Head-Up Displaying Device for a Vehicle

The present application is based on and claims the priority from Japanese patent application No. Hei 6-90054 filed on Apr. 27, 1994, the content of which is incorporated herein by reference.

1. Field of the Invention

The present invention is related to a head-up displaying device for a vehicle.

2. Description of the Prior Art

A conventional head-up display for a vehicle which is used to display vehicle speed or the like is schematically shown in FIG. 8. The head-up display according to the prior art comprises an image displaying unit 100 which includes an image projection unit 5 and a mirror (optical path) 7 therein. The image displaying unit 100 is installed inside a dashboard 2 of the vehicle and a combiner (reflecting member) 8 which is vapor-deposited on an inner surface of a windshield 200 to focus an image 17 ahead of the windshield 200.

However, such a conventional head-up displaying device for a vehicle has a separate image projection unit 100 and a separate combiner 8 and they must be separately installed in a vehicle. Therefore, such installation brings about a considerable increase in time-consuming work, resulting in high cost and difficulty of installation.

Therefore, the primary object of the present invention is to provide a head-up displaying device for a vehicle which solves the above problems and can be installed more easily than prior art devices.

Another object of the present invention is to provide a head-up displaying device in which a projecting unit, a reflecting member and a combiner are integrally secured to a suitable portion of a vehicle, and hence, the device may be formed as a unit.

Another object of the present invention is to provide a head-up displaying device for a vehicle in which the combiner is foldable so that the device may be made compact.

Still another object of the present invention is to provide a head-up displaying device for a vehicle in which the combiner may swing to adjust the position of the image as seen by the driver in the vertical direction.

A further object of the present invention is to provide a head-up displaying device for a vehicle in which the combiner is rotatable to adjust the position of the image as seen by the driver in the horizontal direction.

A still further object of the present invention is to provide a head-up displaying device for a vehicle in which the combiner includes a thin reflection hologram sheet enhancing the reflection efficiency of the device at a specific wavelength.

A still further object of the present invention is to provide a head-up displaying device for a vehicle in which the aforementioned hologram has an aspherical concave lens disposed thereon to magnify the image viewed by the driver.

A further object of the present invention is to provide a head-up displaying device for a vehicle in which the combiner includes an anti-reflection coating disposed on at least one side thereof to reduce undesired reflection and to provide a sharp image without double images.

A still further object of the present invention is to provide a head-up displaying device for a vehicle in which an optical sensor for sensing the ambient light level and a controller automatically dimming the head-up display in response to the ambient light level are further provided to enhance visibility.

Still another object of the present invention is to provide a head-up displaying device for a vehicle in which a main case housing the device includes a shade member to prevent the image projection unit from coming into the users field of vision.

Still further object of the present invention is to provide a head-up displaying device for a vehicle in which a concave tray portion is formed at the upper surface of the device.

Other objects, features and characteristics of the present invention as well as the functions of related parts of the present invention will become clear from a study of the following detailed description, the appended claims and the drawings. In the drawings:

FIG. 1 is a side cross-sectional view of a head-up displaying device according to the first embodiment of the present invention;

FIG. 2 is an exploded-perspective view illustrating the connecting structure of a combiner and a main case of the first embodiment;

FIG. 3 is a cross-sectional side view of the combiner shown in FIG. 2;

FIG. 4 is a side view of a head-up displaying device for a vehicle according to the second embodiment of the present invention;

FIG. 5 is a schematic circuit diagram of the above embodiment;

FIG. 6 is a cross-sectional side view of a head-up displaying device for a vehicle according to the third embodiment of the present invention;

FIG. 7 is a schematic view illustrating installation of a head-up displaying device for a vehicle according to the forth embodiment of the present invention; and

FIG. 8 is a schematic view illustrating a conventional head-up displaying device.

The preferred embodiments according to the present invention will be described as follows with reference to the appended drawings.

As shown in FIG. 1, a head-up displaying device 1 includes a base member 3 formed with a stem 3a and secured to a dashboard 2 of a vehicle close to an instrument panel (not shown), a main case 4 which is formed with a bottom plate 4a rotatably carried around the stem 3a of base member 3 and which houses an image projection unit 5, a control unit 6 and a reflecting member (mirror) 7 therein. A flat combiner 8 is foldably mounted on the upper portion of the main case 4. The base member 3 and the bottom plate 4a form a turn table rotatable horizontally with respect to the dashboard 2. The main case 4 has a cover 4c on which an opening 4b, a couple of openings 4e and a shade member 4d are formed. The shade member 4d blocks the image projection unit 5 housed in the main case 4 from the driver's line of sight.

Image projection unit 5 is composed of a light source 5a, an optical lens 5b, a transmissive liquid crystal panel 5c and a case 5d to house these components. The case 5d is secured to the bottom plate 4a of the main case 4. The control unit 6 is secured to the bottom plate 4a of the main case 4.

The reflecting member 7 is secured to the bottom plate 4a so that it faces the image projection unit 5, and is inclined relative to the bottom plate 4a at such an angle that an image beam may be reflected from the image projection unit 5 through the opening 4b to the surface of the combiner 8. As shown more clearly in FIG. 2, the combiner 8 is held by a holder 9 at its lower end and is fitted into a groove 9a formed in the holder 9 and extending along the longitudinal direction thereof. The holder 9 rotates around a couple of shafts 9b formed on its sides and is secured to the cover 4c by a couple of clips 10. Each clip 10 has a pair of hooks 10a which hold a corresponding shaft 9b therebetween and is fitted into a corresponding hole 4e in cover 4c. As a result, the holder 9 functions as a hinge so that the combiner 8 may be raised or lowered as shown by the ghost view in FIG. 1. When the combiner 8 is lowered, it covers the opening 4b to protect the interior of the displaying device 1 from dust, water and the like. The inclination angle of the combiner 8 may be adjusted as shown by lines .alpha. and .beta. in FIG. 1 using the frictional retaining force of the clips 10 to catch the shafts 9b of the holder 9.

The combiner 8 has a thin reflection hologram 13 which is formed with an aspherical concave lens (not shown) disposed thereon and is enclosed between glass panes 11 and 12 as shown in FIG. 3. Anti-reflection coatings 15 and 16 are also formed to cover the exposed surfaces of the combiner 8.

When head-up displaying device 1 described above is being used, the combiner 8 is first raised from the folded position. A light beam is emitted from light source 5a and passes through the optical lens 5b and the liquid crystal panel 5c which is controlled by control unit 6 to form an image pattern thereon. The light beam is then formed into a displaying image beam and projected out of the image projection unit 5 to the reflecting member 7, which reflects the displaying image beam to direct it to one side of the combiner 8 through the opening 4b. Then, the image is magnified by the aspherical lens formed on the combiner 8 into an image magnified several times over to focus a virtual image 17 in front of the other side of the combiner 8. Since the image is magnified several times by the aspherical lens, a large-sized image may be obtained with a short optical length, which enables integration (unification) of the components of the device 1. Since the combiner 8 has anti-reflection coatings 15 and 16 formed thereon, light which is reflected by the sides of glass panes 12 and 14 may be reduced. Thus, the image light beam coming into the combiner 8 is substantially reflected by the hologram 13 so that the virtual image 17 is sharp without being doubled and also so that the driver can maintain an unobstructed view through the combiner 8. Since the combiner 8 has a thin sheet hologram enclosed therein, the reflection efficiency of the device 1 at its specific display wavelength may be enhanced.

In case the driver wants to change the position of the image 17, it may be adjusted in the horizontal direction merely by rotating the main case 4 around the stem 3a of the base member 3 to an appropriate angle. The vertical position of the image 17 may also be adjusted by swinging the combiner 8 around the shafts 9b of the holder 9 to form an appropriate inclination angle. As a result, about 99% of the driver's field of vision may be preserved.

The combiner 8 may be composed of resinous transparent plates 11, 12 and 14 such as acrylic plates instead of the glass panes. In this structure, the shafts 9b may be integrally formed on the sides of the resinous plates and, therefore, the combiner 8 and the holder 9 may be integrated into a unit, resulting in a reduction in the number of parts and the manufacturing cost and also resulting in an enhancing of the device's safety level.

The liquid crystal panel 5c may be replaced by a self-illuminating image formation device such as a vacuum fluorescent display (VFD) or an electroluminescent panel (EL), in which case the light source 5a may be eliminated if appropriate.

FIGS. 4 and 5 illustrate a structure of a head-up displaying device 1 for a vehicle according to the second embodiment of the invention, in which the main case 4 of the first embodiment further contains therein an optical sensor 18 and a dimmer knob 19 to provide control unit 6 with automatic dimmer control and manual dimmer control. Reference numerals in the figures for this embodiment generally used correspond to those in the figures of the first embodiment. The optical sensor 18 generates a signal in response to the ambient light level in the vicinity of the display image 17 and the dimmer knob 19 generates a signal for the control unit 6 to change the contrast or brightness of the display image 17 as desired by the driver. As a matter of course, the control unit 6 is powered by a battery and controls the liquid crystal panel 5c to form image patterns in response to signals sent thereto.

In this embodiment, the brightness adjustment may be made automatically in response to the ambient light conditions and, thereby, optimal visibility of the image is always assured. Further, a driver may manipulate the dimmer knob 19 as desired to adjust a desired brightness or contrast of the display image 17.

A third embodiment of the present invention is illustrated in FIG. 6, in which the main case 4 of the first embodiment is formed with concave portions 4f and 8a on its cover 4c and on the back of the combiner 8, respectively. Such concave portions may be used for trays.

A fourth embodiment of the head-up displaying device 1 according to the present invention is mounted on a rear panel 300 of the vehicle as illustrated in FIG. 7. This embodiment displays such information as brake signals or turn signals to other vehicles or persons behind the vehicle. For this purpose, the combiner 8 of the first embodiment additionally has a red colored member on its hologram 13 onto which light beams are projected in the same manner as in the first embodiment, so that a red three-dimensional image may come to the front of the combiner 8 and be projected through the rear windshield 400. Thus, the device 1 may be used for a high-position-mounted brake light.