JPH09113995A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bright displayed picture, to excellently perform observation in accordance with the posture of an observer, and to prevent the deterioration of image quality in the display device of a system observing the picture as a real image. SOLUTION: This device is equipped with a transmission type hologram screen 1 provided to be opposed to an observer O and constituted by forming a hologram layer 12 on a base plate 11, and a projection means 3 projecting the displayed picture on the screen 1 at a specified projection angle θ from an oblique direction. Then, by setting the projection angle f) as an angle that the strong diffraction angle of projected light θ made incident on the screen 1 from the projection means 3 on the layer 12 is directed toward the observer O, the radiated light from the light source from the projection means 3 to the eye of the observer O is efficiently diffracted and made incident on the screen 1. The screen 1 and the projection means 3 are provided on a common pedestal 2, which is supported so that the angle of elevation and an azimuth are varied. The hologram layer 12 exerting an influence on the image quality is positioned on the rear side of the base plate 11 which is not directly touched by the observer O.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device capable of superimposing a display image on a background.

[0002]

2. Description of the Related Art Conventionally, CRTs, liquid crystal display boards, etc. have been widely used as display devices. Since only the display screen is displayed on these display devices, for example, when inputting a slip or the like, the line of sight is frequently moved to burden the worker. Therefore, there has been a demand for a display device capable of superimposing a display image on a background. As such a display device, there is a head-up display device, which has a display unit for outputting a display image and a semi-transmissive / semi-reflective combiner provided facing the observer. Is reflected by a combiner so that the virtual image of the displayed image is reflected in the eyes of the observer. It has been put to practical use as a meter display for airplanes and automobiles by taking advantage of the fact that both the displayed image and the background can be seen without moving the line of sight significantly. However, in the above head-up display device, the position of the virtual image recedes from the combiner by the length of the optical path between the image output surface of the display section and the combiner, which is not suitable for desk work. Therefore, the display image output from the display unit is projected on the hologram screen like the display devices described in JP-A-4-293032 and JP-A-4-298710 so that the display image can be observed as a real image. There is something.

[0003]

By the way, in the case of superimposing a display image on the background for observation, it is necessary to obtain a display image brighter than or equal to the background. However, in the above display device, the light source of the projection device is large in order to obtain a bright display image. Also, because the hologram screen is fixed to the casing or desk and the posture and position of the observer are limited, the displayed image cannot be seen well depending on the sitting height of the observer,
There is a problem in usability. Further, since the hologram screen as the display surface is located close to the observer as in the conventional display device, the hologram layer is easily damaged and the image quality of the display image seen by the observer is deteriorated.

Therefore, the present invention has been made in view of the above problems, and a bright display image can be efficiently obtained with a small light source while avoiding an increase in the size of the light source, and the display image can be displayed regardless of the observer's posture or position. It is an object of the present invention to provide a display device which can be viewed well and whose display image is less deteriorated.

[0005]

According to the present invention, in a display device, a transmission type hologram screen 1 provided facing an observer O shown in FIG. 1 and a projection means 3 for obliquely projecting a display image on the hologram screen 1. And the projection angle θ in oblique projection is set to the hologram layer 1 of the projection light L.
The strong diffraction angle at 2 was set as the angle oriented in the direction of the observer O. As a result, the projection light diffracted by the hologram layer 12 is efficiently incident on the eyes of the observer O and the displayed image is felt bright, and the light source of the projection means 3 is made as small as possible to save power and reduce the size of the apparatus. It was made possible (Claim 1).

The present invention has a structure in which the hologram screen 1 and the projection means 3 of the display device are supported on a common base 2 whose elevation angle and azimuth angle are variable, whereby the projection angle .theta. The viewing area can be changed according to the sitting height of the observer O while maintaining the diffraction angle at the angle directed in the direction of the observer O, thereby improving the practical effect of the apparatus (claim 2).

According to the present invention, the hologram screen 1 is positioned so that the substrate 11 side faces the observer O, and even if the observer O or the like touches the hologram screen 1, the diffraction pattern formed on the hologram layer 12 is formed. Is not scratched, and the image quality is prevented from deteriorating during use (claim 3). Further, a protective film such as acrylic is formed on the surface of the hologram layer 12 of the hologram screen 1 so as to protect the diffraction pattern (claim 4).

According to the present invention, the hologram screen 1 is removably installed on the base 2, and the hologram screens 1 having different observable regions are appropriately replaced so that a display according to the application can be made. ).

In the display device of the present invention, the projection means 3 is connected to the top plate 2.
1 is stored in a casing 2 which is a base having an opening 22 formed therein, the projection direction of the projection means 3 is directed to the opening 22, and the hologram screen 1 is provided in the casing 2 so as to face the projection means 3 and the projection angle θ. Is easily carried while the strong diffraction angle of the projection light at the hologram layer 12 is directed to the observer (claim 6).

In the display device of the present invention, a brightness correction filter for correcting non-uniformity of display brightness on the hologram screen 1 is provided in the optical path of the optical system formed by the hologram screen 1 and the projection means 3 or the hologram screen 1.
It is provided in a position close to, and reduces unevenness in brightness of a display image caused by projecting the image on the hologram screen 1 from an oblique direction (claim 7). Further, by making the display device in which the diffraction efficiency of the hologram screen 1 is high at the position where the brightness is low on the hologram screen 1 and is low at the position where the brightness is high, it is possible to reduce the brightness unevenness of the display image (claim 8).

[0011]

1 shows a display device of the present invention.
The casing 2, which is the base of the display device, has a thin box shape and is supported by the stand 6, and the top plate 21 thereof has an opening 22 formed therein. A hologram screen 1 is arranged above the casing 2. The hologram screen 1 is formed by forming a hologram layer 12 on a transparent substrate 11 to form a rectangular flat plate. The substrate 11 is positioned on the observer O side, and the lower end of the substrate 11 is the top plate 21 of the casing 2. It is fitted in the groove of the hologram screen receiving portion 71 provided along the front edge. The hologram screen receiving portion 71 and the hologram screen 1 are coupled by a mounting screw 72 that inserts them. The hologram screen receiving portion 71 is connected to a hinge 8 provided in the front portion of the top plate 21, and the hologram screen 1 is locked at a predetermined tilt angle when the display device is used and when not used.
1 is tilted upwards so that it can be easily stored and prevents dust from entering through the opening 22.

A projection optical unit 3 as a projection means is housed inside the casing 2 on the back side. Projection optical unit 3
The case 31 has a thin rectangular shape, and the upper surface is swollen on the back side. The projection lens 3 faces the hologram screen 1 in the opening formed in the inclined surface on the front side of the bulge.
2 is fitted. A liquid crystal display element 33 is provided at a position behind the projection lens 32 where the hologram screen 1 forms an image so as to face the hologram screen 1, and a display image output to the liquid crystal display element 33 is passed through the projection lens 32 to the hologram screen 1. It is designed to magnify and project upward. These form the projection optical system. The main optical axis L from the liquid crystal display element 33 to the hologram screen 1 and the hologram screen 1
Angle formed by the normal to the display surface of (the projection angle) θ
Is set to an angle described later based on the characteristics of the hologram screen 1.

A halogen lamp 36 and a concave reflector 37 disposed so as to surround the halogen lamp 36 are provided in the front part of the housing 31, and the light emitted from the halogen lamp 36 is condensed by the reflector 37 to produce parallel light. The light is efficiently emitted to the back side of the housing 31 in a condensed state such as. An optical filter 3 for removing infrared rays and ultraviolet rays on the optical axis
5 and a mirror 34, and a halogen lamp 36
The light emitted from the mirror 3 via the optical filter 35.
4, the liquid crystal display element 33 is illuminated by changing its direction to the front side and diagonally upward, and forms an illumination optical system.

A cooling fan 5 is provided on the upper surface of the housing 31 to radiate heat from the halogen lamp 36 and the like. A circuit board 4 is provided on the front side of the casing 2, and drives the liquid crystal display element 33 by inputting video signals such as a video connected to a video input terminal (not shown) or a computer or the like such as NTSC or RGB. A driver circuit, a halogen lamp 36, a power supply circuit for the cooling fan 5, and the like are formed.

On the lower surface of the casing 2, downwardly convex spherical shell portions 23 and 24 are formed in an inner and outer double manner, and an outer spherical shell portion 24 has an opening formed at the center. As for the inner spherical shell portion 23, the stand 6 is a spherical shell-shaped saucer portion 61 concave upward.
When the casing 2 moves along the tray 61, its elevation angle and azimuth angle are changed. The diameter of the opening of the spherical shell portion 24 outside the casing 2 is smaller than the diameter of the pan 61 of the stand 6 so that the casing 2 and the stand 6 cannot be accidentally removed.

The hologram screen 1 and the projection angle will be described. As shown in FIG. 2, the hologram screen 1 is a photopolymer or DCG (dichromated gelatin).
The object light L1 that is transmitted through the diffusion plate 92 made of frosted glass or the like is projected onto the dry plate 91 formed by the above, and the reference light L2 is projected from the same side as the object light L1. As a result, the dry plate 91 becomes a transmissive hologram optical element in which the hologram diffraction grating containing the information of the diffusion plate 92 is recorded. This is the hologram screen 1.
The direction in which the light incident on the hologram screen 1 at a constant incident angle is strongly diffracted depends on the angle at which the object light L1 and the reference light L2 are projected and is uniquely determined. The diffusion angle φ of the light incident on the hologram screen 1 depends on the diffusion characteristics of the diffusion plate 91 and is uniquely determined. The hologram screen 1 is locked at a predetermined tilt angle when the display device is used, and the projection light having a projection angle θ incident on the hologram screen 1 is a strong diffraction angle in the direction of the observer O (usually with respect to the hologram screen 1 as shown in FIG. 1). (Almost right angle)
The angle is fixed to point.

The operation of the above display device will be described. The observer first adjusts the elevation angle and azimuth angle of the display device so that the hologram screen 1 is easy to see (usually the observer and the hologram screen 1 face each other in a straight line), depending on his or her sitting height and the installation place of the display device. Adjust it. When a video signal from a video or the like is input, the driver circuit of the circuit board 4 drives the liquid crystal display element 33, and a display image is output to the liquid crystal display element 33.

On the other hand, the radiated light of the halogen lamp 36 has its infrared rays and ultraviolet rays removed by the optical filter 35, and only visible light is reflected obliquely upward by the mirror 34 and enters the liquid crystal display element 33. Then, the display image output to the liquid crystal display element 33 forms a real image on the hologram screen 1 by the projection lens 32, and the light that forms the real image is diffracted by the hologram layer 12 and emitted as a cone at a constant diffusion angle φ. . The range taken by the position where the cones from all the points of the display area of the hologram screen 1 overlap is the area D in which the display image can be seen (the hatched portion in the drawing is referred to as the viewing area) D. Since the projection angle θ is the angle at which the strong diffraction angle of the projection light incident on the hologram screen 1 from the projection optical unit 3 on the hologram layer 12 is directed toward the observer, the light emitted from the halogen lamp 36 is efficiently viewed in the viewing area D. Reach. Therefore, the observer O can see a bright display image in the viewing area D without increasing the size of the light source of the projection optical unit 3.

FIG. 3 shows an optical path diagram equivalent to the optical system of the above display device. The hologram screen 1 is 14 inches (hence the short side length is 222 mm) and the projection angle is 40.
Degree, the inclination angle of the hologram screen 1 is 10 degrees, and the horizontal optical distance between the halogen lamp 36 and the hologram screen 1 (hereinafter referred to as the projector projection distance) is 2 degrees.
It is set to 50 mm, and the observer's eye point O is set to 500 mm in front of the hologram screen 1 (this is a general distance when viewing a display device of about 14 inches, and is hereinafter referred to as an assumed viewing distance). Of the light emitted from the halogen lamp 36, the light diffracted by the hologram screen 1 advances toward the eyepoint O of the observer and forms a viewing area D around the eyepoint O of the observer. On the other hand, the 0th-order diffracted light that travels further straight from the hologram screen 1 is emitted toward the upper side of the eyepoint O of the observer (the range sandwiched by the two arrows extending from the halogen lamp 36 in the figure). When the observer's eye point is located at the position where the 0th-order diffracted light is emitted, the halogen lamp 36 appears in the eyes and looks dazzling. Is very small, and the observer's eye point O is far from the range where the 0th order diffracted light is emitted. Therefore, normally, the halogen lamp 36 is not visible and the displayed image can be viewed comfortably.

Since the eye point O of the observer faces the hologram screen 1 at a close distance of about 500 mm like a normal display device, it may touch the surface of the hologram screen 1, but it is located on the observer side. The substrate 11 of the holographic screen 1 does not affect the image quality of the displayed image observed by the observer O, and does not touch the hologram layer 12 formed on the back surface side of the hologram layer 12. The fine diffraction pattern is not damaged and the image quality is not deteriorated. Moreover, dirt on the substrate 11 side can be wiped off with a cloth, and maintenance is easy.

If the hologram layer 12 is damaged, it is sufficient to remove the mounting screw 72 to remove the hologram screen 1 and mount a new hologram screen, which facilitates maintenance. It is also possible to prepare a plurality of hologram screens having different viewing areas, and to appropriately use the ones having a wide viewing area for observing a plurality of people and those having a narrow viewing area for observing a single person.

As another embodiment, a plurality of projection optical units are arranged in parallel at different positions and a plurality of different display images are projected on the hologram screen. The hologram screen is formed by multiple exposure with a plurality of combinations of the incident angles of the reference light and the object light. And the projection angle of each projection optical unit is an angle at which the strong diffraction angle in the hologram layer of the projection light incident on the hologram screen from each projection optical unit is directed in a different direction for each projection optical unit, and in each of the different directions described above. Form the viewing zone of.
In such a display device, a plurality of display images projected on one hologram screen can be viewed separately by changing the viewing angle. In this case, in order to improve the separation of the display image, it is preferable to weaken the diffusion characteristic of the diffusion plate so that the diffusion angle of the hologram screen becomes small.

Although the hologram screen and the projection optical unit are integrally stored in the casing, the present invention is not limited to this, and the hologram screen and the projection optical unit may be incorporated in a desk or the like as a base. Alternatively, the hologram screen and the projection optical unit may be separate bodies.

Further, although the stand has a mechanism in which the stand is supported by the spherical shell-shaped saucer portion so that the elevation angle and the azimuth angle can be changed together, the elevation angle and the azimuth angle may be independently adjusted. . For example, a hinge mechanism and a rotary table mechanism can be combined.

Although the substrate side of the hologram screen is positioned on the observer side, a hard coat of acrylic or the like as a protective film may be formed on the surface of the hologram layer to prevent the hologram layer from being damaged. In this case, it is not always necessary to position the substrate side on the observer side.

The display image projected on the holographic screen by projecting the display image obliquely has a display luminance that is high in the central part of the optical axis and low in the peripheral part, but the optical paths of the projection optical system and the illumination optical system are the same. A luminance correction filter having a higher transmittance in the peripheral portion than in the central portion can be inserted in the middle of, or near the hologram screen to make the luminance distribution uniform. Alternatively, the same effect can be obtained by using a hologram screen in which the diffraction efficiency of the hologram layer of the hologram screen is lower in the central portion than in the peripheral portion. When manufacturing such a hologram screen, the brightness distribution of the diffusion plate may be set to be lower at the position corresponding to the center of the optical axis than at the position corresponding to the peripheral part. For example, a filter that reduces the transmittance is arranged on the emission side at a position corresponding to the center of the optical axis of the diffusion plate. Also, by projecting the display image obliquely, the display image projected on the hologram screen has a trapezoidal distortion in which the projection magnification is large on the upper side and small on the lower side, but the display image output to the liquid crystal display element cancels the trapezoidal distortion. If the image is distorted in advance, a display image without trapezoidal distortion can be projected on the hologram screen.

The projection angle is set to 40 degrees, but the projection angle is not limited to this. The projection optical unit changes from the projection optical unit to the hologram screen in accordance with the projection angle of the reference light and the object light when manufacturing the hologram screen. It suffices that the strong diffraction angle of the incident projection light in the hologram layer is an angle directed toward the observer. Therefore, the projection angle can be made large or small by appropriately selecting the angles at which the reference light and the object light are projected when manufacturing the hologram screen. If you want to reduce the depth of the display device, you can set a larger projection angle.
The diffracted light may be small as long as it does not impair the viewing zone. Further, the inclination angle of the hologram screen is set to 10 degrees, but this is a general number in the display device and can be set to another inclination angle depending on the use and size of the display device. Further, the assumed viewing distance and the projection distance of the projector may be determined at the design stage of the device according to the use and size of the display device.

The projection lens may be composed of a combination of a concave lens and a convex lens made of a usual material such as glass, or may be a hologram lens having a hologram having a light condensing function. In the case of the hologram lens, the device can be downsized, and the function of a filter for removing unnecessary ultraviolet rays and infrared rays can be recorded in the diffraction pattern.

Although a halogen lamp is used as the light source, a xenon lamp, a metal halide lamp or the like may be used.

[Brief description of the drawings]

FIG. 1 is an overall vertical sectional view of a display device of the present invention.

FIG. 2 is a diagram illustrating a main part of a display device of the present invention.

FIG. 3 is an optical path diagram for explaining the operation of the display device of the present invention.

[Explanation of symbols]

 1 Hologram Screen 11 Substrate 12 Hologram Layer 2 Casing (Base) 21 Top Plate 22 Opening 3 Projection Optical Unit (Projection Means) L Main Optical Axis (Projection Light) O Eyepoint (Observer) θ Projection Angle

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Jun Hashikawa 14 Iwatani, Shimohakaku-cho, Nishio-shi, Aichi Japan Auto Parts Research Institute

Claims (8)

[Claims] 1. A transmission type hologram screen, which is provided so as to face an observer and has a hologram layer formed on a substrate, and a projection means for projecting a display image on the hologram screen from an oblique direction at a predetermined projection angle. In the display device, wherein the observer observes the display image projected on the hologram screen, the projection angle is the hologram layer of the projection light incident on the hologram screen from the projection means. The display device characterized in that the strong diffraction angle of is set to an angle directed toward the observer. 2. The display device according to claim 1, wherein the hologram screen and the projection means are provided on a common base, and the base is made variable in elevation angle and azimuth angle. 3. The display device according to claim 1, wherein the hologram screen is installed with the substrate side facing the observer. 4. A display device according to claim 1, wherein a transparent protective film is formed on a surface of the hologram layer of the hologram screen. 5. The display device according to claim 1, wherein the hologram screen and the projection means are provided on a common base, and the hologram screen is detachably installed on the base. 6. The display device according to claim 1, wherein the base is composed of a casing in which a top plate is provided with an opening portion, and the projection means is provided in the casing in a direction in which a display image is projected. A display device that is stored in the casing and is installed in the casing with the hologram screen placed at the image formation position of the display image. 7. The display device according to claim 1, wherein the brightness distribution of the display image is corrected in the optical path of an optical system formed by the hologram screen and the projection means or close to the hologram screen. A display device provided with a brightness correction filter for controlling. 8. A display device according to claim 1, wherein the diffraction efficiency of the hologram screen is distributed in a tendency opposite to that of the brightness distribution of the projected image.