Head-up display for motor vehicles

Disclosed herein is a head-up display for a motor vehicle having a dashboard with a top surface, which comprises a projector enclosed in the dashboard, the projector including a light source, an object from which visual information is to be displayed and a lens, an aperture formed on the top surface of the dashboard which is covered by the lens or a transparent member for preventing dust or the like from entering thereinto, a reflecting member provided in front of a driving seat on which light projected from the projector through the aperture is reflected to produce the image of the visual information thereon, and a reflection preventing member for preventing the reflection of light entering from the outside of the vehicle on the lens of the projector or on the transparent member. An antireflection coating such as a black paint is applied on the upper surface of the reflection preventing member. The reflection preventing member being shiftable between a first position in which the member covers the lens or the transparent member to close the aperture and a second position in which the member uncovers the lens or the transparent member to open the aperture. The reflection preventing member is shifted to the second position from the first position only when the head-up display is employed. Accordingly, it can prevent external light from being reflected on the lens or the transparent member toward eyes of the driver of the vehicle.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a head-up display for motor vehicles, in 
particular to a head-up display having a projector enclosed in a dashboard 
of a motor vehicle, in which an image of an object is projected through an 
aperture provided at the top of the dashboard onto a reflecting member 
such as a front windshield provided in front of the driver's seat of the 
motor vehicle, whereby a driver can observe the visible information of the 
image produced thereon. 
2. Description of the Prior Art 
Referring now to the drawings in FIGS. 1 and 2, the structures of two types 
of conventional head-up displays are explained. 
FIG. 1 shows the basic structure of one of these conventional head-up 
displays, which has a projector 5 enclosed in a dashboard 1 arranged in 
front of the driver's seat. The dashboard 1 has an aperture 1a provided at 
the top of the dashboard 1. The projector 5 comprises a light source 2, a 
liquid crystal display 3, and a lens 4 covering the aperture 1a . In the 
projector 5, an image of the liquid crystal display 3 is projected onto 
the front windshield serving as the reflecting member 7 through the 
aperture 1a, and a driver 9 can observe a virtual image 6 produced in 
front of the front windshield 7. 
FIG. 2 shows the basic structure of the other conventional head-up display. 
In this head-up display, a projector 5 is also enclosed in a dashboard 1 
which has an aperture 1a provided at the top thereof. The aperture 1a is 
covered by a transparent cover 11. Although the projector 5 is formed as a 
unit type, the internal structure thereof is in common with that of the 
head-up display shown in FIG. 1. The unit type projector 5 is mounted with 
rotation capabilities with respect to an axis 10 in the dashboard 1, so 
that it is possible to adjust the position of the image 6 on the front 
windshield 7 so as to reflect the visual image to a position where the 
eyes of a driver 9 are normally directed during operation of the vehicle. 
In these conventional head-up displays, the aperture la formed on the top 
of the dashboard 1 is either covered by a lens 4, as in FIG. 1, or by the 
transparent cover 11 as in FIG. 2 for protecting the lens 4 or for 
preventing dust from entering into the projector compartment. 
In the apertures 1a of both these structures, however, the surfaces of the 
lens 4 and the transparent cover 11 are usually formed by mirror grinding 
methods in order to improve the display performance. Therefore, there was 
the problem that the visibility of the driver is impaired by the 
reflection of external light entered from the outside, such as sunlight, 
on the surface of the lens 4 or the transparent cover 11 not only in the 
employment of the head-up display but also in the unemployment thereof. 
In order to overcome this problem, one can conceivably apply antireflection 
treatment, such as creating fine irregularities or masking, to the surface 
of the lens 4 or the transparent cover 11. However, such antireflection 
treatment has, a disadvantage in that it also reduces the quantity of 
projected light available for display, thereby deteriorating the display 
capability of the head-up display. 
SUMMARY OF THE INVENTION 
Accordingly, one of the main objectives of the present invention is to 
provide a head-up display which can prevent the reflection of external 
light from the transparent member such as a lens or transparent cover 
without reducing the quantity of projected light from the projector. 
Another objective of the present invention is to provide a head-up display 
which can prevent dust from entering into the projector and also protect 
the lens from intensive light from the outside. 
Still another objective of the present invention is to provide a head-up 
display which can protect an indication device, such as a liquid crystal 
display, in the projector from intensive light from the outside. 
In order to achieve the above objectives, the head-up display for motor 
vehicles having a dashboard with a top surface thereof according to the 
present invention comprises a transparent member provided on the top 
surface of the dashboard, means for projecting an image of visual 
information through said transparent member, and said projecting means 
being enclosed in said dashboard, reflection means for producing the image 
of the visual information thereon, and means for preventing reflection of 
light entering from the outside of said vehicle on said transparent 
member, said reflection preventing means being shiftable between a first 
position covering said transparent member and a second position uncovering 
said transparent member. 
In accordance with the head-up display of the present invention having the 
above structure, since there is provided the reflection preventing means 
which is shiftable between the first position covering said transparent 
member and the second position uncovering said transparent member, it will 
prevent intensive light from the outside from being reflected on the 
transparent member. Therefore, it is possible to prevent the reflection of 
the intensive light which impairs the vision of the driver on the 
transparent member. 
Furthermore, the reflection preventing means may be constructed so as to 
enable the transparent member to be covered when intensive light enters 
into the projector, so that it becomes possible to protect the lens in the 
projector from such intensive light. Furthermore, with the provision of 
the reflection preventing means, it also becomes possible to prevent dust 
and other small particles from entering into the projector. Moreover, 
since the reflection preventing means is provided on the dashboard, the 
structure of the projector is not affected by the provision of the 
reflection preventing means, thereby allowing compactification of the 
apparatus to be attained. 
These and the other objects, features and advantages of the present 
invention will be more apparent from the following description of 
preferred embodiments, taken in conjunction with the accompanying 
drawings, in which:

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the drawings, the embodiments of the present invention are 
described as follows. 
FIG. 3 shows the first embodiment of the present invention. In the drawing, 
the numeral 1 denotes a dashboard 1 of a motor vehicle. In the dashboard 
1, there is provided a projector 5 which is rotatably mounted on an axis 
10. The projector 5 comprises a light source, a liquid crystal display and 
a lens and so forth (not shown), as described in conjunction with the 
conventional head-up display of FIG. 2. 
The dash board 1 has an aperture 1a on the top surface thereof. On the 
underside of the aperture 1a, there is provided a transparent member such 
as a transparent cover 11 for preventing dusts from entering the projector 
5, which covers the aperture 1a. The transparent cover 11 is formed of a 
synthetic resin such as acryl and has a U-shape in cross sectional thereof 
as shown in the drawing. The upper surface of the transparent cover 11 is 
formed by mirror grinding method. The transparent cover 11 is attached on 
the underside of the dashboard 1a with some distance therebetween. In the 
drawing, the numeral 7 denotes a front windshield as reflection means, on 
which an image of visual information in the liquid crystal display is 
produced. 
Reflection preventing means 12 for light coming from the outside is 
provided in the aperture 1a. The reflection preventing means 12 comprises 
a plurality of visors 12a. Each of the visors 12a is pivotably supported 
by a support rod 13 which is mounted between the opposite edges of the 
aperture 1a. On the upper surface of each visor 12a, reflection preventing 
treatment such as fine irregularities or black paint is applied. Each of 
the visors 12a can be pivotally turned between their horizontal and 
vertical positions with respect to the top surface of the dashboard 1. As 
a result, the visors 12a completely close the aperture 1a when rotated to 
their horizontal position and fully open the aperture 1a when rotated to 
their vertical position. 
FIG. 4 (a) and (b) show operations of the visors 12. When the projector 5 
is in operation, the visors 12a are rotated to their vertical positions to 
open the aperture 1a, as shown in FIG. 4(a). On the other hand, when the 
projector 5 is not in operation or when visual information from the object 
is not required, then the visors 12a are turned to their horizontal 
positions to close the aperture 1a, as shown in FIG. 4(b). The visors 12a 
are actuated by drive means 14 (FIG. 3). The details of the drive means 14 
are omitted because the drive means 14 is an ordinary mechanism which 
comprises a motor, drive gears, driven gears, and so forth. 
FIG. 5 shows a control system for the reflection preventing means 12 (FIG. 
3). For example, the visors 12a are first located at their horizontal 
positions to close the aperture 1a, as shown in FIG. 4(b). Then, an 
indication request signal is inputted to the controller 15 including a 
central processing unit (CPU), the drive means 14 is actuated by a signal 
outputted from the CPU 15, and then each visor 12a is rotated with respect 
to the support axis 13 and turned to its vertical position, thereby 
opening the aperture 1a. Simultaneously, the indication signal is also 
sent to the projector 5 (FIG. 3) from the CPU 15, which activates the 
liquid crystal display and the light source in the projector 5 in order to 
project visual information from the liquid crystal display onto the front 
windshield 7 serving as the reflecting member. As a result, a driver can 
observe the visible information 6 (FIG. 1) produced on the front 
windshield 7. When the projector 5 is turned off, an indication request 
signal is sent to the CPU 15 to drive the drive means 14 which then turns 
the visors 12a to their horizontal positions thereby closing the aperture 
1a, as shown in FIG. 4(b). 
In addition, if intensitive light enters into the projector 5 from the 
outside during the operation of the projector 5 or if the quantity of 
reflected light from the transparent member 11 is large, a detector 16, 
which is provided inside the projector 5 or outside thereof for detecting 
the quantity of external light and outputting a signal. The signal is 
amplified by an operational amplifier and the amplified signal is inputted 
to the CPU 15 through an A/D converter. By this signal, the drive means 14 
is also actuated to move the visors 12a to their horizontal positions, 
thereby closing the aperture 1a. Therefore, it is possible to protect the 
indication device such as the liquid crystal display from this intensive 
light and to prevent the reflection of light from the transparent member 
11 which can impair the vision of the driver. 
FIG. 6 is a flow diagram showing the operation of the CPU 15. At first, it 
is decided whether an indication request signal is on or off. When the 
signal is on, then the process is advanced to the next step and then it is 
decided whether level of the light from the outside is over the 
predetermined level or not. When the level of the light from the outside 
is under the predetermined level, then the visors 12 are rotated to their 
vertical positions to open the aperture 1a and simultaneously the 
projector 5 is turned on. On the other hand, when the indication request 
signal is off, the visors 12 are turned to their horizontal positions to 
close the aperture 1a and simultaneously the projector 5 is turned off. In 
addition, when the level of the light from the outside is over the 
predetermined level, then the visors 12 are also turned to their 
horizontal positions to close the aperture 1a and simultaneously the 
projector 5 is turned off. 
FIGS. 7 and 8 show a second embodiment of the present invention. In this 
embodiment, a reflection preventing means 12 comprises a sheet of a 
flexible plate like member or a flexible sheet like member having an 
substantially square shape, and the upper surface thereof is coated with 
an antireflection coating such as fine irregularities or black paint. Said 
plate like member 12 has a sliding door structure which can move between a 
first position in which the plate like member 12 covers and closes the 
aperture 1a and a second position in which the plate like member 12 slides 
under the top surface of the dashboard and opens the aperture 1a. 
Specifically, on the underside of the dashboard 1, a pair of guide rails 
17 are provided along the opposite sides of the aperture 1a, respectively. 
On the opposite sides of the plate like member 12 there is provided a 
plurality of pins 18, respectively. The pins 18 of each side of the plate 
like member 12 are slidably engaged with each guide rail 17, respectively. 
A belt 21, which is interconnected between a pulley attached to a rotating 
shaft of a motor 19 and a pulley 20, is coupled to the pins 18 of one side 
of the plate like member 12. Accordingly, the rotational force of the 
motor 19 is transmitted to the pins 18 by means of belt 21, so that the 
plate like member 12 can be moved between the first position and the 
second position in accordance with the movement of the pins 18 which are 
moved by the rotational force of the motor 19. The controlling mechanism 
for the movement of the plate like member 12 as the reflection preventing 
means is same as that of the first embodiment. 
In accordance with the second embodiment, there is the additional advantage 
that the structure of the reflection preventing means 12 becomes simpler 
than that of the first embodiment, since the reflection preventing means 
12 comprises a plate like member. Further, while in the structure of the 
first embodiment the images of the support rods may obstruct the projected 
visual information, in the structure of this embodiment there is no fear 
of such obstruction. 
It will become apparent from the foregoing description that the head-up 
display of the present invention has a number of advantages, some of which 
have been described above. Also, obvious modifications and variations can 
be made to the head-up display of the present invention without departing 
from the scope of the invention. Accordingly, the scope of the invention 
is not limited as necessitated by the accompanying claims.