JPH0410134B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fast playback function of a magnetic recording and reproducing device, and more particularly to a motor drive circuit for running a tape suitable for a system capable of fixing bar noise during variable speed integer multiple speed fast playback.

In conventional magnetic recording and reproducing apparatuses, even if the speed of quick playback (hereinafter referred to as search playback) is variable, it is common for bar noise to appear on the screen. The authors have previously applied for a patent for fixing bar noise during integer speed quick playback (Japanese Patent Application No. 125280/1982), but as will be described later, a better system can be created by adding correction for capstan speed deviation. This was confirmed. The problems of integer multiple speed search will be explained below. Figure 1,
Figure 2 is an explanatory diagram of the deviation rate of the rotational speed of the tape drive capstan from the normal value and its correction. corresponds to forward rotation, and the left side corresponds to reverse rotation, and the further away from the center, the greater the double speed number. Further, the vertical axis 2 indicates the capstan rotation speed deviation rate. The rotational speed deviation rate is detected by replacing it with a frequency signal deviation rate or the like. In general, as the number of speeds for quick playback increases, the load on the tape increases and the capstan speed does not increase to the desired number of speeds, resulting in a characteristic where speed deviation increases in proportion to the number of speeds, as shown in 3 in the diagram. . If the degree of this speed deviation is large, phase synchronization of the capstan becomes difficult, and the bar noise on the screen begins to flow without being fixed. In order to correct this, it is necessary to correct the speed deviation amount indicated by 4 in FIG. This amount of deviation indicates an insufficiency in the capstan speed, and corresponds to a correction signal (generating a speed increase indicated by reference numeral 4) that increases the capstan speed in accordance with the speed.

Furthermore, if we add color shift correction to the cylinder motor due to changes in the relative speed of the cylinder head and tape during high-speed search playback, the desired characteristics of the capstan motor will be acceleration in the forward direction search and deceleration in the reverse direction (accurately). is not point symmetrical in the forward and reverse directions), which is the characteristic of 5 in Fig. 2. Therefore, at this time, it is necessary to correct the speed deviation amount shown by the arrow 6 in the figure for normal rotation and reverse rotation, respectively. In other words, color shift occurs because the time axis of the reproduced signal during quick playback is different from the time axis of the signal during recording, resulting in a difference in the amount of reproduction delay between the color reproduction system and the luminance reproduction system. . If the amount of speed deviation shown by arrow 6 is corrected by finely adjusting the rotational speed of the cylinder motor, the time axis of the reproduced signal becomes almost equal to the time axis during recording, and as a result, the color shift is reduced.

From the above, when the search speed is small, the amount of speed deviation from the desired speed characteristic is small, so the bar noise position on the screen is fixed within the phase synchronization system pull-in range, but on the other hand, when the search speed is At extremely high speeds, there was a problem in that the nozzle would flow out of the drawing range.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic recording and reproducing apparatus capable of variable speed quick playback without causing noise on the screen.

The main purpose of the present invention is to apply a correction signal proportional to the speed deviation in quick playback to the capstan motor, facilitate phase synchronization, fix the bar noise position on the screen, and smoothly perform an integer multiple speed search. Furthermore, the correction signal is applied to the reel motor.

An embodiment of the present invention will be described below with reference to FIG. In Fig. 3, 11 is a capstan motor, 12 is a frequency generator (CFG signal generator) that generates a signal (CFG signal) with a frequency proportional to the rotation speed of the capstan motor, and 13 is an amplifier for the CFG signal. (CFG amplifier), 14 is a frequency divider, 15 is a frequency-voltage converter (f-v converter), 16 is a magnetic tape, 17 is a control head, 18 is a control pulse (CTLP) amplifier (CTLP amplifier), 19 is a frequency divider, 20 is a pulse generator that generates a constant frequency, 21 is a phase comparator, 22 is an adder, 23 is a capstan motor drive circuit, 2
6 is a digital quantity holder, 27 is a digital quantity holder, and 27 is a digital quantity holder.
It is an analog converter (D/A converter). The digital quantity held in 26 determines the frequency division ratio of the frequency dividers 14 and 19, and the output D/A converted by the D/A converter 27 becomes monotonous as the frequency division ratio increases, that is, as the search becomes faster. It is as if the amount increases to .

In this embodiment, the CFG signal generator 12, the CFG amplifier 13, the f-v converter 15, and the drive circuit 23 control the speed control loop normally used in a VTR system.
Also, control head 17, CTLP amplifier 1
8. The pulse generator 20, the phase comparator 21, and the drive circuit 23 form a phase control loop, and the added signal of both loops by the adder 22 ensures stable tape running. The frequency dividers 14 and 19 are described in detail in the aforementioned patent application (Japanese Patent Application No. 125280/1982), and are designed to change the reproduction speed by an integral multiple by changing the frequency division ratio. In this embodiment, the digital quantity in the digital quantity holder 26 can be freely changed by some external signal, and this change is a change in the search speed. In this system, the amount of correction is small at low speeds,
Further, at high speeds, a large correction amount is added to the control input of the capstan motor drive circuit 23, so that the speed deviation shown by 4 in FIG. 1 can be corrected.

Another specific example will be explained below using FIG.
In the figure, 31 is a reel motor drive circuit, and 30 is a reel motor. During the search playback operation, the reel motor 30 winds up the tape running by the capstan motor 11, so during low-speed search the speed deviation is small and can be corrected with less torque, but during high-speed search the speed deviation is large. Therefore, unless a strong torque commensurate with the search speed is generated, this cannot be corrected, causing the tape to sag and making it impossible to operate smoothly. In this embodiment, the output of the D/A converter 27 described above is also used as a reel motor control signal, and the reel motor can be driven with low torque at low speeds and high torque at high speeds, ensuring stable tape running. Ru. D/A converter 27
Of course, it is also possible to apply the output of 1 to the drive circuit 31 via a suitable amplifier.

Another embodiment of the present invention will be described with reference to FIG. In the figure, reference numeral 28 denotes an amplifier which can appropriately vary the amount of transmission by inputting the forward and reverse rotation signals 29 of the capstan motor, and other elements are the same as those shown in FIG. In this example,
By changing the gain of the amplifier 28 in conjunction with forward and reverse rotations, it is possible to cope with the case where the desired correction amounts during forward and reverse rotations are unbalanced, as shown in FIG.
For example, in the case shown in FIG. 2, if the gain of the amplifier 27 is set to be large during forward rotation and small during reverse rotation, a large correction amount is applied during normal rotation, and a small correction amount is applied during reverse rotation. That is, it is made to match the target speed deviation characteristic shown by the dashed line 5 in FIG.

Still another embodiment of the present invention will be described using FIG. 6. In the figure, numerals 28 and 29 are the same as in FIG. 5, and other elements are the same as in FIG. 4. This embodiment combines the technical ideas shown in Figures 4 and 5 above, and the capstan motor is controlled with an unbalanced correction amount in forward and reverse directions, and the reel motor is controlled with equal torque in both forward and reverse directions. It is possible to add The reason why the reel motor is subjected to the same correction in the forward and reverse directions is that the load on the reel motor is greater during reverse rotation. In other words, a correction amount is added to increase or decrease during forward rotation,
At the time of reverse rotation, a correction amount is added to the load on the tape drive system.

In the embodiments described above, it is also possible to replace the amplifier 28 with an on-off switch and turn it on and off in accordance with forward and reverse rotation.

According to the present invention, the deviation of the noise bar position caused by the tape load of the integral multiple speed noise bar position fixed search system can be prevented by a simple method of D/A converting the double speed information and adding it to the capstan control signal. This has the effect of always stably realizing variable integer multiple speed search playback.

[Brief explanation of drawings]

Figures 1 and 2 are characteristic diagrams to explain the capstan rotation speed deviation to explain the problem, and Figure 3 is a characteristic diagram to explain the capstan rotation speed deviation.
The figure is a block diagram for explaining one embodiment of the present invention, and FIGS. 4, 5, and 6 are block diagrams for explaining other embodiments of the present invention. DESCRIPTION OF SYMBOLS 11... Capstan motor, 14, 19... Frequency divider, 22... Adder, 13, 20... Motor drive circuit, 26... Digital quantity holder, 27... Digital/analog converter, 28... Amplifier, 30... Reel motor.

Claims (1)

[Claims] 1. A frequency generator that generates a signal with a frequency proportional to the rotational speed of the capstan motor, a first frequency dividing means that divides the output signal of the frequency generator, and a first dividing means that divides the output signal of the frequency generator. a frequency-voltage conversion means for converting the output signal of the frequency dividing means into a voltage; a second frequency dividing means for dividing the frequency of the control signal recorded on the magnetic tape; a first signal conversion means that compares the phase with a reference signal and converts it into an error signal; an adder that adds the output signals of the frequency-voltage conversion means and the first signal conversion means; and first and second frequency division means. and a controller for controlling the frequency division ratio of the first and second frequency division means, and a speed deviation correction signal of the capstan motor according to the frequency division ratio of the first and second frequency division means to the input signal or output signal of the adder. What is claimed is: 1. A motor drive circuit for a magnetic recording/reproducing device, characterized in that a motor drive circuit for a magnetic recording/reproducing device is provided with a correction means for adding correction. 2. The magnetic recording and reproducing device according to claim 1, wherein the correction means has a switching means for changing the addition ratio of the signal supplied to the adder according to the forward rotation and reverse rotation signals of the capstan motor. Equipment motor drive circuit.