Marking method and marking apparatus using multiple photon absorption, marked optical element manufactured by using the marking method and the marking apparatus

• US 6,969,820 B2
• Filed: 08/20/2004
• Issued: 11/29/2005
• Est. Priority Date: 08/29/2000
• Status: Expired due to Fees

• Current Assignee: Sumitomo Heavy Industries Limited
• Original Assignee: Sumitomo Heavy Industries Limited
• Inventors: Itoh, Kazuyoshi, Hayashi, Ken-ichi
• Primary Examiner(s): ELVE, MARIA ALEXANDRA
• Application Number:
  US10/921,848
• Publication Number:
  US 20050016973A1
• Time in Patent Office: 466 Days
• Field of Search: 219/121.69, 219/121.85, 219/121.68, 219/121.6
• US Class Current: 219/121.69
• CPC Class Codes: B23K 2101/007 Marks, e.g. trade marks
• CPC Class Codes: B23K 26/361 for deburring or mechanical trimming B23K26/351 takes precedence
• 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: C03C 23/0025 by a laser beam
• CPC Class Codes: G01N 21/4788 Diffraction for sizing particles G01N15/0205
• CPC Class Codes: G02B 5/1857 using exposure or etching means, e.g. holography, photolithography, exposure to electron or ion beams
• CPC Class Codes: G02B 5/1871 Transmissive phase gratings
• CPC Class Codes: G03H 2001/0484 Arranged to produce three-dimensional fringe pattern
• CPC Class Codes: Y10S 430/146 Laser beam

Abstract

A marking method is provided which permits an easy detecting of the presence of a mark without using a specific reading apparatus, and is capable of avoiding a damage as well as a strength deterioration of an object material. The marking method comprises: preparing a marking object; converging, into the marking object, a laser beam having a wave length range so chosen that the laser beam can transmit through a material forming the marking object, and then effecting a multiple photon absorption; and moving a converging position of the laser beam, in a manner such that an area, whose refractive index is changed due to the multiple photon absorption, can form a diffraction pattern capable of diffracting a visible light.

Claims

1. A marking method comprising:

a first step of irradiating a marking object by a pulse laser beam while at the same time changing NA of an objective lens and an energy per pulse, thereby forming a characteristic-changed area by virtue of move of a light converging spot;

a second step of obtaining a relationship among the length of the characteristic-changed area, an NA and an energy per pulse;

a third step of determining the length of a characteristic-changed area to be formed;

a fourth step of determining an NA and an energy per pulse, in accordance with the relationship obtained in the second step, also in accordance with the length of a characteristic-changed area to be formed; and

a fifth step of converging a laser beam on the marking object to form a characteristic-changed area therein, by using the determined NA and the determined energy per pulse.

2. A marking method according to claim 1, wherein the first step uses a laser beam to conduct an exposure which is continued until the length of a characteristic-changed area becomes saturated, thereby forming a characteristic-changed area having a saturated length.