GB2128836A - Method and apparatus for monitoring discrete surfaces - Google Patents

Abstract

Surveyance of surfaces and volumes as well as of an object located therein. A pulse transmitter (112), by means of a radiating element (116), transmits series of directive pulses (40) which are selectively received (116). The corresponding vectors as well as the variations thereof are processed in a computer (400) to determine the dimension and/or recognize the object and/or set an alarm.

Description

SPECIFICATION Method and apparatus for monitoring discrete surfaces The present invention relates to a method for monitoring discrete surfaces, particularly door or window openings of a building, against unauthorised intrusion by emitting pulsed directional radiation in a defined time sequence in a plane parallel to the surface to be monitored and by using a change of the received signals resulting from an object penetrating into the said plane or surface as a criterium for triggering an alarm.

Different types of light barriers are known from the prior art but they usually have a disadvantage in that they cannot give an indication of the location of the intrusion, ie of the window or the door where an object is penetrating into the building. As buildings which are to be monitored against unauthorised intrusion usually have a large number of openings like windows and doors the systems known to date are unsatisfactory.

An object of the present invention is to provide a method and an apparatus which indicates the location of an unauthorised intrusion.

According to the present invention there is provided a method of monitoring discrete surfaces surrounded by an outline against unauthorised intrusion by emitting pulsed directional radiation in a defined timewise sequence in a plane parallel to the surface to be monitored and by using a change of the received signals resulting from an object penetrating into the said plane or surface as a criterium for triggering an alarm, characterised by evaluating the received signals on the basis of their transit times, by emitting at each surface to be monitored the radiation periodically and by storing temporarily the signals received therefrom and by comparing actually received signals with the signals temporarily stored.

According to a further aspect of the present invention there is provided an apparatus for monitoring discrete surfaces surrounded by an outline comprising a directional radiation emitter provided with a pulse transmitter for emitting pulsed directional radiation in a defined timewise sequence and in defined directions and a receiver for the spatially directed reception of reflected energy of the directional radiation transmitted by the radiation emitter, characterised by a beam splitting system operatively associated with the pulse transmitter for dividing the transmitted energy in beams in different directions, said beam splitting system being also operatively associated with the receiver for the directed reception of reflected energy from the different directions, a computer serving as an evaluation device for the arithmetic evaluation of the received reflected signals on the basis of their transit times from the output of the pulse transmitter to the input of the receiver, whereby the beams of the beam splitting system are directed to the outlines surrounding the surfaces to be monitored and are reflected by these outlines back to the beam splitting system.

A directional beam emitter may consist of a beam splitter system for the splitting or fanning of the beam is positioned behind at least one transmitter.

With such a system, for example pulsed electromagnetic radiation, especialy light radiation, for example, infra red radiation is then transmitted in different defined diections, and the radiation reflected at the objects or background is infed to at least one receiver by means of one or a number of analogous radiation fanning systems and is evaluated. The relected radiation is thus received preferably spatially selective.

With the energy transmission occurring in different directions in succession as a function of time, then the corresponding reflected radiation portions are preferably likewise received in succession and evaluated individually. A transmission channel is then provided for the transmission of the radiation and a receiver channel for the spatially selective reception of the reflected radiation for its further transmission to the receiver. These channels are preferably decoupled with respect to one another, in order to prevent spill-over of transmitted radiation from the transmission channel directly into the receiving channel. This is striven for in consideration of the large signal peak difference in both channels, so that the receiver can be protected against over-control.

For particular applications, for example monitoring a number of discrete surfaces while using only one transmitter and receiver, it is advantageous to transmit radiation pulses according to a predetermined programme in groups in different directions and to receive reflections in groups in each case from the mentioned directions and also to evaluate such received reflections in groups.

If radiation pulses are transmitted in groups in different directions and received in groups from such directions, then it is not necessary to evaluate individually each signal from each direction. If, in the radiation splitting region a change in the reflection properties occurs, ie reflection of at least one of the fanned beams to a different location from before, due to an intruding object, then also with common evaluation of an entire group of signals, a change occurs in the thus obtained summation signal. This change of the summation signal, in relation to the undisturbed condition, can be beneficially employed as the criterion for alarm tripping.

If at least two radiation splitting systems are used, each with a surface-like fanning of the radiation in different surfaces, in other words staggered spatially, then an object moving through at least two surfaces causes timewise staggered changes of the received signals. Consequently, by evaluating the timewise difference and the sequence of the change of the output signal in the at least two systems, it is possible to determine the direction of movement of an intruding object and such can be employed as a further criterion for the directional-dependent alarm tripping.

Basically, the method can be used for all energy which is irradiated as pulses, for example ultrasonic energy, especially however also electromagnetic energy. Pulse-shaped laser radiation is preferably suitable and especially in the region of invisible light, for example, in the infra red region.

In consideration of controlling the dynamics of the receiver system ie the faultless processing of both very weak and also very strong signals, it can also be expedient in certain situations to control the transmission output and/or the receiver sensitivity as a function of the radiation direction.

However, it is also possible for this purpose to control the transmission output and/or the receiving sensitivity as a function of the magnitude of the measuring beams or distance vectors and/or the intensity of the reflection.

The method can be further designed such that not only are the distance vectors themselves evaluated but also the intensity of the radiation reflected to the receiver. For example, in this manner it is possible to detect certain objects based upon their greater reflection capability in contrast to other objects and/or in contrast to the background. Their related measuring data, obtained from their distance vectors, can be specially processed or evaluated, based upon the additional evaluation of the higher intensity of the reflected radiation infed to the receiver. It is also possible to obtain an appreciable data reduction if only such selection of data which is fed into the computer and storage, based upon the greater intensity of the reflection, is at least periodically of particular interest.

The evaluation of the received vectors thus is limited, for example, as concerns site of the reflection and/or movement behaviours of the relevant object, only to a desired number of objects.

This selection can be effected, for example, by the arrangement of a conventional threshold value device in the receiving channel and/or by an intentional at least periodic, reduction of the transmission output of the directional beam emitter and/or the receiver sensitivity in relation to normal operation.

It is also possible for the determination of certain points in the area or space, for example selected points ofvirtual lines and/or virtual surfaces which are to be fixed, to arrange periodically at the relevant locations, of the area or space particularly highly relecting objects, for example, so-called retroreflectors, to then measure these as described previously and select the relevant distance vectors based on the increased reflectivity and to store the thus obtained coordinates of the erection site of these particularly strongly reflecting objects i.e.

retro-reflectors for the purpose determining the virtual lines and/orvirtual surfaces.

Embodiments of the present invention is described in the following by way of example, with reference to the accompanying drawings, in which: Figure 1 shows an arrangement for monitoring discrete areas; Figure 2 shows a detail of the beam splitting system of the arrangement of Figure 1; Figure 3 is a block circuit diagram of the embodiment of Figure 1; Figure 4 illustrates schematically the serial evaluation of distance vectors; and Figure 5 illustrates schematically the groupwise evaluation of distance vectors.

The monitoring arrangement shown in the Figures is designated to monitor discrete surfaces like doors 601 orwindows 602 of a building 603 against unauthorised intrusion. In Figure 1 reference number 600 designates a beam splitting system in its entirety which is provided for this purpose.

The beam splitting system 600 is connected on one side, to a pulse transmitter 112 and, on the other side to a receiver 125. By means of a transmitter coupling element 604, for instance a first lens arrangement for coupling a laser diode of the pulse transmitter 112 with glass fibres of a transmission conducting system 605 composed of one or a number of glass fibre bundles, preferably of different length, the transmission energy is infed by means of the individual fibres of each glass fibre bundle to a respective transmitting lens 606 of a beam splitter 607 and from such lenses is propogated in the form of transmission beams 608 in different directions in a surface extending parallel to the door plane. The thus formed transmission beams 608 are directed towards the outline of the door, and then when the door opening is free, are reflected thereby.Receiving lenses 609 of the beam collector 610 remove received beams 611 correlated with certain transmission beams and travelling opposite to these beams from the more or less diffuse reflections. The receiving lenses 609 conduct the received energy, by means of the individual fibres of a glass fibre bundle of a receiving transmission system 612, by means of a further lens system of a receiver coupling element 613,to the receiver 125.

Figure 2 illustrates in detail a preferred structure of an assembled beam splitter 607 and beam collector 609. The lenses 606 and 609 can preferably be structurally combined in conventional fashion with the relevant ends of the related glass fibres.

The beam splitter system 600 extends from the pulse transmitter 112 to the surfaces 601,602 to be maintained and possibly further surfaces and then again back to the receiver 125. Preferably, the glass fibre bundle belonging to the transmission conductive system 605 and the glass fibre bundle belonging to the receiver conductive system 612, with optical decoupling, are laid in a common channel, for example, a tube so as to be protected against damage, for example, inside the building 1.

In order to obtain directional-dependent information concerning objects penetrating the monitored surfaces, it is possible to carry out monitoring in spatially tandemly arranged surfaces, in order to obtain timewise differences of penetration of the surfaces. Preferably, then, the momentarily related beam splitter 607 and beam collector 610 are arranged in neighbouring corners of the surfaces 601 and 602 to be monitored.

Figure 3 is a block diagram of the embodiment shown in Figure 1. The pulse transmitter 112 transmits transmitter beams 608, eg laser pulses in the infra red region, by means of the generally illustrated beam splitter system 600. The received beams 611 are infed from the beam splitter system 600 on the other side to the receiver 125.

From the transit times of the transmitted pulses from the output of the transmitter 112 until the reception of the signals related to the received beams, it is possible to form distance vectors. It is to be observed, however, that both the transit times in the beam splitter system 600 and also the transit times in the free space of the monitored surfaces are incorporated into distance vectors E of such embodiment, that is to say, are mathematically processed.

Now in order to be able to implement the method of the invention, the apparatus contains a computer 400* composed of a first input/output unit (I/O-port) 201, a second input/output unit (I/O-port) 301, a central processor unit (CPU) 203, a programmeable storage (PROM) 204, and a first and a second write-read memory with random acess (RAM) 205 and 206, all of these components being connected in known manner with one another by means of a multiple bus 207 or can be brought into operative connection with one another.

The apparatus also contains a group of auxiliary devices 403 to 407 operatively correlated with the computer400*: a real time clock 403 which is provided both as the time or frequency base for the pulse transmitter 112 and for the control of the computer 400*, a current supply 404 with an associated control unit 405, an input unit 406 both for turning-on and turning-offthe pulse transmitter/ receiver 122/125 and also for the selection of the desired operating state, and an output unit 407 for the output of the data obtained via the pulse transmitter/receiver 112/125, such as information with respect to detected objects, alarm signals etc.

Such data can preferably be delivered by coded signals which are suitable for use in known indicator and/or alarm devices. The mode of operation of the equipment is as follows: By means of the input unit 406 te equipment is set in operation and the current supply 404 is turned on. The pulse transmitter 112 emits via the beam splitter system 600 transmitter beams 608 which are reflected by the door frame or window frame of each door or window to be monitored via the beam splitter system 600 to the receiver 125. The transit times of the beams and thus the distance vectors for each opening to be monitored are stored as defined vectors and are periodically formed and compared with the vectors which were previously formed for the corresponding opening.The storage and evaluation of the vectors is achieved by appropriately programming the computer 400*, the values of the vectors are stored in the first write-read memory 205 in a timewise order.

After the equipment has processed these reference values it is capable of performing the normal operation for the monitoring with the programme in the programme storage 204.

From each received vector obtained by reflection, a distance actual-value is produced and stored on-line, ie in step, in the write-read memory 205 and is compared with the corresponding reference-value stored. Normally the difference between the stored and the actual value is equal to zero. As soon as an object penetrates into the surface monitored, then this difference becomes greater than zero, and thus, is stored in the write-read memories 205 and 206.

The second input/output unit 301 avails itself of the difference values from the write-read memory 206. These difference values which are processed in accordance with local and timewise correlations trigger a pre-alarm or an alarm which is transmitted via the second input/output unit 301 to the output unit 407.

When the apparatus is turned off there are distinguished two cases, namely: - Turning off the apparatus within the time of employment thereof. In this case the current supply for the computer 400* is maintained, only the peripheral units containing measuring and regulating portion are disconnected from the current supply.

- Turning off the apparatus in general. All units are disconnected from the current supply, ie are without power.

If, as mentioned, the transit times, are computed and thus, the received vectors, for example, at the transmitter output, then there wil be recognised from Figure 1 that to each monitored surface i.e. 601 and 602 and possibly further surfaces, a quite specific region can be correlated which, in each instance, results from the sum of the transit time between the pulse transmitter 112 to the beam splitter 607 plus the travel time of the transmitted beams. The shortest transmitted beam at the opening 601 is produced when a disturbing object is located directly at the beam splitter 607. The related transit time is then the shortest value which can be determined in conjunction with the opening 601, and thus, the shortest distance vector is produced here.

The longest travel time and, therefore, the largest distance vector produces at the opening 601 a diagonally extending transmitted beam 608 or received beam 611, repectively.

Due to the periodic measuring of each opening 601,602 and possibly further openings, it is therefore possible continuously to form and store defined received vectors. Upon the intrusion of an object in any one of the monitored surfaces (openings), at least one distance vector changes in relation to the temporarily stored distance vector which was previously formed for the relevant surface (opening) and direction or directions. Such change accordingly can be correlated to a certain surface (opening) due to the correlatability to the range of distance vectors (transit times) correlated to the relevent surface (opening).

Consequently, it is not only possible to sound an alarm when an intruder unlawfully enters, as concerns the point in time therefore, but simultaneously an idication can be effected as to the location of the intrusion, namely the surface, opening 601,602 etc.

Figure 4 schematically shows the serial evaluation of the distance vectors E obtained with an arrangement according to Figures 1 and 3. The distance vectors E, as mentioned, correspond to the related transit times, wherefore in the depiction a of Figure 4, both the time t and also the distance E have been plotted along the ordinate.

The abscissa axis X designates the monitoring site and is structured such that it corresponds to a point in time to, for example, the time that the transmitted beam moves out of the beam splitter 607 located closest to the transmitter 112.

The illustration of Figure 4a designates three groups of distance vectors each containing five distance vectors, wherein the first group is correlated with opening 601, the second with opening 602 and the third with a further opening 614.

The full-line distance vectors bounded by a point represent the normal state, ie no intrusion of an object in the opening.

The broken-line designated distance vectors, bounded by a cross, designate the case where an object 615 has intruded.

These conditions are shown in the illustrations of Figures 4b, 4c, 4d and 4e.

It can be easily seen from Figure 4 that the transit time range t4 tot5 is to be correlated in the undisturbed case to the opening 601, the transit time range t6 tot7 in the undisturbed case to the opening 602 and the transit time range t8 to tg to the opening 614.

If an intruding object 615 appears, for example, at the opening 601,then a premature reflection at the object 615 instead of at the border of the opening 601 takes place. This leads to shortened transit times t1, t2, and t3 and to shortened distance vectors; the latter are shown in broken lines in Figures 4a and with a cross.

By comparison of the shortened distance vectors with the normal distance vectors (full lines) correlated with the same opening 601 is produced where an intrusion has occurred.

These are mathematical operations which occur automatically by appropriately programming the computer 400* (Figure 3). Thereby, all of the individual distance vectors are processed in series.

In a simplified case, it is possible to determine the intrusion of an object also with groupwise processing of the distance vectors. This will be explained based upon Figure 5. If an electro-optical distance measuring device of known construction is used, (see for example, German Offenlegungsschrift No.

2,634,627), as the receiver 125, then by suitably dimensioning the system, an input oscillation circuit is commonly driven in each case by a whole group of received signals correlated to an opening 601,602 or 614 thereby realising a groupwise evaluation ofthe distance vectors. Hence, there is provided only one received vector per group or opening. While referring to the conditions according to Figure 4, for the undisturbed case a respective common distance vector E 601, E 602, E 614, is recognized, shown in Figure 5 by full lines terminating at a point.

In an object 615 appears at the opening 601, then the related distance vector is shortened as indicated in Figure 5a by the broken line designated by E 601 * and terminating with a cross. The occurence of such shortened distance vector constitutes an indication of the penetration of object 615 into the opening 601.

Claims (7)

1. A method of monitoring discrete surfaces surrounded by an outline against unauthorised intrusion by emitting pulsed directional radiation in a defined timewise sequence in a plane parallel to the surface to be monitored and by using a change of the received signals resulting from an object penetrating into the said plane or surface as a criterium for triggering an alarm, characterised by evaluating the received signals on the basis of their transit times, by emitting at each surface to be monitored the radiation periodically and by storing temporarily the signals received therefrom and by comparing actually received signals with the signals temporarily stored.

2. A method according to claim 1, characterised in that the radiation pulses are transmitted individually in different directions in accordance with a pre-determined programme and that the successively received reflected signals are evaluated individually.

3. A method according to claim 1, characterised in that the radiation pulses are transmitted in groups in different directions and in accordance with a pre-determined programme whereby each such group is associated with a surface to be monitoed and that the reflected signals are received in groups from the mentioned directions and are also evaluated in groups.

4. A method according to any one of the claims 1 to 3, characterised in that the emitting of the radiation in different directions at the surface to be monitored is achieved by at least one transmitter in front of which is positioned at least one beam splitting system for splitting the radiation in terms of the surface.

5. A method according to claim 4, characterised in that by using at least two beam splitting systems splitting the radiation into different surfaces and by evaluating the timewise difference of the change of the received signals associated with the said at least two beam splitting system respectively, the direction of movement of an object penetrating into the surface to be monitored is determined and is used as another criterium of an alarm.

6. A method for monitoring discrete surfaces surrounded by an outline substantially as herein described with reference to Figures 1 to 3 with reference to either of Figures 4 and 5 of the accompanying drawings.

7. An apparatus for monitoring discrete surfaces surrounded by an outline comprising a directional radiation emitter provided with a pulse transmitter for emitting pulsed directional radiation in a defined timewise sequence and in defined directions in a plane parallel to the surface to be monitored and a receiver for the spatially direction reception of reflected energy of the directional radiation transmitted by the radiation emitter, characterised by a beam splitting system operatively associated with the pulse transmitter for dividing the transmitted energy in beams in different directions, said beam splitting system being also operatively associated with the receiver for the directed reception of reflected energy from the different directions, a computer serving as an evaluation device for the arithmetic evaluation of the received reflected signals on the basis of their transit times from the output of the pulse transmitter to the input of the receiver, whereby the beams of the beam splitting system are directed to the outlines surrounding the surfaces to be monitored and are reflected by these outlines back to the beam splitting system.

7. An apparatus for monitoring discrete surfaces surrounded by an outline comprising a directional radiation emitter provided with a pulse transmitter for emitting pulsed directional radiation in a defined timewise sequence and in defined directions and a receiver for the spatially directed reception of reflected energy of the directional radiation transmitted by the radiation emitter, characterised by a beam splitting system operatively associated with the pulse transmitter for dividing the transmitted energy in beams in different directions, said beam splitting system being also operatively associated with the receiver for the directed reception of reflected energy from the different directions, a computer serving as an evaluation deviceforthe arithmetic evaluation of the received reflected signals on the basis of their transit times from the output of the pulse transmitter to the input of the receiver, whereby the beams of the beam splitting system are directed to the outlines surrounding the surfaces to be monitored and are reflected by these outlines back to the beam splitting system.

8. An apparatus according to claim 7, characte rised in that the beam splitting system comprises a transmitter coupling element for coupling the beam splitting system with the pulse transmitter, a transmission conducting system for conducting the transmitted energy to a beam splitter and also provided with a beam collector, a receiving conducting system for conducting received energy by means of a receiver coupling element to the receiver, which is operatively associated with the computer for evaluating the received signals.

9. An apparatus according to claim 8, characterised in that the transmitter channel and the receiver channel are mutually decoupled with respect to one another.

10. An apparatus according to claim 8 or9, characterised by a laser pulse transmitter having a lens arrangement as the transmitter coupling element for coupling the laser pulse transmitter to the transmission conducting system which is structured as a glass fibre bundle for further conducting the transmitted energy which has been divided at the individual fibres to a beam splitter connected to the glass fibre bundle, consisting of transmitting lenses having differently directed axes, and also characterised by a beam collector consisting of receiving lenses each having a differently directed axis, and fibres of another glass fibre bundle operatively associated with said receiving lenses and serving as the receiving conducting system for conducting the received energy further by means of another lense arrangement constructed as the receiver coupling element.

11. An apparatus for monitoring discrete surfaces surrounded by an outline substantially as herein described with reference to Figures 1 to 3 with or without reference to either of Figures 4 and 5 of the accompanying drawings.

New claims or amendments to claims filed on 14th December, 1983 Superseded claims 1 and 7 New or amended claims:

1. A method of monitoring discrete surfaces surrounded by an outline against unauthorised intrusion by emitting pulsed directional radiation in a defined timewise sequence in a plane parallel to the surface to be monitored and by using a change of the received signals resulting from an object penetrating into the said plane or surface as a criterium for triggering an alarm, characterised by emitting the radiation at each surface to be monitored periodically in defined directions towards the outline by which the radiation is reflected back to a receiving system, by evaluating the received signals on the basis of their transit times, and by storing temporarily the information received therefrom and by comparing the information evaluated from the actually received signals with the information temporarily stored.