JPS6248958B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a video tape recorder (VTR).
The present invention relates to a video signal generator suitable for a test signal generator used to tune the receiving frequency of a television receiver (TV) to the output frequency of an RF modulator.

The RF modulator built into the VTR is
The received signal or reproduced signal is converted into a TV radio wave form and sent to the TV, and the output frequency is fixed at a constant frequency or set at a constant frequency of several channels. Therefore, the TV connected to the VTR
If you want to receive TV broadcasts on , the channel selection operation is
This is done by the VTR's tuner, while TV tuners require tuning the receiving frequency to the output frequency of the VTR's RF modulator in order to obtain accurate images.

Generally, when the RF modulator is configured for receiving UHF band television broadcasts, and the TV tuner includes an auto-tuning mechanism that allows tuning by push-button operation,
In synchronization between VTR and TV, a video signal generator is essential in order to provide test signals from the VTR to the TV.

Figure 1 shows a built-in conventional video signal generator.
The configuration of VTR and TV is shown. In the figure, when receiving television broadcasts on a TV 4 to which a VTR 2 is connected, an antenna 6 is connected to an antenna terminal 8 of the VTR 2. The received signal input to the antenna terminal 8 is tuned by a tuner 10, and the output of this tuner 10 is sent to a video signal processing system 12 and an audio signal processing system 14.
After being separated and subjected to signal processing, it is applied to the RF modulator 18 via the switch circuit 16.

Further, a video signal as a test signal generated by a video signal generator 20 separately from these signal processing systems 12 and 14 is given to an RF modulator 18 via a switch circuit 16. The switch circuit 16 connects the outputs of the signal processing systems 12 and 14,
The output of the video signal generator 20 is configured to be alternatively selected by an external operation and input to the RF modulator 18. That is, the switch circuit 16
is switched to the video signal generator 20 side during a tuning operation. Then, the output of the RF modulator 18 is taken out in the form of TV radio waves from the output terminal 22 and given to the antenna input terminal 24 of the TV 4.
The output of the RF modulator 18 passes through a tuner 26 and undergoes signal processing in a video signal processing system 28 and an audio signal processing system 30, and the video output is sent to a cathode ray tube 32.
Also, the audio output is provided to the speakers 34, respectively.

In such a configuration, the VTR-TV tuning operation is performed by switching the switch circuit 16 to the video signal generator 2.
By switching to the 0 side, the output video signal of the video signal generator 20 is applied to the RF modulator 18. FIG. 2 shows the waveform of the video signal applied to the RF modulator 18 in this case, where S _H is the horizontal synchronizing signal, S _W is the white signal, S _B is the black signal, V _S is the sync chip level, and V _R indicates the black signal level, V _W indicates the white signal level, T _H indicates the horizontal synchronization time, and the VS ratio is set to 7:3. RF modulator 18 obtained based on this video signal
The output is applied to the tuner 26 of the TV 4, and by operating the tuner 26 to select a channel, a black and white test image in the form of vertical stripes can be displayed on the cathode ray tube 32. In this case, synchronization between the VTR and the TV can be achieved by accurately operating the tuner 26 to clearly display the boundary line L of the black and white test image.

In such a tuning operation, if the tuner 26 of the TV 4 is configured to include an auto-tuning mechanism that allows tuning by operating the push button 36, and the tuning operation is performed with or without a vertical synchronization signal, the vertical synchronization signal is not used. If the video signal does not contain this, it will be impossible to select the station, and you will not be able to tune in.

Also, if you perform tuning operation using only the video signal,
Because the video signal has a wide band, the test image will be displayed even if accurate synchronization is not achieved.
If the tuning condition is insufficient, the audio signal may not be obtained. To obtain highly accurate tuning, it is necessary to find the optimal tuning point for both the image and the audio.

Therefore, the present invention generates an audio signal at the same time as a video signal including a vertical synchronization signal, enables tuning operation with a TV that performs tuning operation depending on the presence or absence of a vertical synchronization signal, and enables both image and audio to be tuned. It is an object of the present invention to provide a video signal generator that achieves an optimal tuning state.

The video signal generation device of the present invention includes an oscillator that generates a reference signal, and a vertical synchronization signal, a horizontal synchronization signal, and the generation timing and signal width of a video signal representing white or black based on the reference signal generated by the oscillator. a timing circuit that generates a timing pulse to be set; a waveform conversion circuit that converts the timing pulse generated by the timing circuit into a signal waveform representing a white or black video signal together with a vertical synchronization signal and a horizontal synchronization signal; An object of the present invention is to provide a video signal generation device including an audio signal generation circuit that frequency-divides and smoothes a reference signal obtained by generating an audio signal to form an audio signal.

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

FIG. 3 shows an embodiment of the video signal generator of the present invention. In the figure, the video signal generator of this embodiment includes a reference oscillator 4 that generates a reference signal.
0, a timing circuit 42 that forms a timing pulse that sets the generation timing and signal width of a white or black video signal together with a vertical synchronization signal and a horizontal synchronization signal based on a reference signal; A waveform conversion circuit 4 that converts a signal waveform representing a white or black video signal together with a vertical synchronization signal and a horizontal synchronization signal in accordance with the width.
4, and an audio signal generation circuit 46 that frequency-divides and smoothes a reference signal to form an audio signal. The reference oscillator 40 is a capacitor 4
A ceramic oscillator 52 connected to the outside together with 8 and 50 is used as an oscillation element, and a stable clock pulse is generated as a reference signal. The timing circuit 42 to which this pulse is given as a timing signal has 1/2 frequency dividers 54, 56, 58, 6.
0, counters 62, 64, 66, count select circuit 68, OR circuit 70 and inverter 72,
It consists of 74 and 76. That is, the timing pulse that sets the generation timing and signal width of the vertical synchronization signal is generated by the 1/2 frequency dividers 54, 56, 58, and 6.
0 and counters 62 and 64, while a timing pulse that sets the generation timing of the horizontal synchronization signal and its signal width is formed by a 1/2 frequency divider 54 and a counter 66. Furthermore, a timing pulse for setting the generation timing and signal width of the white and black video signals is formed by a counter 66 and a count select circuit 68. The count select circuit 68
It is composed of AND circuits 78, 80, 82 and OR circuit 84, and is composed of 1, 2, 4 given by counter 66.
and 8 counting inputs, a timing pulse is formed within the horizontal synchronization signal time that combines these inputs and converts them into white and black video signals.

The waveform conversion circuit 44 to which the timing pulse is given as a waveform conversion input includes transistors 86 and 8.
8, 90, resistors 92, 94, 96, and power supplies 98, 100, 102 for level setting. A power supply 98 sets a white signal level V _W , a power supply 100 sets a sync chip level V _S , and a power supply 102 sets a black signal level V _B . Each transistor 86,8
A voltage V _CC is applied from the power supply terminal 104 to the collectors of the transistors 86 and 8, and each transistor 86 and 8
The video signal output from emitters 8 and 90 by waveform conversion is taken out from an output terminal 108 via a buffer amplifier 106.

The audio signal generation circuit 46 also includes a 1/2 frequency divider 110, a buffer amplifier 112, and a smoothing circuit 11.
4, and the smoothing circuit 114 is composed of a resistor 116 and a capacitor 118. That is, an audio signal formed by dividing and smoothing the output of the counter 62 is taken out from the output terminal 120.

In the above configuration, the formation of video signal waveforms will be explained with reference to the waveforms shown at A to J in FIG. 4.

In FIG. 4, A indicates the output clock pulse of the reference oscillator 40, and B indicates the clock pulse output from the reference oscillator 40.
A pulse obtained by dividing the frequency by 1/2 by the 1/2 frequency divider 54 is shown. This pulse is counted by a counter 66, and C indicates a timing pulse provided by a hexadecimal count output, which timing pulse provides the timing of occurrence of the horizontal synchronization signal and its signal width. Here, the period of the Kutsuroku pulse is t ₀
(μ sec), the period of the pulse shown in B is
2t ₀ (μ sec), the period of the timing pulse shown in C is 2t ₀ × 16 (32t ₀ ) (μ sec), and its pulse width is
It is given in 2t ₀ (μ sec). Further, D indicates a timing pulse formed by the count select circuit 68 based on the 1, 2, 4, and octal count outputs of the counter 66, and this timing pulse determines the generation timing of the white signal and its signal width. It will be done. That is, the white signal is formed during the horizontal synchronizing signal time T _H and has a signal width of 2t ₀ (μ sec). In addition, since white and black images are given relatively by the difference in brightness, the white signal and black signal are set by the level difference, so the time when the timing pulse of the white signal is not present becomes the black signal. .

Further, E is a pulse obtained by sequentially dividing the output pulse of the 1/2 frequency divider 54 by the 1/2 frequency dividers 56, 58, and 60, and F is obtained by counting this pulse with the counter 62. 39-decimal count output, and G is counter 6
It shows the timing pulse given by the hex count output of 4. This timing pulse gives the generation timing of the vertical synchronization signal and its signal width. Here, since the period of the pulse shown at E in FIG. 4 is given by 16t ₀ (μ sec), the pulse width of the pulse shown at F is 624t ₀ (μ sec), and the period of the timing pulse shown at G is given by: 624t ₀ ×16(μ
sec).

The thus formed timing pulses shown in C and G in FIG.
After being converted into a timing pulse of the form shown in
It is inverted by an inverter 72 and applied to the base of a transistor 90. On the other hand, the timing pulse generated by the count select circuit 68 is applied to the base of the transistor 86 in the form shown by I in contrast to the timing pulse shown by H. That is, the transistors 86 and 90 are switched between on and off states depending on the level of the timing pulse, and the transistor 88 is always on. Therefore,
During the period when transistors 86 and 90 are both off, a horizontal synchronization signal and a vertical synchronization signal are formed, the level V _S of which is provided by power supply 100 by the on state of transistor 88 .

The black signal is applied to the transistor 9 by inverting the timing pulse shown at H in FIG.
0 is in the on state, that is, the transistor 86
is formed during the time that V B is placed in the off state, and its level V _B is provided by power supply 102 .

Further, the white signal is formed at the time when the transistor 86 is turned off by the timing pulse shown in _FIG . As a result, the video signal shown in FIG. 4J is output from the output terminal 108 via the buffer amplifier 106.

The audio signal is given as an AC signal obtained by frequency-dividing a pulse having a pulse width shown in F using a 1/2 frequency divider 110 and smoothing it using a smoothing circuit 114. In this embodiment, a 400 Hz audio signal can be taken out from the output terminal 120.

In this way, the audio signal can be obtained simultaneously with the video signal, so by tuning the TV's receiving frequency to the VTR's output frequency, it is possible to perform highly accurate tuning operations based on the images and audio, making the tuning operation easier. At the same time, the optimum tuning point can be easily found, and inconveniences such as not being able to obtain an audio signal due to tuning deviation can be prevented.

Furthermore, since the vertical synchronization signal is included in the video signal, highly accurate tuning operations can be easily performed even in TVs that include tuners that perform automatic tuning operations depending on the presence or absence of the vertical synchronization signal.

Note that the video signal generator of the embodiment is a VTR.
Although a case has been described in which the test signal device is installed inside a VTR, the present invention can be configured as an independent test signal device that is externally connected to the VTR, and is not limited to a built-in device.

As explained above, according to the present invention, since a video signal including a vertical synchronization signal is generated,
It is possible to perform tuning operations with extremely high precision on TVs that use the presence or absence of a vertical synchronization signal to select channels, and by generating an audio signal at the same time as a video signal, it is possible to perform tuning operations for both images and audio. The optimum tuning point can be easily found.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the VTR-TV tuning mechanism, Figure 2 is a waveform diagram showing the video signal, and Figure 3 is a block diagram showing the VTR-TV tuning mechanism.
FIG. 4 is a block diagram showing an embodiment of the video signal generating device of the present invention, and FIG. 4 is a diagram showing operating waveforms of various parts of the video signal generating device shown in FIG. 3. 40... Reference oscillator, 42... Timing circuit, 44... Waveform conversion circuit, 46... Audio signal generation circuit.

Claims (1)

[Claims] 1. An oscillator that generates a reference signal and, based on the reference signal generated by this oscillator, the timing that generates a timing pulse that sets the generation timing and signal width of a video signal representing white or black as well as a vertical synchronization signal and a horizontal synchronization signal. a waveform conversion circuit that converts the timing pulse generated by the timing circuit into a signal waveform representing a white or black video signal together with a vertical synchronization signal and a horizontal synchronization signal;
and an audio signal generation circuit that frequency-divides and smoothes a reference signal generated by the oscillator to form an audio signal.