JPS6080105A - Recording device - Google Patents

Abstract

PURPOSE:To perform recording with an optimum recording current and a simple constitution by estimating the friction state of a head to correct the recording current of the head after detecting the impedance of another head having the same friction state as said first head. CONSTITUTION:The video signals supplied to an input terminal 1 are applied to rotary recording heads HV1 and HV2 via a recording circuit 2, switches 3 and 4, a recording amplifier 5 and a rotary transformer 8 and then recorded on a tape T. While the audio signals supplied to an input terminal 9 are applied to rotary recording heads HA1 and HA2 via a recording circuit 10, a recording amplifier 11 and a rotary transformer 12 respectively and recorded on the tape T. At the same time, the output signal of the amplifier 11 is supplied to comparators 15 and 16 via a clampling circuit 13 and a peak detecting circuit 14 and then compared with reference voltages V1 and V2 (V1 > V2) given from a voltage dividing circuit 17. When the output signal of the amplifier 11 is less than V1 and V2 owing to the wear, switches 3 and 4 are turned off. Then the recording is carried out via resistances 6 and 7 and with an optimum current.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a recording apparatus that performs magnetic recording, such as a video tape recorder (VTR).

BACKGROUND TECHNOLOGY AND PROBLEMS Therewith, for example, in V'l'R, the recording current of a video signal is adjusted to an optimum value during manufacturing, but this optimum value changes over time, for example due to wear of the video head. That is, as the head wears down, the recording efficiency increases and the optimum recording current decreases.

On the other hand, the actual recording current tends to increase due to a decrease in head impedance due to head wear, and the synergistic effect of these causes video recording to result in excessive current. As a result, as is well known, problems such as C/N deterioration, overmodulation, and increase in crosstalk occur.

In addition, in the so-called deep recording method, in which the audio signal is FM modulated and recorded in the deep layer of the magnetic layer, and the video signal is recorded in the surface layer, the video recording rate is reduced due to the excessive flow of FM in the deep layer.
The area of the M audio signal is eroded, and there is a risk that the S/N ratio of the audio signal will deteriorate and phenomena such as so-called sound and vibration due to FM may occur.

OBJECTS OF THE INVENTION In view of the above-mentioned points, the present invention is intended to ensure that recording is always performed using the optimum recording current through a simple configuration.

SUMMARY OF THE INVENTION The present invention supplies a predetermined signal to another head that is in the same wear state as the head (-), detects the impedance of the other head, estimates the wear state of the head (-), and detects the impedance of the other head. This is a recording apparatus that corrects the recording current for the head, and according to this, recording can always be performed using the optimum recording current with a simple configuration.

Embodiment FIG. 1 shows a case in which the present invention is applied to a VTR that performs so-called deep recording of audio signals.

In the figure, a video signal supplied to an input terminal 111 is supplied to a recording circuit (2; that performs FM modulation of a luminance signal, low-frequency conversion of a chroma signal, etc.), and the formed recording signal is sent to a normally on switch 13+, It is supplied to the recording amplifier (5; through +41. Also, the switch +3+, (41
Resistors (6) and (7) are provided in parallel with each other.

Then, the signal from the recording amplifier (5) is sent to the rotating recording head via the rotary transformer (8).
2 and recorded on tape T.

Also, the audio signal supplied to the input terminal (9) is FM
The recording signal is supplied to the recording circuit (101) that performs modulation, etc., and the formed recording signal is sent to the recording amplifier AV, rotary transformer (12
+ to the rotary recording head HAI + HA2 and recorded on the tape T.

In this case, head HAI + HA2 is head HVlt
Provided prior to HV2, heads HAS, HA2
The FM audio signal is recorded deep into the magnetic layer of the tape T, and then the heads Hy+ and HV2
A recording video signal is recorded on the surface layer of the magnetic layer.

And these heads HVl + I-IV2 + H
AI! The HA2s are usually mounted on the same rotating drum at the same time, and contact with the tape T etc. is performed in exactly the same manner, and it is considered that problems such as wear occur in exactly the same way.

Furthermore, the head HA is
1 tHA2 impedance change can be detected. That is, since the output signal of the amplifier Uυ is an FM signal, the amplitude is constant and it can be considered to be a substantially constant current. Therefore, the potential at the output terminal of the amplifier QU is initially approximately constant as shown in FIG. 2, but when the head impedance decreases due to wear of the head, the potential also decreases in proportion to the impedance.

Therefore, the potential at this output terminal is supplied to a clamp circuit 03), and the median value is clamped to a predetermined level, for example, and this signal is peak-detected by a peak detection circuit α4. This peak-detected signal is supplied to a comparator (J51.

V2 (Vt > V2) reference voltage is compared
(151* (L6J K supplied.

As a result, a signal is output from the comparator (151) when the peak voltage becomes less than ■1, and a signal is output from the comparator (161) when the peak voltage becomes less than ■2. The switches (3+ and (41) are turned off, respectively.

Therefore, in this device, when the head impedance decreases due to head wear, the comparator a9 outputs an output when the impedance drops to a predetermined value, and the switch (3) is turned off. As a result, the input signal to the recording amplifier (5) is attenuated by the resistor (6), and the recording current is reduced. When the wear of the head further progresses and the value drops to the next predetermined value, comparators (151 and (le) are both output, and switches 131 and +41 are both turned off.

As a result, the input signal to the recording amplifier (5) is connected to the resistor +
61, (71 further attenuates, and the recording current is further reduced.

That is, correction is performed so that the recording current is always close to the optimum value, thereby eliminating the risk of reduction of the FM audio signal or deterioration of the video signal.

In this case, since detection and correction are performed simultaneously during recording, tracking performance is good, and there is no need to check beforehand before starting recording.
) is detected and corrected, there is a risk that oscillation will occur due to positive feedback.

In addition, in the circuit described above, audio signal recording is deep recording, and the recording current □ is originally large due to saturation recording.Also, since the output of recording amplifier old 1 has a strong constant current characteristic, this recording amplifier (111) There is no need to perform the above correction.

Furthermore, in the above circuit, two comparators were provided to perform stepwise correction in three stages, but this is because the peak detection circuit Q41
The output may be supplied to the gain control terminal of the recording amplifier (5) for continuous correction.

Conversely, there are cases in which only one comparator is sufficient for two-step correction.

Further, the above-mentioned comparator is provided with some hysteresis to prevent chattering.

Furthermore, in the above example, the detection was performed using a head for deep recording, but if such a head is not available, a dummy head for detection may be provided.

When using this dummy head, detection is performed by passing a frequency signal outside the recording band, or positive feedback is applied to the signal system of the dummy head to oscillate it, and the oscillation signal is frequency-discriminated to find the resonance point due to the drop in impedance. It may also be possible to detect a change in .

Or, using two rotating heads,
While recording with one head, a signal is sent to the other head,
The impedance change is detected using this signal and the recording current of one head is corrected.

This may be done for each other. In this case, it is necessary to provide a recording amplifier for each head.

Effects of the Invention According to the present invention, it has become possible to perform recording using an optimal recording current with a simple configuration.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an example of the present invention, and FIG. 2 is a diagram for explaining the same. (l), (9) are input terminals, 12+, (101 is a recording circuit, (3+, (41 is a switch, (5+,
(Ill is a recording amplifier, t6+, (71 is a resistor,
(81.
161 is a comparator, an A voltage dividing circuit, I(Vl
tHV2, HAI, and HA2 are recording heads, and T is a tape.

Claims (1)

[Claims] 1. Supplying a predetermined signal to another head that is in the same wear state as the head -, detecting the impedance of the other head, and estimating the wear state of the head -; A recording device that corrects the recording current for the head of -. 2. In claim 1, the above head (-) is a surface head that records a main signal on the surface layer of the tape magnetic layer, and the other heads record the tape magnetic layer in advance of the - (-) head. 1. A recording device characterized by being a deep layer head that records sub-signals in a deep layer of the substrate.