| 摘要 |
PURPOSE:To attain the increasing of the light quantity of a light receiving part by making an exit light from a light emitting part pass through an coaxial path before and after it is reflected at a part to be irradiated and receiving the light at the light receiving part. CONSTITUTION:A light emitting part 1 and a light receiving part 4 are made integral on a common substrate 9, the light emitting part 1 has a semiconductor laser 8 having a horizontal resonator and a reflection mirror 7 and the light receiving part 4 is constituted of photodiodes. In the case of a constitution in which the semiconductor 8 has the horizontal resonator the exit light is reflected at the reflection mirror 7 to coincide with the path heading to the part to be irradiated 2. Then, a returned light LR heading to the light receiving part 4 is converged to the vicinity of the limit of a light diffraction and the light receiving part 4 is provided so that at least one part of a light receiving plane is positioned within the limit of the light diffraction, that is, within a position where the distance from the optical axis (a) of the exit light from the light emitting part 1 transversing the arrangement reference plane S of the light receiving plane is smaller than 1.22lambda/NA, where the wave length of the exit light from the light emitting part 1 is defined as an lambda and the numerical aperture of a converging means 3 is defined as an NA. Thus, the whole of a device is miniaturized and the light quantity of the light returned to the light receiving elements can be increased. |
