JPS62193473A - Simultaneous coinciding circuit for television signal - Google Patents

Abstract

PURPOSE:To take out a high SN, line sequential signal while reducing the fluctuation of a hue at every line and color error at a color edge and coinciding simultaneously by providing a circuit that coincides and takes out a signal in which the input of a delay element at an initial step and the output of the delay element at the succeeding step are added, and the output of the delay element with a switching signal at every cycle period. CONSTITUTION:A signal (d) is obtained by subtracting a signal (a) inputted to a terminal 13 from the output signal (c) of a 1H delay circuit 16. The signal (d) is changed to a noise signal (e) passing through a non-linear amplifier 18, and a signal (g), the noise component of which is reduced by adding the signal (e) on the signal (a) at an adder 14, and a signal (h) in which the signal (c) of the 1H delay circuit 16 is averaged, can be obtained, and also, a signal (b) from which the noise component is reduced at a 1H delay circuit 15, can be obtained, and the signals (h), and (b) are coincided and taken out at a switch circuit 10.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a television signal synchronization circuit, for example, a circuit for synchronizing line-by-line time-division multiplexed signals in a color television camera and extracting the signals. Regarding.

(Prior Art) FIG. 5 shows a block diagram of an example of a synchronization circuit of a general color television camera. In front of it is Figure 6 (A
) is equipped with the complementary color filter 1a shown in 'fli@
The charges for each color accumulated in the photoelectric conversion section in element 1 are mixed vertically in two pixels in an ink-line CCD, and combined for each odd field and even field.
are taken out with different values.

The signal from the image sensor 1 is passed through a low-pass filter 2 to produce a luminance signal y.
w and is supplied to the adder 3 (,:). On the other hand, it is supplied to sample and hold circuits 41 and 42 and held with sampling pulses with a 180° phase difference, and from the sample and hold circuit 41, for example, (W+Ye) and (W+C
For example, the sample and hold circuit 42 outputs (G
+Cy) and (G+Ye) are taken out, subtracted by the subtractor 5 to take out the R signal and B signal, and the subtractor 6' takes out the color difference signals (R-Y), (B-Y) (time division multiplexed signal )
are output line-sequentially.

The color difference signals (R-Y) and (B-Y) are supplied to a synchronization circuit 8 via a low-pass filter 7, where they are synchronized by a 1H delay circuit 9 and a switch circuit 10 that is switched for each line. The signal is taken out, converted into a modulated chroma signal by the balanced modulation circuit 11, and added with the luminance signal @YW by the adder 3 to form a composite video signal, which is taken out from the output terminal 12.

By the way, in general, a single-chip color television camera using the complementary color filter 1a shown in FIG.
It is known that the SN ratio of the color signal to the luminance signal is worse than that using the primary color filter 1b shown in FIG. 6(B), but this will be explained next.

The dynamic range of incline COD is vertical (CO
It is determined by the amount of transferred charge (per stage of D), and this amount of charge is now set as Q max. The amount of charge generated is Qmax
/k (however, constant = 3 to 4), and this state is defined as a standard state. In the standard state, the level (lli degree signal level) of two adjacent pixels of the field accumulation mode CCD of the complementary color filter 1a shown in FIG. 6(A) is (W+Ye')+(G+CV)=4fJ+2r+2b=2 - Qllax / becomes. Here, for simplicity, the spectral characteristics of illumination and COD are flattened ((1: r: b=1:1:
1), then g = r = b = Qmax /4 from the above equation. Therefore, the amount of demodulation of the color signal is, for example, R signal: R=(W+Ye)-(G+Cy)2r=(lax/2k (1)).

On the other hand, if the frame accumulation mode COD of the primary color filter 1b shown in FIG. 6(B) is calculated in the same way, the level of two adjacent pixels (Ii degree signal level) will be G+R=g+r=2-Qmax/, If ri:r:b=1:1:1, then g=r
-b=Qmax/, and therefore, the demodulation amount of the color signal is, for example, R=r=Qmax/k (2).

If there is no difference in the noise generated per packet of COD transfer charges between field accumulation and frame accumulation, the SN ratio of the color signal is proportional to the amount of demodulated signal charge, and in the above calculation, Equation (1), Equation (2) Therefore, the 6 dBSN ratio becomes worse when the complementary color filter 1a is used.

As a method for solving such problems, the present applicant previously filed Japanese Patent Application No. 194289-1989 ``Television Signal Synchronization Circuit''.

This allows line-sequential color difference signals to be synchronized with a high S/N ratio, but a problem with the synchronization circuit is that the vertical phases of the synchronized signals do not match. This problem occurs because when the imager output is R-Y, the B-Y signal is interpolated with a signal 1H earlier. For example, at a vertical edge as shown in FIG. 7, a false color signal is generated because the vertical phases of the R-Y and B-Y signals are not aligned. Further, as shown in FIG. 8, in the case of an R image of a subject in which the hue is constant and the brightness changes gradually, blurring occurs in the hue of each scanning line.

(Problems to be Solved by the Invention) As described above, the conventional circuit has a problem in that when the complementary color filter 1a is used, the degree of modulation of the color signal decreases, and the S/N ratio of the color signal decreases.

Furthermore, during synchronization, since the interpolated signal is a signal from 1H earlier, a vertical phase difference occurs between the R-Y and B-Y signals output from the synchronization circuit, resulting in false edges. However, there are problems in that hue changes occur line by line even when there is a smooth change in saturation.

The present invention provides a television signal synchronization circuit that can synchronize and extract line-sequential color difference signals with a high signal-to-noise ratio even when a complementary color filter is used, and can reduce the generation of color pseudo signals during synchronization. The purpose is to provide

(Means for Solving the Problem) In Fig. 1, the one-day delay circuits 15 and 16 have delay amounts corresponding to the period of signals composing the time division multiplexed signal, and are connected in cascade of the time division multiplexed signals. Means, subtractor 17 is 1H
A calculation means for subtracting the input of the N delay circuit 15 and the output of the one-day delay circuit 16, a non-linear amplifier 18, a means for changing the output characteristic non-linearly by inputting the output of the calculation means to the input of the one-day delay circuit 15, and addition. The switch circuit 10 adds and averages the input of the delay element 15 and the output of the delay element 16, and the switch circuit 10 equalizes each input of the cascaded delay elements to 11:1 using a switching signal every two cycles. 3A and 3B are examples of means for extracting the data.

(Function) The signal a (FIG. 2 (A)) input to the terminal 13 is subtracted from the output signal C (FIG. 2 (C)) of the one-day delay circuit 16 to obtain the signal d (FIG. 2 (D)). The signal d is passed through the nonlinear amplifier 18 to become a noise signal e ((E) in the same figure), and the adder 14 adds the signal e to the signal a to create a signal g ((G) in the same figure) with the noise component reduced. ) and C of 1-day delay circuit 16
A signal h ((H) in the same figure) is obtained by averaging the
-(Signal whose noise component is reduced by the delay circuit 15 @b
((B) in the same figure) is obtained, and a signal is sent from the switch circuit 10,
are simultaneously extracted.

(Embodiment) FIG. 1 shows a block system diagram of an embodiment of the circuit of the present invention. In the figure, the color difference signal (B-Y
) and (RY) (the output of the low-pass filter 7 shown in FIG. 5, the color difference signal (B-Y) is shown in FIG. 15 and 16, the signal C ((C) in the same figure) is taken out from the H delay circuit 16, and the signal C is supplied to the subtracter 17 to produce a color difference signal (B
−Y). Color difference signals inherently have strong vertical correlation, and line sequential signals are repeated every two days.
The two color difference signals supplied to the subtracter 17 have a strong vertical correlation, so that the subtracter 17 outputs a signal d ( (D)) is taken out.

The signal d is supplied to a nonlinear amplifier 18 having the input-output characteristics shown in FIG. 3(A), for example, and thereby the signal e (FIG. 2(E)) in which the uncorrelated components of the color difference signals are suppressed is generated.
). This is essentially considered to be a negative phase component of noise.

This noise component e is sent to the adder 14 as a color difference signal (B - Y
'), and as a result, the adder 14 outputs the color difference signal (B-Y)' with the noise component e reduced ((
G)) is taken out and added to the output C of the one-day delay circuit 16 in an adder 25, and then its level is halved in a 1/2 multiplier 26 and supplied to the switch circuit 10.

Further, from the one-day delay circuit 15, the color difference signal (B-Y
)', the color difference signal (R-
Y)' is taken out and supplied to the switch circuit 10.

In the switch circuit 10, switching is performed for each line by a line switching signal as in the conventional circuit, and the color difference signal (
B-Y)' and (RY)' are synchronized and connected to terminal 191.
．． 192.

Note that the input-output characteristics of the nonlinear amplifier 18 may be as shown in FIG. 3(B). In this case, the noise component which is the output of the nonlinear amplifier is as shown in FIG. 2(F). It is possible to obtain a color difference signal in which the noise component is reduced in substantially the same way as in the case of the above method.

Further, if the time division multiplexed signal input to the terminal 13 is a signal that is inverted every 2H, an adder is used in place of the subtracter 17 in FIG.

By the way, there is a circuit in which a synchronization signal is input to the terminal 13 shown in FIG. is a so-called cyclic noise reducer. If the slope near the origin of the input-output characteristics shown in Figure 3 (A>, (B) is K, and the unit delay operator corresponding to the 1H delay is 71, then there is a vertical correlation of 2H periods in the input signal. The transfer function H(Z) in this case is H(Z) = (1-K)/ (1-KZ'2) = (1-
K) (1+KZ'2 + to 2 Z -4+-KnZ-2n+-)...
■ It becomes. Since the signal is the amplitude average and the random noise is the square root of the power phase, the signal transfer function Hs (K) and the noise transfer function Hn (K) are Hs (K) = (1-K) (1+ to + 2 + 3
+...+l(n+...) = 1 Hn (K)= ((1-k)(1+ to 2+'+
ni & +...+K 2n+...)) ding=J (1
−, K> / (1+K).

Therefore, for signals with vertical correlation, noise can be reduced by making K close to 1, while for signals without vertical correlation, by reducing K,
In the equation, the term below KZ″2 can be ignored, and the blur of the image in the vertical direction can be reduced.

Furthermore, in synchronization, as shown in FIG. 9, missing signals are interpolated using the average value of the upper and lower lines. Therefore, the interpolated signal and the non-interpolated signal are not out of phase in the vertical direction, and the hue change for each line as shown in FIG. 8 is unlikely to occur.

Furthermore, the error amount for color edges as shown in FIG. 7 is reduced by half, and is distributed on both sides, making it less visually noticeable as shown in FIG. 10.

FIG. 4 shows a block system diagram of another embodiment of the circuit of the present invention, in which the same components as in FIG. 1 are given the same numbers and their explanations will be omitted. The color difference signal input to the terminal 13 is multiplied by a gain (1-K) in a variable gain amplifier 20, and this output is multiplied by a gain (1-K) in a variable gain amplifier 22.
The output of the day delay circuit 16 and the adder 21 are added to 11
1 delay circuit 15 and switch circuit 10.

In this case, the output of the 1H delay circuit 16 and the signal input to the terminal 13 are subtracted by the subtracter 23, and the absolute value circuit 24 having the input-output characteristic shown in FIG. Signals CI and C2 are taken out and sent to a variable gain amplifier 20.
The value of K in 22 is varied. When the value of the signal obtained by the subtracter 23 exceeds the threshold value, K is controlled to be small.

The other operations are the same as those of the circuit shown in the first diagram, so the explanation thereof will be omitted.

(Effects of the Invention) According to the present invention, line-sequential signals can be simultaneously extracted with a high signal-to-noise ratio and with fewer line-by-line changes in hue and color errors at color edges.

[Brief explanation of drawings]

1 and 2 are respectively a block system diagram and its signal waveform diagram of an embodiment of the circuit of the present invention, FIG. 3 is an input-output characteristic diagram of the nonlinear amplifier and absolute value circuit used in the circuit of the present invention, and FIG. Figure 5 is a block diagram of another embodiment of the circuit of the present invention, Figure 5 is a block diagram of an example of a conventional circuit, Figure 6 is a configuration diagram of a complementary color filter and a primary color filter, and Figure 7
8 and 8 are explanatory diagrams of the conventional circuit, and FIGS. 9 and 10 are explanatory diagrams of the circuit of the present invention. 10... Switch circuit, 13... Color difference signal input terminal, 14.21.25... Adder, 15.16... 1H delay circuit, 17.23... Subtractor, 18... Nonlinear amplifier, 191.192... Color difference signal output terminal, 20.22.
...Variable gain amplifier, 24...Absolute value circuit, 26...1/2 multiplier (gain amplifier), K...Gain. ＾ -To Figure 2 Figure 5 iJ6 Figure 7 Figure 8 Figure 8
R-V B-Y Figure 9 R-Y channel Image output B-Y channel Figure 10

Claims (1)

[Claims] In a television signal synchronization circuit that synchronizes and extracts time-division multiplexed signals that are time-division multiplexed at a constant repetition period corresponding to the television signal and have a correlation for each repetition period, the time-division multiplexed signal is configured. a circuit in which two delay elements each having a delay amount corresponding to the period of one signal are connected in cascade; an arithmetic circuit that subtracts or adds the input of the first stage and the output of the second stage of the cascaded delay elements; A circuit that feeds back the output of the circuit to the input of the cascaded delay elements via an element whose input-output characteristics change non-linearly, and a signal that is the sum of the input of the first-stage delay element and the output of the second-stage delay element. and a circuit for synchronizing and extracting the outputs of the first-stage delay element using the switching signal for each repetition period.