JPH0347628B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a color television camera (hereinafter referred to as
The present invention relates to a noise reduction circuit that reduces noise components in color difference signals, chrominance signals, etc. in television signal circuits such as cameras) and significantly improves the signal-to-noise ratio of television signals.

[Conventional technology]

Fig. 2 is a block diagram showing a conventional example when taking a camera as an example, and each primary color signal R (red), G (green), B (blue) obtained from each color image pickup tube etc. is connected to a matrix circuit MTX. Here, the luminance signal Y and the color difference signals R-Y, B-Y are generated, and the color difference signals R-B, B-Y are each passed through the low frequency filters LPF ₁ and LPF ₂ . The signal is subjected to band restriction for noise component suppression and is applied to adders ADD ₁ and ADD ₂ and delay circuits DL ₁ and DL ₂ .

In addition, each output of delay circuits DL ₁ and DL ₂ is connected to an adder.
It is directly applied to ADD ₁ and ADD ₂ , and is also applied to adders ADD 1 and ADD ₂ via similar delay circuits DL ₃ and DL ₄ .
ADD ₂ , and each delay circuit DL ₁ to DL ₄ provides a signal for one scanning line, that is, 1H (H
has a delay time of (period from the beginning of the horizontal scanning line to the beginning of the next horizontal scanning line), so in the adders ADD ₁ and ADD ₂ , the current color difference signals R-Y, B-Y and , the same signal RY, R- 1H ago
Y and the same signals R-Y and B-Y from 2H ago are added individually.

Therefore, the output of the adders ADD ₁ and ADD ₂ is a signal obtained by adding the color difference signals R-Y and B-Y by 3H each, and generally the video signal has a correlation with respect to the vertical direction of the image plane. By having this property, the voltage of the video component is tripled, whereas the correlation of the noise component is unspecified and becomes √13 of the power average.

Therefore, the difference between the video component and the noise component is increased, and the signal-to-noise ratio is improved.

Adder ADD ₁ with improved signal-to-noise ratio,
Each output of ADD ₂ can be connected to a modulator such as a double balanced modulator.
MOD ₁ and MOD ₂ , subcarrier SC shifted by 90° by phase shifter PS ₁ , and phase shifter PS _1.
The signals that do not go through the chrominance signal are individually modulated to become color signals, which are then applied to the adder ADD ₃ .

The adder ADD ₃ is supplied with the luminance signal Y and synchronization signal SYN from the matrix circuit MTX, and is also supplied with the burst signal generated in the burst signal generator BG based on the subcarrier SC, and these are synthesized. In addition, it is transmitted as a television signal _SV in the standard television format.

[Problem to be solved by the invention]

However, in the case of the configuration shown in Fig. 2, four delay circuits DL ₁ to _{DL 4} are required for noise reduction, and if digital memory is used for this, a large storage capacity is required and data access is difficult. Since peripheral circuits for control, an analog-to-digital converter, a digital-to-analog converter, etc. are required, it is expensive and has drawbacks such as a complicated circuit configuration.

Furthermore, if ultrasonic delay elements such as glass delay circuits are used in the delay circuits DL ₁ to _{DL 4} , the color difference signals R-Y and B-Y cannot be given as they are due to the transmission frequency band. It is necessary to perform frequency conversion and then apply it to the delay element, and then demodulate the output again to the original frequency band, which again has the drawback of complicating the circuit configuration and increasing the cost.

In addition to the above-mentioned drawbacks, the delay circuit DL ₁ ~
There is a signal delay component due to DL ₄ , and the delay component appears in the vertical blanking period, which should normally be a no-signal state, which violates the regulations of the television standard system and also has the disadvantage of causing various problems. It is occurring.

[Means to solve the problem]

The present invention has the purpose of fundamentally eliminating such drawbacks of the conventional art, in which the same signal is repeatedly passed through a single delay circuit, and the signal to be passed in response to a vertical blanking pulse is By preventing this, it is possible to provide an extremely effective color signal noise reduction circuit that has a simplified configuration and prevents delay components from appearing in the vertical blanking period.

〔Example〕

The details of the present invention will be explained below with reference to FIG. 1 and subsequent figures showing embodiments.

Figure 1 is a block diagram similar to Figure 2, but
Color difference signal R- via low-pass filters LPF ₁ and LPF ₂
Give Y, BY to the first coefficient multipliers FM ₁ and FM ₂ ,
Here, a predetermined coefficient 1-K (however, 0<
The color difference signals R-B and B-Y are multiplied by K<1) and then supplied to the adders ADD ₁₁ and ADD ₁₂ .

Furthermore, the outputs of adders ADD ₁₁ and ADD ₁₂ are sent to modulators MOD ₁ and MOD ₂ , and are also sent to delay circuits.
It is given to DL ₁₁ and DL ₁₂ , and the adder ADD ₁₁ ,
Delay circuit DL ₁₁ with each output of ADD ₁₂ as input,
DL ₁₂ provides a delay time of 1H and provides it as an input signal to the second coefficient multipliers FM ₃ and FM ₄ .

The coefficient multipliers FM ₃ and FM ₄ multiply the input signal by a coefficient K that has a complementary relation to the coefficient 1-K of the coefficient multipliers FM ₁ and FM ₂ , and the output of these multiplies the input signal.
Provided to adders ADD ₁₁ , ADD _{12 ,}
In ADD ₁₂ , each coefficient multiplier FM ₁ and FM ₃ and
The respective outputs of FM ₂ and FM ₄ are added together.

Therefore, the color difference signal R multiplied by the coefficient 1-K
-Y and B-Y are added after being delayed by 1H and multiplied by a coefficient K, and this is repeated infinitely, providing the same noise reduction effect as in FIG. 2.

In other words, the input signals of coefficient multipliers FM ₁ and FM ₂ are
Then, the output So of adders ADD ₁₁ and ADD ₁₂ is
It is given by the following equation.

So=(1-K)Si+(1-K)Si・K+(1-K)Si・K ² +(1-K)Si・K ³
+...=Si(1- ^Kn )...(1) Moreover, the power Pn of the noise component is expressed by the following equation.

Therefore, as shown by equation (1), the video component is almost constant when 0<K<1, but when K=0.5, for example, the noise component is √13 from equation (2).
As a result, the signal-to-noise ratio is improved.

In FIG. 1, a vertical blanking pulse VBL supplied from a synchronizing signal generator or the like in the same way as the synchronizing signal SYN is given to each coefficient unit FM ₁ to _{FM 4} , and thereby each coefficient Instrument FM ₁ ~
As a result of decreasing the value of the coefficient K to which FM ₄ is multiplied, the coefficient multipliers FM ₁ and FM _{2 increase} during the vertical blanking period.
The output level of coefficient multipliers FM ₃ and FM ₄ is decreased.

Therefore, the signals circulating through the adders ADD ₁₁ and ADD ₁₂ via the delay circuits DL ₁₁ and DL ₁₂ are reduced, and the inputs of the adders ADD ₁₁ and ADD ₁₂ are almost the same as those of the coefficient multipliers FM ₁ ,
Only FM ₂ is output, and no delay component appears during the vertical blanking period, resulting in a no-signal state.

Note that the above noise reduction circuit can be installed not only in cameras but also in various video equipment such as camera control devices and color encoders depending on the conditions.The delay circuits DL ₁₁ and DL ₁₂ are configured to In addition to converting into digital signals, memory, shift registers, etc. may be used, and in some cases, only the coefficient multipliers FM ₃ and FM ₄ may be controlled by the vertical blanking pulse VBL. Various modifications are possible. be.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, each single delay circuit reduces color difference signals and color signal noise, and at the same time, the vertical blanking period becomes a no-signal state, thereby improving the image quality of reproduced video. , it is possible to ensure compatibility with the television standard system, and also to easily realize simplification of structure and reduction in price, and therefore it exhibits remarkable effects in cameras and various video equipment.

[Brief explanation of drawings]

FIG. 2 is a block diagram of a conventional example, and FIG. 1 is a block diagram showing an embodiment of the present invention. FM ₁ , FM ₂ ... first coefficient multiplier, FM ₃ , FM ₄ ...
...Second coefficient unit, ADD ₁₁ , ADD ₁₂ ...Adder,
DL ₁₁ , DL ₁₂ ...Delay circuit, VBL...Vertical blanking pulse.

Claims (1)

[Claims] 1. A first coefficient multiplier that multiplies a color difference signal by a predetermined coefficient; and a second coefficient that multiplies an input signal by a coefficient having a complementary relationship with the predetermined coefficient, and the value of the coefficient decreases in response to a blanking pulse. an adder for adding the respective outputs of the first and second coefficient multipliers; the output of the adder is inputted and given a delay time of at least one scanning line, and then input to the second coefficient multiplier; 1. A color signal noise reduction circuit comprising a delay circuit that provides a signal.