POLARIZATION CONVERSION ELEMENT, ILLUMINATION OPTICAL DEVICE, EXPOSURE DEVICE, AND EXPOSURE METHOD

摘要

PROBLEM TO BE SOLVED: To provide a polarization conversion element that can convert incident light having a polarization direction to an almost one direction of a linear polarization state into light having a polarization direction to an almost peripheral direction of a peripheral direction polarization state, while suppressing a light amount loss.SOLUTION: A polarization conversion element 10 converting a polarization state of incident light into a prescribed polarization state is formed by an optical member having an optical rotary power, for example, such as crystal, and has thickness distribution varying in a peripheral direction. The thickness distribution is set so as to convert light having a polarization direction to almost one direction of a linear polarization state into light having a polarization direction to almost peripheral direction of a peripheral direction polarization state. The polarization conversion element has a plurality of areas 10A to 10D divided in the peripheral direction, and thickness of optional two adjacent areas in the plurality of areas is mutually different. Further, optional two areas facing each other in the plurality of areas mutually have the almost same optical rotary angle.