Hitachi-High-Technologies Corporation

Shingo Tanaka

Hiroyuki Kawakami

Kazuhiro Zama

Yusuke Miyazaki

Kazuo Takahashi

Noriyuki Aizawa

A laser beam oscillated from a laser source is folded in its path by first and second plane mirrors and enters a beam expander. The surface of each plane mirror is deteriorated with illumination by the laser beam and the reflectance is reduced. To avoid a light quantity of the laser beam entering the beam expander from being reduced below a reference value, when the laser beam is illuminated over a certain time, a position on each of the first and second plane mirrors at which the laser beam is illuminated is changed by a structure for rotating and/or translating a reflecting surface of each plane mirror on a plane, which includes the plane mirror, while an optical axis is kept same. Thus, the useful life of each plane mirror can be prolonged without displacing the optical axis.

Growing community of inventors

Hitachinaka, Japan

Shingo Tanaka