JPH0374994A - Measuring signal generator - Google Patents

Abstract

PURPOSE:To easily and accurately measure a delay time difference between a luminance signal and a chrominance signal by superimposing a chrominance signal comprising a complementary color pair onto an original signal for a 1st horizontal period and superimposing a luminance signal whose level is in matching with that of the chrominance signal and whose average luminance level is equal to that of the chrominance signal at each prescribed position for 2nd and 3rd horizontal periods so as to form a measuring signal. CONSTITUTION:A chrominance 19A signal comprising a pair of complementary colors 20, 21 is superimposed onto an original signal for a 1st horizontal period and a luminance signal 28A whose level is in matching with that of the chrominance signal and whose average luminance level is equal to that of the chrominance signal 19A at each prescribed position for 2nd and 3rd horizontal periods so as to form a measuring signal. As a result, the fluctuation of a trigger level between the luminance signal and the chrominance signal is suppressed and the measuring reference point of the luminance signal is easily specified as a cross point of the luminance signal for the 2nd and 3rd horizontal periods. Thus, the difference of the delay time between the luminance signal and the chrominance Signal is easily and accurately measured.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is used, for example, to quantitatively measure the difference in delay time between a luminance signal and a color signal during recording and playback of a video tape recorder (VTR). The present invention relates to a suitable measurement signal generator.

[Summary of the invention]

The present invention provides a measurement signal generator that generates a measurement signal for measuring the difference between the delay time of a luminance signal and the delay time of a sudden signal during recording and reproduction of a VTR, for example, in which a complementary color is applied to the first horizontal period. The measurement signal is formed by superimposing a pair of color signals and superimposing a luminance signal whose levels match each other and whose average luminance level is equal to that of the color signal at a predetermined position in each of the second and third horizontal periods. By doing so, it is possible to suppress fluctuations in the meter trigger level between the luminance signal and the chrominance signal, and to make it possible to accurately read the cross points where the luminance signal levels match each other. The delay time difference can be easily and accurately measured.

[Conventional technology]

Since the bandwidth of the luminance signal and the bandwidth of the chrominance signal are different, V
In a transmission system such as a TR, a difference in delay time occurs between a luminance signal and a color signal, and if no correction is performed, there is a risk that the luminance and color of a reproduced image will deviate. In particular, in VTRs, the color signal is separated from the luminance signal, converted to low frequencies, and recorded on videotape, so it is necessary to correct the difference in delay time. A measurement system for quantitative measurement is required.

Figure 4 shows a conventional measurement system for measuring the delay time difference (Y/C delay amount) between the luminance signal and color signal. This measurement signal generator (1) is a central processing unit (CPU) (2) that generates a measurement signal as a video signal corresponding to an image of a predetermined pattern as a digital signal train.
, R A M (3
), a clock pulse generator (4) that supplies clock pulses (CP) for reading data to this RAM (3).
and its RAM (3), which converts the digital measurement signal read out into an analog measurement signal R5.
Consists of an analog converter (5). The measurement signal R
3 is supplied to the recording signal input terminal of the VTR under test (6), and the measurement signal PS recorded and reproduced by this VTR under test (6) is supplied to the measurement signal input terminal of the oscilloscope (7) and the monitor [8 ) is supplied to the video signal input terminal. Therefore, the waveform of the measurement signal PS after recording and reproduction is displayed on the display screen of the oscilloscope (7), and a color image corresponding to the measurement signal PS is displayed on the screen of the monitor (8).

Measurement signal R3 output from the measurement signal generator (1)
During the 1-field period, the horizontal scanning signal (FIG. 5A) corresponding to the color signal and the horizontal scanning signal (FIG. 5B) corresponding to the luminance signal are boosted to the same extent.

In one horizontal period corresponding to the color signals shown in FIG. 5, following the horizontal periodic pulse (9) and color burst (10), the green signal (11) and The magenta signal (12) is alternately divided into four pairs at a constant period. Those green lights (11
〉 and magenta signal (12) are between the pedestal level and the DC level, and the amplitude is 2L2. For example, L, = 501RE, L2 = 401R.
It is set to E.

In addition, in one horizontal period corresponding to the luminance signal in FIG.
) followed by seven triangular wave-shaped pulses with a pulse width ΔT (hereinafter referred to as "2T pulses". > (13^) to (13
G) is formed. This pulse width ΔT is 5QQn
sec, and these seven 2T pulses (13^〉~
The peaks of (13G) are ' 3r ' 2+ ' l+ with respect to the phase change point of the color signal (Fig. 5A), respectively.
0+rIn τ2+τ3. For example, τ1=5Qnsec, r2=loon
sec, rs=150 nec, and the height L3 of the peaks of these 2T pulses (13^) to (13G) from the black level is set to, for example, 301 RE.

The measurement signal R3 shown in Fig. 5 A and B is the test signal V T
Manually input R(6) and monitor the regenerated measurement signal PS (
8), the screen of this monitor (8) shows a green area (14) in the upper half area (14), as shown in Figure 6.
5) and magenta portion (16) are displayed alternately, and seven bright white lines (18) are displayed in the lower half area (17). In this case, the horizontal scanning line (14a) of the area (■4)
and the horizontal scanning line (17a) of region <17) correspond to the measurement signals of FIGS. 5A and 5B, respectively. Then, calculate the distance l from the bright white line (18) to the boundary between the green part (15) and the magenta part (16) for each white line (18).
By reading the difference in delay time between the luminance signal and the color signal, it is possible to quantitatively measure the difference in delay time between the luminance signal and the color signal. However, the monitor (
It is difficult to measure with high precision on the screen of 8), and there is also a risk that the Y/C delay amount of the monitor (8) itself may be mixed in. Therefore, in order to measure the Y/C delay amount more accurately,
Measurement signal PS reproduced from the test VTR (6)
The oscilloscope (7) is triggered by a horizontal sync pulse.
It is necessary to observe it.

As shown in FIG. 7, on the display screen of the oscilloscope (7), the signal of the horizontal scanning line <14a) corresponding to the color signal and the signal r of the horizontal scanning line (17a) corresponding to the luminance signal are superimposed. Since the amplitude of the envelope line (14b) converges to approximately 0 near the point where the phase of the color signal changes by 180°, it is possible to identify the point of phase change. In this way, the envelope line (14
The reason why the amplitude of b) converges to approximately 0 is because the band of the recording/reproducing system of the VTR is finite. Then, there is a time difference r between the phase change point and the peak point of the 2T pulse of the luminance signal.
and convert this time difference τ into the time difference -τ3~τ in Figure 5B.
3, the Y/C delay amount can be quantitatively determined.

C. Problem to be Solved by the Invention] However, using the measurement signal R3 of the example shown in FIG. 5 has the disadvantage that the Y/C delay amount may not be accurately measured. That is, first, the average luminance level (Average Picture Level) of the signal shown in FIG.

APL) has a value corresponding to the level APL+, whereas the APL of the signal in FIG. 5B has a value corresponding to the level APL2. Therefore, for example, when measuring the Y/C delay amount of the reproduced signal before the DC level is clamped by the synchronization signal, the trigger level of the horizontal synchronization pulse (9) of the signal in FIG. ), the trigger level of the signal in FIG. 5B is level (9b
) and the trigger level changes. Generally, the falling edge of the horizontal synchronizing pulse (9) is not vertical, so when one level of the signal changes, the entire signal fluctuates in the time axis direction, making it difficult to accurately measure the difference in delay time.

Furthermore, the 2T pulses (13A) to (13G> in FIG. 5B)
Particularly when the VTR under test (6) is a VTR for general home use, waveform distortion occurs due to nonlinear emphasis and de-emphasis, making it difficult to accurately read the position of the peak.

In view of the above, an object of the present invention is to propose a measurement signal generator that generates a measurement signal that can more accurately and easily measure the difference in delay time between a luminance signal and a chrominance signal.

[Means to solve the problem]

The measurement signal generator according to the present invention, as shown in FIG. Complementary color pairs (20) in the horizontal period (to Figure 1),
(21) In addition to superimposing a more sensitive color signal, the levels match each other at predetermined positions in the second (Fig. 1 E) and third (Fig. 1 F) horizontal periods, and the average luminance level is the same as that of the color. A luminance signal equal to the signal is superimposed to correct the measurement signal.

[Effect]

According to the present invention, since the average luminance levels of the chrominance signal and the luminance signal are equal, the trigger levels of the chrominance signal and the luminance signal are equal, and measurement errors caused by variations in the trigger level are eliminated. In addition, since the luminance signal can be used as a measurement reference point at the cross point of the second horizontal period signal and the third horizontal period signal, the measurement reference point can be easily and accurately identified and the color signal can be measured. The difference from the reference point can be easily and accurately read.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 1 to 3. The circuit configuration of the measurement signal generator in this example is the fourth
It is the same as the measurement signal generator (1) in the example shown, and the RAM
(3) Only the pattern of the measurement signal differs from that of the video signal stored.

1A to 1D are chrominance signals (19A) to (19D) of one horizontal period different from the measurement signal of this example, and FIGS. 1E and F are luminance signals of one horizontal period different from the measurement signal of this example, respectively. (28
A) and (28B), each frame of the measurement signal in this example is a color signal (1 frame) of 60H (LH is horizontal period).
9A) to (190) and 120H luminance signals (
28A) and <288). As shown in FIG. 1A, the color signal (19A) is at DC level L following the horizontal synchronizing pulse (9) and color burst (10).

It is constructed by forming four complementary color pairs at a predetermined period from a color signal (20) with a phase of Oo and a color signal (21) with a phase of 180 degrees at a DC level L. Color signal (19B).

(19C) and (190) are respectively B, C and D in Figure 1.
Complementary color pair (2,0) in color signal (19^) as shown in
, (21) Complementary color pair whose phase is 45° advanced (22)
, (23) , Complementary color pair (24) whose phase is 90° advanced,
(25) and a complementary color pair with a phase lead of 135° (26)
, (27).

In addition, the luminance signal (28^) is composed of four rectangular pulses following the horizontal synchronizing pulse (9) and the color verse (10), as shown in Fig. 1E.
28B) is the luminance signal (28B) as shown in FIG. 1F.
It is constructed by inverting the level of the rectangular pulse in A). In this case, the amplitude of the rectangular pulse of the luminance signal (28A) is set to be the same as the amplitude of the chrominance signal (20), (21), etc., and the DC level of the rectangular pulse of the luminance signal (28A>) is set to the same as the amplitude of the chrominance signal (28A). The brightness signals (28A) and (28B) intersect at this level 4. Also, the brightness signals (28A) and (28B) intersect.
At the seven cross points (measurement reference points) between (8A) and (28B), the color signal (1
-τ8+'S for each of the seven changing points (measurement reference points) where the phase of 9A) to (190) changes by 180°.
+-τ4,0. A time difference of τ4+r5+τe is provided. For example, r 4 =50nsec, τ, =100nsec
c , r s = 150 nsec, but
It is also possible to set τ,=τ5=τ6−0. Furthermore, the duty ratio of the rectangular pulse portions of the luminance signals (28^) and (28B) is set to 50% as a whole. Therefore,
The DC level of the brightness signal (28A) is also L4, and the brightness signal (28A).

(28B) average luminance level (AFL) and color signal (
The average luminance levels of 19A) to (190) both correspond to the level APL3 and match.

An example of how to combine the color signals (19A) to (190) and the luminance signals (28A) and (28B> shown in FIG. 1 will be described with reference to FIG. 2.
A) - (190) and (28A), (28B)
The method of combining them will be explained using a reproduced image when measurement signals composed of the following are supplied to the monitor.

Figure 2 shows the monitor screen that reproduced the measurement signal.
In FIG. 2, one frame of the screen of this monitor is shown in areas (29) to (3) each consisting of 60 horizontal scanning lines.
Divide into 8 equal parts into areas (29), (31), (33
).

(35〉 are the color signals (19^) and (19B) in Figure 1, respectively.
), (19C).

(190) Horizontal scanning line (29a) corresponding to (
31a), (33a).

(35a) Consists of areas (30), (32),
(33) and (36) are the luminance signals (
Horizontal scanning lines (30a) and (30b) corresponding to 28A) and (28B>, respectively, are arranged alternately for each IH. On the monitor screen in FIG. 2,
Area (30), (32), (34), (36)
The point and area of switching between the white pattern and the black pattern in (29>, (31), (33), (35)
The difference in delay time between the luminance signal and the color signal can be quantitatively measured by reading the offset position with respect to the color switching point.

In this case, since four types of complementary color pairs having phases different by 45 degrees are provided in this example, there is an advantage that measurement errors caused by optical illusions of the operator can be eliminated. Furthermore, the measurement reference point of the luminance signal can be easily and accurately read.

In addition, in order to measure the Y/C delay amount with higher accuracy, Figure 3 shows a case where the measurement signal shown in Figure 1 is supplied to a VTR and the measured signal after being recorded and played back is observed with an oscilloscope. To explain with reference, the phases of the waveforms corresponding to the color signals (19^) to (190) in the example in Figure 1 among the observed waveforms obtained by triggering the reproduced measurement signals with horizontal synchronization pulses respectively. The vicinity where 180° changes is shown in Figure 3A, and the luminance signals (28^) and (28^) of the example in Figure 1 are
The vicinity of the cross point of the waveform corresponding to 8B) is as shown in FIG. 3B. The waveform actually observed on the display screen of the oscilloscope is a waveform in which the waveforms A and B in Fig. 3 are superimposed, and the color signals (19A) to (190)
The point where the amplitude of the envelope (37) is minimum (measurement reference point) and the cross point of the luminance signal (28^> and (28B>)
By reading the time difference τ from the measurement reference point for each cross point, the difference in delay time (Y/C delay amount) between the luminance signal and the color signal is quantitatively measured.

In this case, in this example, the color signal (19^) is
~(19()) and luminance signal (28^), (28B
> Since the average luminance level is the same, the trigger levels of the horizontal synchronizing pulses (9) are the same level (9c), and no relative fluctuation occurs in the time axis direction. Therefore, there is an advantage that the amount of Y/C delay can be accurately measured.

Furthermore, in this example, the measurement reference point of the luminance signals (28^) and (28B) is determined by the cross point of two rectangular waves, but the waveform distortion due to non-linear emphasis and de-emphasis of the VTR is
28A) and (28B) do not occur in signals that monotonically increase or decrease at a moderate level, so according to this example, even if the VTR under test is a general household VTR, the luminance signal can be measured accurately. There is the benefit of being able to identify reference points.

In addition, in this example, four types of color signals (19A) to (190), each of which is a different complementary color pair, are used as color signals, so the color signals are displayed on the front screen of the oscilloscope as shown in Figure 3. The envelope (37) becomes clearer, and the measurement reference point, which is the minimum amplitude point of the envelope (37>), becomes clearer, and there is an advantage that the Y/C delay amount can be measured more accurately.

In the above embodiment, the luminance signals (28^), (2
8B) was formed from a rectangular pulse, but for example, if the phase is 18
0' Different sine waves may be used. As described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various configurations may be adopted without departing from the gist of the present invention.

Therefore, there is an advantage that the difference in delay time between the luminance signal and the chrominance signal can be easily and accurately measured.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a measurement signal of an embodiment of the present invention, and FIG.
The figure is a front view showing the monitor screen when the measurement signal in the example in Figure 1 is played back on the monitor, and Figure 3 is a diagram showing the observed waveform when the measurement signal in the example in Figure 1 is observed with an oscilloscope.
FIG. 4 is a block diagram showing a conventional Y/C delay measurement system, and FIGS. 5 to 7 are diagrams for explaining conventional measurement signals. (9) is horizontal sync pulse, (10) is color burst,
(19A) to (190) are color signals, (20),
(21) is a complementary color pair, (28A), (28B)
are each a luminance signal. [Effects of the Invention] According to the present invention, variations in the trigger level between the luminance signal and the color signal are suppressed, and the measurement reference point of the luminance signal is set to the luminance signal of the second and third horizontal periods. It can be easily identified as a cross point.

Claims (1)

[Claims] In a measurement signal generator that generates a measurement signal for measuring the difference between the delay time of a luminance signal and the delay time of a color signal, a color signal consisting of a complementary color pair is superimposed on a first horizontal period. In addition, the measurement signal is formed by superimposing luminance signals whose levels match each other and whose average luminance level is equal to the color signal at predetermined positions in the second and third horizontal periods, respectively. measurement signal generator.