[0001] The present invention involves in fiber optic components to be utilized in security
systems, such as intrusion detection or anti-theft devices, and the like.
[0002] Particularly, this invention has devised equipments applied in security devices that
will create some degree of difficulty in cirmuventing the device in such a way that
any attempt to circumvent the same device will always activate the alarm systems.
One of the objectes of this invention is that of realizing a security system that
reacts both at an intrusion attempt and an attempt to circumvent the device, therefore
always activating alarm devices to which it is connected.
[0003] A second object of the present invention is that of realizing the above mentioned
security systems by means of the application of fiber optic means in cooperation with
electronic means.
[0004] There are in the prior art various examples of surveillance and control means using
optoelectronic techniques showing situations to be controlled or remedied, such as
the U-S-A-4,812,810, granted on March 14, 1989 to Daniel S. Query et al., describing
some kind of systems based on light emission and light detection by means of fiber
light guides signalling the opening or the missclosure of electrical housedhold appliances
that would be preferably closed, such as a refrigerator and freezer doors. Here, among
the many examples given, there is also a system assuring the perfect closure of doors
of both a refrigerator and freezer in a domestic unit which has separate compartments
(top mount) using for example a light emitting unit located in a lower compartment
wall facing a fiber light guide incorporated in the door of the unit, diverting light
towards a hole situated on the upper edge of the same door that will, in the case
of perfect closure of both refrigerator doors, be aligned with a corresponding hole
located on the lower edge of the above freezer door compartment, this hole continuing
with a channel occupied by the light guide terminating against a photodetector located
in the wall of the freezer compartment itself.
[0005] This system works well but the inventors did not realize that the fiber optic light
guide by them used would have been disturbed by any atttempt of tampering with it
and therefore missed the point and the possibility of applying the concept to security
and anti-theft devises of the kind which cannot be circumvented without providing
some type of disturbance that would activate an alarm system. Further, such a similar
hypothesis would have been excluded by them because their objects were to devise a
warning system that would alert a user on doors not properly closed, and therefore
they were not interested in expecting situations that would have brought only false
or unjustified alarms.
[0006] U-S-A- 5,004,908 granted on the April 2nd, 1991 to Arata Nakamura, describes a photoelectric
selective reflection system that emits light on two quite different bands which had
to be utilized for the detection of an object causing interference along an optical
path. This invention apart of relying on a particularly unusual light emitting unit,
such as a GaAs laser with two different emission bands, totally ignores applications
in fiber optic, and therefore, it does not lend itself to applications in the security
surveillance field because it would be easily bypassed by means of applying an abusive
selective reflector, like the one hereby described, positioned immediately in front
of the unit comprehensive of the light emitter and the adjacent optical receiver.
[0007] At last U-S-A- 5,033,112 granted on July 16, 1991 to Geoffrey N. Bowling et al describes
a programmable power system for telecommunications and remote controls relying, with
many electrical connections, also on optical connections, however provided by a single
fiber optic cable in which optical signals propagate in each other opposite directions,
not having different light paths from the light emitting source to optical switches
and from optical switches to optical receivers, resulting particulalrly difficult
to differentiate between optical signals responsible for remote controls and/or telecommunication
and optical signals for surveillance and/or security, unless specific encoded signals
were used that would require particularly sophisticated electronic circuity which
is very costly and less reliable because of their own sophisticated nature.
[0008] However, what the inventors did not realize is the fact that the optical signal,
cannot be bypassed without causing troubles or disruption in the fiber and that this
in turn would have made them ideal for intrusion detection products, also perhaps
wanting to simplify the optical paths by utilizing single fiber with optical propagation
paths in dual directions and also in order to apply alignment systems with microlenses
(lenses with focal lengths of about 1 mm), the inventors were forced to utilize particularly
thin fiber optic cable, as for example a fiber optic cable with core size of 62,5
microns that would result in being particularly fragile as well as unmanageable, especially
in the case of surveillance system applications.
[0009] The above mentioned objects are reached by anti-theft devices comprising a portion
of electronic apparatus and a portion of optical apparatus of which the security or
non tampering ability is based on the fact that the fiber optic conductors of light
signals cannot be tampered, while in operation without the introduction, within the
same unit of signal noise, even of just temporary nature, of such an intensity that
would cause or start an alarm mode.
[0010] In short, a security system according to the invention includes an electronic section
and an optical section, the interface between the electronic section and the optical
one being provided by a light emitting source whose signals are controlled by the
elctronic section, and the opposite interface between the optical section and the
electronic one being provided by an optical receiver unit controlled by light coming
from the optical section, being the light used in the optical section sent out in
only one preselected direction, characterized in that the light emitting medium is
connected to the optical receiver by an optical path comprising at least one piece
of light transmitting optical fiber and one mechanical switch component, triggered
by external events, able to transform actions caused by break-in attempts in a substantial
interruption in the light path, connected to the optical receiving unit.
[0011] According to a first embodiment of this invention, the optical path is formed by
two pieces of optical fiber of equal length laid out in the optical section to connect
the interface components between the electronic section and the optical section by
means of the mechanical switching component.
[0012] Alternatively, according to another embodiment of the invention, the optical path
is comprised of three pieces of fiber optic cable, having each other different lengths,
of which the first one is an optical path between the light emitting means and the
mechanical switching means, the second one is an optical path between the mechanical
switching means and a further intrusion detector of the kind based on fiber optic
interruption and a third one is an optical path between the further intrusion detector
and the optical receiving unit.
[0013] According to another alternative, the optical path is comprised of three pieces of
fiber optic cables, having each other different lengths of which a frist one is an
optical path between the light emitting means and an intrusion detector of the kind
based on fiber optic cable interruption, a second one is an optical path between the
intrusion detector based on fiber optic cable interruption and the mechanical switching
component, and a third one is an optical path between the mechanical switching component
and the optical receiving unit.
[0014] A mechanical switching component, obviously for optical signals, is formed by a first
enclosure housing the extreme ends of two adjacent fiber optic cable pieces inserted
in specific terminating optical plugs called ferrules, the extreme ends of the ferrules
outside facing a reflecting prism housed in an appropriate enclosure conveying light
coming out from the fiber core of a piece of the fiber optic cables into the core
of the adjacent second piece of fiber optic cable.
[0015] In a particular embodiment of the invention, the component for the mechanical switching
as above described, is formed by a first enclosure housing the ends of the fiber optic
cables inserted in a fixed structure, as for an example the frame of a door, and by
a second enclosure housing the reflecting prism inserted in a mobile structure as
for an example in the mobile structure of the same door.
[0016] In a different embodiment of the invention, and alternative to the preceding one,
the mechanical switching component is formed by a first enclosure, housing the ends
of the fiber optic cable, installed externally on a fixed supporting structure, as
for example a door frame, and by a second enclosure, housing the reflective prism,
affixed or mounted externally on the edge of a mobile support, for instance the upper
edge of a door structure.
[0017] Particularly, the light reflecting prism, housed in the second enclosure is a prism
obtained by cutting out from transparent material with high refraction index such
as glass, quartz silica, or plastics for optical applications.
[0018] More specifically, one of the prisms with total reflective capabilities is defined
as a corner cube prism, obtained by cutting a cube along a plane lying on the diagonals
of three adjacent faces, the bottom of which is a circular cylinder circumscribing
the base of the corner cube.
[0019] Alternatively, the second and preferable alternative used is a total reflection prism
known as a light angle prism which is obtained by cutting a cube in half along a plane
lying on two parallel diagonals of two of its opposing faces.
[0020] In a preferred embodiment the light emitting means is a solid state laser like a
GaAs laser.
[0021] In a more preferred embodiment the light source is a light emitting diode (LED).
[0022] In a further preferred embodiment the light receiver contains a fototransistor.
[0023] The features of this invention will particularly pointed out in the claims forming
the conclusive portion of this description. However other features and advantages
of the invention will be carefully described in the following detailed description
of embodiments, which are not to be considered as limiting the scope of the invention,
provided with the enclosed drawings, in which:
- Figure 1 is a block diagram of a first embodiment of a security surveillance system,
particularly an anti-theft device, made up in part of an electronic circuit board
driving an optical system, also according to the invention, including an optical assembly,
also according to the invention, formed by fiber optic cables and a mechanical switching
element for optics.
- Figure 2 is a block diagram of a second embodiment of an anti-theft security device
that includes, in addition to the electronic unit, and a first fiber optic cable piece
leading to the element for mechanical optical switching a second fiber optic cable
piece, partially inserted in elements to be secured, that in turn will signal alarms
caused by damages or breakage of parts or components protected by the second fiber
optic piece.
- Figure 3 is a sectioned view of a mechanical optical switching element for flush mounting
or for insertion in supports to be protected by the unit according to the invention.
- Figure 4 is a sectioned view of a mechanical switch for optical commutation of the
kind to be surface mounted in supports to be protected by the units according to the
invention.
[0024] Let us consider first figure 1. In such a figure is noticed a first example of surveillance
unit 10 comprised of a module 12, containing an electronic circuit generating optical
signals and signals actuating alarm units, a mechanical module 14 for the optical
switching formed by a fixed portion 16 and a mobile one 18, a first fiber optic cable
20, forming an optical path leading from the electronic module 12 to the mechanical
commutation module 14, and by a second fiber optic cable 22 forming an optical path
from the mechanical module 14 to the electronic circuit module 12. The fixed part
16 of the mechanical module 14 houses the means 24 and 26 for mounting in a fixed
mode the ends of the fiber optic cables 20 and 22, while the movable fixture 18 contains
the means 28 allowing for an optical connection between the first fiber optic cable
20 and the second fiber optic cable 22.
[0025] The module 12 of the electronic circuit is essentially made up of a power unit 30
supplying the voltage required to power all the elements contained in the module by
means of multiple lines 32, a signal generator 34, as for instance an astable multivibrator
generating electrical pulses to power unit 36 generating optical signals which might,
for instance, comprise a light emitting diode (LED) 38 emitting light pulses every
time that a signal coming from a generator 34 reaches the voltage level required to
correctly supply the LED 38.
[0026] The optical generating unit 36 is obviously equipped with a system well known to
those skilled in the art, which couples the LED 38 to the fiber optic cable 20 in
such a way that a substantial part of its optical signal is captured by the cable
20. Contained within the same module 12 is an optical receiver 40 which comprises
for instance, a phototransistor 42 converting light signals, such as properly modulated
light pulses coming from the fiber optic cable 22 into corresponding electric signals.
[0027] A synchronized detector 44, synchronized by means of a connection 46 with signals
generated by the LED 38, coordinates the signals coming from the optical receiver
40 with the ones activating the transmitter 36 of optical signals in such a way for
instance that would not emit any signal at the exit of the synchronous detector 44
when both the signals coming from optical receiver 40 and from the transmitter of
optical signals 36 are present, while it would emit a signal when in presence of a
signal on the connection 46, there is no corresponding signal from the receiver 40.
[0028] The signal emitted from the the synchronous detector 44 is routed to a memory circuit
48, which, if activated even by a single electric pulse will remain in an open state
emitting a signal through a connection 50 activating the alarm, up until it is stopped
or turned off by a connection 52 that could be connected to either a switch or a deactuating
key.
[0029] Let us consider now figure 2 depicting a second kind of security system 60 formed
by a module 12, containing the electronic circuit generating optical signals as well
as signals actuating the alarm, an optical mechnical switching module 14 formed by
a fixed fixture 16 and by a mobile component 18, by a first fiber optic cable 20 forming
an optical path from the electronic module 12 to the optical mechanical switching
module 14, by a second fiber optic cable 62 coming out from the mechanical module
14 itself and connected by means of a flexible 63 path to fiber optic cable 64 applied
on or in a board 66 enclosed in a frame 68 which is a portion of a structure 70 in
turn belonging to either doors, windows, hatches, vaults or the like. The board 66
can be transparent, like a glass, or opaque like a door panel, as an example a wood
door or a metal door. The fiber optic cable 64 which has been laid in such a way to
cover substantially all the surface area 66 exits from the same surface area by means
of a second flexible piece 71 leading to fiber 72 finally connected to fiber optic
cable 22 going back into the module 12. The module 12 is identical to module 12 used
in the security system 10 depicted in figure 1 therefore is no more described in order
to simplify the disclosure.
[0030] It results obvious that this second example of security system protects not only
against attempts of opening the structure 70, in turn opening the optical contact
14, but could also safeguard from break-in attempts through the panel 66 of the frame
70, or prevent mechanical, thermal penetration, punctures, other damages inflicted
on surface 66, because any single or combined sabotage attempt, above depicted, would
result in damages on the fiber optic cable 64 with the consequential interruption
of the light signal from the transmitter point 36 to the receiver 40 with the alarm
being activated. For this purpose it is advisable to use an easily tearable fiber
optic cable, as for example a fiber optic cable completely of plastics, therefore
guaranteeing signal interruption at each damaging attempt inflicted on panel 66 of
frame 70.
[0031] It is understood that this second kind of alarm system, depicted in figure 2, has
a higher degree of safety with rispect to the one in figure 1, however this system
also needs greater power requirements for the LED 38, or perhaps a more intense light
source, and/or the choice of a more sensitive optical receiver 40 taking into account
the higher attenuation levels caused by the longer fiber optic cable path used in
the system.
[0032] Let us examine figure 3 depicting an optical mechanical switching element to be flush
mounted on surfaces to be protected. The sensor is comprehensive of a stationary part
16 and a movable fixture 18. The optical mechanical element (optical switch) 14a is
made up of a first enclosure 80, affixed in the stationary area 16, housing in appropriate
recesses the ferrules 82 containing the single fiber optic cables 20 and 22. The ferrules
are kept aligned by a spring loading 84 system enclosed with a cap 86 secured by screws
88. Facing the first enclosure 80 lies the second enclosure 90, affixed in the mobile
18 area containing a total reflection prism 92, equipped with an external flat face
94, placed parallel to the other face 96 of the enclosure 80 and perpendicular to
the axis of the cores of the fiber optic cables 20 and 22. The prism 92 can be of
two kinds: the so called corner cube prism, obtained by cutting a cube along a plane
lying on the diagonals of three adjacent faces, the bottom of which is a circular
cylinder circumscribing the base of the corner cube; and or a 90
o reflecting prism technically known as a right angle prism, simply provided by cutting
a cube in half along a plane lying on two parallel diagonals of two of its opposing
faces. Both kinds of prisms assure a satisfactory amount of reflection for the light
emitted from the fiber optic cable 20 towards the other fiber optic cable 22 as long
as the face 94 of the prism 92 is located adjacent and substantially parallel to the
front face 96 of the enclosure 80.
[0033] Figure 4 depicts an optical mechanical switching unit 14b to be surface mounted on
supports making part of the system to be protected; said supports comprising a fixed
structure 16 and a mobile structure 18. The mechanical optical switching element 14b
is comprehensive of a first enclosure 100, to be mounted on a fixed structure 16,
with recesses housing two spring 84 loaded ferrules 82 containing fiber optic cables
20 and 22 covered by a cap 102 fastened by a plurality of screws 88. The enclosure
100 is equipped with external holes 104 housing fastening screws for affixing the
enclosure 100 on the structure 16. Facing the first enclosure 100 is placed the second
enclosure unit 106, to be mounted on the mobile structure 18 containing in an appropriate
recess 90a a total reflection prism 92 identical to the prism 92 shown in the figure
3 embodiment and having the same operating principles described earlier.
[0034] Enclosure 106 is equipped with holes 108 for fastening mobile surfaces 18.
[0035] Obviously even the mechanical optical switching element 14b depicted in figure 4
operates in a similar manner, as the mechanical element 14a depicted in figure 3,
assuring that the prism 92 reflects in a totally satisfactory manner the light coupled
in from fiber optic cable 20 towards the fiber optic cable 22 as long as the front
surface 94 of prism 92 is located adjacent and substantially parallel to the surface
110 of the housing 100.
[0036] The operation of this invention is selfexplaining. When the fixed structure 16 and
the mobile structure 18 are perfectly lined-up, the light coming from the fiber optic
cable 20 is coupled in a satisfactory manner to the fiber optic cable 22, therefore
avoiding the intervention of the module 12 activating the alarm unit. In the event
of any break-in attempt heading to misalignment, caused by moving mobile structure
18 from the fixed structure 16, would cause insufficient transmission of light from
the cable 20 to the cable 22, allowing the module 12 to intervene. The same would
happen if, as mentioned in the embodiment of figure 2, the fiber optic cable 64 inserted
in the panel or structure 66 would be interrupted or damaged.
[0037] It is to realise that the proper nature of the fiber optic cable will not allow any
attempt to by-pass the optical path since any attempt to maintain any continuity in
the optical path would result with an interruption, even temporary, of the optical
path with consequently permanent actuation of the alarm unit.
[0038] What has been hereabove disclosed consitute only two embodiments of this invention
and have not to be considered limited to them, and those skilled in this art can devise
substitutions of parts which are logically to be considered equivalent and all of
which are hereby claimed and covered.
[0039] As an example, LED 38 could be substituted by any other kind of pulse controlled
light source, for example lasers, flash bulbs or stroboscopic lamps, and the receiver
40 could contain instead of a fototransistor 42 an other kind of optical electronic
element, like a photocell, a photomultiplier, a photodiode, a CCD or the like.
[0040] Furthermore, an anti-theft device can contain, instead of just one mechanical element
for optical switching 14 and single structure 70, a plurality of them without exiting
from the scope of this invention defined in the following claims.
1. Anti-intrusion surveillance system, composed of an electronic unit (12) and an optical
unit (14), the interface between the electronic unit (12) and the optical one (14)
bieng provided by a light emitting unit (36) controlled by the electronic unit (12)
and the inverse interface between the optical unit (14) and the electronic one (12)
being provided by an optical photoreceiver (40) controlled by light coming from the
optical unit (14), the light employed in the optical section propagating in just one
preselected directin, characterized in that the light emitting unit (36) is connected
to the optical receiver (40) by an optical path comprising at least one fiber optic
cable (20,22) transmitting light and a mechanical switching component, actuated by
external events, able to transform actions following breaking attempts in a substantial
interruption of the optical path (20,22), connected with the optical receiver (40).
2. Anti-intrusion surveillance system, as in claim 1, characterized in that the optical
path is formed by two different pieces of fiber optic cable (20,22) of equal lenght
set in the optical section (14) to connect the interface components between the electronic
section (12) and the optical section (14) with the mechanical switching component.
3. Anti-intrusion surveillance system, as in claim 1, characterized in that the optical
path is formed by three fiber optic cables of different lenght of which the first
one (20) forms an optical path between the light emitting means (36) and the mechnical
switching component, the second one (62) forms an optical path between the mechanical
commutation component and another anti-intrusion detector (70), of the kind based
on the interruption of fiber optic, and a third cable (72,22) forms a light path between
the other intrusion detector (70) and the receiver (40).
4. Anti-intrusion surveillance system, as in claim 1, characterized in that the optical
path is formed by three pieces of fiber optic cable of different length of which a
first one (20,62) forms an optical path between the light emitting means (36) and
the anti-intrusion detector (70) of the type based on the interruption of optical
fibers, a second one (72) forms an optical path between the anti-intrusion detector
(70) based on the interruption of optic fibers and the mechanical commutation component,
and a third one (22) forms an optical path between the mechanical commutation component
and the receiving means (40).
5. Mechanical switching component for optical signals, to be employed in the surveillance
systems described in the preceding claims, characterized in that it is formed by a
first housing element (80) containing the end sections of two adjcent fiber optic
cables (20,22) inserted in appropriate optical ferrules (82), which in turn are inserted
in the appropriate housing (80), the ends of the ferrules (82) being pointed towards
the outside facing a reflecting prism (92) conveying light emitted by the core portion
of a fiber optic cable (20) towards the core of the adjacent piece of fiber optic
cable (22).
6. Mechanical switching component as in claim 5, characterized in that it is formed by
a first housing (80), containing the extreme ends of the fiber optic cables (20,22),
inserted in a fixed support (16), as for instance in a door frame, and by a second
housing (90), containing reflecting prism (92), inserted in a mobile structure (18)
as, for instance, the upper edge of the same door.
7. Mechanical switching component, as in claim 5, characterized in that it is formed
of a first housing (100 and 110), containing the extreme ends of the fiber optic cables
(20,22) which is externally mounted on a fixed structure (16), as for instance in
a door frame, and by a second housing (106), containing the reflecting prism (92),
externally mounted on a mobile support (18), as for instance the upper edge of the
same door.
8. Mechanical switching component, as in claims 6 and 7, characterized in that the reflecting
prism (92) contained in the second housing (90,106) is a total reflection prism obtained
from a small block made of a transparent and highly refractive materials such as glasses,
silica quartz or plastic material for optical use.
9. Mechanical switching component, as in claim 8, characterized in that the total reflection
prism (92) consists of a corner cube prism, obtained by cutting a cube along a plane
lying on the diagonals of three adjacent faces, the bottom of which is a circular
cylinder circumscribing the base of the corner cube.
10. Mechanical switching component, as in claim 8, characterized in that the prism (92)
is a total reflection right angle prism (92) which is obtained by cutting a cube in
half along a plane lying on two parallel diagonals of two of its opposing faces.
11. Anti-intrusion surveillance system, as in claims from 1 to 4, characterized in that
the light emitting unit (35) is a solid state laser, like a GaAs laser.
12. Anti-intrusion surveillance system, as in claim 12, characterized in that the light
emitting unit (36) is a light emitting diode (LED).
13. Anti-intrusion surveillance system, as in claim 12 and 13, characterized in that the
receiver (40) contains a phototransistor (42).