Inner mirror of a vehicle having a display device

An inner mirror of a vehicle having a display device includes a mirror body, a rear view mirror provided in a front opening of the mirror body for reflecting an image in the rear of a vehicle back to a driver's visual point, an information display section provided within an area of the rear view mirror in the front opening of the mirror body or within an area adjacent to the area of the rear view mirror, a light emitting display section provided in the mirror body for displaying visual information by emission of light, and an information display mirror provided in the mirror body for reflecting the visual information displayed by the light emitting display section back to the driver's visual point through the information display section.

BACKGROUND OF THE INVENTION 
This invention relates to an inner mirror of a vehicle and, more 
particularly, to an inner mirror of a vehicle capable of facilitating 
watching of visual information in the form of emitted light relating to 
distance of an obstacle located in the rear of a vehicle. 
Various proposals have been made for warning a driver of a vehicle against 
an obstacle located in the rear of the vehicle when the vehicle is driven 
rearwardly for, e.g., putting it into a garage. For example, Japanese 
Patent Application Laid-open No. Sho 59-120877 discloses a device 
according to which an image in the rear of a vehicle is taken by a 
television camera and this image is displayed in a CRT provided in a meter 
panel in front of a driver's seat. Moreover, according to this device, an 
ultrasonic transmitter and an ultrasonic receiver are provided on a rear 
bumper to measure distance of an obstacle located in the rear of the 
vehicle and the measured distance is displayed numerically on the CRT in a 
form superposed on the image in the rear of the vehicle. This device, 
however, requires a relatively large scale device such as a television 
camera and a CRT and therefore is very costly. 
For overcoming the problem of this device, Japanese Patent Publication No. 
Hei 4-25174 proposes an improvement according to which a light emitting 
device such as a fluorescent character display tube is provided in a part 
of an inner mirror to display distance of an obstacle located in the rear 
of a vehicle detected by an obstacle detection sensor. By this 
arrangement, a driver can watch information relating to the distance of 
the obstacle located in the rear of the vehicle while he watches an image 
in the rear of the vehicle over the inner mirror. 
According to the device disclosed in Japanese Patent Publication No. Hei 
4-25174, the display by the light emitting device is made on a mirror 
surface and, therefore, distance between a driver's visual point and the 
display position is smaller than distance between the driver's visual 
point and an image in the rear of the vehicle reflected by the inner 
mirror. For this reason, the driver cannot focus his eye both at the 
display made by the light emitting device and at the image in the rear of 
the vehicle simultaneously and, accordingly, it is difficult for him to 
watch the display and the rear image simultaneously. The driver therefore 
is obliged to watch the display and the rear image alternately but this 
requires a large amount of shifting of the focus and hence focusing causes 
fatigue and trouble to the driver. 
For overcoming this problem, it is conceivable to provide the light 
emitting device at a deep position in the mirror body to prolong the 
distance between the driver's visual point and the light emitting display. 
This however requires extension of the depth of the mirror body with the 
result that such a deep mirror body will become an obstacle to driving. 
It is, therefore, an object of the invention to provide an inner mirror 
having a display device which, when information is displayed by light 
emitting display means provided in the inner mirror, enables an image in 
the rear of the vehicle and a light emitted display to be watched easily 
without shifting the driver's focus largely and without enlarging the size 
of the mirror body. 
SUMMARY OF THE INVENTION 
An inner mirror of a vehicle having a display device achieving the above 
described object of the invention comprises a mirror body, a rear view 
mirror provided in a front opening of the mirror body for reflecting an 
image in the rear of a vehicle back to a driver's visual point, an 
information display section provided within an area of the rear view 
mirror in the front opening of the mirror body or within an area adjacent 
to the area of the rear view mirror, light emitting display means provided 
in the mirror body for displaying visual information by emission of light, 
and an information display mirror provided in the mirror body for 
reflecting the visual information displayed by the light emitting display 
means back to the driver's visual point through the information display 
section. 
According to the invention, since the visual information displayed by the 
light emitting display means is reflected by the information display 
mirror back to the driver's visual point through the information display 
section, the display position of visual information can be extended away 
from the driver's visual point. Accordingly, the difference in distance 
between the image in the rear of the vehicle reflected by the rear view 
mirror and the visual information is minimized so that the rear image and 
the visual information can be watched simultaneously and easily. When the 
rear view and the visual information are watched alternately, the amount 
of shifting of focus is reduced so that the driver's focusing is 
facilitated and his fatigue and trouble are thereby mitigated. Besides, 
since an optical path is extended by reflection of the visual information 
by the information display mirror, the display position of the visual 
information can be extended away from the driver's visual point without 
enlarging the depth of the mirror body whereby enlargement of the mirror 
body can be prevented. 
In one aspect of the invention, the inner mirror further comprises slits 
for deviating the visual information displayed by the light emitting 
display means in the direction of the information display mirror. 
When light is emitted by the light emitting display means in the mirror 
body, light diffused in the mirror body is likely to disclose the inside 
state of the inner mirror to the driver. For preventing this, the slits 
are provided to deviate the visual information in the direction of the 
information display mirror. By this arrangement, diffusion of light is 
prevented and, therefore, disclosure of the inside state of the inner 
mirror to the driver is prevented. 
In another aspect of the invention, the visual information displayed by the 
light emitting display means is information relating to distance of an 
obstacle located in the rear of the vehicle. 
According to this aspect of the invention, the driver can recognize the 
distance of the obstacle located in the rear of the vehicle while watching 
the image in the rear of the vehicle and, therefore, he can easily drive 
the vehicle rearwardly for, e.g., putting it into the garage. 
Preferred embodiments of the invention will be described below with 
reference to the accompanying drawings.

DESCRIPTION OF PREFERRED EMBODIMENTS 
An embodiment of the invention will now be described. FIG. 1 shows an inner 
mirror 10 to which the invention has been applied with a part thereof seen 
through a mirror body 12. The inner mirror 10 is secured to a ceiling of a 
vehicle by means of a bracket 11 at an obliquely front and slightly upper 
position with respect to a driver. In the inner mirror 10, a rear view 
mirror 16 is fitted in a front opening 14 of the box-shaped mirror body 
12. An information display section 17 for transmitting visual information 
in formed in a part of the rear view mirror 16. 
A light emitting display section 18 is provided on a bottom surface 12a 
(FIG. 2) of the mirror body 12. The light emitting display section 18 is 
composed of, e.g., a 7-segment LED having a digit of 1 and a digit of 1 
decimal place, totalling 2 digits and an LED representing a unit "m". The 
display section 18 displays, by emission of light, information in a 
numerical value which represents distance of an obstacle located in the 
rear of the vehicle detected by an ultrasonic sensor attached to a rear 
bumper of the vehicle. The top surface of the light emitting display 
section 18 constitutes a light emitting display surface 18a. One or more 
slits 22 are defined by light shielding plates 24 for deviating visual 
information 20 (i.e., emitted light) in a particular direction (obliquely 
forward upper direction in the embodiment). 
In the deviated direction of the visual information 20 is provided an 
information display mirror 26. The information display mirror 26 reflects 
on its surface the visual information 20 emitted from the light emitting 
display section 18 and transmits the reflected visual information 20 to a 
driver's visual point 28. The optical path of the visual information 20 is 
extended in this manner by the information display mirror 26 and, 
therefore, a light emitted display 30 as viewed from the driver's visual 
point 28 is located behind a back surface 12b of the mirror body 12 with 
the result that distance of the light emitted display 30 from the visual 
point 28 is prolonged. Accordingly, the difference in the distance between 
the position of a rear image reflected by the rear view mirror 16 and the 
light emitted display 30 is reduced as compared with a case where the 
light emitting display 30 is made on a mirror surface of the rear view 
mirror 16, so that it becomes easier for the driver to watch both the 
light emitted display 30 and the rear image simultaneously whereby 
rearward driving of the vehicle for, e.g., putting it into a garage etc. 
is facilitated. Further, the slits 22 prevent diffusion of light in the 
mirror body 12 and thereby prevents disclosure of the inside of the mirror 
body 12 to the driver. Moreover, the slits 22 prevent the light emitting 
surface 18a of the light emitting display section 18 from being exposed 
directly to the driver's eye. Further, by arranging the slits 22 suitably, 
it is possible to restrict a range of reaching of the visual information 
20 to the direction of the driver. 
Another example of the information display section 17 is shown in FIG. 4. 
In this example, the rear view mirror 16 is made of a half mirror. More 
specifically, the rear view mirror 16 is composed of a glass substrate 36, 
a half transmitting reflecting film 40 attached to the entire back surface 
of the glass substrate 36 and a black coated film 42 coated on the back 
surface of the half transmitting reflecting film 40. A part 42a of the 
black coated film 42 is removed to constitute the information display 
section 17 through which the visual information 20 is transmitted 
outwardly. 
In the above described embodiments, a plane mirror is used as the 
information display mirror 26. Alternatively, as shown in FIG. 5, the 
information display mirror 26 may be constructed of a convex mirror 26' 
curved in the vertical direction. In this case, the optical path of the 
visual information 20 can be prolonged further. 
In the above described embodiments, information relating to an obstacle is 
displayed by numerical value information but this information may be 
displayed by graphic information or information according to which a 
warning light is lighted when the vehicle has approached a point which is 
at a predetermined distance from an obstacle. 
This invention is applicable to devices displaying various information 
other than the information representing an obstacle located in the rear of 
a vehicle. Such information includes, for example, clearance information 
representing clearance between four corners of a vehicle and an obstacle 
which has been detected by a clearance detecting ultrasonic transmitter. 
Even when information is unrelated to a rear image (i.e., information with 
which it is not necessary to watch a rear image), the advantageous effect 
of facilitating watching of the information obtained by prolonging the 
display position of the information can be obtained. As the light emitting 
display means, not only an LED but various other types of light emitting 
display means such as a fluorescent character display tube and a liquid 
crystal may be used.