface. In the first embodiment, the first surface, the second surface, the fifth surface, the seventh surface, the eleventh surface, and the twelfth surface are formed into an aspherical shape.

[0257] Furthermore, to avoid the increased complexity of explanations caused by the increase in the number of digits in the reference numerals, Figure 1 Each reference numeral is used independently for each embodiment. Therefore, even if reference numerals are used that are common to drawings of other embodiments, they are not necessarily structures common to other embodiments.

[0258] (Table 1)

[0259] [Overall Parameters]

[0260] [Lens Parameters]

[0261] [Aspherical Data]

[0262] Page 1, κ=1.0000, A4=-1.78550E-04, A6=5.97416E-07, A8=-6.09944E-09

[0263] Page 2, κ=1.0000, A4=1.47007E-05, A6=4.44177E-07, A8=0.00000E+00

[0264] Page 5, κ=0.3948; A4=1.94090E-04; A6=-3.70012E-07; A8=1.57181E-09

[0265] Face 7: κ=0.1447, A4=8.58992E-06, A6=2.97567E-08, A8=0.00000E+00

[0266] Page 11, κ=1.0000, A4=-3.37528E-05, A6=2.22950E-07, A8=-4.76586E-10

[0267] Page 12, κ=1.0000, A4=5.89071E-05, A6=6.30686E-08, A8=0.00000E+00

[0268] [Variable Interval Data]

[0269] [Lens Group Data]

[0270] According to the parameters shown in Table 1, the eyepiece optical system EL1 of the first embodiment satisfies the conditions (1) to (21).

[0271] Figure 2 The eyepiece optical system EL1 of the first embodiment shows a diopter of -1 [m]. -1 Aberration diagrams for various aberrations (spherical aberration, astigmatism, coma, distortion, and chromatic aberration at magnification).

[0272] In each aberration diagram, the vertical axis of the spherical aberration diagram represents the incident height of light emanating from the center of the optical axis of the observed object Ob, incident on the tangent plane of the lens surface of the first lens L1 of the eyepiece optical system EL1 on the side of the observed object Ob. The vertical axis YO of the astigmatism diagram and the distortion diagram represents the size (radius) of the observed object Ob. D represents the aberration curve below the d-line, and g represents the aberration curve below the g-line. Additionally, the aberration curve below the d-line is not explicitly stated. In the astigmatism diagram, the sagittal image plane is represented by the dashed line, and the meridional image plane by the dashed line. Furthermore, in the aberration diagram showing coma, meridional coma is shown. In the spherical aberration diagram and the astigmatism diagram, the units of the horizontal axis are [m]. -1 ], which is represented by "D" in the diagram.

[0273] The above description of aberration maps is also applicable to other embodiments, and its description is omitted.

[0274] from Figure 2 As can be clearly seen from the aberration diagrams shown, the eyepiece optical system EL1 of the first embodiment effectively corrects various aberrations, especially astigmatism and distortion, ensuring excellent optical performance.

[0275] (Second Embodiment)

[0276] use Figure 3 , Figure 4 Table 2 illustrates the second embodiment. For example... Figure 3 As shown, the eyepiece optical system EL (EL2) of the second embodiment consists of a first lens L1 with positive optical power, a second lens L2 with positive optical power, a third lens L3 with negative optical power, a fourth lens with positive optical power, a fifth lens with negative optical power, and a sixth lens with positive optical power, arranged sequentially along the optical axis from the side of the observed object (image display element) Ob.

[0277] The first lens L1 is a biconvex positive lens. The lens surfaces on both sides of the first lens L1 are formed aspherical. On the aspherical surfaces, there are inflection points where the curvature changes from positive to negative or from negative to positive in the periphery within the effective aperture.

[0278] The second lens, L2, is a meniscus-shaped positive lens with its concave surface facing the side of the observed object, Ob.

[0279] The third lens, L3, is a meniscus-shaped negative lens with its concave surface facing the ob side of the observed object. The lens surface of the third lens L3 on the ob side of the observed object is formed aspherical.

[0280] The fourth lens, L4, is a meniscus-shaped positive lens with its concave surface facing the ob side of the observed object.

[0281] Lens L5 is a meniscus negative lens with its convex surface facing the ob side of the observed object. Aspherical surfaces are formed on both sides of lens L5.

[0282] Lens L6 is a meniscus positive lens with its convex surface facing the ob side of the observed object.

[0283] Diopter adjustment is performed by moving the first lens L1 to the sixth lens L6 as a single unit along the optical axis.

[0284] In this embodiment, the second lens L2 constitutes the first positive lens Lp1, and the fourth lens L4 constitutes the second positive lens Lp2. Furthermore, the third lens L3 constitutes the first negative lens Ln1, and the fifth lens L5 constitutes the second negative lens Ln2. Additionally, the first lens L1 constitutes a lens La with an inflection point on an aspherical surface. Furthermore, the lens positioned closest to the observed object is the first lens L1, and the lens positioned closest to the viewpoint is the sixth lens L6.

[0285] Table 2 below shows the values ​​of each parameter in the second embodiment. The face numbers in Table 2 are... Figure 3 Each optical surface corresponds to the other. In the second embodiment, the first, second, fifth, ninth, and tenth surfaces are formed into aspherical shapes.

[0286] (Table 2)

[0287] [Overall Parameters]

[0288] [Lens Parameters]

[0289] [Aspherical Data]

[0290] Page 1, κ=1.0000, A4=-2.42203E-04, A6=-8.43861E-08, A8=-1.44518E-09

[0291] On the second face, κ=1.0000, A4=3.45500E-05, A6=-5.75821E-08, A8=0.00000E+00

[0292] Face 5: κ=0.5205, A4=2.24960E-04, A6=-5.18571E-07, A8=1.83367E-09

[0293] Page 9, κ=1.0000, A4=-6.26763E-05, A6=2.15008E-07, A8=0.00000E+00

[0294] Page 10, κ=1.0000, A4=5.85286E-06, A6=9.69503E-08, A8=0.00000E+00

[0295] [Variable Interval Data]

[0296] [Lens Group Data]

[0297] According to the parameters shown in Table 2, the eyepiece optical system EL2 of the second embodiment satisfies the conditions (1) to (21).

[0298] Figure 4 The diopter of the eyepiece optics system EL2 in the second embodiment is shown as -1 [m]. -1 Aberration diagrams for various aberrations (spherical aberration, astigmatism, coma, distortion, and chromatic aberration at magnification).

[0299] from Figure 4 As can be clearly seen from the aberration diagrams shown, the eyepiece optical system EL2 of the second embodiment effectively corrects various aberrations, especially astigmatism and distortion, ensuring excellent optical performance.

[0300] (Third embodiment)

[0301] use Figure 5 , Figure 6 Table 3 illustrates the third embodiment. For example... Figure 5 As shown, the eyepiece optical system EL (EL3) of the third embodiment consists of a first lens L1 with positive optical power, a second lens L2 with positive optical power, a third lens L3 with negative optical power, a fourth lens with negative optical power, a fifth lens with positive optical power, and a sixth lens with positive optical power, arranged sequentially along the optical axis from the side of the observed object (image display element) Ob.

[0302] The first lens L1 is a biconvex positive lens. The lens surfaces of the first lens on the object-observed side (Ob) and the viewpoint side (EP) are formed aspherical. On the aspherical surface, there are inflection points where the curvature changes from positive to negative or from negative to positive in the periphery within the effective aperture.

[0303] The second lens, L2, is a biconvex positive lens.

[0304] The third lens, L3, is a meniscus-shaped negative lens with its concave surface facing the ob side of the observed object. The lens surface of the third lens L3 on the ob side of the observed object is formed aspherical.

[0305] Lens L4 is a negative lens with a biconcave shape. The lens surface of lens L4 on the ob side of the observed object is aspherical.

[0306] The fifth lens, L5, is a biconvex positive lens.

[0307] Lens L6 is a biconvex positive lens. The lens surfaces on both sides of lens L6 are aspherical.

[0308] Diopter adjustment is performed by moving the first lens L1 to the sixth lens L6 as a single unit along the optical axis.

[0309] In this embodiment, the second lens L2 constitutes the first positive lens Lp1, and the fifth lens L5 constitutes the second positive lens Lp2. Furthermore, the fourth lens L4 constitutes the first negative lens Ln1, and the third lens L3 constitutes the second negative lens Ln2. Additionally, the first lens L1 constitutes a lens La with an inflection point on an aspherical surface. Furthermore, the lens positioned closest to the observed object is the first lens L1, and the lens positioned closest to the viewpoint is the sixth lens L6.

[0310] Table 3 below shows the values ​​of each parameter in the third embodiment. The face numbers in Table 3 are... Figure 5 Each optical surface corresponds to another optical surface. In the third embodiment, the first, second, fifth, seventh, eleventh, and twelfth surfaces are formed into aspherical shapes.

[0311] (Table 3)

[0312] [Overall Parameters]

[0313] [Lens Parameters]

[0314] [Aspherical Data]

[0315] Page 1, κ=1.0000, A4=-1.10743E-04, A6=6.01836E-07, A8=-2.17619E-09

[0316] Page 2, κ=1.0000, A4=-1.10097E-05, A6=2.55575E-07, A8=0.00000E+00

[0317] Face 5: κ=0.3380, A4=1.50503E-04, A6=-2.10439E-07, A8=7.91597E-10

[0318] Face 7: κ=1.0000, A4=7.74802E-06, A6=-2.58880E-08, A8=0.00000E+00

[0319] Page 11, κ=1.0000, A4=-5.30790E-05, A6=2.68087E-07, A8=-8.14673E-10

[0320] Page 12, κ=1.0000, A4=6.21114E-05, A6=6.22836E-08, A8=0.00000E+00

[0321] [Variable Interval Data]

[0322] [Lens Group Data]

[0323] According to the parameters shown in Table 3, the eyepiece optical system EL3 of the third embodiment satisfies the conditions (1) to (21).

[0324] Figure 6 The eyepiece optical system EL3 of the third embodiment shows a diopter of -1 [m]. -1 Aberration diagrams for various aberrations (spherical aberration, astigmatism, coma, distortion, and chromatic aberration at magnification).

[0325] from Figure 6 As can be clearly seen from the aberration diagrams shown, the eyepiece optical system EL3 of the third embodiment effectively corrects various aberrations, especially astigmatism and distortion, ensuring excellent optical performance.

[0326] (4th embodiment)

[0327] use Figure 7 , Figure 8 Table 4 illustrates the fourth embodiment. For example... Figure 7 As shown, the eyepiece optical system EL (EL4) of the fourth embodiment consists of a first lens L1 with positive optical power, a second lens L2 with negative optical power and a third lens L3 with positive optical power arranged sequentially along the optical axis from the side of the observed object (image display element) Ob, a fourth lens with negative optical power, a fifth lens with positive optical power and a sixth lens with positive optical power.

[0328] The first lens L1 is a biconvex positive lens. The lens surface on the ob side of the observed object of the first lens is formed aspherical. On the aspherical surface, there are inflection points where the curvature changes from positive to negative or from negative to positive in the periphery within the effective aperture.

[0329] The second lens L2 is a negative lens with a biconcave shape. The second lens L2 is combined with the third lens L3.

[0330] The third lens L3 is a biconvex positive lens. The third lens L3 is combined with the second lens L2.

[0331] Lens L4 is a negative lens with a biconcave shape. The lens surface of lens L4 on the ob side of the observed object is aspherical.

[0332] The fifth lens, L5, is a biconvex positive lens.

[0333] Lens L6 is a biconvex positive lens. The lens surface on the viewpoint side of lens L6 is aspherical.

[0334] Diopter adjustment is performed by moving the first lens L1 to the sixth lens L6 as a single unit along the optical axis.

[0335] In this embodiment, the third lens L3 constitutes the first positive lens Lp1, and the fifth lens L5 constitutes the second positive lens Lp2. Furthermore, the fourth lens L4 constitutes the first negative lens Ln1, and the second lens L2 constitutes the second negative lens Ln2. Additionally, the first lens L1 constitutes a lens La with an inflection point on an aspherical surface. Furthermore, the lens positioned closest to the observed object is the first lens L1, and the lens positioned closest to the viewpoint is the sixth lens L6.

[0336] Table 4 below shows the values ​​of each parameter in the fourth embodiment. The face numbers in Table 4 are... Figure 7 The optical surfaces correspond to each other. In the fourth embodiment, the first, sixth, and eleventh surfaces are formed into aspherical shapes.

[0337] (Table 4)

[0338] [Overall Parameters]

[0339] [Lens Parameters]

[0340] [Aspherical Data]

[0341] Page 1, κ=1.0000, A4=-1.55680E-04, A6=6.56284E-07, A8=-7.93249E-09

[0342] Face 6: κ=0.4463, A4=5.64814E-05, A6=2.63205E-07, A8=-8.15805E-10

[0343] Page 11, κ=1.0000, A4=6.89637E-05, A6=-7.02689E-08, A8=6.89253E-11

[0344] [Variable Interval Data]

[0345] [Lens Group Data]

[0346] According to the parameters shown in Table 4, the eyepiece optical system EL4 of the fourth embodiment satisfies the conditions (1) to (21).

[0347] Figure 8 The eyepiece optics system EL4 of the fourth embodiment shows a diopter of -1 [m]. -1 Aberration diagrams for various aberrations (spherical aberration, astigmatism, coma, distortion, and chromatic aberration at magnification).

[0348] from Figure 8 As can be clearly seen from the aberration diagrams shown, the eyepiece optical system EL4 of the fourth embodiment effectively corrects various aberrations, especially astigmatism and distortion, ensuring excellent optical performance.

[0349] (5th embodiment)

[0350] use Figure 9 , Figure 10 Table 5 illustrates the fifth embodiment. For example... Figure 9 As shown, the eyepiece optical system EL (EL5) of the fifth embodiment consists of a first lens L1 with positive optical power, a second lens L2 with negative optical power and a third lens L3 with positive optical power arranged sequentially along the optical axis from the side of the observed object (image display element) Ob, a fourth lens with negative optical power, a fifth lens with positive optical power and a sixth lens with positive optical power.

[0351] The first lens L1 is a biconvex positive lens. The lens surface on the ob side of the observed object of the first lens is formed aspherical. On the aspherical surface, there are inflection points where the curvature changes from positive to negative or from negative to positive in the periphery within the effective aperture.

[0352] The second lens L2 is a negative lens with a biconcave shape. The second lens L2 is combined with the third lens L3.

[0353] The third lens L3 is a biconvex positive lens. The third lens L3 is combined with the second lens L2.

[0354] Lens L4 is a negative lens with a biconcave shape. The lens surface of lens L4 on the ob side of the observed object is aspherical.

[0355] The fifth lens, L5, is a biconvex positive lens.

[0356] Lens L6 is a biconvex positive lens. The lens surfaces on both sides of lens L6 are aspherical.

[0357] Diopter adjustment is performed by moving the first lens L1 to the sixth lens L6 as a single unit along the optical axis.

[0358] In this embodiment, the third lens L3 constitutes the first positive lens Lp1, and the fifth lens L5 constitutes the second positive lens Lp2. Furthermore, the fourth lens L4 constitutes the first negative lens Ln1, and the second lens L2 constitutes the second negative lens Ln2. Additionally, the first lens L1 constitutes a lens La with an inflection point on an aspherical surface. Furthermore, the lens positioned closest to the observed object is the first lens L1, and the lens positioned closest to the viewpoint is the sixth lens L6.

[0359] Table 5 below shows the values ​​of each parameter in the fifth embodiment. The face numbers in Table 5 are... Figure 9 Each optical surface corresponds to the others. In the fifth embodiment, the first, sixth, tenth, and eleventh surfaces are formed into aspherical shapes.

[0360] (Table 5)

[0361] [Overall Parameters]

[0362] [Lens Parameters]

[0363] [Aspherical Data]

[0364] Page 1, κ=1.0000, A4=-1.42982E-04, A6=4.09497E-07, A8=-4.87892E-09

[0365] Face 6: κ=0.4467, A4=1.02764E-04, A6=-1.82925E-07, A8=6.56706E-10

[0366] Page 10, κ=1.0000, A4=-8.63268E-05, A6=1.81967E-07, A8=0.00000E+00

[0367] Page 11, κ=1.0000, A4=1.24474E-05, A6=-4.20778E-08, A8=4.75928E-10

[0368] [Variable Interval Data]

[0369] [Lens Group Data]

[0370] According to the parameters shown in Table 5, the eyepiece optical system EL5 of the fifth embodiment satisfies the conditions (1) to (21).

[0371] Figure 10 The eyepiece optics system EL5 of the fifth embodiment shows a diopter of -1 [m]. -1 Aberration diagrams for various aberrations (spherical aberration, astigmatism, coma, distortion, and chromatic aberration at magnification).

[0372] from Figure 10 As can be clearly seen from the aberration diagrams shown, the eyepiece optical system EL5 of the fifth embodiment effectively corrects various aberrations, especially astigmatism and distortion, ensuring excellent optical performance.

[0373] (Sixth embodiment)

[0374] use Figure 11 , Figure 12 Table 6 describes the sixth embodiment. For example... Figure 11 As shown, the eyepiece optical system EL (EL6) of the sixth embodiment consists of a first lens L1 with positive optical power, a second lens L2 with positive optical power, a third lens L3 with negative optical power, a fourth lens with negative optical power, a fifth lens with positive optical power, and a sixth lens with positive optical power, arranged sequentially along the optical axis from the side of the observed object (image display element) Ob.

[0375] The first lens L1 is a biconvex positive lens. The lens surfaces on both sides of the first lens L1 are formed aspherical. On the aspherical surfaces, there are inflection points where the curvature changes from positive to negative or from negative to positive in the periphery within the effective aperture.

[0376] The second lens, L2, is a meniscus-shaped positive lens with its concave surface facing the side of the observed object, Ob.

[0377] The third lens, L3, is a meniscus-shaped negative lens with its concave surface facing the ob side of the observed object. The lens surface of the third lens L3 on the ob side of the observed object is formed aspherical.

[0378] Lens L4 is a negative lens with a biconcave shape. The lens surface of lens L4 on the ob side of the observed object is aspherical.

[0379] The fifth lens, L5, is a biconvex positive lens.

[0380] Lens L6 is a meniscus positive lens with its convex surface facing the ob side of the observed object. The lens surface of lens L6 on the ob side of the observed object is formed aspherical.

[0381] Diopter adjustment is performed by moving the first lens L1 to the sixth lens L6 as a single unit along the optical axis.

[0382] In this embodiment, the fifth lens L5 constitutes the first positive lens Lp1, and the second lens L2 constitutes the second positive lens Lp2. Furthermore, the third lens L3 constitutes the first negative lens Ln1, and the fourth lens L4 constitutes the second negative lens Ln2. Additionally, the first lens L1 constitutes a lens La with an inflection point on an aspherical surface. Furthermore, the lens positioned closest to the observed object is the first lens L1, and the lens positioned closest to the viewpoint is the sixth lens L6.

[0383] Table 6 below shows the values ​​of each parameter in the sixth embodiment. The face numbers in Table 6 are... Figure 11 Each optical surface corresponds to the other. In the sixth embodiment, the first, second, fifth, seventh, and eleventh surfaces are formed into aspherical shapes.

[0384] (Table 6)

[0385] [Overall Parameters]

[0386] [Lens Parameters]

[0387] [Aspherical Data]

[0388] Page 1, κ=1.0000, A4=-2.33343E-04, A6=1.14278E-06, A8=-7.74211E-09

[0389] Page 2, κ=1.0000, A4=-7.24654E-06, A6=5.95864E-07, A8=0.00000E+00

[0390] Face 5: κ=0.4165, A4=2.12201E-04, A6=-5.54425E-07, A8=2.60677E-09

[0391] Face 7: κ=0.1799, A4=1.23209E-05, A6=-1.63134E-08, A8=0.00000E+00

[0392] Page 11, κ=1.0000, A4=-7.22449E-05, A6=9.01971E-08, A8=-1.60593E-10

[0393] [Variable Interval Data]

[0394] [Lens Group Data]

[0395] According to the parameters shown in Table 6, the eyepiece optical system EL6 of the sixth embodiment satisfies the conditions (1) to (21).

[0396] Figure 12 The eyepiece optics system EL6 of the sixth embodiment shows a diopter of -1 [m]. -1 Aberration diagrams for various aberrations (spherical aberration, astigmatism, coma, distortion, and chromatic aberration at magnification).

[0397] from Figure 12 As can be clearly seen from the aberration diagrams shown, the eyepiece optical system EL6 of the sixth embodiment effectively corrects various aberrations, especially astigmatism and distortion, ensuring excellent optical performance.

[0398] (Seventh embodiment)

[0399] use Figure 13 , Figure 14 Table 7 illustrates the seventh embodiment. For example... Figure 13 As shown, the eyepiece optical system EL (EL7) of the seventh embodiment consists of a first lens L1 with positive optical power, a second lens L2 with positive optical power, a third lens L3 with negative optical power, a fourth lens with positive optical power, and a fifth lens with positive optical power, arranged sequentially along the optical axis from the side of the observed object (image display element) Ob.

[0400] The first lens L1 is a biconvex positive lens. The lens surfaces on both sides of the first lens L1 are formed aspherical. On the aspherical surfaces, there are inflection points where the curvature changes from positive to negative or from negative to positive in the periphery within the effective aperture.

[0401] The second lens, L2, is a meniscus-shaped positive lens with its concave surface facing the side of the observed object, Ob.

[0402] The third lens, L3, is a negative lens with a biconcave shape. The lens surface of the third lens, L3, on the ob side of the observed object is formed aspherical.

[0403] The fourth lens, L4, is a biconvex positive lens.

[0404] Lens L5 is a meniscus positive lens with its convex surface facing the ob side of the observed object. Both lens surfaces of lens L5 are aspherical.

[0405] Diopter adjustment is performed by moving the first lens L1 to the fifth lens L5 as a single unit along the optical axis.

[0406] In this embodiment, the fourth lens L4 constitutes the first positive lens Lp1, and the second lens L2 constitutes the second positive lens Lp2. Additionally, the third lens L3 constitutes the first negative lens Ln1. Furthermore, the first lens L1 constitutes a lens La with an inflection point on an aspherical surface. The lens positioned closest to the observed object is the first lens L1, and the lens positioned closest to the viewpoint is the fifth lens L5.

[0407] Table 7 below shows the values ​​of each parameter in the seventh embodiment. The face numbers in Table 7 are... Figure 13 Each optical surface corresponds to the others. In the seventh embodiment, the first, second, fifth, ninth, and tenth surfaces are formed into aspherical shapes.

[0408] (Table 7)

[0409] [Overall Parameters]

[0410] [Lens Parameters]

[0411] [Aspherical Data]

[0412] Page 1, κ=1.0000, A4=-1.90801E-04, A6=8.52594E-07, A8=-8.21187E-09

[0413] Page 2, κ=1.0000, A4=5.30258E-06, A6=5.64950E-07, A8=0.00000E+00

[0414] Page 5, κ=0.3570; A4=1.86033E-04; A6=-3.54122E-07; A8=1.51527E-09

[0415] Page 9, κ=1.0000, A4=-4.83443E-05, A6=2.31752E-07, A8=-4.78017E-10

[0416] Page 10, κ=1.0000, A4=4.54289E-05, A6=5.96479E-08, A8=0.00000E+00

[0417] [Variable Interval Data]

[0418] [Lens Group Data]

[0419] According to the parameters shown in Table 7, the eyepiece optical system EL7 of the seventh embodiment satisfies the conditions (1) to (7) and (9) to (19).

[0420] Figure 14 The eyepiece optical system EL7 of embodiment 7 shows a diopter of -1 [m]. -1 Aberration diagrams for various aberrations (spherical aberration, astigmatism, coma, distortion, and chromatic aberration at magnification).

[0421] from Figure 14 As can be clearly seen from the aberration diagrams shown, the eyepiece optical system EL7 of the 7th embodiment effectively corrects various aberrations, especially astigmatism and distortion, ensuring excellent optical performance.

[0422] Next, a table of [corresponding values ​​of conditional expressions] is shown below. In this table, the values ​​corresponding to each conditional expression (1) to (21) are shown in summary for all embodiments (1 to 7).

[0423] Condition (1) 1.700 < Np1 < 2.050

[0424] Condition (2) 1.700 < Np2 < 2.050

[0425] Condition (3) 0.90 < Np2 / Np1 < 1.10

[0426] Condition (4) 0.70 < fLp1 / fe < 1.30

[0427] Condition (5) 0.90 < fLp2 / fe < 1.70

[0428] Condition (6) 1.500<Nn1<1.700

[0429] Conditional expression (7): 16.000 < νn1 < 36.000

[0430] Condition (8) 1.500<Nn2<1.700

[0431] Conditional expression (9): 8.000 < νp1 - νn1 < 35.000

[0432] Conditional expression (10): 8.000 < νp2 - νn1 < 35.000

[0433] Conditional expression (11) 0.400<h / fe<0.500

[0434] Conditional expression (12) 0.000≤Daspe / ΣD<0.200

[0435] Conditional expression (13) 0.000≤Daspо / ΣD<0.200

[0436] Conditional expression (14) 0.20<y / Ry<0.85

[0437] Conditional expression (15): 20.000[mm] < De < 30.000[mm]

[0438] Conditional expression (16): 1.100 < De / fe < 1.500

[0439] Condition (17) 0.250 < D0 / fe < 0.500

[0440] Condition (18) 0.120 < D0 / TL < 0.250

[0441] Conditional expression (19): 0.080 < ΣDair / ΣD < 0.200

[0442] Condition (20) 1.00 < f1 / fe < 2.50

[0443] Conditional expression (21): 1.50 < fep / fe < 5.00

[0444] [Conditional values] (Examples 1-7)

[0445] As described above, according to the present invention, an eyepiece optical system in which various aberrations (especially astigmatism and distortion) are well corrected even when the viewfinder magnification is increased can be achieved.

[0446] To facilitate understanding of the present invention, the constituent elements of the embodiments have been described, but it is self-evident that the present invention is not limited thereto. The following description may be appropriately used without impairing optical performance.

[0447] The lens surface can be formed as a spherical or planar surface, or as an aspherical surface. When the lens surface is spherical or planar, lens processing and assembly adjustments become easier, preventing degradation of optical performance due to processing and assembly adjustments errors, and is therefore preferred. Furthermore, even in the case of image plane shift, the degradation of descriptive performance is minimal, and is therefore preferred. When the lens surface is aspherical, the aspherical surface can be any of the following: a ground aspherical surface, a glass-molded aspherical surface obtained by molding glass into an aspherical shape using a mold, or a composite aspherical surface obtained by forming resin into an aspherical shape on the surface of glass. Additionally, the lens surface can also serve as a diffraction surface, and the lens can also be a refractive index distribution lens (GRIN lens) or a plastic lens.

[0448] To reduce glare and ghosting and achieve high contrast and high optical performance, an antireflective coating with high transmittance over a wide wavelength range can be applied to each lens surface.

[0449] Label Explanation

[0450] CAM digital camera (optical equipment)

[0451] OL objective lens

[0452] C-type imaging element

[0453] Ob image display element (the object being observed)

[0454] EL (EL1~EL7) Eyepiece Optical System

[0455] L1 Lens 1

[0456] L2 Second Lens

[0457] L3 Third Lens

[0458] L4, fourth lens

[0459] L5, 5th lens

[0460] L6 Lens 6

[0461] EP Viewpoint

Claims

1. An eyepiece optical system, wherein, The eyepiece optical system comprises a first positive lens with positive optical power and a second positive lens with positive optical power, and satisfies the following condition: 1.700 < Np1 < 2.050 1.700 < Np2 < 2.050 Wherein, Np1: the refractive index of the first positive lens for the d-line. Np2: The refractive index of the second positive lens for the d-line.

2. An eyepiece optical system, wherein, The eyepiece optical system has at least five lenses and satisfies the following condition: 0.400 < h / fe < 0.500 Wherein, fe: the composite focal length of the eyepiece optical system. h: The maximum height of the object being observed in the eyepiece optical system.

3. An eyepiece optical system for observing an image displayed on an image display element, wherein, The eyepiece optical system has at least five lenses.

4. The eyepiece optical system according to claim 1, wherein, The first positive lens has the strongest positive power in the eyepiece optical system and satisfies the following condition: 0.90 < Np2 / Np1 < 1.

10.

5. The eyepiece optical system according to claim 1 or 4, wherein, The first positive lens has the strongest positive power in the eyepiece optical system and satisfies the following condition: 0.70 < fLp1 / fe < 1.30 Wherein, fLp1: the focal length of the first positive lens, fe: The composite focal length of the eyepiece optical system.

6. The eyepiece optical system according to any one of claims 1, 4, and 5, wherein, The second positive lens has the second strongest positive power in the eyepiece optical system and satisfies the following condition: 0.90 < fLp2 / fe < 1.70 Where, fLp2: the focal length of the second positive lens, fe: The composite focal length of the eyepiece optical system.

7. The eyepiece optical system according to any one of claims 1, 4 to 6, wherein, The eyepiece optical system has a first negative lens, which has the strongest negative power in the eyepiece optical system, and the eyepiece optical system satisfies the following condition: 1.500 < Nn1 < 1.700 16.000 < νn1 < 36.000 Wherein, Nn1: the refractive index of the first negative lens for the d-line, νn1: The Abbe number of the first negative lens relative to the d-line.

8. The eyepiece optical system according to any one of claims 1, 4 to 7, wherein, The eyepiece optical system has a second negative lens, which has the second strongest negative power in the eyepiece optical system, and the eyepiece optical system satisfies the following condition: 1.500 < Nn2 < 1.700 Wherein, Nn2: the refractive index of the second negative lens for the d-line.

9. The eyepiece optical system according to claim 7, wherein, The eyepiece optical system satisfies the following condition: 8.000 < νp1 - νn1 < 35.000 Wherein, νp1: the Abbe number of the first positive lens with reference to the d-line, νn1: The Abbe number of the first negative lens relative to the d-line.

10. The eyepiece optical system according to claim 7 or 9, wherein, The eyepiece optical system satisfies the following condition: 8.000 < νp2 - νn1 < 35.000 Wherein, νp2: the Abbe number of the second positive lens with reference to the d-line, νn1: The Abbe number of the first negative lens relative to the d-line.

11. The eyepiece optical system according to any one of claims 1 to 10, wherein, The eyepiece optical system satisfies the following condition: 0.400 < h / fe < 0.500 Wherein, fe: the composite focal length of the eyepiece optical system. h: The maximum height of the object being observed in the eyepiece optical system.

12. The eyepiece optical system according to any one of claims 1 to 11, wherein, The eyepiece optical system has at least one lens with an aspherical surface formed on the lens surface that satisfies the following condition: 0.000≤Daspe / ΣD<0.200 Wherein, Daspe: the distance on the optical axis from the aspherical surface closest to the viewpoint to the lens surface closest to the viewpoint of the eyepiece optical system. ΣD: The distance along the optical axis from the lens surface closest to the observed object to the lens surface closest to the viewpoint.

13. The eyepiece optical system according to any one of claims 1 to 12, wherein, The eyepiece optical system has at least one lens with an aspherical surface formed on the lens surface that satisfies the following condition: 0.000≤Daspо / ΣD<0.200 Wherein, Dasp0: the distance on the optical axis from the lens surface closest to the observed object in the eyepiece optical system to the aspherical surface closest to the observed object. ΣD: The distance along the optical axis from the lens surface closest to the observed object to the lens surface closest to the viewpoint.

14. The eyepiece optical system according to any one of claims 1 to 13, wherein, The eyepiece optical system has at least one lens with an aspherical surface formed on its lens surface and an inflection point on the aspherical surface where the radius of curvature reverses from positive to negative or from negative to positive, and satisfies the following condition: 0.20 < y / Ry < 0.85 Where y: the distance between the optical axis in the direction perpendicular to the optical axis of the lens and the inflection point. Ry: The radius of the lens.

15. The eyepiece optical system according to any one of claims 1, 2, 4 to 14, wherein, The eyepiece optical system consists of at least five lenses.

16. The eyepiece optical system according to any one of claims 1, 4 to 15, wherein, Both the first positive lens and the second positive lens are lenses whose lens surfaces are formed as spherical surfaces.

17. The eyepiece optical system according to any one of claims 1 to 16, wherein, The eyepiece optical system satisfies the following condition: 20.000 [mm] < De < 30.000 [mm] Wherein, De: the distance on the optical axis from the lens surface closest to the viewpoint of the eyepiece optical system to the viewpoint.

18. The eyepiece optical system according to any one of claims 1 to 17, wherein, The eyepiece optical system satisfies the following condition: 1.100 < De / fe < 1.500 Where De: the distance along the optical axis from the lens surface closest to the viewpoint in the eyepiece optical system to the viewpoint. fe: The composite focal length of the eyepiece optical system.

19. The eyepiece optical system according to any one of claims 1 to 18, wherein, The lens positioned closest to the object being observed has positive optical power.

20. The eyepiece optical system according to any one of claims 1 to 19, wherein, The eyepiece optical system satisfies the following condition: 0.250 < D0 / fe < 0.500 Where D0: from a viewpoint of 0 [m] -1 The distance along the optical axis from the observed object to the lens surface closest to the observed object. fe: The composite focal length of the eyepiece optical system.

21. The eyepiece optical system according to any one of claims 1 to 20, wherein, The eyepiece optical system satisfies the following condition: 0.120 < D0 / TL < 0.250 Where D0: from a viewpoint of 0 [m] -1 The distance along the optical axis from the observed object to the lens surface closest to the observed object. TL: From a viewpoint of 0 [m] -1 The distance on the optical axis from the observed object to the lens surface closest to the viewpoint.

22. The eyepiece optical system according to any one of claims 1 to 21, wherein, The eyepiece optical system satisfies the following condition: 0.080 < ΣDair / ΣD < 0.200 Where, ΣDair: the sum of the air gaps between lenses from the lens closest to the observed object to the lens closest to the viewpoint. ΣD: The distance along the optical axis from the lens surface closest to the observed object to the lens surface closest to the viewpoint.

23. The eyepiece optical system according to any one of claims 1 to 22, wherein, The lens positioned closest to the object being observed has positive optical power, and the lens positioned adjacent to the lens closest to the object being observed on the viewpoint side also has positive optical power.

24. The eyepiece optical system according to any one of claims 1 to 23, wherein, The number of lenses with positive optical power is 4.

25. The eyepiece optical system according to any one of claims 1 to 24, wherein, The eyepiece optical system satisfies the following condition: 1.00 < f1 / fe < 2.50 Where f1 is the focal length of the lens positioned closest to the object being observed. fe: The composite focal length of the eyepiece optical system.

26. The eyepiece optical system according to any one of claims 1 to 25, wherein, The eyepiece optical system satisfies the following condition: 1.50 < fep / fe < 5.00 Where, fep: the focal length of the lens located on the side closest to the viewpoint. fe: The composite focal length of the eyepiece optical system.

27. An optical device, characterized in that, The optical device includes: an objective lens; an imaging element for capturing an image formed by the objective lens; an image display element for displaying the image captured by the imaging element; and an eyepiece optical system for observing the image displayed on the image display element. The eyepiece optical system is the eyepiece optical system according to any one of claims 1 to 26.

28. An observation method, characterized in that, The observed object is observed via the eyepiece optical system according to any one of claims 1 to 26.

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