JPS606034B2 - magnetic recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides, for example, a cassette-type VTR (magnetic green picture reproducing device), in which a one-hour cassette tape can be used to
The purpose is to make it possible to record and reproduce time, and to solve the problems that arise in that case.

An example of this will be described below, in which one hour of recording and playback is performed on a one-hour cassette tape.

Figure 1 shows the recording system, and the luminance signal is input from input terminal 1 1→
AGC amplifier 1 2 → sink clamp circuit 13 →
V is supplied to the pre-emphasis circuit 14 through the line of the pre-emphasis circuit 14, and pre-emphasis is performed.

This pre-emphasis circuit 14 has a pre-emphasis characteristic as shown, for example, by curve 4 in FIG. White and dark clip circuit 17 → FM
V is supplied to the modulation circuit 18 as its modulation input through the modulation circuit 18 line. Also, at this time, the DC power supply 21
A DC voltage of a predetermined value is extracted from the recording time changeover switch 22, and this DC voltage is supplied to the modulation circuit 18 as a voltage for setting the carrier frequency and frequency deviation through the 1-hour side contact S of the recording time changeover switch 22. In this way, in the modulation circuit 18, the luminance signal becomes 3.9 MHz at the sync tip and 4.9 MHz at the white peak, as shown in FIG. 4A, for example.
It is converted into an FM signal with a frequency shift of 8 MHz.

This FM signal is then supplied to the rotating magnetic heads 31A and 318 through the recording amplifier 26.

For example, as shown in FIG. 5, the heads 31A, 318 have an angular interval of 18 pins from each other, are rotated by the motor 33 at a frame frequency, and have an angular range of approximately 18 pins with respect to their rotating circumferential surface. across magnetic tape 3
2 is wound diagonally, and this tape 32 is made to run at a constant speed, for example, at a speed of 4 arcs per second, by a cab stan 35 and a pinch roller 36. Furthermore, as shown in FIG. 6, for example, the heads 31A and 31B have different angles of the operating gaps Ga and Gb, that is, different azimuth angles. Further, the track width of the cores of the heads 31A and 31B is, for example, 40 m. Further, 40 indicates a servo circuit.

That is, the luminance signal from the terminal 11 is transmitted to the sync separation circuit 41.
This pulse is supplied to the frequency dividing circuit 42 to be divided into pulses at the frame frequency, and this pulse is supplied to the phase comparator circuit 43. A pulse generating means 44 is provided on the rotating shaft 34, and from this, the heads 31A,
One pulse is taken out for each rotation of 31B, and this pulse is supplied to comparison circuit 43 through shaping amplifier 45. The comparison output of the comparison circuit 43 is then supplied to the motor 33 through the servo amplifier 46, and thus the head 3
The rotational phases of 1A and 31B are synchronized with the frame of the luminance signal. Therefore, as shown in FIG. 7A, for example, the FM signal from the amplifier 26 has one field that is diagonal.
The magnetic tracks 1 of the book are sequentially recorded on the tape 32.

However, in this case, the width of track 1 will be 40 m, corresponding to the track width of the cores of heads 31A and 318.
By selecting the rotation radius of the heads 31A, 31B, etc., the width of the guard band between the tracks 1 is set to, for example, 20 mm.

Further, so-called date alignment is performed such that the horizontal synchronizing pulses corresponding to each track 1 are located on a line perpendicular to the track 1. Note that the azimuth angles of the tracks IA and IB differ between every other track IA and the remaining every other track IB, corresponding to the azimuth angles of the heads 31A and 31B.

At this time, the pulse from the frequency dividing circuit 42 is supplied to the magnetic head 47 through the recording amplifier 48, and is recorded on the green side of the tape 32 as a control pulse during reproduction.

The luminance signal thus recorded is reproduced by the reproduction system shown in FIG.

That is, a control pulse is reproduced from the tape 32 by the head 47, and this pulse is coupled to the comparator circuit 43 through the reproduction amplifier 49. Therefore, the servo control of the heads 31A, 31B during reproduction is performed, and the heads 31A, 31B are controlled.
31B scans track 1 in the same manner as during recording.

Then, the heads 31A and 31B record the FM from the tape 32.
The signal is regenerated, and this signal is supplied to the demodulation circuit 53 through the line of regeneration amplifier 51 → limiter 52 → demodulation circuit 53, and the luminance signal is demodulated. This de-enphasis circuit 54 has de-enphasis characteristics complementary to curve 4 in FIG.
Therefore, a luminance signal with flat frequency characteristics is extracted from the differential amplifier circuit 54. And this luminance signal is
The output terminal 5M is taken out through the one-hour side contact S of the playback time changeover switch 57. As above, 1
One hour of recording or playback is performed on the time tape 32. On the other hand, when recording for two hours on the one-hour tape 32, the following procedure is performed.

That is, in FIG. 1, the luminance signal from the clamp circuit 13 is supplied to the de-emphasis circuit 15 and de-emphasized.

This de-emphasis circuit 15 has a characteristic as shown by curve 5 in FIG. 3, and has a larger amount of de-emphasis than the characteristic of the de-emphasis circuit 14. The brightness signal from the differential assist circuit 15 is then supplied to the modulation circuit 18 through the 2-hour side contact L of the switch 16 and further through the clip circuit 17.

Also, the command from amplifier 45. The control pulse is supplied to the signal forming circuit 24 to form a rectangular wave signal Sr that is inverted every field period in synchronization with the control pulse, as shown in FIG. A DC voltage is supplied as a control signal to the switch 22 and alternately changes to a first value and a second value every field period in accordance with the level of the signal Sr. The modulation circuit 181 is supplied through the side twill point L for setting the carrier frequency and frequency deviation.

In this manner, in the modulation circuit 18, the luminance signal is transmitted as shown in FIG.
The frequency deviation is smaller than the characteristics of 3. with the sync chip.
89 MHZ and is converted into an FM signal of 4.8 MHz at the white peak, and during the other field period in which track IB is formed, as shown by the straight line 88 in FIG. 10, the characteristics of FIG. 4B and 1/2f (fH is the horizontal frequency) is converted into an FM signal lower than the straight line 8A in FIG.

That is, the modulation characteristic of the FM signal is switched to the straight line 8A or 88 in FIG. 10 every field period.

This FM signal then passes through the amplifier 26 to the head 31.
A, 318, and at this time, the tape 32
is 1/2 the speed of one hour recording, i.e. 2/sec.
It is made to run at the speed of Toga.

Therefore, the tape 32 has a pattern shown in FIG.
M signal is recorded.

Note that the modulation characteristics of this tin-combined FM signal are switched to the straight line 8A or 8B in FIG. 10 for each field period, so the FM signal on track IA has the modulation characteristic of the straight line 8A in FIG. However, the FM signal of track IB has a modulation characteristic of straight line 88. Also, at this time, since the running speed of the tape 32 is set to 1'2, it is possible to record for 2 hours. When reproducing the two-hour recording, the luminance signal from the demodulation circuit 53 is supplied to the de-emphasis circuit 55 and de-emphasized in FIG. 2.

The differential amplifier circuit 55 has characteristics complementary to the differential amplifier circuit 15, and therefore, a luminance signal with flat frequency characteristics is extracted from the differential amplifier circuit 55. Then, this luminance signal is sent to the DC level correction circuit 56.
is supplied as its input signal.

That is, when the luminance signal is converted into an FM signal in the modulation circuit 18, the modulation characteristic is set to the straight line 8A or 88 in FIG. 10 for each field period, so the luminance signal demodulated from this FM signal is as follows. This means that the DC level changes every field period. Therefore, a circuit for correcting this change in the DC level is a correction circuit 56, which is supplied with a luminance signal as an input, and
A rectangular wave signal Sr from the signal forming circuit 24 is supplied as its control signal, and the DC level of the luminance signal is corrected to a constant value.

This corrected luminance signal is then taken out to the terminal 58 through the 2-hour side contact L of the switch 57.

In this way, two hours of recording or playback can be performed using the one-hour tape 32.

In this case, as described above, there is no reduction in S/N, increase in crosstalk between tracks, or increase in beat disturbance due to crosstalk between tracks.

However, in this case, during 2 hours of recording, the luminance signal was changed to FM.
The width of the frequency deviation when converting to a signal is 1'2 at 650kHz compared to 1.3MHZ during one hour recording, so the S/N of the luminance signal demodulated from the FM signal is the same as the original. It will decrease as much as possible.

In order to eliminate this decrease in S/N, it is possible to increase the pre-emphasis amount for the luminance signal during recording, but this cannot be done simply. The present invention attempts to solve these problems. Therefore, in the present invention, the pre-emphasis circuit 15 is
As shown in Figure 1, a nonlinear pre-emphasis circuit 15
0 and a linear pre-emphasis circuit 155, and the de-emphasis circuit 55 is correspondingly structured in the same manner.

That is, the luminance signal from the clamp circuit 13 is supplied to the adder circuit 152, and the high-pass filter 152
The Takagi component of the luminance signal is extracted, and this Takagi component is supplied to the adder circuit 151 via a limiter (nonlinear circuit) 153 having input/output characteristics as shown by the solid line in FIG.

Therefore, in the adder circuit 151, the Takagi component from the limiter 153 is added to the luminance signal having a flat frequency characteristic from the clamp circuit 13, and due to the input/output characteristics of the limiter 153, the higher the level, the more the limiter 153 increases.
Since the proportion of the Takagi component from
That is, the adder circuit 151 takes out a luminance signal that has been subjected to non-linear pixel assist.

This luminance signal is then supplied to a pre-emphasis circuit 155 where it is further pre-emphasized according to the characteristic shown by curve 5 in FIG. And pre-enforcement circuit 15
5 is supplied to the clip circuit 17 through the contact L of the switch 16.

Further, the differential differential circuit 55 is constituted by a nonlinear differential differential circuit 550 and a linear differential differential circuit 555, as shown in FIG. 12, for example.

That is, the luminance signal from the demodulator circuit 53 is supplied to the differential amplifier circuit 555, which has characteristics complementary to those of the pre-amplifier circuit 155, and is differentially assisted.The luminance signal is supplied to the subtracter circuit 551, and its The output signal is supplied to a high-pass filter 552 having the same characteristics as the filter 152 to extract the high frequency component, and this Takagi component is supplied to the subtraction circuit 551 through the limiter 553 having the same characteristics as the limiter 153. Therefore, the de-emphasis circuit 560 has characteristics complementary to those of the pre-emphasis circuit 150,
A luminance signal with flat frequency characteristics is taken out from the de-emphasis circuit 560.

Thus, according to the invention, the enhancement circuit 150,5
50' performs non-linear emphasis, and since the emphasis circuits 155 and 555 perform linear emphasis, a good luminance signal can be reproduced.

In addition, it provides sufficient reinforcement, is easy to design, and is less likely to cause distortion. In the above description, the width of the frequency deviation for the FM signal during 2 hours of recording is 65
0kHz, which is 500kHz for the above values.
It can be made from kHz to about 850kHz.

Further, the difference between straight lines 8A and 8B in FIG. 10 is 1'2fH, but this may be (m+1/2)fH (m is zero or a positive integer). Further, instead of the tape 32, a magnetic medium such as a magnetic sheet may be used. Furthermore, the demodulation characteristics of the demodulation circuit 53 may be changed corresponding to the straight lines 8A and 8B by the signal Sr without providing the correction circuit 56.

Alternatively, when m=0, the change in the DC level of the demodulated luminance signal is very small, so there is no practical problem even if this change in DC level is not corrected.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are system diagrams of an example of the present invention, FIGS. 3 to 10 are diagrams for explaining the same, FIGS. 11 and 12 are system diagrams of an example of the essential parts of the present invention, FIG. 13 and FIG. 14 are diagrams for explaining this. 14 and 15 are pre-emphasis circuits, 18 is an FM modulation circuit, 53 is an FM demodulation circuit, and 54 and 55 are de-emphasis circuits. Figure 1 Figure 2 Figure 5 Figure 6 Figure 3 Figure 4 Figure 11 Figure 12 Figure 7 Figure 8 Figure 9 Figure 10 Figure 13 Figure Boat

Claims (1)

[Claims] 1. The input luminance signal is supplied to a nonlinear pre-emphasis circuit having a series circuit of a high-pass filter and a limiter, and an adder circuit that adds the input signal and output signal of this series circuit, and the level of the input luminance signal is determined in the high frequency domain. Non-linear pre-emphasis is performed in which the pre-emphasis amount is smaller as A magnetic recording device that supplies a signal to an FM modulation circuit to produce an FM signal, and records the FM signal as a plurality of magnetic tracks on a magnetic medium.