Information Reproducing Apparatus

1. Field of the Invention:

This invention relates to apparatus for reproducing information from a tape-shaped recording medium which was run at two or more different speeds during recording. Such reproducing apparatus includes magnetic recording and reproducing apparatus, optical reproducing apparatus and many more various types of apparatus. However, the disclosed embodiments are directed chiefly to an apparatus for reproducing video informations from a magnetic tape on which television signals have been recorded, or a video tape recorder (hereinafter referred to as "VTR").

2. Description of the Prior Art:

Recently, high density magnetic recording has become possible, and VTRs capable of making long-time recordings and reproducing such recordings have been developed and commercially manufactured.

For adaption to the convention format too, these are made to operate at various selected time modes, for example, standard and long, during recording and reproduction in a single VTR item. To reproduce the picture recorded on the magnetic tape by such a dual time mode operating VTR, it is necessary to set up the same time mode as the recording operation. Otherwise, because of the tape format being different, a disturbed picture would be reproduced. Manually choosing the required reproduction time mode while observing the reproduced images is very inconvenient to the user. On this account, according to the prior art, when recording, the tape is given one control signal (hereinafter referred to as "CTL" signal) for every one frame at the vicinity thereof. Then when reproducing, the number of revolutions of the capstan motor proportional to the distance the magnetic tape has run is sensed with a pulse generator, and how many pulses have been produced in the time interval of occurrence of the CTL signal is counted to examine whether or not the time mode is different between the recording and the reproduction. Upon detection of the difference, the preliminary setting of the time mode is automatically changed.

Such prior art is described by way of example with reference to FIG. 1. A magnetic tape 1 is moved in a direction indicated by arrow by a capstan 2 and a pinch roller 3. Reproduced from the magnetic tape 1 is the video signal which has been recorded on the incline track to the length of the magnetic tape 1 by a rotating magnetic head (not shown) fixedly carried on a rotary drum as is well known in the art. The capstan 2 is driven by a motor 4 through an endless belt 5 to rotate at a prescribed speed. To sense the speed of rotation of the capstan motor 4, a frequency generator 6 whose output pulses are proportional in number to the speed of movement of the magnetic tape 1 are applied to a counter 8 at a clock input terminal CK thereof. A control head 9 picks up the CTL signals of repetition in frame unit, and its output is applied through an amplifier 10 and a waveform shaper 11 to the "reset" terminal R of the aforesaid counter 8. With such input stage, the counter 8 recycles counting of the number of pulses in a time interval from one to the next CTL signal and its outputs Q1 to Q4 are applied to a magnitude comparator 13 where they are compared with outputs of a reference control 12 in which a number is preset. When this reference number is exceeded, the output Q5 of comparator 13 assumes a high level. That is to say, for the standard mode, the number of pulses counter 8 has counted in between the successive two CTL signals is assumed to be 44. Then if the recording has been operated in the long time mode, where the tape speed is halved, the CTL time interval becomes 1/2 times that of the standard mode. Therefore, when the magnetic tape which has been run at the long time mode during recording is run at the standard mode during reproduction, the number of pulses counted in every one CTL interval is not 44 as normal, but only a half of that, or 22. With the reference control 12 having preset therein an intermediate number between 22 and 44, therefore, that no more than the reference number is counted during reproduction at the standard mode, shows that the recording has been operated in the long time mode. Conversely that more than the reference number is counted, shows that the recording was operated in the standard mode.

However, if some of the CTL signals have failed to be recorded, as if formats do not have what is called the control signals are employed, a problem arises because such automatic mode setting does not result.

With the foregoing in mind, it is an object of the present invention to provide a reproducing apparatus capable of detecting the difference between the running speed of a recording medium during reproduction and the speed during recording even when no CTL signals were recorded.

More specifically, an object of the invention is to provide a reproducing apparatus having detecting means for detecting whether or not the running speed of a recording medium during reproduction is coincident with the running speed of the recording medium during recording by the reproduction output of reproducing means for reproducing information signals.

Another object of the invention is to provide a reproducing apparatus having control means upon detection of the difference between the running speed during reproduction and the speed during recording to automatically bring the running speed during reproduction into coincidence with the running speed during recording.

Still another object of the invention is to provide a reproducing apparatus which, when information is reproduced from a tape-shaped recording medium on which pilot signals such as those disclosed in U.S. Pat. No. 4,297,733 have been recorded, can examine whether or not the running speed during reproduction is coincident with that during recording, by using the reproduced output of said pilot signal.

These and other objects of the present invention will become apparent from the following detailed description with reference to the accompanying drawings.

FIG. 1 illustrates a prior art technique.

FIG. 2, consisting of (a)-(c), is a diagram of a first embodiment of the invention where the tape which was run in the long time mode during recording is run in the standard mode during reproduction.

FIGS. 3 and 4, both consisting of (a)-(c), are similar to FIG. 2 except that the tape which has been run in the standard mode during recording is run in the long time mode during reproduction

FIG. 5(A) is an electrical circuit diagram of a detector for detecting difference in running speed between recording and reproduction in the first embodiment of the invention.

FIG. 5(B) is a graph illustrating variation of the output of the frequency-to-voltage converter circuit 103 of FIG. 5(A).

FIG. 6 illustrates part of a program of the sequence control circuit of FIG. 5(A).

FIGS. 7(a) and 7(b) are diagrams of a second embodiment of the invention where the tape which was run in the long time mode during recording is run in the standard mode during reproduction.

FIGS. 8(a) and 8(b) are similar to FIGS. 7(a) and 7(b) except that the tape which was run in the standard mode during recording is run in the long time mode during reproduction.

FIG. 9 is an electrical circuit diagram of a detector for detecting difference in running speed between the recording and reproduction in the second embodiment of the invention.

FIG. 10 illustrates a program of the switching control circuit of FIG. 9.

FIGS. 2, 3 and 4 illustrate the principle of the invention, when the helical scan type rotating head is used as a head for recording and reproduction.

FIG. 2(a) illustrates recording tracks on a magnetic tape of which a0, a1 . . . have been recorded by a recording head of plus azimuth, and b0, b1, . . . by another head of minus azimuth, and which has been run in the long time mode. Against this, suppose reproduction is preformed in the standard mode on the assumption that the running speed of the tape in the long time mode is 1/2 times that in the standard mode, and the width of the recording and reproducing head for the long time mode is 1/2 times that of the reproducing head for the standard mode.

When reproducing in the standard mode, therefore, the heads trace as shown by dashed lines. A1, A2, . . . are tracing paths of the plus azimuth head, and B1, . . . are those of the minus azimuth head.

Therefore, the reproduced outputs by the two heads as shown in FIG. 2(b) are such that for A1 field, tracks a0 and a1 are reproduced, for B1 field, b2 and for A2 field, a2 and a3. In other words, in A1 and A2 fields, the crosstalk components of the adjacent two are detected, so that the reproduction level is lowered as compared with that in B1 field.

Then, by comparing the reproduced output with a prescribed threshold level S, comparison output pulses are obtained as shown in FIG. 2(c). These pulses repeat at a rate of one per 2 fields. FIG. 3 is a diagram of another case where recording has been operated in the standard mode, and reproducing is operated in the long time mode. As shown in FIG. 3(a), azimuth-recorded tracks b1 - a1 - b2 - a2 and so on are reproduced by azimuth-reproducing heads of the same width as that of the recording heads as A1 - B1 -A2 - B2 - A3 - B3 and so on. In F1 field, the same azimuth track a1 is reproduced. In B1 field, track b1 is reproduced. In A2 field, track a1 is reproduced. The reproduced output levels become the same as just 1/2 times slow reproduction is preformed. Upon comparison with a prescribed threshold level S, one pulse for every 4 fields is obtained (FIG. 3(c)).

FIG. 4 illustrates another case where similarly to FIG. 3 the magnetic tape which has been run in the standard mode during recording is run in the long time mode during reproduction. However, the width of the reproducing azimuth head is a half of that of the recording head.

When the azimuth recorded tracks are reproduced by the azimuth head, as shown in FIG. 4(b), almost no reproduced outputs are obtained in the B1 and B3 fields. Therefore, as shown in FIG. 4(c), similarly to FIG. 3(c), at a rate of once per 4 fields, comparison output pulses are obtained, and also in the picture display, one noise bar in 4 fields is produced.

Of course, when the running speeds in the recording are the same, both of the comparison output pulse and the noise bar do not take place.

FIG. 5(A) illustrates an embodiment of a detector circuit for detecting difference in the running speed.

The circuit includes a plus azimuth head H1; a minus azimuth head H2; a switching circuit SW for switching between the heads H1 and H2; a comparator 102 for comparison with a threshold level; a frequency-to-voltage converter circuit 103; window comparators 104 to 107; AND gates AND1 and AND2; and resistors R1 to R5.

The reproduced outputs from heads H1 and H2 are amplified by amplifier 100, and reproduction envelope signals are obtained by envelope detector 101. The envelope signal is compared with the prescribed threshold value by comparator 102 to obtain periodic noise bar detection pulses as shown on lines (c) in FIGS. 2, 3 and 4. The detection pulses are converted by converter circuit 103 to a voltage proportional to the reciprocal of the period as shown in FIG. 5(B), and then applied to one of two inputs of each of comparators 104 to 107, the other inputs of which are supplied with respective reference voltages V1 to V4 from a voltage divider of resistors R1 to R5 across an electrical power source or battery Vcc. When the output voltage of converter 103 lies between V1 and V2, the output of AND1 assumes a high level, and when between V3 and V4, the output of AND2 takes on a high level. In other words, when one noise bar in every two fields is detected, it is AND gate AND1 that produces an output of high level indicating that while recording was in the long time mode, reproduction is in the standard mode. And when once in every four fields, it is AND gate AND2 that produces an output of high level, indicating detection of the fact that while recording was in the standard mode, reproducing is in the long time mode.

This output is applied to sequence control circuit 108.

FIG. 6 is a diagram illustrating part of a program of the sequence control circuit 108.

At first, the preset mode by the user is read in and whether it is the standard mode or the long time mode is determined. In the case of the standard mode, the tape is caused to run in the standard mode to examine whether or not the output of AND1 is high level. Upon detection of low level of AND1, the reproduced video signals are given to a TV monitor without further alternation. Upon detection of high level, the long time mode is used. Also in case where the preset mode is the long time one, the tape is caused to run at a speed corresponding to the long time mode, and whether or not the output of AND2 is high level is examined. Upon detection of low level of AND2, the reproduced video signals are applied without further alternation of the TV monitor. Upon detection of high level, the tape is caused to run in the standard time mode. By this the same mode as recording was operated is rendered operative during reproduction, thereupon a noise-bar-free picture is obtained on the TV monitor.

It is to be noted that trhough the foregoing embodiment has been described in connection with the ratio of the running speed of the tape during recording to that during reproduction taken at 2:1 or 1:2, for other values of the running speed ratio, it is of course possible to achieve such detection.

It is also noted that though the period of the noise bar detected pulses is sensed by using a frequency-to-voltage converter, it is of course possible to use a timer circuit or other suitable means for detecting purposes.

Also though the foregoing embodiment has been described taking as the reproducing apparatus an example of an apparatus for reproducing a magnetic tape which was azimuth-recorded, the invention is applicable to another or optical type reproducing apparatus provided that a difference between the recording and reproducing speeds results in aberration from the recording tracks. For, if so, the reproduced output level varies periodically, detection of its period enables adjustment of the reproducing speed.

Next described is a second embodiment of the invention.

FIGS. 7 and 8 are principle diagrams for explaining the second embodiment.

FIG. 7(a) illustrates recording tracks on a magnetic tape, where a1, a2, . . . are those of the tracks which have been recorded by the plus azimuth recording head, and b1, b2, . . . are the others which have been recorded by the minus azimuth recording head, and these tracks alternate as a1 - b1 - a2 - b2 - a3 - b3 and so on in the long time mode.

It is to be noted here that for each of tracks a1, a3, a5, . . . a pilot signal of frequency f1 has been recorded in superimposing relation on the video signals, for each of tracks b1, b3, b5, . . . another pilot signal of frequency f2, for each of tracks a2, a4, a6, . . . another pilot signal of frequency f4, and for each of tracks b2, b4, b6, . . . another signal of frequency f3. The frequencies f1, f2, f3 and f4 have relationships: f1<f2<f3<f4, f2-f1=f4-f3=f5; f4-f2=f3-f1=f6; and f5.noteq.f6. When the f1, f2, f3 and f4 pilot signal-recorded tracks are individually reproduced, those of the pilot signals which have been recorded in the adjacent tracks are reproduced as crosstalk components. By multiplying the reproduced output by the one of signals F1, F2, F3 and F4 which have the same frequency as the pilot signal in the track being reproduced has, the crosstalk components are extracted as signals of the frequencies f5 and f6. Then, the levels of the signals f5 and f6 are compared with each other to obtain a tracking control signal (hereinafter referred to as "ATF" signal). The foregoing description is made as an example of the method for obtaining the "ATF" signal. In this connection it should be pointed out that the frequencies of the signals to be superimposed on the video signals may be combined in another different way, and many other combinations can be considered.

Now suppose that such recorded tracks are reproduced at a faster running speed (standard mode) that the recording speed (long time mode). In FIG. 7(a), the head tracing paths during reproduction in the standard mode are shown by dashed lines with an arrow .alpha. indicating the direction in which the tape is run and another arrow .beta. indicating the direction in which the head scans. Also the running speed of the tape in the long time mode is assumed to be a half of that in the standard mode, and the width of the reproducing head for the standard mode is assumed to be 2 times that of the recording head for the long time mode. With such an arrangement, when tracing at the tape speed for the standard mode, the track pattern on the tape does not match the inclination of the path of the reproducing head, and moreover no correspondence between the reproduced output of the pilot signal (f1-f4) recorded in the track to be reproduced and the frequency signal (F1-F4) to be mixed with the reproduced output can be taken. For this reason, as shown on line (b) in FIG. 7, the "ATF" signal varies by a period of 2 frames. Referring to FIG. 7(a), if the reproducing head scan B2 field, because the frequency signal to be multiplied during scanning of the B2 field is F3, the "ATF" signal would control the phase of rotation of the capstan so that among the tracks on which the pilot signal of the same frequency as that of the signal F3, the nearest track b4 to the B2 is to be reproduced. However, because the direction of movement of the reproducing head is different from the direction of path of the track by the aforesaid reason, a good tracking condition is attained during a B2 field only at an intermediate point in the B2 field. And at the start point of scanning the B2 field, the pilot signal f4 in the preceding adjacent track a4 is largely reproduced, and at the terminal point of scanning, the pilot signal f1 in the following adjacent track a5 is largely reproduce. As a result, the ATF output takes on a high level at the start point in order to speed up the tape movement, and low level at the terminal point in order to slow down the tape movement.

Now assuming that, as usual, the voltage of the ATF output is Vcc/2 when the good tracking condition is attained, then the ATF output represents a vibrating waveform of 2-frame period with Vcc/2 at the center.

FIG. 8 illustrates a mistracking condition resulting from the use of the long time mode during reproduction despite recording has been operated in the standard mode. What is different from FIG. 7 is that the mistracking condition repeats itself in a period of just 4 frames. Therefore, the ATF output vibrates by the 4-frame period as shown on line (b) in FIG. 8. In conclusion, when reproduction is performed at a speed of tape movement different from that at which the tape was run during recording, the ATF output signal varies its magnitude periodically.

FIG. 9 is a block diagram of a fundamental circuit of putting the above-described principles into practice. The circuit includes reproducing heads 28a and 28b; a demodulator circuit 29 of known construction for obtaining the ATF signal from the pilot signals (f1-f4) for tracking reproduced by the reproducing head 28a, 28b (detailed, for example, in the specification of U.S. Pat. No. 4,297,733); a rotation control servo circuit 30 for capstan motor 14; band pass filters 15 and 16 for extracting only 2-frame and 4-frame periodic signals respectively; rectifier and detector circuits 17 and 18 for the filters; comparators 19 and 20 cooperating with a constant voltage source 25 of adjustable output voltage E1; integrator circuits 21 and 22; comparators 23 and 24 cooperating with a constant voltage source of adjustable voltage E2; and switching control circuit 27 for changing the tape running speed.

The ATF signal from the ATF demodulator circuit 29 is directed not only to the capstan servo circuit but also to the band pass filters BPFs 15 and 16 where only the signals of 2-frame period and 4-frame period (in the case of the NTSC signal reproducing VTR, 15 Hz and 7.5 Hz respectively) are allowed to pass therethrough to detectors 17 and 18. The outputs of detectors 17 and 18 in the form of direct current signals, because of their including simple noise components, are compared with the threshold voltage E1 by comparators 19 and 20. Only when above E1 level, the outputs of comparators 19 and 20 are averaged by integrator circuits 21 and 22. Then only when the outputs of integrators 21 and 22 exceed above the threshold voltage E2, comparators 23 and 24 produce outputs A and B of high level respectively that the output A is of H level shows that the tape which was run at the long time mode during recording is reproduced at the standard speed. That the output B is of H level, indicates that the tape which was run at the standard speed during recording is reproduced in the long time mode. Of course, when what has been recorded in the standard mode is reproduced in the same mode, or when what has been recorded in the long time mode is reproduced in the long time mode, both of the outputs A and B do not become H level, as a matter of course. The outputs A and B are applied to the switching control circuit 27 controlling the running speed of the tape in accordance with the outputs A and B.

FIG. 10 illustrates part of a program of switching control circuit 27.

At first, the preset mode by the user is read in, and whether it is the standard mode or the long time mode is discriminated. In the case of the standard mode, the tape is caused to run at the normal speed. Then whether or not the output A is of high level is examined. Upon detection of the output A of low level, the reproduced video signals are emerged to a TV monitor without further alternation. Upon detection of high level, the speed of the tape movement is changed to the slow one. In the case of the long time mode presetting, the tape is caused to run at the slow speed corresponding to the long time mode, while whether or not the output B is of high level is examined. Upon detection of the output B of low level, the reproduced video signals are applied without further alternation onto the TV monitor. Upon detection of high level, the speed of tape movement is changed to the standard one. Thus only after the same mode is set up during reproduction as was set during recording, noise bar free, near pictures are obtained on the TV monitor.

It is to be noted that though the foregoing embodiment has been described in connection with the ratio of the tape speed in the standard mode to that in the long time mode taken at 2:1, generally speaking by the ratio of N:1 (where N is an integer), it is when the tape is run at N times faster a speed than the required one during reproduction that the ATF output signal varies by a period of 2/(n-1), and it is when at 1/N times faster a speed, that the period is 2N-frames. Therefore, as BPFs 15 and 16, those having transmittance in frequencies of 15Hz and 15/N Hz respectively must be selected for use. So long as this requirement is fulfilled, the present invention is applicable to any type reproducing apparatus where the speed ratio is other than 2:1, or three or more different reproduction speeds are provided. In this embodiment the technique of detecting the periodic variation of the ATF output signal uses BPFs and detector circuits. However, is also possible that the ATF output is passed through an LPF to reduce noise, then pulses are formed at points when the ATF output goes across Vcc/2, then the time interval between the successive two pulses is converted to a voltage by the frequency-to-voltage converter, and then the outputs A and B are obtained by the window comparators.

Also though, in this embodiment, the ATF signal itself is utilized, the difference between the recording and reproducing speeds can be otherwise detected by sensing the level of the frequency signal such as f2-f1, or f4-f2 in the front stage. It is also possible to detect the difference between the recording and reproducing speeds by the reproduced period of one pilot signal out of the frequencies f1, f2, f4 and f3.

Also though the foregoing embodiment has been described in connection with the use of four pilot signals of different frequencies (f1-f4) during recording, the present invention is applicable to all other type reproducing apparatus, provided that from the tape on which pilot signals of different frequencies have been recorded in adjacent tracks are reproduced the pilot signals to obtain the tracking signal.

As has been described in greater detail above, even with a recording medium having no CTL signals recorded theron, the invention makes it possible to detect coincidence or difference between the recording speed (the running speed of the recording medium during recording) and the reproducing speed (the running speed of the recording medium during reproduction). This is done by the reproduced output of reproducing means for reproducing information signals.

Also by using its detected output, it is possible to automatically bring the reproducing speed into coincidence with the recording speed.

it is to be understood that the present invention is not limited to the above-described embodiments, and that many applications and variations are possible within the spirit and scope of the invention construed in the appended claims.