JPS6372289A - Display device for head clogging - Google Patents

Abstract

PURPOSE:To judge sufficient head clogging even by a black/white viewfinder by detecting the head clogging state depending on the level of a RF output of a chrominance signal and superimposing the display signal on a luminance signal. CONSTITUTION:The RF signal obtained by a reproducing head 9 is amplified by a head amplifier 12 and becomes a RF luminance signal 13 and a RF chrominance signal 14, the RF luminance signal 13 is demodulated by a FM demodulator 15 and becomes a signal 17. If head clogging takes place in a chrominance signal video head, the RF chrominance signal 14 is as shown in a figure and a dropout pulse 25 is generated by a dropout level detector 24. The signal 25 drives a zebra zone generator 26 to generate a zebra zone signal 27 and the signals 27, 17 are added by an adder 28 to form a monitoring luminance signal 29. When the signal 29 is monitored by a viewfinder, stripe patterns are observed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention can be used in recording and reproducing devices such as video tape recorders (VTRs), and in particular, when a camera and a VTR are connected, a video head that outputs both luminance signals and 2 sudden signals during recording can be used. This invention relates to a head clogging display device that is effective for checking the presence or absence of clogging in a camera's viewfinder.

Detection of video head clogging (hereinafter referred to as ``head clocking'') is one of the important functions in conventional recording-only VTRs (camera integrated type, separate type) used outdoors for news reporting. There are two main types of head clocking methods: a fixed head method and a rotating head method.

In the former case, after recording with a rotating recording head,
This method detects weak video signals using a fixed head installed in the longitudinal direction of the tape. In the latter case,
Recording is performed using a rotating head for recording, and a rotating head exclusively for playback attached to the same drum at different angles is used to record Y.
/C is a method of detecting each signal.

Here, in the fixed head method, the LE is
D Since only a warning is issued with a flashing light or a sound, it cannot be determined that the image is a reproduced image.

Furthermore, since the output signal level of the fixed head is very low, the detection threshold has to be lowered, so the detection accuracy is not sufficient. On the other hand, with the rotating head method, there is a possibility of viewing the playback image by a dedicated playback head during recording.
This is much more advantageous than the fixed head method. However, with this method, on the VTR side, there is a processing circuit that expands the two color signals when they are compressed in the time axis, an encoder circuit that converts them into a composite video signal, and a viewfinder that monitors the simultaneous playback signals on the camera side. It is necessary to colorize the portaple V, which pursues small size and light weight.
The disadvantage of TR is that it increases the circuit scale and costs.

A conventional example will be described below with reference to the drawings. Fourth
7 shows a conventional head clocking detection method.

FIG. 4 shows a block diagram of a head clocking detection method using a fixed head, and FIG. 5 shows a view of the video head drum viewed from directly above. As the magnetic tape 2 passes through the video head drum 1, a recording video head 4 attached to the video head drum 1 records luminance signals and color signals on separate tracks. As shown in FIG. 6, the recording video head 4 described above has heads for luminance signals and chrominance signals mounted at staggered values, and the same heads are mounted at positions 1800 degrees opposite to each other on the video head drum 1.

When the recorded tape passes through the head clocking detection solid head 3 installed in the longitudinal direction of the tape, the already recorded luminance signal 2 electric signal is reproduced and output.
It is added to the head amplifier 5 and amplified to a sufficient level. Subsequently, by appropriately selecting a detection level threshold in the level detection circuit e, the head clocking detection signal 7 shown in FIG. 6(A) is output.

Here, when the head with the color signal 1 of the four video heads attached to the video head drum 1 causes head clocking, the head clocking detection signal 7 is the sixth one.
The signal will be as shown in ■) in the figure. In this case, it is possible to determine which head has caused head clocking by using signals such as head switching synchronized with the rotation of the video head drum 1. Here, the alarm signal generation circuit 8 performs notification. The alarm generating circuit 8 generates an alarm signal when any of the four heads causes head clocking based on the head clocking detection signal 7, and outputs an alarm signal from the L on the camera side.
Drive the ED and -' sodophone, etc. to give a warning to the cameraman.

FIG. 7 shows a block diagram of a head clocking detection method using a rotary head as another conventional example.

In FIG. 7, the magnetic tape 2 is connected to the video head drum 1.
In the same way as the fixed head method described above,
The luminance signal and the color signal are recorded separately by the recording video head 4, that is, the head YI + Y2 + 01 + 02, and the same video is recorded by the reproduction-only video head 9 attached to the drum 1 at a time-delayed position. Pick up the recording signal described above.

Here, four reproduction-only video heads 9 similar to those shown in FIG. 5 are attached. The recorded luminance signal 1 sudden signal is reproduced by the head 9, amplified by the head amplifier 12 with a slight time delay, and then the RF luminance signal 13 is reproduced.
．． They are output as RF color signals 14 and added to FM demodulation circuits 15, 16, respectively, and Y signals 17, . It is demodulated into a C signal 18. In this conventional example, since the C signal 18 has been time-axis compressed, the time-axis expansion processing circuit 19 performs time-axis expansion, and the RY signal 20. The signal is separated into B-Y signals 21. Then, Y signal 17, R-Y signal 20. B-Y signal 2
1 is modulated and added by an encoder 22, thereby outputting a composite video signal 23.

By sending this composite video signal 23 to the camera's color viewfinder or external monitor TV, and visually viewing the image, it is possible to determine which of the two heads is causing head clocking. Easy to identify.

Problems to be Solved by the Invention However, in the above configuration, the clocking detection accuracy is not sufficient because the level of the output signal from the fixed head is low. This is very advantageous because it allows simultaneous monitoring of reproduced images using an improved rotating head, but it requires a circuit similar to a time axis correction device that performs time axis processing of color signals, and the camera side does not have a color viewfinder. In the portable type, which pursues compact size and light weight, the problem is that the scale of the device becomes large and the cost becomes high.

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a display device in which a display signal indicating the head cross-setting state of a color signal is superimposed on a luminance signal and can be monitored using a monochrome viewfinder.

Means for Solving the Problems In order to solve the above problems, the present invention is based on a rotating head system, only the luminance signal is demodulated, and the chrominance signal is processed by head clocking depending on the level of the RF output. The present invention has means for detecting the state and superimposing a display signal indicating the head clocking state on the luminance signal so that sufficient head clocking can be determined even with a monochrome viewfinder.

Effects With the above-described configuration, a recording-only VTR having a head clocking function can be made smaller and lighter, and costs can be reduced.

EXAMPLE Hereinafter, a head clogging display device of the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of the invention. In FIG. 1, 1 is a video head drum, 2 is a magnetic tape, 4 is a recording video head, 9 is a reproduction video head, 11 is a recording amplifier, 12 is a head amplifier, 15 is an FM demodulation circuit, and 24 is a video head for reproduction. The circuit system includes a dropout detection circuit, 26 a zebra zone generator, and 28 an adder.

The operation of the head clogging display device configured as described above will be explained below with reference to FIGS. 1, 2, and 3.

In FIG. 1, a magnetic tape 2 rotates around a video head drum 1 and performs a normal recording run. Here, first, the recording video head 4 attached to the video head drum 1
The RF multiplied signal from the recording amplifier 11 is supplied to the magnetic tape 2, and the luminance signal is recorded on the magnetic tape 2.

Color signals are recorded on each independent track.

This color signal is obtained by compressing the RY signal and the BY signal in advance and multiplexing them.

Next, on the video head drum 1, a reproducing video head 9 is attached at a position with a time delay of 60' from the position where the recording video head 4 is installed. In order to reliably trace the recording track, the playback video head 9 is mounted with a height difference of 28 μm from the recording video head 4 in this embodiment.

The RF multiplied signal obtained by the above-mentioned playback video head is amplified by the head amplifier 12, and the RF luminance signal 13°RF signal 1
4, the RF luminance signal 13 is demodulated by the FM demodulation circuit 16 and becomes the signal 1 shown in FIG. , the RF color signal 14
becomes the signal 14 shown in FIG. 2, and the dropout level detection circuit 24 generates a dropout pulse 25. This signal 26 drives a zebra zone generator 26 to generate a zebra zone signal 2.

By adding this signal 27 and the aforementioned signal 17 in an adder 28, a luminance signal 29 for monitoring is generated. When this signal 29 is monitored with a black and white viewfinder installed on the camera side, an image with half of the zebra sea/ is added as shown in FIG. 3(b). Here, when head clocking occurs in both of the color signal heads C, C2, it is easy to understand that the image becomes an image in which the zebra zone is added to the entire image, so the explanation will be omitted. As for the brightness signal, since the image is constantly monitored, the head clocking status can be confirmed at a glance.

In the embodiment of the present invention, zebra sea/ is added to the image, but clocking information may be superimposed in a viewfinder of a camera having a character cinerator or the like.

Effects of the Invention As described above, according to the present invention, the head clocking status of color signals can be monitored on a monochrome monitor TV without monitoring the head clocking status during simultaneous playback on a color monitor TV, etc. Since the processing circuit system related to signals can be omitted, the VTR and camera can be made smaller, and excellent effects such as cost reduction can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a head clogging reverse display device which is an embodiment of the present invention, Fig. 2 is a waveform diagram of input and output of each part of the above device, and Fig. 3 is a front view showing an image of a head clogging state. 4 and 7 are block diagrams showing the configuration of a conventional device, FIG. 5 is a top view of a video head drum to which a recording video head is attached, and FIG. 6 is a waveform showing a head clocking detection signal. It is a diagram. 24... Dropout detection circuit, 26...
... Dropout pulse, 26 ... Zebra zone generator, 27 ... Zebra zone signal, 28
... Adder, 29 ... Luminance signal for monitor. Name of agent: Patent attorney Toshio Nakao and 1 other person24
-11 Doro 7 Puau Hibunde Hyakube & 2S-11 Dropout Bell Ku 26--Zebra Thorn Selection Takuomi;
--Monitoring serum filter Figure 2 Figure 3 (CL,') (b) Figure 5 I Figure 6

Claims (1)

[Claims] Separates the composite video signal into a luminance signal and two color signal components,
The apparatus records and reproduces the luminance signal and a color signal obtained by multiplexing the two color signal components on two independent tracks, the apparatus recording and reproducing the luminance signal recorded by a first video head into a second video head.
It has a reproducing means for immediately reproducing the color signal by the video head, and a detecting means for immediately reproducing the color signal recorded by the third video head by the fourth head, and detecting whether or not the third head is clogged from the reproduced signal. , a display signal indicating a video head clogging during color signal recording is generated by a third video head clogging detection signal obtained from the detecting means during the instant luminance signal reproduction, and the video signal is superimposed on the reproduction luminance signal. A head clogging display device characterized in that it is configured to obtain an output.