JPH0523111B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an image recording and reproducing apparatus such as a video tape recorder, and particularly to means for improving the resolution of a video signal.

[Technical background of the invention and its problems]

In image recording and reproducing devices such as video tape recorders and video disk devices, it is common to record and reproduce FM waves or the like that are angle-modulated by the video signal to be recorded on a recording medium. In this case, there is a limit to the frequency of the recorded video signal. That is, for example, due to spacing loss and the like occurring between the magnetic head and the magnetic recording medium, the higher the frequency of the signal, the greater the loss.

FIG. 1a is a diagram showing an example of frequency characteristics during reproduction. As can be seen from this figure, when the frequency exceeds a certain range, the reproduction level suddenly decreases.

FIG. 1b is a diagram showing frequency allocation of FM modulation for efficiently recording video signals on a recording medium having frequency characteristics as shown in FIG. 1a. In this figure, 1 is the frequency band of the video signal to be recorded, 2 is the center frequency of the FM carrier wave, 3A is the lower sideband generated by modulation, and 3B is the upper sideband. As a general FM modulation recording method, the lower sideband 3A generated by FM modulation and video signal band 1 do not overlap.
The center frequency 2 of the FM carrier wave is set. However, as shown in FIG. 1a, there is a limit to the frequency band that can be used, so there is a problem that the frequency band 1 of the video signal cannot be made very wide. For this reason, for example, in a home VTR, etc., as shown in Figure 1c,
Video signal band 4 is around 2MHz, 3MHz±
The 500KHz color signal band is low frequency converted to a signal band 5 of around several hundred Hz, which is multiplexed with the FM signal and recorded. However, in this case, it is video signal band 4 that determines the resolution of the reproduced video signal, but this band 4 is 2M
Since the resolution is close to Hz, there was a problem that sufficient resolution could not be obtained.

[Purpose of the invention]

An object of the present invention is to provide an image recording and reproducing apparatus that can record and reproduce high-resolution video signals even when a sufficient frequency band cannot be obtained due to conditions such as the recording medium.

[Summary of the invention]

In order to achieve the above object, the present invention is characterized by the following configuration. That is, during recording, the video signal to be recorded is sampled with multiple types of sampling pulses of different phases to obtain multiple channels of video signals, which are sequentially and selectively extracted for each horizontal synchronization signal period and recorded on the recording medium. are recorded serially in time. During playback, the video signals of multiple channels that are sequentially reproduced from the recording medium are sequentially delayed by one horizontal synchronization signal period in accordance with the number of channels, so that the video signals of multiple channels that are parallel in time are delayed. A reproduced video signal is obtained, and this is sampled and synthesized using a plurality of types of sampling pulses having the same phase as the sampling pulse during recording, thereby obtaining a reproduced video signal having the same frequency band as that during recording. In this way, the video signal to be recorded is time-divisionally divided into bands for recording and reproduction, thereby avoiding a reduction in resolution due to band limitation.

[Embodiments of the invention]

FIG. 2 is a block diagram showing the configuration of a recording system according to an embodiment of the present invention. The video signal to be recorded applied to the input terminal 10 is sent to the sampling circuit 11,1.
2 and sampled, the sampling and hold capacitors 13 and 1
4 are held respectively. Above capacitor 1
Each signal held in 3 and 14 is passed through LPF15,
Bandwidth is limited at 16 and electronic switch 17
given to. In this example, the above LPF15,1
The cutoff frequency of 6 is approximately 2.5MHz,
This value may be determined depending on the selection of the frequency band of the video signal to be recorded. Electronic switch 17
The output signals from LPFs 15 and 16 are alternately switched and selected every horizontal synchronization signal period as described later.
FM modulator 18.

The FM wave modulated by the FM modulator 18 is current-amplified by the recording amplifier 19, and then supplied to the recording/reproducing head 21 via the recording side 20a of the recording/reproducing switch 20. As a result, FM waves are recorded on the magnetic tape 22 as a recording medium.

On the other hand, the video signal applied to the input terminal 10 is also supplied to the horizontal synchronization signal separator 23, and the horizontal synchronization signal is separated and extracted. The horizontal synchronization signal separated and extracted by the horizontal synchronization signal separator 23 is frequency multiplied by 254H (H = frequency of the horizontal synchronization signal) synchronized with the horizontal synchronization signal in an automatic frequency control circuit (hereinafter abbreviated as AFC) 24. be done. Thus
The AFC circuit 24 outputs a signal of approximately 4 MHz. The approximately 4 MHz signal output from the AFC circuit 24 directly triggers the sampling pulse generator 26 on the one hand, and the approximately 4 MHz signal is phase-shifted by 1/2 period in the phase shifter 25 on the other hand, and then the sampling pulse generator 26 is triggered directly. Trigger generator 27. The sampling pulses generated by the sampling pulse generators 26 and 27 are sent to the sampling circuits 11 and 12.
are given to each.

FIG. 3 shows waveforms showing the operation of the sampling circuits 11 and 12, SA is the video signal, SB is the output waveform of the sampling pulse generator 26,
SC is the output waveform of the sampling pulse generator 27. As shown in FIG. 3, a phase difference of 1/2 cycle T is given between both sampling pulses 3B and 3C. Waveform for convenience of explanation below
The pulse of SB will be called φ1, and the pulse of waveform SB will be called φ2. The x marks in the waveform SA are timing points sampled by φ1, and the ○ marks are timing points sampled by φ2.

Let's return to Figure 2. Horizontal synchronization signal separator 23
The horizontal synchronizing signal separated and extracted by is applied as a clock input to a flip-flop circuit (hereinafter abbreviated as FF circuit) 28. The FF circuit 28 performs an inverting operation every time a clock input is applied.
The output of this FF circuit 28 is supplied to the electronic switch 17 as a switching input. Therefore, the electronic switch 17 alternately and sequentially switches and outputs the video signal sampled by φ1 and the video signal sampled by φ2 in synchronization with the horizontal synchronizing signal.

The video signal applied to the input terminal 10 is also supplied to a vertical synchronizing signal separator 29, where the vertical synchronizing signal is separated and extracted. The vertical synchronizing signal separated and extracted by the vertical synchronizing signal separator 29 triggers a reset pulse generator 30. The width of the reset pulse from the reset pulse generator 30 is, for example,
It is approximately 1 μsec, which is sufficiently narrow compared to the horizontal synchronization signal period (1H). This reset pulse is applied as a reset input to the FF circuit 28. As a result, when the reset pulse is generated, the output of the FF circuit 28 is forcibly reset to the "0" level. For this reason FF
The output of the circuit 28 is phase-locked to the vertical synchronization signal.

FIG. 4 is a diagram of operating signal waveforms around the electronic switch 17, where SD is a reset pulse, SE is a horizontal synchronizing signal, SF is the output of the FF circuit 28, and SG is the output waveform of the electronic switch 17. It is.
In FIG. 4, the broken arrow indicates how the output SE of the FF circuit 28 is forcibly reset to the "0" level by the reset pulse SD. Also output
SG marks φ11 and φ12 indicate video signals sampled by φ1 and φ2, respectively. As can be seen from this Figure 4, φ1,
The video signals sampled by 2 are alternately switched at the horizontal synchronization signal period. In this embodiment, a video signal with a band of 0 to 4 MHz is to be recorded and played back, but this band of 0 to 4 MHz is time-divisionally divided into two, and the video signal with a band of 0 to 2 MHz is divided into two.
Channel is generated. As a result, the video signal sampled by φ1 and the video signal sampled by φ2 are FM-modulated on the magnetic tape 22, which is a recording medium, every horizontal synchronization signal period (1H), and are temporally modulated. are recorded alternately in series.

Next, the reproduction system will be explained. FIG. 5 is a block diagram showing the configuration of the reproduction system. Reproduction obtained via the reproduction side 20b of the recording/reproduction switch 20
The FM wave is FM voltage amplified by the voltage amplifier 31.
The signal is supplied to a demodulator 32. The reproduced video signal demodulated by the FM demodulator 32 passes through an LPF 33 with a cutoff frequency of approximately 2.5 MHz, and is supplied to a sampling circuit 35. Also, the output of LPF33 consists of a charge transfer element or a delay line on the other side.
After being delayed by one horizontal synchronizing signal period (1H) in the 1H delay device 34, it is supplied to the sampling circuit 36. Therefore, the video signal supplied to the sampling circuit 36 is delayed in phase by J degrees 1H with respect to the video signal supplied to the sampling circuit 35. The sampling circuits 35 and 36 are composed of analog gate circuits using FETs, for example, and are connected to a sampling pulse generator 4, which will be described later.
When the sampling pulses from 5 and 46 are not given, it is in the OFF state, and it is in the ON state only during the period when the sampling pulses are given.
During this period of not being in the ON state, the LPF3
The video signal which is the output of No. 3 is sampled.

The outputs of the sampling circuits 35 and 36 are sampled and held in common to a sampling and holding capacitor 37. This held video signal is amplified by an amplifier 38 and then sent out from an output terminal 39.

The demodulated video signal output from the FM demodulator 32 is also supplied to a horizontal synchronization signal separator 40, where the horizontal synchronization signal is separated and extracted. The separated and extracted horizontal synchronizing signal is input to the AFC circuit 41. AFC circuit 41
has the same configuration as the AFC circuit 24 shown in FIG. In this way, the AFC circuit 41 outputs a 4MHz signal that is phase synchronized with the reproduced horizontal synchronization signal. This 4MHz signal is supplied to the first switching terminal 43a of the electronic switch 43 and the second switching terminal 44b of the electronic switch 44. Also, AFC circuit 4
The output of 1 is phase-shifted by 1/2 period of 4 MHz by the phase shifter 42 and sent to the second switching terminal 4 of the electronic switch 43.
3 and the first switching terminal 44a of the electronic switch 44. The switching outputs of the electronic switches 43 and 44 are provided by the sampling pulse generators 45 and 46, respectively.
This is the trigger input. Sampling pulses generated by sampling pulse generators 45 and 46 are supplied to the sampling circuits 35 and 36, respectively.

The horizontal synchronizing signal separated and extracted by the horizontal synchronizing signal separator 40 is given to an FF circuit 47 as a clock input. The output of the FF circuit 47 is supplied to electronic switches 43 and 44 as simultaneous switching inputs.

The demodulated video signal that is the output of the FM demodulator 32 is also supplied to a vertical synchronization signal separator 48, where the vertical synchronization signal included in the video signal is separated and extracted. The separated and extracted vertical synchronization signal is sent to the 0 set pulse generator 4.
Trigger 9. The reset pulse generated by the reset pulse generator 49 is applied to the FF circuit 47 to reset the FF circuit.

FIG. 6 is a signal waveform diagram for explaining the operation of the block diagram shown in FIG. In FIG. 6, SH is the input video signal of the sampling circuit 35, and SJ is the input video signal of the sampling circuit 36, and there is a time difference of 1H between the two signals as described above.
The video signal SH is a video signal that is mutually sampled every 1H by φ1 and φ2 during recording, and the video signal SJ is similar, but delayed by 1H, and when viewed on the same time axis, it is a video signal that is sampled by φ1 and φ2 every 1H. Video signals φ11 and φ12 sampled by φ2 are obtained simultaneously. As is well known, in video signals, there is particularly a very strong correlation between scanning lines. Therefore, there is almost no difference between the video signal 1H ago and the current video signal. This device actively utilizes this point. In other words, a sampling signal (254H signal) in which a video signal which is a video signal 1H before and was sampled by φ1 and a video signal which is a current video signal and which was sampled by φ2 are phase-synchronized with the reproduced video signal. By sampling, a video signal of the same band as that at the time of recording is restored.

As shown in FIG. 6, during the period TA, the video signal sampled by φ1 during recording and the video signal sampled by φ2
A video signal sampled by is obtained on the same time axis. As described above, the sampling pulses φ1 and φ2 are out of phase by 1/2 period. Therefore, the video signal to be sampled by sampling pulse φ1 (corresponding to the signal level of × in waveform SA in Figure 3) and the video signal to be sampled by φ2 (corresponding to the signal level of point ○ in waveform SA in Figure 3), (corresponding) are lined up on the same time axis, it would appear that in a two-chip pixel shifting television camera, the pixels (video signal) from the first image sensor and the pixels (video signal) from the second image sensor are taken out in such a way that they are alternately aligned on each horizontal line with their positions (phases) shifted by half the pixel pitch of the image sensor, effectively increasing the resolution by only one image sensor. A situation similar to that in which a video signal with twice the resolution is obtained will appear. That is, each reproduced horizontal line can have twice the resolution of the sampled video signal produced by only either sampling pulse φ1 or φ2. As understood from the embodiments described above, the sampled video signal by the sampling pulse φ1 and the sampled video signal by the sampling pulse φ2
There is exactly a gap between the sampled video signal and
Although there is a time (phase) difference equivalent to 1H, as mentioned above, video signals generally have extremely high vertical correlation, so problems rarely occur.

The output signal of the AFC circuit 41 is the sampling signal φ1' during reproduction, and the output signal of the phase shifter 42 is the sampling signal φ2' during reproduction. And the output level of the FF circuit 47 is "1"
When , electronic switches 43 and 44 are connected to terminal 4, respectively.
3a and 44a, and when it is "0", they are switched to terminals 43b and 44b, respectively. the result,
During the period TA in FIG. 6, the electronic switch 43,
44 is switched to the 43a, 44a side, the electronic switch 43 selects φ1', and the electronic switch 44
selects φ2'. Therefore, during the period TA, the sampling circuits 35 and 36 have φ1' and φ1', respectively.
A triggered sampling pulse is supplied to φ2'. Therefore, the reproduced video signal φ11 is φ1'
On the other hand, the reproduced video signal φ12 is sampled by φ2'.

In FIG. 6, SI and SK are the output waveform modes of the sampling pulse generators 45 and 46, and the sampling pulse modes φ1' and φ2' are switched corresponding to the modes φ11 and φ12 of the video signals SH and SJ. It shows.

Thus, by the sampling circuit 35, φ1'
The video signal level sampled at φ2' is held in the capacitor 37, and at the next timing, the video signal level sampled at φ2' by the sampling circuit 36 is held in the capacitor 37.
Sequential sampling and holding is repeated. As a result, time-division inverse conversion during recording is performed and a video signal in the original frequency band is obtained at the capacitor 37, which is amplified by the amplifier 38 and output terminal 3.
It will be sent from 9.

Next, in the period TB, since φ1 and φ2 are alternately exchanged for each horizontal synchronizing signal period during recording, the relationship between φ1 and φ2 is reversed from that in the period TA.
In other words, the input video signal of the sampling circuit 35
SH is switched from φ11 to φ12, and the input of the sampling hold circuit 36 is switched from φ12 to φ11. When entering the period TB, the FF circuit 47 is triggered by the reproduction horizontal synchronization signal, and the inverted output changes from "1" to "0". Therefore, the electronic switches 43 and 44 are switched to the terminals 43b and 44b, respectively, so that the sampling circuit 35 is supplied with a sampling pulse of φ2, and the sampling circuit 36 is supplied with a sampling pulse of φ1'. The period mentioned below
The same operation as in the case of TA is repeated, and the video signal is sequentially amplified by the amplifier 38 and sent out from the output terminal 39 in the original frequency band. Thereafter, similar operations are repeated for each horizontal synchronization signal period, and a reproduced video signal having the same frequency band as that during recording is obtained.

In addition to the voltage amplification function, the amplifier 38 in FIG. 5 has an LPF function with a cutoff frequency of about 4 MHz, and this LPF function can remove sampling noise caused by sampling. There is.

In Figure 6, SL is a reset pulse created by being triggered by the vertical synchronization signal of playback, and SM
is a horizontal synchronizing signal, and SN is the output waveform of the FF circuit 47. In FIG. 6, the broken line arrow indicates that the FF circuit 47 is reset by the reset pulse SL, and the video signal φ1 sampled at φ1 during recording.
1 is sampled by φ1', and the video signal φ12 sampled by φ2 is sampled by φ2'.

Note that the present invention is not limited to the one embodiment described above, and can be implemented with various modifications as described below.

For example, in the embodiment described above, two channels of video signals obtained by time-divisionally dividing the band into two are recorded alternately and repeatedly for each horizontal synchronization signal period. It is not limited to signals. That is, the video signal to be recorded may be band-divided into signals of a plurality of channels, and these may be sequentially switched and recorded every plural horizontal synchronization signal periods.

Furthermore, in the embodiment described above, a plurality of channel signals are recorded alternately and repeatedly in each horizontal synchronizing signal period, but the video signal is divided into, for example, several parts within the horizontal synchronizing signal period, and each divided video signal is Channel signals divided into a plurality of bands may be distributed and recorded, respectively, and during playback, the plurality of divided band channel signals distributed and recorded may be edited so as to become the same signal as at the time of recording. In the editing described above, alignment with the recording order may be performed using the horizontal synchronization signal as a reference phase.

Further, in the embodiment described above, the sampling pulse for time division is generated from the horizontal synchronizing signal, but a pilot signal of a specific frequency may also be used. In this case, the pilot signal is recorded by superimposing it on the video signal or in an area where it does not interfere with the demodulated video signal in the low range of the FM frequency spectrum,
Inverse time-division conversion may be performed during playback. Note that the pilot signals to be superimposed are φ1,
If recorded in a state corresponding to the phase of φ2, it is convenient because the phase information of φ1 and φ2 can be obtained as is during reproduction.

SO in FIG. 7 is a video signal recorded in the above case, and is φ1 every horizontal synchronization signal period.
1, φ12, φ11, φ12, etc. Therefore, if the pilot signal shown in SP to be superimposed is also switched to φ1'', φ2'', φ1'', φ2'' in correspondence with the above video signal, it will be possible to inversely convert φ1'' and φ2'' during playback. sampling pulses can be easily obtained.

Furthermore, in the above embodiment, the video signal is not transmitted during playback.
Since the sum of the 1H delay and the non-delay is obtained, there is a problem that the vertical resolution on the monitor screen decreases.

FIG. 8 is a diagram showing means for improving this point. In FIG. 8, the output of the LPF 33 and the output of the 1H delay device 34 are supplied to a difference circuit 51, and a difference output between the two is obtained. As is well known, in video signals, the level difference between scanning lines determines the vertical resolution.
In the output of the difference circuit 51, a level difference in the video signal between the scanning lines occurs. Therefore, this difference output is sent to the amplifier 5.
2 and then applied to one input terminal of a mixer 53, and the reproduced video signal obtained at the output terminal 39 of the embodiment described above is applied to the other input terminal of the mixer 53. As a result, a signal obtained by amplifying the level difference signal between scanning lines is mixed with the reproduced video signal and outputted from the mixer 53, resulting in a signal with improved vertical resolution. This signal is sent out from the output terminal 54 as the final reproduced video signal. In FIG. 8, 50 indicates a circuit including the sampling circuits 35 and 36, the capacitor 37, and the amplifier 38 shown in the previous embodiment.

In addition, in the above embodiment, the sampling frequency is
254H (approximately 4MHz), but by selecting this sampling frequency as an interleaving frequency (H/2n, n = an integer other than 0), the sampling noise is interleaved on the monitor screen so that it is not visually noticeable. You can also do it. In the explanation of each of the above embodiments, only the luminance signal processing system was mentioned; however, it is only the luminance signal that substantially contributes to improving the resolution, and due to the characteristics of human vision, the processing system for the luminance signal is This is because there is no problem even if the processing system for unimportant color signals remains the same as before. In view of the above points, in the present invention, the original luminance signal is sampled by multiple systems of sampling signals having phase differences, and the resulting multiple systems of sampled signals are generated on the same time axis by focusing on the vertical correlation of the video signal. By arranging them at the top, resolution is effectively improved within a limited exclusive band (within the limits corresponding to the frequency of one sampling system), while special measures are intentionally taken for color signals. It is possible to apply the conventional signal processing system instead. That is, the technical idea of the present invention relates to a luminance signal processing system, and therefore, in the present invention, a description of the color signal processing system is intentionally omitted.

〔Effect of the invention〕

According to the present invention, resolution degradation due to band limitation is avoided by recording and reproducing recorded video signals by dividing them into bands in a time-division manner, so that when a sufficient frequency band cannot be obtained due to the conditions of the recording medium, etc. However, it is possible to provide an image recording and reproducing apparatus capable of recording and reproducing high-resolution video signals.

[Brief explanation of drawings]

Figures 1a, b, and c are diagrams for explaining conventional recording and reproducing means, Figures 2 to 6 are diagrams showing an embodiment of the present invention, and Figure 2 shows the configuration of the recording system. 3 and 4 are signal waveform diagrams for explaining the operation of the recording system in FIG. 2, FIG. 5 is a block diagram showing the configuration of the reproduction system, and FIG. 6 is a diagram of the reproduction system in FIG. 5. The signal waveform diagrams of each part for explaining the operation, FIGS. 7 and 8 are diagrams for explaining other embodiments of the present invention, respectively. 10...Input terminal, 17, 43, 44...Electronic switch, 20...Record/playback selector switch, 21
...recording/reproducing head, 22...magnetic tape, 3
9, 54...Output terminal, 51...Difference circuit, 53...
...mixer.

Claims (1)

[Scope of Claims] 1. A means for obtaining a plurality of channels of video signals by respectively sampling a video signal to be recorded on a recording medium using a plurality of types of sampling pulses having different phases; means for sequentially and selectively extracting the video signals for each horizontal synchronization signal period and recording them temporally serially on a recording medium; means for obtaining temporally parallel reproduced video signals of a plurality of channels by sequentially delaying the phase by one horizontal synchronization signal period; means for respectively sampling with a plurality of types of sampling pulses having the same phase as the sampling pulse; and means for obtaining a reproduced video signal having the same frequency band as before recording by synthesizing the reproduced video signals of the plurality of sampled channels. An image recording and reproducing device characterized by comprising: 2. The image recording and reproducing apparatus according to claim 1, wherein the sampling pulse is phase-synchronized with a horizontal synchronization signal and a vertical synchronization signal of the video signal.