JP3501143B2 - Viewfinder optical system and viewfinder - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a viewfinder optical system and a viewfinder, and more particularly to a camera used for photographing a still image or a moving image of a subject.
The present invention relates to a finder optical system suitable for (for example, a camera built in or attached to a digital camera, a video camera, a mobile phone, a personal computer, a mobile computer, an information portable terminal, etc.) and a viewfinder using the same. .

[0002]

2. Description of the Related Art Recent video cameras and digital still cameras are generally provided with a 1.5-inch class liquid crystal panel that allows direct viewing. With this liquid crystal panel, a plurality of people can simultaneously confirm the shooting result and the like. However, when such a liquid crystal panel is used as a finder, there are some problems. For example, there is a problem that it is difficult to see in a bright place, a problem that a person with hyperopia cannot see because the diopter does not match, and a problem that it is difficult to see a fine display because the panel display surface is not enlarged. Therefore, in many cases, an optical viewfinder or an electronic viewfinder (so-called EVF) is also installed in addition to the liquid crystal panel for checking the shooting result and the like.

The optical viewfinder has a problem that parallax occurs and a problem that the photographing result cannot be confirmed. Therefore, EVF as a finder
However, the number of cameras equipped with a small liquid crystal panel of about 0.5 inch exclusively for EVF is increasing. An example thereof is shown in FIG. In FIG. 8, 1 is a camera body, 2 is a taking lens, 3 is a backlight unit, LE is an eyepiece lens, DP1 is a 0.5 inch liquid crystal panel, and DP2 is a 1.5 inch liquid crystal panel. The liquid crystal panel (DP1) dedicated to the EVF is illuminated with light from the backlight unit (3), and the displayed image is observed through the eyepiece lens (LE). Meanwhile, camera body
The display image of the liquid crystal panel (DP2) provided on the back surface of (1) can be observed directly.

[0004]

Since the liquid crystal panel is very expensive, use of two liquid crystal panels as described above will naturally increase the cost of the camera. In order to avoid cost increase, it has been desired to have a structure in which a large direct-view liquid crystal panel is shared with the EVF.
If used in common, the size of the eyepiece optical system will be increased. As proposed in JP-A-11-215407,
The size of the eyepiece optical system can be prevented by observing the reduced image on a part of the large liquid crystal panel. However, since the finder display is performed with a small number of pixels, the image quality is lower than when the finder display is performed on the entire screen of the liquid crystal panel. Therefore, a liquid crystal panel with higher pixels is required, which also leads to an increase in cost.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a compact viewfinder optical system which can cope with a large display screen and a viewfinder using the same.

[0006]

In order to achieve the above object, the finder optical system of the first invention comprises a first and a second quarter wave plate, and a first and a second quarter wave plate thereof. A semi-transparent mirror vapor deposition surface for transmitting and reflecting light between the wave plates, and the second
A polarized light selection optical element that transmits linearly polarized light in the first vibration direction and reflects linearly polarized light in the second vibration direction orthogonal to the light that has passed through the / 4 wavelength plate, and light transmitted through the polarized light selection optical element A viewfinder optical system for observing a liquid crystal panel, which comprises an eyepiece of positive power leading to the pupil,
The linearly polarized light in the first vibration direction emitted from the liquid crystal panel is circularly polarized by the first quarter-wave plate, the circularly polarized light is transmitted through the vapor deposition surface of the semi-transmissive mirror, and then the second quarter-wave. The wave plate is linearly polarized in the second vibration direction, the linearly polarized light in the second vibration direction is reflected by the polarization selection optical element, and then circularly polarized by the second quarter wave plate, and the circularly polarized light is obtained. After being reflected by the vapor deposition surface of the semi-transparent mirror and then linearly polarized in the first vibration direction by the second quarter-wave plate, and the linearly polarized light in the first vibration direction passes through the polarization selection optical element. , Is configured to pass through the eyepiece.

In the finder optical system of the second invention, in the structure of the first invention, a mirror for bending an optical path by about 90 degrees is arranged between the vapor deposition surface of the semitransparent mirror and the polarization selecting optical element. Characterize.

A finder optical system of a third invention is characterized in that, in the structure of the first or second invention, the vapor deposition surface of the semi-transmissive mirror has a convex shape or a planar shape on the pupil side.

In the finder optical system according to the fourth invention, in the configuration of the first, second or third invention, linear polarization in the first vibration direction is provided on the liquid crystal panel side of the first quarter wavelength plate. Is arranged, and the first quarter-wave plate and the semi-transparent mirror vapor deposition surface together with the linear polarizing plate are constituted by a single optical element.

A viewfinder according to a fifth aspect of the invention is a viewfinder including the finder optical system according to any one of the first to fourth aspects of the invention and a liquid crystal panel observed by the finder optical system. The liquid crystal panel is commonly used for direct viewing.

[0011]

DETAILED DESCRIPTION OF THE INVENTION A finder optical system and a viewfinder embodying the present invention will be described below with reference to the drawings. The same parts or corresponding parts in the conventional example (FIG. 8) and the embodiment are designated by the same reference numerals, and duplicate description will be omitted as appropriate.

FIG. 1 schematically shows the basic optical structure and light flow of the viewfinder according to the present invention. Figure 1
Inside, the surface with Si (i = 1,2,3, ...) is counted from the pupil (EP) side in the system including the pupil (EP) to the display surface of the liquid crystal panel (DP). It is the i-th surface. This viewfinder has a finder optical system for observing a liquid crystal panel (DP), and constitutes an EVF as a whole including the finder optical system and the liquid crystal panel (DP). The finder optical system comprises, in order from the liquid crystal panel (DP) side, first and second optical elements (D1, D2) each having a laminated structure and an eyepiece lens (LE) having positive power (AX: optical axis). The finder optical system guides the light emitted from the liquid crystal panel (DP) to the pupil (EP). Therefore, the observer can observe the two-dimensional display image of the liquid crystal panel (DP) by adjusting the eyes to the pupil (EP).

The first optical element (D1) has a glass substrate (B1), a first linear polarizing plate (P1), a first quarter-wave plate (Q1), and a glass substrate (B2) which are integrated in a joined state. Is a semi-transparent mirror,
The second optical element (D2) is the second quarter wave plate (Q2), PBS.
(Polarizing Beam Splitter) sheet (RT), glass substrate (B
This is a PBS plate in which 3) and the second linear polarizing plate (P2) are integrated in a joined state. Linear polarization plate (P1, P2) is a specific linear polarization
A function of transmitting (hereinafter, referred to as "linearly polarized light in the first vibration direction") and absorbing linearly polarized light whose vibration plane is perpendicular to the linearly polarized light (hereinafter, referred to as "linearly polarized light in the second vibration direction"). Have The quarter-wave plate (Q1, Q2) has a function of converting circularly polarized light into linearly polarized light and converting linearly polarized light into circularly polarized light.

The pupil (EP) side surface of the first optical element (D1) is a semi-transparent mirror vapor deposition surface (HM), and the semi-transparent mirror vapor deposition surface (HM) is two quarter-wave plates. Light is transmitted and reflected between (Q1, Q2). PBS sheet (RT) forming the second optical element (D2)
Is a polarization selection optical element, which transmits linearly polarized light in the first vibration direction out of light that has passed through the second quarter-wave plate (Q2),
The linearly polarized light in the second vibration direction orthogonal to that is reflected.
Specific examples of the PBS sheet (RT) include DBEF (trade name) manufactured by Sumitomo 3M Limited. The surfaces of the first and second optical elements (D1, D2) on the liquid crystal panel (DP) side are antireflection film deposition surfaces (AR1, AR2).

The eyepiece lens (LE) is composed of a refraction type lens that deflects an incident light beam by refraction (that is, a lens of a type in which deflection is performed at an interface between media having different refractive indexes), but is not limited to this. Absent. For example, a diffractive lens that deflects an incident light beam by diffraction, a refraction / diffraction hybrid lens that deflects an incident light beam by a combination of a diffractive action and a refraction action, a refractive index distribution type that deflects an incident light beam by a refractive index distribution in a medium. Eyepiece lens (LE)
May be configured.

Next, the flow of light in the viewfinder will be described. The liquid crystal panel (DP) has a linear polarizing plate (not shown) on the exit side surface, and the linear polarizing plate transmits linearly polarized light in the first vibration direction. Therefore, linearly polarized light in the first vibration direction is emitted from the liquid crystal panel (DP). The linearly polarized light in the first vibration direction emitted from the liquid crystal panel (DP) enters the first optical element (D1) and passes through the glass substrate (B1). The surface of the glass substrate (B1) on the liquid crystal panel (DP) side is
Since it is a vapor deposition surface (AR1) coated with an antireflection film, reflection at the time of incidence can be suppressed. The linearly polarized light transmitted through the glass substrate (B1) is transmitted through the first linear polarization plate (P1). Since this linearly polarizing plate (P1) also transmits the linearly polarized light in the first vibration direction, the linearly polarized light is transmitted with little influence of the linearly polarizing plate (P1).

The linearly polarized light in the first vibration direction transmitted through the first linearly polarizing plate (P1) is circularly polarized by the first quarter wave plate (Q1). The circularly polarized light passes through the glass substrate (B2) and then through the semi-transparent mirror vapor deposition surface (HM). At this time, the polarization state of circularly polarized light is not affected by the semitransparent mirror vapor deposition surface (HM). The circularly polarized light transmitted through the vapor deposition surface (HM) of the semi-transparent mirror enters the second optical element (D2) and is linearly polarized in the second vibration direction by the second quarter wave plate (Q2). Second quarter wave plate (Q2) liquid crystal panel (D
Since the surface on the (P) side is a vapor deposition surface (AR2) coated with an antireflection film, reflection at the time of incidence can be suppressed.

The second emitted from the second quarter-wave plate (Q2)
The linearly polarized light in the vibration direction is reflected by the PBS sheet (RT). At this time, the polarization state of the linearly polarized light is PBS sheet (RT)
Not affected by. The linearly polarized light reflected by the PBS sheet (RT) again enters the second quarter-wave plate (Q2) to be circularly polarized, and exits from the second optical element (D2). Second optical element
The circularly polarized light emitted from (D2) is reflected by the vapor deposition surface (HM) of the semi-transparent mirror and is converted into circularly polarized light of the reverse rotation. Then again the second
It is incident on the 1/4 wavelength plate (Q2) and is linearly polarized in the first vibration direction.

The first emitted from the second quarter-wave plate (Q2)
The linearly polarized light in the vibration direction passes through the PBS sheet (RT) and then through the glass substrate (B3) and the second linearly polarizing plate (P2). The second linear polarizing plate (P2) transmits linearly polarized light in the first vibration direction as well as the first linearly polarizing plate (P1), so linearly polarized light is hardly affected by the linearly polarizing plate (P2). To Penetrate. However, the linearly polarized light in the second vibration direction, which is unnecessary leaked light, is absorbed by the linearly polarizing plate (P2). The linearly polarized light in the first vibration direction transmitted through the linearly polarizing plate (P2) is guided to the pupil (EP) by the eyepiece lens (LE).

In the above finder optical system, the light is reflected and transmitted by the semi-transparent mirror vapor deposition surface (HM) and the PBS sheet (RT), so that the distance between the semi-transparent mirror vapor deposition surface (HM) and the PBS sheet (RT) is increased.
The space of {that is, between the seventh surface (S7) and the ninth surface (S9)} is the optical path.
Used heavily. As a result, the physical distance from the liquid crystal panel (DP) to the eyepiece lens (LE) is compressed, so that the finder optical system can be downsized. In other words, the optical path space from the liquid crystal panel (DP) to the eyepiece lens (LE) can be shortened to about 1/3 as compared with the case of directly looking at the eyepiece optical system without overlapping the optical paths. .

Further, if the space between the semitransparent mirror vapor deposition surface (HM) and the PBS sheet (RT) is used in triple in the optical path as described above, the focal length of the eyepiece lens (LE) is Can be lengthened. That is, since the same space can be used three times, the focal length of the eyepiece lens (LE) can be made slightly longer than three times. Since the viewfinder magnification is almost inversely proportional to the focal length of the eyepiece optical system, if the focal length of the eyepiece lens (LE) is increased by about 3 times, the same field of view will be obtained even if a liquid crystal panel (DP) that is about 3 times larger is used. It enables finder observation at the corner. For example, a 1.5-inch LCD panel
Even when (DP) is used, it is possible to observe a display image with a viewing angle similar to that of a single-lens reflex camera of a silver salt film.

Therefore, with the above-mentioned viewfinder structure in which the same optical path uses the same space three times, it is possible to realize a compact viewfinder optical system which can cope with a large display screen. The viewfinder having the finder optical system configured as described above can cope with a large display screen of the liquid crystal panel (DP) (that is, the entire screen), so that the image quality of the finder display does not deteriorate. Further, since the liquid crystal panel (DP) observed by the finder optical system can be shared for direct viewing, the cost can be reduced.

Even if the optical path uses the same space three times, the focal length of the eyepiece lens (LE) cannot always be effectively increased. For example, in the optical configuration proposed in Japanese Unexamined Patent Publication No. 2000-275566, the optical paths are formed in the same space.
Although it is used repeatedly, the semi-transmissive mirror has the positive power of the eyepiece optical system, so the optical path from the semi-transmissive mirror to the liquid crystal panel uses part of the space double. Nothing more. Therefore, the focal length of the eyepiece lens (LE) is only doubled. As shown in Fig. 1, by using a semi-transparent mirror vapor deposition surface (HM) that does not have the positive power of the eyepiece optical system, when the eyepiece optical system is made independent from the superposition of the optical paths, the optical paths are tripled in the same space. I will use it. As a result, the principal point of the eyepiece optical system is far away from the display surface of the liquid crystal panel (DP), so that the focal length of the eyepiece lens (LE) can be increased to about 3 times.

In order to use the liquid crystal panel (DP) for direct viewing, the display surface of the liquid crystal panel (DP) must be large to some extent. If a large display surface is observed with a normal EVF eyepiece, it will be enlarged too much. However, if the viewfinder magnification is reduced by using an eyepiece (LE) with a long focal length as described above, a viewfinder with an appropriate viewing angle will be obtained. Observation becomes possible. In the finder structure having the same size and without overlapping the optical paths, the magnification and the viewing angle are greatly increased. This has the following problems, but the finder structure according to the present invention can solve these problems.

The viewing angle is too large to check the entire field of view at the same time. The eyepiece magnification is so large that the pixels become conspicuous unless the number of pixels is increased. Therefore, it is necessary to increase the number of pixels of the liquid crystal panel, which leads to an increase in cost. Since the required diameter of the eyepiece lens is almost proportional to the viewing angle, the diameter of the eyepiece lens becomes large, which hinders miniaturization. It is necessary to greatly increase the power of the eyepiece lens,
It becomes difficult to secure the aberration performance. As a result, it becomes necessary to increase the number of lenses, resulting in an increase in size and an increase in cost.

By the way, the first and second optical elements (D1, D2) used in the finder optical system shown in FIG. 1 are each a single unit in which the respective elements are integrated in a joined state by vapor deposition, pasting or the like. It is one laminated optical element. Since the surface reflection surface is reduced due to the integration by joining, the generation of flare light is suppressed. For example, when light is emitted from the first optical element (D1), light is transmitted through the semi-transparent mirror vapor deposition surface (HM) and at the same time, reflected light that travels in the direction opposite to the normal optical path is generated. Surface (HM) on the liquid crystal panel (DP) side (eg semi-transparent mirror deposition surface
If there is a surface-reflecting surface (that is, a surface in contact with air) between (HM) and the quarter-wave plate (Q1)}, there is a possibility that flare light may be generated due to further reflection there. Then, when the generated flare light reaches the pupil (EP), the images with the diopter shift are observed twice. The generation of the flare light can be prevented by the integration by the above-mentioned joining. LCD panel
Even if flare light is generated by the reflection on the surface of (DP), it is absorbed by the linear polarizing plate (P1) arranged on the liquid crystal panel (DP) side of the quarter-wave plate (Q1). EP) is never reached.

Next, a specific structure of the viewfinder for sharing the liquid crystal panel (DP) for direct viewing will be described.
2 to 4 show the first panel rotation type viewfinder.
~ The third usage state is shown in a sectional view, and FIG. 5 shows an enlarged optical configuration and an optical path of a main part in the first usage state (FIG. 2). Note that FIG. 5B shows the optical path by reducing the number of light rays as compared with FIG. 5A, but the optical configuration is the same.

In the viewfinder shown in FIGS. 2 to 5, the liquid crystal panel (DP) and the backlight section (3) are configured to be rotatable about a rotation axis (4). When the liquid crystal panel (DP) is brought close to the first optical element (D1) as shown in FIG. 2 due to the rotation, the EVF (FIG. 1) described above is constructed and the first
The usage state is obtained, and the two-dimensional display image of the liquid crystal panel (DP) can be observed through the finder optical system. Further, when the display surface is exposed by rotating the liquid crystal panel (DP) or the like, the second and third usage states are obtained as shown in FIGS. 3 and 4, and the display image can be observed directly. It will be possible. For example, in the second use state (FIG. 3), the liquid crystal panel (DP) can be observed so that the line of sight is directed toward the subject side, and in the third use state (FIG. 4), the line of sight is directed toward the lower side. The liquid crystal panel (DP) can be observed with. Since the orientation of the display surface can be freely changed by rotating the liquid crystal panel (DP), it is possible to directly observe the liquid crystal panel (DP) from an angle as necessary.

In the viewfinder shown in FIGS. 2 to 5, an aluminum mirror (MR) which bends the optical path by about 90 degrees is arranged between the first optical element (D1) and the second optical element (D2). . By bending the optical path in this way, the space required for arranging the optical path becomes smaller. That is, the required optical path space can be reduced to about half of the case where the optical path is not bent with the same optical path length. The bending position of the optical path is not limited to the position between the first and second optical elements (D1, D2), but the liquid crystal panel (DP)
Between the first optical element (D1) and the second optical element (D2) and the pupil (EP)
It may be set as necessary, such as between the two, and it is possible to achieve an apparent thinning of the camera by properly bending the optical path.

6 and 7 are sectional views respectively showing the first and second usage states of the optical system detachable viewfinder.
In this optical system detachable viewfinder, the finder optical system is detachably attached to the liquid crystal panel (DP). As shown in FIG. 6, when the viewfinder optical system is attached to the liquid crystal panel (DP) on the back of the camera body (1), the EVF (FIG. 1) described above is configured and the first use state is obtained.
It becomes possible to observe the two-dimensional display image of the liquid crystal panel (DP) through the finder optical system. Further, by removing the finder optical system to expose the display surface of the liquid crystal panel (DP), the second usage state is obtained as shown in FIG. 7, and the display image can be observed directly. Since the second use state corresponds to the state of a general camera that does not have an EVF, if the viewfinder optical system has a mounting structure for the first use state, the present invention also applies to the conventional camera. It is possible to apply a viewfinder.

In the viewfinder shown in FIGS. 6 and 7, the semi-transparent mirror vapor deposition surface (HM) has a convex shape on the pupil (EP) side. If the semi-transparent mirror vapor deposition surface (HM) is made convex, a positive power condenser effect is obtained when light passes through the semi-transparent mirror vapor deposition surface (HM). L
E) will have the effect of focusing on the entrance pupil. When light is reflected by the semi-transparent mirror vapor deposition surface (HM), a negative power convex mirror effect is obtained, so the semi-transparent mirror vapor deposition surface (HM) moves the principal point to the pupil (EP) side as part of the eyepiece optical system. It acts to let you. Therefore, the distance from the liquid crystal panel (DP) to the eyepiece lens (LE) is further shortened, and the viewfinder optical system is further miniaturized. Also, it is possible to reduce the magnification.
When the semi-transparent mirror vapor deposition surface (HM) has a flat shape like the panel rotation type viewfinder (Figs. 2 to 5), the effect of downsizing is smaller than that of the convex shape, but the semi-transparent Mirror evaporation or linear polarizing plate (P1) is attached in a large plate glass state and then cut to cut the first optical element (D
It is possible to manufacture 1). Therefore, the cost at the time of manufacturing can be reduced.

[0032]

EXAMPLES The optical structure of the viewfinder embodying the present invention will be described more specifically below with reference to construction data. Examples 1 and 2 listed here are optical systems applicable to the above-described respective embodiments (FIGS. 1 to 7). The construction data of each example are shown in Table 1 and Table 2 so as to correspond to the above-mentioned optical elements and the like.
Shown in. As construction data, the surface Si (i = 1,
2, 3, ...) Radius of curvature (mm), axial distance (mm), material (for example, PMMA: polymethyl methacrylate), etc. are shown. Further, the surface Si with * is an aspherical surface defined by the following formula (AS), and its aspherical surface data is also shown.

X (H) = (C0 · H ² ) / {1 + √ (1-ε · C0 ² · H ² )} + (A
4 ・ H ⁴ + A6 ・ H ⁶ + A8 ・ H ⁸ + A10 ・ H ¹⁰ ) ... (AS) However, in the formula (AS), X (H): Optical axis (AX) direction at the position of height H Amount of displacement (referenced to surface apex), H: height in the direction perpendicular to the optical axis (AX), C0: paraxial curvature (= 1 / radius of curvature), ε: quadric surface parameter, Ai: i degree The aspherical coefficients of (i = 4,6,8,10) ,.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

As described above, according to the present invention, the space between the vapor deposition surface of the semi-transparent mirror and the polarization selection optical element is tripled in the optical path, so that the focal length of the eyepiece lens is lengthened. be able to. Therefore, it is possible to realize a compact viewfinder optical system that can accommodate a large display screen. In the viewfinder according to the present invention, a large display screen of the liquid crystal panel can be accommodated so that the image quality of the viewfinder display is not deteriorated, and the liquid crystal panel observed by the finder optical system is shared for direct viewing, so that the cost is reduced.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a basic optical configuration and a light flow of a viewfinder according to the present invention.

FIG. 2 is a sectional view showing a first use state of the panel rotation type viewfinder.

FIG. 3 is a cross-sectional view showing a second use state of the panel rotation type viewfinder.

FIG. 4 is a cross-sectional view showing a third use state of the panel rotation type viewfinder.

FIG. 5 is a cross-sectional view showing an optical configuration and an optical path of a main part of the panel rotation type viewfinder in a first use state.

FIG. 6 is a cross-sectional view showing a first use state of the optical system detachable viewfinder.

FIG. 7 is a sectional view showing a second use state of the optical system detachable viewfinder.

FIG. 8 is a sectional view showing a conventional example.

[Explanation of symbols]

DP ... LCD panel D1 ... 1st optical element D2… Second optical element MR… Aluminum mirror B1, B2, B3… Glass substrates P1, P2… Linear polarizing plate Q1, Q2 ... Quarter wave plate RT… PBS sheet (polarization selection optical element) AR1, AR2 ... Anti-reflection film deposition surface HM: Semi-transparent mirror evaporation surface LE ... Eyepiece EP ... Hitomi AX ... optical axis

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI G02F 1/1335 G02F 1/1335 1/13363 1/13363 (58) Fields investigated (Int.Cl. ⁷ , DB name) H04N 5 / 225-5/247

Claims (5)

(57) [Claims] 1. A first and second quarter-wave plate, a semi-transparent mirror vapor deposition surface for transmitting and reflecting light between the first and second quarter-wave plates, and the second A polarization selection optical element that transmits linearly polarized light in the first vibration direction and reflects linearly polarized light in the second vibration direction that is orthogonal to the light that has passed through the quarter-wave plate, and light that has passed through the polarization selection optical element. Is a viewfinder optical system for observing a liquid crystal panel, comprising: a positive power eyepiece that guides the light to the pupil, wherein linearly polarized light in the first vibration direction emitted from the liquid crystal panel is circled by the first quarter-wave plate. After being polarized, the circularly polarized light is transmitted through the vapor deposition surface of the semitransparent mirror, and then linearly polarized in the second vibration direction by the second quarter-wave plate, and the linearly polarized light in the second vibration direction is the polarized light. After being reflected by the selective optical element, it is circularly polarized by the second quarter-wave plate and its circular polarization is changed. After being reflected by the vapor deposition surface of the semi-transparent mirror and then linearly polarized in the first vibration direction by the second quarter-wave plate, and the linearly polarized light in the first vibration direction passes through the polarization selection optical element. A finder optical system configured to pass through the eyepiece. 2. The finder optical system according to claim 1, further comprising a mirror disposed between the vapor deposition surface of the semitransparent mirror and the polarization selecting optical element, the mirror bending an optical path by about 90 degrees. 3. The finder optical system according to claim 1, wherein the vapor deposition surface of the semi-transparent mirror has a convex shape or a planar shape on the pupil side. 4. A linearly polarizing plate that transmits linearly polarized light in the first vibration direction is disposed on the liquid crystal panel side of the first quarter-wave plate, and the first quarter-wavelength is provided together with the linearly polarizing plate. 4. The finder optical system according to claim 1, wherein the plate and the semi-transparent mirror vapor deposition surface are constituted by a single optical element. 5. A viewfinder comprising the viewfinder optical system according to claim 1 and a liquid crystal panel observed by the viewfinder optical system, wherein the liquid crystal panel is for direct viewing. A viewfinder characterized by being shared by.