Optical device

An optical device configured for measuring a distance, comprising:

• a prism having a first light-incident surface and a plurality of first light-transmitting surfaces, the first light-incident surface being disposed opposite to the first light-transmitting surfaces, the first light-transmitting surfaces being mutually inclined and intersecting at a vertex;
• a beam splitter having a light-passing surface, and a second light-incident surface and a second light-transmitting surface mutually connected, the second light-incident surface at least partially facing to the first light-transmitting surfaces, the light-passing surface being disposed opposite to the second light-incident surface, the beam splitter further comprising a partially mirror surface therein, the partially mirror surface at least partially facing to the light-passing surface and the second light-incident surface, the light-passing surface being configured to face to a grating;
• a detector corresponding to the second light-transmitting surface;
• and
• a light source configured to emit a light beam to enter into the prism through the first light-incident surface, an optical axis of the light beam passing through the vertex and the beam splitter, the first light-transmitting surfaces being configured to retract the light beam away the prism.