JP2003149593A - Display optical system, image display unit, and optical system and device for imaging - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a display optical system and an imaging optical system have a wide angle of view by increasing the power of the optical system to constitute the display optical system or imaging optical system by using a small-sized image display element. SOLUTION: The display optical system which guides light from an original picture 3 to the eye of an observer or a projected surface is provided with 1st, 2nd, and 3rd surfaces as optical surfaces and has a 1st surface A which has at least reflecting operation and a 2nd surface C which reflects a light beam reflected by the 1st surface toward the 1st surface again, and a center view angle main light beam which is made incident on the 1st surface again is reflected to travel to the opposite side from the last time about the normal of the surface at its hit point. The imaging optical system which guides light from a subject to an imaging surface has a 1st surface which has at least operating and a 2nd surface which reflects the light beam reflected by the 1st surface to the 1st surface again, and the center field angle main light beam which is made incident on the 1st surface again is reflected to travel to the opposite side from the last time about the normal of the surface at its hit point.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display optical system suitable for an image display device such as a head mounted display or a projector for enlarging and displaying an original image displayed on an image display device or the like, and an imaging optical system suitable for the image pickup device. It is a thing.

[0002]

2. Description of the Related Art A head-mounted image display device (head-mounted display) which uses an image display device such as a CRT or LCD and enlarges an image displayed on the display device through an optical system is well known. Has been.

In the image display device such as the head mounted display, since these devices are mounted on the head, it is particularly required to reduce the size and weight of the entire device. Further, in consideration of weight balance, appearance and the like, it is preferable that the thickness is thin in the visual axis direction of the observer. Further, in order to give a powerful effect to the displayed enlarged image, a magnified image as large as possible is desired.

FIG. 15 shows an image display device using a conventional coaxial concave mirror. In the device, the display element 101
The light flux from the image displayed on the half mirror 102 is reflected by the half mirror 102 to enter the concave mirror 103, and the light flux reflected by the concave mirror 103 is guided to the eye E of the observer through the half mirror 102. The image displayed on the display element 101 is formed as a virtual image enlarged by the concave mirror 103. Thereby, the observer can observe the enlarged virtual image of the image displayed on the display element 101.

Further, for example, JP-A-7-333551, JP-A-8-50256, and JP-A-8-1603.
No. 40 and Japanese Patent Laid-Open No. 8-179238, an LCD as an image display element for displaying an image is disclosed.
There has been proposed an image display device that uses a (liquid crystal) and a thin prism as an observation optical system to reduce the thickness of the entire device.

FIG. 16 shows an image display device proposed in Japanese Patent Laid-Open No. 7-333551. In this device, the light emitted from the LCD 111 is incident on the incident surface 113 of the small decentering prism 112. Then, the light flux is folded between the internal total reflection surface 114 having a curvature formed on the prism 112 and the reflection surface 115, and then emitted from the decentered prism 112 through the surface 114 and guided to the eye E of the observer. As a result, the display element (LC
D) A virtual image of the image displayed on 111 is formed, and an observer observes this virtual image.

The reflecting surface 115 of the decentering prism 112 is composed of a decentered free-form surface composed of a decentered non-rotationally symmetric surface (a surface having a different optical power depending on the azimuth angle, a so-called free-form surface).

The type of optical system shown in FIG. 16 is characterized in that it is easier to make the entire apparatus thinner and to widen the angle of view of the observation field, as compared with the type using the conventional coaxial concave mirror shown in FIG. Have

[0009]

In recent years, LCDs, which are display elements for displaying images, have been made finer, and LCDs having the same number of pixels as the conventional ones but smaller in size than the conventional ones.
Etc. have been developed. Using such a downsized image display element is advantageous for downsizing the device,
In order to achieve the same angle of view as the conventional one, it is necessary to increase the magnification of the optical system.

In view of such a situation, Japanese Patent Laid-Open No. 10-1
Japanese Patent Laid-Open No. 53748 proposes an optical system in which a decentered prism and a relay lens system are combined and an intermediate image is once formed by the relay lens system and then an image displayed on a display element is guided to an observer. As a result, while having the characteristic of a thin type of the type shown in FIG. 16, the magnification is further improved and the angle of view is widened with respect to the LCD size.

Further, in order to further improve the optical performance as compared with the optical system proposed in Japanese Patent Laid-Open No. 10-153748, the internal reflection surface of the decentering prism is increased so that the intermediate image is formed only by the decentering prism. A type in which a second decentering prism is provided in the first decentering prism optical system, and the like in which the image is formed and the image is guided to an observer are disclosed in JP-A-2000-06.
6106, Japanese Patent Laid-Open No. 2000-105338,
JP 2000-131614 A, JP 2000-1
It is proposed in Japanese Patent Laid-Open No. 99853/2000, Japanese Patent Laid-Open No. 2000-227554 and Japanese Patent Laid-Open No. 2000-231060.

Generally, an optical system of the type that temporarily forms an intermediate image has a problem that the optical path length becomes long and the size of the apparatus becomes large. And using a dual-purpose surface that fulfills the reflection function,
We are aiming for miniaturization by devising ways such as intersecting the optical paths.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a display optical system that can achieve a wide display angle of view while using a small display element, and a compact display optical system as a whole, and an image pickup optical system that can achieve a wide image capturing wide angle of view. I am trying.

[0014]

In order to achieve the above-mentioned object, in the first invention of the present application, a display optical system for guiding light from an original image to an observer's eye or a projected surface, at least a reflection function is provided. And a second surface that reflects the light ray reflected by the first surface toward the first surface again,
It is characterized in that the central angle-of-view chief ray re-incident on the first surface is reflected and travels to the side opposite to the previous side with respect to the normal line of the surface on the hit point.

That is, the light path is made to reciprocate between the first surface and the second surface so that the light paths are substantially overlapped (the light path is a reciprocating light path). I am able to secure it. Therefore, it is possible to achieve a wide display angle of view while using a small original image (an image displayed on the image display element or the like), and it is possible to realize a small display optical system as a whole.

A light ray from the original image is reflected on the second surface, re-reflected on the first surface, and then reflected on the eye or the projection surface side by another third surface decentered from the light ray. It is characterized by doing. This is to set a light beam emitted from the reciprocating path formed by the first surface and the second surface in a different direction (eye or projection surface side) from the light beam entering the reciprocating path on the third surface. ,
This is for avoiding interference with incident light on the round-trip optical path.

The display optical system of the present invention is characterized in that it has a turning-back surface having only a reflecting action, in which the central angle-of-view principal ray from the original image is reflected back to substantially the opposite side. This is equivalent to the turning point of the marathon, the forward path and the return path overlap each other with the turning reflection surface as a boundary, and a long round-trip optical path including a surface other than the first surface or the second surface is formed.
Further miniaturization of the optical system becomes possible.

Further, the folding reflection surface is the first surface or the second surface. In this case, the optical system can be configured with the minimum number of surfaces, and it is possible to reduce the size.

Incidentally, it is preferable to form an intermediate image of light in the display optical system (for example, a transparent body). That is, by adopting an intermediate image-forming type in which the intermediate image-forming surface of a small original image is enlarged and displayed, the degree of freedom in layout is increased, the original image can be displayed on a large screen, and the optical path length is considerably long. However, the display optical system can be made compact.

Further, by making the optical surface constituting this display optical system eccentric with respect to the light beam, it is possible to achieve further thinning, and by giving the optical surface a curvature, unnecessary surfaces in the display optical system can be obtained. It is possible to eliminate the above and reduce the size. Furthermore, by making the optical curved surface a rotationally asymmetric surface (free curved surface), various aberrations can be corrected well, and if multiple free curved surfaces are adopted, the aspect ratio of the original image and the aspect ratio of the display image can be made close. It becomes possible to obtain a high quality display image.

This display optical system is a projection type image display device for enlarging and projecting an image on a projection surface such as a head mounted display (HMD) or a screen for an observer to wear on the head to observe the image. It is suitable for image display devices such as (projectors).

In the second aspect of the present invention, the imaging optical system that guides the light from the subject to the imaging surface, has at least the first surface having a reflecting action and the light beam reflected by the first surface again. The central angle-of-view chief ray re-incident on the first surface has a second surface that reflects toward the first surface, and is opposite to the previous time with respect to the normal line of the surface on the hit point. It is characterized in that it reflects and advances.

That is, by making the light substantially reciprocate between the first surface and the second surface to substantially overlap the optical path (reciprocal optical path), it is possible to secure a long optical path in spite of a small optical system. I am trying. For this reason, it is possible to achieve a wide shooting angle of view while being compact.

The light ray from the subject is reflected by the third surface eccentric to the light ray, and then by the first surface, and then by the second surface.
After being reflected by the surface (1), it is reflected again by the first reflecting surface and is guided to the imaging surface. This avoids interference between an incident light ray from a subject and an outgoing light ray guided to the imaging surface on the reciprocating path formed by the first surface and the second surface due to the reflection on the third surface.

The image pickup optical system of the present invention is characterized in that it has a turn-back surface having only a reflecting action, in which the central field angle principal ray from the subject is reflected back to substantially the opposite side. This is equivalent to the turning point of the marathon, and the returning path and the returning path almost overlap with each other at the turning reflection surface, forming a long round-trip optical path including the surfaces other than the first surface or the second surface. It becomes possible to downsize the optical system.

Further, the folding reflection surface is characterized by being the first surface or the second surface. In this case, the optical system can be configured with the minimum number of surfaces, and it is possible to reduce the size.

Incidentally, it is preferable to form an intermediate image of light in the image pickup optical system (for example, a transparent body). That is, by adopting an intermediate image formation type in which the intermediate image formation surface of the subject is reduced and guided to the image pickup surface, the degree of freedom in layout is increased, and it is possible to sufficiently reduce the object image having a wide angle of view and lead it to the image pickup surface. In addition, the image pickup optical system can be made compact even if the optical path length is considerably lengthened.

Further, by decentering the optical surface constituting the image pickup optical system with respect to the light rays, it becomes possible to achieve further thinning, and by giving the optical surface a curvature, It becomes possible to reduce the size by removing unnecessary surfaces. Furthermore, by making the optical curved surface a rotationally asymmetric surface (free curved surface), it is possible to satisfactorily correct various aberrations, and if multiple free curved surfaces are used, the aspect ratio of the subject and the aspect ratio of the captured image can be made close. It becomes possible to obtain a high-quality photographed image.

The image pickup optical system is suitable for an image pickup apparatus such as a digital still camera or a video camera.

Further, in the first and second inventions, the rotationally asymmetric surface is preferably a plane symmetric shape having a local generatrix section as the only symmetric surface. As a result, it becomes possible to facilitate processing and production as compared with the case where there is no symmetry.

Further, by forming an optical surface on the transparent body and totally reflecting the light internally by any one of the optical surfaces, it is possible to reduce the light quantity loss even with a long optical path length. In particular, when the first surface is the internal reflection surface, the display optical system and the image pickup optical system can be compactly assembled.

Further, in both the display optical system and the image pickup optical system, the focal length of the local meridional cross section on the surface having optical refractive power reflects light from the original image a plurality of times on the first surface, and It is preferable that the reflection surface of the third surface that is reflected toward the projection surface side or the reflection surface of the third surface that reflects light from the subject toward the first surface is the most positive and shortest. This is because if an eccentric surface is given a strong refractive power, a double decentering aberration occurs in the local generatrix cross section due to the forward and backward paths of light, so the third surface that reflects only once By giving a strong positive power to
It becomes possible to suppress the occurrence of decentering aberration in the local generatrix cross section.

In both the display optical system and the image pickup optical system, it is preferable that the surface that reflects and returns light is a curved surface. If the folding reflection surface is a flat surface, the directions of the light rays of the peripheral image cannot be individually controlled at the time of reflection, so that the optical system becomes large. If the folding reflection surface is a rotationally asymmetric surface, the light ray direction of the peripheral image can be freely controlled, and therefore the size can be further reduced as compared with the case of a curved surface.

Here, the return reflection surface is a surface having only a reflection effect, and it is desirable to reduce the light amount loss by applying a metal mirror coating that reflects light by almost 100%.

Further, when the light is reflected to the opposite side on the return reflection surface, it is desirable that the angle θ formed by the incident ray and the reflected ray satisfies the following value in the central angle-of-view principal ray described later.

│θ│ <60 ° (1) When the upper limit of this conditional expression (1) is exceeded, the optical path (return path) after the reflected reflection does not return in the forward path, and becomes a zigzag optical path rather than a round-trip optical path. The optical system becomes large.

│θ│ <30 ° (2) If the condition of the conditional expression (2) is not satisfied, a backward movement is possible, but the forward path and the return path do not overlap, the optical system becomes large, and the entire optical system becomes small. This is not preferable because it becomes difficult.

| Θ | <20 ° (3) If this conditional expression (3) is satisfied, the size of the optical system can be further reduced.

The folded reflection surface in the display optical system and the image pickup optical system may also be used as the decentered reflection surface. In this case, since the number of optical surfaces can be reduced, the optical system can be downsized. In particular, if the first surface or the second surface is also used as the folding reflection surface, the size can be reduced most.

When the display optical system of the first invention is used as a head mounted display (HMD), an original image (image display element) and a display optical system which are independent of each other are provided for the left and right eyes. Is good. In other words, by having two original images (the same one) and two display optical systems (the same one) matching them, a brighter display than an HMD in which light is split into the left and right display optical systems with one original image An image is obtained.

In the display optical system according to the first aspect of the present invention, the local meridional section, which is an eccentric section for both the left eye and the right eye, is arranged in the vertical direction of the human face (folding the light beam up and down). Good. In general, the enlarged display image has a wide field of view in the left-right direction of the human and a narrow field of view in the up-down direction (left / right 4: up / down 3 or 1
Therefore, it is preferable to set the local generatrix cross section which is an eccentric cross section and has a large occurrence of eccentric aberration above and below with a small angle of view because the occurrence of eccentric aberration in a display enlarged image can be reduced.

The above optical system is, in other words, the first optical system.
Angle with respect to the normal to the hit point of the central angle of view chief ray that first entered the surface of, and the normal to the hit point of the central angle of view chief ray that is reflected by the second surface and re-enters the first surface The reflection angle with respect to is the opposite sign. That is, the light reflected from the first surface
The surface of the first surface reflects the light so that it returns to the first light reflection area side (reflection area, near the reflection area, or near the reflection area), thereby effectively overlapping the light paths and reducing the long light path length. It is designed to be housed in the optical system of.

[0043]

BEST MODE FOR CARRYING OUT THE INVENTION Before describing the embodiments of the present invention, the definitions of the busbar section, the sagittal section, the local busbar section, and the local sagittal section used in this embodiment will be described.

In the definition of the conventional system that does not correspond to the eccentric system, if the z axis is the optical axis in each surface vertex coordinate system, the yz section is the conventional meridional section (meridional section) and the xz section is the sagittal section (sagittal section). Cross section).

Since the optical system of this embodiment is a decentered system,
Local busbar cross section and local sagittal cross section corresponding to the eccentric system are newly defined.

Central view angle principal ray (in the display optical system, it is a light ray from the image center of the display element to the exit pupil center of the display optical system, and in the imaging optical system, it passes through the entrance pupil center of the imaging optical system. The ray that reaches the center of the image) and the hit points of each surface are the local meridional section that includes the incident light and the exit light of the central angle of view principal ray, and each of them is perpendicular to the local meridional section that includes the hit point. A plane parallel to the sagittal section (normal sagittal section) of the surface vertex coordinate system is defined as a local sagittal section. The local meridian cross-section focal length and the local sagittal cross-section focal length will be described in each embodiment described later.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
1 illustrates a display optical system that is an embodiment. This display optical system is composed of a first optical system 1 and a second optical system 2, which are made of a transparent body filled with an optical medium such as glass or plastic having a refractive index larger than 1.

Three optical surfaces are formed on the transparent body of the first optical system 1 (hereinafter, also referred to as the first optical element 1), and a surface A (first surface) and a surface B (first surface) are formed. 3) is a transmission / reflection combined surface that acts as a transmission surface and a reflection surface.
The surface C (second surface) is a reflecting surface.

A reflection film is formed on a part of the surface A (upper part) and the surface C, and on the surface B, a semi-transmissive reflection film (half mirror).
Are formed.

The upper part of the surface A is an area having a reflection function. The lower part of the surface A is a region where the light flux exits the surface A.

The reflection film and the half mirror are preferably made of a metal film. This is because the metal film has a flat spectral reflectance characteristic, a color is less noticeable, and there is almost no difference in reflectance with respect to light having different polarization directions.

Reference numeral 3 in the figure denotes an image display element (LCD or the like) for displaying an image. In the present embodiment, the surface B functions as an incident surface and a reflection surface of light from the image display element 3, the surface A functions as a reflection surface and an emission surface, and the surface C functions as a reflection surface.

The light emitted from the image display element 3 is
Is guided to the first optical element 1 via the optical system 2. Surface B
The light that has entered the first optical element 1 from is reflected by the surface A, is then reflected by the surface C, and is guided to the upper portion of the surface A. And
After being reflected back on the upper part of the surface A, it is reflected again on the surface C and returned to the vicinity of the first light reflection area on the surface A. Then, the light is re-reflected by the surface A, further reflected by the surface B, transmitted through the lower portion of the surface A, emitted from the first optical element 1, and reaches the exit pupil S.

In this figure, as an example of the light emitted from the image display element 3, a central angle-of-view chief ray that emerges from the center of the display surface of the image display element 3 and reaches the center of the exit pupil S is shown.

In the present embodiment, the observer puts his eyes near the position of the exit pupil S so that an enlarged image of the image displayed on the image display element 3 can be visually recognized.

In the first optical element 1, the light is
Surface B (transmission) → surface A (reflection) → surface C (reflection) → surface A (return reflection) → surface C (rereflection) → surface A (rereflection) → surface B
(Reflection) (→ Surface A (Transmittance))
The optical path up to that point is traced in reverse until the final reflection surface B is reached after the return reflection at.

Here, surface B (transmission) → surface A (reflection) →
Surface C (reflection) → surface A (return reflection), and surface A (return reflection) → surface C (rereflection) → surface A (rereflection)
→ The optical path of the surface B (reflection) is called a return path, and the forward path and the return path are collectively called a round-trip optical path.

In particular, the re-reflection on the surface A is such that the central angle-of-view chief ray is reflected and travels on the side opposite to the first reflection on the surface A with respect to the normal line of the surface on the hit point. Is formed.

As described above, by making the surface A act as a reflection reflection surface and forming a reciprocal optical path in the first optical element 1, the optical paths are almost overlapped and a long optical path is formed. It can fit in one. As a result, the entire display optical system including the second optical system 2 can be downsized.

The light rays from the image display element 3 pass through the reciprocal optical path due to the reflection on the final reflection surface B, and are guided to the eyeball side instead of going to the image display element 3 side.

It is preferable to use total internal reflection as the reflection other than the return reflection on the surface A, because the loss of the amount of light is reduced. Further, at least when the light is totally internally reflected in a region where the reflected light flux on the surface A and the emitted light flux are shared (the lower part of the surface A), and the reflection is performed by the reflection film in the area other than the common area, other than the return reflection on the surface A. It is possible to secure the same degree of brightness while increasing the degree of freedom in design as compared with the case where the total reflection light flux is totally internally reflected.

Since the boundary between the reflective film area and the common area is not clearly visible because the boundary between the reflective films is not visible, the reflectance near the boundary (between the upper part and the lower part of the surface A) gradually decreases from the lower part to the upper part. It is desirable to raise the to make the boundary inconspicuous. The reflective film is preferably a metal film for the reason described above.

In this embodiment, the surface B, which acts as the final reflection surface, is an optical that is very strong with respect to the surface A (reflection, return reflection, rereflection, transmission) and the surface C (reflection, rereflection). It is a concave mirror having a power (1 / focal length) and bears the main power of the first optical system 1.

In the first optical system 1, since the light is reflected twice or more on the surfaces A and C to form the round-trip optical path, the surface B is not reflected.
To have a low power on surfaces A and C to suppress the occurrence of aberration.

Particularly, since the local generatrix cross section is an eccentric cross section, if the power of the surface B and the powers of the surfaces A and C on this cross section in the central field angle chief ray are set to be weak and the powers of the surfaces A and C are set to be weak, the occurrence of decentration aberration can be suppressed. . Also, only the surface B has power,
The surfaces A and C may be flat surfaces.

Since the surface B is a decentered curved surface, it is desirable to minimize the occurrence of decentration aberrations by using a rotationally asymmetric surface (so-called free curved surface). Also, surface B
If the other surface is a free-form surface, the image display element 3
It is possible to set the aspect ratio of and the aspect ratio of the enlarged display screen to be close to each other.

When each of the surfaces A, B, and C is formed of a curved surface, all the surfaces contribute to condensing or diverging or aberration correction, and a cost reduction effect can be expected.

More preferably, by making all three surfaces A, B and C constituting the first optical system 1 rotationally asymmetrical, the degree of freedom of decentering aberration correction is increased and an image of good quality is obtained. Can be displayed.

At this time, if each rotationally asymmetric surface has a shape that is plane-symmetric in the direction of the local sagittal cross-section with the local generatrix cross section as the only symmetry plane, machining and fabrication are easier than when there is no symmetry. It is possible to do so, which is preferable.

By configuring the display optical system as described above, it is possible to provide an image display device which displays the image displayed on the image display element 3 as a magnified image with good optical performance.

Further, by forming an intermediate image once in the transparent body, the degree of freedom of the display angle of view with respect to the display size of the image display element 3 is improved, and a wider angle of view (high magnification presentation) is made possible. At the same time, the total length of the first optical system 1 is suppressed to be short by substantially overlapping the round-trip optical paths having a long optical path length, and a very compact display optical system can be configured.

(Second Embodiment) FIG. 2 shows a second embodiment of the present invention.
1 illustrates an imaging optical system that is an embodiment. Reference numeral 11 in the figure is a first optical system similar to that shown in FIG. 1, 2 is a second optical system, and 4 is an image sensor.

S is an entrance pupil of an image pickup optical system including a first optical system (hereinafter also referred to as a first optical element) 11 and a second optical system 2, and a stop is placed at this position to suppress unnecessary light. It prevents the incidence.

In this embodiment, the surface A (first surface) acts as an incident surface and a reflection surface of light from the subject, and the surface B (third surface) acts as a reflection surface and an exit surface. C (second surface) acts only as a reflecting surface.

The light from the external object that has passed through the diaphragm S enters the first optical element 11 from the surface A, is reflected by the surface B, is reflected by the surface A, is reflected by the surface C, and is reflected by the surface A. Be guided to the top of. Then, after the upper part is reflected back on the surface A having a reflected reflection effect, it is reflected again on the surface C, is reflected again near the first light reflection area on the surface A, and is transmitted through the surface B to the first optical element. 11 is emitted, and heads for the second optical system 2.

The light that has passed through the second optical system 2 is imaged by the image pickup device 4.
And is imaged. At this time, a light beam from a desired external image is formed on the image pickup surface of the image pickup element 4, and the external image can be acquired.

By configuring the image pickup optical system as described above, it is possible to provide an image pickup apparatus which forms an image of a subject in the external world on the image pickup element 4 with good optical performance. In addition, by forming an intermediate image once in the first optical element 11, the degree of freedom of the photographing field angle with respect to the size of the image sensor 4 is improved,
A wide angle of view is made possible, and long optical path lengths are almost overlapped and formed in the first optical element 11, so that
The overall length of the optical system 11 can be suppressed to be short, and a very compact imaging optical system can be configured.

(Third Embodiment) FIG. 3 shows a third embodiment of the present invention.
1 illustrates a display optical system that is an embodiment. This display optical system is composed of a first optical system 21 and a second optical system 2. Three optical surfaces are formed on a transparent body (hereinafter, also referred to as the first optical element 21) that constitutes the first optical system 21, and a surface A (first surface) and a surface B (first surface) are formed. The surface 3) is a surface for both transmission and reflection that acts as a transmission surface and a reflection surface, and the return reflection surface C (second surface) is a surface only for reflection.

A reflection film is formed on the return reflection surface C, and a semi-transmissive reflection film (half mirror) is formed on the surface B.

The reflective film and the half mirror are preferably made of a metal film. This is because the metal film has a flat spectral reflectance characteristic, a color is less noticeable, and there is almost no difference in reflectance with respect to light having different polarization directions.

In the figure, 3 is an image display element (LCD or the like) for displaying an image. In the present embodiment, the surface B functions as an incident surface and a reflection surface of light from the image display element 3, the surface A functions as a reflection surface and an emission surface, and the surface C functions as a reflection surface.

The light emitted from the image display element 3 is
Is guided to the first optical element 21 via the optical system 2. The light enters the first optical element 21 from the surface B, is reflected by the surface A, and is guided to the return reflection surface C. The return reflection surface C reflects the incident light so as to return it in a direction substantially opposite to the incident direction. Then, the light returned to the vicinity of the first light reflection area on the surface A is re-reflected on the surface A, reflected on the surface B, transmitted through the surface A, emitted from the first optical element 21, and exit pupil. Reach S.

In this figure, as an example of the light emitted from the image display element 3, a central angle-of-view chief ray that exits the center of the display surface of the image display element 3 and reaches the center of the exit pupil S is shown.

In this embodiment, the observer puts his eyes near the position of the exit pupil S, so that an enlarged image of the image displayed on the image display element 3 can be visually recognized.

In the first optical element 21, light is incident on the B surface → A surface reflection → return reflection surface C → A surface re-reflection →
The light is passed through each surface in the order of B-side reflection → A-side emission, and the optical path up to that point is traced in reverse, with the reflection at the reflecting surface C as the boundary.

The surface B → the surface A → the return reflection surface C is the outward path, and the return reflection surface C → the surface A → the surface B is the return path,
A round-trip optical path is formed by combining the forward and return paths.

In particular, the re-reflection on the surface A is a reciprocal optical path in which the central angle-of-view chief ray is reflected and advances to the side opposite to the first reflection on the surface A with respect to the normal line of the surface on the hit point. Is formed.

As described above, by forming the reciprocal optical path in the first optical element 21, the optical paths are almost overlapped, the inside of the first optical element 21 is effectively used, and the first optical element is used with respect to the optical path length. The size of the element 21 is reduced. As a result, the entire display optical system can be downsized.

The reflection on the return reflection surface C is due to the reflection film. Further, the light from the image display element 3 passes through the round-trip optical path due to the reflection on the surface B and is guided to the eyeball side instead of going to the image display element 3 side.

If the reflection on the surface A is total internal reflection, the loss of the amount of light is reduced, which is preferable. Further, at least a region where the reflected light beam and the emitted light beam on the surface A are shared (the lower part of the surface A)
If the light is totally internally reflected by and the light is reflected by the reflective film except for the common area, the same degree of freedom can be achieved as in the case where the total reflection of the light flux reflected on the surface A is performed. Brightness can be secured.

Since the boundary between the reflective film area and the common area is not clearly visible because the boundary of the reflective film is not preferable, the reflectance near the boundary (lower side in the reflective film area) gradually increases from the lower part to the upper part. It is desirable to raise it to make the boundary inconspicuous. The reflective film is preferably a metal film. The metal film has a flat spectral reflectance characteristic and the color is not noticeable,
This is because there is almost no difference in reflectance with respect to light having different polarization directions.

In this embodiment, the surface B when acting as the final reflection surface is a concave mirror having a very strong optical power (1 / focal length) with respect to the surface A (reflection, rereflection, transmission). And plays the main power of the first optical system 21. This is because the light is reflected twice on the surface A by the reciprocating optical path, so that the surface B is provided with power and the power of the surface A is set to be weak to suppress the occurrence of aberration.

In particular, since the local generatrix cross section is an eccentric cross section, if the power of the surface B is set to be strong and the power of the surface A is set to be weak on this cross section with respect to the central ray of view, it is possible to suppress the occurrence of eccentric aberration. .

Alternatively, only the surface B may have power and the surface A may be a flat surface. Further, since the surface B is a decentered curved surface, it is desirable to suppress the occurrence of decentering aberration as much as possible by using a rotationally asymmetric surface (so-called free curved surface).

If the reflecting surface other than the surface B is another free-form curved surface, the aspect ratio of the image displayed on the image display element 3 and the aspect ratio of the enlarged display screen can be set close to each other.

Further, when the surfaces A, B, and C are each formed by a curved surface, all the surfaces contribute to converging or diverging or aberration correction, and a cost reduction effect can be expected.

More preferably, by making all three surfaces A, B and C forming the first optical system 21 rotationally asymmetrical, the degree of freedom of decentering aberration correction is increased, and an image with good image quality is obtained. Can be displayed. At this time, if each rotationally asymmetric surface has a shape symmetrical with respect to the local sagittal cross section with the local symmetric cross section as the only symmetric surface, machining and manufacturing can be facilitated as compared with the case where there is no symmetry. Therefore, it is preferable.

(Fourth Embodiment) FIG. 4 shows the fourth embodiment of the present invention.
1 illustrates a display optical system that is an embodiment. This display optical system is composed of a first optical system 31 and a second optical system 2. A first optical system (hereinafter, also referred to as a first optical element) 31 is made of a transparent body having four optical surfaces, and a surface A (first surface) is used both as a transmission surface and a reflection surface for both transmission and reflection. The reflection reflection surface C (second surface) and the surface B (third surface) are reflection-only surfaces, and the incidence surface D is a transmission surface.

Reflecting films are formed on the return reflection surfaces C and B. The reflective film is preferably a metal film. This is because the metal film has a flat spectral reflectance characteristic, a color is less noticeable, and there is almost no difference in reflectance with respect to light having different polarization directions.

Reference numeral 3 in the figure denotes an image display element (LCD or the like) for displaying an image. In the present embodiment, the surface D acts as an incident surface of the light from the image display element 3, the surface A acts as a reflecting surface and an exit surface, and the surfaces B and C act as reflecting surfaces.

The light emitted from the image display element 3 is
Is guided to the first optical element 31 via the optical system 2. The light enters the first optical element 31 through the incident surface D, is reflected by the surface A, and is guided to the return reflection surface C. Folded reflective surface C
Then, the incident light is reflected so as to be returned to the area near the first light reflection area on the surface A, but the angle between the incident light and the reflected light of the central view angle principal ray on the return reflection surface C is reflected at θ. ing.

Thereafter, the light is again reflected on the surface A, reflected on the surface B, transmitted through the surface A, and emitted from the first optical element 31,
The exit pupil S is reached.

In this figure, as an example of the light emitted from the image display element 3, a central angle-of-view chief ray that exits the center of the display surface of the image display element 33 and reaches the center of the exit pupil S is shown.

In the present embodiment, the observer can place an eye near the position of the exit pupil S to visually recognize an enlarged image of the image displayed on the image display element 3.

In the first optical element 31, the light passes through the respective surfaces in the order of the incident surface D → A surface reflection → return reflection surface C → A surface rereflection → B surface reflection → A surface emission, and the return reflection surface. After the reflection at C, the optical path up to that point is reversed.

A forward path is formed from the surface A to the return reflection surface C, a return path is formed from the return reflection surface C to the surface A, and a reciprocal optical path is formed by combining the return path and the return path.

In particular, the re-reflection on the surface A is such that the central angle-of-view principal ray is reflected and travels on the side opposite to the first reflection on the surface A with respect to the normal of the surface on the hit point. Is formed.

By forming the reciprocating optical path in the first optical element 31 as described above, the optical paths are substantially overlapped, and the inside of the first optical element 31 is effectively used, and the first optical element with respect to the optical path length is used. The size of the system 31 can be reduced. As a result, the entire display optical system can be downsized.

Further, the light rays from the image display element 3 pass through the round-trip optical path due to the reflection on the surface B, and thereafter, the image display element 3
It is guided to the eyeball side instead of going to the side.

The display optical system of this embodiment has an advantage in terms of brightness as compared with the display optical systems of the first and third embodiments. In the first and third embodiments, the light from the image display element is incident from the surface B of the first optical system, and the surface B is the first surface.
Since it also had a reflection effect in the optical path of the optical system of, it is necessary to use a half mirror. Therefore, the amount of light from the image display element is almost halved when entering the first optical system.

On the other hand, in this embodiment, the angle θ formed by the incident light and the reflected light of the central angle-of-view principal ray on the return reflection surface C is set to a relatively large value, and the return path is set to the surface A, and thereafter The light is set to go to a surface B different from the incident surface D. In this way, by dividing the incident surface D and the surface B (surfaces having only a reflection effect), a light amount loss at the time of incidence on the first optical system is eliminated and a bright display optical system is realized.

It is preferable that the reflection on the surface A is total internal reflection, because the loss of the amount of light is reduced. Further, at least a region where the reflected light beam and the emitted light beam on the surface A are shared (the lower part of the surface A)
If the light is totally internally reflected by and the light is reflected by the reflective film in areas other than the common area, the same degree of brightness can be achieved while increasing the degree of freedom in design as compared with the case of totally internally reflecting all the light flux reflected on the surface A. Can be secured.

Since the boundary between the reflective film area and the common area is not clearly visible because the boundary of the reflective film is undesired, the reflectance near the boundary (the lower side in the reflective film area) gradually increases from the lower part to the upper part. It is desirable to raise it to make the boundary inconspicuous. The reflective film is preferably a metal film. This is because the metal film has a flat spectral reflectance characteristic, a color is less noticeable, and there is almost no difference in reflectance with respect to light having different polarization directions.

In the present embodiment, the surface B when acting as the final reflecting surface is a concave mirror having a very strong optical power (1 / focal length) with respect to the surface A (reflection, re-reflection, transmission). And is responsible for the main power of the first optical system 31. This is because the light is reflected twice on the surface A by the reciprocating optical path, so that the surface B has power and the power of the surface A is set to be weak to suppress the occurrence of aberration.

In particular, since the local generatrix section is an eccentric section, setting the surface B power on this section to be strong and the surface A power to be weak with respect to the central angle-of-view chief ray suppresses the occurrence of eccentric aberration.

Alternatively, only the surface B may have power and the surface A may be a flat surface. Since the surface B is an eccentric curved surface, by using a surface having a rotationally asymmetric shape (so-called free curved surface),
It is desirable to suppress the occurrence of decentration aberrations as much as possible.

If the reflecting surface other than the surface B is another free-form curved surface, the aspect ratio of the image displayed on the image display element 3 and the aspect ratio of the enlarged display screen can be set close to each other.

When each of the surfaces A, B, C, and D is formed by a curved surface, all the surfaces contribute to converging or diverging or aberration correction, and a cost reduction effect can be expected.

More preferably, by making all four surfaces A, B, C and D forming the first optical system 31 rotationally asymmetrical, the degree of freedom of eccentric aberration correction is increased and good image quality is obtained. It becomes possible to display images.

At this time, if each rotationally asymmetric surface has a shape that is plane-symmetric in the direction of the local sagittal cross-section with the local generatrix cross section as the only symmetrical plane, machining and fabrication are easier than in the case where there is no symmetry. It is preferable because it is possible.

(Fifth Embodiment) FIG. 5 shows a fifth embodiment of the present invention.
1 illustrates a display optical system that is an embodiment. The display optical system includes a transparent optical element 41-a and a reflecting member 41-a.
It is composed of a first optical system 41 composed of b and a second optical system 2.

The optical element 41-a has three optical surfaces, and the surface A (first surface) and the surface B (third surface) are both transmissive and reflective surfaces acting as a transmissive surface and a reflective surface. C (second surface) is a surface only for reflection. The reflecting member 41-b has a transmitting surface D that is decentered with respect to the central angle of view principal ray and a folded back reflecting surface E that is back-reflected.

A reflecting film is formed on the surface C and the return reflecting surface E of the reflecting member 41-b, and the surface B is composed of a half mirror. The reflective film and the half mirror are preferably made of a metal film. This is because the metal film has a flat spectral reflectance characteristic, a color is less noticeable, and there is almost no difference in reflectance with respect to light having different polarization directions.

In the figure, 3 is an image display element (LCD or the like) for displaying an image. In the present embodiment, the surface B acts as an incident surface and a reflection surface for light from the image display element 3, and the surface A is an emission surface (emission toward the reflection member 41-b and emission toward the exit pupil S) and reflection. Acts as a surface.

The light emitted from the image display element 3 is
The optical element 41 of the first optical system 41 through the optical system 2 of
led to a. The light enters the optical element 41-a from the surface B, is then reflected in the order of the surface A and the surface C, and enters and exits the surface A at a critical angle or less. Then, after being emitted from the optical element 41-a, it is transmitted through the transmission surface D of the reflection member 41-b and is reflected by the folded reflection surface E. On the return reflection surface, the incident light is reflected so as to be returned in a direction substantially opposite to the incident direction. There is.

Then, the light is re-incident on the optical element 41-a from the surface A, is reflected by the surface C, is returned to the area near the first reflection area of the light on the surface A, is reflected, and is exited by the surface B. S
After being reflected to the (eyeball) side, the light passes through the surface A and the optical element 41.
-E is emitted, and it reaches the exit pupil S.

In this figure, as an example of the light emitted from the image display element 3, the central angle-of-view chief ray that exits the center of the display surface of the image display element 3 and reaches the center of the exit pupil S is shown.

In the present embodiment, the observer puts his eyes near the position of the exit pupil S, so that an enlarged image of the image displayed on the image display element 3 can be visually recognized.

In the first optical system 41, the light is the surface B (transmission) → the surface A (reflection) → the surface C (reflection) → the surface A (transmission) → the transmission surface D (transmission) of the reflection member 41-b. → Reflecting member 41-b
Return reflection surface E (return reflection) → reflection member 41-
Each surface in the order of the transmission surface D of b (retransmission) → the surface A (retransmission) → the surface C (rereflection) → the surface A (rereflection) → the surface B (reflection) (→ the surface A (retransmission)). After passing through, the optical path up to that point is traced in reverse, with the reflection on the reflection surface as the boundary.

A forward path is formed from the surface B (transmission) to the return reflection surface E, a return path is formed from the reflection reflection surface E to the surface B (reflection), and a reciprocal optical path is formed by combining the return path and the return path.

In particular, the re-reflection on the surface A is such that the principal ray of the central angle of view is reflected and travels on the side opposite to the first reflection on the surface A with respect to the normal of the surface on the hit point. Is formed.

By forming the reciprocating optical path in the first optical system 41 as described above, the optical paths are substantially overlapped, and the inside of the first optical system 41 is effectively used to make the first optical path length longer than the optical path length. The size of the optical system 41 can be reduced. This allows
The entire display optical system can be downsized.

The light rays from the image display element 3 are directed to the surface B
The light passes through the reciprocating optical path due to the reflection at 1, and then is guided to the eyeball side instead of going to the image display element 3 side.

In the present embodiment, θ is set so that the incident light beam on the return reflection surface (return reflection surface E of the reflection member 41-b) is reflected slightly downward in the figure. Accordingly, the second optical system 2 or the image display element 3 can be arranged relatively above the first optical system 41, and thus the top and bottom can be made compact.

In addition, in the first optical system 41, the reflecting member 41-b including the folded reflecting surface is a member different from the optical element 41-a, so that the effective surface in the optical path is increased and the degree of freedom in design is increased. To improve the optical performance.

If the reflection on the surface A is the total internal reflection, the loss of the amount of light is reduced, which is preferable. In addition, the light is totally internally reflected at least in a region where the reflected light flux and the outgoing light flux on the surface A are shared (the lower part of the outgoing surface A toward the exit pupil S and the upper part of the outgoing surface A toward the reflecting member 41-b). When the reflection film is used to reflect the light other than the common area, the same degree of brightness can be secured while increasing the degree of freedom in design as compared with the case where the total reflection light flux on the surface A is totally internally reflected.

Since the boundary between the reflective film area and the common area is not clearly visible and undesirable, the vicinity of the boundary (the lower side and the upper side in the reflective film area) is gradually reflected as the distance from the shared area increases. It is desirable to increase the rate to make the boundaries inconspicuous. The reflective film is preferably a metal film. This is because the metal film has a flat spectral reflectance characteristic, a color is less noticeable, and there is almost no difference in reflectance with respect to light having different polarization directions.

In the present embodiment, the surface B when acting as the final reflection surface is the surface A (reflection, transmission, re-transmission, re-reflection,
It is a concave mirror having very strong optical power (1 / focal length) with respect to (re-transmission) and surface C (reflection, re-reflection), and plays the main power of the first optical system 41. First
In the optical system 41, since the light is reflected twice or more on the surfaces A and C by the reciprocal optical path, the power is given to the surface B and the powers of the surfaces A and C are set weak to suppress the occurrence of aberration.

In particular, since the local generatrix section is an eccentric section, setting the power of surface B and the power of surfaces A and C on this section in the central field angle chief ray to be strong and eccentric aberration can be suppressed. .

Alternatively, only the surface B may have power, and the surfaces A and C may be flat surfaces. Since the surface B is a decentered curved surface, it is desirable to suppress the occurrence of decentering aberration as much as possible by using a rotationally asymmetric surface (so-called free curved surface).

If another surface other than the surface B is a free-form surface, the aspect ratio of the image displayed on the image display element 3 and the aspect ratio of the enlarged display screen can be set close to each other.

When the surfaces A, B, C of the optical element 41-a and the both surfaces D, E of the reflecting member 41-b are curved surfaces, all the surfaces contribute to converging or diverging or correcting aberrations. Therefore, the effect of cost reduction can be expected.

More preferably, all of the surfaces A, B, C constituting the first optical system 41 and both surfaces D, E of the reflecting member 41-b have a rotationally asymmetric shape, so that the degree of freedom of decentering aberration correction can be improved. And an image can be displayed with good image quality.

At this time, if each rotationally asymmetric surface has a plane symmetric shape in the local sagittal section direction with the local generatrix section as the only symmetric surface, machining and manufacturing are facilitated as compared with the case where there is no symmetry. It is preferable because it is possible.

(Sixth Embodiment) FIG. 6 shows the sixth embodiment of the present invention.
1 illustrates a display optical system that is an embodiment. This display optical system is composed of a first optical system 51 and a second optical system 2. The first optical system (hereinafter, also referred to as a first optical element) 51 is composed of a transparent body having four optical surfaces, and the surface A (first surface) and the surface B (third surface) are A transmissive / reflective surface acting as a transmissive surface and a reflective surface, a surface C (second
Surface) is a surface only for reflection. Further, a folded reflection surface D is formed on the transparent body.

A reflection film is formed on the surface C and the return reflection surface D, and the surface B is a half mirror. The reflective film and the half mirror are preferably made of a metal film. This is because the metal film has a flat spectral reflectance characteristic, a color is less noticeable, and there is almost no difference in reflectance with respect to light having different polarization directions.

Reference numeral 3 in the figure denotes an image display element (LCD or the like) for displaying an image. In this embodiment, the surface B acts as an entrance surface and a reflection surface from the image display element 3,
The surface A acts as a reflection surface and an exit surface.

The light emitted from the image display element 3 is
Is guided to the first optical element 51 via the optical system 2. After the light enters the first optical element 51 from the surface B, the surface A, the surface C
Then, the reflected light is reflected by the reflection surface D. afterwards,
By the reflection on the surface C, the light is returned to the first reflection area of the light on the surface A, reflected on the surface B, reflected on the exit pupil S (eyeball) side, and then transmitted through the surface A to pass the first optical element 51. Ejects and reaches the exit pupil S.

In this figure, as an example of the light emitted from the image display element 3, the central angle-of-view chief ray that exits the center of the display surface of the image display element 3 and reaches the center of the exit pupil S is shown.

In the present embodiment, the observer can view the enlarged image of the image displayed on the image display element 3 by placing the eyes near the position of the exit pupil S.

In the first optical element 51, the light is a surface B (transmission) → a surface A (reflection) → a surface C (reflection) → a folded reflection surface D.
(Return reflection) → Surface C (re-reflection) → Surface A (re-reflection) →
Pass each surface in the order of surface B (reflection) (→ surface A (transmission)),
The optical path up to that point is followed in reverse, with the reflection on the reflection surface D as the boundary.

A forward path is formed from the surface B (transmission) to the return reflection surface D, a return path is formed from the reflection reflection surface D to the surface B (reflection), and a reciprocal optical path is formed by combining the return path and the return path.

In particular, the re-reflection on the surface A is performed by making the central angle of view chief ray reflect on the side opposite to the first reflection on the surface A with respect to the normal line of the surface on the hit point and make a round trip optical path. Is formed.

By thus forming the reciprocating optical path in the first optical element 51, the optical paths are almost overlapped, and the inside of the first optical element 51 is effectively used, and the first optical element with respect to the optical path length. The size of the system 51 can be reduced. As a result, the entire display optical system can be downsized.

Further, the light rays from the image display element 3 are reflected by the surface B and are not directed to the image display element side after passing through the reciprocating optical path, but are guided to the eyeball side.

In the present embodiment, in addition to the structure of the first embodiment shown in FIG. 1, the folding reflection surface D is a surface independent of the surface A. As a result, the number of faces is increased by one to increase the degree of freedom in design.

Further, in the structure of the first embodiment, the reflection film is required above the folded reflection area of the surface A, and partial reflection film vapor deposition has to be performed, but in the present embodiment, the folded reflection surface D is formed. Is independent of the surface A, the vapor deposition of the reflective film is easy.

Further, in the present embodiment, it is preferable that the reflection on the surface A is the total internal reflection because the loss of the light quantity is reduced. In addition to this, the light is totally internally reflected at least in a region where the reflected light beam on the surface A and the emitted light beam are shared (the lower part of the surface A), and the light is reflected by the reflection film except the common region. It is possible to secure the same brightness while increasing the degree of freedom in design as compared with the case where all of the above are totally internally reflected.

Further, since the boundary between the reflective film area and the common area is not clearly visible because the boundary of the reflective film is undesired, the reflectance near the boundary (the lower side in the reflective film area) gradually increases as the distance from the shared area increases. It is desirable to make the boundaries inconspicuous. The reflective film is preferably a metal film. This is because the metal film has a flat spectral reflectance characteristic, a color is less noticeable, and there is almost no difference in reflectance with respect to light having different polarization directions.

In this embodiment, the surface B, which acts as the final reflecting surface, has a very strong optical power (1) with respect to the surface A (reflection, re-reflection, transmission) and the surface C (reflection, re-reflection). / Focal length), and is responsible for the main power of the first optical system 51.

In the first optical system 1, since the light is reflected twice or more on the surfaces A and C by the reciprocating optical path, the power is given to the surface B, and the powers of the surfaces A and C are set to be weak so as to reduce the aberration. The occurrence is suppressed. In particular, since the local generatrix cross section is an eccentric cross section, setting the power of the surface B and the power of the surfaces A and C on this cross section in the central ray at the central angle of view to be strong and eccentric aberration can be suppressed. Further, only the surface B may have power, and the surfaces A and C may be flat surfaces.

Since the surface B is a decentered curved surface, it is desirable to suppress the occurrence of decentration aberrations as much as possible by using a rotationally asymmetric surface (so-called free curved surface). Also, surface B
If the other surface is a free-form surface, the image display element 5
It is possible to set the aspect ratio of the image displayed in 3 and the aspect ratio of the enlarged display screen to be close to each other.

When the surfaces A, B, C of the first optical system 51 and the reflection reflection surface D are each formed by a curved surface, all the surfaces contribute to condensing or diverging or correcting aberrations. The effect of cost reduction can be expected.

More preferably, by making all the surfaces A, B, C and D forming the first optical system 51 rotationally asymmetrical, the degree of freedom of eccentric aberration correction is increased and an image with good image quality is obtained. Can be displayed.

At this time, if each rotationally asymmetric surface is plane-symmetrical in the local sagittal cross-section direction with the local generatrix cross section as the only symmetry plane, machining and fabrication are easier than in the case where there is no symmetry. Therefore, it is preferable.

(Seventh Embodiment) FIG. 9 shows a seventh embodiment of the present invention.
1 illustrates a display optical system that is an embodiment. This display optical system includes two optical elements 61-a1 and 61- which are transparent bodies.
The first optical system 61 includes a2 and a reflecting member 61-b. Each of the optical elements 61-a1 and 61-a2 has three optical surfaces, and a surface A (first surface), a surface B (third surface), and a surface E are transmissive and reflective acting as a transmissive surface and a reflective surface. The dual-purpose surface, the surface C (second surface) is a surface only for reflection,
The surface D and the surface F are surfaces having only a transmission effect.

The reflection member 61-b has a folded reflection surface G which is a surface reflection surface formed of a reflection film. A reflection film is formed on the surface C and the reflection reflection surface G of the reflection member 61-b.
Surface B is a half mirror. The reflective film and the half mirror are preferably made of a metal film. This is because the metal film has a flat spectral reflectance characteristic, a color is less noticeable, and there is almost no difference in reflectance with respect to light having different polarization directions.

Reference numeral 3 in the figure denotes an image display element (LCD or the like) for displaying an image. In the present embodiment, the surface B acts as an incident surface and a reflecting surface of the light from the image display element 3, the surface A acts as a reflecting surface and an emitting surface, the surface C serves as a reflecting surface, and the surface E serves as an incident surface. It acts as a reflecting surface and an emitting surface.

The light emitted from the image display element 3 is directly guided to the optical element 61-a1 of the first optical system 61. The light enters the optical element 61-a1 from the surface B, is reflected by the surface A, and exits from the surface D of the optical element 61-a1.
Next, the light enters the optical element 61-a2 from the surface E, is reflected by the surfaces C and E, and then exits from the surface F of the optical element 61-a2. Then, the reflection film (surface G) on the surface of the reflection member 61-b.
It is reflected back at. After that, the light enters the optical element 61-a2 from the surface F, and is reflected again by the surfaces E and C to generate the optical element 6-a2.
Eject from the surface E of 1-a2. Further, the optical element 61-
The light is incident on the surface a1 from the surface D, is returned to the first light reflection area on the surface A, is reflected again, is reflected by the reflection surface B toward the exit pupil S (eyeball) side, and then is transmitted through the surface A to form the optical element 61. Emit −a1 and reach the exit pupil S.

In this figure, as an example of the light emitted from the image display element 3, a central angle-of-view chief ray that exits the center of the display surface of the image display element 3 and reaches the center of the exit pupil S is shown.

In the present embodiment, the observer can view the enlarged image of the image displayed on the image display element 3 by placing the eyes near the position of the exit pupil S.

In the first optical system 61, the light is surface B (transmission) → surface A (reflection) → surface D (transmission) → surface E (transmission) → surface C (reflection) → surface E (reflection) → Surface F (transmissive) → reflective member 6
1-b return reflection surface G (return reflection) → surface F (retransmission) → surface E (rereflection) → surface C (rereflection) → surface E (retransmission) → surface D (retransmission) → surface A (Re-reflection) → Surface B (reflection)
The light passes through the surfaces in the order of (→ surface A (transmission)), and the optical path up to that point is traced in reverse, with the reflection at the folding reflection surface as the boundary.

A forward path is formed from the surface B (transmission) to the return reflection surface G, a return path is formed from the reflection reflection surface G to the surface B (reflection), and a reciprocal optical path is formed by combining the return path and the return path.

In particular, the re-reflection on the surface A is performed by making the central angle-of-view chief ray reflect and travel on the side opposite to the first reflection on the surface A with respect to the normal of the surface on the hit point. Is formed.

By forming the reciprocating optical path in the first optical system 61 in this way, the optical paths are almost overlapped, and the first optical system 6
1 is effectively used, and the first optical system 6 with respect to the optical path length is used.
The size of 1 can be reduced. As a result, the entire display optical system can be downsized.

Further, the light rays from the image display element 3 are reflected by the surface B, and after passing through the reciprocating optical path, do not go to the image display element side but are guided to the eyeball side.

In this embodiment, since the first optical system 61 is composed of two optical elements, the round-trip optical path can be lengthened, and a very long optical path length can be accommodated in the first optical system 61. You can Therefore, unlike the above-described embodiments, it is not necessary to insert another second optical system between the image display element and the first optical system, and the display optical system does not increase in size downward.

In the present embodiment, it is preferable that the reflection on the surface A and the surface E is total internal reflection because the loss of the light quantity is reduced. Further, at least when the light is totally internally reflected in a region where the reflected light flux on the surfaces A and E and the emitted light flux are shared (the lower part of the surfaces A and E), and the reflection is performed by the reflective film except the common region,
It is possible to increase the degree of freedom in design and secure the same degree of brightness as in the case of totally internally reflecting all the reflected light beams on the surfaces A and E.

Since the boundary between the reflective film area and the common area is not clearly visible because the boundary between the reflective films is not visible, the reflectance near the boundary (lower side in the reflective film area) gradually increases as the distance from the shared area increases. It is desirable to make the boundaries inconspicuous. The reflective film is preferably a metal film. This is because the metal film has a flat spectral reflectance characteristic, a color is less noticeable, and there is almost no difference in reflectance with respect to light having different polarization directions.

Further, in this embodiment, the optical power (1 / focal length) of the concave mirror of the surface B acting as the final reflecting surface and the surface C acting as the reflecting surface is stronger than that of the other reflecting surfaces. Among them, the power of the concave mirror of the surface C that acts as a reflecting surface is stronger. This is because the space between the first optical system 61 and the display element 3 cannot be sufficiently secured unless the power of the concave mirror on the surface B is weakened. In particular, the tendency is strong on the cross section of the local bus.

Further, only the surfaces B and C may have power, and the surfaces A and E may be flat surfaces. Since the surfaces B and C are decentered curved surfaces, it is desirable to suppress the occurrence of decentering aberration as much as possible by using a rotationally asymmetric surface (so-called free curved surface).

When the surfaces A, B and C, the surface E of the optical elements 61-a1 and 61-a2 and the folded reflection surface G of the reflection member 61-b are curved surfaces, all the surfaces are focused. It also contributes to divergence or aberration correction, and a cost reduction effect can be expected.

More preferably, by making the surfaces A, B, C, E and G forming the first optical system 61 rotationally asymmetrical, the degree of freedom of eccentric aberration correction is increased and an image with good image quality is obtained. Can be displayed. Further, if all the surfaces are free-form surfaces, even better image quality can be obtained.

At this time, if each rotationally asymmetric surface has a plane symmetric shape in the local sagittal section direction in which the local generatrix section is the only symmetric surface, machining and manufacturing are facilitated as compared with the case where there is no symmetry. Therefore, it is preferable.

(Eighth Embodiment) FIG. 8 shows an eighth embodiment of the present invention.
1 illustrates a display optical system that is an embodiment. This display optical system is composed of a first optical system 71 having a three-faced reflection mirror configuration of reflecting members 71-b1, 71-b2, 71-b3, and a second optical system 2.

The three reflecting members 71-b1, 71-b2,
A reflective film is formed on the surface of 71-b3. The reflection surface of the reflection member 71-b2 is a folded reflection surface. The reflective film is preferably a metal film. This is because the metal film has a flat spectral reflectance characteristic, a color is less noticeable, and there is almost no difference in reflectance with respect to light having different polarization directions.

Reference numeral 3 in the figure denotes an image display element (LCD or the like) for displaying an image. The light emitted from the image display element 73 is guided to the reflecting member 71-b1 of the first optical system 71 via the second optical system 2. The light enters the first optical system 71 from the surface A (first surface) that is the reflection mirror surface of the reflection member 71-b1, is reflected by the surface A, and is folded back that is the mirror surface of the reflection member 71-b2. It is guided to the reflection surface C (second surface). On the return reflection surface C, the incident light is reflected so as to return to the area closer to the first light reflection area on the surface A, but the angle formed by the incident light and the reflected light on the return reflection surface C of the central view angle principal ray. Is reflected so that it becomes θ.

After that, the light is reflected again on the surface A, and the reflection member 7
After being reflected by the surface B (third surface) which is the mirror surface of 1-b3, the light exits from the first optical system 71 and reaches the exit pupil S.

In this figure, as an example of the light emitted from the image display element 3, the central angle-of-view chief ray that exits the center of the display surface of the image display element 3 and reaches the center of the exit pupil S is shown.

In the present embodiment, the observer puts his eyes near the position of the exit pupil S, so that an enlarged image of the image displayed on the image display element 3 can be visually recognized.

In the first optical system 71, light is in the order of surface A (reflection) → mirror surface C of the reflection member 71-b2 (return reflection) → surface A (rereflection) → surface B (reflection). , And the optical path up to that point is traced in reverse, with the reflection on the reflection surface C as the boundary.

A forward reflection path is formed from A (reflection) to the return reflection surface C, a return path is formed from the reflection reflection surface C to A (re-reflection), and a reciprocal optical path is formed by combining the return and return paths.

In particular, the re-reflection on the surface A is such that the central view angle principal ray is reflected and travels on the side opposite to the first reflection on the surface A with respect to the normal of the surface on the hit point. Is formed.

By thus forming the reciprocating optical path in the first optical system 71, the optical paths are almost overlapped, and the first optical system 7
The first optical system 7 with respect to the optical path length
The size of 1 can be reduced. Thereby, the entire display optical system can be downsized.

Further, the light beam from the image display element 3 is reflected by the surface B, and after passing through the reciprocal optical path, does not go to the image display element side but is guided to the eyeball side.

The present embodiment has a merit in terms of brightness as in the sixth embodiment. In this embodiment,
The angle θ between the incident light of the central angle-of-view principal ray on the return reflection surface and the reflected light is set to a relatively large value, the return path is set to the surface A, and the light ray incident on the first optical system 71 is slightly different. Another surface B is arranged at a deviated position, and light rays are set to reach the surface B. Thereby, the reflection mirror having three surfaces (the surface A, the surface B, and the reflection reflection surface C) is formed of the reflection film capable of reflecting almost 100% of the light, and the bright first optical system 71 is realized. The reflective film is preferably a metal film.
This is because the metal film has a flat spectral reflectance characteristic, a color is less noticeable, and there is almost no difference in reflectance with respect to light having different polarization directions.

Further, in this embodiment, the surface B when acting as the final reflecting surface is a concave mirror having a very strong optical power (1 / focal length) with respect to the surface A (reflection, re-reflection). And is responsible for the main power of the first optical system 71. This is because the light is reflected twice on the surface A by the reciprocating optical path, so that the surface B has power and the power of the surface A is set to be weak to suppress the occurrence of aberration.

In particular, since the local generatrix section is an eccentric section, setting the surface B power on this section to be strong and the surface A power to be weak with respect to the central angle of view principal ray suppresses the occurrence of eccentric aberration. Alternatively, only the surface B may have power and the surface A may be a flat surface.

Since the surface B is a decentered curved surface, it is desirable to suppress the occurrence of decentering aberration as much as possible by using a rotationally asymmetric surface (so-called free curved surface).

If the reflecting surface other than the surface B is another free-form curved surface, the aspect ratio of the image displayed on the image display element 73 and the aspect ratio of the enlarged display screen can be set to be close to each other.

Further, when the surfaces A and B and the reflection reflection surface C are each formed by a curved surface, all the surfaces contribute to converging or diverging or aberration correction, and a cost reduction effect can be expected.

More preferably, all the three surfaces A and B and the folded reflection surface C that form the first optical system 71 have a rotationally asymmetric shape, so that the degree of freedom of decentering aberration correction increases.
It is possible to display an image with good image quality. At this time, if each rotationally asymmetric surface has a plane symmetric shape in the local sagittal cross-section direction in which the local generatrix cross section is the only symmetric plane, machining and manufacturing can be facilitated as compared with the case where there is no symmetry. Therefore, it is preferable.

(Ninth Embodiment) FIG. 9 shows a ninth embodiment of the present invention.
1 illustrates a display optical system that is an embodiment. This display optical system includes an optical element 81-a as a transparent body and a reflecting member 81.
A first optical system 81 composed of -b and two optical systems 82
-1, 82-2 and a second optical system.

The optical element 81-a has three optical surfaces, and the surfaces A (first surface) and B (third surface) are both transmission and reflection surfaces which serve as a transmission surface and a reflection surface. The surface D acts as a transmission surface. The reflection member 81-b also has a folded reflection surface C (second surface) having a reflection film formed on its surface. Surface B is a half mirror. The reflective film and the half mirror are preferably made of a metal film. This is because the metal film has a flat spectral reflectance characteristic, a color is less noticeable, and there is almost no difference in reflectance with respect to light having different polarization directions.

Reference numeral 3 in the figure denotes an image display element (LCD or the like) for displaying an image. In the present embodiment, the surface B acts as an incident surface and a reflecting surface of the light from the image display element 3, and the surface A acts as a reflecting surface and an emitting surface.

The light emitted from the image display element 3 emits the second light.
The first optical system 8 via the optical system 82-a
No. 1 optical element 81-a. The light enters the optical element 81-a from the surface B, is reflected by the surface A, and exits from the surface D. Then, the light is reflected by the return reflection surface C on the surface of the reflection member 81-b. After that, the light enters from the surface D of the optical element 81-a, is returned to the first light reflection area on the surface A, is reflected again, and is reflected on the surface B toward the exit pupil S (eyeball), and then the surface A.
Through the second optical system 8-a.
The optical power is adjusted by the other optical system 82-b of 2 and reaches the exit pupil S.

In this figure, as an example of the light emitted from the image display element 3, a central angle-of-view chief ray that emerges from the center of the display surface of the image display element 3 and reaches the center of the exit pupil S is shown.

In the present embodiment, the observer puts his eyes near the position of the exit pupil S, so that an enlarged image of the image displayed on the image display element 3 can be visually recognized.

In the first optical system 81, the light is the surface B (transmission) → the surface A (reflection) → the surface D (transmission) → the reflection member 81-b.
Return reflection surface C (return reflection) → surface D (retransmission)
The light passes through each surface in the order of → surface A (re-reflection) → surface B (reflection) (→ surface A (transmission)), and the optical path up to that point is traced in reverse, with the reflection at the return reflection surface as the boundary.

A forward path is formed from the surface B (transmission) to the return reflection surface C, a return path is formed from the reflection reflection surface C to the surface B (reflection), and a reciprocal optical path is formed by combining the return path and the return path.

In particular, the re-reflection on the surface A is such that the central angle-of-view chief ray is reflected and travels on the side opposite to the first reflection on the surface A with respect to the normal line of the surface on the hit point. Is formed.

By forming the reciprocating optical path in the first optical system 81 as described above, the optical paths are substantially overlapped, and the first optical system 8
1 is effectively used, and the first optical system 8 with respect to the optical path length is used.
The size of 1 can be reduced. As a result, the entire display optical system can be downsized.

The light rays from the image display element 3 are reflected by the surface B, and after passing through the reciprocating optical path, do not go to the image display element side but are guided to the eyeball side.

In this embodiment, since the three surfaces of the optical element 81-a are flat, the optical element 81-a itself has no optical power, and the folded reflection surface of the reflecting member 81-b is optical. Have the power As a result, the cost of the optical element 81-a can be considerably reduced, and the optical element 81-a
Also, the occurrence of aberration is suppressed.

It is preferable that the reflection on the surface A is the total internal reflection because the loss of the amount of light is reduced. Further, at least a region where the reflected light beam and the emitted light beam on the surface A are shared (the lower part of the surface A)
If the light is totally internally reflected by and the light is reflected by the reflective film except for the common area, the same degree of brightness can be obtained while increasing the degree of freedom in design as compared with the case of totally totally reflecting the light flux reflected on the surface A. Can be secured.

Since the boundary between the reflective film area and the common area is not clearly visible because the boundary between the reflective films is not preferable, the reflectance near the boundary (lower side in the reflective film area) gradually increases as the distance from the shared area increases. It is desirable to make the boundaries inconspicuous. The reflective film is preferably a metal film. This is because the metal film has a flat spectral reflectance characteristic, a color is less noticeable, and there is almost no difference in reflectance with respect to light having different polarization directions.

The above embodiments will be described below with reference to numerical examples.

[Numerical Example 1] FIG. 10 shows an optical path sectional view in a numerical example of the first embodiment shown in FIG. In the figure, reference numeral 1 is a first optical system that constitutes a display optical system, and is constituted by a prism-shaped transparent body (optical element) having three optical surfaces. S2, S4, S6, S8
Are the same surface, S3 and S9 are the same surface, and S5 and S7 are the same surface, and these three surfaces respectively correspond to the surfaces A, B and C described in the first embodiment.

Reference numeral 2 denotes a second optical system, here S1.
The transparent body is composed of the same medium and has three surfaces of 0, S11, and S12.

SI is the image display surface, and S1 is the exit pupil S of the display optical system. In addition, the folded reflection surface A (S6) and the surface C
A reflective film is formed on (S5, S7) and the surface B (S3, S
A half mirror is formed in 9).

In this numerical example, all the optical surfaces are rotationally asymmetrical surfaces and have a plane symmetric shape having the paper surface (yz section) as the only symmetric surface.

Table 1 shows optical data of this numerical example.
In this numerical example, an image with an exit pupil diameter of φ10 mm, an image display size of about 10 mm × 7.5 mm, and a horizontal angle of view of 50 ° is z.
It is a display optical system that displays in the positive infinity direction of the axis.

The leftmost item SURF in the optical data in Table 1 indicates the surface number. Further, X, Y, Z, and A are coordinate systems in which the center of the first surface S1 is the origin (0, 0, 0), and the y-axis and z-axis shown in the figure and the x-axis in the depth direction of the paper are taken. Is the position (x, y, z) of the surface apex of each surface and the rotation angle A (unit: degree) about the x axis with the counterclockwise direction as the positive direction on the drawing.

R is the radius of curvature. The term TYP represents the type of surface shape, SPH is a spherical surface, and FFS is a rotationally asymmetric surface according to the following equation.

[0225]

[Equation 1]

The numerical value written next to FFS in the TYP column is the aspherical coefficient k whose surface shape is shown at the bottom of the table.
And ci have a rotationally asymmetric shape corresponding to ci.

Nd and νd (however, indicated as vd in the table) respectively indicate the refractive index and the Abbe number at the d-line wavelength of the medium after that surface, and the change in the sign of the refractive index N on that surface. It shows that the light is reflected. When the medium is an air layer, only the refractive index Nd is displayed as 1.000,
Abbe number νd is omitted.

Further, the absolute value of the angle θ formed by the incident ray and the reflected ray of the central angle-of-view principal ray on the return reflecting surface is | θ |
It has been described as. The items in the above table are the same in the following numerical examples.

[0229]

[Table 1]

The optical system shown in this numerical example has a z
The light flux from an object point at infinity in the negative axis direction
1 to lead to the first optical system 1, and the first optical system 1
Can also be used as an image pickup optical system (second embodiment) that forms an image on the image pickup surface SI through the second optical system 2 after the injection.

[Numerical Example 2] FIG. 11 shows a third embodiment shown in FIG. 3 (slightly similar to the fourth embodiment shown in FIG. 4).
3 is a sectional view of the optical path in the numerical example of FIG.

In the figure, reference numeral 21 denotes a first optical system constituting the display optical system, S2, S4 and S6 are surfaces A, S3 and S7 are surfaces B, and S5 is a folded reflection surface C. A reflection film is formed on the return reflection surface C (S5), and the surface B (S3, S7)
Is formed with a half mirror. SI is an image display surface, and S1 is an exit pupil S of the display optical system.

Reference numeral 2 denotes a second optical system, which comprises two lenses 2-1 and 2-2 each having a two-sided structure.
One surface of -1 is joined to the transparent body that constitutes the first optical system 21, and this surface is indicated as S7.

Further, the optical surfaces from S1 to S10 in the first optical system 21 are all rotationally asymmetrical surfaces in this numerical example, and have a plane symmetric shape having the paper surface (yz section) as the only symmetric surface. is doing. Table 2 shows optical data of this numerical example.

[0235]

[Table 2]

In the fourth embodiment shown in FIG. 4, θ is set so that the effective surfaces of the surface S7 and the surface S3 of this numerical example do not overlap each other, and the surface S7 is defined as the incident surface, and another surface is defined as S3. The surface can be implemented by making the surface only a reflection surface and the surface S7 a bonding surface which is only a transmission function. Further, θ may be set so that the effective surfaces of S7 and S3 do not overlap, S7 and S3 may remain the same surface, the S3 surface may be a reflection-only surface, and the S7 surface may be a cemented surface that is only a transmission function.

As a result, the surface area can be reduced and the brightness remains. If the optical interface 21 and the lens 2-1 are integrated into one member (integrally molded product or the like) by eliminating the S7 cemented surface only for the transmission action, the number of parts is reduced by one and the cost of the optical system can be reduced. Further, the cemented surface of S7, which only has a transmission function, is eliminated, and the optical system 21 and the lens 2-1 are removed.
May be arranged with an air layer at a minute interval.

Considering the numerical value having the dimension of the length in this numerical example as mm, the exit pupil diameter is φ6 mm, the image display size is about 10 mm × 7.5 mm, and the horizontal is about 50 mm.
The display optical system displays an image at an infinity in the positive direction of the z-axis at an angle of view of 90 ° and a vertical angle of about 39 °.

Also, this numerical example can be used as an image pickup optical system similarly to the numerical example 1.

[Numerical Example 3] FIG. 12 shows an optical path sectional view in a numerical example of the fifth embodiment shown in FIG.

In the figure, 41 indicates a first optical system, and 41-
Reference numeral 41-b is a reflection mirror member, and a is an optical element as a transparent body having at least three surfaces. S2, S4, S
6, S8, S10 are on the same plane, S3, S11 are on the same plane, S
Reference numerals 5 and S9 are the same surface and correspond to the surface A, the surface B, and the surface C described in FIG. 5, respectively.

Reference numeral S7 is a return reflection surface. A reflection film is formed on the folded reflection surface (S7) and the surfaces C (S5, S9).
A half mirror is formed on the surface B (S3, S11). SI is an image display surface, and S1 is an exit pupil S of the display optical system.

In the figure, 2 is a second optical system,
It is composed of a lens having S13.

In FIG. 5, the angle θ is set to a certain degree, but in the present numerical example, the value of θ is made considerably small to give priority to the optical performance of the display optical system. Table 3 shows the optical data of this numerical example.

[0245]

[Table 3]

This numerical example is a display optical system having specifications substantially equal to those of the numerical example 1 when the numerical value having the dimension of length is considered as mm.

Also, this numerical example can be used as an image pickup optical system similarly to the numerical example 1.

[Numerical Example 4] FIG. 13 shows an optical path sectional view in a numerical example of the sixth embodiment shown in FIG. In the figure, reference numeral 51 denotes a first optical system which constitutes a display optical system, and is constituted by an optical element as a transparent body having four optical surfaces.

S2, S4 and S8 are the same surface, S3 and S9 are the same surface, S5 and S7 are the same surface, and these three surfaces correspond to the surfaces A, B and C described in the sixth embodiment. .

[0250] S6 is the return reflection surface D. A reflection film is formed on the return reflection surface D (S6) and the surfaces C (S5, S7).
A half mirror is formed on the surface B (S3, S9).

A second optical system 2 is composed of two lenses 2-1 and 2-2 each having two surfaces. One surface S10 of the lens 2-1 is the first optical system 51.
They are bonded on the same surface as the surface S9 of (optical element). SI
Is an image display surface, and S1 is an exit pupil S of the display optical system.

In this numerical example, all the optical surfaces are rotationally asymmetrical surfaces and have a plane symmetric shape having the paper surface (yz section) as the only symmetric surface. Table 4 shows optical data of this numerical example.

[0253]

[Table 4]

This numerical example is a display optical system having substantially the same specifications as Numerical example 2 when a numerical value having a length dimension is considered as mm.

Also, this numerical example can be used as an image pickup optical system similarly to the numerical example 1.

[Numerical Example 5] FIG. 14 shows an optical path sectional view in a numerical example in an embodiment similar to the seventh embodiment shown in FIG. In the figure, reference numeral 61 denotes a first optical system which constitutes a display optical system, and two optical elements 61-a.
1, 61-a2. Both optical elements 61-a1, 61
Both -a2 have three optical surfaces.

S2, S4 and S14 are the same plane, S3 and S1
5 is the same surface, S7, S11 are the same surface, S6, S8, S1
0 and S12 are the same plane, and these four planes are the seventh plane, respectively.
It corresponds to the surfaces A, B, C, E described in the embodiment.

Reference numeral S9 is a return reflection surface G. A reflection film is formed on the folded reflection surface G (S9) and the surface C (S7, S11), and a half mirror is formed on the surface B (S3, S15).

The fifth numerical embodiment is the seventh numerical example shown in FIG.
Unlike the embodiment, the first optical system 61 does not include a reflection member having the folded reflection surface G, and the optical element 61-a2 is not provided.
The inner surface S9 is used as a return reflection surface to simplify the optical adjustment. Moreover, since the two optical elements are used for the first optical system 61, the second optical system is not required between the first optical system 61 and the image display element 63 (SI).

SI is the image display surface, and S1 is the exit pupil S of the display optical system. In this numerical example, the surface B (S3, S1
5), surface C (S7, S11), folded reflection surface G (S
A rotationally asymmetric surface is adopted for 9) and has a plane symmetric shape having the paper surface (yz section) as the only symmetric surface. It should be noted that better optical performance can be obtained by adopting rotationally asymmetric surfaces for all the optical surfaces. Table 5 shows optical data of this numerical example.
Shown in.

[0261]

[Table 5]

This numerical example provides a display optical system having specifications substantially equivalent to those of the numerical example 1 when the numerical value having the dimension of length is considered as mm.

Also, this numerical example can be used as an image pickup optical system similarly to the numerical example 1.

[0264]

As described above, according to the first invention of the present application, the light is substantially reciprocated between the first surface and the second surface so that the optical paths are substantially overlapped (reciprocal optical path). Because
Even though it is a small optical system, a long optical path can be secured.
Therefore, a wide display angle of view can be achieved while using a small original image, and a small display optical system as a whole can be realized.

If the light is formed into an intermediate image in the display optical system, the degree of freedom in layout is increased and the original image can be displayed on a large screen, and the display optical system can be displayed even if the optical path length is considerably long. Can be made small.

Further, according to the second invention of the present application, since the light is substantially reciprocated between the first surface and the second surface so that the optical paths are substantially overlapped (reciprocal optical path), the size is small. Even though it is an optical system, a long optical path can be secured. For this reason, it is possible to achieve a wide shooting angle of view while being compact.

If light is formed as an intermediate image in the image pickup optical system, the degree of freedom in layout is increased, a subject image having a wide angle of view can be sufficiently reduced and guided to the image pickup surface, and the optical path length can be increased. The imaging optical system can be made compact even when the length is considerably long.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a display optical system that is a first embodiment of the present invention.

FIG. 2 is a configuration diagram of an image pickup optical system that is a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a display optical system that is a third embodiment of the present invention.

FIG. 4 is a configuration diagram of a display optical system that is a fourth embodiment of the present invention.

FIG. 5 is a configuration diagram of a display optical system that is a fifth embodiment of the present invention.

FIG. 6 is a configuration diagram of a display optical system that is a sixth embodiment of the present invention.

FIG. 7 is a configuration diagram of a display optical system that is a seventh embodiment of the present invention.

FIG. 8 is a configuration diagram of a display optical system that is an eighth embodiment of the present invention.

FIG. 9 is a configuration diagram of a display optical system that is a ninth embodiment of the present invention.

FIG. 10 is a sectional view of an optical system according to Numerical Example 1 (implementation form of the first embodiment) of the present invention.

FIG. 11 is a sectional view of an optical system according to Numerical Example 3 (implementation form of the third embodiment) of the present invention.

FIG. 12 is a sectional view of an optical system according to Numerical Example 4 of the present invention (an embodiment of the fourth embodiment).

FIG. 13 is a sectional view of an optical system according to Numerical Example 5 (implementation form of the fifth embodiment) of the present invention.

FIG. 14 is a sectional view of an optical system according to Numerical Example 6 (embodiment of the sixth embodiment) of the present invention.

FIG. 15 is a configuration diagram of a conventional display optical system.

FIG. 16 is a block diagram of a conventional display optical system.

[Explanation of symbols]

1, 11, 21, 31, 41, 51, 61, 71, 81
First optical system 2, 22, 52, 82 Second optical system 3 Image image display element 4 Imaging element

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] December 19, 2002 (2002.12.
19)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

17. An image pickup apparatus comprising the image pickup optical system according to claim 16 .

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

Further, in order to further improve the optical performance as compared with the optical system proposed in Japanese Patent Laid-Open No. 10-153748, the internal reflection surface of the decentering prism is increased so that the intermediate image is formed only by the decentering prism. A type in which a second decentering prism is provided in the first decentering prism optical system, and the like in which the image is formed and the image is guided to an observer are disclosed in JP-A-2000-06.
6106, Japanese Patent Laid-Open No. 2000-105338,
JP 2000-131614 A, JP 2000-1
Japanese Patent No. 99853 and Japanese Patent Laid-Open No. 2000-227554.
And Japanese Patent Laid-Open No. 2000-231060.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0028

[Correction method] Change

[Correction content]

In addition, the optical surfaces forming the image pickup optical system are
By making the light beam eccentric, it is possible to further reduce the thickness, and by giving the optical surface a curvature, it is possible to remove an unnecessary surface in the image pickup optical system and achieve size reduction. Furthermore, by making the optical curved surface a rotationally asymmetric surface (free curved surface), it is possible to satisfactorily correct various aberrations, and if multiple free curved surfaces are used, the aspect ratio of the subject and the aspect ratio of the captured image can be made close. It becomes possible to obtain a high-quality photographed image.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0036

[Correction method] Change

[Correction content]

| Θ | <60 ° (1) If the upper limit of this conditional expression (1) is exceeded, the optical path (return path) after the reflected reflection does not return in the forward path, and becomes a zigzag optical path rather than a round-trip optical path. optical system is increased in size.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0090

[Correction method] Change

[Correction content]

If the reflection on the surface A is total internal reflection, the loss of the amount of light is reduced, which is preferable. Further, at least a region where the reflected light beam and the emitted light beam on the surface A are shared (the lower part of the surface A)
If the light is totally internally reflected by and the light is reflected by the reflective film in areas other than the common area, the same degree of brightness can be achieved while increasing the degree of freedom in design as compared with the case of totally internally reflecting all the light flux reflected on the surface A. Can be secured.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0103

[Correction method] Change

[Correction content]

In this drawing, as an example of the light emitted from the image display element 3 , a central angle-of-view chief ray that exits the center of the display surface of the image display element 3 and reaches the center of the exit pupil S is shown.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Name of item to be corrected] 0113

[Correction method] Change

[Correction content]

Since the boundary between the reflective film area and the common area is not clearly visible because the boundary of the reflective film is undesired, the reflectance near the boundary (the lower side in the reflective film area) gradually increases from the lower part to the upper part. It is desirable to raise it to make the boundary inconspicuous. The reflective film is preferably a metal film. Metal film spectral reflectance characteristic is hardly noticeable color flat, polarized
This is because there is almost no difference in reflectance for light having different light directions.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0161

[Correction method] Change

[Correction content]

In the first optical system 51 , the light is reflected twice or more on the surfaces A and C by the reciprocal optical path. Therefore, the surface B is made to have a power, and the powers of the surfaces A and C are set to be weak so as to reduce the aberration. The occurrence is suppressed. In particular, since the local generatrix cross section is an eccentric cross section, setting the power of the surface B and the power of the surfaces A and C on this cross section in the central ray at the central angle of view to be strong and eccentric aberration can be suppressed. Further, only the surface B may have power, and the surfaces A and C may be flat surfaces.

[Procedure Amendment 9]

[Document name to be amended] Statement

[Correction target item name] 0162

[Correction method] Change

[Correction content]

Since the surface B is a decentered curved surface, it is desirable to suppress the occurrence of decentration aberrations as much as possible by using a rotationally asymmetric surface (so-called free curved surface). Also, surface B
If the other surface is a free-form surface, the image display element 3
It is possible to set the aspect ratio of the image displayed in and the aspect ratio of the enlarged display screen to be close to each other.

[Procedure Amendment 10]

[Document name to be amended] Statement

[Name of item to be corrected] 0166

[Correction method] Change

[Correction content]

(Seventh Embodiment) FIG. 7 shows a seventh embodiment of the present invention.
1 illustrates a display optical system that is an embodiment. This display optical system includes two optical elements 61-a1 and 61- which are transparent bodies.
The first optical system 61 includes a2 and a reflecting member 61-b. Each of the optical elements 61-a1 and 61-a2 has three optical surfaces, and a surface A (first surface), a surface B (third surface), and a surface E are transmissive and reflective acting as a transmissive surface and a reflective surface. The dual-purpose surface, the surface C (second surface) is a surface only for reflection,
The surface D and the surface F are surfaces having only a transmission effect.

[Procedure Amendment 11]

[Document name to be amended] Statement

[Name of item to be corrected] 0187

[Correction method] Change

[Correction content]

Reference numeral 3 in the figure denotes an image display element (LCD or the like) for displaying an image. The light emitted from the image display element 3 is guided to the reflecting member 71-b1 of the first optical system 71 via the second optical system 2. Light is transmitted from the surface A (first surface), which is the reflection mirror surface of the reflection member 71-b1, to the first optical system 7.
1 is incident on the surface A, is reflected by the surface A, and is guided to the return reflection surface C (second surface) which is the mirror surface of the reflection member 71-b2. On the return reflection surface C, the incident light is reflected so as to return to the area closer to the first light reflection area on the surface A, but the angle formed by the incident light and the reflected light on the return reflection surface C of the central view angle principal ray. Is reflected so that it becomes θ.

[Procedure Amendment 12]

[Document name to be amended] Statement

[Correction target item name] 0200

[Correction method] Change

[Correction content]

If the reflecting surface other than the surface B is another free-form curved surface, the aspect ratio of the image displayed on the image display element 3 and the aspect ratio of the enlarged display screen can be set close to each other.

[Procedure Amendment 13]

[Document name to be amended] Statement

[Correction target item name] 0206

[Correction method] Change

[Correction content]

The light emitted from the image display element 3 emits the second light.
The first optical system 8 via the optical system 82-1 of the optical system
No. 1 optical element 81-a. The light enters the optical element 81-a from the surface B, is reflected by the surface A, and exits from the surface D. Then, the light is reflected by the return reflection surface C on the surface of the reflection member 81-b. After that, the light enters from the surface D of the optical element 81-a, is returned to the first light reflection area on the surface A, is reflected again, and is reflected on the surface B toward the exit pupil S (eyeball), and then the surface A.
Through the second optical system 8-a.
The optical power is adjusted by the other optical system 82-2 out of 2, and reaches the exit pupil S.

[Procedure Amendment 14]

[Document name to be amended] Statement

[Correction target item name] 0224

[Correction method] Change

[Correction content]

R is the radius of curvature. FFS term (Numerical value
In the second and subsequent examples, the term TYP) indicates the type of surface shape, and SP
H is a spherical surface, and the numeral (FFS after Numerical Example 2) is a rotationally asymmetric surface according to the following formula.

[Procedure Amendment 15]

[Document name to be amended] Statement

[Name of item to be corrected] 0226

[Correction method] Change

[Correction content]

Numbers in the FFS section or FFS in the TYP column
The numerical value beside the item indicates that the surface shape is a rotationally asymmetric shape corresponding to the aspherical coefficients k and ci described in the lower part of the table.

[Procedure Amendment 16]

[Document name to be amended] Statement

[Name of item to be corrected] 0227

[Correction method] Change

[Correction content]

Nd and νd (however, indicated as vd in the table) respectively indicate the refractive index and the Abbe number at the d-line wavelength of the medium after that surface, and the change in the sign of the refractive index Nd at that surface. It shows that the light is reflected. When the medium is an air layer, only the refractive index Nd is shown as 1.000 and the Abbe number νd is omitted.

[Procedure Amendment 17]

[Document name to be amended] Statement

[Correction target item name] 0233

[Correction method] Change

[Correction content]

Reference numeral 22 denotes a second optical system, each of which is 2
Two lenses 22-1 surface structure consists 22-2, one surface of Les <br/> lens 22-1 is bonded to the transparent member constituting the first optical system 21, this surface Notated as S7.

[Procedure 18]

[Document name to be amended] Statement

[Correction target item name] 0234

[Correction method] Change

[Correction content]

In addition, the first optical system 21 and the second optical system
The optical surfaces from S1 to S10 in the system 22 are all rotationally asymmetrical surfaces in this numerical example, and are the paper surface (yz
It has a plane-symmetric shape with a cross-section) as the only plane of symmetry. Table 2 shows optical data of this numerical example.

[Procedure Amendment 19]

[Document name to be amended] Statement

[Correction target item name] 0235

[Correction method] Change

[Correction content]

[0235]

[Table 2]

[Procedure amendment 20]

[Document name to be amended] Statement

[Name of item to be corrected] 0237

[Correction method] Change

[Correction content]

As a result, the surface area can be reduced and the brightness remains. Further, if the optical system 21 and the lens 22-1 are integrated into a single member (integrally molded product, etc.) by eliminating the joining surface of S7, which only has a transmission effect, the number of parts is reduced by one and the cost of the optical system can be reduced. In addition, the optical system 21 and the lens 22 are eliminated by eliminating the cemented surface of S7, which only has a transmission effect.
-1 may be arranged with an air layer having a minute interval.

[Procedure correction 21]

[Document name to be amended] Statement

[Correction target item name] 0251

[Correction method] Change

[Correction content]

Reference numeral 52 denotes a second optical system, which is composed of two lenses 52-1 and 52-2 each having two surfaces. One surface S10 of the lens 52-1 is cemented on the same surface as the surface S9 of the first optical system 51 (optical element). SI is an image display surface, and S1 is an exit pupil S of the display optical system.

[Procedure correction 22]

[Document name to be amended] Statement

[Name of item to be corrected] 0259

[Correction method] Change

[Correction content]

The fifth numerical embodiment is the seventh numerical example shown in FIG.
Unlike the embodiment, the first optical system 61 does not include a reflection member having the folded reflection surface G, and the optical element 61-a2 is not provided.
The inner surface S9 is used as a return reflection surface to simplify the optical adjustment. Moreover, since the two optical elements are used for the first optical system 61, the second optical system is not required between the first optical system 61 and the image display element 3 (SI).

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazutaka Inoguchi             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation (72) Inventor Akinari Takagi             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation (72) Inventor Hideki Morishima             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation F-term (reference) 2H087 KA03 LA12 RA34 TA01 TA02                       TA06                 5C022 AC54 AC55

Claims (30)

[Claims] 1. A display optical system for guiding light from an original image to an observer's eye or a projection surface, wherein a first surface having at least a reflecting action and a light beam reflected by the first surface are re-described. A second surface reflecting toward the first surface, and the central angle-of-view chief ray re-incident on the first surface is opposite to the normal to the surface on the hit point. A display optical system characterized in that the light is reflected to the side and proceeds. 2. The light beam from the original image is reflected by the second surface, re-reflected by the first surface, and then reflected by the third surface decentered with respect to the eye or the projection surface side. The display optical system according to claim 1, wherein: 3. The display optical system according to claim 1, wherein the display optical system has a turn-back surface having only a reflecting action, which returns the central angle-of-view chief ray from the original image to the opposite side. Display optics. 4. The display optical system according to claim 3, wherein the folding reflection surface is the first surface or the second surface. 5. The display optical system according to claim 1, wherein light forms an intermediate image in the display optical system. 6. The display optical system according to claim 5, wherein a transparent body whose inside is filled with an optical medium is used, and light forms an intermediate image in the transparent body. Display optics. 7. The display optical system according to claim 5, wherein at least one of the first surface and the second surface is decentered with respect to an incident light ray. 8. The method according to claim 7, wherein at least one of the first surface and the second surface has a curvature.
The display optical system described in 1. 9. The display optical system according to claim 8, wherein at least one of the first surface and the second surface is a rotationally asymmetric surface. 10. The display optical system according to claim 5, wherein at least the first surface is formed on a transparent body whose inside is filled with an optical medium. 11. The light is totally internally reflected on any one of the optical surfaces formed on the transparent body.
The display optical system according to 0. 12. The display optical system according to claim 2, wherein the third surface has a curvature. 13. The display optical system according to claim 12, wherein the third surface is a rotationally asymmetric surface. 14. The focal length of the local generatrix section in the reflection of the third surface is greater than the focal length of the local generatrix section of the first surface or the second surface that is reflected or transmitted a plurality of times. The positive and shortest display optical system according to claim 2. 15. An image display device comprising the display optical system according to claim 1. 16. An imaging optical system for guiding light from a subject to an imaging surface, comprising: a first surface having at least a reflecting action; and a light beam reflected by the first surface, which is directed to the first surface again. And a second surface that is reflected by the first surface, and the central angle-of-view chief ray that re-enters the first surface is reflected and travels to the opposite side to the normal line of the surface on the hit point. An imaging optical system characterized by the above. 17. A light ray from a subject is reflected by a third surface eccentric to the light ray, is then reflected by the first surface, is reflected by the second surface, and is then again reflected by the first reflection surface. 17. The light is reflected by the surface and travels to be guided to the imaging surface.
The image pickup optical system described in 1. 18. The image pickup optical system according to claim 16 or 17, wherein the central field angle chief ray from the subject is reflected back to substantially the opposite side and has a folding surface having only a reflecting action. Imaging optics. 19. The return reflection surface is the first surface or the second surface.
The image pickup optical system described in 1. 20. The image pickup optical system according to claim 16, wherein the light forms an intermediate image in the image pickup optical system. 21. The imaging optical system according to claim 20, wherein a transparent body whose inside is filled with an optical medium is used, and light is intermediately imaged in the transparent body. Imaging optics. 22. The image pickup optical system according to claim 20, wherein at least one of the first surface and the second surface is decentered with respect to an incident light ray. 23. The imaging optical system according to claim 22, wherein at least one of the first surface and the second surface has a curvature. 24. The image pickup optical system according to claim 23, wherein at least one of the first surface and the second surface is a rotationally asymmetric surface. 25. The imaging optical system according to claim 20, wherein at least the first surface is formed on a transparent body whose inside is filled with an optical medium. 26. The light is totally internally reflected by any one of the optical surfaces formed on the transparent body.
5. The imaging optical system according to item 5. 27. The image pickup optical system according to claim 17, wherein the third surface has a curvature. 28. The image pickup optical system according to claim 27, wherein the third surface is a rotationally asymmetric surface. 29. The focal length of the local generatrix section in the reflection of the third surface is greater than the focal length of the local generatrix section of the surface of the first surface or the second surface that is reflected or transmitted a plurality of times. The imaging optical system according to claim 17, wherein the imaging optical system is positive and shortest. 30. An image pickup apparatus comprising the image pickup optical system according to any one of claims 16 to 29.