Abstract: Various systems and methods for LCD backlight control are disclosed herein. For example, some embodiments of the present invention provide an LCD backlight circuit with an analog inverter circuit that provides a drive voltage to a lamp. A current traversing the lamp is sensed and provided to a digital control circuit. Based on the sensed current, the digital control circuit generates a control signal that is fed back to the analog inverter circuit. In some cases, the digital control circuit is used to cause a gradual increase in voltage applied to the lamp to achieve ignition of the lamp. In other cases, the digital control is used to provide a pre-distorted sine wave that attenuates one or more harmonics introduced into the system by the non-linearities of the lamp.

Abstract: In optical wireless networks, light beams are transmitted over-the-air and maximum performance is achieved when light beams are aligned with corresponding light detectors. A feedback control system is created between transmitting and receiving units, wherein the receiving unit provides positional data about the light beam from the transmitting unit. The transmitting unit uses the data provided to make adjustments to its light beam. However, in order to use the positional data, the units must be operating with a common coordinate basis. A method is provided for determining the basis and generating the transformation needed to modify positional data from one unit into information that is useful for the other unit. Additionally, a method is presented for using the positional data to maintain proper alignment of the light beam.

Abstract: A method that allows a digital communications system to detect the presence of transmitted messages in noisy environments. The system includes an OFDM transmitter and an OFDM receiver. The OFDM transmitter converts a digital signal to be transmitted to a plurality of sub-signals, each corresponding to a respective sub-carrier frequency. The signal is a packet including a preamble field having a known data pattern. The transmitter pre-codes the preamble data pattern, maps the data to corresponding phase information, converts the sub-signals to the time domain, and converts the sub-signals to analog form for subsequent transmission. The OFDM receiver receives the transmitted sub-signals, converts the sub-signals to digital form, converts the sub-signals to the frequency domain, and subjects the sub-signals to preamble detection processing to detect the signals' presence.

Abstract: A system and method of varying the control loop gain of an optical wireless communication link between a transmitting station and a receiving station as an inverse function of distance between the transmitting station and the receiving station to allow the optical wireless communication link to be used reliably over a wide range of distances.

Abstract: The present invention compensates for variations in the angular velocity of the drive's spindle motor by periodically dropping clocks to a counter based upon the previous servo wedge-to-wedge timing. This enables a substantially constant count to be maintained between servo wedges and allows a more predictable generation of the data sector pulses. A more predictable generation of the data sector pulses enables the size of the guard band preceding each data sector to be decreased and the capacity of the disk to be correspondingly increased.

Abstract: A resonant scanning mirror driver configured to drive a micro-electro-mechanical system (MEMS) mirror to a desired deflection utilizes a PWM pattern selected from patterns having 32, 40, 48, 56 or 64 bits. The patterns reflect the first positive and negative quarters of the PWM pattern and the remaining quarters are generated utilizing the symmetry of the sine wave that is generated.

Abstract: A micro-electro-mechanical system (MEMS) resonant scanning mirror driver circuit has separate amplitude and waveshape inputs which allows a relatively slow and therefore inexpensive DAC to be used to control the amplitude of the drive signal for the MEMS device.

Abstract: A technique that eliminates or minimizes the effects of reflective surfaces to reduce or eliminate interference in the data stream and allow an optical wireless communication link to be used reliably. The most important reflective surface is the reflective surface in front of the data detector itself, as that is the one that will be reflected after the transmitting and receiving stations are properly aligned. The greatest reduction in reflected data associated with a remote detector is then achieved by angling the surface in front of the data detector itself, such that reflections from that surface will not fall within the field of view of the remote detector once the stations are properly aligned.

Abstract: A technique that reduces or eliminates the non-linearities associated with the internal feedback sensor used in a micro-electro-mechanical mirror assembly. Using the relatively linear response of the mirror positioning motor, associated driver electronics, and the mirror itself, a calibration is performed that compensates for the internal feedback sensor non-linearity. An expected position can then be calculated simply by multiplying the gain of the system by the output, due to the good inherent linearity in the system. The calibration will compare measured versus expected position criteria for a predefined set of constant outputs. The data will form a look-up table that will be used to correct for the sensor non-linearities.

Abstract: A system and method are provided for controlling the deflection amplitude and offset of a laser beam that is deflected off of a vibrating mirror galvanometer, given only beam deflection timing information.

Abstract: A micro-electro-mechanical system (MEMS) resonant scanning mirror driver circuit has separate amplitude and waveshape inputs which allows a relatively slow and therefore inexpensive DAC to be used to control the amplitude of the drive signal for the MEMS device.

Abstract: A technique that reduces or eliminates the non-linearities associated with the internal feedback sensor used in a micro-electro-mechanical mirror assembly. Using the relatively linear response of the mirror positioning motor, associated driver electronics, and the mirror itself, a calibration is performed that compensates for the internal feedback sensor non-linearity. An expected position can then be calculated simply by multiplying the gain of the system by the output, due to the good inherent linearity in the system. The calibration will compare measured versus expected position criteria for a predefined set of constant outputs. The data will form a look-up table that will be used to correct for the sensor non-linearities.

Abstract: The present invention may be regarded as a disk drive comprising a disk having a plurality of data tracks, each data track comprising a plurality of sectors. A sync mark detector detects a sync mark pattern in a sector, wherein when the sync mark pattern is detected a sync mark detect signal and a polarity signal are generated. The polarity signal represents an expected polarity of pulses in a read signal representing data stored in the sector, wherein the polarity signal enhances the detection of an estimated data sequence from the read signal.

Abstract: A system and method of varying the control loop gain of an optical wireless communication link between a transmitting station and a receiving station as an inverse function of distance between the transmitting station and the receiving station to allow the optical wireless communication link to be used reliably over a wide range of distances.

Abstract: The present invention may be regarded as a disk drive comprising a disk having a plurality of data tracks, each data track comprising a plurality of sectors. A sync mark detector detects a sync mark pattern in a sector by filtering a read signal with a matched filter having an impulse response substantially matched to a dibit response of the disk drive. The output of the matched filter is correlated with a dual polarity correlator to generate first and second correlated signals. The sync mark pattern is detected when either the first or second correlated signals exceeds a threshold.

Abstract: In optical wireless networks, light beams are transmitted over-the-air and maximum performance is achieved when light beams are aligned with corresponding light detectors. A feedback control system is created between transmitting and receiving units, wherein the receiving unit provides positional data about the light beam from the transmitting unit. The transmitting unit uses the data provided to make adjustments to its light beam. However, in order to use the positional data, the units must be operating with a common coordinate basis. A method is provided for determining the basis and generating the transformation needed to modify positional data from one unit into information that is useful for the other unit. Additionally, a method is presented for using the positional data to maintain proper alignment of the light beam.

Abstract: A disk drive is disclosed comprising a bias layer in a magnetoresistive (MR) head actuated over a disk having a plurality of data tracks, each data track comprising a plurality of sectors. A sync mark detector detects a sync mark pattern in a sector, wherein when the sync mark pattern is detected a sync mark detect signal and a polarity signal are generated. The polarity signal indicates when the polarity of the bias layer has deviated from a preferred polarity, wherein the polarity of the bias layer is realigned back toward the preferred polarity.

Abstract: A method for constructing and linearizing a position error signal (PES) derived from primary and quadrature servo burst pairs in an embedded servo disk drive. The construction method mathematically provides predetermined transition values at the commutation positions connecting adjacent PES segments so that the overall, indicated position signal is numerically continuous from segment to segment. The linearization method compensates for nonlinearity in the PES segments, and thereby in the indicated position signal, without affecting the predetermined transition values at all, or by modifying the predetermined transition values while maintaining continuity.

Abstract: A disk drive with a write condition detector generates a write condition signal from a reference signal to warn of a high fly write or a low fly write. The reference signal is generated by the disk drive read/write head by reading a reference segment. The write condition detector processes fly-height varying components from the reference signal. The write condition detector generates a write condition signal, responsive to the fly-height varying components and the threshold, that indicates that the writing of data in a user data segment during the write operation is unsafe when the head deviates from its operating flying-height. The threshold is computed using zone coefficients determined during an intelligent burn in of the disk drive, and is based on a nominal fly height. The write condition signal is processed by a microprocessor that instructs a disk controller to deactivate a write gate controlling the write operation.

Abstract: A method and apparatus is provided which introduces a relative skew between a servo pattern and a magneto-resistive (MR) head in order to reduce interference introduced by inductive reading of shields formed as part of the MR head. The relative skew may be accomplished by introducing a skew angle directly on the head or by skewing the servo pattern formed on the magnetic medium relative to the head. Various skewed patterns may be used to reduce the overall interference.