Abstract: A digital disk device is provided in which the quality of a digital signal is improved without causing the development cost for and power consumption by the digital disk device to increase. An ADC included in a signal conversion circuit samples an analog signal which represents the intensity of a laser beam reflected, after being emitted from a laser source driven by a current superimposed with a high-frequency signal, from an optical disk using a clock signal whose frequency is substantially the same as that of the high-frequency signal and converts the sampled analog signal into a digital signal. An LPF provided in a stage preceding the ADC passes a component, not exceeding a predetermined frequency, of the analog signal with the frequency of the clock signal set to be higher than the predetermined frequency.

Abstract: An auto laser power control circuit is provided which improves the response of the optical output level of a laser diode in accordance with variations in the operation mode. In an auto laser power control circuit for comparing a voltage corresponding to the optical output from the laser diode which emits a light in accordance with a supplied driving current with a reference voltage, and controlling the driving current so as to reduce the difference at the time of the steady operation, by controlling a switch connected between the input and output terminals of an operational unit which compares the voltage corresponding to the optical output from the laser diode and the reference voltage, the driving current to the laser diode is controlled with a smaller time constant upon the start such as a transition of from a read operation mode to a write operation mode as compared with the time of the steady operation.

Abstract: An optical disk recording device is provided with an optical pickup. The optical pickup irradiates laser light onto an area for forming pits at a first output and irradiates laser light onto an area for forming no pits at a second output lower than the first output, during recording data in an optical disk. a first detector detects an intensity of reflected light of the laser light irradiated at the second output from an unrecorded area is detected. A second detector detects an intensity of reflected light of the laser light irradiated at the second output from a recorded area. A processor calculates a ratio of both intensities of the reflected light from the unrecorded area and the reflected light from the recorded area. A voltage adjuster adjusts the first output such that the intensity ratio is within a predetermined range.

Abstract: An auto laser power control circuit is provided which improves the response of the optical output level of a laser diode in accordance with variations in the operation mode.