JPH0740752B2 - Crosstalk measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to guard bandless recording in a rotary head type VTR in which a pair of rotary heads are in sliding contact with a tape and information signals such as video signals are recorded. The present invention relates to a crosstalk measuring device that measures the amount of crosstalk component in a reproduced signal.

[Outline of Invention]

The present invention is a rotary head type VTR crosstalk measuring device in which a pair of rotary heads are in sliding contact with a tape and record information signals such as video signals. The same test tape is used for each rotary head channel by recording another signal that can be distinguished from the desired frequency and measuring the crosstalk component from the signal level of the frequency to be measured in the playback signal of the tape. In addition, the same test tape can be used to measure not only crosstalk between adjacent tracks but also crosstalk between adjacent tracks, adjacent tracks, adjacent tracks, etc. Is.

[Conventional technology]

A rotary head type VTR in which a pair of rotary heads are in sliding contact with a magnetic tape and record information signals such as video signals.
Track pitch T _P (eg 29.2 μm) from _W (eg 37 μm)
There is known a magnetic tape which is magnetically recorded by using inclined azimuth recording having a small (μm).

The use of this inclined azimuth recording has a considerable effect on suppressing crosstalk of signal components in a high frequency band such as between adjacent tracks. In addition, it is known that the phase-inverter method can remove crosstalk from the low-frequency converted chroma subcarrier component (688 KHz) by a comb filter during reproduction.

Even if the crosstalk is removed by the inclined azimuth method or the phase inverter method, the crosstalk on the adjacent track or the adjacent track is left. Since crosstalk affects the playback image quality and sound quality of the VTR, crosstalk evaluation is an important issue in the performance evaluation of the VTR electromagnetic conversion system.

Conventionally, the measurement of this crosstalk has been performed as follows, for example. The adjacent crosstalk of the FM modulated luminance signal Y is measured once in three fields, the frequency to be measured is recorded, and another frequency is recorded in another field. And observe with a spectrum analyzer.

In addition, the measurement of the adjacent crosstalk of the chroma signal is performed, for example, once every 6 fields by the chroma subcarrier (688KH).
z) is recorded, and a magnetic tape in which only the luminance signal Y is recorded in the other field is produced, and it is reproduced and observed with a spectrum analyzer.

[Problems to be solved by the invention]

When measured by the above method, since the measurement method is different between the luminance signal and the chroma signal, from the viewpoint of head performance evaluation,
When attempting to measure the crosstalk for each type of carrier, it is necessary to perform the measurement separately, which complicates the measurement work.

In addition, since the crosstalk measurement method of the chroma signal is recording once in 6 fields, if only A channel can be measured at one measurement in one measurement, both channels can be measured separately. This is a necessary and complicated measurement work.

Furthermore, even when applied to an 8 mm VTR using a magnetic tape having a tape width or 8 mm, the crosstalk measurement method differs for each of the luminance signal, the chroma signal, and the FM-modulated audio signal, which is a complicated measurement work.

Therefore, an object of the present invention is to provide a crosstalk measuring device which can eliminate the complexity of the conventional measuring method and can easily measure the crosstalk between adjacent tracks.

[Means for solving problems]

The present invention relates to a rotary head type VTR crosstalk measuring device in which a pair of rotary heads are in sliding contact with a tape and record an information signal such as a video signal, and a frequency to be measured at a ratio of 1 field to an odd field of 7 fields or more. Signal is recorded, and in the other fields of the odd field of 7 fields or more, another signal that can be distinguished from the frequency to be measured is recorded, and the crosstalk from the signal level of the frequency to be measured in the reproduction signal of the tape is recorded. It is designed to measure the components.

[Action]

The signals of the frequency to be measured are recorded in the field of 7 fields or more in the ratio of 1 field, and the crosstalk component is measured from the level of the signal of the frequency to be measured in the reproduction signal of the tape. By measuring the tape once, not only the crosstalk between the adjacent tracks but also the crosstalk between the adjacent tracks and between the adjacent tracks is measured.

Further, since the signal of the frequency to be measured is recorded in the odd field in the ratio of one field, the same test tape is used, and the crosstalk components of the A channel and the B channel corresponding to each of the pair of magnetic heads are recorded. You can measure.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 shows a recording system of a crosstalk measuring device. In FIG. 1, 1 shows an oscillator that generates a sine wave of a single frequency, and this oscillator 1 has a frequency of 4.5 MHz for automatic tracking control (ATF). Signal is generated and supplied to one input terminal 2a of the switch circuit 2. A 5 MHz signal corresponding to the luminance signal Y formed by the oscillator 3 that generates a single frequency sine wave is supplied to the mixing circuit 6. A signal of 1.5 MHz corresponding to the carrier frequency of the FM audio signal (AFM signal) is supplied to the mixing circuit 6 from the oscillator 4 that generates a sine wave of a single frequency. A signal of 750 KHz corresponding to the chroma signal (C signal) which has been converted to a low frequency band from the oscillator 5 is supplied to the mixing circuit 6. The mixing circuit 6 mixes the signal of frequency 5 MHz, the signal of frequency 1.5 MHz, and the signal of frequency 750 KHz, and the output signal of the mixing circuit 6 is supplied to the other input terminal 2b of the switch circuit 2.

The switch circuit 2 has a trigger pulse (see FIG. 3B).
Is supplied from the terminal 7. This trigger pulse is VTR
It is produced from the switching pulse (see FIG. 3A) produced by the rotary pulse generator of the rotary head of FIG. When this trigger pulse is low level'L ',
The input terminal 2a is connected to the output terminal 2c, and when the trigger pulse is'H ', the input terminal 2b is connected to the output terminal 2c. Therefore, when the trigger pulse is'L ', the recording current of frequency 4.5MHz from the oscillator 1 is generated by the switch circuit 2.
Is output (see FIG. 3C), and when the trigger pulse is'H ', the recording current in which the signals from the oscillator 3, oscillator 4 and oscillator 5 are mixed is output from the switch circuit 2 (see FIG. 3). See D).

This recording current is set using an 8 mm wide magnetic tape
When recording a C format signal, when the recording current of the carrier frequency of the luminance signal is I _Y , the recording radio wave of the carrier frequency of the chroma signal is I _C , and the recording radio wave of the FM-modulated audio signal is I _AFM , Is set to.

The output signal from the output terminal 2c of the switch 2 is supplied to the mixing circuit 8, and the pilot signal for automatic tracking control (ATF) in which four kinds of frequencies change periodically in a predetermined order is mixed from the terminal 9. It is supplied to the circuit 8. Tracking control is performed by the ATF method using this pilot signal.

The output signal of the mixing circuit is amplified by the recording amplifier 10,
The RF switching pulse generated by the pulse generator of the rotary head is supplied from the terminal 12 as the control signal of the switch circuit 11 by being supplied to the input terminal 11a of the switch circuit 11. By this RF switching pulse, the movable terminal of the switch circuit 11 is controlled to be alternately connected to one output terminal 11b and the other output terminal 11c for each field (1/60 sec). The signal obtained at one of the output terminals 11b is supplied to the A channel head 14 via the recording amplifier 13 for recording of the A channel, and at the same time, the output terminal
The signal obtained at 11c is supplied to the B channel head 16 which forms a pair of magnetic heads together with the A channel head at an angular interval of 180 ° via the recording amplifier 15, and rotates in pairs with the A channel head 14. B channel recording is performed on a magnetic tape by a B channel head 16 which is a head.

Further, FIG. 2 shows a reproducing system of the crosstalk measuring apparatus of this embodiment. As shown in FIG. 2, a signal magnetically recorded on the magnetic tape is picked up by the A channel head 14, and the switch circuit 19 is passed through the reproduction amplifier 17.
It is supplied to one of the input terminals 19a. The signal from the B channel head is sent to the switch circuit 19 via the reproduction amplifier 18.
Is supplied to the input terminal 19b of. The movable terminal 19c is alternately connected to the input terminal 19a and the input terminal 19b for each field by the RF switching pulse from the terminal 24. The output signal from the output terminal 19c is output to the output terminal 2 via the reproduction amplifier 20.
Taken out to 1.

Reference numeral 22 is a switch circuit for switching the crosstalk measurement channel. The output signal of the reproduction amplifier 17 is supplied to one input terminal 22a of the switch circuit 22, the output signal of the reproduction amplifier 18 is supplied to the other input terminal 22b of the switch circuit 22, and is output from the output terminal 22c of the switch 22. The signal is supplied to the spectrum analyzer 23. In the spectrum analyzer 23, the A channel head 14 or the B channel head selected by the switch circuit 22 is selected.
Adjacent, side-by-side, side-by-side, of 16 tracks to scan
The level of the crosstalk signal component up to the adjacent tracks is displayed.

In this embodiment constructed as described above, an A channel head forming a pair of magnetic heads with an angular interval of 180 °.
14 and B channel head 16 are in sliding contact with the tape, and the frequency to be measured at a ratio of 1 field to 9 fields, which is an odd field of 7 fields or less (5MHz, 1.5MHz, 750K
Hz) signal is recorded, and in the other fields among the 9 fields, a signal of 4.5 MHz which is a frequency distinguishable from the signal of the frequency to be measured is recorded, and the recording track pattern as shown in FIG. 4A is recorded. It is formed. In FIG. 4A, every nine tracks 31 and 40 with inclination are tracks in which the signals of the frequencies to be measured are recorded as described above.

The pattern of this recording track is alternately traced by the A channel head 14 and the B channel head 16, and the distribution of the signal component of the channel selected from the reproduced signal and the frequency to be observed is observed by the spectrum analyzer 23.

That is, the switch circuit 22 selects one of the reproduced signals of the A channel or the B channel, and the spectrum analyzer
The center frequency f _{C of} 23 is set to, for example, 750 kHz at which crosstalk is to be observed, the span frequency f _S = 0 Hz, and the sweep time is appropriately set.
Observing, the waveform as shown in FIG. 4B is displayed.

In FIG. 4A, the numbers 31 to 39 attached to the respective tracks,
The numbers 41 to 49 given to the respective waveforms in FIG. 4B correspond to each other. The waveform of FIG. 4B will be described in the order of scanning.

The output waveform 48 when scanning track 38 is
The adjacent crosstalk components from the track 31 on the upper side of.

The output waveform 44 when scanning track 34 is
It is the adjacent crosstalk component from the upper track 31 of the.

The output waveform 41 when the track 31 is scanned is the main output waveform.

The output waveform 45 when scanning track 35 is
It is the adjacent crosstalk component from the lower track 31.

The output waveform 49 when scanning track 39 is
It is the next-to-next contact crosstalk component from the lower track 31.

The output waveform 46 when scanning track 36 is
Is a crosstalk component adjacent to each other from the track 40 on which the signal of the frequency to be measured by the upper B channel head 16 is recorded.

The output waveform 42 when scanning track 32 is
Is the adjacent crosstalk component from track 40 above.

The output waveform 43 when scanning track 33 is
The adjacent crosstalk component from the lower track 40.

The output waveform 47 when the track 37 is scanned is the adjacent crosstalk component from the track 40 below the track 37.

The amount of the crosstalk component is defined by the difference between the peak value of the waveform 41 of the main output and the respective peak values of the waveforms 42 to 49 of the crosstalk component.

If the center frequency f _{C is set} to 1.5 MHz or 5 MHz, crosstalk at other frequencies can be measured in the same manner.

It should be noted that the maximum value of the crosstalk can be read by holding the maximum value on the spectrum analyzer in the measurement, and the change of the crosstalk can be read in the normal mode. Also, if an external trigger is applied to the spectrum analyzer in FIG. 3B by using trigger pulses at 9-field intervals, the spectrum waveform shown in FIG. 4B is fixed on the screen of the spectrum analyzer. It is easy to observe the components.

〔The invention's effect〕

According to the present invention, since the main signal whose crosstalk is to be measured is recorded once in the odd field of 7 fields or more, the tracks on which the main signal is recorded are the A channel side and the B track. Since it is switched to the channel side alternately, the crosstalk of each of the A channel and the B channel can be measured with the same recording pattern.

Further, according to the present invention, since the main signal is recorded once in the odd field of 7 fields or more, crosstalk such as adjacent, adjacent, and adjacent contact is separated. Can be displayed, and the crosstalk component can be accurately and easily observed by the spectrum analyzer. Therefore, it is possible to easily perform a sampling check on the production line and use it for a test when changing the shape of the magnetic tape sliding surface of the magnetic head.

[Brief description of drawings]

FIG. 1 is a block diagram of a recording system according to an embodiment of the present invention, and FIG. 2 is a block diagram of a reproducing system according to an embodiment of the present invention.
FIG. 4 is a waveform diagram of one embodiment of the present invention, and FIG. 4 is a schematic diagram showing a recording pattern of one embodiment of the present invention and a waveform diagram in a spectrum analyzer. Description of main symbols in the drawings 14: A channel head, 16: B channel head, 31: Track on which the signal of the frequency to be measured is recorded.

Claims (1)

[Claims] 1. A selecting means to which a main signal including a signal for automatic tracking control and a signal having a frequency corresponding to a luminance signal and a chroma signal as a reference for detecting a crosstalk component is supplied, and the selecting means. A pair of rotary heads for recording the transmitted signal, and a measuring unit for measuring the crosstalk component of each track of the tape based on the signal for the automatic tracking control and the main signal read from the pair of rotary heads. In order to measure the crosstalk component of the adjacent track, the adjacent track of the arbitrary track, the adjacent track of the adjacent track, and the adjacent track of the adjacent track of one track, one field is included in an odd field of 7 fields or more. The main signal is recorded, and the automatic tracking control is performed on other fields in the odd field of 7 fields or more. The crosstalk component of each track is measured for each frequency of each signal from the signal level of the main signal in the reproduction signal read from the tape. Talk measurement device.