OPTICAL DEVICE

摘要

An optical device has an optical element 21 comprising a light-emitting region 1 and a light-detecting region 4 disposed closely to each other on a common substrate 9. Returning light LR from an irradiated medium which is irradiated with light L emitted by the light-emitting region 1 is detected by the light-detecting region 4. The returning light is applied to a light-detecting region 4 at an incident angle alpha in the range of 0 DEG < alpha < 90 DEG .