JPH07118068B2 - Video tape recorder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in the following order.

A Industrial Field B Outline of the Invention C Conventional Technology D Problems to be Solved by the Invention E Means for Solving Problems (Fig. 1) F Action G Example G ₁ Structure of Video Tape Recorder G ₂ Operation during Recording H Effect of Invention A Field of Industrial Application The present invention relates to a video tape recorder in which a magnetic head for recording is attached to a rotary drum via an electro-mechanical conversion element such as a bimorph.

B Outline of the Invention According to the present invention, diagonal tracks are alternately formed on a magnetic tape by first and second magnetic heads mounted on a rotary drum via first and second electro-mechanical conversion elements to form an image. In a video tape recorder for recording a signal, a third magnetic head is mounted on a rotary drum at a position preceding the second magnetic head, and at the time of recording, the third magnetic head at the preceding position records on the magnetic tape. The reproduced reference signal is reproduced by the second magnetic head to detect the edge of the recording track, and the second electro-mechanical conversion element is displaced so that the edge of the second magnetic head is aligned with the detected edge. At this time, the reference signal recorded on the magnetic tape by the first and second magnetic heads is reproduced by the second and first magnetic heads while maintaining the transition state of the second electro-mechanical conversion element. Then, the first electro-mechanical conversion element is moved so that the reproduction levels become equal to each other, so that the absolute positional relationship between the two recording magnetic heads during recording can be favorably maintained. It is a thing.

C Conventional Technology Conventionally, in a helical scanning type video tape recorder,
There is a rotary head drum in which a magnetic head is attached to an electro-mechanical conversion element such as a bimorph. This bimorph is formed by sandwiching both sides of a thin film of silver or the like between piezoelectric ceramics, and supplies a required drive voltage to the bimorph to shift the magnetic head in a direction substantially orthogonal to the scanning direction, Devices are known in which a magnetic head accurately traces a slanted track on a tape from start to finish. Such a device is generally used during variable speed reproduction, and it is used as a DTF (Dynamic Track Fol
lowing) device. In this DTF device, when performing special reproduction, for example, fast forward reproduction (cue) or rewind reproduction (review) at several speeds, as shown in FIG. 6 or 7, the recording track (1a) of the magnetic tape (1) is recorded. In order to correct the difference in the inclination angle of the magnetic head locus (1b) from + V ₀ as shown in FIG. 8B or C.
V ₀ (v) to or -V ₀ (v) from + V ₀ (v) slope voltage to be applied to the bimorph and by the magnetic head locus (1b) is to match the recording track (1a). That is, for example, when a positive voltage is applied to the bimorph, the bimorph (2) bends upward as shown in FIG. 9 so that the magnetic head (3) is raised upward with respect to the tape (1), and the negative direction. When the voltage is applied to the bimorph, the bimorph (2) bends downward and the magnetic head (3) is raised downward with respect to the tape (1) as shown in FIG. The degree of deflection of the bimorph (2) is proportional to the supply voltage, and the higher the supply voltage, the greater the amount of elevation of the magnetic head (3). Therefore, from + V ₀ to −V shown in FIG. 8B.
_When a ramp voltage to ₀ (v) is applied to the bimorph (2), the head (3) gradually moves from a state of being raised upward to a state of being raised downward, and this + V ₀ to −V ₀ ( FIG. 6 shows that the ramp voltage is supplied to v) in synchronism with the magnetic head (3) during one track trace of the tape (1) (at the high level of the pulse wave in FIG. 8A). Such an angle deviation between the recording track (1a) of the tape (1) and the locus (1b) of the magnetic head (3) at the time of cue is eliminated.
Further, when the bimorph (2) is supplied with a gradient voltage from -V ₀ (v) to + V ₀ (v) which is the opposite of that shown in Fig. 8C, the magnetic head (3) is different from the above. Move in the opposite direction, 7th
Tape (1) Recording track (1a) at the time of review shown in the figure
There is no deviation in the angle between the locus (1b) of the head (3).

D Problems to be Solved by the Invention By the way, there are cases where the magnetic head mounted via the electro-mechanical conversion element such as the bimorph as described above is also used during recording. At the time of this recording, it is not always necessary to change the electro-mechanical conversion element for forming the same recording track, but it is possible to change the electro-mechanical conversion element with time (e.g. Change)
May occur, and if such a change with time occurs, there is a disadvantage that good signal recording cannot be performed. That is, in the case of a helical scanning type video tape recorder in which two magnetic heads used in a general video tape recorder alternately scan the magnetic tape, the relative position (height) of the two magnetic heads is used. ) If the relationship is not in a predetermined state, the recording pattern cannot be formed well, so it is necessary to adjust the height of the magnetic head before recording.

As a method of adjusting the height, for example, Japanese Patent Application No. Sho 60-31310.
As shown in FIG. 1, one of the two magnetic heads reproduces the reference signal recorded on the tape by the other magnetic head, and the other magnetic head reproduces the reference signal recorded on the tape by the one magnetic head. It is conceivable that the heights of the magnetic heads are adjusted so that the reproduction levels of both magnetic heads become equal to each other. By adjusting in this way, the relative positional relationship between the two magnetic heads can be kept good.

However, there are cases where such adjustment of the relative positional relationship is insufficient. For example, at the time of recording, it is necessary to erase the information previously recorded on the tape with an erasing head, and a so-called flying erase head attached to a rotary drum may be used as the erasing head. This flying erase head is mounted at a position preceding the magnetic head for recording on the rotating drum, and
Erasing is performed immediately before recording is performed for each track or two tracks. By thus performing the erasing with the flying erase head, it is possible to record a good video signal without image distortion at the joint. When this flying erase head is provided on the rotary drum, it cannot be completely erased because it will remain unerased unless it is located exactly ahead of the recording track formed by the recording magnetic head. Therefore, the magnetic head for recording does not only have a relative relationship between the two heads but also an absolute positional relationship (height) with an erasing head fixed to the rotating drum.
Must also be matched.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a video tape recorder capable of maintaining a good absolute positional relationship between two magnetic heads mounted via an electro-mechanical conversion element during recording. .

E Means for Solving Problems The video tape recorder of the present invention has, for example, as shown in FIG. 1, a rotary drum (4) having first and second electro-mechanical conversion elements (2a), (2b). In a video tape recorder for recording video signals by alternately forming diagonal tracks on the magnetic tape (1) by the first and second magnetic heads (3a), (3b) attached via the rotary drum (4 ) The third magnetic head (3d) is attached at a position preceding the second magnetic head (3b) above, and the third magnetic head (3d) at the position preceding the third magnetic head (3d) is recorded.
Of the reference signal recorded on the magnetic tape (1) and reproduced by the second magnetic head (3b) for detecting the edge of the recording track, and the second magnetic head ( The second electro-mechanical conversion element (2b) is displaced so that the edges of 3b) are aligned, and
While maintaining the transition state of the electro-mechanical conversion element of
The reference signal recorded on the magnetic tape (1) by the first and second magnetic heads (3a) and (3b) is reproduced by the second and first magnetic heads (3b) and (3a), and the reproduction level is The first electromechanical conversion elements (2a) and (2b) are displaced so as to be equal.

According to the video tape recorder of the present invention, the reference signal recorded on the magnetic tape (1) by the third magnetic head (3d) which is fixedly mounted on the rotating drum (4) at the time of recording and whose height does not change. By adjusting the height of the second magnetic head (3b) according to
The absolute height at the time of recording of b) becomes the same, and the relative height of the second magnetic head (3b) and the first magnetic head (3a) whose heights are adjusted is increased by the reference signal. By adjusting the depth, the absolute height of the first magnetic head (3a) during recording becomes the same, and the absolute height of the first and second magnetic heads (3a) and (3b) for recording is adjusted. Good physical relationship is maintained.

G Embodiment An embodiment of the video tape recorder of the present invention will be described below with reference to FIGS. 1 to 5. 1 to 5
In the figure, parts corresponding to those in FIGS. 6 to 10 are designated by the same reference numerals, and detailed description thereof will be omitted.

G ₁ Video Tape Recorder Configuration The video tape recorder of this example is a so-called 8 mm video with a magnetic tape width of 8 mm, and is configured to record a video PCM signal together with a video signal. As shown in the figure, as magnetic heads for recording and reproduction, first and second magnetic heads (3
a) and (3b) are provided at 180-degree symmetrical positions on the rotary drum (4), and the magnetic heads (3a) and (3b) alternate with CH1 and CH2.
Is a helical scanning type for recording and reproducing.
Then, the magnetic tape (1) is wound around the peripheral surface of the rotary drum (4) within a range of, for example, 221 degrees, and recording / reproduction of a sound PCM signal is performed in the first 36 degrees of the 221 degrees. At the same time, the video signal is recorded / reproduced in the remaining 180 ° section. The first and second magnetic heads (3a) and (3b) are fixed to the rotating drum (4) via the bimorph plates (2a) and (2b), respectively, and the bimorph plates (2a) and (2b) 9b depending on the applied voltage supplied to 2b)
The magnetic heads (3a) and (3b) change in height as shown in FIG. 10 or FIG. Also, this rotating drum (4)
90 from the first magnetic head (3a) in the direction of rotation (4r).
The erase head (3c), which is a flying erase head, is directly fixed at the position ahead of the reference magnetic head (3d) at the position 90 ° ahead of the second magnetic head (3b) in the direction of rotation (4r). It is fixed. With this configuration, when the side surface of the rotary drum (4) is developed and shown,
As shown in FIG. In FIG. 3, (4a) shows the center line of the side surface of the rotary drum (4), and the magnetic heads (3a) and (3b) are on this center line (4a) during recording. And the erase head (3c) at the most advanced position
Has a width for simultaneously erasing two tracks of the recording track (1a) on the magnetic tape (1), and the first magnetic head (3
in the position that preceded the track for recording a track for recording in a) (1a ₁₎ and a second magnetic head (3b) (1a _2). The reference head (3d) is provided with an azimuth angle in the same direction as the second magnetic head (3b), and is located at a position preceding the track (1a ₂ ) for recording by the second magnetic head (3b). . The heights of the first and second magnetic heads (3a) and (3b) change in the upward direction u or the downward direction d with respect to the center line (4a) due to the displacement of the bimorph plates (2a) and (2b). To do.

A signal is supplied to each of the heads (3a) to (3d) thus arranged on the rotary drum (4) at the time of recording by the circuit configuration shown in FIG. That is, the recording signal input terminals (5a) and (5b) supplied from a recording system circuit (not shown) for each head for recording a recording signal such as a video signal are mixed circuits (6a) and (6b), respectively. And the first on the bimorph plates (2a) and (2b) via the recording signal amplifiers (7a) and (7b)
And the second magnetic heads (3a) and (3b), and the signals obtained at the terminals (5a) and (5b) are recorded.
Then, a reference signal generator (8) for outputting a reference signal (pilot signal) having a relatively low frequency of about 200 kHz is connected to the mixing circuits (6a) and (6b) via the connection switches (9a) and (9c). Connected and recording timing generation circuit (10)
By controlling the connection switches (9a) and (9b) by the, the reference signal superimposed on the recording signal is supplied to the first and second magnetic heads (3a) and (3b). Further, the reference signal generator (8) is connected to the reference head (3d) through a series circuit of the connection switch (9c) and the recording signal amplifier (7c), and is connected by the recording timing generation circuit (10). By controlling the switch (9c), the reference signal output from the reference signal generator (8) is supplied to the reference head (3d).

Further, the first and second magnetic heads (3a) and (3b) are
It is connected to a reproduction system circuit (not shown) that processes a normal reproduction signal, and is also connected to the above-mentioned reference signal detection circuit. That is, as shown in FIG. 1, the first and second magnetic heads (3a) and (3b) pass through reproduction reference signal amplifiers (11a) and (11b) and detection circuits (12a) and (12b), respectively. Connected to the level comparison circuit (17). This level comparison circuit (17) is a circuit for comparing the output levels of the reference signals reproduced by the first and second magnetic heads (3a) and (3b), and bimorph height control so that the output levels become the same. Instructing the voltage generation circuit (18) to generate a control voltage signal. The control voltage signal output from the bimorph height control voltage generation circuit (18) is passed through the drive circuit (16a).
The bimorph plate (2a) supporting the first magnetic head (3a) is supplied. By thus supplying the voltage signal to the bimorph plate (2a), the bimorph plate (2a) is displaced and the height of the first magnetic head (3a) is varied. Further, the output signal of the detection circuit (12b) for detecting the reference signal reproduced by the second magnetic head (3b) is supplied to the lower edge detection circuit (13). The lower edge detection circuit (13) is a circuit for detecting the lower edge of the recording track of the reproduced reference signal, and supplies a hold signal to the sampling hold circuit (14) according to the detection state of the lower edge detection circuit (13). . The sampling and holding circuit (14) is supplied with the wobbling voltage signal from the wobbling voltage generating circuit (15), and holds the wobbling voltage signal under the control of the lower edge detection circuit (13). The output signal of the sampling and holding circuit (14) is passed through the drive circuit (16b) to the second magnetic head (3
It is supplied to a bimorph plate (2b) supporting b).
By supplying the voltage signal to the bimorph plate (2b) in this way, the bimorph plate (2b) is displaced and the height of the second magnetic head (3b) is varied.

G ₂ Recording Operation Next, the operation of recording a video signal on a magnetic tape with the video tape recorder of this embodiment will be described with reference to FIGS. 4 and 5. First, the first magnetic head (3a) and the second magnetic head (3b) alternate with each other in synchronization with a switching pulse signal (FIG. 5A) that switches every rotation of the rotating drum (4) by 180 degrees. The video signal is recorded at. That is, as shown in FIG. 5D, the drum angle 180 in the latter half of each magnetic tape scanning period CH1 _-1 , CH1 _-2, ... Of the first magnetic head (3a).
Period corresponding to the time and (V-REC), fifth each magnetic tape scanning period of the second magnetic head as shown in FIG. F (3b) CH2 _-1,
The period corresponding to the drum angle of 180 degrees in the latter half of CH2 _-2 (V-
REC) and the video signals supplied to the input terminals (5a) and (5b) are recorded alternately. Then, the drum angle 3 in the first half of the scanning period CH1 _-1 , CH2 _-1 , CH1 _-2 , CH2 _-2 ... of each head
During the period equivalent to 6 degrees (PCM-REC), the PCM audio signal supplied to the input terminals (5a) and (5b) corresponding to the video signal is recorded.

The signal is recorded in this manner, but the heights of the recording magnetic heads (3a) and (3b) are adjusted from the start of the recording to the scanning of several tracks. In the case of this example, as shown in FIG. 4, this height adjustment is performed by adjusting the second magnetic head (3b) in the section I where several tracks are scanned from the start of recording, and the next few tracks are scanned. The adjustment of the first magnetic head (3a) is performed in the section II, and the recording that does not require the height adjustment is performed in the following section III.

First, the adjustment of the second magnetic head (3b) in the section I will be described. As shown in FIG. 5E, the scanning periods CH2 _-1 , CH2 of the second magnetic head (3b) in the section I from the start of recording. _-2
... 90 degrees ahead corresponding to the section between the PCM audio signal recording unit PCM-REC and the video signal recording unit V-REC of CH2- _m (for example, part of the vertical blanking period in which the vertical synchronizing signal is recorded) During the section, for example, the connection switch (9c) is closed only by the period P-REC corresponding to the three horizontal scanning periods (3H) of the video signal according to the instruction from the recording timing generation circuit (10), and the reference signal generator is generated. The reference signal output by (7) is recorded by the reference head (3d).

Then, the reference signals thus recorded on the magnetic tape at predetermined intervals are reproduced by the second magnetic head (3b) arranged immediately after the reference signal as shown in FIG.

That is, the PC during the scanning period of the second magnetic head (3b) described above.
M Audio signal recording section PCM-REC and video signal recording section V-REC
The recording operation is switched to the reproducing operation only for the period of 3H between and, the reference signal is reproduced, and the lower edge detection circuit (17) detects the lower edge of the reference signal recording track. As shown in FIG. 3, if the reference signal is recorded on the track (1a ₂ ) by the reference head (3d), the lower edge to be detected is located at the lower end e of the track (1a ₂ ) by the second magnetic field. The wobbling voltage signal when the lower edge e is aligned with the lower edge of the second magnetic head (3b) is detected by the lower edge detection circuit (13) below the reproduction signal of the head (3b), The lower end e and the lower end of the magnetic head (3b) are aligned (3rd
The state shown in the figure) is maintained. In order to align the lower ends in this way, it is actually necessary to scan several tracks shown as section I.

When the height adjustment of the second magnetic head (3b) is completed in this way, the height adjustment of the first magnetic head (3a) is then performed in section II with reference to the second magnetic head (3b). Do. This adjustment is performed from the scanning period immediately after the last scanning period CH2 _-m for adjusting the height of the second magnetic head (3b)
The reference signal is recorded and reproduced by the second magnetic heads (3a) and (3b). That is, as shown in FIG.
Scanning period of both heads (3a) and (3b) of II CH1 _{-m + 1} , CH2
_{-m + 1} ... CH1 _-n , CH2 _-n , PCM audio signal recording section PCM-REC
3H period (P-REC) between the video signal recording unit and V-REC
Only the connection switch (9a) or (9b) is closed by the instruction from the recording timing generation circuit (10), and the reference signal output from the reference signal generator (8) is obtained at the terminals (5a) and (5b). Recording is performed from the first and second magnetic heads (3a) and (3b) so as to be superimposed on the recorded signal. Simultaneously with this recording, the same magnetic heads (3a) and (3b) reproduce the crosstalk component of this reference signal recorded by the other head.
That is, the signal reproduced by the first magnetic head (3a) reproduces the crosstalk component of the reference signal of the track recorded immediately before by the second magnetic head (3b) by the detection circuit (12a), and the second magnetic head (3b) reproduces the crosstalk component. The detection circuit (12b) reproduces the crosstalk component of the reference signal of the track recorded immediately before by the first magnetic head (3a) by the signal reproduced by the magnetic head (3b). Then, the signal level of the crosstalk component reproduced by both heads (3a) and (3b) is compared with the level comparison circuit (17).
And a control signal is supplied to the bimorph height control voltage generation circuit (18) so that the signal levels become the same, and the bimorph plate () supporting the first magnetic head (3a) until the signal levels become the same. Change the bimorph height control voltage signal supplied to 2a). By doing so, the first magnetic head (3a) is in a state of being ahead of the second magnetic head (3b) by one track. For example, as shown in FIG. 2) scans the track (1a ₁ ), the second magnetic head (3b) accurately scans the adjacent track (1a ₂ ). Then, in this case, this head height is maintained during recording. In this way, both magnetic heads (3a), (3b)
In order to align the lines, it is necessary to actually scan several tracks shown as section II.

In section III after height adjustment is performed in this way,
The reference signal is not recorded by each head, and the head height is maintained to maintain the first and second magnetic heads (3a) and (3b).
The video signal and PCM audio signal are recorded at.

As described above, according to the video tape recorder of this example, the reference signal is recorded by the reference head (3d) whose height is fixed for several tracks at the start of recording, and the bimorph plate ( 2b) the second magnetic head (3
In order to adjust the height of b), the second magnetic head (3
b) can be adjusted to the same height. And the first
The magnetic head (3a) of the first magnetic head (3a) adjusts the relative position with respect to the second magnetic head (3b) whose absolute position is adjusted, and as a result, the first magnetic head (3a) also absolutely moves. The position is adjusted. Therefore, not only the relative relationship between the two magnetic heads (3a) and (3b) but also the position (height) relationship between the erasing head (3c) and the recording magnetic heads (3a) and (3b). Is maintained satisfactorily, the erasing head (3c) does not erase and leave no miserase, and a good signal can be recorded. Further, in this example, since the erasing head (3c) is not used as the reference signal recording head and the one-track width reference head (3d) is used, the reference signal recording can be minimized and the recording track can be effectively used. Can be used efficiently.

The magnetic head (3d) for recording the reference signal was provided at a position 90 degrees ahead of the video signal recording (3b).
Other angles may be selected. However, in this case, it is necessary to change the timing of recording the reference signal. In the above-described embodiment, the first and second magnetic heads (3
In each of a) and (3b), the adjustment is performed only once, but the adjustment may be performed at a predetermined interval when recording for a long time. Furthermore, the present invention is not limited to the above-described embodiments, and it goes without saying that various other configurations can be adopted without departing from the gist of the present invention.

H Effect of the Invention According to the video tape recorder of the present invention, recording is performed on the magnetic tape (1) by the third magnetic head (3d) which is fixedly mounted on the rotating drum (4) and does not change in height during recording. The height of the second magnetic head (3b) is adjusted according to the reference signal, and the first and second magnetic heads (3b) are adjusted.
By adjusting the height of the first magnetic head (3a) according to the reference signal recorded on the magnetic tape (1) in a) and (3b), the absolute height during recording is always In the same manner, the positional relationship between the first and second magnetic heads (3a) and (3b) for recording and the erasing magnetic head is kept good, and good signal recording without miserasure by the erasing head is performed. Have a profit

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a video tape recorder of the present invention, FIGS. 2 and 3 are block diagrams showing a rotary drum of an embodiment respectively, and FIGS. 4 and 5 are drawings showing an embodiment. 6 and 10 are diagrams for explaining the conventional example, respectively. (1) is a magnetic tape, (2a) and (2b) are bimorph plates, (3a) and (3b) are first and second magnetic heads respectively, (3c) is an erasing head, (3d) is a reference head, (4)
Is a rotating drum.

Claims (1)

[Claims] 1. A magnetic tape is mounted on a magnetic tape by a first magnetic head mounted on a rotary drum via a first electro-mechanical conversion element and a second magnetic head mounted on a second electro-mechanical conversion element. In a video tape recorder that alternately forms diagonal tracks to record a video signal, a third magnetic head is attached to the rotary drum at a position preceding the second magnetic head, and at the time of recording, the third magnetic head is moved to the preceding position. The reference signal recorded on the magnetic tape by the certain third magnetic head is reproduced by the second magnetic head to detect the edge of the recording track, and the edge of the second magnetic head is aligned with the detected edge. As described above, the second electro-mechanical conversion element is displaced, and while the transition state of the second electro-mechanical conversion element at this time is maintained, the first and second magnetic transducers are Is adapted to reproduce the reference signal recorded on the magnetic tape by the second and first magnetic heads and to shift the first electromechanical conversion element so that the reproduction levels become equal. Video tape recorder.