PURPOSE: To suppress crosstalk from an adjacent track sufficiently lower by providing a V-shaped groove having the depth of 1/4 of the operating laser wavelength in a radial direction on the surface and forming a signal pit having the depth of 1/4 of the laser wavelength on each slope of the grooves.
CONSTITUTION: The grooves whose cross section is of V-shape and optical depth is 1/4 of the operating laser wavelength are provided, and information signal pits 3 provided to each of both slopes 2 of the grooves have the same direction as the direction of depth of the V-shaped grooves, the optical depth is 1/4 of the laser wavelength and the bottom face is nearly in parallel with the slope 2 formed onto the V-shaped grooves. Thus, the crosstalk from adjacent slopes is kept sufficiently low, a photodetector N reproduces the information signals 3 recorded on the slope B and a photodetector M reproduces the signals 3 on the slope C, the track pitch is made narrower and the recording density of the optical disc is improved.
TAKEMURA YOSHIYA
NAGASHIMA MICHIYOSHI
