JPH05183914A - Contour compensating circuit - Google Patents

Abstract

PURPOSE:To enable contour compensation by digital signal processing while reducing circuit scale and reducing power consumption in a contour compensating circuit for executing the contour compensation with respect to signals from image pickup sensors repeatedly horizontally arranging the two kinds of color filters. CONSTITUTION:Delay elements 2a and 2b are connected in series while providing integer-fold delay time in the repeating cycle of the color filters, an adder 3a adds a delayed luminance signal and a not-delayed luminance signals, an adder 3b adds a signal passing through a coefficient equipment 4 and the output signal of the delay element 2a, and a contour compensating signal is generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contour compensating circuit for contour compensating a luminance signal obtained from the output of an image sensor.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing a configuration of a main part of a conventional contour compensation circuit in which a color filter array of an area sensor (imaging sensor) is a repeating pattern of two colors in a horizontal direction. Yellow), Cy (cyan),
The case of a complementary color mosaic filter of Mg (magenta) and G (green) will be described. In the figure, 10 is an LPF (low pass filter) to which a video signal from the area sensor is input, 11a and 11b are delay elements having a delay time of T, 12a, 12b and 12c are adders, and 13 is -1.
A coefficient multiplier having a coefficient of / 2, 14 is a BC (base clip) circuit for removing low-level signal components, and 15 is a coefficient multiplier having a coefficient of K.

Next, the operation will be described.

The input signal supplied to the LPF 10 is an output signal of an area sensor having the above-mentioned Ye, Cy, Mg, and G complementary color mosaic filters, which is subjected to signal processing such as sample hold, and is actually modulated. The luminance signal is a superimposed luminance signal. Then, the color difference signal is removed from the input signal by the LPF 10, and only the luminance signal is extracted. FIG. 4 shows how the input signal from the area sensor passes through the LPF 10. The modulated color difference signal is included before passing through the LPF, but the color difference signal is included after passing through the LPF. Absent.

The luminance signal extracted by the LPF 10 is input to the delay element 11a having the delay time T and further to the delay element 11b having the delay time T, and the delayed luminance signal which is the output of the delay element 11b. Is added to the undelayed luminance signal from the LPF 10 by the adder 12a. The added signal is input to the coefficient unit 13 having a coefficient of −1/2, and the output of the coefficient unit 13 and the delay element 11
The output of a is added by the adder 12b, whereby a contour compensation signal obtained by quadratic differentiation of the luminance signal is obtained.

The contour compensation signal thus generated is subjected to base clip processing by the BC circuit 14 and then multiplied by K by the coefficient unit 15 to become a signal of an appropriate level, which is a luminance signal from the delay element 11a. Is added by the adder 12c. As a result, contour compensation is performed on the luminance signal, and the luminance signal is output to the subsequent circuit.

[0007]

However, in the conventional contour compensating circuit as described above, if contour compensation is performed while the chrominance signal modulated on the luminance signal is superposed, the contour compensation signal is also modulated. Since the base clip does not operate properly, contour compensation is performed after extracting only the luminance signal by the LPF. Therefore, when contour compensation is performed by digital signal processing, a digital LPF having a steep frequency characteristic and a flat group delay characteristic is required to extract only a luminance signal, and the number of taps also increases. Therefore, there is a problem that the circuit scale becomes large and the power consumption also becomes large.

The present invention has been made in view of the above problems, and provides a contour compensating circuit having a small circuit scale and capable of performing contour compensation by digital signal processing with low power consumption. is there.

[0009]

The contour compensating circuit of the present invention is a contour compensating circuit for contour compensating a video signal from an image sensor in which two kinds of color filters are repeatedly and alternately arranged in a horizontal direction. A plurality of delay elements having a delay time which is an integral multiple of the repetition period of the color filter are connected in series, and the contour compensation signal is generated from the outputs of these delay elements.

[0010]

In the contour compensating circuit of the present invention, since the delay time of each delay element is set to an integral multiple of the horizontal repetition period of the same color filter, the input / output signals of each delay element are all signals of the same color filter. Therefore, the contour compensation signal is not affected by the modulated color difference signal.

[0011]

FIG. 1 is a block diagram showing the configuration of a contour compensating circuit according to an embodiment of the present invention. This circuit is a video signal from an area sensor in which two kinds of color filters are repeatedly and alternately arranged in a horizontal direction. Contour compensation is performed on the (luminance signal) (see FIG. 4). In the figure, 1 is an AD converter for converting an analog input signal from the area sensor into a digital signal, and 2a and 2b are integer multiples of the repetition period of the color filter, that is, a period corresponding to the horizontal pixel interval of the area sensor. Is a plurality of delay elements having a delay time of 2τ × N (integer), and two delay elements are connected in series here. 3a, 3b and 3c are adders, and 4 is a coefficient −
1/2 coefficient unit, 5 BC circuit for performing base clip processing, 6 coefficient unit with K coefficient, 7 DA converter for converting digital signal to analog signal, 8 LPF for analog signal is there.

In the circuit having the above configuration, the AD converter 1
The signal input to is a signal obtained by subjecting the output signal of the area sensor to signal processing such as sample hold, as in the conventional case, and is a signal in which the modulated color difference signal is superimposed on the luminance signal. Then, the input signal is converted into a digital signal by the A / D converter 1. At this time, the input signal is converted into a digital signal in a state where the color difference signal is superposed on the luminance signal, and then input to the delay element 2a. ..

The luminance signal input to the delay element 2a is further input to the delay element 2b in the subsequent stage, and this delay element 2
The luminance signal output from b is added to the non-delayed luminance signal from the AD converter 1 by the adder 3a.
The output of the adder 3a passes through a coefficient unit 4 having a coefficient of -1/2, and is added by the brightness signal from the delay element 2a and the adder 3b to form a contour compensation signal.

Since the delay times of the delay elements 2a and 2b are set to 2τ × N, that is, an integral multiple of the horizontal repetition period of the same color filter of the area sensor as described above, the delay elements 2a and 2b have the same delay times. All input / output signals are signals of the same color filter. Therefore, as described above, the adder 3
The contour compensation signal generated by second-order differentiating the input signal using a, 3b and the coefficient unit 4 is not affected by the modulated color difference signal.

Next, this contour compensation signal is input to the BC circuit 5, where low-level components are removed, and then the coefficient multiplier 6 multiplies it by K to obtain an appropriate level signal. Then, it is added to the luminance signal output from the delay element 2a by the adder 3c, and thereby contour compensation is performed on the luminance signal. The contour-compensated signal is converted into an analog signal by the DA converter 7, and the LPF 8 is further converted.
In this way, the modulated color difference signal is removed, and finally output as a contour-compensated luminance signal to the subsequent circuit.

The contour compensation is performed in this manner, but according to the above circuit, only the contour compensation can be performed by the digital signal processing without using the digital LPF. That is, it is possible to perform contour compensation by digital signal processing with a small circuit scale and low power consumption.

FIG. 2 is a block diagram showing another embodiment of the present invention, and the same reference numerals as those in FIG. 1 indicate the same components. In this embodiment, two DA converters 7a and 7b are provided, and the addition of the input luminance signal and the contour compensation signal is performed by each DA.
This is performed after conversion into analog signals by the A converters 7a and 7b. With such a configuration, the dynamic range after addition can be widened.

[0018]

As described above, according to the present invention, a plurality of delay elements having a delay time which is an integral multiple of the repetition period of the color filter of the image sensor are used, and the contour compensation is performed from the output of these delay elements. Since the signal is generated, there is an effect that the circuit scale is small and the contour compensation can be performed by the digital signal processing with low power consumption.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing the configuration of another embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a conventional example.

FIG. 4 is a waveform diagram of a signal from an area sensor before and after filtering.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 AD converter 2a Delay element 2b Delay element 3a Adder 3b Adder 3c Adder 4 Coefficient device 5 BC circuit 6 Coefficient device 7 DA converter 8 LPF

Claims (1)

[Claims] 1. A contour compensation circuit for performing contour compensation on a video signal from an image sensor in which two types of color filters are repeatedly arranged alternately in the horizontal direction, and a delay time which is an integral multiple of a repetition period of the color filter is set. A contour compensating circuit comprising a plurality of delay elements connected in series, wherein the contour compensating signal is generated from outputs of these delay elements.