Eyepiece, optical instrument having an eyepiece, and method for manufacturing an eyepiece

Abstract

Conventional eyepieces struggle to achieve good optical performance when high magnification is required. [Solution] An eyepiece having, in order from the observation object side, a first lens with positive refractive power, a second lens with negative refractive power, a third lens with positive refractive power, and a fourth lens with positive refractive power, and satisfying the following conditional equation. 0.25 < (-f2) / f3 < 0.53 0.34 <d1 / fe<0.60 however, f2: Focal length of the second lens f3: Focal length of the third lens d1: Distance along the optical axis from the surface of the observed object to the lens surface of the first lens on the side of the observed object when the diopter of the eyepiece is -1 [1 / m]. fe: The focal length of the eyepiece when the diopter of the eyepiece is -1 [1 / m].

Description

[Technical Field]

[0001] The present invention relates to an eyepiece, an optical instrument having an eyepiece, and a method for manufacturing an eyepiece. [Background technology]

[0002] Conventional eyepieces for use in electronic viewfinders have been proposed (see, for example, Patent Document 1). However, conventional eyepieces like those described above have the problem that it is difficult to achieve good optical performance when high magnification is required. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2007-225835 [Overview of the project]

[0004] The present invention comprises, in order from the observation object side, a first lens having positive refractive power, a second lens having negative refractive power, a third lens having positive refractive power, and a fourth lens having positive refractive power. The eyepiece was chosen to satisfy the following condition. 0.25 < (-f2) / f3 < 0.53 0.34 <d1 / fe<0.60 however, f2: Focal length of the second lens f3: Focal length of the third lens d1: Distance along the optical axis from the surface of the observed object to the lens surface of the first lens on the side of the observed object when the diopter of the eyepiece is -1 [1 / m]. fe: The focal length of the eyepiece when the diopter of the eyepiece is -1 [1 / m]. [Brief explanation of the drawing]

[0005] [Figure 1]Figure 1 is a cross-sectional view of the eyepiece according to the first embodiment at a diopter of -1 [1 / m]. [Figure 2] Figures 2(a), 2(b), and 2(c) show the aberration diagrams of the eyepiece according to the first embodiment at diopters of -1 [1 / m], -3 [1 / m], and +3 [1 / m], respectively. [Figure 3] Figure 3 is a cross-sectional view of the eyepiece according to the second embodiment at a diopter of -1 [1 / m]. [Figure 4] Figures 4(a), 4(b), and 4(c) show the aberration diagrams of the eyepiece according to the second embodiment at diopters of -1 [1 / m], -3 [1 / m], and +3 [1 / m], respectively. [Figure 5] Figure 5 is a cross-sectional view of the eyepiece according to the third embodiment at a diopter of -1 [1 / m]. [Figure 6] Figures 6(a), 6(b), and 6(c) show the aberration diagrams of the eyepiece according to the third embodiment at diopters of -1 [1 / m], -3 [1 / m], and +3 [1 / m], respectively. [Figure 7] Figure 7 is a cross-sectional view of the eyepiece according to the fourth embodiment at a diopter of -1 [1 / m]. [Figure 8] Figures 8(a), 8(b), and 8(c) show the aberration diagrams of the eyepiece according to the fourth embodiment at diopters of -1 [1 / m], -5 [1 / m], and +5 [1 / m], respectively. [Figure 9] Figure 9 is a cross-sectional view of the eyepiece according to the fifth embodiment at a diopter of -1 [1 / m]. [Figure 10] Figures 10(a), 10(b), and 10(c) show the aberrations of the eyepiece according to the fifth embodiment at diopters of -1 [1 / m], -3 [1 / m], and +3 [1 / m], respectively. [Figure 11] This is a cross-sectional view of an optical instrument having an eyepiece according to an embodiment. [Figure 12] This is a flowchart illustrating the general method for manufacturing an eyepiece lens according to the embodiment. [Figure 13]It is a flowchart showing an outline of another manufacturing method of an eyepiece lens according to an embodiment.

Mode for Carrying Out the Invention

[0006] Hereinafter, an eyepiece lens, an optical device, and a method for manufacturing an eyepiece lens according to embodiments of the present application will be described. First, the eyepiece lens according to the embodiment will be described.

[0007] The eyepiece lens according to the present embodiment is an eyepiece lens for magnifying and observing an observation object. Here, the observation object is an intermediate image formed by an objective lens or a display surface of an image display element such as a liquid crystal display element or an organic EL (Electroluminescence) display, and particularly preferably the display surface of the liquid crystal display element. Therefore, the eyepiece lens according to the present embodiment is suitable for use in an electronic viewfinder for observing an image displayed on the display surface of an image display element. In the following description, the observation object is also referred to as an "observation object surface".

[0008] In the following description of embodiments and numerical examples, the diopter, which is the unit of visual acuity, uses [1 / m]. For example, visual acuity X [1 / m] indicates a state in which an image formed by an eyepiece lens can be formed at a position of 1 / X [m (meter)] on the optical axis from the eye point. The sign is positive when the image is formed on the eye point side of the eyepiece lens.

[0009] The eyepiece lens according to the present embodiment has, in order from the observation object side along the optical axis, a first lens having a positive refractive power, a second lens having a negative refractive power, a third lens having a positive refractive power, and a fourth lens having a positive refractive power.

[0010] Thus, the eyepiece according to this embodiment arranges a first lens having a positive refractive power to magnify and observe an observation object. Further, the eyepiece according to this embodiment arranges a second lens having a negative refractive power to correct chromatic aberration, field curvature, and astigmatism generated by the first lens with a positive refractive power. Further, the eyepiece according to this embodiment arranges a third lens having a positive refractive power and a fourth lens having a positive refractive power to well-correct coma aberration and distortion aberration.

[0011] By adopting such a configuration, the eyepiece according to this embodiment can well correct various aberrations and achieve high magnification. For example, in order to magnify and observe an observation object with a diagonal length of around 10 mm, it is possible to achieve a high magnification with an apparent field angle of 30° or more.

[0012] Under such a configuration, the eyepiece according to this embodiment satisfies the following conditional expression (1). (1) -13.00 < (R2a + R1b) / (R2a - R1b) < -2.75 However, R2a: The radius of curvature of the lens surface on the observation object side of the second lens R1b: The radius of curvature of the lens surface on the eye point side of the first lens

[0013] The conditional expression (1) is a conditional expression for defining the shape of an air lens formed by the lens surface on the eye point side of the first lens and the lens surface on the observation object side of the second lens. By satisfying the conditional expression (1), good aberration correction can be performed.

[0014] If the corresponding value in conditional equation (1) falls below the lower limit, it becomes difficult to correct various aberrations, especially field curvature and coma aberration, which is undesirable. Also, the edge thickness of the first lens becomes thin, making manufacturing difficult, which is undesirable. To ensure the effect of this embodiment, it is preferable to set the lower limit of conditional equation (1) to -12.00. Furthermore, to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional equation (1) to -11.65. Furthermore, to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional equation (1) to -11.30.

[0015] On the other hand, if the corresponding value in conditional equation (1) exceeds the upper limit, it becomes difficult to correct various aberrations, especially field curvature and coma aberration, which is undesirable. In order to ensure the effect of this embodiment, it is preferable to set the upper limit of conditional equation (1) to -3.50. Furthermore, in order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional equation (1) to -4.25. Furthermore, in order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional equation (1) to -5.00.

[0016] The eyepiece lens according to this embodiment satisfies the following condition (2) under this configuration. (2) 0.78 <TL / fe<1.60 however, TL: Distance along the optical axis from the observation object surface to the lens surface closest to the eye point when the diopter of the eyepiece is -1 [1 / m]. fe: The focal length of the eyepiece when the diopter of the eyepiece is -1 [1 / m].

[0017] Conditional equation (2) is a conditional equation for defining an appropriate range for the ratio between the optical axis distance from the observation object surface to the lens surface closest to the eye point when the diopter of the eyepiece is -1 [1 / m], i.e., the total optical length of the eyepiece, and the focal length of the eyepiece when the diopter of the eyepiece is -1 [1 / m]. By satisfying conditional equation (2), miniaturization and high magnification can be achieved, and good aberration correction can be performed.

[0018] If the corresponding value in conditional equation (2) falls below the lower limit, it becomes difficult to correct various aberrations, especially field curvature and coma aberration, which is undesirable. To ensure the effectiveness of this embodiment, it is preferable to set the lower limit of conditional equation (2) to 1.00. Furthermore, to further ensure the effectiveness of this embodiment, it is preferable to set the lower limit of conditional equation (2) to 1.15. Furthermore, to further ensure the effectiveness of this embodiment, it is preferable to set the lower limit of conditional equation (2) to 1.30.

[0019] On the other hand, if the corresponding value in conditional equation (2) exceeds the upper limit, the overall optical length of the eyepiece becomes larger. Furthermore, attempting to achieve high magnification makes it difficult to correct various aberrations, especially field curvature and coma aberration, which is undesirable. In conditional equation (2), TL is the air-equivalent length when a parallel plate is placed between the observation object plane and the lens surface of the eyepiece closest to the eye point. To ensure the effectiveness of this embodiment, it is preferable to set the upper limit of conditional equation (2) to 1.45. Furthermore, to further ensure the effectiveness of this embodiment, it is preferable to set the upper limit of conditional equation (2) to 1.43. Furthermore, to further ensure the effectiveness of this embodiment, it is preferable to set the upper limit of conditional equation (2) to 1.40.

[0020] Furthermore, the eyepiece according to this embodiment has, in order from the observation object side along the optical axis, a first lens having positive refractive power, a second lens having negative refractive power, a third lens having positive refractive power, and a fourth lens having positive refractive power.

[0021] Thus, the eyepiece according to this embodiment is equipped with a first lens having positive refractive power for magnifying and observing the object being observed. Furthermore, the eyepiece according to this embodiment is equipped with a second lens having negative refractive power to correct chromatic aberration, field curvature, and astigmatism that occur in the first lens with positive refractive power. Furthermore, the eyepiece according to this embodiment is equipped with a third lens having positive refractive power and a fourth lens having positive refractive power to effectively correct coma aberration and distortion aberration.

[0022] The eyepiece lens according to this embodiment, with this configuration, can effectively correct various aberrations and achieve high magnification. For example, to magnify an object with a diagonal length of approximately 10 mm, it is possible to achieve a high magnification with an apparent field of view of 30° or more.

[0023] The eyepiece lens according to this embodiment satisfies the following condition (3) under this configuration. (3) 0.25 < (-f2) / f3 < 0.53 however, f2: Focal length of the second lens f3: Focal length of the third lens

[0024] Conditional equation (3) is a conditional equation for defining an appropriate range for the ratio of the refractive power of the second lens to the refractive power of the third lens. By satisfying conditional equation (1), good aberration correction can be achieved.

[0025] If the corresponding value in conditional equation (3) falls below the lower limit, it becomes difficult to correct coma aberration and distortion aberration, which is undesirable. In order to ensure the effectiveness of this embodiment, it is preferable to set the lower limit of conditional equation (3) to 0.29. Furthermore, in order to further ensure the effectiveness of this embodiment, it is preferable to set the lower limit of conditional equation (3) to 0.31. Furthermore, in order to further ensure the effectiveness of this embodiment, it is preferable to set the lower limit of conditional equation (3) to 0.33.

[0026] On the other hand, if the corresponding value in conditional equation (3) exceeds the upper limit, the refractive power of the second lens relative to the third lens decreases, the Petzval sum increases, and it becomes difficult to correct field curvature and astigmatism simultaneously, which is undesirable. Furthermore, it becomes difficult to correct coma aberration, which is also undesirable. In order to ensure the effects of this embodiment, it is preferable to set the upper limit of conditional equation (3) to 0.48. Furthermore, in order to further ensure the effects of this embodiment, it is preferable to set the upper limit of conditional equation (3) to 0.45. Furthermore, in order to further ensure the effects of this embodiment, it is preferable to set the upper limit of conditional equation (3) to 0.42.

[0027] The eyepiece lens according to this embodiment satisfies the following condition (4) under this configuration. (4) 0.34 <d1 / fe<0.60 however, d1: Distance along the optical axis from the surface of the observed object to the lens surface of the first lens on the side of the observed object when the diopter of the eyepiece is -1 [1 / m]. fe: The focal length of the eyepiece when the diopter of the eyepiece is -1 [1 / m].

[0028] Conditional equation (4) is a conditional equation for defining an appropriate range for the ratio between the distance along the optical axis from the observation object surface to the observation object-side lens surface of the first lens when the diopter of the eyepiece is -1 [1 / m], and the focal length of the eyepiece when the diopter of the eyepiece is -1 [1 / m]. By satisfying conditional equation (4), miniaturization can be achieved and good aberration correction can be performed.

[0029] If the corresponding value in conditional equation (4) falls below the lower limit, it becomes difficult to correct various aberrations, especially coma aberration and distortion aberration, which is undesirable. Also, because the distance from the observation object surface to the observation object side lens surface of the first lens becomes shorter, the focus may shift to foreign matter attached to the eye point side lens surface of the first lens, which is undesirable. To ensure the effect of this embodiment, it is preferable to set the lower limit of conditional equation (4) to 0.35. Furthermore, to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional equation (4) to 0.355. Furthermore, to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional equation (4) to 0.36.

[0030] On the other hand, if the corresponding value in conditional equation (4) exceeds the upper limit, it becomes difficult to correct various aberrations, especially coma aberration and distortion aberration, which is undesirable. Also, the overall optical length of the eyepiece becomes larger, which is undesirable. In conditional equation (4), d1 is the air equivalent length when a parallel plate is placed between the observation object surface and the observation object side lens surface of the first lens. To ensure the effect of this embodiment, it is preferable to set the upper limit of conditional equation (4) to 0.52. Furthermore, to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional equation (4) to 0.49. Furthermore, to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional equation (4) to 0.45.

[0031] Furthermore, it is desirable that the eyepiece lens according to this embodiment satisfies the following condition (5). (5)0.5<(R2b+R2a) / (R2b-R2a)<2.4 however, R2b: Radius of curvature of the lens surface of the second lens on the eye point side. R2a: Radius of curvature of the lens surface of the second lens on the object-observing side.

[0032] Condition (5) is a condition for defining the shape of the second lens. By satisfying condition (5), good aberration correction can be achieved.

[0033] If the corresponding value in conditional equation (5) falls below the lower limit, it becomes difficult to correct field curvature, coma aberration, and distortion aberration, which is undesirable. In order to ensure the effectiveness of this embodiment, it is preferable to set the lower limit of conditional equation (5) to 0.8. Furthermore, in order to further ensure the effectiveness of this embodiment, it is preferable to set the lower limit of conditional equation (5) to 1.0. Furthermore, in order to further ensure the effectiveness of this embodiment, it is preferable to set the lower limit of conditional equation (5) to 1.2.

[0034] On the other hand, if the corresponding value in conditional equation (5) exceeds the upper limit, it becomes difficult to correct field curvature, coma aberration, and distortion aberration, which is undesirable. In order to ensure the effects of this embodiment, it is preferable to set the upper limit of conditional equation (5) to 2.1. Furthermore, in order to further ensure the effects of this embodiment, it is preferable to set the upper limit of conditional equation (5) to 2.0. Furthermore, in order to further ensure the effects of this embodiment, it is preferable to set the upper limit of conditional equation (5) to 1.9.

[0035] Furthermore, it is desirable that the eyepiece lens according to this embodiment satisfies the following condition (6). (6) 0.7 <f3 / f4<1.5 however, f3: Focal length of the third lens f4: Focal length of the fourth lens

[0036] Conditional equation (6) specifies an appropriate range for the ratio of the refractive power of the third lens to the refractive power of the fourth lens. This is the conditional equation for achieving this. By satisfying condition (6), good aberration correction can be achieved.

[0037] If the corresponding value in conditional equation (6) falls below the lower limit, it becomes difficult to correct coma aberration and distortion aberration, which is undesirable. In order to ensure the effectiveness of this embodiment, it is preferable to set the lower limit of conditional equation (6) to 0.80. Furthermore, in order to further ensure the effectiveness of this embodiment, it is preferable to set the lower limit of conditional equation (6) to 0.88. Furthermore, in order to further ensure the effectiveness of this embodiment, it is preferable to set the lower limit of conditional equation (6) to 0.95.

[0038] On the other hand, if the corresponding value in conditional equation (6) exceeds the upper limit, it becomes difficult to correct coma aberration and distortion aberration, which is undesirable. In order to ensure the effects of this embodiment, it is preferable to set the upper limit of conditional equation (6) to 1.42. Furthermore, in order to further ensure the effects of this embodiment, it is preferable to set the upper limit of conditional equation (6) to 1.39. Furthermore, in order to further ensure the effects of this embodiment, it is preferable to set the upper limit of conditional equation (6) to 1.35.

[0039] Furthermore, it is desirable that the eyepiece lens according to this embodiment satisfies the following condition (7). (7) 0.97 <f34 / (-f2)<1.5 however, f34: The combined focal length of the third lens and the fourth lens when the diopter of the eyepiece is -1 [1 / m]. f2: Focal length of the second lens

[0040] Condition (7) is a condition that defines an appropriate range for the ratio of the combined focal length of the third and fourth lenses to the focal length of the second lens when the diopter of the eyepiece is -1 [1 / m]. By satisfying condition (7), good aberration correction can be achieved.

[0041] If the corresponding value in conditional equation (7) falls below the lower limit, the combined refractive power of the third and fourth lenses relative to the second lens increases, the Petzval sum increases, and it becomes difficult to correct field curvature and astigmatism simultaneously, which is undesirable. Furthermore, it becomes difficult to correct coma aberration, which is also undesirable. In order to ensure the effect of this embodiment, it is preferable to set the lower limit of conditional equation (7) to 1.07. Furthermore, in order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional equation (7) to 1.14. Furthermore, in order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional equation (7) to 1.21.

[0042] On the other hand, if the corresponding value in conditional equation (7) exceeds the upper limit, it becomes difficult to correct coma aberration and distortion aberration, which is undesirable. In order to ensure the effect of this embodiment, it is preferable to set the upper limit of conditional equation (7) to 1.45. Furthermore, in order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional equation (7) to 1.40. Furthermore, in order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional equation (7) to 1.37. Furthermore, in order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional equation (7) to 1.34. Furthermore, in order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional equation (7) to 1.30.

[0043] Furthermore, it is desirable that the eyepiece lens according to this embodiment satisfies the following condition (8). (8) 0.4 < (-f²) / fe < 1.0 however, f2: Focal length of the second lens fe: The focal length of the eyepiece when the diopter of the eyepiece is -1 [1 / m].

[0044] Conditional equation (8) is a conditional equation for defining an appropriate range for the ratio of the focal length of the second lens to the focal length of the eyepiece when the diopter of the eyepiece is -1 [1 / m]. By satisfying conditional equation (8), good aberration correction can be achieved.

[0045] If the corresponding value in conditional equation (8) falls below the lower limit, the refractive power of the second lens increases, making it difficult to correct coma aberration, which is undesirable. To ensure the effectiveness of this embodiment, it is preferable to set the lower limit of conditional equation (8) to 0.45. Furthermore, to further ensure the effectiveness of this embodiment, it is preferable to set the lower limit of conditional equation (8) to 0.50. Furthermore, to further ensure the effectiveness of this embodiment, it is preferable to set the lower limit of conditional equation (8) to 0.55. Furthermore, to further ensure the effectiveness of this embodiment, it is preferable to set the lower limit of conditional equation (8) to 0.65. Furthermore, to further ensure the effectiveness of this embodiment, it is preferable to set the lower limit of conditional equation (8) to 0.70.

[0046] On the other hand, if the corresponding value in conditional equation (8) exceeds the upper limit, the Petzval sum increases, making it difficult to correct field curvature and astigmatism simultaneously, which is undesirable. Furthermore, it becomes difficult to correct coma aberration, which is also undesirable. In order to ensure the effects of this embodiment, it is preferable to set the upper limit of conditional equation (8) to 0.90. Furthermore, in order to further ensure the effects of this embodiment, it is preferable to set the upper limit of conditional equation (8) to 0.84. Furthermore, in order to further ensure the effects of this embodiment, it is preferable to set the upper limit of conditional equation (8) to 0.77.

[0047] Furthermore, it is desirable that the eyepiece lens according to this embodiment satisfies the following condition (9). (9) 0.50 < ΣD / fe < 1.24 however, ΣD: The distance along the optical axis from the lens surface closest to the observation object to the lens surface closest to the eye point when the diopter of the eyepiece is -1 [1 / m]. fe: The focal length of the eyepiece when the diopter of the eyepiece is -1 [1 / m].

[0048] Conditional equation (9) is a conditional equation for defining an appropriate range for the ratio between the distance on the optical axis from the lens surface closest to the observation object to the lens surface closest to the eye point when the diopter of the eyepiece is -1 [1 / m], and the focal length of the eyepiece when the diopter of the eyepiece is -1 [1 / m]. By satisfying conditional equation (9), the thickness of the eyepiece on the optical axis can be reduced, and good aberration correction can be achieved.

[0049] If the corresponding value in conditional equation (9) falls below the lower limit, it becomes difficult to correct field curvature, coma aberration, and distortion aberration, which is undesirable. In order to ensure the effects of this embodiment, it is preferable to set the lower limit of conditional equation (9) to 0.70. Furthermore, in order to further ensure the effects of this embodiment, it is preferable to set the lower limit of conditional equation (9) to 0.82. Furthermore, in order to further ensure the effects of this embodiment, it is preferable to set the lower limit of conditional equation (9) to 0.93.

[0050] On the other hand, if the corresponding value in conditional equation (9) exceeds the upper limit, it becomes difficult to correct field curvature, coma aberration, and distortion aberration, which is undesirable. Also, the thickness of the eyepiece lens on the optical axis increases, which is undesirable. In order to ensure the effects of this embodiment, it is preferable to set the upper limit of conditional equation (9) to 1.15. Furthermore, in order to further ensure the effects of this embodiment, it is preferable to set the upper limit of conditional equation (9) to 1.08. Furthermore, in order to further ensure the effects of this embodiment, it is preferable to set the upper limit of conditional equation (9) to 1.00.

[0051] Furthermore, it is desirable that the eyepiece lens according to this embodiment satisfies the following condition (10). (10) 1.2 <f4 / fe<2.2 however, f4: Focal length of the fourth lens fe: The focal length of the eyepiece when the diopter of the eyepiece is -1 [1 / m].

[0052] Conditional equation (10) is a conditional equation for defining an appropriate range for the ratio of the focal length of the fourth lens to the focal length of the eyepiece when the diopter of the eyepiece is -1 [1 / m]. By satisfying conditional equation (10), good aberration correction can be achieved.

[0053] If the corresponding value in conditional equation (10) falls below the lower limit, the refractive power of the fourth lens increases, the Petzval sum increases, and it becomes difficult to correct field curvature and astigmatism simultaneously, which is undesirable. It is also undesirable because it becomes difficult to correct coma aberration. In order to ensure the effects of this embodiment, it is preferable to set the lower limit of conditional equation (10) to 1.35. Furthermore, in order to further ensure the effects of this embodiment, it is preferable to set the lower limit of conditional equation (10) to 1.43. Furthermore, in order to further ensure the effects of this embodiment, it is preferable to set the lower limit of conditional equation (10) to 1.50.

[0054] On the other hand, if the corresponding value in conditional equation (10) exceeds the upper limit, it becomes difficult to correct various aberrations, especially coma aberration, which is undesirable. In order to ensure the effect of this embodiment, it is preferable to set the upper limit of conditional equation (10) to 2.00. Furthermore, in order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional equation (10) to 1.90. Furthermore, in order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional equation (10) to 1.80.

[0055] Furthermore, it is desirable that the eyepiece lens according to this embodiment satisfies the following condition (11). (11) 0.15 <D1 / fe<0.40 however, D1: Thickness of the first lens along the optical axis fe: The focal length of the eyepiece when the diopter of the eyepiece is -1 [1 / m].

[0056] Conditional equation (11) is a conditional equation for defining an appropriate range for the ratio between the thickness of the first lens on the optical axis and the focal length of the eyepiece when the diopter of the eyepiece is -1 [1 / m]. By satisfying conditional equation (11), the thickness of the eyepiece on the optical axis can be reduced, and good aberration correction can be achieved.

[0057] If the corresponding value in conditional equation (11) falls below the lower limit, it becomes difficult to correct field curvature and coma aberration, which is undesirable. Also, the edge thickness of the first lens becomes thin, making manufacturing difficult, which is undesirable. To ensure the effects of this embodiment, it is preferable to set the lower limit of conditional equation (11) to 0.20. Furthermore, to further ensure the effects of this embodiment, it is preferable to set the lower limit of conditional equation (11) to 0.23. Furthermore, to further ensure the effects of this embodiment, it is preferable to set the lower limit of conditional equation (11) to 0.25.

[0058] On the other hand, if the corresponding value in conditional equation (11) exceeds the upper limit, it becomes difficult to correct field curvature and coma aberration, which is undesirable. Also, the thickness of the eyepiece in the optical axis direction increases, which is undesirable. In order to ensure the effect of this embodiment, it is preferable to set the upper limit of conditional equation (11) to 0.34. Furthermore, in order to further ensure the effect of this embodiment, the conditional equation It is preferable to set the upper limit of (11) to 0.32. Furthermore, in order to further ensure the effects of this embodiment, it is preferable to set the upper limit of conditional expression (11) to 0.29.

[0059] Furthermore, it is desirable that the eyepiece lens according to this embodiment satisfies the following condition (12). (12) 0.05 <D2 / fe<0.20 however, D2: Thickness of the second lens along the optical axis. fe: The focal length of the eyepiece when the diopter of the eyepiece is -1 [1 / m].

[0060] Conditional equation (12) is a conditional equation for defining an appropriate range for the ratio between the thickness of the second lens on the optical axis and the focal length of the eyepiece when the diopter of the eyepiece is -1 [1 / m]. By satisfying conditional equation (12), the thickness of the eyepiece on the optical axis can be reduced, and good aberration correction can be achieved.

[0061] If the corresponding value in conditional equation (12) falls below the lower limit, it becomes difficult to correct field curvature and coma aberration, which is undesirable. In order to ensure the effects of this embodiment, it is preferable to set the lower limit of conditional equation (12) to 0.07. Furthermore, in order to further ensure the effects of this embodiment, it is preferable to set the lower limit of conditional equation (12) to 0.08. Furthermore, in order to further ensure the effects of this embodiment, it is preferable to set the lower limit of conditional equation (12) to 0.09.

[0062] On the other hand, if the corresponding value in conditional equation (12) exceeds the upper limit, it becomes difficult to correct field curvature and coma aberration, which is undesirable. Also, the thickness of the eyepiece lens on the optical axis increases, which is undesirable. In order to ensure the effects of this embodiment, it is preferable to set the upper limit of conditional equation (12) to 0.17. Furthermore, in order to further ensure the effects of this embodiment, it is preferable to set the upper limit of conditional equation (12) to 0.16. Furthermore, in order to further ensure the effects of this embodiment, it is preferable to set the upper limit of conditional equation (12) to 0.15.

[0063] Furthermore, in the eyepiece lens according to this embodiment, it is desirable that at least one surface of the first lens is aspherical. This configuration allows for good correction of field curvature, astigmatism, and coma aberration.

[0064] Furthermore, in the eyepiece lens according to this embodiment, it is preferable that at least one surface of each lens constituting the eyepiece lens is aspherical. This configuration allows for good correction of field curvature, astigmatism, and coma aberration.

[0065] Furthermore, in this embodiment, it is preferable that the first lens, second lens, third lens, and fourth lens of the eyepiece are made of plastic. This configuration allows for weight reduction and cost reduction. In addition, since an aspherical shape can be easily formed, spherical aberration, field curvature, astigmatism, coma aberration, and distortion can be effectively corrected.

[0066] Furthermore, in this embodiment, it is desirable that the distance between the first lens and the second lens, the distance between the second lens and the third lens, and the distance between the third lens and the fourth lens remain constant. This configuration makes it possible to reduce fluctuations in field curvature, coma aberration, and distortion aberration compared to cases where the distance between adjacent lenses changes.

[0067] Furthermore, in this embodiment, it is preferable that the diopter adjustment of the eyepiece is performed by moving the first lens, the second lens, the third lens, and the fourth lens along the optical axis. This configuration makes it possible to reduce variations in various aberrations during diopter adjustment, particularly field curvature, coma aberration, and distortion.

[0068] Furthermore, in this embodiment, it is desirable that diopter adjustment be performed by moving all the lenses constituting the eyepiece lens as a whole. This configuration makes it possible to reduce fluctuations in various aberrations during diopter adjustment, particularly field curvature, coma aberration, and distortion aberration.

[0069] The optical instrument according to the embodiment of this application has an eyepiece with the above configuration. This makes it possible to realize an optical instrument that is high magnification, compact, and has high optical performance.

[0070] The method for manufacturing an eyepiece according to the embodiment of the present application is a method for manufacturing an eyepiece for observing an object to be observed, wherein the eyepiece is configured to have, in order from the object to be observed, a first lens having positive refractive power, a second lens having negative refractive power, a third lens having positive refractive power, and a fourth lens having positive refractive power, and is configured to satisfy the following conditions (1) and (2). (1)-13.00<(R2a+R1b) / (R2a-R1b)<-2.75 (2) 0.78 <TL / fe<1.60 however, R2a: Radius of curvature of the lens surface of the second lens on the object-observing side. R1b: Radius of curvature of the lens surface on the eye point side of the first lens. TL: Distance along the optical axis from the surface of the observed object to the lens surface closest to the eye point when the diopter of the eyepiece is -1 [1 / m]. fe: The focal length of the eyepiece when the diopter of the eyepiece is -1 [1 / m].

[0071] By this method of manufacturing eyepieces, it is possible to manufacture eyepieces that are high-magnification, compact, and possess high optical performance.

[0072] Furthermore, another method for manufacturing an eyepiece according to the embodiment of the present application is a method for manufacturing an eyepiece for observing an object to be observed, wherein the eyepiece is configured to have, in order from the object to be observed, a first lens having positive refractive power, a second lens having negative refractive power, a third lens having positive refractive power, and a fourth lens having positive refractive power, and is configured to satisfy the following conditions (3) and (4). (3) 0.25 < (-f2) / f3 < 0.53 (4) 0.34 <d1 / fe<0.60 however, f2: Focal length of the second lens f3: Focal length of the third lens d1: Distance along the optical axis from the surface of the observed object to the lens surface of the first lens on the side of the observed object when the diopter of the eyepiece is -1 [1 / m]. fe: The focal length of the eyepiece when the diopter of the eyepiece is -1 [1 / m].

[0073] By using other manufacturing methods for eyepieces, it is possible to produce eyepieces that are high-magnification, compact, and possess high optical performance.

[0074] (Examples of numerical values) The eyepiece lens according to the numerical embodiment of this model will be described below with reference to the attached drawings.

[0075] (First embodiment) Figure 1 is a cross-sectional view of the eyepiece according to the first embodiment at a diopter of -1 [1 / m]. In Figure 1, EP indicates the eye point and Ob indicates the object being observed. Note that these symbols The same numbering will be used in the figures of each embodiment described later. In this embodiment, the observed object Ob is the display surface of the liquid crystal display element of the electronic viewfinder, and the image displayed on the display surface of the liquid crystal display element is observed at the eye point EP. In each embodiment described later, the observed object Ob is the display surface of the liquid crystal display element of the electronic viewfinder.

[0076] As shown in Figure 1, the eyepiece lens according to this embodiment consists of, in order from the observation object Ob side, a first lens L1 which is a biconvex lens, a second lens L2 which is a negative meniscus lens with its convex surface facing the eye point EP side, a third lens L3 which is a positive meniscus lens with its convex surface facing the eye point EP side, and a fourth lens L4 which is a positive meniscus lens with its convex surface facing the eye point EP side.

[0077] In this embodiment, the eyepiece lenses are aspherical lenses on the observation object Ob side and the eye point EP side of the first lens L1, aspherical lenses on the observation object Ob side and the eye point EP side of the second lens L2, aspherical lenses on the observation object Ob side and the eye point EP side of the third lens L3, and aspherical lenses on the observation object Ob side and the eye point EP side of the fourth lens L4.

[0078] In this embodiment, the eyepiece adjusts the diopter by moving the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 together along the optical axis.

[0079] Table 1 below lists the specifications of the photographic lens according to this embodiment. In the [Overall Specifications], Y0 represents the height of the observed object, and TL represents the distance along the optical axis from the surface of the observed object to the lens surface closest to the eye point EP, when the diopter is -1 [1 / m].

[0080] In [Surface Data], the surface number indicates the order of the optical surfaces counted from the side of the observed object, r is the radius of curvature, d is the surface interval (the interval between the n-th surface (n is an integer) and the (n + 1)-th surface), nd is the refractive index for the d-line (wavelength 587.6 nm), and νd is the Abbe number for the d-line (wavelength 587.6 nm). Also, the 0-th surface indicates the observed object surface, that is, the display surface of the liquid crystal display element which is the observed object Ob. Further, Variable indicates the variable surface interval, and EP indicates the eye point EP. Note that a curvature radius r = ∞ indicates a plane. The description of the refractive index of air nd = 1.0000 is omitted. Also, when the lens surface is an aspherical surface, an asterisk is attached to the surface number and the paraxial radius of curvature is shown in the column of the radius of curvature r.

[0081] [Aspherical Data] shows the conic coefficient and the aspherical coefficient when the shape of the aspherical surface shown in [Surface Data] is represented by the following formula. X(y)=(y 2 / r) / [1+{1-κ(y 2 / r 2 )} 1 / 2 +A4y 4 +A6y 6 + A8y 8 +A10y 10 Here, let the height in the direction perpendicular to the optical axis be y, the displacement amount in the optical axis direction at the height y be X(y), the radius of curvature of the reference sphere (paraxial radius of curvature) be r, the conic coefficient be κ, and the n-th aspherical coefficient be An. The second-order aspherical coefficient A2 is 0 (zero) and the description is omitted. Also, "E-n" indicates "×10 -n ", for example, "1.234E-05" indicates "1.234×10 -5 " is shown.

[0082] In [Variable Interval Data], fe indicates the focal length of the eyepiece lens at each viewing angle, and di (i is an integer) indicates the surface interval between the i-th surface and the (i + 1)-th surface.

[0083] [Data of Each Lens] shows the starting surface number and the focal length of each lens. The [Conditional Expression Corresponding Value] column shows the corresponding value for each conditional expression.

[0084] Here, the units of focal length fe, radius of curvature r, and other lengths listed in Table 1 are generally "mm". However, this is not the only unit used, as optical systems can achieve equivalent optical performance even when proportionally enlarged or reduced. The reference numerals in Table 1 described above shall also be used in the tables for each of the embodiments described later.

[0085] (Table 1) First Example [Overall Specifications] Y0 5 TL 22.97080 [Surface data] Face number rd nd νd 0) ∞ Variable *1) 38.5000 4.7000 1.5311 55.91 *2) -7.9324 1.9500 *3) -5.9015 1.6000 1.6349 23.96 *4) -31.3532 0.4000 *5) -81.3698 3.6000 1.5311 55.91 *6) -13.4312 0.3000 *7) -86.6666 3.8000 1.5311 55.91 *8) -12.5836 Variable EP ∞ [Aspherical data] Surface number κ A4 A6 A8 A10 1) 1.0000 -1.07830E-04 3.90090E-07 -8.84450E-09 0.00000E+00 2) 0.2300 1.46600E-04 -2.00600E-06 1.12720E-08 -1.76010E-10 3) 0.2000 6.32360E-06 -7.08210E-07 9.97080E-09 6.05370E-12 4) 2.4698 -4.51520E-05 3.34100E-07 5.44460E-09 -3.19170E-12 5) 1.0000 2.87140E-05 -4.06830E-07 8.06580E-09 -1.05880E-10 6) 0.4764 3.15160E-05 6.77160E-07 4.22120E-09 -1.12500E-10 7) 1.0000 1.61050E-05 -1.27860E-07 -6.30500E-10 1.97650E-11 8) -1.3000 -6.03300E-05 -2.60140E-07 5.18670E-10 1.33770E-11 [Variable interval data] Diopter -1 -3 +3 fe 16.69882 16.69882 16.69882 d0 6.62 6.04 7.72 d8 22.00 22.58 20.90 [Data for each lens] Starting surface f L1 1 12.83484 L2 3 -11.73613 L3 5 29.74230 L4 7 27.23347 [Conditional expression corresponding value] fe=16.69882 -f2=11.73613 f3 = 29.74230 f4 = 27.23347 f34 = 14.92250 ΣD = 16.35000 (1)(R2a+R1b) / (R2a-R1b)=-6.81171 (2) TL / fe = 1.37559 (3)(-f2) / f3=0.39459 (4) d1 / fe = 0.39648 (5)(R2b+R2a) / (R2b-R2a)=1.46374 (6) f3 / f4 = 1.09212 (7) f34 / (-f2)=1.27150 (8)(-f²) / fe=0.70281 (9)ΣD / fe=0.97911 (10) f4 / fe = 1.63086 (11) D1 / fe = 0.28146 (12) D2 / fe = 0.09582

[0086] Figures 2(a), 2(b), and 2(c) show the aberration diagrams of the eyepiece according to the first embodiment at diopters of -1 [1 / m], -3 [1 / m], and +3 [1 / m], respectively. That is the case.

[0087] In each aberration diagram, Y1 represents the height at which light emitted from the optical axis center of the observed object enters the tangent plane of the first lens L1 on the observed object side, and Y0 represents the height of the observed object. In the diagrams, d represents the aberration curve at the d line (wavelength λ=587.6nm), g represents the aberration curve at the g line (wavelength λ=435.8nm), and unless otherwise indicated, the aberration curve is at the d line. In the aberration diagrams showing astigmatism, solid lines represent the sagittal image plane, and dashed lines represent the meridional image plane. The unit D on the horizontal axis of the spherical aberration diagram and astigmatism diagram is [1 / m] (diopter). The same reference numerals as in this example are used in the aberration diagrams of each embodiment shown below.

[0088] From the aberration diagrams, it can be seen that the eyepiece lens according to the first embodiment has excellent optical performance, with various aberrations well corrected within the diopter adjustment range.

[0089] (Second example) Figure 3 is a cross-sectional view of the eyepiece according to the second embodiment at a diopter of -1 [1 / m]. As shown in Figure 3, the eyepiece lens according to this embodiment consists of, in order from the observation object Ob side, a first lens L1 which is a biconvex lens, a second lens L2 which is a negative meniscus lens with its convex surface facing the eye point EP side, a third lens L3 which is a positive meniscus lens with its convex surface facing the eye point EP side, and a fourth lens L4 which is a biconvex lens.

[0090] In this embodiment, the eyepiece lenses are aspherical lenses on the observation object Ob side and the eye point EP side of the first lens L1, aspherical lenses on the observation object Ob side and the eye point EP side of the second lens L2, aspherical lenses on the observation object Ob side and the eye point EP side of the third lens L3, and aspherical lenses on the observation object Ob side and the eye point EP side of the fourth lens L4.

[0091] Furthermore, in this embodiment, the eyepiece adjusts diopter by moving the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 together along the optical axis. The observation object Ob is the display surface of the liquid crystal display element of the electronic viewfinder, and the image displayed on the display surface of the liquid crystal display element is observed at the eye point EP.

[0092] Table 2 below lists the specifications of the photographic lens according to this embodiment.

[0093] (Table 2) Second Example [Overall Specifications] Y0 5 TL 22.44140 [Surface data] Face number rd nd νd 0) ∞ Variable *1) 54.1310 4.6000 1.5311 55.91 *2) -7.1966 1.9000 *3) -5.1089 1.5000 1.6392 23.41 *4) -19.3192 0.4000 *5) -102.7678 3.7000 1.5311 55.91 *6) -15.0883 0.2000 *7) 10238.8333 3.7000 1.5311 55.91 *8) -13.2729 Variable EP ∞ [Aspherical data] Surface number κ A4 A6 A8 A10 1) 3.0000 -1.08886E-04 9.45037E-07 -3.04555E-08 6.36072E-10 2) 0.5371 2.59662E-04 4.45097E-07 -7.58586E-09 1.52063E-10 3) -0.0106 -6.11178E-05 1.09499E-06 -4.80532E-08 -1.41908E-11 4) 0.9777 -6.22815E-05 1.22908E-06 -6.71364E-09 6.40334E-11 5) 1.0000 4.50000E-05 -3.08295E-08 1.00000E-09 -1.68575E-11 6) 1.0000 1.23962E-04 -1.63662E-06 1.82978E-08 -1.04522E-10 7) 1.0000 6.03686E-05 -1.05695E-06 3.14589E-09 5.91446E-11 8) -0.4502 6.02914E-05 4.18032E-07 -1.69597E-08 1.55783E-10 [Variable interval data] Diopter -1 -3 +3 fe 16.26559 16.26559 16.26559 d0 6.44 5.89 7.48 d8 20.00 20.55 18.96 [Data for each lens] Starting surface f L1 1 12.27984 L2 3 -11.33254 L3 5 32.81807 L4 7 24.96209 [Conditional expression corresponding value] fe=16.26559 -f2=11.33254 f3 = 32.81807 f4 = 24.96209 f34 = 14.74024 ΣD = 16.00000 (1)(R2a+R1b) / (R2a-R1b)=-5.89429 (2) TL / fe = 1.37969 (3)(-f2) / f3=0.34531 (4) d1 / fe = 0.39601 (5)(R2b+R2a) / (R2b-R2a)=1.71904 (6) f3 / f4 = 1.31472 (7) f34 / (-f2)=1.30070 (8)(-f²) / fe=0.69672 (9)ΣD / fe=0.98367 (10) f4 / fe = 1.53466 (11) D1 / fe = 0.28281 (12) D2 / fe = 0.09222

[0094] Figures 4(a), 4(b), and 4(c) show the aberration diagrams of the eyepiece according to the second embodiment at diopters of -1 [1 / m], -3 [1 / m], and +3 [1 / m], respectively. That is the case. From the aberration diagrams, it can be seen that the eyepiece lens according to the second embodiment has excellent optical performance, with various aberrations well corrected within the diopter adjustment range.

[0095] (Third embodiment) Figure 5 is a cross-sectional view of the eyepiece according to the third embodiment at a diopter of -1 [1 / m]. As shown in Figure 5, the eyepiece lens according to this embodiment consists of, in order from the observation object Ob side, a first lens L1 which is a biconvex lens, a second lens L2 which is a negative meniscus lens with its convex surface facing the eye point EP side, a third lens L3 which is a biconvex lens, and a fourth lens L4 which is a positive meniscus lens with its convex surface facing the eye point EP side.

[0096] In this embodiment, the eyepiece lenses are aspherical lenses on the observation object Ob side and the eye point EP side of the first lens L1, aspherical lenses on the observation object Ob side and the eye point EP side of the second lens L2, aspherical lenses on the observation object Ob side and the eye point EP side of the third lens L3, and aspherical lenses on the observation object Ob side and the eye point EP side of the fourth lens L4.

[0097] Furthermore, in this embodiment, the eyepiece adjusts diopter by moving the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 together along the optical axis. The observation object Ob is the display surface of the liquid crystal display element of the electronic viewfinder, and the image displayed on the display surface of the liquid crystal display element is observed at the eye point EP.

[0098] Table 3 below lists the specifications of the photographic lens according to this embodiment.

[0099] (Table 3) Third Example [Overall Specifications] Y0 5 TL 22.69130 [Surface data] Face number rd nd νd 0) ∞ Variable *1) 36.8718 4.7000 1.5311 55.91 *2) -7.2203 1.7000 *3) -6.0441 1.5000 1.6392 23.41 *4) -58.5446 0.3000 *5) 2088.0633 4.0000 1.5311 55.91 *6) -16.6991 0.2000 *7) -294.5173 3.3500 1.5311 55.91 *8) -12.6937 Variable EP ∞ [Aspherical data] Surface number κ A4 A6 A8 A10 1) 1.0000 -2.77100E-04 3.28531E-06 -5.95866E-08 5.56135E-10 2) -0.1834 3.98963E-05 3.59354E-07 -5.44538E-08 7.79143E-10 3) 0.0254 -4.50556E-05 -2.01226E-06 3.28413E-09 5.79187E-11 4) 11.4670 -1.64243E-04 4.99568E-07 2.72460E-09 3.97790E-11 5) 1.0000 1.99028E-06 -9.39927E-08 -6.16687E-10 1.30958E-11 6) 1.0000 -9.14500E-05 2.76509E-07 -2.08324E-10 -2.24194E-11 7) 1.0000 3.31997E-05 -9.70440E-07 9.59206E-09 -1.59816E-11 8) -1.9398 3.92293E-05 1.49940E-08 1.09811E-09 1.45671E-12 [Variable interval data] Diopter -1 -3 +3 fe 16.25648 16.25648 16.25648 d0 6.94 6.39 7.98 d8 20.00 20.55 18.96 [Data for each lens] Starting surface f L1 1 11.80525 L2 3 -10.66309 L3 5 31.21356 L4 7 24.87468 [Conditional expression corresponding value] fe=16.25648 -f2=10.66309 f3 = 31.21356 f4 = 24.87468 f34 = 14.48819 ΣD = 15.75000 (1)(R2a+R1b) / (R2a-R1b)=-11.27733 (2) TL / fe = 1.39583 (3)(-f2) / f3=0.34162 (4) d1 / fe = 0.42699 (5)(R2b+R2a) / (R2b-R2a)=1.23025 (6) f3 / f4 = 1.25483 (7) f34 / (-f2)=1.35872 (8)(-f²) / fe=0.65593 (9)ΣD / fe=0.96884 (10) f4 / fe = 1.53014 (11) D1 / fe = 0.28912 (12) D2 / fe = 0.09227

[0100] Figures 6(a), 6(b), and 6(c) show the aberration diagrams of the eyepiece according to the third embodiment at diopters of -1 [1 / m], -3 [1 / m], and +3 [1 / m], respectively. That is the case. From the aberration diagrams, it can be seen that the eyepiece lens according to the third embodiment has excellent optical performance, with aberrations well corrected within the diopter adjustment range.

[0101] (Fourth embodiment) Figure 7 is a cross-sectional view of the eyepiece according to the fourth embodiment at a diopter of -1 [1 / m]. As shown in Figure 7, the eyepiece lens according to this embodiment consists of, in order from the observation object Ob side, a first lens L1 which is a biconvex lens, a second lens L2 which is a negative meniscus lens with its convex surface facing the eye point EP side, a third lens L3 which is a positive meniscus lens with its convex surface facing the eye point EP side, and a fourth lens L4 which is a positive meniscus lens with its convex surface facing the eye point EP side.

[0102] In this embodiment, the eyepiece lenses are aspherical lenses on the observation object Ob side and the eye point EP side of the first lens L1, aspherical lenses on the observation object Ob side and the eye point EP side of the second lens L2, aspherical lenses on the observation object Ob side and the eye point EP side of the third lens L3, and aspherical lenses on the observation object Ob side and the eye point EP side of the fourth lens L4.

[0103] Furthermore, in this embodiment, the eyepiece adjusts diopter by moving the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 together along the optical axis. The observation object Ob is the display surface of the liquid crystal display element of the electronic viewfinder, and the image displayed on the display surface of the liquid crystal display element is observed at the eye point EP.

[0104] Table 4 below lists the specifications of the photographic lens according to this embodiment.

[0105] (Table 4) Fourth Example [Overall Specifications] Y0 5 TL 23.17110 [Surface data] Face number rd nd νd 0) ∞ Variable *1) 45.0000 4.7000 1.5311 55.91 *2) -7.7479 2.0000 *3) -6.1500 1.6000 1.6349 23.96 *4) -31.9899 0.4500 *5) -72.0000 3.6000 1.5311 55.91 *6) -13.5279 0.3000 *7) -70.8540 3.9000 1.5311 55.91 *8) -12.6502 Variable EP ∞ [Aspherical data] Surface number κ A4 A6 A8 A10 1) 1.0000 -1.07831E-04 3.90090E-07 -8.84455E-09 -1.00000E-11 2) 0.0556 1.36830E-04 -1.76475E-06 -1.38657E-09 -7.67919E-11 3) 0.2000 4.81429E-05 -9.80409E-07 -8.91375E-09 2.08310E-11 4) 1.2082 -5.40750E-05 5.44833E-07 1.22407E-09 -2.28888E-11 5) 1.0000 2.00599E-05 -3.00041E-07 5.73160E-09 -7.15876E-11 6) 1.0000 6.47050E-05 2.82244E-07 8.66025E-10 -3.63247E-11 7) 1.0000 5.59470E-05 -2.82099E-07 -3.84079E-09 3.66963E-11 8) -0.6000 1.20751E-06 -3.65237E-07 -3.60726E-10 1.20918E-11 [Variable interval data] Diopter -1 -5 +5 fe 16.70093 16.70093 16.70093 d0 6.62 5.44 8.25 d8 20:00 21:18 18:37 [Data for each lens] Starting surface f L1 1 12.84253 L2 3 -12.28670 L3 5 30.70855 L4 7 28.33712 [Conditional expression corresponding value] fe=16.70093 -f2=12.28670 f3 = 30.70855 f4 = 28.33712 f34 = 15.47065 ΣD = 16.55000 (1)(R2a+R1b) / (R2a-R1b)=-8.69760 (2) TL / fe = 1.38741 (3)(-f2) / f3=0.40011 (4) d1 / fe = 0.39645 (5)(R2b+R2a) / (R2b-R2a)=1.47601 (6) f3 / f4 = 1.08369 (7) f34 / (-f2)=1.25914 (8)(-f²) / fe=0.73569 (9)ΣD / fe=0.99096 (10) f4 / fe = 1.69674 (11) D1 / fe = 0.28142 (12) D2 / fe = 0.09580

[0106] Figures 8(a), 8(b), and 8(c) show the aberration diagrams of the eyepiece according to the fourth embodiment at diopters of -1 [1 / m], -5 [1 / m], and +5 [1 / m], respectively. That is the case. From the aberration diagrams, it can be seen that the eyepiece lens according to the fourth embodiment has excellent optical performance, with aberrations well corrected within the diopter adjustment range.

[0107] (Fifth example) Figure 9 is a cross-sectional view of the eyepiece according to the fifth embodiment at a diopter of -1 [1 / m]. As shown in Figure 9, the eyepiece lens according to this embodiment consists of, in order from the observation object Ob side, a first lens L1 which is a biconvex lens, a second lens L2 which is a negative meniscus lens with its convex surface facing the eye point EP side, a third lens L3 which is a positive meniscus lens with its convex surface facing the eye point EP side, and a fourth lens L4 which is a positive meniscus lens with its convex surface facing the eye point EP side.

[0108] In this embodiment, the eyepiece lenses are aspherical lenses on the observation object Ob side and the eye point EP side of the first lens L1, aspherical lenses on the observation object Ob side and the eye point EP side of the second lens L2, aspherical lenses on the observation object Ob side and the eye point EP side of the third lens L3, and aspherical lenses on the observation object Ob side and the eye point EP side of the fourth lens L4.

[0109] Furthermore, in this embodiment, the eyepiece adjusts diopter by moving the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 together along the optical axis. The observation object Ob is the display surface of the liquid crystal display element of the electronic viewfinder, and the image displayed on the display surface of the liquid crystal display element is observed at the eye point EP.

[0110] Table 5 below lists the specifications of the photographic lens according to this embodiment.

[0111] (Table 5) Example 5 [Overall Specifications] Y0 5 TL 23.58660 [Surface data] Face number rd nd νd 0) ∞ Variable *1) 35.4135 4.5000 1.5311 55.91 *2) -8.6762 1.8000 *3) -7.0000 1.7000 1.6392 23.41 *4) -45.0000 0.3000 *5) -62.6687 3.7000 1.5311 55.91 *6) -13.8064 0.3000 *7) -63.9198 3.9000 1.5311 55.91 *8) -12.7708 Variable EP ∞ [Aspherical data] Surface number κ A4 A6 A8 A10 1) 1.0000 -1.07831E-04 3.90090E-07 -8.84455E-09 -1.00000E-11 2) 0.0556 1.17846E-04 -2.11624E-06 3.16358E-08 -5.76944E-10 3) 0.2000 -1.38822E-04 -2.32251E-07 -3.48817E-08 1.02138E-10 4) 1.2082 -1.31713E-04 -1.87116E-08 5.54969E-10 -1.00641E-11 5) 1.0000 2.00599E-05 -3.00041E-07 5.73160E-09 -7.15876E-11 6) 1.0000 1.48790E-05 4.25697E-07 2.40718E-09 -2.65452E-11 7) 1.0000 5.63031E-05 -3.41994E-07 -4.83096E-09 2.44539E-11 8) -0.6000 1.67664E-05 -9.47558E-08 -1.86866E-09 -6.88487E-12 [Variable interval data] Diopter -1 -3 +3 fe 17.16747 17.16747 17.16747 d0 7.38 6.77 8.55 d8 21.00 21.61 19.83 [Data for each lens] Starting surface f L1 1 13.60313 L2 3 -13.19877 L3 5 32.48781 L4 7 29.27539 [Conditional expression corresponding value] fe=17.16747 -f2=13.19877 f3 = 32.48781 f4 = 29.27539 f34 = 16.11274 ΣD = 16.20000 (1)(R2a+R1b) / (R2a-R1b)=-9.35223 (2) TL / fe = 1.37391 (3)(-f2) / f3=0.40627 (4) d1 / fe = 0.43027 (5)(R2b+R2a) / (R2b-R2a)=1.36842 (6) f3 / f4 = 1.10973 (7) f34 / (-f2)=1.22078 (8)(-f²) / fe=0.76882 (9)ΣD / fe=0.94365 (10) f4 / fe = 1.70528 (11) D1 / fe = 0.26212 (12) D2 / fe = 0.09902

[0112] Figures 10(a), 10(b), and 10(c) show the various characteristics of the eyepiece according to the fifth embodiment at diopters of -1 [1 / m], -3 [1 / m], and +3 [1 / m], respectively. This is an aberration diagram. From the aberration diagrams, it can be seen that the eyepiece lens according to the fifth embodiment has excellent optical performance, with various aberrations well corrected within the diopter adjustment range.

[0113] As described above, according to each of the above embodiments, it is possible to realize an eyepiece that is high-magnification, compact, and has high optical performance. In particular, it is possible to realize an eyepiece that is suitable for use in an electronic viewfinder for observing an image displayed on an image display element. The above embodiments are merely examples of this embodiment, and this embodiment is not limited to these. The following details can be appropriately adopted as long as they do not impair the optical performance of the eyepiece of this embodiment.

[0114] Although this embodiment shows a four-lens eyepiece configuration as an example, it can also be applied to other lens configurations, such as five lenses. Furthermore, configurations with an additional lens closest to the object being observed, or a configuration with an additional lens closest to the eye point, are also acceptable.

[0115] Furthermore, the lens surface of the lens constituting the eyepiece in this embodiment may be spherical, flat, or aspherical. When the lens surface is spherical or flat, lens processing and assembly adjustment are easier, and deterioration of optical performance due to errors in lens processing and assembly adjustment can be prevented, which is preferable. It is also preferable because even if the image plane is misaligned, the deterioration of image rendering performance is less. When the lens surface is aspherical, it may be an aspherical surface produced by grinding, a glass molded aspherical surface formed by molding glass into an aspherical shape, or a composite aspherical surface formed by forming a resin on the glass surface into an aspherical shape. In addition, the lens surface may be a diffractive surface, and the lens may be a refractive index distribution type lens (GRIN lens) or a plastic lens.

[0116] Furthermore, the lens surface of the lens constituting the eyepiece of this embodiment may be coated with an anti-reflective coating having high transmittance over a wide wavelength range in order to reduce flare and ghosting and achieve high contrast optical performance.

[0117] Furthermore, although the eyepiece in this embodiment is shown as having a configuration in which the first lens L1, second lens L2, third lens L3, and fourth lens L4 move together as a single unit, or the entire eyepiece moves together as a single unit to adjust the diopter, it is also acceptable to fix the lens closest to the eye point and move the entire lens on the observation object side of that lens together, or to move at least some of the lenses of the first lens L1, second lens L2, third lens L3, and fourth lens L4.

[0118] Next, an optical instrument equipped with an eyepiece according to this embodiment will be described. Figure 11 shows a camera 1 as an optical device equipped with an eyepiece lens according to this embodiment. Camera 1 is a digital camera equipped with an objective lens OL, an image sensor C such as a CCD or CMOS, and an electronic viewfinder EVF. The electronic viewfinder EVF is configured to have an image display element such as a liquid crystal display element, which is the object to be observed Ob, and an eyepiece optical system EL for magnified observation of the image displayed on the image display element. Here, camera 1 is equipped with the eyepiece lens according to the first embodiment as the eyepiece optical system EL.

[0119] In camera 1 with this configuration, light from an object (subject) not shown is focused by the objective lens OL and formed on the image sensor C to form an image of the subject. The image of the subject formed on the image sensor C is captured by the image sensor C, and the image of the subject captured by the image sensor C is displayed on the image display element, which is the object Ob being observed. By positioning the eye at the eye point EP, the photographer can magnify and observe the image of the object (subject) formed by the objective lens OL through the eyepiece optical system EL.

[0120] Furthermore, when the photographer presses the release button (not shown), the image captured by the image sensor C at that time, that is, the image displayed on the image display element observed through the eyepiece optical system EL, is stored in the memory (not shown) as an image of the object (subject). In this way, the photographer can take a photograph of the object (subject) with the camera 1.

[0121] With the camera 1 described above, by equipping the eyepiece lens according to the first embodiment as the eyepiece optical system (EL), it is possible to realize a camera with high magnification, a compact size, and high optical performance. Furthermore, the same effects as camera 1 can be achieved by configuring a camera equipped with the eyepiece lenses according to the second to fifth embodiments. Also, the same effects as camera 1 can be achieved by equipping a camera with a quick-return mirror with the variable magnification optical system according to each embodiment. Additionally, the eyepiece lenses according to the first to fifth embodiments may be used as the eyepiece optical system (EL) of a viewfinder device that can be attached to the camera body. A camera equipped with such a viewfinder device can also achieve the same effects as camera 1.

[0122] Next, the method for manufacturing the eyepiece lens according to this embodiment will be described. Figure 12 is a schematic diagram of the method for manufacturing the eyepiece lens according to this embodiment.

[0123] The method for manufacturing an eyepiece according to this embodiment is a method for manufacturing an eyepiece for observing an object to be observed, and as shown in Figure 12, it includes the following steps S1 and S2. Step S1: The eyepiece is configured to have, in order from the observation object side, a first lens with positive refractive power, a second lens with negative refractive power, a third lens with positive refractive power, and a fourth lens with positive refractive power. Step S2: Configure the system to satisfy the following conditions (1) and (2). (1)-13.00<(R2a+R1b) / (R2a-R1b)<-2.75 (2) 0.78 <TL / fe<1.60 however, R2a: Radius of curvature of the lens surface of the second lens on the object-observing side. R1b: Radius of curvature of the lens surface on the eye point side of the first lens. TL: Distance along the optical axis from the observation object surface to the lens surface closest to the eye point when the diopter of the eyepiece is -1 [1 / m]. fe: The focal length of the eyepiece when the diopter of the eyepiece is -1 [1 / m].

[0124] According to the eyepiece manufacturing method of this embodiment, it is possible to realize an eyepiece that is high-magnification, compact, and has high optical performance. In particular, it is possible to realize an eyepiece that is suitable for use in an electronic viewfinder for observing an image displayed on an image display element.

[0125] Next, another method for manufacturing the eyepiece lens according to this embodiment will be described. Figure 13 is a schematic diagram of another method for manufacturing the eyepiece lens according to this embodiment.

[0126] Another method for manufacturing an eyepiece according to this embodiment is a method for manufacturing an eyepiece for observing an object to be observed, and as shown in Figure 13, includes the following steps S1 and S2. Step S1: The eyepiece is configured to have, in order from the observation object side, a first lens with positive refractive power, a second lens with negative refractive power, a third lens with positive refractive power, and a fourth lens with positive refractive power. Step S2: Configure the system to satisfy the following conditions (3) and (4). (3) 0.25 < (-f2) / f3 < 0.53 (4) 0.34 <d1 / fe<0.60 however, f2: Focal length of the second lens f3: Focal length of the third lens d1: Distance along the optical axis from the surface of the observed object to the lens surface of the first lens on the side of the observed object when the diopter of the eyepiece is -1 [1 / m]. fe: The focal length of the eyepiece when the diopter of the eyepiece is -1 [1 / m].

[0127] According to this alternative manufacturing method for the eyepiece of this embodiment, it is possible to realize an eyepiece that is high-magnification, compact, and has high optical performance. In particular, it is possible to realize an eyepiece suitable for use in an electronic viewfinder for observing an image displayed on an image display element. [Explanation of Symbols]

[0128] L1 First Lens L2 Second Lens L3 3rd lens L4 4th lens Op Observation Object EP Eye Point 1 Camera OL objective lens C Image sensor EVF (Electronic Viewfinder) EL eyepiece optical system

Claims

[Claim 1] The system has, in order from the side of the observed object, a first lens with positive refractive power, a second lens with negative refractive power, a third lens with positive refractive power, and a fourth lens with positive refractive power. The second lens is a meniscus lens with a convex surface facing the eye point. The third lens is a meniscus lens with a convex surface facing the eye point. An eyepiece that satisfies the following condition. 0.25<(-f2) / f3<0.53 0.34<d1 / fe<0.60 however, f2: Focal length of the second lens f3: Focal length of the third lens d1: Distance along the optical axis from the surface of the observed object to the lens surface of the first lens on the side of the observed object when the diopter of the eyepiece is -1 [1 / m]. fe: The focal length of the eyepiece when the diopter of the eyepiece is -1 [1 / m].

Images