KR100247318B1 - Brightness amending device of image signal - Google Patents

Abstract

The present invention relates to an apparatus for compensating for brightness of an image signal, comprising: an A / D converter (20) for sampling an electrical signal read out from an imaging unit (10) and storing it at an address designated by the microcomputer (90); A normal exposure signal memory (30) for storing a video signal in a normal exposure state digitally input by the A / D converter (20); An enlarged exposure signal memory 41 for storing an image signal through an aperture opened more than the normal exposure state and an image signal through an aperture opened less than the normal exposure state; and a reduced exposure signal memory 51; A normal signal extracting unit (42, 52) which reads out an image signal from the enlarged and reduced exposure signal memories (41, 51), and removes and outputs an image signal section above and below a predetermined level; A level detector (31) for detecting a signal level while reading an image signal from the normal exposure signal memory (30); A signal level adjusting unit (43, 53) for adjusting and outputting the level of the video signal extracted by the normal signal extracting unit (42, 52) to reflect the detected level; A signal synthesizer 60 for synthesizing the video signals each level adjusted by the signal level adjusting units 43 and 53; And a digital video signal processing unit 70 for processing the synthesized video signal with luminance and color signals, thereby reproducing both a dark region and a bright region having a large difference in brightness even when the image having a large difference in brightness is photographed for the entire image. It is a very useful invention that can obtain a natural video signal closer to the image detected by the real eye more.

Description

Video signal brightness correction device

The present invention relates to a brightness correction apparatus for a video signal, and more particularly, to a normal signal level section of a video signal input through an aperture that is forcibly enlarged and reduced open compared to an aperture opening in a normal exposure state. By adjusting to the level of the video signal in the exposed state and combining it, the brightness of the video signal can be reproduced so that both dark areas and bright areas having a large difference in brightness compared to the average brightness can be reproduced. Relates to a device.

In general, an image photographing device such as a camcorder adjusts the opening degree of the aperture (IRIS) according to the level of the luminance (Y) signal corresponding to the brightness component of the input image signal, thereby being reflected from the subject to be photographed and incident on the image pickup device. The amount of light (light received) is being controlled. That is, after setting the standard opening of the standard aperture corresponding to the amount of light of a predetermined value, if the amount of incident light is greater based on this, the aperture is further closed accordingly, and If the amount is smaller, the aperture is further opened accordingly to maintain the overall brightness of the video signal at a constant level.

FIG. 7 illustrates a configuration of a brightness correction apparatus for a conventional video signal which automatically adjusts an opening degree of an aperture according to the brightness of an input video signal. The aperture IRIS adjusts the amount of light incident from a subject. 110; An imaging unit (CCD) which detects a subject reflected light formed in each pixel arranged in a matrix form through the aperture 110 as an electrical signal using a photodetector and sequentially reads it in a horizontal and vertical direction by a scanning circuit. 10a; An image signal processing unit 120 for processing the electrical signal read out from the imaging unit 10a into an image signal of luminance and color signals; An AE (Auto Exposure) integrator 80a for integrating only the luminance signal components of the image signal processing unit 120 on a frame-by-frame basis; A microcomputer (μ-com) 90a outputting a control signal for adjusting the opening amount of the aperture 110 in correspondence to the integral value; And an aperture driver 100a outputting a driving voltage of the motor for opening the aperture 110 according to the output control signal. It was configured to include.

In the brightness correction apparatus of the conventional video signal configured as described above, the AE integrator 80a integrates the luminance (Y) component output from the video signal processor 120 in units of frames and calculates the magnitude value. In this case, the AE integrator 80a virtually divides the image pickup unit 10a as shown in FIG. 8, and then integrates the image signals corresponding to the divided regions for each image signal. Thereafter, the value is transmitted to the microcomputer 90a, and the microcomputer 90a determines the brightness of the currently output image by giving an appropriate weight to each integrated value. Accordingly, a subject located in a certain area (for example, a subject located in the center portion A2 of the divided areas) has a greater influence on the adjustment of the screen brightness.

The microcomputer 90a may determine a preset aperture opening amount corresponding to the determined brightness of the video screen, and then apply a control signal to the aperture driver 100a to open the aperture 110 further. Close more.

The light incident through the diaphragm 110 whose opening degree is adjusted in the above manner is adjusted to an appropriate amount of light and converted into an electrical signal through the image capturing unit 10a. The color signal is converted into an image signal, and this process is repeatedly performed, so that the brightness of the output signal can be properly maintained.

However, the brightness correction apparatus of the conventional video signal configured and operated as described above, although the AE integrator 80a distinguishes the captured image for each area and detects the respective brightness, Even if the brightness is determined by assigning a weight to the brightness of the area, the amount of opening of the aperture 110 affects the brightness of the entire image, so that the lighter or darker subject is lighter than the average brightness of the entire image. When an image is imaged together with the imaging unit 10a, there is a problem that a more accurate and natural video signal cannot be obtained for the corrugated body.

For example, as shown in FIG. 9, when a subject having a subject has a different brightness from each region, that is, when the center of the subject is bright as shown in FIG. 9A, the above-described brightness correction is performed. The amount of opening of the diaphragm 110 is reduced, and the electrical signal (finally the image signal) converted by the imaging unit 10a by the amount of light incident from a relatively dark subject surface is relatively constant compared to the average brightness of the overall image. The clip is clipped below the level so that it is not reflected on the final video signal and is displayed black on the screen as shown in FIG.

In addition, if the center of the subject is dark as shown in (a) of FIG. 9b, the opening amount of the aperture 110 is enlarged by the above-described brightness correction, and the subject is relatively bright compared to the average brightness of the overall image. The video signal converted by the image pickup section 10a by the amount of light incident from the image is too clipped because the luminance signal level is too large. Therefore, the bright subject is not reflected on the final image signal as shown in (b) of FIG. 9B, so that the bright subject is displayed in white on the screen, and thus the subject cannot be identified.

As a result, by simply adjusting the opening amount of the aperture by the brightness of each area of the video screen, especially when a dark subject and a bright subject exist on the screen at the same time, it is difficult to adjust the overall brightness to obtain a natural video signal as a whole. there was.

Accordingly, the present invention was created to solve the above problems, and the video signal enables to obtain a more natural video signal without losing the video signal even when a brighter or darker subject is captured than the brightness of the entire screen. The purpose is to provide a brightness correction device.

1 is a block diagram showing an embodiment of a brightness correction apparatus of an image signal according to the present invention,

2 is a block diagram showing another embodiment of the brightness correction device of an image signal according to the present invention,

FIG. 3 illustrates an imaginary surface having different degrees of brightness for each region.

4 is a diagram illustrating a video signal in a normal exposure state when the shot surface of FIG. 3 is photographed.

FIG. 5 shows an image signal when the subject of FIG. 3 is photographed in an enlarged exposure state.

6 shows a video signal when the subject of FIG. 3 is photographed in a reduced exposure state,

7 is a block diagram showing a conventional brightness correction device for a video signal,

FIG. 8 illustrates dividing the imaging unit into a virtual area to correct brightness of a subject.

FIG. 9 illustrates an image screen output when brightness of a screen having a difference in brightness for each region is corrected by using a conventional image signal brightness correction device.

* Explanation of symbols for main parts of the drawings

10, 10a: imaging unit (CCD) 10, 20a: A / D converter

30: normal exposure signal memory 31: level detector

41: expanded exposure signal memory 42, 52: normal signal extraction section

43, 53: signal level adjusting unit 51: reduced exposure signal memory

60: signal synthesizer 70: digital video signal processing unit

80, 80a: AE (Auto Exposure) Integrator 90, 90a: Microcomputer (μ-com)

100, 100a: aperture driving unit 110: aperture (IRIS)

120: image signal processing unit

According to an aspect of the present invention, there is provided a brightness correction apparatus for a video signal, comprising: level detecting means for detecting a level of a video signal input through an open aperture corresponding to brightness of the video signal; Fluctuation exposure signal storage means for storing an image signal input through the aperture forcibly applying a predetermined fluctuation amount to the aperture opening amount; Normal signal extracting means for removing excess and undersignal portions from the stored video signal in the variable exposure state and extracting only normal signals within a predetermined level range; And level adjusting means for adjusting and outputting the level of the extracted normal signal based on the detected video signal level.

An apparatus for compensating brightness of an image signal according to the present invention includes: an enlarged exposure signal storage means for storing an image signal input through an aperture that is more open than an aperture opening in a normal exposure state; Reduced exposure signal storage means for storing an image signal input through the aperture that is less open than the aperture opening in the normal exposure state; Normal signal extracting means for removing excess and undersignal portions from the stored video signals in the enlarged and reduced exposure states and extracting only normal signals within a predetermined level range, respectively; And video signal synthesizing means for synthesizing the extracted normal signals.

In the brightness correction apparatus of the video signal according to the present invention configured as described above, the level detection means is the level from the video signal of the normal exposure state input through the aperture which is automatically adjusted according to the brightness of the video signal Is detected.

The variable exposure signal storage means stores image signals input from the aperture which is forcibly enlarged and reduced open compared to the aperture opening in the normal exposure state, and the normal signal extracting means stores the signal stored in the variable exposure signal storage means. By removing the signal part above and below a certain level, only the normal signal within a certain level range is extracted.

At the same time, the level adjusting means adjusts the level of the extracted normal signal to match the level of the normal exposure video signal based on the level detected in the normal exposure state of the aperture, thereby reproducing the video signal in the normal exposure state. If not, the area below the average brightness and the area above the average brightness can be reproduced together.

Hereinafter, the configuration and operation of the brightness correction apparatus of the video signal according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram showing a part of a camcorder to which an embodiment of an apparatus for correcting brightness of an image signal according to the present invention is applied, which is an AE (Auto Exposure) integrator 80 performing the same operation as in the prior art; Microcomputer (μ-com) 90; Aperture driving unit 100; Aperture (IRIS) 110; An imaging unit (CCD) (10); and an A / D converter (20) for sampling and storing an electrical signal read out from the imaging unit (10) at an address designated by the control of the microcomputer (90); A normal exposure signal memory (30) for storing a video signal in a normal exposure state digitally input by the A / D converter (20); An enlarged exposure signal memory 41 for storing an image signal through an aperture more open than the normal exposure state and an image signal through an aperture less open than the normal exposure state; and a reduced exposure signal memory ( 51); A normal signal extracting unit (42, 52) for reading out the video signals from the enlarged and reduced exposure signal memories (41, 51), respectively, and removing and outputting video signal sections above and below a predetermined level; A level detector (31) for detecting a level of the signal while reading an image signal from the normal exposure signal memory (30); A signal level adjusting unit (43, 53) for adjusting and outputting the level of the video signal output from the normal signal extracting unit (42, 52), respectively, reflecting the level detected by the level detector (31); A signal synthesizer 60 for synthesizing the video signals level adjusted by the signal level adjusting units 43 and 53, respectively; And a digital video signal processor 70 for processing the synthesized video signal with luminance and color signals. It is configured to include.

In the brightness correction apparatus of the video signal according to the present invention configured as described above, the AE integrator 80 integrates the luminance signal component of the previous video signal output from the digital video signal processor 70 on a frame-by-region basis. Calculates a brightness value of the microcomputer 90, determines a preset aperture opening amount corresponding to the calculated brightness value of the video screen, and then applies a control signal according to the aperture driver 100 to the aperture 110. By controlling the opening degree of, the brightness of the image signal output from the digital image signal processor 70 can be properly maintained at all times as in the conventional apparatus.

On the other hand, the microcomputer 90, during the operation of adjusting the opening degree of the aperture 110, forcing the control signal to open more than the opening degree of the aperture in the normal exposure state to the aperture driver 100. The enlarged exposure signal memory having an address different from that of the video signal in the normal exposure state while controlling the opening degree of the diaphragm 110 by controlling the opening degree, and controlling the A / D converter 20. Output to (41).

In the case of photographing a surface having a brightness state as shown in FIG. 3, since a large amount of light is incident on the imaging unit 10 due to the enlarged opening of the aperture 110, the light is incident. As shown in FIG. 5A, the digital image signal stored and read in the enlarged exposure signal memory 41 is an image of which the level is increased at a constant value in each section compared to the image signal in the normal exposure state shown in FIG. 4. It becomes a signal.

The normal signal extracting unit 42 removes the read-out video signal from a too bright portion corresponding to a signal section of a predetermined level or more and a dark portion corresponding to a time-division section of a predetermined level or less, and then removes the normal image within a predetermined level range. Only the signal is extracted. Accordingly, the signal of the high intensity D section (refer to FIG. 4B) to be removed in the normal exposure state as well as the signal of the C section to be detected in the normal exposure state is removed together, as shown in FIG. 5B as a whole. Only signals within a certain level range are extracted. As compared with FIG. 4B, the extracted video signal is a video signal in a normal exposure state, it can be seen that the signal component of section B is reproduced without being removed by an under clip.

The signal level adjusting unit 43 has a level in the extracted expanded exposure image signal (FIG. 5B) and a corresponding section signal level detected by the level detector 31 after being read from the normal exposure signal memory 30. In order to reduce the difference between and at a predetermined ratio, the level value L ₀ of the A and B section video signals reproduced in the enlarged exposure video signal is multiplied by α (0 <α <1), and the level detector 31 is By multiplying the output level L _N by (1-α) and adding each other, the enlarged exposure video signal is lowered to an appropriate ratio (see FIG. 5C).

In addition, the microcomputer 90 controls the opening degree of the aperture 110 by forcibly applying a control signal to the aperture driving unit 100 to open the aperture less than the opening degree of the aperture in the normal exposure state. The write address of the A / D converter 20 is controlled to output and store the digitally converted video signal to the reduced exposure signal memory 51.

When the diaphragm 110 is reduced and opened, a smaller amount of light is incident on the image capturing unit 10 than in a normal exposure state, and thus an image signal stored and read in the reduced exposure signal memory 51 is illustrated in FIG. 6A. As shown in FIG. 4, the image signal is reduced in all levels by a predetermined value compared to the video signal in the normal exposure state shown in FIG. 4.

The normal signal extracting unit 52 also extracts the normal video signal within a predetermined level range by removing the signal sections above the predetermined level and below the predetermined level, respectively, as in the case of enlarged opening. In addition to the signal of section B of low luminance (see FIG. 4b) removed from the clip state, the signal of section A detected during normal exposure is also removed, so that only signals within a certain level range as shown in FIG. Extracted. Compared to FIG. 4B, which is a video signal in a normal exposure state, it can be seen that the signal component of the section D is reproduced without being removed by an excessive clip.

The signal level adjusting unit 53 includes a level of the extracted reduced nozzle image signal (FIG. 6B), a corresponding section signal level detected by the level detector 31 after being read from the normal exposure signal memory 30. In order to reduce the difference of the video signal by a predetermined ratio, the level value of the C and D section video signals reproduced in the reduced nozzle video signal is expressed by the formula L _U · β + L _N (1-β) (L _U : reduced nozzle video signal). Level, L _N : the level of the normal exposure video signal, β: the value between 0 and 1 to be set) to increase to an appropriate ratio (FIG. 6C).

As a result, in the image signal output from the signal level adjusting unit 43 in the enlarged nozzle state, the section B, which has been removed from the clip in the normal exposure state, is reproduced and output to the image signal output from the signal level adjusting unit 53 in the reduced exposure state. Since the D section to be clipped is reproduced and output in the normal exposure state, when each image signal is finally synthesized through the signal synthesizer 60, the digital image signal processing unit outputs a natural image signal expressing all the brightness levels of the photographed subject. You can get it through 70.

FIG. 2 illustrates another embodiment of a brightness correction apparatus of an image signal according to the present invention. In the configuration of the embodiment of FIG. 1, the level of the enlarged and reduced exposure image signal is adjusted according to the brightness of the normal exposure image signal. The normal exposure signal memory 30, the level detector 31, the signal level adjusting units 43 and 53, and the AE integrator 80 and the microcomputer 90 which automatically correspond to the opening degree of the aperture to the signal brightness. Will remove the associated program.

In general, when there is no change in overall screen brightness during shooting, such as in a surveillance system using a time-lapse video recording / reproducing apparatus, a component block for automatically adjusting the opening degree of the aperture 110 and a signal level adjustment according to brightness are controlled. Since it is not necessary to use the configuration block for the aperture block, it is removed, and the aperture is repeatedly forced to repeatedly enlarge and reduce the aperture amount calculated on the basis of the initially set screen brightness. After storing the video signal using only the enlarged exposure signal memory 41 and the reduced exposure signal memory 51, the normal signal extractors 42 and 52 extract the video signals within a predetermined level, respectively. By compositing, a natural image that expresses all the brightness levels of the subject in the place where the device is installed at a lower cost. The call can be obtained.

The brightness correction apparatus of the image signal according to the present invention configured and operated as described above can obtain a clear signal for both the bright and dark portions of the signal having a large difference in brightness with respect to the entire image, so that the image is detected with real eyes. In addition to obtaining a natural video signal close to, it is possible to obtain the same effect as above but at a lower cost when applied to a recording device (time-lapse video recording system, etc.) used in a place where the brightness of the subject to be photographed is small. It is a useful invention that can be implemented.

Claims (3)

Level detection means for detecting the level of the video signal input through the aperture opened in correspondence with the brightness of the video signal; Fluctuation exposure signal storage means for storing an image signal input through the aperture forcibly applying a predetermined fluctuation amount to the aperture opening amount; Normal signal extracting means for removing excess and undersignal portions from the stored video signal in the variable exposure state and extracting only normal signals within a predetermined level range; And And a level adjusting means for adjusting and outputting the level of the extracted normal signal based on the detected video signal level. The method of claim 1, The variable exposure signal storage means separately stores and stores the image signal input through the aperture more open than the normal exposure state and the image signal input through the less open aperture, The normal signal extracting means extracts normal signals within a predetermined level range from the divided and stored video signals, respectively. And the level adjusting means adjusts the level of each extracted video signal based on the stored video exposure level in the normal exposure state and outputs the synthesized output. Enlarged exposure signal storage means for storing an image signal input through the aperture more open than the aperture opening in the normal exposure state; Reduced exposure signal storage means for storing an image signal input through the aperture that is less open than the aperture opening in the normal exposure state; Normal signal extracting means for removing excess and undersignal portions from the stored video signals in the enlarged and reduced exposure states and extracting only normal signals within a predetermined level range, respectively; And And a video signal synthesizing means for synthesizing the extracted normal signals.

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