JP2757390B2 - Video signal recording and playback device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal recording / reproducing apparatus, and more particularly to a video signal recording / reproducing apparatus in which four or more even-numbered video heads are arranged on a cylinder.

[Conventional technology]

Conventionally, a video signal recording / reproducing apparatus for consumer use (hereinafter referred to as VTR) has two heads having different azimuth angles mounted on a rotating cylinder 180 degrees opposite to each other, and a tape is slanted to the cylinder at an angle of 180 degrees or more. Basically, a continuous video signal is recorded and reproduced while drawing an oblique pattern on a tape by winding and alternately using the two heads.

Also, for the purpose of miniaturizing such a VTR set, two or more (four) heads having different azimuth angles are used, and these heads are shifted at equal intervals within 90 degrees on a rotary head cylinder. In some cases, the heads at the corners are arranged adjacent to each other. This makes it possible to economically reduce the diameter of the above-mentioned cylinder to two-thirds of the basic diameter.

[Problems to be solved by the invention]

In the above-mentioned VTR set with a reduced cylinder diameter, taking a head with four heads as an example, there are two heads with the same azimuth angle. In some cases, a different head is used to trace a track during playback. Even with this, normal reproduction is possible, but in consideration of the difference in mechanical or electrical characteristics of the head to be used and the problem of the processing accuracy of the rotary cylinder, etc., the head that reproduces a certain track and the reproduction are performed. It is clear that the quality of the reproduced image is higher when the head is the same.

That is, these problems arise from the fact that once recorded on the tape, tracks recorded by two different heads having the same azimuth angle cannot be distinguished from the pattern on the tape. .

An object of the present invention is to perform self-recording / reproducing in a VTR using a small-diameter cylinder, and to reproduce a reproduced image due to a difference in electrical characteristics of the head and a difference in mechanical accuracy caused when tracing with such a different head. Can prevent
To provide a VTR.

[Means for solving the problem]

The VTR according to the present invention has four or more even-numbered heads arranged in pairs on a rotary head cylinder to record video signals on a tape or reproduce video signals recorded on the tape. A mixing circuit for superimposing a pilot signal on the video signal from an input terminal, and amplifying an output from the mixing circuit and supplying the amplified signal to the even number of heads, thereby forming a signal on the tape. A recording amplifier for recording the video signal on each track of the track and recording the pilot signal in a portion where there is no chroma signal, switch means for switching the pilot signal supplied to the mixing circuit, A reproduction preamplifier for reproducing a video signal by the even number of heads; and an output terminal for removing the pilot signal from an output of the reproduction preamplifier. A trap circuit that reproduces and outputs the video signal, a band-pass filter that passes the pilot signal from the output of the reproduction preamplifier, and a switch circuit and the trap circuit that use a head switch signal for switching the even number of heads. A gate pulse generation circuit for creating a gate pulse for control, and a pilot signal detection circuit for detecting the pilot signal that has passed through the band-pass filter by the gate pulse and controlling a servo circuit, By driving the switch means using a gate pulse, the pilot signal for reproduction tracking is superimposed during a vertical blacking period of the video signal, and at the time of reproduction, the trap circuit and the pilot signal are used using the gate pulse. Detection circuit Driven, by extracting the pilot signal as the tracking information, configured to always identical head traces the same track during recording and reproducing.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a VTR for explaining a first embodiment of the present invention.
3 is a block diagram of a video signal processing unit of FIG.

As shown in FIG. 1, during recording, the input terminal 1
, A video signal modulated for recording on a tape is input. Further, the pilot signal generation circuit 2 creates a pilot signal to be superimposed on the video signal,
This pilot signal is supplied to the mixing circuit 4 only when the switch 3 is ON, and is superimposed on the video signal. The above-described switch 3 is controlled by a gate pulse supplied from a gate pulse generation circuit 5. The video signal on which the pilot signal is superimposed is supplied to the video head 7 by the recording amplifier 6 and recorded on the tape.

On the other hand, during reproduction, a signal is picked up from the tape by the video head 7 and amplified by the reproduction amplifier 8. One of the amplified reproduced signals is output to a trap circuit 9 from which a pilot signal component is removed.
Output to 10. The trap circuit 9 is supplied with a gate pulse from the gate pulse generation circuit 5 and is trapped only when the gate pulse is in an active state. On the other hand, only the frequency band corresponding to the pilot signal is extracted from the amplified reproduced signal by the band-pass filter 11 and supplied to the pilot signal detection circuit 12. The pilot signal detection circuit 12 also receives a gate pulse from the gate pulse generation circuit 5, detects the presence or absence of a pilot signal when the gate pulse is in an active state, and controls a servo circuit (not shown).

FIG. 2 is a timing chart of the gate pulse in FIG. The gate pulse is generated by a servo system.

As shown in FIG. 2, a cylinder pulse generator signal and a frequency generator signal (both not shown)
And the four-phase head switch signal 14 (Q _A1 , Q _B1 , Q _A2 ,
Q _B2 ) is created to control the recording amplifier 6 and the reproduction preamplifier 8. Further, a 30 Hz signal 15 synchronized with the rotation of the cylinder is simultaneously generated and used as a phase comparison signal of the cylinder servo system. 15Hz signal 16 is 30Hz
The signal 15 is obtained by dividing the frequency by 1/2. The positional relationship between these signals is the same during recording and during reproduction. Further, the gate pulse 17 at the time of recording is generated at a position slightly delayed from the rise of the 15 Hz signal 16, and the gate pulse 18 at the time of reproduction is
It is generated at a position slightly delayed from the rise of the 30 Hz signal 15.

By the way, when the cylinder servo is locked in, the vertical synchronizing signal in the video signal exists at a position slightly delayed from the rise of the head switch signal 14. Further, in the vertical synchronizing signal, the equalizing pulse section before and after the vertical synchronizing signal, and a part of the vertical blanking section, there is no chroma signal including the burst signal. That is, the gate pulses 17 and 18 at the time of recording and at the time of reproduction are generated in a portion where there is no chroma signal.

As a result, the pilot signal is recorded in a section having no chroma signal including the vertical synchronization signal of the video track recorded by the A1 head.

FIG. 3 is a diagram showing a recording pattern on a tape recorded using the VTR according to the present invention, showing the above-described state.

As shown in FIG. 3, characters A1, B1, A2, and B2 in each track on the tape 19 indicate a head on which the track is recorded, and a hatched portion 20 indicates a portion of the video track where there is no chroma signal. The black coloring portions 21 indicate portions where pilot signals are actually recorded.

By performing the above-described processing, it is possible to determine the A1 track and the A2 track on the tape pattern. That is, the servo circuit at the time of reproduction performs control so that a video track recorded by a head having a certain azimuth angle is traced by a bed having the same azimuth angle. Therefore, for example, a track recorded by the A1 head is traced by the A1 head or the A2 head during reproduction. At this time, a gate pulse 18 at the time of reproduction is output to a portion where it is assumed that the pilot signal of the video track traced by the A1 and A2 heads is recorded, and whether or not the pilot signal exists in this section. The first
The pilot signal detection circuit 12 shown in the drawing makes a determination, and can determine whether the currently traced track is recorded by the A1 head or recorded by the A2 head.

Further, in a servo circuit (not shown), it is possible to determine from the head switch signal 14 what kind of head is actually tracing. At this time, if the signal traced by the A2 head for reproduction was recorded by the A1 head, it is determined that this point is not a phase lock point, and the same head is traced for recording and reproduction. Perform control.

FIG. 4 is a VTR for explaining a second embodiment of the present invention.
FIG. 5 is a block diagram of the signal processing section, and FIG. 5 is a timing chart of the gate pulse in FIG.

As shown in FIGS. 4 and 5, in this example, there are four types of pilot signals, and the pilot signals are recorded on all the tracks corresponding to the recording video heads. The pilot signal generation circuit 2 outputs the head switch signal 14 (Q _A1 ,
_{Q B1, Q A2, Q B2} ) is supplied, thereby the pilot signal frequency 24 changes the _{f A1, f B1, f A2} , f B2. Further, the gate pulse 23 is output to a portion of all tracks where no chroma signal is present, whereby a pilot signal corresponding to the recording head is recorded on all tracks.

On the other hand, at the time of reproduction, the pilot signal is extracted by the band pass filter 11, and the pilot signal written in the track currently traced by the frequency discriminator 22 is f _A1
Determines which one of the ~f _B2, thereby to determine whether those recorded in any head track. This information is sent to the servo circuit. In this embodiment, since the pilot signal is recorded on all the tracks, the deviation of the phase lock point can be determined even during the reproduction of the B1 and B2 tracks, thereby shortening the final pull-in time and recording the gate pulse. This has the advantage that it can be used for both playback and playback.

〔The invention's effect〕

As described above, the VTR of the present invention records a pilot signal in a section where a chroma signal is not present in a video signal, that is, a section in which a band in which a chroma signal is to be recorded is vacant. Can be determined, so even in VTRs using small-diameter cylinders,
Reproduction can be performed with the same head as the head on which the track was recorded. As a result, when performing self-recording / reproduction, differences in the electrical characteristics of the head and the mechanical characteristics caused when tracing with a different head are performed. There is an effect that deterioration of a reproduced image due to a difference in target accuracy can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram of a VTR signal processing section for explaining a first embodiment of the present invention, FIG. 2 is a timing chart of gate pulses in FIG. 1, and FIG. FIG. 4 is a block diagram of a signal processing section of a VTR for explaining a second embodiment of the present invention, and FIG. 5 is a timing chart of gate pulses in FIG. . 1 ... input terminal, 2 ... pilot signal generation circuit, 3 ...
... Switch, 4 mixed circuit, 5 gate pulse generating circuit, 6 recording amplifier, 7 video head, 8
Reproduction preamplifier, 9 trap circuit, 10 output terminal, 11 bandpass filter, 12 pilot signal detection circuit, 14 head switch signal (four-phase), 15
30Hz signal, 16… 15Hz signal, 17… Gate pulse at the time of recording, 18… Gate pulse at the time of reproduction, 19 …… Tape, 20 ……
No chroma signal part, 21: Pilot signal recording part, 22: Frequency discriminator, 23: Gate pulse, 24 ...
Output frequency of pilot signal generation circuit.

Claims (1)

(57) [Claims] 1. An even number of four or more heads are arranged in pairs on a rotary head cylinder to record video signals on a tape or reproduce video signals recorded on the tape. In the video signal recording / reproducing apparatus, a mixing circuit for superimposing a pilot signal on the video signal from an input terminal, and amplifying an output from the mixing circuit and supplying the amplified output to the even-numbered heads on the tape. A recording amplifier that records the video signal on each track and records the pilot signal in a portion where there is no chroma signal, switch means for switching the pilot signal supplied to the mixing circuit, and the video on the tape. A reproduction preamplifier for reproducing a signal by the even number of heads; and an output terminal for removing the pilot signal from an output of the reproduction preamplifier. A trap circuit for reproducing and outputting the video signal, a band-pass filter for passing the pilot signal from the output of the reproduction preamplifier, and a head switch signal for switching the even number of heads, controlling the switch means and the trap circuit. A gate pulse generation circuit for generating a gate pulse for performing the detection, and a pilot signal detection circuit for detecting the pilot signal passed through the band-pass filter by the gate pulse, and controlling a servo circuit, By driving the switch means using a pulse, the pilot signal for reproduction tracking is superimposed during the vertical blacking period of the video signal, and at the time of reproduction, the trap circuit and the pilot signal detection are performed using the gate pulse. Circuit Dynamic and, by taking out the pilot signal as the tracking information, the video signal recording and reproducing apparatus characterized by always the same head during recording and playback is to trace the same track.