JP2000098924A - Image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized image display device displaying an image of a normal aspect ratio with simple constitution. SOLUTION: Relating to the image display device, an illumination beam 31 is made incident at an incident angle of 75 deg. to the normal of a reflection type LCD(liquid crystal display) 18. An image beam emitted from the reflection type LCD 18 is compressed to nearly 1/4 times in the direction horizontal to a paper surface. This compressed image beam 32 is reflected by a mirror 12, and is made incident from an end surface 4 of a parallel transparent substrate 1 so that the incident angle becomes 75 deg. to the normal of a second plane 3. The incident image beam is totally reflected by the second plane 3 to be made incident on a diffraction element 11. At this time, when an eye of an observer is moved in the vicinity of the converged point of the diffraction element 11, and the image is observed, the contents displayed on the reflection type LCD 18 are observed clearly in the normal aspect ratio and sufficient brightness.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device, and more particularly, to a small and high-resolution image display device.

[0002]

2. Description of the Related Art A head mounted display (HMD) is a small image display device which is mounted on a head to observe an image. The HMD is an image forming unit including a display element typified by a liquid crystal display (LCD), a lens,
An image transmission unit consisting of a mirror is arranged in front of the eyes, and is fixed to the head with a belt or other mounting mechanism. The image displayed on the display element of the image forming unit is displayed by forming a large virtual screen in a place that is easy to see by the aberration correction and enlargement functions by the lens and the mirror of the image transmission unit.

[0003] Taking advantage of this feature, HMD is a device for displaying flight information such as altitude and speed for aircraft, personal movies,
It has been developed and commercialized to realize video games and artificial reality. Recently, Wearable
Research as a computer display is also being conducted.

[0004] Such HMDs are classified into a type that can see the outside world (see-through type) and a type that cannot see the outside world (closed type). In some cases, a closed type rather than a see-through type such as artificial reality is preferable, but in many cases, a see-through type that allows simultaneous observation of the outside world is more convenient for portable use. In this see-through HMD,
In addition to the above-described image forming unit and image transmitting unit, a beam combiner is required as an element for realizing the see-through function.

The beam combiner is, for example, a CRT or LC
The display image D is enlarged and displayed, and at the same time, incident light from the outside can be observed. As a typical method, there is a method using a half mirror, a prism, or a hologram. Half mirrors and prisms are based on the principle that the sum of the amount of image light and the amount of external light is 100%. Therefore, if a high reflectance is set to obtain a bright image, the amount of external light decreases and the see-through performance may decrease. Inevitable. On the other hand, the hologram method has a sharp wavelength selectivity with respect to a specific wavelength and can reflect and diffract only that wavelength, so that 100% of the image display light of the specific wavelength and 100% of the external world excluding that wavelength are displayed. You can see the light overlaid. This function is a method in which a display image is displayed by the beam combiner and 100% of light from the outside can be taken in at the same time, and a high see-through property can be realized.

The HMD is excellent in portability because it can display a screen virtually larger than the entire apparatus size. An ideal form of the portable display device is a glasses-type display. In order to realize a small size and light weight like a glasses-type display, it is necessary to reduce the size of a display element (display) and also the size of an image transmission unit and a combiner. Half mirrors, prisms, and ordinary asymmetric optics (Small-off axis: SOA) holograms all require a large device size in front of their eyes due to restrictions due to their principle, and the thickness must be reduced to a shape like glasses. It is difficult. In contrast, by using a large asymmetric optical system (Large-off axis: LOA) hologram for the combiner, it is possible to greatly reduce the thickness of the member in front of the eyes.

A display device using a LOA hologram is disclosed in, for example, US Pat. No. 4,309,070. In this apparatus, a reproduction light including image data incident from a substrate end face of a thin transparent substrate having a LOA hologram formed on its surface is diffracted and displayed in a direction substantially perpendicular to the substrate by the LOA hologram. In this method, the only member formed in front of the eyes is the transparent substrate on which the hologram diffraction element is formed. This device is basically proposed assuming a head-up display (HUD), but it can also be applied as a glasses-type HMD by configuring the transparent substrate to be thin and about the size of glasses. It is something.

[0008]

As described above, the HMD
By using the LOA hologram for the combiner for
Realization of high see-through performance, size in front of the eyes, and especially its thickness can be greatly reduced. However,
When using an image display device such as a normal CRT or LCD,
In order to enter image light from the end face of the substrate that is thinner than the size of the display element, it is necessary to compress the display image from ４ to ５. Moreover, even if a simply compressed image is input, the aspect ratio of the image is changed depending on the incident angle, and an image that extends vertically or horizontally is formed.
On the other hand, it is conceivable to display the image by correcting the aspect ratio of the image to be displayed in advance. However, in this case, a means for newly converting the image information is required, which causes a problem that the apparatus becomes complicated. .

Accordingly, an object of the present invention is to solve these problems and to provide a small-sized image display device capable of displaying an image having a normal aspect ratio with a simple configuration.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image display spatial modulation device that receives illumination light and emits image light according to an image pattern, and compresses image light emitted from the image display spatial modulation device. This is achieved by an image display device comprising: an image compression unit for performing the above, a transparent substrate on which the obtained image light is incident, and a diffraction element provided on the transparent substrate for diffracting the image light incident on the transparent substrate. You.

The image compressing means compresses the image light emitted from the image display spatial modulation device in one direction. This compression is performed, for example, by adjusting the irradiation angle of the illumination light to the image display spatial modulation device, or by providing a cylindrical lens or a hologram optical element between the image display spatial modulation device and the optical member. be able to. Further, the diffraction element is preferably constituted by a reflection hologram.

According to the image display method of the present invention, an aspect ratio of image light according to an image pattern is compressed, the image light having the compressed aspect ratio is introduced into a transparent substrate, and the image light introduced into the transparent substrate is transformed into a transparent substrate. The aspect ratio is restored by being incident on the diffraction element provided above. The compressed image light having the aspect ratio may be reflected on the surface of the transparent substrate and then enter the diffraction element.

With this configuration, it is possible to obtain a small-sized image display device capable of displaying an image having a normal aspect ratio with a simple configuration. Here, the image having the normal aspect ratio refers to the restored image having the original aspect ratio, but in the present invention, an image having a different aspect ratio can be obtained as required.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing an example of the configuration of a head-mounted display device as an image display device according to the present invention. As shown in the figure, the present device has a reflective LCD 18 that emits image light as a spatial modulation device for image display.
And a mirror 12 for reflecting the compressed image light in the direction of the end face 4 of the parallel transparent substrate 1. The parallel transparent substrate 1 has a diffraction element 11 closely attached to the first plane 2, and this diffraction element is a reflection type diffraction grating.

In FIG. 1, the illumination light 31 is adjusted to substantially parallel light by an optical device (not shown), and is applied to the reflective LCD 18. An image pattern corresponding to the image data is formed on the reflective LCD 18 by an image generator (not shown), and the illumination light 31 applied to the reflective LCD 18 is reflected under conditions corresponding to the image pattern. Reflective type L
The image light formed by the CD 18 is reflected by the mirror 12 and enters the end face 4 of the parallel transparent substrate 1. The incident image light 32 is reflected by the second plane 3 of the parallel transparent substrate 1 and enters the diffraction element 11. Here, as the diffraction element 11,
Specifically, a reflection type LOA hologram is used, and the incident light is diffracted in a direction largely different from the incident direction. The image light 32 is reflected by the diffraction element 11 and condensed light 3
The light is focused on the center of the pupil 22 of the eyeball 21 and projected onto the retina 23. With such a configuration, a large angle of view can be realized.

Here, the reflection type LCD 18 is used as a spatial modulation device for image display, because the resolution is increased due to the display manufacturing method. Normally, a transmissive display is manufactured using a large area photolithography technique on a transparent substrate, generally a glass substrate, whereas a reflective display can be manufactured using an LSI process on a silicon wafer. The control electrodes can be arranged at a high density, and a display with higher resolution can be realized. The display size can be reduced by increasing the resolution, and a high-quality image can be reproduced by increasing the number of pixels and decreasing the pixel pitch.

When the incident angle of the image light incident on the diffraction element 11 is an angle Θ with respect to the normal line of the diffraction element as shown in FIG. 4, L / D = 1 / sin (90 ° -Θ) It is magnified twice in the direction parallel to the paper surface (when と き = 75 °, about 4
Times). Therefore, in order to observe the displayed image at a normal aspect ratio, the si
What is necessary is just to compress the image light by n (90 ° -Θ) times. In the configuration example of FIG. 1, the illumination light 31 is incident at an incident angle of 75 ° with respect to the normal line of the reflection type LCD 18, so that the reflection type LCD 1
The image light of No. 8 is compressed about 1/4 times only in the direction horizontal to the paper surface.

FIGS. 5A to 5C are diagrams showing a state of compression of image light. FIG. 5A shows an aspect ratio (L: H) of image light in the reflective LCD 18 and FIG. ) Indicates the aspect ratio of the image light incident on the mirror 12 (L / 4:
H) and (c) show the aspect ratio (L: H) of the image light in the diffraction element 11, respectively. The aspect ratio shown in FIG. 7A is compressed as shown in FIG.
Is restored to the normal aspect ratio. Here, the normal aspect ratio means equal to the original aspect ratio, but does not have to be completely equal, and includes a range in which an observer can view an image without a sense of incongruity.

FIG. 2 is a diagram showing another configuration example of a head mounted display device as an image display device according to the present invention. As shown in the figure, the present apparatus has a transmission type LCD 15 for emitting image light, cylindrical lenses 13 and 14 for compressing image light from the transmission type LCD 15, and a compressed image light in the direction of the transparent substrate end face 4. A reflecting mirror 12 is provided. The parallel transparent substrate 1 has a diffraction element 11 closely attached to the first plane 2, and this diffraction element is a reflection type diffraction grating.

In FIG. 2, the illumination light 31 is adjusted to substantially parallel light by an optical device (not shown) and is applied to the transmission LCD 15. An image pattern corresponding to image data is formed on the transmissive LCD 15 by an image generator (not shown), and the illumination light 31 applied to the transmissive LCD 15 is transmitted under conditions corresponding to the image pattern. Transmission LC
The image light formed by D15 is converted into parallel image light compressed in a direction horizontal to the paper by cylindrical lenses 13 and 14 as image compression means. The compressed image light is reflected by the mirror 12 and is applied to the end face 4 of the parallel transparent substrate 1.
Incident on. The incident image light 32 is reflected by the second plane 3 of the parallel transparent substrate 1 and enters the diffraction element 11. Here, the diffraction element is a reflection type LOA hologram, and diffracts incident light in a direction largely different from the incident direction. The image light 32 is reflected by the diffraction element 11 and condensed light 3
The light is focused on the center of the pupil 22 of the eyeball 21 and projected onto the retina 23. With such a configuration, a large angle of view can be realized.

Here, when the incident angle of the image light incident on the diffraction element 11 is an angle に 対 し て with respect to the normal line of the diffraction element as shown in FIG. 4, L / D = 1 / sin (90 ° -Θ). ) Times in the direction parallel to the plane of the paper (approximately 4 times when Θ = 75 °). Therefore, in order to observe a displayed image at a normal aspect ratio, a sin (90 °) is applied only in a direction horizontal to the paper surface by a cylindrical lens as a compression unit.
−Θ) Image light may be compressed by a factor of two.

FIG. 3 is a diagram showing another example of the configuration of a head-mounted display device as an image display device according to the present invention. As shown in the figure, the present apparatus includes a reflective LCD 18 for emitting image light, hologram optical elements 16 and 17 for compressing image light from the reflective LCD 18, and an end face of the parallel transparent substrate 1 for compressing image light. And a mirror 12 that reflects light in the direction 4. The parallel transparent substrate 1 has a diffraction element 11 closely attached to the first plane 2, and this diffraction element is a reflection type diffraction grating.

In FIG. 3, the illumination light 31 is adjusted to substantially parallel light by an optical device (not shown) and is applied to the reflection type LCD 18 which is a spatial modulation device for image display. Reflective LCD
An image pattern corresponding to the image data is formed on the LCD 18 by an image generator (not shown).
Illumination light 31 applied to 8 is reflected under conditions corresponding to the image pattern. The image light formed by the reflection type LCD 18 is applied to the hologram optical element 1 serving as an image compression unit.
At 6 and 17, the light is converted into parallel image light compressed in a direction horizontal to the plane of the paper. The compressed image light is reflected by the mirror 12 and enters the end face 4 of the parallel transparent substrate 1. The incident image light 32 is reflected by the second plane 3 of the parallel transparent substrate 1 and enters the diffraction element 11. Here, the diffraction element is a reflection type LOA hologram, and diffracts incident light in a direction largely different from the incident direction. The image light 32 is reflected by the diffraction element 11 to become a condensed light 33, condensed at the center of the pupil 22 of the eyeball 21, and projected onto the retina 23. With such a configuration, a large angle of view can be realized.

Here, hologram optical elements 16 and 17 are used as image compression means. This hologram optical element is a transmission type hologram optical element formed of a photopolymer adhered on a glass substrate, and is manufactured so as to focus only in one axial direction (here, a direction perpendicular to the paper surface). . By using a hologram optical element,
The device can be reduced in weight as compared with the case where a lens is used. Further, by using an appropriately manufactured hologram optical element, it is also possible to avoid chromatic aberration when performing color display. When the glasses-type display using the LOA hologram is realized, by adopting the above-described configuration, a small and high-quality apparatus can be realized.

[0025]

(Embodiment 1) A description will be given with reference to FIG. As the transparent substrate 1, an optical glass having a thickness of 5 mm was used. The important points here are high parallelism between the two surfaces, no scratches on the surface, and high transparency. A resin may be used as long as it satisfies these requirements. For example, acrylic resin is used. It is possible. The diffractive element 11 is a reflection hologram made of photopolymer and has a thickness of 15 μm and a size of 15 m in length.
m and 20 mm in width. Further, it was set so that the light incident on the diffraction element 11 at an incident angle of 75 ° was condensed and focused at a position of a distance of 15 mm. As the hologram photosensitive material, silver salt emulsion, gelatin dichromate, etc. are used. However, if the thickness is small, diffraction efficiency may not be sufficiently obtained. The reflective LCD 18 is monochrome and has 640 × 4 pixels.
80 dots and a screen size of 1 inch diagonally were used.

In the above apparatus, L (not shown)
Light from the ED red light source is converted into diffused light by a special filter, and this is collimated by a collimator lens.
It was set to 1. When the illumination light 31 is incident at an incident angle of 75 ° with respect to the normal line of the reflective LCD 18, the reflective LCD 18
Was compressed about 1/4 times only in the direction parallel to the paper surface. The reflection type LCD 18 has a personal computer (not shown).
A computer was connected and a monochrome document image was displayed.

The image light 32 which was compressed and displayed was reflected by the mirror 12 and was incident from the end face 4 of the parallel transparent substrate 1 so that the incident angle with respect to the normal of the second plane 3 was 75 °. The incident image light was totally reflected by the second plane 3 and entered the diffraction element 11. Here, the observer's eyes were taken near the converging point of the diffraction element 11 and the image was observed.
The content displayed in 18 could be clearly observed with sufficient brightness. At the same time, the outside scenery could be observed with almost the same brightness as normal. The aspect ratio was almost normal.

(Embodiment 2) In FIG.
Used an optical glass having a thickness of 5 mm. Diffraction element 11 is a reflection hologram made of photopolymer and has a thickness of 15 microns.
The size was 15 mm long and 20 mm wide. Further, it was set so that the light incident on the diffraction element 11 at an incident angle of 75 ° was condensed and focused at a position of a distance of 15 mm. Transmission type L
CD15 is monochrome and has 640 x 480 pixels.
The screen size used was 1 inch diagonal. The cylindrical lens 14 has a width of 25 mm and a focal length of 60 mm, and the cylindrical lens 13 has a width of 15 mm and a focal length of 15 mm. In this case, the image light is 1 /
4 compressed. The width of the image light in the horizontal direction is about 5
mm.

In the above apparatus, L (not shown)
Light from the ED red light source is converted into diffused light by a special filter, and this is collimated by a collimator lens.
As 1, the transmissive LCD 15 was illuminated. Transmissive LCD1
5 is connected to a personal computer (not shown)
A monochrome document image was displayed.

The displayed image light 32 is compressed to １ ／ by the cylindrical lenses 14 and 13, reflected by the mirror 12, and incident from the end face 4 of the parallel transparent substrate 1 with respect to the normal to the second plane 3. The light was incident at an angle of 75 °. The incident image light was totally reflected by the second plane 3 and entered the diffraction element 11. Here, the observer's eyes were taken near the converging point of the diffraction element 11 and the image was observed.
The content displayed in No. 15 could be clearly observed with sufficient brightness. At the same time, the outside scenery could be observed with almost the same brightness as normal. The aspect ratio was almost normal.

(Embodiment 3) In FIG.
Used an optical glass having a thickness of 5 mm. Diffraction element 11 is a reflection hologram made of photopolymer and has a thickness of 15 microns.
The size was 15 mm long and 20 mm wide. Further, it was set so that the light incident on the diffraction element 11 at an incident angle of 75 ° was condensed and focused at a position of a distance of 15 mm. Reflective type L
The CD 18 is monochrome and has a number of pixels of 640 × 480 dots and a screen size of 1 inch diagonally. The hologram optical element 17 has a width of 17 mm and a focal length of 30 mm, and the hologram optical element 16 has a width of 10 mm and a focal length of 10 mm. In this case, the image light is 1 /
3 compressed. The width of the image light in the direction horizontal to the paper surface is about 4.7 mm.

In the above apparatus, L (not shown)
Light from the ED red light source is converted into diffused light by a special filter, and this is collimated by a collimator lens.
It was set to 1. When the illumination light 31 is incident at an incident angle of 45 ° with respect to the normal of the reflective LCD 18, the reflective LCD 18
Of image light was compressed by a factor of ^{1/2 1/2} only in the direction parallel to the paper surface. A personal computer (not shown) was connected to the reflective LCD 18 to display a monochrome document image.

The displayed image light 32 is compressed to 1/3 by using the hologram optical elements 17 and 16, and this is
And incident from the end face 4 of the parallel transparent substrate so as to have an incident angle of 75 ° with respect to the normal to the second plane 3. The incident image light is totally reflected by the second plane 3 and the diffraction element 11
Incident on. Here, when the observer's eyes were taken near the converging point of the diffraction element 11 and the image was observed, the reflection type LC was observed.
The content displayed on D18 could be clearly observed with sufficient brightness. At the same time, the outside scenery could be observed with almost the same brightness as normal. The aspect ratio was almost normal.

As described above, in the image display device using the LOA hologram, the image light displayed on the image display spatial modulation device is compressed and incident on the transparent substrate, so that the ordinary image display spatial modulation device can be used. As a result, a compact display device capable of displaying an image with a normal aspect ratio can be configured, and a glasses-type display can be realized. In the above embodiment, a monochrome display using a single color light source has been described.
By using light sources of three colors of GB, a full-color image can be easily reproduced. The diffraction grating used at that time can be created in consideration of a normal color hologram panel.

[0035]

According to the present invention, it is possible to obtain a small-sized image display device capable of displaying an image having a desired aspect ratio with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration example of an image display device according to the present invention.

FIG. 2 is a diagram showing another configuration example of the image display device according to the present invention.

FIG. 3 is a diagram showing another configuration example of the image display device according to the present invention.

FIG. 4 is a diagram for explaining restoration of compressed image light.

FIGS. 5A to 5C are diagrams showing an aspect ratio of an image in each section.

DESCRIPTION OF SYMBOLS 1 Parallel transparent substrate 2 First transparent substrate surface 3 Second transparent substrate surface 11 Diffractive element 12 Mirror 13, 14 Cylindrical lens 15 Transmission LCD 16, 17 Hologram optical element 18 Reflective LCD 21 Eyeball 22 Pupil 23 retina 31 illumination light 32 image light 33 condensed light

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takao Tomino 430 Nakai-cho, Sakaigami-gun, Kanagawa Prefecture Green Tech Nakai Inside Fuji Xerox Co., Ltd. (72) Inventor Kazuhiro Hayashi 430 Nakai-cho Sakai, Ashigara-gun, Kanagawa Green Tech Nakai Fuji Xerox Stock Inside the company (72) Inventor Kiichi Kamyanagi 430 Nakaicho, Ashigarakami-gun, Kanagawa Prefecture Green Tech Nakai Fuji Xerox Co., Ltd. F-term (reference) 5G435 AA18 BB12 BB15 BB16 DD02 FF15 GG01 LL13

Claims (8)

[Claims] An image display spatial modulation device that receives illumination light and emits image light according to an image pattern; an image compression unit that compresses image light emitted from the image display spatial modulation device; An image, comprising: a transparent substrate that receives image light obtained through an image compression unit; and a diffraction element provided on the transparent substrate that diffracts the image light that has entered the transparent substrate. Display device. 2. The image display device according to claim 1, wherein said image compression means compresses image light emitted from said image display spatial modulation device in one direction. 3. The image display device according to claim 2, wherein the image light is compressed in one direction by adjusting an irradiation angle of the illumination light to the image display spatial modulation device. 4. The image display device according to claim 2, wherein said image compression means comprises a cylindrical lens provided between said image display spatial modulation device and said transparent substrate. 5. The image display device according to claim 2, wherein said image compression means comprises a hologram optical element provided between said image display spatial modulation device and said transparent substrate. 6. The image display device according to claim 1, wherein said diffraction element is constituted by a reflection hologram. 7. An image light according to an image pattern, wherein an aspect ratio of the image light is compressed, the image light having the compressed aspect ratio is introduced into a transparent substrate, and the image light introduced into the transparent substrate is provided on the transparent substrate. An image display method for restoring the aspect ratio by making incident on the diffractive element. 8. The image display method according to claim 7, wherein the compressed image light having an aspect ratio is reflected on a surface of the transparent substrate and then enters the diffraction element.