Deutsche Thomson-brandt Gmbh

Friedrich Fuldner

Gunter Gleim

Bernd Rekla

Hans-Robert Kuhn

Dieter Storz

Dieter Baas

Arthur Kurz

Peter Hoch

Engelbert Laufer

Resilient scanning head support made of deformable material

With an optical playback device, for example, with a compact disk player, care should be taken to see that the light beam scanning the data radiates as perpendicular as possible onto the disk. However, as a consequence of disk slap or chattering, the radial and the tangential angles alter during every revolution of the disk. As a result of the tolerances in the disk and the device, the optical axis deviates from the perpendicular in many cases. In order to regulate the radial angle .phi.R and the tangential angle .phi.T, under which the light beam strikes the disk, the data signal is demodulated in an amplitude demodulator. The regulating signal UR=C* sin .phi.* cos .alpha. for the radial angle .phi.R and the regulating signal UT=-C* cos .phi.* sin .alpha. for the tangential angle .phi.T are generated from the amplitude C and the phase position .phi. of the demodulated data signal.

Method for measuring and regulating the radial and tangential angles of

A regulation circuit which guides a laser beam along the data track of a recording medium includes a first comparator which receives an HF signal and a first threshold signal. The HF signal is normally high and goes low when the laser scans a dirty or damaged area of the recording medium. The first comparator provides a first output signal when the HF signal is less than the first threshold signal. A second comparator receives a tracking error signal and a second threshold signal. The tracking error signal is normally low and goes high when the laser leaves the data track. The second comparator provides a second output signal when the tracking error signal is high and exceeds the second threshold signal. The first and second output signals are input to an AND gate which provides a signal indicating that the laser beam has left the data track when the first and second output signals are both high.

Track error control signal generation apparatus as for a disc player

Direction determining logic for a regulation circuit which guides a detection device along the data tracks of a recording medium receives an HF signal indicating when the detection device scans a dirty or damaged area of the recording medium, and a tracking error signal when the detection device leaves the track. The direction determining logic includes first and second multiple input terminal logic gates for respectively providing first and second complimentary output signals. A bistate logic circuit is selectively responsive to the HF signal and the tracking error signal and provides complementary output signals to one input terminal of each of the multiple input terminal logic gates. Other logic selectively inhibits the other input terminal of one of the multiple input terminal logic gates as the detection device scans a dirty or damaged area of the recording medium and the other of the multiple input terminal logic gates when the tracking device leaves the track.

Direction-determination logic as for a signal pickup in recorded signal

A digital tuner for a radio in the medium frequency range includes a microprocessor and a keyboard. All frequencies are three digit numbers and are whole number multiples of nine. The desired three digit frequency is input to the microprocessor by manually entering the first two digits using the keyboard If, the third digit is ambiguous it must be inputted manually. The operator is made aware of the ambiguity by the flashing of an indicator where the digit is to be displayed.

Method of automatically tuning a radio

A system for controlling the number of data tracks crossed by the tracking head of a recording/playback device as the tracking head moves in a desired direction over a recording medium includes a counter having n output terminals. The counter is initially set to a count representative of the desired number of data tracks to be crossed as the tracking head moves in the desired direction. An further counter, also having n output terminals individually corresponding to the output terminals of the counter, is set to a predetermined count. Counting pulses are provided to the counter when the tracking head moves in the desired direction and to the further counter when the tracking head moves in a direction opposite from the desired direction. The output terminals are compared and a stop signal is generated when all terminals of both counters show that both counters are in the same state.

Track crossing method using dual counters

An arrangement for track skipping in a track control circuit with an optical scanner, in which two light beams reflected from an information medium, strike each onto a separate photodetector. The two outputs of the photodetectors are subtracted to generate a sine-shaped track error signal representing a difference between a track being scanned and a desired track to be scanned. The track control circuit is supplied at the beginning of track skipping with an offset quantity for skipping across a number of tracks. This offset quantity is dimensioned so that a light beam incident on the information medium for tracking data thereon, becomes displaced by a predetermined amount of track center and thereby radiates partially on the track being scanned and partially on the space between the track being scanned and an adjacent track. The track error signal becomes inverted by an amount equal to twice the number of tracks skipped. The offset quantity becomes separated from the track control circuit earliest after the first inversion and latest after the last inversion of the track error signal. The track control circuit remains closed during track skipping.

Process for track jumping

A servo control arrangement for an optical scanner for focusing a light beam onto a recording medium or for guiding the light beam along data tracks of the recording medium. Light reflected from the recording medium is directed onto a plurality of photodiodes which are connected to a differential amplifier. The amplifier takes differences of the output signals from the photodiodes to generate a servo signal having superimposed high frequency noise components from data recorded on the recording medium. The high frequency noise components are eliminated by short circuiting through a capacitor connected between the inputs of the differential amplifier, whereby the inputs of the differential amplifier become free of the high frequency noise components.

Servo control loop

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.

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Villingen-Schwenningen, Germany

Friedrich Fuldner