JPS58164384A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent a reproduced signal from deteriorating, by controlling the characteristics of a reproduced signal processing circuit such as a reproductive equalizer according to the tape running speed of reproduction. CONSTITUTION:If the running speed of a tape has deviation from a normal reproduction speed and the frequency axis of the reproduced signal (a) varies, the equalizing characteristics of the equalizer 2, delay characteristics of a filter 3, and discrimination thresh-old of a data discriminator 4 are all optimized by a control signal (f) outputted from a microcomputer 7 according to variation in relative speed. At the same time, the center frequency of a BPF5 and leading-in characteristics and leading-in center frequency of a PLL6 are optimized by the control signal (f) and a switching signal (g) to supply a clock (p) in the best state from the PLL6 to the data discriminator 4.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to (1) a videotape recorder using helical scanning.

A helical scan video tape recorder (hereinafter referred to as a single channel VTR) has relatively long individual tracks that are sequentially and discontinuously recorded on a magnetic tape (hereinafter simply referred to as tape). Because of this, it is easy to write a so-called non-segment type record in which one field of the pre-visit access signal is stored in one top card. By the way, such H-V'f'R has the advantage that trick playback such as search can be performed simply by changing the tape running speed, and it is also possible to fast-forward the tape or monitor ImgI even when the tape is slow. If you perform the above-mentioned trick playback or image %2, the tape running speed will be different from the recording time, and the operation will be performed again, and the magnetic head and The relative speed to the tape is also different during recording and playback.

Therefore, in the case of a limited-capacity (I-VTR), there was a drawback that the image quality of the FI7J was easily deteriorated when playing tricks or when fast forwarding or rewinding the tape.

The reason for this will be explained below.

First, in a general analog H-VTR,
Usually, FM modulation recording method is adopted, so
The reproduction signal processing circuit is equipped with a reproduction equalizer and an FM demodulator, and it goes without saying that the optimum results for the equalization characteristics and carrier frequency depending on these factors are obtained when there is no change in relative speed. Therefore, if a shift occurs in the frequency axis of the reproduced signal due to the change in relative speed as described above, appropriate equalization will not be performed, resulting in a decrease in 87H or a change in frequency percentage. , ・If the width of the pulse output in proportion to the frequency deviates from the optimum value during FM demodulation, the demodulated output will saturate due to K, or the gain of the demodulated output will change due to the shift of the frequency axis, and the image quality will deteriorate. I end up doing it.

In addition, the shift in the frequency axis at this time also causes a change in the time axis of the playback signal, which appears as a change in the horizontal and vertical synchronization periods. The synchronization signal may be caught in the gate pulse for protection.

Next, the digi/le diary that has come to be used in recent years
The same goes for the 7F type H-VTRCPCM VTR) 4c; changes in relative speed cause the equalization characteristics to no longer match, resulting in a drop in 8/N, and at the same time, the playback waveform also changes.
There was also a change in the eye pattern after the test III.
Furthermore, since the data is judged in the same time slot, the judgment is made at a position shifted from the maximum aperture of the eye pattern, resulting in a dramatic worsening of the error rate.

In addition, since the characteristics of filters for extraction of clocks tend to match, the extraction jitter increases.

Therefore, in this case as well, the quality of the reproduced signal deteriorates and the image quality deteriorates.The purpose of the present invention is to eliminate the above-mentioned drawbacks of the conventional technology, and to improve 51C H allows you to obtain image playback with sufficient image quality even when monitoring.
-VTRt- provided. .

In order to achieve this object, the present invention detects a change in the relative speed between the magnetic head and the tape due to a change in the tape running speed, and adjusts the playback signal to a playback equalizer or the like according to the change in relative speed t. Automatically change the characteristics of the processing circuit to km5
The point K is 41IgIkO.Hereinafter, an embodiment of the magnetic recording repopulation device according to the present invention will be described with respect to the inner surface. □ Figure 1 shows the present invention in a digital recording type H-VTR)C.
In one applied example, 1 is a preamplifier, 2 is no equalization, 3 is an echo synthesis filter, 4 is a data discriminator, and 5 is a BP.
F (band pass filter), 6 is PLL (phase locked loop), 7 is microcomputer (-w microcomputer), 8 is D/A (digital-to-analog converter) ◇ Also, the heat is from the tape reproduction signal, b is CTL signal, C
is the speed detection pulse, d is the time code signal, e is the mode signal, f is the control signal, g is the switching signal, h is the tape timer display signal, quantity is the control voltage, j is the equalized playback signal, and k is the The data (lI image signal) %I) each represent a clock.

The preamplifier 1 functions to amplify the reproduced signal a to a predetermined level K.

The equalizer 2 is capable of controlling equalization characteristics using a control voltage 41.

The echo threat filter (hereinafter simply referred to as a filter) 3 has a configuration such that its delay amount is controlled by a control voltage lK.

The data discriminator 4 uses the clock p supplied from the PLL@ as a detection window, and determines whether the amplitude of the input data signal supplied from the filter 3 exceeds the threshold during this detection window by checking the 11# level of the data from K. and @O# level, and generates data k at the output. The threshold voltage level at this time is controlled by the control voltage ik.

The BPF 5 functions to extract a lock component from the equalized reproduction signal j and supply it to PI and L6K, and is configured to have a center frequency of its passband controlled by a control voltage i1c. Further, the center potential (frequency) of the PLL 6 is controlled by the same IHC.

The microcomputer 7 edits the CTL code obtained by pulse-forming the signal reproduced from the control track recorded along the longitudinal direction of the tape, and the speed detection pulse C1 representing the tape running speed obtained from the tape timer roller. Time code signal d1 used for cH-VTR
A mode signal C indicating the state IIVc in which the tape traveling speed of is controlled by fk is inputted, and a control signal f corresponding to the relative speed J[K is calculated and outputted.

A switching signal for optimally switching the parameters of the loop filter of PLL 6 according to the control state of the tape running speed, so that PLL @ is always pulled in the shortest time even at speeds other than the normal tape running speed. g, and a tape timer display signal h (pulse) corrected for errors due to slip of the tape timer roller.

1) Since the control signal f output from the microcomputer 7 is a digital signal, /A @ functions to convert it into a control voltage lK which is an analog signal.

Therefore, according to this embodiment, when the H-VTkL is controlled to trick playback states such as stop, still, and search during regeneration crop rotation, or when performing fast forwarding, rewinding, etc. , even when the tape running mode is different from that during over-current playback9, and the frequency axis of the reproduced signal 10 fluctuates, the equalizer 24F) equalization characteristics, filter 30 long-range characteristics, and data discrimination The discrimination threshold voltage of the device 4 is always controlled to the optimum state 11 by the control signal f outputted from the microcomputer 7 in response to changes in the relative speed (tK), and at the same time, the middle and sixth frequencies of the BrF3 and the PLL1i The pull-in characteristic and pull-in center frequency are each controlled to the optimum state by the control signal f and the switching signal g, and the clock p in the best state is P.
Since the data is supplied from LL@ to the data discriminator 4, the data k can be reproduced at its output in exactly the same state as at the normal tape running speed, and can be used for trick play or fast forward I/
II can be monitored during return using Takaga Sho ms.

Next, regarding the calculation of the control signal f by the microcomputer 7, FIG.
It is clear from this figure that the scanning vector (i.e. relative velocity vector) of the magnetic head is 1n. Relative velocity vector at n times speed; = 4+, 9
There is a relationship between

Here, if the tape line speed is 01, that is, B m Q, and the angle that vector Jo, which represents when the tape is at rest, makes with the tape running direction is 00, then the angle between vector jo and vector 7 is π-0. , the following formula % formula % Here, Ijo 1=Lo −I vl−v*μm1−
If Ln is Ln-JT, %+ is V" + 2nLg
It becomes Vco@#@.

Here, the relative speed at n times speed is Ln, the frequency of the corresponding reproduction signal is fn1, and those at normal speed are L□e
If fl, then these ratios are as follows:O However, -pfo! Since it is a constant determined by , )l-VTkL, there are many known ones in which the tape running and tape timer are controlled by a microcomputer. Therefore, in this case, the free processing time of the microcomputer is used to ), there is no need to add bars or hardware, and there is no need to increase costs.

In addition, in the )1-VTR, the above #0 is generally an extremely small value, and V is much smaller than Lo. That is, cos #? =-1# Lo
＞ ■Most of the cases.

Therefore, using this relationship, it is possible to perform various approximations regarding the calculation of equation (1), and an example thereof will be explained with reference to FIG. Regarding A11, B, and H2, [, respectively, are Aζ■, Rho■, H&vV, Knee■, and therefore, the following holds true and IB/11 can be easily calculated.

For example, type C
For format H-VTR, L1/V-
252, 5/2. '5 Thea'), while from Figure 3 m
Formula % Formula % As a result, L, agL・+■, and the following formula is obtained 0
L1fI L@+V L(1+V □.

・ 252.5 01 This formula (3) is an extremely simple function and can be easily calculated. For example, using an operational amplifier, setting the sono gain to 1/301 and giving an offset of 100/101, It is sufficient to input a voltage proportional to the speed number nK to this.

Incidentally, in the above, relative speed fLn=Ls, etc. are expressed by corresponding frequencies fn and fl, but they may be expressed by periods.

In other words, the period at n times speed is Tn1, and the period at normal speed is T
If 1, then these ratios can also be expressed as the deviations or li''l Lo + nV.

Next, FIG. 4 shows an embodiment of the equalizer 2 which can achieve the maximum equalization characteristic, K11ll, according to the control voltage 1 (FIG. 1) k. In FIG. 4, 40 is an input terminal for the equalized spec* raw signal, 41 is an output terminal for the equalized reproduced signal j, 42 is a control terminal to which a control voltage 5 is applied, 43 and 44 are resistors, 45.411 is a field effect transistor (called FET), 41 to 4s is 0, and now the resistance value of the resistor 43.44 is 8%. If the resistance value between the drains is R (mi) and the capacitance value of the capacitors 47 to 49 is Cs, then the cut-off frequency fc of the equalizer 2 is expressed by the following equation.

Here, let m and l be the gate voltage at the center of the dynamic range of PET45.46, and let R (m) be the resistance between the source and the vine at this time. /K (however, K is a constant determined by the tape format; for example, in the above-mentioned type C7 format, it is -100). If each k is added to or subtracted from the control voltage 1, the equalization characteristic is controlled according to the change in relative speed as described above, and the reproduced signal j appearing at the output terminal 411/C is always in the optimal state lIK, Ikotize. 〇Also, as another example, the resistor 4 in FIG.
Replace the capacitors 47, 48, 4!1 with variable capacitance diodes, and control the capacitance of these variable capacitance diodes with the control voltage. Good too.

At this time, the inductance value of the inductance element is Q, and the capacitance value of the variable capacitance diode is C(vi
), then fc≠□ 2π, /QC(vi), and if the capacitance value of the variable capacitance diode at normal speed is 0 times, then the capacitance -Cn at n times speed becomes.

Furthermore, a part of the capacitor in a primary CB filter consisting of one resistor and a capacitor may be replaced with a variable capacitance diode.

At this time, k becomes, and this cutoff frequency fc is converted into a frequency ratio fn/
It is sufficient to change it in proportion to f*'=n+Zoo/101, so the value of the variable capacitance diode when fn is Cn-1! If the resistance value of the resistor is Rn, and fl is cl# R1, then Cn9101-, where R1-Rn28, therefore, becomes, but furthermore, if n is (1oo>115) In a satisfying range, n-1101-n Cn tsl −-kq − 100+ n 100 0 Therefore, by making the fixed capacitor and variable capacitance diode parallel, when n = 1, each variable capacitance diode has its dynamic range. 'The capacitance at that time is set to be biased to the center of the capacitance; 1/looo of the sum of the capacitances of the capacitors is set to be biased to the center of the capacitance;
Alternatively, when n decreases by 1, it may increase.

However, this is only an approximation, so a wide range of #
For fc/) control over IK, it is desirable to use a microcomputer 1 or the like to perform calculations.

This □ and tK are 5eC as mentioned above.

that's why, So, R1! If Rfl ″ However, M, B, and C are the aforementioned constants.

On the other hand, the voltage-capacitance characteristic of a variable capacitance diode is g(B)
Then, in general, k g(E)=Kl(E+φ)-' where Kxer is a constant and φ is the junction potential of silicon.

bawl. In particular, for stepped junction diodes,
Since it becomes r-i, it becomes .

Therefore, the voltage of the variable capacitance diode may be controlled so that E=nl+Bn+C+φ.

Note that such calculations may be performed by the microcomputer 7 (Figure 1), but the calculations are performed in advance and the results are sent to the RO.
M (read-only memory) k memorized, speed number n
It is also possible to read by using ′ as the address. In this case, the results of correcting the nonlinearity of the variable capacitance diode in advance through experiments or the like may be stored in memory.

Furthermore, both the resistance and the capacitor may be controlled by using % FhiT and a variable capacitance diode.

Also, by using Ic RAM (Random Accelerator Memo V) instead of ROM, calculations are performed with Icq Ien immediately after the power of the H-VTR is turned on, and the results are stored in the RAM.
5K may be used so that control is performed by reading out this RAM after inputting K.

Incidentally, although the embodiments of the digital memory fi (PCM) method have been described above, the present invention is of course applicable to analog memory (F
M) type H-VTRK is also applicable, and in this case?
Control over the raw equalizer is difficult.

Therefore, for example, in a system using a balanced peak gelator, the carrier frequency may be controlled according to the relative speed.

5. The same applies to the system using a pulse count type PM detector, and if the relative speed changes and the frequency fn is shifted, the output level will change and the quality of the reproduced signal will deteriorate. Parskaran)! An IFM demodulator is a device that converts the input signal into a constant width pulse kII, rectifies it to obtain an output with a level proportional to the frequency, and the dyno range is determined by the width of the pulse. The output level reaches its maximum at a frequency where the interval between adjacent pulses becomes OK, and reaches its minimum when the input signal becomes DC. That is, the width of the above pulse is T1 and the period of the human input signal is t.
Then, the output level is proportional to T/llc, the maximum output is given when t=T, and the reciprocal of T at this time is 1/T
becomes the saturation frequency f.However, in general, to remove interference, input signal 4 is subjected to a risa vine, and the above pulse is generated at each rising and falling edge of 5K, so in this case, The saturation frequency f$ is the above A and becomes %fs-MT.

However, in either case, the saturation frequency f1 or f is inversely proportional to the pulse width TK. On the other hand, if the frequency displacement is Δf, the amount of displacement also changes by the rate of change of relative speed f(n), which means that the signal level becomes no fxf.
(n) It is nothing but K. In other words, the output video signal has a gain multiplied by f(n) and has been shifted to direct current.

Therefore, k to prevent this is the pulse width of 1/f(n
) function to control it.

If such an FM demodulator is replaced with the data discrimination 1) 1c & in the embodiment of FIG. 1 and BrF3 and PLL@ are removed, an embodiment of the present invention using an analog recording method can be obtained. Note that in the above 8114N, , control is performed by calculating the relative speed from the tape running speed, but if the characteristics of the variable element itself included in the equalizer etc. is a function of the relative speed or a transfer function of its approximate expression, k Needless to say, it is also possible to use the signal representing the tape running speed as it is.

Although not described in this embodiment, since the clock extraction filter (icl) has a constant voltage, the relative phase of the clock with respect to the data signal also changes as the frequency changes, and the discrimination phase is no longer optimal.In other words, the delay Time is t(1,
If the clock frequency at normal speed is fl and the discrimination phase at normal speed is φl, then td/(1/h)-φ! =O n times the speed, ta/I 1/fn) - φn=Q The relationship between f1 and fn is as described at the beginning of the present invention. Therefore, it is necessary for the variable delay element that compensates for this to always follow up so as to realize φn that satisfies the above formula, and if 'd is known, it can be easily calculated, so store this in a ROM etc. It is sufficient.

As explained above, according to the present invention, the characteristics of the playback signal processing circuit such as the playback equalizer are automatically controlled according to the tape running speed during playback. Or, even when monitoring is performed at the time of return, the playback signal is always properly compensated, and the playback signal does not deteriorate. can do.

[Brief explanation of drawings]

Figure 111 is a bookmark diagram showing an embodiment of the present invention using a digital recording method, and Figures 2 and #I3 are explanatory diagrams showing a method for calculating relative speed from tape running speed.
Figure E4 is a circuit diagram showing one embodiment of a reproduction equalizer. 0 1... Preamplifier, 2... No equalization, 3... Echo synthesis filter, 4... ...Data discriminator, 5...BPF (band pass filter), 6...PLL (7A's locked loop), 7...Micro combinator, 8・・・
...D/A (digital/analog conversion 1))
. 71 Second year? 3 circles 74 FZr

Claims (2)

[Claims] (1) In a helical scan magnetic recording/reproducing device capable of reproducing signals at a tape running speed different from that during signal recording, means for detecting the tape running speed and generating a control voltage corresponding to the detected tape running speed, and a scissor control voltage What is claimed is: 1. A magnetic recording and reproducing apparatus, comprising: a reproduction signal processing circuit capable of controlling signal processing characteristics, and configured to automatically compensate for deterioration of a reproduction signal due to change in tape running speed. (2) In claim 1111, 1. Magnetic recording characterized in that the reproduced signal processing circuit includes at least an equalizer whose equalization characteristics can be controlled by a control voltage, or the clock signal processing circuit is configured to be controlled by the control voltage according to item 1. Playback device D