| 摘要 |
In a record disk having a spiral groove in a surface thereof with the depth of the groove varying along the latter for representing recorded information, such as video signals; the groove has an inverted bell-shaped cross-section which is symmetrical about the median of the groove with each of the opposite side surfaces of the groove, at any location therealong, being defined approximately by the equation DX=DOxEXP [-(X/W)2] IN WHICH DO IS THE DEPTH OF THE GROOVE AT THE MEDIAN THEREOF, W IS THE DISTANCE FROM THE MEDIAN OF THE GROOVE TO THE POINT AT THE SIDE SURFACE OF THE GROOVE WHERE THE DEPTH IS DO/E (E BEING THE BASE OF THE NATURAL LOGARITHM), AND DX IS THE DEPTH OF THE GROOVE AT THE RESPECTIVE SIDE SURFACE AT A DISTANCE X FROM THE MEDIAN. The foregoing record disk is conveniently molded in correspondence with an original recording disk produced by directing a laser light beam which has a Gaussian energy distribution thereacross against a layer of positive type photo-resist material on the original recording disk while the latter and the light beam are moved relative to each other for scanning a spiral track of constant pitch on the original recording disk and while the intensity of the laser light beam is modulated by the information signals to be recorded, and then developing the layer of photo-resist material. |
