JPS60249495A - Magnetic picture recording and reproducing device - Google Patents

Abstract

PURPOSE:To improve the resolution to obtain vivid pictures by synthesizing an FM luminance signal with a low band converted color signal after allowing the FM luminance signal to pass a comb line filter which eliminates a frequency part where the spectrum of the low band converted color signal exists. CONSTITUTION:In case of recording, the FM luminance signal is allowed to pass a comb line filter 13, which eliminates the frequency of the part where the spectrum of the low band converted color signal converted to a low band exists, before the FM luminance signal and the low band converted color signal are added by an adder 7. As the result, since the spectrum of the side band of the FM luminance signal in parts other than the part where the spectrum of the low band converted color signal exists passes through the filter 13 through the spectrum of the side band of the FM luminance signal in said part is dropped out, the band width of the luminance signal is widened practically, and the resolution is improved. In case of reproducing, the output of a head amplifier 14 is separated into the FM luminance signal and the low band converted color signal by a comb line filter 15, and they are supplied to signal processing circuits 16 and 17 respectively.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a technique for improving image quality, particularly resolution, in magnetic recording and reproducing devices such as current home video tape recorders (VTRs). .

[Prior art]

As a conventional magnetic recording/reproducing apparatus of this type, there is one shown in FIG. FIG. 1 is a diagram showing the frequency arrangement of video signals in the NTSC color television system, and FIG. 2 is a block diagram showing the recording system of a home VTR as a conventional magnetic recording and reproducing device. As shown in Figure 1, in the frequency distribution of a video signal, the frequency of the luminance signal is generally distributed in a range up to approximately 4.2 MHz, and the chrominance signal is distributed in the upper range of 4.2 MHz. 3.58MB
They are arranged in a range of 1:500 KHz centering on Z so as not to overlap with the spectrum of the luminance signal. The case where such a color television signal is recorded on a home VTR as shown in FIG. 2 will be explained. In Fig. 2, l is a long terminal, 2 is a low-pass filter, 3 is a luminance signal processing circuit, 4 is a frequency modulator, 5 is a band-pass filter, 6 is a color signal processing circuit, 7 is an adder, and 8 is a recording array. , 9 is a video head, and 10 is a tape.

Next, the operation of the conventional home VTR shown in FIG. 2 will be described. A color video signal as shown in Fig. 1 applied to the input terminal 1 is filtered by a low-pass filter 2 to extract a luminance signal, and this luminance signal is processed by a luminance signal processing circuit 3 such as applying emphasis. After that, the signal is frequency modulated (FM) by a frequency modulator 4 to become an FM luminance signal. On the other hand, the carrier color signal is extracted by a bandpass filter 5, subjected to processing such as low frequency conversion in a color signal processing circuit 6, combined with the above-mentioned FM luminance signal in an adder 7, and current amplified in a recording amplifier 8. After that, the video head 9 records the video onto the tape 10. In this case, in order to ensure the separation of the luminance signal and the carrier color signal by the low-pass filter 2, the cutoff frequency cannot be set too high; , so the resolution is also limited accordingly. As shown in the recording signal frequency cocoon arrangement recorded on the tape 10 as shown in FIG. The sideband waves are distributed as shown in the upper and lower sideband components 11 of the FM luminance signal. Further, as shown in FIG. 3, the low frequency converted color signal that has been subjected to low frequency conversion is distributed as shown in the low frequency converted color signal component 12. In order to avoid disturbances due to interference between the luminance and chrominance signals, the FM luminance signal is normally tuned to a cant-off frequency F, not shown in FIG. 2, before it enters the adder 7. goes into a bypass filter. The spectrum of the FM brightness signal is distributed at intervals of signal frequencies above and below the carrier, and the amplitude of this sideband is determined by the modulation index mp (indicated by the ratio of frequency deviation Δf to signal frequency fp). . When a video signal is subjected to low carrier wave FM, the modulation index mp of the low frequency part of the video signal (the part corresponding to a flat screen over a large area) becomes a large value, but the modulation index mp becomes a large value in the low frequency part of the video signal (the part with many steep rises and (corresponding to the displayed screen, etc.)
The modulation index mp is a small value.・Modulation index mp is 1/
When it is smaller than 2, as shown in FIG. 4, the proportion of the second sideband or higher is less than 1%, so only the carrier and the upper and lower first sidebands need to be considered.

Therefore, the maximum value of the multi-signal frequency fp, that is, the resolution, is determined by the bandwidth through which the first sideband passes. Due to its magnetic properties, the r-oxide magnetic tape used in household VTRs records the first upper i-wave as the signal frequency fp increases.

Since reproduction becomes difficult, the first lower sideband becomes important. By the way, as mentioned above, in order to avoid interference between the luminance signal and the color signal, the cutoff frequency F is set.

Since this bypass filter is included, this cant-off frequency F from the carrier. The resolution is almost determined in the frequency band up to. In addition, this frequency band is
As explained using the diagram, the design is well-balanced with the luminance signal band.

The performance of recent television receivers has improved significantly, and some of them employ comb filters to separate luminance and color signals, bringing the resolution quite close to the limits of television broadcasting systems. However, one of the drawbacks is that the resolution of home-use VTRs is not always fully satisfactory.

[Summary of the invention]

This invention was made for the purpose of improving the drawbacks of the conventional devices as described above, and is a magnetic recording/playback device that uses FM.
By passing the FM luminance signal through a comb filter that removes the frequency portion of the spectrum of the low-pass converted color signal before adding the two signals, the brightness signal and the low-pass converted color signal, The present invention provides a magnetic recording and reproducing device that has a simple configuration and can substantially improve resolution.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 5 is a block diagram showing the recording system and playback system of a home VTR as a magnetic recording/playback device, which is an embodiment of the present invention, and the same parts as in FIG. 2 are designated by the same reference numerals. Op, detailed explanation will be omitted. In FIG. 5, (a) shows the recording system, and (b) shows the reproducing system. In the figure, 13 is a recording system comb filter, 14
is the head amplifier, 15 is the reproduction system comb filter, 16
17 is a reproduction luminance signal processing circuit, and 17 is a reproduction color signal processing circuit.

Next, the operation of the home VTR shown in FIG. 5, which is an embodiment of the present invention, will be described. In a VTR, in order to improve the resolution, it is necessary to widen the bandwidth of the luminance signal. For this reason, the cant-off frequency of the low-pass filter 2 as shown in Fig. 2 should be made as high as possible within a range that does not mix with the color signal, or a comb-shaped filter configuration should be used so that the cant-off frequency also enters the color signal. By extracting the luminance signal, it is necessary to widen the bandwidth of the luminance signal and, as shown in FIG. 4, to secure a bandwidth sufficient for the first lower sideband to pass. However, as shown in FIG. 3, the cutoff frequency F. The no-pass filter limits the band. Therefore, if this bypass filter is removed, the band limit will disappear, but
Since the FM carrier changes continuously between frequencies F and ~F, its sidebands also change continuously, and the low-frequency conversion color signal and sidebands are mixed and can no longer be separated, causing interference. There is the inconvenience of leaving. By the way, if we look at the spectrum of the color television signal as shown in Fig. 1 in detail, as shown in Fig. 6, in the spectrum of the luminance signal, there are harmonics of fH at intervals from DC to horizontal frequency fH, The energy of the luminance signal is distributed around it. Similarly, the color signal is divided into fH at intervals of horizontal frequency fH.
There are harmonics of
It has been chosen to be immersive. By the way, in a VTR, color signals are converted to a low frequency range for recording, but it should be noted that even with such low frequency conversion, the spectra are still lined up at intervals of the horizontal frequency fH. This invention was created. That is, during recording, the image shown in FIG. 5 (a
), the cant-off frequency F is set before adding the FM luminance signal together with the low-pass converted color signal in the adder 7. Instead of the bypass filter, if the low-pass converted color signal is passed through a comb filter 13 of the type that removes the frequency of the part where the spectrum exists, and then inputted to the adder 7, As shown in Figure 7, the spectrum of the sideband of the FM luminance signal in the part where the spectrum of the low-pass converted color signal is present is lost, but the other parts are passed through, so the band of the FM luminance signal is essentially the same. The breadth has expanded,
This improves resolution. During reproduction, as shown in FIG. 5(b), the output of the head angle 14 is separated into DFMFM luminance signal area converted color signals by a comb filter 15, and each is sent to the reproduction luminance signal processing circuit 1.
6. If the information is led to the reproduced color signal processing circuit 17, the information can be extracted without loss of information, and resolution can also be improved. In the above embodiment, the comb filter 13 during recording and the comb filter 15 during reproduction are treated as separate filters, but in an actual configuration, it is possible to use both in common.

〔Effect of the invention〕

As explained above, in a magnetic recording and reproducing apparatus, the present invention converts the FM luminance signal into the spectrum of the low-frequency converted color signal before adding the two signals, the FM luminance signal and the low-frequency converted color signal. It is configured to pass through a comb filter that removes the frequency part, so it is an extremely simple configuration.
It can substantially improve the resolution, and has the excellent effect of achieving a substantial improvement in resolution and providing an extremely clear screen, especially in the case of a narrowband transmission line such as a home VTR. It is.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the frequency arrangement of video signals in the NTSC color television system, Fig. 2 is a block diagram showing the recording system of a home VTR as a conventional magnetic recording and reproducing device, and Fig. 3 is a FIG. 4 is a diagram showing the frequency distribution of recording signals recorded on tape in the home VTR shown in FIG. FIG. 5 is a block diagram showing the recording system and playback system of a home VTR as a magnetic recording/playback device which is an embodiment of the present invention, and FIG. 6 is a detailed diagram of the frequency arrangement of the video signal shown in FIG. A diagram showing a spectrum, FIG. 7, is a diagram showing the concept of frequency allocation of a recorded video signal in the home VTR of FIG. 5. In the figure, 1... input terminal, 2... low pass filter, 3... luminance signal processing circuit, 4... frequency modulator, 5... band pass filter, 6... chrominance signal processing circuit , 7... Adder, 8... Recording amplifier, 9...
Video head, 10... Tape, 11... FM luminance signal upper and lower side band components, 12... Low frequency conversion color signal component, 13.15... Comb filter, 14... Head Amplifier, 16... Reproduction luminance signal processing circuit, 17...
・Reproduction color signal processing circuit. In each figure, the same reference numerals indicate the same or equivalent parts. Agent Masuo Oiwa Figure 1 Solid-liquid (Drops (MHz) Figure 2 Figure 3 Figure 4 Section -1-----
-111--1--1-0 j and →□ ○ 2 boxes or e □

Claims (1)

[Claims] A composite color television signal is separated into a luminance signal and a carrier chrominance signal, the luminance signal is frequency modulated to become an FM luminance signal, and the carrier chrominance signal is frequency-converted to the FM luminance signal.
In a magnetic recording and reproducing device, a low-frequency converted color signal is obtained by low-frequency conversion on the lower side of the frequency distribution of an M luminance signal, and two signals, the jump luminance signal and the low-frequency converted color signal, are added together and recorded on a tape. , before adding the two signals together, the F
1. A magnetic recording and reproducing apparatus, characterized in that the M luminance signal is passed through a comb-shaped filter that removes a frequency portion where the spectrum of the low-pass converted color signal exists.