Method and apparatus for traffic monitoring

Claim 1

A method of traffic monitoring which comprises forming at least first and second scene images of a scene in which traffic may be present, the images being formed at instants of time separated by a time interval, each scene image being an array of pixels, processing at least one of the first and second scene images to form an edge image representing the occurrence of edges in the scene, determining on the basis of the said edge image the presence or absence, and spatial location, of traffic in the scene, forming a difference image in which each pixel represents the difference between the intensity of the pixels of the first and second scene images at the corresponding point in the image, and determining from the distribution of pixels of different intensities in the difference image the presence or absence of movement in the scene, wherein the edge image and difference image are each subdivided into an array of cells, each edge cell and its related difference image cell corresponding to a given sub-area of the image constituting a scene image cell, the presence or absence of traffic and the presence or absence of movement being separately determined for each scene image cell, characterised in that each of a plurality of scene image cells lying along the image of the line of a traffic lane is analysed as aforesaid, and the presence of predetermined traffic objects detected on the basis thereof.

Claim 2

A method of traffic monitoring which comprises forming at least first and second scene images of a scene in which traffic may be present, the images being formed at instants of time separated by a time interval, each scene image being an array of pixels, processing at least one of the first and second scene images to form an edge image representing the occurrence of edges in the scene, determining on the basis of the said edge image the presence or absence, and spatial location, of traffic in the scene, forming a difference image in which each pixel represents the difference between the intensity of the pixels of the first and second scene images at the corresponding point in the image, and determining from the distribution of pixels of different intensities in the difference image the presence or absence of movement in the scene, wherein the edge image and difference image are each subdivided into an array of cells, each edge cell and its related difference image cell corresponding to a given sub-area of the image constituting a scene image cell, the presence or absence of traffic and the presence or absence of movement being separately determined for each scene image cell, characterised in that each of a plurality of scene image cells lying along the image of the line of a traffic lane is analysed as aforesaid, and the presence of predetermined traffic objects detected on the basis thereof.

Claim 5

A method according to any preceding claim, wherein the presence or absence of traffic and the presence or absence of movement is determined for each scene image cell in accordance with the following table: Movement parameter <T m ≧T m Edge Parameter <T e None Analyse further ≧T e Stop Moving where the movement parameter is a measure of the amount of movement detected in the cell, the edge parameter is a measure of the amount of edges detected in the cell, T m is a movement threshold value, T e is an edge threshold parameter, "None" is a representation that no traffic is present in the cell, "Stop" is a representation that traffic is present and is stopped, and "Moving" is a representation that traffic is present and is moving.

Claim 7

A method according to any preceding claim, wherein the presence or absence of the said traffic objects is visually displayed and/or fed to means for controlling the traffic.

Claim 8

A method according to any preceding claim, wherein a value is determined for the proportion of road space in a given lane which is occupied by traffic.

Claim 9

A method according to any preceding claim, wherein for each traffic object at least one of the following is determined, namely location, the length in cells, a weight expressive of the relative importance of the object, the proportion of movement per unit area and the proportion of movement normalised for the edge parameter.

Claim 11

An apparatus for traffic monitoring which comprises means for forming at least first and second scene images of a scene in which traffic may be present, the images being formed at instants of time separated by a time interval, each scene image being an array of pixels; and means for processing at least one of the first and second scene images to form an edge image representing the occurrence of edges in the scene, determining on the basis of the said edge image the presence or absence, and spatial location, of traffic in the scene, forming a difference image in which each pixel represents the difference between the intensity of the pixels of the first and second scene images at the corresponding point in the image, and determining from the distribution of pixels of different intensities in the difference image the presence or absence of movement in the scene, wherein means are provided for subdividing the edge image and the difference image each into an array of cells, each edge image cell and its related difference image cell corresponding to a given sub-area of the image constituting a scene image cell the presence or absence of movement being separately determined for each scene image cell, characterised in that each of a plurality of scene image cells lying along the image of the line of a traffic lane is analysed as aforesaid, and the presence of predetermined traffic objects detected on the basis thereof.

Claim 12

An apparatus for traffic monitoring which comprises means for forming at least first and second scene images of a scene in which traffic may be present, the images being formed at instants of time separated by a time interval, each scene image being an array of pixels; and means for processing at least one of the first and second scene images to form an edge image representing the occurrence of edges in the scene, determining on the basis of the said edge image the presence or absence, and spatial location, of traffic in the scene, forming a difference image in which each pixel represents the difference between the intensity of the pixels of the first and second scene images at the corresponding point in the image, and determining from the distribution of pixels of different intensities in the difference image the presence or absence of movement in the scene, wherein means are provided for subdividing the edge image and the difference image each into an array of cells, each edge image cell and its related difference image cell corresponding to a given sub-area of the image constituting a scene image cell the presence or absence of movement being separately determined for each scene image cell, characterised in that each of a plurality of scene image cells lying along the image of the line of a traffic lane is analysed as aforesaid, and the presence of predetermined traffic objects detected on the basis thereof.

Claim 17

An apparatus according to any one of claims 10 to 14, comprising visual display means for receiving data from the said processing means, whereby to display the presence or absence of the said traffic objects, and/or traffic control means connected to receive data from said processing means and operate in accordance therewith.

Claim 18

An apparatus according to any one of claims 10 to 15, wherein means are provided for forming said scene images at a plurality of locations, and a scene image is displayed of that scene in which the traffic object having the greatest importance is to be found.