Illumination optical system, exposure apparatus, and exposure method
First Claim
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1. An illumination optical system that illuminates an irradiated surface based on linearly polarized light supplied from a light source, the illumination optical system comprising:
- a depolarizer, which is selectively positioned between a first position in an optical path of the illumination optical system and a second position outside of the optical path, and has a crystal member whose thickness in a direction along an optical axis of the illumination optical system varies in a direction crossing the optical axis.
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Abstract
An illumination optical system and method illuminates an irradiated surface based on linearly polarized light supplied from a light source. The illumination optical system includes a depolarizer which is selectively positioned between a first position in an optical path of the illumination optical system and a second position outside of the optical path, and has a crystal member whose thickness in a direction along an optical axis of the illumination optical system varies in a direction crossing the optical axis.
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Citations
13 Claims
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1. An illumination optical system that illuminates an irradiated surface based on linearly polarized light supplied from a light source, the illumination optical system comprising:
a depolarizer, which is selectively positioned between a first position in an optical path of the illumination optical system and a second position outside of the optical path, and has a crystal member whose thickness in a direction along an optical axis of the illumination optical system varies in a direction crossing the optical axis. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of illuminating an irradiated surface based on linearly polarized light supplied from a light source, comprising:
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arranging, in an illumination optical path, a depolarizer that has a crystal member whose thickness in a direction along the illumination optical path varies in a direction crossing the illumination optical path; and changing a polarization direction of the linearly polarized light entering the depolarizer and a direction of a crystal axis of the crystal member in order to switch between a first illumination mode, in which the irradiated surface is illuminated with the linearly polarized light, and a second illumination mode, in which the irradiated surface is illuminated with unpolarized light. - View Dependent Claims (10, 11, 12, 13)
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Specification