JPH041422B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to data signal recording in which a data signal containing information such as date, time, location, etc. is frequency-multiplexed with respect to a video signal and recorded on a recording medium. The present invention relates to a device and a recording/reproducing device.

[Background technology and its problems]

Video tape recorders, video sheet recorders, etc. are generally known as video signal recording devices, but in particular, in the case of video signal recording devices used as electronic cameras that record still images,
It is desired to simultaneously record a data signal containing various information related to the content of the video, such as the date, time, location, name of the photographer, lens used, aperture, shutter speed, etc., at the same time as the video signal.

In this way, when multiplexing a data signal with a video signal and recording them simultaneously, it is necessary to give sufficient consideration to at least the following two points. In other words, it is necessary to eliminate the adverse effects on the image due to mutual interference between the data signal and the video signal, and to prevent the recording medium from hitting the recording head with the recording head, or under adverse conditions such as fluctuations in relative speed or the mixing of external noise. This means that data can be reproduced reliably.

Furthermore, considering the application to a small portable video signal recording device such as an electronic camera, it is important that the configuration be simple.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and can perform simultaneous recording by superimposing a data signal on a video signal with a simple configuration, has no adverse effect on images, and is reliable even under some adverse conditions. The object of the present invention is to provide a data signal recording device and a recording/reproducing device that can perform data reproduction.

[Summary of the invention]

That is, the feature of the data signal recording device according to the present invention is that in a data signal recording device that superimposes a data signal on a video signal and records it on a magnetic recording medium using a magnetic head, the data signal can be separated from the frequency component of the video signal. A signal with a constant frequency lower than the frequency of the video signal is used as a carrier wave signal of the data signal, and this carrier wave signal is phase-locked to the horizontal periodic signal of the video signal, and the carrier wave signal is adjusted according to the value of the data signal. Data modulation is performed by normal rotation or inversion of the phase of the video signal, and the modulated signal is recorded on the magnetic recording medium together with the video signal.

Further, a feature of the data signal recording and reproducing apparatus according to the present invention is that the data signal recording and reproducing apparatus records and reproduces a data signal by superimposing it on a video signal. Using a signal with a constant frequency lower than the frequency of the signal as a carrier wave signal of the data signal,
This carrier wave signal is phase-locked to the horizontal synchronizing signal of the video signal, and data modulation is performed by normal rotation or inversion of the phase of the carrier wave signal according to the value of the data signal, and the modulated signal is is recorded on the magnetic recording medium together with the video signal, and when reproducing the recorded data-superimposed video signal, the carrier frequency component of the data signal is separated and phase-locked to the horizontal synchronization signal of the reproduced video signal. A carrier wave signal having a constant frequency is formed, and the frequency-separated data signal is synchronously detected using the carrier wave signal.

〔Example〕

An embodiment in which a data signal recording device and a data signal recording/reproducing device according to the present invention are applied to an electronic camera will be described below. This electronic camera is
This is a small portable video signal magnetic recording device for color still image recording previously proposed by the present applicant, in which concentric recording tracks are sequentially formed on a rotating magnetic sheet for video signals of color images of multiple fields. It records magnetically in a way that In addition, the video signal to be recorded is, for example, a frequency division multiplexed signal of a luminance signal and a color signal, both of which are FM modulated, and the color signal is composed of two signals, an R-Y signal and a B-Y signal. The color difference signal is a line sequential signal that is alternately switched every horizontal scanning period.

FIG. 1 is a block circuit diagram for explaining an embodiment in which the data signal recording device of the present invention is applied to the above electronic camera. In FIG. 1, an input terminal 1 is supplied with a horizontal synchronizing signal component of a video signal to be recorded. The signal from the input terminal 1 is sent to a half-H killer circuit 2, where the equivalent pulse of the vertical synchronizing signal portion is removed, resulting in a horizontal synchronizing signal as shown in FIG. 2a. This horizontal synchronization signal is sent to a PLL (phase lock loop) circuit 3 to phase lock the data carrier signal.
That is, the PLL circuit 3 is provided with an oscillator that oscillates at a constant data carrier frequency signal _DC , and a phase-locked loop is configured such that the phase of this oscillation output signal is synchronized with the horizontal synchronization signal. has been done. Here, the above data carrier frequency
When _DC is an integral multiple of the horizontal scanning frequency _H , for example 13 times ( _DC = 13 _H ), the output signal from the PLL circuit 3 appears as a data carrier wave pulse signal as shown in FIG. 2b, for example. This data carrier wave pulse signal is modulated using a PSK (phase shift keying) method according to input data "1" or "0".

That is, the data carrier wave pulse signal shown in FIG. 2b from the PLL circuit 3 is sent to one selection terminal ₄₁ of the changeover switch 4, which is a phase switching means for PSK modulation, and The inverter 5 converts the signal into a pulse signal whose phase is inverted (the phase is shifted by 180 degrees) as shown in _FIG . It is being This changeover switch 4 is controlled to change according to the output data signal from the data input interface circuit 6, and for example, when the data is "0", the selection terminal ₄₁ is connected, and when the data is "1", the selection terminal ₄₂ is connected. Each is switched and connected.

The data input interface circuit 6 mainly controls data switching timing. That is, the data input terminal 7 of the data input interface circuit 6 receives data signals to be recorded superimposed on the video signal, such as shooting date data, time data, shooting location data, and photographer name data. A digital data signal containing mechanical data such as lens, aperture, shutter speed, etc. is supplied.
The "0" bit switching timing is determined, for example, according to the horizontal synchronizing signal from the half-H killer circuit 2, and the bit switching period T _B is an integral multiple of one horizontal scanning period (1H time) (T _B = nH). It is set so that it becomes the output data signal. For example, in the example shown in Figure 2, the bit switching of the output data signal is performed at time _tS , and this time
The data changes to "0" before t _S , and changes to "1" after t _S. The bit switching period (or bit interval) T _B may be determined by taking into consideration the total number of bits of data to be recorded for one field of video signal. For example, if it is set to four times the horizontal scanning period (T _B = 4H), one field is 262.5H, so theoretically it is possible to record up to 65 bits of data, but in reality, it is possible to record up to 65 bits of data. Approximately 50 bits of data can be recorded with some margin.

Also, a series of (for example, 50
When data bit groups (of the order of bits) are arranged, for example, a vertical synchronization signal of the video signal to be recorded is used to determine the timing of the start and end of the data bit groups in one field. That is, the vertical synchronization signal of the video signal supplied through the input terminal 8 is sent to the data input interface circuit 6, and the recording start timing of the series of data bit groups is determined based on this vertical synchronization signal.

Next, as shown in FIG. 2d from the changeover switch 4,
The PSK modulated data pulse signal is a rectangular wave and contains many harmonic components, which may have an adverse effect on the video signal frequency band during _frequency division multiplexing. is extracted to obtain a substantially sinusoidal PSK modulated data signal as shown in FIG. 2e. This data signal is sent to the adder 10, where it is added and mixed with the FM-modulated luminance signal FM-Y from the input terminal 11 and the FM-modulated color signal FM-C from the input terminal 12. The signal is taken out from the recording signal output terminal 14 via 13. The recording signal from this output terminal 14 has a frequency spectrum as shown in FIG. 3, for example.
From the low frequency side to the high frequency side, the data signal PSK-D, the color signal FM-C, and the luminance signal FM-Y.
They are arranged in this order. If the above data carrier frequency _DC is selected as _13H , _DC ≒204K
Hz, and the data signal PSK-D is located at the bottom of the low frequency side of the frequency spectrum curve of the color signal FM-C.
are arranged, and mutual interference is extremely reduced.

Further, by setting the level of the data signal PSK-D to be sufficiently lower than the carrier wave signal level of the luminance signal FM-Y, for example, about 35 dB, the adverse effect of the data signal on the video signal can be extremely reduced.

Next, an example of a device for reproducing data from a data superimposed video signal recorded by the data signal recording device as described above will be described with reference to FIG.

In FIG. 4, the horizontal synchronizing signal component of the reproduced video signal is supplied to the input terminal 21.
The half-H killer circuit 22 removes the equivalent pulse of the vertical synchronizing signal portion to obtain a horizontal synchronizing signal as shown in FIG. 5a. This horizontal synchronization signal
By sending it to the PLL circuit 23, the data carrier pulse signal shown in FIG. 5b is obtained which is phase-locked to the horizontal synchronizing signal at frequency _DC as described above. Only the above-mentioned _DC component of this data carrier wave pulse signal is extracted by a low-pass filter 24 and further phase-corrected by a phase shifter 25, as shown in FIG.
Obtain a sinusoidal data carrier signal as shown in
This signal is sent to the multiplier 26.

On the other hand, the input terminal 27 is supplied with a data-superimposed video signal reproduced by a reproduction magnetic head or the like. This reproduced signal is passed through a bandpass filter 28
by sending the data signal PSK-D to
Only the components are extracted and amplified by an amplifier 29 to obtain a reproduced data signal as shown in FIG. 5d. By sending this reproduced data signal to the multiplier 26 and multiplying it by the data carrier signal, so-called synchronous detection is performed. Here, the phase shifter 25
This is to compensate for the phase shift caused by each signal passing through the low-pass filter 24, band-pass filter 28, etc., and to accurately match the reference phase of each input signal to the multiplier 26.

In the example of FIG. 5, the reproduced data signal of d is at time t _S
Before that, it appears in phase with the data carrier signal c and indicates "0", and after time t _S it appears in phase opposite to the data carrier signal and indicates "1". These signals in Fig. 5c and d are sent to multiplier 2
By multiplying by 6, the multiplication output appears on the substantially positive side before time _tS , and appears on the substantially negative side after time _tS .

For example, if the data is “0”, “1”, “0”, “1”
,
..., the multiplication output (synchronous detection output) from the multiplier 26 appears as shown in FIG. 6e. The bit switching period (bit interval) T _B at this time is equal to the above T _B during recording,
For example, it is four times the horizontal scanning period (T _B =4H). The synchronous detection output of FIG.
By integrating the signals, an integral output as shown in FIG. 6f is obtained. The integrating circuit 30 has an internal capacitor, and performs an integrating operation by controlling charging of this internal capacitor according to an input signal (signal shown in FIG. 6 e). The zero level reset is performed in response to a discharge control pulse as shown in FIG. 6h. That is, when the signal in Figure 6e appears on the positive side, the internal capacitor is charged with a forward current to obtain an integral output that increases on the positive side, and the signal in Figure 6e appears on the negative side. Sometimes, charging is performed with a reverse current to obtain an integrated output that increases in the negative direction, that is, the level decreases. At the same time, when the discharge control pulse is input, both ends of the capacitor are short-circuited and grounded to reset the integral output to zero level.

The timing generation circuit 31 receives a horizontal synchronization signal from the half-H killer circuit 22 (see FIG. 5a),
and a vertical synchronizing signal in the reproduced video signal from the input terminal 32. According to these signals, phase synchronization is performed with the horizontal synchronizing signal, and the discharge shown in FIG. A control pulse and a latch pulse (or strobe pulse or sampling pulse) as shown in FIG. 6i, which will be described later, are output.

Next, the integrated output from the integrating circuit 30 as shown in FIG. As a result, a binary comparison output as shown in FIG. 6g is obtained. Immediately after the bit switching timing, this comparison output is unstable due to chattering because the integrated output is near zero level. Therefore, the comparison output is sent to the latch circuit 34, and when the comparison output becomes sufficiently stable after a certain delay time τ _D has elapsed from the bit switching timing, the comparison output is set by a latch pulse as shown in FIG. 6i. I try to latch it. It is preferable that the delay time _.tau.D is set to a value shorter than the bit switching period _T.sub.B but close to the bit switching period _T.sub.B so that the latching operation is performed immediately before the bit switching period. The latch pulse shown in FIG. 6i is obtained from the timing generation circuit 31 mentioned above.

The output from the latch circuit 34 becomes stable binary data without chattering, as shown in FIG. 6j, and is kept within the above delay time with respect to the reproduced data (for example, the data in the synchronously detected output in FIG. 6e). It appears with a delay of τ _D.

According to one embodiment of the data signal recording method and recording/reproducing method according to the present invention described above, since the PSK (phase shift keying) method is adopted for data modulation, it is resistant to disturbance noise, level fluctuations, etc. Data can be recorded and played back reliably.
In other words, in the case of other modulation methods, such as the on-off keying method, data "1" or "0" is expressed depending on the presence or absence of a carrier signal, so if disturbance noise is mixed in an area where there is no signal, Also, during playback, the levels are generally compared after envelope detection of the modulated data. If the playback level itself changes due to a difference in tangential speed with the outer circumference, the overall level of the envelope waveform will change, so it is difficult to set the reference level (threshold) for the above level comparison, and this reference level If it is set too high, carrier wave detection cannot be performed when the playback level drops, and if it is set too low, malfunctions are likely to occur due to noise. Also,
In the case of FSK (Frequency Shift Keying), carrier waves with two different frequencies are required, so the circuit configuration on the recording side and playback side becomes more complex, and the frequency band of the modulated data signal also increases compared to the PSK method. Since the data spreads out, mutual interference is more likely to occur, and the accuracy of data reproduction is also inferior to the PSK method. On the other hand, in the PSK method,
Since a single frequency carrier wave is used, the above
The circuit configuration is simpler than the FSK method, and
By performing synchronous detection during playback, the detection output appears on the positive and negative sides based on the zero level (as a threshold), so it is resistant to disturbance noise as well as fluctuations in the playback level itself, allowing accurate data playback. .

In addition, in the above embodiment, the frequency _DC of the data carrier wave is 13 times the horizontal scanning frequency _H ( _DC = 13 _H ).
By selecting _DC ≒204KHz, the third
As is clear from the frequency allocation in the figure, the color signal FM− of the simultaneously recorded video signal is
The data signal PSK-D is modulated at a frequency position where it has less influence on C and the luminance signal FM-Y. Furthermore, this data signal PSK-D
The recording level is set sufficiently low (for example, -35 dB) with respect to the carrier wave of the luminance signal FM-Y.
Therefore, even if a data signal is superimposed on a video signal by frequency division multiplexing, mutual interference with the video signal is extremely reduced, and adverse effects on images and deterioration of image quality can be prevented. In addition, in the frequency spectrum of Fig. 3, the color signal FM-C and the luminance signal
The above data signal PSK-D is in the valley between FM-Y.
In this case, _{the CD} is about 2.5M.
Hz, and to synchronize with a horizontal synchronization signal, _CD = 159 _H , for example.

Furthermore, since the bit switching period T _B of the data is set to an integral multiple of the horizontal scanning period, detection of the bit switching timing can be easily performed with a simple circuit configuration based on the horizontal synchronizing signal. For example, if T _B is set to approximately 4H, the required number of bits per field (approximately 50 bits) can be read and recorded and reproduced without errors. This bit switching period T _B can be arbitrarily set in addition to the above. and,
The longer the bit switching period T _B is, the lower the probability of an error will be, but with the method of the present invention, which has excellent basic performance, sufficiently accurate data recording and reproduction can be achieved even if the bit switching period T _B is shortened. As a result, many bits can be superimposed on the video signal and recorded.

Furthermore, a PLL circuit is used to synchronize the phase of the data carrier signal with the horizontal synchronization signal, making it possible to achieve highly accurate phase synchronization with a simple circuit. In addition to using a PLL circuit, for example, when the data carrier frequency _DC is an integral multiple of the horizontal scanning frequency _H , a frequency signal higher than the above _DC is obtained from an oscillator, and this high frequency signal is counted down. Alternatively, the data path transmission signal may be generated using a horizontal synchronization signal, and the counter may be reset using a horizontal synchronization signal.

Furthermore, on the reproduction side of the above embodiment,
The so-called matched filter configuration, which integrates the output from the synchronous detection means using a multiplier, guarantees optimality in terms of error probability and ensures reliable data reading. Furthermore, after the integrated output is level-compared and converted into a binary signal, the latch circuit latches the level-compared output when it becomes sufficiently stable, making data reading more accurate.

In the above embodiment, an example in which the present invention is applied to an electronic camera for recording color still images has been described, but the present invention may not be applied to various other video signal recording devices, video signal reproducing devices, etc. It's easy.

〔Effect of the invention〕

According to the data signal recording device and the recording/reproducing device according to the present invention, since a data carrier wave signal having a single constant frequency that can be separated from the frequency components of a video signal recorded at the same time is used, the data signal can be added to the video signal. Even when multiplexed, mutual interference between these signals is extremely low, and adverse effects on images and deterioration of image quality can be effectively prevented. Furthermore, as a method for modulating the data carrier signal according to the data, a data modulation method such as the PSK method that changes the phase of the data carrier signal according to the data is used, so that binary discrimination of the data is possible. The standard level (threshold) of the system can be set to an unchanging value such as the zero level, which is superior to other methods in terms of the probability of error, and even when the recording level or playback level is low. Even if level fluctuations occur due to uneven head contact, etc., data can be read reliably. Furthermore, since the phase of the data carrier signal is locked by the horizontal synchronization signal of the video signal, the reference phase of the data carrier signal can be determined with a simple circuit configuration.

Next, since the data bit switching period is an integral multiple of the period of the horizontal synchronization signal (horizontal scanning period), each timing signal for bit detection can be easily obtained based on the horizontal synchronization signal, and the circuit configuration Easy and accurate data reading.

Furthermore, when reproducing data signals, the data signal separated from the reproduced video signal is synchronously detected using the data carrier signal, so the data "0",
The detection output appears, for example, on the positive side and the negative side depending on the “1”, and not only is the data reproduced clearly, but the threshold (reference level) for determining “0” and “1” is set to an unchanging zero level. Therefore, even if the recording level or reproduction level fluctuates, the occurrence of reading errors can be kept to an extremely low level, and data can be reproduced reliably.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram showing an example of a circuit on the data signal recording side according to an embodiment of the present invention, and FIG. 2 is a time chart for explaining the operation of the circuit in FIG.
FIG. 3 is a graph showing the frequency spectrum of a data superimposed video signal to be recorded and played back, FIG. 4 is a block circuit diagram showing an example of the circuit on the data signal playback side of the above embodiment, and FIGS. This is a time chart for explaining the operation of the circuit shown in the figure. 3, 23...PLL circuit, 4...PSK modulation switch, 6...data input interface, 9, 28...bandpass filter, 10...
Adder, 24... Low pass filter, 26... Multiplier for synchronous detection, 30... Integrating circuit, 31...
Timing generation circuit, 33...Level comparator, 3
4...Latch circuit.

Claims (1)

[Scope of Claims] 1. In a data signal recording device that superimposes a data signal on a video signal and records it on a magnetic recording medium using a magnetic head, the data signal can be separated from the frequency component of the video signal and is higher than the frequency of the video signal. A signal with a low constant frequency is used as a carrier wave signal of the data signal, and this carrier wave signal is phase-locked to the horizontal frequency signal of the video signal, and the phase of the carrier wave signal is rotated forward or backward depending on the value of the data signal. 1. A data signal recording device, characterized in that data is modulated by inversion, and the modulated signal is recorded on the magnetic recording medium together with the video signal. 2. In a data signal recording and reproducing device that records and reproduces a data signal by superimposing it on a video signal, at the time of recording, a signal of a constant frequency that is separable from the frequency component of the video signal and that is lower than the frequency of the video signal is used as the data signal. data modulation is performed by locking the phase of this carrier signal to the horizontal synchronizing signal of the video signal and rotating or inverting the phase of the carrier signal according to the value of the data signal. , recording the modulated signal on the magnetic recording medium together with the video signal, and when reproducing the recorded data superimposed video signal,
Separating the carrier wave frequency components of the data signal, forming a carrier wave signal of the constant frequency that is phase-locked to the horizontal synchronizing signal of the reproduced video signal, and synchronously detecting the frequency-separated data signal using the carrier wave signal. A data signal recording and reproducing device characterized in that: