Optical: systems and elements – Single channel simultaneously to or from plural channels – By partial reflection at beam splitting or combining surface
Patent
1997-07-08
1999-01-26
Ben, Loha
Optical: systems and elements
Single channel simultaneously to or from plural channels
By partial reflection at beam splitting or combining surface
359822, 355 71, 353101, 250548, 356375, G02B 2714
Patent
active
058644334
ABSTRACT:
In a projection exposure apparatus, two plane-parallel plates, which are equal in thickness and refractive index, are interposed between a projection optical system and a wafer. By tilting these two plane-parallel plates at the same angle in opposite directions with respect to the optical axis of the optical system by means of an adjusting device, astigmatism caused in the optical system by exposure is corrected. The amount of astigmatism is calculated by a calculating device based on the amount of light incident on the optical system per unit of time which is obtained according to the output of a light amount sensor.
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Shinonaga Hirohiko
Takahashi Kazuhiro
Ben Loha
Canon Kabushiki Kaisha
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