OPTICAL RECORDING AND REPRODUCING DEVICE

摘要

PURPOSE:To keep the intensity of a magnetic field due to an electromagnet at a minute light spot position to a constant value without being affected with a positional fluctuation (face fluctuation) of a recording medium by controlling a drive current of the electromagnet positioned near the light spot depending on the position fluctuation in a direction of optical axis caused by an objective lens. CONSTITUTION:A thin light beam is made vertically incident to a face vertical to a recording medium 6 from a light source 13 among faces formed by a structure 12 operated incorporatedly with the objective lens 5. A light spot 16 of the incident light from the light source 13 is formed to a 2-split photodetector photodetecting face 15 and a signal depending on the amount of received light detected at both split photodetecting faces is converted into a drive current control signal of the electromagnet 10 of an amplifier 18 for driving electromagnet via a differential amplifier 17 in response to the positional fluctuation of the objective lens 5. Thus, when the position of the objective lens controlled so as to keep a prescribed distance with the recording medium 6 at all times is fluctuated in response to the warp of the recording medium 6, a control signal inputted to the electromagnet 10 from the amplifier 18 for driving electromagnet is changed so as to keep the intensity of magnetic field of the recording medium 6 to a constant value.