| 摘要 |
PROBLEM TO BE SOLVED: To change a transmission beam diameter by an ambient temperature change. SOLUTION: An operation part 35 derives the spared angle of an appropriate beam, based on a temperature signal sent from a temperature detection part 34 and sends operation output to a driving part 36. The driving part 36 drives a lens 22 along an optical axis, in accordance with a signal outputted from the operation part 35 and varies the spread angle of the beam. Thus, transmission light can surely be transmitted to an opposite device without the waste of light quantity since the spread angle of transmitted light in a self-device is adjusted, when the temperature is high by performing control with the temperature change. |
