JP3501984B2 - Digital CCD camera - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital CCD camera with reduced noise components.

[0002]

2. Description of the Related Art Conventionally, a digital CCD camera divides an image pickup screen into several areas, and determines the illuminance environment such as backlight or forward light based on the iris data of each area and is suitable for a shooting scene. Iris is controlled.

This data detection screen division is shown in FIG.
Is set by the data areas of horizontal division H1 to H6 as shown in FIG. 5 and vertical division V1 to V5 as shown in FIG. Each area data is determined by the setting of the vertical divisions V1 to V5, and is input from the digital signal processing circuit to the control circuit (CPU) at the timing of the pulse signals EP1 to EP3 output from the digital signal processing circuit.

[0004]

However, in the conventional digital CCD camera described above, the pulse signals EP1 to EP3 become noise components of the output image when input from the digital signal processing circuit to the control circuit. There is a problem. The noise component appears more prominently as shown in FIG. 6 when the output screen becomes dark.

According to the present invention, the operation of the analog automatic gain control device is determined, and when the analog automatic gain control device is ON, the division / formation of the screen is changed to change the timing of the pulse signal. The objective is to reduce the noise component during illuminance environment shooting so that it is not noticeable.

[0006]

SUMMARY OF THE INVENTION The present invention has been devised to solve the above-mentioned problems of the prior art. The invention of claim 1 is directed to an imager for picking up an image, and an analog from the imager. A signal amplifier circuit for removing a noise component of a video signal and amplifying the signal component, an analog / digital converter for converting an analog video signal component amplified by the signal amplifier circuit into a digital signal, and processing the digital signal. A digital signal processing circuit that controls the imager, the signal amplification circuit, and the analog-digital converter to output a color difference signal and a luminance signal, an analog automatic gain control of the signal amplification circuit, and a digital automatic gain control of the digital signal processing circuit. And a control circuit for controlling the electronic shutter, and a luminance / color signal for synthesizing the color difference signal and the luminance signal to output a video signal In digital CCD camera consisting of a formed circuit, said control circuit, when the analog automatic gain control is activated, consisting of converting the data segmentation of iris control in a predetermined division shape.

According to a second aspect of the present invention, in the invention according to the first aspect, the control circuit determines the operation of the analog automatic gain control, and moves the data area division of the iris control to the edge of the screen. Become.

According to a third aspect of the present invention, in the invention according to the first or second aspect, the control circuit divides a vertical division of an iris control data area into upper and lower edges of a screen during low illuminance when analog automatic gain control is activated. This is done by dividing the area into parts.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to FIGS. In FIG. 1, reference numeral 1 is an imager 1 including a CCD image pickup device for picking up an image. Two
Is a signal amplifier circuit 2 for removing a noise component of the analog video signal from the imager 1 and amplifying the signal component.
The signal amplification circuit 2 is, for example, a correlated double sampling signal amplification circuit (Co-r) of an analog automatic gain control method.
Elated double sampling is used.

The signal amplification circuit 2 extracts a smooth continuous signal from the output signal of the imager 1, performs analog automatic gain control processing, and then outputs an analog video signal from which noise components have been removed. Since the CCD image pickup device of the imager 1 alternately outputs a noise component and a signal component including the noise component, the S / N ratio is deteriorated. The correlated double sampling signal amplification circuit of the signal amplification circuit 2 is the imager 1
Of the output signal, the noise component of the output signal is clamped to a constant voltage to remove low-frequency noise, and the signal component containing noise is sample-held to replace the noise with the signal component and generate a continuous signal. To generate. The signal amplification circuit 2 includes a clamp circuit, a sample hall circuit, and an inverting amplifier.

An analog / digital (A / D) converter 3 converts an analog video signal into a digital video signal.

Reference numeral 4 denotes a digital signal processing circuit 4, which, when the digital video signal is input, performs luminance (Y) processing and color (R, G, B) processing and outputs a luminance signal Y and a color difference signal C. . Further, the digital signal processing circuit 4 is
Timing and data relating to images such as white balance and iris (aperture) are digitally processed, and control signals are sent to each element, the imager 1, the signal amplification circuit 2, and the analog / digital (A / D) converter 3. Control.

Reference numeral 5 denotes a luminance / color signal synthesizing circuit 5 which synthesizes the luminance signal (Y) and the color difference signal (C) and outputs a video signal to the video 7.

Reference numeral 6 is a control circuit (CP) for controlling the operations of the analog automatic gain control of the signal amplification circuit 2 and the electronic shutter of the digital signal processing circuit 4, and the digital automatic gain control.
In U), a microcomputer is used.

In the digital CCD camera having the above-mentioned structure, the parameters for amplifying the video signal include the electronic shutter and digital automatic gain control in the digital signal processing circuit 4 and the analog automatic gain control in the signal amplifying circuit 2. The digital automatic gain control performs color processing and edge enhancement (enhancer) processing according to the signal level when the illuminance is low.

Next, the operation of the present invention will be described in detail with reference to FIG. The screen noise is generated on the electric circuit and control. For example, when the screen is divided into areas, the video signal is controlled by the pulse signal from the digital signal processing circuit 4, so that the pulse signal may be superimposed on the video signal as a noise component. . Particularly, a popping noise component appears in the horizontal division. The pulse signals that cause the noise are vertical division V3 and vertical division V3.
5 is a pulse that determines the line.

When a dark place is photographed, a noise component is mixed and the noise is noticeable. In this case, control is performed to convert the vertical division V3 and the vertical division V5 into divisions that move to the upper end and the lower end on the screen.

The trigger for changing this division is the analog gain ON in step S2. Step S2
Then, it is determined whether the analog gain is ON or OFF. When the control circuit 6 determines from the signal of the digital signal processing circuit 4 that the analog gain is ON in step S2, steps S3 and S in the YES direction are performed.
5, the division control is performed by moving the vertical division V3 and the vertical division V5 to the upper and lower ends of the screen. In addition, the step S
When the control circuit 6 determines from the signal of the digital signal processing circuit 4 that the analog gain is OFF in step 2, the process proceeds to steps S4 and S5 in the NO direction to perform normal control.

In step S3, a dark scene or the like is photographed, and the ON state of the analog automatic gain control device is turned on by the control circuit 6.
When it is determined that the screen is divided, the screen is divided as shown in FIG. In step S3, the set values of the vertical division V3 and the vertical division V5 that cause a noise component are moved to the upper end of the vertical division V3 and the lower end of the vertical division V5 on the output screen. When shooting in a dark place, the level of the video signal decreases, but the analog gain is used to increase the level of the video signal. As a result, the noise on the screen is
As shown in FIG. 4, it moves to the upper and lower ends of the screen, and the visibility of the image is also improved.

In step S4, considering all scenes such as when a bright scene is photographed, the above-mentioned FIG.
Screen division is performed as in the conventional case shown in FIG.

[0021]

According to the present invention, the control circuit converts the iris control data area into a predetermined area division, so that noise can be reduced and the image can be made clear to improve the visibility of the image. The digital CCD camera of the present invention can maintain the image signal level in the case of shooting in a dark place at the same level as the image in a case of shooting in a bright place to eliminate the variation in the sharpness of the image. it can.

[Brief description of drawings]

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

FIG. 2 is a flowchart showing an embodiment of the present invention.

3A and 3B are diagrams showing an embodiment of the present invention, in which FIG. 3A is a timing chart showing a pulse shape, and FIG. 3B is an explanatory diagram showing area division of a screen when a dark scene is photographed.

FIG. 4 is an explanatory diagram showing an image when noise is reduced in the drawings showing the embodiment of the present invention.

5A and 5B are diagrams showing a conventional technique, in which FIG. 5A is a timing chart showing a pulse shape, and FIG. 5B is an explanatory diagram showing area division of a screen when a dark scene is photographed.

FIG. 6 is a diagram showing a conventional technique and is an explanatory diagram showing an image when noise occurs.

[Explanation of symbols]

1 imager 2 signal amplifier circuit 3 analog-digital converter 4 Digital signal processing circuit 5 Luminance / color signal synthesis circuit 6 control circuit V3, V5 vertical division

Claims (3)

(57) [Claims] 1. An imager (1) for picking up an image, a signal amplifier circuit (2) for removing a noise component of an analog video signal from the imager (1) and amplifying the signal component, and the signal amplifier circuit (2). ), An analog / digital converter (3) for converting the analog video signal component amplified by the above) into a digital signal, and the imager (1), the signal amplification circuit (2) and the analog / digital converter for processing the digital signal. A digital signal processing circuit (4) for controlling (3) to output a color difference signal and a luminance signal, and an analog automatic gain control of the signal amplification circuit (2) and a digital automatic gain control of the digital signal processing circuit (4). And a control circuit (6) for controlling the electronic shutter, and a luminance / color signal synthesizing circuit (5) for synthesizing the color difference signal and the luminance signal and outputting a video signal. In Tal CCD camera, wherein the control circuit (6), when the analog automatic gain control is activated, a digital CCD camera, characterized by converting the data segmentation of iris control in a predetermined division shape. 2. The invention according to claim 1, wherein the control circuit (6) discriminates the operation of the analog automatic gain control, and divides the image area for detecting the iris control data into the end portion of the screen. A digital CCD camera that can be moved. 3. The invention according to claim 1 or 2, wherein the control circuit (6) displays a vertical division (V3, V5) of an iris control data area on a screen during low illuminance when analog automatic gain control operates. A digital CCD camera characterized by being divided into regions which are moved to the upper and lower ends.