Optical reproducing device and optical memory medium

An optical reproducing device comprising:

• a reproducing signal production section, which projects a light beam onto an optical memory medium, and, based on reflected light of the light beam, produces a reproducing signal corresponding to recorded marks recorded in the optical memory medium:
• a control signal output section, which detects a mean value of a signal quantity of the reproducing signal produced by the reproducing signal production section, and produces a first control signal corresponding to the mean value;
• and
• a reproducing power control section, which, based on the first control signal produced by said control signal output section, controls reproducing power of the light beam projected by said reproducing signal production section such that the signal quantity of the reproducing signal is a predetermined value,
• wherein said reproducing signal production section comprises:
• a light beam projecting section, which projects the light beam onto the optical, memory medium comprising a recording layer in which recorded marks are recorded and a reproducing layer to which the recorded marks are copied, and which forms on the reproducing layer an aperture of a size corresponding with reproducing power of the light beam;
• and
• wherein said control signal output section comprises:
• an amplitude value detecting section, which detects amplitude values of a reproducing signal corresponding to the recorded marks of the optical memory medium;
• a mean value producing section, which produces mean value of a predetermined number of the amplitude values detected by said amplitude value detecting section;
• and
• a control signal producing section, which, based on the mean value produced by the mean value producing section, produces a first control signal;
• wherein:
• said amplitude detection section detects a predetermined quantity of amplitude values of a reproducing signal corresponding to first recorded marks of a predetermined mark length, and a predetermined quantity of amplitude values of a reproducing signal corresponding to second recorded marks of a mark length differing from that of the first recorded marks;
• and
• said mean value producing section comprises a first mean value calculating section, which, based on the amplitude values of the reproducing signal corresponding to the first recorded marks, calculates a mean value of the amplitude thereof, and a second mean value calculating section, which, based on the amplitude values of the reproducing signal corresponding to the second recorded marks, calculates a mean value of the amplitude thereof;
• and
• said control signal producing section produces the first control signal by finding a ratio between the mean value calculated by said first mean value calculating section and the mean value calculated by said second mean value calculating section;
• and the predetermined quantity is 5 bytes or more.