| 摘要 |
PURPOSE:To omit the use of an expensive prism by using a means which polarizes and divides a laser beam as a transmissive grating type polarized beam splitter which separates the 0th-order diffracted light from the 1st-order diffracted light according to the polarizing direction of the incident light. CONSTITUTION:The radiated light 2 of a semiconductor laser 1 is turned into parallel beams 4 by a collimating lens 3 and made incident on a polarizing beam splitter grating 5. For the polarizing direction of an incident beam, and 1st-order diffracted light 6 is obtained and made incident on a 1/4 wavelength grating 7 since the direction of the laser 1 is set so that the electric vector is set parallel with the groove of the grating 5. Thus the incident rectilinear polarized light is converted into a light beam 8 and focused at a point 11 on a disk 10. The reflected light sent from the disk 10 is converted again into the rectilinear polarized light by the grating 7 via a focusing lens 9 and turned into the light beam 6. As a result, a light beam having the electronic spectrum in the direction orthogonal to the groove of the grating 5 is made incident on the grating 5. Thus the diffracting efficiency is approximately equal to '0'. Then the 0th-order diffracted light 12 is obtained and made incident on a critical angle diffraction grating 13 and then on a four-split photodetector 15. |
