Patent ID: 6844915

Claim:
A projection optical system that projects an image of a pattern formed on a first surface onto a second surface, comprising: a first group of radiation transmissive members, the first group of radiation transmissive members transmitting light having a wavelength of 200 nm or less, being formed of a crystal material, and having an optical axis that substantially coincides with one of a crystal axis and a crystal axis optically equivalent to the crystal axis of the crystal material; a second group of radiation transmissive members, the second group of radiation transmissive members transmitting light having a wavelength of 200 nm or less, being formed of a crystal material, and having an optical axis that substantially coincides with one of a crystal axis and a crystal axis optically equivalent to the crystal axis of the crystal material; a third group of radiation transmissive members, the third group of radiation transmissive members transmitting light having a wavelength of 200 nm or less, being formed of a crystal material, and having an optical axis that substantially coincides with one of a crystal axis and a crystal axis optically equivalent to the crystal axis of the crystal material; and a fourth group of radiation transmissive members, the fourth group of radiation transmissive members transmitting light having a wavelength of 200 nm or less, being formed of a crystal material, and having an optical axis that substantially coincides with one of a crystal axis and a crystal axis optically equivalent to the crystal axis of the crystal material, wherein the first group of radiation transmissive members and the second group of radiation transmissive members have a positional relationship rotated substantially 45° about the optical axis relative to each other, and wherein the third group of radiation transmissive members and the fourth group of radiation transmissive members have a positional relationship rotated substantially 60° about the optical axis relative to each other.