JP3474923B2 - Video tape recorder - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video tape recorder, and more particularly to a video tape recorder for driving a capstan motor so that a reproduction envelope becomes maximum by shifting a tracking value by a predetermined value.

[0002]

2. Description of the Related Art As a conventional video tape recorder of this type, the envelope amount is obtained by sampling a reproduction signal at a certain tracking value, then the envelope amounts at different tracking values are obtained, and these envelope amounts are calculated. There is a method in which the optimum tracking value is obtained by comparing Further, as another video tape recorder, there is one that obtains the optimum tracking value by obtaining the transition of the change amount of the envelope amount with respect to the change of the tracking value, instead of simply comparing the envelope amounts.

In such a video tape recorder, the tracking value at the time of starting the auto tracking is set to a predetermined value (for example, a tracking center value) within the tracking variable range, and the control signal CTL recorded on the tape and the track. If and have a predetermined positional relationship, the relationship between the tracking value and the envelope amount is as shown in FIG. That is, the tracking center value becomes the optimum tracking value.

[0004]

However, if the relationship between the tracking value and the envelope amount becomes as shown in FIG. 5 because the positional relationship between the control pulse and the tape track is deviated, the center value at the start of auto-tracking is There is a problem that the detected envelope amount changes due to noise, and it becomes difficult to detect the change in the envelope amount due to the tracking value shift. In addition, when the optimum tracking value is largely deviated from the tracking center value as shown in FIG. 5, it takes time to detect the optimum value.

Therefore, a main object of the present invention is to provide a video tape recorder which can easily detect a change in envelope amount with respect to a change in tracking value. Another object of the present invention is to provide a video tape recorder capable of easily detecting an optimum tracking value.

[0006]

SUMMARY OF THE INVENTION A video test according to the present invention.
-The precoder has a track formed on the videotape.
Optimal tracking value that regulates the positional relationship with the head
In a video tape recorder that is adjusted to
The envelope of the playback signal played from the track.
The detecting means for detecting, the envelope detected by the detecting means.
Discrimination to determine whether the rope level is below the reference value
Means, when the discrimination result of the discriminating means is affirmative
Shift means for shifting the ringing value in a predetermined direction, and
When the result of discrimination by another means is negative
Locking means for executing the locking.
It

[0007]

A signal correlated to the reproduction envelope, for example, an envelope detection signal is given to, for example, a microcomputer, and the level (envelope amount) of this envelope detection signal is compared with a reference value in the microcomputer. Then, if envelope amount <reference value, the microcomputer shifts the tracking value by, for example, 1/8 of the variable range, and the microcomputer again compares the envelope amount with the reference value. If the envelope amount ≧ the reference value, the microcomputer performs the normal auto-tracking process and adjusts the tracking value to the optimum value.

[0008]

According to the present invention, since the normal auto-tracking process is performed at the time when the envelope amount becomes equal to or larger than the reference value, the envelope amount does not largely change due to noise, and the envelope amount changes with respect to the tracking change. Can be easily detected. Further, since the automatic tracking process is performed when the envelope amount ≧ the reference value, the optimum tracking value can be detected in a short time.

The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments with reference to the drawings.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a video tape recorder 10 of this embodiment includes a reproducing head 12 and a reproducing head 12
The video signal is reproduced by tracing the track 14a recorded on the tape 14. The reproduced video signal is supplied to the amplifier and DC detection circuit 18 via the preamplifier 16, and the reproduction envelope is detected by the amplifier and DC detection circuit 18. And amplifier and D
The envelope detection signal output from the C detection circuit 18 is given to the microcomputer 20, and the tracking value is set by the microcomputer 20. Therefore, the tracking setting signal is given from the microcomputer 20 to the servo circuit 22,
The servo circuit 22 generates a capstan control signal based on the tracking setting signal, and gives the capstan control signal to the capstan motor 24. The capstan motor 24 is driven based on this capstan control signal, and tracking is adjusted by this.

When the video signal is recorded on the tape 14 in the triple mode, the track 1 recorded on the tape 14 is recorded.
The width W1 of 4a to 14c is 19.2 μm, and the head 1
It is narrower than the width W2 of 2 (for example, 26 μm). Therefore, the relationship between the track 14b and the head 12 when the tracking is adjusted (when the tracking value is the center value) is as shown in FIG. The one end of the head 12 and the one end of the track 14b are made to coincide with each other in order to reduce the influence of crosstalk from an adjacent track.

Next, the processing of the microcomputer 20 when setting the tracking value will be described. First, step S
At 1, the level (envelope amount) of the envelope detection signal is sampled by A / D conversion, and then at step S3, it is determined whether or not envelope amount <reference value. Then, if “YES”, step S
In step 5, the tracking value is shifted in the positive direction by ⅛ of the variable range, and the process returns to step S1. Here, the variable range is one track width from both ends of the head 12, that is, 19.2 μm on each of the left and right sides, and thus the shift amount in this case is 4.8 μm. On the other hand, if the envelope amount ≧ reference value in step S3, the normal auto-tracking process is performed, and the process ends. It should be noted that the shift amount per one time during normal auto-tracking is 0.6 μm, which is 1/8 of the shift amount in step S5. Further, as the reference value, for example, the maximum envelope amount × {(W2-W1) / W1} is set as a value whose envelope amount is not greatly affected by noise. In addition,
This reference value is the envelope amount when the head 12 depicted by the dotted line in FIG. 2 reproduces the video signal of the track 14b.

In operation, when the relationship between the tracking value and the envelope amount is as shown in FIG. 4 because the control signal CTL recorded on the tape 14 and the track have a predetermined positional relationship, at the start of auto-tracking. Since the tracking value (center value) of is the optimum tracking value, the microcomputer 20 immediately ends the tracking process. On the other hand, when the relationship between the tracking value and the envelope amount is as shown in FIG. 5 because the control signal CTL and the track are not in the predetermined positional relationship, the envelope amount at the tracking start position (center value) is greater than the reference value. Since it is also low, the microcomputer 20 shifts the tracking value by 1/8 of the variable range. As a result, the envelope amount increases up to the point A, and the envelope amount ≧ the reference value. Therefore, the microcomputer thereafter performs a normal auto-tracking process to adjust the tracking value to the optimum value (point B).

According to this embodiment, since the microcomputer 20 starts the normal auto-tracking process when the envelope amount ≧ the reference value, the envelope amount does not largely change due to noise, and the envelope for the tracking change is not changed. Changes in quantity can be easily detected. Moreover, since the normal auto-tracking process is started when the envelope amount ≧ the reference value, the time until the optimum tracking value is detected can be shortened.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is an illustrative view showing a part of the operation of the embodiment in FIG.

FIG. 3 is a flowchart showing a part of the operation of FIG. 1 embodiment.

FIG. 4 is a graph showing a relationship between a tracking value and an envelope amount.

FIG. 5 is a graph showing a relationship between a tracking value and an envelope amount.

[Explanation of symbols]

10… Video tape recorder 18 ... Amplifier and DC detection circuit 20 ... Microcomputer 22 ... Servo circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G11B 5/56-5/60 G11B 15/467-15/473

Claims (3)

(57) [Claims] 1. A track and a head formed on a video tape.
Adjust the tracking value that defines the positional relationship with the
In the video tape recorder, the playback signal reproduced from the track by the head is adjusted.
Detecting means for detecting an envelope of the issue, the level of the envelope detected by said detecting means
Discriminating means for discriminating whether or not is lower than a reference value, and if the discrimination result of the discriminating means is affirmative,
A shift means for shifting the king value in a predetermined direction, and a predetermined auto when the determination result of the determination means is negative.
Characterized by comprising an execution means for executing tracking
To, video tape recorder. 2. The predetermined direction is a direction in which a numerical value increases.
The videotape recorder according to claim 1, 3. The tracking value by the shift means
The single shift amount of
Larger than the amount of one shift of the tracking value ,
The video tape recorder according to claim 1.