DD298325A5

DD298325A5 - DETECTION CIRCUIT

Info

Publication number: DD298325A5
Application number: DD90344296A
Authority: DD
Inventors: Guenter Gleim; Friedrich Fueldner; Bernd Rekla
Original assignee: ��@��`��@��k��
Priority date: 1989-09-30
Filing date: 1990-09-28
Publication date: 1992-02-13
Also published as: CN1050637A; AU6418690A; FI921365A0; JP2854131B2; ES2071829T3; TR24612A; HUT61118A; KR100227668B1; CN1020009C; MY107309A; KR920704281A; HU9200995D0; DE3932831A1; FI921365A; JPH05500577A; DE59008679D1; EP0494892A1; WO1991005340A1; ATE119706T1; HK81796A

Abstract

A light beam which scans the data on an optical recording support, generates an r.f. signal in the recording and/or playback device. As the r.f. signal is interrupted when the light beam leaves a data track, the detector circuit recognises from the r.f. signal level whether the beam is passing from one data track to the next. As the interruptions in the r.f. signal can also be caused by dirt, damage or errors on the recording support, it is impossible to be certain whether such an interruption has been caused by a track change or by dirt, damage or errors on the recording support. In order to recognise track changes reliably, the detector circuit does not generate a signal indicating a track change until the r.f. signal (HF) is below a first predetermined threshold (R1) and at the same time a track error signal (TE) is above a second predetermined threshold (R2). Detector circuit which recognises when a scanner leaves a mark or data track, e.g. in CD players, video record players, DRAW-disc players and magneto-optical recording and/or playback devices.

Description

Hierzu 5 Seiten ZeichnungenFor this 5 pages drawings

The invention relates to a detection circuit which indicates when a scanner scanning marks makes a mark

verläßt, wobei ein erstes Fehlersignal und ein zum ersten Fehlersignal phasenverschobenes zweites Fehlersignal erzeugt wird.leaves, wherein a first error signal and a first error signal phase-shifted second error signal is generated.

CD players, video disc players, DRAW disc players or magneto-optical recording and playback devices are

beispielsweise mit einem Spurregelkreis und einer optischen Abtastvorrichtung ausgestattet.for example, equipped with a tracking control loop and an optical scanning device.

The structure and function of an optical pick-up, a so-called optical pick-up, are available in Electronic Components & Applications, Vol.6, No.4,1984 on page 209-215. The light beam emitted by a laser diode is focused by means of lenses on the compact disc and from dor ι to a Photodetector reflected. From the output signal of the photodetector are stored on the CD-disk data and

der Istwert für den Fokus- und für den Spurregelkreis gewonnen. In der genannten Literaturstolle wird die Abweichung desthe actual value for the focus and for the tracking control loop won. In the mentioned literature the deviation of the

Actual value of the target value for the focus control loop referred to as focusing errohr, while for the deviation of the actual value forward Setpoint of the tracking loop of the expression radial tracking error is selected. As an actuator for the focus control loop is a coil, on the magnetic field, an objective lens along the optical axis

bewegbar ist. Der Fokusregelkreis bewirkt nun durch Verschieben der Objektivlinse, daß der von der Laserdiode ausgesendeteis movable. The focus control loop now causes by moving the objective lens, that emitted by the laser diode

Light beam is always focused on the disc. By means of the tracking loop, which is often referred to as a radial drive, is

die optische Abtastvorrichtung bezüglich der CD-Platte in radialer Richtung verschiebbar. Dadurch kann der Lichtstrahl auf denspiralförmigen Datenspuren der CD-Platte geführt werden.the optical scanning device with respect to the CD plate in the radial direction displaceable. Thereby, the light beam can be guided on the spiral data tracks of the compact disc.

Be some devices, the radial drive from a so-called coarse and a so-called fine drive constructed. The Coarse drive is designed for example as a spindle, by means of which the entire optical scanning device from the laser diode,

den Linsen, dem Prismenstrahlteiler und dem Photodetektor radial verschiebbar ist. Mit dem Feinantrieb ist der Lichtstrahlzusätzlich in radialer Richtung verschiebbar oder z. B. um einen vorgebbaren kleinen Winkel kippbar. Mittels des Feinantriebskann daher der Lichtstrahl ein kleines Stück- etwa 1 mm - entlang einem Radius der CD-Platte gefahren werden.the lenses, the prism beam splitter and the photodetector is radially displaceable. With the fine drive the light beam is additionally displaced in the radial direction or z. B. tiltable by a predetermined small angle. By means of the fine drive, therefore, the light beam can be driven a small distance - about 1 mm - along a radius of the compact disc.

To a perfect reproduction of the data, be it now z. As picture and sound in a video disc player or merely the sound

einem CD-Spieler oder die Daten einer magneto-optischen Platte, zu erzielen, ist neben einer genauen Fokussierung desTo achieve a CD player or the data of a magneto-optical disk, in addition to a precise focusing of the

Light beam on the plate requires precise guidance along the data tracks of the plate. FIG. 1 shows the photodetector PD of the optical scanning device of a CD player, in which three laser beams L1, L2 and L3 are focused on the compact disc. The laser beams L2 and L3 are the diffraction beams +1. and -1. Order. Such a scanning device is referred to in the aforementioned reference as a three-beam pick-up, because they are with

drei Lichtstrahlen arbeitet.three beams of light works.

In the photodetector, four square-shaped photodiodes A, B, C and D are joined together to form a square

bilden. Vor dem aus den vier Photodioden A, B, C und D gebildeten Quadrat liegt eine rechteckige Photodiode E; hinter demform. In front of the square formed by the four photodiodes A, B, C and D is a rectangular photodiode E; behind the

Square uine further photodiode F is provided. The middle laser beam L1, which is incident on the four photodiodes A, B, C and D.

fokussiert wird, erzeugt das Datensignal HF = AS + BS + CS + DS und das Fokusfehlersignal FE = (AS + CS) - (BS + DS). Diebeiden äußeren Lichtstrahlen L2 und L3, von denen der vordere L3 auf die Photodiode E, der hintere L 2 auf die Photodiode F fällt,erzeugen das Spurfehlersignal T = ES - FS. Mit AS, BS, CS, DS, ES und FS sind jeweils die Photospannungen der Dioden A, B, C,is focused, the data signal generates HF = AS + BS + CS + DS and the focus error signal FE = (AS + CS) - (BS + DS). The two outer light beams L2 and L3, of which the front L3 falls on the photodiode E, the rear L 2 on the photodiode F, generate the tracking error signal T = ES - FS. With AS, BS, CS, DS, ES and FS, the respective photovoltage of the diodes A, B, C,

D, E and F are designated. In FIG. 1, the middle laser beam L1 follows exactly the middle of a track S. The tracking error signal TE has the zero.

TE = ES - FS = 0.TE = ES - FS = 0.

Wenn der mittlere Lichtstrahl von der Mitte einer Spur S abweicht, bewegt sich der eine Beugungsstrahl mehr zur Spurmitte hin, während der andere Beugungsstrahl auf den Zwischenraum zwischen zwei Spuren S strahlt. Weil aber die Reilexionseigenschaften einer Spur und eines Zwischenraumes unterschiedlich sind, wird der eine Beugungsstrahl stärker reflektiert als der andere.When the center light beam deviates from the center of a track S, one diffractive beam moves toward the track center more, while the other diffraction beam irradiates the space between two tracks S. However, because the reflection properties of a track and a space are different, one diffractive beam is reflected more than the other.

In der Figur 2 ist der Fall dargestellt, daß die Laserstrahlen L1, L2 und L3 nach rechts von der Spur S verschoben sind. Das Spurfehlersignal nimmt einen negativen Wert an:FIG. 2 shows the case that the laser beams L1, L2 and L3 are shifted to the right of the track S. The tracking error signal assumes a negative value:

TE = ES - FS < 0.TE = ES - FS <0.

The actuator of the tracking loop now moves the optical scanning device to the left until the tracking error signal TE

null wird.becomes zero.

In the opposite case, when the load beams are shifted to the left of the track, the tracking error signal is positive: TE = ES - FS> 0. Now, the actuator of the tracking control circuit moves the optical pickup to the right until the Track error signal TE becomes zero. This case is shown in FIG. When the light beam L1 and the associated diffraction beams L2 and L3 cross several data tracks, this decreases Track error signal TE to the sinusoidal waveform shown in Figure 4. From JP-OS 6010429 a tracking control loop is known, in which detected at the lower and upper envelope of the RF signal

wird, ob der Lichtstrahl Datensp"-*n kreuzt. Wenn der Lichtstrahl über mehrere Datenspuren läuft, bricht das HF-Signalregelmäßig zwischen zwei Spuren zusammen.If the light beam crosses multiple data tracks, the RF signal breaks down regularly between two tracks.

To determine the number of tracks swept by the light beam, the envelope of the RF signal is formed and put into a

impulsförmiges Signal umgewandelt, das dem Zähleingang eines VorwSrts-Rückwärts-Zählers zugeführt wird. Auf diese Weisewerden von dem Vorwärts-Rückwärts-Zähler die HF-Einbrüche gezählt.converted pulse signal, which is the counting input of a forward-backward counter supplied. In this way, from the forward-backward counter, the RF-dips are counted.

To determine in which direction the light beam is moved, radially inward or outward, is a so-called Directional logic is required, which determines the phase shift between the tracking error signal TE and the envelope of the Evaluates RF signal. But because dust, dirt, fingerprints or scratches on a CD disk also cause a breakdown of the RF signal

verursachen können, sind Maßnahmen zu treffen, die HF-Einbrüche, verursacht durch Schmutz oder Beschädigung auf demMeasures must be taken to prevent RF intrusion caused by dirt or damage on the surface

Record carrier, from such RF-breaks, which causes a lane change of the light beam from each other to

können.can.

It is therefore an object of the invention to design a Deftlrtionsschaltung so that dirt or scratches on the Record carrier can no longer simulate a lane change of the scanning light beam. The invention solves this problem in that the detection circuit er.st then outputs a signal indicating that the Marks scanning scanner leaves a mark when the first error signal below a first predetermined Threshold and at the same time the second error signal is above a second predetermined threshold. The invention is based on the finding that when scanning soiled or damaged areas of the Record carrier, although the level of the RF signal decreases, the tracking error signal but not appreciably by dirt and Damage to the record carrier is disturbed. Therefore, if only the RF signal collapses, the tracking error signal, the Deviation of the actual value from the target value, but approximately maintains the value zero, it can be assumed that the RF-break through Dirt, damage or fault on the record carrier, but not caused by a change of track of the light beam

wurde. Sinkt dagegen der Pegel des HF-Signals unter einen ersten vorgebbaren Schwellwert und steigt gleichzeitig dashas been. If, on the other hand, the level of the HF signal drops below a first predefinable threshold value and simultaneously increases

Spurfehlersignal über einen zweiten vorgegebenen Schwellwert, so befindet sich der Lichtstrahl nicht mehr auf einer Spur, sondern auf dem sogenannten Rasen, der zwischen den Spuren vorgesehen ist. Es zeigenTracking error signal over a second predetermined threshold, so the light beam is no longer on a track, but on the so-called lawn, which is provided between the tracks. Show it

5 shows a first embodiment 6 shows a second embodiment Fig. 7 u. 8: Timing diagrams for explaining the second embodiment.

Anhand des ersten Ausführungsbeispiels in Figur 5 wird nun die Erfindung beschrieben und erläutert. In der Figur 5 wird die Einhüllende EH des HF-Signals HF dem ersten Eingang eines Vergleichers V1 zugeführt, an dessen zweitem Eingang eine Referenzspannung R1 liegt. Das sin isförmige Spurfehlersignal TE wird dem zweiten Eingang eines Vergleichers V2 zugeführt, an dessem zweiten Eingar.g eino Referenzspannung R2 liegt. Die Ausgänge der beiden Vergleicher V1 und V2 sind mit den Eingängen einös UN J-t atters U verbunden, das an seinem Ausgang eine logische Eins abgibt, wenn der Pegel des HF-Signals! IF unter der Refer«. - «r. Innung R1 und gleichzeitig das Spurfehlersignal TE über der Referenzspannung R2 liegt.With reference to the first embodiment in Figure 5, the invention will now be described and explained. In FIG. 5, the envelope EH of the HF signal HF is supplied to the first input of a comparator V1, to the second input of which a reference voltage R1 lies. The sin isförmige tracking error signal TE is supplied to the second input of a comparator V2, at whose second Einar.g eino reference voltage R2 is located. The outputs of the two comparators V1 and V2 are connected to the inputs of UN J-t atters U, which outputs a logic one at its output when the level of the RF signal! IF under the Refer. - "r. Guild R1 and at the same time the tracking error signal TE is above the reference voltage R2.

The second embodiment shown in FIG. 6 will now be described.

Dem Eingang eines mit fallender Flanke triggerbaren Monof lops M1 wird ein impulsförmiges Hüllkurvensignal HP zugeführt, das aus der Hüllkurve des HF-Signals gewonnen wird. Ein impulsförmiges Spurfehlersignal TZ, das aus dem sinusförmigen Spurfehlersignal TE erzeugt wird, wird dem ersten Eingang eines ODER-Gatters 01 und einem mit fallender Flanke triggerbaren Monoflop M2 zugeführt. Das invertierte impulslörmige Spurfehlersignal T Z wird dem ersten Eingang eines ODER-Gatters 02 und einem mit steigender Flanke triggerbaren Monoflop M 3 zugeführt. Die Ausgänge der Monoflops M 2 und M 3 sind mit den Eingängen eines ODER-Gatters 03 verbunden, dessen Ausgang mit dem Rücksetzeingang eines RS-Flipflops P6 verbunden ist. Der Ausgang des Monoflops M1 ist mit dem ersten Eingang eines UND-Gatters U 9 verbunden, dessen Ausgang mit dem Setzeingang des RS-Flipflops F6 verbunden ist. Der eine Ausgang einer Richtungslogik RL, die in Abhängigkeit von der Bewegungsrichtung des Lichtstrahls entweder an ihrem einen oder anderen Ausgang eine logische Eins abgibt, ist mit dem zweiten Eingang des ODER-Gatters 01 verbunden, während der andere Ausgang der Richtungslogik RL an den zweiten Eingang des ODER-Gatters 02 angeschlossen ist. Die Ausgänge der ODER-Gatter 01 und 02 sind mit den Eingängen eines UND-Gatters U10 verbunden, dessen Ausgang mit dem zweiten Eingang des UND-Gatters U 9 verbunden ist. Wenn der Lichtstrahl auf den zwischen zwei Spuren liegenden Rasen strahlt, ist das RS-Flipflop F6 gesetzt; dagegen ist es zurückgesetzt, wenn der Lichtstrahl auf eine Spur gerichtet ist.The input of a falling edge triggerable Monof lops M1 is supplied to a pulse-shaped envelope signal HP, which is obtained from the envelope of the RF signal. A pulse-shaped tracking error signal TZ, which is generated from the sinusoidal tracking error signal TE is supplied to the first input of an OR gate 01 rs and a triggerable with falling edge monostable M2. The inverted impulse-shaped tracking error signal TZ is supplied to the first input of an OR gate 02 and to a monostable M3 triggerable with a rising edge. The outputs of the monoflops M 2 and M 3 are connected to the inputs of an OR gate 03 whose output is connected to the reset input of an RS flip-flop P6. The output of the monoflop M1 is connected to the first input of an AND gate U 9 whose output is connected to the set input of the RS flip-flop F6. The one output of a directional logic RL, which outputs a logical one either at its one or the other output depending on the direction of movement of the light beam is connected to the second input of the OR gate 01, while the other output of the directional logic RL to the second input the OR gate 02 is connected. The outputs of the OR gates 01 and 02 are connected to the inputs of an AND gate U10 whose output is connected to the second input of the AND gate U 9. When the light beam is irradiated on the lawn lying between two tracks, the RS flip-flop F6 is set; however, it is reset when the light beam is directed at a track.

Das Monoflop M1 gibt bei jeder fallenden Flanke des impulsförmigen Hüllkurvensignals HP an seinem Ausgang eine logische Eins ab. Weil das impulsförmige Hüllkurvensignal HP aus der Hüllkurve des HF-Signals gewonnen wird, tritt eine fallende Flanke im impulsförmigen Hüllkurvensignal immer dann auf, wenn der Pegel der Hüllkurve unter einen vorgebbaren Schwellwert sinkt. Wenn der Lichtstrahl in der einen Richtung bewegt wird, gibt das UND-Gatter U10 bei jedem positiven Impuls des impulsförmigen Hüllkurvensignals TZ eine logische Eins ab; das RS-Flipflop F6 wird nur gesetzt, wenn das Monoflop M1 gesetzt ist und gleichzeitig das impulsförmige Spurfehlersignal TZ einen positiven Impuls aufweist. Wird der Lichtstrahl in der anderen Richtung bewegt, so gibt das UND-Gatter U10 bei jedem positiven Impuls des invertierten impulsförmigen Spurfehlersignals T Z eine logische Eins ab. Das RS-Flipflop F6 wird gesetzt, wenn das Monoflop M1 gesetzt ist und gleichzeitig das invertierte impulsförmige Spurfehlersignal T Z einen positiven Impuls aufweist.The monoflop M1 outputs a logic one at each falling edge of the pulse-shaped envelope signal HP at its output. Since the pulse-shaped envelope signal HP is obtained from the envelope of the RF signal, a falling edge occurs in the pulse-shaped envelope signal whenever the level of the envelope falls below a predefinable threshold value. When the light beam is moved in one direction, the AND gate U10 outputs a logic one at each positive pulse of the pulse-shaped envelope signal TZ; the RS flip-flop F6 is set only when the monoflop M1 is set and at the same time the pulse-shaped tracking error signal TZ has a positive pulse. When the light beam is moved in the other direction, the AND gate U10 outputs a logic one every positive pulse of the inverted pulse-shaped tracking error signal T Z. The RS flip-flop F6 is set when the monoflop M1 is set and at the same time the inverted pulse-shaped tracking error signal T Z has a positive pulse.

Durch eine fallende Flanke im impulsförmigen Spurfehlersignal TZ oder durch eine steigende Flanke im invertierten impulsförmigen Spurfehlersignal TZ wird das RS-Flipflop F6 zurückgesetzt.By a falling edge in the pulse-shaped tracking error signal TZ or by a rising edge in the inverted pulse-shaped tracking error signal TZ, the RS flip-flop F6 is reset.

In den Figuren 7 und 8 sind das HF-Signal HF, das daraus gebildete impulsförmige Hüllkurvensignal HP, das sinusförmige Spurfehlersignal TE, das impulsförmige Spurfehlersignal TZ, das invertierte impulsförmige Spurfehlersignal T Z, die Ausgangssignale der Monoflops M1, M 2 und M 3, das Signal am Ausgang der UND-Gatter U 9 und U10, das Signal am Ausgang des ODER-Gatters 03 sowie am Ausgang des RS-Flipflops F6 gezeigt.In FIGS . 7 and 8, the RF signal HF, the pulse-shaped envelope signal HP formed therefrom, the sinusoidal tracking error signal TE, the pulse-shaped tracking error signal TZ, the inverted pulse-shaped tracking error signal TZ, the output signals of the monoflops M1, M 2 and M 3 are shown in FIGS. the signal at the output of the AND gates U 9 and U10, the signal at the output of the OR gate 03 and the output of the RS flip-flop F6 shown.

Die Erfindung ist allgemein für Zählvorrichtungen zum Zählen von Markierungen oder für Regelkreise zum Positionieren einer Einheit, beispielsweise eines Abtasters, geeignet, bei der die Einheit durch Abtasten von Markierungen positioniert wird. Die Art der Abtastung, mechanisch oder berührungslos, spielt keine Roi.'e. Insbesondere ist die Erfindung für Spurregelkreise geeignet, wie sie z. B. in CD-Spielern, Viedeoplattenspielern, DRAW-Disc-Spielern oder magneto-optischen Aufzeichnungs- und/oder Wiedergabegeräten anzutreffen sind.The invention is generally applicable to counting devices for counting markers or control circuits for positioning a unit, for example a scanner, in which the unit is positioned by scanning marks. The type of scanning, mechanical or non-contact, does not play any role. In particular, the invention is suitable for tracking loops, as z. B. in CD players, Viedeoplattenspielern, DRAW disc players or magneto-optical recording and / or reproducing devices are encountered.

Claims

A detection circuit which indicates when a scanner scanning markers leaves a marker, generating a first error signal (EH) and a second error signal (TE) out of phase with the first error signal, characterized in that the detection circuit only generates a signal indicating that the scanner leaves a mark when the first error signal (EH) below a first predetermined threshold (R 1) and at the same time the second error signal (TE) is above a second predetermined threshold (R 2).

2. Detection circuit according to claim 1, characterized in that the detection circuit is provided for a tracking control circuit and that the signal emitted by it indicates that the scanner has left a data track of a recording medium.

3. Detection circuit according to claim 2, characterized in that a data scanning the light beam, an RF signal (RF) and a tracking error signal (TE) generates, that the detection circuit only then emits a signal indicating that the scanning of the data light beam Data trace leaves when the envelope (EH) of the RF signal (HF) below the first predetermined threshold (R 1) and at the same time the tracking error signal (TE) is above the second predetermined threshold (R2).

4. detection circuit according to claim 3, characterized in that the envelope (EH) of the RF signal (RF) to the first input of a first comparator (V 1) is supplied to the second input of a first reference voltage (R 1) is that the tracking error signal (TE) is supplied to the first input of a second comparator (V2), to whose second input a second reference voltage (R2) is located, and in that the outputs of the comparators (V1, V2) are connected to the inputs of an AND gate (U) whose output signal indicates when the light beam leaves a data track.

5. Detection circuit according to claim 3, characterized in that the pulse-shaped envelope signal (HP) is fed to a falling edge triggerable first monoflop (M 1) whose output is connected to the first input of a first AND gate (U 9) the pulse-shaped tracking error signal (TZ) is fed to a falling edge triggerable second monoflop (M 2) and the first input er least one OR gate (01), that the inverted pulse-shaped tracking error signal (TZ) a triggerable with rising edge third monoflop ( M 3) and the first input of a second OR gate (02) is supplied, that the outputs of the second and third monoflop (M2, M3) to the inputs of a third OR gate (03) are connected, whose output to the reset input an RS flip-flop (F6) is connected, that the output of the first AND gate (U 9) is connected to the set input of the RS flip-flop (F6) that the outputs of the first and second OR gate (01,02) are connected to the inputs of a second AND gate (U 10) whose output is connected to the second input of the first AND gate (U 9), that in each case an output of a directional logic (RL ) is connected to the second input of the first and second OR gate (01,02) that the directional logic (RL) depending on the direction of movement of the light beam either at its one or the other output outputs a logical one and that the signal at Q Output of the RS flip-flop (F6) indicates whether the light beam is radiating on a data track or on the space between two tracks.