JPH06303465A - Image flicker correcting circuit - Google Patents

Abstract

PURPOSE:To correct the variance of luminance between the frames and the fields of an image that is generated in a place other than a point where a video image linearly changes. CONSTITUTION:The odd fields of an interlace system of a video image signal are fetched into an odd field memory 8, and the even fields of the interlace system are fetched into an even field memory 9. Then an odd field luminance averaging unit 10 and an even field luminance averaging unit 11 calculate the odd and even field luminance average values respectively as the flicker correction values. A subtractor 6 calculates the difference between both average values, and this calculated difference is added to the original video signal by an adder 7. Thus a corrected digital video signal is acquired.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a correction circuit for correcting image flicker in an image pickup device.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram of a conventional image flicker correction circuit. In FIG.
Reference numeral 9 is a multiplier, and 7 is an adder.

In the figure, R for correcting flicker of an image
The multiplier 19 multiplies the correction data read from the correction data storage 18 such as the OM and the digital video image signal. This output and the digital video image signal are added by the adder 7, and the corrected video image signal is output.

[0004]

Since the conventional image flicker correction circuit is configured as described above, complete correction cannot be performed in a region where the image signal and the flicker level are non-linear, so that the frame or field between images cannot be corrected. There remains a flicker that the brightness varies.

The present invention has been made to solve the above problems, and an object thereof is to correct flicker in an image in real time even when the image signal does not change linearly.

[0006]

An image flicker correction circuit according to the present invention captures a video image signal in a frame memory, calculates an average luminance in the captured frame, and calculates an average luminance value between frames or one after that. The flicker is detected by comparing with the average luminance value of the frame, and the difference in the luminance value is added to the video image signal for correction.

Further, an image flicker correction circuit according to another embodiment takes in an odd field and an even field separately in an interlace system of a video image signal into a field memory and adds a difference in luminance value between the fields to the video image signal. To correct.

An image flicker correction circuit according to another embodiment samples a black level detection image area of an analog signal output from a solid-state image sensor at timings of odd fields and even fields in the interlace system, and determines the voltage level The difference is added to the output of the solid-state image sensor to correct it.

[0009]

According to the image flicker correction circuit of the present invention,
Since the flicker level can be detected and corrected in real time, an improved and stable video image can be output even when the flicker level of the solid-state image sensor is non-linear.

[0010]

EXAMPLES Example 1. 1 is a block diagram showing an embodiment of the present invention, in which 1 is a frame memory, 2 is a luminance averaging device in a frame memory, 3 is a luminance storage device, 4 is an interframe luminance averaging device, and 5 is a flicker determination. And 7 is an adder.

In the figure, a digital video image is captured in the frame memory 1, and the average value of the captured brightness values in the frame memory is calculated as the brightness averager 2 in the frame memory.
Calculate with. This brightness average value is stored in the brightness storage unit 3, and the inter-frame brightness average unit 4 calculates the average value. The flicker judging unit 5 compares the average value calculated by the inter-frame luminance averaging unit 4 with the average value calculated by the in-frame luminance averaging unit 2, and if the difference is a certain value or more and the current frame If the difference between the average luminance value and the average luminance value of the next frame is equal to or more than a certain value, it is determined that flicker has occurred, and otherwise it is determined that flicker has not occurred. If the flicker determiner 5 determines that flicker has occurred, it outputs the difference between the average value calculated by the inter-frame brightness averager 4 and the average value calculated by the frame memory brightness averager 2, and the flicker is not detected. If it is determined to occur, zero level is output. This output and the digital video image are added by the adder 7,
Output the corrected image.

Example 2. FIG. 2 is a configuration diagram showing another embodiment. In the figure, 6 is a subtractor, 8 is a field memory for odd fields in the interlace system, 9 is a field memory for even fields in the interlace system, and 10 is in an odd field memory. Brightness averager,
Reference numeral 11 is a luminance averager in the even field memory.

In the figure, a digital video image is taken into a field memory 8 for odd fields in the interlace system and a field memory 9 for even fields in the interlace system. The luminance averaging device 10 in the odd field memory outputs the average value of the outputs of the field memory 8 for the odd field as the average value of the odd field. The luminance averaging device 11 in the even field memory outputs the average value of the outputs of the field memory 9 for even fields as the even field average value. The subtractor 6 subtracts the difference between this output and the average value of the odd-numbered field,
This output and the digital video image are added by the adder 7 and the corrected image is output.

Example 3. 3 is a block diagram showing an embodiment of the present invention, in which 12 is a solid-state image sensor, 13 is an odd field sample hold in the interlace system, 14 is an even field sample hold in the interlace system, and 15 is a first A differential operational amplifier, 16 is an analog switch, and 17 is a second differential operational amplifier.

In the figure, the analog output signal of the image area for black level detection of the solid-state image pickup device 12 is sampled by an odd field sample hold 13 in the interlace system and an even field sample hold 14 in the interlace system at the timing of the odd field and the even field. Hold the sample. This output level difference is calculated by the first differential amplifier 15 and output. The analog switch 16 turns on the output of the first differential amplifier 15 only in the odd field. Also, 0 is output in the even field. The difference between this output and the output of the solid-state image sensor 12 is calculated by the second differential amplifier 17, and the corrected image is output.

[0016]

As described above, according to the present invention, even if the image signal does not change linearly, flicker in the image can be corrected in real time, so that an image flicker correction circuit capable of outputting an image without flicker can be obtained. .

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of an image flicker correction circuit of the present invention.

FIG. 2 is a configuration diagram showing a second embodiment of an image flicker correction circuit of the present invention.

FIG. 3 is a configuration diagram showing a third embodiment of an image flicker correction circuit of the present invention.

FIG. 4 is a configuration diagram showing an embodiment of a conventional image flicker correction circuit.

[Explanation of symbols]

 1 frame memory 2 luminance averaging device in frame memory 3 luminance memorizing device 4 luminance averaging device between frames 5 flicker judging device 6 subtractor 7 adder 8 field memory for odd field 9 field memory for even field 10 luminance averaging device in odd field memory 11 Luminance Averager in Even Field Memory 12 Solid-state Image Sensor 13 Sample Hold for Odd Field 14 Sample Hold for Even Field 15 First Differential Amplifier 16 Analog Switch 17 Second Differential Amplifier 18 Correction Data Storage 19 Multiplier

Claims (3)

[Claims] 1. A frame memory for capturing a digital video image in an image pickup apparatus, an in-frame average brightness unit for calculating an in-frame average brightness value in the frame memory, and an in-frame average brightness value for storing the data in real time. A brightness storage unit to be updated, an inter-frame average brightness unit that calculates the stored inter-frame average brightness value, and a flicker that outputs the presence or absence of flicker and the difference based on the difference between the intra-frame average brightness value and the inter-frame average brightness value. A judgment device,
An image flicker correction circuit comprising an adder for adding this output and the digital video image 2. In an imaging device, a field memory for an odd field for capturing a digital video image of an odd field in an interlace system, a luminance averaging device in an odd field memory for calculating an average value of luminance in the field of the output, and an interlace A field memory for an even field which takes in a digital video image of an even field in the system, an even field memory brightness averaging device for calculating an average value of brightness in the field of this output, and an output of the odd field memory brightness averaging device. A flicker correction circuit comprising: a subtractor for subtracting a difference from the output of the luminance averaging device in the even field memory; and an adder for adding the digital video image and the output of the subtractor. 3. An odd field sample hold for sampling a video area for black level detection of an odd field analog signal in an interlace system of a solid-state image sensor output, and an even field in an interlace system of the solid-state image sensor output in an image pickup apparatus. An even field sample and hold that samples the black level detection video area of the analog signal, a first differential operational amplifier that outputs the two types of voltage level differences sampled and held, an analog switch that turns this output on and off, and A second for outputting a difference between an output and an output of the solid-state image sensor
Image flicker correction circuit including the differential operational amplifier