JPH0235394B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording device, and in particular, during insert recording, by erasing a plurality of tracks at once, the erasing head can be smaller than the recording head, and when the insert recording is finished, the number of tracks that have already been recorded can be reduced. It is an object of the present invention to provide a magnetic recording device in which there is no signal loss between the signals and the recorded signals.

Traditionally, magnetic recording and reproducing equipment (hereinafter referred to as VTR)
In order to have a so-called insert recording function in which only an arbitrary part of the already recorded video signal is replaced with a new video signal, a flying erase head is required to erase only the relevant signal part before the recording head. The number of recording heads required is equal to the number of recording heads. For example, in normal recording and playback, a two-head helical scan method is used.
For VTRs, two additional flying erase heads were required to erase already recorded video signals during insert recording, and insert recording was performed using a total of four heads. Therefore, the machining required to attach the four heads to the rotating drum is quite complex, and the cost is extremely high, making it difficult for household use.
It had drawbacks such as difficulty in applying it to VTRs and the like.

The present invention eliminates the above-mentioned drawbacks, and embodiments thereof will be described below with reference to the drawings. 1st
Figures A and B show a first embodiment of the positional relationship of magnetic heads 1, 2, and 3 on a rotating drum 4 according to the present invention. The flying erase magnetic head 1 has an effective track width of, for example, 98 μm, is in front of the recording/reproducing magnetic head 2 by 70° in the rotational direction of the rotary drum 4, and the lower end of the magnetic head 1 is located between the magnetic heads 2 and 3. It is mounted on the rotating drum 4 at a height of 19.1 μm higher than the lower end. The recording/reproducing magnetic head 3 has the same effective track width as the magnetic head 2, 49 μm, and is disposed 180° symmetrically with respect to the magnetic head 2.

2A to 2F show track patterns on the magnetic tape 5 when the magnetic heads 1, 2, and 3 are set on the rotating drum 4 as shown in FIGS. 1A and 1B.
FIG. 2A shows a normally recorded track pattern before insert recording. When the insert recording mode is entered, the flying erase head 1 operates as shown in FIG. 2B, erasing two tracks of already recorded video at once. The flying erase head 1 is installed 70 degrees ahead of the magnetic head 2, but it is offset from the magnetic head 2 by 49 μm x 70 degrees/180 degrees = 19.1 μm in the track width direction. Only two track widths can be erased at once, leaving no blank space. Figure C shows track CH1' recorded by magnetic head 2.
It shows. Figure D shows a state in which track CH2' recorded by the magnetic head 3 is added to track CH1' in figure C.
Figure E shows a state in which two tracks of previously recorded video are once again erased at once by the flying erase head 1. In this way, as shown in FIG. 2F, a recording pattern is formed without creating a break between the normally recorded image and the insert recording image, and without causing double writing.

This difference in installation height changes the timing of channel switching of the magnetic heads 2 and 3 during special playback. Then, {(0.0191/tan5.96°) ÷ 62π} × 360° ≒ 0.34°, so it is necessary to set the switching timing about 0.34° earlier than the drum angle, but the tape winding angle is the minimum required 180°. There is a considerable margin for ゜, so this is not a problem.

Here, FIG. 3A shows a recording pattern at the end of insert recording in this first embodiment. Flying erase head 1 leads recording heads 2 and 3 by 70° or 180° + 70°,
Since twice the width of the recording track is erased at once, when the flying erase head 1 and the recording heads 2 and 3 finish their operations at the same time, a blank area as shown in a is generated. In the first embodiment, due to the occurrence of such a blank area, an image is missing between the end of insert recording and the restart of the already recorded normal video recording, causing a problem that it is very difficult to see during playback.

FIG. 3B shows a second embodiment that solves the above problems. That is, even after the erasing by the flying erase head 1 is stopped, the time of the (1+x/π) field (x; the leading angle of the flying erase head 1 with respect to the recording head 2, 70° in this embodiment) is as follows.
Insert recording by recording heads 2 and 3 continues. FIG. 4 shows an embodiment of a control signal generating circuit for causing a magnetic head to draw a recording pattern as shown in FIG. 3B. 5A-5D show control signal timing charts for this circuit. The fifth terminal entered terminal 6.
The insert recording control signal shown in Figure A is applied to the gate circuit (or switch circuit) provided in the erase current transmission path from the terminal 7 to the flying erase head 1, and the The erase current is passed through and supplied to the flying erase head 1 only during the level period. On the other hand, when this insert recording control signal is input to the monomulti 8, the monomulti 8 is triggered by the fall of this insert recording control signal and generates the rectangular wave shown in FIG. 5C. This square wave is a capacitor
C ₁ , a single pulse with a pulse width of time t determined by the time constant of resistor R ₁ . This time t corresponds to the (1+x/π) field of the video track.

After passing through the diode _D2 , this rectangular wave is logically added to the insert recording control signal that has passed through the diode _D1 at the connection point 9, and is outputted from the terminal 10 as a signal as shown in FIG. 5D. Diode D ₁ ,
Capacitor C ₂ which together with D ₂ constitutes a logic adder circuit
This is to avoid noise at the joint between the rectangular wave and the insert recording control signal. The control signal outputted from the terminal 10 is supplied as an operation control signal to the recording amplifiers provided on the input side of the recording heads 2 and 3, and the recording amplifier is operated only during the H level period to pass and output the video signal. During the L level period, the recording amplifier is inactive so that no video signal is output from its output terminal.

In this manner, when the insert recording of the second embodiment is completed, the recording heads 2 and 3 continue insert recording for the (1+x/π) field after the operation of the flying erase head 1 is completed, thereby eliminating missing video. will not occur. Furthermore, by starting and ending the insert mode on a field-by-field basis to avoid signal switching within a single image, it is possible to insert more beautiful joints. Also,
In this implementation, only one time constant of the monomulti 8 needs to be adjusted.

However, in the second embodiment, as shown in FIG. 3B, the already recorded video and the insert recorded video are double-written, and the screen switches in the middle of one field, resulting in extreme problems. The problem is that it is unnatural. Furthermore, even when starting insert recording, if heads 1, 2, and 3 receive a command to start insert recording in the middle of a video field that has already been recorded, another screen may change within one field, resulting in an error. There was a problem with natural-looking images.

Next, a third embodiment that solves the above problems will be described. FIGS. 6A to 6F are charts showing operation timings of the magnetic heads 1, 2, and 3 such that no screen switching or omission occurs within one field. A in the figure shows a field section recorded on the magnetic tape 5. In FIG. Figure B shows the timing at which the flying erase head 1 contacts the magnetic tape 5, Figure C shows the timing at which the recording head 2 of channel 1 contacts the magnetic tape 5, and Figure D shows the timing at which the recording head 3 of channel 2 contacts the magnetic tape 5. shows the timing at which the magnetic tape 5 comes into contact with the magnetic tape 5. 1
As an example, assume that an instruction to start insert recording is given in the range shown in c in FIG. 6D. When there is an instruction to start insert recording in this range, the erase start signal is sent to the recording head 3 of channel 2 as shown in Figure E.
From the time when the erase current starts to come into contact with the magnetic tape 5, the erase current is applied to the gate circuit (or switch circuit) provided in the erase current transmission path to the flying erase head 1, and the erase current is passed only during the H level period, and the flying erase is started. It is supplied to head 1.
The erasure may be started at any time before the flying erase head 1 first starts contacting the tape after the insert recording start instruction. This range is shown in Figure 6E, e. After the erase starts, when the recording head 2 of the channel 1 starts to come into contact with the magnetic tape 5, the insert recording signal as shown in FIG. The signal is supplied as a signal, and the recording amplifier is operated only during the H level period to pass and output the video signal, and during the L level period, the recording amplifier is inactive so that no video signal is output from its output terminal. In this way, erasure does not start in the middle of a field and insert recording is not performed, but insert recording always starts from the start of the field.

Next, a description will be given of the time when insert recording ends.
Assume that an instruction to finish inserting is given in the range d as shown in FIG. 6D. As shown in FIG. 6E, the supply of the erase signal to the flying erase head 1 is stopped from the time when the recording head 3 of the channel 2 begins to come into contact with the magnetic tape 5. The erasure may be completed at any time before the flying erase head 1 first starts contacting the tape after the instruction to end the insert is given. This range is shown at f in FIG. 6E. After the above erasing is completed, at the time when the recording head 2 of the channel 1 starts to come into contact with the magnetic tape 5, the supply of the insert recording signal to the recording heads 2 and 3 is stopped as shown in F in FIG. In this way, the insert recording is completed at the end point of the field, without ending the erasing and completing the insert recording in the middle of the field.

7 and 8 show a control circuit and its timing chart for controlling the erase control signal and insert recording signal shown in FIGS. 6E and 6F. An insert recording instruction signal shown in FIG. 8A is supplied to the flip-flop 12 via the input terminal 11. On the other hand, _the head switching signal that alternately switches between channel ₁ and channel ₂ shown in FIG. Recording head 3 like
The signal is supplied to the flip-flop 12 as a differential pulse synchronized with the recording start timing of each field. The flip-flop 12 latches the insert recording signal shown in FIG. 8A with the pulse signal shown in FIG. Supplies the circuit (or switch circuit). That is, the erase control signal is generated when the magnetic head of the first channel 2 is switched after the insert recording instruction signal is supplied to the input terminal 11 as shown in FIG. 8D, and is generated after the insert recording instruction signal has stopped. It stops when switching to the first channel 2 magnetic head.

Further, the head switching signal is connected to a capacitor C ₄ ,
It is supplied to the flip-flop 16 as a differential pulse through the resistor R ₃ and the diode D ₄ , and the polarity is inverted by the inverter 15, and the capacitor C ₅ ,
It is also supplied to flip-flop 16 as a differential pulse through resistor R ₄ and diode D ₅ . In this way, the signal shown in FIG. 8E (i.e.
Both the rising and falling edge detection pulses of the head switch signal are applied to the flip-flop 16 clock terminal. The flip-flop 16 delays the erase control signal shown in FIG. 8D in synchronization with the pulse signal shown in FIG. It is supplied as an operation control signal to the recorded recording amplifier. In this way, the signal output from the terminal 14 erases the flying erase head 1.
is operated, and the recording heads 2 and 3 are operated by the signal output from the terminal 17.

According to this embodiment, since the erasing operation by the flying erase head 1 is started one field earlier than the start of recording by the recording/reproducing head, the screen does not change even when insert recording is started, thereby preventing the occurrence of unnatural images. It also has the advantage that there is no need for a delay time adjustment section.

Only one flying erase head is provided in front of one of the at least two recording heads by an angle x (however, x is less than 180°) in the rotational direction of the rotating drum, and A single flying erase head is disposed with a height position shifted in the track width direction by x/180° times the track width of the recording head, and the effective track width of the flying erase head is set to the width of the recording head formed by the recording head. An erase control signal is branched and supplied to the head mechanism selected to be an integral multiple of 2 or more of the width of the track pitch on the track pattern, and the erase control signal gate outputs the erase current to the flying erase head when insert recording is completed. a pulse generating circuit that is triggered when the erase current changes to a level that prohibits the gate output of the erase current and generates and outputs a pulse having a width of {1+(x/π)} field; and the erase control signal, and supply the logical addition signal as an operation control signal to the recording amplifier provided on the input side of the at least two recording heads, and add the pulse of the {1+(x/π)} field. Since the recording amplifier is provided with a logic adder circuit that continuously puts the recording amplifier into an active state for a period of 100 seconds and then puts it into an inactive state, there is no break between the insert recording and the already recorded video at the end of the insert recording. Since the flying erase head can erase multiple tracks of already recorded video signals, the number of flying erase heads can be reduced compared to the conventional structure. can be simplified. Further, at the start of insert recording, a head switching signal having a width corresponding to each recording period of at least two recording heads is supplied, and a head switching signal having a width corresponding to each recording period of at least two recording heads is supplied. A pulse generation circuit generates a pulse phase-synchronized with the recording start timing of each field of another recording head that starts scanning, and an insert recording instruction signal is latched with the pulse generated by the pulse generation circuit, and an output is obtained. a first flip-flop that outputs a signal as an erase control signal to gate-output an erase current to the flying erase head; an edge detection circuit that outputs detection pulses for both rising and falling edges of the head switching signal; The output signal of the first flip-flop is latched by the output edge detection pulse of the edge detection circuit, and the obtained output signal is supplied as an operation control signal to the recording amplifier provided on the input side of the at least two recording heads. Since it is equipped with a second flip-flop, there is no break between insert recording and normal recording at the start and end of insert recording, and there is no double writing.
In addition, since the screen does not change in the middle of one field, the image is easy to see, and it can be realized by a circuit configuration without a time adjustment part.

[Brief explanation of drawings]

1A and 1B are layout diagrams of the magnetic head according to the present invention, FIGS. 2A to 2F are recording pattern diagrams of the insert recording process in the first embodiment of the present invention, and FIGS. 3A and 3B are diagrams of the recording pattern according to the present invention. 4 is a circuit diagram for forming the recording pattern shown in FIG. 3B. FIGS. 5A to 5D are timing chart diagrams of FIG. 4, respectively. FIG. 7 is a timing chart of a magnetic head according to another embodiment of the invention, FIG. 7 is a circuit diagram of an embodiment that implements the timing shown in FIG. 6, and FIGS. 8A to 8F are timing charts of FIG. 7, respectively. . 1... Flying erase head, 2, 3...
Recording/reproducing head, 4...rotating drum, 5...magnetic tape, 8...mono multi, 12, 16...flip-flop, 15...inverter.

Claims (1)

[Scope of Claims] 1. A magnetic recording device in which at least two recording heads provided opposite to each other and a flying erase head for erasing signals already recorded during insert recording are attached to a rotating drum, Only one flying erase head is provided in advance of one of the at least two recording heads by an angle x (where x is less than 180°) in the rotational direction of the rotary drum;
And, the single flying erase head is moved in the track width direction by x/of the track width of the recording head.
In addition to shifting the height position by 180 degrees,
A head mechanism in which the effective track width of the flying erase head is selected to be an integral multiple of 2 or more of the width of the track pitch on the track pattern formed by the recording head, and an erase current is applied to the flying erase head when insert recording is completed. An erase control signal to be output from the gate is branched and supplied, and when the erase control signal changes to a level that prohibits the gate output of the erase current, it is triggered and a pulse having a width of {1+(x/π)} field is generated. A pulse generating circuit that generates and outputs a pulse, logically adding the output pulse of the pulse generating circuit and the erasing control signal, and applying the logically added signal to a recording amplifier provided on the input side of the at least two recording heads for operation control. Supplied as a signal, the {1+
(x/π)} A magnetic recording device, comprising: a logic adder circuit that continuously puts the recording amplifier into an active state and then into an inactive state for a period of a pulse width of a field. 2. A magnetic recording device in which at least two recording heads facing each other and a flying erase head for erasing signals already recorded during insert recording are attached to a rotating drum, the flying erase head comprising: Only one recording head is provided in advance of one recording head of the at least two recording heads by an angle x (however, x is less than 180°) in the rotational direction of the rotary drum,
and the single flying erase head is aligned in the track width direction with respect to the track axis x/of the recording head.
In addition to shifting the height position by 180 degrees,
a head mechanism in which the effective track width of the flying erase head is selected to be an integral multiple of 2 or more of the width of the track pitch on the track pattern formed by the recording head; A head switching signal having a width corresponding to each recording period is supplied to each field of another recording head that starts scanning the magnetic tape during the period when the flying erase head is not scanning the magnetic tape. A pulse generation circuit generates a pulse phase-synchronized with the recording start timing, and an insert recording instruction signal is latched by the pulse generated by the pulse generation circuit, and the obtained output signal is outputted as an erase control signal to the flying erase head. a first flip-flop for gate-outputting an erase current; an edge detection circuit for outputting detection pulses for both rising and falling edges of the head switching signal; and an edge detection pulse output from the edge detection circuit for controlling the first flip-flop Latch the output signal of
A magnetic recording device comprising: a second flip-flop that supplies the obtained output signal to a recording amplifier provided on the input side of the at least two recording heads as an operation control signal.