Abstract:
An apparatus and method measure the recording quality of a magnetic recording medium (21). A magnetic medium recorder (14) records signals on the recording medium (21) and detects signals recorded on the medium (21). A pattern generator (13) coupled to the magnetic medium recorder (14) produces a test signal (202) that includes at least one pulse that has an amplitude that is a minimum read amplitude relative to the amplitude of a reference condition. The sequence of pulses preferably represents the data pattern (302) that will be recorded on the medium (21) under normal operating conditions and that has such a minimun amplitude. A pulse amplitude detector (20) has a first input coupled to the magnetic medium recorder (14). The pulse amplitude detector (20) supplies a pulse detect signal (27) having a first state indicative of a detected pulse, in response to the pulse amplitude of the detected signal applied to the first input of the pulse generator (13) being greater than a threshold, and supplies the pulse detect signal (27) having a second state indicative of a missing pulse, in response to the pulse amplitude of the detected signal applied to the first input of the pulse generator (13) not being greater than a threshold.
Abstract:
Disclosure is given of a device and method for recording by means of a radiation beam (15) user information on a record carrier (1). The user information is written in the form of optically detectable marks (30, 31) in concentric tracks. The tracks are subdivided into sectors (98). The record carrier used (81) has ring-shaped zones (84, 85, 86). Within these zones (84, 85, 86) lie the sectors aligned seen in radial direction. For writing the marks in the tracks, a write intensity of the radiation beam (15) is set to a determined set value. For this purpose, a test information pattern is written in a buffer sector which is situated on an edge of a zone. Then the test information pattern is read back during which operation the test information pattern is converted to a corresponding test data pattern. Based upon the test data pattern a set value for the write intensity is determined.
Abstract:
In accordance with an exemplary embodiment of the present invention, a method (100) for measuring a quality parameter of an optical storage system comprising a non-diffraction-limited optical storage medium and a readout device, the method comprising the process of deriving (110) an impulse response of the optical storage system, and the process of analyzing (120) the impulse response to determine at least one of a width of the impulse response and a skewness of the impulse response as the quality parameter.
Abstract:
There is disclosed a method and apparatus for measuring a signal (15) using a measurement system (20). The signal (15) has a frequency component that is to be detected by the measurement. The frequency component has a varying phase. The signal (15) has at least one interruption thereto. The method comprises: processing the signal (15) with the measurement system (20) to detect said frequency component in the signal (15) and stalling the measurement system (20) before the start of the interruption. The stall period is calculated such that the processing of the signal (15) is resumed: i) after the end of the interruption, and ii) where there is substantially no discontinuity between the phase of the frequency component in the signal (15) at the end of the stall and in the phase of the frequency component in the signal at the beginning of the stall.
Abstract:
Data are stored on a random-access storage medium. A user set of data is received. The user set of data is mapped to multiple frames. For each frame, error-correction bytes are generated over the data mapped to that frame. In addition, the data mapped to that frame are written to a number of data blocks of that frame and the error-correction bytes generated for that frame are written to a number of error-correction blocks of that frame. At least one of the number of error-correction blocks and the number of data blocks differs among at least some of the frames.
Abstract:
The present invention relates to a method, apparatus and record carrier for controlling read-out and/or synchronization between an external magnetic field and written data during a reading operation from a magneto-optical recording medium comprising a storage layer and a read-out layer. An expanded domain leading to a pulse in a reading signal is generated in said read-out layer by copying a mark region from said storage layer to said read-out layer upon heating by a radiation power and with the aid of the external magnetic field. The waveform of the reading signal is analyzed, and the analysis result is used for correcting a phase deviation and/or for controlling a copy window size of the mark copying. Phase errors can thus be corrected for any size of the copy window. Even small changes in the copy window can be detected and corrected.
Abstract:
A method is disclosed for detecting defects in a recordable medium such as a hard disc drive based on error energy. The method may include the steps of writing test data (28) to the medium and reading back (16) the test data (28). The method may also include the steps of computing an error energy based on the square of the difference between the read back data and an ideal version of the test data and comparing the error energy with an energy threshold. The method generates a defect signal when the error energy exceeds the energy threshold. The method may also be used to identify the media defect according to its error energy profile. An apparatus for detecting defects in a recordable medium is also disclosed.
Abstract:
A system determines bit error rate in a sampled data system having a disc (112) formed of a magnetic medium and a data head (126) for writing data on the disc (112) and retrieving data from the disc (112). A pattern is written on the disc (112) which includes isolated instances (248) associated with a predetermined event. The pattern is retrieved from the disc (112) and the isolated instances (248) are combined to obtain a representative instance sav(n) having a reduced media noise component. The representative instance sav(n) is combined with each of the isolated instances (248) to obtain noise sequences. An autocorrelation component (R) is obtained based on the instances read from the disc (112) and the noise sequences. A channel filter is developed having an impulse response h(n) based on the representative instance and based on the channel requirements for a predetermined channel model. A representative instance is passed through the filter to obtain a filter output sample (smp), and an error value indicative of the bit error rate is determined based on the filter output sample and the autocorrelation component (R).