| 摘要 |
PURPOSE:To apply sufficient returning light to a photosensor without rising the temperature of a photomagnetic recording medium by arranging a lambda/2 wavelength plate in an optical path between a beam splitter and a photomagnetic recording body so as to cover any one side of planes divided by a division line meeting with the optical axis at right angles. CONSTITUTION:Out of the returning light flux from an optical disc D which is modulated by the magnetism of the photomagnetic recording medium, the light flux (a) passing through the lambda/2 wavelength plate 12 is formed to parallel light flux by an objective 13 so as to pass the optical path passed through by light flux (b) reversely and is made directly incident to a polarized beam splitter 11. The light flux (b) is formed to parallel light flux by the objective 13 so as to pass the optical path passed through by the light flux (a) reversely and passed through the lambda/2 wavelength plate 12 perpendicularly to be incident to the polarized beam splitter 11. Therefore, all the returning light flux are passed through the lambda/2 wavelength plate 12 once and the polarization axis is made straight polarization rotated by 90 deg., so that almost all the returning light flux is reflected without returning to a semiconductor laser and is made incident to the photosensor. |
