Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Patent
1995-02-21
1996-09-03
Psitos, Aristotelis
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
360 7712, 32420725, G11B 2020, G11B 556
Patent
active
055529445
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to the determination of azimuth error between determination as may be utilised in audio cassette recording and playback.
It is known that azimuth accuracy is a fundamental feature of good audio cassette duplication. By azimuth is meant the angle between the gap of the read head relative to the direction of movement of the tape and also the gap of the write head relative to the direction of movement of the tape. The write head having supplied information to the tape. If these two angles are both zero, the azimuths are zero and optimum high-frequency performance may be achieved. Should either azimuth deviate from zero, then deterioration in this high-frequency range may result.
Conventionally azimuth accuracy is achieved by maintaining the write head gap, during recording, at exactly 90.degree. to the direction of tape movement and also maintaining the read head at the same angle during playback. U.S. Pat. No. 4,709,288 discloses such a mechanism. A fine adjustment mechanism, such as a micrometer screw is provided by which either the cassette tape guide elements or the write or read head itself may be partially rotated or pivoted in order to maintain the head normal to the direction of the tape travel.
The above system, whilst adequate, suffers from the shortcomings that in order for accurate micrometer calibration to be achieved, a test tape must be used. This tape bears a recording of a sine wave at a frequency towards the upper end of the bandwidth over which the machine is to operate. The micrometer screw is then adjusted until the maximum signal output level is achieved.
It will be appreciated that to use such a test tape prior to each playback is, at best, a nuisance in, for example, mass reproduction situations.
It is, therefore, an attractive proposition to have a system for the measurement of azimuth error which does not necessarily require the use of a test tape. Furthermore it is an object of the present invention to provide a method of measurement of the azimuth error by utilising the signals actually recorded on the tape--rather than necessarily using a dedicated test tape.
Thus according to a first aspect of the present invention there is provided a method for the determination of azimuth error between write and read heads moving relative to first and further signals borne by a carder comprising: analysing the same signals as received by the read head, wherein analysing of the write head and read head signals includes temporally delaying the first signals with respect to the further signals, passing the further signals through a plurality of time delays thereby to provide a plurality of time-delayed further signals each having a different associated time delay, and providing time-delay values corresponding to the best correlation between the time-delayed first signals and each of the plurality of time-delayed further signals; from the time-delay value of the best-correlation write head signal to provide a timing error value from which the azimuth error may be derived.
Thus the invention provides the advantage that a dedicated test tape is no longer necessary as the signals recorded on the carder by the write head may themselves be analysed--as read by the read head--in order to provide a timing error which directly relates to the azimuth error. Use of a test tape is, however, not precluded.
Preferably the write and read heads move at speed, v, relative to the carrier, and the first and further signals are spaced apart on the carder by distance, d; and wherein the azimuth error is derived by multiplying the timing error by v/d.
Additionally the time delays may be cascaded, or in parallel.
According to a second aspect of the present invention there is provided apparatus for determination or azimuth error between write and read heads moving relative to first and further signals borne by a carder, including; further signals, both first and further signals supplied by both the write head and the read head; and read heads respectively to provide a plurality of time-delay
REFERENCES:
patent: 3678220 (1972-07-01), Luhr
patent: 4101937 (1978-07-01), Jenkins
patent: 4317144 (1982-02-01), De Niet et al.
patent: 4468752 (1994-08-01), Chatham
patent: 4472747 (1984-09-01), Schwartz
patent: 4506309 (1985-03-01), Joannou et al.
patent: 4686470 (1987-08-01), Bond
patent: 5309299 (1994-05-01), Crossland et al.
Donnelly, T., et al., "Real-time Microprocessor Monitoring of Skew Angle in a Compact Cassette Multitrack Magnetic Tape System", Journal of the Institution of Electronic and Radio Engineers, vol. 56, No. 2, pp. 49-52, Feb. 1986.
Taryshkin, A. G., "Measurement and Correction of Interchannel Phase-Frequency Response of a Magnetograph", 2353 Measurement Techniques 27, No. 3, pp. 257-260, Mar. 1984.
Rosback, Thomas J., "A Digital Audio Time-Base Corrector for Linear Magnetic Recording", SMPTE Journal, pp. 1180-1184, Nov. 1985.
Central Research Laboratories Limited
Cullen Larry
Psitos Aristotelis
LandOfFree
Method and apparatus for the determination of azimuth error does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for the determination of azimuth error, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for the determination of azimuth error will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1955504