Ushio Denki Kabushiki Kaisha

Kazuaki Hotta

Koji Kakizaki

Kyohei Seki

Takao Kobayashi

Motohiro Arai

A corona preionization electrode unit for use in gas laser apparatus, wherein the electric field for corona discharge is concentrated, and ultraviolet radiation is not blocked, and further the laser gas stream is not obstructed, thereby allowing efficient, stable and uniform corona preionization. The corona preionization electrode unit is disposed in a gas laser apparatus together with a pair of main discharge electrodes for ionizing and exciting a laser gas. The corona preionization electrode unit includes a first electrode covered with a dielectric material and a second electrode placed in contact with the outer surface of the dielectric material around the first electrode. The corona preionization electrode unit is positioned in the vicinity of either one of the main discharge electrodes. The second electrode is a plate-shaped member having a straight edge contacting at least the outer surface of the dielectric material. A portion of the plate-shaped member other than the edge is provided with a plurality of openings for passage of ultraviolet light for preionization and a circulating laser gas.

Corona preionization electrode unit for use in gas laser apparatus

The present invention relates to a wavelength monitoring apparatus capable of measuring both standard light and laser light for semiconductor exposure simultaneously and highly accurately, without a time lag. Entrance-side optical systems and allow light from a laser for semiconductor exposure and reference light from a He&mdash;Ne laser to be incident on different areas of a single etalon in the form of diverging light, converging light or diffused light in such a manner that the respective center axes thereof are displaced relative to each other. Two focusing optical systems and are provided in approximately coaxial relation to the respective center axes of the laser light and reference light passing through the etalon A one-dimensional array optical sensor is placed in a plane P coincident with the back focal planes of the focusing optical systems and to receive interference fringes produced by the laser light and the reference light. The positions of the interference fringes on the one-dimensional array optical sensor are detected to calculate the wavelength of the laser light for semiconductor exposure.

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Gotenba, Japan

Kazuaki Hotta