Eyepiece optical system, electronic viewfinder and image capturing device

Abstract

The present invention relates to an eyepiece optical system, an electronic viewfinder and an image pickup device, wherein light is imaged through the eyepiece optical system, the direction toward the observer's eyes is the eye side, and the other side is the display side, and the eyepiece optical system is provided with a first lens group with negative refractive power and a second lens group with positive refractive power in sequence from the eye side to the display side; the first lens group is fixed, and the second lens group can move along the optical axis. The eyepiece optical system of the present invention has a strong positive refractive power and high optical performance. At the same time, by setting the first lens group as a fixed structure and the second lens group as movable along the optical axis, the structure is conducive to using more optical mirrors in a limited space, so that the eyepiece optical system improves the optical performance in the electronic viewfinder without increasing the space. Therefore, the electronic viewfinder equipped with the eyepiece optical system has the characteristics of small size while having a large viewing angle and high optical performance.

Description

Technical Field

[0001] The present invention relates to the field of optics, and in particular to an eyepiece optical system and an optical device using the eyepiece optical system, such as an electronic viewfinder having the eyepiece optical system and an image capturing device equipped with the electronic viewfinder. Background Art

[0002] Since the advent of digital cameras, cameras equipped with EVF (electronic viewfinder) have begun to be commercialized. The previous OVF (optical viewfinder) directly observes the image of the object through the optical system, while the working principle of EVF is to convert the image captured by the camera's main lens to the EVF display, and observe the image on the display with the naked eye through the optical system.

[0003] Generally speaking, in order to make the image on the electronic viewfinder larger and to clearly see the details in the image, the electronic viewfinder must have a larger viewing angle. However, in order to make the electronic viewfinder have a larger viewing angle, an eyepiece optical system with strong positive refractive power is required. For such an eyepiece optical system, it is difficult to correct aberrations such as field curvature and distortion. Due to the influence of these aberrations such as field curvature and magnification chromatic aberration, the optical resolution performance around the display will be reduced. In addition, an optical system with strong positive refractive power requires each lens to have strong positive or negative refractive power. In this case, when the lens is slightly offset or tilted perpendicular to the optical axis, it will have a greater impact on the resolution performance of the optical system imaging periphery, that is, the decentering sensitivity tends to increase.

[0004] The current cameras on the market have electronic viewfinders with relatively low field of view and optical performance due to size control. In other words, it is difficult for current electronic viewfinders to ensure both a large field of view and high performance while being relatively small in size. Summary of the invention

[0005] In view of this, an object of the present invention is to provide an eyepiece optical system, an electronic viewfinder and an image capture device, which can ensure that the electronic viewfinder has a large viewing angle and high optical performance while having the characteristics of small size.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] An eyepiece optical system, through which light is imaged, the direction toward the observer's eyes is the eye side, and the direction opposite to the eye side is the display side. The eyepiece optical system is provided with a first lens group with negative refractive power and a second lens group with positive refractive power in sequence from the eye side to the display side; the first lens group is fixed, and the second lens group can move along the optical axis.

[0008] The first lens group and the second lens group satisfy the following conditions:

[0009] -48.4<f1 / f2<-1.4;

[0010] -48.4<f1 / f<-1.0;

[0011] Among them, f1 is the focal length of the first lens group, f2 is the focal length of the second lens group, and f is the focal length of the eyepiece optical system.

[0012] The first lens group is composed of a first lens with negative refractive power; the second lens group includes a second lens, a third lens, a fourth lens and a fifth lens arranged in sequence from the eye side to the display side.

[0013] The second lens has positive refractive power, the third lens has positive refractive power or negative refractive power, the fourth lens has positive refractive power or negative refractive power, and the fifth lens has positive refractive power.

[0014] The second lens group meets the following conditions:

[0015] 0.83<f21 / f2<3.0;

[0016] -0.5<f22 / f2<2.71;

[0017] -1.1<f23 / f2<0.90;

[0018] 0.55<f24 / f2<2.6;

[0019] Among them, f21 is the focal length of the second lens, f22 is the focal length of the third lens, f23 is the focal length of the fourth lens, f24 is the focal length of the fifth lens, and f2 is the focal length of the second lens group.

[0020] The first lens, the second lens, the third lens, the fourth lens, and the fifth lens are lenses made of materials that meet the following conditions:

[0021] 1.48<N11<1.54;

[0022] 1.53<N21<1.73;

[0023] 1.53<N22<1.73;

[0024] 1.53<N23<1.69;

[0025] 1.53<N24<1.59;

[0026] Among them, N11 is the refractive index of the first lens, N21 is the refractive index of the second lens, N22 is the refractive index of the third lens, N23 is the refractive index of the fourth lens, and N24 is the refractive index of the fifth lens.

[0027] The first lens, the second lens, the third lens, the fourth lens, and the fifth lens are lenses made of materials that meet the following conditions:

[0028] V11≥64, V21≥54, V22≥21, V23≥21, V24≥55;

[0029] Among them, V11 is the Abbe number of the first lens, V21 is the Abbe number of the second lens, V22 is the Abbe number of the third lens, V23 is the Abbe number of the fourth lens, and V24 is the Abbe number of the fifth lens.

[0030] The first lens, the second lens, the third lens, the fourth lens and the fifth lens meet the following conditions:

[0031] 0.02<T1 / T2<0.05;

[0032] 0.20<T21 / T2<0.40;

[0033] 0.04<T22 / T2<0.45;

[0034] 0.04<T23 / T2<0.38;

[0035] 0.17<T24 / T2<0.42;

[0036] Wherein, T1 is the thickness of the first lens group on the optical axis, T2 is the thickness of the second lens group on the optical axis, T21 is the thickness of the second lens on the optical axis, T22 is the thickness of the third lens on the optical axis, T23 is the thickness of the fourth lens on the optical axis, and T24 is the thickness of the fifth lens on the optical axis.

[0037] The second lens group has lenses with an aspherical structure.

[0038] An electronic viewfinder comprises a viewfinder frame and a display arranged in the viewfinder frame. The viewfinder frame is also provided with the above-mentioned eyepiece optical system. The first lens group of the eyepiece optical system is fixed in the viewfinder frame, and the second lens group is movably arranged in the viewfinder frame.

[0039] The second lens group is arranged in a movable housing, a slide rail is arranged on the movable housing, and correspondingly, a slide groove cooperating with the slide rail is arranged in the viewfinder frame, and an adjustment knob for moving the second lens group forward and backward is arranged on the outside of the movable housing.

[0040] An image pickup device comprises a body and a camera lens group arranged on the body, the body is also provided with an image sensor which converts the optical signal of the camera lens group into a digital signal and outputs it, and the above-mentioned electronic viewfinder which monitors the digital signal of the image sensor.

[0041] After adopting the above scheme, the present invention arranges the first lens group and the second lens group in the eyepiece optical system so that the first lens group has negative refractive power and the second lens group has positive refractive power, so that the eyepiece optical system has strong positive refractive power and good optical performance, thereby ensuring that the electronic viewfinder equipped with the eyepiece optical system has a large viewing angle while improving the optical performance of the electronic viewfinder and ensuring its imaging quality. At the same time, the present invention arranges the first lens group as a fixed structure and the second lens group as a movable structure along the optical axis. This structure is conducive to using more optical mirrors in a limited space, so that the eyepiece optical system improves the optical performance in the electronic viewfinder without increasing the space. Therefore, the electronic viewfinder equipped with the eyepiece optical system of the present invention has the characteristics of a small size while having a large viewing angle and high optical performance.

[0042] In addition, the present invention limits the focal length, refractive index, Abbe number and thickness of the first lens group and the second lens group, so that the field curvature, distortion and decentering sensitivity of the eyepiece optical system are further improved, and the optical performance of the eyepiece optical system is further improved, so that the electronic viewfinder using the eyepiece optical system has better imaging quality based on the field of view angle, so as to be equipped with a higher pixel display. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The internal schematic module structure diagram of the image pickup device of the present invention;

[0044] Figure 2 is a schematic structural diagram of an electronic viewfinder of the present invention;

[0045] Figure 3 is a schematic structural diagram of a second lens group of the eyepiece optical system of the present invention;

[0046] Figure 4a Schematic diagram of the structure of the eyepiece optical system of Embodiment 1 of the present invention;

[0047] Figure 4b This is a schematic diagram of the structure of the eyepiece optical system adjusted with the observer's refractive power in Embodiment 1 of the present invention;

[0048] Figure 5a A spherical aberration diagram of the eyepiece optical system of Embodiment 1 of the present invention;

[0049] Figure 5b A field curvature diagram of an eyepiece optical system according to an embodiment of the present invention;

[0050] Figure 5c This is a distortion diagram of the eyepiece optical system of Embodiment 1 of the present invention;

[0051] Figure 6The MTF (Modulation Transfer Function) diagram of the eyepiece optical system of the first embodiment of the present invention;

[0052] Figure 7a Schematic diagram of the structure of the eyepiece optical system of Embodiment 2 of the present invention;

[0053] Figure 7b This is a schematic diagram of the structure of the eyepiece optical system according to the second embodiment of the present invention, which is adjusted according to the refractive power of the observer;

[0054] Figure 8a A spherical aberration diagram of the eyepiece optical system of Embodiment 2 of the present invention;

[0055] Figure 8b A field curvature diagram of the eyepiece optical system of Embodiment 2 of the present invention;

[0056] Figure 8c is a distortion diagram of the eyepiece optical system of embodiment 2 of the present invention;

[0057] Fig. 9 This is a diagram of the MTF (Modulation Transfer Function) of the eyepiece optical system of the second embodiment of the present invention.

[0058] Fig.10a Schematic diagram of the structure of the eyepiece optical system of the third embodiment of the present invention;

[0059] Fig.10b This is a schematic diagram of the structure of the eyepiece optical system according to the third embodiment of the present invention that is adjusted according to the observer's refractive power;

[0060] Fig.11a A spherical aberration diagram of the trinocular optical system of an embodiment of the present invention;

[0061] Fig.11b A field curvature diagram of a trinocular optical system according to an embodiment of the present invention;

[0062] Fig.11c This is a distortion diagram of the trinocular optical system according to an embodiment of the present invention;

[0063] Fig.12 This is a diagram of the MTF (modulation transfer function) of the eyepiece optical system of embodiment 3 of the present invention.

[0064] Fig.13a It is a schematic structural diagram of a four-eyepiece optical system according to an embodiment of the present invention;

[0065] Fig.13b It is a schematic diagram of the structure of the four-eyepiece optical system according to the embodiment of the present invention that is adjusted according to the refractive power of the observer;

[0066] Fig.14a A spherical aberration diagram of the four-eyepiece optical system of an embodiment of the present invention;

[0067] Fig.14bA field curvature diagram of a four-eyepiece optical system according to an embodiment of the present invention;

[0068] Fig.14c : is a distortion diagram of the four-eyepiece optical system according to an embodiment of the present invention;

[0069] Fig.15 This is a diagram of the MTF (modulation transfer function) of the eyepiece optical system of embodiment 4 of the present invention. DETAILED DESCRIPTION

[0070] The eyepiece optical system, the electronic viewfinder having the eyepiece optical system, and the image capturing device equipped with the electronic viewfinder according to the present invention will be described in detail below with reference to the accompanying drawings of the specification.

[0071] First, refer to Figure 1 As shown, the image acquisition device includes a body 1 and a camera lens group 2, wherein the camera lens group 2 is arranged on the body 1, and the body is also provided with an image sensor 3, an image processing chip 4, a display screen 5, an electronic viewfinder 6, etc.

[0072] After the light passes through the camera lens group 2, the image sensor 3 converts the optical signal into a digital signal, and then the image processing chip 4 transmits the digital signal to the display screen 5 and the electronic viewfinder 6 for display.

[0073] The electronic viewfinder 6 is used to monitor the image signal captured by the image sensor 3. Figure 2 and Figure 3 As shown, the electronic viewfinder 6 includes a viewfinder frame 61, a display 62 and an eyepiece optical system 7, both of which are arranged in the viewfinder frame 61. The eyepiece optical system 7 includes a first lens group 71 and a second lens group 72. The first lens group 71 is fixed in the viewfinder frame 71, and the second lens group 72 can move forward and backward in the viewfinder frame 61 according to the refractive power of the observer. When in use, the observer observes the image on the display 62 from the first lens group 71 via the second lens group 72.

[0074] The movement of the second lens group 72 in the viewfinder frame 61 can be achieved by the following structure: the second lens group 72 is arranged in the movable housing 725, a slide rail is arranged on the movable housing 725, and accordingly, a slide groove cooperating with the slide rail is arranged in the viewfinder frame 61, and an adjustment knob 726 for moving the second lens group 72 forward and backward is arranged outside the movable housing 725. The observer can control the adjustment knob 726 according to his / her refractive power, and move the distance of the second lens group 72 relative to the first lens group 71 and the display 62 by adjusting the knob 726.

[0075] Continue to refer to Figure 2 and Figure 3As shown, the eyepiece optical system 7 is suitable for imaging light of a display screen (display 62 of the electronic viewfinder) entering the observer's eyes through the eyepiece optical system 7 to form an image. The direction toward the observer's eyes is the eye side, and the direction toward the display screen is the display side. The eyepiece optical system 7 is provided with a first lens group 71 and a second lens group 72 in sequence from the eye side to the display side. The first lens group 71 has a negative refractive power, and the second lens group 72 has a positive refractive power. The absolute value of the refractive power of the second lens group 72 is greater than the absolute value of the refractive power of the first lens group 71. The first lens group is fixed, and the second lens group can move along the optical axis. When the imaging light of the display screen is emitted, the imaging light will pass through the second lens group 72 and the first lens group 71 in sequence, enter the observer's eyes, and form an image in the observer's eye retina.

[0076] The first lens group 71 has negative refractive power, the second lens group 72 has positive refractive power, and the absolute value of the refractive power of the second lens group 72 is greater than the absolute value of the refractive power of the first lens group 71, so that the eyepiece optical system 7 has a strong positive refractive power, thereby ensuring that the electronic viewfinder equipped with the eyepiece optical system 7 has a large viewing angle and high optical performance; therefore, the electronic viewfinder equipped with the eyepiece optical system has a large viewing angle while improving the optical performance of the electronic viewfinder and ensuring its imaging quality. At the same time, the present invention sets the first lens group as a fixed structure and the second lens group as movable along the optical axis, that is, when the eyepiece optical system is in use, it only needs to adjust the second lens group, while the first lens group remains fixed. Compared with the overall adjustment of the entire eyepiece optical system, the present invention fixes the first lens group and adjusts the second lens group. This structure is conducive to the use of more optical mirrors in a limited space, so that the eyepiece optical system can improve the optical performance of the electronic viewfinder without increasing the space, so that the electronic viewfinder equipped with the eyepiece optical system has the characteristics of a large field of view and high optical performance while also having a small size.

[0077] In order to make the eyepiece optical system have greater positive refractive power and better optical performance, and to ensure the field of view and imaging quality of the electronic viewfinder, the first lens group 71 and the second lens group 72 need to meet the following conditions:

[0078] -48.4<f1 / f2<-1.4;

[0079] -48.4<f1 / f<-1.0;

[0080] Among them, f1 is the focal length of the first lens group 71, f2 is the focal length of the second lens group 72, and f is the focal length of the eyepiece optical system 7. The eyepiece optical system that meets the above conditions further expands the field angle of the electronic viewfinder, and at the same time, it also well compensates for the field curvature of the eyepiece optical system, improves the resolution ability of the electronic viewfinder screen periphery; and can effectively compensate for the distortion of the optical system and improve the picture quality.

[0081] In the above-mentioned eyepiece optical system, the first lens group 71 is composed of a first lens 711 with negative refractive power; the second lens group 72 includes a second lens 721, a third lens 722, a fourth lens 723 and a fifth lens 724 arranged in sequence from the eye side to the display side, wherein the second lens 721 has positive refractive power, the third lens 722 has positive refractive power or negative refractive power, the fourth lens 723 has positive refractive power or negative refractive power, and the fifth lens 724 has positive refractive power. Among them, the four lenses in the second lens group 72 may have an aspherical structure, and the second lens group 72 meets the following conditions:

[0082] 0.83<f21 / f2<3.0;

[0083] -0.5<f22 / f2<2.71;

[0084] -1.1<f23 / f2<0.90;

[0085] 0.55<f24 / f2<2.6;

[0086] Among them, f21 is the focal length of the second lens 721, f22 is the focal length of the third lens 722, f23 is the focal length of the fourth lens 723, f24 is the focal length of the fifth lens 724, and f2 is the focal length of the second lens group 72.

[0087] On the basis of expanding the field of view of the electronic viewfinder, in order to improve the optical performance of the eyepiece optical system, the refractive indexes of the first lens group 71 and the second lens group 72 may be set as follows to further correct the field curvature of the eyepiece optical system:

[0088] 1.48<N11<1.54;

[0089] 1.53<N21<1.73;

[0090] 1.53<N22<1.73;

[0091] 1.53<N23<1.69;

[0092] 1.53<N24<1.59;

[0093] Among them, N11 is the refractive index of the first lens 711, N21 is the refractive index of the second lens 721, N22 is the refractive index of the third lens 722, N23 is the refractive index of the fourth lens 723, and N24 is the refractive index of the fifth lens 724.

[0094] On the basis of the above, in order to reduce the chromatic aberration of the eyepiece optical system and further improve its imaging quality, the Abbe numbers of the first lens group 71 and the second lens group 72 can be defined as follows:

[0095] V11≥64;

[0096] V21≥54;

[0097] V22≥21;

[0098] V23≥21;

[0099] V24≥55;

[0100] Among them, V11 is the Abbe number of the first lens 711, V21 is the Abbe number of the second lens 721, V22 is the Abbe number of the third lens 722, V23 is the Abbe number of the fourth lens 723, and V24 is the Abbe number of the fifth lens 724.

[0101] In addition, in order to reduce the decentering sensitivity of the eyepiece optical system and improve the yield rate during assembly of the eyepiece optical system and the electronic viewfinder, the thicknesses of the first lens group 71 and the second lens group 72 are limited as follows:

[0102] 0.02<T1 / T2<0.05;

[0103] 0.20<T21 / T2<0.40;

[0104] 0.04<T22 / T2<0.45;

[0105] 0.04<T23 / T2<0.38;

[0106] 0.17<T24 / T2<0.42;

[0107] Among them, T1 is the thickness of the first lens group 71 on the optical axis, T2 is the thickness of the second lens group 72 on the optical axis, T21 is the thickness of the second lens 721 on the optical axis, T22 is the thickness of the third lens 722 on the optical axis, T23 is the thickness of the fourth lens 723 on the optical axis, and T24 is the thickness of the fifth lens 724 on the optical axis.

[0108] In order to further elaborate the technical content of the invention, four embodiments are listed below to describe the eyepiece optical system in detail.

[0109] Embodiment 1

[0110] like Figure 4a As shown, the eyepiece optical system of the first embodiment includes a first lens group 71 and a second lens group 72, wherein the first lens group 71 includes a first lens 711 with negative refractive power, the surface of the first lens 711 facing the eye side is a first surface 7111, and the surface facing the display side is a second surface 7112. The second lens group 72 includes a second lens 721, a third lens 722, a fourth lens 723 and a fifth lens 724 arranged in sequence from the eye side to the display side, the second lens 721 has positive refractive power, the surface of the first lens 721 facing the eye side is a first surface 7211, and the surface of the first lens 7212 facing the display side is a second surface 7212. The third lens 722 has positive refractive power, the surface of the first lens 7221 facing the eye side is a first surface 7221, and the surface of the first lens 7222 facing the display side is a second surface 7222. The fourth lens 723 has negative refractive power, the surface of the first lens 7231 facing the eye side is a first surface 7231, and the surface of the first lens 7232 facing the display side is a second surface 7232. The fifth lens 724 has positive refractive power, and its surface facing the eye side is a first surface 7241 , and its surface facing the display side is a second surface 7242 .

[0111] In the eyepiece optical system of this embodiment, the focal length f11 of the first lens 711 is -145.47, the refractive index N11 is 1.517, the Abbe number N11 is 64.2, and the thickness T11 is 0.7. The focal length f21 of the second lens 721 is 47.47, the refractive index N21 is 1.587, the Abbe number N21 is 59.5, and the thickness T21 is 4.796. The focal length f22 of the third lens 722 is 23.55, the refractive index N22 is 1.593, the Abbe number V22 is 68.6, and the thickness T22 is 8.744. The focal length f23 of the fourth lens 723 is -14.08, the refractive index N23 is 1.657, the Abbe number V23 is 21.3, and the thickness T23 is 2.988. The focal length f24 of the fifth lens 724 is 14.36, the refractive index N24 is 1.534, the Abbe number V24 is 55.6, and the thickness T24 is 4.63. Other optical parameters of the eyepiece optical system are shown in Table 1-1.

[0112]

[0113] Table 1-1

[0114] As can be seen from the above, in the eyepiece optical system of this embodiment, the focal length of the first lens group 71 is the focal length of the first lens 711, that is, f1 is -145.47; the focal length of the second lens group 72 is the combined focal length of the second lens 721 to the fifth lens 724, that is, f2 is 17.60; the focal length f of the entire eyepiece optical system is 18.77. Then, f1 / f2 is -8.27, f1 / f is -7.75, and the eyepiece optical system with a focal length within this numerical range has a large positive refractive power, so that the electronic viewfinder equipped with the eyepiece optical system has a large field of view. At the same time, the field curvature and distortion of the eyepiece optical system are improved, thereby improving the imaging quality of the eyepiece optical system and the electronic viewfinder.

[0115] In this embodiment 1, the thickness of the first lens group 71 is the thickness of the first lens, that is, T1 is 0.7, and the thickness T2 of the second lens group 72 is 21.16; T1 / T2 is 0.033, T21 / T2 is 0.227, T22 / T2 is 0.413, T23 / T2 is 0.141, and T24 / T2 is 0.219.

[0116] Refer to Table 1-1 and combine Figure 4b As shown, the distance from the first lens 711 to the second lens 721 and the spacing between the fifth lens 724 and the display 62 of the electronic viewfinder are related to the eye point distance of the observer, which indicates that the position of the lens optical system 7 in the electronic viewfinder 6 will move with the different refractive powers of the observer, as shown in Table 1-2.

[0117] Eye point EP(mm) Diopter The distance between the first lens and the second lens Distance between the fifth lens and the display 12.5 +2 0.74 7.65 12.5 -1 1.85 6.53 12.5 -4 2.94 5.44

[0118] Table 1-2

[0119] According to Table 1-2, this embodiment sets the eyepiece optical system to an adjustable structure, and the observer can adjust the position of the eyepiece optical system in the electronic viewfinder according to his / her diopter. Specifically, the eyepiece optical system in this embodiment is set to have the first lens group fixed, and the second lens group adjustable along the optical axis. By adjusting the second lens group, not only can the spacing between the first lens and the second lens, and the spacing between the fifth lens and the display be adjusted, solving the problem of matching the electronic viewfinder with the observer's diopter, but this structure also reduces the space occupied by the eyepiece optical system in the electronic viewfinder, reducing the volume of the electronic viewfinder.

[0120] In order to reduce spherical aberration and distortion and improve the on-axis resolution performance of the eyepiece optical system, the two surfaces of the second lens 721, the fourth lens 723 and the fifth lens 724 in the eyepiece optical system are all aspherical structures, that is, the first surface 7211 and the second surface 7212 of the second lens 721, the first surface 7231 and the second surface 7232 of the fourth lens 723, and the first surface 7241 and the second surface 7242 of the fifth lens 724 are all aspherical structures, and these aspherical surfaces are defined by the following formulas:

[0121]

[0122] Wherein, F(r,R) represents the depth of the aspheric surface, that is, the distance from the point of the aspheric surface at a distance r from the optical axis I to the tangent plane of the aspheric vertex;

[0123] R is the vertical distance between the point on the aspheric curve and the optical axis I;

[0124] R is the radius of curvature of the lens surface near the optical axis I;

[0125] K is the conic constant;

[0126] A4, A6, A8, A10, A12, A14, and A16 are aspherical coefficients.

[0127] The conical coefficient K and aspherical coefficient of the second lens 721, the fourth lens 723 and the fifth lens 724 are specifically shown in Table 1-3.

[0128]

[0129] Table 1-3

[0130] Figure 5 to Figure 6 The aberration diagrams and MTF performance diagrams of the eyepiece optical system of the first embodiment show that the aberration performances will determine the aberrations and resolution performances of the imaging light from the display screen on the retina of the observer's eyes. When the aberrations are relatively small, the aberration performances of the imaging of the retina of the observer's eyes are also relatively small, so that the observer can observe an image with better imaging quality.

[0131] Specifically, Figure 5a is a spherical aberration diagram of the eyepiece optical system of Example 1. Figure 5a In the figure, the horizontal axis is the amount of spherical aberration, in mm, and the vertical axis is the pupil. From the distribution of spherical aberration, it can be seen that the spherical aberration of the eyepiece optical system is controlled within ±0.06mm, so that the image resolution quality of the image plane center of the eyepiece optical system is good.

[0132] Figure 5b is a field curvature diagram of the eyepiece optical system of Example 1, Figure 5bIn the figure, the horizontal axis is the offset of the image plane, in mm, and the vertical axis is the image plane height. From the distribution of field curvature, it can be seen that the field curvature of the eyepiece optical system is controlled within ±0.19mm, so that the image resolution quality of the eyepiece optical system is good.

[0133] Figure 5c is a distortion diagram of the eyepiece optical system of Example 1. Figure 5c In the figure, the horizontal axis is the distortion amount, in %, and the vertical axis is the image plane height. From the distribution of distortion, it can be seen that the distortion of the eyepiece optical system is controlled within ±1.5%, so that the image quality of the entire image plane of the eyepiece optical system is good.

[0134] Figure 6 is the MTF (modulation transfer function) of the eyepiece optical system of Example 1, as shown in Figure 6 As shown in the figure, the horizontal axis is the spatial frequency, the unit is cycles / mm, and the vertical axis is the modulation, that is, MTF. In the figure, F1 to F4 are the relative image plane heights 0.0FA, 0.5FA, 0.7FA and 1.0FA, respectively, and T and R are the sagittal direction and the meridian direction, respectively. From the MTF, it can be seen that when the spatial frequency of the eyepiece optical system is 80 cycles / mm, the MTF can be guaranteed to meet more than 20%, so that the eyepiece optical system has good resolution quality in the entire image plane.

[0135] Embodiment 2

[0136] like Figure 7a As shown, the structure of the eyepiece optical system in the second embodiment is similar to that in the first embodiment, and also includes a first lens 711, a second lens 721, a third lens 722, a fourth lens 723 and a fifth lens 724. The difference is that the fourth lens 723 is made of a material with a relatively high Abbe number, and the optical parameters of each lens are slightly different from those in the first embodiment.

[0137] Specifically, in the eyepiece optical system of the second embodiment, the focal length f11 of the first lens 711 is -105.71, the refractive index N11 is 1.517, the Abbe number N11 is 64.2, and the thickness T11 is 0.7. The focal length f21 of the second lens 721 is 34.22, the refractive index N21 is 1.583, the Abbe number N21 is 59.5, and the thickness T21 is 5.620. The focal length f22 of the third lens 722 is 17.1716, the refractive index N22 is 1.729, the Abbe number V22 is 54.7, and the thickness T22 is 8.9947. The focal length f23 of the fourth lens 723 is -6.7788, the refractive index N23 is 1.688, the Abbe number V23 is 31.1, and the thickness T23 is 1.4. The focal length f24 of the fifth lens 724 is 9.7019, the refractive index N24 is 1.534, the Abbe number V24 is 55.6, and the thickness T24 is 8.2. Other optical parameters of the eyepiece optical system are shown in Table 2-1.

[0138]

[0139] Table 2-1

[0140] As can be seen from the above, in the eyepiece optical system of this embodiment, the focal length of the first lens group 71 is the focal length of the first lens 711, that is, f1 is -105.71; the focal length of the second lens group 72 is the combined focal length of the second lens 721 to the fifth lens 724, that is, f2 is 17.94; the focal length f of the entire eyepiece optical system is 19.14. Then, f1 / f2 is -5.89, f1 / f is -5.52, and the eyepiece optical system with a focal length within this numerical range has a large positive refractive power, so that the electronic viewfinder equipped with the eyepiece optical system has a large field of view. At the same time, the field curvature and distortion of the eyepiece optical system are improved, thereby improving the imaging quality of the eyepiece optical system and the electronic viewfinder.

[0141] Refer to Table 2-1 and combine Figure 7b As shown, the distance from the first lens 711 to the second lens 721 and the spacing between the fifth lens 724 and the display 62 of the electronic viewfinder 6 are related to the eye point distance of the observer, which indicates that the position of the lens optical system 7 in the electronic viewfinder 6 will move with the different refractive powers of the observer, as shown in Table 2-2.

[0142] Eye point EP(mm) Diopter The distance between the first lens and the second lens Distance between the fifth lens and the display 12.5 +2 0.74 7.56 12.5 -1 1.92 6.37 12.5 -4 3.08 5.22

[0143] Table 2-2

[0144] According to Table 2-2, this embodiment sets the eyepiece optical system to an adjustable structure, and the observer can adjust the position of the eyepiece optical system in the electronic viewfinder according to his / her diopter. Similar to the first embodiment, the eyepiece optical system in this embodiment is set to have the first lens group fixed, and the second lens group can be adjusted along the optical axis. By adjusting the second lens group, not only can the spacing between the first lens and the second lens and the spacing between the fifth lens and the display be adjusted to solve the problem of matching the electronic viewfinder with the observer's diopter, but this structure also reduces the space occupied by the eyepiece optical system in the electronic viewfinder and reduces the volume of the electronic viewfinder.

[0145] In order to reduce spherical aberration and distortion and improve the on-axis resolution performance of the eyepiece optical system, the two surfaces of the second lens 721, the fourth lens 723, and the fifth lens 724 in the eyepiece optical system are all aspherical structures, that is, the first surface 7211 and the second surface 7212 of the second lens 721, the first surface 7231 and the second surface 7232 of the fourth lens 723, and the first surface 7241 and the second surface 7242 of the fifth lens 724 are all aspherical structures. The cone coefficient K and the aspherical coefficient of the second lens 721, the fourth lens 723, and the fifth lens 724 are specifically shown in Table 2-3.

[0146]

[0147] Table 2-3

[0148] Figure 8 to Fig. 9 The aberration diagrams and MTF performance diagrams of the eyepiece optical system of the second embodiment show that the aberration performances will determine the aberrations and resolution performances of the imaging light from the display screen on the retina of the observer's eyes.

[0149] Specifically, Figure 8a is a spherical aberration diagram of the eyepiece optical system of Example 2. Figure 8a In the figure, the horizontal axis is the amount of spherical aberration, in mm, and the vertical axis is the pupil. From the distribution of spherical aberration, it can be seen that the spherical aberration of the eyepiece optical system is controlled within ±0.06mm, so that the image resolution quality of the image plane center of the eyepiece optical system is good.

[0150] Figure 8b is a field curvature diagram of the eyepiece optical system of Example 2. Figure 8b In the figure, the horizontal axis is the offset of the image plane, in mm, and the vertical axis is the image plane height. From the distribution of field curvature, it can be seen that the field curvature of the eyepiece optical system is controlled within ±0.19mm, so that the image resolution quality of the eyepiece optical system is good.

[0151] Figure 8c is a distortion diagram of the eyepiece optical system of Example 2. Figure 8cIn the figure, the horizontal axis is the distortion amount, in %, and the vertical axis is the image plane height. From the distribution of distortion, it can be seen that the distortion of the eyepiece optical system is controlled within ±1.5%, so that the image quality of the entire image plane of the eyepiece optical system is good.

[0152] Fig. 9 The MTF (Modulation Transfer Function) of the eyepiece optical system of Example 2 is shown in FIG. Fig. 9 As shown in the figure, the horizontal axis is the spatial frequency, the unit is cycles / mm, and the vertical axis is the modulation, that is, MTF. In the figure, F1 to F4 are the relative image plane heights 0.0FA, 0.5FA, 0.7FA and 1.0FA, respectively, and T and R are the sagittal direction and the meridian direction, respectively. From the MTF, it can be seen that when the spatial frequency of the eyepiece optical system is 80 cycles / mm, the MTF can be guaranteed to meet more than 20%, so that the eyepiece optical system has good resolution quality in the entire image plane.

[0153] Embodiment 3

[0154] like Fig.10a As shown, the structure of the eyepiece optical system in the third embodiment is similar to that in the first embodiment, and also includes a first lens 711, a second lens 721, a third lens 722, a fourth lens 723 and a fifth lens 724. The difference is that the third lens 722 has a negative refractive power, the fourth lens 723 has a positive refractive power, and the optical parameters of each lens are slightly different from those in the first embodiment.

[0155] Specifically, in the eyepiece optical system of the third embodiment, the focal length f11 of the first lens 711 is -294.944, the refractive index N11 is 1.4875, the Abbe number N11 is 70.4, and the thickness T11 is 0.7. The focal length f21 of the second lens 721 is 16.5625, the refractive index N21 is 1.72916, the Abbe number N21 is 54.7, and the thickness T21 is 8.2336. The focal length f22 of the third lens 722 is -9.0130, the refractive index N22 is 1.6883, the Abbe number V22 is 31.1, and the thickness T22 is 1.05. The focal length f23 of the fourth lens 723 is 15.3519, the refractive index N23 is 1.5831, the Abbe number V23 is 59.5, and the thickness T23 is 7.4. The focal length f24 of the fifth lens 724 is 44.1173, the refractive index N24 is 1.5831, the Abbe number V24 is 59.5, and the thickness T24 is 6.7692. Other optical parameters of the eyepiece optical system are shown in Table 3-1.

[0156]

[0157] Table 3-1

[0158] As can be seen from the above, in the eyepiece optical system of this embodiment, the focal length of the first lens group 71 is the focal length of the first lens 711, that is, f1 is -294.944; the focal length of the second lens group 72 is the combined focal length of the second lens 721 to the fifth lens 722, that is, f2 is 18.4077; the focal length f of the entire eyepiece optical system is 18.801. Then, f1 / f2 is -16.0229, f1 / f is -15.6877, and the eyepiece optical system with a focal length within this numerical range has a large positive refractive power, so that the electronic viewfinder equipped with the eyepiece optical system has a large field of view. At the same time, the field curvature and distortion of the eyepiece optical system are improved, thereby improving the imaging quality of the eyepiece optical system and the electronic viewfinder.

[0159] Refer to Table 3-2 and combine Fig.10b As shown, the distance from the first lens 711 to the second lens 721 and the spacing between the fifth lens 724 and the display 62 of the electronic viewfinder are related to the eye point distance of the observer, which indicates that the position of the lens optical system 7 in the electronic viewfinder 6 will move with the different refractive powers of the observer, as shown in Table 3-2.

[0160] Eye point EP(mm) Diopter The distance between the first lens and the second lens Distance between the fifth lens and the display 12.5 +2 0.63 7.32 12.5 -1 1.71 6.24 12.5 -4 2.79 5.16

[0161] Table 3-2

[0162] According to Table 3-2, this embodiment sets the eyepiece optical system to an adjustable structure, and the observer can adjust the position of the eyepiece optical system in the electronic viewfinder according to his / her diopter. Similar to the first embodiment, the eyepiece optical system in this embodiment is set to have the first lens group fixed, and the second lens group can be adjusted along the optical axis. By adjusting the second lens group, not only can the spacing between the first lens and the second lens, and the spacing between the fifth lens and the display be adjusted to solve the problem of matching the electronic viewfinder with the observer's diopter, but this structure also reduces the space occupied by the eyepiece optical system in the electronic viewfinder, thereby reducing the volume of the electronic viewfinder.

[0163] In order to reduce spherical aberration and distortion and improve the on-axis resolution performance of the eyepiece optical system, the two surfaces of the third lens 722, the fourth lens 723, and the fifth lens 724 in the eyepiece optical system are all aspherical structures, that is, the first surface 7221 and the second surface 7222 of the third lens 722, the first surface 7231 and the second surface 7232 of the fourth lens 723, and the first surface 7241 and the second surface 7242 of the fifth lens 724 are all aspherical structures. The cone coefficient K and the aspherical coefficient of the third lens 722, the fourth lens 723, and the fifth lens 724 are specifically shown in Table 3-3.

[0164]

[0165]

[0166] Table 3-3

[0167] Figure 11 to Fig.12 The aberration diagrams and MTF performance diagrams of the eyepiece optical system of the third embodiment show that the aberration performances will determine the aberrations and resolution performances of the imaging light from the display screen on the retina of the observer's eyes.

[0168] Specifically, Fig.11a is a spherical aberration diagram of the eyepiece optical system of Example 3. Fig.11a In the figure, the horizontal axis is the amount of spherical aberration, in mm, and the vertical axis is the pupil. From the distribution of spherical aberration, it can be seen that the spherical aberration of the eyepiece optical system is controlled within ±0.06mm, so that the image resolution quality of the image plane center of the eyepiece optical system is good.

[0169] Fig.11b is a field curvature diagram of the three-eyepiece optical system of the embodiment, Fig.11b In the figure, the horizontal axis is the offset of the image plane, in mm, and the vertical axis is the image plane height. From the distribution of field curvature, it can be seen that the field curvature of the eyepiece optical system is controlled within ±0.19mm, so that the image resolution quality of the eyepiece optical system is good.

[0170] Fig.11c is a distortion diagram of the eyepiece optical system of Example 3. Fig.11c In the figure, the horizontal axis is the distortion amount, in %, and the vertical axis is the image plane height. From the distribution of distortion, it can be seen that the distortion of the eyepiece optical system is controlled within ±1.5%, so that the image quality of the entire image plane of the eyepiece optical system is good.

[0171] Fig.12 The MTF (Modulation Transfer Function) of the eyepiece optical system of Example 3 is shown in FIG. Fig.12 As shown in the figure, the horizontal axis is the spatial frequency, the unit is cycles / mm, and the vertical axis is the modulation, that is, MTF. In the figure, F1 to F4 are the relative image plane heights 0.0FA, 0.5FA, 0.7FA and 1.0FA, respectively, and T and R are the sagittal direction and the meridian direction, respectively. From the MTF, it can be seen that when the spatial frequency of the eyepiece optical system is 80 cycles / mm, the MTF can be guaranteed to meet more than 20%, so that the eyepiece optical system has good resolution quality in the entire image plane.

[0172] Embodiment 4

[0173] like Fig.13aAs shown, the structure of the eyepiece optical system in the fourth embodiment is similar to that in the first embodiment, and also includes a first lens 711, a second lens 721, a third lens 722, a fourth lens 723 and a fifth lens 724. The difference is that the second lens 721 is a spherical lens, and the optical parameters of each lens are slightly different from those in the first embodiment.

[0174] Specifically, in the eyepiece optical system of the fourth embodiment, the focal length f11 of the first lens 711 is -134.21, the refractive index N11 is 1.517, the Abbe number N11 is 64.2, and the thickness T11 is 0.7. The focal length f21 of the second lens 721 is 41.16, the refractive index N21 is 1.593, the Abbe number N21 is 68.6, and the thickness T21 is 5.14. The focal length f22 of the third lens 722 is 22.55, the refractive index N22 is 1.729, the Abbe number V22 is 54.7, and the thickness T22 is 7.50. The focal length f23 of the fourth lens 723 is -13.06, the refractive index N23 is 1.640, the Abbe number V23 is 23.5, and the thickness T23 is 2.68. The focal length f24 of the fifth lens 724 is 16.17, the refractive index N24 is 1.535, the Abbe number V24 is 55.7, and the thickness T24 is 6.13. Other optical parameters of the eyepiece optical system are shown in Table 4-1.

[0175]

[0176]

[0177] Table 4-1

[0178] As can be seen from the above, in the eyepiece optical system of this embodiment, the focal length of the first lens group 71 is the focal length of the first lens 711, that is, f1 is -134.21; the focal length of the second lens group 72 is the combined focal length of the second lens 721 to the fifth lens 724, that is, f2 is 16.99; the focal length f of the entire eyepiece optical system is 18.90. Then, f1 / f2 is -7.8994, f1 / f is -7.1010, and the eyepiece optical system with a focal length within this numerical range has a large positive refractive power, so that the electronic viewfinder equipped with the eyepiece optical system has a larger field of view angle. At the same time, the field curvature and distortion of the eyepiece optical system are improved, thereby improving the imaging quality of the eyepiece optical system and the electronic viewfinder.

[0179] Refer to Table 4-2 and combine Fig.13b As shown, the distance from the first lens 711 to the second lens 721 and the spacing between the fifth lens 724 and the display 62 of the electronic viewfinder are related to the eye point distance of the observer, which indicates that the position of the lens optical system 7 in the electronic viewfinder 6 will move with the different refractive powers of the observer, as shown in Table 4-2.

[0180] Eye point EP(mm) Diopter The distance between the first lens and the second lens Distance between the fifth lens and the display 12.5 +2 0.7276 6.1041 12.5 -1 1.839 4.9927 12.5 -4 2.9058 3.9259

[0181] Table 4-2

[0182] According to Table 4-2, this embodiment sets the eyepiece optical system to an adjustable structure, and the observer can adjust the position of the eyepiece optical system in the electronic viewfinder according to his / her diopter. Similar to the first embodiment, the eyepiece optical system in this embodiment is set to have the first lens group fixed, and the second lens group can be adjusted along the optical axis. By adjusting the second lens group, not only can the spacing between the first lens and the second lens, and the spacing between the fifth lens and the display be adjusted to solve the problem of matching the electronic viewfinder with the observer's diopter, but this structure also reduces the space occupied by the eyepiece optical system in the electronic viewfinder, thereby reducing the volume of the electronic viewfinder.

[0183] In order to reduce spherical aberration and distortion and improve the on-axis resolution performance of the eyepiece optical system, both surfaces of the fourth lens 723 and the fifth lens 724 in the eyepiece optical system are aspherical structures, that is, the first surface 7231 and the second surface 7232 of the fourth lens 723, and the first surface 7241 and the second surface 7242 of the fifth lens 724 are aspherical structures. The cone coefficient K and the aspherical coefficient of the fourth lens 723 and the fifth lens 724 are specifically shown in Table 4-3.

[0184] K A4 A6 A8 A10 The fourth lens Page 1 0.00 -8.3525E-05 6.9551E-07 -4.1137E-10 -5.6482E-12 Side 2 -0.10289 -4.3352E-04 5.4854E-07 5.2478E-08 -1.4541E-09 The fifth lens Page 1 -0.94563 -2.4029E-04 3.1399E-06 -3.5648E-09 -9.6854E-11 Side 2 0.00 1.4163E-04 -9.1713E-06 2.8776E-07 -3.0855E-09

[0185] Table 4-3

[0186] Figure 14 to Fig.15 The aberration diagrams and MTF performance diagrams of the eyepiece optical system of the fourth embodiment, the aberration performances presented therein will determine the aberrations and resolution performances of the imaging light from the display screen on the retina of the observer's eyes.

[0187] Specifically, Fig.14a is a spherical aberration diagram of the eyepiece optical system of Example 4. Fig.14a In the figure, the horizontal axis is the amount of spherical aberration, in mm, and the vertical axis is the pupil. From the distribution of spherical aberration, it can be seen that the spherical aberration of the eyepiece optical system is controlled within ±0.06mm, so that the image resolution quality of the image plane center of the eyepiece optical system is good.

[0188] Fig.14b is a field curvature diagram of the eyepiece optical system of Example 4, Fig.14b In the figure, the horizontal axis is the offset of the image plane, in mm, and the vertical axis is the image plane height. From the distribution of field curvature, it can be seen that the field curvature of the eyepiece optical system is controlled within ±0.19mm, so that the image resolution quality of the eyepiece optical system is good.

[0189] Fig.14c is a distortion diagram of the eyepiece optical system of Example 4. Fig.14c In the figure, the horizontal axis is the distortion amount, in %, and the vertical axis is the image plane height. From the distribution of distortion, it can be seen that the distortion of the eyepiece optical system is controlled within ±1.5%, so that the image quality of the entire image plane of the eyepiece optical system is good.

[0190] Fig.15 The MTF (Modulation Transfer Function) of the eyepiece optical system of Example 4 is shown in FIG. Fig.15 As shown in the figure, the horizontal axis is the spatial frequency, the unit is cycles / mm, and the vertical axis is the modulation, that is, MTF. In the figure, F1 to F4 are the relative image plane heights 0.0FA, 0.5FA, 0.7FA and 1.0FA, respectively, and T and R are the sagittal direction and the meridian direction, respectively. From the MTF, it can be seen that when the spatial frequency of the eyepiece optical system is 80 cycles / mm, the MTF can be guaranteed to meet more than 20%, so that the eyepiece optical system has good resolution quality in the entire image plane.

[0191] The above description is merely an embodiment of the present invention and does not limit the technical scope of the present invention. Therefore, any minor modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. An eyepiece optical system, through which light is imaged, the direction toward the observer's eyes is the eye side, and the direction opposite to the eye side is the display side, characterized in that: The eyepiece optical system is provided with a first lens group with negative refractive power and a second lens group with positive refractive power in sequence from the eye side to the display side; the first lens group is fixed, and the second lens group can move along the optical axis direction; The first lens group and the second lens group satisfy the following conditions: -48.4<f1 / f2<-1.4; -48.4<f1 / f<-1.0; Wherein, f1 is the focal length of the first lens group, f2 is the focal length of the second lens group, and f is the focal length of the eyepiece optical system; The first lens group is composed of a first lens with negative refractive power; the second lens group includes a second lens, a third lens, a fourth lens and a fifth lens arranged in sequence from the eye side to the display side; the second lens has positive refractive power, the third lens has positive refractive power or negative refractive power, the fourth lens has positive refractive power or negative refractive power, the fifth lens has positive refractive power, and the optical focal lengths of the third lens and the fourth lens are opposite.

2. An eyepiece optical system according to claim 1, characterized in that: The second lens group meets the following conditions: 0.83<f21 / f2<3.0; -0.5<f22 / f2<2.71; -1.1<f23 / f2<0.90; 0.55<f24 / f2<2.6; Among them, f21 is the focal length of the second lens, f22 is the focal length of the third lens, f23 is the focal length of the fourth lens, f24 is the focal length of the fifth lens, and f2 is the focal length of the second lens group.

3. An eyepiece optical system according to claim 1, characterized in that: The first lens, the second lens, the third lens, the fourth lens, and the fifth lens are lenses made of materials that meet the following conditions: 1.48＜N11＜1.54； 1.53＜N21＜1.73； 1.53＜N22＜1.73； 1.53＜N23＜1.69； 1.53＜N24＜1.59； Among them, N11 is the refractive index of the first lens, N21 is the refractive index of the second lens, N22 is the refractive index of the third lens, N23 is the refractive index of the fourth lens, and N24 is the refractive index of the fifth lens.

4. An eyepiece optical system according to claim 1, characterized in that: The first lens, the second lens, the third lens, the fourth lens, and the fifth lens are lenses made of materials that meet the following conditions: V11≥64, V21≥54, V22≥21, V23≥21, V24≥55; Among them, V11 is the Abbe number of the first lens, V21 is the Abbe number of the second lens, V22 is the Abbe number of the third lens, V23 is the Abbe number of the fourth lens, and V24 is the Abbe number of the fifth lens.

5. An eyepiece optical system according to claim 1, characterized in that: The first lens, the second lens, the third lens, the fourth lens and the fifth lens meet the following conditions: 0.02<T1 / T2<0.05; 0.20<T21 / T2<0.40; 0.04<T22 / T2<0.45; 0.04<T23 / T2<0.38; 0.17<T24 / T2<0.42; Wherein, T1 is the thickness of the first lens group on the optical axis, T2 is the thickness of the second lens group on the optical axis, T21 is the thickness of the second lens on the optical axis, T22 is the thickness of the third lens on the optical axis, T23 is the thickness of the fourth lens on the optical axis, and T24 is the thickness of the fifth lens on the optical axis.

6. An eyepiece optical system according to claim 1, characterized in that: The second lens group has lenses with an aspherical structure.

7. An electronic viewfinder, comprising a viewfinder frame and a display disposed in the viewfinder frame, characterized in that: The viewfinder frame is also provided with an eyepiece optical system as described in any one of claims 1 to 6, wherein the first lens group of the eyepiece optical system is fixed in the viewfinder frame, and the second lens group is movably arranged in the viewfinder frame.

8. The electronic viewfinder according to claim 7, characterized in that: The second lens group is arranged in a movable housing, a slide rail is arranged on the movable housing, and correspondingly, a slide groove cooperating with the slide rail is arranged in the viewfinder frame, and an adjustment knob for moving the second lens group forward and backward is arranged on the outside of the movable housing.

9. An image capturing device, comprising a body and a camera lens group arranged on the body, characterized in that: The camera body is also provided with an image sensor for converting the optical signal of the camera lens group into a digital signal and outputting the digital signal, and an electronic viewfinder as claimed in claim 7 for monitoring the digital signal of the image sensor.

Images