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: We describe and claim an error detecting memory module and method. The module comprises a plurality of memory devices, each memory device to receive an address signal and a command signal from a memory controller, and to detect an error in the address and command signals responsive to an input parity signal. In an embodiment, each memory device is adapted to provide an output parity signal to the memory controller responsive to the detection.

Abstract: An optical pickup apparatus includes a detection unit detecting a light beam reflected/diffracted by the recording medium and passing through the objective lens by dividing the light beam into a plurality of light areas, and a signal processor detecting a difference between widths T1 and T2 indicating that first and second focusing signals are greater than a predetermined threshold value and a thickness signal of the recording medium by using the detected difference when an S-curve of a focus error signal detected by using detection signals of the light areas output from the detection unit is obtained by subtracting a second detecting signal from a first detecting signal or by subtracting the first focusing signal from the second signal. Thus, a spherical aberration due to a change in thickness of the recording medium can be corrected by driving a spherical aberration correcting device according to a thickness signal corresponding to the change in thickness of the recording medium.

Abstract: An optical pickup is provided for a recording medium, including: a light source generating and emitting a light beam; a light beam division and detection unit dividing a particular light beam portion of the light beam after being reflected/diffracted from the recording medium into sub-divided light beams portions, and detecting the sub-divided light beam portions; and a spherical aberration detection circuit processing the sub-divided light beam portions to detect spherical aberration caused by thickness variation of the recording medium.

Abstract: A method and circuit for providing a playback signal which is compensated for time delay. The circuit includes a time delay compensator for detecting a time difference between outputs of a photodetector and temporally matching part of the outputs of the photodetector and another part of the outputs of the photodetector, between which the time difference occurs, to compensate for time delay between different outputs of the photodetector, and an operational unit for summing the part of the outputs of the photodetector, which is compensated for the time delay, and the other part of the outputs of the photodetector to provide a playback signal. Accordingly, the circuit compensates for the time delay between the outputs of the photodetector, thereby increasing the degree of modulation of the data playback signal.

Abstract: A memory module, a memory unit, and a hub with a non-periodic clock and methods for using the same. An example memory module may include a phased locked loop, receiving an external, periodic clock and generating one or more internal periodic clocks and a plurality of memory units, receiving one of the internal periodic clocks or a non-periodic clock from an external source.

Abstract: An optical pickup device includes a light source to emit light, an objective lens to focus the light on a recording medium to form a light spot, an optical path changer on an optical path between the light source and the objective lens to change the path of incident light, a chromatic aberration correction lens disposed on an optical path between the light source and the objective lens, and a photodetector to receive light which is reflected from the recording medium and is then incident thereon through the optical path changer. The chromatic aberration correction lens corrects a chromatic aberration occurring due to a change in the wavelength and/or due to an increase in a wavelength bandwidth of the light. The chromatic aberration correction lens includes at least two lenses such that a lens having a positive power and a lens having a negative power are adjacent to each other.

Abstract: An optical pickup for a recording medium includes a light beam division and detection unit including receiving portions dividing an incident light beam reflected on the recording medium into a first light beam portion and a second light beam portion around the first light beam portion and converting the first and second light beam portions into first and second detection signals, respectively. A thickness variation detection circuit detects a variation in thickness of the recording medium according to the first and second detection signals and outputs a thickness variation signal indicative thereof.

Abstract: An optical pickup and a lens assembling apparatus and a method thereof are provided. The optical pickup includes a plurality of objective lenses and a lens holder. The lens holder has a plurality of installation holes into which the plurality of objective lenses are inserted. In the lens holder, a seat surface of at least one of the installation holes is formed as a curved surface so that an inclination adjustment of the objective lens installed thereon can be performed. Since the seat surface of at least one of the installation holes provide to the lens holder is formed as a curved surface so that the inclination adjustment of the lens can be performed, the inclination adjustment between the plurality of objective lenses can be performed without an increase in the number of the parts or an increase in the number of the assembling processes.

Abstract: A test board for a high-frequency system level test: The test board includes a main board having through holes filled with a conductive material. These holes may be located at a portion of the main board from which an existing module socket has been removed. An interface board has surface mounted device (SMD) pads on front and rear surfaces. The SMD pads on the front surface of the interface board are connected with the SMD pads on the rear surface thereof through cross connection wiring within the interface board for a pin swap. The through holes of the main board are connected with the SMD pads on the rear surface of the interface board via iron cores fixed at a guide. A test module socket is mounted on surfaces of the SMD pads on the front surface of the interface board.

Abstract: Memory modules and methods of testing memory modules are provided that include at least one memory device responsive to a memory clock signal having a memory clock frequency and a data buffer. The data buffer is responsive to a buffer clock signal having a first buffer clock frequency that is different from the memory clock frequency during a normal mode of operation and having a second buffer clock frequency that is equal to the memory clock frequency during a test mode of operation.

Abstract: A multi-layer circuit board having an improved heat spreading performance is described. In a multi-layer circuit board structure configured such that insulating layers and interconnection conductive layers are alternately stacked, the interconnection conductive layers include a top interconnection conductive layer having a main surface on which circuit elements are mounted, a bottom interconnection conductive layer as a bottom surface layer facing the top interconnection conductive layer, an inner power conductive layer having a predetermined thickness, disposed between the top interconnection conductive layer and the bottom interconnection conductive layer, with some of the insulating layers interposed between the top and bottom interconnection conductive layers. The interconnection conductive layers can be of various thicknesses to facilitate heat diffusion. Heat diffusion can be accomplished with variations in thickness of either the insulating layers or electrically conductive layers.

Abstract: An optical pickup device includes a light source to emit light, an objective lens to focus the light on a recording medium to form a light spot, an optical path changer on an optical path between the light source and the objective lens to change the path of incident light, a chromatic aberration correction lens disposed on an optical path between the light source and the objective lens, and a photodetector to receive light which is reflected from the recording medium and is then incident thereon through the optical path changer. The chromatic aberration correction lens corrects a chromatic aberration occurring due to a change in the wavelength and/or due to an increase in a wavelength bandwidth of the light. The chromatic aberration correction lens includes at least two lenses such that a lens having a positive power and a lens having a negative power are adjacent to each other.

Abstract: An optical pickup including an optical member which inhibits interference light reflected from an adjacent layer from being received by a photodetector when an optical information storage medium includes a plurality of recording layers on at least one side thereof. The optical pickup suppresses a photodetector, especially first and second sub-photodetectors of the photodetector, from receiving the interference light reflected from the adjacent layer.

Abstract: An optical pickup actuator having: a moving part on which an objective lens to focus an incident beam onto an optical recording medium is mounted, a magnetic driver that drives the moving part in track and focus directions of the optical recording medium, and a support element that movably supports the moving part and has a first support portion with a first predetermined stiffness and a second support portion with a second predetermined stiffness different from the first predetermined stiffness. A center of gravity of the moving part, a center of support of the support element, and a center of a force determined by arrangement of the magnetic driver are coincident.

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: An optical pickup includes an aberration correction element to correct chromatic aberration caused by variation of power from a light source when changing between operating modes in a recording medium. The aberration correction includes a first retardation member, which includes a stepped convex pattern with a plurality of steps at one side, and a second retardation member combined with the first retardation member. The second retardation member includes a stepped concave pattern with a plurality of steps at one side facing the first retardation member, the stepped concave pattern corresponding to the stepped convex pattern. The first and the second retardation members include different refractive indices for a light beam, which allows the first and the second retardation members to selectively create a phase difference of an incident light beam according to a polarization of the incident light beam.

Abstract: A memory module test system including at least one memory module. The at least one memory module includes a first hub and a plurality of semiconductor memory devices. The system includes a tester for testing the at least one memory module. A second hub is located between the first hub and the tester. The second hub is for converting a memory command and memory data output from the tester into packet data and transmits the packet data to the first hub. The second hub converts the packet data output from the first hub into memory data and transmits the memory data to the tester.

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

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.