JP3287183B2 - Magnetic recording / reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a helical scan type magnetic recording / reproducing apparatus such as a VTR (Video Tape Recorder), and more particularly, to economical use of a motor servo circuit of a general magnetic recording / reproducing apparatus which is widely used at home. Moreover, it is realized with good performance.

[0002]

2. Description of the Related Art A prior art relating to switching between high-speed and low-speed reproduction is disclosed in Japanese Utility Model Publication No. 63-4271. The technique disclosed in this document detects the capstan speed and switches the speed when the speed reaches a speed corresponding to the speed command, and performs the next speed setting. By repeating this process stepwise, a speed change up to the target speed is realized.

[0003]

However, in the prior art, since the speed of the capstan motor is changed stepwise, it takes time to change the speed. There is a problem that a complicated process is required in order to memorize the speed and gradually move to a new target. Still another method is to convert the reproduced horizontal synchronizing frequency into a voltage and add it to a motor control signal by an analog circuit or the like, but there is a disadvantage that the circuit scale is extremely increased.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a speed switching means for switching a target speed of a capstan motor based on a command, a motor driver and servo means for each of the capstan and cylinder motors, and a phase reference signal generating means for the servo means. , Speed detection means of the capstan motor (reflecting the tape speed), setting means for setting the phase reference signal and the center frequency of the motor speed to the target count value from the detected speed ,
Target count value for each of the servo control of the stun and cylinder
Means for storing the target count value from the table.
Search setting means for searching and setting is provided.

[0005]

Among these, the means for switching the target speed of the capstan motor need not set a stepwise target value as described in the prior art, but may be changed instantaneously by a command. Therefore, the processing is simple even when the processing is realized by a microprocessor. Next, a center frequency for controlling the speed of the cylinder and the capstan corresponding to the instantaneous value of the tape speed and a reference signal frequency for controlling the phase are calculated. As a result, since the capstan speed changes rapidly toward the target value, the response is faster than in the stepwise control.
In addition, the center frequency for controlling the speed of the cylinder and the capstan and the reference signal frequency for controlling the phase can be obtained by comparing the table data without depending on the calculation. In this case, the same effect can be obtained. In addition, since all of them can be processed by a one-chip microprocessor, it is economically significant.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Now, description will be made below with reference to specific embodiments. Generally, in a magnetic recording / reproducing apparatus that records and reproduces a video signal, phase synchronization servo (phase control) for synchronizing with the video signal and speed control for quick control are performed in parallel. This takes a form almost common to the servo for the rotating head for the image and the servo for the tape drive. One embodiment of the present invention will be described with reference to the magnetic recording / reproducing apparatus shown in FIG. In FIG. 1, 1 is a magnetic tape, 2 is a rotary head, 3 is a cylinder motor equipped with a rotary head,
4 is a frequency signal generator which is a signal proportional to the rotation speed of the cylinder, 5 is a phase signal generator showing the rotation phase of the cylinder, 6 is a cylinder motor driver, 7 is a cylinder servo, 8 is a phase reference signal generator, 9 Is a tape speed detector, 10 and 11 are center frequency calculators, 12 is a speed switcher, 13 is a capstan servo, 14 is a capstan driver, 15 is a capstan motor, 16 is a capstan frequency signal generator, 17 is Control head, 1
8 to 21 are amplifiers, 22 is a frequency calculator of the phase reference signal frequency, and 40 to 47 are signals.

The speed switching signal 43 set by the speed command switches the frequency division ratio of the signals 40 and 41 to be input to the capstan servo 13. For example, the frequency division ratio is 5 when reproducing at 5 × speed, and 9 when reproducing at 9 × speed.
Becomes Therefore, as shown in FIG. 2, the capstan servo 13 has frequency dividers for the frequency signal 40 to be subjected to the speed control and the phase signal 41 to be subjected to the phase control. Switch at the same time. Here, the motor servo of the magnetic recording / reproducing apparatus will be described. In controlling the motor, speed control using a relatively high-frequency signal and phase control using a relatively low-frequency phase signal are performed simultaneously. The former roughly adjusts the rotation frequency, and the latter is the frequency of the recorded / reproduced video (30 Hz for NTSC signals).
The former is necessary for the fast response of the motor. Here, the target frequency which the former attempts to substantially match is referred to as the center frequency (even though the frequency is slightly shifted, the frequency is locked by the force of the phase control, and the motor rotates at the correct frequency). Accordingly, the servo block is constituted by the block diagrams shown in FIGS. 2 and 3, 61 and 65 are frequency dividers, 62 and 62 'are speed control blocks, 63 and 63' are adders, and 64 and 64 'are phase control blocks. FIG. 2 has a frequency divider as described above in order to double the rotation speed of the capstan motor.

When the reproducing speed is different from that at the time of recording, the speed of both the capstan and the cylinder is finely adjusted in order to absorb a change in the relative speed between the tape and the head. This is because the processing of the reproduced signal is often performed in units of scanning lines, and if the frequency of the reproduced signal is shifted, the processing may not be successful. Using the double speed number N,
= Α × (N-1) /262.5 (NTSC). Therefore, the center frequency set as the target of the speed control by the signals 44 and 47 is set to be this finely adjusted value. Here, the expression of the speed fine adjustment will be briefly described with reference to FIG. In FIG. 4, reference numerals 70 to 72 denote head trajectories during reproduction. In a system in which the running direction of the tape and the rotation direction of the head are in the same direction (for example, the VHS system), the tape is inclined like a trajectory 73 in a direction in which the tape slows or reverses with respect to the head trajectory 71 in the standard reproduction. If the tape slowly moves in the same direction as the recording,
The inclination is steep like 0. At this time, for example, when the 1-time running becomes 0 times, that is, when the locus 73 changes to stop reproduction, the reproducing portion of the tape increases by α. In the NTSC system, in one scan of standard reproduction (according to the locus 71), 262.
Reproduction is performed for five scanning lines, and when α is added thereto, 26
2.5 + α. When the inclination becomes gentle, the number of scanning lines to be reproduced increases and the frequency increases. To reproduce the same 262.5 lines as at the time of recording, use -α /
The rotational speed of the head, that is, the rotational speed of the cylinder may be finely adjusted (decelerated) by 262.5 minutes. Similarly, in double speed reproduction, it is sufficient to accelerate by α / 262.5. As described above, the fine adjustment can be represented by the above-described equation as a function of the double speed N. Incidentally, in the standard mode of the VHS system, α is 1.5 (for 1.5 horizontal scanning lines), so the fine adjustment for the 1 × speed change is 0.57%.
Becomes Therefore, for example, if the center frequency at 1 × speed is f0, the center frequency at 10 × speed is f0 × (1 + 0.0057).
X9) = 1.051 x f0.

As described above, the motor control includes speed control and phase control. Therefore, the center frequency data (signals 44 and 47) for speed control and the reference signal 4 for phase control are used.
The frequencies of 2, 42 'are also changed by the same amount.

The control operation when the speed of the capstan is suddenly changed in the above control will be described below. For example, V
When the speed is changed from 1 × speed to 10 × speed by the HS method, first, the speed switching means 12 which has received the command changes the frequency division ratio 43 applied to the capstan servo from “1” to “10”. Then, the control system of the capstan is accelerated because the divided signal moves so as to match the original signal frequency.
However, the speed of the capstan motor is not instantaneously completed due to the relationship between inertial force and load. 1 from the microscopic perspective
It gradually changes like 2, 3, 4,.... The tape speed detector 9 catches this speed, and makes the center frequency calculators 10 and 11 calculate center frequency data finely defined with respect to the instantaneous value of the tape speed at that time, and at the same time, calculates the reference frequency for phase control to the frequency calculator 2.
Let 2 calculate.

Although the operation is performed as described above, the tape speed detector 9 generally performs conversion from the signal period data to the tape speed (the calculation at the subsequent stage uses the double speed number N as an argument), so that the division is executed. I have to do it. However, since division requires a lot of time to be executed by a microprocessor, it is not desirable to use the division as much as possible. Therefore, another embodiment of the present invention which does not use this division is shown in FIG.

In FIG. 5, reference numeral 80 denotes a period detecting means for counting and measuring the frequency signal period of the capstan with a high frequency clock (not shown), and 81 to 83 denote table retrieval means. The table retrieving means is prepared in advance with a table capable of retrieving data for obtaining a desired frequency from the capstan frequency signal period. An example of the table is shown in Table 1 below for further explanation. For simplicity, the high frequency clock is 10 MHz (the cycle is 100 nanoseconds), the cylinder rotation frequency signal during recording is 720 Hz, the capstan rotation frequency signal is 1080 Hz, and the reference phase signal is 30 Hz.
Is assumed. Also, consider variable speed playback up to 10 × speed in the forward and reverse directions. Then, this is divided into regions of 2 × speed and tabulated. First each count at the time of recording phase reference signal: 10 × 10 ⁶ /30=3.333×10 ⁵ capstan frequency signal: 10 × 10 ^6/1080 =
9.259 × 10 ³ cylinder frequency signal: 10 × 10 ⁶ /720=1.38
It becomes 9 × 10 ⁴ . Further, the central values (representative values) divided into regions of 2 × speed, that is, 10 × reverse speed to 8 × reverse speed, 8 × reverse speed to 6 × reverse speed, 6 × reverse speed to 4 × reverse speed, etc., are 9 × normal speed and reverse rotation. 7 times speed, 5 times reverse rotation, etc. The fine adjustment amount of the reverse rotation 9 times speed, the reverse rotation 7 times speed, the reverse rotation 5 times speed, etc. is obtained as follows. That is, α = 1.5, N = −9, −7, −5... Are substituted into the above equation Δf = α × (N−1) /262.5, and −6 is obtained.
%, -5%, -3%, etc. Since the obtained value is a frequency conversion, it is converted into a count value which is periodic data, and +
6%, + 5%, + 3%, etc. By adding fine adjustment values such as + 6%, + 5%, + 3%... Based on the above-described count value at the time of recording, the relationship between the velocity region of the divided capstan and the center value is obtained as shown in Table 1.

[0013]

[Table 1]

The values described in Table 1 are all count values of the high-frequency clock, and the data at the left end in which region the frequency signal cycle of the capstan is located is retrieved from the table by the elements 81 to 83 and output. . At this time,
When the capstan rotates slowly near the stop, the frequency signal period data has an extremely large value. This is detected as an overflow of the frequency signal period detector 80 (OV
F). In practice, smooth rotation cannot be obtained with such a slow rotation. Therefore, measures are taken by intermittently driving the tape. For this reason, a value that cannot be obtained from this table is used as the center frequency of the capstan speed control during intermittent driving.
In addition, the phase control of the capstan is not performed during the intermittent driving. Therefore, for simplicity, capstan control during slow motion reproduction is not included in this figure (cylinder control can use the values in this table). Here, the operation of searching this table will be specifically described. now,
Assuming that the capstan is traveling in the same forward direction as that at the time of recording and the count value of the frequency signal period detector 80 is 1820 during the speed change, the double speed 4 in the table is assumed.
6 and the search outputs of the table searchers 81, 82, and 83 are respectively 13610, 9097, and 32666.
It becomes 7. These data become motor frequency or phase reference frequency data.

Next, another embodiment of the present invention will be disclosed. FIG.
In the figure, 90 is a recording mode discriminator, and 91 is a discrimination result signal. There are a plurality of recording modes in VHS recording, and the tape running speed changes depending on the mode. This is referred to as a standard mode or a triple mode, and the tape running speed in the triple mode recording is three times slower than that in the standard mode, that is, one third the speed. Then, the values of α are 1.5 and 0.
The fine adjustment amount is 5 even at the same double speed. Conversely, the fine adjustment amount is the same even at different double speeds. The tape speed command is changed as shown in Table 2 depending on the recording mode.

[0016]

[Table 2]

This is an example in which the same speed region is allocated to a relatively low speed variable speed reproduction even if the recording mode is different, and a different speed region is allocated to a relatively high speed variable speed reproduction depending on the recording mode. During reproduction, the recording mode discriminator 90 determines which of the two modes has been recorded. This is performed, for example, by measuring a control signal period when the tape is run at a constant speed. After that, the double speed number according to the determined mode signal 91, that is, the frequency division ratio of the capstan frequency signal is changed by the speed switch 12
Is set by The instantaneous value of the tape speed is also detected by the capstan frequency signal period detector 80 in the transient period in which the speed changes, as in the above-described example, and the target value of each value is searched in a table by the elements 81 to 83 according to the calculated value. You. However, in this example, which of the standard and triple times of Table 2 is to be searched is selected from the recording mode information.

As described above, in the present embodiment, a method called table retrieval, which is realized at a very high speed by a microprocessor, is used, and a process with a sufficient time can be performed.

Although the processing time becomes difficult, a method of calculating the finely-signed value by the above-mentioned formula Δf = α × (N−1) /262.5 including the recording mode is also used. be able to.

In the above example, the capstan frequency signal is used to detect the tape running speed. However, it is calculated from the control signal reproduced from the tape or the rotation cycle of the tape reel base (not shown). It is of course possible to use values.

[0021]

As described above, according to the present invention, even when the tape running speed changes, it is not necessary to change the speed of the capstan motor in a stepwise manner. This eliminates the need for management and monitoring whether or not the target speed has been reached, and has the effect of realizing servo control that can be easily softened by a microprocessor and has a short processing time.

[Brief description of the drawings]

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

FIG. 2 is an internal block diagram of the capstan servo 3 of FIG.

FIG. 3 is an internal block diagram of a cylinder servo 7 of FIG. 1;

FIG. 4 is a diagram illustrating the operation principle of one embodiment of the present invention.

FIG. 5 is a block diagram of another embodiment of the present invention.

FIG. 6 is a block diagram of still another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Magnetic tape, 2 ... Rotating head, 3 ... Cylinder motor, 7 ... Cylinder servo, 8 ... Phase reference signal generator, 9 ... Tape speed detector, 10, 11 ... Frequency calculator, 13 ... Capstan servo, 15 ... capstan motor, 80 ... frequency signal period detector, 81, 82, 83 ... accumulator, 90 ... recording mode discriminator.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masayuki Kijima 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Inside the Multimedia Systems Development Division of Hitachi, Ltd. (72) Inventor Yukinobu Tada Totsuka-ku, Yokohama-shi, Kanagawa 292 Yoshida-cho, Ltd. Multimedia System Development Division, Hitachi, Ltd. (72) Inventor Takeo Okochi 1410 Inada, Hitachinaka-shi, Ibaraki Pref. Personal Computer Equipment Business Division, Hitachi, Ltd. (56) References JP-A-6 -68555 (JP, A) JP-A-7-169151 (JP, A) JP-B 3-61258 (JP, B2) JP-B 3-32312 (JP, B2) JP-B 5-10739 (JP, B2) ) Tokiko Hei 6-81290 (JP, B2) Jiko 63-4271 (JP, Y1) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 15 / 467 G11B 5/588

Claims (1)

(57) [Claims] 1. A helical scan type magnetic recording / reproducing apparatus having a function of performing recording / reproduction by a rotary head and performing reproduction at a reproduction speed different from that at the time of recording, wherein a high-frequency clock generating means and a rotation of a capstan motor are provided. Capstan motor rotation frequency detection means for detecting a frequency, first frequency division means for dividing the rotation frequency detection signal of the capstan motor, and the high frequency clock during one cycle of the output of the first frequency division means A capstan motor speed control means for controlling the count value of the high-frequency clock to a capstan target count value, and detecting the rotational frequency of the cylinder motor equipped with the rotary head, and counting the high-frequency clock in one cycle of the signal. Cylinder motor speed control means for controlling the numerical value to become the cylinder target count value; Phase reference frequency signal generating means for setting a value for counting the high frequency clock during a period as a cyclic count value; detecting means for detecting the running phase of the tape; and second dividing means for dividing the tape running phase detection signal A capstan motor phase control means for controlling the rotation of the capstan motor so that the phase difference between the divided second frequency dividing means output and the phase reference frequency signal is constant. A cylinder motor phase control means for controlling the rotation of the cylinder motor so that the phase difference between the rotation phase of the cylinder motor and the phase reference frequency signal is constant; and a tape for detecting a running speed of the tape. A speed detecting means, and a double speed number N substantially at the center of the range corresponding to each of a plurality of multiple speed ranges for the tape speed at the time of recording. , The count value at the time of recording C0, the constant α,
The respective tables of the capstan target count value, the cylinder target count value, and the cyclic count value of the phase reference frequency signal, which are substantially equal to C = C0 × [1−α (N−1) / M], are set as M. The stored table means and the table means are searched for where the detection result of the tape speed detecting means for detecting the tape running speed falls within the above-mentioned divided range, and the capstan target count value and the cylinder target count value described above are searched according to the search results. And a search setting unit for reading and setting the cyclic count value of the phase reference frequency signal from the table, and setting the search value.