JPH0727670B2 - Video tape recorder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention has a video tape recorder suitable for application to a portable type camera-integrated video such as an 8 mm video, and particularly has a time-lapse function. Video tape recorder.

[Prior Art] If a time-lapse recording function can be added as a recording function to a camera-integrated video (portable video) such as 8 mm video, this enables intermittent long-time recording or slow-motion shooting. , It is very convenient for users because the field of use increases.

Here, the time-lapse shooting is to record an image of one to several fields at regular intervals or at arbitrary times. Therefore, in order to enable such time-lapse photography, a button dedicated to time-lapse photography is provided in addition to the normal operation button. Needless to say, such an operation button can also be used in combination.

In the time-lapse shooting, as shown in FIG. 7, once the time-lapse button is turned on, a video signal is recorded for a predetermined period W at regular intervals. To end the time-lapse shooting, the time-lapse shooting button may be operated again.

On the other hand, in the example shown in FIG. 8, the video signal is recorded for a certain period W each time the time-lapse button is turned on.

[Problems to be Solved by the Invention] In the time-lapse recording shown in FIG. 7, time-lapse recording is performed by the following means.

That is, when the time-lapse button is operated, the recording mode is set as shown in FIG. 9, the video signal is recorded for a predetermined number of fields, and when the recording of the last field is completed, the rewinding state is automatically set. After rewinding for a certain period of time, the unit enters the standby state. In the next time-lapse shooting, it will be in a playback state for a certain period of time, tracking servo will be made with this,
The recording mode is first entered when tracking is completed.

Therefore, in such a time-frame shooting mode, it takes a relatively long time from the end of recording the last field to the transition to the next time-frame shooting mode. A long one requires an interval time of about 5 to 7 seconds.

Of course, in the case of designing to transit a plurality of modes in this way, the inertia of the reel or the like cannot be ignored. Therefore, when the reel inertia is large, there is a drawback that the interval time becomes longer.

In the case where the interval time is taken in this way, it is impossible to meet a request for performing slow motion shooting at, for example, one second intervals. However, I often experience encountering situations where I want to record the desired image at short intervals.

In the case of FIG. 8 as well, it is obvious that the same interval time as in the case of FIG. 7 is required.

Even when recording for a long time at an interval of 1 to 3 seconds, there are the same drawbacks as described above.

As described above, the one using the time-lapse mode as shown in FIG. 9 is not suitable for the time-lapse recording at a short time interval.

Therefore, the present invention solves all the drawbacks of such a conventional apparatus, and proposes a video tape recorder in which the interval time is shortened and the continuous shots are not disturbed by the shortening of the interval time. Is.

[Technical Means for Solving Problems] In order to solve the problems described above, in the present invention, four types of pilot signals having different frequencies are sequentially repeated for each field and recorded together with a video signal, and at the time of reproduction. When tracking is performed based on the pilot signal, and when the time-lapse mode is selected, the video signal is recorded at an integral multiple of at least 4 fields, and then the magnetic tape is automatically driven for a predetermined field inversion and then automatically stopped or automatically. A video tape recorder having a time-lapse function that is inverted has a beat detection circuit that detects the beat components of the pilot signals recorded in the third and fourth fields of the four types of pilot signals. However, in this detection circuit, the pilot signal recorded in the fourth field A reference signal composed of the same signal is supplied, and detection means for detecting the signal corresponding to the end of the beat component first output from the beat detection circuit is provided, and based on the output of the detection means when the time-lapse mode is selected. When the magnetic tape is driven to reverse, the magnetic tape is automatically stopped or automatically reversed in the second field after the magnetic tape is driven to reverse.

[Operation] The beat detection circuit 13 is supplied with the reproduced pilot signal Pf and the reference signal Po, and the fourth pilot signal f ₄ of the pilot signal tracking signals is used as the reference signal Po.

Therefore, if the horizontal pass frequency f _H is selected as the band pass frequency of the band pass filter 14, a band pass output can be obtained in a field rewound by two fields from the rewind point. At this time, since the rewinding field detection signal, that is, the stop signal S4 is output, when the tape is rewound to this field, the tape surely stops.

Therefore, according to the present invention, the tape can be stopped at the time when the tape is rewound by two fields, and the tape can be prepared for the next time-lapse recording.

This can greatly reduce the interval time.

Further, since the rewinding field of the tape can be detected reliably, the joint shooting between the time-lapse scenes becomes smooth.

[Embodiment] Next, an example of the video tape recorder according to the present invention will be described in detail with reference to FIG.

For convenience of explanation, the outline time-lapse mode of the present invention will be described with reference to FIG. However, in the following example, once the time-lapse button is turned on, until the next time-lapse button is operated or the time set by the timer elapses,
Time-lapse mode shall continue.

As shown in FIG. 4, when the time-lapse shooting mode is started, a video signal is first recorded for a predetermined period m. Simultaneously with this signal recording, a pilot signal Pf for performing reproduction tracking servo is recorded.

As shown in FIG. 5, the pilot signal Pf is inserted on the lower frequency side than the low frequency conversion color signal C, and has a frequency peculiar to each field. Specifically, it is composed of _four frequencies f _{1 to} f ₄ as is well known. The frequency relationship is shown in FIG.

In FIG. 5, Y is an FM luminance signal.

The predetermined period m to be recorded is 4α fields (α is an integer), and in this example, it is 4 fields.

Now, when the last field is recorded, the playback mode is automatically changed and the capstan is automatically switched to the reverse mode.

As a result, only the tape traveling system is in the rewinding state. In this rewind mode, the signal system is the playback mode,
The video signal recorded immediately before is reproduced.

The rewind period is 2 fields. The reason for setting 2 fields is the shortest rewind period that can be detected by the reproduction pilot signal, and it can be said that it is the minimum time of the time required for the capstan drive motor to rise to the normal speed in the next time-lapse recording. Is.

During this rewinding period, the rewinding amount is detected based on the reproduction pilot signal Pf. The rewinding amount is detected by the rewinding field detection circuit 10, a specific example of which will be described later.

When two fields are detected after rewinding, the apparatus is stopped in that state.

In the recording mode again, the capstan is driven in the normal direction and at the same time in the reproducing state, the previous video signal is reproduced from the stop point q, and thereby the tracking servo is executed. Then, when the magnetic head approaches the field of the rewind point p, the capstan drive motor has reached normal rotation.

The video signal is intermittently recorded again from the rewind point, that is, the recording start point p over the period m of four fields. After that, the same frame-taking operation is repeated.

FIG. 1 shows an example of a circuit for realizing preset rewinding field detection even in the time-lapse mode as described above.

In FIG. 1, reference numeral 10 indicates this detection circuit as a whole,
The video signal reproduced by the rotary magnetic head H is a preamplifier 11
After being supplied to the low-pass filter 12, the reproduction pilot signal Pf is extracted.

The reproduction pilot signal Pf is supplied to the beat detection circuit 13 at the next stage. The beat detection circuit 13 is further supplied with the fourth pilot signal having the frequency f ₄ output from the generator 20 of the pilot signal Pf as the reference signal Po.

The beat output is supplied to the bandpass filter 14, and the frequency component having substantially the same frequency as the horizontal synchronizing frequency is extracted from the beat output. In this example, the pass band width is selected so that the beat output near 16 kHz can be extracted, so that the band pass filter 14 outputs the filter output S1 shown in FIG. 2A.

That is, as shown in FIG. 3, the relationship between the video signal and the pilot signal superimposed and recorded on the video signal is that the first pilot signal whose frequency is f ₁ on the recording start track T1.
Pf is always recorded, and from the next, the second from f ₂ to f ₄
4 pilot signals are sequentially recorded as shown.

Therefore, even in the time-lapse shooting mode, if it is set so that the first pilot signal Pf having the frequency f ₁ is always recorded in the first field to be recorded, the rewind point (also the recording end point). ) In track T4 of p, the frequency is
The fourth pilot signal Pf, which is f ₄ , will be recorded.

Therefore, the relationship between the reproduction track based on the rewind point p and the first beat output centering around 16 kHz, that is, the filter output S1 is as shown in FIG. 2A. This can be easily understood from the fact that the frequency relationship of pilot signals is selected as shown in FIG.

In FIG. 6, f _H represents the horizontal synchronizing frequency.

For this reason, as shown in FIG. 2, the beat output of a predetermined level is obtained only when the magnetic head H crosses the third track T3.

The envelope of the filter output S1 which is the first beat output is detected by the envelope detection circuit 15, and the envelope detection output S2 (B in the same figure) is supplied by the reference voltage source 17 from the reference voltage source 17 in the comparator 16. (Figure B)
Is compared with the voltage.

As a result, the comparator 16 outputs the comparison output shown in FIG.
S3 is generated, and is supplied to the mono-multi 18 for the rising operation, whereby the pulsed stop signal S4 shown in FIG. This stop signal S4 functions as a detection signal of the rewind field, a drive motor (not shown) is controlled to a stop state, and the magnetic head H is located just between the third and second tracks T3, T2. Stop at.

Thus, by using the reproduction pilot signal Pf as a reference, the rewinding end point q can be reliably detected and the tape running can be stopped at this rewinding end point q. Therefore, the bandpass filter 14, the envelope detection circuit 15, the comparator 16 and the monomulti 18 described above constitute a detection means for detecting the signal corresponding to the end of the beat component.

Needless to say, if the relationship between the video signal and the pilot signal is not shown in FIG. 3, the frequency of the reference signal supplied to the beat detection circuit 13 is changed accordingly.

[Effects of the Invention] As described above, according to the present invention, the rewinding field detection circuit controls the rewinding of the tape by detecting the predetermined number of fields to be rewound.

According to this, firstly, the rewinding amount can be made extremely small as compared with the conventional case. This is because, even in the rewind mode, only the capstan is driven to rotate in the reverse direction, which eliminates mechanical mode transition. It is also important that there is no influence of the reel inertia. Due to this relationship, even when intermittent recording is performed at intervals of 0.4 to 0.5 seconds, the requirement can be surely met.

Secondly, even if the rewinding amount is set short, the set rewinding amount can be reliably detected. Therefore, the connection between the recording start field at the time of the next frame shooting and the last field recorded immediately before that will be perfectly aligned. This does not cause the screen to be disturbed even when the time-lapse recording video signal is reproduced.

Thirdly, the rewind field detection circuit 10 can use a part of the existing pilot signal detection circuit system (including the reference signal generator 20 from the circuit 11 to the circuit 15 in FIG. 1). Can be greatly simplified.

From the above, the present invention is extremely suitable for application to a video tape recorder having a time-lapse function, which is an integrated video such as a miniaturized 8 mm video.

[Brief description of drawings]

FIG. 1 is a system diagram showing an example of a rewinding field detection circuit which is a main part of a video tape recorder according to the present invention, FIG. 2 is a waveform diagram for explaining the operation, and FIG. 3 is a recording track and a pilot signal. FIG. 4 is an explanatory view of time-lapse recording according to the present invention, FIG. 5 is an explanatory view of a video signal, FIG. 6 is a spectrum diagram showing a frequency relationship of pilot signals, FIGS. FIG. 8 is an explanatory view of the time-lapse shooting mode, and FIG. 9 is an explanatory view similar to FIG. 4 used for explaining the time-lapse shooting recording. 10 …… Rewinding field detection circuit 13 …… Beat detection circuit 14 …… Band pass filter 15 …… Detection circuit 16 …… Comparator 20 …… Reference signal generator Pf …… Pilot signal Po …… Reference signal S ₁ …… Filter output (beat output) S4 …… Detection signal (stop signal)

Claims (1)

[Claims] 1. Four kinds of pilot signals having different frequencies are sequentially repeated for each field and recorded together with a video signal, tracking is performed based on the pilot signal at the time of reproduction, and at least when a time-lapse mode is selected. After the video signal has been recorded with an integral multiple of 4 fields, after the magnetic tape is driven for a predetermined field inversion,
In a video tape recorder having a time-lapse function that is automatically stopped or automatically inverted, beat components of pilot signals recorded in the third and fourth fields of the above four types of pilot signals Has a beat detection circuit for detecting a beat, which is supplied with a reference signal composed of the same signal as the pilot signal recorded in the fourth field and which is first output from the beat detection circuit. Detection means for detecting a signal corresponding to the end of the component is provided, and the magnetic tape is reversely driven based on the output of the detection means when the time-lapse mode is selected. The above-mentioned magnetic tape is automatically stopped or automatically reversed. Video tape recorder with time-lapse function.