JPS6256717B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a video signal recording device, and by setting the diameter of a rotating body such as a rotating drum or a rotating plate, and the tape winding angle, it is possible to achieve an extremely compact configuration, especially compared to the current two. An object of the present invention is to provide a video signal recording device capable of recording and creating a magnetic tape having the same tape pattern format and signal recording form as a head type helical scan type magnetic recording/reproducing device (VTR).

As the mainstream of simple VTRs for home use, the azimuth two-head type helical scan type VTR is currently becoming extremely popular. For devices such as VTRs that use magnetic tape as a recording medium, standards are needed to unify the recording conditions on magnetic tape, and this will ensure that all common items are consistent.
Compatibility of so-called magnetic tapes is established. In VTRs, the diameter of the rotating surface of a rotating body (hereinafter referred to as a rotating drum for convenience of explanation) to which a rotating head is fixed, such as a rotating drum or rotating plate, is one of the most important items in the standard. All VTRs of the same standard have a fixed diameter. The diameter of this rotating drum (hereinafter also referred to as ``drum diameter'') has a significant influence on the overall size of the VTR, especially in portable types.

FIG. 1 is a diagram showing the configuration of an example of the tape running system of a current two-head helical scan type VTR. A magnetic tape 1 unwound from a supply reel (not shown) touches the gap surface of a full-width erasing head 2. passing through and being guided by the poles 3 and 4, respectively, and wound around the rotating drum 5;
After passing through an audio and control head 8 and being pinched by a capstan 9 and a pinch roller 10, it is wound onto a winding reel (not shown). As is well known, the magnetic tape 1 is held and driven by a rotating capstan 9 and a pinch roller 10, and is caused to travel in the direction of the arrow. On the other hand, the rotating drum 5
Video heads _H1 and _H2 having gaps with different azimuth angles are mounted facing each other at an angle of 180°.

The magnetic tape 1 is connected to poles 4 and 6 as shown in FIG.
As shown in FIG. 2, the lower fixed drum 1 is rotated over 180 degrees to the rotating drum 5, and rotates counterclockwise in FIG.
The tape is wound obliquely along a tape guide band provided at 1. As mentioned above, the winding angle of the magnetic tape 1 on the rotating drum 5 is 180° plus the overlap, which is a relatively gentle winding angle, so the tape running is stable, and the magnetic tape 1 is automatically wound. Easy loading.
Further, since the magnetic tape 1 is wound at an angle with respect to the rotating surface of the rotary drum 5 as shown in FIG. It is well known that it is formed by H ₁ and H ₂ . With this tape pattern, the maximum playback output is obtained when the video head that plays back the video track has a gap with the same azimuth angle as when recording, but when it has a gap with a different azimuth angle than when recording, the maximum playback output is obtained. Taking advantage of the azimuth loss effect that prevents reproduction output from being obtained, video tracks are recorded closely together without guard bands, thereby improving the recording density of magnetic tape.

However, although it is desired that portable VTRs be made smaller, the size of the drum diameter has such a large effect that it influences the overall size of the device. However, once the standard was established, this drum diameter became constant, and even portable VTRs had to use rotating drums with the above-mentioned large diameter, which placed restrictions on miniaturization of the device.

The present invention eliminates the above-mentioned drawbacks, and one embodiment thereof will be described with reference to FIG. 3 and the following drawings.

FIG. 3 shows the configuration of an embodiment of the tape running system of the video signal recording apparatus according to the present invention. In the same figure, the first
Components that are the same as those in the figures are given the same reference numerals, and their explanations will be omitted. In FIG. 3, reference numeral 12 denotes a rotating drum, on which video heads _H3 and _H4 having gaps with different azimuth angles are mounted close to each other and separated by a predetermined distance, and poles 3, 4, 13, 14, etc., magnetic tape 1 is approximately
It is wrapped around 300°. The pole 15 is provided to change the running path of the magnetic tape 1.

Next, to explain the relationship between the tape winding angle and the drum diameter, in this example, the tape winding angle is
300° plus the angle for recording the overlap
The angle is selected to be a little over 100 degrees. This 300° is the first
This corresponds to the tape winding angle of 180° for the VTR shown. Therefore, the first requirement for equalizing the track trajectories on the magnetic tape is to make the circumferential distances of the rotating drum 5 and the rotating drum 12 of this embodiment equal at each effective winding angle. Therefore, in order to establish compatibility between the two rotating drums 5 and 12, the drum diameter of the rotating drum 5 should be _D1 , the drum diameter of the rotating drum 12 should be _D2 , and the effective winding angle in FIG. 3 should be α. degree, the drum diameter D ₂ has the following relationship: 1/2D ₁ ≒α/360D ₂ ∴D ₂ ≒180/α·D ₁ (180°<α<360°). Since α=300° here, the drum diameter D ₂ is 3/5 times the drum diameter D ₁ . Note that the angle of inclination when winding the tape around the rotating drum 12 needs to be the same as that around the rotating drum 5. Although the drum diameter D ₂ and the inclination angle are extremely small in relation to the signal recording format described later, each requires dimension correction, and the amount of correction differs slightly depending on the conditions, so it is omitted here and the above equation is approximated. It is shown.

As is clear from the above equation, if the tape winding angle is further increased, the drum diameter of the rotating drum 12 can be further reduced, but this is determined by considering the ease of tape winding operation and running stability. . Incidentally, if the tape winding angle is about 315 degrees, the drum diameter can be made 4/7 times smaller than that shown in FIG. Therefore, the area occupied by the rotating drum is reduced to about 1/3, which greatly contributes to miniaturization of the device.

Further, the distance between the audio and control head 8 shown in FIG. 3 and the tape exit side of the effective winding angle α is made to match that of the current VTR shown in FIG. Further, in FIG. 3, video heads _H3 and _H4 having gaps with different azimuth angles are mounted on the rotating drum 12, which rotates counterclockwise, facing each other at 180 degrees.

As described above, the greatest feature of the present invention is that the diameter of the rotating drum can be set relatively freely in relation to the tape winding angle. In this embodiment, the effective winding angle is 300 degrees, and as a result, the drum diameter is 3/5 of that of the rotating drum 5 having the configuration shown in the first diagram, and the area occupied by the rotating drum 12 is also approximately 36%. This greatly helps in downsizing.

Next, a signal recording form of this embodiment having a tape running mechanism as shown in FIG. 3 will be explained. In FIG. 3, the video heads H ₃ and H ₄ are synchronously rotated in the counterclockwise direction with the rotary drum 12, and are wound over the effective winding angle α (here, 300°) while the capstan 9 is being wound. A video signal corresponding to one field is recorded on one inclined video track on a magnetic tape 1 which is pinched and driven by pinch rollers 10 and made to run in the direction of the arrow. That is, as shown by the diagonal line RH ₃ in FIG. 4, the video head H ₃ first records a little more than one field's worth of video signal in the angular range α and a slight overscan before and after that, and then the video head Recording is interrupted until H ₄ reaches the overscan position before the angular range α. Then video head _H4 starts recording, and as shown in Figure 4.
After recording a little more than one field worth of video signals in the α angle range and a slight overscan part before and after it, as shown in RH ₄ , the next video head H ₃
Recording is interrupted until the point reaches the overscan position before the angular range α. Thereafter, recording is performed intermittently in the same manner as above.

The above recording operation can be expressed in another way as follows. In other words, the video head rotates every 1.5 rotations (540° rotation) of the rotating drum 12.
Within the range of 540°, which is alternately recorded by H ₃ and H ₄ , each video head records the effective winding angle α and a slight overscan before and after the effective winding angle α. Recording is stopped for the remaining range excluding this recording range from the 540° range.

As described above, no signal is recorded until the recording of one of the video heads _H3 and _H4 is completed and the recording of the other video head is started. Therefore, it is necessary that the recorded video signal does not contain important image information in this non-recording section (in other words, one field's worth of image information and vertical synchronization required only in the signal recording section) is required. (must contain both signals). Therefore, the video signal recorded in the present invention is not a standard video signal, but a special modified video signal. When such a special video signal is generated from a television camera, it can be created relatively easily by setting constants, or it can be created by converting the number of scanning lines from a standard video signal using field memory, etc. This is also possible with current technology.

In this way, when a magnetic tape on which a special video signal is recorded by the above-mentioned means is played back on a current two-head helical scan VTR, a standard video signal can be obtained with complete compatibility. The special recording video signal will be explained in more detail. FIG. 5 shows the waveform etc. of the recording video signal recorded according to the present invention. This recording video signal differs from the standard video signal in the number of horizontal scanning periods (H number) within one field and the range of image information within one field. As a result, the horizontal scanning frequency changes and the frequency components of the video signal also change.

In this example, since the effective winding angle α is 300°, as shown in FIG.
The number is 540/α×(H number of standard video signal) = 540/300×262.5=472.5(H). On the other hand, since the field frequency of the recording video signal corresponds to the number of tracks per unit time,
Must match the standard video signal.

In the present invention, rotation control is performed such that 1.5 rotations (540° rotation) of the rotating drum 12 corresponds to one field period of the recording video signal, and the vertical synchronization signal of the recording video signal is the start of the effective winding angle α. Adjust the phase so that it is located at the part. As in this example, if the effective winding angle α is set to 300°, the number of H in one field is 472.5H (but
(in the case of NTSC system). It is extremely important for the present invention to set the value of α such that the number of H within one field is an odd multiple of 1/2. In other words, the number of H (here, 472.5H) from the recording start point of the effective winding angle α to the recording start point of the next video head is related to the arrangement (H arrangement) of the horizontal scanning period recording sections on the tape pattern. It is coming.

Two heads that reproduce each of the track length of the effective winding angle α, the number of H included in the track, and the inclination angle of the video track with respect to the longitudinal direction of the tape.
Compatibility cannot be achieved simply by matching the VTR standards. This is because it is even more important to ensure that the horizontal synchronization signal intervals do not become uneven when moving from one video track to the next.
Considering this point, if the number of H from the recording start point of one track to the recording start point of the next track is set to be an odd multiple of 1/2H, the current Same H as head VTR
You will be able to obtain a sort relationship.

If the above relationship is such that the number H from the recording start point of one track to the recording start point of the next track is an integer, then the distance between video heads _H3 and _H4 should be set at an angle from that point instead of 180°. The same result can be obtained by shifting one video head by a distance equivalent to 0.5H.

Furthermore, if the two-head VTR itself that records and plays back standard video signals is set so that the two video heads are not installed at a 180° interval, video heads _H3 and _H4 of the device of the present invention should also be played back on the VTR. Install them at the same spacing as the two video heads in
Either set the H number from the recording start point of the effective winding angle to the next recording start point to be an odd multiple of H/2, or install the video heads H ₃ and H ₄ at 180° intervals. , it is also conceivable to make a correction using the above-mentioned H number.

Next, the frequency relationship of recording video signals will be explained. In this embodiment, the number of H per one rotation of the rotary drum 12 is 472.5H as explained in conjunction with FIG.
Since it is a number, this H number is the standard video signal.
It is 1.8 times that of 262.5H. Here, the current 2-head
In order to record on a magnetic tape that is compatible with a VTR, the recording wavelength of 1H of the standard video signal recorded by a 2-head VTR and the 1H recording wavelength of the recording video signal recorded on the magnetic tape 1 are required. Because the recording wavelengths must have the same length,
The relative linear velocity between the tape and head of the present embodiment shown in FIG. 3 must be 1.8 times that of the current two-head VTR. Therefore, the signal frequency when recording on the magnetic tape 1, for example, when recording a multiplexed signal of a frequency modulated luminance signal and a low frequency converted carrier color signal, the FM frequency of the luminance signal and the color of the low frequency converted carrier color signal are The current 2-head subcarrier frequency
Set it to 1.8 times that of the VTR. If other signals are added (for example, pilot signals, FM audio signals, etc.), the frequencies of these other signals must also be set to 1.8 times. In other words, the frequency of the signal recorded on the magnetic tape 1 is higher than that of the two-head VTR for standard video signals shown in FIG.
It is necessary to select 540/α times.

By the way, in the apparatus of the present invention, only a part of the recording is performed during one rotation period of the rotary drum 12 (only a part of the recording video signal during one field period of the recording video signal shown in FIG. 5 is recorded). ). Therefore, the video head trajectory is only partially affected by the tape running. That is, the length and inclination angle of the video track on the magnetic tape include the distance traveled by the tape while scanning one video track (in this embodiment, it is α/540 times that of the current VTR). ing. Therefore, if the drum diameter is made 180/α times the current diameter and the inclination angle is made the same, the difference in influence due to the tape running distance will result in an error. Although this error is extremely small,
Strictly speaking, it is something that needs to be corrected. In this way, an H-aligned tape pattern is obtained that is completely compatible with current two-head VTRs.

Next, the recording format of the video signal will be explained. The recording video signal according to the present invention is mainly used in combination with a television camera for the purpose of providing a small portable VTR, and it is desirable to generate the recording video signal with a television camera.

A video signal for recording as shown in FIG. 5 is obtained from a television camera.Although the luminance signal and synchronization signal are shown, the carrier color signal is not mentioned, so it will be explained here. If the color video signal to be reproduced is of the NTSC format, the recording color video signal obtained from the television camera must also be of the NTSC format. However, the color subcarrier frequency of the carrier color signal is not limited to 3.58MHz of the NTSC system. The reason for this is that in the carrier color signal recording method that uses low frequency conversion, which is used in home VTRs, the carrier color signal is first frequency-converted to the low frequency range before recording, so the frequency after frequency conversion is important. The frequency before the frequency conversion to is not important. Therefore, if the device is designed on the assumption that it will be combined with a television camera, the color subcarrier frequency of the carrier color signal of the color video signal obtained from the television camera may be arbitrary. In this example, the number of horizontal scanning periods in one field is 472.5H, which is 1.8 times that of the standard video signal, so the color subcarrier frequency is also 3.58MHz.
Although the frequency is set to 1.8 times, you may choose any frequency to interleave.

FIG. 6 shows a block system diagram of an embodiment of the signal processing system of the apparatus of the present invention. In the figure, a recording color video signal taken out from a television camera (not shown) is passed through an input terminal 16 to a low-pass filter 1.
7, band filter 18, and synchronous separation circuit 19, respectively. The luminance signal is separated and taken out by the low-pass filter 17 and supplied to the frequency modulator 20, where it is frequency modulated. The carrier wave frequency at this time is set to 1.8 times the carrier wave frequency standardized in the current VTR shown in FIG. This frequency modulated luminance signal is supplied to a synthesis circuit 21.

On the other hand, the carrier color signal is separated and taken out by the bandpass filter 18 and supplied to the frequency converter 22, where the local signal processing circuit 2 (to be described later)
6 and the frequency was converted into a low frequency converted carrier color signal having a color subcarrier frequency 1.8 times the color subcarrier frequency of the low frequency converted carrier color signal recorded by the VTR shown in Figure 1. Thereafter, unnecessary noise is removed by the low-pass filter 23 and the signal is supplied to the synthesis circuit 21.

Further, the synchronization signal separated by the synchronization separation circuit 19 is supplied to the local signal processing circuit 26, while the vertical synchronization signal is taken out by the vertical synchronization separation circuit 24 and supplied to the switching control circuit 25. The switching control circuit 25 is supplied with a rotation pulse synchronized with the rotation of the rotary drum 12 from an input terminal 27 and the vertical synchronization signal, and generates a switching control signal whose polarity changes for each field. is applied to the changeover switch 29 to alternately switch and connect each field.
A local signal processing circuit 26 is provided. The local signal processing circuit 26 operates in the same manner as the corresponding circuit of the VTR shown in the first diagram. As an example, the color subcarrier frequency of the low-pass conversion carrier color signal is set to a frequency 40 times the horizontal scanning frequency, and the phase is shifted in a fixed direction by 90 degrees every horizontal scanning period, and the phase is shifted alternately every field. When a method of switching the direction of the phase shift is used, the local signal processing circuit 26 shifts the phase in a fixed direction by 90 degrees every horizontal scanning period based on the synchronization signal, and the direction of the phase shift is A switching control signal from the switching control circuit 25 generates a local signal of a predetermined frequency that is inverted for each field.

The composite signal of the low-frequency converted carrier color signal and the frequency modulated luminance signal obtained in this way is sent to the recording amplifier 2.
After the signal is amplified to a predetermined level suitable for magnetic recording at step 8, it is applied to video head _H3 or _H4 via changeover switch 29, and is sequentially recorded forming a video track tilted with respect to the longitudinal direction of the tape. . In this case, the frequencies of the low frequency conversion carrier chrominance signal and the frequency modulation luminance signal supplied to video heads _H3 and _H4 are respectively set to 1.8 times that of the current VTR shown in FIG. However, as mentioned above, the relative linear velocity between the tape and head in this embodiment is 1.8 times that of the current VTR, so the recording wavelength on the recording track is the same as that recorded with the current VTR. . That is, when a magnetic tape recorded by the apparatus of the present invention is played back on a current VTR, it can be played back normally without any problems.

Note that the effective winding angle in the present invention is not limited to 300° as in the above embodiment, but may be any angle that satisfies the above formula. Furthermore, although the azimuth recording method has been described in the above embodiment, the present invention can be applied to a two-head helical scan type recording apparatus that is not an azimuth recording method.

As mentioned above, the video signal recording device according to the present invention has the following relationship: D ₂ ≒180/αD 1 (where D ₁ is the diameter of the rotating drum or rotating plate of the existing two-head helical scan recording/reproducing device used during playback ₎ . , α is the effective winding angle of _the tape-shaped recording medium, and is expressed by the formula: 180° < α < 360°. , at the same frequency as the field frequency of the standard video signal,
The number of horizontal scanning periods in one field N _H is expressed by the formula N _H ≒ 540/α × (number of horizontal scanning periods in one field of standard video signal), and out of N _H , the number of horizontal scanning periods in one field of standard video signal is A recording video signal having image information is transmitted to the first and second recording video signals for a period equal to the horizontal scanning period.
and rotating means for rotating the rotating body so that the relative linear velocity between the rotating body and the first and second heads is approximately (540/α) times that of the recording/reproducing device. Since the first and second heads alternately record the image information in the recording video signal on the tape-shaped recording medium within the effective winding angle α and a slight range before and after the effective winding angle α, the above-mentioned A tape pattern format and a signal recording form that are completely tape compatible with a two-head helical scan recording and reproducing device have a diameter D ₂ smaller than the diameter D ₁ of the rotating drum or rotating plate of the recording and reproducing device. This can be done using two heads attached to a rotary body, and therefore, when applied to a portable VTR that particularly requires miniaturization, the configuration can be made even more compact than a conventional portable VTR. It has the following features.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the configuration of an example of the tape running system of a current two-head helical scan VTR.
Figure 2 is a front view showing an example of the main parts of Figure 1;
The figure shows the configuration of an embodiment of the tape running system of the apparatus of the present invention, FIG. 4 is a diagram explaining the recording timing by the apparatus of the present invention, and FIG. 5 shows the waveform of the video signal to be recorded by the apparatus of the present invention. Figure showing an example, No. 6
The figure is a block system diagram showing an embodiment of the signal processing system of the apparatus of the present invention. 1...Magnetic tape, 2...Full-width erase head, 5,1
2...Rotating drum, 8...Audio and control head, 9...Capstan, 10...Pinch roller, 16...Input terminal, 17...Low pass filter for luminance signal separation, 18...Band filter for carrier color signal separation, 22...Frequency conversion device, 25... switching control circuit,
27...Rotation pulse input terminal, 29...Selector switch, _H1 , _H2 , _H3 , _H4 ...Video head, α...Effective winding angle.

Claims (1)

[Claims] 1. When the diameter of the rotating drum or rotating plate of the existing two-head helical scan recording and reproducing device used during reproduction is D ₁ , D ₂ ≒180/αD ₁ (where α is the tape-shaped recording medium). The first and second heads are attached at approximately equal intervals to a rotating body with a diameter _D2 expressed by the formula: 180° < α < 360°), and the field frequency of the standard video signal. At the same frequency as , the number of horizontal scanning periods in one field N _H is expressed by the formula N _H ≒ 540/α × (number of horizontal scanning periods in one field of standard video signal), and the number of horizontal scanning periods in one field of the standard video _signal is means for supplying a recording video signal having image information to the first and second heads for a period equal to the horizontal scanning period of one field of the standard video signal; the rotating body and the first and second heads; The relative linear velocity of the recording/reproducing device is (540/α)
the first and second heads alternately wrap the tape-shaped recording medium within the effective winding angle α and a slight range before and after the effective winding angle α; A video signal recording device characterized in that image information in a video signal is recorded together with a synchronization signal.