Method and apparatus for the identification of metal surface finishes

• US 5,010,578 A
• Filed: 07/17/1989
• Issued: 04/23/1991
• Est. Priority Date: 07/20/1988
• Status: Expired due to Fees

• Current Assignee: Institut de Recherches de La Siderurgie Francaise-Irsid Immeuble Elysees La Defense
• Original Assignee: Institut de Recherches de La Siderurgie Francaise
• Inventors: Siener, Pierre, Steiner, Antoine
• Primary Examiner(s): Moore, David K.
• Assistant Examiner(s): Cammarata, Michael R.
• Application Number:
  US07/380,354
• Time in Patent Office: 645 Days
• Field of Search: 382/8, 382/18, 382/28, 382/68, 382/41, 382/51, 358/101, 73/104
• US Class Current: 382/108
• CPC Class Codes: G01B 11/303 using photoelectric detection means

Abstract

The apparatus includes a specialized scanning system for sampling the metal includes an annular light source for omindirectionally illuminating the surface, a light regulator, and a matrix camera for forming a grey level image of the surface. The image is histogramed according to grey level. The first four statistical moments are calculated from the histogram. The moments are then used as a feature vector to identify the metal surface. If no match is found within the catalogued metal surfaces, allowing for predetermined tolerances for each moment, then the feature vector is catalogued for future recognition.

Claims

1. Method for the identification of metal surface finishes, wherein:

at least a sample portion of said surface is omnidirectionally lit,

a numerical matrix image of said surface is formed, in which each matrix point is associated with a value of grey intensity as a function of the luminous intensity reflected by the corresponding element of the surface,

the set of collected values is processed in the following way;

a histogram is established, for the entire set of matrix points, of the number of points per level of grey intensity,

the first four statistical moments are calculated for said histogram, forming a quadruplet constituting four coordinates of an identification vector of the image, of order equal to or greater than four, said quadruplet being representative of the image,

said image quadruplet is compared to at least one of several pre-identified and catalogued quadruplets,

and if the image quadruplet is equal, allowing for predetermined tolerances for each moment, to one of said catalogued quadruplets, said image quadruplet is attributed the identity of said catalogued quadruplet.

2. Method according to claim 1, wherein the image quadruplet is compared by successive tests on the graded statistical moments beginning by the moment of the first order.

3. Method according to claims 1 or 2, wherein if the image quadruplet to be identified is not equal, within said tolerances, to one of said catalogued quadruplets, said image quadruplets is catalogued.

4. Apparatus for the identification of metal surface finishes, comprising:

means for globally and omnidirectionally lighting said surface,

means for forming a numerical matrix image of said surface, in which each matrix point is associated with a value of grey intensity as a function of the luminous intensity reflected by the corresponding element of the surface,

means for processing the set of collected values, said means arranged in such a way as;

to calculate the first four statistical moments of a histogram, formed for the entire set of matrix points, of the number of points per level of grey intensity,

to form with said four moments a quadruplet representative of the image and constituting four coordinates of an identification vector of the image, of order equal to or greater than four,

to compare the image quadruplet to at least one of several pre-identified and catalogued quadruplets,

and if said image quadruplet is equal, allowing for predetermined tolerances for each moment, to one of said catalogued moments, to attribute to said image quadruplet the identify of said catalogued quadruplet,

and means for the restitution of the results of said processing.

5. Apparatus according to claim 4 wherein the means for lighting are annular.

6. Apparatus according to any one of claims 4 or 5, wherein the means for lighting are associated with a luminous intensity regulating device.

7. Apparatus according to claim 4, wherein the means for forming an image comprise a matrix camera.

8. Apparatus according to claim 4, wherein the means for processing are associated with a viewing screen and/or a printer.