JPS6184195A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent a cross color and moire phenomenon and to reproduce a picture with high resolution by providing a comb-shaped filter at the succeeding stage of an FM demoudlator circuit for demodulating a luminance signal separated from a reproduction video signal. CONSTITUTION:A magnetic recording and reproducing device 21 can set the filter frequency band of a low pass filter circuit 10 provided between an FM demodulator circuit 9 and de-emphasis circuit 11 higher than frequency of a chrominance subcarrier. Thus a comb-shaped filter 22 is provided between the circuit 11 and an adder circuit 12 not to mix an interference component to a chromaticity signal in the midst of outputting a signal to the circuit 12. The filter 22 is constituted of a band-pass filter circuit 23 having a central frequency of 3.58MHz, a circuit obtained by connecting serially 1H delay circuits 24 for delaying a signal by 1H and a parallel signal line 25 connected to said circuit and an adder circuit 26, and removes the chromaticity signal whose phase inverts by 1H. Moreover the filter 22 serves as emphasizing the high frequency of a luminance signal having the line correlation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording and reproducing apparatus that is capable of increasing the resolution of reproduced images without degrading the image quality.

[Conventional technology]

In the conventional magnetic recording/reproducing apparatus 1 shown in FIG. 4, only the signal reproducing system is shown, but as is well known, images are read alternately from the magnetic tape 3 by a pair of rotating magnetic heads 2a and 2b. The signal is guided to a high-frequency P-wave circuit 6 and a low-frequency P-wave circuit 7 via reproduction amplifier circuits 4a and 4b and a head changeover switch 5. The high-pass filter circuit 6 separates and extracts the frequency modulated luminance signal component in the video signal, and passes the extracted luminance signal component through the limiter circuit 8 to the FM demodulation circuit 9.
supply to. The luminance signal demodulated by the FM demodulation circuit 9 is
After high-frequency components that affect the band of the chromaticity signal are removed by a low-pass filter circuit 10, the signal is supplied to an adder circuit 12 via a de-emphasis circuit 11.

On the other hand, the low-band r-wave circuit 7 separates and extracts the low-band converted chromaticity signal component in the video signal, and supplies the extracted chromaticity signal component to the chromaticity signal processing circuit 13 . The chromaticity signal processing circuit 13 frequency-converts the chromaticity signal to the original signal band before low frequency conversion, performs necessary signal processing, and then supplies the signal to the adder circuit 12 via the band P-wave circuit 1-4. do.

The luminance signal and chromaticity signal thus supplied to the adder circuit 12 are outputted via the amplifier circuit 15 as a composite video signal.

[Problem that the invention seeks to solve]

In the conventional magnetic recording and reproducing apparatus 1, the F-wave band of the low-pass filter circuit 10 provided at the next stage of the FM demodulation circuit 9 is 3.2 M.
Hz, but in an attempt to obtain image information contained in the luminance signal component exceeding this band, if the wave band of the low-pass P-wave circuit 10 is expanded to the chromaticity signal band, the color mixed into the luminance signal component When the luminance signal and chromaticity signal are added together in the adding circuit 12, the chromaticity signal component may cause cross color with the chromaticity signal, or a beat may remain due to cross-modulation distortion with the luminance signal. , moiré phenomenon? However, although it is possible to change the reproduced image at high resolution, there are problems such as unavoidable image quality deterioration.

[Means for solving problems]

This invention solves the above problems by high-pass filtering the video signal read by the magnetic head, separating and extracting the FM-modulated luminance signal component from the low-pass converted chromaticity signal. In a magnetic recording/reproducing device that demodulates with a post-FM demodulation circuit, a comb-shaped filter removes a chromaticity signal component mixed into the luminance signal component before mixing with the reproduced chromaticity signal after the FM demodulation circuit. The main point is that it has been established.

[Effect]

This invention provides a comb-shaped filter after the FM demodulation circuit that demodulates the luminance signal separated from the reproduced video signal, removes the chromaticity signal component mixed into the luminance signal component, and eliminates cross color and moiré phenomena. prevention and play back high-resolution images.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to FIG. FIG. 1 is a schematic circuit diagram showing an embodiment of the magnetic recording and reproducing apparatus of the present invention.

In FIG. 1, the same components as in FIG. 2 are given the same reference numerals.

In FIG. 1, a magnetic recording/reproducing device 21 includes a low-frequency P-wave circuit 1 provided between an FM demodulation circuit 9 and a de-emphasis circuit 11.
The r-wave band of zero is set higher than the frequency of the color subcarrier. For this reason, a comb filter 22 is provided between the de-emphasis circuit 11 and the addition circuit 12 to prevent interference components from entering the chromaticity signal during output to the 7IO calculation circuit 12.

This comb filter '22 has a center circumference of 3.58M.
) Lz bandpass filter circuit 23 and IH delay circuit 24 for IH (one horizontal scanning period) signal delay are connected in series, and a signal line 25 parallel to this circuit is connected to an adder circuit 26. While removing the chromaticity signal whose phase is inverted for each IH, it works to emphasize the high frequency range of the luminance signal with line correlation. ! By expanding the FM demodulation circuit 9 which demodulates the 4 degree signal and the low pass filter circuit 1001 wave band, the band of the reproduced luminance signal is expanded as shown by the solid line from the conventional band shown by the dotted line in the middle of Figure 2. In addition to increasing the resolution, the comb filter 22 having P-wave characteristics shown by the dashed line in the figure eliminates the chromaticity signal component mixed into the fi$1 degree signal and the cross-modulation of the luminance signal and chromaticity signal. Beat components and the like based on distortion can be removed, and interference with the chromaticity signal caused by unnecessary components mixed in the luminance signal can be reduced.

Note that, in place of the comb filter 22, a comb filter 32 shown in FIG. 3, which is a partially modified circuit of a conventional circuit known as a noise reduction circuit for reproduced luminance signals, may be used. , without degrading the horizontal resolution of the luminance signal.
Only unnecessary chromaticity signal components can be removed. This comb filter 32 connects the IH delay circuit 24 and a signal line 33 that bypasses the IH delay circuit 24 to a subtraction circuit 34, and
A high-frequency wave circuit 36 and a limiter circuit 37 for limiting the amplitude of the output thereof are provided between the subtraction circuit 35 replacing the subtraction circuit 35 and the subtraction circuit 34 described above.

〔Effect of the invention〕

As explained above, 1. According to the present invention, a comb-shaped filter is provided at the subsequent stage of the FM demodulation circuit that demodulates the luminance signal separated from the reproduced video signal, and removes the chromaticity signal component mixed into the luminance signal component. Because of the configuration, the F-wave band of the low filter circuit provided at the next stage of the FM demodulation circuit is expanded to include the chromaticity signal band, and the luminance signal, which causes cross color when achieving high resolution, is Mixture of chromaticity signal components can be effectively removed by a comb-shaped filter, and the loss can be reduced by adding the luminance signal, which is free of chromaticity signal components, to the color signal and supplying it to the receiver. O has excellent effects such as preventing color and moiré phenomena and reproducing high-resolution images.

[Brief explanation of the drawing]

FIG. 1 is a schematic circuit configuration diagram showing an example of the magnetic recording/playback device of the present invention, FIG. 2 is a frequency characteristic diagram of the reproduced brightness signal by the magnetic recording/playback device shown in FIG. 1, and FIG. FIG. 4 is a circuit configuration diagram of a main part showing a modified example of the magnetic recording/reproducing apparatus of the present invention, and FIG. 4 is a schematic configuration diagram showing an example of a conventional magnetic recording/reproducing apparatus. 2a, 2b...Rotating magnetic head, 6...1 high frequency circuit, 9...FM demodulation circuit, 21...Magnetic recording main device,
22.32...Comb filter.

Claims (1)

[Claims] In the magnetic recording and reproducing apparatus, which high-pass filters the video signal read by the magnetic head, separates and extracts the FM-modulated luminance signal component from the low-pass converted chromaticity signal, and demodulates it in the FM demodulation circuit after extraction. A magnetic recording/reproducing device comprising a comb-shaped filter that removes a chromaticity signal component mixed into the luminance signal component at a subsequent stage of an FM demodulation circuit and before mixing with the reproduced chromaticity signal.