| 摘要 |
<p>Method and apparatus for rotating an information storage disc about its central axis at a prescribed angular velocity that varies according to the radial position of an optical transducer for recording information thereon, whereby a uniformly high density of information can be recorded over the entire disc. The apparatus includes a register for storing a digital measure of the radius of the current track being recorded by the transducer, along with velocity signal circuitry for producing a disc velocity signal having a frequency inversely proportional to the measure of radius, and a spindle motor servo, responsive to the disc velocity signal, for controlling the angular velocity of the information disc, accordingly. The velocity signal circuitry includes a crystal oscillator, a counter for counting the clock pulses produced by the oscillator, and a digital word magnitude comparator for generating a reset pulse to reset the counter to an initial zero count every time it determines that the count is equal to the digital measure of radius. The disc velocity signal is then derived by frequency dividing the successive reset pulses.</p> |
