JPH0828887B2 - Video signal magnetic reproduction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a VTR regeneration system.

[Outline of Invention]

According to the present invention, in the VTR reproduction system, the delay circuit for crosstalk removal at the time of still reproduction is also used for correction of the video signal reproduced from the auxiliary rotary head, so that image blurring at still reproduction is prevented. This is a low cost compensation.

[Conventional technology]

The recording format of the tape in 8mm video is
This is as shown in FIG. That is, in the figure,
(1) shows a magnetic tape, and (2) shows a magnetic track. In this track (2), a video signal of an odd field period is recorded on every other track (2A), and the remaining 1
Video signals of even field periods are recorded on every other track (2B), and the numbers [1] to [525] in the track (2) indicate line numbers.

At this time, the tracks (2) are formed so as to be sequentially shifted in the length direction of the tracks (2) by one horizontal section, and adjacent tracks (2) are in contact with each other, and The azimuth angles of (2A) and (2B) are different from each other.

Further, the video signal recorded on the track (2) is an FM signal modulated by a luminance signal, a carrier color signal frequency-converted to the low frequency side of the FM signal, and an FM signal modulated by an audio signal. It is a frequency-multiplexed signal of a signal and a pilot signal for tracking servo. At this time, the FM luminance signal and the carrier color signal recorded on the track (2A) and those on the track (2B) are changed in frequency or phase so as to be frequency interleaved with each other.

Then, in order to record and reproduce the video signal in such a track format, the rotary magnetic head device is constructed as shown in FIG. That is, the two rotary magnetic heads (3A) and (3B) are rotated at a frame frequency with an angular interval of 180 ° with each other, and the tape (1) is rotated over a 180 ° angular range on the peripheral surface of rotation. It can be run diagonally at a constant speed. At this time, the azimuth angles of the heads (3A) and (3B) are equal to the tracks (2A) and (2
B), respectively.

Therefore, by alternately using the heads (3A) and (3B) every one field period, recording or reproducing in the above-mentioned track format can be performed.

Further, the head (3S) is an auxiliary rotary magnetic head for reproducing still (field still), which has the same azimuth angle as the head (3A) and also has the head (3S).
It is rotated integrally with the heads (3A) and (3B) with an angular interval θ that precedes B) by, for example, 1.5 horizontal periods.

Therefore, as shown by the scanning locus as reference numeral (2S) in FIG. 4, the heads (3A) and (3S) are used during still reproduction.
Scans the same track (2A) alternately every one field period, so that a field still video signal can be obtained.

(Reference: Magazine "Broadcasting Technology", March 1985, etc.) [Problems to be Solved by the Invention] However, in the above rotary head device, blurring occurs in the vertical direction on the playback screen during still playback.

That is, the signal Sw in FIG. 5A is a rectangular wave signal that is inverted every one field period, and this signal Sw is provided, for example, on the rotary drum supporting the heads (3A), (3B), (3S). Every other field period during normal reproduction.
The head (3A) scans the track (2A) on Ta, and the head (3B) scans the track (2A) on every other field period Tb.
B) is scanning. Therefore, with this signal Sw,
The reproduction signal of the head (3A) and the reproduction signal of the head (3B) are alternately selected for each of the periods Ta and Tb to be continuous reproduction signals.

Then, at the time of still reproduction, the reproduction signal of the head (3A) and the reproduction signal of the head (3S) are separated by the signal Sw.
Alternately selected for each Ta and Tb to be a continuous still reproduction signal.

However, during this still playback, the head (3A), (3S)
Is a track (2A) with a scanning locus (2S) as shown in Fig. 4.
Is repeatedly scanned, the head (3A) is not on the track (2A) in the 0.5 horizontal period from the scanning start time of the head (3A) and in the 0.5 horizontal period immediately before the scanning end time. Therefore, as shown in FIG. 5B, the reproduction signal Sa of the head (3A) cannot be obtained in the 0.5 horizontal periods at the beginning and end of the field start Ta.

Further, assuming that the head (3S) is at the angular position of the head (3B), for the same reason, as shown in FIG. 7C, the head (3S) is included in the 0.5 horizontal periods at the beginning and end of the field period Tb. It is not possible to obtain the reproduction signal Ss of). And
In reality, the head (3S) is at an angular position that leads the head (3B) by 1.5 horizontal periods, so the actual head (3S)
The reproduction signal Ss of S) is obtained earlier by 1.5 horizontal periods than the signal Ss of FIG. 9B, and therefore, the signal Ss is one horizontal period earlier than the start point of the field period Tb as shown in FIG. It is obtained in the period from the time point to the time point two horizontal periods earlier than the end point of the field period Tb.

Therefore, when the still screen is reproduced by such reproduction signals Sa and Ss, the screen by the signal Sa of the period Ta and the screen by the signal Ss of the period Tb are alternately reproduced, so that the reproduction screen is vertical. The screen will be blurred by 1.5 lines in the direction.

Of course, in order to eliminate such image blurring, the signal Ss in the period Tb may be delayed by 1.5 horizontal periods to become the signal Ss shown in FIG. 7C, but this requires a large number of parts. And the cost will increase.

The present invention is intended to solve the above problems.

[Means for solving problems]

The magnetic reproducing apparatus for video signals according to the present invention uses two rotary magnetic heads (3A) and (3B) having an angular interval of 180 ° to generate a video signal having a luminance signal and a carrier color signal.
The above video signal is recorded from a magnetic tape that is recorded as one magnetic track that is oblique at interleaving frequencies for each field period and that has adjacent azimuth angles that are different from each other and that are adjacent to or adjacent to each other. In a magnetic reproducing device for reproducing, during normal reproduction, the reproduced luminance signal is removed by a delay circuit (14) for one horizontal period to remove crosstalk components between tracks, and the two rotary magnetic heads (3A), ( A third rotating magnetic head (3S) is provided at a position where it rotates prior to one of the two rotating magnetic heads (3B), and the other of the two rotating magnetic heads (3A) and (3B) is used during still reproduction. Head and
The brightness signal reproduced by the third rotary magnetic head (3S) is still reproduced, and the brightness signal reproduced by the third rotary magnetic head (3S) is 1 by the delay circuit (14).
The image is taken out with a delay in the horizontal period so as to compensate for image blur during still reproduction.

[Action]

The time position of the video signal extracted from the reproduction signal Ss is corrected by the delay circuit for removing crosstalk.

〔Example〕

First, the crosstalk removing circuit and the circuits before and after it when the image blur is not corrected will be described with reference to FIG.

In the figure, (10) Comb filter IC, (2
0) shows a part of an IC having a video signal processing circuit at the time of recording and reproducing, and a switch circuit (4
1) to (45) are connected to the contact point R during recording, and are connected to the contact point P during reproduction.

Then, at the time of recording, the color composite signal (Y + C) of the luminance signal Y and the carrier color signal C is supplied to the adding circuit (11) through the contact point R of the switch circuit (41), and also from the switch circuit (41). The signal (Y + C) is supplied to the inverter (22) and its phase is inverted.
+ C), the signal − (Y + C) is supplied to a delay circuit (12) composed of a CCD and delayed by one horizontal period, and the delayed signal − (Y + C) is added to the adder circuit (11).
Is supplied to.

Therefore, the circuits (11), (12) and (22) form a C-type comb filter, so that the carrier color signal 2C having a doubled level is taken out from the adding circuit (11). However, at this time, since the circuits (11), (12), and (22) do not have bandpass characteristics, the signal 2C from the adder circuit (11) has no unnecessary signal component, that is, no vertical correlation. It also has a luminance signal component.

Then, this signal 2C is supplied to the attenuator (13) to be a signal C having a half level, that is, the original level, and this signal C is supplied to the bandpass filter (31) and unnecessary signal components. Are removed and the carrier color signal C is taken out from the filter (31).

Further, the signal (Y + C) is supplied to the delay circuit (14) through the contact R of the switch circuit (42) to perform delay compensation corresponding to the delay of the signal C from the attenuator (13), and the compensated signal Y is supplied to the subtraction circuit (32), and the signal C from the attenuator (13) is supplied to the subtraction circuit (32). Therefore, since the signal C is subtracted from the signal (Y + C) in the subtraction circuit (32),
The luminance signal Y is taken out from the subtraction circuit (32).

This signal Y is the contact R of the switch circuit (43).
→ Adder circuit (33) → An unnecessary signal component (mainly a carrier color signal without vertical correlation) which is supplied to the trap circuit (34) through the signal line of the contact R of the switch circuit (44) and whose center frequency is the color subcarrier frequency. Component) is removed and the luminance signal Y is taken out from the trap circuit (34).

Further, in this case, vertical emphasis is performed on the signal Y. That is, the signal C from the attenuator (13)
Is supplied to the trap circuit (35) through the contact R of the switch circuit (45) and the luminance signal component without vertical correlation remaining in the signal C is taken out, and this signal component is supplied to the limiter (36). A luminance signal component having no level vertical correlation is extracted, and this signal component is supplied to the addition circuit (33). Therefore, in the adding circuit (33), the luminance signal component without vertical correlation included in the signal C from the attenuator (13) is added to the luminance signal Y, so that the luminance signal Y from the trap circuit (34). Is vertical emphasis.

Then, although not shown, the signal Y from the trap circuit (34) is converted into an FM signal and the filter (31)
The signal C from is converted to the low frequency band and recorded on the tape (1) as described above.

On the other hand, during playback, the luminance signal Y demodulated from the FM signal
Is supplied to the adder circuit (21), and the carrier color signal C whose frequency is converted to the original occupied band is supplied to the adder circuit (21) so that the composite video signal (Y + C) is supplied from the adder circuit (21). This signal (Y + C) is taken out and supplied to the adder circuit (1) and the inverter (22) through the contact P of the switch circuit (41). Therefore, the carrier color signal is output from the attenuator (13) in the same manner as during recording. At the same time as C is taken out, at this time, the inter-track crosstalk component included in the original signal C is removed. However, at this time, the extracted signal C includes a luminance signal component due to crosstalk between tracks as an unnecessary signal component.

Then, the signal C is extracted from the filter (31) after removing unnecessary signal components by the filter (31).

Further, the reproduced signal Y is supplied to the subtraction circuit (38) through the signal line of the contact P of the switch circuit (42) → the delay circuit (14) → the contact P of the switch circuit (43), and at the same time, the attenuator (13 ) Is supplied to the trap circuit (35) through the contact P of the switch circuit (45), and the limiter (36) extracts the luminance signal component due to the crosstalk between tracks, and this signal component is attenuator (37). Through the subtraction circuit (38).

Therefore, the subtraction circuit (38) removes the crosstalk component from the luminance signal Y, and the subtraction circuit (38) extracts the signal Y having no crosstalk.

This signal Y is applied to the contact P of the switch circuit (44).
And a trap circuit (34).

Thus, according to the ICs (10) and (20), at the time of recording, the luminance signal and the carrier color signal C are separated from the composite video signal (Y + C), and the vertical emphasis to the luminance signal Y is performed. Crosstalk between tracks of the signal Y and the carrier color signal C is removed.

Further, in the present invention, as shown in FIG. 1, circuits (51) to (53) are further added.

That is, in the figure, the output signal of the delay circuit (14) is supplied to the "H" side contacts of the subtraction circuit (52) and the switch circuit (53), and the signal C from the attenuator (13) is supplied by the amplifier (51). Subtraction circuit (52) after the level is doubled
Is supplied to the switch circuit, and the subtracted output is "L" of the switch circuit (53).
Supplied to the side contacts. Then, the switch circuit (53) is supplied with a control signal that becomes the “H” level during recording and normal reproduction and becomes the signal Sw during still reproduction.

With such a configuration, the switch circuit (53) is connected to the "H" side contact during recording and normal reproduction, and this circuit has the same connection relationship as the circuit of FIG. Thus, the recording process and the reproducing process of the signals Y and C are performed.

During still reproduction, the switch circuit (53) is connected to the “H” side contact during the period Ta, that is, the field period Ta during which the head (3A) is performing reproduction. ) To the signal Sa as shown in FIG. 6B.
Is reproduced, and the signals Y and C are reproduced from this signal Sa, and the reproduction processing is performed in the same manner as in the above normal reproduction.

However, the period Tb at the time of still reproduction, that is,
Since the switch circuit (53) is connected to the “L” side contact during the field period Tb during which the head (3S) is reproducing, the output signal of the subtraction circuit (52) is transferred to the subsequent stage through the switch circuit (53). Supplied.

Then, at this time, the signal C is taken out from the adder circuit (11) at a double level, and at the same time, the luminance signal Y and
From the circuits (22) and (12), a difference signal ΔY = Y−Yd from the luminance signal −Yd, which has been phase-inverted and delayed by one horizontal period, is taken out. Since the crosstalk component due to the carrier color signal and the luminance signal is removed by the circuit in the subsequent stage as described above, the difference signal ΔY and the luminance signal Y from the delay circuit (14) will be considered.

Then, the difference signal ΔY is supplied to the subtraction circuit (52) through the attenuator (13) and the amplifier (51), and the luminance signal Y is supplied to the subtraction circuit (52).
In the subtraction circuit (52), the subtraction of Y−ΔY = Y− (Y−Yd) = Yd is performed. From the subtraction circuit (52),
The luminance signal Yd delayed by one horizontal period is output.

Since this signal Yd is supplied to the circuit in the subsequent stage instead of the signal Y, the luminance signal Y (= Yd) from the trap circuit (34) is the original reproduction signal as shown in FIG. 5E. Ss
It means that it is delayed by one horizontal period from (D in the same figure),
Only 0.5 horizontal period is deviated from the luminance signal Y reproduced from the signal Sa in the period Ta, so that the vertical blurring on the reproduction screen becomes inconspicuous.

At this time, as is clear from D and E in the same figure, the first 0.5 horizontal periods of the signal Y cannot be obtained, but this is within the vertical blanking period, and there is no problem.

Thus, according to the present invention, image blurring during still reproduction can be prevented. In this case, in particular, according to the present invention, the signal Y is delayed by using the delay circuit (12) for removing crosstalk. Therefore, there are few additional parts and it is low cost. In addition, existing ICs (10), (2
No need to change 0). Alternatively, it can be easily built in the IC (20).

In the example shown in FIG. 2, an inverter (54) and a switch circuit (55) are provided in the signal line between the attenuator (13) and the contact P of the switch circuit (45), and the switch circuit (55) is This is the case when they are connected in the same manner as the switch circuit (53).

Therefore, during the period Tb during still reproduction, the phase of the signal is inverted by the output signal inverter (54) of the attenuator (13) and then supplied to the trap circuit (35) to remove the crosstalk component.

In the above description, the recording format of the tape (1) is the standard time mode, but it can also be applied to the long time mode. It can also be applied when the angular interval θ of the head (3S) corresponds to, for example, 2.5 horizontal periods.

〔The invention's effect〕

According to the present invention, it is possible to prevent image blurring during still reproduction. In this case, in particular, according to the present invention, since the delay circuit (12) for removing crosstalk is used to delay the signal Y, It requires few additional parts and is low cost. Also, there is no need to change the existing ICs (10), (20). Alternatively, it can be easily built in the IC (20).

[Brief description of drawings]

1 and 2 are system diagrams of an example of the present invention, and FIGS. 3 to 6 are diagrams for explaining the same. (10) and (20) are ICs, and (12) is a delay circuit.

Claims (1)

[Claims] 1. A pair of rotating magnetic heads having an angular interval of 180 ° forms one magnetic track diagonally at a frequency at which a video signal having a luminance signal and a carrier color signal is interleaved with each other for each field period. In a magnetic reproducing apparatus for reproducing the above video signal from a magnetic tape in which adjacent magnetic tracks are close to or adjacent to each other and whose azimuth angles are different from each other, the reproduced luminance signal is reproduced during normal reproduction. Crosstalk components between tracks are removed using a delay circuit for one horizontal period, and a third rotary magnetic head is provided at a position where it rotates prior to one of the two rotary magnetic heads, and still reproduction is performed. At this time, the luminance signal is scanned by the other of the two rotary magnetic heads and the third rotary magnetic head. And the luminance signal reproduced by the third rotary magnetic head is taken out after being delayed by one horizontal period by the delay circuit, so that the image blur during still reproduction is compensated for magnetic reproduction. apparatus.