EP0861481B1 - System for monitoring a swimming pool to prevent drowning accidents - Google Patents

Abstract

PCT No. PCT/FR96/01789 Sec. 371 Date May 12, 1998 Sec. 102(e) Date May 12, 1998 PCT Filed Nov. 13, 1996 PCT Pub. No. WO97/18542 PCT Pub. Date May 22, 1997A system for monitoring a swimming pool to prevent drowning accidents includes sensing devices (D1, D2, D3) for providing electrical signals forming images of bodies immersed in the pool water. Appropriate hardware (10) digitizes the resulting images, and the digital image data is compressed and stored at a series of times. Digitized images of a single body are compared at a series of times. The nature of a body, the path of the body and changes in the position of the body are estimated on the basis of the series of images; and an alarm is activated should the path or movement of the body being observed give cause for concern.

Description

The invention relates to a system for monitoring a swimming pool to prevent drowning.

Currently, swimming pool surveillance is either non-existent, or carried out by human surveillance. Such a surveillance is a difficult task requiring sustained attention and causing nervous fatigue of people, especially lifeguards, to which it falls. Indeed, in addition to the limitations inherent in any system based on human intervention, for example decreased alertness due to fatigue or distraction monitoring of swimming pools is made very difficult in due to the reflection of light on the surface of the agitated water, phenomenon which makes it difficult to visually locate an immobile body, except a few meters deep. The problem of monitoring swimming pools arises especially for swimming pools welcoming the public.

The risk of drowning in swimming pools mainly origin is in the fact that a swimmer does not know how to swim sufficiently, for example in the case of a young child, or in the fact that a swimmer is unwell.

In the first case, in a supervised pool, the lifeguard, or people near the troubled bather, have their attention attracted to the bather himself, in particular due to the agitation of his arms when he tries to stay on the surface; on the other hand, in the second case, there is loss of consciousness of the swimmer without the attention of surveillance or the environment is drawn. There is, in general, two possibilities: either the bather has an exercise respiratory movement reflex and in this case his lungs get fill with water, resulting in immediate loss of consciousness; or a reflex apnea occurs and a certain volume of air remains blocked in the lungs. Generally, the injured bather sinks towards the bottom but, more rarely, it sometimes floats without knowledge in a characteristic position just below the surface of the water.

From the loss of consciousness, which marks a beginning of drowning, an experienced rescuer, knowing in particular practice artificial respiration, has about two to three minutes to rescue the drowned man. If this deadline is respected, the drowned will generally not retain any after-effects from the accident, after possible stay in hospital to clean his lungs. In a way general, if rescue takes place between three and five minutes after loss of consciousness, this time being, however, variable depending on the individuals, the drowned person can still be saved, but he risks certain irreversible damage, especially to the brain. Beyond five minutes, the risk of death becomes very high.

It has already been proposed, in US Pat. No. 5,043,705, to use a sonar to monitor the pool. According to this device, there is at least one sonar transceiver on the bottom of the pool and we monitor a horizontal section using this apparatus. However, such a device has a drawback considerable due to the fact that to install the sonar and connect it to processing devices that take information from received echoes, it cables must necessarily be passed through the bottom of the pool and below this bottom, which entails a completely prohibitive cost when the pool is already built. In addition, safety rules prohibit the use of voltages higher than 12 or 24 volts, depending on the country, near the water of a swimming pool: gold, to generate sonar pulses it is necessary to use voltages of several hundred volts. Furthermore, the signal obtained with a sonar incorporates the echoes provided by the pool walls and it is extremely difficult to eliminate the noise signal thus obtained for ability to detect the signal corresponding to the submerged body of a drowned person. In addition, the sonar essentially makes it possible to locate the body of a drowned by the volume of air it contains; if an accident victim has lungs filled with water, the signal obtained will not at all conform to that which we have the right to wait and may, even, not be spotted by the signal processing. We therefore see that such a system is not likely to give satisfaction.

It was also proposed in the request for WO 95/34056, published after the date of the first priority of this application, to use for a pool surveillance cameras working in the visible wave domain, these cameras being arranged so that the observed area is located in a volume near and parallel to the bottom of the pool. In this device, the cameras observe only a slice of water parallel to the bottom, which involves multiplying the cameras if the background is not flat and leaves unattended most of the volume of the pool. In addition, this device does not detect immobile bodies just below from the surface of the water. Finally, the cameras and their accessories are immersed in the pool, which is not acceptable on the plan security and poses considerable problems to ensure their link with signal processing devices associated with them. This device cannot therefore give satisfaction.

The object of the invention is to provide a system for monitoring of a swimming pool, which can trigger an alarm automatically alerting supervisors within a short time, when the behavior of a swimmer indicates a risk of drowning. A such a system must detect the beginning of drowning, but it is desirable to avoid nuisance trips by analyzing correct behavior of swimmers, especially to avoid a bad interpretation relating to the movement of a swimmer voluntarily diving and / or traveling in immersion. The invention also aims to describe such a device that can be installed without excessive costs in a swimming pool already built. The invention also aims to describe such a device, which is out of reach of pool users and which meets all security requirements. The invention finally has for aim of describing such a device which is capable of maintenance and easy maintenance that does not require emptying the pool.

• des moyens de détection propres à donner, sous forme de signaux électriques, des images des corps immergés dans l'eau de la piscine, ces moyens de détection étant prévus sur les parois de la piscine en des endroits judicieusement répartis pour balayer au moins une fraction du volume d'eau de la piscine ;
• des moyens de numérisation des signaux électriques obtenus ;
• des moyens de compression des données numériques obtenues par les moyens de numérisation précités ;
• des moyens de stockage temporaire et permanent des données numériques d'images à des instants successifs ;
• des moyens de comparaison entre les images numérisées d'un même corps à des instants successifs ;
• des moyens d'estimation de la nature d'un corps (corps humain ou non), de la trajectoire et des changements d'attitude du corps d'après ces images successives ;
• et des moyens de décision propres à déclencher des moyens d'alarme en cas de trajectoire ou mouvement suspect du corps observé.

According to the invention, a swimming pool monitoring system for the prevention of drowning, is characterized in that it comprises:

• means of detection suitable for giving, in the form of electrical signals, images of the bodies immersed in the water of the pool, these detection means being provided on the walls of the pool in places judiciously distributed to scan at least a fraction the volume of water in the pool;
• means for digitizing the electrical signals obtained;
• means for compressing the digital data obtained by the aforementioned digitizing means;
• means for temporary and permanent storage of digital image data at successive instants;
• means of comparison between the digitized images of the same body at successive instants;
• means of estimating the nature of a body (human body or not), the trajectory and changes in attitude of the body from these successive images;
• and decision means capable of triggering alarm means in the event of a suspicious trajectory or movement of the body observed.

Preferably, each detection means comprises at least minus a video camera arranged in a sealed waterproof compartment by a side wall of the pool, between the surface of the water of the swimming pool in operation and the bottom of said swimming pool; the waterproof compartment being below the surface of the water, one can provide that an anti-humidity module is disposed inside said waterproof compartment. Advantageously, the sealed compartment submerged has two video cameras, including observation fields each have a substantially equal opening angle or slightly greater than 90 ° and whose axes are substantially orthogonal in a substantially horizontal plane.

Advantageously, means are used to multiplexing of electrical signals from the means of detection, these multiplexing means supplying the means of digitization; said digitizing means and the means of compression of digital data are advantageously made up by a video image digitization and compression card placed in a microcomputer in "multimedia" configuration.

The means of temporary and permanent storage of digital image data at successive instants, the means of comparison between digitized images of the same body at successive instants, the means of estimating the trajectory and changes in a body's attitude and the means of decision are made up of the components of a microcomputer, in particular memory elements and central processing unit of this microcomputer, in which appropriate software has been loaded to allow it to run the operations indicated.

Advantageously, the digitization means allow to digitize 25 images per second, these images being provided by detection means via the multiplexing means.

The means of comparison of the digitized images between successive instants are suitable for taking into account only shapes, the dimensions of which correspond at least to those of a child, to eliminate nuisance alarms that may be caused by foreign bodies. These means of comparison are, moreover, arranged to isolate a shape and follow its path at instants successive.

The means of estimation are suitable for determining, from the results of the means of comparison, the slow nature of a movement and / or immobility of a human body in the pool.

The means of decision are suitable for triggering a alarm if the slow nature of the movement or the almost immobility of the body in the pool extends beyond a specified time, in especially after 15 seconds.

Advantageously, the images which were used for the analyzes which led to the triggering of an alarm are recorded on the microcomputer hard drive so that it can be accessed at any time.

Preferably, one or more control screens are arranged near the lifeguard seats or in the premises of responsible for monitoring the pool, screens on which are displayed images of an area considered suspicious.

The alarm can be given by an audible warning and / or visual, in particular with indication of the pool area in which a suspicious event occurs.

Provision can be made for an immediate stop of pumping and filtration of the pool water in the event of an accident detected, stop device which can be controlled either manually or automatically by the microcomputer.

Advantageously, the detection means are arranged each in a sealed enclosure vis-à-vis the pool water, of which a wall consists of a globe comprising zones, through which are acquired the information necessary to give the images bodies immersed in the pool water, and another wall of which is tightly crossed by cables carrying outwards from the pool, the signals supplied by the detection means. Wall, which the cables pass through, can be fitted with a first connector removable waterproof connected to the first end of a waterproof sheath, the other end of which is connected to a second watertight fitting fixed on the bottom of a case, which crosses tightly the side wall of the swimming pool. It is preferably provided that the interior of the housing is in communication with the pool water and that the waterproof sheath is coiled in the housing so as to have a length at least equal to one that allows the enclosure to be taken out of the pool water without disassembly of the tight fitting fixed on the bottom of the case.

The invention consists, apart from the provisions set out above, in a number of other provisions, of which it will be more explicit question below about an example nonlimiting described with reference to the accompanying drawing.

• la figure 1 est une vue schématique, en perspective, d'une piscine équipée des moyens de détection du système de surveillance selon l'invention ;
• la figure 2 est une vue en plan schématique de la piscine illustrant les champs de vision des moyens de détection qui balayent tout le volume d'eau de la piscine ;
• la figure 3 est une vue en élévation d'un globe immergé contenant un moyen de détection du système de surveillance selon l'invention ;
• la figure 4 est une vue en coupe selon la ligne IV-IV de la figure 3 ;
• la figure 5 est une vue agrandie du détail A de la figure 4 ;
• la figure 6 est une vue en coupe selon la ligne VI-VI de la figure 4 ;
• la figure 7 est une vue agrandie du détail B de la figure 6 ;
• la figure 8 est une vue en perspective du globe de la figure 3 ;
• la figure 9 est un schéma synoptique simplifié du système de surveillance.

On this drawing :

• Figure 1 is a schematic perspective view of a swimming pool equipped with the detection means of the monitoring system according to the invention;
• FIG. 2 is a schematic plan view of the swimming pool illustrating the fields of vision of the detection means which scan the entire volume of water in the swimming pool;
• Figure 3 is an elevational view of a submerged globe containing a detection means of the monitoring system according to the invention;
• Figure 4 is a sectional view along the line IV-IV of Figure 3;
• Figure 5 is an enlarged view of detail A of Figure 4;
• Figure 6 is a sectional view along line VI-VI of Figure 4;
• Figure 7 is an enlarged view of detail B of Figure 6;
• Figure 8 is a perspective view of the globe of Figure 3;
• Figure 9 is a simplified block diagram of the monitoring system.

As illustrated in Figure 1, the monitoring system of a swimming pool P comprises detection means D1, D2, D3 provided on the pool walls in places judiciously distributed to sweep the entire volume of the pool. In the example considered, the three detection means D1, D2, D3 are arranged, in the same horizontal plane, for example at a level of about 1.50 m below the water level in the operating pool. As illustrated on FIG. 2, the detection means D1, D2, D3 are arranged with so that their fields of vision partially overlap so that leave no dead zones and sweep virtually the entire volume of the swimming pool. An element or a body located in the pool will therefore be seen by at least two detection means D1, D2, D3.

These detection means are suitable for providing, under form of electrical signals, images of bodies submerged in water of the swimming pool.

The detection means D1, D2, D3 are all identical and one of them, D1, will be described in detail below. The medium D1 includes two video cameras 1 and 2, preferably cameras "CCD" type electronics. The axes of the two cameras form a 90 ° angle between them and are symmetrical with respect to a plane perpendicular to the wall of the pool passing through the axis of the means of detection. The opening angle of the field of vision for each of the cameras 1 and 2 is greater than 90 ° and one of the edges of the field roughly coincides (plan view) with the pool wall, which carries the detector, so that, for all of the two cameras, the field of vision (seen in plan) is 180 ° with a central zone α, β, γ respectively for the detection means D1, D2, D3 where there is a overlap of the fields of the two cameras. In the example described, the detection means D2 is carried by the transverse wall 100 of the swimming pool P, which is adjacent to the large bath, at a point B of said wall 100 located in the median longitudinal plane of the swimming pool, while the detection means D1 and D3 are carried at A and C by the two walls longitudinal 101, 102 of the swimming pool, directly above the bottom zone inclined 103, which connects the small bath and the large bath, points A and C being in the vicinity of the median transverse plane of the swimming pool P. We have shown diagrammatically in FIG. 2, the observation cones of the two cameras of each detection means, by designating by a1, a2 the cones of the cameras of the detection means D1, by b1, b2 those of the means of detection D2 and by c1, c2 those of the detection means D3. We see so that most areas of the pool are covered more than once by detection means: monitoring is volume since each camera has an observation cone, while in the state of the WO 95/34056, it was only possible to monitor a slice of water near the bottom. However, it exists above and below of each means of detecting areas of water which are not covered only twice. The field of each camera encroaches on a small angle e on the pool wall with which said camera is associated, this which reduces dead zones not covered by the observation of cameras.

The cameras 1 and 2 are arranged in a globe 3, closed in a sealed manner and carried, as indicated below, by the wall 4 of the swimming pool. This wall 4 is crossed by a cylindrical duct 5, wherein is housed a cylindrical housing 7 containing a tubular sheath 8 which are arranged the electric wires 8a of connecting the cameras 1 and 2 to the microcomputer 9 management of the surveillance system of the swimming pool. The sheath 8 is wound in a helix along the wall of the housing 7 and its ends are secured, by watertight connections 20 and 24, respectively with the bottom 7 a of the housing 7 and with a bell 23 associated with a compartment 21, which will be defined below. The compartment 21 is waterproof; the bell 23 is assembled in a sealed manner on the compartment 21; the interior of the bell 23 is connected with the exterior of the housing 7 by the sheath 8.

The two cameras 1 and 2 are oriented approximately 90 ° from each other, and their axes are substantially in a horizontal plane. In the example of FIGS. 3 to 8, the globe 3 is rounded to avoid any injury for a swimmer coming into contact with said globe. Globe 3 is molded from cast aluminum; front of the cameras 1 and 2, it has two circular orifices where one enchassé two lenses 1a, 2a, which cooperate with the objectives of the two cameras 1,2 respectively, to form "assemblies objectives"; the border of each lens forms a collar stuck in a circular recess of the globe. The lenses are made of a glass of high hardness to avoid any risk of deterioration; the design of the lenses 1 a , 2 a makes it possible to adapt the optical characteristics of the "objective assemblies" to the needs of the system.

The conduit 5, which passes through the side wall 4 of the swimming pool, is produced by coring; the cylindrical housing 7 is placed there, the centering being carried out by two O-rings 90, 91. The seal 91 located on the swimming pool side has two holes, one in the vicinity of the low point and the other in the vicinity of the high point . A polymerizable resin is injected through the lower hole to form a gasket 6 between the duct 5 and the housing 7. After polymerization, the front face of the gasket 6 is finished, on the swimming pool side, by fitting a silicone seal 6 a .

The housing 7 is intended to be filled with water from the pool. The cameras 1 and 2 are housed in the sealed compartment 21, one of whose faces pool hand consists of the globe 3, while the other side, the bottom side 7a, is defined by a cylindrical cup 21a, the free edge of which bears a peripheral flange 21 b . When the cameras are installed in compartment 21, the globe 3 is fixed to the flange 21 b by means of screws, which cooperate with threaded bushings placed in bores provided in the thickness of the base 3 a of the globe 3 . the screwing of said screw causes compression of an annular seal 3b which seals the assembly. The bottom 21 c of the bowl 21 a carries an electronic card 92 to which the output wires of the cameras 1 and 2 are connected. The output of said electronic card passes through the bottom 21 c in a sealed manner which, on its external face, carries a female connector 93. The bottom 21 c carries, in addition, two valve fittings 94, 95 intended to cooperate with a nitrogen supply pipe, on the one hand, and with a vent pipe, on the other hand. It is thus possible, when the compartment 21 has been closed by assembling the globe 3 and the bowl 21 a , put the interior of the compartment under dry nitrogen to avoid oxidation, improve the life of the CCD cameras and prevent any problem of fogging; as soon as the pipes are disconnected, the valves of the fittings 94, 95 isolate the inside of the compartment 21 from the outside. On the bottom 21 c , outside the compartment 21, there is the bell 23, which is secured to the bottom 21 c by its rim 23 a ; the rim 23 a bears against the bottom 21 c by means of an annular seal 23 b , the compression of which is ensured by screws.

By screws 96 a, is fixed on the flat end of the casing 7 opposite to the bottom 7 has a flange 96 intended to hide the edge of the core which is disposed the housing 7 as well as the area occupied by the gasket 6. At its end opposite the bottom 7 a , the housing 7 has three peripheral bosses 7 b projecting towards the axis of the housing 7; in these bosses are inserted threaded sockets, which cooperate with screws 25; the heads of the screws 25 are supported on the peripheral rim 3 c of the globe 3. This ensures the maintenance of the sealed compartment 21 relative to the housing 7; but, due to the thickness of the globe 3 in the area where it is traversed by the screws 25, a clearance has been made between the collar 96 and the flange 3 c ; similarly, there is a clearance between the housing 7 and the part of the globe 3, which penetrates there; it follows that the pool water freely penetrates into the housing 7. It is therefore possible, from the swimming pool, to separate from the housing 7 the enclosure (3, 21, 21 a , 23) whatever the depth where is the means of detection in the pool water.

The bottom of the bell 23 carries a tight fitting 24 which ensures the fixing of the sheath 8 on the bell 23. The electrical cables 8a are threaded in the sheath 8 before fixing the bell 23 on the bottom 21 c of the bowl 21 a and the cables 8 a protrude behind the bottom 7 a of the housing 7, the seal at the level of the crossing of the bottom 7 a being ensured by the waterproof connection 20. Between the waterproof connections 20 and 24, a length of waterproof sheath is provided. 8 sufficient for the enclosure (3, 21, 21 a , 23) to be able to be detached from the wall of the swimming pool and reassembled on the edge of the swimming pool for the purposes of maintenance, repair or replacement. At the same time that the cables 8a, is threaded into the sheath a pending thread, for example a nylon thread, which in a known manner, acts as a "needle" for allowing the introduction of a cable, complementary or replacement, in the sheath 8 without it being necessary to disconnect the connector 20 and therefore to empty the pool: it suffices, in fact, to hook the new cable and a new "needle" to the wire nylon behind the bottom 7 a , to put the enclosure out of water (3, 21, 21 a , 23), to disassemble the bell 23. to disconnect the connector 93, to pull by the end thus released from the sheath 8 the nylon thread therein, until the appearance of the new cable and the new "needle", to throw said nylon thread constituting the initial "needle", to connect the new cable put in place on the connector 93, reassemble the bell 23 on the bowl 21 a , lower the enclosure (3, 21, 21 a , 23) under water and reattach it by the screws 25 on the face of the housing 7.

Furthermore, the same set of screws 25 can be used to maintain a sealing cover (not shown) of the housing 7 when the compartment has been removed (3, 21, 21 a ), the bell 23 having, beforehand, been tightly fixed on that of the faces of said cover, which is on the housing side.

Preferably, inside the compartment 21 is provided an anti-humidity module (not shown).

The cables 8a, passing through the casing 7, are coaxial cables connected, via multiplexing means 10a, a microcomputer 9, for example of the type "IBM compatible" is arranged around a microphone -Processor PENTIUM on each cable 8a, establishing a continuous voltage to the corresponding 1,2 camera power and sends said camera on the cable 8 has a modulation which is the signal to be processed. Before entering the multiplexing means 10 a , the separation of the DC component is ensured by demodulation means which supply only on the multiplexing means the signal emanating from the "CCD" type camera. The microcomputer 9 comprises a central processing unit 13, temporary storage means, or random access memory 11 a , permanent storage means, or hard disk 11 b , and a remote control card 14 capable of controlling warning means 15 or valves 16; moreover, it is connected to a control screen E, said screen being a touch screen allowing an operation command. The microcomputer 9 is in a "multimedia" configuration and is equipped with a video acquisition card 10 constituting means for digitizing the electrical signals supplied by the detection means D1, D2, D3, and means for compressing the data. digital image.

The images, in the form of electrical signals, are received, by the demodulation means and the multiplexing means designated by 10 a as a whole, at the rate of 25 images per second, by the video acquisition card 10, which transforms them into digital images.

Thanks to multiplexing, it is possible to process the means detection D1, D2, D3 with the same video card 10. It should be noted than the number of detection means processed by the same card could be greater than three and, for example, be equal to eight.

Storage means 11 for digital image data at successive instants t, (t + 1), etc. are provided. These storage means 11 are constituted by memory means of the microcomputer 9, in particular internal random access memory means 11 a and the hard disk 11 b of the computer.

Means of comparison 12 between digitized images of the same body at successive instants t and (t + 1) are provided. The comparison means 12 are formed by the central processing unit 13 of the computer and appropriate software stored in an area of the internal random access memory 11 a .

The time interval Dt between two instants t and (t + 1) taken into account is sufficient so that in the event of a movement normal of a swimmer, the differences between the two successive images reflect such a movement; the time interval Dt is however as small as possible so that an alert is triggered without delay in the event of a suspicious situation. This interval Dt can be of the order of a few tenths of a second.

The comparison means calculate, between two instants t and (t + 1), the differences between two successive image matrices from the same camera.

The means of comparison thus make it possible to obtain the zones of change between two images at successive instants, i.e. the areas of movement between the two instants considered.

The central processing unit 13 combined with software appropriate, also constitutes a means of estimating the nature of a body, the image of which is obtained (human body or not), of the trajectory and attitude changes of this body. Central unity 13 and the software are, moreover, intended to constitute means of decision to trigger an alarm in the event of a trajectory or suspicious body movement observed.

Software allowing computer 9 and its unit central 13 to perform the functions mentioned above can match various algorithms.

Because we know the matrix of the initial image (empty pool), we can individually count and monitor the different shapes moving in the pool, captured by the means detection.

Using the principle that knowledge of the derived from a function and its initial value, lets you know the function, we can identify and follow various forms, corresponding to different bodies moving in the pool, for example F1, F2 ...... Fn.

We make a correction on the shapes followed, especially in terms of size. In fact, we only consider shapes having at least dimensions corresponding to those of a small child. We can thus remove images of inert objects, small dimensions, and avoid nuisance alarms.

We follow the evolution of the trajectory of the various forms F1, F2 ..... Fn in the reference frame of the pool. In the event of suspect movement, in particular in the event of a vertical movement of slow descent which corresponds to a passive casting, or in the event of immobility at the bottom of the swimming pool, or in the event of immobility just below the surface free of water, the corresponding form F _{i is put} under pre-alert.

The judicious placement of the detection means D1, D2, D3 relative to the bottom of the pool ensures proper operation, the entire pool being covered by these detection means. A shape followed F1 .... Fn should be able to disappear ideally only by "the top "that is to say when leaving the lower area of the pool in going up, or out of the pool.

If after a predetermined interval of time, advantageously approximately 15 seconds, the shape followed F _i has not changed suspicious behavior, that is to say if the immobility at the bottom or the slow vertical movement or even l immobility in the vicinity of the surface continued for these 15 seconds without resuming a non-passive trajectory, the alert is triggered by the computer 9. The latter advantageously comprises a remote control card 14 suitable for actuating various warning means audible or visual.

For example, the computer can set off a vibrator or snorer 15, in particular worn on the belt of a charged lifeguard monitoring the pool. In addition, the swimming pool area where product the event that triggered the alert can be reported on a liquid crystal screen, also worn by the lifeguard, under form of an alphanumeric code, so that the lifeguard can intervene quickly in the right place.

It can also be provided that the computer 9, in the event alert, cut the pool drain valves 16 to remove any suction effect on the exhaust grilles located at the bottom of the pool. We can also send automatically fax to an emergency medical service.

Finally, the software used can order, by the microcomputer 9, storing images on hard drive 11b scanned of the incident.

The examples given above are not limiting and other means of reporting the alert may be used.

In addition, the images of the area where a suspicious movement, including immobilization at the bottom of the pool of a body, are displayed on at least one control screen E at the available to supervisors.

With such a system, you should definitely detect all cases of suspicious movement likely to lead to an alert, but we must also avoid nuisance trips. Through example, a shape consisting of a grayer area in the background of the pool can simply be a shade of sufficient size created suddenly by the sun. Avoid triggering untimely in such a case.

The use of one or more sonars, in particular sonar active at high frequency, in the detection means D1, D2, D3, allows the removal of such a doubt and, if necessary, a second monitoring of the trajectories of the shapes. F _i according to the same sequence as that mentioned in connection with detection means essentially constituted by cameras.

Other means of detection than video cameras could be used, for example thermal imaging cameras.

The removal of the doubt on a detected form could be performed with other means than a sonar, for example with a laser.

Whatever the variant of embodiment adopted, the invention monitoring system improves security swimming pools.

Claims (18)

1. System for monitoring a swimming pool to prevent drowning accidents, characterized in that it comprises:

   detection means (D1, D2, D3) which can give, in the form of electrical signals, images of bodies immersed in the water of the swimming pool, these detection means being provided on the walls of the swimming pool at points which are expediently distributed in order to scan at least a fraction of the volume of water in the swimming pool;

   means (10) for digitizing the electrical signals which are obtained;

   means (11a, 11b) for temporary and permanent storage of the digital data pertaining to images at successive times;

   means (12, 13) for comparing the digitized images pertaining to the same body at successive times;

   means (12, 13) for assessing the nature of a body (whether or not it is a human body), the path and changes in attitude of the body on the basis of these successive images; and

   decision means (12, 13) which can operate alarm means (15) should the path or movement of the body being observed give cause for concern.
2. System according to Claim 1, characterized in that each detection means (D1, D2, D3) comprises at least one video camera (1, 2) arranged in a watertight compartment (21).
3. System according to Claim 2, characterized in that the watertight compartment (21) is immersed and contains two video cameras, the conical observation fields of which have an aperture angle of about 90°, and the axes of which are substantially orthogonal in a substantially horizontal plane.
4. System according to one of Claims 1 to 3, characterized in that it comprises means (10) for compressing the digital data obtained by the aforementioned digitizing means, and the means for digitizing the images which are obtained and for compressing the digital data consist of a card (10) for digitizing and compressing video images which is placed in a microcomputer (9) with multimedia configuration.
5. System according to one of Claims 1 to 4, characterized in that the detection means (D1, D2, D3) feed the digitizing means (10) via multiplexing means (10a).
6. System according to one of Claims 1 to 5, characterized in that the means (11a, 11b) for storage of the digital data pertaining to images at successive times, the means for comparing the digitized images pertaining to the same body at successive times, the means for estimating the path and changes in attitude of a body and the decision means consist of the components of a microcomputer (9), in particular memory elements (11a, 11b) and the central processing unit (12, 13) of this microcomputer, in which suitable software has been loaded in order to allow it to perform the operations which have been indicated.
7. System according to Claim 6, characterized in that the means (12, 13) for comparing the digitized images between successive times are capable of taking into consideration only images whose dimensions correspond at least to those of a child, in order to exclude false alarms which may be caused by foreign bodies.
8. System according to one of Claims 6 and 7, characterized in that the comparison means (12, 13) are designed to isolate a shape and track its path at successive times.
9. System according to one of Claims 6 to 8, characterized in that the estimation means (12, 13) are capable of determining, on the basis of the results of the comparison means, that a human body in the swimming pool is moving slowly and/or is motionless.
10. System according to one of Claims 6 to 9, characterized in that the decision means (12, 13) are capable of operating an alarm if the body in the swimming pool continues to move slowly or remains substantially motionless for more than a determined time, in particular more than 15 seconds.
11. System according to one of Claims 6 to 10, characterized in that the images which were used for the analyses leading to a warning being given are recorded on the hard disk (11b) of the microcomputer (9) so that they can be consulted at any time.
12. System according to one of Claims 1 to 11, characterized in that at least one monitor screen (E) is accessible to the personnel monitoring the swimming pool, on which screen the images of a region considered as giving cause for concern are displayed.
13. System according to one of Claims 1 to 12, characterized in that the alarm means comprise an audible and/or visual warning device (15), in particular with an indication of the region of the swimming pool in which an event giving cause for concern is taking place.
14. System according to one of Claims 1 to 13, characterized in that it includes a device (16) for immediately shutting down the pumping and filtration of the water in the swimming pool should an accident be detected, it being possible for this shutdown device to be controlled either manually or automatically by the microcomputer (9, 14).
15. System according to one of Claims 1 to 14, characterized in that the detection means (D1, D2, D3) are each arranged in a watertight compartment (21), one wall of which consists of a globe (3) having regions (1a, 2a) through which the information is acquired, making it possible to give the images of the bodies immersed in the water in the swimming pool, and another wall (23) of which is passed through in watertight fashion by cables (8a) which convey the information supplied by the detection means (D1, D2, D3) to outside the swimming pool.
16. System according to Claim 15, characterized in that the wall (23) through which the cables (8a) pass is equipped with a first removable watertight connector (24), connected to the first end of a watertight sheath (8) whose other end is connected to a second watertight connector (20) fixed to the end (7a) of a casing (7) which passes in watertight fashion through the side wall (4) of the swimming pool.
17. System according to Claim 16, characterized in that the interior of the casing (7) is in communication with the water in the swimming pool, and in that the leaktight sheath (8) is coiled in the casing (7) so as to have a length at least equal to that which makes it possible to remove the compartment (21) from the water in the swimming pool without detaching the watertight connector (20) fixed to the end (7a) of the casing (7).
18. Swimming pool equipped with the system according to one of Claims 1 to 17, characterized in that the detection means (D1, D2, D3) are arranged in such a way that their fields of view partly overlap so as to leave no blind region and to scan substantially the entire volume of the swimming pool.

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