JPH0315266B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic tape reproducing device, which enables reliable and accurate tape position retrieval, for example, by reproducing a magnetic tape on which at least an address code and a clock pattern are recorded together with main information signals. The purpose of the present invention is to provide a playback device that can perform the following.

Generally, magnetic tapes used in audio tape recorders, VTRs, and other magnetic recording and reproducing devices have a magnetic layer formed on only one side, and this side (hereinafter referred to as the "surface") is used for magnetic recording and recording.
Regeneration takes place. However, the back side of a magnetic tape has only been subjected to physical and chemical treatments, for example, simply to improve the running properties of the tape, and has hardly been used effectively.

In view of the above points, the present invention has been designed to dramatically expand the scope of use, and one embodiment thereof will be described below with reference to the drawings.

FIG. 1 shows a track pattern of an example of a magnetic tape to be reproduced by a magnetic tape reproducing apparatus according to the present invention. In the figure, T ₁ to _{T 6} indicate six tracks formed on the back surface of the magnetic tape 101 along the longitudinal direction of the tape. These trucks
In each of T ₁ to _{T 6} , the shaded area is a recorded part corresponding to "0", that is, low level, and the white part is recorded part corresponding to "1", that is, high level. For example, when detecting optically, The shaded areas are colored black and the white areas are colored white. Track at the top end of the magnetic tape 101
If the repetition frequency of white and black of T ₁ is F, that of tracks T ₂ , T ₃ and T ₄ is 1/2F and 1/4
The colors are arranged to be F and 1/8F.

Track _T5 is a track in which a 14-bit binary pulse code is recorded in chronological order as an address code, and track _T6 is a track in which a clock pattern is used to obtain the pulse that is the reference for reading out the address code of track _T5 . recorded. truck
The address code of _T5 is 4 of the above tracks _T1 to _T4 .
Absolute addresses can be displayed in combination with bit-based address representation from 1 to 15, and as shown in Figure 1, the range of absolute addresses 0 to 15 is _l0 , and the range of absolute addresses 16 to 31 is l ₁ , and then the range of every 16 addresses in sequence
If l ₂ , l ₃ , . . _. represent l ₀ , l ₁ , l ₂ , l ₃ , .
Also, the clock pattern of track T ₆ is 1 word.
It is 16 bits, and a wide white color 102a, 102b, 102c, . . . is arranged at the beginning of each word.

Next, to explain the apparatus of the present invention for reproducing the magnetic tape 101, FIG. 2 shows a circuit diagram of an embodiment of the apparatus of the present invention. In the same figure, 103,1
Reference numerals 04, 105, 106, 107 and 108 are photodetectors each consisting of a light source 120 and a light receiving element 121 as shown in FIG. Photodetector 10
3 is for reproducing track _T5 shown in FIG. 1, and photodetector 104 is for reproducing track _T6 . Tracks T ₁ , T ₂ , T ₃ and T ₄ are also reproduced by photodetectors 105, 106, 107 and 108, respectively. In FIG. 3, light emitted from a light source 120 is irradiated onto one side 119 of the magnetic tape 101 and reflected there, and the reflected light is transmitted to a light receiving element 121.
The light is received and photoelectrically converted. This light receiving element 1
21, the intensity of reflected light from the shaded area (black) shown in Figure 1 is extremely low, and the intensity of reflected light from the white background area (white) is extremely high, so the electric signal is at a low level when reproducing the shaded area. , it is clear that the level is high when the white background area is reproduced.

The photodetector 104 detects the track shown in FIG.
The T ₆ clock pattern is detected optically.
Since the magnetic tape 101 is made to run from left to right in FIG. 1 during reproduction, the signal taken out from the photodetector 104 is as shown by a in FIG. 4A. Here, in FIG. 4A, a ₀ is a wide white color 102a (or 102b,
102c...), a ₁ , a ₂ ,
..., a ₁₄ respectively indicate the signal portions reproduced from the following 14 narrow white portions. This time-series digital signal a is transmitted to an integrating circuit 109 and a waveform shaping circuit 1.
11, only the wide signal portion _a0 is extracted as the signal b. In addition, the time series digital signal a is passed through a 1/14 frequency divider (which can be configured with a counter) 110.
The frequency is divided by 1/14 and applied to the inverter 112, while it is applied to one input terminal of the 2-input AND circuit 113.

Since the 1/14 frequency divider 110 is configured to be reset at the falling edge of the signal b, it counts the signal portions _a1 to _a14 , and the output signal level is inverted when _a14 is counted. . Therefore, inverter 112
The output signal waveform is as shown by c in FIG. 4C, and this signal c is applied to the other input terminal of the AND circuit 113. As a result, AND circuit 11
3, a narrow pulse train a ₁ to a ₁₄ is sequentially output in time series, and this pulse train is applied to the 14-bit shift register 114 as a clock pulse (shift pulse).

The shift register 114 is reset at the fall of the signal b, and the photodetector 103 is connected to the input terminal.
The reproduced signal of the track _T5 detected and reproduced is applied, and this is serial-parallel converted. The output terminals D ₁ , D ₂ , D ₃ , . . . , D ₁₄ of the shift register 114 have values obtained by sampling the reproduction signal of the track T ₅ using the pulse trains a ₁ , a ₂ , a ₃ , . . . , a ₁₄ respectively. Signals are obtained, and these are captured by the next stage 14-bit latch 115 at the rising edge of the signal b,
and retained. The 14-bit binary output of the 14-bit latch 115 (sample and hold output based on the pulse train a ₁ to a ₁₄ of the reproduced signal of track T ₅ ) is as follows.
Tracks T ₁ to _{T 4} from photodetectors 105 to 108
It is applied together with the reproduced signal to an 18-bit binary-to-decimal conversion circuit 116, where it is converted into a decimal number. The output signal of the binary-decimal conversion circuit 116 is sent to a 6-digit display (for example, composed of a light emitting diode) 1 via a known decoder and driver 117.
18 and displayed.

The value displayed on the six-digit display 118 represents the absolute address at the time of reproduction. For example, if a destination address is specified for cueing, etc., the track is initially run at high speed in the forward or reverse direction.
Check the target address range from the address code of T ₅ ,
When the target address range is detected, the tape running speed is reduced to the normal standard speed and the target tape position can be searched from the absolute addresses displayed on tracks _T1 to _T4 . In this case, since the absolute address is recorded on the magnetic tape itself, there is no load on the tape running system, such as a tape counter driven by the rotational force transmitted from the rotating reel via the belt. Position retrieval can be performed extremely accurately without worsening wow and flutter, and without accumulating position retrieval errors unlike tape counters.

Next, we will explain the operation when reproducing a video track recorded on a magnetic tape used in a general home VTR as a control signal to enable the head to accurately track the video track during reproduction. In this case, any track T _o out of tracks T ₁ to _{T 4} on which a single frequency digital signal is recorded is played during standard speed mode playback and output as a control signal to the conventional drum servo circuit. do. In this case, since the control track can be removed, the utilization efficiency of the video track recording side surface can be improved. Also, the track T _o+i is (i+
1) During double speed mode reproduction, track _Toi can be used as a control signal recording track during 1/i+1 double speed mode reproduction.

In addition, if there is unevenness in the running speed of the magnetic tape on tracks _T1 to _T6 , the repetition frequency of these playback signals will vary accordingly, so a predetermined playback signal (for example, about 120 Hz) must be sourced from a stable frequency source. It is also possible to remove unevenness in the tape running speed by comparing the phase with the signal and controlling a tape feeding device such as a capstan using the phase error signal. In this embodiment, the photodetector 1
One of the output signals 03 to 108 can be branched and used for such purposes.

By the way, in the above embodiment, the track pattern shown in FIG. 1 is formed on the back side of the magnetic tape, but it may be formed on the front side.
However, when forming tracks on the front side of the magnetic tape, the track width of each track becomes narrower than when forming tracks on the back side, so for example, as shown in Fig. 5, only tracks _T5 and _T6 are formed on the front side. Good too. In FIG. 5, 124 is an audio track recorded on the surface of the magnetic tape 122, 123 is a video track, and T ₅ and T ₆ are address code records similar to tracks T ₅ and T ₆ shown in FIG. Among the tracks and clock pattern recording tracks, at least tracks 123 and 124 are recorded by a rotating head helical scan VTR, and all tracks are reproduced by this VTR. In this case, the track T ₅ ,
The coercive force of the magnetic layer in the T ₆ forming area is selected to be high compared to that of other magnetic layers on the tape surface to prevent erasure by the full width erase head.

Note that only one photodetector is shown in FIG.
A mechanism that can shift this in the width direction of the magnetic tape may also be used. Also, the tracks shown in Figures 1 and 5
In addition to the optical white and black color pattern, methods for forming T ₁ to _{T 5} include magnetic methods, mechanical methods (e.g., unevenness using Culver film, and formation of intermittent pit rows such as those used in optical video discs). etc.), electrostatic methods (formation with or without polarization of electrets, etc.), electrical resistance methods (evaporation of metals, plastic films based on conductivity distribution, etc.), etc. can also be applied. . Since these are all known techniques, detailed explanation thereof will be omitted. Furthermore, a 3-value, 4-value, or other digital signal may be recorded on each track.

Furthermore, only a plurality of digital signal recording tracks having a single repetition frequency, such as tracks _T1 to _T4 , may be provided.

As described above, in addition to the main information signal recording track formed on the front surface, the magnetic tape reproducing device of the present invention has a first recording track on which a predetermined repetition frequency is recorded as an optical pattern printed on the back surface on which no magnetic layer is formed. , a second track in which the frequency obtained by dividing the repetition frequency is recorded as an optical pattern, and the optical patterns recorded in the first and second tracks to determine the absolute address. A magnetic tape having a third track on which a displayable address code is recorded as an optical pattern, and a fourth track on which a clock pattern for obtaining a reference pulse for reading out the address code is recorded as an optical pattern. Since the reproduction signal obtained by optically reproducing the first to fourth tracks is used to control the reproduction device, the range of use of magnetic tape can be dramatically expanded. In addition, even if the magnetic tape is wound and stored, the optical pattern will not be transferred to the front surface, and higher quality signal reproduction can be performed compared to the case where identification signals are recorded on the magnetic layer on the back side. When used for tape position search control, it is possible to perform accurate position searches without accumulating errors compared to those using conventional tape counters, and in this case, it does not place a load on the tape running system. It is possible to perform magnetic tape run unevenness removal control that does not worsen wow and flutter and reduces the phase error of the reproduced signal from the digital signal recording track. If tracking control is performed using a digital signal recording track reproduction signal instead of the control signal for accurately scanning the head over the track, the control track can be eliminated, and the magnetic field where the main information signal recording track is located can be It has many features such as being able to expand the utilization efficiency of the tape magnetic surface.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a track pattern of a magnetic tape to be reproduced by the apparatus of the present invention, and FIG.
The figure is a circuit diagram showing one embodiment of the device of the present invention, and FIG. 3 is a diagram showing the configuration of one embodiment of the main part of FIG.
4A to 4C are signal waveform diagrams for explaining the operation of the second illustrated apparatus, respectively, and FIG. 5 is a diagram showing another example of a track pattern of a magnetic tape to be reproduced by the apparatus of the present invention. 101, 122...Magnetic tape, 103-10
8...Photodetector, 109...Integrator circuit, 110...
...1/14 frequency divider, 114...14-bit shift register, 115...14-bit latch, 116...18-bit binary-decimal conversion circuit, 120...light source, 12
1... Light receiving element.

Claims (1)

[Scope of Claims] 1. In addition to the main information signal recording track formed on the front surface, a first track in which a predetermined repetition frequency is recorded as an optical pattern printed on the back surface on which no magnetic layer is formed, and the repetition frequency A second track in which the frequency obtained by frequency division is recorded as an optical pattern, and an address code capable of indicating an absolute address is created by a combination of the optical patterns recorded in the first and second tracks. A magnetic tape having a third track recorded as a pattern and a fourth track recorded as an optical pattern with a clock pattern for obtaining a reference pulse for reading out the address code is reproduced, and the first ~A magnetic tape reproducing apparatus characterized in that a reproduction signal obtained by optically reproducing the fourth track is used for controlling the reproduction apparatus. 2. The playback device is controlled by checking the target absolute address from the address code obtained by playing the third track, and then using the playback output obtained by playing the first and second tracks. 2. The magnetic tape reproducing apparatus according to claim 1, wherein the magnetic tape reproducing apparatus is a magnetic tape position search control that searches for a target tape position from an absolute address. 3. The playback device is controlled by using a phase error signal obtained by comparing the phase of a playback signal that is played from any one of the first to fourth tracks and has frequency fluctuations with a signal from a frequency source. The magnetic tape reproducing apparatus according to claim 1, characterized in that the magnetic tape running unevenness removal control is performed to reduce a phase error with a reproduced signal having frequency fluctuations. 4. The playback device is controlled by using a playback signal of any one of the first and second tracks instead of a control signal for causing the head to accurately scan the main information signal recording track. 2. The magnetic tape reproducing apparatus according to claim 1, wherein the magnetic tape reproducing apparatus employs tracking control.