| 摘要 |
PURPOSE:To obtain a preformat signal of uniformity and less variation by forming a cross-sectional shape into a trapezoidal shape with a longer upper base than a lower base, having an angle made by an oblique side of the trapezoid and a plane of an information recording medium at <=35 deg. and making the depth of a recessed part more than lambda/4n. CONSTITUTION:A recessed tracking track 7 has its cross section in the trapezoidal shape with the longer upper base than the lower base, and this trapezoid is regulated by the angle theta made with the oblique side of this trapezoid and the plane of the information recording medium 1, the height of the trapezoid, i.e. the depth (d) of the recessed part, and moreover its width (l). By forming the angle theta as <=35 deg., and also forming the depth (d) of the recessed part deeper than lambda/4n which is a depth of making a phase difference of normal reflecting light max., the preformat signal of high contrast can be obtained (N.B. lambda: wavelength of optical emission beam and (n): refractive index). By this method, the good preformat signal is obtained. |
