JPH04252575A - Video signal correction device - Google Patents

Abstract

PURPOSE:To utilize effectively a margin of a dynamic range to be caused by flair correction and to improve the contrast by correcting the flair generated in a video camera. CONSTITUTION:An image pickup signal is extracted through an AGC circuit 7 and a subtraction circuit 13. The subtraction circuit 13 shifts a DC component to correct flair. The image pickup signal level subject to flair correction is detected by an optical detector 15 via the subtractor circuit 13. A gain of the AGC circuit 7 and opening/closing of an iris 2 are controlled depending on the detection level. The image pickup signal level after flair correction is detected and the exposure is corrected to implement flair correction, then a margin of the dynamic range caused by the correction is utilized effectively.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video signal correction circuit suitable for use in, for example, correcting flare of a video camera.

0002

[Prior Art] In a video camera, light other than the target object enters the imaging surface due to reflections on the glass surface of the lens or inside the lens barrel, causing black parts of the image to stand out and contrast to decrease. be. Such a phenomenon is called a flare phenomenon.

[0003]Flare correction has conventionally been performed by detecting the DC level of a black portion of an image signal and shifting the level of the image signal by DC in accordance with the value of this black level.

That is, FIG. 2 shows an example of a conventional flare correction circuit. In FIG. 2, an image signal from a CCD image sensor 51 is supplied to an AGC amplifier 52. The output of the AGC amplifier 52 is supplied to a DC shift circuit 53 and also to a detection circuit 54. Detection circuit 5
At 4, the imaging signal level is detected. This detection circuit 54
The output of is supplied to the comparator 55. The comparator 55 is supplied with a reference level Vr. The output of the comparator 55 is supplied to the AGC amplifier 52. The output of the comparator 55 controls the gain of the AGC amplifier 52.

A DC shift signal is supplied to the DC shift circuit 53 from a black level detection circuit 58 . In the DC shift circuit 53, the DC level of the imaging signal level is shifted in accordance with this DC shift signal.

The output of the DC shift circuit 53 is supplied to a gamma correction circuit 56. The output of the gamma correction circuit 56 is output from the output terminal 57, and the black level detection circuit 58
supplied to A black level detection circuit 58 detects the black level of the imaging signal, and forms a DC shift signal corresponding to the black level of the imaging signal. This DC shift signal is supplied to the DC shift circuit 53.

A DC component generated by flare contained in the image signal from the CCD image sensor 51 is detected by a black level detection circuit 58 . Then, the black level detection circuit 58
A DC shift signal from the DC shift circuit 53 is supplied. The DC shift circuit 53 shifts the imaging signal level so that the DC component generated by flare is canceled. This corrects flare.

[0008]

By the way, when the DC level of the imaging signal is shifted in accordance with the black level of the imaging signal in the DC shift circuit 53 to remove the DC component caused by flare, the There is more room in the dynamic range of the imaging signal. In other words, when the DC level of the video signal is lowered by flare correction, the imaging signal level is lowered by that amount. Therefore, the amplitude of the imaging signal can be increased. If the amplitude of the imaging signal can be increased, the contrast will be improved.

However, in the past, AGC control
The signal level of the GC amplifier 52 is detected by the detection circuit 54,
The configuration is such that the gain of the AGC amplifier 52 is controlled according to this detection level. In this case, the amplitude of the imaging signal is determined by the output of the AGC amplifier 52, and the imaging signal after flare correction is not reflected. For this reason, it is not possible to effectively utilize the dynamic range margin created by flare correction. Therefore, even if the flare component is removed, the contrast cannot be improved.

[0010] Accordingly, an object of the present invention is to provide a video signal processing circuit that can remove flare components, effectively utilize the dynamic range, and improve contrast.

[0011]

[Means for Solving the Problems] This invention extracts an image signal through an AGC circuit and a DC shift circuit, and
This video signal correction device is characterized in that it detects the level of the imaging signal passed through the DC shift circuit, and performs exposure control in accordance with the level of the imaging signal passed through the DC shift circuit.

0012

[Operation] The signal level of the image signal after flare correction is detected by the optical detector 15, and exposure correction is performed using this detection output. In this way, the dynamic range margin created by removing the flare component can be effectively used, and the contrast can be improved.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the invention. In FIG. 1, a subject image is formed on the light receiving surface of a CCD image sensor 3 via a lens 1 and an iris 2. The opening and closing of the iris 2 is controlled by an iris motor 4. The iris motor 4 has a system controller 5.
An exposure control signal is supplied from the driver 6 through the driver 6 .

The output of the CCD image sensor 3 is transmitted to the AGC amplifier 7.
supplied to The gain of AGC amplifier 7 is controlled according to the output of D/A converter 8. An exposure control signal is supplied to the D/A converter 8 from the system controller 5. The output of the AGC amplifier 7 is the A/D converter 9
supplied to An A/D converter 9 digitizes the image signal from the CCD image sensor 3.

The output of the A/D converter 9 is transmitted to the divider circuit 10.
supplied to The output of ROM 11A and the output of ROM 11B are multiplied by a multiplication circuit 12, and the output of this multiplication circuit 12 is supplied to a division circuit 10. ROM11A and ROM
11B stores horizontal and vertical brightness correction data for each pixel of the CCD image sensor 3. The brightness unevenness of the image signal output from the A/D converter 9 is corrected by the division circuit 10. This performs shading correction.

The output of the division circuit 10 is supplied to a subtraction circuit 13. The subtraction circuit 13 is supplied with a DC shift value from the black level detection circuit 16 . A subtraction circuit 13 subtracts this DC shift value from the imaging signal level.

The output of the subtraction circuit 13 is transmitted to the gamma correction circuit 14.
and is also supplied to the optical detector 15. The output of the gamma correction circuit 14 is taken out from the output terminal 17 and is also supplied to the black level detection circuit 16. The black level of the imaging signal is detected by the black level detection circuit 16, and a DC shift value corresponding to the black level of the imaging signal is formed. This DC shift value is supplied to the subtraction circuit 13. The subtraction circuit 13 removes the DC component caused by the flare phenomenon.

The optical detector 15 detects the level of the imaging signal. This imaging signal level is supplied to the system controller 5. The system controller 5 generates an exposure control signal according to the imaging signal level. This exposure control signal is supplied to the driver 6, and
The signal is supplied to the D/A converter 8. Thereby, the opening and closing of the iris 2 is controlled according to the brightness of the image pickup signal, and the gain of the AGC circuit 7 is controlled.

In one embodiment of the present invention, the image signal from the CCD image sensor 3 is digitized by the A/D converter 9 and subjected to signal processing. For this reason, R.O.
Brightness correction data in the horizontal and vertical directions for each pixel of the CCD image sensor 3 is stored in M11A and ROM11B, and by supplying the multiplication outputs of ROM11A and ROM11B to the division circuit 10, the brightness of the image signal is adjusted. It is possible to correct unevenness (shasing correction). Also, C
Since the image signal from the CD image sensor 3 is digitized by the A/D converter 9 and subjected to signal processing,
The subtraction circuit 1 removes the DC component caused by the flare phenomenon.
It can be done in 3.

In one embodiment of the present invention, the optical detector 15 detects the signal level of the image signal after shading correction is performed in the division circuit 10 and flare correction is performed in the subtraction circuit 13, and this detection output is used to detect the signal level of the image signal. Exposure compensation is performed using Therefore, exposure control is performed according to the corrected imaging signal level, and the dynamic range can be effectively utilized.

[0021]

According to the present invention, the signal level of the image signal after flare correction is detected by the optical detector 15, and the detection output is used to perform exposure correction. Therefore, it is possible to improve the contrast by effectively utilizing the dynamic range margin created by removing the flare component.

[Brief explanation of the drawing]

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

FIG. 2 is a block diagram used to explain a conventional example.

[Explanation of symbols]

2 Iris 7 AGC circuit 13 Subtraction circuit 15 Optical detector 16 Black level detection circuit

Claims (1)

[Claims] 1. Taking out an imaging signal via an AGC circuit and a DC shift circuit, detecting the level of the imaging signal passed through the DC shift circuit, and exposing according to the level of the imaging signal passed through the DC shift circuit. A video signal correction device characterized in that it performs control.