JPH02103710A - Video head clogging detector - Google Patents

Abstract

PURPOSE:To easily and accurately detect clogging without trouble some work where recording is interrupted and is switched to reproducing by using the pause period of interrupted recording to automatically detect whether a video head is clogged or not. CONSTITUTION:Since an interrupted magnetic recording device 1 performs interrupted recording, video heads 116A and 116B are switched to the reproducing mode in the interruption period of recording, namely, the period other than the recording period, and recording tracks on a magnetic tape 119 recorded before are traced by video heads 116A and 116B to obtain a reproduced signal. When video heads 116A and 116B are clogged at this time, the envelope of the reproduced signal becomes smaller than a preliminarily set envelope clogging value as the comparison result. Thus, clogging is automatically detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a video head clogging detection device for detecting clogging of a video head in an intermittent magnetic recording device such as a VTR.

[Prior Art] If the video head becomes clogged, recording on the magnetic tape becomes incomplete or becomes impossible, and if a magnetic tape with such incomplete recording is used, Even if the video is played back using a regular VTR equipped with a video head, there may be a lot of noise in the played video, or there may be no video at all.

Moreover, contrary to the above, even if a normally recorded magnetic tape is played back on a video head with a clogged IJ, a lot of noise may be generated as described above, or no video may be produced at all.

Symptoms of clogging can be easily corrected by gently wiping the tip of the video head with cleaning liquid or running clean link tape.

Most of the causes of clogging are due to the fact that magnetic powder from the magnetic tape or adhesion to the cap of the hito head prevents a normal magnetic circuit from being formed, and this is unavoidable in VTRs and the like.

By the way, 11 blockage can be detected by detecting it in the cylinder through the monitor screen during playback, or 1]5 during recording.
It is difficult to detect ＾ri. If you want to detect 11 crystals during recording, for example, it may be necessary to stop recording once during recording and restart four times during playback.

[Problem to be solved by the invention] As described above, the problems with the conventional intermittent magnetic recording device)
In this case, it is not possible to automatically detect video jams 1 to 11 during recording, and in order to detect them, it is necessary to interrupt recording and restart playback. It was very troublesome.

Furthermore, devices that record automatically and unattended for long periods of time, such as the intermittent magnetic recording device Y1 for crime prevention monitoring, do not care at all when the video head 11 is clogged.
It wasn't until I was 11 years old that I realized that my IF wasn't always recorded.

This invention was made in order to solve the above-mentioned problems, and it is possible to automatically and accurately correct the 1-1 blockage of video heads 1 to 1 during recording without causing any hindrance to the recording operation. An object of the present invention is to provide a video head clogging detection device that can detect clogging.

[F-stage to solve the problem] Video head clogging detection device according to the present invention (:l,
During the intermittent recording period of the intermittent magnetic recording device, the video heads 1 to 1 are set to recording mode 1, and during periods other than intermittent recording, the video heads 1 to 1 are set to the recording mode 1. Compare the recording and playback command circuit that generates a head cutting command signal so that the head can be cut into the mote, and the envelope of the playback irises in the dry playback mode 1-1 and the preset envelope l-I Mi value. The present invention is characterized in that it is equipped with a +M Chishu encoder comparison circuit which performs the comparison, and an 11-clog output circuit which detects the 11-crystallization of the above-mentioned Hitohets 1 to 1 and generates the 11-clog signal in response to the comparison.

[Function] Since the present invention is an intermittent magnetic recording device that performs intermittent recording, during a recording interruption period, that is, a period other than intermittent recording, the video head 1 is switched to the reproduction mode, and the previous magnetic tape record 1 recorded on
The FIF raw signal can be obtained by tracing the Herakku-1 with the video head. At this time, if the video head is clogged, the envelope of the playback signal No. 451 will be smaller in comparison with the preset envelope clogging value, and the clog will be automatically removed by lowering the envelope of the playback signal. It can be detected accurately.

[Embodiments of the Invention] Hereinafter, embodiments of the present invention will be described based on the drawings.

FIG. 1 is a block diagram showing the configuration of a heat recorder 1 to a clogging detection device according to an embodiment of the present invention, in which (1) is an intermittent magnetic recording device vI, and (2) is a recording device II.
) is the raw command circuit, (3) is the reproduction envelope comparison circuit, (
4) is a clogging output circuit, and (5) is an output terminal for [I-clogging].The intermittent magnetic recording device (1) is constructed as follows. That is, in Fig. 1, (+15) is the rotation F plane, and the rotation surface F (II6A) is on its circumferential surface.

(I +, 6 B) is attached. (+24)
is a tram motor, and this 1-ram motor (124) is 1
- The ram controllers 1 to 125 are controlled to synchronize the frequency and phase with the vertical signal separated from the video signal. (] 20 ) is a capstan shaft, which is driven by a capstan motor (+21) to run a magnetic tape (+19). (+22) is a capstan controller, which drives the capstan motor (12+) intermittently based on the intermittent drive command signal output from the intermittent drive command circuit (12:l) to drive the magnetic tape (+19).
Roll from Control 1 to make the car run at the roughly set running pitch.

(Ill) is the video signal power terminal, (+12) is the recording signal processing circuit, (II:l) is the recording head amplifier, (117)
A).

(I 1711)i; 11111 Raw Hetsu I, (
1st, o, m4n) is a switch that connects the recording (hereinafter referred to as REC) side to the FQ raw (hereinafter referred to as PB) side (+ switch, I- input input terminal (III) The video signal input from the recording/reproduction command circuit (+12) is converted into an FM signal necessary for magnetic recording, and then sent to the recording spatula (113), head off (+ switch (1I4A), (
1148) to the video head (]l6A), (116
1+).

(+18) (+ switch, this four-player switch (+18)
, (II61i) or the magnetic tape (+19).

Finally, the operation of the above configuration will be explained.

The capstan motor (+2) is driven intermittently with a trapezoidal wave speed pattern of acceleration → constant speed → deceleration, as shown in Figure 2 (b), or this speed pattern varies depending on the intermittent drive control type. Become.

Also, to Hideohetsu I (II6A), (+'+611)
As shown in Figure 2 (c), the timing for supplying the current for recording credibility is before and after the rotational speed of the capstan motor (121) reaches its maximum, and when the rotation speed of the capstan motor (12+) is supplied to the capstan motor (12+). There are two types: or immediately after stopping after intermittent driving. In the case of the former running record, the video head (11 to A) and (1168) spatula 1 - 2 are normal continuous recordings since there is no need to make much of a step.
Time mote recording is also possible with this video head (115Δ), (
+1611) You can also do it as a function.

However, in this case, it is necessary to keep the speed pattern of the capstan motor (+21) constant.

In the case of BuJ, Gonagisa's record of Shizuka 1, Hiteohetsu 1 ~ (1
16A), (1161()), the difference between spatula 1 and step is set to the specified recording track width, for example, in the case of VH3 standard NTSC 2-hour upper-upper recording, unless 59 gm is added, intermittent recording for one frame cannot be performed. No. Therefore, normal continuous recording for 2 hours is impossible due to the large difference in level, so another set of video heads for recording 2 hours up to 1 is equipped on the rotation 1 frame. However, in this case, the speed pattern of the capstan motor (+21) may be a rough controll-roll.

In addition, the intermittent recording current supplied to video heads 1 to (II6A) and (+1611) corresponds to 1 frame of the video signal,
In other words, there is a frame recording method that covers only one rotation from rotation 1 to Ram (+15), and a frame recording method that covers only one field of the video signal, that is, a period that corresponds to ``V-rotation from rotation 1 to Ram (+15). It is classified into field recording method.

The above explanation is about the operation of the intermittent magnetic recording device (1).
, (1148) or [-11 remains fixed on the REC side.

However, according to the configuration shown in FIG. 1, during intermittent recording, the intermittent drive command as shown in second [M (a) is sent from the intermittent drive command circuit (+23) to the recording m raw command circuit (2). A signal is applied. In this way, when the intermittent command signal (81) is applied to the two recording/reproducing command circuits, a recording command signal as shown in FIG. 2(d) is applied to the recording head amplifier (+13). The recording head amplifier (II:l) starts operation.This recording command signal ((I) is shown in Fig. 2 (
c) It is applied earlier than the recording number (tl) in order to avoid the transient state at the time of X70 of the recording spatula 1 to amp (+13). At the same time, the head changeover switches (114A), (]14B) are activated by the head changeover signal output from the recording/reproduction command circuit (2).
or switched to the REC side.

In the case of the intermittent magnetic recording device (1) or the above-mentioned frame recording method, the recording current for one frame of the video signal is simultaneously supplied to the video heads (]] [iA) and (++6B). Frame worth of video signal or magnetic tape (I
I! I). In addition, in the case of field recording method, video head (++68), (1161()
Either the specified side of the magnetic tape (+19)#)l
The recording current is simultaneously supplied to the video heads (16A) and (116B) over the period of ~1 feel 1 ~ racing, and the video recording current for ~1 feel 1 ~ is recorded on the magnetic tape (+19). .

Immediately after the intermittent recording in step 1-1 is completed, a reproduction command signal as shown in FIG. As soon as the playback operation starts, the recording head
~The amplifier (+13) is cut off, and the spatula 1~changeover switches (]]4A) and (l]4B) are switched to the PB side.

This reproducing operation is an intermittent recording operation from the perspective of the entire intermittent magnetic recording device (1), or the video head (]]6A), (115B), head cut-off switch (114A), ( 1148) and the reproduction head amplifier (++7A) and (11711) are forcibly switched to the reproduction side.

The video heads (116A) and (1168) are amplified by the playback head amplifiers (17A) and (17B), and switched by the playback selector switch (+18), as shown in FIG. 2(A). The signal becomes a reproduced signal and is sent to the reproduction envelope comparison circuit (3) at the primary stage. The switching timing of the playback selector switch (11B) is commanded from the F ram controller (+25), and the video head (]]
6A), (116B) is synchronized with the timing of tracing the magnetic tape (119).

Here, the reproduction value which is an FM signal! −r(f) envelope 0
The relationship between the waveform (hereinafter referred to as a reproduction envelope) and the recording method of the intermittent magnetic recording device (+), running recording or static IF recording, and frame recording or recording to field 1 will be described.

First, in the case of driving records, the playback l/rack angle is smaller than the recording track angle, so the playback envelope is
As shown in the middle of the figure (f), it becomes a triangular waveform with an upward slope.

In addition, in the case of static II-recording, since the recording track angle and the rack angle for reproduction 1 are the same, a flat flat waveform is obtained for reproduction EN.

In addition, in the case of frame recording and running recording, as the magnetic tape (119) runs all the way, the video tape 1 to
Among (]16A) and (II6B), the first recorded record 1 to the next recorded record 1-
It becomes proportionally smaller compared to the playback envelope of the rack. The rate of decrease is the magnetic tape (] + 19
is inversely proportional to the running speed of 1. Magnetic tape (
119) is stopped, each video head (]16A) and (1]6B) traces the rack to the same rack 1 both during recording and during playback, so that a sufficient playback envelope can be obtained.

In addition, in the case of field recording, sufficient playback power can be obtained by tracing the video head used for recording during playback.

As described above, the amount of energy applied to the reproduction envelope differs depending on the recording method, and in either case, an amount sufficient to detect clogging is applied to the reproduction envelope comparison circuit (3). However, as mentioned above, in the case of frame recording and running recording, if the tape speed at the time of recording is J2, the playback envelope will drop, only with the video head that recorded the previous recording.
In some cases, it may be difficult to distinguish it from clogging.

The reproduction envelope applied to the reproduction envelope comparison circuit (3) is compared with the preset envelope clogging value, and a comparison signal as shown in FIG. 2(g) is obtained in accordance with the magnitude comparison. It will be done.

Here, the video head (II 6A), (] ],
6B) will be described about the regeneration engine when it is clogged.

The amplifier cane of the playback head amplifier (I17A), (117B) is generally designed to be about 60dB, so the video head amplifier (I17A), (116B)
), the amplifier output will be approximately 200mv.

Figure 3 shows the relationship between the decline in playback envelope due to clogging and the S/N ratio of the video signal demodulated to baseband.As can be seen from this graph, a good video head with no clogging It's more than 200mvpp"
are doing. Clogging occurs and the playback envelope becomes low.
When mvpp is less than this, relatively good image quality is maintained; however, below this level, the image quality rapidly deteriorates and clogging symptoms occur.

From the above, clogging can be sufficiently detected by setting the envelope clogging value (m) to less than half of the reproduction envelope of a good video head.

One example of the circuit configuration of the playback envelope comparison circuit (3) is that since the playback signal is an FM signal of 3 to 5 MHz, a band amplifier that amplifies this band to 20 dB or more is used to convert the playback envelope. The purpose is to detect the envelope [1-] by increasing the amplitude of the signal and using an AM detector based on the timer 1.

So, enΔ, rope! ] By passing the blockage value (m) through a comparator which uses the comparison reference level, a comparison signal as shown in FIG. 2(g) is obtained at the output of the comparator. In addition, as the envelope clogging value of the comparator marked "-", the envelope clogging value (
Is it necessary to multiply by the gain of the band amplifier in m)?

Another example of the circuit configuration of the reproduction envelope comparison circuit (3) described in 2 is that if the reproduction signal is suddenly passed through the comparator, it will be output as an FM signal or a comparison signal that is higher than the envelope clogging value. , for example, through a low-pass filter consisting of a resistor and a capacitor, as shown in Figure 2 (
g) to obtain a comparison signal as shown in FIG.

As shown below, the playback envelope comparison circuit (3)
The comparison signal (g) obtained is sent to the next stage clogging output circuit (
4) is applied. The role of this clogging output circuit (4) is clear. That is, the reproduction engine has a triangular waveform or a flat waveform with a flat part that is somewhat bumpy, and it is not always possible to obtain a constant comparison output over the entire period of the l field. At the end of the l field, if a comparison output is obtained even once in this field, it is determined that this field is not clogged, and if a comparison output is not obtained even once during the entire period of the l field,
This field is determined to be clogged. Furthermore, in order to eliminate malfunctions caused by noise, in other words, to more reliably detect the presence of clogging, we have created a circuit that determines that clogging occurs when clogging is detected continuously over several fields. It is also an nf function to add.

The circuit configuration of the clogging output circuit (4) described above can be easily obtained by combining flip-flops.

As described above, the final output clogging signal as shown in FIG. 2(h) is output from the clogging output circuit (4) and appears at the clogging signal output terminal (5).

Here it is! 2. As shown in FIG. 2, during the period of intermittent recording, the video head (]] 6A).

(l+68) is switched to playback operation, detects whether or not it is clogged, and when the next cycle intermittent drive command signal shown in FIG. 2(a) is applied, the video head (]l
5A) and (1168) to perform intermittent recording, and thereafter, intermittent recording and clogging detection are sequentially repeated in the same cycle.

In the above embodiment, the video head is (]]6A),
(+1611) 2-head 1 system and switched the intermittent recording video head to playback to determine whether it is clogged or only for playback of a so-called 3-head or 4-head system with a composite video head. By using the video head for clogging detection, it becomes possible to check for clogging during both recording and playback, that is, during self-recording and playback.

[Effects of the Invention] As described above, according to the present invention, it is possible to automatically detect whether or not the video head is clogged by using the pause period of intermittent recording, so it is possible to automatically detect whether or not the video head is clogged. Clogging can be easily and accurately detected without the hassle of switching to regeneration. Therefore, it can be effectively applied to long-term unattended recording, such as for crime prevention monitoring.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a video head clogging detection device according to an embodiment of the present invention, FIG. 2 is a signal waveform diagram showing operation timing, and FIG. 3 is a playback envelope and playback S/S/
It is a graph explaining the relationship of N ratio. (1)...Intermittent magnetic recording device, (2)...Recording/reproduction command circuit, (3)...Reproduction envelope comparison circuit, (
4)...Clogged output circuit, (11:l)...Recording head amplifier, (]l14A, (114B)...Four head switch, (l16A). (116B)...Video head, (]l7A), (]
17B)...Playback head amplifier, (19)...Magnetic tape. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] (1) A video head that performs recording and playback on magnetic tape, a recording head amplifier that supplies recording signals to this video head, a playback head amplifier that amplifies the playback signal from the video head, and a video head that performs recording and playback operations on the video head. an intermittent magnetic recording device having a built-in head selector switch for switching between the recording head and the recording head; A recording/playback command circuit that generates a head switching command signal to switch the head switching switch, a playback envelope comparison circuit that compares the envelope of the playback signal from the playback head amplifier with a preset envelope clogging value, and the playback envelope comparison circuit. A video head clogging detection device comprising: a clogging output circuit that detects clogging of the video head and generates a clogging signal in response to a circuit comparison signal.