JPS6160638B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ghost delay time measuring device, and an object thereof is to measure the delay time of a ghost signal included in a television signal.

A ghost delay time measuring device according to an embodiment of the present invention will be described with reference to FIGS. 1 to 4.

FIG. 1 shows a block diagram of this ghost delay time measuring device, and FIG. 2 shows an explanatory diagram of its operation. In these figures, the television composite video signal applied to input terminal 1 (Figure 2 a, b)
One of them is applied to the vertical synchronization signal extraction/differentiation circuit 2. This vertical synchronization signal extraction/differentiation circuit 2 is
After extracting the first vertical synchronizing signal (Fig. 2 d) containing ghosts by adding an extraction pulse (Fig. 2 c) to be described later, it is differentiated to obtain a differential pulse as shown in Fig. 2 e. Output. Further, the other of the television composite video signals (FIG. 2 a, b) is applied to the synchronization separation circuit 3. This sync separation circuit 3 generates horizontal H and vertical V sync separation signals, and applies the sync separation signals to a counter 4. This counter 4 generates a signal to set the extraction pulse generation circuit 5 every time it counts 525 horizontal synchronization pulses, and the start of counting is synchronized with the rise of the vertical synchronization pulse of the synchronization separation circuit 3. The extraction pulse generation circuit 5 is composed of a monostable multivibrator, and the oscillation pulse width is set to 30 μsec. Furthermore, the set pulse of the counter 4 is set so that this extraction pulse can extract the first vertical synchronizing pulse at the timing shown in FIG. It is set.

Now, by adding the output of the vertical synchronization signal extraction/differentiation circuit 2 to the flip-flop circuit (pulse generation circuit) 6, and setting the flip-flop circuit 6 with the first differential pulse and resetting it with the next differential pulse, the flip-flop circuit 6 is set. outputs a square pulse as shown in FIG. 2f. When this square pulse is applied to the constant current source discharge circuit 7,
A waveform as shown in FIG. 2g is obtained as an output. The ghost delay time is detected from the output of the constant current source discharge circuit 7 and displayed on the display section 8.

Next, the configuration and operation of the constant current source discharge circuit 7 will be explained with reference to FIGS. 3 and 4. Now, when the square pulse shown in FIG. 4B is applied to the transistor _Q1 , it is inverted and amplified by the transistor _Q1 and transmitted from the collector to the base of the transistor _Q2 via the resistor _R1 . A resistor _R2 is connected to a DC power supply _VB , and a voltage is applied to the collector of the transistor _Q1 via the resistor _R1 , and a voltage is applied to the base of the transistor _Q2 . When a negative polarity pulse is applied to the base of transistor Q ₂ , transistor Q ₂ becomes conductive, and charge is instantly accumulated in capacitor C from the emitter connected to DC power supply V _B , and the base becomes negative polarity. During the pulse period, the collector of transistor _Q2 is held at the potential of DC power supply _VB . Next, at the end of the pulse period, the base of transistor Q ₂ suddenly becomes positive, transistor Q ₂ is cut off, and the charge stored in capacitor C is linearly discharged through constant current source I until it reaches ground potential. The potential of the collector of transistor _Q2 decreases along the broken line y in FIG. 4A, reaches 1/2 in 30 μsec and reaches the ground potential in 45 μsec. By similar operation, when the square pulse shown in Fig. 4C is applied, the solid line x in Fig. 4A is
It decreases to 1/2 in 45μsec and reaches the ground potential in 60μsec. Further, when a pulse with an extremely narrow pulse width is applied, the pulse width decreases along the dashed line z in FIG. 4A, reaches 1/2 in 15 μsec and reaches the ground potential in 30 μsec. If we consider this kind of voltage change by fixing the point U at 30μsec from the rise of the pulse, we get
Depending on the input pulse width, that is, the ghost delay time, a large voltage appears when the delay time is long, and a small voltage appears when the delay time is short. The ghost delay time is measured by sampling and holding the voltage at point U, 30 seconds after the rise of this pulse, and displaying it as a DC voltage on the display section 8.

In this way, the capacitor C is kept fully charged during the period when a square pulse is generated from the flip-flop circuit 6, and the capacitor C is discharged at a constant current from the time when the square pulse disappears, and the capacitor C is charged at a predetermined time after the rise of the square pulse. Since the voltage of C is detected as the voltage corresponding to the ghost delay time,
Ghost delay time can be measured accurately using analog technology.

As described above, the ghost delay time measuring device of the present invention includes a vertical synchronizing pulse extraction means for extracting a vertical synchronizing pulse from a television signal including a main signal and a ghost signal, and a differentiated pulse signal by differentiating this vertical synchronizing pulse. a differentiating circuit that outputs a differential pulse; a pulse generating circuit that generates a pulse having a pulse width from the first differential pulse to the second differential pulse of the differential pulse signal; A capacitor that is held in a charged state, a constant current source for discharging the accumulated charge of this capacitor, and a voltage across the capacitor that is detected after a predetermined time from the rise of a pulse generated from the pulse generating circuit. Since the present invention is equipped with a display section for displaying images, it has the advantage that the ghost delay time can be measured accurately using analog technology.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is an explanatory diagram of its operation, Fig. 3 is a circuit diagram of the main part of the ghost delay time measuring device of Fig. 1, and Fig. 4 is an explanatory diagram of its operation. It is. 2... Vertical synchronization signal extraction/differentiation circuit, 3... Synchronization separation circuit, 4... Counter, 5... Extraction pulse generation circuit, 6... Flip-flop circuit, 7... Constant current source discharge circuit, 8... Display section, Q ₁ , Q ₂ ... transistor, R ₁ , R ₂ ... resistor, C ... capacitor, I ... constant current source, V _B ... DC power supply.

Claims (1)

[Claims] 1. A vertical synchronizing pulse extraction means for extracting a vertical synchronizing pulse from a television signal including a main signal and a ghost signal, a differentiating circuit for differentiating this vertical synchronizing pulse and outputting a differential pulse signal, and a first differential pulse signal of the differential pulse signal. A pulse generation circuit that generates a pulse having a pulse width from the second differential pulse to the second differential pulse, a capacitor that is kept fully charged during the pulse generation period of this pulse generation circuit, and an accumulated charge of this capacitor. A ghost delay time measuring device comprising: a constant current source for discharging the pulse; and a display section that detects and displays the voltage across the capacitor after a predetermined time from the rise of the pulse generated from the pulse generating circuit.