JP2613298B2 - Helical scanning type magnetic recording / reproducing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to tape running control, drum rotation control, and reproduction signal processing during high-speed reproduction in a helical scanning type magnetic recording / reproducing apparatus.

[Conventional technology]

In general, in a helical scanning type magnetic recording / reproducing apparatus such as a video tape recorder (VTR), in the case of search reproduction, that is, when reproducing at a tape speed higher than the tape speed at the time of recording, the frequency of a reproduction signal obtained from the tape is changed. Moving, resulting in significant degradation of the reproduced image. Therefore, in order to suppress image deterioration during search reproduction, for example, Japanese Patent Application Laid-Open No. Sho 57-80881
At the time of search reproduction, the rotational speed of the drum equipped with a rotary head is made different from the rotational speed at the time of recording, and the relative speed between the rotary head and the tape is made equal to that at the time of recording. 2. Description of the Related Art Deterioration of an image due to movement of a signal frequency is prevented.

The above conventional example will be quantitatively described with reference to FIG. FIG. 2 is a diagram showing the tape speed, the head speed, and the relative speed between the tape and the head in vector form. [A] in Fig. 2
, V _t1 , v _h1 , and v _r1 are a tape speed, a head speed, and a relative speed at the time of recording, respectively, and Nv _t1 and v _rn represent a tape speed and a relative speed at the time of N-times speed search. Note that θ
₀ represents the angle between the longitudinal direction of the tape when the tape is stopped and the head scanning direction.

During playback, regardless of the tape speed, as in the case where the head speed constant shown in [A], by the search for multiple N, the relative velocity v _r of the tape and the head, if the N> 1 v
_r1 < _vrn , and if N <1, _vr1 > _vrn , which is different from the relative speed _vr1 at the time of recording. So, conventionally,
As shown in FIG. 2B, during the search, the control target is changed so that the speed of the rotating head changes from v _h1 to Mv _h1 for the multiple N of the search, and the relative speed v of the tape and the head is changed. ′
_r1 was set to be equal to the relative speed v _r1 at the time of recording.

Also, in a helical scanning type magnetic recording / reproducing apparatus for recording / reproducing a digital signal, it is possible to read a correct reproduced digital signal even when a relative speed between a tape and a head changes during a high-speed search and a reproduction signal frequency changes. , A device as shown in FIG. FIG. 3 is a block diagram of a reproducing system of a magnetic recording and reproducing apparatus for recording and reproducing digital signals. The most important point in the reproduction of a digital signal is the correct reading of the code, for which a clock synchronized with the reproduced digital signal is indispensable. Hereinafter, the conventional digital signal reproducing system will
This will be briefly described with reference to the drawings.

In FIG. 3, the reproduced digital signal detected by the head 14 from the magnetic tape 15 is amplified by a preamplifier 37 and then supplied to an equalizing circuit 38. The equalization circuit 38 is a tape
It suppresses intersymbol interference due to the differential characteristics and band limiting characteristics of the head system. The equalized digital reproduction signal is supplied to a phase detection circuit 48 and a waveform shaping circuit 52. Phase detection circuit 48
, LPF 49, and a voltage controlled oscillator (VCO) 50 constitute a phase locked loop (PLL), and generate a clock phase-synchronized with the reproduced digital signal. The clock generated by the PLL is converted into a logic level signal by the waveform shaping circuit 53 and supplied to the latch circuit 54 as a latch clock. Using this clock, the latch circuit 54 latches the reproduced digital signal, which has been converted to a logic level supplied through the waveform shaping circuit 52, and outputs the digital signal to the digital processor 40.

Generally, the above-mentioned clock generating PLL (constituted by 48, 49, 50) has a pull-in range set to about ± several% with respect to the center frequency of the VCO 50 in order to prevent a pseudo lock phenomenon. Therefore, when the tape running speed during reproduction is significantly different from that during recording, the relative speed between the tape and the head changes, and the PLL cannot generate a clock synchronized with the reproduced digital signal. Therefore, in the conventional clock generation PLL, the switch 44 and the plurality of voltage sources 45 to 47 are used to switch the reference potential of the control voltage of the VCO 50 according to the tape speed of the search reproduction. In FIG. 3, the tape traveling control system 43 drives a reel motor or a capstan motor 42 in response to a search / reproduction command signal supplied from an input terminal 35, and drives the tape 15 to a desired tape by a reel or a capstan 41. Run at search speed. The search reproduction command signal switches the switch 44 and supplies a reference voltage of the VCO 50 having a center frequency matching the reproduction signal frequency at a desired search speed to the VCO 50 via the addition circuit 51. The addition circuit 51 is an addition circuit of a reference voltage for determining the center frequency of the VCO 30 and a feedback voltage obtained by phase detection. With the above configuration, even during high-speed search reproduction, a clock synchronized with a reproduced digital signal can be generated, and reading of reproduced data is realized.

A helical scanning type magnetic recording / reproducing apparatus which realizes reading of a digital signal and generation of a synchronous clock at the time of the high-speed search is disclosed in
Nos. 067785 and 62-067786.

[Problems to be solved by the invention]

However, in the above-mentioned conventional techniques, it is found that in the high-speed search reproduction, if a steady state is reached, sufficient effects can be obtained, but no consideration is given in the transient state, and the following problems occur. .

First, in the method of changing the rotary head speed described in the second previous figures during search reproduction, for example, when changing the tape speed from the normal reproduction speed v _t1 to N times speed search reproduction speed Nv _t1, the actual tape speed v _{When t} changes as shown in [A] of FIG. 4, and when the rotating head speed is changed from the normal reproducing speed v _h1 to the rotating head speed Mv _h1 at the N-times speed search reproducing, the actual rotating head speed v _{h is changed.} Changes as shown in FIG. 4B. In this case, as shown in [C] in FIG. 4, the relative speed v _r between the tape and the head in the transient state in which the tape speed changes is the relative speed v during normal reproduction.
This changes with respect to _r1 , and during this period, the reproduced image deteriorates.

Also in the digital signal reproducing system shown in FIG. 3, the reproducing signal frequency and the clock are generated during the transition period until the tape speed reaches the desired search speed.
The stop frequency of the VCO 50 does not match, and the reading of the reproduction data becomes defective.

Accordingly, an object of the present invention is to provide a helical scanning type magnetic recording / reproducing apparatus having a search / reproducing function. An object of the present invention is to provide a helical scanning type magnetic recording / reproducing apparatus which keeps a relative speed of a head constant and thereby prevents image deterioration due to a change in a reproduction signal frequency even in a transition period in which a tape speed is changing. Further, when reproducing a digital signal for another purpose, even during a transition period when the tape speed is changing, the phase synchronization between the reproduced digital signal and the clock generated by the phase locked loop is realized, and the reproduced digital data is always reproduced. An object of the present invention is to provide a helical scanning type magnetic recording / reproducing apparatus which enables reading.

[Means for solving the problem]

In order to achieve the above object, the present invention has the following configuration. Tape running speed detecting means; tape running speed controlling means for negatively feeding back the difference between the tape running speed detected by the tape running speed detecting means and the desired tape running control target speed to the capstan motor or the reel motor; Rotating head scanning speed detecting means, and a rotating head for negatively feeding back a difference between the rotating head scanning speed detected by the rotating head scanning speed detecting means and a desired rotating head scanning control target speed to a drum motor equipped with the rotating head. Scanning speed control means, and a helical scanning type magnetic recording / reproducing apparatus comprising: the detected tape running speed according to the tape running speed detected by the tape running speed detecting means;
The control target speed of the rotary head scanning speed, which sets the control target speed of the rotary head scanning speed control means such that the sum with the rotary head scanning speed detected by the rotary head scanning speed detection means becomes a predetermined constant value. The configuration includes a setting unit.

Further, a tape running speed detecting means, and a capstan motor which calculates a difference between the tape running speed detected by the tape running speed detecting means and a desired tape running control target speed,
Alternatively, a tape running speed control unit that negatively feeds back to the reel motor, a rotating head scanning speed detecting unit, and a difference between the rotating head scanning speed detected by the rotating head scanning speed detecting unit and a desired rotating head scanning control target speed are calculated. A helical scanning type magnetic recording / reproducing apparatus, comprising: a rotary head scanning speed control means for negatively feeding back to a drum motor equipped with a rotary head; The control target speed of the tape traveling speed control means is set so that the sum of the detected rotational head scanning speed and the tape traveling speed detected by the tape traveling speed detecting means becomes a predetermined constant value. The tape drive speed control target speed setting means is provided.

Further, a tape running speed detecting means, and a capstan motor which calculates a difference between the tape running speed detected by the tape running speed detecting means and a desired tape running control target speed,
Alternatively, a tape running speed control unit that negatively feeds back to the reel motor, a rotating head scanning speed detecting unit, and a difference between the rotating head scanning speed detected by the rotating head scanning speed detecting unit and a desired rotating head scanning control target speed are calculated. A rotating head scanning speed control unit that performs negative feedback to a drum motor equipped with a rotating head, and a phase locked loop that generates a clock that is phase-synchronized with a reproduced signal reproduced by the rotating head, are waveform-shaped using the clock. A helical scanning type magnetic recording / reproducing apparatus provided with a data strobe means for latching the reproduction signal, wherein a relative speed between the tape and the rotary head is predetermined according to the tape traveling speed detected by the tape traveling speed detecting means. The control target speed of the rotating head scanning speed control means is set so that A relative speed calculation for calculating a relative speed between the tape and the rotary head from the tape running speed detected by the tape running speed detecting means and the rotating head scanning speed detected by the rotating head scanning speed detecting means. Means, and control signal generating means for generating a control signal in accordance with relative speed information obtained by the relative speed calculating means, wherein the synchronous clock generating phase lock is provided in accordance with a control signal of the control signal generating means. And a configuration for determining the center frequency of the droop.

[Action]

The rotating head speed control means sets the control target speed of the rotating head speed to a constant value of the relative speed between the tape and the head, that is, the same relative speed as at the time of recording, according to the tape speed information detected by the tape speed detecting means. Since the speed can be set to be the same, the reproduction signal frequency can be made the same as the signal frequency at the time of recording even in a transient state in which the tape speed greatly changes, and image quality deterioration such as color shift of the reproduced image can be prevented. . The operation of the rotating head speed control means corresponds to a system in which the response time of the rotating head scanning speed control system is shorter than the reaction time of the tape running speed control system.

Conversely, when the response time of the tape traveling speed control system is shorter than the response time of the rotary head scanning speed control system, the tape speed control means operates as follows. The tape speed control means can set the rotary head speed detected by the rotary head speed detection means so that the relative speed between the tape and the head becomes the same relative speed as at the time of recording. Even in the transition period of the high-speed search reproduction that needs to change greatly, the reproduction signal frequency can be made the same as the signal frequency at the time of recording, and the same effect as the above operation can be obtained. Further, since the relative speed is determined by the sum of the tape speed and the head speed when setting the relative speed between the tape and the head, this can be easily realized.

Further, when reproducing digital signals, the speed information calculating means calculates the relative speed from the speed information of the tape speed or the rotating head speed which changes every moment during the transition period during search reproduction, and based on the calculation result, the PLL for clock generation. Is supplied to the PLL so that the center frequency of the control signal matches the reproduced digital signal. Therefore, the above PLL
Can be set to a center frequency that matches the reproduced digital signal even in the transient state, so that a clock synchronized with the reproduced digital signal can be always generated, and stable reading of the reproduced digital data can be realized.

〔Example〕

Hereinafter, some representative embodiments of the present invention will be described in detail with reference to the drawings. First, a first embodiment will be described with reference to FIG.

FIG. 1 is a block diagram of a helical scanning type magnetic recording / reproducing apparatus having a search / reproducing function to which the present invention is applied. In FIG. 1, reference numerals 1 and 2 denote a supply reel and a take-up reel (hereinafter, in the reel system, the supply reel side is represented by S, and the take-up reel side is represented by T), 3 is a capstan, 4 is a drum, and 5 is a drum. Tension sensors, 6 and 7 are S and T reel motors, 8 is a capstan motor, 9 is a drum motor, 10 to 13 are FG sensors of each motor (FG: abbreviation of Frequency Generator, signal proportional to motor rotation), 14 is a rotary head, 15 is a magnetic tape, 16 to 19 are cycle measuring circuits for each motor, and 20, 21 are S
And T reel control circuit, 22 is a capstan control circuit, 23
Is a drum control circuit, 24 to 27 are drive circuits for each motor, 28 is a total tape amount calculation circuit, 29 is a reel radius calculation circuit, 30 is a tape speed calculation circuit, 31 is a drum speed calculation circuit, and 35 is a speed command input terminal. , 36 are reference clock input terminals.

The apparatus shown in FIG. 1 has a capstan system and a reel system as tape running means, and the high-speed search reproduction which is a problem in the present invention is realized by a reel system. First, the tape running by the reel system will be described. In tape running on a reel, the relationship between the rotation speed of the reel and the tape speed changes according to the amount of tape wound on the reel. Therefore, information on the radius of the reel is indispensable for detecting and controlling the tape speed by the reel. Therefore, in this embodiment, the radius of both reels is obtained from the rotation cycle of the capstan in the rotation cycle of the S reel and the T reel. The rotation cycle of the S reel and T reel and the capstan is determined by the FG sensor shown in FIG.
The period of the FG signal generated in proportion to the rotation period of each of the motors 6, 7, 8 by the 10, 10, 12 is obtained by counting with the reference clock supplied from the input terminal 36. Specifically, K _S number of FG pulses is generated, for example, one rotation of the S reel motor, the period of the reference clock is T _CK [s], now, F
Assuming that the count value of the G signal by the reference clock is N _S , the rotation cycle T _S of the S reel at that time is T _S = K _S N _{S TCK} [s] (1). The rotation cycle of the T reel and the capstan can be similarly obtained. The counting of the FG cycle and the multiplication processing shown in the above equation (1) are performed by the cycle measuring circuits 16 and 17,
Performed at 18. From the S reel rotation period T _S , T reel rotation period T _t , and capstan rotation period T _c obtained by the period measurement circuits 16, 17, and 18, the S reel radius r _S and the T reel radius are obtained.
by the fifth diagram for calculation of r _t explaining the principle.

FIG. 5 is a top view showing S, T reels, capstans, drums, and tape paths. In FIG. 5, r _S is the S reel radius (winding diameter radius + tape reel hub), r _t is the radius of the T reel, r _c is the capstan radius, w _S is the S reel angular velocity, w _t is The angular velocity of the T reel, w _c is the angular velocity of the capstan, and v _t is the tape velocity. Note that there is a certain relationship between the angular velocity and the rotation cycle,
The above angular velocity is represented by the following equations (2) to (4) according to the rotation cycle.

First, when the tape is run by the capstan, the following formula (5) holds because the amount of tape sent by the capstan is equal to the amount of tape sent by the reel.

_{v t = r c w c =} r S w S = r t w t ... (5) In this case, than it is the radius r _c of the capstan is known, the radius of each reel following formula (6), (7 ).

On the other hand, when the capstan is separated from the tape and the tape runs only on the reel, it is necessary to obtain the total amount of the tape wound on the S reel and the T reel. The total tape amount S is obtained by the following equation (8).

_{^{S = πr 2 S + πr 2}} t = π (r 2 S + r 2 t) ... (8) above the tape total S is the specific value of tapes apparatus, which calculated at the tape running by capstan when the tape device Is done. In the tape total amount calculation circuit 28 shown in this calculation first Figure, S, the rotation period T _s of the T reel and the capstan, T _t, is calculated by the following equation (9) by T _c. The following equation (9) is obtained by substituting the above equations (6) and (7) into the above equation (8).

Using the total tape amount S obtained by the above equation (9) and the following equation (10), the reel radius when the reels are running alone can be calculated by the following equations (11) and (12).

It said reel radius calculation is performed by the reel radius calculation circuit 29 of FIG. 1, to derive the respective reel with a radius r _S and r _t from rotation period of S reel and T reel T _s and T _t.

Radius data r _S of S reel and T reels obtained in the reel radius calculation circuit 29, r _t is the tape velocity calculation circuit 3
0, S, T are supplied to the reel control circuits 20, 21. The tape speed calculation circuit 30 calculates the T reel circuit period T _t and the T reel radius r _t
Calculate the tape speed and calculate the tape speed data v _t as T
It is supplied to the reel control circuit 21 and the drum control circuit 23.
The T reel control circuit 21 compares the target tape speed determined by the speed command information supplied from the input terminal 35 with the tape speed v _t supplied from the tape speed calculation circuit 30,
The speed error voltage is supplied to the T reel motor via the drive circuit 25. Incidentally amount of tape wound on T T reel in the reel control circuit 21, i.e., from the inertia of the T reel 2 varies greatly depending on T reel radius, T reel radius r _t
Thus, the gain of the speed error voltage supplied to the T reel motor 7 is changed.

On the other hand, the S reel control circuit 20 compares the tape tension data supplied from the tension sensor 5 with the target tension determined by the speed command signal, and outputs the tension error voltage to the S reel motor 6 via the drive circuit 24. Then, the S reel motor 6 is controlled so that the tape tension becomes a predetermined value. In the S-reel control circuit 20, as in the T-reel system, the inertia of the S-reel 1 greatly changes according to the change of the S-reel radius.
It is changing the gain of the tension error voltage according to the S reel radius r _S.

With the above-described T-reel speed control operation and S-reel tension control operation, tape running only by the reel system is realized.

Next, the tape speed control by capstan driving will be briefly described. In tape speed control by capstan drive, the capstan control circuit 22 compares the rotation period _{Tc of the} capstan supplied from the period measurement circuit 18 with a predetermined rotation period, and determines a period error voltage, that is, a speed error voltage. Is supplied to the capstan motor 8 via the drive circuit 26. The speed control of the T reel system during capstan drive is not operated, supplies a fixed voltage corresponding to the T reel radius r _t to T reel motor, T
The tape tension between the reel and the capstan is made substantially constant.

Next, a drum control system which depends on the tape speed which is the most important in this embodiment will be described. In FIG. 1, the FG signal output at a frequency proportional to the rotation of the drum motor 9 is FG signal.
Detected by the sensor 13 and supplied to the cycle measuring circuit 19.
The cycle measuring circuit 19 derives the rotation cycle _Td of the drum motor 9 by counting the FG signal cycle with the reference clock supplied through the input terminal 36, and calculates the head speed calculation circuit.
Supply to 31. Head speed calculating circuit 31, and the drum motor rotation period T _d, the the radius of the drum 4 is a known value, to calculate the velocity v _h of the rotary head 14, drum control circuit
Supply to 23. Drum control circuit 23, in a steady state, it compares the target rotational head speed determined by the tape speed command information supplied from the input terminal 35, and a rotary head speed v _h supplied from the head speed calculation circuit 31 Then, the speed error voltage is supplied to the drum motor 9 via the drive circuit 27, and the drum motor 9 is rotated at a desired speed. on the other hand,
In a transient state in which the tape speed rises to a predetermined speed at the time of search reproduction or the like, the drum control circuit 23
Target speed of the rotating head in the tape speed calculation circuit
It is determined as follows by the tape velocity information v _t supplied from 30.

The role of the drum control circuit 23 in the above transient state is to change the speed of the rotary head 14 with respect to the change in the tape speed,
By making the relative speed of the tape head constant, the frequency of the reproduction signal is made the same as in normal reproduction. Relationship tape speed v _t and the rotary head speed v _h and the relative velocity v _r is here but are then vectorially shown at Figure 2 earlier represented by formula. The tape speed v _t and the rotary head speed v _h and the relative velocity v _r shown in FIG. 2, can be expressed by the following equation (13) using Toratta tilt the theta ₀ when the tape stopped.

v In ^{_{2 r = v 2 t + v}} 2 h + 2v t × v h cosθ 0 ... (13) Therefore, the drum control circuit 23 in a transient state, and the tape velocity information v _t supplied from the tape velocity calculation circuit 30, known The target rotating head speed is calculated from the track inclination angle θ ₀ and the desired relative speed v _{r0 according} to the following equation (14), and the target speed and the head speed calculating circuit are calculated.
Compare with the actual rotating head speed v _h supplied from 31,
The speed error voltage is applied to the drum motor 9 via the drive rotation 27.
To be supplied.

In the drum control circuit 23, the determination between the steady state and the transient state is made when the target head speed of the above equation (14) coincides with the target head speed based on the tape speed command information described above or within a predetermined deviation. The state after the point of time is defined as a steady state, and the state before that is defined as a transient state.

As described above, according to the present embodiment, the tape speed can be detected even in a state where the tape speed is high, such as a transient state in search reproduction, and the speed greatly changes. Since the rotating head speed can be controlled so that the relative speed of the tape head becomes the same as the recording speed by the tape speed, it is possible to always suppress the change in the frequency of the reproduced signal even in the transient state and prevent the deterioration of the reproduced information. Can be.

In the above embodiment, as the operation of the drum control circuit 23 in a transient state, to derive a target speed of the rotary head than the tape velocity information v _t, but so as to compute in accordance with the previous equation (14), this The operation involves a plurality of square calculations and square root calculations, and is a complicated calculation process. Therefore, the search multiple is about 50 times speed, and the change of the reproduction frequency is 0.5
For systems that can be tolerated up to about%, cos [theta] ₀
= 1, the target speed v _h [target] = vr ₀ −v _t (15) of the rotary head can be easily calculated by the following equation (15).

In the embodiment shown in FIG. 1, the [A] of FIG.
And [B], a case has been described where the response time of the rotary head speed control system is shorter than the response time of the tape speed control system. The response time relationship is not necessarily the same as that described above, and such a limitation is not preferable because it limits the degree of freedom of the system. Therefore,
An embodiment in which the present invention is applied to a system in which the response time of the tape speed control system is shorter than the response time of the rotary head speed control system will be described with reference to FIG.

FIG. 6 is a block diagram showing a case where the present invention is applied to a helical scanning type magnetic recording / reproducing apparatus in which the response time of the tape speed control system is set earlier than the response time of the rotary head speed control system. In FIG. 6, a T-reel control circuit
Except for 21 and the drum control circuit 23, the blocks assigned the same reference numerals as those in FIG. 1 are the same blocks as those in FIG. 1, and perform the same operations as those in FIG. Therefore, the difference between the present embodiment and the embodiment shown in FIG.
And the operation of the drum control circuit 23. Hereinafter, the operation of the above two blocks 21 and 23 will be described in detail.

In the system of the present embodiment, as described above, the response time of the tape speed control system is shorter than the response time of the rotating head speed control system. As described above, even if an attempt is made to control the rotational head speed following the tape speed, the response of the rotary head control system is always delayed, and it is difficult to keep the relative speed between the tape and the head constant. Therefore, in the present embodiment shown in FIG. 6, the rotating head speed information v _k derived by the head speed calculating circuit 31 is supplied to the T reel control circuit 21.
In a transient state during search reproduction, a relative speed of the tape and the head is a target speed of the tape as to be the same as the time of recording is calculated by the following equation (16) by the rotary head velocity information v _h, T reel speed control system Is controlled so that the tape speed becomes the target speed.

The T reel control circuit in the steady state of the tape speed
The drum control circuit 21 and the drum control circuit 23 determine the target tape speed and the target rotary head speed in accordance with the speed command information supplied from the input terminal 35, respectively. Drum motor 9
Are supplied with the respective speed error voltages.

The discrimination between the steady state and the transient state in the T-reel control circuit 21 is based on the rotational head speed information by the above equation (16).
v target tape speed calculated using _h is the target time tape speed to match or a predetermined deviation normal state after the point has been reached in the transient state earlier, as determined by the speed command information.

As described above, according to the present embodiment, even in a system in which the response of the rotary head speed control system is slower than the response of the tape speed control system, the tape and the head are in a transient state during the search reproduction when the rotary head speed changes. Since the tape speed can be controlled so that the relative speed becomes the same as during recording, it is possible to always suppress the frequency change of the reproduction signal,
Deterioration of reproduction information can be prevented.

Note in the above second embodiment, as the operation of the T reel control circuit 21, to derive the target tape speed by a rotary head velocity information v _h, but so as to compute in accordance with the previous equation (16), the calculation Is a complicated calculation as in the above equation (14). Therefore, depending on the maximum search multiple and the allowable change rate of the reproduction frequency, the target taper speed can be easily calculated by the following equation (17) by approximating cos θ ₀ of the above equation (16) to 1.

v _t [target] = v _r0 −v _h (17) An embodiment of a helical scanning type magnetic recording / reproducing apparatus in which a signal to be recorded / reproduced next is a digital signal will be described with reference to FIG.

FIG. 7 is a block diagram of a helical scanning type magnetic recording / reproducing apparatus for reproducing a digital signal to which the present invention is applied. 7, blocks denoted by the same reference numerals as those in FIG. 7 except for the drum control circuit 23 are the same blocks as those in FIG. 1, and perform the same operations as those in FIG. Also,
Preamplifier 37, equalization circuit 38, data strobe circuit 39,
The digital processor 40 is the same block as the block given the same reference numeral in FIG. 3 and performs the same operation. The newly provided block in FIG.
A tape / head relative speed calculation circuit 32, a PLL control data generation circuit 33, and a DA converter 34.

The difference between the drum control circuit 32 of FIG. 7 and that of FIG. 1 is that the tape speed information vt is not supplied. Accordingly, in the apparatus of FIG. 7, in the transient state of the search reproduction, the reproduction signal frequency fluctuates due to the relative speed fluctuation as shown in FIG. 4 [C]. Therefore, in the present embodiment shown in FIG. 7, the digital signal reproducing system takes advantage of the feature that if the read digital data is correctly read, the frequency fluctuation during reproduction does not affect the reproduced information at all. With the configuration, correct reading of the reproduced digital data is realized.

In Figure 7, the relative speed detection circuit 32, the rotary head velocity information v _h supplied from the tape speed information v _t and the head speed calculation circuit 31 supplied from the tape speed calculating circuit 50 is supplied. Relative velocity calculation circuit 32, the two velocity information v _t, v _h from Rearranging Equation (13) was the following formula according to (18), derives the relative velocity v _r of the tape and the head.

The ratio of the equation (18) the relative velocity v _r and the recording time of the relative velocity v _r0 derived by are directly made to the rate of change of the reproduction signal frequency. The relative velocity information v _r derived at a relative velocity calculating circuit is supplied to the PLL control data generation circuit 33. P
Accordance LL control data generating circuit 33 in the relative velocity information v _r, VC clock generation in a data strobe circuit 39
Control data for controlling the center frequency of O50 (shown in FIG. 3) is generated. The control data is converted into an analog control voltage V _c by the DA converter 34, it is supplied to the VCO50 of the data strobe circuit 39. Specific relationships of the relative velocity v _r and the analog control voltage V _c, VCO 50 is an LC oscillator, the center frequency _c The following is an example of the case. The frequency control is
Capacitor C is achieved by using a voltage controlled variable diode according to equation (20) below. Equation (20) C ₀ is a proportional constant, V _d is the diffusion potential, and is V _c is the control voltage at.

As described above, there is a relationship between the relative speed v _r and the reproduction signal frequency, _assuming that the relative speed at the time of recording is v _r0 and the signal frequency is ₀ , as in the following equation (21).

Therefore, the center frequency _c is the above formula of the VCO50 in the case where the relative speed is v _r (21) Must be in a relationship. Therefore, the above equations (19) and (2
0), VCO 50 when the relative speed is v _r from (22)
The center frequency in order to conform to reproduction signal frequency of the following formula when determining the VCO control voltage V _c required (23) It suffices to generate a control voltage Vc that satisfies.

In the PLL control data generation circuit 33, the above equation (23)
The control voltage V _c which satisfies, be generated by calculation using the relative velocity v _r is undesirable leading to prolonged and increased operation time of the hard or calculation software. Therefore, in the present embodiment, constitutes a PLL control data generating circuit 33 at a ROM (Read Only Memory), a relative velocity data v _r as the address data supplied from the relative speed calculation circuit 32,
The PLL control data calculated in advance by the above equation (23) is read and supplied to the DA converter 34.

As described above, according to the present embodiment, the center frequency of the clock generation PLL in the data strobe circuit is always set to the reproduction signal frequency even during the transition period when the tape speed changes during the search reproduction and the reproduction signal frequency changes. Can be set to match. Thus, a clock phase-synchronized with the reproduced digital signal can be generated, and the reproduced digital data can be stably read, so that the deterioration of the reproduced information can be prevented even in a transient state.

As the operation of the third embodiment relative velocity calculating circuit 32 in the example, with the tape speed information v _t rotary head velocity information v _h, but to calculate the relative speed by the previous equation (18),
This calculation is a complicated calculation including square calculation and square root calculation. Therefore the maximum search multiple, depending on the allowable calculation error in the relative speed, by approximating the cos [theta] ₀ to 1 of the formula (18), it is also possible to calculate the relative velocity v _r in the following equation (24).

v _r = v _t + v _h (24) In the third embodiment shown in FIG. 7, the influence of the fluctuation of the relative speed between the tape and the head in the transient state during search reproduction is detected, and the relative speed is detected. The center frequency of the clock generating PLL in the data strobe circuit is eliminated by controlling it so as to match the reproduced signal depending on the speed.

On the other hand, the fourth embodiment shown in FIG. 8 proceeds one step further by controlling the speed of the rotary head following the tape speed described in FIG. 1 in the embodiment shown in FIG. It has a function to keep the relative speed constant. In FIG. 8, blocks 32-34 and 37-40 are the same as the blocks of the same reference numerals shown in FIG. 7, and the other blocks are the same blocks as the same reference numerals blocks shown in FIG. An operation similar to the operation described above is performed.

Therefore, in the embodiment shown in FIG. 8, the control is performed so that the relative speed between the tape and the head is the same as that during recording even in the transient state during search reproduction. Furthermore, relative speed fluctuations that cannot be covered by the responses of the tape speed control system and the rotary head speed control system, that is, fluctuations in the reproduction signal frequency, are detected by the relative speed, and the center of the clock generation VCO in the data strobe circuit is detected. and controls to match the frequency to the reproduction signal, the same effect as the embodiment of FIG. 7 in a state of setting small range of variation of the frequency variation range and the VCO control voltage V _c of the VCO is obtained. In addition, in this embodiment, since the reproduced signal frequency does not fluctuate greatly, the equalizing circuit 38 can also be set to the optimum equalizing characteristic limited to a specific frequency band, so that the circuit scale can be reduced and the performance can be improved, that is, the error can be reduced. The rate can be reduced.

〔The invention's effect〕

As described above, according to the present invention, the relative speed between the tape and the head can be easily controlled to be the same as during recording even in the transient state until the tape speed becomes stable in search reproduction or the like. Can be suppressed, and the deterioration of the reproduction information, for example, the deterioration of the image quality can be prevented. Also, when reproducing a digital signal, a clock synchronized with the reproduced digital signal can be generated stably regardless of the tape speed.
With this clock, read digital data can always be read correctly, loss of reproduced data due to a data strobe error during special reproduction can be prevented, and high-quality reproduced data can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram of a helical scanning type magnetic recording / reproducing apparatus according to a first embodiment, FIG. 2 is a vector diagram showing a relationship between a tape speed, a head speed, and a relative speed of a tape head.
FIG. 4 is a block diagram showing a conventional digital signal reproducing system, FIG. 4 is a diagram showing transient response characteristics of tape speed, head speed and relative speed, and FIG. 5 is a diagram showing S, T reels, capstans, drums and tape paths. FIG. 6 to FIG.
The figure is a block diagram of the helical scanning type magnetic recording / reproducing apparatus of the second to fourth embodiments. 16, 17, 18, 19 ... rotation cycle measurement circuit 20 ... S reel control circuit 21 ... T reel control circuit 22 ... capstan control circuit 23 ... drum control circuit 28 ... tape total amount calculation circuit 29 ... Reel radius calculation circuit 30 Tape speed calculation circuit 31 Rotating head speed calculation circuit 32 Tape head relative speed calculation circuit 33 PLL data generation circuit 39 Data strobe circuit 50 Voltage controlled oscillator (VCO)

Continued on the front page (72) Inventor Yuji Inaba 4-3-3 Kanda Surugadai, Chiyoda-ku, Tokyo (Nissan Building) Inside the New Media Business Division, Hitachi, Ltd. (72) Inventor Yuji Sato 1410 Inada Inada, Katsuta City, Ibaraki Pref. (56) References JP-A-60-253047 (JP, A) JP-A-63-317965 (JP, A)

Claims (3)

(57) [Claims] A tape running speed detecting means, and a tape running for negatively feeding back a difference between the tape running speed detected by the tape running speed detecting means and a desired tape running control target speed to a capstan motor or a reel motor. A speed control unit, a rotary head scanning speed detecting unit, and a difference between the rotary head scanning speed detected by the rotary head scanning speed detecting unit and a desired rotary head scanning control target speed is supplied to a drum motor equipped with the rotary head. A helical scanning type magnetic recording / reproducing apparatus comprising: a rotating head scanning speed control means that returns; and a tape running speed detected by the tape running speed detecting means. The sum with the rotating head scanning speed detected by the rotating head scanning speed detecting means becomes a predetermined constant value. A helical scanning type magnetic recording / reproducing apparatus, further comprising a rotating head scanning speed control target speed setting means for setting a controlling target speed of the rotating head scanning speed control means. 2. Tape running speed detecting means, and tape running for negatively feeding back a difference between the tape running speed detected by the tape running speed detecting means and a desired tape running control target speed to a capstan motor or a reel motor. A speed control unit, a rotary head scanning speed detecting unit, and a difference between the rotary head scanning speed detected by the rotary head scanning speed detecting unit and a desired rotary head scanning control target speed is supplied to a drum motor equipped with the rotary head. A helical scanning type magnetic recording / reproducing apparatus comprising: a rotating head scanning speed control unit that returns the rotating head scanning speed detected by the rotating head scanning speed detected by the rotating head scanning speed detecting unit. And the sum of the tape running speed detected by the tape running speed detecting means becomes a predetermined constant value. like,
A helical scanning type magnetic recording / reproducing apparatus comprising a tape running speed control target speed setting unit for setting a control running speed of the tape running speed control unit. 3. Tape running speed detecting means, and tape running for negatively feeding back a difference between the tape running speed detected by the tape running speed detecting means and a desired tape running control target speed to a capstan motor or a reel motor. A speed control unit, a rotary head scanning speed detecting unit, and a difference between the rotary head scanning speed detected by the rotary head scanning speed detecting unit and a desired rotary head scanning control target speed is supplied to a drum motor equipped with the rotary head. A data strobe that includes a rotating head scanning speed control unit that feeds back and a phase-locked loop that generates a clock phase-synchronized with the reproduced signal reproduced by the rotating head, and that latches the reproduced signal whose waveform is shaped using the clock. Helical scanning type magnetic recording / reproducing apparatus comprising: According to the configuration, the control target speed of the rotary head scanning speed control unit is set such that the relative speed between the tape and the rotary head becomes a predetermined constant value according to the tape traveling speed detected by the detection unit. A relative speed calculating means for calculating a relative speed between the tape and the rotary head from the tape running speed detected by the tape running speed detecting means and the rotary head scanning speed detected by the rotary head scanning speed detecting means; Control signal generating means for generating a control signal in accordance with relative speed information obtained by the means, and determining a center frequency of the synchronous clock generating phase locked loop in accordance with a control signal of the control signal generating means. And a helical scanning type magnetic recording / reproducing apparatus.