JPH0466062B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a helical scan video tape recorder (hereinafter referred to as Y/
This invention relates to a detection device for detecting tracking errors during playback in a C-separate VTR (referred to as a C-separate VTR).

Conventional structure and its problems Traditionally, a helical scan video tape recorder (hereinafter simply referred to as
In a video recorder (VTR), a method is known in which four types of pilot signals with different frequencies are sequentially selected and recorded while being superimposed on a video signal, and tracking control is performed using these pilot signals during playback. This method will be explained below.

FIG. 1 shows the state of recording tracks on a magnetic tape recorded by a conventional method in a two-head VTR. 101 is a magnetic tape, 102 is a recording track on which signals of a certain frame are recorded, 103 is a recording track of the next frame, and 104 is a recording track of the next frame. The numeral "a" attached to each recording track indicates one of the two magnetic heads (not shown) attached at positions 180 degrees apart from each other on a rotating drum (not shown).
The symbol b means the track recorded by the A head when the other head is the B head.
This means that it is a track recorded by a head.

Now, in this method, a pilot signal is superimposed on a frequency-modulated video signal and recorded, and this pilot signal consists of four types of signals with different frequencies. Assuming that the four types of frequencies are ₁ , ₂ , ₃ , and ₄ , they are selected such that, for example, ₁ = 6.5 _{H 2} = 7.5 _{H 3} = 9.5 _{H 4} = 10.5 _H. In addition, _H is the horizontal synchronization frequency of the video signal.

During recording, four types of pilot signals are
The frequencies are recorded periodically for each track in the order of ₁ , ₂ , ₄ , ₃ , ₁ .

As a result, the frequency difference between the pilot signals between adjacent tracks becomes _H and _3H .

Next, during reproduction, a reference signal having the same frequency as the pilot signal recorded on the recording track to be scanned is created, and the reproduced pilot signal and the reference signal are multiplied by a multiplier. For example, when reproducing a track on which a pilot signal of frequency ₁ is recorded, when the scanning locus of the rotating magnetic head deviates upward from that track, the signal component of frequency _H increases in the output of the multiplier. When shifted downward, the signal component of frequency _3H increases. The same applies when reproducing a track on which a pilot signal of frequency ₄ is recorded.
Furthermore, when reproducing a track on which pilot signals of frequencies ₂ and ₃ are recorded, when the scanning of the magnetic head shifts upward, the signal component of frequency _3H increases, and when it shifts downward, the signal component of frequency _H increases. component increases. In this way, the amount and direction of the tracking error are detected, and tracking control can be performed.

However, in this method, the circuit configuration is complicated, and when editing, at the editing point,
A drawback is that it becomes necessary to maintain continuity in the recording order of pilot signals.

Purpose of the Invention The present invention eliminates these conventional drawbacks, and takes advantage of the characteristics of the Y/C separated type VTR.
The present invention provides a device that detects the amount and direction of tracking error with a simple configuration.

Structure of the Invention The present invention provides a Y/C separation type VTR in which two types of pilot signals with different frequencies obtained from a pilot signal generation circuit are alternately selected for each recording track by a switch circuit, and a mixing circuit The two types of pilot signals are recorded by mixing them with either the luminance signal or the color signal of the video signal, and during playback, the two types of pilot signals leak into the output of the magnetic head that is scanning the track on which the pilot signal is not recorded. A tracking error signal is obtained from the output terminal of the differential amplifier by extracting the signal using a narrowband filter circuit or the like and then supplying the signal to the differential amplifier via, for example, a switch circuit.

DESCRIPTION OF EMBODIMENTS A Y/C separated VTR according to an embodiment of the present invention will be described below.
This will be explained with reference to the drawings.

FIG. 2 shows only the rotary magnetic head used for both recording and reproduction in a Y/C separated type VTR. Here, the Y/C separation type VTR is a helical scan type video tape recorder that separates a video signal into a luminance signal and a color signal, and records and reproduces the signals on separate tracks using separate magnetic heads.

In FIG. 2, 201ca and 201cd are magnetic heads for recording and reproducing color signals, hereinafter referred to as C heads. Further, 201ya and 201yb are magnetic heads for recording and reproducing luminance signals, and are hereinafter referred to as Y heads. These four heads are attached to and rotate on a rotating drum (not shown). That is,
A color signal track (hereinafter referred to as C track) and a luminance signal track (hereinafter referred to as Y track) are recorded adjacently and in parallel on a magnetic tape over the period of one field by C head 201ca and Y head 201ya. In the next one field period, the C track and Y track are similarly recorded by the C head 201cb and the Y head 201yb. FIG. 3 shows the state of recording tracks on the magnetic tape recorded in this manner.

In FIG. 3, 301 is a magnetic tape, 302
303 is a recording track in a certain frame, and 303 is a recording track in the next frame. In recording tracks 302 and 303, ya, ca,
The magnetic heads 201ya, 201ca, and 201ca shown in FIG. 2 are denoted by yb and cb, respectively.
This indicates that the tracks were recorded by 201yb and 201cb.

Now, in such a Y/C separated VTR,
To detect tracking errors during playback,
The pilot signal is recorded only on the C track, superimposed on the frequency modulated color signal. This pilot signal consists of two types of frequencies ₁ and ₂ , and these are recorded alternately for each field. Values ₁ and ₂ are set to avoid disturbing the video signal as much as possible.
Select a value within the range of 100K to 150KHz and an odd multiple of _H /2. However, _H is the horizontal synchronization frequency of the video signal. Now, assume that a pilot signal of frequency ₁ is recorded on the C track of the first field, and a pilot signal of frequency ₂ is recorded on the C track of the second field.

Next, when reproducing the first field, the recording track and the rotating magnetic head have the positional relationship shown in FIG. 4.

In FIG. 4, 401 is the Y head, 402 is the C head, 404 is the Y track of the first field to be reproduced, 405 is also the C track, 403
indicates the C track of the second field of the previous frame.

For example, Y head 401 and C head 402
When the scanning locus deviates upward from the track to be reproduced, the signal component of frequency ₁ increases in the Y head reproduction output, and when it deviates downward, the signal component of frequency ₂ increases.

In addition, when reproducing the second field, if the scanning locus of the rotary head deviates upward from the track to be reproduced, the Y head reproduction output will have a frequency _{of 2} .
When the signal component increases and shifts downward, the frequency ₁
The signal component of increases.

In this way, the amount and direction of the tracking error can be determined simply by detecting the signal components of frequencies ₁ and ₂ .

FIG. 5 is a block diagram of the recording section of this embodiment. 2
The two output signals of the pilot signal generation circuit 501 which generate pilot signals with different frequencies are controlled by the switch circuit 502 which is controlled by the field discrimination signal applied to the terminal ₅₀₃ . The pilot signals are applied to the mixing circuit 505 after each pilot signal of frequency ₂ is selected in the second field. A color signal is applied to a terminal 504 of the mixing circuit 505, and the pilot signal and color signal are mixed and amplified by a current amplification circuit 506, and then supplied from a terminal 507 to a C head (not shown). and recorded on magnetic tape (not shown).
FIG. 6 is a block diagram of the reproduction section of this embodiment. A reproduced signal from a Y head (not shown) is input to a terminal 601, amplified by a head amplifier 602, and then converted into a luminance signal, a pilot signal of frequency ₁ , and a pilot signal of frequency ₂ by filters 603, 604, and 605. Can be divided. Brightness signal is at terminal 60
6 and sent to a luminance signal processing circuit (not shown). On the other hand, the pilot signal is sent to switch circuit 6.
07, the signal levels are compared by a differential amplifier 609, and taken out from a terminal 610 as a tracking error signal. A signal for determining the playback file (actually a head switching signal) is applied to the terminal 608 in order to control the switch circuit 607. That is, when the first field is being regenerated, the output of the filter 604 is added to the + terminal of the differential amplifier 609, and the output of the filter 605 is added to the - terminal; conversely, when the second field is being regenerated, the output of the filter 604 is applied to the + terminal of the differential amplifier 609. is applied to the negative terminal of the differential amplifier 609, and the output of the filter 605 is applied to the positive terminal, the level of the tracking error signal increases when the head scan in FIG. 4 shifts upward, regardless of the reproduction field. When it shifts downward, it starts to decrease.

Effects of the Invention As described above, according to the present invention, tracking errors can be detected with a simple configuration. In addition, since the selection of two types of pilot signals is determined for each field, it is easy to maintain continuity in the recording order of pilot signals during editing. You can see which field is actually being played.

It is clear that the same function can be obtained by recording the pilot signal on the Y track and detecting it on the C head, but in the recording pattern shown in Fig. 3, the pilot signal is recorded on the C track. In this case, even if a head dedicated to recording and playback is provided and simultaneous playback is performed, the playback Y head that tracks immediately after the recording head will always be narrowed to the C track where the pilot signal is recorded. , tracking errors can be detected stably.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing the state of recording tracks on a magnetic tape in the conventional method of detecting tracking errors using pilot signals, and Fig. 2 shows the arrangement of the rotating magnetic head of a Y/C separated type VTR. FIG. 3 is a plan view showing the state of recording tracks on a magnetic tape recorded by a Y/C separated VTR, and FIG. 4 is a diagram showing the recording track and playback head during playback in the present invention. A plan view showing the positional relationship, and FIGS. 5 and 6 are block diagrams showing an embodiment of a tracking error detection device for a magnetic recording/reproducing apparatus according to the present invention. 201ca, 201ya, 201cb, 201yb,
401, 402...Rotating magnetic head, 302, 3
03, 403, 404, 405...recording track, 501...pilot signal generation circuit, 502
...Switch circuit, 503...Field discrimination signal input terminal, 504...Color signal input terminal, 505
... Mixing circuit, 506 ... Current amplification circuit, 507
... Recording current output terminal, 601 ... Y head reproduction signal input terminal, 602 ... Head amplifier, 603
... High pass filter, 604, 605 ... Narrow band filter, 606 ... Luminance signal output circuit, 60
7... Switch circuit, 608... Head switching signal input terminal, 609... Differential amplifier, 610... Tracking error signal output terminal.

Claims (1)

[Claims] 1. By a pair of first and second magnetic heads mounted in close proximity on the rotating drum,
At the time of recording, two adjacent recording tracks inclined with respect to the longitudinal direction of the magnetic tape are formed at the same time, and
In addition to the first video signal, two types of pilot signals having different frequencies are alternately frequency-multiplexed on the first recording track by the first magnetic head of a set of magnetic heads, using the recording track as a unit. By detecting the leakage amount of each of the two types of pilot signals leaked from the first recording track, which are included in the signal that is recorded and reproduced by the second magnetic head during reproduction, A tracking error detection device for a magnetic recording/reproducing device, which detects a tracking error.