JPS6325802Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording device that runs a magnetic tape at low speed during recording to extract and record video signals.

Such a magnetic recording device is known as a time-lapse VTR (or surveillance VTR), which is a type of video tape recorder (hereinafter referred to as VTR), and is used, for example, in banks,
It is used for monitoring inside department stores. This time-lapse VTR supplies a video signal from the above-mentioned monitoring television camera or the like to a rotating magnetic head to sequentially form diagonal recording tracks 2 on a magnetic tape 1 as shown in FIG. The recording track 2 on the magnetic tape 1 is scanned by a rotating magnetic head to reproduce the video signal, which is similar to a general helical scan type VTR, but it uses a magnetic tape of normal length. In order to realize long-term recording (for example, 24-hour recording) or short-term playback, the following operations are performed, for example. That is, signals of one vertical period are extracted every predetermined number n of vertical periods of temporally continuous video signals from the television camera, etc., and are sequentially recorded. This may be done by extracting one frame of signals every n frames, and the signal extraction ratio 1/n in this case is equal to the ratio of the tape running speed to the normal speed (hereinafter referred to as slow ratio).
Furthermore, long-time recording can be performed using magnetic tapes of equal length, n times the recording time at normal speed. In FIG. 1, the audio track 3 and the control track 4 are recorded along the running direction a of the magnetic tape 1. Also,
Let α be the inclination angle of the tracking direction b of the rotating magnetic head with respect to the running direction a of the magnetic tape 1.

By the way, traditional time-lapse like this
In a VTR, the recording tracks 2 are sequentially formed while driving the magnetic tape 1 to run in the direction of the arrow a. Therefore, the inclination angle α of the recording track 2 changes depending on the tape running speed. When attempting to make the frame stand still (so-called still reproduction), the rotating magnetic head no longer accurately tracks the recording track 2, resulting in guard band noise.

The present invention was developed to eliminate the above-mentioned drawbacks of the conventional technology.By recording video signals while the magnetic tape is stationary, it prevents the generation of guard band noise during still playback, and also prevents the generation of guard band noise in the magnetic tape intermittently. It is an object of the present invention to provide a magnetic recording device that effectively prevents the adverse effects of mechanical vibrations and the like immediately after transition from a running state to a stationary state during feeding.

In other words, the gist of the magnetic recording device according to the present invention is that the magnetic tape is fed intermittently while being alternately switched between a running state and a stationary state at a constant cycle, and that the magnetic tape is fed intermittently while being alternately switched between a running state and a stationary state at a constant cycle, and at the same time when the magnetic tape is switched from the stationary state to the running state. The purpose is to obtain a recording command signal at least one vertical period before, and to record the video signal. This recording command signal can be obtained based on the running/standstill switching control signal or from a generating circuit for the switching control signal. Furthermore, the above-mentioned point at least one vertical period before is preferably a point a unit time before the video signal is recorded, for example, when recording one field at a time, one vertical period before, and when recording one frame at a time, For this purpose, the recording command signal may be obtained two vertical periods before.

Therefore, since the video signal is recorded while the tape is running, a recording track with a constant inclination angle is always formed even if the tape speed changes, and good reproduced images without guard band noise etc. can be obtained during still playback. Obtainable. Moreover, since the recording of the video signal is performed immediately before the tape moves from a stationary state to a running state, there is no deterioration in recording due to sliding contact of the rotating magnetic head on the recording track that has been recorded once. Since recording is performed at the time most distant from the time when the tape moves from the running state to the stationary state, good recording can be performed with the least adverse effects such as mechanical vibrations of the magnetic tape itself immediately after the tape comes to rest.

Hereinafter, preferred embodiments of the magnetic recording/reproducing apparatus according to the present invention will be described with reference to FIGS. 2 to 5.

Here, to briefly explain the general structure of the embodiments shown in FIGS. 2 to 5, first, a magnetic tape on which a video signal is recorded on diagonal tracks by a rotating magnetic head is driven by a motor 5. It is designed to be driven and driven. The input terminal 10 has
The vertical synchronization signal of the above video signal is supplied,
This vertical synchronizing signal is counted by a counter circuit 29, and the counter circuit 29 outputs a pulse every time the count value reaches a preset value according to the average running speed of the magnetic tape.
The output pulses from the counter circuit 29 are sent to a motor intermittent drive control circuit consisting of shift registers 31 and 32 and an S-R flip-flop 33. Based on this, the motor 5 is switched to a driving state only during a predetermined period of one cycle of the output pulse, thereby controlling the running of the magnetic tape intermittently while switching between a running state and a stationary state. The output pulse from the counter circuit 29 is also sent to an S-R type flip-flop 19 as a recording command signal forming circuit.
On the basis of the output pulses from the counter circuit 29, a recording command signal is generated for causing the rotating magnetic head to record the video signal on the diagonal track. Further, a D-type flip-flop 35 serving as a control signal recording circuit forms a control signal that serves as a reference for the position of the diagonal track based on the vertical synchronization signal of the video signal, and transmits the control signal as described above in the tape running state. It is recorded on a control track on a magnetic tape.

In FIG. 2, a so-called stepping motor is used as a capstan motor 5 for driving the magnetic tape to travel, which is rotated by being driven step by step by a predetermined minute angle in response to a pulse signal. The rotation angle and rotation speed of this stepping motor are determined according to the number and frequency of drive pulses, and highly accurate rotation control is possible. Now, when the magnetic tape 1 as shown in FIG. Number of pulses supplied to the motor 5 (this is called the unit step number)
Let there be k pieces. Under this condition, in order to set the tape running speed ν to the normal speed ν ₀ , that is, the speed at which the tape is fed by one track pitch p every one vertical period, the frequency of the drive pulse supplied to the capstan motor 5 is set as follows. It may be set as k _v , the product of the above unit step number k and the frequency _v of the vertical synchronizing signal. In this case, if a driving pulse with a frequency k _v is continuously supplied to the capstan motor 5, the capstan motor 5 will rotate continuously and smoothly at an almost constant speed, and the magnetic tape 1 will be rotated at the above normal speed ν ₀ to drive the vehicle. Also, for example, the frequency k _v /
If two drive pulses are supplied to the capstan motor 5, the magnetic tape 1 is driven to run at a speed ν ₀ /2.

Next, the reference pulse generating circuit section 6 generates a reference pulse having a frequency _kv , for example. Although the frequency of the output reference pulse of the reference pulse generation circuit section 6 may be an integral multiple of _kv , it is set to _kv to simplify the explanation. This reference pulse of frequency _kv undergoes signal processing such as frequency division according to the desired tape running speed and is supplied to the capstan motor 5, but it is necessary to synchronize with the vertical synchronization signal of the video signal. There is. For this reason, the reference pulse generation circuit section 6 is configured as a PLL circuit using a phase comparator 7 and a voltage controlled oscillator (hereinafter referred to as VCO) 8, and a vertical synchronization signal separated from the video signal is input. The signal is supplied to the phase comparator 7 via the terminal 10. The reference pulse output from the VCO 8 is divided into 1/k by a frequency divider 9 and sent to the phase comparator 7 as a signal with a frequency _v . Therefore, when a vertical synchronization signal as shown in FIG. 3A is supplied to the input terminal 10, the reference pulse from the VCO 8 becomes synchronized as shown in FIG. 3B. In addition,
In an actual circuit, a so-called tracking control delay circuit 11 is used in the synchronization signal system to match the mechanical timing of tape running or rotation of a rotating magnetic head with the timing of a vertical synchronization signal in a video signal. This is a conventionally known technique, so its explanation will be omitted.

Here, as the tape running speed selected in the above-described time-lapse VTR, there are a plurality of slow speeds such as ν ₀ /2, ν ₀ /3, . . . in addition to the normal speed ν ₀ . This slow speed is generally defined as ν ₀ /n (where n=2, 3,...), and 1/n
is called the throw ratio. In a normal time-lapse VTR, the tape speed during recording is the normal speed ν ₀
For example, a slow speed with a slow ratio of several tenths is selected, whereas a normal speed ν ₀ is selected during playback, and ν 0 /2, ν ₀ /2, if necessary. A slow speed of ν ₀ /3 or approximately the same as that during recording is selected. In other words, the normal speed ν ₀ and the slow speed of about ν ₀ /2, ν ₀ /3 are:
It is only selected during playback.

In the present invention, when the magnetic tape is generally driven to run at a slow speed of ν ₀ /n, the magnetic tape 1 shown in FIG. 1 is fed intermittently every at least one track pitch p. By setting the speed at a constant value and changing the period of the intermittent feeding operation, the average speed is made to be the slow speed ν ₀ /n. for example,
In the case of this embodiment, the tape speed in the tape running state is set to ν ₀ /2, and after actually running the tape for 2 vertical periods, the tape is stopped for (n-2) vertical periods, and the overall By performing the tape feeding operation intermittently with n vertical periods as one cycle, the average tape running speed is set to ν ₀ /n. In order to obtain the actual tape speed ν ₀ /2 in the above-mentioned tape running state, a drive pulse with a frequency k _v /2 may be supplied to the capstan motor 5. For example, the reference pulse generation circuit section 6
The reference pulse of frequency k _v outputted from VCO 8 (see Fig. 3B) is divided by 1/2 frequency divider 12,
It is sufficient to obtain a pulse of frequency k _v /2 as shown in FIG. 3C and send it to the capstan motor 5.
It goes without saying that when the selected slow speed is ν ₀ /2 (only during playback), the tape rest period disappears and the tape runs continuously at the tape speed of ν ₀ /2. It is.

Here, the tape speed in the actual tape running state is set to ν ₀ /2 because the tracking trajectories by the rotating magnetic head during playback are arranged as trajectories Ta and Tb shown by the broken line in FIG. This is to drive the band noise to the vertical blanking position in the reproduced video signal or to the edge (top or bottom) of the reproduced screen. By setting such tracking trajectories Ta and Tb, it is possible to prevent guard band noise from appearing in the main central portion of the playback screen, and to enable playback in a good screen condition.

Mode switching control signals for switching and selecting these tape speeds (average speeds) are supplied to each input terminal 21, 22, 23, and 24 in FIG. The signal format of this mode switching control signal can be various, but in this embodiment, only the signal corresponding to the selected tape speed is "H" (high level), and all others are "L" (low level). be. Input terminal 21 corresponds to normal speed ν ₀ , input terminal 22 corresponds to slow speed ν ₀ /2, input terminal 23 corresponds to slow speed ν ₀ /n, and input terminal 24 corresponds to tape stationary, so-called still speed. corresponds to the mode. In addition to this, the slow speed can be configured so that a desired slow ratio can be selected.

Mode switching control signals from these input terminals 21, 22, 23, and 24 are sent to D-type flip-flops 25, 26, and 24 for determining mode switching timing.
27 and 28, respectively. These D
The clock signals of type flip-flops 25, 26, 27, and 28 are 1/2 the vertical synchronization signal of FIG. 3A.
This is a signal with a divided frequency _v /2 (period 2V) (see Figure 3D). Therefore, as shown in FIG. 3E, the mode switching control signal becomes "L" at any time _t0 .
Even if the voltage changes from high to high, the Q output from the D-type flip-flop will not change in frequency as shown in Figure 3F.
At time _t1 when the clock pulse p of the signal D of _v /2 is supplied, it changes from "L" to "H".

The Q output from the D-type flip-flop 25 corresponding to the normal speed is sent to the AND gate 13, which gate-controls the reference pulse (see FIG. 3B) from the VCO 8 of the reference pulse generation circuit section 6. The output signal from this AND gate 13 is sent to the capstan motor 5 via an OR gate 14 and an AND gate 15.

D type flip-flop 2 corresponding to slow speed
The Q outputs from 6, 27, etc. are sent to a counter circuit 29. This counter circuit 29 counts the vertical synchronizing signal (see FIG. 3A) from the input terminal 10, and the count value is determined according to the selected slow speed. That is, when the slow ratio of the selected slow speed is 1/n, the count value is set to n, and one pulse is output every time n vertical synchronizing signals A are counted.
To explain this in conjunction with Figure 4, first, Figure 4A
3A shows a vertical synchronizing signal with a period of 1 V per vertical period, and in FIG. 4, the time axis (horizontal axis in the figure) is shrunk compared to FIG. 3.
When the slow speed ν ₀ /2 is selected, the “H” signal from the D-type flip-flop 26 is sent to the counter circuit 29.
When the count value is 2, the count value is 2.
As a result, a pulse output with a period of 2V for two vertical periods as shown in FIG. 4B is obtained. Further, as an example of the general slow speed ν ₀ /n, when n=5, the counter circuit 29 outputs one pulse every five pulses of the vertical synchronizing signal A, that is, the fourth pulse. A pulse as shown in Figure C is output. Therefore, in operation, when the slow ratio is 1/n, the vertical synchronizing signal of frequency _v is divided by 1/n to obtain the frequency _v /n.
Various circuit configurations are possible as long as the circuit outputs n signals, that is, signals having one cycle of n vertical periods. Note that since the counter circuit 29 is supplied with the vertical synchronization signal A,
D-type flip-flop 26 for slow speed selection;
It is also easy to have the counter circuit 29 perform the operation of 27, and in this case, the D flip-flops 26 and 27 can be omitted.

n outputted from such a counter circuit 29
A pulse signal having a vertical period period is sent to a series circuit of first and second shift registers 31 and 32.
These first and second shift registers 31 and 32
are connected in series via a changeover switch 34, and the sum of the number of stages is the number of steps k.
By using the pulse signal of frequency k _v /2 from the 1/2 frequency divider 12 as a clock, the output pulse from the counter circuit 29 is delayed by two vertical periods (one frame period) and output. . These two vertical periods, 2V, are equal to one rotation period of a two-head type rotating magnetic head.

Further, the output pulse from the counter circuit 29 is connected to the set terminal S of the S-R flip-flop 33.
Then, by sending the delayed output pulses from the second shift register 32 to the reset terminal R of the S-R flip-flop 33, the Q output of the S-R flip-flop 33 has a pulse width (“H The pulse signal is a pulse signal whose period (duration time) is two vertical periods of 2V, which is the above-mentioned delay time, and whose period is nV, which is the above-mentioned n vertical periods. For example, at the slow speed ν ₀ /n, when n=5, the Q output of the S-R flip-flop 33 has two vertical periods as one cycle, and the "H" time is 2V, as shown in FIG. 4D. The "L" period becomes a 3V pulse signal. Note that when the slow speed ν ₀ /2 is selected, the Q output from the S-R flip-flop 33 is always "H", but as described above, this is only during reproduction.

Therefore, the drive pulse of the frequency k _v /2 is gate-controlled by the Q output from such an S-R flip-flop 33 (see FIG. 4D),
By feeding the magnetic tape to the capstan motor 5, the magnetic tape can be fed intermittently as described above. For example, the Q output of the S-R flip-flop 33 is connected to the AND gate 16, and the frequency divider 12
The output of the AND gate ₁₆ may be sent to the capstan motor 5 via the OR gate 14 and the AND gate 15.

FIG. 4E shows the relationship between the tape running state and the stationary state when the slow speed ν ₀ /5 is selected as an example, and the vertical axis represents the tape running amount.
As is clear from Fig. 4E, the tape actually runs at a speed of ν ₀ /2 for a 2V interval, and after advancing by the above-mentioned one track pitch p, the tape stands still for a 3V period. By performing this at a cycle of 5V, the average running speed of the tape becomes ν ₀ /5, as shown by the broken line in FIG. 4E.

By the way, as mentioned above, time lapse
During recording on a VTR, a tape running speed that is relatively slow compared to the normal speed is selected, so the period during which the tape remains stationary is extremely long, for example, several to several tens of vertical periods. This idea is
The gist of this is to record a video signal in, for example, one vertical period immediately before transitioning to the tape running state during the tape stationary period, and the signal for controlling this recording operation is, for example, sent from the counter circuit 29. Obtainable. That is,
Generally, when a slow speed of ν ₀ /n is selected, the counter circuit 29 operates as an n-ary counter, but the output is obtained after counting n-1 pulses during this n-ary counting operation. The output is supplied to the set input terminal of the S-R flip-flop 19, and the n-ary count output is supplied to the reset input terminal of the S-R flip-flop 19. For example, in the case of n=5, that is, a slow speed of ν ₀ /5, the counter circuit 2
9, as shown in Figure 4F, from Figure 4C
A pulse output is obtained at a point before 1V, and the S-R type flip-flop 19 is set by this pulse output F. Since this S-R type flip-flop 19 is reset by the pulse output C, the S-R type flip-flop 19 is reset by the pulse output C.
As shown in FIG. 4G, the output of the -R type flip-flop 19 becomes "H" for a period of 1 V immediately before the pulse shown in FIG. 4D rises. Using this pulse output of FIG. 4G as a recording command signal of a video signal,
By controlling the video signal recording state in the above-mentioned "H" state, the video signal is recorded in the 1V period immediately before the tape shifts from the stationary state to the running state. In addition, for example, a serial-in, parallel-out type shift register may be used to obtain the recording command signal of the video signal.

Next, the OR gate 14 receives the drive pulse of frequency k _v from the AND gate 13 when the normal speed is selected, and the AND gate 1 when the normal speed is selected.
The drive pulses of frequency k _v /2 from 6 are sent to the next AND gate 15, respectively. and gate 1
5 is for preventing the drive pulse from being supplied to the capstan motor 5 when the still mode is selected, and the output from the D-type flip-flop 28 corresponding to the still mode is connected to the inverter 17.
Supplied via.

Next, a circuit configuration for recording and reproducing control signals and its operation will be explained.

The first and second shift registers 31 and 32
The S-R type flip-flop 33 is kept in the set state only during the period when the input pulse is being transferred within the register, and during this time the capstan motor 5 rotates and the magnetic tape is actually running. Therefore, it is sufficient to record the control signal while the input pulse data is being transferred within these serially connected shift registers 31 and 32. For example, by taking out the output of the first shift register 31, , the pulse for recording the control signal may be obtained from this output. The recording timing of the control signal is the first and second timing mentioned above.
The number of stages is determined by the number of stages of the shift registers 31 and 32. For example, if each stage is k/2, at a time exactly 1 V behind the output pulse generation time from the counter circuit 29,
Output pulses are obtained from the first shift register 31. Generally, if the number of stages of the first shift register 31 is m (where m<k), the clock cycle is 2V/k, so the delay from the output pulse generation time of the counter circuit 29 is 2mV/k. Become. At this time, the number of stages of the second shift register 32 is set to (k
-m) stage, it goes without saying that the output pulse from the second shift register 32 is delayed by 2V from the output pulse from the counter circuit 29. Here, when recording the control signal on the control track 4 (see FIG. 1), the signal form is inverted every track pitch P, so the output of the first shift register 31 is
For example, it is sent to the T input terminal (timing pulse input terminal) of the D-type flip-flop 35, and the Q output of this D-type flip-flop 35 is fed back to the D input terminal (data input terminal). Therefore, D
The Q output of the type flip-flop 35 inverts from "H" to "L" or from "L" to "H" every time the output pulse of the first shift register 31 is supplied. This Q output is supplied to a control head 37 via an amplifier 36 and recorded on the magnetic tape 1.

The control head 37 is generally a recording/reproducing head, and during reproduction, it slides into contact with the control track 4 of the magnetic tape 1 to reproduce the magnetic recording signal. For example, during normal reproduction, the reproduction signal from the control head 37 is inverted every 1V as shown in FIG. 5A, so the period is 2V. This reproduced signal is amplified by the amplifier 38 and sent to the frequency multiplier circuit section (or control pulse detection circuit section) 39, and is sent to the 1V
Obtain a periodic control pulse signal. The frequency multiplier circuit 39 may be configured to obtain pulses at each of the rising and falling points in FIG. 40 and an exclusive OR circuit (hereinafter referred to as Ex.OR circuit) 41. That is,
The reproduced signal A is delayed by the delay time corresponding to the pulse width τ in the delay circuit 40 to obtain the delayed signal shown in FIG. 5B, and by taking the exclusive OR of these signals A and B, Pulse width τ
A control pulse signal (see Fig. 5C) with a period of 1V (frequency _v ) is obtained. During reproduction at such normal speed ν ₀ , the control pulse signal shown in FIG. The timing can be aligned with the vertical synchronization signal inside. In this case, the signal of frequency _v from the 1/k frequency divider 9 is sent to the switching terminal a of the switching switch 42, and during recording, the switching switch 42 is switched to the terminal a side.

In addition, during slow playback, the control pulse signal C from the Ex. The amount of tape intermittent feeding to be performed can be determined. During recording, it goes without saying that the changeover switch 34 is connected to the changeover terminal a to connect the first and second shift registers 31 and 32 in series.

In this way, the control signal is recorded and reproduced while the tape is actually running during the tape intermittent feeding operation, and at this time, the control head ₃₇ and the magnetic Since the tape 1 is moved relative to the tape 1, magnetic recording and reproducing characteristics are improved, and control signals can be easily and accurately recorded and reproduced. This is a significant improvement in the difficulty and inaccuracy of magnetic recording due to the extremely slow relative speed of the control head when the tape is driven continuously as in the past.

As is clear from the above description, according to one embodiment of the present invention, a stepping motor is used as the capstan motor 5, and the magnetic tape 1 is run at a cycle according to the throw ratio and is intermittently fed while being stopped. At the same time, a video signal is recorded during one vertical period (1V period) immediately before the magnetic tape 1 changes from a stationary state to a running state. Therefore,
Since the video signal is recorded in a state where the longitudinal vibrations of the tape itself are sufficiently attenuated immediately after the tape transitions from the running state during intermittent tape feeding operation to the stationary state, it is possible to effectively prevent recording deterioration due to the above vibrations. Since the tape enters the running state immediately after recording, there is no adverse effect caused by the rotating magnetic head sliding over and over again on this recording track after recording the video signal. Furthermore, since video signals are always recorded with the tape stationary, the inclination angle α of the recording track 2 on the magnetic tape 1 remains constant even when the tape running speed (average speed) is changed, and the guide band during still playback remains constant. Good reproduced images without noise can be obtained, and even in slow reproduction, as the tape speed (average speed) decreases, the proportion of time during which still images are reproduced increases, and the image quality improves. Furthermore, in the tape intermittent feeding operation during slow playback, by setting the actual tape running speed to ν ₀ /2, the playback tracks Ta and Tb will be as shown by the broken line in Figure 1, and the guide bang noise will be at the center of the screen. , and a good reproduced image can be obtained.

It should be noted that the magnetic recording device according to the present invention is not limited to the above-mentioned embodiments, but may record one frame of the video signal for each tape intermittent feed, and in this case, , just before the transition from the tape stationary state to the tape running state.
It is sufficient to record the video signal within the 2V period.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an example of a recording track pattern on a magnetic tape 1, FIG. 2 is a block circuit diagram showing an embodiment of the present invention, FIGS. 3 A to F, and FIGS. 4 A to G. , and FIGS. 5A to 5C are time charts for explaining the operation of the circuit shown in FIG. 2, respectively. 1...magnetic tape, 2...recording track, 4...
... Control track, 5 ... Capstan motor, 6 ... Reference pulse generation circuit section, 10 ... Vertical synchronization signal input terminal, 12 ... 1/2 frequency divider, 17
...S-R type flip-flop, 21, 22, 2
3, 24...Switching signal input terminal, 25, 26, 2
7, 28, 35...D type flip-flop, 29
... Counter circuit, 31, 32 ... Shift register, 37 ... Control head.

Claims (1)

[Scope of Claim for Utility Model Registration] A magnetic recording device configured to record video signals on diagonal tracks on a magnetic tape by means of a rotating magnetic head, comprising: a motor for running and driving the magnetic tape; and the input video image. A counter circuit that counts the vertical synchronization signal of the signal and outputs a pulse every time the count value reaches a preset value according to the average running speed of the magnetic tape, and based on the output pulse from this counter circuit. motor intermittent drive control for intermittently controlling the running of the magnetic tape while switching between a running state and a stationary state by switching the motor to a driving state only for a predetermined period of one cycle of the output pulse; circuit, and the video signal is tracked diagonally by the rotating magnetic head during a predetermined period immediately before switching from the stationary state to the running state by the motor intermittent drive control, based on output pulses from the counter circuit. a recording command signal forming circuit for forming a recording command signal for recording on the vehicle; and a recording command signal forming circuit for forming a recording command signal for recording on the vehicle; and a control signal recording circuit for recording on a control track on the magnetic tape.