JPS62111594A - Rotary head type reproducing device - Google Patents

Abstract

PURPOSE:To prevent a reproduced signal from the generation of color shade due to shock caused by the contact of a head by switching a response speed for the correction of a time base of a color signal in accordance with the rota tional phase of the head. CONSTITUTION:A chrominance signal component is extracted from a reproduced signal through an LPF 8 and converted into a color signal. A burst signal is extracted from the converted color signal through a bust gate 11 and phase- compared with 3.58MHz reference signal generated from an oscillator 19 by a phase comparator 12 and the compared result is outputted as an error voltage. In a phase portion where color shade may be generated, the phase comparator 12 is connected to a time constant circuit 15 having a time constant for accelerating a response speed higher than a normal one by a switching signal through a SW 13. Consequently, the reproduced signal can be prevented from color shade due to chock caused by the contact of the head without losing the SN ratio at another reproducing timing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rotary head type reproducing device including a plurality of rotary heads.

[Conventional technology]

This type of device is the video tape recorder (VTR).
However, in recent years, reflecting the market needs for multi-functionality in VTRs, in addition to the two standard recording/playback heads, there is also a head for special playback or long-time recording/playback on the drum. There are more and more VTRs. Furthermore, in recent years, VTRs have been developed in which the diameter of the drum has been reduced to 2/3 of the conventional one, four heads are arranged orthogonally on the drum, and recording and playback is performed using the four heads alternatively, or an erasing head is arranged on the drum. ,
There are VTRs that have improved image quality during continuous shots, etc.

Therefore, a VTR in which the diameter of the drum described above is reduced to 2/3 of that of the conventional drum and four heads are disposed orthogonally on the drum will be described with reference to FIGS. 3 to 5.

Fig. 3 is a diagram showing the arrangement of the heads on the drum and the positional relationship between the tape and the heads, Fig. 4 is a diagram showing the position of the heads on the tape pattern, and Fig. 5 is a diagram showing color unevenness on the playback screen. It is. In the figure, 5 is a drum, 1. 2.
3. Reference numeral 4 designates a recording/reproducing head disposed perpendicularly to each other on the drum 5, 6 a tape, and 7 a tape guide member.

[Problem that the invention seeks to solve]

In the above-mentioned apparatus, the state in which the head 2 is currently playing will be described. The rotating direction of the drum and the advancing direction of the tape are indicated by arrows in FIGS. 3 and 4. The head 2 first starts reproduction from the position a in FIG. 3, and when it reaches the position a in FIG. 3, the head 1 comes into contact with the tape. At this time, fluctuations in the reproduction waveform occur due to fluctuations in the drum rotational speed due to fluctuations in the load on the drum due to the head 1 starting to come into contact with the tape, or vibrations of the tape that occur when the head 1 comes into contact with the tape. Next, when the head 2 comes to the position C in the figure, the head 1 begins to come into contact with the tape, causing fluctuations in the reproduced waveform as described above.

In this way, when a certain head is playing a certain track, the above-mentioned phenomenon occurs at a position exactly divided into thirds, and this appears as two color irregularities on the playback screen as shown in Figure 5G. appear. As can be seen from the cause of this discoloration, the position where it appears on the screen is fixed by the placement of the drum's north head.

As mentioned above, in conventional devices, when the W head comes into contact with the tape or separates from the tape, the speed of the drum or tape changes due to the impact, and the reproduction wavelength changes. However, there is a problem in that fixed color unevenness occurs in the reproduced image.

The present invention has been made to solve these problems, and an object of the present invention is to provide a rotating head type reproducing device that can eliminate fixed color unevenness that occurs during reproduction.

[Means for solving problems]

The rotary head reproducing device according to the present invention switches the response speed of time axis correction of color signals in accordance with the rotational phase of the head.

[For production]

In this invention, color unevenness can be removed by increasing the response speed of time axis correction of color signals when other heads enter or leave the recording medium.

〔Example〕

FIG. 1 is a schematic block diagram of the main parts of a VTR which is an embodiment of the present invention, and FIG. 2 is a waveform diagram showing the switching signals shown in FIG.

In the figure, 8 is a low-pass filter (LPF) for extracting color signal components from the reproduced signal, 9 is a frequency converter for returning the frequency of the color signal converted to a low frequency, and 10 is a band-pass filter ( BPF), 11 is a burst gate that extracts a burst signal from the reproduced color signal using a burst gate pulse, 12 is a phase comparator that compares the phase of this extracted burst signal with a reference signal, and 13 is a time constant circuit that is controlled by a switching signal. 14.15 as an alternative to phase comparator 1
This is a switch (SW) for connecting to 2.

14.15 is for determining the time constant of the response of the phase comparator 12, ]・1 is a time constant circuit for providing a sufficient response during normal playback, and 15 is a time constant circuit for determining the response time constant of the phase comparator 12. This is a time constant circuit for faster response. 16 is A
A voltage controlled oscillator (VCO) that converts the AFC error voltage into a frequency based on the PC error voltage and the time axis error of the reproduced horizontal synchronization signal, 17 is a frequency converter, and 18 is a band pass filter (BPF). ), 19 is 3.
This is a crystal oscillator that oscillates a 58MH2 reference signal.

In the apparatus configured as described above, first, the color signal component is extracted from the reproduced signal by the LPF 8. The extracted signal is converted into a 3.58 MHz color signal by the frequency converter 9.

The converted color signal is output through BPFIO and mixed with the luminance signal. An automatic phase control (APC) circuit is generally used to correct time axis fluctuations during this frequency conversion. An example of the APC circuit according to the present invention is shown by the dotted line in FIG.

Then, a burst signal is extracted from the converted color signal by the burst gate, and the phase is compared with the standard 3.58MH2 by the oscillator 19 in the phase comparator 12, and the signal is output as an error voltage. At this time, the response speed of the phase comparator 12 is
It is determined by each time constant of the time constant circuits 14 and 15. The time constants of the time constant circuits 14 and 15 are usually set a little large, because if the response becomes too fast, the noise component will react and the S/N will worsen, so Unable to catch up and compensate for time axis fluctuations.

Therefore, in this embodiment, focusing on the fact that color unevenness occurs only when the drum rotational position reaches a predetermined phase, the switching signal shown in FIG. A time constant circuit 15 having a time constant faster than the normal response speed is connected to the phase comparator circuit 12 by SWI 3. This makes it possible to prevent color unevenness due to impact caused by head contact without damaging the S/N ratio at other reproduction timings.

This invention Q has been explained above using an example in which the drum diameter is 2/3 and the wrapping angle is 3/2 times G. It is possible to eliminate unevenness in the same way.

〔Effect of the invention〕

As explained above, this invention switches the response speed of the time axis correction of the color signal according to the rotational phase of the head, which has the effect of preventing color unevenness in the reproduced signal due to impact caused by head contact. .

[Brief explanation of drawings]

FIG. 1 is a block diagram of a VTR which is an embodiment of the present invention, FIG. 2 is a waveform diagram showing the switching signal shown in FIG. 1, and FIG. FIG. 4 is a diagram showing the positional relationship, FIG. 4 is a diagram showing the position of the head on the tape pattern, and FIG. 5 is a diagram for explaining color unevenness on the playback screen. In the figure, 8 is an LPF, 9.17 is a frequency converter, and l
0 is a BPF, 11 is a burst gate, ], 2 is a phase comparator, 13 is a SW, 1.4. , 15 is a time constant circuit,
16 is a VCo, 18 is a BPF, and 19 is an oscillator. Agent Patent attorney... : IIZ Takaharu Figure 1 Figure 2 Figure 3 □ Figure 4 Figure 5

Claims (1)

[Claims] A rotary head type reproducing device comprising a plurality of rotary heads, characterized in that the response speed of time axis correction of a color signal is switched according to the rotational phase of the head.