PROBLEM TO BE SOLVED: To provide an illumination apparatus which irradiates either right-circularly polarized light or left-circularly polarized light with excellent energy efficiency.SOLUTION: There is provided an illumination apparatus which selectively emits either one of right-circularly polarized light and left-circularly polarized light. The apparatus includes a reflection type polarizing plate 1, a light source and a reflection type polarizing plate 2 in this order, and further includes a phase difference plate. The reflection type polarizing plate 1, the light source and the reflection type polarizing plate 2 are arranged such that polarized light reflected on the reflection type polarizing plate 1 transmits the reflection type polarizing plate 2, and polarized light reflected on the reflection type polarizing plate 2 transmits the reflection type polarizing plate 1, and phase difference and arrangement of the phase difference plate are adjusted such that either one of the circularly polarized lights is emitted to both of a direction of the reflection type polarizing plate 1 and a direction of the reflection type polarizing plate 2 with the light source as a reference.【課題】右円偏光または左円偏光のいずれか一方をエネルギー効率良く照射する照明装置を提供する。【解決手段】右円偏光または左円偏光のいずれか一方を選択的に出射する照明装置であって、反射型偏光板１、光源、および反射型偏光板２をこの順で含み、さらに位相差板を含み、反射型偏光板１、前記光源、および反射型偏光板２が、反射型偏光板１を反射した偏光が反射型偏光板２を透過し、かつ反射型偏光板２を反射した偏光が反射型偏光板１を透過するように配置されており、かつ、前記位相差板の位相差および配置が、前記光源を基準として反射型偏光板１の方向および反射型偏光板２の方向の双方に前記のいずれか一方の円偏光が出射されるように調整されている照明装置。
