CN110146966B

CN110146966B - Lens optical system, electronic viewfinder and image pickup device

Info

Publication number: CN110146966B
Application number: CN201810146406.9A
Authority: CN
Inventors: 刘晓凤
Original assignee: Panasonic AVC Networks Xiamen Co Ltd
Current assignee: Panasonic AVC Networks Xiamen Co Ltd
Priority date: 2018-02-12
Filing date: 2018-02-12
Publication date: 2024-06-21
Anticipated expiration: 2038-02-12
Also published as: CN110146966A

Abstract

The present invention relates to a lens optical system, an electronic viewfinder, and an image pickup apparatus, wherein light is imaged through the lens optical system, and the lens optical system is provided with, in order along an optical axis from an observation side to an object side: a first lens having a positive diopter and a second lens having a negative diopter, the first lens and the second lens satisfying the following conditions: -0.8 < f1/f2 < -0.4,0.40 < f1/f < 0.75, -1.2 < f2/f < -0.8; wherein f1 is the focal distance of the first lens, f2 is the focal distance of the second lens, and f is the focal distance of the lens optical system. The lens optical system of the invention has a large viewing angle and high performance.

Description

Lens optical system, electronic viewfinder and image pickup device

Technical Field

The present invention relates to the field of optics, and more particularly to a lens optical system and an optical device using the lens optical system, for example, an electronic viewfinder including the lens optical system and an image pickup apparatus having the electronic viewfinder mounted thereon.

Background

Since the field of digital cameras, cameras equipped with electronic viewfinders (EVFs, electronic viewfinder) have been commercialized. The traditional optical viewfinder directly observes the image of an object through an optical system, and the working principle of the electronic viewfinder is to convert the image shot by the main lens of the camera to the display of the electronic viewfinder, so that naked eyes can observe the image of the display through the optical system to observe the image shot by the main lens of the camera, the field of view rate reaches 100%, and the problem that the field of view is inconsistent with the shot picture during framing is solved.

Thin card cameras currently on the market carry few electronic viewfinder functions due to control costs and size. The electronic viewfinder of the display with a relatively small size is distributed at 0.46-0.5 times, and compared with the electronic viewfinder without a counter camera, the electronic viewfinder has lower magnification, and the pixels of the display are only 64 ten thousand-117 ten thousand, so that the resolution of the electronic viewfinder is lower than that of an image sensor mounted on a digital camera in recent years.

Disclosure of Invention

The invention provides a lens optical system, an electronic viewfinder and an image pickup device, which have large viewing angle and high performance.

In order to achieve the above purpose, the invention adopts the following technical scheme:

A lens optical system through which light is imaged, the lens optical system being provided with, in order along an optical axis from an observation side to an object side: a first lens having a positive diopter and a second lens having a negative diopter, the first lens and the second lens satisfying the following conditions: -0.8 < f1/f2 < -0.4,0.40 < f1/f < 0.75, -1.2 < f2/f < -0.8;

wherein f1 is the focal distance of the first lens, f2 is the focal distance of the second lens, and f is the focal distance of the lens optical system.

The first lens and the second lens satisfy the following conditions: 2.3 < T1/T2 < 5.7, wherein T1 is the thickness of the first lens on the optical axis, and T2 is the thickness of the second lens on the optical axis.

The first lens and the second lens are made of materials meeting the following conditions: n1 is more than 1.45 and less than 1.57,1.60, N2 is more than 1.68; wherein N1 is the refractive index of the first lens and N2 is the refractive index of the second lens.

The first lens and the second lens are made of materials meeting the following conditions: v1 is more than or equal to 52, and V2 is less than or equal to 27; wherein V1 is the Abbe number of the first lens, and V2 is the Abbe number of the second lens.

The first lens is a biconvex lens, and the second lens is a convex-concave lens.

An electronic viewfinder includes a viewfinder housing and a display provided at a rear portion in an optical axis direction in the viewfinder housing, wherein a lens optical system that can be corrected by adjusting a viewer's eyesight in a front portion in the optical axis direction is provided.

The front and back adjustment of the lens optical system is realized through a vision degree adjusting knob.

An image pickup apparatus includes a main body and a photographing lens group provided on the main body, an image sensor converting an optical signal from the photographing lens group into a digital signal and outputting the digital signal, and an electronic viewfinder monitoring the digital signal of the image sensor are provided on the main body.

After the scheme is adopted, the first lens and the second lens in the lens optical system are arranged, so that the focal distance of the first lens and the second lens meets the following conditions: -0.8 < f1/f2 < -0.4,0.40 < f1/f < 0.75, -1.2 < f2/f < -0.8; wherein f1 is the focal distance of the first lens, f2 is the focal distance of the second lens, and f is the focal distance of the lens optical system, thereby enhancing the positive refractive power of the lens optical system, improving the performance of the lens optical system, further improving the view angle of the electronic viewfinder with the lens optical system, and ensuring the imaging quality thereof.

In addition, the present invention satisfies the following conditions by defining the refractive index, abbe number, and thickness of the first lens and the second lens: T1/T2 is more than 2.3 and less than 5.7,1.45, N1 is more than 1.57,1.60, N2 is more than 1.68, V1 is more than or equal to 52, and V2 is more than or equal to 27; wherein T1 is the thickness of the first lens on the optical axis, and T2 is the thickness of the second lens on the optical axis; v1 is the Abbe number of the first lens, and V2 is the Abbe number of the second lens; n1 is the refractive index of the first lens, and N2 is the refractive index of the second lens, so that the performance of the lens optical system is further improved, and the electronic viewfinder using the lens optical system can have good imaging quality on the basis of having a large viewing angle, so as to mount a display with higher pixels.

Drawings

FIG. 1 is a block diagram of an internal schematic module of an image capture device of the present invention;

FIG. 2 is a schematic view of an electronic viewfinder according to the present invention;

FIG. 3 is a schematic diagram of a lens optical system according to a first embodiment of the present invention;

FIG. 4 is a graph of spherical aberration and chromatic aberration of a lens optic system according to a first embodiment of the invention;

FIG. 5 is a ray aberration diagram of a lens optical system according to a first embodiment of the present invention;

FIG. 6 is a distortion chart of a lens optical system according to a first embodiment of the present invention;

FIG. 7 is a graph of MTF (modulation transfer function) of a lens optical system according to a first embodiment of the present invention;

FIG. 8 is a schematic diagram of a lens optical system according to a second embodiment of the present invention;

FIG. 9 is a graph of spherical aberration and chromatic aberration of a lens optic system according to a second embodiment of the invention;

FIG. 10 is a ray aberration diagram of a lens optical system according to a second embodiment of the present invention;

FIG. 11 is a distortion chart of a lens optical system according to a second embodiment of the present invention;

FIG. 12 is a graph of MTF (modulation transfer function) of a lens optical system according to a second embodiment of the present invention;

FIG. 13 is a schematic diagram of a lens optical system according to a third embodiment of the present invention;

FIG. 14 is a graph of spherical aberration and chromatic aberration of a lens optic system according to a third embodiment of the invention;

FIG. 15 is a ray aberration diagram of a lens optical system according to a third embodiment of the present invention;

FIG. 16 is a distortion chart of a lens optical system according to a third embodiment of the present invention;

Fig. 17 is an MTF (modulation transfer function) diagram of a lens optical system according to a third embodiment of the present invention.

Detailed Description

The lens optical system, the electronic viewfinder provided with the lens optical system, and the image pickup apparatus provided with the electronic viewfinder according to the present invention will be described in detail below with reference to the drawings.

First, referring to fig. 1, the image pickup apparatus includes a main body 1 and an imaging lens group 2, wherein the imaging lens group 2 is provided on the main body 1, and an image sensor 3, an image processing chip 4, an LCD5, an electronic viewfinder 6, and the like are further provided on the main body 1.

After passing through the camera lens group 2, the light rays are converted into digital signals through the image sensor 3, and then the digital signals are transmitted to the LCD5 and the electronic viewfinder 6 for display through the image processing chip 4 and the like;

The electronic viewfinder 6 is for monitoring an image signal picked up by the image sensor 3, and as shown in fig. 2, the electronic viewfinder 6 includes a viewfinder frame 7, a visibility adjustment knob 10 for adjusting the position of the lens optical system 9 in the viewfinder frame 7 so as to accommodate observers of different eyesight, a display 8 provided at the rear in the optical axis direction in the viewfinder frame 7, and a lens optical system 9 provided at the front in the optical axis direction in the viewfinder frame 7. The rear portion referred to herein is the end of the display 8 near the electronic viewfinder 6, i.e., the interior of the image pickup device, and the front portion is the end near the viewer.

As shown in fig. 3, 8 and 13, the lens optical system 9 of the present invention is suitable for imaging light entering the eyes of an observer through the lens optical system 9, the direction toward the eyes of the observer is the observation side, the direction toward the display screen is the object side, and the lens optical system 9 is provided with a first lens 91 and a second lens 92 in this order from the observation side to the optical axis direction in the object side direction, wherein the first lens 91 has a positive diopter and the second lens 92 has a negative diopter. When the imaging light of the display screen is emitted, the imaging light sequentially passes through the second lens 92 and the first lens 91 and enters the eyes of the observer through the pupils of the observer, and then the imaging light forms an image on the retina of the eyes of the observer.

The electronic viewfinder 6 is intended to have a large field of view, and can be realized by a lens optical system 9 having a strong positive refractive power. However, it is difficult to correct aberrations such as curvature of field and distortion in the lens optical system 9 having a strong positive refractive power. The optical performance around the display 8 is reduced due to the influence of aberrations such as curvature of field and distortion. In addition, the lens optical system 9 having a strong positive refractive power is required to have a strong positive refractive power or a strong negative refractive power for each lens, and thus, the deviation and inclination of the lens in the parallel direction may cause the deviation of the visibility, that is, the decentration sensitivity tends to be large.

Therefore, in the lens optical system 9 of the present invention, the first lens 91 and the second lens 92 are constituted so as to satisfy the following conditions:

-0.8＜f1/f2＜-0.4；

0.40＜f1/f＜0.75；

-1.2＜f2/f＜-0.8；

Where f1 is the focal distance of the first lens 91, f2 is the focal distance of the second lens 92, and f is the focal distance of the lens optical system 9. The lens optical system 9 satisfying the above conditions can ensure a sufficient back focal length, expand the viewing angle, and correct curvature of field and distortion well.

In order to ensure the imaging performance even better in the case of enlarging the viewing angle of the lens optical system 9, the materials of the first lens 91 and the second lens 92 are defined as follows:

1.45＜N1＜1.57；

1.60＜N2＜1.68；

V1≥52；

V2≦27；

Where N1 is the refractive index of the first lens 91 and N2 is the refractive index of the second lens 92; v1 is the abbe number of the first lens 91, and V2 is the abbe number of the second lens 92. When the refractive index of the first lens 91 and the refractive index of the second lens 92 are set within the above ranges, the curvature of field of the lens optical system 9 can be further corrected, and the imaging quality of the lens optical system 9 can be improved. When the abbe number of the first lens 91 and the abbe number of the second lens 92 are set within the above ranges, chromatic aberration of the lens optical system 9 can be reduced.

In addition, the thicknesses of the first lens 91 and the second lens 92 may be defined as follows to reduce the decentering sensitivity of the lens optical system 9: 2.3 < T1/T2 < 5.7, where T1 is the thickness of the first lens 91 on the optical axis and T2 is the thickness of the second lens 92 on the optical axis.

In order to further detail the technical content of the present invention, three embodiments of the lens optical system of the present invention will be described below in detail.

Fig. 3 is a schematic view of a lens optical system according to a first embodiment of the present invention, fig. 4 to 6 are aberration diagrams of the lens optical system according to the first embodiment of the present invention, fig. 7 is an MTF (modulation transfer function) diagram of the lens optical system according to the first embodiment of the present invention, as shown in fig. 3, the lens optical system 9 according to the first embodiment of the present invention includes a first lens 91 and a second lens 92, wherein the first lens 91 is a lenticular lens, a surface facing the observation side is a first surface 911, and a surface facing the object side is a second surface 912; the second lens 92 is a convex-concave lens, and a surface facing the observation side is a first surface 921 and a surface facing the object side is a second surface 922. The first face 911 and the second face 912 of the first lens 91 and the first face 921 and the second face 922 of the second lens 92 are aspherical surfaces, and these aspherical surfaces are defined by the following formulas:

Wherein f (R, R) represents the aspherical depth, i.e., the distance from the point of the aspherical surface having a height R from the optical axis to the tangent plane of the aspherical vertex;

r is the height from the optical axis;

r is the radius of curvature at the paraxial region of the lens surface;

k is a conical surface coefficient (conic constant);

a4, A6, A8, a10, a12 represent aspherical coefficients.

In this first embodiment, the focal distance f1 of the first lens 91 of the lens optical system 9 is 6.54mm, the refractive index N1 is 1.5338, the abbe number V1 is 55.6, and the thickness T1 of the first lens 91 on the optical axis is 7.722mm. And the focal distance f2 of the second lens 92 is-10.56 mm, the refractive index N1 is 1.651, the abbe number V1 is 21.49, and the thickness T1 of the second lens 92 on the optical axis is 1.642mm. Whereas the focal distance f of the entire lens optical system 9 was 11.86mm, other detailed optical data of this example are shown in table 1.

TABLE 1

As shown in table 1, the distance of the pupil to the first lens 91 and the distance between the second lens 92 and the display 8 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 9 in the electronic viewfinder 6 is shifted depending on the vision of the observer, as shown in table 1-1 in particular.

Eye point EP (mm)	Visibility (diopter)	Distance between pupil and first lens	Spacing between second lens and display
				12.5	+3	0.70	5.83
12.5	-1	1.27	5.27
				12.5	-4	1.70	4.83

TABLE 1-1

From this, it is clear that f1/f2 is-0.62, f1/f is 0.55, and f2/f is-0.89, thereby ensuring that the lens optical system 9 has a proper back focal length, ensuring a large viewing angle, and correcting aberrations such as curvature of field, distortion, and the like. The refractive index N1 of the first lens 91 is smaller than the refractive index N2 of the second lens 92, and the abbe number V1 of the first lens 91 is larger than the abbe number V2 of the second lens 92, so that a low refractive index high-dispersion convex lens is formed to be matched with a high refractive index low-dispersion concave lens, chromatic aberration is effectively reduced, and field curvature is corrected. In addition, T1/T2 is 4.70, reducing the decentration sensitivity of the lens optical system 9.

The first surface 911 and the second surface 912 of the first lens 91 and the first surface 921 and the second surface 922 of the second lens 92 are aspherical, and the aspherical coefficients are shown in table 2. The arrangement of the aspherical surface can reduce spherical aberration and distortion of the lens optical system 9.

TABLE 2

Fig. 4 to 6 are aberration diagrams of the lens optical system of the first embodiment, which show aberration performances determining aberration performances of imaging light from the display screen on retina of eye of observer. When the pixel differences are small, aberration performances of imaging of the retina of the eye of the observer are also small, so that the observer can observe an image with better imaging quality.

Specifically, fig. 4 is a graph of spherical aberration and chromatic aberration of the first embodiment, and as shown in fig. 4, the distribution curves of spherical aberration and chromatic aberration on the optical axis are taken as reference wavelength by an e-line with a wavelength of 546.07nm, a c-line with a wavelength of 656.27nm and a g-line with a wavelength of 435.84nm, the abscissa is the amount of aberration in mm, and the tip of the ordinate is a half-angle, that is, corresponds to a maximum viewing angle.

Fig. 5 is a ray aberration diagram of the first embodiment, in which, as shown in fig. 5, the left side is a ray aberration in the meridian direction, the right side is a ray aberration in the sagittal direction, the abscissa is a pupil, and the ordinate is an amount of aberration in mm, and as can be seen from fig. 5, the ray aberration of the lens optical system 9 is controlled within ±0.02mm.

Fig. 6 is a distortion chart of the first embodiment, and as shown in fig. 6, the abscissa indicates the amount of distortion in% and the ordinate indicates the half-angle, that is, the maximum viewing angle. As can be seen from fig. 6, the distortion of the lens optical system 9 is controlled within ±1.0%.

Fig. 7 is an MTF (modulation transfer function) diagram of the first embodiment, and the higher the MTF curve, the straighter the imaging quality. As shown in fig. 7, the relative image height is 0.0 to 1.0 on the abscissa, and the MTF value is the maximum value of 1.0, i.e., 100%. The higher solid line represents the MTF value in the sagittal direction at a spatial frequency of 48lp/mm (line pair per millimeter), the higher broken line represents the MTF value in the meridional direction at a spatial frequency of 48lp/mm (line pair per millimeter), the higher solid line represents the MTF value in the sagittal direction at a spatial frequency of 48lp/mm (line pair per millimeter), and the higher solid line represents the MTF value in the meridional direction at a spatial frequency of 48lp/mm (line pair per millimeter). As can be seen from fig. 7, the lens optical system has good imaging performance in both the meridional direction and the sagittal direction in each field of view.

Fig. 8 is a schematic view of a lens optical system structure according to a second embodiment of the present invention, and fig. 9 to 12 are aberration diagrams of a lens optical system 9 according to the second embodiment, as shown in fig. 8, wherein the lens optical system 9 according to the second embodiment is similar to the first embodiment in structure, and only slightly different in terms of optical data and aspheric coefficients.

Specifically, in this second embodiment, the focal distance f1 of the first lens 91 of the lens optical system 9 is 6.85mm, the refractive index N1 is 1.544, the abbe number V1 is 56, and the thickness T1 of the first lens 91 on the optical axis is 6.696mm. And the focal distance f2 of the second lens 92 is-12.2 mm, the refractive index N1 is 1.655, the abbe number V1 is 21.49, and the thickness T1 of the second lens 92 on the optical axis is 1.564mm. Whereas the focal distance f of the entire lens optical system 9 was 11.86mm, other detailed optical data of this example are shown in table 3.

TABLE 3 Table 3

As shown in table 3, the distance of the pupil to the first lens 91 and the distance between the second lens 92 and the display 8 are related to the eye-point distance of the observer, as shown in table 3-1 in particular.

Eye point EP (mm)	Visibility (diopter)	Distance between pupil and first lens	Spacing between second lens and display
				12.5	+3	0.96	5.58
12.5	-1	1.52	5.02
				12.5	-4	1.95	4.59

TABLE 3-1

As can be seen from the above, in the lens optical system of the second embodiment, f1/f2 is-0.56, f1/f is 0.58, and f2/f is-1.02, so that the lens optical system 9 has a proper back focal length, a large viewing angle, and aberrations such as curvature of field and distortion are corrected. The refractive index N1 of the first lens 91 is smaller than the refractive index N2 of the second lens 92, and the abbe number V1 of the first lens 91 is larger than the abbe number V2 of the second lens 92, so that a low refractive index high-dispersion convex lens is formed to be matched with a high refractive index low-dispersion concave lens, chromatic aberration is effectively reduced, and field curvature is corrected. In addition, T1/T2 is 4.28, reducing the decentration sensitivity of the lens optical system 9.

In addition, the first surface 911 and the second surface 912 of the first lens 91 and the first surface 921 and the second surface 922 of the second lens 92 of the second embodiment are each aspherical, and the aspherical coefficients thereof are shown in table 4.

TABLE 4 Table 4

Fig. 9 is a graph of spherical aberration and chromatic aberration of the second embodiment, as shown in fig. 9, with an e-line of wavelength 546.07nm as a reference wavelength, a c-line of wavelength 656.27nm and a g-line of wavelength 435.84nm as distribution curves of spherical aberration and chromatic aberration on the optical axis, the abscissa being the amount of aberration in mm, and the tip of the ordinate being a half angle, that is, corresponding to the maximum field angle. Fig. 10 is a ray aberration diagram of the second embodiment, and as can be seen from fig. 10, the ray aberration of the lens optical system 9 is controlled within ±0.02 mm. Fig. 11 is a distortion chart of the second embodiment, and as can be seen from fig. 11, the distortion of the lens optical system 9 is controlled within ±1.0%.

Fig. 12 is an MTF (modulation transfer function) diagram of the second embodiment, with higher MTF curves indicating better imaging quality. As can be seen from fig. 12, the lens optical system 9 has excellent imaging performance in both the meridional direction and the sagittal direction in each field of view.

Fig. 13 is a schematic view of a lens optical system according to a third embodiment of the present invention, and fig. 14 to 17 are aberration diagrams of a lens optical system 9 according to the third embodiment, wherein the lens optical system 9 according to the third embodiment is similar to the first embodiment in structure, and only optical data and aspheric coefficients are slightly different.

Specifically, in this third embodiment, the focal distance f1 of the first lens 91 of the lens optical system 9 is 6.45mm, the refractive index N1 is 1.544, the abbe number V1 is 56, and the thickness T1 of the first lens 91 on the optical axis is 6.829mm. And the focal distance f2 of the second lens 92 is-10.9 mm, the refractive index N1 is 1.655, the abbe number V1 is 21.49, and the thickness T1 of the second lens 92 on the optical axis is 2.090mm. Whereas the focal distance f of the entire lens optical system 9 was 11.86mm, other detailed optical data of this example are shown in table 5.

TABLE 5

As shown in table 5, the distance of the pupil from the first lens 91 and the distance between the second lens 91 and the display 8 are related to the eye-point distance of the observer, as shown in table 5-1 in particular.

Eye point EP (mm)	Visibility (diopter)	Distance between pupil and first lens	Spacing between second lens and display
				12.5	+3	0.94	5.59
12.5	-1	1.51	5.03
				12.5	-4	1.95	4.59

TABLE 5-1

As can be seen from the above, in the lens optical system of the third embodiment, f1/f2 is-0.59, f1/f is 0.54, and f2/f is-0.92, so that the lens optical system 9 has a proper back focal length, a large viewing angle, and aberrations such as curvature of field and distortion are corrected. The refractive index N1 of the first lens 91 is smaller than the refractive index N2 of the second lens 92, and the abbe number V1 of the first lens 91 is larger than the abbe number V2 of the second lens 92, so that a low refractive index high-dispersion convex lens is formed to be matched with a high refractive index low-dispersion concave lens, chromatic aberration is effectively reduced, and field curvature is corrected. In addition, T1/T2 is 3.27, reducing the decentration sensitivity of the lens optical system 9.

In addition, the first surface 911 and the second surface 912 of the first lens 91 and the first surface 921 and the second surface 922 of the second lens 92 of the third embodiment are each aspherical, and the aspherical coefficients thereof are shown in table 6.

TABLE 6

Fig. 14 is a graph of spherical aberration and chromatic aberration of the third embodiment, in which, as shown in fig. 14, an e-line of a wavelength of 546.07nm is taken as a reference wavelength, a c-line of a wavelength of 656.27nm and a g-line of a wavelength of 435.84nm are taken as distribution curves of spherical aberration and chromatic aberration on the optical axis, the abscissa is the amount of aberration in mm, and the tip of the ordinate is a half-angle, that is, corresponds to a maximum viewing angle. Fig. 15 is a ray aberration diagram of the third embodiment, and as can be seen from fig. 15, the ray aberration of the lens optical system 9 is controlled within ±0.02 mm. Fig. 16 is a distortion chart of the third embodiment, and as can be seen from fig. 16, the distortion of the lens optical system 9 is controlled within ±1.0%.

Fig. 17 is an MTF (modulation transfer function) diagram of the third embodiment, and the higher the MTF curve, the straighter the imaging quality. As can be seen from fig. 12, the lens optical system 9 has excellent imaging performance in both the meridional direction and the sagittal direction in each field of view.

The lens optical systems described in the first to third embodiments can be applied to other optical devices such as an electron microscope, in addition to an electronic viewfinder.

The foregoing embodiments of the present invention are not intended to limit the technical scope of the present invention, and therefore, any minor modifications, equivalent variations and modifications made to the above embodiments according to the technical principles of the present invention still fall within the scope of the technical proposal of the present invention.

Claims

1. A lens optical system applied to an electronic viewfinder, through which light is imaged, characterized in that: the lens optical system is provided with: a first lens having a positive diopter and a second lens having a negative diopter, the first lens and the second lens satisfying the following conditions: -0.8 < f1/f2 < -0.4,0.54 > to < f1/f < 0.75, -1.2 < f2/f < -0.8;

Wherein f1 is the focal distance of the first lens, f2 is the focal distance of the second lens, and f is the focal distance of the lens optical system;

the first lens and the second lens are made of materials meeting the following conditions: v1 is more than or equal to 52, and V2 is less than or equal to 21.49; wherein V1 is the Abbe number of the first lens, and V2 is the Abbe number of the second lens.

2. The lens optical system applied to an electronic viewfinder according to claim 1, characterized in that: the first lens and the second lens satisfy the following conditions: 2.3 < T1/T2 < 5.7, wherein T1 is the thickness of the first lens on the optical axis, and T2 is the thickness of the second lens on the optical axis.

3. The lens optical system applied to an electronic viewfinder according to claim 1, characterized in that: the first lens and the second lens are made of materials meeting the following conditions: n1 is more than 1.45 and less than 1.57,1.60, N2 is more than 1.68; wherein N1 is the refractive index of the first lens and N2 is the refractive index of the second lens.

4. The lens optical system applied to an electronic viewfinder according to claim 1, characterized in that: the first lens is a biconvex lens, and the second lens is a concave-convex lens.

5. An electronic viewfinder comprising a viewfinder housing and a display disposed at a rear portion in an optical axis direction in the viewfinder housing, characterized in that: the lens optical system according to any one of claims 1 to 4, which is provided in the viewfinder housing at a front portion in an optical axis direction and is capable of being corrected by adjusting the observer's eyesight.

6. The electronic viewfinder according to claim 5, characterized in that: the front and back adjustment of the lens optical system is realized through a vision degree adjusting knob.

7. An image pickup apparatus comprising a body and a photographing lens group provided on the body, characterized in that: the body is provided with an image sensor for converting an optical signal from an imaging lens group into a digital signal and outputting the digital signal, and the electronic viewfinder according to claim 5 for monitoring the digital signal of the image sensor.