JPH11346326A - Digital ccd camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an output of an image without a sense of incongruity by reducing a noise component at a low illuminance, recognizing an object clearly and quickening convergence of an automatic iris even when the lightness is rapidly changed. SOLUTION: A digital signal processing circuit 4 processes a video signal from a CCD image pickup element 1 to provide an output of a luminance signal Y and a color difference signal C to a signal synthesis circuit 5 and gives a control signal to the CCD image pickup element 1, a signal amplifier circuit 2 and an A/D converter 3 to control the color, the image quality and the iris or the like. A CPU 6 controls analog automatic gain control of the signal amplifier circuit 2 and an electronic shutter and digital automatic gain control of the digital signal processing circuit 4. A chroma gain and an enhancer level are changed largely at a low illuminance through the control to reduce noise and to largely change a gain level of digital automatic gain control thereby increasing a gain of the digital automatic gain control and viewing an object clearly. In the case that the lightness is rapidly changed, a change amount of automatic iris is increased to provide an output of an image without a sense of incongruity following to the change amount.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a digital CCD camera, and more particularly, to an improvement of a digital CCD camera for improving the sensitivity and controlling the auto iris at a high speed.

[0002]

2. Description of the Related Art A conventional in-vehicle CCD camera has a drawback that a captured image of a target object is unclear and difficult to see at low illuminance, such as when the night light is not turned on. Further, in the above-mentioned CCD camera, the gain of the output video signal can be further increased. However, since the noise component is also amplified, there is a problem that the image becomes more difficult to see. Further, in the case of an in-vehicle CCD camera, if the brightness suddenly changes when the vehicle enters or exits a tunnel, the auto iris control cannot follow the change, and a black or white video signal is output for a while. There is also a problem.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, to obtain a clear image of a target even at low illuminance, and to follow a rapid change in brightness. Digital C that can output a video signal without discomfort
To provide a CD camera.

[0004]

In order to solve the above-mentioned problems, a digital CCD camera according to the present invention comprises a CCD image pickup device for picking up an image, and a signal which removes a noise component of an analog video signal from the CCD image pickup device. Signal amplifying means for amplifying the component, A / D converting means for converting the analog video signal component amplified by the means into a digital signal, and processing the digital signal and the CCD image sensor, signal amplifying means and A / D Digital signal processing means for controlling the D conversion means and outputting a chroma gain signal and a luminance signal; control means for controlling the analog automatic gain control of the signal amplification means and the digital automatic gain control of the digital signal processing means and the electronic shutter; Signal synthesizing means for synthesizing the chroma gain signal and the luminance signal and outputting a digital video signal, Serial control means summarized in that which is adapted to control the digital signal processing unit to perform the color processing and edge enhancement processing according to the signal level at the time of low illuminance.

In the digital CCD camera of the present invention,
The control means may control the digital signal processing means so as to increase the change amount of the iris of the CCD image pickup device when the brightness of the screen changes by a predetermined value or more for a predetermined time or more.

[0006]

FIG. 1 shows an embodiment of a digital CCD camera according to the present invention. In FIG. 1, reference numeral 1 denotes a CCD image sensor for capturing an image of a target, and 2 denotes a CCD image sensor 1
This is a signal amplifying circuit that amplifies the signal component by removing the noise component of the analog video signal from the camera. As the circuit 2, for example, a correlated double sampling signal amplifying circuit (Co-related double samplin) of an analog automatic gain control system is used.
g) is used. This circuit extracts a smooth continuous signal from the output signal of the CCD image sensor 1, and after analog automatic gain control processing, outputs an analog video signal from which noise components have been removed. Since the CCD image sensor alternately outputs noise and signal components containing noise, the S / N ratio is deteriorated if it is used as it is.
Receiving the output signal of the image sensor 1, the noise component of the signal is clamped to a constant voltage to remove low-frequency noise, and the signal component containing the noise is sampled and held to replace the noise with the signal component to convert the continuous signal. It is composed of a clamp circuit, a sample hold circuit, and an inverting amplifier.

An analog-to-digital (A / D) conversion circuit 3 converts an analog video signal into a digital video signal.

Reference numeral 4 denotes a digital signal processing circuit which receives luminance (Y) processing and color (R,
G, B) and outputs a luminance signal Y and a color difference signal C.
The circuit 4 digitally processes timings and data related to images such as color, image quality, white balance, and iris (aperture), and sends control signals to the respective elements and the circuits 1 to 3 for control.

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

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

In the digital CCD camera having the above-described configuration, parameters for amplifying a video signal include an electronic shutter and digital automatic gain control in the digital signal processing circuit 4 and an analog automatic gain control in the signal amplification circuit 2. Normally, however, digital automatic gain control is used only in special cases such as flicker cancellation. In the present invention, color processing and contour enhancement (enhancer) processing are performed at low illuminance in accordance with the signal level.

FIG. 2 shows a routine of the automatic iris control by the CPU 6. In FIG. 2, in step S1,
The CPU 6 reads necessary data from the digital signal processing circuit 4, and calculates the screen brightness in step S2.
In step S3, it is determined whether or not the electronic shutter is at maximum based on the calculated value. If it is maximum, analog automatic gain control of the signal amplifier circuit 2 is performed in step S4. The electronic shutter control of the circuit 4 is performed. After the analog automatic gain control, the chroma gain and the enhancer level are calculated in step S5.

The chroma gain amplifies the color signal, and the enhancer amplifies the outline of the image, and slightly increases or decreases in accordance with the change in the analog automatic gain of the signal amplifier circuit 2. If the level exceeds a certain level, the CPU 6 determines that the illuminance is low, and calculates the chroma gain and the Hansa level in step S5 to greatly reduce the level and increase the digital automatic gain of the digital signal processing circuit 4. As a result, the noise component is suppressed, and the image of the target object is made clear and clearly visible even at lower illuminance.

When the brightness changes abruptly, the CPU 6 follows the electronic shutter and analog automatic gain control routines shown in FIG. 3 in order to advance the auto iris control time and quickly converge to the optimum shutter speed. The digital signal processing circuit 4 and the signal amplification circuit 2 are controlled.

In FIG. 3, steps S10... S
n is a value obtained by comparing the calculated value of the screen brightness calculated in step S2 of the routine of FIG. 2 with each of the thresholds 1 to n. In step S10, the calculated value is larger than the threshold 1 (the brightest), or It is determined that Sn is smaller than the threshold value n (darkest), and steps S11 and S (n + 1)
In steps S12 and S (n + 2), the amount of change in the iris is set to be greatly increased, for example, from -40 to +40 only when it is determined that this state has continued for a certain period of time. The CPU 6 controls the signal amplifying circuit 2 and the digital signal processing circuit 4 by calculating the change amount of the electronic shutter and the analog automatic gain control so that the change amount is obtained. This hastens iris convergence.

[0016]

As described above, the digital C of the present invention is used.
According to the CD camera, a target object can be clearly recognized even at lower illuminance, and it can sufficiently follow a sudden change in brightness, so that an image without a sense of incongruity can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a flowchart showing an auto iris control routine according to the embodiment.

FIG. 3 is a flowchart showing an electronic shutter and automatic gain control control routine according to the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 CCD imaging element 2 Signal amplification circuit (CDS / AGC) 3 A / D converter 4 Digital signal processing circuit (DSP) 5 Luminance / color signal synthesis circuit (Y / C MIX) 6 Control signal (CPU)

Claims (2)

[Claims] A CCD image pickup device for picking up an image; a signal amplifying means for removing a noise component of an analog video signal from the CCD image pickup device and amplifying the signal component; and an analog video signal component amplified by the means. A / D conversion means for converting to a digital signal, digital signal processing means for processing the digital signal and controlling the CCD image pickup device, signal amplifying means and A / D conversion means, and outputting a chroma gain signal and a luminance signal. Control means for controlling the analog automatic gain control of the signal amplifying means and the digital automatic gain control of the digital signal processing means and the electronic shutter; signal synthesizing means for synthesizing the chroma gain signal and the luminance signal to output a digital video signal; The control means performs color processing and contour emphasis processing according to the signal level at low illuminance. Wherein the digital signal processing means is controlled.
camera. 2. The method according to claim 1, wherein the control means controls the digital signal processing means so as to increase a change amount of an iris of the CCD image pickup device when the brightness of the screen changes by a predetermined value or more for a predetermined time or more. 2. The digital CCD camera according to claim 1, wherein: