Sub-surface marking

  • US 5,206,496 A
  • Filed: 08/15/1991
  • Issued: 04/27/1993
  • Est. Priority Date: 08/15/1990
  • Status: Expired due to Term
First Claim
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1. A method of forming a sub-surface mark within a body, at least a portion of said body being of a material to be marked, said method comprising the steps of:

  • (a) directing at said portion a high energy density beam to which the material is transparent; and

    (b) focusing the beam at a location in the material, within said portion, and spaced from the surfaces of said portion so as to cause localised ionisation of the material at said location and the creation at said location of a mark in the form of an area of increased opacity to electromagnetic radiation, substantially without any detectable change at said surfaces or at the surfaces of said body.

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