WO2000033261A1

WO2000033261A1 - Pedestrian monitoring system

Info

Publication number: WO2000033261A1
Application number: PCT/GB1999/003902
Authority: WO
Inventors: Brian Samuel Barnes
Original assignee: Footfall Limited
Priority date: 1998-11-27
Filing date: 1999-11-24
Publication date: 2000-06-08
Also published as: AU1283700A; GB9825918D0; IL143383A0; CN1334943A; PL347827A1; BR9915698A; CA2351465A1; EP1133758A1

Abstract

A pedestrian monitoring system defines a series of beams (12) of electromagnetic radiation, each beam (12) extending across a target area (14) substantially transverse to the movement of pedestrians (30) through the target area (14). Each beam (12) of the series of beams (12A-12N) being spaced relative to the other beams (12A-12N) in the general direction (D) of movement of pedestrians through the target area (14), the series of beams being located substantially horizontally at a height above the floor of the target area (14) so that the beams will be interrupted by the legs of pedestrians (30) moving through the target area (14). The monitoring system including means for detecting reflections of each of the beams (12A-12N) and the transverse location at which the beam (12A-12N) is interrupted, in order to identify an object moving through the target area (14) and the direction of movement of the object.

Description

PEDESTRIAN MONITORING SYSTEM

The present invention relates to monitoring systems and in particular to systems for monitoring the passage of pedestrians through an area.

Hitherto, beams of light or other electromagnetic radiation have been used to count the number of pedestrians passing through an area. These systems count one pedestrian each time the beam is broken. Such systems provide only limited information of the pedestrian traffic passing through the area and are not able to provide information relating to the direction of movement of the pedestrians or the nature of the traffic. Furthermore, if a group of pedestrians move through the area together, the monitoring system is unable to discriminate between the individual pedestrians and a false count is produced.

WO98/08208 discloses a sophisticated video monitoring system, which is capable of not only monitoring pedestrians moving through an area but also the direction of movement of the pedestrians and also distinguishing adults from children and other objects such as pushchairs or trolleys. The sophisticated nature of this system makes it relatively expensive and furthermore significant amounts of processing power are required to analyse the video images.

The present invention provides a relatively inexpensive monitoring system which is not only capable of monitoring the number of pedestrians passing through an area but also the direction of movement of the pedestrians and can also distinguish the type of pedestrian or object passing through the area.

In accordance with one aspect of the present invention, a pedestrian monitoring system comprises; a series of beams of electromagnetic radiation, each beam extending across a target area substantially transverse to the movement of pedestrians through the target area; each beam of the series of beams being spaced relative to the other beams in the general direction of movement of pedestrians through the target area; the series of beams being located substantially horizontally at a height above the floor of the target area, so that the beams will be interrupted by the legs of pedestrians moving through the target area; and means to detect reflections of each of the beams and the transverse location at which the beam is interrupted.

With the monitoring system disclosed above, as pedestrians move through the area, movement of the legs of the pedestrians may be tracked by detecting the reflection of beams by the pedestrians legs as they interrupt successive beams as they move across the target area.

According to one embodiment of the invention the beams are pulsed which enables the position at which the beam is interrupted, transversely of the target area, to be determined. Alternatively the transverse location of which the beam is interrupted may be detected by a triangulation technique. As the legs of each pedestrian passing through the area would be spaced apart transversely by a distance that will normally be less than the spacing of legs of different pedestrians, this permits the differentiation of one pedestrian from another and provided that a group of pedestrians are not passing through the area strictly in step, the identification of individual pedestrians in a group.

Furthermore, the monitoring system can give the stride pattern of the individual pedestrians. As the stride pattern will generally differ with the size and age of the pedestrian, it will consequently enable distinction between adults and children. Furthermore, as pushchairs and trolleys will give a totally different pattern, these may also be distinguished from pedestrians.

The direction and speed of movement of the pedestrians may also be detected by monitoring the interruption of successive beams.

According to a preferred embodiment of the invention, the beams are arranged parallel to one another transversely of the general direction of movement of the pedestrians through the target area, the beams being spaced at regular intervals in the general direction of movement of pedestrians through the area, in a horizontal plane located between 10 and 30 centimetres above the floor of the area.

Such an array of beams may be provided by independent sources, each coupled with independent means for detecting reflection of the beams. However, according to a preferred embodiment of the invention, the beams are produced by a single source, reflecting means being provided to scan the radiation from the single source to produce the series of beams. The reflected beams may be redirected by the reflecting means to a single detection means.

According to one embodiment of the invention, a laser beam or columnated light beam is directed onto a series of mirrors which are mounted on a cylindrical drum in spaced axial and circumferential relationship, so that upon the rotation of the drum, the series of pulsed beams is produced.

According to an alternative embodiment a laser beam or columnated light beam is scanned by a first mirror in turn onto a series of secondary mirrors spaced longitudinally of the target area, the secondary mirrors directing the beam transversely across the target area. Alternatively, the series of beams may be produced by scanning a pulsed laser or light beam horizontally using a pivoting mirror.

Typically, the target area of the monitoring system will be from 1 5 centimetres to 130 centimetres long more preferably, from 30 centimetres to 100 centimetres long. The pitch of the beams covering the target area will preferably be from 5 millimetres to 200 millimetres. The width of the target area may be set as required, the system being arranged to take account of interruptions of the beams only within a specified range of transverse locations.

According to a further embodiment of the invention, each beam of the series of beams may be scanned horizontally to further enhance the resolution of the monitoring system. Furthermore, the beams may be scanned vertically, in order to provide further information, for example relating to the height of the pedestrians moving through the area.

The invention is now described, by way of example only, with reference to the accompanying drawings, in which:-

Figure 1 is an isometric diagrammatic illustration of a pedestrian monitoring system in accordance with the present invention;

Figure 2 is a diagrammatic plan view of the system illustrated in Figure 1 ;

Figure 3 is a diagrammatic isometric view of an alternative embodiment of the present invention;

Figure 4 is a diagrammatic plan view of the embodiment illustrated in Figure 3; Figure 5 is a diagrammatic side view of the embodiment illustrated in Figure 3; and

Figure 6 illustrates a typical camera view of the system illustrated in Figures 3 to 5.

As illustrated in Figures 1 and 2, a monitoring system comprises a laser source 1 0 which directs a laser beam 1 2 substantially parallel to a target area 14, through which pedestrians pass. A drum 1 6 is rotatably mounted by the side of the target area 14, the drum 1 6 being drivingly connected to an electric motor 1 8 by means of which it may be rotated. A plurality of mirrors 20 extend from the outer surface of the drum 1 6, the mirrors 20 extending into the path of the laser beam 1 2 as the drum 1 6 is rotated. The mirrors 20 are located at axially and circumferentially spaced locations on the drum 1 6 and are angled to reflect the laser beam 1 2 at right angles, transversely across the target area 14. Upon rotation of the drum 1 6, the laser beam 1 2 will be sequentially reflected by each of the mirrors 20 to provide a series of beams 1 2A to 1 2P extending transversely across the target area 1 4, the beams 1 2A to1 2P being spaced from one another in the general direction D of movement of pedestrians through the target area 14.

The laser beam 1 2 is pulsed either electronically or by means of a rotating shutter 24.

Detector means 26 is provided adjacent the laser 1 0 for detection of the beams 1 2A to 1 2P which are reflected back through mirrors 20, by an obstruction passing through the target area 14.

The drum is positioned so that the beams 1 2A to 1 2P are formed in a horizontal plane at a height of about 20 centimetres above the floor of the target area 14.

As illustrated in Figure 2, as a pedestrian 30 moves through the target area 14, the legs 31 ,32 of the pedestrian will interrupt the beams 1 2A to 1 2P, causing reflections of the beams 1 2A to 1 2P, to be detected by the detector means 26.

The time taken for the reflected pulse of the beam 1 2A to 1 2P to return to the detector means 26, may then be used to detect the transverse position of the obstruction in the target area 14. Typically, for an adult, the normal maximum transverse separation of the legs will be of the order of 20 centimetres. Consequently, if the transverse separation between detected objects is 20 centimetres or less, it can be assumed that the objects are a pair of legs belonging to a single pedestrian. If however the separation is say 30 centimetres or greater, then it can be assumed that two pedestrians 34,35 are moving side-by-side through the target area 14. It is consequently possible to differentiate between individual pedestrians moving through the target area 14, in a group of pedestrians.

Furthermore, by observing the sequence in which each leg breaks the beams 1 2A to 1 2P, that is if beam 1 2A is broken first followed by beams 1 2B and then 1 2C etc. rather than beam 1 2P being broken first followed by beams 1 2N and then 1 2M etc., the direction in which the pedestrian is moving through the target area 14, may be determined. For wider target areas 14, this information may be combined with the transverse distance measured by the reflected beam, to track non-axial and even non-linear movement through the target area 14.

As a pedestrian 34,35 moves through the target area, one leg will remain substantially stationary while the other leg is moving. By observing the positions at which the legs are stationary, it is furthermore possible to obtain details of the stride pattern of the pedestrian 34,35. From the stride pattern it would be possible differentiate between different sizes of pedestrians, i.e. adults or children, an adult 34 generally having a wider stride pattern than a child 35.

Furthermore, pushchairs or trolleys moving through the area will produce a totally different pattern to the "oscillating" pattern of pedestrian legs and may consequently be distinguished from pedestrians.

In the alternative embodiment illustrated in Figures 3 to 6, a laser source 1 1 0 is arranged to direct a laser beam 1 1 2 vertically downwards onto a mirror 1 20. The mirror 1 20 is disposed at 45° and is mounted for rotation, by motor 1 1 8. The mirror 1 20 is thereby arranged to reflect the laser beam 1 1 2, in turn onto a series of stationery secondary mirrors 1 22, the secondary mirrors 1 22 being disposed longitudinally along the target area 1 14. The secondary mirrors 1 22 reflect the laser beam 1 1 2 transversely across the target area 1 14, in a horizontal plane at about 20 cm above the floor of the target area 1 14.

A camera 1 26 is mounted above the height of the rotating mirror 1 20. A first mirror array comprises a mirror 140 with a series of facets 142. Each facet 142 directs the field of view of the camera 1 26, to one of a series of secondary viewing mirrors 144. Each viewing mirror 144 is associated with a different one of the mirrors 1 22, so that the field of view of the camera 1 26 looks downwardly along each of the beams 1 1 2A to 1 1 2F, formed by a reflection of the laser beam 1 1 2 through rotating mirror 1 20 and secondary mirrors 1 22.

The camera 1 26 is arranged so that the beams 1 12A to 1 1 2F traverse an associated line 1 52 of the camera image 1 50, each line 1 52 representing one side of the target area 1 14 at one side of the camera image 1 50 and the other side of the target area 1 14 at the other side of the camera image 1 50. A graduated disc 160 is mounted for rotation with the mirror 120 in order to synchronise the camera 126 with the reflected laser beam 1 12. Alternatively an optical coupling may be used to synchronise the camera 126.

When an object 130 passes through the target area 1 14, as the beams 1 12A to 1 12F are interrupted, the reflection of the laser beam 1 12A to 1 12F is picked up by the camera 126 and provides an image 1 54. The position of that image 1 54 with respect to the X-axis indicates the beam 1 1 2A to 1 12F that has been interrupted by the object, that is the longitudinal position of the object 130 in the target area 1 14, while the position of the image 1 54 with respect to the Y-axis, represents the transverse location of the object 130 in the target area 1 14. The passage of objects 130 through the target area 1 14 may consequently be tracked by following the images 154 of the reflected beams 1 12A to 1 12F.

The camera 126 is preferably fitted with filter means which will filter out all but the reflections of beams 1 12A to 1 12F by objects passing through the target area 1 14.

With this embodiment, movement of mirror 120 may be used to scan each individual beam 1 12A to 1 12F in the horizontal plane. This may be used to look round objects in the target area 1 14 to see objects which may otherwise be obscured. Furthermore, scanning of the beams 1 12A to 1 12F in this manner may be used to provide a measure of the thickness of an object in the target area 1 14. Alternatively, however the mirrors 122 may, for example, be masked so that only a pencil beam

1 12A to 1 12F is produced.

As with the embodiment illustration in Figures 1 and 2, the present embodiment will provide information on the number, type, speed and direction of movement of pedestrians and other objects through the target area 1 14.

Various modifications may be made without departing from the invention. For example, in order to increase the target area covered by the system or increase the resolution, several such systems may be used in combination. Moreover, in accordance with the embodiment illustrated in Figures 3 to 6, depending on the mirror array 140 and a number of images required, it may be possible to capture the first half of the images on the odd field and the second half of the images on the even field of the camera 126.

Alternatively, a second camera 1 26 could be used, both cameras would be line-locked, the first camera capturing images associated with the left half and the second camera capturing images associated with the right half of the target area 1 14.

The mirrors of the embodiments described above could be replaced by prisms.

As an alternative to the use of a camera as disclosed above, any suitable electromagnetic radiation sensitive element or array of elements may be used to detect reflections of the beams and the transverse location at which the beam is interrupted.

Claims

1. A pedestrian monitoring system comprising; a series of beams (12;112) of electromagnetic radiation, each beam (12;112) extending across a target area (14;114) substantially transverse to the movement of pedestrians (30;130) through the target area (14;114); each beam

(12; 112) of the series of beams being spaced relative to the other beams (12;112) in the general direction (D) of movement of pedestrians through the target area (14;114); the series of beams being located substantially horizontally at a height above the floor of the target area (14;114), so that the beams will be interrupted by the legs of pedestrians (30; 130) moving through the target area (14;114); characterised in that means (26; 126) is provided to detect reflections of each of the beams (12;112) and the transverse location at which the beam (12;112) is interrupted.

2. A monitoring system according to Claim 1 characterised in that the beams (12;112) of electromagnetic radiation are laser beams or columnated light beams.

3. A monitoring system according to Claim 1 or 2 characterised in that the beams (12;112) are arranged parallel to one another transversely of the general direction (D) of movement of pedestrians through the target area (14;114).

4. A monitoring system according to any one of the preceding claims characterised in that the beams ( 12; 112) extend in a generally horizontal plane located between 10 and 30 centimetres above the floor of the target area (14;114).

5. A monitoring system according to any one of the preceding claims characterised in that the series of beams { 12; 112) are provided by independent sources.

6. A monitoring system according to Claim 5 characterised in that independent means are provided for detecting reflection of the beams (12;112).

7. A monitoring system according to any one of Claims 1 to 4 characterised in that the beams (12;112) are produced by a single source (10; 110) of electromagnetic radiation, reflecting means (20; 120) being provided to scan the radiation from the single source (10;110), to produce the series of beams (12;112).

8. A monitoring system according to Claim 7 characterised in that the beam (12) is scanned by means of a cylindrical drum (16) mounted for rotation about an axis parallel to a beam (12) of radiation emitted from the radiation source (10), a series of mirrors (20) being provided on the surface of the drum (16) the mirrors (20) being spaced axially and circumferentially, so that upon rotation of the drum (16), the mirrors (20) will sequentially interrupt the beam (12) emitted from the radiation source (10) and deflect the beam (12) to form a series of beams (12A-12N) extending transversely across the target area (14).

9. A monitoring system according to Claim 7 characterised in that a rotating mirror (120) reflects a beam (112) of radiation emitted from the radiation source (110) onto a series of stationery mirrors (122) spaced longitudinally of the target area (114).

10. A monitoring system according to any one of the preceding claims characterised in that the target area ( 14; 114) is from 15 to 130 centimetres long.

11. A monitoring system according to Claim 10 characterised in that the target area (14;114) is from 30 to 100 centimetres long.

12. A monitoring system according to any one of the preceding claims characterised in that the pitch of the beams (12;112) covering the target area (14; 114) is preferably from 5 millimetres to 200 millimetres.

13. A monitoring system according to any one of the preceding claims characterised in that the beams ( 12; 112) are scanned horizontally.

14. A monitoring system according to any one of the preceding claims characterised in that the beams (12; 112) are scanned vertically.

15. A monitoring system according to any one of the preceding claims characterised in that the beam of electromagnetic radiation (12;112) is pulsed, the transverse location at which the beam (12; 112) is interrupted being determined by the time taken for the reflected beam (12;112) to be detected.

16. A monitoring system according to any one of Claims 1 to 14 characterised in that the transverse location at which the beam (12; 112) is interrupted is determined by a triangulation technique.

17. A monitoring system according to Claim 16 characterised in that a camera (126) is provided to detect reflections of the beams (112), the camera (126) being located above the plane of the beams (112).

18. A monitoring system according to Claim 17 characterised in that the field of view of the camera (126) is split to view each beam (112) individually.

19. A monitoring system according to Claim 18 characterised in that each beam (1 12) is represented by a separate line of the image produced by the camera (126).

20. A monitoring system substantially as described herein with reference to, and as shown in Figures 1 and 2 of the accompanying drawings.