| 摘要 |
PURPOSE:To stably control a focus and to simplify a detecting circuit by processing a detecting signal from the signal output terminal of a detecting means and converting it to a signal to control least a focusing means. CONSTITUTION:A light beam emitted from a light source 11 is focused on an information recording medium 1 by using a focusing means, and light beam components passing through plural refracting bodies provided in the light path of the light beam reflected from the information recording medium 1 and arranged in a point symmetry and the light beam components made incident without passing the refracting bodies are detected. The detected detecting signal is processed, the control signal is generated, and the condition of the light beam focused on the information recording medium 1 is controlled by the control signal. Thus, a blurring detecting signal is made hard to receive the influence of the shade of a guiding groove, and the light detector 19 is divided into 2n- number of light detecting areas. Since the areas are mutually connected to each other and connected to four detecting signal output terminals, the circuit constitution of a converting circuit processing the detecting signal can be simplified. |
