FR2474208A1 - IMPROVEMENTS ON INTRUDER ALARM DEVICES - Google Patents

Abstract

An intrusion alarm device, particularly for detecting burglars intruding into a building over the roof but which can also be used for indicating an attempt to remove a protected object, exhibits a radiation source which projects a moving ray which is reflected approximately parallel to the projected path and is compared with the reflection of a previously projected ray at the same location. The projected ray can scan an entire area horizontally or vertically and can be deflected to produce a conical scan in order to enclose a special object.

Description

Improvements to intruder alarm systems.

The present invention relates to intruder alarm devices; it relates, more particularly but not exclusively, to alarm devices which signal the penetration of an intruder by the roof of a construction substantially open in plan, for example warehouse, store, office or hangar.

 The alarm devices according to the prior art for such constructions are expensive and difficult to install.

In addition, it is generally considered that they are not very effective, since invariably only the glazing for lighting or ventilating the roof, or the like, are protected by this safety device, which leaves the cover roof in condition to be penetrated. In a large construction, which can easily include a roof comprising approximately one third of glazing, the cost of protecting each tile or series of tiles against intruders is prohibitive, if not by reinforcing the glass. In roof areas with less glazing, security devices are generally installed at each window, but here too, a large part of the roof can be penetrated and an intruder would not be detected.

 The present invention relates to an alarm device against intruders, which makes it possible to detect not only penetration by the glazed part of the roof, but also penetration by any part of the roof.

 The invention also relates to an alarm device against intruders, which is more economical and easier to install than known devices.

The intruder alarm device according to the invention is characterized in that it comprises: means for emitting a mobile scanning beam that is substantially undetectable; means for receiving the reflected scanning signals generated by this moving beam; storage and comparison means for recording a first reflected scanning signal and comparing the successive reflected scanning signals with this first signal; and signaling means which are activated when any of the successive reflected polling signals differs from the first reflected polling signal.

The invention will be better understood in the light of the description of its non-limiting embodiments, shown in the accompanying drawings, in which
Figure 1 shows an alarm device according to the present invention
Figure 2 illustrates a method of covering blind spots or places
Figure 3 shows another embodiment of the device of Figure 1, which covers the perimeter of a floor or a particular object; and
Figure 4 is a block diagram of electronic circuits.

 It can be seen in FIG. 1 that the device according to the invention comprises a box. 1, containing the electronic circuits, hence a first element 2 substantially tubular, directed downwards. A second substantially tubular element 3, concentric with the element 2, can rotate, preferably by means of bearings 4, around the element 2. The element 3 can be rotated by a motor 5 of low power , via a transmission 6, for example gears or a transmission belt.

An extension of the wall of the element 3 carries, appropriately fixed, supports 7, only part of which is shown for clarity of the drawing, intended to hold in position optical deflectors such as mirrors or prisms 8 and 9 and a converging lens 10. Inside and in the axis of the element 2 are placed a radiation source, preferably a low power laser 11, a collimation lens 12, and a translucent plate 13, transparent of preference. A support, for the installation of an optoelectric cell 14, is directed downwards from the plate 13. Preferably, an optical filter 15 is disposed between the optical deflector 9 and the cell 14. As a variant, it can be placed in front of or behind the lens 10. A laser beam 16, collimated by the lens 12, is reflected by the mirror or prism 8 and transmitted, substantially horizontally at any suitable distance below from the level of the roof, towards the walls of the building where it is reflected by reflection, substantially parallel to the exit beam, towards the mirror or prism 9. This directs the beam, through the filter 15 which rejects all the lengths d wave other than that of the beam, on the optoelectric cell 14. The output of the cell, for a first scan, is processed and entered into a memory where it is stored with an address code signal from a position detector, preferably an encoder disc 17 placed on the second tubular element 3 and moving with the latter. Thus, when a second scanning signal and then successive scanning signals from a determined location are received, this location is recognized by the code signal address supplied by the encoder disk and the scanning signals are compared. Preferably, the encoder disk or master clock can comprise approximately 2000 coded pulse signals per revolution, each having address codes, with a separation of 60 microseconds at 500 rpm, to access the appropriate memory. During the separation of 60 microseconds between successive coding pulses, the laser transmits a light pulse of 200 nanoseconds.

 At each revolution of element 3, 2000 samples are taken and, in a construction of 240 meters on the periphery, this provides a sample approximately every 120 mm and therefore two samples when a human torso passes. Each sample taken is preferably stored in memory as a level of gloss, but other methods can be used, for example a time coefficient. When the scan returns to the same point, 120 milliseconds later, the new brightness level is compared to the previous level and, if there is a difference to two consecutive samples, the alarm signal is triggered. If the new brightness is only slightly different, or if only one sample is different, the new levels are stored and the comparison continues at the rate of 8.3 times per second.

 We now refer to FIG. 2, which illustrates a method of covering or protecting blind places.

It is known that most large area roofs are supported on posts 18 placed inside the construction.

These posts reflect the beam before it reaches the wall, which creates a blind spot between the post and the wall, through which an intruder can enter the building through the roof. To overcome this difficulty, it is possible to place on the wall surfaces with relatively high reflecting power, for example mirrors 19, in order to reflect the scanning beam in blind places, or one can use a series of surfaces with relatively high reflecting power. forming a continuous path for the beam between the posts so that all blind spots can be scanned and checked at the same time.

To avoid failures, due to power outages, batteries can be charged from the main mains distribution and the device supplied with 12 or 24 volts, so that in the event of a mains supply fault, due to a breakdown or sabotage, the device still works with the batteries until the main supply returns.

 FIG. 3 represents another embodiment of the device of FIG. 1, which makes it possible to cover the perimeter of a floor or a particular object 20. Additional beam deflectors 21 and 22 are placed in the paths beams transmitted and received, in order to constitute a conical scan through which an intruder should pass, which would trigger the alarm.

 In a variant of FIG. 3, the radiation from the deflector 21 can be directed towards a surface with high reflecting power before returning to the deflector 22, thus forming a curtain of radiation whose interruption would trigger the alarm. In this arrangement, the use of memory circuits can be avoided.

Figure 4 shows a block diagram of electronic circuits and explains itself.

 It is understood that modifications of detail can be made in the form and construction of the device according to the invention, without departing from the scope thereof. For example, depending on the type of radiation source and receiver used, different reflective surfaces can be used to reflect the scanning beam and return it to the cell. A white painted wall or an aluminum or other self-adhesive strip can be used, as well as a cell capable of receiving a specific part of the colored spectrum, the electronic circuits being programmed accordingly. It is also clear to those skilled in the art that, although the mechanism is shown in the middle of the room, it can just as easily be placed at an angle or laid on its side to scan a wall.

Claims (8)

 1. Alarm device against intruders, characterized in that it comprises: means (11) for transmitting a rotating scanning beam, which is substantially undetectable; means (14) for receiving the reflected scanning signals from this rotating beam; storage and comparison means (1) for recording a first reflected scanning signal and comparing the successive reflected scanning signals to this first reflected scanning signal and signaling means which are actuated when the any of the successive reflected scanning signals differs from the first reflected signal. 2. Device according to claim 1, characterized in that a filter (15) capable of rejecting all received wavelengths other than that of the beam, is placed on the path of the reflected scanning signal. 3. Device according to claim 1 or 2, characterized in that the rotating beam is produced by a low power laser.  4. Device according to any one of the preceding claims, characterized in that reflecting surfaces (19) are used to cover the blind spots resulting for example from the presence of posts. 5. Device according to claim 4, characterized in that the rotating beam is horizontal.  6. Device according to claim 4, characterized in that the rotating scanning beam is inclined so as to obtain a conical scan in the form of a shelter.  7. Device according to claim 4, characterized in that the rotating scanning beam is used for scanning a wall.  8. Device according to any one of the preceding claims, characterized in that a secondary power source is installed, to allow the operation of the device in the event of a breakdown or sabotage of the main energy supply.