Abstract: Disclosed is an optical head device which has: a laser light source; an objective lens to which light emitted from the laser light source is entered through a beam splitter and in which the light is collected to be focused as a very small spot on a recording surface of an optical disk medium; an optical detector to which modulated light reflected on the recording surface of the optical disk medium is entered through the objective lens and the beam splitter; and a shading plate which is located between the laser light source and the beam splitter and through which a central part of the light emitted from the laser light source is passed; wherein the objective lens is designed to have an effective diameter greater than a diameter of the laser light output from the beam splitter.

Abstract: The optical head seek controller disclosed has an optical head for producing three beam spots on an optical disk and receiving three beam spots reflected therefrom, a matrix circuit for processing data contained in the three beam spots formed on the optical head to generate and output a predetermined track error signal when accessing a track, and a controller for controlling the movement of the optical head to a desired track position by calculating a relative position and a speed of the optical head according to the predetermined track error signal from the matrix circuit. The matrix circuit comprises a first track error signal generator for generating a first track error signal for track accessing on the optical disk, and a second track error signal generator for generating a second track error signal necessary for the relative position and the speed of the optical head with respect to the optical disk.

Abstract: The optical head seek controller disclosed has an optical head for producing three beam spots on an optical disk and receiving three beam spots reflected therefrom, a matrix circuit for processing data contained in the three beam spots formed on the optical head to generate and output a predetermined track error signal when accessing a track, and a controller for controlling the movement of the optical head to a desired track position by calculating a relative position and a speed of the optical head according to the predetermined track error signal from the matrix circuit. The matrix circuit comprises a first track error signal generator for generating a first track error signal for track accessing on the optical disk, and a second track error signal generator for generating a second track error signal necessary for the relative position and the speed of the optical head with respect to the optical disk.

Abstract: An optical disk drive has a rough actuator for moving an optical head with respect to an optical disk and a fine actuator for moving an object lens with respect to the optical head, to transfer an optical spot from a present address to a target address. The optical disk drive controls the radial speed of an optical spot based on a trapezoidal speed profile. A deceleration period is effected when the remaining track number is at a threshold value. During the deceleration period when a rough actuator moves the optical head, fine actuator is moved in the direction opposite to the moving direction of the optical head to generate a stationary state of the optical spot. An address detector is activated during the stationary state to read the present address, thereby correcting the remaining track number. When the rough actuator is stopped, the seeking operation is completed without an additional fine seeking operation.

Abstract: A velocity detection circuit which detects the velocity of movement of an optical head. The velocity detection circuit includes an edge detection circuit for detecting an edge of a position detection signal and outputting an edge signal, a divider for dividing a clock signal of a predetermined period, a first binary counter and a first D-type flipflop for counting the number of pulses of the divided clock signal within an interval from an edge signal to a next edge signal to calculate time data, a second binary counter for counting the clock signal, a comparator for outputting, when the time data outputted from the first D-type flipflop and the data counted by the second binary counter coincide with each other, a pulse (reference signal) to be used to reset the count data of the second binary counter, and a third binary counter and a second D-type flipflop for counting the number of pulses of the comparison signal based on a sampling signal generated at fixed time intervals to calculate velocity data.

Abstract: A velocity detection circuit which detects the velocity of movement of an optical head. The velocity detection circuit includes an edge detection circuit for detecting an edge of a position detection signal and outputting an edge signal, a divider for dividing a clock signal of a predetermined period, a first binary counter and a first D-type flipflop for counting the number of pulses of the divided clock signal within an interval from an edge signal to a next edge signal to calculate time data, a second binary counter for counting the clock signal, a comparator for outputting, when the time data outputted from the first D-type flipflop and the data counted by the second binary counter coincide with each other, a pulse (reference signal) to be used to reset the count data of the second binary counter, and a third binary counter and a second D-type flipflop for counting the number of pulses of the comparison signal based on a sampling signal generated at fixed time intervals to calculate velocity data.

Abstract: Irradiation of the optical disk medium is pulsized to achieve reading, erasing and recording with binarized read power and write power; setting of erase power is dispensed with to shorten the process required to adjust the optical head; and the shapes of pits formed on the optical disk medium are optimized by varying the switching time between the write power and the read power to improve the CNR of read signals and the jitter characteristic.Division is accomplished by a logical circuit into an area A in which a variation from the erase temperature to the write temperature is to take place, area B in which the write temperature is to be kept constant, area C in which a variation from the write temperature to the erase temperature is to take place, and area D in which the erase temperature is to be kept constant to generate, from data to be recorded and a clock pulse having a frequency equal to an integral multiple of the bit clock thereof, a recording signal representing the timing of laser irradiation.