KR940000361B1 - Contrast revision apparatus in camcorder - Google Patents

Abstract

The contrast corrector includes a controller for controlling the operation of a video camera and generating a gamma correction control signal, a driving signal generator for outputting a CCD driving control signal, a chrominance separation control signal, a white balance control signal, and an encoding control signal, a CCD for photoelectrically converting the image and outputting a video signal, an amplifier for amplifying the video signal, a chrominance separator for separating chrominance signals and luminance signal, a gamma corrector for gamma-correcting the luminance signal and chrominance signals, a diaphragm driving portion for driving the diaphragm by receiving the gamma-corrected luminance signal,an encoder for encoding the white-balance- corrected luminance signal and chrominance signals, and a contrast discriminator for discriminating the contrast of the gamma- corrected luminance signal.

Description

Contrast Correction Device by Changing Gamma Correction Factor

1 is a block diagram of a conventional video camera block.

2 is a CCD structure diagram of a conventional mid-point metering.

3 is a characteristic diagram of a conventional gamma correction output signal.

4 is a conventional gamma correction characteristic curve.

5 is a block diagram of a video camera block according to the present invention.

6 is a concrete circuit diagram of the contrast determining unit 12 in FIG.

7 is a concrete circuit diagram of the gamma supplementary government 8 of FIG.

8 is a CCD structure diagram of split metering according to the present invention.

9 is a gamma correction characteristic curvature according to the present invention.

10 is a characteristic diagram of a gamma correction output signal according to the present invention.

* Explanation of symbols for main parts of the drawings

1: control unit 2: signal generating unit

3: lens 4: aperture

5: CCD 6: amplifier

7: color separation unit 8: gamma correction

9: aperture driving unit 10: white balance correction unit

11: encoder 12: contrast determination unit

The present invention relates to a contrast correction apparatus of a video camera, and more particularly, to a contrast correction apparatus capable of automatically adjusting contrast by changing a gamma (γ) correction coefficient according to a screen state.

In general, a video camera refers to a device that stores a still image of a predetermined subject in a memory device and reproduces the same. The output of the video camera can be printed on a video printer or displayed on a monitor or the like, and the memory device uses a floppy disk.

FIG. 1 is a block diagram of a conventional video camera and includes a CCD driving control signal, a color separation control signal, and a white balance control signal according to an output signal of the control unit 1 and the output signal of the control unit 1. A driving signal generator 2 for outputting an encoding control signal, a lens 3 for forming an image of a subject, an aperture 4 for adjusting an exposure amount of a camera, the lens 3, and an aperture 4 CCD 5 for outputting an image signal by photoelectric conversion of the image of the object to be imaged through the image, amplifying section 6 for amplifying the video signal output from the CCD 5, and in the amplifying section 6 A color separation unit 7 for inputting an amplified video signal to separate the luminance signal Y and the color signals RY and BY according to the driving signal of the driving signal generation unit 2, and the color separation unit 7; Gamma (γ) to input luminance signal (Y) and color signal (RY, BY) separated from A diaphragm driver 9 for inputting the gamma correction luminance signal Y at the gamma gamma correction part 8 to drive the diaphragm 4, and the gamma correction part 8) the white balance corrector 10 for inputting the gamma corrected luminance signal Y and the color signals RY and BY to correct the white balance and output the white balance correction; And an encoder 11 for encoding the white balance corrected luminance signal Y and the color signals RY and BY, and outputting them as a composite video signal.

2 is a CCD structure diagram of conventional mid-point metering.

Referring to FIGS. 1-2, the operation of the conventional video camera is described. The CCD 5 which inputs the subject image incident through the lens 3 and the aperture 4 is photoelectrically converted to output a composite image signal. Done. The composite image signal photoelectrically converted by the CCD 5 is amplified and output through the amplifier 6. The color separation unit 7 for inputting the composite image signal amplified by the amplifying unit 6 separates the luminance signal Y and the color signals RY and BY by the control signal of the driving signal generator 2. Will print. The gamma correction unit 8 for inputting the luminance signal Y and the color signals RY and BY separated by the color separation unit 7 performs gamma correction as shown in FIG. 4 with a gamma correction coefficient of 0.45. Will print.

The white balance corrector 10 inputting the gamma correction luminance signal Y and the color signals R-Y and B-Y by the gamma correction unit 8 corrects and outputs the white balance. The encoder 11 inputting the white balance corrected luminance signal Y and the color signals R-Y and B-Y by the white balance corrector 10 encodes and outputs a composite video signal. In this case, the luminance signal Y gamma-corrected by the gamma correction unit 8 is inputted to the aperture driver 9 to select and integrate only the signal of the CCD central unit a as shown in FIG. 2 to the integral value and the reference voltage difference. The driving signal is output by the. Therefore, in the bright state, the brightness of the central figure (B) and the background brightness (A, C), as shown in FIG. 3 (3b), are not very different. This is well expressed. However, in the backlighting state, the brightness of the background (A, C) is too bright compared to the brightness (B) of the central person as shown in FIG. 3 (3a). However, the background is too bright to be recognized.

In the conventional video camera as shown in FIG. 1, since the center weighted metering is performed using the signal size of the center of the CCD (Charge Coupled Device), the exposure is determined based on the center of the backlight, so that the peripheral part is too bright. There is a problem in that the expression of the peripheral screen is biased with high contrast.

Accordingly, an object of the present invention is to provide a contrast correction apparatus capable of expressing the entire screen by selectively reducing the amplification degree of the high luminance part of the background which is too bright compared to the central subject in backlight by changing the gamma correction coefficient according to the screen state. .

The present invention for achieving the above object is a control means for controlling the overall operation of the video camera, receiving the output signal of the control means for outputting the CCD drive control signal, color separation control signal, white balance control signal, encoding control signal Inputs drive signal generating means, a lens for forming an image of a subject, an aperture controlling an exposure amount of a camera, and an image of a subject imaged through the lens and the aperture to photoelectrically convert the drive signal to output an image signal A luminance signal (Y) and a color signal (RY, BY) by inputting a CCD, an amplifying means for amplifying the video signal output from the CCD, and a video signal amplified by the amplifying means, and driven by a driving signal of the driving signal generating means. ) Is separated from the color separation means, the luminance signal Y separated from the color separation means, and the color signals RY and BY to input the control signal of the control means. Gamma correction means for outputting by gamma correction, aperture stop means for driving the aperture by inputting the gamma correction luminance signal Y, and in the gamma correction means Contrast determination means for inputting a gamma corrected luminance signal Y to determine the state of the contrast by the control signal of the control means and outputting it to the control means, and the luminance signal Y gamma corrected by the gamma correction means, White balance correction means for inputting color signals RY and BY to correct white balance and outputting the white balance correction means, and encoding the white balance corrected luminance signal Y and the color signals RY and BY of the white balance fixing means. And an encoder for outputting the composite video signal.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

5 is a block diagram of a video camera according to the present invention. The control unit 1 controls the overall operation of the video camera and generates a gamma correction control signal, and the CCD drive control signal according to the output signal of the control unit 1. A driving signal generator 2 for outputting a color separation control signal, a white balance control signal and an encoding control signal, a lens 3 for forming an image of a subject, an aperture 4 for adjusting an exposure amount of a camera, A CCD 5 for outputting an image signal by photoelectrically converting an image of an object formed through the lens 3 and the aperture 4, and an amplifier 6 for amplifying the image signal output from the CCD 5; And a color separation unit for inputting a video signal amplified by the amplification unit 6 and separating the luminance signal Y and the color signals RY and BY by the driving signal of the driving signal generator 2. 7) and the luminance signal Y and the color signals RY and BY separated by the color separator 7. A diaphragm for driving the aperture 4 by inputting a gamma correction unit 8 for outputting gamma correction and outputting a gamma correction luminance signal Y at the gamma correction unit 8. The white balance corrector 10 for inputting the driver 9 and the luminance signal Y and the color signals RY and BY that are gamma-corrected by the gamma correction unit 8 to perform white balance correction and output the white balance correction unit 10. And an encoder 11 for encoding the white balance corrected luminance signal Y and the color signals RY and BY of the white balance correction unit 10 and outputting them as a composite video signal, and the gamma correction unit 8. And a contrast determination section 12 for inputting the gamma corrected luminance signal to determine the state of the contrast.

FIG. 6 is a concrete circuit diagram of the contrast discriminating unit 12 of FIG. 5 for inputting a gamma-corrected luminance signal and selectively switching the central and peripheral portions of the CCD 5 by the control signal of the control unit 1. And gamma correction of the peripheral area of the first integrator 31 and the CCD 5 switched by the switch SW1 by integrating and outputting the gamma corrected luminance signal of the center of the CCD 5 switched and switched by the switch SW1. A second integrator 32 for integrating and outputting the integrated luminance signal, a divider 33 for dividing a value integrated in the second integrator 32, an integral value of the first integrator 31, and the divider ( A first comparator 34 for comparing and outputting the divided values of 33), a detected part 35 for inputting a gamma-corrected luminance signal to detect a peak signal, and a peak signal detected by the peak detector 35; And a second comparator 36 for comparing and outputting the reference 120 IRE.

FIG. 7 is a detailed circuit diagram of the gamma correction unit 8 of FIG. 5. The comparator 41 inputs a luminance signal and outputs a switching control signal by an enable signal of the controller 1 compared with a reference 100IRE. A gamma correction of 0.45 is performed on the 1-2 switches 42 and 45 selected to be switched to change the gamma correction coefficient by the switching control signal of the comparator 41, and the luminance signal to be selected by the first switch 42 to be 0.45. A first gamma correction unit 43 for gamma correction by a coefficient and a second gamma correction unit 44 for gamma correction by a gamma correction coefficient of 0.45 or less are selected from the first switch 42.

8 is a CCD structure diagram of split metering according to the present invention,

9 is a gamma correction characteristic diagram according to the present invention,

10 is a characteristic diagram of a gamma correction output signal according to the present invention.

An embodiment of the present invention based on the above-described configuration will be described in detail with reference to FIGS. 5-10. The CCD 5 inputting the subject image incident through the lens 3 and the aperture 4 is photoelectrically converted to output a composite image signal. The composite image signal photoelectrically converted by the CCD 5 is amplified by the amplifier 6 and output. The color separator 6 inputting the composite image signal amplified and output from the amplifier 6 separates the luminance signal Y and the color signals RY and BY by the control signal of the driving signal generator 2. Will print. The gamma correction unit 8 for inputting the luminance signal Y and the color signals RY and BY separated by the color separation unit 7 performs gamma correction as shown in FIG. 4 with a gamma correction coefficient of 0.45. Will print.

The white balance corrector 10 inputting the gamma correction luminance signal Y and the color signals R-Y and B-Y by the gamma correction unit 8 corrects and outputs the white balance. The encoder 11 inputting the white balance corrected luminance signal Y and the color signals R-Y and B-Y by the white balance corrector 10 encodes and outputs a composite video signal. In this case, the luminance signal Y gamma-corrected by the gamma correction unit 8 is input to the aperture driver 9 to select and integrate signals from the center portion a and the peripheral portion b of the CCD 5 as shown in FIG. After that, the driving signal is output by the integral value and the reference voltage difference.

In addition, the contrast determination unit 12 inputting the gamma corrected signal from the gamma correction unit 8 determines the contrast state, and a detailed operation of determining the contrast state will be described with reference to FIG. First, the controller 1 controls the switch to be connected to the normal cross (NC) terminal when the peripheral light of the CCD (5) as shown in FIG. 8, and to be connected to the normal open (NO) terminal during the central light metering. Therefore, the first integrator 31 integrates the signal metered in the center portion and the second integrator 32 integrates the signal metered in the peripheral portion. The value integrated in the second integrator 32 is three times the value integrated in the first integrator 31 as shown in FIG. In other words, the periphery part b is 12 when the midpoint portion a is subtracted from 4 × 4 = 16, and the midpoint portion a is 2 × 2 = 4, so the periphery portion b is three times the midpoint portion a. . Therefore, the value integrated in the second integrator 32 divides to 3 in the divider 33.

The first comparator 34, which inputs the integral value of the first integrator 31 and the value divided by the divider 33, compares the two values and outputs a high signal. do. In addition, the peak to be detected is detected by the to-be-detected unit 35 that inputs the gamma corrected luminance signal.

The second comparator 36 which inputs the peak signal detected by the peak detector 35 and the reference 120 IRE signal compares the two signals to determine whether the signal has information of 120 IRE or more. If the contrast determining unit 12 determines that the luminance signal is less than 120 IRE or less than 120 IRE, the brightness B of the central person and the brightness A and C of the background do not differ as shown in FIG. 10A. The center subject and the background are well represented by the exposure value determined by the center metering and the ambient metering such as 8 degrees. However, if it is determined that the contrast discriminating unit 12 is a backlight or a luminance signal of 120 IRE or more, the control unit 1 sends a gamma correction control signal to the gamma correction unit 8 to perform gamma correction. Explain.

When the gamma correction control signal is output from the control unit 1, the comparator 41 is enabled to enter an operation state. Then, the comparator 41 which inputs the luminance signal separated by the color separation unit 7 and the 100IRE signal compares the two signals and outputs the two signals. When the input luminance signal is less than 100IRE, the low signal is outputted. Connect the switches 42 and 45 to the normal cross (NC) terminals. When the 1-2 switches 42 and 45 are connected to the normal cross (NC) terminal, the first gamma correction unit 43 performs gamma correction up to Q of FIG. 9 with a gamma correction coefficient of γ = 0.45. However, when the input luminance signal is greater than or equal to 100 IRE, the comparator 41 outputs a high signal so that the 1-2 switches 42 and 45 are connected to the normal open terminal. When the 1-2 switches 42 and 45 are connected to the normal open terminal NO, the second gamma correction unit 44 performs gamma correction as shown in R of FIG. 9 with a gamma correction coefficient of γ <0.45. All luminance signals should be within 0-120IRE. In other words, as shown in Fig. 10 (10a), when gamma correction is done with γ = 0.45 and clipping signals over 120 IRE, ambient brightness (A, C) other than the central subject is accounted for in the case of backlight, so that there is no distinction of contour and there is no background. do. Therefore, as shown in FIG. 10 (10b), gamma correction of signals below 100IRE is gamma-corrected to γ = 0.45, and gamma correction of signals above 100IRE to gamma correction to be weak, but information loss due to clipping even if the luminance signal exceeds 120IRE There will be no.

As described above, when the video camera captures an image, the gamma correction coefficient is converted according to the captured image state to automatically adjust the contrast so that the entire screen can be expressed in high contrast during backlighting.

Claims (3)

In the contrast correction apparatus by changing the gamma correction coefficient in a video camera, the control unit 1 controls the overall operation of the video camera and generates a gamma correction control signal, and CCD drive control according to the output signal of the control unit 1. A drive signal generator 2 for outputting a signal, a color separation control signal, a white balance control signal, and an encoding control signal, a lens 3 for forming an image of a subject, and an aperture 4 for adjusting an exposure amount of a camera And a CCD 5 for photoelectrically converting an image of a subject formed through the lens 3 and the aperture 4 to output an image signal, and an amplifier for amplifying the image signal output from the CCD 5. 6) and a color separation unit for inputting a video signal amplified by the amplifying unit 6 and separating the luminance signal Y and the color signals RY and BY by the driving signal of the driving signal generator 2. (7) and the luminance signal (Y) separated by the color separator (7) A gamma (γ) correction unit 8 for inputting color signals RY and BY to gamma correction and outputting the gamma correction unit, and a luminance signal Y gamma-corrected at the gamma correction unit 8, for inputting the aperture The white balance correction unit outputs the aperture driving unit 9 for driving (4), the luminance signal Y gamma-corrected by the gamma correction unit 8, and the color signals RY and BY to correct the white balance. An encoder 11 for encoding the white balance corrected luminance signal Y and the color signals RY and BY of the white balance correcting unit 10 and outputting them as a composite video signal, and the gamma correction unit. And a contrast determining unit (12) for inputting the gamma corrected luminance signal in (8) to determine the state of the contrast. The switch SW1 of claim 1, wherein the contrast determining unit 12 inputs a gamma-corrected luminance signal and selectively switches the signals of the central and peripheral portions of the CCD 5 according to the control signal of the control unit 1. And a first integrator 31 which integrates and outputs a gamma corrected luminance signal of the center of the switched CCD 5 selected by the switch SW1, and a gamma around the CCD 5 selected by the switch SW1. A second integrator 32 that integrates and outputs the corrected luminance signal, a divider 33 that divides the value integrated in the second integrator 32, an integral value of the first integrator 31, and the divider A first comparator 34 for comparing and outputting the divided values of (33), a to-be-detected part 35 for inputting a gamma-corrected luminance signal to detect a peak signal, and a peak detected by the peak-detector 35 The second comparator 36 compares the signal with the reference 120IRE and outputs the result. Contrast correction device according to claim a. The comparator 41 according to claim 1, further comprising: a comparator 41 for inputting a gamma correction unit 8 and a luminance signal, and outputting a switching control signal by an enable signal of the controller 1 in comparison with a reference 100IRE; The first and second switches 42 and 45 for selective switching so that the gamma correction coefficient can be changed by the switching control signal of &lt; RTI ID = 0.0 &gt;), and &lt; / RTI &gt; A first gamma correction unit 43 for gamma correction with a gamma correction coefficient, and a second gamma correction unit 44 for gamma correction with a gamma correction coefficient of? <0.45 by the first switching selection. Contrast correction device.

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