JPS60167584A - Magnetic record reproduction device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention relates to a magnetic recording/reproducing device, particularly a helical video tape recorder (VTR), in which the moving direction of the magnetic tape and the recording track are at an angle, and the The present invention relates to a magnetic recording/reproducing device that may operate at different speeds during reproduction.

[Background of the invention]

In magnetic recording and reproducing devices, for example, slow still playback or searching may be performed, but when reproducing at a speed different from the recording speed, the reproducing head may have parts that straddle different recording tracks. In this part, the signals of each of the image recording tracks are reproduced by the same head, and the different signals of both tracks produce a beat-like sound (isband).

An example of using an appropriate sub-head to prevent this is slow playback in the so-called VH8 system. For example, when reproducing at a recording speed of 173, a sub-head with a scanning width of 1/3 of the main head is used exclusively for reproduction (Japanese Patent Laid-Open No. 54-21118). This is the first
As shown in the figure.

1 is the recording pattern during recording by the main head, and 2
is the reproduction scanning pattern of the sub head at ⅓ speed. At this time, the tape 3 skips only once every three fields and moves by an amount corresponding to one field during recording. Therefore, the reproduced image is updated once every three fields], thereby achieving reproduction at a speed of /3 times. However, this method has the following drawbacks. That is, it is difficult to control tape running, and it is necessary to precisely control the amount of skipping. Also, slow playback at a limited speed, or playback at other speeds where only still playback is possible,
In other words, it cannot handle playback during fast forwarding or rewinding. Also, since the width of the head becomes narrower, during slow playback, S/
N decreases.

[Purpose of the invention] The purpose of this invention is to slow, steal, and fast feed.

It is an object of the present invention to realize a magnetic recording/reproducing device which obtains reproduced images without noise banding when reproducing at an arbitrary speed different from that during recording, such as during rewinding. Another object of the present invention is to simplify the mechanism for obtaining a reproduced image without the noise band and to prevent the S/N ratio from decreasing in the noise band portion.

[Summary of the invention]

In order to achieve the above object, the present invention provides a main reproducing head (
In a magnetic recording/reproducing device that obtains a reproduction signal by switching between a recording trunk pin and a sub-reproducing head based on the scanning pattern of the main head (hereinafter referred to as the "main head"), the position of the sub-reproducing head with respect to the main reproducing head is determined. , the pitch of the recording track is P, the guard band width is g, and the scanning center of the sub-reproducing head with respect to the scanning center line of the reproducing head - 3 = When the amount of deviation of the line in the track pitch direction is L, it is set as follows. The switching means for the main and auxiliary reproducing heads is configured to detect a noise signal in the reproduction signal and generate a switching control signal for the main and auxiliary reproducing heads based on the detected noise signal.

[Embodiments of the invention]

The preferred method for detecting the above noise is to use error detection and correction normally provided in the playback signal processing circuit to detect noise caused by crossing the main playback head guard band when the main playback head straddles two or more tracks or racks. It can be detected using the code. Switching the output signal in this way means splicing together images from different fields, but since the image signals have an extremely strong correlation between fields, the image quality is significantly improved compared to reproduced images with noise bands. Ru. Note that a dedicated head may be used as the reproducing head 4-, but a recording/reproducing head used for other purposes may also be used. Further, although it is preferable that switching between the main head and the sub-head be performed using only a single recording track signal, this figure shows the configuration of the section. Note that the configuration of the recording section is not shown because it is the same as that conventionally known.

In the figure, television signals are recorded on a magnetic tape 3 at a constant angle with respect to the traveling direction of the magnetic tape by a helical scan type magnetic recording head, as in a conventional magnetic recording/reproducing device for image signals. The playback head includes a main head 4-1 and a sub-head 4-2 arranged in a predetermined geometrical relationship as will be described in detail later, and the output signal of each head is sent to a preprocessing circuit 5-1, 5-2 (for example, The signal is added to the signal synthesis circuit 6 via a preamplifier or (in the case of digital recording, a code error correction circuit, etc.). The signal synthesis circuit 6 converts the output signal of the preprocessing circuit 5 into an original signal, ie, a television signal, etc., and applies the signal to the display device 7. When the playback section reproduces at the normal speed, that is, the same speed as the recording speed, the path of the playback head 4-1, preprocessing circuit 5-1, signal synthesis circuit 6, and display device is taken, and its operation is as conventionally known. The operation is the same as that of a video tape recorder. However, when playing back at a speed different from the recording speed (including playback of still images), the main head straddles multiple tracks, and as explained in detail in Figure 3, noise occurs near the girt band. Generate a band. In order to remove this noise band, preprocessing circuit 5-1.5-2
Based on the output, the noise band detection circuit 8 determines whether each reproduced signal is in the correct reproduced signal noise band,
The discrimination signal and other control signals (clock signal, playback speed control signal, etc.) are added to the signal synthesis circuit 6, and the correct playback signal is spliced among the output signals of the main head 4-1 and sub-head 4-2. to create a signal with virtually no noise bands. For convenience of explanation, the drawing shows a configuration in which the noise band detection circuit 8 is provided independently, but in devices that record and reproduce digital signals, error detection and correction codes are used, and the reproduced code is determined by these. Since there is a circuit that performs error detection, it is desirable to use that circuit.

Figure 3 is a diagram showing the situation when the recording speed during recording and the playback speed during playback are different, and the trajectories of the recording track and the playback head are different. (,) shows the relationship between each track on the magnetic tape. , (b) show the relationship between the main and sub-reproducing head outputs. In the figure (a), 9 is a recording track, and 10 is a guard band provided between the recording tracks. Usually, it is formed at a constant angle with respect to the running direction of the magnetic recording tape, as in a helical scan VTR. 11
is the reproduction scanning pattern of the main head 4-1, and 12 is the reproduction scanning pattern of the sub-head 4-2.

When the recording speed and the reproducing speed are equal, the recording track 7-9 and the reproducing scanning pattern 11 match, but when the recording speed and the reproducing speed are different, the recording track 3 and the reproducing scanning pattern 11 intersect as shown. Therefore, the reproduction scanning pattern 11.12 is divided into a portion X in which two recording tracks are simultaneously scanned and a portion y in which only one recording track is scanned. When an output corresponding to this portion X is obtained, it becomes a mixture of image signals of two fields, which causes a so-called noise band. Therefore, it can be seen that in order to eliminate the noise band, the main head 4-1 and the sub-head 4-2 can be switched and selectively combined so that the portion X does not occur.

Below, the sub head 4 to prevent part X from occurring.
The relationship between the position of -2, the track (pattern), and the width of the card band will be described. Here, playback scanning pattern 1
The distance I2g that the upper end of 1 crosses the guard band 10 and the distance L that the upper end of the scanning line pattern 11 crosses the recording track 9
The ratio of m is g:(P-g), where g and P are the guard band width and 1 to rack pitch width, respectively. Further, the distance Lm obtained by subtracting the noise band portion X from distance = 8-Lm is equal to the distance Lg due to the isopermeability of the parallelogram. Therefore, x:
y=P-2g:2g.

On the other hand, the scanning pattern 12 is located at a position shifted from the scanning pattern 11 by a distance (deviation amount) L with respect to the track pitch P.
If scanning is performed with
x 1'I)X L/P. In this case, the outputs S and S2 of the main head 4-1 and sub-head 4-2 are:
The output S appearing on the main head 4-1 as shown in Figure (b)
□ and the output S2 appearing on the sub head 4-2 are reproduced with a difference of Z.

Therefore, in order to switch the outputs of scanning patterns 11 and 12 to join them together and prevent part X from appearing, it is determined that at least part X is smaller than the deviation 2, and z = (x + y) XL/P≧X, that is, it is necessary that

For the amount of deviation between the main head 4-1 and the sub-head 4-2, if the track pitch width P exceeds P/2, it is sufficient to consider the amount of deviation seen from the opposite track.
The amount of deviation may be less than P/2.

(P-2g)/P≦L/P≦1/2 is the condition under which no noise band appears.

However, even if the signal is obtained from the normal portion y, the reproduction ratio of the guard band 10 is large near the noise band portion X, resulting in a decrease in the reproduction output and a decrease in S/N. Therefore, it is desirable to use this part as little as possible. For this purpose, the center of the portion X in the main head 4-1 and the normal signal y in the sub head 4-2 must be
It is desirable that the centers of x and y coincide. That is, 2=-1, that is,
It is sufficient that the sub head 4-2 is located at the position of L/P=1/2, but this position is nothing but the center position of the guard band. In this case, the subhead output S3 (Fig. 3(b)) is as follows.
It is shown as L=P/2.

In the present invention, if the sub head 4-2 for noise band removal is placed at the optimal position, (P-2g)/P
≦1/2 That is, by satisfying the condition of P≦4g, an image free of noise bands can be obtained. That is, the ratio of the guard band width g to the main track width (P - g) is 1 = 3.
If it is below, the image signal without noise band is recorded by converting the vertical signal into a digital signal by using the sub head 4-2 having the scanning center line on the center line of the guard band. This system is applied to a system in which a signal is recorded, an audio signal is recorded by the sub-head 11-, and two channels are used for high-density recording, with each channel recording and reproducing half of the screen.

The digital image signals and audio signals applied to the input terminals 17 and 18 are respectively expanded or compressed in time series by time series converters 19 and 20, and each is divided into two channels, and then sent to the buffer memory 21. ~24
added to. As will be described later, the buffer memories 21 to 24 store intermittent signals of continuous signals so that the signals continuously input to the main head side 13.14 and the sub head side 15.16 are recorded only in the recording area of each head. This function performs the conversion to , and adjusts the recording time. Buffer memory 21
24 are added with error correction codes in error correction coders 25-28, and are sent to the main head 13, respectively.
．． 14 and sub-heads 15 and 16, the information is recorded at a predetermined position on the magnetic tape 3.

FIGS. 5(a) and 5(b) are diagrams respectively showing the pattern of recording tracks on the magnetic tape 3 and the arrangement of the main head 13, 14 and sub-head 15, 16 in the above embodiment. As shown in Figure (b), the rotating drum 64
The magnetic tape 3 is wound in Ω, and the main heads 13 and 14 and the sub heads 15° and 16 are mounted on the rotating drum 64, and the recording pattern is (
a) As shown in the figure, it has a constant center angle (30°) and is installed with a constant height difference. The feature of this embodiment is that the guard band width is half the track width of the recording pattern (10-A, 11-A, 10-B, 11-B, etc.) by the main head 13.
A recording pattern (14- The main head 13.14 and the sub-head 15.degree. 16 are arranged so that the main head 13.14 and the sub-head 15.degree.

The sub head 15.16 scans the guard band of the main head 13.14, a part of the recording pattern, and the pattern area by the radar for other controls.
Recording pattern 14-=A.

The drive of the error correction coder shown in FIG. 4 to the readout sub-head is controlled so that the audio signal is recorded only in portions such as 15-A.

Further, during playback, the sub head 15.1 is configured to read the playback signals of the original recording signals such as the recording patterns 14-A and 15-A only when playing back at the normal speed (same speed as during recording).
6, and when scanning other areas, use the sub head 15.
．． 16 output is blocked.

With the constraints of having different scanning areas and scanning on the centerline of the guard band, a distance must be provided between the respective scanning trunks of the main head 13.14 and the secondary head 15.16.

From this value, the height difference between the main and sub heads in FIG. 5(b) is determined.

Furthermore, in order to satisfy the condition that the main head 13.14 and the secondary head 15 ゜ 16 are always on the magnetic tape 3, the main head 13 ゜ 14 and the secondary head 15.
16 must be given a certain angular difference.

In addition, under the above conditions, the main head 13.14 and the sub head 15
．． If the height difference and angle difference of 16 are determined, the sub-head 15.1
6, the recording start time of the main head 13, 14, the recording time of the main head 1.3.14, and the sub head 15.
16 recording start times may not match.

However, if time continuity is required between the signals recorded on the main heads 13, 14 and the sub heads 15, 16, it is easy to achieve this using a buffer memory and there is no particular problem.

Next, a case will be described in which the magnetic recording/reproducing apparatus of the above embodiment is used to reproduce data at a speed other than the normal speed.

FIG. 6 shows a recording track pattern and a reproduction track pattern when reproducing data at twice the recording speed. In the figure, tracks ICI-A and 11-A indicated by solid lines
, 10-B, and 11-B are recording patterns by the main head 13.14, and 16-A and 17-B shown by dashed lines are reproduction patterns by the main head 13.14. 18-A, 1
9-B is 15- sub-head 14. ] 5 is shown.

For the sake of simplicity, the time difference due to the above-mentioned arrangement angles and vertical differences of the main heads 13, 14 and the sub-heads 15, 16 are ignored.

On the right side of FIG. 6, solid lines (53 to 62) indicate portions where each head (13, 15, 14.degree. 16) outputs an output signal from a single recording track. Following the signal appearing on the main head 13, at time 53, the main head I3
Since the recorded pattern 1°-A and guard band are reproduced, the reproduced signal can be used. However, after that, the main head 13 starts reproducing the three recording patterns 10-A, the guard band, and the recording pattern 11-A, and the signal becomes unusable due to crosstalk. And time 5
When the number reaches 4, the main head 13 starts scanning only the guard band and the recording pattern 11-A again, and the signal can be used. After time 54, the signal becomes unusable again due to crosstalk, and at time 55, recording pattern 1
One field ends when only 0-B is scanned and the signal becomes 16- so that it can be used.

Next, when following the signal appearing on the sub head 15, at first,
Since the scanning pattern 18-A scans the recording pattern 10-A, the guard band, and the recording pattern 11-A, the signal is unusable due to crosstalk. time 5
6, the sub head 15 can reproduce only the pattern 11-A and the guard band and use the signal. However, after time 56, the signal becomes unusable again due to crosstalk. At time 57, only the recording pattern 1o-B and the guard band are scanned, and the signal can be used.

If this is exceeded, the signal becomes unusable due to crosstalk, and the ■ field ends.

The main head 13 and sub-head 15 have been described above, but the same applies to the main head 14 and sub-head 16. FIG. 7 shows the temporal correlation of signals reproduced from these heads.

As is clear from FIG. 7, the signals of the same track are continuously transmitted diagonally upward to the right, for example, from 11 to 11 of the head 14. -A
Signal and 11-A signal of head 15 and head] 3-1.
1-A signal), and furthermore, the signal of the same track of the next field (corresponding to 11-B) continues again diagonally upward to the right from the bottom.

Therefore, although the fields are different, such as l1-A,] l-B, signals from 1 to 1000 recorded by the same main head 14 can be obtained continuously.

Generally, there is a strong correlation between pixel information between fields,
If the position on the screen is the same, there is little deterioration in image quality even if the signal is replaced with a signal from another adjacent field.
A, ] 1. - Two screens made up of B can be stitched together to form one image.

In addition, in FIGS. 6 and 7, for the purpose of simplifying the explanation, the time relationship is shown in the case where the main head 13, 14 and the sub-head 15, 16 have no angular difference or vertical difference in the rotating drum. Ta. However, in reality, as shown in FIG. 5(b), the main head 13.14 and the sub-head 15.16 are often arranged with an angular difference, and this creates a gap between the main head output and the sub-head output. It is necessary to further consider the time difference.

For example, if this angle is 30 degrees and the rotation speed of the rotating drum 64 is 60 times/second, this time difference corresponds to about 21 horizontal scanning lines, and it is necessary to synthesize signals taking this difference into consideration.

Furthermore, it is preferable that the main head 1, 3, 14 and the sub-head 15, 16 be provided with different scanning areas in order to utilize the magnetic tape 3 effectively. To achieve this, the sub head 15.
16 must be brought slightly below the main head 15.16 on the rotating drum 64.

As a result, the signal recorded by the main head 13.14 and the signal when the sub head 15.16 reproduces the signal and the main head 13.1
There will be a difference of several fields between the signals when reproduced at 4.

Returning to FIG. 4, the configuration and operation of the reproducing section will be explained.

When reproducing at the same speed as when recording (normal speed), the signal 29.30 reproduced from the main head 13.14 has the error 19- corrected by the error correction decoder 33.34, and also measures the amount of error. . Next, the channel changeover switches 39 and 40 are entered, but since there is no channel changeover phenomenon at normal speed, the switch 39 is connected to the error correction decoder 33 side, and the switch 40 is connected to the error correction decoder 34 side. Next, these signals are applied to buffer memories 44 and 45, converted into a time series corresponding to 1 channel from 2 channels, and subjected to time axis correction before entering switch 50. Either go from this switch 50 to the chroma inverter 48 (a circuit that separates the luminance component and chromaticity component and inverts the color component), or in the case of normal speed playback, there is no need to invert the chromaticity component.
If chromaticity and luminance are separated, they are added to the field memory 49 with a delay corresponding to the delay. field memory 4
In step 9, this signal is stored for one field, and if there is a signal portion that cannot be used due to dropout or the like, a signal with only the color components of the previous signal inverted one field is stored instead. After an appropriate time, the original image signal data is read out and outputted from the output terminal 51 (20-).

On the other hand, the signal 31.3 read from the sub-head 15.16
2 enters the error correction decoders 37 and 38, and then is returned to the original audio data by the time series converter 43 and output to the output terminal 52.
is output from.

Next, a configuration for realizing the operation described in FIGS. 6 and 7 will be described for the case of reproducing at a speed different from that during recording.

As explained with reference to FIG. 6, when reproduction is performed at a speed different from that during recording and reproduction, image signals also appear in the sub heads 15 and 16. This is an error correction decoder 35.36
Correct the error. On the other hand, the channels of data output from each of the four error correction decoders 33, 34, 35, and 36 are switched midway as shown in FIG.

The above channel switching control is performed by detecting noise when the playback head straddles two tracks. The code error rate in digital magnetic recording is expressed as a function of the signal-to-noise ratio (S/N), excluding burst errors due to dropouts and the like. When tracking is performed accurately, the S/N is maximum, but when tracing the guard band, the S/N deteriorates,
Bit error rate increases. Therefore, when the reproduction speed differs from the recording speed, the S/N ratio deteriorates and, therefore, the number of code errors increases periodically depending on the speed. Therefore, the system is configured to switch channels in accordance with the period so as to reduce errors. Of course, it is clear that any channel may be selected as long as there is no code error.

Channel switching as described above is done using switches 39° and 40.
4], 42, only the signal from the error correction decoder 25 is stored in the buffer memory 44, and only the signal from the error correction decoder 26 is stored in the buffer memory 45. Similarly, only the signal from the error correction decoder 25 is stored in the buffer memory 46;
7 stores only the signal from the error correction decoder 26.

These buffer memories 44 to 47 convert the two channels into a time series corresponding to one channel, and at the same time convert the signals reproduced by the main head 13.14 and the sub head 15.16.
Absorbs the time difference in the signal played back. For example, during continuous feeding, the signal from the main head side is delayed by several fields in the buffer memory 44, 45 to absorb the time difference due to the vertical difference in the head, and at the same time, the signal from the sub head side is delayed by the buffer memory 46° 47 to absorb the angle difference. do. This delay amount is approximately equivalent to 21H if the angle difference is 30 degrees as described above.

Also, when rewinding at a speed higher than a certain level, the main head 13.14
Since the time relationship between the sub heads 15 and 1.6 is reversed, the signal on the sub head side is delayed by several fields + 21H in the buffer memory 46.47.

Buffer memory 44.45°46.47
A signal with the time axes matched is sent to the switch 50. In this case, as described above, it is necessary to combine into one image signal divided into n different fields, so the chroma inverter 48 is used to maintain the continuity of subcarriers according to the field of each signal. The images are controlled and combined into one screen in the field memory 49 to obtain image signal data 30.

The chroma inverter 48 either uses a signal one horizontal scanning period before or after the corresponding signal, separates the luminance component and color component and inverts the grain phase of only the color component and remixes it, or uses a signal corresponding to half a period of the subcarrier. This can be achieved by shifting and using it.

As explained above, according to the present invention, it is possible to obtain an image signal free of noise bands no matter what speed it is played back, and moreover, the tape can be used effectively as before.

In addition, here, the main head 13.14 and the sub head 15.1
Although the embodiment has been described in which the buffer memories 44 to 47 are provided for absorbing the time difference between the reproduced signals of
6.47, it can still perform the minimum functions. In other words, it is possible to create a screen in which no noise 24-band appears. However, among the n divided screens, only the screen reproduced from the sub head corresponds to the angle difference between the main head 13.14 and the sub head 15.16 (approximately 218 in the case of 30 degrees). If the field of the spliced screen is shifted or the fields of the spliced screen are significantly different, and the image moves quickly, the secondary head 15. ] The difference between the reproduced image of 6 and the image reproduced by the main head 13 and 14, resulting in unnatural deterioration, corresponds to the omission of the angular difference absorption memory and the vertical difference absorption memory, respectively. However, if this is allowed, a reasonable image can be obtained.

In addition, in the above embodiment, an example was explained in which reproduction is possible at twice the recording speed, but the present invention is not limited to the second embodiment, but can be reproduced at twice the recording speed or more. Although the screen is a combination of divided screens of each plurality of fields, there is a correlation between the screens of each field, so there is no significant deterioration in image quality as in the case of noise bands.

〔Effect of the invention〕

As described above, in the magnetic recording and reproducing apparatus according to the present invention, the noise band of the main head can be effectively removed by the reproduction signal of the sub head, and even during reproduction at a speed different from recording, such as fast forward, slow, still, etc., the noise band can be eliminated. You can obtain high-quality images without

[Brief explanation of the drawing]

FIG. 1 is for explaining the operation of a conventional magnetic recording/reproducing device.
A diagram showing a portion of a track on a magnetic tape. FIG. 2 is a diagram showing the main part configuration of an embodiment of the magnetic recording/reproducing apparatus according to the present invention, and FIGS. 3(a) and (b) are diagrams showing the recording track and reproduction track patterns, respectively, for explaining the principle of the present invention. FIG. 4 is a diagram showing the structure of an embodiment of the magnetic recording/reproducing apparatus according to the present invention, and FIGS. 5(a) and (
b) is a diagram of a recording track on a magnetic tape and a perspective view of a recording/reproducing head in an embodiment of a magnetic recording/reproducing apparatus according to the present invention, and FIG. FIG. 7 is a time chart of the output of the reproducing head in the case of FIG. 6, which is a diagram showing the relationship between the recording track and the reproducing track on the magnetic tape and the state of the output signal thereof. 1... Recording pattern, 2... Scanning pattern, 3...
・Magnetic tape, 4-1... Main playback head, 4-2...
- Sub-reproduction head, 5... pre-processing circuit, 6... signal synthesis circuit. 7...Display device, 8...Noise band detection circuit.

Claims (1)

[Claims] 1. Record image signals on a large number of parallel tracks on a magnetic tape, and install a sub-playback head at a position separated by a certain distance in the pitch direction of the recording track from the main playback head and the scanning pattern of the main head, at least during playback. In the magnetic recording and reproducing apparatus that obtains a reproduction signal by switching the output signals of the main reproduction head and the sub-reproduction head, the position of the auxiliary reproduction head with respect to the main reproduction head is such that the pitch of the recording track is P, the width of the guard band is g, and the pitch of the recording track is P, the girth band width is It is set when the amount of shift in the pitch direction of the scanning center line of the sub-reproducing head with respect to the scanning center line of the main reproducing head is L, and the switching means for the main and sub-reproducing heads is set to A magnetic recording/reproducing apparatus characterized in that it is configured to detect a disturbance in regularity and thereby generate a switching control signal for the output signals of the main and sub-reproducing heads.