Deutsche Thomson-brandt Gmbh

Dieter Baas

Arthur Kurz

Hans-Robert Kuhn

Friedrich Fuldner

Hans-Robert Ku/ Hn

An optical recording and/or playback system having tracking and focus regulating circuits. Mechanical shock and/or disc defects are detected and the adverse effects on the tracking and focus regulating circuits are reduced.

Optical recording and reproducing apparatus with servo compensation for

An optical disc record playback apparatus includes tracking circuitry for radially translating the scanning pickup device during normal playback of the disc. Coarse and fine drive circuits are responsive to tracking error signals to provide coarse and more precise radial translations respectively. The tracking error signals are monitored for the occurrence for abnormalities such as may be produced by dust on the disc surface, and responsive to the detection of such abnormalities the coarse drive system is disabled to preclude the pickup from leaving the track.

Tracking regulation circuit including apparatus for disabling coarse

A disc playback apparatus includes a system for scanning a disc and storing in memory, an address associated with every point on the disc where the scanning device mistracks. A modified regulating signal is calculated for guiding the scanning device back onto the desired data track, from the value of the regulating signal generated by the tracking regulation circuit prior to track loss. The modified regulating signal is also stored in the memory, and during every subsequent reading of the disc, upon encountering track areas associated with stored addresses, the tracking regulation circuit is provided a corresponding modified regulating signal in order to maintain the scanning device near the desired data track. In further scans of the disc successive modified track regulating signals are iteratively generated and tested for tracking response until a substantially optimum modified signal is generated. The optimum modified regulating signal is then stored in memory associated with the address of respective disc defects. The optimum regulating signal is determinable by monitoring the polarity of the tracking signal after application of the modified signal. The first occurrence of a polarity change is an indication that the respective iteration of generating a modified signal has produced the desired signal.

Method for correcting tracking errors in a disc record reproduction

Process for stopping a rotating disc-shaped record medium

A method of reading recorded-data on a spiral data track of a rotating recording medium which is scanned by a radially moveable scanning device. The scanning device follows the spiral data track and appears to shift from one track to another. The directory data are divided into a plurality of directory data blocks and stored on the spiral data track. Each of the data blocks represents a different characteristic of the recorded-data and at least n+1 identical blocks for each characteristic are sequentially arranged on the spiral data track, n being a whole number. The directory data are read by moving the scanning device from one data block to another. The motion between data blocks occurs either along the same track, inwardly from one track to another, or outwardly from one track to another and therefore the scanning of all n+1 blocks for every characteristic is not necessary.

Method of reading data off a rotating recording medium

A method of adjusting the moveable unit of a positioning device having a light source and a photodetector for scanning markers identifying positions at which the moveable unit is to be located includes the steps of accurately and manually positioning the unit at one of the identifying positions. The unit is then automatically driven to a second position where the output signal of the photodetector is maximum. The deviation from the first position to the second position is stored as an offset which is subsequently used to accurately position the moveable unit.

Process for positioning a record changing device having reflective

In CD-players with a memory having A storage positions for the storage of titles recorded on a CD-record it can happen, that more titles C are on the CD-record than storage positions A provided therefore in the CD-record. In order to use the storage space better in these cases and to keep the access times to the single titles low, the difference of the start times of each two consecutive titles are stored, instead of storing the start times of the individual titles. The more titles that are recorded on a inserted CD-record, the better the storage space is used, and the more the access times are reduced.

Method for reducing access time in a CD-player with a memory by storing

Compact disk reader

A tracking circuit for guiding a beam of light along data tracks of a recorded medium as compact disks and video disks, in which the recorded medium reflects a light beam onto a photodetector. The photodetector has an output voltage that is applied to a servo through a variable-gain amplifier. A compensation voltage is superimposed over the output voltage from the photodetector during the open state of the circuit to compensate off said voltages. This compensation voltage is varied until the sum of the output voltage from the photodetector and the compensation voltage attains a predetermined value. Thereafter the circuit is closed.

Tracking circuit for guiding a beam of light along data tracks of a

A method for skipping tracks in apparatus playing back data that is readable from data-storage tracks on a recording medium by an optical scanner when a base of light is positioned on the tracks by a tracking circuit. The optical scanner is shifted from one data track to another by a skipping pulse during a track-skipping procedure, and is halted in place there by a braking pulse. The tracking circuit is opened not prior to the beginning of the skipping pulse and not later than the departure from the data-storage track. The optical scanner is braked by a first braking pulse of constant length and amplitude, but which is too small. A second braking pulse is produced with pulse characteristics dependent on the time that elapses until a predetermined point on the next data-storage is arrived at. The second braking pulse thereby halts the scanner in the middle of the next data-storage track. The tracking circuit is then closed, but not prior to the beginning of the second braking pulse and not later than the middle of the next data-storage track.

Equipment for playing back data

An arrangement for inserting and extracting a recorded medium in which a movable slidable member is slidable in directions into and out of said stationary housing member. The slidable member is provided with two nose-shaped elements that are spaced from one another. A single switch mounted on the stationary housing member is actuated by the nose-shaped elements when the slidable member moves in-and-out of the stationary housing member. The in-and-out motion of the slidable member is made dependent on the states of the single switch.

Insertion/removal arrangement for a recording carrier

In CD-players with a memory (S) having A storage locations for the storing of the titles recorded on a CD-record, it can occur that the number of titles C recorded on the CD-record exceeds the number of storage locations A in the CD-player. In order to keep the access times for individual titles low, the memory (S) is partitioned into a first part (T1), having B storage positions, and a second part T2, having A-B storage positions. The titles 1 to B are stored in sequence in the B storage locations of the T1 portion of memory S. The remaining titles are distributed to the A-B storage locations of the part (T2) such that, no continuing sequence with the first B titles is formed. For example, the remaining C-B titles may be distributed evenly in the second part (T2) of memory S.

Method of partitioning the memory in a CD-player in order to reduce

A servo loop arrangement for the reproduction of data from a record medium has interleaved pulse trains of opposite polarity pulses applied to it to add to the servo loop control signal which undesirably includes an offset voltage. The resultant increasing opposite polarity changes in the control signal in successive pulse train intervals are threshold detected. The numbers of opposite polarity pulses required to reach the threshold values are compared and any difference in number is converted to a compensation signal which is added to the servo loop to compensate for the offset voltage.

Servo apparatus with offset compensation

Compact-disk players read out some of the redundant table of contents on a compact disk and enter the data in a memory. Since the position of the beam of scanning light is random at the commencement of the read-out and entry process, it can in certain situations take longer for the beam to arrive at the first block (A0) in the table of contents, at which entering is to begin. To decrease the read-out and entry time the beam of light is diverted to the first block (A0) from whatever block it happens to be at at the commencement of the process. In a variant of the process the data are stored commencing with the block that the beam happens to be at at the commencement and ending with the next block with the same content. In a third version the entry commences with the block that the beam happens to be at at the commencement and, when the beam arrives at the last block to be entered, it skips back to the first block (A0) and enters the rest of the data.

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Kehl, Germany

Dieter Baas