JPH0670203A - Automatic noise suppressing image pickup device - Google Patents

Abstract

PURPOSE:To prevent the conspicuouness of noises even though a subject of low illuminance is photographed by correcting the amplification degree of the image pickup signal in its high band based on the amplification degree increase/ decrease detecting signal of the automatic gain control. CONSTITUTION:The signal obtained through a CCD 1 is amplified at a fixed degree by a preamplifier 2 and inputted to an AGC circuit 3. The circuit 3 outputs the signal which is inputted to a frequency characteristic correcting circuit 4 after the control of increase/decrease of the amplification degree and also an amplification degree increase/decrease detecting signal 5 which is inputted to the circuit 4 after detection of the increase/decrease of the amplification degree. Then the circuit 4 functions to reduce the amplification degree of a signal of high frequency if a high amplification degree of the signal is detected by the signal 5. Then the signal undergone the reduction of its high amplification degree is inputted to a gamma clamper CLP 6 which corrects the received signal in accordance with the monitor characteristic and outputs the corrected signal. A SYNC MIX 7 superposes a synchronizing signal on the signal received from the gamma.CLP 6 and outputs these signals from an image pickup device via a buffer 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus having an automatic gain control built-in, and more particularly to an automatic noise suppression image pickup apparatus for realizing a correction system for improving S / N which is deteriorated by the increase or decrease of the amplification degree of the automatic gain control. It is about.

[0002]

2. Description of the Related Art Some conventional image pickup apparatuses have an automatic gain control circuit for automatically increasing the gain of an amplifier when the illuminance of an object to be imaged is low and a sufficient level of signal cannot be obtained. An example of a conventional image pickup apparatus of this type will be described with reference to FIG. CCD as shown in FIG.
(Charge Coupled Device) 11
The signal obtained from the signal is input to the auto gain control (AGC) circuit 13 after being amplified by the preamplifier 12 to a certain degree, and the gain is adjusted to increase or decrease, and then input to the gamma (γ) clamp (CLP) 14 to the SYNC MIX 15. Then, the synchronization signal is superimposed and output from the image pickup apparatus via the buffer 16. In this case, as the amplification degree increases in the AGC circuit 13, the noise generated from the CCD 11 is simultaneously amplified and the noise increases, and the S / N deteriorates.

[0003]

In the conventional image pickup apparatus having the built-in auto gain control, when the subject becomes dark, correction is performed so that a constant output is obtained by increasing the amplification degree of the auto gain control. Although I am doing it, there was a problem that noise due to S / N deterioration was a problem. Further, when the subject becomes dark, the image pickup signal becomes extremely small and only noise is very problematic. The present invention has been made to solve such a problem, and when an image of a low-illuminance subject is imaged, the automatic gain control works to automatically eliminate noise due to S / N deterioration when the amplification degree becomes high. An object is to obtain a noise suppression image pickup device.

[0004]

SUMMARY OF THE INVENTION An automatic noise suppression image pickup apparatus of the present invention is an image pickup apparatus having an automatic gain control built-in, and a detection circuit for detecting an increase / decrease in amplification factor of the automatic gain control, and a detection circuit obtained by this detection circuit. A correction circuit that corrects the frequency characteristic by the detection signal of the auto gain control amplification degree and an interlocking means that interlocks the control voltage of the auto gain control and the correction of the frequency characteristic according to the increase or decrease of the auto gain control amplification degree. Be prepared.

[0005]

In the present invention, the amplification degree increase / decrease detection signal of the automatic gain control corrects the amplification degree in the high frequency band of the image pickup signal.

[0006]

1 is a block diagram showing an embodiment of an automatic noise suppression image pickup apparatus according to the present invention. In FIG. 1, reference numeral 1 is a CCD, 2 is a preamplifier for amplifying the signal obtained from the CCD 1, and 3 is an AGC circuit for adjusting the amplification degree by using the output of the preamplifier 2 as an input. A detection circuit for detecting increase / decrease in amplification degree is configured. Reference numeral 4 is a frequency characteristic correction circuit which receives the signal from the AGC circuit 3 and the amplification degree increase / decrease detection signal 5 as input, and the frequency characteristic correction circuit 4 uses the detection signal of the automatic gain control amplification degree obtained by the detection circuit to change the frequency. A correction circuit that corrects the characteristics is configured.
Further, the frequency characteristic correction circuit 4 cooperates with the AGC circuit 3 to form an interlocking means for interlocking the control voltage of the automatic gain control and the correction of the frequency characteristic according to the increase or decrease of the amplification degree.

Reference numeral 6 is a gamma (γ) clamp (CLP) that receives the output of the frequency characteristic correction circuit 4 and corrects and outputs it to match the monitor characteristics. Reference numeral 7 is the gamma (γ)
SYNC MIX which receives the output of the clamp (CLP) 6 and superimposes a synchronizing signal, and 8 is a buffer which receives the output of this SYNC MIX 7.

Next, the operation of the embodiment shown in FIG. 1 will be described. First, the signal obtained from the CCD 1 is amplified by the preamplifier 2 to a certain degree and then input to the AGC circuit 3. This A
The GC circuit 3 adjusts the increase / decrease of the amplification degree, and then outputs a signal to be inputted to the frequency characteristic correction circuit 4 and an amplification degree increase / decrease detection signal 5 to be inputted to the frequency characteristic correction circuit 4 upon detecting the increase / decrease of the amplification degree. Next, in the frequency characteristic correction circuit 4, when the amplification degree increase / decrease detection signal 5 has a high amplification degree, the signal from the AGC circuit 3 works so as to reduce the amplification degree of a signal in a high frequency band, and gamma (γ) Input to the clamp (CLP) 6.

This gamma (γ) clamp (CLP) 6
Then, the output is corrected and adjusted to match the characteristics of the monitor.
Then, the sync signal is superimposed on the SYNC MIX 7 and output from the imaging device via the buffer 8.

[0010]

As described above, according to the present invention, the amplification degree increase / decrease detection signal of the automatic gain control is used to correct the amplification degree in the high frequency band of the image pickup signal.
Since S / N does not deteriorate even when a subject with low illuminance is imaged, there is an effect that noise does not stand out even when the image pickup signal becomes extremely small. In this case, since the high frequency component is lowered, the resolution is lowered when the amplification degree is increased, but in most cases, the purpose can be achieved rather than the increase in noise for the monitoring purpose, and the effect is great. , Exert a remarkable effect.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an automatic noise suppression image pickup device according to the present invention.

FIG. 2 is a block diagram showing an example of a conventional imaging device.

[Explanation of symbols]

 1 CCD 2 Preamplifier 3 Auto gain control circuit 4 Frequency characteristic correction circuit 5 Amplitude increase / decrease detection signal 6 Gamma (γ) clamp (CLP) 7 SYNC MIX 8 Buffer

Claims (1)

[Claims] 1. An image pickup apparatus having a built-in auto gain control, wherein a detection circuit for detecting an increase / decrease in amplification degree of the auto gain control, and a frequency characteristic is corrected by a detection signal of the auto gain control amplification degree obtained by the detection circuit. An automatic noise suppression image pickup device, comprising: a correction circuit for controlling the automatic gain control;