Patent ID: 6359847
Filing Date: 2002-03-19
Classification: G11B

Abstract:
In an apparatus utilizing a beam of light for optically writing and reading information on a rotating disk, a light beam intensity control system comprising:(a) a light source; (b) a pulse generator for generating a series of write pulses; (c) a driver circuit connected to the light source for causing the same to emit a light beam of consistently read intensity and, in response to the write pulses, of alternating write intensity and read intensity; (d) beam intensity detector means optically coupled to the light source for providing an actual write intensity signal indicative of actual write intensity of the light beam, and an actual read intensity signal indicative of actual read intensity of the light beam; (e) a write intensity target generator for generating a write intensity target signal indicative of a target value at which the write intensity of the light beam is to be held; (f) a write intensity control circuit connected to the beam intensity detector means and the write intensity target generator for finding a difference between the actual write intensity signal and the write intensity target signal, and to the driver circuit for causing the same to control the write intensity of the light beam according to the difference found; (g) a read intensity target generator for generating a read intensity target signal indicative of a target value at which the read intensity of the light beam is to be held; (h) a read intensity control circuit connected to the beam intensity detector means and the read intensity target generator for finding a difference between the actual read intensity signal and the read intensity target signal, and to the driver circuit for applying thereto a read intensity control signal thereby to cause the driver circuit to control the read intensity of the light beam according to the difference found; (i) means included in the read intensity target generator and connected to the read intensity control circuit for detecting an offset component of the read intensity control signal; and (j) means included in the read intensity target generator for amending the read intensity target signal so as to cancel the detected offset component of the read intensity control signal.