| 摘要 |
PURPOSE:To reduce the loss of the light quantity in the optical pickup optical system of one light path by using a double refraction crystal as the separation element of lighting beams and detecting beams. CONSTITUTION:The divergent light of a linearly polarized light emitted from a semicondutctor laser 1 transmits a double refraction crystal 2 and is made to be parallel beams by a coupling lens 3 to be polarized by a polarizing mirror 4. Light beams polarized by polarizing mirror 4 are converted into circularly polarized beams by a 1/4 frequency plate 5 and converged on the recording surface of an optical recording medium 7 by an objective lens 6. A luminous flux reflected on the recording surface is again made to be parallel beams by the objective lens 6 and converted to the linearly polarized light whose plane of the polarization is rotated by 90 degrees from an incident light at the 1/4 frequency plate 5. Light beans converted at the 1/4 frequency plate 5 are given a concentrative inclination at the coupling lens 3 after passing the polarizing mirror 4 and are refracted to a direction different from the lighting beams at the double refraction crystal 2 to be guided to a light receiving element 8. |
