Patent ID: 6967671

Claim:
A polarization-direction-controlling element to be provided at an upstream side, in an optical-axis direction, of a beam of light in an exposure device using a polarization-separating element for separating the beam of light into two beams of light having mutually orthogonal polarization directions, the polarization-direction-controlling element comprising: a plate-like base, having two mutually parallel flat surfaces for transmitting the beam of light, one of the two surfaces being an incident surface to which the beam of light is irradiated, and the other being an output surface for outputting the light; and a plurality of ½ wavelength plates provided on at least one of the incident surface and the output surface of the base such that a crystal optical axis of each of the ½ wavelength plates is tilted at an angle within a predetermined range, which includes 45 degrees, with respect to a polarization direction of the beam of light to be separated by the polarization-separating element.