Electric heating – Metal heating – By arc
Patent
1995-05-23
1996-12-24
Walberg, Teresa J.
Electric heating
Metal heating
By arc
21912173, 21912177, 347256, B23K 2606
Patent
active
055870945
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a raster-scanning type laser marking apparatus and, more particularly, a laser marking apparatus which branches a laser beam for scanning.
BACKGROUND RELATED ART
A conventional raster-scanning type laser marking apparatus is adapted to scan a mask with a laser beam having a high peak power and to mark on a marking surface the shape of a part of the mask through which the laser beam is transmitted. However, since the laser beam is reduced so as to be narrow, its unit irradiation area is small.
Such laser marking apparatus, which provides a unit irradiation light having a high energy level, is effective for marking on a material having a relatively high marking threshold such as, for example, a metal. However, marking on a material having a low marking threshold such as, for example, a synthetic resin, is carried out on the same irradiation area by reducing this energy level. Therefore, despite a material having a low marking threshold, it requires the same marking time as a material having a high marking threshold, and the resultant efficiency is low.
For marking on the material having a low marking threshold, the energy can be maintained at the same level by increasing the irradiation area. However, if the area of the irradiated surface is expanded in an optical system of the conventional laser marking apparatus, a problem occurs in that satisfactory marking cannot be carried out because there are substantial differences in the distribution of the energy density between the central part of the irradiation area and the periphery thereof.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a laser marking apparatus having a high marking accuracy, which effectively uses the power of the laser, and which is capable of substantially doubling the irradiation area on a surface to be irradiated by the laser beam while maintaining the same intensity distribution of the laser beam from the central part to the periphery, and of marking on a material having a low marking threshold at a scanning speed which is two or more times greater than that of the conventional high output laser marking apparatus providing enough laser power for marking on a material having a high marking threshold.
According to a first aspect of the present invention, a laser marking apparatus, which irradiates an incident laser beam from a laser beam source, for raster-scanning a surface to be marked, through a raster-scanning system comprising an X-direction polarizing mirror, a Y-direction polarizing mirror, a field lens, a mask, etc., is provided with a double polarizing prism comprising a pair of polarizing prisms, for branching the incident laser beam into twin laser beams, arranged in series at intermediate positions between the laser beam source and the upstream one of the X-direction polarizing mirror and the Y-direction polarizing mirror, and adjusting means for varying a distance between the two polarizing prisms. This adjusting means comprises a rotary holder supporting one of the polarizing prisms and having a geared surface on its outer periphery, a slide holder which engages with the rotary holder and accommodates the other polarizing prism, and motors for driving these holders to rotate the rotary holder and to move the slide holder in the direction of the incident laser beam.
A second aspect of the present invention is provided with an adjusting means for a rotation angle at which the two polarizing prisms can be simultaneously rotated. This rotation angle adjusting means comprises a rotary holder which is provided with a pulley on its outer periphery and accommodates the pair of polarizing prisms, a bearing which holds the rotary holder so as to be rotatable, and a motor for driving the pulley to adjust the rotation angle by rotating the rotary holder. In this case, the pair of polarizing prisms can be adapted so that one of these polarizing prisms is independently rotated.
According to a first configuration, the distance between the twin laser b
REFERENCES:
patent: 4367009 (1983-01-01), Suzki
patent: 5309273 (1994-05-01), Mori et al.
Mori Akira
Yamazaki Taku
Yoshida Koji
Kabushiki Kaisha Komatsu Seisakusho
Mills Gregory L.
Walberg Teresa J.
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