WO2005025963A1

WO2005025963A1 - A monitoring device

Info

Publication number: WO2005025963A1
Application number: PCT/SE2004/001341
Authority: WO
Inventors: Börje Eklund; Hans Undin
Original assignee: Safe Rail Scandinavia Ab
Priority date: 2003-09-16
Filing date: 2004-09-16
Publication date: 2005-03-24
Also published as: SE526113C2; SE0302465L; SE0302465D0; EP1730008A1

Abstract

The invention refers to a device (1) and a method for monitoring a relatively large area in order to detect if an undesired object is present within the area, and a use of such a device. A laser (10) is adapted to emit a laser beam of a determined wavelength over the area. A photo sensor (11) is arranged to receive a reflected part of the laser beam and to generate a signal depending on the reflected part of the laser beam. An evaluation unit (20) is arranged to process the generated signal in order to determined if an undesired object is present within the area. Said laser is adapted to emit a laser beam having a wavelength which is longer than or equal to 1200nm.

Description

A monitoring device

BACKGROUND OF THE INVENTION AND PRIOR ART

The present invention refers generally to a device adapted for monitoring an area for detecting an undesired object within the area. The object in this application refers to all imaginable physical objects such as stones, bags, litter, different kinds of vehicles etc, but also human beings and animals.

More specifically, the invention refers to a device adapted for monitoring a relatively large area in order to detect if an undesired object is present within the area, wherein the device includes a laser, which is adapted to emit a laser beam of a determined wavelength over the area, a photo sensor, which is arranged to receive a reflected part of the laser beam and to generate a signal depending of the reflected part of the laser beam, and an evaluation unit, which is arranged to process the generated signal in order to determine if an undesired object is present within the area.

The invention also refers to a use of such a device and to a method for monitoring a relatively large area in order to detect if an undesired object is present within the area.

At underground stations it is today a problem that different objects or persons may be present on the track and cause accidents when an underground train arrives at the station. The underground station is frequently short in relation to the speed of the train. Furthermore, the driver of the train normally has no possibility to see what happens at the platform, i.e. beside the track proper. Consequently, the driver has no real possibility to brake the train in good time if any object moves from the platform out on the track when the train arrives at the station.

DE-10104157 discloses a monitoring arrangement including a relatively large number of vertical laser devices for monitoring a respective door of an underground train, and a relatively large number of horizontal laser devices for monitoring the track. The horizontal laser devices are arranged after each other beneath the platform along the track at an underground station. Furthermore, each of the horizontal laser devices is intended to sense a respective limited field or area of the track for identifying possible objects on the track. The laser devices are connected to a computer for evaluating the sensed fields. The arrangement disclosed has the disadvantage that it is complex and expensive to install at least partly due to the large number of laser devices to be mounted and connected.

JP2000-127972 discloses the possibility of providing a photographic member or a laser for monitoring a platform and a track area. In this case, physical markings have been arranged at the platform for facilitating the reading of the reflected light.

US-A-5,787,369 discloses a further system for monitoring a track area at a railway or a railway crossings. The system includes a laser arranged to scan an area. In the document the wavelength of 904 mm is mentioned.

W093/154160 discloses a device for monitoring railway crossings, i.e. a relatively small area.

WO01/53851 discloses a radar monitoring device for detecting objects at a track area. The known device may be applied in an underground system. US-A-5,500,525 discloses a system for watching an predetermined, limited area by means of a laser beam. The known system includes an algorithm based on a comparison of an actual reflected image and a stored reference image. The system also includes an identification of an object that has been detected within the area.

US-A-4,952,91 1 refers to an intruder watching system for watching an area. The system includes a laser device including an IR-laser diode operating at an effect of 30 mW and at a wavelength spectrum with a peak at 830 nm. The system also includes means for determining the distance to the point from which the laser beam is reflected by means of triangulation. US-A-4,949,074 discloses a similar intruder watching system.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a simple, effective and secure monitoring of a relatively large area. A further object is such a monitoring which may be installed to low costs. A further object is such a simple and effective monitoring of a track area at an underground station.

This object is achieved by the device initially defined, which is characterised in that said laser is adapted to emit a laser beam having a wavelength which is longer than or equal to 1200 nm. With such a wavelength it is possible to provide a monitoring of a relatively large area, for instance the whole track area in the proximity of an underground station by means of one single laser. The relatively long wavelength is less harmful for the human eye than a laser, which operates with a significantly shorter wavelength and which is normally used in such a monitoring context. Thanks to the now proposed wavelength, a laser beam with significantly higher effect may thus be used and in such a way such a range may be achieved that the whole track area at an underground station may be monitored by one single laser. Preferably, the wavelength is longer than or equal to 1300 nm. More preferably, the wavelength is longer than or equal to 1400 nm and especially longer than or equal to 1500 nm. According to a specific embodiment, the wavelength is approximately 1550 nm. Advantageously, the relatively large area may have an extension extending at least 50 m from said laser, preferably 60, 70, 80, 90, 100, 125, 150 m or more from said laser.

According to an embodiment of the present invention, the device is arranged to scan the laser beam to and fro over the area in such a way that substantially the whole area is subjected to the laser beam during one scan. Such a scanning may be provided in that said laser and photo sensor are rotated with a reciprocating movement or by means of optics. Advantageously, the device may operate at such a scanning speed that said scan lasts during a time shorter than 3 s, preferably shorter than 2 s and more preferably shorter than 1 s. Furthermore, the device may include a support element and a carrying element which is arranged on the support element in such a way that the carrying element is rotatable in relation to the support element, wherein at least said laser and said photo sensor are provided on the carrying element. In such a way, the scan movement may be provided in a simple manner by rotating the carrying element.

According to a further embodiment of the present invention, the device is arranged to scan the laser beam over the area with a reciprocating movement in such a way that the scanned area has a sector-like shape with two limiting end lines forming an angle between each other. The device may then advantageously include an angle sensor sensing an angle between the laser beam and one of the end lines. By means of such an angle sensor it is possible to determine the angle position for a possible object within the area.

According to a further embodiment of the present invention, the evaluation unit is arranged to compare the generated signal to a reference signal and to establish that an object is located within the area if the generated signal deviates from the reference signal with a minimum predetermined value. The evaluation unit is thus arranged to process a signal generated by the reflected beam in order to determine if there is any undesired object within the area by comparing the generated signal to a reference signal. A state where an undesired object is present within the area may then be established if the generated signal deviates from the reference signal in any way. Especially, the reference signal can be a curve corresponding to one scan over the area, wherein the generated signal, which also may be a curve corresponding to a new or the latest scan over the area. Said comparison may advantageously include a subtraction of the two curves from each other. Such a comparison between two signals may be made in a very quick manner and with a relatively small computer power. If a normal state prevails, i.e. if no undesired object is present within the area, the curves are substantially equal to each other, wherein a straight line may be obtained on a screen. If a particular state arises, i.e. if an undesired object has arrived at the area, the curve of the generated signal will deviate from the curve of the reference signal, and a clear deviation appears at said line on the screen. This deviation may easily be read manually or in an automatic manner.

According to a further embodiment of the present invention, the device includes a memory unit arranged to store the generated signal. Furthermore, the reference signal may be stored in a memory unit. Advantageously, the evaluation unit is arranged to update of the reference signal by means of the generated signal. A new reference signal, which is stored in the memory unit, may thus be created at each new scanning if the latest generated signal substantially, but not necessarily completely, corresponds to the curve of the reference signal. In such a way, the device may in a convenient manner be self-adapting to changed light conditions, slow permitted changes within the area etc.

According to a further embodiment of the present invention, the evaluation unit is arranged to generate a warning signal if it establishes that an object is present within the area. Consequently, the deviation between the signals, which are compared to each other, may initiate an alarm device or for instance activating a monitoring camera where the deviation arises, i.e. at the position where the undesired object is present.

According to a further embodiment of the present invention, the area includes a track area at an underground station.

The object is also achieved by the use initially defined of a device as defined above for monitoring said relatively large area. Advantageously, the area may include a track area at an underground station or an area at an airport.

The object is also achieved by the method initially defined, which includes the steps of: emitting a laser beam of a determined wavelength over the area, receiving a reflected part of the laser beam, generating a signal depending on the reflected part of the laser beam, and processing the generated signal in order to determine if an undesired object is present within the area, wherein the emitted laser beam has a wavelength which is longer than or equal to 1200 nm.

Advantageous further developments of the method are defined in the dependent claims 23 to 36.

BRIEF DESCRIPTION OF THE DRAWINGS.

The present invention is now to be explained more closely by means of a description of various embodiments and with reference to the drawings attached hereto.

Fig 1 discloses schematically a side view of a device according to the invention.

Fig 2 discloses schematically a view from above of a device in Fig 1.

Fig 3 discloses schematically a screen of the device in Fig 1 at a normal state. Fig 4 discloses schematically a screen of the device in Fig 1 at a particular state.

Fig 5 discloses schematically a view from above of a device according to the invention at an area of an underground station.

Fig 6 discloses schematically a view from above of a device according to the invention at an area of an airport.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION

Figs 1 and 2 discloses a device 1 which is adapted for monitoring a relatively large area 2 in order to detect if an undesired object 3 is present within the area. The device 1 includes a support element 5 and a carrying element 6.

The support element 5 is intended to be located or mounted at one end or side of the area 2 to be monitored. The support element 5 may then include attachment members 7 of any suitable kind for attachment of the support element 5 on a substrate. In the embodiment disclosed, the support element 5 is designed as a horizontal plate for being applied to a horizontal substrate, for instance the ground. The support element 5 may however also be designed in such a way that the device may be attached to for instance a vertical wall. The carrying element 6 is arranged on the support element 5 in such a way that the carrying element 6 is rotatable to and fro in relation to the support element. In the embodiment disclosed, this reciprocating rotation is produced by means of a motor 8.

The device 1 also includes a laser 10, which is adapted to emit a laser beam B of a determined wavelength over the area 2, a photo sensor 11 , which is arranged to receive a reflected part of the laser beam B and to generate a signal depending on the reflected part of the laser beam B. The laser 10 and the photo sensor 1 1 are both fixedly mounted to the carrying element 6 and directed in the same direction. Since the carrying element 6 is rotated in relation to the support element 5 both the laser 10 and the photo sensor 11 may thus be rotated in such a way that the laser beam B scans to and fro over the area 2, wherein the scanned area 2 is sector-shaped.

The device may also include a sight laser 12, which is used at the installation of the device 1 for calibrating the scan sector and which is also fixedly mounted to the carrying element 6 and directed in the same direction as the laser 10 and the photo sensor 1 1.

The laser 10 may be a diode laser operating with a continuous operation or intermittent operation (pulsed laser). The laser 10 is adapted to emit a laser beam B having a wavelength which may be longer than or equal to 1200 nm, preferably longer than or equal to 1300 nm, more preferably longer than or equal to 1400 nm and most preferably longer than or equal to 1500 nm. Especially the wavelength may be approximately 1550 nm. Since laser light with a wavelength over 1200 nm is not visible for the eye, the sight laser 12 is required for the installation of the device. The sight laser 12 thus operates with a wavelength which is shorter than 12 nm. The laser 10 has an effect which may be at least 50 mW at continuous operation and substantially higher at intermittent operation.

The laser beam B may thus scan the area 2 in that the carrying element 6 is rotated by the motor 8 in relation to the support element, wherein the carrying element 6 and the laser 10 performs a reciprocating movement. The motor 8 may then by adjusted to such a scanning speed that said scan in one direction lasts for a time shorter than 3 seconds, preferably shorter than 2 seconds and more preferably shorter than 1 second.

The area 2 or the scan sector is thus limited by the range of the laser 10 and the photo sensor 11 and by the angle distance α between the end lines 13, 14 of the reciprocating laser beam B.

Consequently, the device 1 is advantageously designed in such a way that the laser beam B may scan substantially the whole area 2 during one scan in one direction. The laser 10 and the photo sensor have a long range, which means that the area 2 has an extension which extends at least 50 m, especially 60, 70, 80, 90, 100, 125, 150 m or more from the laser 10.

Furthermore, the device 1 includes an angle sensor 15, 16, which provides the angle β of the laser beam B in relation to one of the end lines 13. The angle sensor may for instance include a semi- circular cam element 15 that is mounted to one of the support element 5 and the carrying element 6, and a sensor 16 which may be inductive, capacitive or of any other kind and which is mounted to the opposite element 5, 6. By sensing the distance from the sensor 16 to the cam element 15 the actual angle β may be determined with a high accuracy. The angle sensor may also be realised in a plurality of other ways, for instance by means of a potentiometer.

The device also includes an evaluation unit 20, which is arranged to process the generated signal in order to determine if an undesired object is present within the area 2. The evaluation unit 20 may include a processor 21 , a memory unit 22 and a screen 23 or the like.

The evaluation unit 20 is by means of the processor 21 arranged to compare the generated signal to a reference signal and to establish if an object is present within the area if the generated signal deviates from the reference signal with a minimum predetermined value.

The reference signal, which is stored in the memory unit 22, may be a curve corresponding to one scan of the area 2 at a normal state, i.e. when no undesired object is located within the area 2. The generated signal may also be a curve corresponding to a new or the latest scan over the area 2. If no object is present within the area at this renewed scanning, the curve for the generated signal will be substantially identical to the curve for the reference signal. The comparison of the two signals may be made by means of a subtraction of the two curves from each other. Such a comparison between the two signals may be made in a very quick manner and with a relatively small computer power. In order to reduce errors from the relation between the angle sensor 15, 16 and the reflected laser beam, the comparing scannings may be done between two scans in the same direction, i.e. between two scans starting at the same end line 13, 14. If scan 1 is clockwise, scan 2 counter clockwise, scan 3 clockwise, scan 1 and scan 3 may thus be compared to each other and scan 2 and scan 4 to each other.

If no object is present within the area 2, i.e. if the normal state prevails, the result of this subtraction is represented by a straight line 24 running in parallel with a time axis and, for instance, be shown on the screen 23, or on any other remotely located screen. However, if an undesired object has arrived at the area 2, i.e. if a particular state arises, the curve of the generated signal will deviate from the curve of the reference signal. The result of the subtraction thus gives a deviating value at the object. This deviating value may on the screen 23, see Fig 4, or any other remotely located screen, be shown as a deviation 25 from the straight line. Such a deviation 25 may easily be read manually by a person being responsible for the monitoring of the track area.

It is also possible to let the processor 21 sense this deviation and to provide an automatic reading, for instance by letting the processor 21 generate a warning signal which may initiate an alarm device 28 or for instance starting a monitoring camera 29 where the deviation arises, i.e. at the position where the undesired object is located. The sensibility of the device 1 or the limit value for initiating the alarm may vary as a function of the distance from the laser 10 to the point where the laser beam B is reflected at the normal state. This sensibility may be adjusted during the installation of the device 1 , wherein a specific sensibility is defined for each individual angle β. Such a varying sensibility over the area 2 or the scan sector improves the dynamics of the system and reduces the risk for false alarm at strong reflecting signals at short distances. The memory unit 22, which stores the reference signal, may be updated continuously by a new reference signal. For instance, the latest generated signal may form the basis for a new updating of the reference signal by letting the latest generated signal continuously form a new reference signal. Of course it is also possible not to use each new generated signal for an updating of the reference signal, for instance every second, every third, every fourth etc generated signal. In such a way, a new reference signal, which is stored in the memory unit 22 is created at each new scanning provided that the curve of the latest generated signal substantially, but not necessarily completely, corresponds to the curve of the reference signal. By such a continuous updating it is possible to let the device be self-adapting to changed light conditions, slow permitted changes within the area etc. By means of a variable average value formation, the speed of the device 1 with regard to changes in the deviation from the normal state may be further improved. The average value of the generated signal at each individual angle β may be calculated by a predetermined number of measured values from the immediately preceding scannings. Such average values may include measured values of the generated signals from 1 , 2, 3, 4, 5 or more preceding scannings. In such a way, the capability of the device to adapt to changed conditions is further improved.

According to an embodiment disclosed in Fig 5, the area 2 includes a track area 42 at an underground station. In this application, the device 1 may be positioned beside the track 43 and beneath the platform 44. Preferably, the device 1 is positioned beneath the platform 44 where it may be protected from damage and the laser beam B may scan freely without being disturbed by the normal activity at the underground station. According to a specific embodiment, the invention is constituted by a monitoring system including a track area 42 at an underground track 43 and a device 1 as defined above for monitoring the track area 42.

According to a second embodiment disclosed in Fig 6, the area 2 includes an airport area 52 at an airport. The airport area 52 may for instance be a parking place for aircraft 55, a runaway, or any similar area where the aircraft 55 is located. By means of the device, the actual airport area 52 may be monitored in an efficient manner and a warning signal may be generated if an undesired object arrives at the airport area 52 when an aircraft 55 is to pass. Such an object may be another aircraft 55, any other airport vehicle, etc.

The invention is not limited to the embodiments disclosed but may be varied and modified within the scoop of the following claims. For instance, it is to be noted that the invention is not limited to a track area 42 at an underground or an airport area 52 but may be employed at various other areas.

Claims

1. A device adapted for monitoring a relatively large area (2) in order to detect if an undesired object is present within the area, wherein the device includes a laser (10), which is adapted to emit a laser beam (B) of a determined wavelength over the area, a photo sensor (11 ), which is arranged to receive a reflected part of the laser beam (B) and to generate a signal depending of the reflected part of the laser beam (B), and an evaluation unit (20), which is arranged to process the generated signal in order to determine if an undesired object is present within the area, characterised in that said laser (10) is adapted to emit a laser beam (B) which has a wavelength longer than or equal to 1200 nm.

2. A device according to claim 1 , characterised in that the wavelength is longer than or equal to 1300 nm.

3. A device according to claim 1 , characterised in that the wavelength is longer than or equal to 1400 nm.

4. A device according to claim 1 , characterised in that the wavelength is longer than or equal to 1500 nm.

5. A device according to claim 1 , characterised in that the wavelength is approximately 1550 nm.

6. A device according to any one of the preceding claims, characterised in that the area (2) has an extension extending at least 50 m from said laser (10).

7. A device according to any one of the preceding claims, characterised in that the device (1 ) is arranged to scan the laser beam (B) over the area in such a way that substantially the whole area is subjected to the laser beam (B) during one scan.

8. A device according to claim 7, characterised in that the device operates at such a scanning speed that said scan lasts during a time shorter than 3 s.

9. A device according to claim 7, characterised in that the device operates at such a scanning speed that said scan lasts during a time shorter than 2 s.

10. A device according to claim 7, characterised in that the device operates at such a scanning speed that said scan lasts during a time shorter than 1 s.

11 . A device according to any one of claims 7 to 10, characterised in that the device (1 ) includes a support element (5) and a carrying element (6) which is arranged on the support element in such a way that the carrying element (6) is rotatable in relation to the support element (5), wherein at least said laser (10) and said photo sensor (11 ) are provided on the carrying element (6).

12. A device according to any one of claims 7 to 11 , characterised in that the device (1 ) is arranged to scan the laser beam (B) over the area (2) with a reciprocating movement in such a way that the scanned area has a sector-like shape with two limiting end lines (13, 14) forming an angle (α) between each other.

13. A device according to claim 12, characterised in that the device (1 ) includes an angle sensor (15, 16) sensing an angle (β) between the laser beam (B) and one of the end lines (13).

14. A device according to any one of the preceding claims, characterised in that the evaluation unit (20) is arranged to compare the generated signal to a reference signal and to establish that an object is present within the area (2) if the generated signal deviates from the reference signal with a minimum predetermined value.

15. A device according to claims 7 and 14, characterised in that the generated signal for one of said scans forms a curve, and that the reference signal includes a corresponding curve, wherein the evaluation unit (20) is arranged to compare these curves.

16. A device according to claim 15, characterised in that said comparison includes a subtraction of these curves, which gives a resulting curve that forms a substantially straight line if no undesired object is present within the area.

17. A device according to any one of the preceding claims, characterised in that the device includes a memory unit (22) arranged to store the generated signal.

18. A device according to claims 14 and 17, characterised in that the evaluation unit (20) is arranged to update the reference signal by means of the generated signal.

19. A device according to any one of the preceding claims, characterised in that the evaluation unit (20) is arranged to generate a warning signal if it establishes that an object (3) is present within the area.

20. A device according to any one of the preceding claims, characterised in that the area (2) includes a track area (42) at an underground station.

21 . Use of a device according to any one of the claims 1 to 20 for monitoring said relatively large area (2).

22. Use according to claim 21 , characterised in that the area (2) includes a track area (42) at an underground station.

23. Use according to claim 21 , characterised in that the area (2) includes an area (52) at an airport.

24. A method for monitoring a relatively large area in order to detect if an undesired object is present within the area, wherein the method includes the steps of: emitting a laser beam of a determined wavelength over the area, receiving a reflected part of the laser beam, generating a signal depending on the reflected part of the laser beam, and processing the generated signal in order to determine if an undesired object is present within the area, wherein the emitted laser beam has a wavelength which is longer than or equal to 1200 nm.

25. A method according to claim 24, wherein the wavelength is longer than or equal to 1300 nm.

26. A method according to claim 24, wherein the wavelength is longer than or equal to 1400 nm.

27. A method according to claim 24, wherein the wavelength is longer than or equal to 1500 nm.

28. A method according to claim 24, wherein the wavelength is approximately 1550 nm.

29. A method according to any one of claims 24 to 28, wherein the area has an extension extending at least 50 m from the laser.

30. A method according to any one of claims 24 to 29, wherein the laser beam is scanned over the area in such a way that substantially the whole area is subjected to the laser beam during one scan.

31 . A method according to claim 30, wherein the laser beam is scanned at such a scanning speed that said scan lasts during a time shorter than 3 s.

32. A method according to claim 30, wherein the laser beam is scanned at such a scanning speed that said scan lasts during a time shorter than 2 s.

33. A method according to claim 30, wherein the laser beam is scanned at such a scanning speed that said scan lasts during a time shorter than 1 s.

34. A method according to any one of claims 24 to 33, wherein the generated signal is compared to a reference signal and wherein it is established that an object is present within the area if the generated signal deviates from the reference signal with a minimum predetermined value.

35. A method according to any one of claims 24 to 34, wherein the generated signal is stored.

36. A method according to claims 34 and 35, wherein the reference signal is updated by means of the generated signal.

37. A method according to any one of claims 34 to 36, wherein a warning signal is generated if it is established that an object is present within the area.

38. A method according to any one of claims 34 to 37, wherein the area includes a track area at an underground station.