JPH09101478A - Head-up display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a head-up display which is small in surface reflection noise and chromatic aberration. SOLUTION: This head-up display device 1 is so constituted that a signal light 31 emitted by a display unit 5 is projected on a hologram combiner 10 and its diffracted light 32 is viewed. The signal light 31 is P-polarized light and diffraction characteristics of a hologram are so set that the angle α of incidence of the signal light 31 becomes nearly equal to the angle β of reflection of the diffracted light 32. The surface of the hologram combiner 10 which is irradiated with the signal light 31 is coated not to reflect light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a head-up display device, and more particularly to a head-up display device capable of suppressing noise and chromatic aberration.

[0002]

2. Description of the Related Art In normal driving of an automobile, in order to confirm a speed display or the like, it is necessary to temporarily move a line of sight from an outside scene to instruments on an instrument panel. This operation is indispensable for driving, but is a very troublesome act. It is also said that frequent eye movements cause considerable fatigue for the driver. Therefore,
In recent years, a head-up display 90 (FIG. 7) has been proposed in which an image combiner is used to simultaneously visually recognize information necessary for driving such as speed and the external scene.

Then, on the head-up display 90, the driver 99 can see a bright and clear display image 8 without distortion.
Various improved methods have been proposed to obtain 2. For example, in order to make the display image 82 a bright image, it is necessary to increase the reflectance of the signal light 31 in the image combiner 91. Therefore, the signal light 31 is so-called S-polarized light that is polarized in the direction perpendicular to the incident surface. Has been proposed (see JP-A-58-139833).

In the head-up display 90 having the structure shown in FIG. 7, a hologram combiner using a reflection hologram is also used as the image combiner 91 for superimposing a plurality of optical information as described above. The hologram combiner is provided with a diffraction characteristic for efficiently reflecting only light in a specific wavelength band as shown in FIG. 4, for example. As a result, the hologram combiner reflects the signal light 31 in a specific wavelength range emitted from the display (information light source) 92 with high efficiency, while having a high transmittance for light other than the specific wavelength range. Since it has, it can transmit most of the light coming from the background.

As a result, the brightness of the outside scene viewed through the hologram combiner 91 and the display image 82 such as the speed reflected by the hologram combiner 91 are not impaired. Further, in order to magnify and visually confirm the display image 82 emitted from the display device 92, the hologram combiner 91 (or the hologram 93 provided in the preceding stage) is often provided with a magnifying glass diffraction characteristic.

[0006]

[Problems to be Solved] Although the hologram combiner has excellent characteristics, one of the causes of making the displayed image unclear is reflection on the surface of the hologram combiner (such as the surface of the glass substrate holding the hologram). There is a problem that noise light is superimposed on regular hologram diffracted light, making the image unclear. In particular, when the incident angle and the outgoing angle with respect to the hologram combiner are almost equal, the noise image is formed near the normal image, so that the influence becomes large,
On the other hand, if the angle difference between the entrance and exit angles is large, the noise image is formed apart from the normal image and is difficult to see.

When S-polarized light (polarized light having a polarization plane perpendicular to the plane of incidence) is used as the signal light, the reflectance on the glass substrate increases, so that the surface reflection noise image becomes strong and the surface The influence of reflection noise becomes large. Therefore,
When S-polarized light is used, it is difficult to completely eliminate the noise image even if the surface is subjected to antireflection coating.

Further, in the hologram combiner, another cause of making the display image unclear is image blurring due to chromatic aberration. As for the diffraction characteristics of the hologram, as shown in FIG. 4, the wavelength band exhibiting high diffraction efficiency has a certain width (for example, the bandwidth at which the diffraction efficiency is 50% of the maximum value, so-called half-value width). When the wavelengths are different within the bandwidth, the reflection angle shifts (color dispersion) due to the change of the diffraction characteristic depending on the wavelength. Therefore, the greater the bandwidth (half-width Δλ), the greater the chromatic aberration (image blur) due to this.

In general, the full width at half maximum of the hologram has a large S-polarized light as shown by the unmarked curve 69 in FIG. 4, so that the S-polarized light increases the reflectance of the image combiner as described above. Then, there is a dilemma that this chromatic aberration increases. In FIG. 4, a curve 68 with dots shows the diffraction characteristic of P-polarized light.

The occurrence of such chromatic aberration becomes more remarkable as the focal length of the magnifying glass (concave mirror) recorded on the hologram is shortened and the magnifying power of the image is increased.
The present invention has been made in view of such conventional problems, and it is possible to provide a clear display image by suppressing image distortion due to surface reflection noise of a hologram combiner and image blurring due to chromatic aberration. It is intended to provide an up-display device.

[0011]

The present invention is a head-up display device configured to project signal light emitted from a display device onto a hologram combiner and visually recognize diffracted light reflected by the hologram combiner. The light is P-polarized light that is linearly polarized in the direction parallel to the incident surface with respect to the hologram combiner, and the hologram diffraction characteristics are such that the incident angle of the signal light and the reflection angle of the diffracted light are substantially equal. The head-up display device is characterized in that at least the signal light irradiation surface of both the front and back surfaces of the hologram combiner is subjected to anti-reflection coating treatment.

First of most noteworthy in the present invention
The point is that the signal light is P-polarized light. The most important point is the diffraction characteristic of the hologram so that the incident angle of the signal light and the reflection angle of the diffracted light have almost the same value. The third point that should be noted most is that at least the signal light irradiation surface of both the front and back surfaces of the hologram combiner is subjected to antireflection coating.

In the head-up display according to the present invention, since the signal light is P-polarized light, the reflectance is smaller than that of other polarized light. Therefore, the surface reflection light of the signal light on the hologram combiner is suppressed. Further, since the signal light irradiation surface of the hologram combiner is subjected to the anti-reflection coating treatment, the surface reflected light is further suppressed by this.

Since the signal light is P-polarized light, even when the antireflection coating is a single antireflection coating layer, the lowest reflectance wavelength of the antireflection coating layer is the center wavelength of the signal light. Thus, a large reflection suppressing effect can be obtained (see curves 611 and 621 in FIG. 6 described later in detail). The single-layer coating process allows the number of coatings to be minimized (1 time), which makes it possible to reduce man-hours and costs. Therefore, the head-up display of the present invention is
Surface reflection noise is extremely reduced and cost can be reduced.

Since the hologram diffraction characteristics are set so that the incident angle and the reflection angle of the signal light are substantially equal to each other,
There is almost no chromatic dispersion due to hologram diffraction, and there is almost no image blurring due to chromatic aberration. This is because the difference (deviation) in the reflection angle caused by the difference in wavelength occurs only when there is a difference between the incident angle and the exit angle, and the smaller the difference, the greater the deviation (dispersion) in the reflection angle. Because it will disappear. Further, since the signal light is P-polarized light, the full width at half maximum in the diffraction characteristics of the hologram is narrowed, and blurring of the display image at the outer peripheral portion of the hologram is reduced. The angle difference between the incident angle and the reflection angle in the present invention is preferably 0 °, but the effect of the present invention can be obtained if the angle difference is up to about 2 °.

Further, as described in claim 2, it is preferable that the signal light is line spectrum light having a narrow bandwidth. Further, as described in claim 3, it is preferable that the antireflection coating treatment is performed by forming a single antireflection coating layer. By making the signal light a light with a narrow bandwidth, an extremely large reflection suppressing effect can be obtained even if the light reflection preventing layer of the antireflection coating is a single layer. That is, by matching the minimum reflectance wavelength of the light reflection preventing layer with the wavelength of the signal light, the reflection of the signal light can be effectively suppressed.

Then, by a single layer coating treatment,
Since the number of times of coating is the minimum (1 time), it is possible to reduce the man-hours and the cost. In addition,
The linear spectrum light having a narrow bandwidth includes laser radiation light and fluorescent light emitted by a fluorescent substance.

In the head-up display for a vehicle, all the optical members from the display to the hologram combiner can be housed in a case as a unit and placed near the dashboard of the vehicle. . Such an independent head-up display can be removed from the vehicle for inspection, adjustment, and repair, has excellent maintainability, and can be installed as an option at any time. On the other hand, in the vehicle head-up display having the hologram combiner provided on the windshield as described in claim 5, a use feeling integrated with the vehicle can be obtained by a method such as embedding the hologram combiner inside the windshield. it can.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 As shown in FIG. 1, this embodiment is configured such that the signal light 31 emitted from the display 5 is projected on the hologram combiner 10 and the diffracted light 32 reflected by the hologram combiner 10 is visually recognized. The head-up display device 1. The signal light 31 is so-called P-polarized light that is linearly polarized in a direction parallel to the incident surface with respect to the hologram combiner 10, and the incident angle α of the signal light 31 and the reflection angle β of the diffracted light 32 are also included.
The diffraction characteristics of the hologram 11 (FIG. 2) are set so that and become approximately equal values. Further, both surfaces of the hologram combiner 10 are anti-reflection coated.

In the head-up display 1, all optical members from the display 5 to the hologram combiner 10 are integrally housed in a case 4, and a vehicle dashboard 8 is provided.
It is placed at a position near the driver's eye 5 where the driver 81 can easily see it. The following is a supplementary explanation for each.

The head-up display 1 is installed in the case body 41, a bottom plate 40 fixed to a dashboard 85 of an instrument panel, a case body 41 rotatable about an upright shaft 40a standing on the bottom plate 40. The display unit 5 includes a display unit 5, a mirror 7, a control unit 6, which is also installed inside the case body 41 and reflects the signal light 31 emitted from the display unit 5, and a hologram combiner 10. The hologram combiner 10 includes a case body 41.
It is held by a holder 42 that is attached to the upper surface of and rotates, and can be undulated in the vertical direction on the upper surface of the case body 41.

The case body 41 has a base plate 41a rotatably fixed around an axis 40a of the bottom plate 40, and a cover 41b having an opening 49. Cover 41
In b, a light shielding plate 41c is provided to prevent the display device 5 from entering the driver's 81 visual field. Display 5
Accommodates a light source lamp 51, a lens 52, and a liquid crystal display element 53, and is fixed to a substrate 41a.

The mirror 7 faces the display 5 and is attached to the substrate 41a at a predetermined inclination angle so as to project the signal light 31 from the opening 49 toward the light receiving surface of the hologram combiner 10. . Hologram combiner 1
0 is press-fitted and fixed in the long groove 42a of the holder 42,
When in use, it is erected as shown by the solid line in FIG. The angle at which the hologram combiner 10 is undulated is adjustable.

As shown in FIG. 2, the hologram combiner 10 has a hologram 11, a glass substrate 12 holding the hologram 11, and non-reflection coated glasses 13 and 14 sandwiching these from both sides. The non-reflective coated glass 13, 14 has a MgF ₂ / TiO ₂ system multilayer film 1 on the surface.
5 and 16 are vapor-deposited. Non-reflective coated glass 1
3 and 14 are shown in FIG. 3 when the incident angle α and the outgoing angle β are 30 °.
As shown in the figure, P-polarized light (dotted curve 63) has a lower reflectance than S-polarized light (simple curve 64).

Therefore, in the head-up display 1 of this example using P-polarized light as the signal light 31, the noise light reflected on the surface of the hologram combiner 10 is reduced.
Therefore, in the head-up display 1 of this example, it is possible to reduce the problem that the surface reflection noise image appears to overlap the regular display image.

The hologram combiner 10 has
An aspherical concave mirror (hyperbolic mirror) is recorded. The hologram 11 is a volume hologram using dichromated gelatin as a photosensitive material, and an off-axis hyperbolic mirror with a focal length of 200 mm is recorded. Further, since the incident angle and the outgoing angle of the hologram combiner 10 are set to be substantially equal to each other, the chromatic aberration generated in the hologram combiner 10 is small.

Further, the signal light 31 is P-polarized light, and the diffraction characteristic of the hologram 11 becomes the diffraction characteristic shown in FIG. 4 when reproducing light is incident at an incident angle of 30 °, and the incident light is P-polarized light. Half-width Δλp for (dotted curve 68)
Is the half-width Δλs for S-polarized light (simple curve 69)
Narrower than. Therefore, the reduction of chromatic aberration is further enhanced by the narrow half width.

As a result, in the hologram combiner 10 having the hologram 11 mounted, the liquid crystal display element 53
When the display image was actually observed with the distance between and as 140 mm, a clear image with little chromatic aberration could be visually recognized. Further, obtaining the P-polarized light at the time of reproduction can be easily realized by disposing the polarizing plate in the optical path, so that the optical system is also simple. As described above, according to this example, the head-up display device 1 capable of providing a clear display image by suppressing the image disturbance due to the surface reflection noise of the hologram combiner 10 and the image blurring due to the chromatic aberration is obtained. be able to.

In this example, dichromated gelatin was used as the photosensitive material for the hologram 13, but silver salts, photopolymers, photoresists or the like may be used. Further, in this example, the MgF ₂ / TiO ₂ system was used as the antireflection coating film, but it is not limited to this, and Si
O ₂ or the like may be used. In addition, although the incident angle α of the signal light is set to 30 ° in this example, the present invention is not limited to this, and α = 10 ° to 45 °.
It may be in the range of °.

Embodiment 2 In this embodiment, as shown in FIG. 5, the hologram combiner 20
Is another example of the embodiment in which is provided inside the windshield 86 of the vehicle and is separate from the indicator 5. Then, in this example, the signal light 31 emitted from the display device 5 is directly (or via the mirror) projected onto the hologram combiner 20 without passing through the mirror. A non-reflective coating film 17 is formed on the surface of the windshield 86 where the signal light 31 is applied inside the vehicle, and suppresses surface reflected light.
Others are the same as in the first embodiment.

Embodiment 3 This embodiment is the same as Embodiment 1 or Embodiment 2 except that a bright line light source is used as the light source of the display 5 and the light reflection preventing layers 15 and 16 of FIG. It is another embodiment example. That is, the signal light 31 is fluorescent light having a wavelength of 543 nm emitted from the fluorescent light source, and the light reflection preventing layer is a single-layer coating made of MgF ₂ .

FIG. 6 shows the reflection characteristics 611 to 45 ° incident light in the MgF ₂ single layer coating for 0 ° incidence.
613 and reflection characteristics 621 to 623 for 45 ° incident light in the MgF ₂ single layer coating for 45 ° incidence.
It is a graph which shows. Curves 611 and 621 show the reflectance with respect to P-polarized light, curves 613 and 623 show the reflectance with respect to S-polarized light, and curves 612 and 622 show the average reflectances for all the polarization planes.

As can be seen from the figure, even if a single-layer antireflection coating treatment is performed by using P-polarized light,
Very low reflectivities are possible with either the ° incident or 45 ° incident coatings. In addition, by using a bright line light source and setting its wavelength near the wavelength of the lowest reflectance, the reflectance can be further suppressed.

[0034]

As described above, according to the present invention, a head-up display capable of providing a clear display image by suppressing image distortion due to surface reflection noise of a hologram combiner and image blurring due to chromatic aberration. The device can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view and an optical path diagram of a head-up display according to a first embodiment.

FIG. 2 is a partial cross-sectional view of the hologram combiner according to the first embodiment.

FIG. 3 is a reflection characteristic diagram of the antireflection coating film according to the first embodiment.

FIG. 4 is a diffraction characteristic diagram of the hologram according to the first embodiment.

FIG. 5 is a system configuration diagram of a head-up display according to the second embodiment.

FIG. 6 is a diagram showing a reflection characteristic of a light reflection preventing film of the head-up display according to the third embodiment.

FIG. 7 is a system configuration diagram of a conventional head-up display.

[Explanation of symbols]

 1. . . . Head-up display, 10. . . Hologram combiner, 11. . . Hologram, 31. . . Signal light, 32. . . Diffracted light, 5. . . . display,

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Ando 1-1, Showa-cho, Kariya city, Aichi prefecture Nihon Denso Co., Ltd.

Claims (5)

[Claims] 1. A head-up display device configured to project a signal light emitted from a display device onto a hologram combiner and visually recognize diffracted light reflected by the hologram combiner, wherein the signal light is the hologram. The hologram is a P-polarized light which is linearly polarized in a direction parallel to the incident surface with respect to the combiner, and the diffraction characteristics of the hologram are set so that the incident angle of the signal light and the reflection angle of the diffracted light have almost the same value. Of the front and back surfaces of the hologram combiner, at least the signal light irradiation surface,
A head-up display device characterized by being subjected to a non-reflective coating treatment. 2. The head-up display device according to claim 1, wherein the signal light is line spectrum light having a narrow bandwidth. 3. The head-up display device according to claim 2, wherein the antireflection coating treatment is a single antireflection coating layer formed. 4. The optical device according to claim 1, wherein all optical members from the display unit to the hologram combiner are integrally housed in a case and arranged near a vehicle dashboard. Head-up display device for vehicles. 5. A head-up display device for a vehicle according to claim 1, wherein the hologram combiner is provided on a windshield.