JP2805945B2 - Display device for vehicles - Google Patents

Description

The present invention relates to a display device for a vehicle, and more particularly, to a display device using a hologram element disposed in a windshield as a combiner.

<< Conventional Technology >> As a conventional device of this type, for example, a device shown in FIG. 6 is known.

In the figure, a windshield 30 is formed by joining a pair of windshield glasses 30a, 30b with a PVC resin (polyvinyl butyral) 32 for lamination, and between the two windshield glasses 30a, 30b and in the passenger compartment side windshield glass. On the 30a side, a combiner hologram 31 is provided.

By the way, as is well known, the combiner hologram 31 is produced by recording interference fringes of a coherent laser beam incident on the hologram surface at a predetermined incident angle. When light having a wavelength λ ₀ (light having a central wavelength component of λ ₀ ) is incident at an incident angle θ ₀ , the light is diffracted at a diffraction angle φ.

Therefore, as shown in the figure, when the display light 37 of the main wavelength λ ₀ is incident on the windshield 30 at the incident angle θ ₀ from the image display 38 installed near the driver's seat in the vehicle cabin, the light enters the windshield 30. The light is diffracted at the diffraction angle φ by the provided hologram 31 for the combiner, and the diffracted light 34 can reach the eyes 10 of the driver.

<< Problems to be Solved by the Invention >> However, in the conventional device as described above, the display light 37 of the image display 38 mostly reaches the driver's eyes 10 as the diffracted light 34, but is used for a combiner. Since the hologram 31 uses a photopolymer as a photosensitive material for hologram recording, its diffraction efficiency is low (about 90%), and about 10% of the display light component of the display light 37 is the windshield glass 30b outside the vehicle.
Side, and the front shield glass 30b
Surface, reflected on the a surface of the windshield glass 30a,
There is a problem that the light is diffracted by the hologram 31 again, becomes the re-diffracted light 33, reaches the driver's eye 10, and the image on the image display 38 is duplicated by the two diffracted lights 34, 33.

Unnecessary reflected light 36 and 35 are also reflected on the display side a surface and the back surface b surface of the windshield 30, but since the reflection angle is equal to the incident angle θ ₀ , the diffraction characteristic of the hologram 31 is previously set to θ. _{If 0} ≠ φ, these reflected light components do not cause the driver's eyes 10 to be double-photographed (or triple-photographed).

In the example shown in FIG. 6, a photopolymer is used as the hologram photosensitive material.
DCG (dichromate gelatin) or the like can be used as a photosensitive material only to prevent double copying. However, those using DCG are inferior in durability and cannot be applied to a vehicle display device using a windshield.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a vehicle display device capable of preventing a double copy and obtaining a clear display image.

<< Means for Solving the Problems >> In order to solve the above-mentioned problems, the present invention provides an image display which is disposed in a vehicle interior and emits display light, and is disposed on the vehicle interior side in a windshield. When display light having a specific main growth component emitted from the image display device is incident, the display light is diffracted in the direction of the driver at a diffraction angle different from the incident angle and with high efficiency. A first display light for transmitting the display light of the specific main wavelength component, which has not been applied, to the outside of the windshield as the second display light.
And the second display light transmitted by the first hologram is incident at the same incident angle as the incident angle, and is diffracted at a same angle as the incident angle in directions other than the driver direction with high efficiency. And a second hologram for transmitting the display light, which has not been diffracted here, as third display light to the outside of the windshield vehicle, and wherein the incident angle is such that the third display light is transmitted by the windshield vehicle. The light is reflected by the outer interface and guided to the second hologram to become fourth display light, and the fourth display light is diffracted by the second hologram out of the windshield car at the same angle as the incident angle. In this invention, the display light from the image display device is diffracted in the direction of the driver with high efficiency, and the display light that has not been diffracted. The second display And a third hologram, which, when the second display light is incident, diffracts the light at an angle equal to the incident angle to a direction other than the driver direction with high efficiency when the second display light is incident and does not diffract the light. A second hologram that transmits light to the outside of the windshield vehicle is provided.

Therefore, most of the display light from the image display device is diffracted by the first hologram, and most of the second display light that is not diffracted by the first hologram is converted by the second hologram to directions other than the driver direction. Diffracted.

The display light not diffracted by the second hologram is transmitted to the outside of the windshield as the third display light, is reflected at the interface of the windshield with the outside of the windshield, and is again reflected by the fourth light.
Is incident on the second hologram as display light. Then, the fourth display light incident on the second hologram is efficiently directed to the windshield at the same angle as the angle of incidence and the fifth display light is directed to the outside of the vehicle.
Is diffracted as display light.

Therefore, even if the display light not diffracted by the second hologram is guided in the direction of the driver by repeating the diffraction and reflection thereafter, the display light is much more than the display light diffracted by the first hologram. Therefore, double copying can be extremely reduced without using a special hologram.

<< Description of Examples >> Hereinafter, the present invention will be described with reference to the drawings.

 FIG. 1 is a sectional view showing an embodiment of the present invention.

First, the configuration will be described. 1a is a vehicle-side windshield glass, 1b is an exterior windshield glass, and a PVB resin (polyvinyl butyral) 2 for lamination is interposed between both windshield glasses 1a and 1b. The windshield 1 is formed by the vehicle-side windshield glass 1a, the PVB resin 2 and the vehicle-side windshield glass 1b.

Also, between the windshield glasses 1a and 1b in which the PVB resin 2 is interposed, and the vehicle-side windshield glass 1a
The first hologram (combiner hologram) 3 on the side
And a second hologram (anti-reflection hologram) 4 is formed on the side of the windshield glass 1b outside the vehicle.

Here, the first hologram 3 for the combiner diffracts the incident light at a predetermined diffraction angle when light having a specific main wavelength is incident at a predetermined incident angle from the passenger compartment side. When the display light 5 having the main wavelength λ ₀ is incident on the windshield 1 from the device 38 at an incident angle θ ₀ , the display light 5 can be diffracted toward the driver's seat at a diffraction angle φ (where θ ₀ ≠ φ).

On the other hand, the second anti-reflection hologram 4 has the same diffraction center wavelength (dominant wavelength) as that of the first hologram 3 and the same incidence angle as the incident angle stored in the diffraction characteristics of the first hologram. When there is an angle, it is configured to be diffracted at the same diffraction angle as the incident angle. Therefore, when the incident light of the wavelength λ ₀ which is the same diffraction center wavelength as the first hologram 3 is incident at the incident angle θ ₀ , the incident light can be diffracted at the diffraction angle θ ₀ .

Note that the first hologram 3 and the second hologram 4
Has a diffraction efficiency of 90%, and 10% of the incident light component passes through each of the holograms 3 and 4.

The image display 38 emits display light 5 having a narrow-band wavelength component centered on the diffraction center wavelength λ ₀ diffracted by each of the holograms 3 and 4.

The above is the basic configuration of the present embodiment. Next, the operation thereof will be described.

First, when the narrow band display light 5 having the center wavelength λ ₀ from the image display 38 is incident on the windshield 1 at an incident angle θ ₀ ,
The display light 5 is diffracted at the diffraction angle φ by the first hologram 3 and reaches the driver's eyes 10 as diffraction light 9.

In this case, 90% of the incident light component of the display light 5 is diffracted by the first hologram 3, and further 94% of the component reaches the driver's eyes 10 through the a-plane (each window). The transmittance of the shield glasses 1a and 1b is 94%).

On the other hand, the incident light component transmitted through the first hologram 3 is
90% of the components are incident on the second hologram 4 at an incident angle θ.
_The light is diffracted at the same diffraction angle θ _{0 as 0} and becomes a diffracted light 7,
Since θ ₀ ≠ φ, the diffracted light 7 does not reach the driver's eyes 10.

In addition, the transmitted light component of the second hologram 4, which has conventionally caused double copying, is transmitted to the outside windshield glass.
The second hologram 4 is partially reflected by the b-side surface of 1b.
From the back side (incident angle θ ₀ ), becoming diffracted light 8 (diffraction angle θ ₀ ), partially transmitting through the second hologram 4, and further diffracted by the a surface of the vehicle-side windshield glass 1 a. The light is reflected, further diffracted by the first hologram 3 at a diffraction angle φ, and reaches the driver's eyes 10 as re-diffracted light 50.

By the way, in this case, each windshield glass 1a, 1
The refractive index of b is 1.5, the diffraction efficiency of each hologram 3,4 is 90%,
Assuming that the transmittance of the a-side and the b-side is 96% and ignoring the attenuation during the passage of light, the diffracted light 9 and the re-diffracted light reaching the driver's eyes 10
The ratio of 50 is as follows:

First, assuming that the intensity of the re-diffraction 50 is I, the intensity of the display light 5 is I, the transmission component on the a-plane is 0.96I (1) The transmission component on the first hologram 3 is 0.96 · 0.1 · I = 0.096 · I (2) The transmission component of the second hologram 4 is 0.096 · 0.1 · I = 0.0096 · I (3) The reflection component on the b-plane is 0.096 · 0.04 · I = 3.84 × 10 ⁻⁴ · I (4) The amount of light passing through the anti-reflection hologram 4 is 3.84 × 10 ^-4 · 10 ^-1 · I (5) The amount of reflection on the a-plane is 3.84 × 10 ^-5 · 0.04 · I = 1.536 × 10 ^-6 I (6) The diffracted component of the combiner hologram 3 is 1.536 × 10 ^-6 × 0.9 I = 1.3824 × 10 ^-6 I (7) Therefore, the intensity of the re-diffracted light 50 transmitted through the a-plane is 1.3824 × 10 ⁻⁶ × 0.94 · I = 1.299456 · I × 10 ⁻⁶ (8)

 On the other hand, the intensity of the diffracted light 9 is 0.96 · I × 0.9 × 0.94 = 0.812 · I (9)

From the above, the diffracted light 9 diffracted by the above hologram 3
And the intensity ratio of the re-diffracted light 50 that causes double copying is 1.298 / 0.821 × 10 ⁻⁶ (10).

By the way, in this case, the contrast (digibel difference) of the two diffracted lights, which is expressed by 10 times the common logarithmic value of the intensity ratio of the two diffracted lights, is about 60 dB.
The effect of 50 can be completely ignored, and double copying of the displayed image can be completely prevented.

In the above example, only the so-called first-order diffracted light 50 is taken up, but theoretically, second-order, third-order,... Diffracted light also exists. However, since these diffracted lights are weaker than the first-order diffracted light 50, their influence can be ignored.

Next, FIG. 2 is a cross-sectional view of an optical system showing a method of manufacturing the first hologram 3.

In the figure, 3A is unexposed hologram (more precisely, the volume hologram), the laser light component L ₁ having passed through the half mirror 17 from the laser 18 is reflected by the mirror 16, a spatial filter
The signal light 11 is formed via the signal light 15 and enters the unexposed hologram 3A as a plane light wave from an oblique direction.

On the other hand, the laser light component L ₂ reflected by the half mirror 17 of the laser beam emitted from the laser 18 is a reference beam 12 through a spatial filter 15 and the collimator lens 14, also obliquely to the unexposed hologram 3A It enters as a plane light wave from the direction.

In this case, the laser beams L ₁ and L ₂ incident on the unexposed hologram 3A are completely coherent waves, that is, continuous waves having a constant period and amplitude. Thus, a slightly slanted plate-like interference fringe 13 is obtained.

Here, the wavelengths of the laser light L ₁ and L ₂ and the signal light 11, the reference light
When the incident angle of 12 is appropriately set, at the time of reproduction, for example, only the incident light of a specific wavelength (for example, λ ₀ ) incident at the incident angle θ ₀ can be diffracted at the diffraction angle φ (where λ ₀ ≠ φ). One hologram 3 is obtained.

Next, FIG. 3 is a cross-sectional view of an optical system showing a method of manufacturing the second hologram 4 for antireflection.

In the figure, reference numeral 4A denotes an unexposed hologram (accurately, a volume hologram), which is arranged to be joined to the plane mirror 21.

Here, the laser beam L ₃ emitted from the laser 18 is a signal light 20 through a spatial filter 24, collimating lens 22, is irradiated on the unexposed hologram 4A. On the other hand, this irradiation light is reflected by the plane mirror 21 disposed on the back side of the hologram 4A, and becomes reflected light 23.

By the way, in this case, the incident angle of the signal light 20 to the unexposed hologram 4A and the reflected light 23 reflected by the plane mirror 21
Are equal to each other, the signal light 20 and the reflected light
The interference fringe 25 formed by 23 is parallel to the surface of hologram 4A as shown in FIG.

Therefore, during reproduction, for example, the light incident angle of the wavelength lambda ₀ theta ₀
In case of incident, so that the second hologram 4 for preventing reflection diffracted at a diffraction angle theta ₀ is obtained.

As described above, according to this embodiment, the configuration is superimposed on the first hologram for the combiner, and
And a second anti-reflection hologram that has the same diffraction light center wavelength as the hologram and is diffracted at the same diffraction angle as the incident angle is arranged. It is possible to prevent the reduction and to provide a fine display pattern.

Next, a second embodiment of the present invention will be described with reference to FIGS.

In this embodiment, a hologram for a combiner is double-exposed, and a hologram for preventing double copying is provided in the hologram for a combiner to prevent double copying.

In this case, first, the unexposed hologram is exposed with the same exposure system as that shown in FIG.
Double exposure may be performed with the same exposure system as that shown in the figure.

FIG. 4 schematically shows the interference fringes in the hologram 45 thus completed. The interference fringes 46 slant on the hologram surface and the interference fringes 47 parallel to the hologram surface.
Are simultaneously formed.

FIG. 5 shows a case where the holograms 45 obtained as described above are arranged on the vehicle interior side and the vehicle exterior side in the windshield 1.

By the way, the hologram 45 thus formed is also effective for a washout.

This will now be described with reference to FIG.
Extraneous light 41 that is incident on the display light 5 in the direction opposite to the emission direction of the display light 5
Is reflected only by the hologram 45 at the same wavelength λ _{0 as} the display light 5 to become reflected light 40, and the transmitted light 42 has almost no component at the wavelength λ ₀ . Therefore, even if the external light 41 irradiates the display 38, the washout hardly occurs.

In the second embodiment, as described above, the hologram for the combiner and the hologram for the anti-reflection are integrally provided.
The mounting and equipment are convenient and the number of parts is reduced.
This has the effect of reducing the total cost.

Also, in this type of apparatus, the adhesion of each windshield glass constituting the windshield is a problem, but in the second embodiment, only one hologram needs to be accurately positioned and disposed. This has the effect of simplifying the process.

<< Effects of the Invention >> As described above, according to the present invention, when display light having a specific main wavelength component is incident from an image display disposed in a vehicle inside a windshield and disposed in a vehicle. A first hologram for diffracting the display light toward the driver at a diffraction angle different from the incident angle thereof, and a light having the same wavelength as the main wavelength of the display light, which is also disposed outside the vehicle in the windshield. A second hologram that diffracts the incident light at the same angle as the incident angle when the light is incident at the same angle as the angle is provided, so that double copying is prevented and a clear display image can be obtained for a vehicle. A display device can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a first embodiment to which the present invention is applied, FIG. 2 is a sectional view of an optical system showing a method of manufacturing a first combiner, and FIG. 3 is a method of manufacturing a second combiner. FIG. 4 is a cross-sectional view schematically showing an interference fringe of a combiner used in the second embodiment, and FIG. 5 is a cross-sectional view showing a case where windout is prevented in the second embodiment. FIG. 6 is a sectional view of a conventional image display device. DESCRIPTION OF SYMBOLS 1 ... Windshield 1a ... Windshield glass on the passenger compartment side 1b ... Windshield glass on the outer side 2 ... PVB resin 3 ... First hologram 4 ... Second hologram 5 ... Display light 9 ... Diffraction Light 10 …… Driver's eyes 38 …… Image display

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B60K 35/00 G02B 27/02 G09F 9/00

Claims (1)

(57) [Claims] 1. An image display which is disposed in a vehicle interior and emits display light, and which is disposed on a vehicle interior side in a windshield and which is provided with a specific main wavelength component emitted from the image display. When the display light is incident, the light is diffracted toward the driver at a diffraction angle different from the incident angle and with high efficiency, and the display light of the specific main wavelength component not diffracted here is converted into the second display light. A first hologram transmitted to the outside of the windshield vehicle, and the second display light transmitted by the first hologram is incident at the same incident angle as the incident angle, and the same angle as the incident angle A second hologram that diffracts the light in directions other than the driver direction with high efficiency and transmits the display light that has not been diffracted here to the outside of the windshield vehicle as third display light. ,Before The third display light is reflected at the outside interface of the windshield car and guided to the second hologram to become the fourth display light, and the fourth display light is reflected by the second hologram at the angle of incidence. A display device for a vehicle, wherein the display light is diffracted out of the windshield at the same angle to be fifth display light.