JPH04280579A - Smear correction circuit in image pickup signal processor - Google Patents

Abstract

PURPOSE:To simplify the signal processing scale and constitution of a detection section of a smear signal without deteriorating the S/N and to attain effective smear correction. CONSTITUTION:A smear information signal Sd and a Y signal including smear position information and level information obtained by detecting an image pickup signal at a smear signal detection circuit 18 are inputted to a gamma correction circuit 20 to reduce the smear signal from the Y signal. Similarly, the smear information signal Sd and a C signal are inputted to a gamma correction circuit 32 to reduce the smear signal from the C signal. Moreover, a color difference signal from a color difference matrix circuit 34 and the smear information signal Sd are inputted to a gain control section 36, in which the smear signal is suppressed in the color difference signal.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a smear correction circuit in an image signal processing apparatus suitable for application to a video camera using an image sensor such as a CCD.

0002

2. Description of the Related Art Conventionally, when strong light is incident on a CCD image sensor section of a video camera of this type, a large-level false signal known as a smear (hereinafter referred to as a smear signal) is generated. A well-known smear reducer (smear correction circuit) is used to correct such smear.

FIG. 6 shows a conventional smear correction circuit. This smear correction circuit is provided with a signal processing circuit 4 to which an imaging signal from the CCD imaging device 2 is input, and a smear signal detection circuit 6. An adder 8 is provided to which a detection signal from the adder 8 is supplied. In the smear correction circuit with this configuration, the detected signal obtained by envelope detection of the imaging signal is input to the adder 8, and at the same time, the original signal from the signal processing circuit 4 is supplied to the adder 8, where the original signal is Smear is corrected by subtracting the smear signal.

0004

[Problems to be Solved by the Invention] Incidentally, the area that requires smear correction is generally a portion of the imaged screen, and of course other areas of the screen do not require smear correction. In the smear correction circuit according to the conventional technology, the adder 6 converts the detected signal from the original signal that is the output of the signal processing circuit 2.
Since the smear is corrected by subtracting it with
/N ratio deteriorates. Therefore, in this smear correction circuit, internal noise generated from the smear signal detection circuit 4 itself that obtains the detection signal becomes a problem. If this internal noise is large and the level of the smear signal is low, a detection signal that is a smear signal cannot be obtained, and smear correction cannot be performed.

[0005] Furthermore, since smear correction is performed by subtracting from the original signal in the adder 6 at once, for example, luminance (hereinafter referred to as Y as necessary) signal, color (hereinafter referred to as C as necessary) This method has a disadvantage in that it is not possible to perform smear correction in a more detailed and effective manner than when smear correction is performed on the smear correction signal and the color difference signal separately and then combined. The present invention has been made in view of the above-mentioned problems, and can achieve
It is an object of the present invention to provide a smear correction circuit in an excellent imaging signal processing device that can effectively perform smear correction.

[0006]

[Means for Solving the Problems] A smear correction circuit in an imaging signal processing apparatus of the present invention detects a smear information signal indicating the position and level of smear from an imaging signal, as shown in FIGS. 1 to 5, for example. detection means (18,
40), a luminance gamma correction circuit (20) that supplies a luminance signal separated from the image signal, a color gamma correction circuit (32) that supplies a color signal separated from the image signal, and a color difference signal formed from the color signal. Color difference signal amplification circuit (36
), and the gain of the luminance gamma correction circuit (20) and the color gamma correction circuit (32) and/or the color difference signal amplification circuit (36) are determined by the smear information signal from the detection means (18, 40).
) to reduce smear.

[0007]

[Operation] The smear correction circuit in the imaging signal processing device of the present invention suppresses and reduces the smear signal by changing the gamma curve of the Y signal using the smear information signal obtained by detecting the imaging signal. From the signal, the gamma curve is changed by the smear information signal, and the gain of the color difference signal is changed to suppress and reduce the smear signal. That is, each smear signal of the Y signal, C signal, and color difference signal is suppressed and reduced based on the smear information signal, and smear correction is substantially performed in the video signal to be synthesized later. In this case, since the smear information signal is not subtracted from the Y signal, C signal, and color difference signal by an adder or the like, noise components are not mixed, and the S/N ratio is not deteriorated. Furthermore, since it is not necessary to consider noise components generated in the detection means itself when obtaining a smear information signal, the signal processing scale and configuration of the detection means can be simplified. Further, since the signal, C signal, and color difference signal are individually smear corrected, detailed and effective smear correction can be performed.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the smear correction circuit in the image signal processing apparatus of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows the configuration of an embodiment. This example is
A CCD imaging device 10 and a sample hold (S/H) circuit 12 to which an imaging signal from the CCD imaging device 10 is input are provided. Further, a Y signal generation section 14 and a chroma signal generation section 16 forming a Y/C separation circuit to which the imaging signal from the S/H circuit 12 is supplied are provided, and a smear signal detection circuit to which the imaging signal is further supplied. 18. Further, a well-known gamma (γ) correction circuit 20 to which the Y signal from the Y signal generation section 14 is supplied is provided. In addition to the γ correction process, the γ correction circuit 20 suppresses and reduces the smear signal included in the Y signal by changing the γ curve using the smear information signal Sd, as will be described in detail later. Then, the Y signal with the smear signal corrected is Y
The signal is supplied to the signal processing circuit 22, where it undergoes predetermined signal processing and is output.

[0009] Furthermore, the C signal from the C signal generating section 16 is W
The signal is supplied to the γ correction circuit 32 through the /B circuit 30. In addition to the γ correction, the γ correction circuit 32 suppresses and reduces the smear signal included in the C signal by changing the gamma curve using the smear information signal Sd, as will be described in detail later.

The C signal with the smear signal corrected is input to the color difference matrix circuit 34, where color difference signals (R-Y, B-Y) are formed and output. This color difference signal is input to the gain control section 36 as will be described in detail below, and its gain is changed by the smear information signal Sd to suppress and reduce the smear signal included in the color difference signal. The smear-corrected color difference signal from the gain control unit 36 is supplied to the C signal processing circuit 38, where it undergoes predetermined signal processing and is output. Further, the detection signal from the smear signal detection circuit 18 is transmitted to the detection signal processing circuit 4.
The smear information signal Sd is supplied to the γ correction circuit 20, the γ correction circuit 32, and the gain control unit 3.
6.

Next, the operation of this configuration will be explained. A smear signal detection circuit 18 performs envelope detection on the imaging signal from the S/H circuit 12 . This detected signal is supplied to a detected signal processing circuit 40, subjected to processing such as a predetermined level for proper operation in a correction circuit 20, a γ correction circuit 32, and a gain control section 36, and outputted as a smear information signal Sd. FIGS. 2(a) and 2(b) show the relationship between a video in which smear has occurred and a detected signal. In FIG. 2(a), the video P
When a high brightness portion HS occurs in the image, smear SM occurs. This signal is detected as shown in FIG. 2(b), and this detected signal includes information on the smear position (position on the time axis) corresponding to the smear SM and its level.

First, suppression of the smear signal included in the Y signal will be explained. FIG. 3 shows the basic circuit configuration for suppressing the smear signal included in the Y signal. In addition, in this FIG. 3, the reference numerals corresponding to the components in FIG. 1 are attached. The γ correction circuit 20, which is an amplifier with γ characteristics, includes a Y signal generation section 14.
The Y signal from S is input, and at the same time the smear information signal S
A drive signal Cs, which is d, is input. Therefore, the smear position matches the smear information signal Sd (drive signal Cs) on the time axis of the Y signal. Here, the gain of the γ correction circuit 20 at this matching point is expressed as the smear information signal Sd (drive signal Cs).
decrease by an amount equivalent to the level of . by this,
This means that the smear signal included in the Y signal can be suppressed and reduced. FIG. 4 shows an operating state in which the γ curve of the γ correction circuit 20 is changed to reduce the gain (arrow V).

Next, reduction of suppression of the smear signal included in the C signal will be explained. This circuit configuration in principle is the same as that shown in FIG. The C signal from the C signal generation unit 16 and the W/B circuit 30 is input to the γ correction circuit 32 of the amplifier having the γ characteristic, and at the same time, the drive signal C which is the smear information signal Sd is input.
Entering s. Therefore, the smear position coincides with the smear information signal Sd (drive signal Cs) on the time axis of the C signal. Here, the gain of the γ correction circuit 20 at this matching point is reduced by an amount corresponding to the level of the smear information signal Sd (drive signal Cs). This makes it possible to suppress and reduce the smear signal included in the C signal. Note that the state in which the γ curve of the γ correction circuit 32 is changed to reduce the gain (arrow V) is the same as in FIG. Furthermore, the color difference signal (R-Y
, B-Y), the smear signal is also suppressed and reduced.

FIG. 5 shows a basic circuit configuration for suppressing smear signals from color difference signals. Note that in FIG. 5, the constituent elements in FIG. 1 are given the same reference numerals. The color difference signals (R-Y, B-Y) from the color difference matrix circuit 34 are inputted to a gain control section 36 which is a variable amplifier, and at the same time, a drive signal Cs which is a smear information signal Sd is inputted. Therefore, the smear position coincides with the smear information signal Sd (drive signal Cs) on the time axis of the C signal. Here, the gain control section 36 at this matching point
is lowered by an amount equivalent to the level of the smear information signal Sd (drive signal Cs). This makes it possible to suppress and reduce the smear signal included in the color difference signal.

Note that the reduction of the smear signal of the C signal and the reduction of the smear signal of the color difference signal are intelligently controlled. For example, if the periphery of an image in which smear has occurred contains a color signal with a high degree of modulation, if the smear signal from the C signal is suppressed and reduced, this part will appear whitish on the displayed image and look unnatural. be. In this case, γ correction circuit 2
The drive signal Cs, which is the smear information signal Sd, is supplied from the detection signal processing circuit 40 to the γ correction circuit 20 so that only the smear signal included in the C signal is suppressed and reduced.

Further, the gain adjustment of the γ correction circuit 20, the γ correction circuit 32, and the gain control section 36 does not have to follow the level of the smear signal included in the image pickup signal from the S/H circuit 12. That is, by individually changing the levels of the smear information signal Sd (drive signal Cs) supplied to the γ correction circuit 20, γ correction circuit 32, and gain control section 36, the smear signals included in the Y signal, C signal, and color difference signal can be effectively adjusted. It is also possible to suppress and reduce the amount.

In this manner, the smear signals included in the Y signal, C signal, and color difference signal are individually suppressed based on the smear information signal, and as a result, smear correction is performed in the combined video signal. In this case, in order to individually suppress and reduce the smear signal by changing the gain, for example, according to the signal characteristics of the Y signal, C signal, and color difference signal,
This has a remarkable effect compared to suppressing and reducing the smear signal included in the combined video signal.

Furthermore, since the smear information signal Sd is not subtracted from the Y signal, C signal, and color difference signal by an adder or the like, the noise component contained in the smear information signal Sd is not mixed into the Y signal, C signal, and color difference signal. A good S/N ratio can be obtained. Furthermore, it is no longer necessary to consider noise generated in the smear signal detection circuit 18, the detection signal processing circuit 40, etc., and the signal processing scale and configuration of the smear signal detection circuit 18 and the detection signal processing circuit 40 are simplified. . In other words, the burden of designing this circuit can be reduced.

[0019]

As can be understood from the above explanation, the smear correction circuit in the imaging signal processing device of the present invention calculates the gamma curve from the luminance signal using the smear information signal obtained by detecting the smear signal of the imaging signal. The smear signal is suppressed and reduced by changing the gain of the color difference signal, and the gain of the gamma curve is changed using the smear information signal from the color difference signal, and the level of the color difference signal is adjusted to suppress and reduce the smear signal. Since the noise component is reduced, there is an effect that the noise component is not mixed into each signal and the S/N ratio is not deteriorated. Furthermore, since it is not necessary to consider noise generated in the detection means itself, there is an effect that the signal processing scale and configuration of the detection means can be simplified. In addition, Y signal,
Since the C signal and the color difference signal are individually smear corrected, it is possible to perform detailed and effective smear correction.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of a smear correction circuit for image pickup signals according to the present invention.

2(a) and 2(b) are diagrams for explaining the operation when obtaining a smear position information signal in the embodiment shown in FIG. 1;

FIG. 3 is a block diagram showing a basic configuration when suppressing and reducing a smear signal included in a Y signal.

FIG. 4 is a characteristic diagram of a gamma correction circuit provided for explaining the operation of the embodiment.

FIG. 5 is a block diagram showing a basic configuration for suppressing and reducing a smear signal included in a color difference signal.

FIG. 6 is a block diagram showing the configuration of a conventional gamma correction circuit.

[Explanation of symbols]

10 CCD imaging device 14 Y signal generation section 16 C signal generation section 18 Smear signal detection circuit 20, 32 Gamma correction circuit 34 Color difference matrix circuit 36 Gain control section Sd Smear information signal

Claims (1)

[Claims] 1. Detecting means for detecting a smear information signal indicating the position and level of the smear from the imaging signal;
a luminance gamma correction circuit that supplies a luminance signal separated from the imaging signal; a color gamma correction circuit that supplies a color signal separated from the imaging signal; and a color difference signal amplification circuit that amplifies a color difference signal formed from the color signal. and controlling the gain of the luminance gamma correction circuit and the gain of the color gamma correction circuit and/or the color difference signal amplification circuit using the smear information signal from the detection means to reduce smear. A smear correction circuit in a featured imaging signal processing device.