GB2097979A - Utilisation of surface textures as a random marking or unique identity - Google Patents

Abstract

A method of identifying articles by analysis of the surface texture thereof comprises selecting a portion of the surface of the article to be identified, analysing the data obtained from the profile of the surface portion, and recording the profile data.

Description

SPECIFICATION Utilisation of surface textures as a random marking of unique identity The present invention relates to a method which utilises the texture or surface condition of an article so as to enable it to be distinguished and identified in a unique fashion.

By this means it would be possible to identify an article or a part of an article by an unalterable feature or characteristic which is peculiar thereto.

There are many known ways of identifying articles: for example, the principle of identification by seal has been known for a long time. However, the seal is itself an article which one endeavours to identify, and it is then necessary to guarantee that the seal does,in fact belong to the article which it protects. It is therefore, of only limited dependability and offers little protection against fraud.

In the field of supervising nuclear installations or plants, random marking techniques are already in use. The marking by dispersion of solid particles in a solid matrix may be mentioned here; the unalterable characteristic being the combination of the distribution of the particles and their size, fixed once and for all in the midst of a solid mass.

Here the means of detection utilises ultrasonic waves and their reflection from the heterogeneous system which, with the specific detecting transducer being used, is intended to constitute an unalterable characteristic of the matrix.

Identification requires the transmission of data by ultrasonics, exact re-positioning of the transducer, and absolute identity between transducers used successively in relation to the three-dimensional network of the dispersed particles. In this case, furthermore, the characteristic requires the use of ultrasonic waves in order to be identified, i.e. it is not directly detected. Moreover, very special technology is required in this method.

In order to seek to obviate the abovementioned disadvantages, according to the invention a new method of identifying articles is proposed.

Every solid object is bounded by a surface. If a solid object is unalterable by nature, then so is its surface when considered as a complete envelope.

In normal use, the surface of an object or article already contributes toward its identification.

Therefore, it is proposed to utilise the texture or surface condition of articles in order to enable them to be identified in a unique manner.

The surfaces has to have, in the region in which it is to be utilised, a certain random characteristic; this being generally the case at the level of the roughness of mechanical surfaces. If it is used just as it is immediately after construction, it can be called "natural". If necessary however, the surface can be locally transformed by surface grinding, surface scratching or scoring, e.g. sandblasting, so as to impart thereto a random texture, i.e. a suitable marking.

The natural or imparted texture constitutes the unalterable characteristic of the article, and its detection by feeler, stylus or any other means generally constitutes the means of identifiction.

In accordance with the present invention, a portion of the surface of the article to be identified is selected, the data obtained from the profile of the surface portion is analysed and the profile data are recorded.

Preferably these profile data are transduced and sampled on a frequency basis.

One embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawing, in which the single Figure is an enlarged perspective view of a section of the surface of an article to be identified.

The Figure shows how the profile of a mechanical surface has a random topographical appearance. The unique characteristic of the profile arises from the wealth of information to be found in the surface of an article; i.e. the peaks, valleys, plateaux, heights, directions etc., when it is scanned at the desired level of scale.

Consequently, if two surfaces have similar dimensions and appearances at the production level of scale (i.e. tolerance, finish, section, etc.), it is always possible to find on a smaller scale a condition of roughness enabling them to be distinguished. In the present case, it is the element of unevenness and the valleys and their location which are important; particularly when the level of scale of the analysis is variable.

Therefore, for identification purposes, the problem then arises of accurately re-positioning the sensing feeler opposite the previously scanned section.

It has been found that an object placed on a simple stand provided with a peg or lug does, in fact, provide repeatedly the same data when replaced on the same stand.

The re-positioning may be of two types: (a) the article to be identified on a small plate or other support) is brought to the identifying apparatus, here it involves a transportable marking; or (b) the apparatus is taken to the marked article, and it is then a question of a stationary marking.

The surface profile data may be recorded directly on to paper or else may be digitized, i.e.

the unevennesses are counted, the heights and distances are measured and a digital code of profile is obtained.

The profile data may thus be transduced and sampled on a frequency basis, so that partial spectra may be utilised at will as an identity code of a texture.

The method of identification proposed by this invention makes it possible to secure articles which are already protected by conventional seals. This method may constitute per se a sealing technique. For example, a threaded rod and bolt assembly can be filed level and then constitute a unique marking: if anyone should unscrew the bolt, it would never be possible to screw it up and re-position it exactly in relation to the screw.

Measurement of the profile across the screw and bolt would detect this fraud.

This method is well suited to the identification of articles by utilising their own topograhical texture, without having to provide a reference hole therein, such as, for example, pictures, statues or furniture. With the other known methods of techniques of identification this would not be possible without damaging the work of art.

Another advantage of the present method lies in the fact that the reading or scanning device may be of small size and does not necessitate bulky means for identification, as is the case with piezoelectric transducers.

Claims (6)

Claims

1. A method of identifying articles by analysis of the surface texture thereof, which method comprises selecting a portion of the surface of the article to be identified, analysing the data obtained from the profile of the surface portion, and recording the profile data.

2. A method as claimed in claim 1 wherein the profile data are transduced and sampled on a frequency basis.

3. A method as claimed in claim 1 or claim 2 wherein the surface portion has previously been treated.

4. A method as claimed in claim 3 wherein the surface portion has been sand-blasted.

5. A method as claimed in any one of the preceding claims wherein the level of scale of the analysis is variable.

6. A method as claimed in claim 1 substantially as hereinbefore described.