JPH11308640A - Method and apparatus for virtual image forming - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a satisfactory virtual image by improving the light utilization efficiency and preventing returning lights at the same time. SOLUTION: A polarized beam splitter 9 which reflects an s-polarized light reflects a polarized luminous flux emitted from an LCD 8 and having prescribed image information to lead the s-polarized light to a quarter-wave plate 11, after which it is reflected in an aspherical concave half mirror 12, and led again to the quarter-wave plate 11, where it is converted into a p-polarized light and the p-polarized light is transmitted through a polarized beam splitter 9 and led to a viewer side 13 to form a virtual image.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a virtual image forming method and a virtual image forming apparatus for forming an image output from an image output device as a virtual image.

[0002]

2. Description of the Related Art Conventionally, in a virtual image forming optical system (virtual image observation optical system) using a light beam splitting element, a non-polarizing beam splitter such as a half mirror or a 1/4 as a light beam splitting element.
A polarizing beam splitter without the use of a wave plate is used.

A virtual image forming optical system using a half mirror as the light beam splitting element will be described with reference to FIG.

In this virtual image forming optical system, a light beam emitted from a backlight 7 is modulated by a liquid crystal display (LCD) 8,
The light beam output from the image output device including the backlight 7 and the LCD 8 is guided to the aspheric concave half mirror 12 via the half mirror 31, and the light beam reflected by the aspheric concave half mirror 12 is further reflected by the half mirror 31. Through the pupil 13.

[0005] At this time, the brightness of the display image is incident on the pupil 13 because the display light beam passes through the half mirror 31 twice assuming that the light amount of the light beam (for example, p-polarized light) emitted from the LCD 8 is 100%. The amount of light flux is 100% × 0.5
× 0.5 = 25%.

The light beam reflected by the aspherical concave half mirror 12 is reflected by the half mirror 31 and returns to the image output device again to cause a ghost image or the pupil 13
The light beam incident from the side may return to the image output device.
Further, external light (stray light) 30 may enter the pupil 13 due to reflection by the half mirror 31, and the brightness of the pupil 13 is such that a light beam having a light amount of 50% with the light amount of the stray light 30 being 100%. 13 is incident.

In place of the half mirror 31, for example, a polarizing beam splitter (PBS) having a transmittance of p-polarized light of 100% and a reflectance of s-polarized light of 50% is used. In a case where the light amount of the light beam emitted from the image output device is 100%, the brightness of the display image is 100% × 0.5 × 0.5 = 25%.
The brightness of the stray light is [50% (s component) × 0.5]
+ [50% (p component) × 0] = 25%. As described above, when the polarizing beam splitter is used instead of the half mirror, although the ratio (S / N ratio) between the brightness of the display image and the brightness of the stray light is improved, it is hard to say that it is still sufficient. .

[0008]

As described above, in the conventional virtual image forming optical system, (1) the light flux emitted from the light source passes through the beam splitter twice with the forward light and the backward light, so that the light use efficiency is reduced. The maximum is only 25%. (2) The light emitted from the image output device returns to the image output device again due to the presence of the beam splitter,
A ghost image is generated due to multiple reflections between the beam splitter and the image output device. (3) When a strong parallel line such as sunlight enters from the pupil side, the light forms an image on the image output device due to the regression of the light, and the heat generated thereby may damage the liquid crystal display panel and the like. There is. There is a problem.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to improve a light use efficiency and at the same time to obtain a clearer virtual image image and a virtual image forming apparatus. Is to provide.

[0010]

That is, the present invention is directed to a process of guiding a polarizing light beam having image information emitted from an image output device to a polarizing light beam splitting element, and a step of guiding the polarized light beam through the polarizing light beam splitting element. Guiding the luminous flux to an optical element that provides a quarter-wavelength optical path difference between orthogonal linearly polarized light components;
A process in which the light flux whose polarization state has changed after passing through this optical element is reflected by a reflective optical element and guided again to the optical element, and the light flux whose polarization state has further changed by passing through the optical element, Through the polarizing light beam splitting element, leading to a light path different from the light path of the polarizing light beam emitted from the image output device to form a virtual image of the output image emitted from the image output device. The present invention relates to a virtual image forming method (hereinafter, referred to as a first virtual image forming method of the present invention).

According to the first virtual image forming method of the present invention, in particular, the linear polarization component of the polarizing light flux (particularly, linearly polarized light) is interposed between the polarizing light beam splitting element and the reflective optical element. The optical element (for example, a quarter-wave plate) that gives a quarter-wavelength optical path difference to the image output device is disposed, and the light flux (forward light flux) guided from the image output device is reflected by the reflection type optical element. Then, the polarization state (polarization direction) of the light flux (light flux on the return path) guided to the side on which the virtual image is formed is made different from each other, so that the light flux on the outward path and the light flux on the return path by the polarizing light beam splitting element. The light beam can be split at a high rate to increase the light use efficiency. At the same time,
Return light that produces ghost images (multifold light)
However, returning to the image output device or the like is suppressed.

According to the present invention, as a device for implementing the first virtual image forming method of the present invention with good reproducibility, a polarizing beam having image information emitted from an image output device is guided to a polarizing beam splitter. And dividing the polarizing light beam having passed through the polarizing light beam splitting element by a quarter between orthogonal linearly polarized light components.
Guiding the optical element to give an optical path difference of wavelength, and passing the optical element and changing the polarization state of the light beam, reflecting the reflected optical element and guiding the optical element again to the optical element, Guiding the light flux whose polarization state has been further changed by passing through the polarizing light beam splitting element to a light path different from the light path of the polarizing light beam emitted from the image output device, to obtain the image. A virtual image forming apparatus that forms a virtual image of an output image output from an output device, wherein the image output device, the polarizing light beam splitting element, the optical element, and at least one of the reflective optical elements Wherein the optical element is provided between the polarizing light beam splitting element and the reflective optical element,
A virtual image forming apparatus (hereinafter, referred to as a first virtual image forming apparatus of the present invention) is provided.

Further, according to the present invention, a step of guiding a polarizing beam having image information emitted from an image output device to a polarizing beam splitting element, and intersecting the polarizing beam passing through the polarizing beam splitting element at right angles. A process of leading to an optical element that gives a quarter-wavelength optical path difference between linearly polarized light components, and a light beam that has passed through this optical element and has changed its polarization state is reflected by a reflection-type diffractive optical element, and the optical beam is again reflected. The process of leading to the element and the light beam whose polarization state has been further changed by passing through the optical element are different from the light path of the polarizing light beam emitted from the image output device via the polarizing light beam splitting element. The present invention relates to a virtual image forming method (hereinafter, referred to as a second virtual image forming method of the present invention) for forming a virtual image of an output image emitted from the image output device through a process of leading to an optical path. is there.

According to the second virtual image forming method of the present invention, in particular, the linearly polarized light component of the polarizing light beam is interposed between the polarizing light beam splitting element and the reflection type diffractive optical element (for example, a volume hologram). The optical element that provides a quarter-wavelength optical path difference therebetween is provided, and the light flux (forward light flux) guided from the image output device is reflected by the reflective diffraction optical element to form the virtual image. Since the respective polarization states (polarization directions) of the light beam (light beam on the return path) guided to the image forming side are made different from each other, the polarization light beam splitting element causes the light beam on the outward path and the light beam on the return path at a high ratio. By dividing, the light use efficiency can be increased. At the same time, return light (multiple return light) that causes a ghost image or the like is suppressed from returning to the image output device or the like. Further, since the reflection type diffractive optical element has wavelength selectivity,
All of the strong parallel light such as sunlight does not return to the image output device from the side where the virtual image is formed, and damage to the image output device due to the return of the parallel light is suppressed.

According to the present invention, as a method of implementing the second virtual image forming method of the present invention with good reproducibility, a polarizing beam having image information emitted from an image output device is guided to a polarizing beam splitter. And dividing the polarizing light beam having passed through the polarizing light beam splitting element by a quarter between orthogonal linearly polarized light components.
A step of leading to an optical element that gives an optical path difference of a wavelength, a step of reflecting a light beam having a changed polarization state after passing through the optical element, reflecting the light beam by a reflective diffractive optical element, and guiding the reflected light to the optical element again; Through the polarizing light beam splitting element, through a process of guiding the light beam having a different polarization state to a light path different from the light path of the polarizing light beam emitted from the image output device. A virtual image forming apparatus that forms a virtual image of an output image output from an image output device, wherein the image output device, the polarizing light beam splitting element, the optical element, and at least one of the reflective diffractive optics A virtual image forming apparatus (hereinafter, referred to as a second virtual image forming apparatus of the present invention, wherein the optical element is provided between the polarizing beam splitter and the reflective diffractive optical element. Call ) It is intended to provide.

Further, according to the present invention, there is provided a process for guiding a light beam emitted from a light source to a polarizing beam splitting device, and a process for dividing a polarizing beam passing through the polarizing beam splitting device into a quarter between orthogonal linearly polarized light components. The process of leading to an optical element that gives an optical path difference of wavelength, the process of guiding a polarizing light flux whose polarization state has been changed by this optical element to a reflective image output device, and the image information reflected by the reflective image output device Having a polarizing light beam having a light beam whose polarization state has been further changed after passing through the optical element and guiding the light beam to the refractive optical element through the polarizing light beam splitting element,
The present invention relates to a virtual image forming method for forming a virtual image of an output image emitted from the reflection type image output device (hereinafter, referred to as a third virtual image forming method of the present invention).

According to the third virtual image forming method of the present invention, in particular, the polarization light beam is interposed between the polarization light beam splitting element and the reflection type image output device (for example, a reflection type liquid crystal display element). The optical element that gives a quarter-wavelength optical path difference between linearly polarized light components is disposed, and a light beam (a forward light beam) guided from the light source to the image output device is output from the reflection type image output device. Since the respective polarized states (polarization directions) of the light flux (light flux on the return path) reflected and guided to the side on which the virtual image is formed are made different from each other, the light flux on the outward path and the return path on the polarizing light beam splitting element are different. Can be split at a high rate to increase the light use efficiency. At the same time, return light (multiple return light) that produces a ghost image or the like is minimized from returning to the image output device or the like.

According to the present invention, as a method for implementing the third virtual image forming method of the present invention with good reproducibility, a step of guiding a light beam emitted from a light source to a polarizing beam splitting element, Guiding the polarizing luminous flux having passed through the element to an optical element that provides a quarter-wavelength optical path difference between orthogonal linearly polarized light components, and converting the polarizing luminous flux whose polarization state has been changed by the optical element to a reflective image output device And the process of guiding the polarizing light beam having image information reflected by the reflective image output device to the optical element again, and the light beam that has passed through the optical element and has changed its polarization state. And a step of guiding the light to the refractive optical element through the polarizing light beam splitting element to form a virtual image of an output image emitted from the reflective image output device. Device and said A light beam splitting element, the optical element, and at least one refractive optical element, wherein the optical element is provided between the polarizing light beam splitting element and the reflective image output device; It is intended to provide a virtual image forming apparatus (hereinafter, referred to as a third virtual image forming apparatus of the present invention).

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a first virtual image forming method of the present invention and a first virtual image forming apparatus of the present invention will be described.

In the first virtual image forming method of the present invention and the first virtual image forming apparatus of the present invention, a linearly polarized light component (for example, s) emitted from the image output device such as a liquid crystal display.
Guiding the polarizing light beam having polarized light to the polarizing light beam splitting device such as a polarizing beam splitter; and the polarizing light beam splitting device (for example, a polarizing beam splitter that reflects s-polarized light and transmits p-polarized light). Guiding the light beam reflected by the に wavelength plate to a 波長 wavelength plate that gives a quarter wavelength optical path difference (that is, a phase difference of 90 °) between its orthogonal linearly polarized light components, The light flux (for example, clockwise circularly polarized light) that has passed through the plate and changed in polarization state is reflected by the reflective optical element (for example, becomes clockwise circularly polarized light),
The step of guiding the light again to the 波長 wavelength plate and the step of transmitting the light flux (for example, p-polarized light) whose polarization state has changed by passing through the 前 記 wavelength plate again, through the polarizing light beam splitting element. Thus, a virtual image of the output image emitted from the image output device can be formed (see FIG. 1).

Here, the 波長 wavelength plate (or λ / 4)
Plate) whose optical axis is at 45 ° to the polarization direction of the light beam.
It is desirable to install it inclining. With this arrangement, the polarizing light beam can be efficiently polarized in a predetermined polarization direction.

The reflection type optical element may be one kind of optical element selected from the group consisting of a concave mirror, a concave translucent mirror, an aspheric concave mirror, and an aspheric concave semitransparent mirror.
In particular, when the background light beam and the light beam having the image information are overlapped, it is desirable to use a semi-transparent mirror (half mirror) having a concave surface or an aspheric concave surface.

The quarter-wave plate can be provided integrally with the reflective optical element. That is, by integrating the １ ／ wavelength plate and the reflection type optical element, 1 /
Spatial fluctuation (for example, light scattering) between the four-wavelength plate and the reflective optical element can be reduced. In particular, since the light beam reciprocates between the quarter-wave plate and the reflective optical element, it is desirable that the spatial fluctuation is small.

The image output device is a liquid crystal image output device (liquid crystal display element or LCD: Liquid Crystal Displ.).
ay). For this liquid crystal image output device, for example, a backlight such as a cold-cathode tube or a light-emitting diode can be used. Further, between this backlight and the liquid crystal display element, illumination brightness is made uniform, and a diffusion angle is obtained. It is desirable that a diffusion plate for controlling the temperature be provided.

The polarizing beam having image information emitted from the image output device is a beam having s-polarized light, and the transmittance (T _p ) of the polarizing beam splitter for p-polarized light is 90% or more. , S-polarized light reflectance (R _s )
Is desirably 90% or more. However, the polarizing light flux is p-polarized light, and the reflectance for p-polarized light is 90%.
As described above, a polarizing beam splitter having a transmittance of 90% or more for s-polarized light may be used, and other polarization states may be used. However, since the polarizing light beam splitting element has an action of splitting the polarizing light beam, even if the polarizing light beam having the image information is a light beam in which s-polarized light and p-polarized light are mixed, the polarizing light beam splitting element The light beam having passed through becomes a light beam having a desired polarization state.

The polarizing beam splitting element may be mainly composed of an oblique plate glass, and the polarizing beam splitting element is an optical element including a polarizing beam splitter and a polarizing beam splitting film. May be. That is, the polarizing beam splitting element splits the beam according to the polarization state.

Further, the quarter-wave plate has a wide band of 1/4.
It is desirable to use a wave plate. The broadband quarter-wave plate may be, for example, a film in which two polycarbonates are bonded together with their optical axes changed, and it is particularly desirable that the plate has little wavelength dependence in the visible light region.

Further, in the present invention, the formed virtual image can be observed. For example, a stereoscopic image can be obtained by superimposing a background light beam incident from the background side of the reflective optical element and a predetermined image from the image output device. Alternatively, the background light flux may be used as a backlight of a predetermined image by the image output device, as realized by a viewfinder of a video camera. The background light beam may be a so-called see-through background image (an image seen through an optical system). In the present invention, “imaging” refers to making the image observable to human eyes (the same applies hereinafter).

Next, a second virtual image forming method and a second virtual image forming apparatus according to the present invention will be described.

According to the second virtual image forming method of the present invention and the second virtual image forming apparatus of the present invention, the method has a linearly polarized component (for example, s-polarized light) emitted from the image output device such as a liquid crystal display. The process of guiding the polarizing beam to the polarizing beam splitting element such as a polarizing beam splitter, and the process of guiding the polarizing beam splitter (for example, a polarizing beam splitter that reflects s-polarized light and transmits p-polarized light). Guiding the luminous flux to a quarter-wave plate that gives a quarter-wavelength optical path difference (that is, a phase difference of 90 °) between the orthogonal linearly polarized light components, and passing through the quarter-wave plate. The luminous flux whose polarization state has changed (for example, clockwise circularly polarized light) is reflected by the reflection type diffractive optical element such as a volume hologram (here, for example, counterclockwise circularly polarized light), and the 前 記 wavelength is again obtained. The process of leading to the board and before Further light beam polarized state is changed by passing through the quarter-wave plate again (e.g. p-polarized light)
Through the polarizing light beam splitting element to form a virtual image of an output image emitted from the image output device (see FIG. 5).

The quarter-wave plate is desirably installed so that its optical axis is inclined by 45 ° with respect to the polarization direction of the light beam. With this arrangement, the polarizing light beam can be efficiently polarized in a predetermined polarization direction.

Preferably, the reflection type diffractive optical element is a Lippmann volume hologram. A Lippman volume hologram is a hologram that forms an image by Bragg reflection by a three-dimensional grating of interference fringes, and is a reference beam
am) and an object beam (object beam) are incident from the front side and the back side of the hologram, respectively, so that a layer of interference fringes substantially parallel to the surface is formed inside the hologram, and becomes a three-dimensional diffraction grating. This Lippman volume hologram has particularly high wavelength selectivity and exhibits good wavelength selectivity in the visible light region. However, in the present invention, other volume holograms than the Lippmann volume hologram may be used.

The quarter-wave plate may be provided integrally with the reflection type diffractive optical element. That is, by integrating the quarter wavelength plate and the reflection type diffractive optical element, 1 /
Spatial fluctuation (for example, light scattering) between the four-wavelength plate and the reflection type diffractive optical element can be reduced. In particular, since the light beam reciprocates between the quarter-wave plate and the reflective diffractive optical element, it is desirable that the spatial fluctuation is small.

Further, the image output device may be a liquid crystal image output device (liquid crystal display device or LCD). For this liquid crystal image output device, for example, a backlight such as a cold-cathode tube or a light-emitting diode can be used. Further, between this backlight and the liquid crystal display element, illumination brightness is made uniform, and a diffusion angle is obtained. It is desirable that a diffusion plate for controlling the temperature be provided.

The polarizing beam having image information emitted from the image output device is defined as a beam having s-polarized light, and the transmittance of the polarizing beam splitter for p-polarized light is 90% or more and the reflectance for s-polarized light is 90%. % Is desirable. However, the polarizing beam may be p-polarized light, and a polarizing beam splitting element having a reflectance of 90% or more for p-polarized light and a transmittance of 90% or more for s-polarized light may be used. It is also possible to use it. However, since the polarizing light beam splitting element has a function of splitting the polarizing light beam, even if the polarizing light beam having the image information is a light beam in which s-polarized light and p-polarized light are mixed, the polarizing light beam splitting element The light beam having passed through becomes a light beam having a desired polarization state.

The polarizing beam splitting element may be made of an oblique plate glass, and the polarizing beam splitting element may be an optical element consisting of a polarizing beam splitter and a polarizing beam splitting film. That is, the polarizing beam splitting element splits the beam according to the polarization state.

Further, the 波長 wavelength plate has a wide band １ ／ wavelength.
It is desirable to use a wave plate. The broadband quarter-wave plate may be, for example, a film in which two polycarbonates are bonded together with their optical axes changed, and it is particularly desirable that the plate has little wavelength dependence in the visible light region.

Further, in the present invention, the formed virtual image can be observed. For example, a stereoscopic hologram can be obtained by superimposing a background light beam (reference light), such as a volume hologram, incident from the background side of the reflection type diffractive optical element and a predetermined image (object light) from the image output device. . Further, the background light flux is a peripheral scene that can be seen through an optical system, and may be used as a so-called see-through background image. Further, this light beam can be used as a backlight as realized by a viewfinder of a video camera.

Next, a third virtual image forming method according to the present invention and a third virtual image forming apparatus according to the present invention will be described.

In the third virtual image forming method of the present invention and the third virtual image forming apparatus of the present invention, a light beam having a linear polarization component emitted from the light source as a backlight (this is a s-polarized light and a p-polarized light beam). It may be a light beam in which polarized light is mixed.)
To the polarizing beam splitter such as a polarizing beam splitter, and the light beam (for example, p) passing through the polarizing beam splitting element (for example, a polarizing beam splitter that reflects s-polarized light and transmits p-polarized light). (Polarized light) to give a quarter-wavelength optical path difference between orthogonal linearly polarized light components.
The process of leading to the wave plate and the polarizing luminous flux whose polarization state has been changed by the quarter wave plate (for example, counterclockwise circularly polarized light)
A process of leading to a reflection type image output device such as a reflection type liquid crystal display, and the light beam having a linear polarization component reflected by the reflection type image output device (for example, clockwise circularly polarized light);
The process of guiding the light again to the 波長 wavelength plate, and the light flux (for example, s-polarized light) having passed through the 波長 wavelength plate and further changed in the polarization state is passed through the polarizing light beam splitting element to a lens or the like. Through the process of leading to the refractive optical element, a virtual image of the output image emitted from the reflective image output device can be formed (see FIG. 9).

The quarter-wave plate is desirably installed so that its optical axis is inclined by 45 ° with respect to the polarization direction of the light beam. With this arrangement, the polarizing light beam can be efficiently polarized in a predetermined polarization direction.

The refractive optical element may be a lens, especially an eyepiece. However, another optical element for giving a predetermined refractive index may be used.

The quarter-wave plate may be provided integrally with the reflection type image output device. That is, by integrating the １ ／ wavelength plate and the reflection type image output device, 1 /
Spatial fluctuation (for example, light scattering) between the four-wavelength plate and the reflection type image output device can be reduced. In particular, since the light beam reciprocates between the quarter-wave plate and the reflection type image output device, it is desirable that the spatial fluctuation is small.

This reflection type image output device may be composed of a laser light source and a digital micromirror image display device. In addition, a reflective liquid crystal display element (reflective LC
D) can also be used.

The transmittance of the polarizing beam splitter for p-polarized light is 90% or more, and the reflectance for s-polarized light is 9%.
Desirably, it is 0% or more. However, a polarizing beam splitter having a reflectance of 90% or more for p-polarized light and a transmittance of 90% or more for s-polarized light may be used, and other polarization states may be used. Further, in the present invention, since only a light beam having a predetermined polarization state is passed (or reflected) by the polarizing light beam splitting element, the light beam emitted from the light source has a specific polarization state (polarization direction). You don't have to.

The polarizing beam splitting element may be made of an oblique plate glass, and the polarizing beam splitting element may be an optical element consisting of a polarizing beam splitter and a polarizing beam splitting film. That is, the polarizing beam splitting element splits the beam according to the polarization state.

The quarter-wave plate may be a wide-band quarter-wave plate. The broadband quarter-wave plate may be, for example, a film in which two polycarbonates are bonded together with their optical axes changed, and it is particularly desirable that the plate has little wavelength dependence in the visible light region.

Further, in the present invention, the formed virtual image can be observed. For example, a three-dimensional image can be obtained by superimposing a background light beam incident from the background side of the reflective optical element and a predetermined image from the image output device. Alternatively, the background light flux may be used as a backlight of a predetermined image by the image output device, as realized by a viewfinder of a video camera.

Hereinafter, the present invention will be described in accordance with preferred embodiments.

[First Embodiment] The present embodiment is based on the above-described first virtual image forming method and first virtual image forming apparatus of the present invention.

FIG. 1 shows a transmission type liquid crystal image output device (projection type liquid crystal display) according to the present embodiment, a polarizing beam splitter 9 having a polarizing beam splitting film 10 as a polarizing beam splitting element, and a broadband 1 / A schematic configuration of a virtual image forming optical system using a four-wavelength plate 11 and an aspherical concave half mirror 12 as a reflective optical element is shown.

Next, the operation of the virtual image forming optical system will be described.

First, when a video signal 1 is inputted to a liquid crystal display driving circuit (LCD driver or LCD driving circuit) 2, a backlight voltage (cold cathode tube voltage) 4 and a liquid crystal display driving signal (drive) are supplied from the LCD driving circuit 2. 3) are output and input to the cold cathode tube 5 of the backlight 7 and the liquid crystal display (LCD) 8, respectively.

Here, the backlight 7 comprises a cold cathode tube 5 as a light source and a diffusion plate 6 provided on the LCD 8 side for making the irradiation luminance uniform and controlling the diffusion angle. Further, as the liquid crystal display 8 as an image output device, for example, a 0.55 inch transmissive liquid crystal display is used. Here, an electric image signal is converted into an actual image, and light emitted from the backlight 7 is modulated. You.

As is well known, a light beam emitted from the LCD 8 as a liquid crystal image output device is linearly polarized by a polarizing plate (not shown) provided on the light emission side.
Here, the polarization direction of the light beam emitted from the LCD 8 is set perpendicular to the paper surface.

The polarizing beam splitter to which the polarizing beam subsequently enters is a polarizing beam splitter 9 having a polarizing beam splitting film 10. The polarizing beam splitter 9 is incident on the polarizing beam splitting film 10. A polarization component (p-polarized light) in which the polarization direction of the light beam is parallel to the incident surface (the surface including the incident light and the reflected light) is transmitted by nearly 100% (T _p ≒ 100).
%), And the vertical polarization component (s-polarized light) has a characteristic of reflecting near 100% (R _S ≒ 100%). That is, most of the light beam emitted from the LCD 8 (s-polarized light with respect to the polarizing beam splitting film 10 of the polarizing beam splitter 9) is reflected by the polarizing beam splitting film 10 of the polarizing beam splitter 9.

Next, the light beam reflected by the polarizing beam splitting film 10 has an optical axis of 45 ° with respect to the polarization direction of the light beam.
The light enters the inclined quarter-wave plate 11.

The quarter-wave plate 11 is made of a uniaxial birefringent substance (quartz, calcite, etc.), and has a property that the refractive index differs depending on the polarization direction of the incident light beam. As in the present embodiment, when the incident light beam is incident at an angle of 45 ° with respect to the optical axis of the crystal of the quarter-wave plate 11, the component parallel to the optical axis of the incident polarized light and the component perpendicular to the optical axis of the incident polarized light And a phase difference of π / 2 (λ / 4 in optical path length) is generated.

Now, let the linearly polarized light (amplitude A, period T) incident on the quarter-wave plate be E = A sin [2πt / T], and the polarized light component E _o perpendicular to the optical axis is polarized light parallel to the optical axis. When lambda / 4 advances as compared with the component E _e (i.e., the magnitude relationship between the ordinary refractive index n _o and an extraordinary ray refractive index n _e, the phase is advanced or delayed or are determined.), parallel to the optical axis = Do polarization components E _e, respectively perpendicular polarization components E _o is the optical axis, _{E e} (A√2) sin [2.pi.t / T] E _o = (A√2) sin2π [t / T + (λ / 4 ) / Λ] = (A√2) cos [2πt / T], and clockwise circularly polarized light is obtained (see FIG. 2).

The quarter-wave plate 11 used in the present embodiment is a film (１ ／ wavelength film) formed by laminating two pieces of polycarbonate having a thickness of about 60 μm while changing the optical axis. Very little wavelength dependence in the visible light range.

FIG. 3 shows a conventional quarter-wave plate and the quarter-wave film 11 used in the present embodiment.
Shows the wavelength dependence of the phase difference. That is, the quarter-wave film (shown by a black circle in the figure) used in the present embodiment has a phase difference in a relatively wide wavelength range as compared with a conventional quarter-wave plate (shown by a white circle in the figure). Is stable, and the wavelength dependence of the phase difference in the visible light region is extremely reduced.

Next, the light beam converted into clockwise circularly polarized light is converted into an aspheric concave half mirror 1 as a reflective optical element.
2 is incident. Here, a part of the light flux is transmitted through the aspherical concave half mirror 12, and another part is reflected.
Here, the reflected light beam is given a refractive power for forming a virtual image of the output image of the image output device. In addition, since the traveling direction changes by 180 °, the light is counterclockwise circularly polarized light.

Next, since the light beam reflected by the aspherical concave half mirror 12 is left-handed circularly polarized light, the light beam passes through the quarter-wave plate 11 again, so that the light beam is immediately emitted from the polarization beam splitter. , That is, p-polarized light (see FIG. 2). That is, the light beam (p-polarized light) having the linearly polarized light subsequently re-enters the polarizing beam splitter 9, but this time becomes almost p-polarized light for the polarizing beam splitting film 10 of the polarizing beam splitter 9. Passes.

Therefore, according to the present embodiment, the LCD 8
The amount of light returning to the image output device constituted by the LCD and the backlight 7 is extremely small, and multiple reflection light between the LCD panel 8, the polarizing beam splitting film 10, and the aspherical concave half mirror 12 is incident on the pupil 13. Ghosting can be prevented. At the same time, it is possible to achieve approximately four times the light use efficiency as compared with a case where a polarizing beam splitter is used without using a quarter wavelength plate or a case where the reflectance of a half mirror is set to 50%.

Next, the light beam transmitted through the polarizing beam splitter 9 is formed into an image, and is guided to the pupil 13 as a virtual image. Then, a predetermined superimposed image (particularly, a hologram) is obtained by superimposing the background light beam A incident from the back side of the aspherical concave half mirror 12 and the output image (virtual image) emitted from the image output device.

The present embodiment can be used as shown in FIG. That is, in the embodiment shown in FIG. 1, a quarter-wave plate is provided as a separate component between the polarizing beam splitter 9 and the aspheric concave half mirror 12, but as shown in FIG. Concave half mirror 1
A quarter-wave plate (a quarter-wave film) 14 can be integrated along the mirror surface of No. 5.

That is, since the ４ film 14 is integrated along the mirror surface of the aspheric concave half mirror 15, the light flux between the 波長 wavelength film 14 and the aspheric concave half mirror 15 is formed. Can be prevented from scattering. Of course,
As in the embodiment shown in FIG. 1, the amount of light returning to the image output device including the LCD 8 and the backlight 7 is extremely small, and the LCD panel 8, the polarizing beam splitting film 10, the aspherical concave half mirror 12 Between the pupils 13
Ghosts that occur when the light is incident on the surface can be prevented. At the same time, when a polarizing beam splitter is used without using a quarter-wave plate, or when the reflectance of the half mirror is 5
It is possible to achieve approximately four times the light use efficiency as compared with the case of 0%.

[Second Embodiment] The present embodiment is based on the above-described second virtual image forming method and second virtual image forming apparatus of the present invention.

FIG. 5 shows a transmission type liquid crystal image output device (projection type liquid crystal display) according to the present embodiment, a polarizing beam splitter 9 having a polarizing beam splitting film 10 as a polarizing beam splitting element, and a broadband 1 / Four-wavelength plate 11 and Lippmann volume hologram 19 as a reflection type diffractive optical element
1 shows a schematic configuration of a virtual image forming optical system using the above.

Next, the operation of the virtual image forming optical system will be described.

First, when the video signal 1 is input to the liquid crystal display drive circuit (LCD driver, LCD drive circuit) 2, the LCD drive circuit 2 outputs an LED (light emitting diode) lighting current (LED current).
16 and a liquid crystal display drive signal (drive signal) 3 are output and input to an LED array 17 and a liquid crystal display (LCD) 8 constituting the backlight 7, respectively.

Here, as the backlight 7, an LED array 17 in which a total of eight chips of a chip size having a center wavelength of 535 nm, for example, two rows and four columns are mounted as a light source on a plane is used. A diffusion plate 6 is provided on the side to make the irradiation luminance uniform and to control the diffusion angle. In this case, the diffusion plate 6 has a half-value angle of about 10 °.

As the liquid crystal display 8 serving as an image output device, for example, a transmission type liquid crystal display of 0.55 inch is used. Here, an electric image signal is converted into an actual image, and a light beam emitted from the backlight 7 is modulated. Is done.

As is well known, LC as an image output device
The light beam emitted from D8 is linearly polarized by a polarizing plate (not shown) provided on the surface of LCD8.
Here, the polarization direction of the light beam emitted from the LCD 8 is perpendicular to the paper surface.

A polarizing beam splitter 9 on which a polarizing light beam having image information emitted from the LCD 8 subsequently enters.
In the polarizing beam splitting film 10, p is such that the polarization direction of the incident light beam is parallel to the incident surface (the surface including the incident light and the reflected light).
Polarized light has a characteristic of transmitting near 100%, and vertical s-polarized light has a characteristic of reflecting close to 100%. That is, most of the light beam emitted from the LCD 8 (s-polarized light with respect to the polarizing beam splitting film 10 of the polarizing beam splitter 9) is reflected by the polarizing beam splitting film 10 of the polarizing beam splitter 9.

Next, this light beam is applied to a Lippmann volume hologram substrate (hologram substrate or HOE substrate: Holographi).
c Optical Elemant) 18
The light enters the four-wavelength plate (a quarter-wave film) 20, where the linearly polarized light is converted into the circularly polarized light as described above.
This light beam passes through the Lippman volume hologram substrate 18 and enters a Lippman volume hologram 19 provided on the other surface of the substrate 18.

Here, the structure and function of the Lippman volume hologram 19 will be described.

FIG. 6 shows a schematic sectional structure of a Lippmann volume hologram. Examples of the hologram material include photopolymer and dichromated gelatin. The fringe pattern in the figure represents an interference fringe, and the refractive index is actually modulated here. When a typical photopolymer is used as a hologram material, the central refractive index n and the refractive index modulation Δn after the heat treatment are n = 1.52 and Δn = 0.06, respectively.

FIG. 6 shows that the interference fringes of the Lippmann volume hologram are in the thickness direction of the material. This can be achieved by printing two luminous fluxes from the front and back of the hologram surface when printing the hologram.

Next, the principle of reproducing the Lippman volume hologram will be described. The reproduction principle of the Lippman volume hologram has the following two conditions.

First, as shown in FIG. 7, it is necessary that two different scattering components on a certain layer reinforce each other. Assuming that the distance between these two points is L, Ls
in [θ ₁ ] −Lsin [θ ₂ ] = mλ. In order for this to hold for any L, it is sufficient that the identity is about L. That is, θ ₁ = θ ₂ (1) may be satisfied.

The other is, as shown in FIG.
It is necessary that the scattering components between the layers reinforce each other. That is, in order for the scattering components of the two different layers to reinforce each other, dcos [θ ₁ ] −dcos [θ ₂ ] = mλ (2) may be satisfied. Here, d is the distance between two different layers.

Therefore, from the above (1) and (2), 2dcos [θ ₁ ] = mλ... Bragg diffraction condition, and when m = 1 (first order), 2dcos [θ ₁ ] = λ Should be satisfied. In other words, Bragg diffraction is specular reflection having wavelength selectivity or angle selectivity.

In this embodiment, by appropriately forming the interference fringes, the Lippman volume hologram is provided with a refractive power for forming a virtual image of the output image from the image output device.

Next, the light beam incident on the Lippmann volume hologram 19 is
A specific wavelength range (in this case, 525 nm which is the wavelength of the light source)
(Only about 10 nm in full width at half maximum with respect to the hologram substrate 1) is selectively given refraction power and reflected, and the hologram substrate 1
After passing through 8, the light passes through the quarter-wave plate 20.

With the quarter-wave plate 20, as described above,
The light is converted into linearly polarized light orthogonal to the polarization direction immediately after the light is emitted from the polarization beam splitter, and then enters the polarization beam splitter 9 again. At this time, almost 100% of the light flux passes through the polarizing beam splitter 9 and is guided to the pupil 13.

On the other hand, the background light beam A traveling from the left side of the Lippman volume hologram 18 is reflected by the Lippman volume hologram 19, the HOE substrate (hologram substrate) 18,
The light also enters the pupil 13 through the four-wavelength plate 20 and the polarization beam splitter 9.

At this time, since the intensity of the spectrum reaching the pupil 13 from the background near the wavelength of 525 nm is reflected by the Lippman volume hologram 19, the intensity decreases almost in inverse proportion to the diffraction efficiency. Further, by passing through the polarizing beam splitter 9, the amount of light incident on the pupil 13 decreases.

As described above, according to the optical system of the present embodiment, the amount of light returning to the image output device is very small, and the LCD panel 8 and the polarizing beam splitter 9 are used, as in the first embodiment. The ghost that occurs when the multiple reflection light between the Lippman volume holograms 19 enters the pupil 13 can be prevented. Further, it is possible to achieve approximately four times the light use efficiency as compared with a case where a polarizing beam splitter is used without using a quarter-wave plate or a case where the reflectance of a half mirror is set to 50%.

Further, there is a known problem that relatively strong parallel light such as sunlight may enter from the pupil side, and this light beam focuses on the LCD, and the heat damages the LCD panel. According to the embodiment, due to the wavelength selectivity of the Lippman volume hologram 19, in this case the wavelength 52
Since only about 10 nm of light with a full width at half maximum of about 5 nm is reflected, the amount of light returning to the LCD 8 is also reduced, and damage to the LCD panel and the like is suppressed.

In this embodiment, green (525n
m) is used, and the display image has been described as an example in which the display image is a single green color. However, the Lippman diffracting each of the three primary colors of red (R), green (G), and blue (B) has been described. By using a volume hologram and a light source including the above-mentioned three primary color spectra as a backlight, full colorization is possible. Although the Lippman volume hologram 19 and the quarter-wave plate 20 are provided integrally via the hologram substrate 18, the Lippman volume hologram and the quarter-wave plate may be provided independently.

[Third Embodiment] The present embodiment is based on the third virtual image forming method and the third virtual image forming apparatus of the present invention described above.

FIG. 9 shows a reflection type liquid crystal image output device (reflection type liquid crystal display) 22, a broadband quarter-wave plate 23, and a polarizing beam splitting film 10 as a polarizing beam splitting element according to the present embodiment. A polarizing beam splitter 9 having
A schematic configuration of a virtual image forming optical system using an eyepiece lens 24 as a refractive optical element is shown.

The operation of the virtual image forming optical system is as follows.

First, a video signal 1 is input to a reflection type liquid crystal display driving circuit (LCD driver or reflection type LCD driving circuit) 2. Then, the reflection type LCD drive circuit 2
Output a light source current (LED current) 16 and a reflection type liquid crystal display drive signal (drive signal) 3, and output the three primary color light emitting diodes 21 of the light source (backlight) 7 and the reflection type polymer dispersed liquid crystal display 22, respectively. Is input to

Here, the backlight (light source) 7 is an LED capable of emitting three primary colors of red (R), green (G) and blue (B). The diffusion plate 6 is provided as an optical element for irradiating the reflective LCD 22 with a light beam that is approximately parallel.

Further, as the reflection type polymer dispersed liquid crystal display 22 as an image output device, for example, a 0.55 inch reflection type polymer dispersed liquid crystal display is used. Here, an electric image signal is converted into an actual image. The light emitted from the light source is modulated and reflected.

As is well known, the reflection type polymer dispersed liquid crystal image output device 22 outputs an image by changing the reflectance of incident light for each pixel according to the intensity of the electric field in each pixel. The reflected light beam can be obtained without changing the polarization state of the light beam. In addition to the reflective polymer dispersed liquid crystal image output device, for example, a phase change type guest host display, a digital micromirror device, and the like can be used (the same applies to other embodiments).

The luminous flux emitted from the backlight 7 is a luminous flux in which s-polarized light and p-polarized light are mixed. The direction of the parallel polarized light component (p-polarized light) is 10
Transmits near 0%, vertical polarization component (s component) is 100%
Since it has a characteristic of near reflection, only p-polarized light passes therethrough, and the １ ／ wavelength plate 23 and the reflective polymer dispersed LCD 22
It is led to.

Next, this light beam enters a quarter-wave plate (a quarter-wave filter) 23 whose optical axis is inclined by 45 ° with respect to the polarization direction of this light beam. The luminous flux transmitted through the 波長 wavelength plate 23 is converted into circularly polarized light (tentatively right-handed circularly polarized light),
The light enters the reflection type polymer dispersed liquid crystal image output device 22 and is modulated.

Next, the luminous flux having the image information reflected by the reflection type polymer dispersed liquid crystal image output device 22 becomes 1 /
The light passes through the four-wavelength plate 23. At this time, the polarization state of the light beam reflected by the reflection type polymer dispersed liquid crystal image output device 22 hardly changes. However, since the traveling direction of the light beam is opposite, the polarized light beam that was clockwise circularly polarized at the time of incidence becomes, after reflection, left-handed circularly polarized light due to a change in how coordinates are taken. When the left-handed circularly polarized light passes through the quarter-wave plate, it is converted into linearly polarized light orthogonal to the polarization direction immediately after exiting the polarization beam splitter.
Incident on. At this time, the incident light incident on the polarization beam splitter 9 is s-polarized light, so that it is reflected by the polarization beam splitter 9 at a rate of almost 100% and guided to the lens (eyepiece lens) 24. By this lens 24, refracting power for forming a virtual image is added to the wavefront, and a light beam transmitted through the lens 24 is guided to the pupil 23.

Therefore, also in the present embodiment, 1/4
As compared with the case where a polarizing beam splitter is used without using a wave plate or the case where the reflectance of a half mirror is set to 50%, the light use efficiency can be approximately doubled. In the optical system according to the present embodiment, the arrangement of each optical element to be used is easy.

As described above, according to the first, second, and third embodiments of the present invention, a quarter-wave plate (particularly, a quarter-wave filter) and a polarizing beam splitter having a polarizing beam splitting film are provided. By using in the optical path, beam splitting (light beam splitting) is performed by the polarization beam splitter due to the difference in the polarization state, and the light use efficiency is greatly improved.
Light utilization efficiency is improved about 4 times (about 2 times in the third embodiment) as compared with the case of using a non-polarizing beam splitter or a polarizing beam splitter without using a quarter-wave plate.
I do.

Further, by using a quarter-wave plate and a polarizing beam splitter having a polarizing beam splitting film in the optical path, isolation of a returning beam to an image output device (particularly a liquid crystal display) can be realized. In addition, the occurrence of a ghost image due to multiple reflections in the optical path can be prevented. The generation of the ghost image due to the multiple reflection becomes more remarkable as the aperture ratio decreases as the number of pixels of the image display device increases, and is particularly effective in a high-resolution virtual image forming optical system.

Further, particularly in the second embodiment,
Even if strong parallel light such as sunlight enters from the pupil side, most of the spectrum does not enter the image output device due to the wavelength selectivity of the reflective diffractive optical element.
An image is formed on the image output device due to the regression of the light, and the risk of damage to the LCD panel or the like due to the heat generated thereby can be reduced. At the same time, external light (stray light)
Is less likely to enter the pupil, so that the ratio of the stray light to the desired display light flux (ie, the S / N ratio) is improved.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments.

For example, in the above-described first and second embodiments, a liquid crystal image output device is adopted as an image output device. However, as another image output device for emitting linearly polarized light, for example, a semiconductor laser is used. A display or the like can be used.

The virtual image forming optical system according to the present embodiment can be applied to various uses such as a head-mounted display (three-dimensional display is also possible), a viewer of a portable information terminal device, and a finder of a video camera.

[0109]

According to the first virtual image forming method of the present invention,
Guiding the polarizing beam having image information emitted from the image output device to the polarizing beam splitter, and dividing the polarizing beam passing through the polarizing beam splitter by a quarter between orthogonal linear polarization components. Guiding the optical element to give an optical path difference of wavelength, and passing the optical element and changing the polarization state of the light beam, reflecting the reflected optical element and guiding the optical element again to the optical element, Guiding the light flux whose polarization state has been further changed by passing through the polarizing light beam splitting element to a light path different from the light path of the polarizing light beam emitted from the image output device, to obtain the image. Since the virtual image of the output image output from the output device is formed, the polarization state of the polarizing optical element is different between the forward path and the return path of the polarizing optical element, and the polarizing optical element The split elements, the a and the return of the light flux light flux and of the outgoing path of separation from one another, and at the same time use efficiency of light is improved, the return light is reduced to the image output device.

According to the first virtual image forming apparatus of the present invention, the process of guiding the polarizing light beam having the image information emitted from the image output device to the polarizing light beam splitting element, and passing through the polarizing light beam splitting element Guiding the polarizing luminous flux to an optical element that provides a quarter-wavelength optical path difference between orthogonal linearly polarized light components, and passing the luminous flux having passed through the optical element and changing the polarization state to a reflective optical element. The light flux whose polarization state has been further changed by passing through the optical element, and the polarized light emitted from the image output device via the polarizing light beam splitting element. Through a process of guiding the light beam to a light path different from the light path of the polarized light beam, wherein the virtual image forming device forms a virtual image of the output image emitted from the image output device, the image output device, the polarizing light beam splitting Element and Since the optical element is composed of the optical element and at least one reflective optical element, and the optical element is provided between the polarizing beam splitting element and the reflective optical element, the first aspect of the present invention. The virtual image forming method is implemented with a simple configuration with good reproducibility.

According to the second virtual image forming method of the present invention, the process of guiding the polarizing light beam having the image information emitted from the image output device to the polarizing light beam splitting element, and passing through the polarizing light beam splitting element is performed. Guiding the polarizing luminous flux to an optical element that provides a quarter-wavelength optical path difference between orthogonal linearly polarized light components, and converting the luminous flux passing through the optical element and changing the polarization state into a reflective diffractive optical element The step of reflecting the light at the optical element and guiding it again to the optical element, and the light flux whose polarization state has been further changed by passing through the optical element, is emitted from the image output device through the polarizing light beam splitting element. A virtual image of an output image emitted from the image output device is formed through a process of leading to a light path different from the light path of the polarizing light beam, so that the forward and backward paths of the polarizing light beam with respect to the reflective diffractive optical element. The polarization states are different from each other, so that the forward light beam and the backward light beam are separated from each other by the polarizing light beam splitting element, and the light use efficiency is improved, and at the same time, Return light is reduced. Further, by the wavelength selectivity of the reflection type diffractive optical element, the image output device can be prevented from being damaged without irradiating the image output device with light traveling backward from the image forming side of the virtual image.

According to the second virtual image forming apparatus of the present invention, the process of guiding the polarizing light beam having the image information emitted from the image output device to the polarizing light beam splitting device, and passing through the polarizing light beam splitting device is performed. Guiding the polarizing luminous flux to an optical element that provides a quarter-wavelength optical path difference between orthogonal linearly polarized light components, and converting the luminous flux passing through the optical element and changing the polarization state into a reflective diffractive optical element The step of reflecting the light at the optical element and guiding it again to the optical element, and the light flux whose polarization state has been further changed by passing through the optical element, is emitted from the image output device through the polarizing light beam splitting element. A virtual image forming device for forming a virtual image of an output image emitted from the image output device through a process of guiding the polarizing light beam to a light path different from the light path of the polarizing light beam, wherein the image output device and the polarizing light beam Split element And the optical element, at least one
And the reflection type diffractive optical element, and the optical element is provided between the polarizing beam splitter and the reflection type diffractive optical element, so that the second virtual image forming method is simplified. It is realized with a configuration and implemented with good reproducibility.

According to the third virtual image forming method of the present invention, the process of guiding the light beam emitted from the light source to the polarizing light beam splitting device and the process of converting the polarizing light beam passing through the polarizing light beam splitting device into an orthogonal straight line A step of leading to an optical element that gives a quarter-wavelength optical path difference between the polarized light components, a step of guiding a polarizing light beam whose polarization state has been changed by the optical element to a reflective image output device, and the reflective image output device. A step of guiding a polarizing light beam having image information reflected at the optical element again,
Through the process of guiding the light flux whose polarization state has changed further through this optical element to the refractive optical element through the polarizing light beam splitting element, a virtual image of the output image emitted from the reflection type image output device is obtained. Since the image is formed, in the forward path and the return path of the polarizing light flux with respect to the reflective image output device,
The polarization states are different from each other, and the forward light beam and the backward light beam are separated from each other by the polarizing light beam splitting element, and the light use efficiency is improved, and at the same time, the light output to the image output device is improved. Return light is reduced.

According to the third virtual image forming apparatus of the present invention, the process of guiding the light beam emitted from the light source to the polarizing light beam splitting element, and the process of converting the polarizing light beam passing through the polarizing light beam splitting element into an orthogonal straight line A step of leading to an optical element that gives a quarter-wavelength optical path difference between the polarized light components, a step of guiding a polarizing light beam whose polarization state has been changed by the optical element to a reflective image output device, and the reflective image output device. A step of guiding a polarizing light beam having image information reflected at the optical element again,
Through the process of guiding the light flux whose polarization state has changed further through this optical element to the refractive optical element through the polarizing light beam splitting element, a virtual image of the output image emitted from the reflection type image output device is obtained. A virtual image forming apparatus for forming an image,
The reflective image output device, the polarizing beam splitter, the optical element, and at least one refractive optical element, wherein the optical element is the polarizing beam splitter and the reflective image output device. Therefore, the third virtual image forming method can be realized with a simple configuration and at the same time with high reproducibility.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a main part of a virtual image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram for explaining a change in a polarization state in a quarter-wave plate.

FIG. 3 is a graph showing the wavelength dependence of the phase difference in a general quarter-wave plate and the wavelength dependence of the phase difference in the quarter-wave plate used in the first embodiment.

FIG. 4 is a schematic diagram of a main part of another virtual image forming apparatus according to the first embodiment of the present invention.

FIG. 5 is a schematic diagram of a main part of a virtual image forming apparatus according to a second embodiment of the present invention.

FIG. 6 is a schematic diagram for explaining a Lippman volume hologram used in the virtual image forming apparatus.

FIG. 7 is another schematic view for explaining the Lippmann volume hologram.

FIG. 8 is another schematic view for explaining the Lippman volume hologram.

FIG. 9 is a schematic diagram of a main part of a virtual image forming apparatus according to a third embodiment of the present invention.

FIG. 10 is a schematic view of a main part of a conventional virtual image forming apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Video signal, 2 ... LCD driver, 3 ... Drive signal, 4 ... Cold cathode tube voltage, 5 ... Cold cathode tube, 6 ... Diffusion plate, 7
... backlight, 8 ... LCD (liquid crystal display element), 9 ... polarizing beam splitter, 10 ... polarizing light beam splitting film, 11,
14, 20, 23: 1/4 wavelength plate, 12, 15: aspherical concave half mirror, 13: pupil, 16: LED current, 17
... LED array, 18 ... Hologram substrate, 19 ... Lipman volume hologram, 21 ... Three primary color light emitting diodes, 2
2: reflective liquid crystal image output device, 30: stray light, 31: half mirror

Claims (66)

[Claims] 1. A process of guiding a polarizing beam having image information emitted from an image output device to a polarizing beam splitter, and converting the polarizing beam passing through the polarizing beam splitter between orthogonal linear polarization components. And a process of guiding a light beam having a changed polarization state that has passed through the optical device to a reflection type optical device and guiding the light beam to the optical device again. A step of guiding the light flux whose polarization state has been further changed by passing through the optical element to a light path different from the light path of the polarizing light flux emitted from the image output device via the polarizing light beam splitting element. And forming a virtual image of an output image emitted from the image output device through the method. 2. A step of guiding the polarizing light beam having a linearly polarized light component emitted from the image output device to the polarizing light beam splitting element, and intersecting the light beam reflected by the polarizing light beam splitting element with an orthogonal light beam. Guiding a quarter-wave plate that gives a quarter-wavelength optical path difference between the linearly polarized light components, and passing the luminous flux that has passed through the quarter-wave plate and whose polarization state has changed to the reflective optical element. And reflect it again
A light beam whose polarization state has been further changed by passing through the quarter-wave plate again, and passing through the polarizing light beam splitting element, and emitted from the image output device. The virtual image forming method according to claim 1, wherein a virtual image of the output image is formed. 3. The virtual image forming method according to claim 2, wherein the quarter-wave plate is installed so that its optical axis is inclined by 45 ° with respect to the polarization direction of the light beam. 4. The optical element according to claim 1, wherein the reflective optical element is one kind of optical element selected from the group consisting of a concave mirror, a concave translucent mirror, an aspheric concave mirror, and an aspheric concave semitransparent mirror. Virtual image forming method. 5. The virtual image forming method according to claim 2, wherein the quarter-wave plate and the reflective optical element are provided integrally. 6. The virtual image forming method according to claim 1, wherein the image output device is a liquid crystal image output device. 7. A polarizing light beam having image information emitted from the image output device is a light beam having s-polarized light, and the polarizing light beam splitting element has a transmittance of 90% or more for p-polarized light and a reflectance for s-polarized light. Is set to 90% or more. 8. The virtual image forming method according to claim 7, wherein the polarizing beam splitter is an oblique plate glass. 9. The virtual image forming method according to claim 7, wherein the polarizing beam splitting element is an optical element including a polarizing beam splitter and a polarizing beam splitting film. 10. The virtual image forming method according to claim 2, wherein the quarter-wave plate is a broadband quarter-wave plate. 11. The virtual image forming method according to claim 1, wherein the formed virtual image is observed. 12. A process of guiding a polarizing beam having image information emitted from an image output device to a polarizing beam splitting element, and converting the polarizing beam passing through the polarizing beam splitting element between orthogonal linear polarization components. And a process of guiding a light beam having a changed polarization state that has passed through the optical device to a reflection type optical device and guiding the light beam to the optical device again. A step of guiding the light flux whose polarization state has been further changed by passing through the optical element to a light path different from the light path of the polarizing light flux emitted from the image output device via the polarizing light beam splitting element. A virtual image forming apparatus for forming a virtual image of an output image emitted from the image output device through the image output device, the polarizing light beam splitting element, the optical element, and at least one of: The reflective consists an optical element, said optical element is provided between said polarizing beam splitting element and the reflective optical element, virtual imaging device. 13. A process of guiding the polarizing light beam having a linearly polarized light component emitted from the image output device to the polarizing light beam splitting element, and intersecting the light beam reflected by the polarizing light beam splitting element with an orthogonal light beam. Guiding a quarter-wave plate that gives a quarter-wavelength optical path difference between the linearly polarized light components, and passing the luminous flux that has passed through the quarter-wave plate and whose polarization state has changed to the reflective optical element. And reflect it again
A light beam whose polarization state has been further changed by passing through the quarter-wave plate again, and passing through the polarizing light beam splitting element, and emitted from the image output device. The virtual image forming apparatus according to claim 12, which is a virtual image forming apparatus that forms a virtual image of an output image. 14. The virtual image forming apparatus according to claim 13, wherein the quarter-wave plate is installed such that its optical axis is inclined by 45 ° with respect to the polarization direction of the light beam. 15. The reflection type optical element is one kind of optical element selected from the group consisting of a concave mirror, a concave translucent mirror, an aspheric concave mirror, and an aspheric concave semitransparent mirror.
3. The virtual image forming apparatus according to 2. 16. The virtual image forming apparatus according to claim 13, wherein the quarter-wave plate and the reflective optical element are provided integrally. 17. The virtual image forming device according to claim 12, wherein the image output device is a liquid crystal image output device. 18. A polarizing light beam having image information emitted from the image output device is a light beam having s-polarized light,
The transmittance for the p-polarized light of the polarizing beam splitter is 90.
The virtual image forming apparatus according to claim 12, wherein the reflectance to s-polarized light is 90% or more. 19. The virtual image forming apparatus according to claim 18, wherein the polarizing beam splitter is an oblique plate glass. 20. The virtual image forming apparatus according to claim 18, wherein the polarizing beam splitter is an optical element including a polarizing beam splitter and a polarizing beam splitting film. 21. The virtual image forming apparatus according to claim 13, wherein the quarter-wave plate is a broadband quarter-wave plate. 22. The virtual image forming apparatus according to claim 12, wherein the formed virtual image is observed. 23. A step of guiding a polarizing beam having image information emitted from an image output device to a polarizing beam splitting element, and converting the polarizing beam passing through the polarizing beam splitting element between orthogonal linear polarization components. Guiding an optical element that gives a quarter-wavelength optical path difference to the optical element, and reflecting a light flux whose polarization state has changed after passing through the optical element with a reflection type diffractive optical element and guiding it again to the optical element. Guiding the light beam, the polarization state of which has been further changed by passing through the optical element, to a light path different from the light path of the polarizing light beam emitted from the image output device via the polarizing light beam splitting element. And forming a virtual image of the output image emitted from the image output device through the method. 24. A process in which the polarizing light beam having a linearly polarized light component emitted from the image output device is guided to the polarizing light beam splitting element, and the light beam reflected by the polarizing light beam splitting element is orthogonally crossed. Guiding a quarter-wave plate that gives a quarter-wavelength optical path difference between the linearly polarized light components, and a light beam whose polarization state has changed after passing through the quarter-wave plate is reflected by the reflection type diffractive optical element. And again
Exiting from the image output device through a process of leading to a 波長 wavelength plate, and a process of transmitting a light beam whose polarization state has been further changed by passing through the 波長 wavelength plate again through the polarizing beam splitter. The virtual image forming method according to claim 23, wherein the virtual image of the output image is formed. 25. The virtual image forming method according to claim 24, wherein the quarter-wave plate is installed so that an optical axis thereof is inclined by 45 ° with respect to a polarization direction of the light beam. 26. The virtual image forming method according to claim 23, wherein the reflection type diffractive optical element is a Lippmann volume hologram. 27. The virtual image forming method according to claim 24, wherein the quarter-wave plate and the reflective diffractive optical element are provided integrally. 28. The virtual image forming method according to claim 23, wherein the image output device is a liquid crystal image output device. 29. A polarizing beam having image information emitted from the image output device is a beam having s-polarized light, and the transmittance of the polarizing beam splitter for p-polarized light is 90%.
The virtual image forming method according to claim 23, wherein the reflectance for s-polarized light is 90% or more. 30. The virtual image forming method according to claim 29, wherein the polarizing beam splitter is an oblique plate glass. 31. The virtual image forming method according to claim 29, wherein the polarizing beam splitting element is an optical element including a polarizing beam splitter and a polarizing beam splitting film. 32. The virtual image forming method according to claim 24, wherein the quarter-wave plate is a broadband quarter-wave plate. 33. The virtual image forming method according to claim 23, wherein the formed virtual image is observed. 34. A step of guiding a polarizing light beam having image information emitted from an image output device to a polarizing light beam splitting element, and converting the polarizing light beam passing through the polarizing light beam splitting element between orthogonal linear polarized light components. Guiding an optical element that gives a quarter-wavelength optical path difference to the optical element, and reflecting a light flux whose polarization state has changed after passing through the optical element with a reflection type diffractive optical element and guiding it again to the optical element. Guiding the light beam, the polarization state of which has been further changed by passing through the optical element, to a light path different from the light path of the polarizing light beam emitted from the image output device via the polarizing light beam splitting element. And a virtual image forming device that forms a virtual image of an output image emitted from the image output device through the image output device, the polarizing light beam splitting element, the optical element, at least One of the is composed of a reflection type diffractive optical element, said optical element is provided between said polarizing beam splitting element and said reflective diffractive optical element, virtual imaging device. 35. A process in which the polarizing light beam having a linearly polarized light component emitted from the image output device is guided to the polarizing light beam splitting element, and the light beam reflected by the polarizing light beam splitting element is orthogonally crossed. Guiding a quarter-wave plate that gives a quarter-wavelength optical path difference between the linearly polarized light components, and a light beam whose polarization state has changed after passing through the quarter-wave plate is reflected by the reflection type diffractive optical element. And again
Exiting from the image output device through a process of leading to a 波長 wavelength plate, and a process of transmitting a light beam whose polarization state has been further changed by passing through the 波長 wavelength plate again through the polarizing beam splitter. 35. The virtual image forming apparatus according to claim 34, wherein the virtual image forming apparatus forms a virtual image of the output image. 36. The virtual image forming apparatus according to claim 35, wherein the quarter-wave plate is installed such that its optical axis is inclined by 45 ° with respect to the polarization direction of the light beam. 37. The virtual image forming apparatus according to claim 34, wherein the reflection type diffractive optical element is a Lippman volume hologram. 38. The virtual image forming apparatus according to claim 35, wherein the quarter-wave plate and the reflective diffractive optical element are provided integrally. 39. The virtual image forming device according to claim 34, wherein the image output device is a liquid crystal image output device. 40. A polarizing light beam having image information emitted from the image output device is a light beam having s-polarized light,
The transmittance for the p-polarized light of the polarizing beam splitter is 90.
35. The virtual image forming method according to claim 34, wherein the reflectance to s-polarized light is 90% or more. 41. The virtual image forming apparatus according to claim 40, wherein the polarizing beam splitter is an oblique plate glass. 42. The virtual image forming apparatus according to claim 40, wherein the polarizing beam splitter is an optical element including a polarizing beam splitter and a polarizing beam splitting film. 43. The virtual image forming apparatus according to claim 35, wherein the quarter-wave plate is a broadband quarter-wave plate. 44. The virtual image forming apparatus according to claim 34, wherein the formed virtual image is observed. 45. A process of guiding a light beam emitted from a light source to a polarizing beam splitter, and converting a polarizing beam passing through the polarizing beam splitter into a quarter-wavelength optical path difference between orthogonal linearly polarized light components. Guiding the polarized light flux whose polarization state has been changed by the optical element to the reflective image output device; and polarizing light flux having image information reflected by the reflective image output device. To the optical element again, and a step of guiding a light flux having passed through the optical element and further changed in polarization state to the refraction optical element through the polarizing light beam splitting element. A virtual image forming method for forming a virtual image of an output image emitted from an output device. 46. A step of guiding a light beam having a linearly polarized light component emitted from the light source to the polarizing light beam splitting element, and dividing the light beam having passed through the polarizing light beam splitting element by four minutes between orthogonal linearly polarized light components. Guiding the polarized light flux whose polarization state has been changed by the quarter wavelength plate to a reflective image output device; and providing the reflective image output device with the reflective image output device. Guiding the luminous flux having the linearly polarized light component reflected by the 再 び wavelength plate again to the ４ wavelength plate, and dividing the luminous flux passing through the 波長 wavelength plate and further changing the polarization state into the polarizing luminous flux 46. The virtual image forming method according to claim 45, wherein a virtual image of an output image emitted from the reflection-type image output device is formed through a step of guiding the optical image to the refractive optical element via an element. 47. The virtual image forming method according to claim 46, wherein the quarter-wave plate is installed so that its optical axis is inclined at 45 ° with respect to the polarization direction of the light beam. 48. The virtual image forming method according to claim 45, wherein the refractive optical element is an eyepiece. 49. The virtual image forming method according to claim 46, wherein the quarter-wave plate and the reflection type image output device are provided integrally. 50. The virtual image forming method according to claim 45, wherein the reflection type image output device is a digital micromirror image display device. 51. The polarizing beam splitter has a transmittance of at least 90% for p-polarized light and a reflectance of 90 for s-polarized light.
The virtual image forming method according to claim 45, wherein the ratio is not less than%. 52. The virtual image forming method according to claim 51, wherein the polarizing beam splitter is an oblique plate glass. 53. The virtual image forming method according to claim 51, wherein the polarizing beam splitter is an optical element including a polarizing beam splitter and a polarizing beam splitting film. 54. The virtual image forming method according to claim 46, wherein the quarter-wave plate is a wide-band quarter-wave plate. 55. The virtual image forming method according to claim 45, wherein the formed virtual image is observed. 56. A process of guiding a light beam emitted from a light source to a polarizing light beam splitting element, and converting a polarizing light beam passing through the polarizing light beam splitting element into a quarter-wavelength optical path difference between orthogonal linearly polarized light components. Guiding the polarized light flux whose polarization state has been changed by the optical element to the reflective image output device; and polarizing light flux having image information reflected by the reflective image output device. To the optical element again, and a step of guiding a light flux having passed through the optical element and further changed in polarization state to the refraction optical element through the polarizing light beam splitting element. A virtual image forming apparatus that forms a virtual image of an output image emitted from an output device, wherein the reflective image output device, the polarizing beam splitter, the optical element, and at least one refractive optical element And it is composed of, the optical element is disposed between the reflection type image output apparatus and the polarization beam splitter, virtual imaging device. 57. A step of guiding a light beam having a linearly polarized light component emitted from the light source to the polarizing light beam splitting element, and dividing the light beam passing through the polarizing light beam splitting element into four orthogonal linearly polarized light components. Guiding the polarized light flux whose polarization state has been changed by the quarter wavelength plate to a reflective image output device; and providing the reflective image output device with the reflective image output device. Guiding the luminous flux having the linearly polarized light component reflected by the 再 び wavelength plate again to the ４ wavelength plate, and dividing the luminous flux passing through the 波長 wavelength plate and further changing the polarization state into the polarizing luminous flux Through a process of leading to the refractive optical element through an element, a virtual image forming apparatus for forming a virtual image of the output image emitted from the image output device,
The virtual image forming apparatus according to claim 56. 58. The virtual image forming apparatus according to claim 57, wherein the quarter-wave plate is installed so that its optical axis is inclined by 45 degrees with respect to the polarization direction of the light beam. 59. The virtual image forming apparatus according to claim 56, wherein the refractive optical element is an eyepiece. 60. The virtual image forming device according to claim 57, wherein the quarter-wave plate and the reflection type image output device are provided integrally. 61. The virtual image forming device according to claim 56, wherein the reflection type image output device is constituted by a digital micromirror image display device. The polarizing beam splitter has a transmittance of 90% or more for p-polarized light and a reflectance of 90% for s-polarized light.
The virtual image forming apparatus according to claim 56, wherein the ratio is not less than%. 63. The virtual image forming apparatus according to claim 62, wherein the polarizing beam splitter is an oblique plate glass. 64. The virtual image forming apparatus according to claim 62, wherein the polarizing beam splitter is an optical element including a polarizing beam splitter and a polarizing beam splitting film. 65. The virtual image forming apparatus according to claim 57, wherein the quarter-wave plate is a broadband quarter-wave plate. 66. The virtual image forming apparatus according to claim 56, wherein the formed virtual image is observed.