Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Including radiation storage or retrieval
Patent
1986-11-04
1989-01-03
Richardson, Robert L.
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Including radiation storage or retrieval
360 69, 358342, 369 44, 369 43, 369 54, 369 58, 369133, 369240, G11B 700
Patent
active
047962496
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a system for determining the scanning speed of audio disks with remote scanning.
BACKGROUND OF THE INVENTION
Any point on an audio disk that is scanned remotely can be rapidly located by calculating the tracks between the starting point and the target point. The number of tracks between the starting diameter, which is established in accordance with the standards at do=50 mm, and the scanning point accordingly depends on the scanning speed Vo. Scanning speed Vo is specific to each disk and can in accordance with the standards be between 1.2 and 1.4 m/sec. A specific scanning speed Vo is established for calculating the number of tracks. This leads, when a disk has a scanning speed that deviates from this value, to not inconsiderable errors as the skip width increases.
SUMMARY OF THE INVENTION
The object of the invention is to determine the disk-specific scanning speed at low expenditure.
Once the disk-specific scanning speed has been determined, the exact number of tracks between the starting and target points can be determined. This makes it possible to attain the target point of any disk in one skip without corrective measures. The results is substantially shorter access times.
The invention will now be specified with reference to the drawing.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram of a system for determining the scanning speed of audio disks with remote scanning, in accordance with the present invention;
FIG. 2 is a schematic diagram of another embodiment of the arrangement of FIG. 1.
DESCRIPTION OF THE PREFERRED EMODIMENTS
FIG. 1 is a block diagram demonstrating how the scanning speed is determined. A servo and pickup system 1 supplies both the read-out data to a decoder 6 that generates a low-frequency signal and the data prescribed by servo system 1, like the actual diameter di that results from the actual position of the scanner on the disk and the duration of revolution ti, in conjunction with a separate sensor 3 if necessary, to a processing circuit 2 for determining the scanning speed. The results from processing circuit 2 are retained in a memory 4 and the skip coordinates for example called up from a skip-control circuit 5 during the calculation. Skip-control circuit 5 also obtains the actual address data that are part of the data flow from decoder 6. The output terminal of skip-control circuit 5 is connected to the control-input terminal of pickup system 1. It is also possible to supply the address data to processing circuit 2. If address data that are in a definite relation between disk diameters di, like the starting point of the first piece (do=50 mm) for instance, are present, the position will be determined by the address data. In this case the information as to the actual diameter di can be eliminated from sensor system 1.
Servo circuit 1 generates a radial error signal UR that is employed for readjusting the fine and coarse drive mechanism. Signal UR can also be employed to determine disk rotation. The frequency of rotation of the error signal is then determined from the low-pass filtered radial error signal to determine scanning speed Vo. The scanning speed can easily be determined from the mathematical equation sensor signal. The speed of rotation of the disk in the vicinity of inner diameter do is about 8 rps. The beat defect is accordingly exploited to determine scanning speed. If a disk has several eccentricities, frequency fi will be a whole multiple of the speed of approximately 8 rps. In this case, it will be divided by a factor thereof.
In case the disk has no eccentricities, a scanning speed Vo in the vicinity of 1.2 to 1.4 m/sec will be prescribed. This situation, however, hardly occurs in practice.
FIG. 2 illustrates a circuit for measuring disk rotation without an additional decoder. A radial error signal UR is supplied both to a precision drive mechanism 7 and, through a low pass 8 and 9, to a comparator 10. The output terminal of comparator 10 leads to the input terminal of a counter 12. Another input terminal on c
REFERENCES:
patent: 4388713 (1983-06-01), Tatsuguchi
patent: 4641294 (1987-02-01), Yoshimaru
patent: 4675855 (1987-06-01), Iso et al.
patent: 4680746 (1987-07-01), Senso
Deutsche Thomson-Brandt GmbH
Fogiel Max
Richardson Robert L.
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