JPS61243980A - Tape speed detecting device - Google Patents

Abstract

PURPOSE:To detect exactly tape speed information irrespective of a tape speed by detecting its information from a period of a voltage converting output of a reproducing pilot signal. CONSTITUTION:A reproducing video signal and a pilot signal of heads 3 (4) are supplied to a BPF 12, all pilot signals that have been recorded are extracted. This extracted signal is converted to a voltage corresponding to a frequency of a reproducing pilot signal by an F/V converter 13, and as for this converted output, its fundamental wave component is fetched through an LPF 14. Also, the converted output is compared with a reference voltage of a prescribed level in a comparator 15, this compared output is supplied to a counter 18, and a clock of a prescribed frequency is counted by only an existence period of the compared output, and it is supplied as a tape speed to an indicator 19.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a tape speed detection device suitable for use in VTRs and the like that employs a pilot signal recording method track following system that utilizes a plurality of pilot signals of different frequencies. .

[Summary of the invention]

This invention utilizes multiple pilot signals with different frequencies. Pilot signal recording method track following system (
Regarding a tape speed detection device that is suitable for use with VTRs and the like that employ the ATF method (hereinafter referred to as the ATF method), the tape speed can be determined by converting the frequency of a reproduced pilot signal into a voltage and detecting the period of this converted output. It is designed to detect the tape speed with a simple configuration and to be able to accurately detect the tape speed.

[Conventional technology]

In a VTR that is capable of recording and reproducing control signals, information for controlling and displaying the tape speed can be obtained by reproducing the control signals recorded on the tape. That's what I do.

However, VTRs that control the tape speed without recording such control signals
Therefore, it is necessary to obtain tape speed information using the signal recorded on the tape.

For example, in 8 mm video, instead of recording a control signal, a pilot signal recorded on a video track is used to obtain information for tape speed control.

Figure 1O shows an example of a rotating head device used for the above-mentioned 8mm video, where l is a rotating drum, 2 is a tape helically wound around it, and 3 and 4 are approximately 1
The head is mounted on a rotating drum l with an angular spacing of 80°. These heads 3.4 are mounted on an electrostrictive element 5.6 such as a bimorph plate, and the deflection state of the head 3.4 is controlled by a control signal formed based on a reproduction pilot signal, which will be described later, to control the tracking servo during reproduction. executed.

In order to perform playback tracking servo, a pilot signal Sp recorded on the video track 8 of the tape 2 in a manner superimposed on the video signal is used.

This pilot signal Sp uses four different viroft frequencies r1 to f4, and the four pilot signals Sp having these frequency components are cyclically and sequentially transferred to the corresponding video track 2 as shown in FIG. It is recorded superimposed on the signal.

The frequency of the pilot signal Sp is selected as follows.

f1=102kHz f2=118kHz fa=165kHz f4=149kHz Now, the control signal is recorded as described above,
In the case of a VTR that does not have a tape drive, the following two methods can be considered as means for obtaining tape speed information during playback.

The first case is when the reproduction envelope output of an FM-modulated video signal is used.

The second case is when the reproduction level of one or more reproduced biloft signals among the pilot signals recorded on the video track 8 is used.

[Problem that the invention seeks to solve]

When using the above-mentioned first means as a means for obtaining tape speed information, there are the following problems.

In the first method, the envelope of the playback video signal is detected and the tape speed information is obtained from the period of the detected output. However, the playback envelope has a predetermined DC potential at normal playback speed, and only during FF/REW. Since the playback envelope period corresponds to the tape speed, F
Tape speed can only be detected during F/REW.

Also, since the frequency of the reproduced video signal is high frequency,
Since the contact between the tape and the head during the high-speed running mode (FF/REW) is often not accurately obtained, the precision of the tape speed information during the high-speed running mode is poor. For this reason, it is not a good idea to use the playback envelope output as tape speed information.

In the second method, since the recording level of the pilot signal Sp is very low, the S/N of the reproduced pilot signal Sp is not sufficient, and a Q-quotient filter is required. moreover,
The level of the reproduced pilot signal also varies due to the difference in characteristics between the tape and the head, and in order to eliminate this, it is necessary to provide an AGC circuit or the like. Of course, in high-speed running mode, the relative speed changes, so the frequency of the reproduced pilot signal Sp drifts, making it necessary to change the bandwidth of the bandpass filter for detecting the reproduced pilot signal Sp depending on the tape speed, etc. This causes the above problem.

Thus, it is difficult to say that either the first or second means is a satisfactory tape speed detection device.

Therefore, this invention solves these conventional problems, and regardless of the difference in tape speed,
The tape speed information can be reliably detected from the pilot signal Sp.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention utilizes one or more regenerated pilot signals Sp, as shown in FIG. 1 or FIG. Tape speed information is detected from the cycle.

[Effect]

According to this configuration, since the frequency of the pilot signal Sp is converted into voltage instead of the level of the reproduced pilot signal Sp, the level of the recorded pilot signal Sp is low and the S/N of the reproduced pilot signal Sp is poor. Even in high-speed driving mode, the pilot frequency is considerably lower than the video signal and is not affected much by head hits. Therefore, when detecting the tape speed, the reproduced biloft signal Sp
By using the reproduction frequency rather than the reproduction level of , it is possible to always obtain the converted output ■P corresponding to the reproduction biloft frequency in any tape running mode.

【Example〕

FIG. 1 is a system diagram showing an example of a tape speed detection device IO according to the present invention, in which a video signal Sp and a pilot signal Sv reproduced by a head 3 (or 4) are passed through an amplifier 11 to a bandpass filter 12. All pilot signals Sp ([1 to f4) recorded on video track 8 in this example are extracted. Therefore, the bandwidth of the bandpass filter 12 is selected to cover frequencies f1 to f4 as shown in the curve L1 in Figure 3, and the reproduced pilot frequency changes (drifts) as the tape speed changes. However, in order to be able to completely extract the pilot signal at that time, the bandwidth is set wide. In this example, 80 kHz and 200 kHz are the lower and upper cutoff frequencies r
t,,ru.

The extracted pilot signal Sp is sent to the frequency/voltage converter 1
3, and is converted into a voltage corresponding to the frequency of the reproduced pilot signal Sp. The conversion characteristic of the frequency/voltage converter 13 is linear from frequency f1 to frequency f3 as shown in curve L2 in Figure 4, and furthermore, the conversion output V is linear even when the tape speed changes.
A region of linear transformation characteristics is selected so that p is obtained.

In the normal reproduction mode, if the converted output of frequency f1 is vl, when the frequency is f2 to f4, the converted output Vp of v2 to v4 is obtained, and the level relationship is as shown in FIG. 4, Vl < V2 <V4<Vl.

As a result, the RF switching pulse now supplied to the head 3.4 is as shown in FIG. 2A, and the reproduced pilot signal Sp
When the frequency is as shown in B of the figure, a conversion output Vp shown in C of the figure is obtained.

The converted output Vp is supplied to a low-pass filter 14, where the fundamental wave component of the converted output Vp is extracted, and unnecessary components included in the converted output Vp are removed. The cutoff frequency of the filter 14 is selected to be 1 to 2k)Iz, as shown by curve L3 in FIG. This is because even if the tape speed is HlfIJ, the fundamental frequency of the converted output Vp cannot exceed 2 kHz.

The converted output Vp is supplied to a level comparator 15, and the level is compared with a reference voltage VR of a predetermined level applied thereto. 16 is a source of this reference voltage VR.

The reference voltage VR is equal to the conversion output v2 and ■ as shown in Figure 2C.
It is set to a level between 4 and 4. However, when the tape speed changes, the reproduction pilot frequency also changes, and the level of the converted output V2 + v4 also increases and decreases accordingly, so this reference voltage VR is the value of the converted output V2 and v4 obtained at the highest tape speed. It is set at a predetermined level that is between the conversion output (2) and the conversion output (v4) obtained at the lowest tape speed.

Therefore, if the curve of the conversion output characteristic of the frequency/voltage converter 13 is selected to have a non-linear characteristic as shown in curve L4 in Figure 5, the output voltage difference between frequencies f2 and f4 will be Since the reference voltage VR is larger than that in the case of , it is easy to set the reference voltage VR.

When the reference voltage ■λ of the level comparator 15 is set in this way, the comparison output obtained from this becomes the conversion output VPtf of only the conversion output Vp shown in FIG. 2C at a level higher than the reference voltage VR. . Since the width of this comparison output VPu corresponds to the head rotation period T, the conversion output Vp
The tape speed can be detected from the width T. Comparison output vP
U is supplied to the counter 18, and the clock G of a predetermined frequency is supplied only during the period (=T) during which the comparison output Vp■ is obtained.
K is counted and the count data is supplied to the tape speed indicator 19. As the counter 18, for example, a down counter can be used, whereby the counter 18 operates for a period T.

In this way, content corresponding to the tape speed (30H2) will be displayed on the display 19.

for example,! i82 Figures A-C are waveforms at normal tape speed, and Figures D-F are waveforms when tape speed is doubled, so when tape speed is doubled, comparative d force vpu The width T is also 1/2 of the normal tape speed, which reduces the down-count period to 1
/2.

Therefore, it is displayed that the tape is running at twice the normal tape speed.

By the way, even if the level of the recorded pilot signal Sp is low and the S/N of the reproduced pilot signal Sp is poor, the reproduced pilot frequency is not affected, and even in high-speed driving mode, the pilot frequency is considerably lower than the video signal, and it is due to the head hit. Therefore, when detecting the tape speed, the playback pilot signal Sp
If a certain reproduction frequency is used instead of the reproduction level of , the converted output Vp corresponding to the reproduction pilot frequency can always be obtained in any tape running mode.

It goes without saying that the output of the counter 18 can be used not only as an information signal for displaying the tape speed, but also as an information signal for tracking servo during playback.

Now, for 8mm video etc., the recording mode is S P.
(Short Play) mode and L P (
In the case of a configuration in which two types of Long Play modes can be arbitrarily selected, the head used is of a dual-purpose configuration. In this case, the recording track pitch in LP mode is lθμ, and the recording track pitch in SP mode is 2.
When approximately 0μ is selected, the track width of the dual-purpose head is generally selected to be approximately 15μ.

When recording and reproducing signals in LP mode using a head with such a dual-purpose configuration, the track pitch is narrower than the track width, so in high-speed running mode, etc. At the same time, the pilot signal Sp is regenerated, and the regenerated pilot signal Sp at this time
If the playback levels are the same, it becomes unclear which track should use the playback pilot signal Sp to detect the tape speed information.

In such a case, the pilot signal Sp (fz and f3 or f2 and f4) recorded every other track
You only need to use .

FIG. 7 is a system diagram of a tape speed detecting device IO showing an example of a case configured with such considerations taken into consideration.

The same parts as in FIG. Sp is further supplied to a trap circuit 22 to trap a predetermined frequency band. In this example, the frequency characteristics are selected such that the pilot frequencies f2 and f4 are trapped as shown by curve L5 in FIG. 8, and the recovered pilot signal Sp after the trap is supplied to the LP terminal of the switching circuit 21.

The switching circuit 21 outputs the selected recording mode pulse S.
Controlled by WP, when the LP mode is selected, the state is switched to the state shown in the figure, and the pilot signal Sp of the frequency components fl and f3 is transmitted to the frequency-voltage converter 1 in the subsequent stage.
3.

Since the circuit configuration after the frequency/voltage converter 13 is the same as that shown in FIG. 1, its explanation will be omitted.

When this configuration is adopted, as shown in FIG. 9A-C, only the pilot signals Sp for frequencies f1 and f3 are output, so the levels of the reproduced pilot signals Sp for frequencies f1 and f3 are If it is held for the next one field period, the conversion output Vp at that time will be as shown in Figure 9C, so by comparing the level with the reference voltage vR based on this, the result will be the same as described above. You can get tape speed information.

Unlike the configuration described above, it goes without saying that as long as the configuration described above is used, tape speed information etc. can be detected even if any one pilot signal having just one frequency component is used in the reproduced pilot signal Sp. stomach.

Further, in the above embodiment, the comparison output of the level comparator 15 is supplied to the counter 18 to obtain tape speed information, but the digital data obtained by A/D converting this comparison output is It is also possible to calculate the tape speed from the comparative output V by supplying it to a computer. Therefore, tape speed information and the like can be easily obtained through the calculation process.

〔Effect of the invention〕

As explained above, according to the present invention, the frequency of the pilot signal Sp is converted into voltage instead of the level of the reproduced pilot signal Sp, so the level of the recorded pilot signal Sp is low and the level of the reproduced pilot signal Sp is S/
Even if N is bad, the reproduced pilot frequency is not affected, and even in high-speed running mode, the pilot frequency is considerably lower than the video signal and is not affected much by head hits.

Therefore, if the reproduction frequency of the reproduction pilot signal Sp is used instead of the reproduction level of the reproduction pilot signal Sp when detecting the tape speed, the conversion output Vp corresponding to the reproduction pilot frequency can always be obtained in any tape running mode. .

Furthermore, since the bandwidth of the bandpass filter 12 is selected to be a frequency bandwidth that can cover the range in which the tape speed can be varied, the bandwidth can be fixed. That is, there is no problem with the drift of the detection frequency. Additionally, the configuration for detecting tape speed is relatively simple;
We can provide a useful detection device that can be easily integrated into an IC.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an example of a tape speed detecting device according to the present invention applied to a video device employing a four-frequency pilot signal recording type track following system; FIG. 2 is a waveform diagram for explaining its operation; 3 is a frequency characteristic diagram of a band pass filter, FIGS. 4 and 5 are diagrams showing an example of frequency/voltage conversion characteristics, FIG. 6 is a frequency characteristic diagram of a low pass filter, and FIG. 7 is a diagram showing another example of the frequency/voltage conversion characteristics. 1st example
Fig. 8 is a trap characteristic diagram, Fig. 9 is a waveform diagram for explaining its operation, Fig. 10 is a diagram showing an example of a rotating head device, and Fig. 11 is a recording mode of a biloft signal. FIG. 3J4 is a head, 12 is a bandpass filter, 13 is a frequency/voltage converter, 15 is a level comparator, 18 is a counter, Sp is a reproduced biloft signal, and Vp is a conversion output. f-V4L inspection Fig. 4 Searching for f-V Fig. 5 Fig. 8 Tape λ section/de release 4 pieces 1, h is a good country Fig. 8 2F continuation? City Paperback July 27, 1985 Patent Application No. 85865 2, Title of invention Tape speed detection device 3, Relationship with the person making the amendment case Patent applicant address Tokyo Parts for diagrammed products 6-7-35 Name (2
18) Sony Corporation Representative Director Norio Ohga 4, Agent Address: 1-8-1 Nishi-Shinjuku, Shinjuku-ku, Tokyo 03-
343-5B2111 cut (Shinjuku Building) 6, Number of inventions increased by amendment 7, Subject of amendment Detailed explanation column and drawings of the invention of Meikisho. (1) In the specification, page 11, line 9, "Width is head rotation period T" is corrected to "Pulse width (period) is tape speed." (2) Same page, lines 13 and 17, and page 11, line 9 rTJ
Correct it to rT/2J. (3) Delete "(30 lines)" on page 11, line 19. (4) In the drawings, correct Figure 2 as shown in the attached sheet. that's all

Claims (1)

[Claims] A plurality of pilot signals having different frequencies used for reproduction tracking servo recorded superimposed on the video signal are reproduced, and the reproduced pilot signals are supplied to a frequency-voltage converter to control the tape speed. A tape speed detection device is configured to form a converted output corresponding to the frequency of a reproduced pilot signal that changes according to the frequency of the reproduced pilot signal, and to detect tape speed information from the period of this converted output.