Patent ID: 8414158

Claim:
An illumination device comprising: a cover having a flat plate shape; a straight tube fluorescent lamp including a cylindrical light emitting unit, the fluorescent lamp being disposed at one side of the cover in a thickness direction thereof, the cover being substantially in a parallel relationship with a central axis of the light emitting unit of the fluorescent lamp; and a doppler sensor disposed on the same side as the fluorescent lamp with respect to a first plane including a surface of the cover which faces the fluorescent lamp, the doppler sensor including a receiving unit for receiving an electric wave from a detectable range having a part of the first plane, wherein, in a cross section that intersects the receiving unit and is orthogonal to the central axis of the light emitting unit of the fluorescent lamp, an angle “θ” between a boundary line of the detectable range close to the fluorescent lamp and a normal to the first plane, a distance “d” between the central axis of the light emitting unit and the first plane, a radius “r” of the light emitting unit; a distance “y” between the first plane and the receiving unit; and a distance “x” between the receiving unit and a second plane that includes the central axis of the light emitting unit and is orthogonal to the first plane satisfy the following equation x > ( y + d ) ⁢ tan ⁢ ⁢ θ + r cos ⁢ ⁢ θ .