Electric heating – Metal heating – By arc
Patent
1991-11-29
1993-11-09
Albritton, C. L.
Electric heating
Metal heating
By arc
21912169, B23K 2600
Patent
active
052605426
ABSTRACT:
A laser marking apparatus comprises a pulse laser oscillator which emits a linearly polarized laser beam; a transmission type liquid crystal mask which displays a pattern to be marked on an article in one of a positive pattern display mode and a negative pattern display mode by dots arranged in a matrix form and which allows to pass the emitted laser beam but differentiates the polarization plane of the laser beam which has passed through masked portions from that through unmasked portions; a polarized beam splitter disposed downstream the transmission type liquid crystal mask for selectivity passing the laser beam to be irradiated on the article to be marked from the transmission type liquid crystal mask; a TV camera for detecting a discriminator indicating the thermal conductivity of the article to be marked; a recognition unit which determines the thermal conductivity of the article to be marked based upon the detected discriminator; and a control unit which controls the transmission type liquid crystal mask to operate in one of the positive pattern display mode and the negative pattern display mode based upon the determined thermal conductivity of the article to be marked in such a manner that when the determined thermal conductivity of the article to be marked is low, the positive pattern display mode is selected and when the determined thermal conductivity of the article to be marked is high, the negative pattern display mode is selected.
REFERENCES:
patent: 4128752 (1978-12-01), Gravel
patent: 4734558 (1988-03-01), Nakano et al.
patent: 4818835 (1989-04-01), Kuwabara et al.
patent: 5157235 (1992-10-01), Okumura et al.
Fujimoto Minoru
Ishiguro Kouji
Kuwabara Kouji
Ohkawa Hiroo
Okumura Kiyoshi
Albritton C. L.
Hitachi , Ltd.
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