JPH07262646A - Method and device for detecting partial erasure of video tape - Google Patents

Abstract

PURPOSE:To automatically detect partial erasure or partial rewrite of a program by continuously recording an identification signal on a section incorporating a recording section of a program signal and detecting the presence of the identification signal. CONSTITUTION:The continuous identification signal 10 is recorded on a video tape 1 beforehand over neatly the whole length of a video tape 1 in addition to a program signal 7. The inflation signal 10 is recorded on the sound track and the control track of the video tape 1, and is made the signal to be hardly recorded by a usual tape recorder beforehand. A partial erasure detection device allows the video tape 1 to travel while reproducing the identification signal 10 in the video tape 1. Then, when the interruption of the identification 10 is detected while traveling, the device decides that the partial erasure exists.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video tape partial erasure detection method and a detection device for detecting partial erasure of a video tape on which a program is recorded in advance.

[0002]

2. Description of the Related Art A cassette type video tape is used as a medium for commercially renting a movie or recorded video program. This is because video tape recorders for playing back video tapes are widely used, and the video tapes have high durability and can withstand repeated use sufficiently.

A general problem in using a videotape for renting a program is that a part of the program may be erased or a part of the program may be rewritten by another program. In order to solve this problem, the cassette type video tape has a mechanism for preventing erroneous erasure. As a mechanism for preventing erroneous erasure, a hole is provided in a part of the case of the cassette. The video tape recorder has a function of detecting this hole. When a video tape provided with a hole for preventing accidental erasure is inserted into the video tape recorder, the recording system of the video tape recorder does not work. However, this mechanism can be easily released. Therefore, it is impossible to completely prevent erroneous erasure. Further, it is impossible to completely prevent the failure, malfunction, and operation of the video tape recorder without releasing the mechanism for preventing erroneous erasure. Moreover,
Since one video tape has a length of about 250 meters, it is very difficult to find a partial abnormal portion in a program.

One of the methods for knowing whether or not the program rewriting or erroneous erasure has occurred on the video tape used for rental is surely to play the returned video tape. The reproduction for this confirmation can be performed at about 10 times the normal reproduction speed. However, the inspection by this method cannot be applied when 100 or more inspections are required per day because the fatigue of the inspector is severe.

As an apparatus for inspecting a recorded video tape, an apparatus described in Japanese Patent Laid-Open No. 3-38001 (G11B5 / 00) is known. The apparatus described herein is used primarily in the process of producing prerecorded videotapes. The device described therein is adapted to measure the duration of a video signal or audio signal when the video signal or audio signal falls below a preset level, and to inspect the video tape depending on the duration.

In addition, JP-A-60-205832 (G11
B5 / 86) describes a device for automatically inspecting the contents recorded on a tape. The device described here is adapted to automatically compare preset reference data with data reproduced on a tape. However, it was not possible to detect partial erasure in the video tape with the above two techniques.

[0007]

DISCLOSURE OF THE INVENTION The present invention, by inspecting a video tape in which a program is recorded in advance,
An object of the present invention is to provide a method and apparatus for automatically detecting partial erasure or partial rewriting of a program.

[0008]

In order to solve the above-mentioned problems, the present invention provides a partial erasure detection method for detecting partial erasure of a video tape in which a program signal is recorded in advance. In the longitudinal direction, an identification signal is continuously recorded in a section including at least the recording section of the program signal, the medium is run at a speed capable of reproducing the identification signal, and the identification signal is While it can be detected, it is determined that the program signal has not been erased or re-recorded, and the program signal has been rewritten when the identification signal cannot be detected over a preset section while the medium is running. This is a method for detecting partial erasure of a video tape that is determined to be a thing.

Further, according to the present invention, in order to detect the partial erasure of the video tape which has been subjected to the above-described method for detecting the partial erasure of the video tape, the traveling means for traveling the video tape and the operation of the traveling means are From the running control means for controlling, the identification signal reproducing means for reproducing the identification signal recorded on the video tape, the interruption detecting means for detecting interruption of the identification signal reproduced by the identification signal reproducing means, and the control means. A video tape partial erasure detection device configured to stop the running of the video tape when the interruption detecting means detects an interruption of the identification signal while the video tape is running. It is what

[0010]

In contrast to the conventional recorded video tape, the video tape in the case of implementing the video tape partial erasure detection method of the present invention has an identification signal added in addition to the signal to be recorded on the conventional video tape. To record. This identification signal is recorded in a section including the section in which the program signal is recorded. Further, the identification signal is continuously recorded without interruption. To detect partial erasure of the video tape having the identification signal recorded, the presence or absence of the identification signal is detected.

Further, the apparatus for detecting the partial erasure of the video tape on which the identification signal is recorded makes the video tape run by the running control means. The identification signal reproducing means reproduces the identification signal from the running video tape. The interruption detecting means detects that the identification signal reproduced by the identification signal reproducing means is interrupted. Then, the control means stops the running of the video tape when the interruption detecting means detects the interruption of the identification signal.

[0012]

FIG. 1 is an explanatory diagram of a video tape for explaining an embodiment of the present invention. Video tape 1 starts at 2
Starts with and ends with end 3. A leader tape 4 is connected to the starting end 2. A trailer tape 5 is connected to the terminal end 3. The leading end 6 of the leader tape 4 and the trailing end 81 of the trailer tape 5 are respectively connected to reels (not shown). The leader tape 4, the video tape 1, and the trailer tape 5 are contained in a cassette case (not shown) together with the reels. A program signal 7 is recorded on the video tape 1. The program signal 7 is recorded between the program signal start point 8 and the program signal end point 9. The start end 2 of the video tape 1 and the program start point 8 are normally separated by 0.3 meters or more, but the positions may be the same. Moreover, the distance between the end 3 of the video tape 1 and the program end point 9 is usually 0.3 m or more, but the positions may be the same.

The video tape 1 also has an identification signal 10
Is recorded. The identification signal 10 is the identification signal starting point 1
It is recorded between 1 and the end point 12 of the identification signal. The program signal 7 is recorded between the identification signal start point 11 and the identification signal end point 12. That is, the program signal start point 8
Is at the same position as the identification signal start point 11 or at the identification signal end point 12 side, and the program signal end point 9 is at the same position as the identification signal end point 12 or at the identification signal start point 11 side. The identification signal starting point 11 is located at the same position as the starting end 2 of the video tape 1 or at a position several cm away from the starting end 2. The identification signal end point 12 is the end 3 of the video tape 1.
At the same position as or a few cm apart. The identification signal 10 is continuously recorded from the identification signal start point 11 to the identification signal end point 12 without interruption. The program signal 7 is recorded between the program signal start point 8 and the program signal end point 9, but need not be continuous.
There may be a break in the middle. That is, the identification signal 10 is recorded from the identification signal start point 11 to the program signal start point 8, both the identification signal 10 and the program signal 7 are recorded from the program signal start point 8 to the program signal end point 9, and the program signal The identification signal 10 is recorded from the end point 9 to the identification signal end point 12.

FIG. 2 shows an example of the magnetization pattern of the video tape 1. The magnetization pattern of the video tape 1 used in the video tape recorder is strictly defined according to the standard. The magnetization pattern shown in FIG. 2 is a standard pattern used in home video tape recorders. The magnetization pattern shown in FIG. 2 is
It is an example of the magnetization pattern defined by one standard, and the magnetization pattern according to another standard is different from the magnetization pattern shown in FIG. The video tape 1 can be divided into three areas in the width direction. The first area is the area 13 of the audio signal. The second area is the area 14 of the video signal. The third area is the area 1 of the control signal.
It is 5.

The audio signal area 13 includes a first audio track 16 and a second audio track 17.
Are arranged. Two audio tracks 16, 1
In order to record a stereo audio signal, 7 can record a signal with an independent audio frequency. The audio tracks 16 and 17 are recorded in the longitudinal direction of the video tape 1 by a fixed audio head. In the area 14 of the video signal, the video track 1
8 are arranged and a video signal is recorded. The video track 18 is recorded obliquely by the rotary head.
A control signal track 19 is arranged in the control signal area 15. Control track 1
A pulse signal is recorded on 9 in the longitudinal direction of the video tape 1. This pulse signal serves as a reference signal for controlling the running speed of the video tape 1 when the video tape 1 is reproduced. The control track 19 is recorded by a fixed control head.

Identification signal 10 to be recorded on the video tape 1.
Preferably satisfies the following three conditions. (1) It can be easily detected even when the video tape 1 is running at high speed. (2) The presence of the identification signal 10 does not interfere with the reproduction of the video tape 1 by the home video tape recorder. (3) The identification signal 10 or a signal similar to the identification signal 10 cannot be easily recorded by a home video tape recorder.

However, the above-mentioned three conditions are 10 of the model of the video tape recorder capable of reproducing the video tape 1.
It is not necessary to be satisfied with 0%. The standard provides several options for one item. Then,
There can be as many videotape recorder types as there are combinations of options. However, the options adopted for the actually manufactured video tape recorder are
It will be limited. That is, the above three conditions are
For example, 95% or more of commercially available video tape recorders should be satisfied.

For example, in the standard of a certain video tape 1,
There are two rules for the area 13 of the audio signal. One is a definition for monaural sound, and the area 13 of the audio signal includes one monaural audio track. The second is a standard for stereo sound, and the area 13 of the audio signal includes a set of stereo audio tracks. In order to maintain compatibility with each other, these two rules are such that the recording width of a monaural audio track is substantially the same as the recording width of a pair of stereo audio tracks. By doing so, the video tape recorder having a stereo head capable of reproducing a stereo audio track can normally reproduce the sound of the video tape 1 of the monaural audio track in monaural. on the other hand,
A video tape recorder equipped with a monaural head so that a monaural audio track can be reproduced can reproduce a stereo recorded audio signal in monaural by simultaneously reproducing one set of stereo audio tracks. And more than 95% of commercially available video tape recorders are designed to play monaural audio tracks.

From the above, the identification signal 10 has various recording patterns within a range satisfying the above-mentioned three conditions. Two preferred examples are shown for recording the identification signal 10 on the video tape 1 having the magnetization pattern shown in FIG. An example of the first recording pattern is an example of recording the identification signal 10 in the audio area 13, and an example of the second recording pattern is an example of recording the identification signal 10 in the control signal area 15.

(1) First Recording Pattern FIG. 3 is an example of the first recording pattern and shows a recording pattern when the identification signal 10 is recorded in the area 13 of the audio signal of the video tape 1. is there. Identification signal 1
0 is the first recorded in the first audio track 16.
Test signal 20 and a second test signal 21 recorded on the second audio track 17. First
The inspection signal 20 and the second inspection signal 21 have the same frequency and the phases are inverted. The frequency of the inspection signals 20 and 21 is preferably 150 Hz or less. The waveform of the inspection signals 20 and 21 is preferably a sine wave or a triangular wave. The representative inspection signals 20 and 21 are continuous sine waves having a frequency of about 25 Hz when the video tape 1 is reproduced and run. The recording levels of the inspection signals 20 and 21 are possible in a range that does not significantly affect the original audio signals recorded in the audio tracks 16 and 17, and in a range where the distortion of the recording waveform of the inspection signals 20 and 21 is small. It's as big as possible. It is desirable that the recording levels of the inspection signals 20 and 21 are the same. The presence or absence of the identification signal 10 is checked by checking the check signals 20 and 21.

If the identification signal 10 is recorded as shown in FIG. 3, the identification signal 10 can be easily detected even when the video tape 1 is running at a high speed. That is, since the frequency of the inspection signals 20 and 21 is about 25 Hz, even if the video tape 1 is run at 100 times,
It is only detected as a 500 Hz signal. Also,
Most home video tape recorders reproduce two audio tracks 16, 17 with one mono fixed head. Then, the first inspection signal 2
The 0 and the second test signal 21 cancel each other out. Two
When one audio track 16 and 17 is reproduced by one monaural fixed head, the inspection signals 20 and 21 are
It is not output as an audio signal to the outside. Further, it is impossible for a home video tape recorder to record the identification signal 10 on the two audio tracks 16 and 17. The first reason is that it is impossible to record separate signals on the two audio tracks 16 and 17 with a monaural fixed head. The second reason is that even if the video tape recorder is equipped with a stereo fixed head, in order to record the inspection signals 20 and 21 whose phases are accurately inverted, a special signal transmitting means and a phase inversion means are used. This is because it is necessary to prepare.
Therefore, the recording pattern of the identification signal 10 shown in FIG.
The condition that the identification signal 10 should have is satisfied.

(2) Second Recording Pattern FIG. 4A is an example of the second recording pattern, showing an example of recording the identification signal 10 in the area 15 of the control signal. The identification signal 10 based on the second recording pattern is recorded by applying a pulse width to the control signal recorded on the control track 19. The control signal recorded on the control track 19 of the control signal area 15 is recorded as magnetic saturation recording.
The magnetization pattern of the control track 19 is S pole and N pole.
The poles are recorded alternately. The reproducing head for reproducing the control track 19 outputs a positive pulse signal when the magnetization pattern of the control signal changes from the S pole to the N pole and a negative pulse signal when the magnetization pattern of the control signal changes from the N pole to the S pole. . Of these, the video tape recorder uses only the positive pulse signal as the control signal. The video tape recorder can normally reproduce the video tape 1 if it can reproduce only the positive pulse signal.

In the magnetization pattern of the control signal recorded by a normal video tape recorder, the ratio between the N-pole region and the S-pole region is specified in advance by the standard, and the ratio is 6: 4. As a result, control track 1
The reproducing head 9 outputs the ratio of the interval from the positive pulse signal to the negative pulse signal and the interval from the negative pulse signal to the next positive pulse signal at an interval of 6: 4.
When the ratio of the N-pole and S-pole regions is 6: 4, the identification signal 10 does not exist.

On the other hand, in the magnetization pattern of the control track 19 recording the identification signal 10, the N pole is wider than the S pole, and the ratio thereof is 1/6: 5/6. As a result, based on the positive pulse signal, the negative pulse signal is generated at 5/6 of one cycle. That is, the identification signal 10 is recorded as the pulse width modulation signal 30 in which the ratio of the width of the S pole to the width of the N pole is 1/6: 5/6. Whether or not the identification signal 10 is present on the control track 19 is determined by detecting the ratio of the S pole and the N pole of the control track 19.

If the identification signal 10 is recorded as shown in FIG. 4, the identification signal 10 can be easily detected even when the video tape 1 is running at a high speed. That is, the frequency of the control signal recorded on the control track 19 is defined by the standard and is about 30.
Hz. Therefore, even if the video tape 1 is run 100 times, it is only detected as a signal of about 3000 Hz. Further, the video tape recorder uses only the positive pulse signal of the control signal. Therefore, the negative pulse signal is based on the positive pulse signal,
It does not hinder the reproduction of the video tape 1 at any position. Furthermore, in a normal video tape recorder, the positive pulse signal of the control signal is used as a reference,
The position of the negative pulse signal cannot be moved and recorded. Therefore, it is impossible to record the control track 19 including the identification signal 10 with an ordinary video tape recorder. Therefore, the recording pattern of the identification signal 10 shown in FIG. 4 satisfies the condition that the identification signal 10 should have. The ratio of the width of the S pole to the N pole is 1/6 to 5/6.
However, other ratios may be used. The pulse width modulated signal 30 obtained by pulse width modulating the control signal can be easily detected if the position of the negative pulse signal changes by about 10% with respect to the positive pulse signal.

Next, the recording procedure of the identification signal 10 will be described. In order to record the identification signal 10 together with the program signal 7 on the video tape 1, the process of duplicating the video tape can be industrially used. The process of industrially reproducing a video tape consists of two steps. The first step is
This is the process of creating a mother tape. The second step is to copy from the mother tape to the copy tape.

FIG. 5 is an explanatory diagram of a step of producing a mother tape. The mother tape has the same length as the video tape 1 shown in FIG. 1 and the recorded contents are almost the same, but the magnetization pattern of the mother tape is a mirror image of the video tape 1. The mother tape 22 runs between the reels 23 and 24. A rotary head 25 and a fixed head 26 are arranged on the traveling path of the mother tape 22. The rotary head 25 records a signal corresponding to the video signal 18 shown in FIG. 2 on the mother tape 22.
The fixed head 26 records signals on the mother tape 22 on the audio tracks 16 and 17 and the control track 19 shown in FIG. 27 is a program signal circuit. 28 is an identification signal generation circuit. 29 is a recording circuit. The output of the program signal circuit 27 and the output of the identification signal generating circuit 28 are connected to the recording circuit 29. The output of the recording circuit 29 is connected to the fixed head 26.

The program signal circuit 27 is a circuit for sending the program signal 7 shown in FIG. 1 to the recording circuit 29. The signal source of the program signal circuit 27 is a signal reproduced from a master tape (not shown) in which a signal to be recorded on the mother tape 22 is recorded. The identification signal generation circuit 28
According to the above-mentioned first recording pattern or second recording pattern, the inspection signals 20 and 21 are generated, or a signal for pulse-width modulating the control signal output from the program signal circuit 27 is generated. The recording circuit 29 combines the signals output from the program signal circuit 27 and the identification signal generating circuit 28 and outputs the combined signal to the recording head 26.

FIG. 6 is an explanatory diagram of a process of transferring the magnetization pattern from the mother tape 22 to the copy tape. 31
Is a transfer wheel. The transfer wheel 31 is a metal cylinder that rotates freely. 32 is a copy tape. The copy tape 32 runs from the supply reel 33 toward the take-up reel 34. A transfer wheel 31 is provided between the supply reel 33 and the take-up reel 34, and the copy tape 32 travels via the transfer wheel 31. The mother tape 22 connects the start end and the end to make endless. The magnetic surface of the mother tape 22 and the magnetic surface of the copy tape 32 are in close contact with each other on the outer circumference of the transfer wheel 31. 35 is
It is a laser light source. The light source 35 is the laser beam 3
Radiates 6. The laser beam 36 is used for the copy tape 3
It is radiated so as to have a slit-like shape on the magnetic material of No. 2 which is almost the same as the tape width. As a result, the laser beam 36
Heats only the magnetic material of the copy tape 32 on the transfer wheel 31 in a short time. As a result, the mother tape 22
The magnetization pattern of 1 is transferred to the copy tape 32 as a mirror image.

The length of the copy tape 32 shown in FIG. 6 is about 20 times the length of the mother tape 22. Mother tape 2
The magnetization pattern of 2 is repeatedly transferred to the copy tape 32. The copy tape 32 on which the transfer is completed is entirely wound up on the winding reel 34. Then copy tape 32
Is cut according to the length of the mother tape 22 and a leader tape and a trailer tape are connected to both ends, thereby completing the video tape shown in FIG.

The large-scale duplication of the video tape by this transfer is suitable for mass-producing the video tape 1 shown in FIG. The reason is that the video tape has the identification signal 10
The difference between whether the mother tape 22 includes the identification signal 10 and whether the mother tape 22 does not include the identification signal 10.
Therefore, the video tape 1 including the identification signal 10 shown in FIG. 1 can be manufactured only by changing the manufacturing process of the mother tape 22 shown in FIG.

Next, a method of detecting partial erasure on the video tape 1 shown in FIG. 1 will be described. First, in order to detect partial erasing, the reproducing head capable of reproducing the identification signal 10 is caused to run while at least contacting the video tape 1 from the identification signal start point 11 to the identification signal end point 12.
At this time, the running speed of the video tape 1 is determined by the identification signal 10
It only needs to be a speed that can reproduce. As for the traveling direction, as long as the identification signal 10 can be detected, the traveling direction may be from the starting end 2 to the ending end 3 of the video tape 1 or from the ending end 3 to the starting end 2. When the interruption of the identification signal 10 is detected while the video tape 1 is running, it is determined that the video tape 1 is partially erased. The interruption of the identification signal 10 is judged to have been interrupted when there is interruption for a preset judgment reference time or longer. This judgment reference time is preferably 0.5 seconds or more and 10 seconds or less when the video tape 1 is reproduced by the video tape recorder. The reason for this is that if it is set to 0.1 seconds or less, the dropout of the track on which the identification signal 10 is recorded is judged to be partial erasure. Also, 10
This is because if the time is longer than a second, partial erasure in a short time cannot be detected. The actual judgment reference time is preferably about 2 seconds.
When partial erasure is detected while the identification signal 10 is being detected, it is desirable to immediately stop the running of the video tape 1 and display a message indicating that partial erasure is detected.

FIG. 7 shows the structure of the video tape partial erasure detection device 44. The video tape partial erasure detection device 44 is a device for inspecting the video tape 1 shown in FIG. The video tape partial erasure detection device 44 is used for inspecting the partial erasure of the video tape 1 returned from the customer when the video tape 1 is used for rental.

Reference numeral 40 denotes a running means for running the video tape 1. Reference numeral 42 is a running control means for controlling the running of the video tape 1 mounted on the running means 40.
43 is a video tape 1 that is run by the running means 40.
From the identification signal reproducing means. Reference numeral 45 is interruption detecting means for detecting interruption of the identification signal reproduced by the identification signal reproducing means 43. 46 is
When the interruption detecting means 45 detects the interruption of the identification signal, the running control means 42 causes the video tape 1
It is a control means for stopping the traveling of. 47 is an output terminal of the control means 46. When the interruption detecting means 45 detects partial erasure, the output terminal 47 outputs a signal notifying that a display device (not shown) or the like has detected partial erasure.

The running means 40 runs the video tape 1 with the video tape 1 kept in the cassette case. The traveling means 40 includes a reproducing head for reproducing the audio tracks 16 and 17 and / or the control track 19 shown in FIG. The running means 40 can run the video tape 1 in the first direction and the second direction.

The traveling control means 42 controls the operation of the traveling means 40. The running control means 42 controls the running direction of the video tape 1, the running speed, the running position, and the start end 2 and the end 3 of the video tape 1. The running control means 42 detects the state of the video tape 1 necessary for these controls by detecting the rotation of the reel of the video tape 1 or the control signal recorded on the control track 19.

The identification signal reproducing means 43 is the video tape 1
Then, the identification signal 10 recorded on the video tape 1 is reproduced. The identification signal reproducing means 43 detects the identification signal 10 recorded on the video tape 1 while distinguishing it from the video signal 7. The interruption detecting means 45, when the identification signal 10 reproduced by the identification signal reproducing means 43 is interrupted, determines whether or not there is partial erasure according to the length of the interruption.

FIG. 8 shows the identification signal reproducing means 4 shown in FIG.
3 shows the configuration of the identification signal reproducing means 43 when the identification signal 10 is recorded on the audio track as shown in FIG. The identification signal 10 shown in FIG.
In one audio track 16, 17, the inspection signal 20,
It is recorded as 21. Identification signal reproducing means 4 shown in FIG.
3 includes a first input terminal 50, a second input terminal 51, and an output terminal 52. Reference numeral 48 is a first reproducing circuit, and 49 is a second reproducing circuit. 53 is an inverting circuit. 54 is a discrimination circuit. In the input terminal 50,
The reproduction signal of the first audio track 16 shown in FIG. 3 is input. The reproduction signal of the second audio track 17 is input to the second input terminal 51. The first reproduction circuit 48 and the second reproduction circuit 49 are provided with the inspection signals 20 and 2
It is desirable to include a filter that selectively passes 1. In this filter, the inspection signals 20 and 21 are 25
In the case of a sine wave of Hz, a band pass filter or a low pass filter may be used. The inverting circuit 53 inverts the phase of the output signal of the first reproducing circuit 48. Discrimination circuit 54
Is an addition circuit for adding the output of the inverting circuit 53 and the output of the second reproduction circuit 49, and a level determination circuit for determining whether the signal added by the addition circuit is higher or lower than a preset level. Contains. Discrimination circuit 54
The determination result of is output from the output terminal 52.

According to such a configuration, the phase of the signal input from the first input terminal 50 is inverted by the inverting circuit 53. First input terminal 50 and second input terminal 51
Since the inspection signals 20 and 21 input to the signal are inverted in phase, they are in phase when added by the determination circuit 54. As a result, the level discriminating circuit of the discriminating circuit 54 can clearly discriminate the presence or absence of the discrimination signal 10.

FIG. 9 shows the identification signal reproducing means 4 shown in FIG.
3 shows another configuration of the identification signal reproducing means 43 when the identification signal 10 is recorded on the control track 19 as shown in FIG. The identification signal reproducing means 43 shown in FIG. 9 includes an input terminal 55 and an output terminal 56. A signal reproduced from the control track 19 shown in FIG. 4 is input to the input terminal 55. A signal indicating the presence or absence of the identification signal is output from the output terminal 56.

Reference numeral 57 is a reproducing circuit. Reference numeral 58 is a separation circuit. The separation circuit 58 separates the positive pulse signal and the negative pulse signal from the control signal output from the reproduction circuit 57. Reference numeral 60 is a clock recovery circuit. The clock reproduction circuit 60 reproduces a clock signal from the positive pulse signal separated by the separation circuit 58. 61
Is a timer circuit. The timer circuit 61 outputs a timer signal having a preset time width based on the clock signal output from the clock reproduction circuit 60. 62 is a discrimination circuit. The determination circuit 62 determines, based on the timer signal output from the timer circuit 61, whether or not the negative pulse signal output from the separation circuit 58 includes the identification signal 10.

The operation of the identification signal reproducing means 43 shown in FIG. 9 will be described with reference to FIG. The signal reproduced from the control track 19 input to the input terminal 55 is shown in FIG.
It is a signal obtained by reproducing the signal shown in FIG. The signal is
A positive pulse signal appears when the magnetization pattern of the control track 19 changes from the S pole to the N pole, and a negative pulse signal appears when the magnetization pattern of the control track 19 changes from the N pole to the S pole.
The separation circuit 58 separates and outputs the positive pulse signal and the negative pulse signal. FIG. 4B shows a positive pulse signal, and FIG. 4C shows a negative pulse signal. Figure 4
The positive pulse signal shown in (b) is output when the magnetization pattern shown in FIG. 4 (a) changes from the S pole to the N pole. The negative pulse signal shown in FIG. 4C is output when the magnetization pattern shown in FIG. 4A changes from the N pole to the S pole. The clock regeneration circuit 60 regenerates the clock signal from the positive pulse signal shown in FIG. 4 (b), as shown in FIG. 4 (d). The clock signal shown in FIG. 4 (d) is generated at the rising edge of the positive pulse signal shown in FIG. 4 (b). As shown in FIG. 4E, the timer circuit 61 generates a timer signal having a preset time interval based on the clock signal shown in FIG. 4D. The timer signal shown in FIG. 4 (e) is generated in synchronization with the clock signal shown in FIG. 4 (d). The determination circuit 62 determines that the identification signal 10 does not exist when the negative pulse signal shown in FIG. 4C is present during the period in which the timer signal shown in FIG. When there is no identification signal 10
Is determined to exist.

FIG. 10 is a flow chart for explaining the operation of the video tape partial erasure detection device 44 shown in FIG. If the device 44 operates according to the flowchart shown in FIG. 10, it is useful for detecting partial erasure of a video tape used for rental.

When renting the video tape 1, the video tape is rewound so that the beginning of the program can be immediately reproduced so that the beginning 2 is at the beginning. However, when the rented video tape 1 is returned, it may not be returned at the position where the start end 2 comes to the beginning. Therefore, even when the partial erasure detection device 44 of the video tape detects partial erasure, the state of the returned video tape 1 is confirmed and the video tape 1 is rewound once or fast forwarded to It is necessary that the beginning end 2 or the end end 3 of the tape 1 be at the beginning.

If the partial erasure detection device 44 of the video tape is operated according to the flow chart shown in FIG. 10, the partial erasure is automatically detected, and the video tape 1 is detected when the partial erasure is detected. It is possible to set the starting end 2 of the to the beginning. As a result, the video tape 1 that has been inspected for partial erasure by the device 44 can be immediately lent.

The operation of the video tape partial erase detection device 44 begins at step 65 and ends at step 66. In the start step 65, first, the returned video tape 1 is mounted on the video tape partial erasure detection device 44. Then, in step 67, the device 44
Checks whether the current position of the video tape 1 is at the end 3 shown in FIG. 1 or at a position other than the end 3. If it is not the end 3, the current position of the video tape 1 is between the end 3 and the start 2. Therefore,
If the current position of the video tape 1 is other than the end point 3, the device 44 runs the video tape 1 toward the end point 3 in step 68.

Next, in step 69, the device 44 runs the video tape 1 from the end 3 to the start 2. Step 70 is a step of detecting the start end 2 of the video tape 1. If the start end 2 is detected in step 70, the process proceeds to step 66, and all operations are stopped.

Step 71 is a step of detecting the identification signal 10. The operation of detecting the identification signal 10 is performed while the video tape 1 is running from the end 3 to the start 2.

Step 72 is a step of determining whether or not the identification signal 10 is present. If the identification signal 10 is present on the video tape 1, the process returns to step 69 to continuously detect the presence of the identification signal 10. If the identification signal 10 is not detected, step 73
Move on to.

In step 73, it is determined whether or not the cause of the absence of the identification signal 10 is partial erasure. If the partial erasure is not performed, the process returns to step 69 and the identification signal 10 is continuously detected. If it is determined that there is partial erasure, the process proceeds to step 74 and the running of the video tape 1 is immediately stopped. Then, in step 75, the fact that partial erasure is detected is displayed.

Next, a typical operation of the device 44 will be described. First, when the video tape 1 is returned, the video tape 1 is loaded into the device 44. Then,
The device 44 fast-forwards the video tape 1 to the end 3 at high speed regardless of the winding state of the video tape 1. Next, the identification signal 10 is detected while rewinding at high speed. Then, when partial erasure is not detected in the video tape 1, the video tape 1 is taken out from the device 44 at that time. The beginning 2 of the video tape 1 taken out from the device 44 is always at the beginning. Therefore, the video tape 1 can be rented immediately.

[0052]

According to the present invention, when the video tape is used for rental, even if the program is partially erased at the rental destination, it can be completely detected.
Further, even if the present invention is carried out, the reproduction function is not affected at all when reproduced by a home video tape recorder.

Further, according to the present invention, not only partial erasure of the video tape but also partial damage of the video tape can be detected. That is, while using a videotape, the audio track or control track recorded at the end of the videotape should be the first to be damaged due to a failure of the videotape recorder or the life of the videotape. There are many. By practicing the invention, the device 44 monitors the audio or control track along the entire length of the videotape 1 to detect the identification signal 10. As a result, not only partial erasing of the video tape but also damage to the audio track and control track can be detected in the same manner as partial erasing. As a result, by implementing the present invention, it is possible to rent higher quality video tapes.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a video tape embodying the present invention.

FIG. 2 is a partially enlarged view of a magnetization pattern of a video tape.

FIG. 3 is an enlarged view of a first recording pattern

FIG. 4 is an enlarged view of a second recording pattern and an operation explanatory view.

FIG. 5 is an explanatory diagram of a mother tape manufacturing process.

FIG. 6 is an explanatory diagram of a duplication process of a video tape.

FIG. 7 is a block diagram showing a configuration of a partial erase detection device.

FIG. 8 is a block diagram showing a configuration of a first embodiment of an identification signal reproducing means.

FIG. 9 is a block diagram showing the configuration of a second embodiment of the identification signal reproducing means.

FIG. 10 is a flowchart showing the operation of the partial erasure detection device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 video tape 2 start end 3 end 7 program signal 10 identification signal 40 traveling means 42 traveling control means 43 identification signal reproducing means 45 interruption detecting means 46 control means

 ─────────────────────────────────────────────────── (72) Inventor Hideo Tanaka 4-33-3 Kokuryo-cho, Chofu-shi, Tokyo 3 Otari Co., Ltd. (72) Shoichi Matsumoto 4-33-3 Kokuryo-cho, Chofu-shi, Tokyo Ota Re Inc. (72) Inventor Masaaki Watanabe 4-33-3 Kokuryo-cho, Chofu-shi, Tokyo 3 Otari Co., Ltd.

Claims (6)

[Claims] 1. A partial erasure detection method for detecting partial erasure of a video tape on which a program signal is recorded in advance, wherein an identification signal is present in a section including at least a recording section of the program signal in a longitudinal direction of the video tape. The recording medium is continuously recorded, the medium is run at a speed capable of reproducing the identification signal, and the program signal is not erased or re-recorded while the identification signal can be detected while the medium is running. And a method for partially erasing a video tape, wherein it is determined that the program signal has been rewritten when the identification signal cannot be detected over a preset section while the medium is running. 2. The recording of the identification signal on the video tape is performed by first recording the program signal and the identification signal on a mother tape and then recording the magnetization pattern of the mother tape on the video tape. The method for detecting partial erasure of a video tape according to claim 1. 3. The identification signal is a first signal on a first track.
The second signal is recorded on the second track, and the first signal and the second signal are inverted signals whose phases are mutually inverted. 1
Or the method for detecting partial erasure of a video tape according to item 2. 4. The video tape according to claim 1, wherein the video tape includes a control track on which a pulse signal is recorded, and the identification signal is a pulse modulation signal obtained by modulating a pulse on the control track. Partial erasure detection method. 5. An apparatus for detecting partial erasure of a video tape in which an identification signal is continuously recorded in a section including at least a program signal recording section in a longitudinal direction of the video tape, the video tape is run. Means for controlling the traveling means, traveling control means for controlling the operation of the traveling means, identification signal reproducing means for reproducing the identification signal recorded on the video tape, and interruption of the identification signal reproduced by the identification signal reproducing means. And a control means for detecting interruption of the identification signal while the interruption detecting means detects the interruption of the identification signal while the video tape is running. Partial erasure detection device for videotape that stops the running of the video tape. 6. An apparatus for detecting partial erasure of a video tape in which an identification signal is continuously recorded in a section including at least a program signal recording section in a longitudinal direction of the video tape, wherein Traveling means for traveling in the second direction and the second direction, traveling control means for controlling the operation of the traveling means, and identification signal reproducing means for reproducing the identification signal recorded on the video tape.
It comprises interruption detecting means for detecting interruption of the identification signal reproduced by the identification signal reproducing means, and control means. The control means first causes the video tape to run in the first direction, When it reaches the end, it is run in the second direction, and when the interruption detecting means detects the interruption of the identification signal while the video tape is running in the second direction, the running of the video tape is stopped. Video tape partial erasure detection device.