JPH10197824A - Holographic display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of drastic brightness lowering even in the case the reproduced wavelength of a hologram is varied due to manufacturing variation and temperature fluctuation by making the angle of light made incident on a hologram nearly equal to the angle of light diffracted by the hologram and also specifying the distance between a virtual image and the hologram. SOLUTION: An information display source for emitting light 3 including information is constituted of a fluorescent display tube 21. The light 3 including the information is diffracted by a combiner 20 so as to be viewed as the displayed virtual image 10 by an observer 1. The combiner 20 is obtained by arranging the hologram on a base material such as a glass substrate and a transparent resin substrate, etc. The angle θ1 of light made incident on the combiner 20 from the fluorescent display tube 21 is nearly equal to the angle θd diffracted from the combiner 20 to the observer 1. And also, a distance (rd) from the combiner 20 to the displayed image 10 is less than three times a distance (r1) from the fluorescent display tube 21 to the combiner 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a holographic display device.

[0002]

2. Description of the Related Art With the recent development of hologram materials and laser technology, products using holograms are increasing.
For example, a hologram is used as an optical element in a holographic display device that diffracts light containing information and displays the information to an observer. In addition, forgery prevention marks on ID cards and credit cards, decorative holograms, hologram calendars, and the like use holograms on which images are recorded.

The following are specific examples. 2. Description of the Related Art In order to display information to a driver of a vehicle such as an automobile, a display device such as a head-up display (hereinafter, referred to as HUD) has recently been used. In this method, optical information projected from an information projection unit such as a liquid crystal display device is projected onto a combiner including a hologram and a half mirror incorporated in a windshield of an automobile or the like, and a driver almost moves a viewpoint from a driving state. This allows information to be read without the need.

[0004] In particular, the one using a hologram as a combiner can not only set the incident angle and the diffraction angle freely but diffract optical information toward the driver,
Since it can also have a lens function, it is possible to diffract optical information in the direction of the driver's field of view, or to form an image at any position without using an optical system such as a lens. It is. In addition, since the half width of the diffraction spectrum is narrow, a high-luminance display image can be obtained without deteriorating the foreground luminance, which is effective as a combiner for a display device.

FIG. 3 is a conceptual diagram showing an example of such a HUD. Light 3 including information to be displayed, which is emitted from a light source 6 and passes through a transmission type liquid crystal display element 5 via a lens system 4 and a wavelength selection filter 11, is applied to a hologram 2 provided on a windshield 7 of a vehicle body. The light is diffracted and is visually recognized at the observation position 1 by the driver. The lens system 4 has a function as a collimator. At this time, the windshield 7 is a laminated glass, and the hologram 2 is sealed in the laminated glass. The hologram 2 has a wavelength selection function, and a desired multicolor image can be displayed by using a hologram subjected to multiple exposure. For example, by setting the speed display 8 to green and the warning display 9 to red, it is possible to more accurately transmit information to the driver.

[0006]

However, since holograms utilize diffraction, there is a problem of blurring of an image due to occurrence of chromatic aberration. Therefore, conventionally, it has been necessary to use a cathode ray tube having a narrow wavelength half width as a light source of the transmission type liquid crystal display element, or to use an interference filter having a narrow wavelength half width as in the above example.

When a cathode ray tube is used as a light source, an inverter circuit is required, which is expensive, and it is difficult to adjust the brightness (dimming). As for the interference filter, a filter having a small half width and a high transmittance requires a multilayer coating, and is very expensive.

When a light source with a narrow half width is used, it is necessary to match the peak wavelength of the light source with the diffraction wavelength of the hologram, which also requires a precise hologram fabrication technique. When the reproduction wavelength fluctuates due to manufacturing variations of the hologram and the interference filter, there is also a problem that the brightness of the display image is reduced. Furthermore, even if ideal wavelength matching is enabled, there is a problem of temperature characteristics. When the diffraction wavelength of the hologram fluctuates due to a change in the temperature of the environment, there is a problem that the brightness of the displayed image is also lowered.

An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a new holographic display device which has not been known.

[0010]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has an information display source for generating information to be displayed as light, and an information display source arranged on a base material, for transmitting the light. A holographic display device comprising at least a combiner having a hologram that diffracts towards the observer and displays it as a virtual image, wherein the information display source comprises a fluorescent display tube, and the light is diffracted by the angle and the hologram at which the light enters the hologram. And a distance between the virtual image and the hologram is less than three times a distance between the information display source and the hologram. is there.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the drawings. FIG. 1 is a schematic sectional view showing an example of the holographic display device of the present invention. The information display source that emits the light 3 containing information includes the fluorescent display tube 21.
The light 3 containing information is diffracted by the combiner 20 in which the hologram is arranged on the base material, and is visually recognized as a display virtual image 10 by the observer 1.

The optical arrangement of the display device shown in the drawing is such that the incident angle θ _i of light from the fluorescent display tube 21 to the combiner 20 is substantially equal to the diffraction angle θ _d from the combiner 20 to the observer 1, and the display image from the combiner 20 is The distance r _{d to} 10 is less than three times the distance r _i from the fluorescent display tube 21 to the combiner 20.

In the holographic display device of the present invention having such an optical arrangement, the occurrence of chromatic aberration is small, and a sufficiently acceptable display image can be obtained within the viewing range in which the observer moves his or her eyes. Japanese Industrial Standard JIS
And an eye range specified by D0021.

That is, when a fluorescent display tube is used as the information display source, even if the observer moves his or her eyes even a little within the viewing area, the display virtual image is easily blurred due to the characteristics of the hologram. However, in the present invention, while using a fluorescent display tube, substantially equal to the theta _i and theta _d, and the r _d r
_By setting it to be less than three times _i , the above chromatic aberration can be reduced, and blurring can be reduced. In particular, when r _d is three times or more than r _i , the occurrence of the above-described blur is remarkable. Therefore, setting r _d to less than three times r _i as in the present invention is a very effective means. , 2.5 times or less.

Since the fluorescent display tube has been found to have an optical configuration which is sufficiently satisfactory for use as described above, it is relatively inexpensive without using an expensive liquid crystal display element and a cathode tube or an interference filter. A holographic display device can be realized by a simple fluorescent display tube. Further, since a light source having a wide half width can be used, even if the diffraction wavelength of the hologram slightly fluctuates due to manufacturing variations and temperature characteristics, a large decrease in luminance does not occur.

The fluorescent display tube of the present invention is preferably used because a green light-emitting fluorescent display tube using zinc oxide (ZnO: Zn) as a phosphor is bright and reliable. The peak wavelength of the emission spectrum is 505 nm and the half width is about 100 nm or more. In addition to zinc oxide, sulfide-based phosphors can also be used. For example, ZnS: Cu, Al or Zn
CdS: Ag, Cl and the like. All have a half width of 10
At about 0 nm, the color tone changes depending on the composition, from green to yellow,
There are oranges. A color display can be obtained by appropriately using them. As a display pattern, a phosphor may be patterned and arranged in a segment shape, but a dot matrix type arrangement is preferable in that more advanced information can be displayed. In ZnO: Zn, the left side (ZnO) of the: mark represents the base material of the phosphor, and the right side (Zn)
Represents a substance that contributes to light emission (referred to as an activator). Other exemplified substances also have the same meaning on the left and right of the mark.

The combiner according to the present invention is one in which a hologram is arranged on a base material such as a glass substrate or a transparent resin substrate.

As the hologram, a hologram having an area of usually several tens mm to several hundred mm square and a thickness of several μm to several tens μm is exemplified. This hologram is preferable in that a volume / phase hologram such as a Lippmann type can obtain a high diffraction efficiency, but a hologram such as an emboss type or a rainbow type can be widely used. The type of the hologram is not particularly limited, such as a transmission type and a reflection type. Examples of hologram materials include photopolymers such as acrylic and polyvinyl carbazole, dichromated gelatin, optical resist,
Various photosensitive materials such as silver salts can be used.

The substrate in the present invention is appropriately selected according to the use and the state of use. It goes without saying that the incident side of the reproduction light and the exit side of the diffracted light with respect to the hologram are transparent substrates, but this may be one that partially transmits light. For example, a non-colored transparent glass plate or a glass plate colored with bronze or green can be used as the base material. Further, a portion through which the reproduction light or the diffracted light does not pass may be opaque. As a material of the base material, besides glass, a resin substrate such as acryl, polycarbonate, polyvinyl chloride, polyolefin, or the like, or a transparent crystal may be used. The thickness of the substrate may be a plate having a thickness of several mm, a film having a thickness of 1 mm or less, or a block having a thickness of several cm. Furthermore, if the diffraction image of the hologram and the reflection image on the surface of the substrate overlap, visibility deteriorates. Therefore, it is preferable that an antireflection coating is applied to the surface of these substrates. Further, a hard coating may be applied as necessary.

Further, an optical member such as a lens and a mirror, a light polarizing means, or a non-linear optical element may be arranged in the optical path before the light is projected onto the hologram.

The holographic display device of the present invention is suitably used in a conventional HUD for automobiles. Also, a so-called separately mounted HUD (FIG. 2) in which a combiner is pivotally supported by a main body provided with an information display source and is mounted on a dashboard of a vehicle to allow a driver or the like to visually recognize driving information.
(See Reference). The information display source and the combiner are integrated, and the fluorescent display tube has both functions in comparison with the conventional information display source, which is composed of a combination of a light source and a transmissive liquid crystal display element and is large. Therefore, a small and lightweight holographic display device can be realized. Furthermore, it is preferable to use a resin material as the base material of the combiner, since it is lighter in weight than glass, and even if it hits, there is less damage to the human body.

FIG. 2 shows an example of the separate type HUD. The combiner 20 is rotatably supported near the end of the main body 22 of the HUD via a holding member 24. Angle to the horizontal of the combiner during use is theta _w. An adjustable leg 23 is provided on the bottom surface of the main body 22 as needed, and the leg 23 is held at a location where the HUD is installed (for example, on a dashboard of a vehicle). Main unit 2
An information display source 21 composed of a circuit section 25 and a fluorescent display tube is provided in 2 and irradiates a light 3 containing information at an incident angle θ _i to a combiner. The light is reflected and diffracted by the diffraction angle theta _d by the hologram, it becomes an observer (e.g., a driver) 1 to be visually recognized as a display image 10 of the operation information.

When the holographic display device of the present invention is used for a vehicle, the information to be displayed is appropriately selected according to the display purpose, and may be a speedometer, a tachometer, a shift lever display of a vehicle, and various other information. Warning lamps, navigation information, information on ancillary equipment such as air conditioners and audio equipment, and the like.
Further, it is of course possible to display information from outside the vehicle such as road information and parking lot availability information. For aircraft and ships, various information related to vehicle operation and duties, such as position and orientation information such as latitude, longitude, altitude, direction of travel, weather information, radar obstacle information, fish finder information, etc. can be considered. . The observer is mainly a driver of a vehicle such as a vehicle, but may include a passenger seat and other passengers, and all of these persons.

The holographic display device of the present invention can be used for various applications other than the example applied to the HUD for automobiles. For example, the present invention can also be used for a holographic display device in which a hologram is arranged in a dark-colored ceramic painted portion around a windshield of an automobile. In this case, because the dark ceramic painted part absorbs solar heat and the temperature fluctuates drastically,
The configuration of the present invention is particularly effective. Further, the present invention can be widely applied to all display devices using holograms, such as a virtual image corner marker for indicating a corner of a vehicle.

[0025]

Embodiments of the present invention will be described below. FIG. 2 shows an example in which the present invention is applied to a separately placed HUD. Combiner 2
No. 0 was produced by integrally molding a hologram with an acrylic resin. The angle of the combiner to the horizontal is 75 °. The fluorescent display tube 21 has a driver circuit built-in on a semiconductor chip and has a phosphor formed in a dot matrix. The number of dots is 128 × 32 and the size is 44 × 11 mm
It is. The light emitted from the fluorescent display tube 21 enters the combiner 20 at θ _i = 20 ° and is diffracted at θ _d = 20 °. The distance r _d from the combiner 20 to the display image 10 is about 200 mm, and the distance between the fluorescent display tube 21 and the combiner 20
The distance r _i is 80 mm. That is, rd is r
It is about 2.5 times _i . The diffraction wavelength of the hologram is about 53
At 0 nm, the diffraction efficiency is 95%.

By using the HUD of this embodiment, a small, light and thin holographic display device free from blur due to chromatic aberration can be realized even when a fluorescent display tube having a wide half width is used.

[0027]

According to the present invention, by using a fluorescent display tube as an information display source, there is provided a holographic display device which does not cause a large decrease in luminance even when the reproduction wavelength of the hologram fluctuates due to manufacturing variations or temperature fluctuations. can get. Moreover,
Even when a fluorescent display tube having a wide half-value width is used, the angle of incidence of light including information on the hologram is substantially equal to the angle of diffraction diffracted by the hologram, and the distance between the displayed virtual image and the hologram is information. By making the distance less than three times the distance between the display source and the hologram, a holographic display device free from blur due to chromatic aberration can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a holographic display device of the present invention.

FIG. 2 is a schematic sectional view showing another example of the holographic display device of the present invention.

FIG. 3 is a conceptual diagram showing an example of a HUD.

[Explanation of symbols]

 1: observer 3: light containing information 10: display image 20: combiner 21: fluorescent display tube 22: main body 23: legs 24: holding unit 25: circuit unit

Claims (2)

[Claims] 1. A holo comprising at least an information display source for generating information to be displayed as light, and a combiner having a hologram disposed on a base material and diffracting the light toward an observer and displaying it as a virtual image. In the graphic display device, the information display source includes a fluorescent display tube, an angle at which the light is incident on the hologram and an angle at which the light is diffracted by the hologram are substantially equal, and a distance between the virtual image and the hologram is the information. A holographic display device, wherein the distance is less than three times the distance between the display source and the hologram. 2. The apparatus according to claim 1, wherein the combiner is rotatably supported by the main body in the vicinity of a lower side thereof, the combiner and the main body are integrated, and the information display source is provided in the main body. The holographic display device according to claim 1.