Motion video signal processing for recording or reproducing – Local trick play processing – With randomly accessible medium
Reexamination Certificate
1998-01-30
2001-01-09
Nguyen, Huy (Department: 2715)
Motion video signal processing for recording or reproducing
Local trick play processing
With randomly accessible medium
C386S349000, C386S349000
Reexamination Certificate
active
06173111
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for controlling a capstan phase during slow playback and a servo system for a video cassette recorder (VCR) adopting the same, and more particularly, to a method for controlling a capstan phase during slow playback and a servo system for a video cassette recorder (VCR) adopting the same in which a slow motion image can be clearly viewed without noise during slow playback in the VCR.
A servo system for use in a VCR includes a drum servo for controlling the rotational speed of a head to be constant and a capstan servo for controlling a track and maintaining a tape speed to be constant. The capstan servo controls the phase and speed of a capstan motor so that a head can accurately travel over a particular track, and maintains a tape speed to be constant according to a reproduction or recording mode.
A capstan speed control means controls rotation of a capstan motor by obtaining a capstan speed error voltage from a capstan frequency signal corresponding to a tape speed. During abnormal speed playback such as slow playback, a pause and a selective playback operation, a step slow control voltage output from a microcomputer is applied to a capstan speed control voltage.
During reproduction, a capstan phase controller controls a capstan motor by the procedure which compares the frequency of a control signal recorded on a control track of a tape with a reference frequency to thereby obtain a capstan phase error voltage, and adds the obtained capstan phase error voltage to a capstan speed control voltage.
However, the above conventional VCR controls a capstan speed by using a step slow method which makes a capstan motor repetitively rotate and stop during slow playback, with a result that an image is discontinuously displayed. For this reason, a slow motion image which can be seen from a general TV or movie cannot be provided. Also, since a control signal which becomes a reference during reproduction is irregularly read from a tape, the phase of a capstan motor cannot be controlled, and thereby produces noise on a screen.
SUMMARY OF THE INVENTION
To solve the above problems, it is an object of the present invention to provide a method for controlling the phase of a capstan motor by setting a sampling frequency so that a control signal having a frequency and phase appropriate for a slow playback mode which is used on the basis of a head switching signal is generated, and by using the set sampling frequency, with a result that a slow motion image can be clearly viewed without noise during slow playback in a VCR.
It is another object of the present invention to provide a servo system for a VCR which controls the phase and speed of a capstan motor to thereby enable a tracking control, by adopting a capstan phase control method during slow playback.
To accomplish the above object of the present invention, there is provided a method for controlling a phase of a capstan motor during slow playback in a VCR, the capstan phase control method comprising the steps of:
(a) generating a reference control signal having a frequency and phase corresponding to desired slow playback on the basis of a head switching signal; (b) reading a control signal from a tape according to corresponding slow playback; (c) judging whether the phase of the reference control signal generated in the step (a) is the same as that of the control signal read in the step (b); (d) calculating a phase error to make the phase of the read control signal coincide with that of the reference control signal on the basis of the judgement result of the step (c); and (e) controlling a capstan motor using the phase error calculated in the step (d).
There is also provided a servo system for a VCR comprising:
a capstan motor; speed error calculation means for calculating a capstan speed error by comparing an actual speed of the capstan motor with target speed corresponding to desired slow playback on the basis of a received capstan frequency signal; phase error calculation means for generating a reference control signal having a frequency and phase corresponding to desired slow playback on the basis of a head switching signal, judging whether the phase of the generated reference control signal is identical with that of a received control signal, and calculating a capstan phase error so as to make the phase of the received control signal coincide with that of the reference control signal on the basis of the judgement result; and control means for controlling the phase and speed of the capstan motor by summing the calculated capstan phase error and the calculated capstan speed error.
REFERENCES:
patent: 4890169 (1989-12-01), Kobayashi et al.
patent: 4910613 (1990-03-01), Mabuchi et al.
patent: 5684916 (1997-11-01), Hong
patent: 5887113 (1999-03-01), Park et al.
Kwon Young-Gi
Lee Jong-gyu
Nguyen Huy
Samsung Electronics Co,. Ltd.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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