Identification method and apparatus

Claim 2

A method according to Claim 1 wherein the operation of using the data sets to map one entity upon the other comprises reproducing representations of the assemblies of arcs from the data sets and mapping one set of reproduced arcs upon the other in such a manner as to maximise the correlation between the representations of respective arcs in the assemblies of arcs while simultaneously minimising the elastic distortions in the mapping between the representations of the arcs.

Claim 3

A method according to Claim 1 or Claim 2 wherein the mapping between the plurality of authentic images to produce the statistically determined differences between the authentic images to establish the criterion of an acceptable level of probability of identify between the two identifies is done in the same manner as that between the two assemblies of arcs.

Claim 4

A method according to Claim 1, Claim 2 or Claim 3, wherein each of the images is analysed into an assembly of arcs by scanning the image to produce a plurality of pixels, producing signals related thereto, determining whether a pixel chosen at random contains an element of the image and if it does recording the co-ordinates of the centre of that pixel, constructing an area about the pixel having a size approximately equal to twice the thickness of an expected linear feature of the image and centred upon the pixel, determining a best fit straight line to pixels in the said area containing elements of the image, the said straight line defining a first segment of an extracted arc, estimating therefrom the co-ordinates of the centre of a similar area adjacent the first area containing another segment of the line represented by the pixels containing elements of the image, determining the best fit straight line to the line represented by the pixels in the second area containing elements of the image to yield a possible second segment of the extracted arc, determining: a) whether the second possible segment of extracted arc is of similar width to the first segment of extracted arc, b) whether the second segment of extracted arc joins onto the first segment with a displacement of less than half a line width and c) whether the second segment of extracted arc has an angle with reference to the previous one which is consistent with a curve of constant curvature within a pre-determined value; accepting the second straight line as representing part of an extracted arc if the above criteria are satisfied, repeating the operation in one direction until the above criteria no longer are satisfied, repeating the operation in the reverse direction, temporarily storing data relating to the possible segments of the extracted arc, determining whether the length of the possible extracted arc exceeds a pre-determined value and if it does, determining the co-ordinates of its centre, the angle of the tangent to the arc at its centre, the curvature of the arc and the chordal length of the arc, storing these parameters, deleting the temporarily stored data and used pixels from the image, and repeating the process in other parts of the image until the entire image has been processed.

Claim 6

A method according to Claim 5 wherein the said portions of faces to be compared comprises the ears.

Claim 8

An apparatus according to Claim 7 for comparing two entities and providing an indication of the probability of the identity of the two entities wherein there is included means (122, 124) for electronically scanning images of the two entities and providing arrays of binary pixels related thereto, means (123, 126) for scanning the arrays of pixels and deriving data sets relating to arcs contained in respective arrays of pixels, means (127) for reproducing the arcs represented by the data sets, and mapping the reproduced arcs relating to one image upon the other and determining the differences therebetween, means (128) for comparing the determined differences between the two images with a standard set of differences determined statistically by repeated comparisons between images of one of the entities so as to provide a criterion of an acceptable level of probability of identity between the two entities, and means (129) for providing an indication of the acceptance or rejection of the proposition that the two entities are identical.

Claim 9

An apparatus according to Claim 7 or Claim 8 wherein the means (73, 122, 124) for providing arrays of binary pixels corresponding to images of the identifies to be compared comprise charged couple device video cameras.