JPH06274978A - Video tape recorder - Google Patents

Abstract

PURPOSE:To make the reproduction envelope quantities of starting time and braking time coincident by adjusting the start timing of a capstant motor and to eliminate the generation of noise on a screen. CONSTITUTION:The envelope quantities of the starting and braking times of a capstan motor 12 are calculated by a microcomputer 22 and compared. Then, when the envelope quantity of the starting time is larger, the start timing is made faster and when that of the braking time is larger, the start timing is made slower. Then, the envelope quantities of both are compared again and when they are made coincident, its start timing is set as an optimum value. Based on this timing, starting and braking pulses are outputted from a servo circuit 24 and the capstan motor 12 is intermittently driven.

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 which prevents noise generation during slow reproduction.

[0002]

2. Description of the Related Art Referring to FIG. 7, in a conventional video tape recorder 1, the start timing of a capstan motor 2 during slow playback is stored in a ROM 4 of a microcomputer 3 in advance, and a servo circuit 5 is used in accordance therewith. It controls the capstan motor 2. Therefore, when the start-up characteristic is normal, the tape track is traced as shown in FIG.

[0003]

However, even if the microcomputer 3 operates normally, the temperature of the capstan motor 2 changes and the start timing deviates, the tape 6 is stiff, and a gear (not shown). When the rotation speed of the capstan motor 2 changes (when the start-up characteristic changes), the tape track is traced as shown in FIG. 9 and noise is generated on the screen.

Therefore, a main object of the present invention is to provide a video tape recorder which does not generate noise.

[0005]

According to the present invention, in a video tape recorder for slow tape reproduction by intermittently driving a capstan motor, a means for calculating an envelope amount at the time of starting and braking the capstan motor, and A video tape recorder comprising means for adjusting the start timing of the capstan motor so that the envelope amounts match.

[0006]

The envelope amount at the time of starting and braking of the capstan motor is calculated by, for example, a microcomputer, and both are compared. Then, when the envelope amount at the time of activation is larger, the activation timing is advanced. on the other hand,
If the envelope amount during braking is large, the start timing is delayed. After that, the envelope amounts at the time of starting and braking are compared again, and when they match, the starting timing is set as the optimum value. When the envelope amounts match at the first comparison, the activation timing is set as the optimum value.

[0007]

According to the present invention, since the start timing is adjusted so that the envelope amounts at the time of starting and braking of the capstan motor are adjusted, noise does not occur on the screen. 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.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, a video tape recorder 10 of this embodiment includes a capstan motor 12. The capstan motor 12 operates at the initial start timing at the beginning of the transition to the slow reproduction mode. As a result, when the video head 14 traces the magnetic tape 16 as shown in FIG. 2 (A), the reproduction envelope as shown in FIG. 2 (B) is reproduced through the preamplifier 18 as a reproduction envelope detection circuit 20 and a video circuit (not shown). ) Is entered. The envelope detection signal as shown in FIG. 2 (D) detected by the reproduction envelope detection circuit 20 is input to the microcomputer 22, and the microcomputer 22 is used for starting and braking the capstan motor 12 as shown in FIG. 2 (E). The sum of the envelopes is sampled. Based on this, the microcomputer 22 outputs to the servo circuit 24 a start timing signal having a constant phase relationship with the head switching signal as shown in FIG. 2C, and the servo circuit 24 responds to the start timing signal shown in FIG. Drive pulse is output. Therefore, the capstan motor 12 starts rotating at a constant speed. Control head 2
6 detects the control signal CTL recorded on the magnetic tape 16 as shown in FIG. 2G, and when this control signal CTL is input to the servo circuit 24, the servo circuit 2
4 outputs a braking pulse as shown in FIG. 2 (H) after a certain time has elapsed from the input. Therefore, the capstan motor 12
Stops constant speed rotation. After that, the rotation of the capstan motor 12 is controlled by the start pulse based on the start timing signal and the braking pulse based on the control signal CTL.

The processing operation of the microcomputer 22 is as follows. First, in step S1, the initial start timing is set to t ₀ . Next, in step S3, from the reproduction envelope obtained by the operation of the capstan motor 12 based on the initial start timing, the start-up envelope of the magnetic tape 16 is sampled,
The sum A is calculated. In step S5,
The envelope at the time of braking the magnetic tape 16 is sampled from this reproduction envelope, and the sum B thereof is calculated.
Then, in step S7, the total sum A and the total sum B are compared, and if the total sum A = total sum B, the start timing at this time is set as an optimum value in step S9. Therefore, from the next time onward, the capstan motor 12 operates based on this start timing. On the other hand, if the total sum A> the total sum B, the constant time t is subtracted from the current start timing in step S11, and the processes of steps S3 to S7 are repeated. If the total sum A <the total sum B, the current start timing in step S13. The fixed time t is added to the timing, and the processes of steps S3 to S7 are repeated.

In operation, a start pulse is output at the timing shown in FIG. 4 (D), and then a braking pulse as shown in FIG. 4 (F) is output based on the control signal CTL of FIG. 4 (E). When the magnetic tape 28 is head-traced as shown in FIG. 4A, the sum of envelopes when the capstan motor 12 is started and when the brake is applied becomes equal as shown in FIG. Not changed However, when the start characteristic of the capstan motor 12 changes and the head trace is performed as shown in FIG. 5A, the total envelope during braking is greater than the total envelope during starting, as can be seen from FIG. 5B. Since it becomes smaller, the start timing of the capstan motor 12 is adjusted by the microcomputer 22. That is, FIG.
The start timing is advanced as in (D). As a result, the magnetic tape 16 is head-traced as shown in FIG. 6A, and the total envelopes at the time of starting and braking of the capstan motor 12 become equal as shown in FIG. 5B. The capstan motor 12 is driven by.

In this embodiment, the start timing is adjusted only when the slow reproduction is started, but the start timing may be adjusted every time the capstan motor 12 is intermittently driven.

[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 an illustrative view showing a part of the operation of the embodiment in FIG. 1;

FIG. 5 is an illustrative view showing a part of the operation of the embodiment in FIG. 1;

FIG. 6 is an illustrative view showing a part of the operation of the embodiment in FIG. 1;

FIG. 7 is a block diagram showing a conventional technique.

FIG. 8 is an illustrative view showing a part of the operation of the conventional technique.

FIG. 9 is an illustrative view showing a part of the operation of the conventional technique.

[Explanation of symbols]

 10 ... video tape recorder 12 ... capstan motor 20 ... reproduction envelope detection circuit 22 ... microcomputer 24 ... servo circuit

Claims (1)

[Claims] 1. A video tape recorder for slow-playing a tape by intermittently driving a capstan motor, wherein a means for calculating an envelope amount at the time of starting and braking of the capstan motor and the envelope amount are matched. A video tape recorder, further comprising means for adjusting a start timing of the capstan motor.