Over-door interphone system provided with a night-vision monitoring device

An over-door interphone system for telephonic communication between a master station unit inside of a house and a remote station unit outside of an entrance door of the house is provided with a night-vision monitoring device. The night-vision monitoring device has a television camera comprising a solid-state camera sensitive to an infrared light. The solid-state camera is responsible for successfully incorporating the television camera within a less bulky housing of the remote station unit as well as for monitoring the image of a visitor by the camera without being noticed. Also, there can be utilized an illumination device producing an infrared which is hardly perceived by the visitor, ensuring monitoring of the visitor at night without a giving unfavorable impression thereto. The illumination device may be driven to operate for a predetermined period of time starting from the actuation of a calling switch, or a communication interval from the actuation of the calling switch to the hangup of a handset on the master station unit. The illumination device may be also driven in response to the actuation of an illumination operating switch or to a low illuminance level of the object. Thus, the illumination device can be operated with a minimum power requirement. The illumination device is controlled to operate in synchronous with the video signal from the television camera, providing an effective monitoring illumination free from flicker.

TECHNICAL FIELD 
The present invention is directed to an over-door interphone system for a 
telephonic intercommunication between inside and outside of a house, and 
more particularly to an over-door interphone system provided with a 
night-vision monitoring device. 
BACKGROUND ART 
It is well known that a conventional interphone system includes a master 
station inside a house and a remote station installed at an entrance of 
the house. The stations are electrically connected for a telephonic 
intercommunication between a visitor and an occupant of the house upon 
operation of a system actuation switch provided at the remote station. 
However, this interphone system, has often been unsatisfactory for the 
house occupant to surely indentify the visitor, because the personal 
identification is made only through the telephonic or verbal 
intercommunication. 
For elimination of the above problem, there has been an attempt made to 
annex a video monitor subsystem to a conventional telephonic 
intercommunication system as shown in FIG. 1 to obtain a more ensured 
identification of the visitor with the aid of visual information. The 
conventional video monitor subsystem includes a tube type television 
camera 4 such as a vidicon installed near the remote station at the 
entrance for picking up the facial image of the visitor and a video 
monitor display installed at the master station for displaying the image 
thereon to provide a helpful visual information for the house occupant. 
The above system, however, has been problematic for the reason that the 
television camera 4 tends to give an offensive impression to the visitor 
with its relatively bulky and conspicuous appearance. It has of course 
been tried to integrate the vidicon type television camera 4 into the 
housing of the remote station 1 for alleviation of such an unfavorable 
factor, which conversely leads to another problem that the vidicon type 
television camera 4 requires renewal every certain period due to burning 
of the image plate thereof. The vidicon type television camera 4 
integrated into the housing of the remote station brings about the further 
problem that it necessitates a control circuit provided close thereto 
controlling the convergence of the electron beam and so forth, which 
inevitably ends in the increase in size of the housing of the remote 
station. More precisely as shown in FIG. 2, the vidicon type television 
camera 4 occupies a considerable amount of the total internal space of the 
housing 6 of the remote station 1 even with respect to an audio unit U and 
requires an optical opening of a relatively large size, which again ends 
in bulky and conspicuous appearance of the remote station 1 giving an 
unfavorable impression to the visitor. 
In addition, the vidicon type television camera 4 being innately designed 
to be sensitive only to visible daylight is generally operated at night 
with the assistance of an illumination device to obtain an image of a 
sufficient brightness, which may induce a far more repugnance of the 
visitor thereaganist with a feeling of being subjected to severe 
observation. Such an illumination device 44 has been conventionally 
mounted or integrated with the television camera 4 within the remote 
station installed at the entrance as shown in FIG. 2, where the 
illumination device 44 occupies a greater amount of space to provide light 
of a sufficient illuminance, which also ends in the dimensional increase 
of the remote station marring the appearance around the entrance of the 
house. 
Although it is expedient to adopt an image orthicon sensitive to an 
infrared light for the television camera 4 to overcome the above problem, 
the adoption of the image orthicon still accompanies the dimensional 
increase of the remote station as well as the same drawbacks inherent to 
the vidicon with a practically prohibitive cost for use by the general 
public. 
There is a color camera device sensitive to light of relatively low 
illuminance as disclosed in the unexamined Japanese Utility Model 
Publication No. 55-166617. However, such a color camera device is 
unbenefitting for the interphone of home use because it employs an 
instrument generally referred to as the image intensifier being which is 
too large and expensive. 
In consideration of the above-mentioned problems, the present invention is 
made to provide an interphone system with an improved video monitor 
subsystem. 
DISCLOSURE OF THE INVENTION 
An oven-door interphone system provided with a night vision monitoring 
device in accordance with a first form of the present invention includes a 
master station unit located inside of a house and a remote station unit 
located outside of an entrance door of the house. The station, units are 
connected for telecommunication between a visitor and a dweller. The 
remote station unit includes a housing and a television camera which is 
mounted within the housing to comprise an optical unit including a solid 
state camera sensitive to infrared light and optical lens means device 
disposed in front thereof. Also included in the remote station unit are a 
control circuit device mounted adjacent to the optical unit for 
controlling the same, a call switch device within the housing for calling 
the master station unit, and a telecommunication device within the housing 
for telephonic intercommunication betweeen the master and remote station 
units. The master station unit comprises a video display for monitoring 
the image of the visitor picked up by the televison camera. Since the 
solid state camera is sensitive to infrared light as well as to visible 
light, it is capable of obtaining a video signal for a visitor so as to 
monitor the video image thereof on the video display of the master station 
unit even at night without being noticed by the visitor. The solid state 
camera eliminates a particular control circuit for converging the electron 
beam which is indispensable in the conventional camera tubes and makes it 
possible to be disposed away from a control circuit for processing the 
scan and video signals thereof. Further, since the solid state camera 
defines its target site on its element surface, the distance between the 
optical lens device and the target site of the solid camera can be reduced 
while the target site area is kept relatively small. All of the above 
contribute to the realization of a small-sized television camera of 
reduced depth which is readily incorporated in the housing of the remote 
station unit and particularly suitable for the over-door interphone 
system. 
In the night-vision monitoring device for the over-door interphone system 
in accordance with the first form of the present invention, the television 
camera is composed of the optical unit having the solid state camera 
sensitive to infrared light and the optical lens device placed in front 
thereof and of the control circuit device disposed around the optical 
unit. This enables the use of a small sized optical unit as well as 
enabels the control circuit device to be disposed separately from the 
optical lens device and the solid state camera. This allows the television 
camera to be made compact in size so that the camera can be successfully 
incorporated within the housing of the remote station unit which is of a 
relatively small size and of an appearance closer to the conventional 
remote station unit. Thus, it is possible to pick up the image of the 
visitor for monitoring the same on the display of the master station unit 
without giving an obtrusive impression to the visitor. Further, the 
picking up of the visitor's image can be made even at night without being 
noticed by the visitor with the aid of the infrared light to which the 
solid state camera is sensitive. 
Another advantageous feature disclosed in the first form of the present 
invention is that the the television camera can capture the facial image 
of the visitor who comes close to the remote station unit with visitor's 
hand manipulating the pushbutton on the front of the housing of the unit 
for successfully identifying the visitor. To this end, the viewing range 
of the television camera is set so as to cover the face and its vicinity 
of the visitor who is in a position with a hand extending onto the 
pushbuttom of the call switch device for manipulation thereof, whereby the 
television camera can pick up the facial image of the visitor for 
identification on the video display. 
A second form of the present invention discloses an infrared light emitting 
illumination device added to the construction of the first form of the 
present invention for an illumination purpose. The infrared light emitting 
illumination device is mounted on the side of the remote station unit and 
produces the invisible infrared light, enabling night-vision monitoring 
without being noticed by the visitor. 
With the provision of the infrared light emitting illumination device, the 
second form of the present invention is capable of producing the infrared 
light for illuminating the visitor at night without being noticed thereby 
so as to successfully pick up the image of the visitor at night without 
suffering from illumination deficiency by better utilization of the 
characteristic of the solid state camera being sensitive to the infrared 
light. 
Another advantageous feature of the second form of the present invention is 
to provide an effective illumination and prevent the illumination from 
being totally inoperative in case of possible failure occurring in a 
particular illumination circuit thereof. To this end, there are utilized 
as the infrared light emitting illumination device a plurality of infrared 
light emitting diodes which are divided into a plurality of groups in each 
of which the idodes are series connected. The groups of the diodes are 
connected in parallel circuit relation to the output of an illumination 
control device so as to produce the light efficiently with a number of the 
series connected diodes as well as to protect against total illumination 
failure even if one of the diodes is broken down, ensuring the constant 
and stable monitoring of the visitor. 
A further advantageous feature of the second form of the invention is to 
control the illuminating operation of the infrared light emitting 
illumination device in proportion to the environmental illumination level. 
To this end, there is employed an illumination control device for 
controlling the infrared light emitting illumination device. The 
illumination control device is arranged to provide an output for driving 
the infrared light emitting illumination device when it determines based 
upon the video signal from the television camera that the illumination 
level of the object to the monitored is lower than a predetermined level. 
With this arrangement, the television camera can be best utilized to sense 
the environment illumination level, enabling the illumination control 
device to be made simple and at a low cost, yet assuring optimum 
illumination control based upon the video signal from the television 
camera. 
A still further advantageous feature of the second form of the present 
invention is to intermittently drive the infrared light emitting 
illumination device in synchronism with the video signal from the 
television camera when the sensed environment illumination level around 
the remote station unit is determined to be lower than a predetermined 
level. To this end, the illumination control circuit is so arranged as to 
intermittently drive the infrared light emitting illumination device in 
synchronism with the video signal from the television camera when the 
sensed environmental illumination level around the remote station unit is 
below the predetermined level, enabling the infrared light emitting 
illumination device to be driven only when there is an insufficient 
illumination level for the television camera, yet reducing the power 
requirement with this intermittent driving operation. 
A further advantageous feature of the second form of the present invention 
is to make the infrared light emitting illumination device unnoticeable by 
the visitor as well as to facilitate the installation and handling 
thereof. For this purpose, the infrared light emitting illumination device 
is incorporated within the housing of the remote station unit such that 
the infrared light emitting illumination device is concealed within the 
housing from the eyes of the visitor as well as that it is held in 
position simulaneously with the installation of the remote station unit. 
The other feature of the second form is that the installation place of the 
infrared light emitting illumination device can be arbitrarily determined 
with respect to that of the remote station unit. For obtainment of this 
effect, the present form adopts the construction that the infrared light 
emitting illumination device is designed to be mountable on a joinder 
device electrically and mechanically connected to the remote station unit 
in a detachable manner. With this construction the infrared light emitting 
illumination device can be detached from the jointed device when the 
environmental illuminance is sufficient by virtue of another night 
illumination device such as a street lamp or a porch lamp. The infrared 
light emitting illumination device is used as being mounted on the joinder 
device when no other illumination device is available thereabout. Thus in 
either case a safe and secured pickup of the image of the visitor at night 
can be attained without being noticed by the visitor. 
A third form of the present invention has its basic construction as 
discussed on the second form, and further includes an illumination control 
device for controlling the infrared light emitting illumination device for 
a predetermined period from the operation of the call switch device 
provided at the remote station unit. The illumination control means device 
to operate the infrared light emitting illumination device upon the 
operation of the call switch device by the visitor for the predetermined 
period to achieve an ensured image pickup at night where the environmental 
illumunance is insufficient. 
The third form of the above construction has the effect of operating the 
infrared light emitting illumination device automatically upon the 
operation of call switch device by the visitor having no connection with 
the master station unit while eliminating useless consumption of the 
electric power. 
A fourth form of the present invention has its basic construction as 
discussed on the second form and further includes an illumination operator 
device on the side of the master station unit. The illumination operator 
means is operated by the house occupant through monitoring the face image 
of the visitor. 
The fourth form of the above construction has the effect that the 
illumination can be controlled on the side of the master station unit by 
the house occupant in accordance with the environmental illuminance level 
around the remote station unit, the presence of a reflection light and so 
forth to obtain an ensured image pickup with the television camera. 
Another feature of the fourth form of the present invention is that the 
operation of the infrared light emitting illumination device is continued 
until the hand set of the master station is restored or put back to the 
hang-up position thereof. For establishment of this construction an 
illumination operator device is provided on the side of the master station 
unit, by which the infrared light emitting illumination device is made to 
be operated from the actuation of call switch device to the restoration of 
the hand set of the master station unit. Adoption of this construction 
enables an automatic operation of the infrared light emitting illumination 
device in connection with the call switch device and the hand set to 
facilitate the operation of the interphone system. In consequence the 
switching of the power of the infrared light emitting illumination device 
can be well managed without fail to curtail wasteful power consumption.

PREFERRED EMBODIMENTS FOR CARRYING OUT THE PRESENT INVENTION. 
The following discusses several embodiments of the present invention in 
detail based on the drawings. 
EMBODIMENT 1 
An over-door interphone system in accordance with the first embodiment of 
the present invention comprises a remote station unit 1 installed at an 
entrance of a house, a master station unit 2 installed inside the house 
and a signal transmission line 3 comprising an audio signal line and a 
video signal line connecting the remote station unit 1 and the master 
station unit 2 as shown in FIG. 3. The master station unit 2 comprises a 
video display 42 on which an object image obtained from a television 
camera 4 mounted in the remote station unit 1 is displayed and a hand set 
5 for telecommunication with the remote station unit 1. 
The remote station unit 1 includes a television camera 4, a call switch 7, 
a speaker 8, a microphone 9 necessary for the telecommunication means and 
so forth in a housing 6 thereof as shown in FIGS. 4 to 6. The housing 6 
consists of a cover 61, a chassis 62 and a base 63. The base 63 is 
provided with terminals 43 to which the signal transmission line 3 and a 
power supply line are connected. The television camera 4 is composed of an 
optical unit 10 which is coupled to a printed board 15 carrying thereon 
solid state camera 14 of CCD or MOS type by means of coil springs 12 and 
screws 13 passing therethrough. The coil springs 12 are provided to hold 
the optical unit 10 and the solid state camera 14 mounted on the printed 
board 15 in a suitable distance, whereby an object image is focused on the 
photosensitive target site of the solid state camera 14 through an optical 
lens means 101 of the optical unit 10. As shown in FIG. 7, the optical 
unit 10 includes a printed 11 mounting centrally thereof a casing 102 
covers the solid state camera 14 on the printed board 15, and includes the 
optical lens means 101 received in the front opening of the casing 102. A 
light entering through the optical lens means 101 will pass inside of the 
casing 102 and through an opening (not shown) formed in the printed board 
11 to be focused on the target site of the solid state camera 14 on the 
printed board 15. A display controller 34 for the television camera 4 
including the optical unit 10 and the solid state camera 14 is formed on a 
printed board 18 mounted at a location sideward of the optical unit 10 and 
behind the speaker 8 for arranging the television camera 4 to have a 
reduced thickness. On either side of the casing 102 there are formed a 
suitable number of infrared light emitting diodes 16 producing infrared 
light for an illumination purpose. These infrared light emitting diodes 16 
are preferably divided into groups A and B located respectively on both 
sides of the casing 102 with the infrared light emitting diodes 16 being 
series connected in each group. As shown in FIG. 8, the infrared light 
emitting diodes 16 forming the groups A and B are connected in parallel 
relation to an illumination controller 25 such that one circuit of the 
diode groups will operate to produce enough amount of illumination even if 
the other fails, providing safequard against total illumination failure. 
An infrared light transmissive filter 33 is provided in an opening 61a of 
the cover 61 located in front of the optical unit 10 and the infrared 
light emitting diodes 16 in order to conceal the television camera 4 as 
well as the infrared light emitting diodes 16 from the eyes of the 
visitor. 
The printed board 18 carrier the illumination controller 25 other than the 
display controller 34, while a printed board 18a beside the printed board 
18 carries the call switch 7 for actuating the interphone system, the 
printed boards 18 and 18a being fixed to bosses 19 and 19a provided on the 
interior of the cover 61. A pushbutton 71 for the call switch 7 is urged 
by means of a coil spring 22 to project outwardly through a window 21 in 
the cover 61, the coil spring 22 being wound around a rib 72 projecting on 
the rear the pushbotton 71 and compressed between the enclosure of the 
call switch 7 and the pushbotton 71. When the pushbotton 71 is pressed 
against the bias of the coil spring 22, it pivots about an axis F1 to push 
an actuator button 73 of the call switch 7 at the end of the rib 72, 
actuating the call switch 7. On the other hand, there is provided in the 
center of the pushbotton 71 a window 74 for passing therethrought ligh 
emitted from a position indicating light emitting diode 23 provided on the 
printed board 18. The speaker 8 for outputting a verbal message from the 
master station unit 2 is heat-welded to the cover 61 through a water-tight 
packing 20 while a microphone 9 for dispatching a verbal message from the 
remote station unit 1 is put in a rubber case 40 which is received in a 
cavity 24 of the cover 61 with a waterproof packing 41 interposed 
therebetween as shown in FIG. 9. 
The infrared light emitting diodes 16 are controlled by the illumination 
controller 25. The illumination controller 25 has a circuit configuration, 
as shown in FIG. 10 that a synchronizing signal from a camera 
synchronizing signal generator 26 is amplified in a signal amplifier 27 
and then output to drive the infrared light emitting diodes 16 for a 
predetermined period set up in a timer 28. The infrared light emitting 
diodes 16 are driven to ensure a sufficient illuminance level in an 
intermittent manner generating no flicker under the control of the 
synchronizing signal in a synchronous relation with the input of a trigger 
signal from a calling circuit 29 in response to the call switch 7 for a 
predetermined period set up in a time variable setting section 30 provided 
at the master station unit 2. The trigger signal to the timer 28 is 
rendered valid only when the latter receives from an illumination level 
discriminator 31 a signal indicative of insufficient environmental 
illumination level (which signal is referred to as a "dark signal" 
hereinafter). The illumination level discriminator 31 produces the dark 
signal when it determines based upon a video signal from a video signal 
amplifier 32 of the television camera 4 whether the illuminance of the 
object image (facial image of the visitor) ia lower than a predetermined 
level. 
In this end, when the visitor operates the pushbotton 71 to actuate the 
call switch 7, a telecommunication circuit is set on operation to start 
calling and communicating in the same manner as in the conventional 
over-door interphone system, and simultaneously the timer 28 acts to 
initiate the illumination by the infrared light emitting diodes 16 for the 
predetermined period of time when the illumination level discriminator 31 
determines that there is insufficient illuminance level. 
When a visitor pushes the pushbotton 71 to actuate the call switch 7, the 
telecommunication circuit is ready for calling and communication 
operations. At this occurrence, the calling circuit 29 activates the 
camera synchronizing signal generator 26 which responds to drive the 
display controller 34 of the television camera 4 and the video display 42 
of the master station unit 2, and to drive the infrared light emitting 
diodes 16 for intermittently producing the light and simultaneously 
provides the trigger signal to the timer 28. Upon this consequence, the 
illumination level discriminator 31 determines the illuminance level of 
the face of the visitor based upon the level of the output signal from the 
video signal amplifier 32 of the television camera 4 so that it produces 
the dark signal when the illumination level is determined to be lower than 
a predetermined minimum level for satisfactory monitoring, allowing the 
trigger signal to be fed to the timer 28. When there is a sufficient 
illumination level, the dark signal is not produced so as to disable the 
trigger signal to be fed to the timer 28. Accordingly, the infrared light 
emitting diodes 16 can be driven for a predetermined period of time 
determined by the timer 28 only when the pushbotton 71 is pressed and the 
illumination level is determined to be insufficient based upon the output 
of the television camera 4. It is noted at this time the television camera 
4 has a viewing range such that it has a focus on the face of the visitor 
who is in a position with a hand extending onto the pushbutton 71 for 
manipulation thereof, ensuring satisfactory moritoring of the facial image 
of the visitor with a sufficient illumination. 
EMBODIMENT 2 
As shown in FIG. 11, the present embodiment contemplates that the timer 28 
is always actuated by the trigger signal from the calling circuit 29 to 
produce the light for a predetermined period of time starting from the 
actuation of the call switch 7, irrespective of the illumination level of 
the object image, in contrast to the above first embodiment in which the 
illumination controller 25 is arranged to include the video signal 
amplifier 32 and the illumination level discriminator 31 for defining the 
trigger signal from the calling circuit 29 as a valid signal for driving 
the timer 29 only when the illumination level of the object image is below 
the predetermined level. 
EMBODIMENT 3 
As shown in FIG. 12, the illumination controller 25 of the present 
embodiment is arranged so that the camera synchronizing signal generator 
26 responds to the trigger signal from the calling circuit 29 for driving 
the infrared light emitting diodes 16 in synchronous with the video signal 
of the television camera 4 until it receives from a handset detector 35 a 
signal indicative of the handset 5 being hung up of the master station 
unit 2 after termination of the telecommunication, which is in contrast to 
the above embodiments 1 and 2 in which the illumination controller 25 is 
arranged to include the timer 28 for driving the infrared light emitting 
diodes 16 for the predetermined period of time. 
EMBODIMENT 4 
As shown in FIG 13, the present embodiment discloses the illumination 
controller 25 which is similar to that of the previous embodiment in that 
the camera synchronizing signal generator 26 responds to the output of the 
calling circuit 29 for producing a synchronizing signal to a display 
controller 34 which in turn control the television camera 4. But, the 
infrared light emitting diodes 16 are driven by the amplified signal 
originating from the camera synchronizing signal generator 26 and are kept 
producing the light only while an operation switch 36 provided as the 
illumination operator means on the side of the master station unit 2 is 
manipulated. 
EMBODIMENT 5 
As shown in FIG. 14, the present embodiment includes an illumination device 
37 which is separately formed from the housing 6 of the remote station 
unit 1 and incorporates the infrared light emitting diodes 16, the 
illumination device 37 being electrically and mechanically connected in a 
detachable manner to a joinder 38 located adjacent to the remote station 
unit 1, which is in contrast to the previous embodiment 1 in which the 
infrared light emitting diodes 16 are incorporated within the housing 6 of 
the remote station unit 1. That is , the present embodiment allows the 
removal of the illumination device 37 when installing the remote station 
unit 1 on a site where a street lamp or porch lamp is available for 
eliminating the requirement of the illumination device. The joinder 38 is 
connected in circuit with the remote station unit 1 through wires 39 so 
that the infrared light emitting diodes 16 are supplied with driving 
voltage therefrom. The illumination controller 25 of the present 
embodiment may take the form of any one of those disclosed in the previous 
embodiments 1 to 4. 
It should be noted at this time that an automatic exposure control means 
capable of varying its aperture may be provided in front of the solid 
state camera 14 in each of the previous embodiments 1 to 5 so as to 
regulate the amount of incoming light to the solid state camera 14 in 
proportion to the level of the video signal, enabling the solid state 
camera 14 to successfully pick up the image even at its minimum 
illumination level and therefore realizing an improved embodiment.