PROBLEM TO BE SOLVED: To provide a circular polarization illumination device for plant growth control which is capable of irradiating right-circular polarization with high light quantity from a highly efficient right-circularly polarized light source, and capable of irradiating left-circular polarization with high light quantity from a highly efficient left-circularly polarized light source.SOLUTION: A circular polarization illumination device for plant growth control has: a light-emitting light source a reflection type polarizing plate which transmits one polarization component of incident light from the light-emitting light source, and reflects the other polarization component re-irradiation means for changing a polarized state of light reflected from the reflection type polarizing plate and irradiating the reflection type polarizing plate with the light again and circular polarization conversion means for converting light having transmitted through the reflection type polarizing plate into circular polarization, in which the reflection type polarizing plate is any one of a total reflection type polarizer, a polarizer in which different birefringence thin films are laminated, a wire grid type polarizer, a thin film type polarizer, and a birefringence type polarizer, and the circular polarization conversion means is a wavelength plate expressed by (λ/4)×(2n+1) [where n denotes integer].SELECTED DRAWING: NoneCOPYRIGHT: (C)2016,JPO&INPIT【課題】効率の高い右円偏光光源から高い光量の右円偏光を照射することができ、また効率の高い左円偏光光源から高い光量の左円偏光を照射することができる植物成長制御用円偏光照明装置。【解決手段】発光光源と、該発光光源からの入射光の一方の偏光成分を透過し、他方の偏光成分を反射する反射型偏光板と、前記反射型偏光板から反射した光の偏光状態を変化させて前記反射型偏光板に再度照射させる再照射手段と、前記反射型偏光板を透過した光を円偏光に変換させる円偏光変換手段とを有し、前記反射型偏光板が、全反射型偏光子、複屈折の異なる薄膜を積層した偏光子、ワイヤーグリッド型偏光子、薄膜型偏光子、及び複屈折型偏光子のいずれかであって、前記円偏光変換手段が、(λ/4)×(2n+1)〔ただし、nは、整数を表す。〕で表される波長板である植物成長制御用円偏光照明装置である。【選択図】なし
