JPH08234274A - Finder optical system - Google Patents

Abstract

PURPOSE: To make it possible to decrease the number of faces near an imaging plane without increasing the size in the optical axis direction of a finder by arranging the polarizing plates apart from a crystal plate and arranging a reflection optical element of an erecting optical system in the space generated by this arrangement. CONSTITUTION: The liquid crystal display optical system of the real image type finder provided, successively from an object side, with the erecting optical system consisting of an objective lens system 60, a roof mirror 21 and a pentagonal prism 31 and an eyepiece lens 70 is constituted of the crystal plate 50 disposed nearly flush with the imaging plane of the objective lens system 60 and the polarizing plates 10, 40 disposed before and behind this crystal plate. The polarizing plate 40 is arranged in the position parted from the crystal plate 50. The pentagonal prism 31 which is a part of the reflection optical system constituting the erecting optical system is arranged in the space between the crystal plate 50 and the polarizing plate 40 formed in such a manner. Then, the face visually recognized in the case where dust sticks nearer the eyepiece lens system 70 side than the crystal plate 50 is only the end face of the incident face of the pentagonal prism 31. The number of the faces visually recognized when the dust sticks near the imaging plane is thus decreased by one face.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a finder optical system used in a camera or the like, and more particularly to a real image type finder optical system including a liquid crystal display optical system for superimposing and displaying information on an object image.

[0002]

2. Description of the Related Art In a real image finder, an image of an object formed on an image plane by an objective lens system is observed through an eyepiece lens system. The liquid crystal display optical system disposed between the objective lens system and the eyepiece lens system is provided with a liquid crystal plate disposed in the vicinity of the image plane of the objective lens system and on both sides with the liquid crystal plate sandwiched therebetween. And a first and a second polarizing plate.

The two polarizing plates are arranged so that their transmission axes are orthogonal to each other in a plane perpendicular to the optical axis. Each polarizing plate transmits linearly polarized light in a direction coinciding with the transmission axis. The liquid crystal plate is configured by filling liquid crystal between two transparent plates. Inside the transparent plate, transparent electrodes having a shape corresponding to a pattern to be displayed are provided so as to face each other with a liquid crystal layer interposed therebetween. There is. In the liquid crystal plate, in the portion where the transparent electrode is not provided, the direction of the linearly polarized light transmitted through the first polarizing plate is 90 °.
In the part where the transparent electrode is provided by rotating and transmitting,
When voltage is applied, linearly polarized light is transmitted as it is,
The direction of linearly polarized light is 90 ° when no voltage is applied.
Rotate and let through.

The linearly polarized light transmitted through the liquid crystal plate as it is is the second
Since the light is blocked by the polarizing plate, the observer can see the shape of the transparent electrode portion to which a voltage is applied as a black pattern that does not allow light to pass through it by superimposing it on the object image through the eyepiece lens system.

[0005]

However, in the conventional real image type finder described above, a total of six surfaces, that is, the front surface and the back surface of the liquid crystal plate, and the front surface and the back surface of each of the two polarizing plates are the image planes. Since there are a relatively large number of surfaces that are present in the vicinity of the optical path and are in the range where the diopter of the observer's eyes matches, there is a problem that dust and scratches are highly visible in the viewfinder field. Since the observer's diopter is matched to the surface arranged in the vicinity of the image forming surface, when dust is attached or scratched on the surface, they are conspicuously seen. Therefore, in order to reduce the possibility of dust and scratches being noticeable, it is desirable to reduce the number of surfaces arranged in the range where the diopter is matched, that is, in the vicinity of the image plane.

In the liquid crystal display optical system, the liquid crystal plate itself needs to be arranged in the vicinity of the image forming plane so that the observer can see the information to be displayed, but the polarizing plate has no effect even if it is separated from the liquid crystal plate. Since there is no change, as one means for reducing the number of surfaces in the vicinity of the image plane, a method of setting the distance between the liquid crystal plate and the polarizing plate to a large value such that the diopter does not match the polarizing plate can be considered. However, if the distance between the liquid crystal plate and the polarizing plate is simply increased, the size of the finder in the optical axis direction increases, which hinders downsizing of the camera.

The present invention has been made in view of the above-mentioned problems of the prior art, and it is possible to reduce the number of surfaces in the vicinity of the image plane without increasing the size of the finder in the optical axis direction. The purpose is to provide the system.

[0008]

In order to achieve the above object, the present invention includes a first polarizing plate, a second polarizing plate and a liquid crystal plate disposed between the objective lens system and the eyepiece lens system. In the finder optical system in which the liquid crystal display optical system including is arranged, the second polarizing plate is arranged at a position away from the liquid crystal plate,
It is characterized in that a part of the reflective optical element constituting the erecting optical system is arranged in the space between the liquid crystal plate and the second polarizing plate generated by this.

When the reflective optical element forming the erecting optical system is a mirror, the number of surfaces in the vicinity of the image plane should be reduced by one as compared with a polarizing plate which is a plane-parallel plate having two surfaces. You can When the reflective optical element is a prism, only the end face on the incident side is arranged near the image plane,
Since the end surface on the exit side is separated from the image forming surface, the number of surfaces in the vicinity of the image forming surface can be reduced by one as in the case of the mirror.

The normal eye has accommodation power in the range of about -5 to 0 diopters, and the image plane of the finder is generally designed so that it can be observed at a diopter of about -1 diopter. Therefore, when observing the viewfinder, dust and scratches on the surface can be seen in a relatively wide range of -5 to -1 diopter on the side closer to the eye than the image plane, and the side away from the eye than the image plane. For, the dust and scratches are visible in a relatively narrow range of -1 to 0 diopters.

Therefore, a relatively large space is required between the liquid crystal plate and the second polarizing plate in order to arrange the second polarizing plate outside the range in which the diopter is matched. However, simply increasing the space increases the total length of the finder, and therefore at least a part of the reflection optical element of the erecting optical system is arranged in this space.

In the case where the reflective optical elements constituting the erecting optical system are divided into two groups, the first reflective optical element is provided between the first polarizing plate and the liquid crystal plate, and the second reflective optical element is provided. The element can be provided between the liquid crystal plate and the second polarizing plate. According to this configuration, for example, when the two reflective optical elements are prisms, the number of surfaces arranged in the vicinity of the image forming surface where the diopter of the observer matches is 4, and scratches and dust are conspicuous. The visibility can be further reduced.

The first and second polarizing plates are arranged such that their transmission axes are orthogonal or parallel to each other in a plane perpendicular to the optical axis, depending on the driving method of the liquid crystal plate.

In the liquid crystal display optical system, the directionality of the linearly polarized light which has passed through the first polarizing plate is adjusted by the liquid crystal plate, so that the second
The luminous flux that passes through the polarizing plate is controlled to display a pattern. Therefore, when at least a part of the reflective optical element forming the erecting optical system is provided between the first and second polarizing plates as in the present invention, when the provided reflective optical element changes the polarization state of the light beam significantly. , Display may be disturbed. Therefore, it is necessary to set the change in the polarization state due to the reflective optical element to be small, that is, the phase difference between the P and S components of the polarized light at the time of reflection should be small.

An erecting optical system reflective optical element disposed between the first polarizing plate and the second polarizing plate is a reflective optical element having two reflective surfaces whose incident surfaces are parallel to each other, such as a penta prism. In some cases, the transmission axis of the first polarizing plate is 0 ° with respect to the direction of the incident surface in the plane perpendicular to the optical axis, or 9
By arranging so as to form 0 °, it is possible to suppress the occurrence of a phase difference on the reflecting surface. The "incident surface" means
A plane including an incident ray and a normal to the surface on which the ray is incident.

When the transmission axis of the first polarizing plate is arranged at + 45 ° or −45 ° with respect to the direction of the incident surface, in order to suppress the occurrence of a phase difference, each reflecting surface is positioned at the time of reflection. It is necessary to apply a coat that does not cause a phase difference. Specific examples of such coats are provided in the embodiments.

Further, the reflection optical element of the erecting optical system arranged between the first polarizing plate and the second polarizing plate is an element having two reflecting surfaces whose incident surfaces are orthogonal to each other, such as a Porro prism. In some cases, as long as the two reflecting surfaces have the same characteristic with respect to the phase difference, two reflections cancel the phase difference regardless of the characteristics.

Furthermore, when the reflection optical element of the erecting optical system arranged between the first polarizing plate and the second polarizing plate is a roof mirror, the transmission axis of the first polarizing plate is perpendicular to the optical axis. It is set so as to form 0 ° or 90 ° with the ridgeline of the roof mirror in the plane. With other settings, the phase difference caused by the roof mirror becomes large, making correction difficult.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a finder optical system according to the present invention will be described below.

First, the basic concept of the arrangement of optical elements in the real image type finder of the present invention will be described with reference to FIGS.

The real image type viewfinder of the present invention comprises an objective lens system for forming a subject image, an erecting optical system for inverting and erecting the formed object image, and an eyepiece lens system for observing the image. It is composed of a liquid crystal display optical system for displaying information in the field of view of the finder. The liquid crystal optical system includes a liquid crystal plate arranged at the image forming position of the objective lens system,
It is composed of a first polarizing plate and a second polarizing plate which are sandwiched therebetween.

In order to solve the problem of dust and scratches which are noticeable in the field of view of the finder, it is necessary to reduce the number of surfaces of the optical elements arranged near the liquid crystal plate.

FIG. 15 shows a first arrangement example of the optical element. The first polarizing plate 10 is arranged in the vicinity of the liquid crystal panel 50, and the rear reflective optical element 30 forming an erecting optical system is arranged between the liquid crystal panel 50 and the second polarizing plate 40.
In this example, the second polarizing plate 40 on the eyepiece system side of the liquid crystal plate 50, which is easily matched by the observer's diopter, is arranged apart from the liquid crystal plate 50. When the rear reflective optical element 30 is a prism, according to the arrangement of FIG. 15, only the end surface on the incident side of the prism is arranged in the range where the diopter is matched on the eyepiece system side with respect to the image forming surface. , The liquid crystal plate 50 and the second polarizing plate 4
Compared with the conventional example in which 0 and 0 are arranged close to each other, it is possible to reduce the number of surfaces to be arranged by 1 in the range where the diopter matches.

Further, even when the rear reflective optical element 30 is a mirror, only the reflective surface of the mirror is disposed as the surface disposed in the range where the diopter is matched on the eyepiece system side with respect to the image forming surface. Compared with, the number of surfaces arranged in the range where the diopter matches is 1
One can be reduced.

FIG. 16 shows a second arrangement example of the optical element. The front reflection optical element 20 of the erecting optical system is arranged between the first polarizing plate 10 and the liquid crystal panel 50, and the rear reflection of the erecting optical system is arranged between the liquid crystal panel 50 and the second polarizing plate 40. The optical element 30 is arranged. In the arrangement example of FIG. 16, when the front reflection optical element 20 and the rear reflection optical element 30 are prisms, the surfaces arranged in the range where the diopter is matched before and after the image formation surface are the entrance sides of the two prisms. Since only the end faces are provided, the number of faces arranged in the range where the diopter is matched is reduced by two as compared with the conventional example in which the liquid crystal plate 50 and the first and second polarizing plates 40 are arranged close to each other. You can

Also, when one or both of the front reflection optical element 20 and the rear reflection optical element 30 are mirrors, a surface arranged in the range where the diopter is closer to the eyepiece system side than the image plane. Is only the reflecting surface of the mirror, the number of surfaces arranged in the range where the diopter is matched is 2 compared with the conventional example.
One can be reduced.

FIG. 17 shows a third arrangement example of the optical element.
In this arrangement, the front optical element 20 constituting the erecting optical system is provided between the first polarizing plate 10 and the liquid crystal plate 50, and the second optical element 20 is provided.
The polarizing plate 40 is provided adjacent to the liquid crystal plate on the eye side thereof. When the front reflective optical element 20 is a prism,
According to the arrangement of No. 7, the liquid crystal plate 50 and the second polarizing plate 40 are close to each other because the surface arranged in the range where the diopter is matched on the objective lens system side from the image forming surface is the end surface on the exit side of the prism. It is possible to reduce the number of surfaces to be arranged in the range where the diopter is matched by one, as compared with the conventional example arranged by.

Further, even when the front reflective optical element 20 is a mirror, the surface arranged in the range where the diopter is matched on the objective lens system side with respect to the image forming surface is only the reflective surface of the mirror, which is different from the conventional example. By comparison, set the number of surfaces to be placed in the range where the diopter matches to 1
One can be reduced.

With any of the arrangement examples shown in FIGS. 15 to 17, it is possible to reduce the number of surfaces visually recognized when dust adheres in the vicinity of the focused image surface by at least one surface. In addition,
In order to reduce the number of surfaces on which dust is visually recognized, the distance between the polarizing plate and the liquid crystal plate may be increased, but simply increasing the distance increases the total length of the finder. According to the above arrangement example, by disposing the reflection optical element of the erecting optical system between the first and second polarizing plates, the number of surfaces on which dust is visually recognized is reduced without increasing the total length of the finder. be able to.

Next, a specific embodiment of the finder system based on the above arrangement example will be described. FIG. 1 shows a first embodiment of a finder optical system arranged according to the first arrangement example of the optical elements shown in FIG.

The real image type finder of FIG. 1 comprises an objective lens system 60, an erecting optical system including a roof mirror 21 and a pentaprism 31, and an eyepiece system 70, which are provided in this order from the object side. The liquid crystal display optical system includes a liquid crystal plate 50 provided so as to substantially coincide with the image plane of the objective lens system,
It is composed of first and second polarizing plates 10 and 40 provided before and after that.

In FIG. 1, a pentaprism 31 which is one of the two reflective optical elements constituting the erecting optical system is provided between the liquid crystal plate 50 and the second polarizing plate 40. The roof mirror 21, which is the other reflective optical element, includes an objective lens system 6
It is arranged between 0 and the first polarizing plate 10. here,
In FIG. 1, the y axis is set parallel to the optical axis Ax of the objective lens system 60, and the x axis parallel to the long side direction of the finder field and the z axis perpendicular to the short side direction are defined in a plane orthogonal to this. I'll do it.

As shown in FIG. 2, the roof mirror 21 has two mirror surfaces 211 and 211 arranged perpendicularly to each other.
A ridge A having 12 and formed by intersecting these mirror surfaces is parallel to the xy plane and intersects the optical axis x at 45 ° in a plane parallel to the xy plane. Is arranged. In the roof mirror 21, the upper half of the light flux including the incident light ray IR is reflected by the upper reflecting surface 212 and then is reflected by the lower reflecting surface 211, and the lower half of the light flux is the lower reflecting surface 211.
After being reflected by, the reflection surface 212 on the upper side is reflected. As a result, the image formed by the light flux is inverted upside down and left-right reversed.

The ray IR incident on the ridge A is a reflected ray R.
It becomes R. Reference numerals PN1 and PN2 are normals to the reflecting surfaces 211 and 212 at the point where the light ray IR enters. Reflective surface 211
The plane of incidence of is defined as the plane containing the incident ray IR and the normal PN1. Similarly, the entrance surface of the reflecting surface 212 is defined as a plane containing the incident light ray IR and the normal line PN2. The roof mirror belongs to the first type element group in which the incident surfaces of the two reflecting surfaces are neither parallel nor orthogonal to each other.

The pentaprism 31 reflects the light flux incident from the incident end face on the liquid crystal plate 50 side, thereby xy
It has two reflecting surfaces 311 and 312 which are vertically deflected in a plane and emitted from the end surface on the second deflecting plate 40 side. The pentaprism 31 belongs to a second type element group in which the entrance surfaces of the reflecting surfaces 311 and 312 are parallel to each other. The pentaprism 31 is arranged so that the direction of the incident surface coincides with the long side direction of the finder field within a plane perpendicular to the optical axis.

The roof mirror 21 via the objective lens system 60.
The light from the subject incident on is reflected on the reflecting surface 21 of the roof mirror.
The light is reflected in order by 1 and 212, is inverted vertically and horizontally, is transmitted through the first polarizing plate, and forms an image on the image plane that coincides with the liquid crystal plate 50. The light flux that has passed through the liquid crystal plate 50 receives the penta prism 31.
The reflective surfaces 312 and 311 of the second polarizing plate 4 are reflected in this order.
0 is transmitted and enters the observer's eye through the eyepiece lens system 70. Since the light flux is reflected by the roof mirror so that the upper half and the lower half are interchanged with the ridgeline as a boundary,
The center line of the light flux is not displaced in the z-axis direction, and the size of the finder in the z-axis direction can be minimized.

In the structure shown in FIG. 1, some elements of the erecting optical system are provided between the liquid crystal plate 50 and the second polarizing plate 40, and dust adheres to the eyepiece system 70 side of the liquid crystal plate. In this case, since the only visible surface is the end surface of the pentaprism 31 on the incident side, the total length of the finder does not need to be increased as compared with the conventional example in which the second polarizing plate is provided close to the liquid crystal plate 50. The number of surfaces visually recognized when dust adheres in the vicinity of the image plane can be reduced by one.

Next, the structure and operation of the liquid crystal plate 50 arranged so as to coincide with the image plane of the objective lens system 60, and the influence caused when the polarization state is changed by the erecting optical system will be described.

The liquid crystal plate 50 is composed of two transparent glass plates in which liquid crystal is sealed. At positions where a pattern is displayed, the liquid crystal plates 50 face each other with the liquid crystal sandwiched therebetween. A transparent electrode (segment) that matches the shape of the pattern is provided. In this example, a twisted nematic type (TN type) element is used as the liquid crystal plate. In the TN type liquid crystal plate, in the part without electrodes,
Liquid crystal molecules are oriented parallel to the electrodes and twisted by 90 ° from the electrode on one side to the electrode on the other side, and have an optical rotatory property of rotating the oscillation direction of the transmitted electric field vector of linearly polarized light by 90 °. On the other hand, in the part sandwiched between the electrodes, when the on-voltage is applied, the liquid crystal molecules stand in a direction perpendicular to the electrodes and lose the optical rotatory power. Although it operates in the same manner as the part without electrodes, the alignment is slightly disturbed by the application of the off voltage.

Therefore, the first and second polarizing plates 10, 40
When the transmission axes of are orthogonal to each other, the luminous flux is transmitted through the segment portion to which the voltage is not applied, and the luminous flux is blocked at the segment portion to which the voltage is applied, so that a black segment pattern can be seen in the viewfinder field. In this specification, a segment in which a voltage is applied and the light flux is blocked is an on-segment,
A segment through which a light beam is transmitted without applying a voltage is defined as an off segment. In addition, when the transmission axes of the polarizing plates are set to be parallel to each other, this logic is reversed.

FIG. 3 shows a display example when the panoramic mode of the liquid crystal plate 50 is selected. When the panorama mode is selected, the light blocking plate blocks part of the shooting range, and thus the light reaching the film surface is partly blocked. In the finder system of the present invention, a part of the field of view of the finder system becomes opaque so that the photographing range on the film surface can be confirmed when the panorama mode is used. In this example, when the panorama mode is selected, the segments 54A and 54B of the liquid crystal plate 50 are turned on to make the portions opaque, and the size of the viewfinder field seen by the photographer is changed.

Further, the liquid crystal plate 50 has three sets of autofocus frames 51A, 51B, 52A, 52B and 53.
A and 53B are provided. An optimum set of these frames is selectively displayed according to the change of the focal length of the taking lens. When the segment of the liquid crystal plate corresponding to each frame is turned on, that portion in the viewfinder becomes opaque and the photographer can see the frame. When the focal length of the taking lens is short, the innermost pair of autofocus frames 51A and 51B are displayed. Intermediate frames 52A and 52B are displayed at the intermediate focal length, and outermost frames 53A and 53B are displayed at the long focal length.

The above description is based on the assumption that the light flux incident on the liquid crystal plate 50 and the light flux transmitted through the liquid crystal plate 50 and incident on the second polarizing plate 40 are ideal linearly polarized light. When ideal linearly polarized light is incident, the disturbance of the polarization due to slight disturbance of the light distribution in the off-segment portion is relatively small, and the influence on the visibility is small.

However, the first and second polarizing plates 10 and 4
When the reflection optical element of the erecting optical system provided between 0 changes the polarization state, for example, when it has the characteristic of converting linearly polarized light into elliptically polarized light, the influence of slight disturbance of the orientation of the off-segment part is It becomes relatively large. Then, when the reflected light of the elliptically polarized light passes through the off-segment of the liquid crystal plate 50 and enters the second polarizing plate, a part of the light flux that would otherwise be transmitted unless the polarization state changes is blocked.

When the light beam to be shielded is not completely shielded and partially penetrates, that is, in the on-segment portion, the dark portion displayed as a pattern becomes slightly brighter, but the influence on the visibility is small. On the contrary, when the light flux of the part to be transmitted is partly blocked, that is, in the off-segment part, the pattern image appears thin at the position that should be transparent, which has a relatively large effect on the visibility. . Therefore, the light amount attenuation due to the off segment needs to be minimized in order to improve the visibility of the finder.

Generally, when linearly polarized light is reflected, a phase difference occurs between the P polarized light component and the S polarized light component of the linearly polarized light. The magnitude of the phase difference is determined by the azimuth angle (the angle between the normal of the incident surface and the vibrating surface of the linearly polarized light), the characteristics of the reflecting surface, and so on. When it is arranged between the second polarizing plates, it is necessary to determine the above-mentioned direction and characteristics so that the light amount attenuation due to the off-segment is minimized.

In the finder optical system shown in FIG. 1, a pentaprism 31 belonging to a second type element group in which two reflecting surfaces are parallel to each other is arranged between the first and second deflecting plates. In such an optical system, as shown in FIG. 4, the first polarizing plate 10 is arranged such that its transmission axis is 0 ° with respect to the direction of the incident surface of the pentagonal prism 31 (x-axis direction). The second polarizing plate 40 is arranged so that its transmission axis is orthogonal to the transmission axis of the first polarizing plate. In this specification, the direction of the transmission axis of the polarizing plate is the longitudinal direction of the finder field in the plane perpendicular to the optical axis, that is, the direction of the incident surface of the reflection surface of the pentaprism 31 (x-axis). direction)
Display as an angle to.

When the transmission axis of the polarizing plate is set to 0 ° and 90 ° with respect to the incident surface of the pentaprism as shown in FIG. 4, it depends on the structure of the reflecting surface of the pentaprism 31. The directionality of linearly polarized light does not change. Therefore, the linearly polarized light that has passed through the liquid crystal plate 50 can be reflected as the linearly polarized light toward the second polarizing plate 40 without rotating the light as it is, and the attenuation of the light amount in the off-segment portion can be suppressed.

Since the directions of the transmission axes of the first and second polarizing plates have a meaning as a combination thereof, the directions of the transmission axes of the first and second polarizing plates are interchanged. In that case, the characteristics do not change. That is, in the example of FIG. 4, the transmission axis of the first polarizing plate may be 90 ° with respect to the direction of the incident surface of the pentagonal prism, and the transmission axis of the second polarizing plate may be 0 °.

FIG. 5 is an explanatory view showing another example of the first and second polarizing plates. In this example, the transmission axis of the first polarizing plate 10 is 45 ° with respect to the incident surface of the pentaprism 31, and the transmission axis of the second polarizing plate is −45 °.

In the viewfinder of the camera, the shape of the polarizing plate in the plane perpendicular to the optical axis is rectangular, so that one of the first and second polarizing plates is parallel to the long side direction in order to make the transmission axes orthogonal to each other. When the other is made parallel to the short side direction, it is necessary to prepare these as separate elements. On the other hand, when one transmission axis is set to + 45 ° with respect to the long side direction and the other transmission axis is set to −45 ° with respect to the long side direction, the polarizing plates having the same configuration are reversed by inverting the front and back. Can be shared. If parts can be shared, manufacturing and management will be easier. When the transmission axes of the first and second polarizing plates are set to be parallel, the polarizing plates having the same configuration can be shared regardless of the directions of the transmission axes.

However, when the linearly polarized light incident on the pentaprism makes an angle other than 0 ° and 90 ° with respect to the direction of the incident surface, a phase difference occurs at the time of reflection depending on the structure of the reflecting surface. Therefore, in the case of the arrangement of FIG. 5 and the arrangement of ± 45 °, it is necessary to consider the configuration of the reflecting surface.

Next, the structures of the reflecting surfaces of the roof mirror 21 and the pentaprism 31 will be described with reference to FIGS. 6 and 7.

FIG. 6 shows a structure of a reflecting surface for reflecting the light flux of the roof mirror 21 on the surface. The roof mirror 21 is formed by coating a plastic substrate with an aluminum layer and covering the aluminum layer with a reflection increasing film. In the example of FIG. 6, the light flux incident from the outside of the mirror passes through the reflection increasing film, is reflected by the aluminum layer, and returns to the air through the reflection increasing film again.

The reflection-increasing film is formed by stacking a plurality of dielectric layers, and can increase the reflectance of aluminum itself of 85% to about 95%. Depending on the configuration of the reflection increasing film, the phase difference generated when reflecting the polarized light flux differs.

Table 1 shows a concrete example of the structure of the surface reflection mirror shown in FIG. Examples 1 to 4 are configured by providing an aluminum layer with a dielectric reflection increasing film, and Example 5 is configured by providing an aluminum layer alone. The symbol nd in the table indicates the optical film thickness, which is the product of the refractive index n and the thickness d of the dielectric layer, and its unit is μm. For example, the combination of Example 1 uses a silicon dioxide layer (nd =
74.75), a titanium dioxide layer (nd = 48.25), and a silicon dioxide layer (nd = 177.00) are stacked in this order.

[0057]

[Table 1] Material name nd Material name nd Example 1 Al-Example 3 Al-SiO2 74.75 Al2O3 75.50 TiO2 48.25 MgF2 152.50 SiO2 177.00 Example 4 Al-Example 2 Al-SiO2 89.97 SiO2 25.25 TiO2 89.97 TiO2 93.50 Al2 O3 89.97 SiO2 148.00 Example 5 Al-

FIG. 7 shows the structure of a reflecting surface for internally reflecting the light flux of the pentaprism 31. The reflecting surface is formed by coating the outer surface of the glass prism with a reflection increasing film and forming an aluminum layer on the film.
In the example of FIG. 7, the light flux that has passed through the glass once exits the prism, is reflected by the aluminum layer through the reflection increasing film, and returns to the glass through the reflection increasing film again.

Table 2 shows a concrete example of the structure of the surface reflection mirror shown in FIG. Examples 6 to 9 are configured by providing a dielectric reflection increasing film between the glass that constitutes the prism and the aluminum layer that is the reflecting film, and Example 10 is configured by providing the aluminum layer alone. There is.

[0060]

Table 2 Substance nd Substance nd Example 6 Al-Example 8 Al-MgF2 47.53 MgF2 208.75 TiO2 23.25 TiO2 40.75 Glass-MgF2 100.75 Example 7 Al-TiO2 269.25 MgF2 134.50 Al2O3 271.50 TiO2 96.35 Glass-Glass-Example 9 Al-MgF2 135.00 TiO2 135.00 Glass Example 10 Al-Glass-

FIG. 8 is a spectral distribution graph showing the relationship between the structure of each reflecting surface shown in Table 2 and the phase difference generated by this structure over a visible wavelength range of 400 to 700 nm. Here, there is shown the phase difference that occurs when linearly polarized light of 45 ° is reflected in a plane perpendicular to the optical axis with respect to one incident surface of the pentaprism. Reference symbols B, G, and R indicate the hues of light in the respective wavelength ranges, and indicate the respective color components of blue, green, and red. The five polygonal lines in the graph show the characteristics of the five combination examples shown in Table 2.

As shown in FIG. 8, ± 45 when the reflecting surface of the pentaprism has the structure shown in Example 7 of Table 2.
Even when a linearly polarized light of 0 ° is made incident, the phase difference with respect to the polarized light can be suppressed to a negligible level in the visible wavelength range. Therefore, if a pentaprism having a reflecting surface of this film structure is used, even if a polarizing plate having a transmission axis of ± 45 ° is used, the polarization state is not changed by the pentaprism, and the attenuation of the light quantity in the off-segment part is suppressed. .

FIG. 9 shows a second optical element shown in FIG.
2 shows a second embodiment of the finder optical system arranged according to the arrangement example of FIG. The difference from the first embodiment shown in FIG. 1 is that the first polarizing plate 10 is arranged close to the objective lens system 60, and the roof mirror 21 is provided between the first polarizing plate 10 and the liquid crystal plate 50. It is the point that is arranged.

According to the arrangement of FIG. 9, the two elements of the erecting optical system are located between the first polarizing plate 10 and the liquid crystal plate 50, and between the liquid crystal plate 50 and the second polarizing plate 40. The surfaces located in the range where the diopter is matched near the liquid crystal plate 50 are only the reflecting surface of the roof mirror 21 and the incident end surface of the pentaprism 31. Although the roof mirror 21 has two reflecting surfaces, the total area is smaller than the total area of the end faces on the incident side and the exit side of the polarizing plate, so that two polarizing plates are conventionally arranged near the liquid crystal plate. Compared to the example, without increasing the total length of the viewfinder, the pentaprism side reduces the number of faces located in the range where the diopter matches the observer, and the roof mirror side reduces the number of faces that fall within the range where the diopter matches. The area can be reduced.

In the embodiment of FIG. 9, the first liquid crystal plate 1
By using 0 as a cover, the first liquid crystal plate 10
The optical element between the eyepiece lens system 70 and the eyepiece lens system 70 can be shielded from the outside world to prevent dust from entering the space.

When the objective lens system 60 is fixedly provided, the objective lens system 60 can be used as a cover, and in that case, the first embodiment shown in FIG. 1 can also be applied. is there. However, when the objective lens system 60 moves due to zooming or the like, the objective lens system 60 itself cannot be used as a cover, and in the example of FIG. Since it cannot be used as a cover because it is placed at a suitable position,
In the above example, it is necessary to provide a cover separately. On the other hand, in the embodiment of FIG. 9, it is possible to prevent the intrusion of dust by using the existing element without providing a separate cover.

In the second embodiment, not only the penta prism 31 but also the roof mirror 21 is arranged between the first polarizing plate 10 and the second polarizing plate, so that the change in polarization by the roof mirror 21 is set to be suppressed. There is a need. As described above, the Dach mirror belongs to the first type element group in which the incident surfaces of the two reflecting surfaces are neither parallel nor orthogonal to each other.

When the roof mirror 21 is arranged between the polarizing plates, the direction of the transmission axis of the first polarizing plate 10 is 0 ° or 9 °.
In the case of 0 °, that is, when the transmission axis of the first polarizing plate 10 is parallel or perpendicular to the ridgeline A of the roof mirror in the plane perpendicular to the optical axis, the phase difference caused by the roof mirror may be minimal. It was confirmed by the experiments of the inventors.

Since the ridgeline A of the roof mirror 21 is included in the xy plane parallel to the incident surface of the reflection surface of the pentaprism 31, the transmission axis of the first polarizing plate is 0 ° and 90 ° with respect to the ridgeline.
When set to, 0 ° and 90 ° are also formed in the plane perpendicular to the optical axis with respect to the incident surface of the reflecting surface of the pentaprism. Therefore, in the second embodiment shown in FIG.
The transmission axes of the respective polarizing plates are arranged so as to be 0 ° and 90 ° with respect to the x axis in a plane perpendicular to the optical axis as shown in FIG. In other arrangements, for example, the arrangement of ± 45 ° shown in FIG. 5, the phase difference caused by the roof mirror becomes large, and the light amount attenuation in the off-segment becomes large.

FIGS. 10 (A) and (B) show how the linearly polarized light reflected by the roof mirror changes with the Poincare sphere when the transmission axis is 0 ° and when the transmission axis is 45 °. FIG. In the following description, the angle of the linearly polarized light is defined as the vibration direction of the electrolytic vector of the linearly polarized light in the plane perpendicular to the optical axis and the long side direction (x
It will be expressed as an angle with the (axial direction). For example,
Linearly polarized light whose electric field vector oscillates in a direction parallel to the long side direction is defined as 0 ° linearly polarized light, and linearly polarized light oscillating in a direction perpendicular to this is defined as 90 ° linearly polarized light.

The Equator of the Poincare sphere shown in FIGS. 10A and 10B is linearly polarized light, both polarities are circularly polarized light, and the remaining regions are elliptically polarized light. A point P0 indicates a linearly polarized light of 0 °, and a point P45 indicates a linearly polarized light of + 45 °. The linearly polarized light that has passed through the first polarizing plate 10 and is incident is reflected by one of the reflecting surfaces 211 and then reflected by the other reflecting surface 212 and enters the liquid crystal plate 50.

The change in polarization due to the reflection on the reflecting surface 211 is represented as rotation about the axis Ax1 of the equatorial plane including the points P0 and P45. By this rotation, the point P located on the equatorial plane
0 and P45 are points P on the surface after rotation indicated by hatching
Move to 0'and P45 'respectively. The reflected light from the reflecting surface 211 is elliptically polarized light indicated by these points P0 'and P45'.

The direction of the axis Ax1 is determined based on the azimuth angle of the first reflecting surface 211 of the roof mirror 21 with respect to the incident light beam, and the rotation angle of the equatorial plane is when the light beam is reflected by the first reflecting surface 211. It is determined by the resulting phase difference.

The change in the polarization due to the reflection on the second reflecting surface 212 of the roof mirror 21 is caused by the axis Ax2 of the plane including the points P0 'and P45' indicating the polarization state of the light beam after being reflected by the first reflecting surface.
Expressed as a rotation around. By this rotation, the point P0 'before the movement moves to P0 ", and P45' moves to P45".

The direction of the axis Ax2 is determined based on the azimuth angle of the second reflecting surface 212 with respect to the light flux reflected by the first reflecting surface 211, and the plane rotation angle is the light flux of the second reflecting surface 2
It is determined by the phase difference that occurs when the light is reflected at 12.
The generation amount of the phase difference differs depending on the structure of the reflecting surface, but here, the same structure, for example, the film structure shown in Example 1 of Table 1 is adopted, and the generation amount of the phase difference is the same. .

It can be seen from FIG. 10 that the point P0 "showing the polarization at the time of emission of the light beam incident as 0 ° linearly polarized light is very close to the point P0 showing the polarization at the time of incidence. °
When the light is incident as linearly polarized light, it means that there is little change in polarization, that is, there is little influence on the liquid crystal display. On the other hand, the point P45 "indicating the polarization at the time of emission of the light beam incident as the 45 ° linearly polarized light is far from the point P45 indicating the polarization at the time of incidence.
This means that when the light beam enters as 45 ° linearly polarized light, the change in polarization is large, that is, the influence on the liquid crystal display is large.

The 90 ° and −45 ° linearly polarized lights are at the same positions as the 0 ° and 45 ° linearly polarized lights on the Poincare sphere, respectively, and the 0 ° and 45 ° linearly polarized lights are reflected by the Dach mirror, respectively. Similarly, the polarization state changes. In the above description, the first surface 21 of the roof mirror 21
Although only the light beam reflected by the first reflection surface and then by the second reflection surface is described, this description is similarly applied to the light beam reflected by the first reflection surface after being reflected by the second reflection surface. .

FIG. 11 shows a finder of the third embodiment based on the third arrangement example shown in FIG. As the erecting optical system, the roof mirror 21 and the pentaprism 31 are used as in the first and second embodiments. Figure 9
The difference from the second embodiment shown in FIG.
Is provided in the vicinity of the liquid crystal plate 10, and the pentaprism 31 is arranged between the second polarizing plate 40 and the eyepiece lens system 70.

On the objective lens system 60 side of the liquid crystal plate 50, only the reflecting surface of the roof mirror 21 is located in the range where the diopter is matched. Although the roof mirror 21 has two reflecting surfaces, the total area is smaller than the total area of the end faces of the polarizing plate on the incident side and the emitting side.
Compared with the conventional example which is arranged near 0, the area of the surface that falls within the range where the diopter matches can be reduced.

Also in the example of FIG. 11, by using the first liquid crystal plate 10 as a cover, even when the objective lens system 60 moves for zooming or the like, a separate cover is not provided. It is possible to prevent dust from entering the space between the first liquid crystal plate 10 and the eyepiece lens system 70.

In this third embodiment, the roof mirror 21
Is provided between the first and second polarizing plates, the polarizing plates 10 and 40 are in the same plane as the second embodiment, the transmission axis of which is perpendicular to the optical axis as shown in FIG. Are arranged at 0 ° and 90 ° with respect to the x-axis. With this arrangement, light amount attenuation in the off-segment portion can be minimized.

FIG. 12 shows a finder system according to the fourth embodiment in which optical elements are arranged according to the first arrangement example shown in FIG. In the fourth embodiment, a double Porro prism 32 is used as an erecting optical system, and this is arranged between the liquid crystal plate 50 and the second polarizing plate.

As shown in FIG. 13, the double Porro prism 32 is formed by combining two sets of two right-angled prisms arranged such that the incident surfaces of the reflecting surfaces 401 and 402 of each prism are orthogonal to each other.

In the configuration of FIG. 13, the light beam incident on the first prism is internally reflected by the reflecting surface 401 and is deflected by 90 ° toward the second prism. The light beam that has entered the second prism is internally reflected by the reflecting surface 402, is deflected by 90 °, and exits from the second prism. By these two reflections, the direction of the image formed by this light flux is rotated by 90 ° in the plane perpendicular to the optical axis Ax. Therefore, by providing two sets of reflecting surfaces having such a relationship,
It is possible to rotate the direction of the image by 180 °, that is, to flip the image vertically and horizontally.

According to the structure shown in FIG. 12, the double Porro prism 32 constituting the erecting optical system is provided between the liquid crystal plate 50 and the second polarizing plate 40, and the liquid crystal plate 50 is closer to the eyepiece lens system 70. Since only the end surface of the double Porro prism 32 on the incident side is visible when dust adheres to it, compared with the conventional example in which the second polarizing plate is provided close to the liquid crystal plate 50, It is possible to reduce the number of surfaces visually recognized when dust adheres in the vicinity of the image plane by one without increasing the total length.

The double Porro prism 32 is a third type reflective optical element in which the incident surfaces of a pair of reflective surfaces are orthogonal to each other. In the reflective optical element of the third type, the phase difference generated on one reflection surface is canceled by the other reflection surface, so that if the amount of the phase difference generated on both reflection surfaces is the same, that is, the same. With the above coating configuration, regardless of the configuration of the reflecting surface, the polarized light can be reflected as a result without giving a phase difference.

Therefore, in the third embodiment, the direction of the transmission axis of the polarizing plate may be either 0 °, 90 ° shown in FIG. 4 or ± 45 ° shown in FIG. 5, and further, the first, As long as the transmission axes of the second polarizing plate are orthogonal to each other, they can be used regardless of their angles.

FIG. 14 shows a finder system according to the fifth embodiment in which optical elements are arranged according to the second arrangement example shown in FIG. In this example, the first polarizing plate 1
0 and the liquid crystal plate 50, a first Porro prism 23 having two reflecting surfaces forming a part of the double Porro prism is arranged as a front optical element, and the liquid crystal plate 50 and the second polarizing plate 4 are arranged.
A second Porro prism 33, which constitutes the remaining portion of the double Porro prism, is arranged as a rear element between the second Porro prism and the zero.

The optical functions of the first and second Porro prisms 23 and 33 are the same as those of the double Porro prism 32 shown in the fourth embodiment. Therefore, also in the fifth embodiment, if the transmission axes of the first and second polarizing plates are 90 ° to each other, they can be used in either direction.

According to the configuration of FIG. 14, the two elements of the erecting optical system are located between the first polarizing plate 10 and the liquid crystal plate 50 and between the liquid crystal plate 50 and the second polarizing plate 40. The surface located in the range where the diopter matches near the liquid crystal plate 50 is the end surface of the first Porro prism 23 on the exit side and the second Porro prism 3.
3 is only the end surface on the incident side. Therefore, as compared with the conventional example in which two polarizing plates are arranged in the vicinity of the liquid crystal plate, it is possible to reduce the number of surfaces located in the range where the diopter of the observer is matched by two without increasing the total length of the finder. You can

[0091]

As described above, according to the present invention, at least one of the polarizing plates is separated from the liquid crystal plate, and at least a part of the erecting optical system is formed between the polarizing plate and the liquid crystal plate. By providing it, it is possible to reduce the number of surfaces arranged near the image plane of the objective lens diameter that matches the diopter of the observer without increasing the total length of the finder, and the dust that has adhered can be seen in the viewfinder field of view. The possibility of being visible can be reduced.

Further, by appropriately setting the direction of the polarizing plate transmission axis according to the type of the reflection optical element of the erecting optical system used, the attenuation of the light quantity in the off-segment portion of the liquid crystal plate is suppressed, and the visual field of the viewfinder is visually recognized. Can maintain sex.

[Brief description of drawings]

FIG. 1 is a perspective view showing an arrangement of optical elements of a finder system according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing a light ray incident on a roof mirror in the finder system of FIG.

FIG. 3 is an explanatory diagram showing an example of a liquid crystal display in the finder system of FIG.

4 is an explanatory diagram showing an example of directions of transmission axes of first and second polarizing plates in the finder system of FIG. 1. FIG.

5 is an explanatory diagram showing another example of the transmission axis directions of the first and second polarizing plates in the finder system of FIG. 1. FIG.

6 is a cross-sectional view showing a configuration of a reflection surface of surface reflection of an element of an erecting optical system used in the finder system of FIG.

7 is a cross-sectional view showing a configuration of a reflection surface of internal reflection of an element of an erecting optical system used in the finder system of FIG.

8 is a graph showing a phase difference generated in linearly polarized light when reflected by the reflecting surface shown in FIG. 7, showing distributions in the visible region for five different coatings.

FIG. 9 is a perspective view showing an arrangement of optical elements of a finder system according to a second embodiment of the present invention.

FIG. 10 is an explanatory diagram of a Poincare sphere showing a change in polarization of light reflected by a roof mirror.

FIG. 11 is a perspective view showing an arrangement of optical elements of a finder system according to a third embodiment of the present invention.

FIG. 12 is a perspective view showing an arrangement of optical elements of a finder optical system according to a fourth embodiment of the present invention.

FIG. 13 is an explanatory diagram showing light incident on a pair of reflecting surfaces whose incident surfaces are orthogonal to each other.

FIG. 14 is a perspective view showing an arrangement of optical elements of a finder system according to a fifth embodiment of the present invention.

FIG. 15 is an explanatory diagram showing a first arrangement of respective elements of the liquid crystal display optical system and the erecting optical system of the present invention.

FIG. 16 is an explanatory diagram showing a second arrangement of each element of the liquid crystal display optical system and the erecting optical system of the present invention.

FIG. 17 is an explanatory diagram showing a third arrangement of each element of the liquid crystal display optical system and the erecting optical system of the present invention.

[Explanation of symbols]

 10 First Polarizing Plate 20 Front Reflecting Optical Element 21 Dach Mirror 30 Rear Reflecting Optical Element 31 Penta Prism 32 Double Porro Prism 40 Second Polarizing Plate 50 Liquid Crystal Plate 60 Objective Lens System 70 Eyepiece Lens System

Claims (31)

[Claims] 1. An objective lens system, an erecting optical system, and an eyepiece lens system are arranged in this order from the object side, and a first lens and a second lens are provided between the objective lens system and the eyepiece lens system. A finder optical system in which a liquid crystal display optical system including a polarizing plate and a liquid crystal plate disposed between the polarizing plate and the second polarizing plate is provided in the finder optical system. A finder optical system characterized in that at least a part of the element is provided. 2. The reflective optical element arranged between the liquid crystal plate and the second polarizing plate has two reflecting surfaces whose incident surfaces are parallel to each other, and the transmission axis of the first polarizing plate is The viewfinder optical system according to claim 1, wherein the viewfinder optical system forms 0 ° or 90 ° with respect to the direction of the incident surface in a plane perpendicular to the optical axis. 3. The reflective optical element disposed between the liquid crystal plate and the second polarizing plate has two reflecting surfaces whose incident surfaces are parallel to each other, and the transmission axis of the first polarizing plate is + 45 ° with respect to the direction of the incident surface in a plane perpendicular to the optical axis,
Alternatively, the viewfinder optical system according to claim 1, wherein the viewfinder optical system has an angle of -45 °, and each reflection surface of the reflection optical element is provided with a coat for suppressing a phase difference generated at the time of reflection. 4. The reflection optical element arranged between the liquid crystal plate and the second polarizing plate has incident surfaces which are orthogonal to each other.
The finder optical system according to claim 1, comprising at least one pair of two reflecting surfaces. 5. The reflection optical element arranged between the liquid crystal plate and the second polarizing plate has incident surfaces which are orthogonal to each other.
The finder optical system according to claim 4, comprising two sets of one reflecting surface. 6. The transmission axis of the first polarizing plate is 0 ° or 90 ° with respect to one of the incident surfaces in a plane perpendicular to the optical axis. Viewfinder optical system. 7. The transmission axis of the first polarizing plate is +45 relative to one direction of the incident surface in a plane perpendicular to the optical axis.
5. The angle is −45 ° or −45 °.
The finder optical system described in. 8. The erecting optical system is composed of first and second reflective optical elements, and at least the second reflective optical element is arranged between a liquid crystal plate and the second polarizing plate. The finder optical system according to claim 1, wherein: 9. The finder optical system according to claim 8, wherein the first reflective optical element is arranged between the objective lens system and the first polarizing plate. 10. The first reflective optical element is a roof mirror, the second reflective optical element is an element having two reflective surfaces whose incident surfaces are parallel to each other, and the transmission axis of the first polarizing plate is The finder optical system according to claim 9, wherein the angle is 0 ° or 90 ° with respect to the direction of the incident surface in a plane perpendicular to the optical axis. 11. The first reflective optical element is a roof mirror, the second reflective optical element is an element having two reflecting surfaces whose incident surfaces are parallel to each other, and the transmission axis of the first polarizing plate is , + 45 ° or −45 ° with respect to the direction of the incident surface in a plane perpendicular to the optical axis, and each reflection surface of the second reflective optical element is provided with a coat for suppressing a phase difference generated during reflection. It is provided, It is characterized by the above-mentioned.
The finder optical system described in. 12. The finder optical system according to claim 8, wherein the first reflective optical element is arranged between the first polarizing plate and the liquid crystal plate. 13. The first reflective optical element is a roof mirror, and the second reflective optical element has two reflective surfaces parallel to a ridgeline of the roof mirror in a plane in which a direction of an incident surface is perpendicular to an optical axis. The transmission axis of the first polarizing plate is 0 ° with respect to the direction of the ridge in a plane perpendicular to the optical axis,
Alternatively, the viewfinder optical system according to claim 12, wherein the viewfinder optical system forms 90 °. 14. The finder optical system according to claim 12, wherein each of the first and second reflective optical elements is an element having two reflective surfaces whose incident surfaces are orthogonal to each other. 15. The transmission axis of the second polarizing plate is orthogonal to the transmission axis of the first polarizing plate in a plane perpendicular to the optical axis. Viewfinder optical system described. 16. An objective lens system, an erecting optical system, and an eyepiece lens system are arranged in this order from the object side, and a first lens and a second lens are provided between the objective lens system and the eyepiece lens system.
In a finder optical system in which a liquid crystal display optical system including a polarizing plate and a liquid crystal plate disposed between the polarizing plates is arranged, the erecting optical system is formed between the first polarizing plate and the second polarizing plate. A finder optical system in which a roof mirror is disposed, and a transmission axis of the first polarizing plate forms 0 ° or 90 ° with respect to a ridge line direction of the roof mirror in a plane perpendicular to an optical axis. 17. The viewfinder optical system according to claim 16, wherein the roof mirror is arranged between the first polarizing plate and the liquid crystal plate. 18. Between the liquid crystal plate and the second polarizing plate,
18. The viewfinder according to claim 17, wherein a reflection optical element having two reflection surfaces, each of which has an incident surface in a plane perpendicular to the optical axis and is parallel to the ridgeline direction of the roof mirror, is arranged. Optical system. 19. The transmission axis of the second polarizing plate is orthogonal to the transmission axis of the first polarizing plate in a plane perpendicular to the optical axis. Viewfinder optical system described. 20. An objective lens system, an erecting optical system, and an eyepiece lens system are arranged in this order from the object side, and first and second lenses are provided between the objective lens system and the eyepiece lens system.
A finder optical system in which a liquid crystal display optical system including a polarizing plate and a liquid crystal plate disposed therebetween is disposed, and a part of the erecting optical system is provided between the first polarizing plate and the second polarizing plate. The finder optical system is characterized in that an element having two reflecting surfaces whose incident surfaces are parallel to each other is provided as the reflecting optical element constituting the. 21. The transmission axis of the first polarizing plate is 0 ° or 90 ° with respect to the direction of the incident surface in a plane perpendicular to the optical axis. Viewfinder optical system. 22. The reflective optical element having two reflecting surfaces whose incident surfaces are parallel to each other, is arranged between the liquid crystal plate and the second polarizing plate. Viewfinder optical system. 23. A roof mirror having a ridge line parallel to the direction of the incident surface in a plane perpendicular to the optical axis is arranged between the first polarizing plate and the liquid crystal plate. Two
The finder optical system described in 2. 24. The transmission axis of the first polarizing plate forms + 45 ° or −45 ° with respect to the direction of the incident surface in a plane perpendicular to the optical axis, and each of the reflecting surfaces has a reflection axis at the time of reflection. The viewfinder optical system according to claim 20, wherein a coat that does not cause a phase difference is applied. 25. The reflective optical element having two reflecting surfaces whose incident surfaces are parallel to each other, is arranged between the liquid crystal plate and the second polarizing plate. Viewfinder optical system. 26. The viewfinder optical system according to claim 25, wherein a roof mirror is arranged between the objective lens system and the first polarizing plate. 27. The transmission axis of the second polarizing plate is orthogonal to the transmission axis of the first polarizing plate in a plane perpendicular to the optical axis. Viewfinder optical system described. 28. An objective lens system, an erecting optical system, and an eyepiece lens system are arranged in this order from the object side, and first and second lenses are provided between the objective lens system and the eyepiece lens system.
In a finder optical system in which a liquid crystal display optical system including a polarizing plate and a liquid crystal plate disposed between the polarizing plates is disposed, the erecting optical system is incident between the first polarizing plate and the second polarizing plate. Two reflective surfaces whose surfaces are orthogonal to each other
A finder optical system characterized in that a reflective optical element provided as a set is provided. 29. The viewfinder optical system according to claim 28, wherein the erecting optical system is disposed between the liquid crystal plate and the second polarizing plate. 30. The erecting optical system comprises first and second reflective optical elements each having two sets of two reflective surfaces whose entrance surfaces are orthogonal to each other, and the first reflective optical element is the first reflective optical element. 29. The one polarizing plate is disposed between the liquid crystal plate and the second reflective optical element is disposed between the liquid crystal plate and the second polarizing plate. Viewfinder optical system. 31. The transmission axis of the second polarizing plate is orthogonal to the transmission axis of the first polarizing plate in a plane perpendicular to the optical axis. Viewfinder optical system described.