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

• Current Assignee: Laser Design International LLC (Laser Design International)
• Original Assignee: United Distillers PLC
• Inventors: Ledger, Neville R., Sunman, Robert P., Clement, Robert M.
• Primary Examiner(s): Berman, Jack I.
• Assistant Examiner(s): NGUYEN, KIET TUAN
• Application Number:
  US07/745,170
• Time in Patent Office: 621 Days
• Field of Search: 250/271, 219/121.6, 219/121.65, 219/121.66, 219/121.85, 427/12, 427/53.1, 427/54.1, 427/55
• US Class Current: 250/271
• CPC Class Codes: B23K 26/035 Aligning the laser beam automatically B23K26/042
• CPC Class Codes: B29C 2035/0838 using laser
• CPC Class Codes: B29C 35/0866 using particle radiation
• CPC Class Codes: B29C 71/04 by wave energy or particle radiation , e.g. for curing or vulcanising preformed articles during moulding, e.g. in a mould B29C35/08
• CPC Class Codes: B41M 5/26 Thermography B41M5/20, B41M5/24 take precedence; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used B23K takes precedence; thermographic or photothermographic systems using noble metal compounds G03C1/494
• CPC Class Codes: B41M 5/262 recording or marking of inorganic surfaces or materials, e.g. glass, metal, or ceramics marking of plastic artifacts with inorganic additives B41M5/267
• CPC Class Codes: B41M 5/267 Marking of plastic artifacts, e.g. with laser
• CPC Class Codes: B44B 7/00 Machines, apparatus or hand tools for branding, e.g. using radiant energy such as laser beamsburning or charring wood stock B27M1/06
• CPC Class Codes: C03C 23/001 by infrared light
• CPC Class Codes: C03C 23/0025 by a laser beam
• CPC Class Codes: G06K 1/126 by photographic or thermographic registration recording apparatus for measuring instruments G01D15/00

Abstract

A method and apparatus for providing a body of material (14) with sub-surface marking in the form of an area of increased opacity to electromagnetic radiation. The method includes directing at a surface of the body (14) a high energy density beam (12, 26) to which the material (14) is transparent, and bringing the beam (12,26) to a focus at a location spaced from the surface and within the body (14) so as to cause localized ionization of the material (14). In a prefered embodiment the apparatus includes a laser (10) as a high energy density beam source and provides means (36, 38) to move the focus of the beam (12,26) relative to the body (14) so as to enable the mark to be of a predetermined shape.

Claims

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.

2. A method in accordance with claim 1, wherein the body is transparent to electromagnetic radiation at wavelengths within the visible region.

3. A method in accordance with claim 1, wherein at least a portion of the body is opaque to electromagnetic radiation at wavelengths within the visible region such that the mark may only be detected by optical instruments operating at an appropriate wavelength within the electromagnetic spectrum.

4. A method in accordance with claim 1, wherein step (b) includes moving the focus of the beam relative to said portion so as to create the mark with a predetermined shape.

5. A method in accordance with claim 4, wherein the mark is three dimensional.

6. A method in accordance with claim 4 or claim 5, wherein the mark comprises one or more numerals, letters or symbols, or a combination thereof.

7. An apparatus for forming a sub-surface mark within a body, at least a portion of said body being of a material to be marked, said apparatus comprising:

means for creating a high energy density beam to which the material is transparent; and

means for 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.

8. An apparatus in accordance with claim 7, wherein the high energy density beam is a focusable particle beam.

9. An apparatus in accordance with claim 7, wherein the means for creating a high energy density beam is a laser.

10. An apparatus in accordance with claim 9, wherein the laser has a peak energy density at the focus of at least 10 J/cm².

11. An apparatus in accordance with claim 9 or claim 10, wherein the laser has a power density at the focus of at least 10⁷ W/cm² and is pulsed with a pulse duration of less than 10^-6 seconds.

12. An apparatus in accordance with claim 9, wherein the laser is a Nd-YAG laser.

13. An apparatus in accordance with claim 9, further comprising means for moving the focus of the beam relative to said portion so as to create the mark with a predetermined shape.

14. An apparatus in accordance with claim 13, wherein the means for moving the focus of the beam includes at least one movable mirror disposed in the path of the beam.

15. An apparatus in accordance with claim 14, wherein the means for moving the focus further includes a programmed computer for controlling the movement of the at least one movable mirror.

16. An apparatus in accordance with claim 14 or claim 15, wherein the at least one movable mirror is a galvanometer mirror.

17. An apparatus in accordance with claim 9, wherein the means for focusing the beam includes a lens element of variable focal length.

18. An apparatus in accordance with claim 9, further comprising a secondary source of visible laser radiation for facilitating alignment of the high energy density beam.

19. An article of manufacture comprising a at least a portion of said body being of a material having an internal zone of damage resulting from localized ionization and spaced from the surfaces of said portion and the surfaces of said body to form a mark within said portion.

20. An article of manufacture in accordance with claim 19, wherein the body is transparent to electromagnetic radiation at wavelengths within the visible region.

21. An article of manufacture in accordance with claim 20, wherein the body is glass or plastic.

22. An article of manufacture in accordance with claim 19, wherein at least a portion of the body is opaque to electromagnetic radiation at wavelengths within the visible region such that the mark may only be detected by optical instruments operating at an appropriate wavelength within the electromagnetic spectrum.

23. An article of manufacture in accordance with claim 19, wherein the mark is three dimensional.

24. An article of manufacture in accordance with claim 19, wherein the mark comprises one or more numerals, letters or symbols, or a combination thereof.

25. An article of manufacture in accordance with claim 19, wherein the article is a container.