Abstract: An optical pickup can be provided, the optical pickup being capable of recording and playback of a plurality of optical disks having different specs by using light beams of different wavelengths, and further being suitable for integrating the semiconductor lasers and light receiving elements into a single package, by including: first and second semiconductor lasers adjacently disposed; a three-beam diffraction grating for generating three beams for tracking control; a second hologram element for diffracting light of the second semiconductor laser to guide it to a photosensor; a complex polarization beam splitter (PBS) for reflecting only light from the first semiconductor laser; and a first hologram element for diffracting light of the first semiconductor laser to guide it to the photosensor.

Abstract: An optical pickup can be provided, the optical pickup being capable of recording and playback of a plurality of optical disks having different specs by using light beams of different wavelengths, and further being suitable for integrating the semiconductor lasers and light receiving elements into a single package, by including: first and second semiconductor lasers adjacently disposed; a three-beam diffraction grating for generating three beams for tracking control; a second hologram element for diffracting light of the second semiconductor laser to guide it to a photosensor; a complex polarization beam splitter (PBS) for reflecting only light from the first semiconductor laser; and a first hologram element for diffracting light of the first semiconductor laser to guide it to the photosensor.

Abstract: An optical pickup can be provided, the optical pickup being capable of recording and playback of a plurality of optical disks having different specs by using light beams of different wavelengths, and further being suitable for integrating the semiconductor lasers and light receiving elements into a single package, by including: first and second semiconductor lasers adjacently disposed; a three-beam diffraction grating for generating three beams for tracking control; a second hologram element for diffracting light of the second semiconductor laser to guide it to a photosensor; a complex polarization beam splitter (PBS) for reflecting only light from the first semiconductor laser; and a first hologram element for diffracting light of the first semiconductor laser to guide it to the photosensor.

Abstract: An optical pickup can be provided, the optical pickup being capable of recording and playback of a plurality of optical disks having different specs by using light beams of different wavelengths, and further being suitable for integrating the semiconductor lasers and light receiving elements into a single package, by including: first and second semiconductor lasers adjacently disposed; a three-beam diffraction grating for generating three beams for tracking control; a second hologram element for diffracting light of the second semiconductor laser to guide it to a photosensor; a complex polarization beam splitter (PBS) for reflecting only light from the first semiconductor laser; and a first hologram element for diffracting light of the first semiconductor laser to guide it to the photosensor.

Abstract: An information reproducing apparatus which includes: pickup section for converting information recorded in a recording medium into an electrical signal; preprocessing section for amplifying a signal output from the pickup section; automatic gain control circuit for receiving a signal output from the preprocessing section as an input signal and for eliminating an amplitude change component other than the information from the input signal; and digital signal reproducing section for reproducing a digital signal corresponding to a signal output from the automatic gain control circuit, the automatic gain control circuit including: amplifier section for amplifying the input signal so as to be output as an output signal, and for receiving a control signal for controlling a gain; and control section for controlling the gain of the amplifier section, the control section including: amplitude detector for detecting an amplitude of the output signal; control signal generator for generating a control signal corresponding

Abstract: A recorded signal reproduction circuit in an optical disc information reading and recording apparatus converts a recorded signal recovered from an optical disc to PR (1, 2, 1) characteristics through a equalizer circuit, digitizes it through an A/D converter and at the same time also generates a clock signal synchronized in phase with the equalizer circuit output signal by using a binary edcoder circuit and a PLL circuit. This clock signal is then provided to an A/D converter as the sampling clock. The A/D converter output signal is then decoded to the original channel bit stream based on the clock signal. Because the equalizer circuit output signal is provided to both the binary encoder/PLL circuit and the A/D converter together, additional circuity for converting signals into a binary series of pulses is unnecessary and reduction of circuit scale is possible.

Abstract: An A/D conversion circuit for use in an information reproduction apparatus, includes an envelope generator for extracting an upper-side envelope signal and a lower-side envelope signal from a reproduced signal read out from a recording medium, and an A/D converter for converting the reproduced signal into digital data by using a reference voltage that is obtained from a difference between an upper-side reference voltage and a lower-side reference voltage. In the analog-to-digital conversion circuit, the upper-side reference voltage is set to the level of the upper-side envelope signal, while the lower-side reference voltage is set to the level of the lower-side envelope signal. With this arrangement, the difference between the level of the upper-side envelope signal and the level of the lower-side envelope signal fluctuates together with an amplitude fluctuation component and a low-frequency superimposed component in a fluctuation of the reproduced signal.

Abstract: An information reproducing circuit for reproducing digital information from a signal read by scanning an optical disk comprises an HPF 1 inputting the read signal and removing a low-frequency component from the input signal for outputting the same, an adder 2 inputting the signal outputted from the HPF 1 and adding a feedback signal having an amplitude matching with half that of the input signal to the input signal for outputting the same, a comparator 3 inputting the signal outputted from the adder 2 and converting the input signal to a binarized signal through a threshold value signal for outputting the binarized signal, a compensation circuit 5 inputting the binarized signal outputted from the comparator 3 and outputting the input signal while compensating the same through a compensation signal for compensating the low-frequency component of the read signal, and an LPF 6 inputting the signal outputted from the circuit 5 and removing a high-frequency component from the input signal for supplying the same to