Patent ID: 7106678

Claim:
A disk playback device wherein a disk is irradiated with a laser beam from an optical head to reproduce signals from the disks, the disk playback device comprising a laser drive circuit for feeding a drive signal to the optical head and adjusting the power of the laser beam irradiated by the optical head, an evaluation data detecting circuit for detecting evaluation data representing quality of a signal reproduction state, and a control circuit for controlling operation of the laser drive circuit based on an output of the evaluation data detecting circuit, the control circuit comprising reproduction power optimizing means for optimizing the power of laser beam for signal reproduction so as not to permit evaluation data to exceed a prescribed value, the reproduction power optimizing means comprising: retrieving means for retrieving one limit value of two limit values of the reproduction power wherein evaluation data is not beyond the prescribed value, and calculating means for determining the optimum reproduction by adding, to the retrieved lower limit value, a value which is approximately one half of the difference between a maximum reproduction power and a minimum reproduction power within the range wherein the reproduction power is not dependent on the recording power in the relationship between the laser power for signal reproduction and the laser power for signal recording wherein each evaluation data is in an allowable range.