| 摘要 |
PURPOSE:To effectively utilize an ordinary image forming lens to obtain fine convergency by expanding the diameter of light beams incident upon the image forming lens by a non-parallel face prism. CONSTITUTION:A laser beam is converted into parallel beams by a collimeter lens system 2 and its polarizing face is aligned in a direction along a paper face by the 1st lambda/4 wavelength polarizing plate 3. Then, the beams are bent at a right angle by a polarizing beam splitter 4, converted into a circularly polarized state through the 2nd lambda/4 wavelength polarizing plate 5 and converged upon an optical disk 7 by an objective lens 6. The reflected light from the disk 7 is converted into parallel beams again by the lens 6 and then converted into the beams having a polarizing plane vertical to a paper surface by the polarizing plate 5. The beams is projected as parallel beams whose diameter is extended in a non-parallel face prism 8 through the beam splitter 4 and converged upon a photodetector 10 by the image forming lens 9. Consequently, finer convergence can be obtained by utilizing the ordinary image forming lens 9. |
