Optical space transmission device including rotatable member

An optical space transmission device comprising:

• a first portion;
• and
• a second portion which is rotatably connected to the first portion and performs space transmission of signals using light between the first portion and the second portion, wherein the device comprises:
• a first light emitting and receiving module which is provided for the first portion and includes:
• a first light emitting element composed of a light emitting diode emitting first signal light modulated based on a signal transmitted from the first to second portion;
• and a first light receiving element receiving second signal light modulated based on a signal transmitted from the second to first portions;
• and
• a second light emitting and receiving module which is provided for the second portion and includes:
• a second light emitting element composed of a semiconductor laser emitting the second signal light;
• and a second light receiving element receiving the first signal light;
• wherein an optical axis of the second signal light coincides with a central axis of rotation of the second portion relative to the first portion;
• and
• the second portion rotates around the optical axis of the second signal light.