| 摘要 |
PURPOSE:To realize long life and high response with a simple constitution, by using a light source with variable wavelength, and performing focusing exclusively electronically through the use of a lens the refractive index of which is changed depending on the wavelength. CONSTITUTION:In changing the injecting current of a light source 1 with a modulator 10, a wavelength of illuminated light and a focus are changed and an optical spot on a medium 5 and a photodetector 8 is subject to modulation radially. As the photo detector 8, a 2-split photo diode is used and the spot size is kept at a constant value or below by controlling the modulator 10 so that the optical spot can be controlled within an inside part 83. In this case, although the optical spot size can always be changed with the modulator 10, the fluctuated amount can be suppressed by selecting a concentric circle 82 smaller to minimize the spot. |
