Method and device for producing subsurface markings in a transparent material body

• US 7,388,889 B2
• Filed: 04/07/2006
• Issued: 06/17/2008
• Est. Priority Date: 04/27/2005
• Status: Expired due to Fees

• Current Assignee: Vitro Laser Technologies AG
• Original Assignee: Vitro Laser GMBH
• Inventors: Renaud, Remy
• Primary Examiner(s): Harvey; Minsun Oh
• Assistant Examiner(s): Nguyen; Tuan N.
• Application Number:
  US11/399,955
• Publication Number:
  US 20060249490A1
• Time in Patent Office: 802 Days
• Field of Search: 372/75, 372/21, 372/6, 372/74, 372/25, 372/70, 372/10, 219/121.69, 264/400
• US Class Current: 372/10
• CPC Class Codes: B23K 26/361 for deburring or mechanical trimming B23K26/351 takes precedence
• CPC Class Codes: B23K 26/53 for modifying or reforming the material inside the workpiece, e.g. for producing break initiation cracks
• CPC Class Codes: B41M 5/24 Ablative recording, e.g. by burning marks; Spark recording marking by high energetic means, e.g. by laser otherwise than burning or ablative removal B41M5/26; materials or methods for recording or reproduction by optical means G11B7/00
• 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 7/007 using a computer control means

Abstract

A method and device for producing subsurface markings in a transparent material body by focusing a pulsed laser beam in the interior of the material body so that the laser beam exceeds the destruction threshold of the material body to produce a permanent marking. Individual markings form a freely selectable internal engraving as a result of a relative movement between the laser beam and the material body. The laser pulse is varied with respect to its pulse energy (P) by means of a discharge pulse (E) that has an adjustable time delay from an excitation pulse (A). Markings that have varying optical properties depending on the pulse energy (P) are produced in this fashion.

Claims

1. A method for producing subsurface markings in a transparent material body comprising the following steps:

applying excitation pulses to an optical pump source for a laser material, in order to produce population inversion in the laser material;

focusing a pulsed laser beam in the interior of the material body in such a way that the laser beam exceeds a destruction threshold of the material body at least in a respective focal point to produce a permanent marking; and

creating a relative movement between the laser beam and the material body to create individual markings that form a freely selectable internal engraving;

wherein a pulse energy (P) of a laser pulse from the laser beam is varied by means of a discharge pulse (E) using a Q-switch selected from the group consisting of an active light switch, an acousto-optical modulator and an electro-optical modulator, said discharge pulse having an adjustable time delay from an excitation pulse (A) such that markings with different optical properties are produced in dependence on the pulse energy (P); and

wherein a falling edge of the excitation pulse (A) is utilized as a starting pulse for the adjustable delay time up to a beginning of the discharge pulse.

2. The method according to claim 1, wherein individual laser monopulses are generated with a pulse energy (P) that is defined by the time delay (V).

3. The method according to claim 1, wherein the marking produced in the material body corresponds to a spherical inhomogeneity, a radius r of which varies in dependence on the pulse energy (P).

4. A device for producing subsurface markings in a transparent material body comprising:

a pulsed laser;

optical unit that is adapted to focus a pulsed laser beam from the pulsed laser on an interior of the material body in such a way that the laser beam exceeds a destruction threshold of the material body at least in a respective focal point to produce a permanent marking;

wherein individual markings form a freely selectable internal engraving as a result of a relative movement between the laser beam and the material body;

an optical pump source for a laser material of the laser, said pump source having excitation pulses applied to it to produce population inversion in the laser material; and

a laser resonator having an optical Q-switch in the form of an active light switch within the laser resonator, said switch defining a discharge pulse (E) that modulates optical losses in the laser resonator, said discharge pulse having an adjustable time delay from an excitation pulse (A) such that laser pulses with varying and predetermined pulse energies (P) are emitted by the laser resonator in order to respectively produce markings with varying optical properties in the material body depending on the pulse energy (P); and

wherein a falling edge of the excitation pulse is utilized as a starting pulse for the adjustable delay time up to a beginning of the discharge pulse (E).