JP2550202B2 - Rotating head type playback device - Google Patents

Description

The present invention relates to a rotary head type reproducing apparatus suitable for application to, for example, a rotary head type video tape recorder, a PCM tape recorder or the like.

[Outline of Invention]

The present invention relates to a rotary head type reproducing apparatus suitable for application to, for example, a rotary head type video tape recorder, a PCM tape recorder, etc., in which a block is formed for each digital information signal of a predetermined length, and an address signal is added to each block. ,
Arranged so that a predetermined number of blocks are alternately recorded at different azimuth angles so that scanning is doubled, and that the tracks have different azimuth angles and the traveling loci coincide with the recording tracks. A pair of reproducing rotary heads are provided, and one of the pair of reproducing rotary heads also serves as a recording rotary head, and the other reproducing rotary head is the other recording rotary head of the recording rotary head. It is the same as the azimuth angle of, and the scanning loci on this recording track are separated by (N + 1/2) track pitch (N is an integer), and is also one of the pair of recording rotary heads and also serves as the reproducing rotary head. A recording rotary head for recording and a rotary rotary head for reproduction of the other, and a storage means for writing the reproduced digital information signal in accordance with the reproduced address signal, Since the digital information signals written in the storage means are serialized by reading them in a predetermined order, the information signals recorded at high density can be reproduced without tracking with high accuracy. It is a thing.

[Problems to be Solved by Prior Art and Invention]

A VTR (Video Tape Recorder) is well known as a rotary head reproducing apparatus. In the conventional VTR, the track width is set to several tens of μm or less for high density recording, the control signal recorded in the longitudinal direction of the side edge of the magnetic tape is reproduced together with the recording signal, and rotation is performed by this control signal. By controlling the rotation of the head and the capstan, tracking servo is applied so that the scanning locus of the head at the time of reproduction matches the recording track. Also,
In a high-end VTR, the rotary head can be moved not only by the control signal but by a piezoelectric element, and the envelope of the reproduced signal obtained by wobbling the rotary head changes, or different frequencies between several recording tracks. By the crosstalk component of the pilot signal
The rotating head is moved to ensure correct tracking.

Further, as a premise for performing regular tracking, it is necessary that the tape traveling path including the tape guide drum has high mechanical accuracy and that the tape guide drum has high hardness.

These high-precision tracking servos, high work precision, and the like are factors that hinder the cost reduction of the rotary head type reproducing apparatus.

An object of the present invention is to realize a rotary head type reproducing apparatus that does not require any of high-precision machining, high-hardness cylinder, high-precision servo and the like required for tracking.

[Means for solving the problem]

The rotary head type reproducing apparatus of the present invention, for example, forms a block for each digital information signal of a predetermined length as shown in FIG. 1, an address signal is added to each block, and a predetermined number of blocks are alternately recorded at different azimuth angles. _A pair of reproducing rotations having different azimuth angles and arranged so that the traveling loci coincide with the recording tracks so that the recorded recording tracks T _A and T _B are doubled in scanning. head H _a, 'with provision of this pair of reproducing rotary heads H _a, H _B' H _B one H _a of also combined recording rotary head, the rotary head H _B for the other playback 'is recorded Rotary heads H _A , H _B
This recording rotary head H _{B has} the same azimuth angle as that of the other recording rotary head H _{B and} the scanning loci on this recording track are separated by (N + 1/2) track pitch (N is an integer). Recording rotary head H _A which is one of _A and H _B and also serves as a playback rotary head, and this playback rotary head
A storage means (21) in which the reproduced digital information signal is written according to the reproduced address signal is provided by H _B ′, and the digital information signals written in the storage means (21) are read out in a predetermined order for continuous operation. It was designed to be transformed.

[Action]

According to the present invention, recording tracks T _A and T _B in which a predetermined number of blocks are alternately recorded at different azimuth angles are used.
The rotary heads H _A and H _B ′ having different azimuth angles so that the scanning is doubled, and the reproduced information is written in the memory (21) according to the reproduced address signal. Since the digital information signals written in the memory (21) are read out in a predetermined order, they can be reproduced without taking highly accurate tracking.

〔Example〕

An embodiment of the rotary head type reproducing apparatus of the present invention will be described below with reference to the drawings. This example is an example applied to a rotary head type PCM tape recorder.

FIG. 2 shows the rotary head device in this example. In FIG. 2, (2) shows a tape guide drum, the size of which is, for example, 30 mm to 40 mm in diameter. On this tape guide drum (2), the magnetic tape (1) is run obliquely along an angular range of, for example, 180 °. Further, H _A , H _B and H _B ′ are rotary magnetic heads, respectively. The magnetic heads H _A and H _B are used at the time of recording, and are attached with a sufficiently small angular interval θ _{1 with} respect to the rotation direction x, for example, 1 °, and the magnetic head H _A precedes. Further, the azimuth angles (the tilt angles of the gap with respect to the direction perpendicular to the scanning direction) of the magnetic heads H _A and H _B are made different from each other. Further, the magnetic heads H _A and H _B are arranged so that the scanning loci on the magnetic tape (1) coincide with each other. For example, the magnetic head H _A Only the magnetic head H _B is made lower in the rotation axis direction.
The magnetic heads H _A and H _B ′ are used during reproduction and are attached with an angular interval θ _{2 with} respect to the rotation direction x. In this example, θ ₂ = 180 °. Azimuth angle of the magnetic head H _B 'is like the azimuth angle of the magnetic head H _B.
The magnetic heads H _A and H _B ′ are magnetic tapes (1).
The scanning trace on the (N is an integer). That is, when the recording track pitch is T _P and the angular interval of the corresponding magnetic head is θ _T , the magnetic heads H _A and H _B ′ are relative to the rotation axis direction. It can be attached by shifting it. In this example, N =-
1, θ _T = 360 °, θ ₂ = 180 °, and T _P = 0 is attached. It is made to shift only. In addition, the magnetic heads H _A , H _B and
H _B ′ holds the above-mentioned positional relationship and is x rotation at, for example, 60 rotations / second.
Can be rotated in the direction.

During recording, every time the magnetic heads H _A and H _B scans the magnetic tape (1) above with one rotation, together with the recording signal S _REC is supplied sequentially alternately, the recording signal S _REC to the magnetic head H _A When supplied, the erasing signal S _ELASE is supplied to the magnetic head H _A.

In FIG. 1, an analog signal, for example, an audio signal is supplied to an input terminal (3), and this audio signal is converted into an audio PCM signal by an AD converter (4), which is supplied to an encoder (5). To be done. In this encoder (5), a sync signal, an error correction code,
The error detection code is added and the time axis is compressed. FIG. 3 shows the code structure of the recording data obtained at the output of the encoder (5). A sync signal, a block address signal, and a CRC code for error detection are added to the data consisting of a plurality of samples of audio PCM signals or error correction codes. A parity code, an adjacent code, or the like can be used as the error correction code, and interleaving may be used together. The block address signal is for individually distinguishing blocks in a series of reproduction data input to the memory of TBC (time base collector) as described later,
It is possible to use a simple incremental code signal, a combination of a plurality of types of addresses, and the like. The CRC code is
The presence or absence of errors in both the block address signal and the data is detected. Then, the output of this encoder (5) is supplied to the modulator (6), and NRZI, 3P
It is modulated by a modulation method such as M or MFM. A recording signal existing on the output side of the modulator (6) corresponding to a 180 ° range in which the magnetic heads H _A and H _B scan the magnetic tape (1) as shown in FIG. 4A. S _REC is obtained. This recording signal S
_REC is supplied to the B side terminal of the changeover switch (7) and the A side terminal of the changeover switch (8). Further, (9) is an oscillator for generating the erasing signal S _ELASE . For example, a signal having a frequency twice or more the highest frequency of the recording signal S _REC is generated as the erasing signal S _ELASE . The level of the erasing signal S _ELASE is, for example, 1.2 to 3 times the level of the recording signal S _REC . This erasing signal S _ELASE is A of the changeover switch (7).
Is supplied to the terminal on the side. The terminal on the B side of the changeover switch (8) is grounded. A changeover control signal S _C as shown in FIG. 4B is supplied to the changeover switches (7) and (8), and these changeover switches (7) and (8) are interlocked and changed over. That is, when the control signal S _C is at the high level “1”, it is switched to the A side respectively, and when the control signal S _C is at the constant level “0”, it is switched to the B side respectively.
Switched to the side.

As shown in FIG. 4D, only the recording signal S _REC is obtained from the changeover switch (8), which is a recording amplifier (10), a recording side terminal R of the recording / reproducing switch (11) and a rotary transformer (not shown). ) To the magnetic head H _B. Further, as shown in FIG. 4C, the recording signal S _REC and the erasing signal S _ELASE are alternately obtained from the changeover switch (7), and these are the recording side terminals of the recording amplifier (12) and the recording / reproducing switch (13). And to the magnetic head H _A through a rotary transformer (not shown). The erasing signal S _ELASE from the changeover switch (7) is obtained at the same timing as the recording signal S _REC obtained from the changeover switch (8).

In this way, at the time of recording, the magnetic heads H _A and H _B have the recording signal S for each 180 ° angular range for scanning the magnetic tape (1).
Since _REC is supplied sequentially alternately, on the magnetic tape (1) is due to the recording tracks T _A and T _B are sequentially formed magnetic head H _A and H _B as shown in Figure 5. And in this case, when the scanning locus of the magnetic head H _B is the same rot and the scanning locus of the magnetic head H _A, yet the recording signal S _REC to the magnetic head H _B is supplied, the signal S _ELASE erase the magnetic head H _A Is supplied, the magnetic head H _A erases, for example, the previously formed recording track T _O before the recording track T _B is formed by the magnetic head H _B.

On the magnetic tape (1) on which the recording tracks T _A and T _B are alternately formed, the magnetic heads H _A and H _B ′ are arranged as described above during reproduction. Scan with a shift. Since the magnetic heads H _A and H _B ′ are mounted with an angular interval of 180 ° in this example, the magnetic heads H _A and H _B ′ are shown in FIGS.
As shown in, the reproduction signal S _PB is obtained for each angular range of 180 °.

The reproduction signal S _PB from the magnetic head H _A is a rotary transformer (not shown), the reproduction side terminal P of the recording / reproducing switch (13),
It is supplied to the detector (15A) through the reproduction amplifier (14A). The detector (15A) shapes the reproduction signal _SPB into a pulse signal. The output of the detector (15A) is supplied to the clock extraction circuit (16A), and the clock pulse synchronized with the reproduction data is extracted. The output of this clock extraction circuit (16A) is supplied to the demodulation circuit (17A),
Reproduced data having the same code structure as the recorded data is obtained.

This reproduced data is sent to the delay circuit (18A) and the sync separation circuit (1
9A) and CRC checker (20A). The CRC checker (20A) uses a sync signal to check whether or not there is an error in each block of the reproduction data and block address signal.
This is detected by a code, and an error flag indicating the presence / absence of an error is generated for each block in the output, and this is supplied to the TBC (21). The error flag is, for example, "1" when it is detected that there is an error and "0" when it is detected that there is no error. The delay circuit (18A) delays the reproduction data and the block address signal by the time required for error detection by the CRC checker (20A). The delayed reproduction data and block address signal are supplied to the TBC (21).

The reproduction signal S _PB from the magnetic head H _B ′ is passed through a rotary transformer (not shown), the reproducing side terminal P of the recording / reproducing switch (22) and the reproducing amplifier (14 B ′) to a detector (15 B).
B '). Detector (15B '), clock extraction circuit (16B'), demodulation circuit (17B '), delay circuit (18
B '), sync separation circuit (19B'), CRC checker (20B ')
Is the detector (15A) and clock extraction circuit (16
A), a demodulation circuit (17A), a delay circuit (18A), a sync separation circuit (19A), and a CRC checker (20A).
Therefore, an error flag is generated in the CRC checker (20B ') and this is supplied to the TBC (21). Also, the reproduction data and the block address signal delayed by the delay circuit (18B ') are supplied to the TBC (21).

The TBC (21) is composed of a memory (RAM) and its peripheral circuits. Basically, the reproduction data is written by the clock synchronized with the reproduction data, and the reference clock from the timing generation circuit (23) is used by the memory. It is configured to read the data and remove the time axis variation. The writing of the TBC (21) to the memory is performed using the address by the block address signal, and the writing of the data determined to have an error by the error flag is prohibited. As described above, the error flag indicates not only the data but also the presence / absence of an error in the block address signal. Therefore, when there is an error, it is necessary to prohibit the writing in order to prevent writing to an incorrect address. To be If writing is prohibited, the previously written data remains at the corresponding address. To prevent this from being read as correct data, the data at that address must be error data. Write an error flag that indicates. This error flag is written immediately after reading the correct data. TBC (2
The reading of the memory in 1) is sequentially performed in a predetermined order, and a data series and an error flag indicating the presence or absence of an error for each block are obtained at the output and are supplied to the decoder (24). It

The decoder (24) corrects the data determined to have an error with an error correction code, and corrects the uncorrectable data by interpolating data. The interpolation data is, for example, an average value of correct data located before and after. The output data from the decoder (24) is supplied to the D / A converter (25), and the audio signal is taken out to the output terminal (26).

In the above-described present example, the magnetic heads H _A and H _B ′ that obtain the reproduction signal S _PB at the time of reproduction are set on the magnetic tape (1). Since it is designed to scan with a deviation, the error rate during playback is averaged, and the S / N of the playback audio signal is averaged.
Can be prevented from being significantly deteriorated locally. That is, when the magnetic heads H _A and H _B ′ have the relationship shown in FIG. 7A with respect to the recording track pattern on the magnetic tape (1), the magnetic head H _A accurately scans the recording track T _A. Therefore, the error rate of the reproduction signal S _PB reproduced from the recording track T _A becomes good. On the other hand, since the magnetic head H _B ′ scans the middle of the recording tracks T _A and T _B , the level of the reproduction signal S _PB reproduced from the recording track T _B is lowered and the error rate is deteriorated. . However, the sum of these error rates does not deteriorate so much, and the S / N of the reproduced audio signal does not deteriorate so much. Similarly, when the relationship is as shown in FIG. 7B, the S / N of the reproduced audio signal does not deteriorate so much.
Therefore, according to this example, the error rates during reproduction are averaged, and it is possible to prevent the S / N of the reproduced audio signal from locally significantly deteriorating. Therefore, according to the present invention, since the tracking in which the head scans with the recording track on a one-to-one basis is not required at all, it is not necessary to perform highly accurate tracking servo, and the mechanical accuracy is released. That is, firstly, since it is not necessary to define the phase relationship between the recording track and the reproduction scanning locus, high-precision phase servo becomes unnecessary, and secondly, the inclination of the recording track and the inclination of the reproduction scanning locus. Does not have to coincide with each other, so that the accuracy of the tape path may be low. Thirdly, the recording track or the reproduction scanning locus may meander. Therefore, the accuracy of the tape path may be low. When the magnetic tape is wound around the guide drum, it is not necessary to apply lateral pressure to the magnetic tape to regulate the position of the tape edge on one side, so the sliding contact state between the rotary head and the magnetic tape can be made stable. it can.
For these reasons, the tape guide drum can be formed of molded plastic, and the rotary head type reproducing device can be manufactured easily and inexpensively.

In addition, in the above-mentioned embodiment, the example in which the angular interval θ _T corresponding to the track pitch T _P is 360 ° has been described.
The same configuration can be applied even in the case of 0 °. In this case, The mounting position of the reproducing magnetic head may be determined by changing θ _T in the equation.

〔The invention's effect〕

As described above, according to the present invention, there is an advantage that a high-density recorded resignation signal can be reproduced without performing highly accurate tracking.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a rotary head type reproducing apparatus of the present invention, FIG. 2 is a block diagram showing an example of a rotary head device, and FIGS. 3 to 7 are diagrams for explaining the respective cases. is there. (1) is a magnetic tape, (2) is a tape guide drum, (2
1) is TBC, (23) is a timing generation circuit, (26) is an output terminal, and H _A , H _B and H _B ′ are rotary magnetic heads, respectively.

Claims (1)

(57) [Claims] 1. A recording track in which a block is formed for each digital information signal of a predetermined length, an address signal is added to each block, and a predetermined number of blocks are alternately recorded at different azimuth angles, twice as much. So that the scanning of
A pair of reproducing rotary heads each having a different azimuth angle and arranged so that the traveling loci coincide with the recording tracks are provided, and one of the pair of reproducing rotary heads also serves as a recording rotary head. However, the other reproducing rotary head has the same azimuth angle as the other recording rotary head of the recording rotary head, and the scanning loci on the recording track are separated by (N + 1/2) track pitch (N is an integer). Provided, the reproduced digital information signal is written according to the reproduced address signal by the recording rotary head which is one of the pair of recording rotary heads and also serves as the reproducing rotary head and the other reproducing rotary head. A storage means is provided, and the digital information signals written in the storage means are read out in a predetermined order so as to be continuous. Rotary head type reproducing apparatus.