Patent ID: 7907845

Claim:
An optical space transmission module for transmitting an optical signal through an external space as a medium, the optical space transmission module comprising: a light emitting section operable to output a transmission light; a base section including a reflection section operable to reflect the transmission light; and a reflection type diffusion section operable to reflect and convert the reflected transmission light, which has been reflected by the reflection section, into a diffused light, wherein the reflection section has a function to increase a beam diameter of the transmission light after reflection, the reflection section has a center on an optical axis of a light beam emitted perpendicularly from the light emitting section, and has an inclination angle α with a surface perpendicular to the optical axis of the light beam, and where a distance between the light emitting section and the reflection section is denoted as D and a diameter of a light emitting region of the light emitting section is denoted as φ, the inclination angle α is set so as to satisfy a formula (1): D tan(2α)>φ/2 (1).