Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the record
Reexamination Certificate
1993-12-22
2001-08-28
Neal, Regina Y. (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the record
Reexamination Certificate
active
06282048
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a tracking control method and apparatus for controlling capstan speed by using a variable capstan speed instruction in the image recorder/reproducer, wherein the amount of tracking error is reflected, thereby carrying out correct tracking.
2. Discussion of Related Art
An image recorder/reproducer such as a VCR or a video camera/recorder (camcorder) generates a poor display when beat frequencies are not properly controlled by tracking. Therefore, good tracking control is essential to obtain a good screen image.
Tracking control operation involves controlling the head correctly to scan a predetermined track, thereby maximizing envelope output during reproduction.
A separate control signal is used for tracking control. In a VHS-VCR, tracking is performed using a control signal which is recorded on a control track of a respective tape by a fixed head. Further, in an 8 mm VCR system, the pilot signal used in automatic track finding (ATF), has four different frequencies, and is recorded on the track of the tape. The pilot signal is used for reproduction in such a way that the tracking error, i.e., the degree of deviation from the track which the current head is scanning, is detected and reduced.
It will be noted that, the detected tracking error can be minimized by controlling the spinning speed of the capstan motor. That is, the object of the tracking control is to determine the optimum spinning speed of a capstan motor.
A conventional tracking control method will be described with reference to the attached drawings.
FIG.
1
A and
FIG. 1B
show the relation between the scanning traces of the head and tracking error of a conventional VCR. For convenience, the generation of a positive error indicates that the head is located prior to the track to be scanned while the generation of a negative error indicates that the head is located after the track is scanned.
Referring to
FIGS. 1A and 1B
, when the head is located prior to the predetermined track, that is, when the head is located in a P1-level track, the tape proceeds slowly by slowing down the speed of the capstan motor. When the head is behind the predetermined track, that is, when the head is located in a P2-level track, the tape proceeds faster by increasing the speed of the capstan motor. Therefore, the head is controlled to scan the predetermined track correctly.
This basic principle of tracking control is still appropriate for the present invention as well as for the conventional method.
The conventional structure of a capstan servo for tracking control is shown in FIG.
2
.
Referring to
FIG. 2
, the speed control signal for a capstan motor
20
applied to a capstan motor driver
18
is determined by the amount of capstan speed control detected from a tracking controller
12
and the amount of tracking control detected from a capstan controller
14
, respectively. An adder
16
adds the above two amounts.
FIG. 3
shows an embodiment wherein the capstan servo system shown in
FIG. 2
is applied to a VHS-VCR.
Here, the amount of capstan speed control is calculated under the assumption that there is a predetermined normal track, and the capstan speed instruction (f), which corresponds to the regular spinning speed of the capstan motor and which is needed when the head correctly runs above the normal track, is the reference value. Also, the reference value and the actual speed of a capstan motor
27
, as measured by a frequency generator
29
when capstan motor
27
spins, are compared in a capstan speed error detector
21
. The degree of error calculated from this comparison is changed into a degree of speed control of capstan motor
27
in a capstan speed controller
22
, which is not affected by the degree of tracking control for compensating the tracking error.
The record pulse which is synchronized with the track start point (hereinafter, termed a ‘control pulse’) is recorded on the control track. Also, the degree of capstan tracking error is output from the capstan phase comparator
23
by means of phase comparison between the control pulse which is reproduced by a fixed head
28
(called a ‘control head’) and the head switching pulse wherein the prearranged frequency is provided. Then, the degree of capstan error is proportional-integration-differentiation (PID) controlled so as to be output as a degree of capstan tracking control, i.e., a predetermined physical amount, in a capstan phase controller
24
, thereby performing phase control of a capstan motor in order to control tracking.
The degree of capstan speed control of capstan speed controller
22
and the degree of tracking control of capstan phase controller
24
are added in an adder
25
, and the capstan motor
27
is driven by a capstan motor driver
26
.
However, the above-mentioned conventional method generates various kinds of problems when the direction for controlling the speed of the capstan motor and the direction for controlling the tracking are different. The following is an explanation with reference to FIG.
2
and FIG.
4
.
FIG. 4
shows the tracking when the head runs along a deviating track modified from the normal track.
As can be seen in
FIG. 4
, the traces of the head which capstan speed controller
14
aims to control are on the predetermined normal track (the A direction of FIG.
4
), while the traces of the head which tracking controller
12
aims to control are on the modified track (the B direction of FIG.
4
).
Accordingly, when the direction for controlling the speed of capstan motor
20
and the direction for controlling the tracking are different, correct tracking is difficult since the speed controller prevents the capstan motor
20
from moving in the direction of reducing the tracking error.
Precise gain control for the degree of control for the above two directions is needed to solve the problems. Therefore, the gains of tracking controller
12
and capstan speed controller
14
should be controlled precisely. However, the design of the device which is additionally required for the gain control as well as the gain control itself is difficult. Even though the device has a gain control function, there is still a problem of compatibility between the two devices if the recording device and the reproduction device are different.
The deterioration in tracking is not a significant problem in a VHS-VCR or in an 8 mm VCR, since the width of the track is quite large (58 &mgr;m for VHS, and 21 &mgr;m for 8 mm). However, there is a problem of lowered performance for the case of digital VCR which requires high density recording, because very high performance tracking is needed if the track width is below 10 &mgr;m.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a method and device thereof which can control tracking by using a variable capstan speed instruction, wherein the degree of tracking control calculated from the tracking error is reflected in the capstan speed instruction, instead of using the conventional capstan speed instruction wherein the tracking error is not reflected as in the prior art. The capstan speed instruction is used as a reference value which is used for calculating the degree of capstan motor speed control.
According to an aspect of the present invention, there is provided a tracking control method for an image recorder/reproducer which converts the applied tracking error into a degree of capstan speed control and in generating a driving signal for a capstan motor, wherein the tracking control method comprises the steps of:
calculating a degree of tracking control, which performs a predetermined gain control on the tracking error and converting the gain-controlled tracking error into the degree of tracking control;
generating a speed instruction, which generates the variable capstan speed instruction reflecting the degree of tracking control;
determining a speed error, which compares the capstan speed instruction and the actual spinning speed of the capstan motor and then determines the de
Neal Regina Y.
Nguyen Son Hoang
Samsung Electronics Co,. Ltd.
Sughrue Mion Zinn Macpeak & Seas, PLLC
LandOfFree
Tracking control method and apparatus for controlling... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Tracking control method and apparatus for controlling..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Tracking control method and apparatus for controlling... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2481222