JPH09222583A - Holographic display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the decreases in the transmissivity and contrast of a liquid crystal display element due to a temperature rise and to increase the display luminance and contrast by providing a dimming element having a function for cutting off or attenuating unnecessary light. SOLUTION: A light emitting display means arranged below windshield glass 7 emits the light from a light source 6, using a halogen lamp, to a hologram combiner 2 by passing the light through a lens system 4 as a collimator, and reflecting and diffracting light 3, which is passed through a light shield plate 21 with a rectangular opening, a wavelength selective filter (heat-ray absorbing filter) 22, a diffusion plate 23, and a display body 5 consisting of a transmission type color liquid crystal display element in order and contains information to be displayed, by an aberration compensating hologram 24. This light 3 irradiates the hologram combiner 2 mounted on the windshield glass of a vehicle body and is diffracted and viewed by a driver at an observation position 1. Further, the light shield plate 21, heat-ray absorbing filter 22, diffusion plate 23, and liquid crystal display element 5 are cooled by an air cooling fan.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a holographic display device, and more particularly to a holographic display device equipped with a windshield of a vehicle such as a vehicle, an aircraft or a ship and a hologram laminate in the vehicle, which is required for an observer in the vehicle. It relates to a holographic display device for projecting various information.

[0002]

2. Description of the Related Art Recent advances in hologram materials and laser technology have increased the number of products using holograms.
For example, a laser scanner for a bar code reader, a diffraction grating for a pickup used for recording and reading an information recording medium using a laser beam such as a compact disc or a magneto-optical disc, and a light including information are diffracted to give information to an observer. Holograms are used as optical elements in display holographic display devices and the like. In addition, forgery prevention marks for ID cards and credit cards, decoration holograms, hologram calendars, and the like use holograms on which images are recorded.

The following are specific examples. As a method of displaying 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. This means that the optical information projected from the information projection means such as a liquid crystal display device,
The image is projected on a combiner including a hologram and a half mirror incorporated in a windshield of an automobile or the like, so that the driver can read information from the driving state without moving the viewpoint.

In particular, a hologram using a hologram as a combiner can have a function of diffracting optical information toward the driver as well as a lens function, so that the optical information is diffracted in the direction of the driver's visual field. , Or
In addition, it is possible to form an image at any position without using an optical system such as a lens. Also, since the diffraction spectrum has a narrow half-value width, a high-luminance display image can be obtained without impairing the foreground luminance. The feature is that it can be obtained, and it is effective as a combiner of a display device.

FIG. 5 is a conceptual diagram showing an example of a HUD which is an example of a conventional automobile holographic display device. The light 3 emitted from the light source 6 and passing through the transmissive liquid crystal display element 5 via the lens system 4 and containing information to be displayed is applied to the hologram 2 provided on the windshield 7 of the vehicle body,
It is diffracted and visually recognized by the driver at the observation position 1. The lens system 4 has a function as a collimator.

If the hologram 2 has a magnification,
It is also possible to form the display images of the speed display 8 and the warning display 9 in a distant place. In addition to the hologram 2, a wavelength selection filter or a hologram for aberration correction may be used if necessary. Further, since the hologram 2 has a wavelength selection function, an image of a desired color can be displayed.
Usually, the color is often a single color, but multi-color display using a hologram subjected to multiple exposure is also possible, and the amount and quality of display information can be improved. 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.

[0007]

The display contents of the HUD are required to be various display contents in addition to the conventional speed display and warning display. For example, with the recent development of social infrastructure, various types of information regarding transportation have begun to be provided. For example, in a road traffic information communication system (VICS), beacons provided at various places on the road, road conditions such as traffic jams and accidents, and surrounding parking lot information can be used by FM multiplex broadcasting. Also, route guidance displays from navigation devices, which have become very popular in recent years, and advanced safety vehicles (ASV)
The HUD is expected as a medium for displaying information from various safety devices such as a drowsiness sensor, an obstacle sensor, an inter-vehicle distance sensor, and a road surface condition sensor which are considered in the above. Due to such a demand, a dot matrix type color liquid crystal display device capable of freely changing display contents is used as a display element of the HUD instead of a conventional segment type liquid crystal display device or a fixed pattern display element such as a fluorescent display tube. Tend to

On the other hand, such a HUD is used under various environments, and the display is read even when the foreground has a high brightness such as when traveling on a snowy road or traveling in the direction of the sun. It needs to be taken. Therefore, it is desirable that the display brightness of the HUD is as high as possible. However, T
At present, the dot matrix type color liquid crystal display device represented by FT has a very low light transmittance of about 4%. Therefore, it is desired to increase the brightness of the backlight of the liquid crystal display device.

When a halogen lamp, a hot cathode tube, or the like is used as a backlight with high brightness, the temperature of the liquid crystal display element rises due to the heat radiated from the halogen lamp or the hot cathode tube. as a result,
The transmittance and contrast of the liquid crystal display element are reduced, and the HUD
However, there is a problem in that the displayed image has a low brightness and a low contrast and is poor in visibility.

[0010]

The present invention has been made to solve the above-mentioned problems, and should be provided with at least a light source and a display body composed of a liquid crystal display device for displaying information to be displayed. In a holographic display device comprising at least a light emitting display means for generating information as light and an optical element made of a hologram for diffracting the light toward an observer, the light emitting display means includes a light source and a display body. The present invention provides a holographic display device, which is provided with a light control element having a function of blocking or attenuating light unnecessary for display.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The present invention is a display device in which light including information emitted from a light emitting display unit is diffracted toward an observer by a combiner made of a hologram so that the observer can visually recognize the displayed information.

The above light emitting display means is provided with a light control element having a function of blocking or attenuating light unnecessary for display. Therefore, it is possible to suppress the temperature rise of the liquid crystal display element. Further, the temperature of the liquid crystal display element can be further kept low by adding a cooling device for cooling the display body composed of the liquid crystal display element.

A first example of the light control element of the present invention is a light shielding plate having an opening. This is to prevent unnecessary light from being irradiated to the entire area of the liquid crystal display element other than the use area related to display, and it is possible to prevent the temperature rise of the display element.

A second example is a wavelength selection filter. This uses a filter that selectively cuts light in a wavelength range unnecessary for display, and can prevent a temperature rise of the liquid crystal display element due to absorption of light in an unnecessary wavelength range. Therefore, this is also an effective method for the use area related to display on the entire surface of the liquid crystal display element.
For example, since only visible light is necessary for display, it is effective to use a filter that absorbs or reflects infrared rays. Further, for example, when the display color is in a limited wavelength range from green to red, it is also effective to use a long-pass filter that absorbs light in the blue region and transmits light having a wavelength of green or more. .

Further, when a slight temperature rise cannot be avoided even with the use of the above light control device, it is effective to provide a cooling device such as an air cooling fan for cooling the display body. .

The hologram usually has an area of about several 10 mm to several 100 mm square and a thickness of several μm to several 10 μm. Such a hologram is desirable 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. Further, as the hologram material, a photopolymer such as polyvinylcarbazole or acrylic is used.
Various photosensitive materials such as dichromated gelatin, photo resist, and silver salt can be used.

The luminescent display means of the holographic display device according to the present invention has a function of emitting light to display, and a halogen lamp, a hot cathode tube ( HCT), cold cathode tubes, fluorescent display tubes (VF), light emitting diodes, semiconductor lasers, and the like, which emit light emitted from a light source, and may also have these functions.

When the combiner according to the present invention is used for color display, the liquid crystal display element includes a color filter and a transmission type twisted nematic type liquid crystal element, a super twisted nematic type liquid crystal display element, or the like. And the like can be preferably used, and light emitted from one light source can be irradiated as light of a desired color.

In this way, the lights of a plurality of colors can be emitted from the same light emitting display means, and when the lights of a plurality of colors are simultaneously displayed, the display images are displayed in an overlapping manner, and conversely, In order to prevent overlapping of displayed images, a combination of a color filter and a light source or a color liquid crystal display element may be controlled as necessary so that light of a plurality of colors is not simultaneously irradiated.

In the case where the light source is also used for the light receiving display element, an appropriate light collimating means such as a lens system or a curved reflecting mirror, a light guide plate or a light diffusing means is provided between the light receiving display element and the light source. Appropriate light guide means such as may be arranged. further,
If necessary, a light polarizing means or a non-linear optical element such as KNO ₃ may be arranged in the optical path before the light is projected on the hologram.

Further, when the holographic display device of the present invention is used for color display, if the distance from the combiner to the display image is the same for each color, color display can be performed in the same plane, and if the color is changed, It is possible to obtain a three-dimensional image in which the display image is viewed at different distances depending on the display color.

Here, the information to be displayed when the holographic display device of the present invention is applied to a vehicle is appropriately selected according to its display application, and includes a vehicle speedometer, a tachometer, and a shift lever. Examples include displays, various warning lamps, navigation information, information on auxiliary devices such as air conditioners and audio devices, or displays on azimuth meters and car body inclinometers. Further, it is of course possible to display information from outside the vehicle such as road information and parking lot availability information. Also, for aircraft and ships, position / azimuth information such as latitude, longitude, altitude, and heading, weather information, radar obstacle information,
Various information related to vehicle operation and work such as information on fish finder can be considered. The observer is mainly a driver of a vehicle such as a vehicle, but the passenger seat and other passengers,
All of these can be included.

Further, the description so far has been focused on an example in which the present invention is applied to a HUD for an automobile, but the present invention is not limited to this. For example, a high mount stop that arranges a hologram on the rear glass and diffracts braking information toward an observer such as a driver of a rear vehicle by using a hologram to emit light from a light emitting display means that emits light in synchronization with the braking operation of the driver. The present invention can be applied to a lamp. Further, in addition to vehicles, the present invention can be used for partitioning of buildings and the like, and holographic display devices that add a decorative effect to window glass in stores, and can be widely applied to other display devices using holograms. Is.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the holographic display device of the present invention is applied to a HUD for an automobile will be described below with reference to the drawings. FIG. 1 is a conceptual diagram showing an example of the HUD of the present invention. A light emitting display means is provided below the windshield 7, and the light emitting display means has a light shielding plate 21 having a rectangular opening, through which light emitted from a light source 6 using a halogen lamp is passed through a lens system 4 which is a collimator. The aberration-corrected hologram 2 transmits the light 3 containing information to be displayed, which has passed through the display 5 including the wavelength selection filter (heat-ray absorption filter) 22, the diffusion plate 23, and the transmissive color liquid crystal display element.
The light is reflected and diffracted by 4 and emitted toward the hologram combiner 2. This light 3 is applied to the hologram combiner 2 provided on the windshield 7 of the vehicle body,
It is diffracted and is visually recognized by the driver at the observation position 1.

The hologram 2 has a magnification, and the display image 10 of the route guidance display is formed at a distance. In addition, since the hologram has a wavelength selection function, it is possible to display an image of a desired color, and multiple exposure or stacking of multiple holograms enables multicolor display, improving the quantity and quality of display information. it can. In this embodiment, green (545 nm) and red (61 nm)
A multiple exposure hologram that diffracts light of 2 nm) is used. It was indicated as green and red or amber (orange) in which they were appropriately mixed. As a result, it is possible to transmit information to the driver more accurately.

FIG. 2 is a conceptual diagram of a portion of the light emitting display means. The light emitted from the halogen lamp 6 passes through the lens system 4 which is a collimator and is substantially collimated. The substantially collimated light is shielded by the light-shielding plate 21 having the rectangular opening 21a so that light in the peripheral portion which is not necessary for display is shielded and passes through only the rectangular opening 21a. Next, after the light in the infrared region is absorbed by the heat ray absorption filter 22 used as a wavelength selection filter, it is diffused by the diffusion plate 23 and transmitted through the transmissive color liquid crystal display element 5 to become the light 3 containing information to be displayed. The opening 21a of the light-shielding plate is the use area 5 used for displaying the liquid crystal display element.
The size is made necessary and sufficient for irradiating a. The light 3 containing information that has passed through the liquid crystal display element 5 is reflected and diffracted by the aberration correction hologram 24 and travels toward the hologram combiner 2. Even if the above means for blocking unnecessary light is used, the temperature rise of the liquid crystal display element cannot be completely prevented. Therefore, the light-shielding plate 21, the heat ray absorbing filter 22, the diffusion plate 23, and the liquid crystal display element 5 are cooled by the air-cooling fan 25.

FIG. 3 and FIG. 4 show how the luminance of the display image changes with time when these unnecessary light shielding means are provided. FIG. 3 shows the results of measuring the difference in the temporal change of the display image brightness after the halogen lamp 6 is turned on, depending on the presence or absence of the heat ray absorption filter 22. The measurement was performed without using the light shielding plate 21 of FIG. The air cooling fan 25 is used. As can be seen from FIG. 3, the heat ray absorption filter 22
When is not used, light is not attenuated by the filter, so immediately after lighting it is about 4 times more than when using the filter.
0% brightness was high. However, the brightness decreased due to the rapid temperature rise, and the relationship was reversed. By cutting infrared rays using the heat ray absorption filter 22, the display luminance in the stable state could be doubled even though the initial luminance was slightly low.

FIG. 4 shows the results of measuring the difference in the temporal change of the display image brightness after the halogen lamp 6 is turned on, depending on the presence or absence of the light shielding plate 21. The heat ray absorbing filter 22 is used during this measurement. Further, the air cooling fan 25 is also used. As can be seen from FIG. 4, the use of the light shield prevents the brightness from lowering further, and the brightness at the time of stability is further reduced to about 2
I was able to double it. The light shielding plate used in this embodiment is 2
A rectangular opening is formed in an aluminum plate having a thickness of mm. The surface temperature of the heat ray absorption filter 22 was examined in order to examine the effect of the light shielding plate for preventing the temperature rise. Since the temperature of the transmissive liquid crystal display device 5 cannot be directly measured, the surface temperature of the heat ray absorption filter 22 was used as a substitute. Stable display brightness 10
The temperature of the heat ray absorbing filter 22 after the minute was 59 ° C. without the light shielding plate and 37 ° C. with the light shielding plate, and the effect of the light shielding plate was confirmed. The heat ray absorbing filter also radiates the absorbed heat in the form of radiation and is in an equilibrium state at a certain temperature. Therefore, naturally, when the temperature becomes high, it has an adverse effect as a heating element. The effect of the light shielding plate is that the transmissive liquid crystal display device 5
Not only does this also contribute to preventing the temperature rise of the heat ray absorption filter 22.

Although not shown in FIG. 2, another wavelength selection filter may be inserted between the light shield plate 21 and the heat ray absorption filter 22. For example, the display brightness is increased by about 30% when the heat ray reflection filter is used. Further, since the display colors of the HUD of this embodiment are green and red, light having a wavelength shorter than that of green is unnecessary. Then, when a long wavelength transmission filter was used, the display brightness increased by about 10%. The long-wavelength transmission filter used in this example is a colored glass filter called Y50 (transmittance of 50% at 500 nm). Further, when the display wavelength is limited, it is effective to use an interference filter.

The above description is merely an example, and the types and forms of the light shielding plate and the wavelength selection filter are not limited to the above. It is also effective to manufacture the diffusion plate 23 shown in FIG. 2 with a wavelength selection filter as one embodiment of the present invention. For example, the surface of the heat ray absorbing filter or the colored glass filter may be the rubbing surface, or the non-coated surface side of the heat ray reflecting filter may be the rubbing surface.

By providing the light control element having the function of blocking or attenuating the unnecessary light described above, the temperature rise of the liquid crystal display device can be suppressed to the minimum. as a result,
It has been possible to realize a holographic display device having a high display brightness and a high contrast, since it is possible to prevent a decrease in transmittance and contrast of a liquid crystal display element due to a temperature rise. It is preferable that the bias adjustment of the liquid crystal is not optimized at room temperature, but the brightness and contrast are optimized in a state where the temperature rises and stabilizes after the lamp is turned on.

The hologram combiner of this embodiment has a size of 150 mm wide × 150 mm long, and the aberration correction hologram has a size of 150 mm wide × 130 mm long. Both holograms had a thickness of 20 μm, and a photosensitive material made of an acrylic photopolymer was used to form a volume phase reflection hologram.

Such a hologram combiner is provided on the windshield, and may be provided on the surface of the windshield (the outer surface of the vehicle) or the inner surface of the vehicle, for example, in view of the protection of the hologram. As in the example, it is preferable to use it by enclosing it inside the windshield which is a laminated glass. Further, it may be installed on the dashboard or the like instead of the windshield.

[0034]

Since the holographic display device according to the present invention is provided with the light control element having a function of blocking or attenuating unnecessary light, the temperature rise of the liquid crystal display device can be suppressed. As a result, it is possible to prevent a decrease in the transmittance and contrast of the liquid crystal display element due to a rise in temperature, and it is possible to realize a holographic display device having high display brightness and contrast.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing an example of a holographic display device of the present invention.

FIG. 2 is a conceptual sectional view showing the structure of a hologram laminate of the present invention.

FIG. 3 shows an example of use of the wavelength selection filter of the present invention,
Diagram showing the change over time of display brightness

FIG. 4 is a diagram showing an example of use of the light shielding plate of the present invention, which is a change in display luminance with time.

FIG. 5 is a conceptual diagram showing a conventional holographic display device.

[Explanation of symbols]

 1: Observation position of an observer in the vehicle 2: Holographic combiner 3: Light including information 4: Lens system 5: Transmissive liquid crystal display device 6: Halogen lamp 7: Windshield 8: Speed display 9: Warning display 10: Navigation display 21: Light shield 22: Wavelength selection filter 23: Diffuser 24: Aberration correction hologram 25: Air cooling fan

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location G02F 1/1335 530 G02F 1/1335 530

Claims (3)

[Claims] 1. A light emitting display means which includes at least a light source and a display body made of a liquid crystal display element for displaying information to be displayed and which generates information to be displayed as light, and diffracts the light toward an observer. In a holographic display device including at least an optical element formed of a hologram, the light emitting display means includes a light control element having a function of blocking or attenuating light unnecessary for display between a light source and a display body. A holographic display device characterized in that 2. The holographic display device according to claim 1, wherein the light control element includes at least one of a light shielding plate having an opening and a wavelength selection filter. 3. The holographic display device according to claim 1, further comprising a cooling device for cooling the display body including the liquid crystal display element.