JPS61217953A - Helical scan magnetic recording/reproducing device - Google Patents

Abstract

PURPOSE:To run a magnetic tape at a constant high speed, and also to simplify a detecting circuit by transferring the magnetic tape at a high speed in a state that it has been wound around a rotary drum, detecting a variation of an envelope of an RF signal and its level, and controlling the transfer speed of the magnetic tape so that a frequency of the level variation becomes constant. CONSTITUTION:At the time of retrieval, when a user designates a position to be retrieved, a setting circuit 11 outputs a signal corresponding to a prescribed value to a comparing circuit 10, and the comparing circuit 10 outputs an error signal of a signal from a counter 9 and a signal from the setting circuit 11. This error signal is converted to an analog signal by a D/A converting circuit 12, and supplied to a driving circuit 14 through a sample and hold circuit 13. As a result, a reel motor 5 is drive by the driving circuit 14, and in accordance with the retrieval direction, a supply reel 3 or a take-up reel 4 is rotated through an idler 6. Accordingly, a magnetic tape 2 is traversed quickly or rewound in a state that it remains wound by 90 deg. around a rotary drum 1.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a helical scan magnetic field that records and reproduces information on inclined tracks on a magnetic tape wound at a predetermined angle around a rotating drum having at least two rotating magnetic heads. The present invention relates to a recording/reproducing device.

[Summary of the invention]

The present invention provides a helical scan magnetic recording and reproducing device.
The magnetic tape is transported at high speed while being wound around a rotating drum, the RF multiplied signal envelope is detected from the playback signal of the rotating magnetic head, the change in the level of the envelope corresponding to the number of tracks is detected, and the level change is detected. The magnetic tape transport speed is controlled so that the frequency remains constant.

[Conventional technology]

In a helical scan magnetic recording and reproducing device, such as a video tape recorder, in order to search for a desired program from multiple recorded programs, a system that corresponds to the non-information portion (between songs) between each program is used. An index signal or cue signal for cueing is recorded at the position.

Such signals are generally recorded and reproduced by a fixed magnetic head on a cue track or the like parallel to the running direction of the magnetic tape. Another method is to record an address signal at a predetermined position on a track on which a video signal is recorded that is inclined with respect to the running direction of the magnetic tape, and to search for the predetermined position by reading out this address signal.

The magnetic tape on which such cue signals are recorded is transported at a speed faster than the normal recording and reproducing speed during retrieval. To achieve such high-speed transfer, simply rotating the supply reel or pick-up reel at a predetermined rotational speed,
The speed of the magnetic tape changes depending on the winding radius of the reel. Therefore, the frequency of the cue signal changes significantly, making its detection difficult. Therefore, the rotational speed of the supply reel and the pick-up reel is detected, and the rotation of each reel is controlled based on the difference in rotational speed so that the running speed of the magnetic tape is constant, and the capstan is moved at a constant speed. A method is used in which the magnetic tape is transferred at high speed while being rotated and pressed against it by a capstan and a pinch roller.

[Problem that the invention seeks to solve]

However, the method of detecting the rotational speed of the supply reel and pick-up reel has the disadvantage that it is not affected by the thickness of the magnetic tape, and it is difficult to use magnetic tapes from different manufacturers or from the same manufacturer. However, if there is variation, accurate speed control becomes difficult. In addition, the method of transport using capstans and pinch rollers can only transport at a speed that is at most ten times the speed during recording and playback (for example, it is almost impossible to transport at a speed of about 200 times). ), so there was a drawback that it took a long time to search.

[Means for solving problems]

FIG. 1 shows the R-DAT, which records and reproduces digital audio signals on a magnetic tape using a rotating magnetic head.
(Rotary head Digital
FIG. 2 is a block diagram when applied to Audio Taperecorciθr). In the same figure, reference numeral 1 is a rotating drum, which is spaced 180 degrees apart from each other and is different (for example, ±2
Two rotating magnetic heads A, B with azimuth (0 degrees)
have.

2 is a magnetic tape, for example 9 to the rotating drum 1.
It is wound 0 degrees. 3.4 is a supply reel and a pick-up reel for supplying, winding, and taking out the magnetic tape 2. A reel motor 5 rotates the reel 3 or 4 via an idler 6.

7 is an equalizer amplifier circuit, which connects rotating magnetic heads A and B.
equalizes and amplifies the playback signal output from the 8
is a detection circuit that detects the RF multiplied signal envelope output from the amplifier circuit 7. 9 is a counter for counting the output of the detection circuit 8, and 10 is a comparison circuit, which compares the output of the counter 9 and the output from the setting circuit 11. 12 is D/
The A conversion circuit converts the digital signal output from the comparison circuit 10 into an analog signal. 13 is a sample hold circuit that samples and holds the output of the D/A conversion circuit 12, and 14 is a drive circuit that drives the reel motor 5.

[Effect]

The effect will now be explained. When recording digital audio signals, the rotary drum 1 is rotated at a speed of, for example, 200 rpm by a motor (not shown), and the magnetic tape 2 is rotated at a speed of, for example, 7.2 (or 9°0) ma+/ by a capstan and a pinch roller (not shown). The zero-rotation magnetic heads A and B, which run at a speed of s, are alternately switched by switching pulses, and as shown in FIG. An angularly inclined track is formed on which a digital audio signal is recorded.

On the other hand, during a search, when the user specifies a position to be searched, the setting circuit 11 outputs a signal corresponding to a predetermined value to the comparison circuit 10. Comparison circuit 10 outputs an error signal between the signal from counter 9 and the signal from setting circuit 11.

This error signal is converted into an analog signal by the D/A conversion circuit 12 and supplied to the drive circuit 14 via the sample hold circuit 13. As a result, the reel motor 5 is driven by the drive circuit 14, and the supply reel 3 or the pick-up reel 4 is rotated via the idler 6 in accordance with the search direction. Therefore, the magnetic tape 2 is fast-forwarded or rewound while being wound around the rotating drum 1 at 90 degrees.

If the speed of the magnetic tape 2 during fast forwarding or rewinding is n times (for example, 200 times) the speed during recording and reproducing, then the second
As shown in the figure, the magnetic heads A and B cross one turn of n/2 tracks in one trace.

Since the magnetic tape 2 is wound only 90 degrees around the rotating drum 1, one rotating magnetic head A (B
) traces n/2 tracks, then the next 9
The n/2 tracks of the 0 degree rotation will not be traced by any of the rotating magnetic heads, and furthermore, during the next 90 degree rotation, the rotating magnetic head B (A) will be n/2 tracks.
/ Two tracks are traced, and the next n/2 tracks of the 90 degree rotation are not traced by any of the rotating magnetic heads, and so on. Also, the rotating magnetic head A (B) traces n/
Of the two tracks, every other n/4 track has the same azimuth. Therefore, rotating magnetic heads A and B
The RF multiplied signal outputted from the RF signal is as shown in FIG. 3 (,). That is, every time the rotary drum 1 rotates 90 degrees, a portion where the RF multiplied signal appears and a portion where it does not appear alternately. In the portion where the RF multiplied signal appears, the level reaches a peak every other track.

After being amplified by the RF double signal equalizer amplification circuit 7, its envelope is detected by the detection circuit 8. The envelope is sliced at a predetermined level, and the counter 9 counts, for example, the number of level changes (the number of peaks) above the predetermined level. counter 9 is 1
Figure 3 (b), which alternately switches between rotating magnetic heads A and B.
It is reset at the falling and rising edges of the head switching pulse as shown in FIG. Therefore, the count value of the counter 9 immediately before being reset is 1 when the magnetic head A or B rotates once.
1/4 of the number of tracks crossed while rotating 80 degrees (90
The value corresponds to 1/2 of the number of tracks crossed during one degree of rotation. Therefore, if the running speed of the magnetic tape 2 is multiplied by n during recording and reproducing, it becomes n / 41. For example, when recording and reproducing When running at high speed 200 times faster, n/4
Since the value of is 50, the value 50 is input from the setting circuit 11 to the comparison circuit 10 as a reference value. As a result, the comparison circuit 10 outputs an error signal between the count value of the counter 9 and the reference value of value 5o, and this error signal is converted into an analog signal by the D/A conversion circuit 12 and then sent to the sample hold circuit 13.
is input. The sample and hold circuit 13 samples the signal from the D/A converter circuit 12 at the time of the rise or fall of the head switching pulse, and holds the value until the next fall or rise (time of next sampling). Therefore, the signal output from the sample and hold circuit 13 is an analog signal corresponding to the error signal between the value of the counter 9 immediately before being reset and the reference value, and this signal is supplied to the reel motor 5 via the drive circuit 14. Ru. As a result, the magnetic tape 2 runs at a constant speed such that the multiplier (n) for the speed during recording and reproduction is four times the value output by the setting circuit 11. This means that the servo is applied so that the frequency of the RF multiplied signal envelope is constant. Therefore, for example, the output of the detection circuit 8 may be frequency-voltage converted, the output voltage may be compared with a predetermined reference potential, and the error signal may be input to the sample-and-hold circuit 13.

If the speed at the time of search is constant in this way, R-D
When a time code indicating the time from the beginning of the program or the magnetic tape is recorded on each track, such as in AT, if the time code of the search position is known, the time of the search position and the current position is recorded. By calculating the difference in real time from the code and running the magnetic tape for a time corresponding to the calculated value, it is possible to access the search position without reading the time code along the way.

Furthermore, when reading a time code or the like, since the running speed can be kept constant, the PLL circuit or the like required for reading the code and extracting the lock from the reproduced signal can be of a simple configuration.

〔effect〕

As described above, in the present invention, the magnetic tape is transported at high speed while being wound around a rotating drum, the RF multiplied signal envelope is detected from the reproduction signal of the rotating magnetic head, and the level of the envelope changes in accordance with the number of tracks. Since the magnetic tape is detected and the transport speed of the magnetic tape is controlled so that the frequency of the level change is constant, it is possible to run the magnetic tape at a constant speed without being affected by the thickness of the magnetic tape. Since the reproducing frequency of the cueing signal is also constant, the detection circuit can also be of a simple configuration.

[Brief explanation of the drawing]

FIG. 1 is a block diagram when the present invention is applied to an R-DAT, FIG. 2 is a schematic plan view of its track pattern, and FIG. 3 is a waveform diagram of its RF multiplied signal head switching pulse. 1... Rotating drum 2... Magnetic tape 3... Supply reel 4... Tick-up reel 5... Reel motor 6... Idler 8... Detection circuit 9... Counter 10...・Comparison circuit 1
1... Setting circuit 12... D/A conversion circuit 13... Sample hold circuit or higher

Claims (1)

[Scope of Claim] A helical scan magnetic recording and reproducing device for reproducing information recorded on inclined tracks on a magnetic tape wound at a predetermined angle around a rotating drum having at least two rotating magnetic heads of different azimuths, comprising: transporting the magnetic tape at high speed while wound around a rotating drum, detecting an envelope of an RF signal from a reproduction signal of the rotating magnetic head, and detecting a change in the level of the envelope corresponding to the number of tracks; A helical scan magnetic recording/reproducing apparatus characterized in that the transport speed of the magnetic tape is controlled so that the frequency of the level change is constant.