DK166055B - A method and a circuit for automatic correction of the servo-circuit in a device with optical scanning of a rotating information support - Google Patents

Abstract

An automatic correction system for the servo-circuit of a device with optical scanning of a rotating information support, with a known servo-circuit, for detecting anomalies in the scanning system (1) to whose outputs is connected a gate circuit, providing as necessary a mute control signal at the decoder (2) connected to the scanning system (1) and thus ensuring the mute control of its outputs. According to the invention, anomalies in scanning caused by external faults and/or disc faults, such as scratches, can largely be reduced, in terms of the disturbance caused by this phenomenon, by the fact that a triggering criterion for correction signals can be produced, in the event of anomalies, by sequential address comparison. This is achieved by the fact that a comparator (6) compares any newly read data with the preceding information, which is temporarily stored in a latch circuit (7) and by the fact that a preliminary indication is made available, in the form of a measurement window $g(D) D in order to determine whether the comparison lies outside the measurement window and in order then to emit a correction signal from the comparator (6) to the servo system (3) and by the fact that the scanning system (1) refers back to the last valid scanning point.

Description

in

DK 166055 B

The present invention relates to a method and circuit for automatic correction according to the preamble of claims 1 and 3 and claim 4 respectively.

The scanning of rotating information carriers by means of optical sensors can be disrupted in various ways. CD players, for example, respond to external shocks in a similar way as to scratches or similar damage to the disc to be scanned. Thereby the sensing system can be thrown at least one track backwards or in front of the noisy track. In the worst case, even loss 10 of the focal point occurs. When the existing servo system breaks down, this state is detected by the prior art and a corresponding new activation is initiated. During this time, the signal data becomes muted (mute) to avoid interfering noise.

After the re-stabilization of the control circuit, the mute control is again abolished. In FIG. 1, such a circuit is shown in block diagram form. Here, it is a disadvantage that the instantaneous or last valid scan point in the event of a disturbance is lost in the data, and after the end of the noise phase or the end of the disturbing effect is continued at some random scan point. This means that not only interruptions due to the mute switching are audible, but that regular information shifts conditional on the random application point are noticed acoustically very disturbing.

From GB-A-2,060,207 there is known a picture plate player, where a 25 scanning pin scans the grooves in a bi 11 edpiad containing eight half pictures per minute. second. The bi 11 oak plate is therefore divided by the half-images into eight sectors, which constantly return in the same periodic order, even when the scanning pin, e.g. as a result of a shock skips several grooves. Each half-car 30-line has as its address a half-by-11 oath number which during playback operation is stored in a storage and continuously increased, so that a sequential address comparison can be carried out.

EP-A 139.332 also describes a correction system which indicates by means of a sports loss detector readable 35 non-readable data respectively. With unreadable data, wait until a readable address is found again, and based on the time decoding of the last valid address and the new address, a correction signal is determined so that the scanner moves on to a location where it would stand if the interruption did not existed. Thus one is also performed

DK 166055B

2 sequential address comparison.

JP-A-59167879 finally shows a detector for readable and unreadable addresses. Furthermore, there is shown a spur jump detector which indicates when the track difference becomes too large. In the case of 5 unreadable characters, the previous address is retained by a register and a counter activated by the "unreadable character" signal produces a correction signal.

The object of the present invention is to prevent the loss of the last valid scan point in the event of disturbance 10 by means of a self-controlling correction system such as improvement of the known servo system and to make this system so responsive that noise levels are largely unobservable acoustically.

According to the invention, this is achieved by designing the correction method and circuit as defined in the characterizing portion of claims 1 and 3 and 15 respectively of claim 4.

Further details and designs are set forth in the upper claims and the following description of embodiments.

By means of the invention, the last valid scan point before the beginning of a noise phase is maintained by continuous data storage of the scanned information detected by sequential address comparison. A corresponding correction signal is then produced which enables an automatic correction of the last valid scan point. Thus, in a very fast way of working, information is provided to a large extent with information holes, jumps and displacements which would be audibly annoying.

Two embodiments will then be explained in more detail with reference to the drawing, in which fig. 1 is a block diagram of the prior art servo system mentioned above; FIG. 2 is a block diagram of a correction system which can correct errors due to external impact; and FIG. 3 is a block diagram of a correction system similar to that of FIG. 2, which is extended by a control circuit, so that all kinds of disturbances can be corrected in a short time.

In the correction system shown in block diagram form in FIG.

2, a correction occurs by sequential address comparison, i.e. when the sequence of the read out addresses is interrupted,

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3

there is a disturbance. A comparator 6 and a storage circuit 7 are essential for the operation. The comparator 6 each time compares newly loaded data DATA 1 with prior information which is stored in the storage circuit 7. If the comparison is 5 outside a measurement window WD, which is predetermined in block 4 (AD = Dyar + i. Dm_jn) »the comparator 6 issued a correction signal to the servo system 3. This signal is so directed that the sensing system is positioned at the old address value Dg = DATA

2. With the issuing of a "not-ok" signal, the storage circuit 7 10 is deactivated over ports 5 and 9. Thus, new data cannot be entered into the storage circuit 7. Thus, the reference Dre ^ is retained.

This state is maintained until the correct scanning point is found, and consequently comparator 6 resets the "not-ok" signal.

By means of block 4, a variable measurement window Dyar before 15 can be fixed between DATA 1 and DATA 2. No correction signal is output within the measurement window AD.

Since some data information (addresses) may be corrupted, for example due to plate errors such as scratches, ie not from outside effect, and even if there is no disturbance of the scanner, the measuring window AD must be increased at each invalid address. with the minimum coding system used for recording the predetermined address width Dm ^ n. If this adjustment of the measurement window to the consecutive invalid address data did not occur, this could, depending on the size of the present value of Dyar, lead to an unwanted activation of the correction system. The consequence would be that correction signals constantly affect the servo system, which would prevent continuous readout (playback) of the sensor.

This necessary adjustment of the measurement window is performed by blocks 30 4 and 10. In block 10, the successive invalid data is counted and passed to block 4 for changing AD. In block 4, the measurement window AD is formed as follows: AD = D + i · D. with i = 1, uu uvar. mine. '35 where D = determined measurement window was D = minimal address unit (system specific) min i = number of consecutive invalid address units AD measurement window, within which is the comparison

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4 positive.

With each valid address unit, "i" is reset to one by means of the "data-ok" signal from the data check block 8 over a delay block 11. Thus, the measurement window Δ D is constantly kept at the predetermined default value D,. . ^ + D_. .

In case of correction, the measurement window AD over the "not-ok" line from comparator 6 is set to zero. Thereby, an accurate comparison is made with the old value D2, which is the last read and stored address before the disturbance, and the corresponding servo system correction signal is generated and fed to it.

FIG. 3 shows that in FIG. 2 corresponding block diagram of the dotted horizontal line. Below is a block diagram of a control circuit that cooperates with the correction circuit. The circuits are interconnected so that their functions 15 are superimposed. This automatic control and correction circuit of FIG.

3 is capable of correcting all kinds of playback disturbances so that no significant acoustic impairment of playback interferes even when noise locations occur during scanning.

During the normal undisturbed reproduction operation, the control circuit is largely in the idle state. Only the storage 13, a storage circuit, and the comparator 14 are activated. The storage 13 is activated over a port 20 with each new data information (= address) to take over the current addresses Dg = DATA 2 over the port 21. At this point, a counter 15 is in zero position -25. In the comparator 14, the current current address data (data 1 = D1) is also taken over. In this uninterrupted playback operation, the address information D1 and D2 are the same. In this mode, comparator 14 has no practical significance. The comparator 14 will, with each newly loaded information, output an "ok" signal to the counter 15, but only when the predefined data from the predetermined block 17 is equal to zero (Δ datayar «0). However, this is of no significance since the counter 15 is already in the reset position. Prior to the determination data from the pre-fixing block 17, determine the width of the measuring window AD, within which the data comparisons of comparators 12 and 14 are assessed positive.

When a disturbance occurs, the comparator step 6 emits a "not-ok" signal. This signal blocks gate 18 comparator 14 so that, initially, no comparison is made. At this point, however, comparator 12 becomes

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5 enabled. This compares the data from the storage circuit 13 with the last valid address data Since Dfef and D2 are at this time the comparator 14 will output an "ok" signal to the counter 15.

This now counts one upwardly, thereby blocking ports 20 and 21. A further 5 data transfer in the storage circuit 13 can therefore no longer take place. The correction system now causes the sensor 1 to be positioned at the last valid sensing value DATA 2 = from the storage circuit 7. If the disturbance is triggered by a plate error, the sensor 1 will immediately lose its sensing point at the noise location.

The consequence is that the comparator 6 immediately activates the comparator 12 again and that it delivers a further counting pulse to the counter 15. This repeats until counter 15 runs over and activates the unit 16. This then adds to the last valid scan value D selectable ADg and delivers the result to the storage circuit 7 15 as a new reference. The comparator 6, as a result, causes the scanner 1 to move this ΔD ^ behind the noise location, i.e. over this. As soon as this point is found, the "not-ok" signal will deactivate comparator 12 and the circuit is in its initial position again. In this case, comparator 14 has remained unaffected. It serves to reset the counter 15 once again in the event of a correction.

When the scan proceeds after a correction once, the current address information Dj becomes larger than the last reference value Dfef plus a predetermined window AD, so that the comparator 14 gives an "ok" signal to the counter 15 and in this way again puts the entire circuit in the starting position.

30 35

Claims (4)

A method of automatically correcting the servo circuit in an optical scanner apparatus for rotary information carriers, wherein the servo circuit is arranged so that disturbance of the sensing system with respect to focus and / or trace is detected in a servo system and where applicable emits a mute signal to the decoder terminated by the sensing system and thus mute its outputs, where a sequential address comparison supplies the trigger criterion for output of a correction signal in the event of a disturbance, each time comparing newly read addresses (DATA 1) with prior addresses (DATA 2) intermediate stored in a storage circuit (7) and with the last valid address stored in the storage circuit (7) and with a data control circuit 15 (8) as for each address unit delivers a validity or invalidity signal, characterized in that by valid data, a backslash of the light beam scanning the data occurs to the place of the last valid address (DATA 2) when the newly read address (DATA 1) relative to the last valid address (DATA 2) 20 lies outside a pre-fixed measurement window AD, that in the case of invalid data no light beam is reversed which scans the data to the last correctly read address, but the successive invalid signals are counted and according to the measurement result the measurement window AD is increased and the sequential address comparison activated by the validity signal continues at the first valid address, the storage circuit (7). is set to the new address and the measurement window is set to an output value. Method of automatic correction according to claim 1, 30, characterized in that resetting none of the sensing system (1) to the last valid address unit is initiated by the output of a "not OK" signal from the comparator (6), however, this over the ports (5.9) renders the storage circuit inactive, whereby no new data can be entered into the field circuit (7), and sets a variable measurement window AD of the preset block (4) to zero, by means of which an accurate comparison in the comparator (6) with the address information stored in the storage circuit (7) is secured and that during the playback process a variable measurement window AD is formed in the pre-fixing block (4) according to the following formula 5 7 = 16 + 555 AD = D + i · D. with i> 1, var. mine. - 'where Dyar = predetermined measurement window, Dmin = minimal address unit (system specific), i = the number of consecutive invalid signals, AD = measurement window, within which the comparison is positive, 10 and which measurement window constantly adjusts to the noise type and - duration, counting successive invalid signals and validity signals resetting to "i = Γ. 15 A method of automatically correcting the servo circuit in an optical scanner apparatus for rotary information carriers, wherein the servo circuit is arranged so that disturbance of the sensing system with respect to focus and / or track is detected in a servo system and where applicable a mute signal is output to the decoder connected to the sensing system and thus mute its outputs, where a sequential address comparison provides the triggering criterion for output of a correction signal in the event of a disturbance, each time comparing (6) to newly read addresses with preceding addresses which are intermediately stored in a storage circuit (7) and wherein the last valid address is stored in the storage circuit (7) and with a data control circuit (8) which provides for each address unit a validity or invalidity signal, characterized in that there is a 30 flashback of the light beam which scans the data to the last valid address when the n Newly read address (D1) relative to the last valid address (D2) is outside of a preset measurement window AD, that the number of callbacks to the last valid address (D2) is counted by invalid data and when the number of the spoken callbacks reaches a predetermined value, a preset address distance (AD2) is added in the memory to the last valid address, and the light beam is positioned at the address thus calculated. DK 166055B 8 A circuit for carrying out the method according to claim 3, characterized by a) a memory (13) for an address Dre and a comparator (14), which are activated by undisturbed normal operation, wherein the memory (13) is activated over a gate ( 20) with each new data information to take over a port (21) the last valid address D2, b) a counter (15) which is in normal operation in the zero path 1 -10 ring, c) an ENABLE input of the comparator (14), which performs the determination of D1> D1 + D1 and has the inputs of the newly read address data D1 and D1, d) a further comparator (12) to determine D1D D1 <D2 <D1 ^. + ÅD1, 20 e) a circuit (16) which cooperates with the counter (15) and outputs a signal to the memory (7) when activated by the overflow counter (15) and increases D2 by ÅD2. 25 30 35