| 摘要 |
PURPOSE:To miniaturize and lighten a device by eliminating the need for a lens located between a beam splitter and light receiving part by forming the joining face of a polarizing beam splitter on a recessed cylindrical face toward the light receiving part. CONSTITUTION:The joining face 22a of the polarizing beam splitter 22 transmitting and reflecting the laser beam L emitted from a light emitting part 21 is formed on a recessed cylindrical face toward a light receiving part 25. An astigmatism is then made not to cause in the state of no focusing error. When the focusing error is generated in this state, it can be detected by generating the astigmatism. The need for the convex lens and cylindrical lens provided between the beam splitter and light receiving part heretofore is therefore eliminated and the device can be miniaturized and lightened. |
