GB2212964A

GB2212964A - Holographic multi-display apparatus

Info

Publication number: GB2212964A
Application number: GB8727861A
Authority: GB
Inventors: Maso Suzuki; Kazuhiro Kimura
Original assignee: Yazaki Corp
Current assignee: Yazaki Corp
Priority date: 1987-11-30
Filing date: 1987-11-27
Publication date: 1989-08-02
Anticipated expiration: 2007-11-27
Also published as: GB8727861D0; GB2212964B; DE3740557A1; DE3740557C2

Description

TITLE OF THE INVENTION

22it2964 HOLOGRAPHIC DISPLAY APPARATUS 5OR AUTOMOTIVE VEHICLE BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates generally to a holographic display apparatus for an automotive vehicle and rnore specifically to a holographic display apparatus which can simultaneously display both instrument board images and hologram images reproduced from a hologram plate disposed in front of the instrument board on the basis of a reproducing light source.

is Description of the Prior Art

Recently, holographic display apparatus adoptable for an automotive vehicle have been proposed as a novel display apparatus. In these apparatus, a hologram plate is disposed in front of an instrument board disposed on an instrument panel assembled within a vehicle dashboard, and irradiated with a hologram image reproducing light- source disposed in front of the hologram plate, in order to display both a holographic image reproduced from the hologram plate and an instrument image obtained through the transparent hologram plate in superimposed positional relationship to each other.

In the holographic display apparatus as described above, the hologram image reproducing light source is usually disposed within an instrument board hood or on a steering column.

Where the light source is disposed within the instrument board hood, it is n(cessary to arrange the light source near the extreme rear end (on the driver side) of the instrument board hood in order,-to prevent a regular 1 - reflection image of the light source from being reflected from the hologram plate toward a driver's eye. Therefore, it is necessary to lengthen the instrument board hood or the dashboard extremely toward the drive, so that there exists a problem in that the passenger compartment space is reduced. Further, in the above arrangement, although it is possible to prevent the regular reflection image of the light source from being reflected from the hologram plate toward a driver's eye by disposing the light source rearer to the instrument board, since it is impossible to secure a sufficient distance between the hologram plate and the light source, excellent hologram images are not obtainable.

Further, where the light source is disposed on the steering column, although it is unnecessary to modify the shape of the instrument board, since the driver must see the instrument board through spaces between spokes of the steering wheel, it is impossible to increase the size of the light source. Further, where the steering column is of movable type for tilt adjustment, since the light source should be adjusted so as to always to be directed toward the hologram plate, there exists a problem in that the light source mounting mechanism is complicated.

SUMMARY OF THE INVENTION

With these problems in mind, therefore, it is the primary object of the present invention to provide a holographic display apparatus for an automotive vehicle which can provide good hologram images without increasing the size of the conventional instrument board or complicating the light source mounting mechanism.

To achieve the above-mentioned object, a holographic display apparatus for an automotive vehicle, according to the present invention, having an instrument board assembled in a dashboard, a hologram plate disposed in front of the 2 instrument board, and a light source disposed in front of said hologram plate for emitting light to the hologram plate to reproduce a hologram image recorded on the hologram plate in superimposed positional relationship to an instrument board image, is characterized in t hat the light emitted from the light source is reflected to the hologram plate by light reflecting means disposed within a hood of the instrument board.

The light source is disposed below the instrument board hood and between a steering column and a lower part of said instrument board, and the light reflecting means is disposed over said light source. The light reflecting means is a mirror.

In the holographic display apparatus of the present invention, since the reproducing light source, the reflection means and the hologram plate can freely be located relative to the instrument board under preferable conditions as follows: an incident angle of hologram image reproducing light upon the hologram light is determined substantially equal to that of the reference light used in hologram recording; the mutual positional relationship between the hologram, panel, the reproducing light source and the driver's eye can be determined near to the regular reflection state without reflecting the light source image from the hologram plate to the driver's eye; the apparent distance between the hologram plate and the light source is increased for providing a clear hologram image, etc. Therefore, it is possible to reproduce a clear hologram image without markedly changing the dimensions of the instrument board or the dashboard of an automotive vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the holographic display 35 apparatus for an automotive vehicle according to the 1 3 - present invention will be more clearly appreciated from the following description of the preferred embodiment of the invention taken in conjunction with the accompanying drawings in which like reference numerals designate the same or similar elements or sections throughout the figures thereof and in which:

Fig. 1 is a cross-sectional view showing an embodiment of the holographic display apparatus according to the present invention; Fig. 2A is an illustration for assistance in explaining the method of recording a Lippmann hologram plate; Fig. 2B is an illustration for assistance in explaining the method of reproducing a hologram image from the hologram plate; Fig. 3A is an illustration for assistance in explaining the selectivity of hologram light source wavelength during recording; Fig. 3B is an illustration for assistance in explaining the selectivity of hologram light source wavelength during reproducing; Fig. 4A is a front view showing an example of displal,7 images reproduced by the display apparatus of the present invention; and Fig. 4B is a side view showing the example of the display image shown in Fig. 4A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the holographic display apparatus for an automotive vehicle will be described hereinbelow with reference to the attached drawings.

In Fig. 1, the display apparatus roughly comprises an instrument board 12, a Lippmann hologram plate 13, an instrument board hood 14, and a hologram image reproducing light source 16.

1 4 The instrument board 12 is apparatus composed of a plurality an electronic display of display devices 12a such as fluorescent character tube display unit, light-emitting diode display unit, liquid crystal display unit, etc. and their driving circuits 12b. These display devices 12a and the driving circuits 12b are all housed within an instrument board casing 12c. Further, without being limited to the above-mentioned electronic display apparatus, it is of course possible to construct the instrument board 12 by a mechanical display apparatus using a pointer or the like.

The Lippmann hologram plate 13 is disposed in front of the instrument board 12 being sandwiched between a front glass 12d whose periphery is fixed to the instrument case 12 and the instrument board front casing 12e. The front glass 12d is formed with an aperture corresponding to an effective display area of the hologram plate 13, and the other area except the aperture is covered with a black mat.

Further, the hologram plate 13 is coated by a multilayer interference film formed by multilaying two or more transparent substances each having different refraction indices to a predetermined thickness in order to prevent driver's face from being reflected from the hologram plate 13 (reflection prevention processing).

The reproducing light source unit 16 is made up of a reproducing light source 16a and a light source casing 16b.

The light source unit 16 is fixed by a stay 12f projecting from the lower surface of the instrument board 12, and arranged in a space S formed between the instrument board 12 and a steering column 15. An aperture 16bl is formed in the upper portion of the light source casing 16b, and an aperture 14a is formed in the lower portion of the instrument hood 14. Light is emitted from the reproducing light source 16a to a flat mirror 20 through these openings 16bl and 14a, and then reflected toward the hologram plate 13. The flat mirror 20 is fixed by a stay 129 projecting. from both the side surfaces of the instrument board 12 and arranged within a gap G formed between the dashboard 11 and the instrument board hood 14. Further, an aperture l4b is formed in this instrument board hood 14 to expose the surface of the flat mirror 20.

The hologram reproducing light source 16a is a pseudo point light source such as an incandescent lamp, a halogen lamp, etc. Further, the dimensions and shapes of the 10 opening 16b' in the light source casing 16b, the opening 14a of the instrument board hood 14, a mask plate 14c fitted to the opening 14a, and the flat mirror 20 are all so determined that light emitted from the reproducing light source 16a can be effectively introduced only to an effective display area on the hologram plate 13. The mask plate 14c is a metallic plate or an acrylic plate. The opening is formed by etching or punching in the case of the metallic mask plate and by mask printing in the case of the acrylic mask plate.

With reference to Figs. 2A and 2B, the method of recording and reproducing an image on or from a Lippmann hologram plate will be described hereinbelow. In Fig. 2A, laser light located a distance ' 0 away from a hologram photographic dry.plate 13, is allowed to be incident upon the dry plate 131 as a reference light L R of spherical wave. Further, an object light L 0- reflected from an object 0 is allowed to be incident upon the dry plate 131 on the reverse side thereof. Therefore, the reference light L R and the object light L 0 are superimposed on the hologram photographic dry plate 131, so that interference fringes are formed thereon in the thickness direction of the hologram emulsion agent layer.

In recording an object image on the dry plate 131, it is preferable to determine the incident angle a of the reference light L to the dry plate. 131 as a 15 degrees. R - 6 Z.

h This is because if a is too small, other interferences will be produced within the hologiam photographic dry plate 13' obtained by applying a hologram emulsion agent to a glass subs.trate, so that a reproduced hologram image is deteriorated in display quality.

Fig. 2B shows the way of reproducing a hologram image from the hologram plate 13. When light from the reproducing light source 16a located a distance away from the hologram plate 13 is allowed to be incident upon the hologram plate 13 in the same direction as that of the reference light L R used in hologram recording, only light having a wavelength satisfying the Bragg diffraction condition is reflected therefrom, so that a hologram image 0' of the object 0 can be seen in back of the hologram plate 13.

In observation of the hologram image, when the driver sees the hologram plate 13 from a regular reflection direction (a=13) as shown in Fig. 2B, he can recognize an excellent reproduced hologram image of less blur. In practice, however, it is not preferable that the driver can see an image of the reproduced light source 16a, reflected from the hologram panel 13. Therefore, where the hologram plate 13 is disposed in front of the instrument board, since the range within which the driver sees the instrument board 12 is limited within a certain range, it is preferable to determine the positional relationship between the driver's eye 17, the hologram plate 13 and the reproducing light source 16a so that the driver cannot see the light source image reflected from the hologram panel 13 but the regular reflection relationship between them will not be deviated much from the correct position.

Further, it is preferable to increase the distance between the hologram plate 13., and the reproducing light source 16a as much as possible. For instance, where the hologram plate size is 220 x 92 mm and the distance 10 is 800 mm in Fig. 2A, the distance between the hologram plate 13 and the light source 16a is preferably / > 250 mm. The shorter the distance is, the more will be the uneven brightness, the blur and distortion of the reproduced hologram image.

In the Lippmann-type hologram plate 13 thus formed, when the hologram plate 13 is irradiated with light from a reproducing light source 16a placed as shown in Fig. 2B, only light having a wavelength which satisfies Bragg diffraction condition is reflected, so that a hologram image 01 can be seen.

In the Lippmann-type hologram plate 13 as described above, as shown in Fig. 3A, a plurality of interference patterns 13b substantially parallel to surfaces of the emulsion agent layer.13a are recorded in the hologram plate 13. The distances x between two interference patterns 13b can be expressed as dx = A 2n sin G/2 where x denotes the wavelength of laser light; n denotes the refraction index of the emulsion layers, and e denotes a cross angle between the reference light L R and the object light L 0' In the emulsion layers 13a on which the above-mentioned interference patterns 13b are recorded, as shown in Fig. 3B, when light is allowed to be incident thereupon at an incidence angle a from the reproducing light source 16a, only light having a specific wavelength x is reflected from each interference pattern 13b from among light having various wavelengths. This phenomenon is called Bragg diffraction and expressed as 1 tp i X - X 2 cosa Where the hologram plate 13 provided with the above-mentioned characteristics is disposed in front of the instrument board as shown in Fig. 1, it is possible to see an image of the instrument board 12 and a holographic image in mutual superimposed positional relationship to each other.

Fig. 4A and 4D show an example of display images obtained by the apparatus of the present invention, in which the symbol A denotes a reproduced hologram image and the symbol B denotes an instrument board image overlapped each other. The hologram image A is a three-dimentional picture frame image. The instrument board image B includes vehicle speed Bl, engine revolution number B 21 fuel quantity B 3 and coolant temperature B 4 As depicted in Fig. 4B, the instrument board image B is displayed in relation to a stereographic display manner.

With reference to Fig. 1 again, the preferable positional relationship between the light source 16a, the mirror 20, the hologram plate 13 and the instrument board 12 will be explained under (due) consideration of actual hologram reproducing conditions.

The light emitted from the light source 16a, reflected from the mirror 20 and further from the uppermost position of the hologram plate 13 becomes a horizontal line Y. In other wordst the instrument board 12 is mounted under this horizontal line Y. The incident angle a of the light from the reproducing light source 16a upon the hologram plate 13 is a = 30.5 degrees; the observation angle 5 of the driver to the hologram plate 13 is B = 1.5 degrees; the observation angle y of the driver to the horizontal line Y is Y = 20.5 degrees. Further, the distance + I I 1 1 2 - 9 between the light source 16a and the hologram plate 13 is 1 + 12 = -298 mm.

As. described above, in the holographic display apparatus for an automotive vehicle according to the present invention, since the hologram image reproducing light is introduced upon the hologram plate via light reflecting means, it is possible to obtain good hologram images under appropriate hologram reproduction conditions without changing the shape or dimensions of the instrument 10 board or the dashboard of an automotive vehicle.

1 - 1

Claims

WHAT IS CLAIMED IS:

A - holographic display apparatus for an automotive vehicle having a dashboard (11), which comprises: instrument board (12) assembled in the dashboard for indicating various vehicle information; (a) an (b) a transparent hologram plate (13) disposed close in front of said instrument board, for recording a solid holographic display image in relation to the various 10 vehicle information of said instrument board; (c) a hologram image reproducing light source (16a) disposed in front of said hologram plate, for holographically reproducing the holographic display image from said hologram plate; and (d) light reflecting means (20) disposed within a hood (14) of the instrument board (12), for reflecting light from said hologram image reproducing light source to said transparent hologram plate.
2. The holographic display apparatus as set forth in claim 1, wherein said light source is disposed below the instrument board hood (14) and between a steering column (15) and a lower part of said instrument board (12), and said light reflecting means (20) is disposed over said 25 light source (16a).
3. The holographic display apparatus as set forth in claim 1, wherein said light reflecting means is a mirror.
4. The holographic display apparatus as set forth in claim 1, wherein an incident angle a of light emitted from said light source upon said hologram plate is about 30 degrees.
5. The holographic display apparatus as set forth in claim 1, wherein a driver observation incident angle 2 upon said hologram plate is about 2 degrees and a driver observation incident angle y with respect to a horizontal line is about 20 degrees.
6. The holographic display apparatus as set forth in claim l, wherein a distance ( 1 + '1 2) from said light source. through said reflecting means, to said hologram plate is about 250 to 300 mm.
7. A holographic display apparatus for an automotive vehicle, having an instrument board (12) assembled in a dashboard (11), a hologram plate (13) disposed in front of the instrument board, and a light source (16a) disposed in front of said hologram plate, for emitting light to the hologram plate to reproduce a hologram image recorded on the hologram plate in superimposed relationship to an instrument board image, characterized in that the light emitted from the light source (16a) is reflected to the hologram plate (13) by light reflecting means (20) disposed within a hood (14) of the instrument board (12).
8. A holographi,c display apparatus substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.
9. Any novel feature or combination of features described herein.

Published 1989 at The Patent Office, State House, 66.71 High Holborn, LondonWClR 4TP. Further copies maybe obtained from The Patent Office, Sales Branch, St Mary Cray, Orpington. Rent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent, Con- 1/87