JPH08169257A - Head-up display device - Google Patents

Abstract

PURPOSE: To effectively reduce flare incident from the outside of a vehicle by using a hologram as a combiner for diffracting light toward an observer in a vehicle with low diffraction efficiency for S-polarized light and high diffraction efficiency for P-polarized light. CONSTITUTION: Regarding a head-up display using a hologram as a combiner 2 built into the windshield or the like of a vehicle, a display source is provided at the lower position of a windshield 47. This display source emits information to be indicated as light 26 after the passage thereof through a display body 5, using light reaching from a light source 46 via a lens system 44. Then, the light 26 is irradiated to the combiner 2 and diffracted for recognition by a driver. In this case, a hologram with high diffraction efficiency for P-polarized light and low diffraction efficiency for S-polarized light is used, or the hologram is a combined body made of a transmissive hologram 10 diffracting only the S-polarized light without any diffraction of the P-polarized light, and a reflective hologram 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a head-up display system (hereinafter referred to as HUD) device, and more particularly to a HUD in which flare light from outside the vehicle is reduced.

[0002]

2. Description of the Related Art HUD has recently been used as a method of displaying information to a driver in an automobile or the like.
This is because the optical information projected from the information projection means such as a liquid crystal display device is projected on a combiner composed of a hologram or a half mirror incorporated in the windshield of an automobile, etc., and the driver almost moves the viewpoint from the driving state. The information can be read without any need.

In particular, a hologram using a hologram as a combiner can have a lens function and the like as well as a function of diffracting optical information toward the driver.
It is possible to diffract optical information in the direction of the driver's visual field, or to form an image at any position without using any other optical system such as a lens, and without impairing the foreground brightness. It is effective as a combiner for HUD because it has a feature that a high-intensity display image can be obtained.

FIG. 3 is a conceptual diagram showing an example of a conventional HUD. The light emitted from the light source 46 and passing through the transmissive liquid crystal display element 45 via the lens system 44 and containing the information to be displayed is the hologram 42 provided on the windshield 47 of the vehicle body.
The light is radiated, is diffracted, and is visually recognized by the driver at the observation position 41.

The lens system 44 has a function as a collimator, and the function is the hologram 4.
2 can be provided, and the display image of the speed display 48 and the warning display 49 can be formed in the distance.

Further, since the hologram 42 has a wavelength selection function, an image of a desired color can be displayed. Usually, the color is often single, but multi-color display by multiple exposure is also possible, and the amount and quality of display information can be improved. For example,
By setting the speed display 48 in green and the warning display 49 in red, it becomes possible to more accurately transmit information to the driver.

As such a holographic combiner, a reflection type hologram is usually used. In the production of the reflection hologram, one side of the photosensitive material surface of the hologram is irradiated with reference light and the other side is irradiated with object light. Then, a diffraction grating is manufactured.

Inside the hologram photosensitive material, these two
The two laser beams interfere with each other to produce light and dark interference fringes, which are recorded as a diffraction grating based on the difference in physical properties such as the refractive index or density of the photosensitive material. In this type of reflection hologram, when the incident angle of light and the reflection diffraction angle are different, the diffraction grating surface is inclined with respect to the hologram surface and is not parallel to the surface.

FIG. 4 is a conceptual cross-sectional view showing a hologram enclosed in the windshield, and 42 is a reflection hologram which functions as a combiner. Inside the hologram 42, a diffraction grating having an inclination with respect to the surface as shown in the figure is formed. The hologram 22 is provided on the inside glass 23 of the windshield, and is made of polyvinyl butyral (PV
Together with the intermediate film 25 made of B), it is enclosed inside the vehicle outside glass 24 to form a safety laminated glass. The interface 21 between the intermediate film 25 and the hologram 42 is a protective layer that prevents the hologram characteristics from being affected by the plasticizer contained in the intermediate film.

Light 2 containing information emitted from the information display source
6 is incident on the glass 23 on the inside of the vehicle at an angle of θ 1, and is refracted due to the difference in refractive index between air and glass, and θ
The angle is 1 '. The light entering the glass is reflected and diffracted by the hologram 42 toward the driver. Since the diffraction grating inside the hologram is tilted with respect to the surface, the glass internal angle of the diffracted light becomes θ2 ′ and is refracted at the glass surface and emitted at an angle θ2 inside the vehicle and visually recognized as light 27 by an observer such as a driver. To be done. Generally, θ1 and θ2 are different in order to prevent a double image due to reflected light on the glass surface outside the vehicle, and in a passenger car, θ1 <θ2 due to the positional relationship between the light source, the combiner and the driver.

[0011]

[Problems to be Solved by the Invention] Such hologram HU
When the external light 28 indicated by the dotted line enters a vehicle equipped with D, the external light reaches the surface of the glass on the inside of the vehicle at θ1 ′ and enters θ again when the incident angle θin is a certain angle.
At 1 ', it reflects toward the inside of the glass. Since this angle is the same as the angle of the information-containing light 26 inside the glass, the external light is reflected and diffracted by the hologram 42 and exits from the vehicle interior glass surface at an angle θ2. And reach an observer such as a driver.
The noise light due to this external light is called flare light.

When such flare light is generated, it may appear as bright unevenness or as a spot-like bright spot depending on the incident angle of light from the outside of the vehicle, which may reduce the visibility of the display image of the HUD. Bring Especially, when sunlight is observed as flare light, the brightness is high, which may cause dazzling, which is a safety problem. In addition, weak lights such as street lights, which are not noticeable in the daytime due to the dark surroundings at night, were observed as flare lights, which was very annoying when driving. Since this flare light is observed at an angle different from that when an external light source such as the sun or a street light is viewed linearly, one light source can be seen by a plurality of eyes, which is very annoying.

[0013]

The present invention has been made to solve the above problems, and provides a HUD having the following features.

An information display source that includes at least a light source and a display body that displays information to be displayed and that generates information to be displayed as light, and a windshield of the vehicle that is provided with an observer in the vehicle. In a head-up display including at least a combiner made of a hologram that diffracts toward, a hologram has a high diffraction efficiency for P-polarized light and a low diffraction efficiency for S-polarized light. , A P-polarized light is not diffracted and only a S-polarized light is diffracted to form a hologram combiner, and the incident angle θ1 from the display light source to the combiner is a Brewster angle. HUD is provided.

[0015]

The external light, which causes flare light, after passing through the hologram combiner, is partially reflected inside the glass at the boundary between the inside of the windshield and the inside of the vehicle, and the rest is transmitted outside the glass. At this time, the reflected light to the inside that causes flare is light having a large amount of S-polarized component, and the transmitted light to the outside is light having a large amount of P-polarized component. Therefore, when the HUD according to the present invention is used, the hologram combiner has polarization characteristics (high efficiency for P-polarized light and low efficiency for S-polarized light), so that the S-polarized light component causing flare light is generated. It is possible to reduce the amount of internal reflected light, which is often diffracted into the vehicle interior by the hologram combiner, and to effectively reduce flare light.

Further, by providing a transmission hologram having a polarization characteristic for diffracting only S-polarized light at a predetermined angle on the outside or inside of a normal reflection-type hologram having no polarization, The flare light can be effectively reduced. That is, the light that passes through the transmission hologram without being diffracted becomes P-polarized light, and there is almost no reflection inside the glass at the boundary between the inside of the windshield and the inside of the vehicle.

Further, the flare light can be completely removed by setting the incident angle θ1 from the display light source to the hologram combiner to the Brewster angle.

[0018]

Embodiments of the present invention 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, and FIG. 2 is an enlarged view thereof. An information display source is provided below the windshield 47. This information display source is a transmission type color liquid crystal display device in which light emitted from a light source 46 using a hot cathode tube is passed through a lens system 44 which is a collimator. The light 26 emits the information to be displayed which has passed through the display body 45. The light 26 is applied to the combiner 2 formed of a hologram provided on the windshield 47 of the vehicle body, diffracted, and visually recognized by the driver at the observation position 41.

The lens system 44 has a function as a collimator, and this function can be provided in the hologram, and the display images of the speed display 48 and the warning display 49 can be formed at a distance. It will be possible.

If desired, another hologram or lens for aberration correction may be provided between the display body 45 and the combiner 2.

Further, since the hologram has a wavelength selection function, an image of a desired color can be displayed, and further, multi-exposure and stacking of a plurality of holograms enable multi-color display, and the quantity and quality of display information. Can be improved. In this embodiment, 540 nm and 6 corresponding to the emission peak wavelength of the hot cathode tube are used.
Using a multiple exposure hologram that diffracts 12 nm light,
The speed display 48 is displayed in green, and the warning display 49 is displayed in amber (orange) with a mixture of green and red. as a result,
It becomes possible to transmit information to the driver more accurately.

In the present embodiment, the inclination θw of the windshield is 30.
And the reflection hologram 21 exposed so that the incident angle θ1 of the light 26 containing information on the hologram 2 is Brewster's angle (56.3 °) and the outgoing angle θ2 is 65 °.
Incident angle θr = 33.7 in glass that causes flare
Randomly polarized incident light 28 incident at ° (solid line in the drawing)
On the other hand, P-polarized light 1 (dashed-dotted line in the drawing) is transmitted as it is without being diffracted, and S-polarized light 9 (dashed line in the drawing) is θs = in the glass.
The exposed transmission hologram 10 was encapsulated in glass to diffract at 70.6 °. Here, the transmissive hologram 10 is enclosed more on the outside of the vehicle than the reflective hologram 21. In this way, it was possible to prevent light outside the vehicle from entering the vehicle as flare light. Further, the transmission hologram may be enclosed inside the vehicle rather than the reflection hologram.

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. Although such a hologram is desirable in that a volume / phase type hologram such as a Lippmann type can obtain high diffraction efficiency, a hologram called an embossed type or a rainbow type can be widely used. Further, as the hologram material, a photopolymer such as polyvinylcarbazole or acrylic is used.
Various light-sensitive materials such as dichromated gelatin, photoresists and silver salts can be used.

In this embodiment, the reflection hologram 22 is 150 mm wide and 200 mm long and has a thickness of 20 μm.
Using a photosensitive material made of acrylic photopolymer of
A volume phase hologram was used. Further, as the transmissive hologram 10, a photosensitive material made of an acrylic photopolymer having a size of 150 mm in width and 200 mm in length and a thickness of 17.7 μm is used, and n = 0. 04, λ = 540 nm, θr = 33.7.
A volume phase type hologram produced under the conditions of θ and θs = 70.6 ° was used.

Such a hologram is provided on the windshield, and for example, the surface of the windshield (the outer surface of the vehicle).
It may be provided on the inner surface of the vehicle or on the inside surface of the vehicle, but in view of protection of the hologram in particular, it is preferably enclosed and used in the windshield which is a laminated glass as in the present embodiment.

The information display source in the present invention has a function of displaying light by emitting light, and a hot cathode tube (HC) is attached to a display body composed of a so-called light receiving display element such as a liquid crystal display element.
T), a cold cathode tube, a fluorescent display tube (VF), a halogen lamp, an LED, or the like for irradiating light emitted from a light source, or may have these functions together.

When the combiner of the present invention is used for color display, the liquid crystal display element includes a color nematic liquid crystal display element including a transmission type twist nematic liquid crystal element and a super twist nematic liquid crystal display element. It 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 information display source, and when the lights of a plurality of colors are simultaneously displayed, the display images are displayed in an overlapping manner.
On the contrary, in order to prevent the overlapping of the 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.

Alternatively, instead of using the light receiving type display element, the light source itself may be patterned and arranged to generate specific information as light. In the case where the light source is used together with the light receiving display element, an appropriate light collimating means such as a lens system or a curved reflecting mirror, and a suitable light guiding means such as a light guide plate are provided between the light receiving display element and the light source. You may arrange. Further, if necessary, an optical polarization means or KNO is provided in the optical path until the light is projected on the hologram.
Non-linear optical elements such as ₃ may be arranged.

Further, when the HUD of the present invention is displayed in color, 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, the display color is changed. Thus, it is possible to obtain a three-dimensional image in which the display image is observed at different distances.

Next, a second embodiment of the present invention will be described with reference to FIG.
Will be explained. As the hologram combiner 5, a reflection hologram having low diffraction efficiency for S-polarized light and high diffraction efficiency for P-polarized light was used. At this time, as the light 26 from the display light source, the reduction in the brightness of the display image diffracted by using the P-polarized light was prevented. In this method, randomly polarized light 28 (one-dot chain line in the drawing) that causes flare light is divided into almost P-polarized transmitted light 6 and almost S-polarized reflected light 4 at the interface between the inner windshield and the vehicle interior. Since the reflection hologram 5 hardly diffracts S-polarized light, the diffracted light 3 (dotted line in the drawing) is very weak and flare light can be effectively reduced.

[0032]

The reflected light to the inside that causes flare is light having a large amount of S-polarized component, and the transmitted light to the outside is light having a large amount of P-polarized component. Therefore, when the HUD according to the present invention is used, the hologram combiner is provided with polarization characteristics (high efficiency for P-polarized light and low efficiency for S-polarized light), so that the S-polarized light component causing flare light is generated. It is possible to reduce the amount of reflected light that is reflected into the interior of the vehicle, which is often diffracted into the vehicle by the hologram combiner, and it is possible to effectively reduce flare light. Further, by providing a transmission hologram having a polarization characteristic such that only S-polarized light is diffracted at a predetermined angle on the outside or inside of a normal reflection-type hologram having no polarization characteristics, flare light is generated. It can be effectively reduced. That is, the light that passes through the transmission hologram without being diffracted becomes P-polarized light, and there is almost no reflection inside the glass at the boundary between the inside of the windshield and the inside of the vehicle. Further, the incident angle θ from the display light source to the hologram combiner
By setting 1 to Brewster's angle, flare light can be completely removed.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing an example of a HUD in the present invention.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is a conceptual diagram showing a conventional HUD.

FIG. 4 is a conceptual cross-sectional view for explaining a hologram and a flare light generation mechanism enclosed in a windshield.

FIG. 5 is an enlarged view of an essential part showing an example of a HUD in the present invention.

[Explanation of Codes] 2: Hologram combiner 10: Transmission hologram 21: Reflection hologram 41: Driver's observation position 43: Light containing information 44: Lens system 45: Display element 46: Light source 48: Speed display 49: Warning display

Claims (4)

[Claims] 1. An information display source that includes at least a light source and a display that displays information to be displayed, and an information display source that generates the information to be displayed as light, and the windshield of the vehicle. In a head-up display including at least a combiner made of a hologram that diffracts toward an observer, the hologram has low diffraction efficiency for S-polarized light and high diffraction efficiency for P-polarized light. . 2. An information display source that includes at least a light source and a display body that displays information to be displayed, and an information display source that generates information to be displayed as light, and a windshield of a vehicle, the light being provided inside the vehicle. In a head-up display at least including a combiner made of a hologram that diffracts toward an observer, the hologram is configured by a combination of a transmissive hologram that diffracts P-polarized light and diffracts only S-polarized light and a reflective hologram. A head-up display system characterized in that 3. The transmission hologram is n · d / [λ
(Cos θr · cos θs)] = m + 1/2, n · d ·
cos (θs−θr) / [λ (cosθr · cosθ
3. The head-up display system according to claim 2, wherein the head-up display system comprises a hologram satisfying s)] = m. Here, n is the refractive index modulation of the hologram material, d is the thickness of the hologram material, λ is the recording / reproducing wavelength, θr is the incident angle inside the glass, θs is the diffraction angle inside the glass, and m is a positive integer. . 4. The head-up display system according to claim 1, wherein an incident angle θ1 of light entering the hologram combiner from the information display source is equal to Brewster's angle.