Abstract: A method of detecting a reproduction signal from an optical disc. A light beam reflected from a recording surface of an optical disc is divided into a central light beam portion and outer light beam portions in a direction corresponding to a radial direction of the optical disc. The central light beam portion and outer light beam portions are detected and a first detection signal from the central light beam portion and a second detection signal from at least one of the outer light beam portions are output. The amplitude of at least one of the first and second detection signals is adjusted and the reproduction signal is detected by subtraction between the first detection and second detection signals so that where reproduction is carried out on an optical disc having a varying track width the reproduction signal is improved.

Abstract: A method of and a circuit for providing a playback signal, which is compensated for time delay, from a photodetector having a plurality of outputs. A time difference between a first signal corresponding to a part of the outputs of the photodetector and a second signal corresponding to another part of the outputs of the photodetector is detected and one of the first and second signals is temporally shifted to compensate for a time delay between different outputs of the photodetector. The temporally shifted signal is summed with the other signal to provide a playback signal. Accordingly, the time delay between the outputs of the photodetector is compensated, thereby increasing the degree of modulation of the data playback signal. In addition, distortion or degradation of the signal is suppressed and occurrence of errors in the playback signal is minimized, thereby improving the reliability of the playback signal.

Abstract: A device for and method of reducing intersymbol interference (ISI) and/or crosstalk is disclosed. The ISI and crosstalk reducing device includes an optical detector which divides an optical signal reflected from an optical disk into central and peripheral parts in the tangential direction of the optical disk, and a correcting unit for controlling the gain value of a peripheral detection signal detected by the optical detector and adding the gain-controlled detection signal and a central detection signal to each other to provide an ISI corrected signal. Instead of using the existing waveform equalizer, the device uses a multiple-divided detection signal output from the optical detector to thereby obtain a jitter value of the same level as that obtained when the waveform equalizer is used. Further, in HD-DVD system requiring high density recording, it is possible to reduce crosstalk and ISI at the same time even when the high density recording causes crosstalk or interference between neighboring tracks.

Abstract: An optical recording medium having groove tracks and land tracks, first wobbles formed along both sidewalls of each of the groove tracks, second wobbles formed along both sidewalls of each of the land tracks and which are independent of the formation of the first wobble. A middle portion is formed at a predetermined position on each of the sidewalls between adjacent pairs of the land and groove tracks. This optical recording medium can significantly reduce the non-recordable area as compared to conventional optical recording media, resulting in a great improvement in recording density.

Abstract: An optical pickup apparatus for compensating for the deviation in the thickness of the optical disk and method therefor.

Abstract: An objective lens device and an optical pickup employing the objective lens device. The objective lens device is formed of three lenses including a lens having a negative power and formed of material having an Abbe number which is 45 or less in line d. At least one surface of surfaces of the three lenses is formed to be aspherical. Thus, in the objective lens device, a high numerical aperture of 0.70 or more is realized and chromatic aberration is corrected with respect to blue light enabling improved recording and/or reproduction using blue light.

Abstract: An optical pickup capable of focusing a main light spot and an auxiliary light spot including optical aberration when an optical disk is not tilted, and analyzing the main light spot and the auxiliary light spot with a photodetector, thereby correcting aberration.

Abstract: An integrated circuit device includes a delay circuit that is configured to delay a clock signal and is further configured to generate an output data signal in response to the delayed clock signal and an input data signal. Multiple devices are configured to respectively receive the output data signal in response to the clock signal.

Abstract: An optical pickup having a plurality of objective lenses. At least one of the plurality of objective lenses is configured so that a type of wavefront error mainly generated by a tilt of the at least one of the plurality of objective lenses is the same as a type of a wavefront error mainly generated by an angle at which light is incident upon the at least one of the plurality of objective lenses.

Abstract: A flip-flop circuit includes a latch that holds an input signal responsive to an internal clock signal, a comparing circuit that compares the input signal with a latch output to provide a comparison signal, and an internal clock generator that receives an external clock signal and generates an internal clock signal responsive to the comparison signal. The internal clock generating circuit performs a NAND operation on the external clock signal and a delayed inverted version of the external clock signal, to generate the internal clock signal having pulse width smaller than the external clock signal and having rising and falling edges synchronized with the external clock signal. Power consumption is low because the clock buffer and the internal clock generating circuit do not perform switching operations when there is little or no variation in the input signal of the flip-flop.

Abstract: A spherical aberration compensator for compensating for spherical aberration resulting from a thickness deviation of a recording medium. The spherical aberration compensator includes a central compensation which provides a phase distribution that is effective for compensating for spherical aberration resulting from the thickness deviation and a peripheral compensation portion which surrounds the central compensation portion and provides a phase distribution that is effective for reducing a worsening of the spherical aberration caused by axial displacement of an objective lens from the central compensation portion. The spherical aberration compensator effectively relieves an optical pickup having an objective lens of an NA of 0.7 or greater of worsening of the spherical aberration resulting from thickness deviation of the recording medium.

Abstract: A flip-flop circuit includes a master latch and a slave latch, where a latch operation of the slave latch is controlled by a comparison result between an output signal of the master latch and an output signal of the slave latch. For example, a master latch gate receives an input signal and outputs the input signal under control of a clock signal and an inverted clock signal. A master latch receives the signal output by the master latch gate and latches the signal output by the master latch gate under control of the clock signal and the inverted clock signal. A slave latch gate receives the signal latched by the master latch and outputs the signal latched by the master latch under control of the clock signal and the inverted clock signal. A slave latch receives the signal output by the slave latch gate and latches the signal output by the slave latch gate under control of a slave latch control signal and an inverted slave latch control signal.

Abstract: A compatible optical pickup compatibly using a high density recording medium and at least one low density recording medium, includes an objective lens to form a light spot suitable for use on a recording surface of the high density recording medium by focusing a corresponding incident light beam with a high NA suitable for the high density recording medium and a light spot suitable for use on another recording surface of the low density recording medium by focusing another corresponding incident light beam, and an actuator provided to apply tilt to the objective lens. The light beam for the low density recording medium is incident on the objective lens as a divergent beam. When the objective lens is shifted in a radial direction, a tilt is applied to the objective lens corresponding to the shift.

Abstract: An objective lens includes an aspherical lens facing a disk and having a predetermined first focal distance and a predetermined numerical aperture, and a holographic lens installed adjacent to the aspherical lens and having a second focal distance longer than that of the first focal distance and having a diffraction lattice to compensate for the chromatism due to a change in wavelength of laser light having a wavelength of 670 nm or less. Thus, during the shift between recoding and reproduction of a DVD or an HD-DVD, the change in wavelength due to the change in power of the laser light and chromatism according to the change can be effectively corrected. Also, since the objective lens is formed of one aspherical lens and one holographic lens, the material for each of the lenses can be easily selected and also the structure of the optical pickup using the objective lens according to the present invention can be simplified.

Abstract: A land/groove discriminating method and an optical recording and/or reproducing apparatus employing the method are provided. The land/groove discriminating method emits a light beam onto an optical disc having lands and grooves through an optical element capable of causing and varying an effect of thickness variation of the optical disc, detects a light beam reflected/diffracted from the optical disc by dividing the reflected/diffracted light beam into inner and outer light beam portions, and discriminates between a land and a groove of the optical disc by detecting variation in a difference signal between detection signals from the inner and outer light beam portions while varying the degree of the effect of thickness variation of the optical disc by driving the optical element.

Abstract: An apparatus for and a method of producing a push-pull tracking error signal in an optical disc system having four light-receiving sections A, B, C, and D arranged in a radial direction of the optical disc. Pairs of signals PA, PB, PC and PD, corresponding to light receiving sections A, B, C and D, respectively are differentially combined to provide differential signals. One differential signal is filtered, amplified and differentially combined with another differential signal to output a tracking error signal. Accordingly, distortion of the tracking error signal during jumping to a desired track and distortion of the tracking error signal due to a defect of the optical disc are prevented.

Abstract: An optical pickup apparatus which reduces cross talk by adjacent tracks. The optical pickup apparatus divides light reflected from an optical recording medium as a spot into center and side portions defined with respect to the radial direction of the recording medium and provides electrical signals corresponding to the reflected light in divided form. An operation unit multiplies signals corresponding to the side portions by an operation constant, adds the multiplication results and the detected signal of the center portion, and outputs an information signal of a main track with reduced cross talk by adjacent tracks in real time. The optical efficiency is sufficient that recording of an information signal can be performed with the optical pickup.

Abstract: An optical pickup including: first and second light sources for generating first and second laser beams having different wavelengths corresponding to first and second media having different thicknesses, respectively; an objective lens that has diverging and converging/focusing portions, to focus the first and second laser beams from the first and second light sources onto the first and second media, respectively; a photodetector to receive the first and second laser beams that are emitted from the first and second light sources and reflected, respectively, by the first and second media; and a collimating lens arranged on the optical path between the objective lens, and the first and second light sources. The optical pickup is compatible with both existing digital versatile disks (DVDs), and high-definition (HD)-DVDs, which need a blue light source near 405 nm and an objective lens that has a numerical aperture of 0.6 or more.

Abstract: An optical pickup including a light detection element to divide light reflected from an optical recording medium into first through fourth light beam portions in a radial direction of the optical recording medium. From detection signals from the light detection element, a reproduction signal detection portion detects an information signal, and a tracking error signal detection portion detects a tracking error signal. The light source emits light that is focused as a single light spot on a main track of the optical recording medium. The tracking error signal detection portion gain controls and sums push-pull signals from the detection signals to detect, during a recording operation, a tracking error signal with reduced push-pull offset without erasing existing signals on adjacent tracks. The reproduction signal detection portion sums and gain controls the detection signals to detect an information signal containing reduced crosstalk from adjacent tracks.

Abstract: A compatible optical pickup includes an optical disc, an objective lens, a diffractive device, and a divergent lens. The optical unit emits a short wavelength light beam corresponding to a high density optical disc and a long wavelength light beam corresponding to a low density optical disc. The objective lens forms a light spot on the high density optical disc and the low density optical disc and the diffractive device diffracts the short wavelength light beam to correct chromatism according to a change in a wavelength of the short wavelength light beam. The divergent lens refracts the long wavelength light beam toward the objective lens to increase a working distance with respect to the low density optical disc.