Abstract: A semiconductor laser apparatus comprises a semiconductor laser, a photodetector, first and second variable gain units, a controllable amplifying unit, a driving unit, and a compensation unit. A control signal is supplied to one of input terminals of each of the first and second variable gain units and an output signal of the photodetector is negative-fed back to the other of the input terminals of each of the first and second variable gain units. A varied gain of an error between the control signal and the output signal is output independently from each of the first and second variable gain units. The controllable amplifying unit amplifies the error signal from the first variable gain unit with desired frequency characteristics. The driving unit supplies a driving current to the semiconductor laser in accordance with a drive control signal from the controllable amplifying unit.

Abstract: An optical disk apparatus includes a semiconductor laser for emitting a light beam, and an automatic power control or APC circuit for driving the laser. A compound prism structure is optically coupled to the laser in an optical head section, and defines a first optical path for causing a front laser light to be projected onto a rotating optical disk and guiding a reflected light therefrom toward a first photodetector, and a second optical path for guiding a part of the reflected light toward a second photodetector. An output signal of the first photodetector is used to generate a reproduced information signal. An output signal of the second photodetector is fed back to the APC circuit as a front light monitor signal. A part of a laser control signal internally generated in the APC circuit is supplied through a wiring line to a noise reduction circuit as a laser noise monitor signal.

Abstract: An optical recording medium comprises a transparent substrate, an inner protection layer, a recording material layer, an outer protection layer, and a reflection layer, which are laminated in this order. In an in-groove recording mode, the ratio of the thickness of the recording material layer to the thickness of the outer protection layer is in a range between 0.52 and 0.95. In an on-land recording mode, the ratio of the thickness of the recording material layer to the thickness of the outer protection layer is in a range between 0.32 and 0.6.

Abstract: An optical recording medium comprises a transparent substrate, an inner protection layer, a recording material layer, an outer protection layer, and a reflection layer, which are laminated in this order. In an in-groove recording mode, the ratio of the thickness of the recording material layer to the thickness of the outer protection layer is in a range between 0.52 and 0.95. In an on-land recording mode, the ratio of the thickness of the recording material layer to the thickness of the outer protection layer is in a range between 0.32 and 0.6.

Abstract: An optical disk apparatus includes a semiconductor laser for emitting a light beam, and an automatic power control or APC circuit for driving the laser. A compound prism structure is optically coupled to the laser in an optical head section, and defines a first optical path for causing a front laser light to be projected onto a rotating optical disk and guiding a reflected light therefrom toward a first photodetector, and a second optical path for guiding a part of the reflected light toward a second photodetector. An output signal of the first photodetector is used to generate a reproduced information signal. An output signal of the second photodetector is fed back to the APC circuit as a front light monitor signal. A part of a laser control signal internally generated in the APC circuit is supplied through a wiring line to a noise reduction circuit as a laser noise monitor signal.

Abstract: A phase-lock control circuit suitable for an optical disk apparatus of a sample-servo format scheme includes an injection-synchronized control loop in addition to a normal phase-lock loop control loop. The phase-lock loop control loop includes a phase-comparator, a low-pass filter, a voltage-controlled oscillator, i.e., a VCO, a frequency-dividing counter, and a decoder. The phase-comparator detects a phase difference between a clock pit pulse signal and a feedback pulse signal supplied through the frequency-dividing counter and the decoder. The VCO is oscillated to compensate for the phase difference and generates a reference clock signal.

Abstract: A semiconductor laser control apparatus includes a semiconductor laser, a current driver connected to the semiconductor laser, a semiconductor p-i-n photodiode for generating a monitoring current, and an operational amplifier. The inverting input of the operational amplifier receives a modulated or control signal through a resistor and a feedback current based on the monitoring current. The non-inverting input of the operational amplifier receives a reference signal. When a variation in output light amount of the semiconductor laser occurs, the operational amplifier generates an error signal in accordance with the feedback current and supplies the error signal to the current driver, thereby compensating for the variation in output light amount of the semiconductor laser.