| 摘要 |
PURPOSE:To obtain a lightweight and convenient lens by using a thin film type micro Fresnel lens, providing piezoelectric elements on the lens, and controlling their impressed voltages and adjusting its focus. CONSTITUTION:A coupling lens is the micro Fresnel lens, so the shape of a spot formed on a photodetector 7 varies with the distance between an objective 5 and a disk 9, which is obtained as an increase or decrease of the signal of the detector. For the purpose, the distance between the objective 5 and disk 9, i.e. focusing and a radial direction, i.e. tracking is controlled by using the signal of the photodetector 7. The focusing and tracking are performed by controlling voltages impressed to piezoelectric elements 54 and 56 provided to a spring 53 which supports the objective 5. |
