Display apparatus for elevator car

A display apparatus has a light modulator with an electrooptical Pockels cell disposed in a machine room to modulate a laser beam with a modulating signal from a signal source as determined by a piece of image information to be displayed. After its passage through an optical fiber, the modulated laser beam enters an elevator car where it is focussed on a horizontal deflector by a diminishing lens and then reflected to be focussed on a vertical deflector by a collecting lens. The focussed laser beam is collected on an inner surface of an elevator door by an objective lens. Each deflector is a galvanometer mirror attached to a coil and horizontally or vertically deflecting the laser beam through an angle proportional to a saw tooth current flowing through the coil under the control of the signal source. This results in the display of the piece of image information on the inner surface of the elevator door.

BACKGROUND OF THE INVENTION 
This invention relates to improvements in a display apparatus for 
displaying an image information within an elevator car. 
A known display apparatus of the type referred to has been located within a 
box-shaped housing having an end open and detachably closed with a thin 
transparent cover and fixed at that end opposing to the open end to an 
upper-portion of an operating board disposed on one of two opposite 
lateral walls defining an entrance of an elevator car therebetween. The 
display apparatus is of a projection type and has comprised a projection 
screen applied to the inner surface of the thin transparent cover, and a 
plurality of projection lamps, for example, three lamps disposed at 
predetermined equal intervals adjacent to the end of the housing fixed to 
the operating board to be substantially equidistant from the projection 
screen. Disposed between the projection screen and each of the projection 
lamps have been an image printed film and a projection lens for the film. 
The films and the projection lenses have been positioned so that the 
images on all the films are selectively focussed on a common area of the 
projection screen by means of the associated projection lenses to be 
displayed to a passenger or passengers within the elevator car as 
different pieces of image information. 
The projection lamps have been connected to a signal source disposed on a 
stationary part for example, in a machine room for the elevator car 
through respective electrical conductors included in a tail cord extending 
between the elevator car and the stationary part. 
When the signal source fires a selected one of the projection lamps, the 
image on that film irradiated with the fired lamp is projected and 
focussed on the projection screen by means of the associated projection 
lens to be exhibited to a passenger or passengers within the elevator car 
as a piece of image information intended to be displayed to the passenger 
or passengers. Also by selectively firing the projection lamps, a 
plurality of pieces of image information or displayed contents can be 
selected. 
However, the projection type display apparatus as described above have been 
disadvantageous in the following respects: A space of the operating board 
given by the projection screen is limited and also the projection lamps 
and the image printed films should be arranged in a limited space. Thus 
the number of the projection lamps and that of the image printed films 
have limited the number of different pieces of information to be 
displayed. Furthermore, upon a change in pieces of image information, an 
attendant in charge had been necessary to go to the elevator car in order 
to exchange the image printed film resulting in a troublesome job. 
Moreover since the projection screen is required to be disposed in a 
limited place, there has been a fear that the projection screen is out of 
a visual field or fields of a passenger or passengers within the elevator 
car. 
Accordingly it is an object of the present invention to provide a new and 
improved display apparatus for an elevator car enabled to selectively 
display different pieces of image information without a limitation due to 
the number of the pieces of image information. 
It is another object of the present invention to provide a new and improved 
display apparatus for an elevator car in which a piece or pieces of image 
information to be displayed can readily be changed without a necessity of 
causing an attendant in charge to go to the elevator car. 
It is still another object of the present invention to provide a new and 
improved display apparatus for an elevator car difficult to be subjected 
to a limitation due to a visual field or fields of a passenger or 
passengers within the elevator car. 
SUMMARY OF THE INVENTION 
The present invention provides an apparatus for displaying image 
information within an elevator car, comprising a projector disposed in an 
elevator car and formed of a light deflector, a diminishing lens disposed 
on an entrance side of the light deflector and an objective lens disposed 
on an exit side thereof; a laser disposed on a stationary part for an 
elevator system including the elevator car to form a light source for 
generating a light beam, a signal source disposed on the stationary part 
to generate a modulating signal as determined by a piece of image 
information to be displayed, a light modulator disposed on the stationary 
part to modulate the light beam from the light source with the modulating 
signal from the signal source; an optical fiber for leading the modulated 
light beam from the light modulator to the diminishing lens included in 
the projector, and a set of electrical conductors for connecting the 
signal source to the light deflector; the arrangement being such that the 
light beam deflected by the light deflector is focussed on an inner 
surface of the elevator car by means of the objective lens.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to FIG. 1 of the drawings, there is illustrated a display 
apparatus according to one embodiment of the present invention. The 
arrangement illustrated comprises an elevator car 10 including an entrance 
defined by a pair of lateral walls 12 closed when a pair of opposite 
sliding doors 14 abut against each other. The entrance is opened when the 
sliding doors 14 are moved away from each other. An operating board 16 is 
disposed on one of the lateral walls 14, in this case, the righthand 
lateral wall 12 as viewed in FIG. 1. 
In FIG. 1, a projector generally designated by the reference numeral 18 is 
shown as being fixed to the central portion of the upper inner wall 
surface of the elevator car 10 facing the entrance thereof so as to 
contact the adjacent portion of a ceiling (not shown) of the elevator car 
10. The projector 18 includes light deflector 20, a diminishing lens 22 
located on the entrance side of the deflector 20 adjacent to the wall of 
the elevator car 10 to which the projector 18 is fixed, and an objective 
lens 24 on the exit side thereof opposite to the entrance of the elevator 
car 10 to form a rectangular projection field 26 occupying the substantial 
portion of the upper inner surfaces of the sliding doors 14 put in their 
closed position for the purpose as will be apparent later. 
The display apparatus further comprises a signal source 28, a light 
modulator 30 and a laser 32 as a light source disposed on a stationary 
part 34, for example, in a machine room for the elevator car 10. The 
signal source 28 drives the light modulator 30 and is connected to the 
light deflector 20 through a set of electrical conductors 36 to drive the 
light deflector 20. The light modulator 30 is optically coupled to the 
diminishing lens 22 through an optical fiber. To this end the optical 
fiber 38 has one end opposing to the diminishinq lens 22, although that 
end of the optical fiber 38 is not illustrated only for the purposes of 
illustration. 
As shown in FIG. 1, a tail cord 40 has included therein those portions of 
the electrical conductors 36 and the optical fiber 38 extending between 
the elevator car 10 and the stationary part 34. 
In the operation the light source or the laser 32 disposed on the 
stationary part 34 generates a laser beam while the signal source 28 
applies to the light modulator 30 a modulating signal from a video signal 
generator (not shown) or the like selected in accordance with a piece of 
image information to be displayed. Thus the light modulator 30 modulates 
the laser or light beam from the laser 32 with the modulating signal 
applied thereto from the signal source 20 to form an amplitude modulated 
light beam. The amplitude modulated light beam is entered into the optical 
fiber 38 and then reaches the diminishing lens 22 included in the 
projector 18 disposed within the elevator car 10. The diminishing lens 22 
collects the modulated light beam on the light deflector 20. 
At that time, the light deflector 20 receives a scanning signal generated 
by the signal source 28 and passed through the set of electrical 
conductors 36 to be driven. Thus the light deflector 20 deflects the light 
beam collected thereon in the horizontal direction and simultaneously in 
the vertical direction. The objective lens 24 collects the light beam thus 
scanned in the horizontal and vertical directions on the projection field 
26 on the upper, inner surfaces of the sliding doors 14 in their closed 
positions. 
From the foregoing it is seen that the sliding doors 14 in their closed 
positions have an image displayed on the upper inner surfaces thereof with 
the light beam modulated by the light modulator 30 and then subjected to a 
raster or a random scan. The image thus displayed can be viewed by a 
passenger or passengers within the elevator car 10. 
In the arrangement shown in FIG. 1, a piece of image information or a 
displayed content can be changed only by changing video signal by the 
signal source 28 disposed on the stationary part 34 without the necessity 
of causing an attendant in charge to go to the elevator car to change on 
image printed film or films as in the conventional display apparatus as 
described above. Therefore a displayed contents can readily be changed 
even with the number and types of displayed contents large. Also the 
displayed field can utilize a wide area of the sliding doors in their 
closed positions and therefore a visual field or fields of a passenger or 
passengers within the elevator car is or are less subjected to a 
limitation due to the displayed field. 
FIG. 2 shows, by way of example, the details of the light modulator 30 
illustrated in FIG. 1. The arrangement illustrated utilizes the Pockels 
effect, and comprises the light modulator 30 disposed between the laser 32 
and the optical fiber 36 to be aligned with one another in a common 
optical axis. A laser beam 32a generated from the laser 32 is not 
polarized but it passes through a polarizer 30a to change to a linearly 
polarized light beam 32b which is, in turn, incident upon a 
quarter-wavelength plate 30b. The quarter-wavelength plate 30b may be 
formed of a material exhibiting a spontaneous birefrigerance, for example, 
a quartz or a mica. The linearly polarized light beam 32b passes through 
the quarter-wavelength plate 30b to change a circularly polarized light 
beam 32c which is, in turn, applied to an electrooptical Pockels cell 
modulator 30c. The Pockels cell modulator 30c is formed, for example, of a 
single crystal Bi.sub.12 SiO.sub.20 and includes a pair of transparent 
electrodes attached to the entrance and exit ends thereof and connected 
across the signal source 28 showing as an AC type. The electrooptic 
crystal has a pair of refractive indices in two orthogonal directions in a 
plane perpendicular to a direction in which a voltage is applied 
thereacross, variable in accordance with a magnitude of the applied 
voltage. After having passed through the electrooptical Pockels cell 30c, 
the circularly polarized light beam 32c is changed to an elliptically 
polarized light beam 32d which, in turn, falls on an analyser 30d. A light 
beam 32e leaving the analyzer 30d has an intensity or an amplitude 
variable in accordance with the magnitude of the voltage applied across 
the electrooptic Pockels cell 30c is entered into the optical fiber 38. 
In other word, the laser beam 32a with a constant output generated by the 
laser 32 is changed to an amplitude modulated light beam 32e which is, in 
turn, applied to the optical fiber 38. 
The amplitude modulated light beam 32e is passed through the optical fiber 
38 and incident upon the diminishing lens 22 included in the projector 18 
disposed in the elevator car 10. 
FIG. 3 shows, by way of example, the details of the projector 18 including 
the light deflector 20 which utilizes galvanometer mirror. Thus the 
projector 18 also functions as a light scanner. As shown in FIG. 3, the 
amplitude modulated light beam 32e is focussed on an X galvanometer mirror 
20a by the diminishing lens 22. The mirror 20a is fixedly connected to an 
X galvanometer coil 20b and the resulting connection is arranged in a 
spanned state along a vertical axis as viewed in FIG. 3 through a spring 
so as to be rotatable about the vertical axis. 
The light beam 32e focussed on the X mirror 30a is reflected therefrom 
toward a collecting lens 20c which, in turn, focusses the reflected light 
beam on a Y galvanometer mirror 20d. The mirror 20d is fixedly connected 
to a Y galvanometer coil 20e and the resulting connection is arranged in a 
spanned state along a horizontal axis as viewed in FIG. 3 through a spring 
so as to be rotatable about the horizontal axis. 
The light beam focussed on the Y mirror 20d is again reflected therefrom 
toward the objective lens 24, which, in turn, focusses the reflected light 
beam on the projection field 26 on the upper, inner surfaces of the 
sliding doors 14 in their closed positions. 
As shown in FIG. 3, a horizontal and a vertical deflection circuit 42 and 
44 respectively are connected to the X and Y coils 20b and 20e 
respectively to supply saw tooth currents thereto respectively under the 
control of synchronizing signals generated by a synchronizing signal 
generator 46. The synchronizing signal generator 46 is connected to the 
signal source 28 disposed on the stationary part 34 through the set of 
electrical conductor 36 to be put in synchronization with the signal 
source 28. 
The deflection circuits 42 and 44 and the synchronizing signal generator 46 
may be similar to those used with conventional television receivers. 
The X coil 20b and therefore the X mirror 20a is deflected through a 
rotational angle as determined by the saw tooth current flowing through 
the coil 20b and about the vertical axis as described above. Thus the 
light beam scans a horizontal line extending along the X axis on the 
projection field 26 as shown on the lower portion in FIG. 3. 
Similarly the Y coil 20e and therefore the Y mirror 20d is deflected 
through a rotational angle as determined by the saw tooth current flowing 
through the coil 20e and about the horizontal axis as described above. 
Thus the light beam scans the projection field 26 in a vertical direction 
or along the Y axis as shown on the lower portion in FIG. 3. 
It is noted that if an image from the projector 18 fails to be accurately 
projected on the projection field 26, a trapezoid or a trapezium 
deformation results. This trapezoid or trapezium deformation can be 
compensated for by the objective lens 24. Alternatively such a deformation 
may be compensated for by modulating an angle of deflection of the mirror 
in the X direction with a Y signal. 
FIG. 4 shows one example of a piece of image information or a displayed 
content is projected on the projection field 26 which reads 
"EXHIBITION SITE IS AT 6-TH FLOOR". 
This displayed content can lead a passenger or passengers within the 
elevator car to the exhibition site without any misguiding. 
While the present invention has been illustrated and described in 
conjunction with a single preferred embodiment thereof it is to be 
understood that numerous changes and modifications may be resorted to 
without departing from the spirit and scope of the present invention. For 
example, pieces of image informations including figure patterns other than 
letters can be selectively displayed on the projection field. While one 
embodiment of the present invention has been illustrated and described in 
conjunction with the projection of a laser beam on a door for an elevator 
car, it is to be understood that the projector can be mounted to a wall 
surface of the elevator car different from that facing the entrance 
thereof. In the latter case the projection field can be formed on a wall 
surface of the elevator car opposing to the wall surface to which the 
projector is mounted. Also a pair of projectors may be used to 
simultaneously display different pieces of image information on the 
surface of a door and on the wall surface orthogonal to the door's 
surface. Furthermore a plurality of elevator cars may be operatively 
associated with a single set of the laser, the light modulator and the 
signal source disposed on the stationary part so as to cause each of 
projectors disposed in the respective elevator cars to effect a display. 
Moreover while the present invention is has been discribed in terms of the 
stationary part disposed in the machine room it is to be understood that 
the same is not limited thereto or thereby and the it is equally 
applicable to the stationary part located on a supervision board disposed 
in a supervision room for the elevator car. Also while the present 
invention has been illustrated and described in conjunction with the 
optical fiber 38 it is to be understood that the optical fiber may be 
replaced by a bundle into which a multitude of optical fibers are 
arranged.