JP2003259385A - Color camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct contrast drop due to an increased dark level in a video signal, a decreased highlight peak of an incident light and a decreased color signal peak. <P>SOLUTION: An imaging unit having at least one or more imaging elements, and at least one function of gain variable, automatic aperture control, automatic electronic sensitivity control, black level variable, gamma variable, dark part expansion compression variable, white compression expansion variable, high luminance color expansion, color difference arithmetic emphasis, color signal gain variable, contour emphasis variable, and flare correction, varies at least one of gain, automatic aperture, automatic electronic sensitivity, black level, gamma correction, dark part expansion, dark part compression, white compression, white expansion, color difference arithmetic emphasis, color signal gain, contour emphasis and flare correction, interlocked with two-dimensional contrast emphasis. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improving the contrast of color camera output signals.

[0002]

2. Description of the Related Art A color solid-state image pickup device (hereinafter referred to as a single-plate color camera) using one solid-state image pickup device with an on-chip color filter, and a color solid-state image pickup using a low-cost color separation optical system and three solid-state image pickup devices. In general, the device (hereinafter, 3 plate color camera) has few variable image quality adjustment functions,
The output signal is 8 bits. Therefore, there is a precedent example in which a device for enhancing the output signal until the contrast becomes constant is externally attached in order to cope with imaging in a mist or fog. On the other hand, high-performance 3-panel color cameras generally have various detection functions for video signals, many variable image quality adjustment functions, 12 bits or more for internal signals and 10 bits for output signals.
Is. Therefore, there is a precedent in which the black level is lowered and gamma is strengthened in order to deal with the dusty condition of a racetrack.

When a fog is thick and fog is applied, or when a long-distance mist is present, the dark level of the incident light rises to about 30% of the rated value (55 to 65% of the output signal), The highlight peak drops to about 70% of the rated value (85 to 90% of the output signal) and the amplitude of the luminance output signal is about 3
It drops to 0%. With conventional single-chip color cameras and low-priced 3-plate color cameras, the iris control output tends to be reduced, and the highlight peak is about 60% of the rating.
(About 80% of the output signal).

The color signal input peak is also reduced to about 30% of the rated value (10 to 20% of the output signal). FIG. 2 shows the luminance distribution of the incident light, the luminance distribution of the camera output, and the luminance distribution of the output of the two-dimensional contrast enhancing apparatus of the conventional single-panel color camera, low-cost three-panel color camera and the two-dimensional contrast enhancing apparatus. Indicates.

According to SMPTE244-1995, the white level of the NTSC analog composite video signal (Video Burst Sync, abbreviated as VBS below) is 100% (NTSC official unit is 100IRE, but it is 100% or less because it is aligned with the unit% of PAL and component signals. And the minimum quantization level below the sync tip level -40% -42.1%
To digitize from the highest quantization level edge up to 138.6% above the peak chroma level of 130.8%. For studio equipment, 4 to 10 with 10-bit and gradation 1024
Assign up to 19, but 8bi for low-priced general-purpose devices
t and gradations 1 to 254 are assigned, and the blanking level is 60 and the white level is 200.

Therefore, even if a general-purpose 8-bit device with 256 gradations is added to the output of a single-plate color camera or a low-priced three-plate color camera until the contrast becomes constant, the single-chip color camera output signal brightness The amplitude of the output signal is about 30%, 42 gradations, about 5.4bit is forcibly expanded to the output of the two-dimensional contrast enhancing device, 140 gradations, about 7.1bit. It is difficult to distinguish.

FIG. 4 shows the correspondence between the luminance distribution of incident light and the luminance distribution of camera output in a conventional high-performance three-plate color camera. Even if the black level is lowered with a high-performance 3-panel color camera, the amplitude of the output signal brightness output signal is about 35%, and the D / A
At 10 bits, there are about 200 gradations, but for a general-purpose 8 bit and 256 gradation interface such as a color monitor or a consumer recording device, it becomes about 52 gradations and about 5.7 bits, making it difficult to determine the subject component of the video signal.

It is an object of the present invention to eliminate the above-mentioned drawbacks and to realize a color camera capable of photographing a high-contrast image even in bad weather such as thick fog, long-distance haze, etc. To do.

[0008]

In order to solve the above-mentioned problems, the present invention has at least one image pickup device, and has a variable gain, an automatic aperture control, an automatic electronic sensitivity control, a black level variable, and a gamma. Variable, dark part expansion compression variable, white compression expansion variable, high brightness color expansion, color difference calculation enhancement, color signal gain variable, contour enhancement variable, and flare correction. Then, at least one of gain, automatic aperture, automatic electronic sensitivity, black level, gamma correction, dark part expansion, dark part compression, white compression, white expansion, color difference calculation enhancement, color signal gain, contour enhancement and flare correction can be changed. To do.

Further, it has at least one image pickup device, and is capable of varying the black level, varying the gamma, compressing and expanding the dark part, compressing and expanding the white part, expanding the high-brightness color, enhancing the color difference calculation, varying the color signal gain, varying the edge enhancement, and color. In an image pickup apparatus having at least one function of variable edge enhancement, flare correction, and DC output of iris control, if the dark level rise of an input video signal is less than a predetermined value, gamma correction or dark area expansion is strengthened and dark area compression is weakened to a predetermined value. If the above is satisfied, weaken the gamma correction or the dark part expansion and increase the dark part compression, and detect the dark level rise of the input video signal, and change at least one of the black level, gamma, dark part compression / expansion, and flare correction. , Keeping the dark level of the output video signal constant,
Increasing the contour enhancement, detecting the decrease of the highlight peak of the input video signal, varying the white compression / expansion to make the highlight peak of the output video signal constant, and increasing the high-luminance color expansion And a decrease in the color signal peak (saturation) of the input video signal is detected, and at least one of high-brightness color expansion, color difference calculation enhancement, color signal gain, and color contour enhancement is changed, and the color signal peak of the output video signal is changed. Iris control DC using a video signal with a constant dark level
At least one of producing output.

Further, the corresponding variable processing is analogized.
/ It is performed before digital conversion or with an accuracy of 9 bits or more.

When the dark portion of the incident light rises to around 25% of the rated value (50 to 60% of the output signal), the output contrast can be secured without increasing the gamma correction. When the dark part of the incident light rises to around 30% of the rated value (55 to 65% of the output signal), gamma correction is reduced and the dark part is compressed, so that the output contrast can be secured. Also, if the iris control DC output is generated using a video signal with a constant dark level, the iris will not be narrowed down, the highlight peak will not be reduced, and about 85% of the rated value (85 to 95% of the output signal) will be generated.
%).

FIG. 1 shows the luminance distribution of incident light, the luminance distribution of the camera output, and the output of the two-dimensional contrast enhancing apparatus of the single-panel color camera or the low-priced three-panel color camera of the present invention and the two-dimensional contrast enhancing apparatus. The brightness distribution correspondence is shown. In the single-chip color camera and the low-priced three-plate color camera, the black level is greatly reduced to around -50% of the rated value to reduce the gamma correction in conjunction with the two-dimensional contrast enhancement external to the image pickup device, and the dark level is reduced. Reduce the output signal from about 55% to about 15%. In addition, the increase of the gain level, the opening of the aperture, or the slowing of the electronic shutter causes the dark level to increase and the decrease in the highlight peak due to the decrease of the black level to about 60% of the rating and about 80% of the output signal. %
To about 70% of the rating and about 85% of the output signal. Amplitude of luminance output signal is about 70% 105 gradations about 6.8b
become it Furthermore, the edge emphasis is strengthened. In the two-dimensional contrast enhancement external to the image pickup device, the amplitude of the single-chip color camera luminance output signal is about 70%, 105 gradations, about 6.8bit are 14
Since it is slightly expanded to 0 gradations of about 7.1 bits, there are few false signals and the subject component of the video signal can be easily discriminated.

FIG. 4 shows the correspondence between the luminance distribution of the incident light and the luminance distribution of the camera output of the high performance three-plate color camera of the present invention. A high-performance 3-panel color camera detects an increase in the dark level of the input video signal and greatly reduces the black level to around -100% of the rated value or performs dark area compression and then slightly lowers the black level to perform gamma correction. To enhance the contour enhancement of the dark part and make the dark level of the output video signal constant (about 5% in FIG. 4). An iris control DC output is generated using a video signal with a constant dark level, and the highlight peak of the output signal is restored. further,
Detecting a decrease in the highlight peak of the input video signal, weakening the white compression, strengthening the high-intensity color expansion, strengthening the outline enhancement of the highlight, and making the highlight peak of the output video signal constant (about 4 in FIG. 4). 95%). Color signal peak drop of input video signal is detected, high brightness color expansion is strengthened, color difference calculation is strengthened, color signal gain is increased, color contour enhancement is strengthened, and color signal peak of output video signal is increased. To be constant.

In the two-dimensional contrast enhancement external to the image pickup device, the amplitude of the luminance output signal of the three-plate color camera is about 90%,
Since 135 gradations and about 7.1 bits are slightly expanded to 140 gradations and about 7.1 bits, there are few false signals and the subject component of the video signal can be easily discriminated. There is little need for two-dimensional contrast enhancement external to the imaging device.

In a single-plate color camera or a low-priced three-plate color camera, the dark level of the output signal rises to about 55% in conjunction with the two-dimensional contrast enhancement external to the image pickup device, and the iris is narrowed down to highlight. The peak is reduced to about 80% of the output signal because the dark part is about 15% of the output signal.
%, The highlight peak rises to about 85% of the output signal, and the output contrast can be secured to about 70% of the output signal. With the two-dimensional contrast enhancement external to the image pickup device, the amplitude of the single-chip color camera luminance output signal is about 70%,
Since 05 gradations and about 6.8 bits are slightly expanded to 140 gradations and about 7.1 bits, there are few false signals and the subject component of the video signal can be easily discriminated.

In a high-performance three-plate color camera, the dark level is reduced to about 5% of the output signal by only adding the devises of various detection functions of internal calculation and the image quality adjusting function, and the video signal with the dark level kept constant can be obtained. Since the iris control DC output is generated by using the iris, the iris is not narrowed down, the highlight peak rises to about 95% of the output signal, and the output luminance signal amplitude can secure about 90% of the output signal. There is little need for two-dimensional contrast enhancement external to the imaging device.

In the case where the fog is thick and fog is present, or a long-distance mist is present, the dark level of the incident light is about 30% of the rated value.
Even if the highlight peak decreases to about 70% of the rated value, the contrast of the subject component of the output video signal can be easily determined. Therefore, long-distance monitoring can be performed without increasing the size of the imaging device and increasing the cost.

[0018]

FIG. 5 shows a block diagram of a configuration example of a single-plate color camera or a three-plate color camera of the present invention and a two-dimensional contrast enhancing apparatus.

FIG. 5 will be described below. In the three-plate color camera, the incident light Lin passes through the diaphragm 9, the lens 11 and the color separation optical system 12 including the optical low-pass filter, and the red incident light Lir,
It becomes the green incident light Lig and the blue incident light Lib. Incident light Lir, Lig, Li
b are solid-state image pickup devices 1, 2 and 3, respectively, which are signals Vir and Vi.
g, Vib converted to gain control amplifier circuit A1, A2, A3
Then, the gain is changed by the gain control voltages Ergain, Eh, and Ebgain to become video signals Vmr, Vmg, Vmb, which are converted into digital signals by the analog-digital converters 4, 5 and 6, and one horizontal scanning is performed by the line memories 14 to 19. After delaying the period twice, the digital signal processing circuit 7 causes the camera composite video signal (Video Burst S
ync or less VBS) VBSm, camera serial digital video signal (Se
Serial Digital Interface or less SDI) SDIm, Camera serial digital video signal (Serial Digital Interface or less SDI) I
It becomes EEE1394m. VBSm to analog / digital converter 28
The signal converted into a digital signal by SDIm and IEEE1394m are selected by the switch 29, and the digital signal processing circuit 30 and the field memories 31 and 32 two-dimensionally enhance the contrast.

The two-dimensional contrast enhancement level is output from the digital signal processing circuit 30, and the CPU 33 controls the digital / analog converter 34 based on the result of detecting the enhancement level to control the gain control voltages Ergain, Eh, Ebgai
n, black level control voltage Erblack, Egblack, Ebblack,
The iris control DC output is voltage-controlled, the digital signal processing circuit 7 is controlled, and various video signal corrections such as gamma correction are performed to perform appropriate video signal processing linked with two-dimensional contrast enhancement.

In the single-plate color camera, 12 is only the optical low-pass filter, and the system from the solid-state image sensor to the line memory is one system. Specifically, the incident light Lin passes through the diaphragm 9, the lens 11 including the spot filter 10 and the optical low-pass filter 12, and becomes incident light Lig. Incident light L
ig is a solid-state image sensor 2 and is converted into a signal Vig. In the gain control amplifier circuit A2, the gain is changed by the gain control voltage Eh to become the video signal Vmg, and the analog / digital converter 5
Is converted into a digital signal by the digital signal processing circuit 7 and the line memories 16 to 17 delay one horizontal scanning period twice.
The camera composite video signal VBSm, camera serial digital video signal SDIm, camera serial digital video signal IEEE139
It will be 4m. The two-dimensional contrast enhancing device is the same as the three-plate color camera.

A two-dimensional contrast enhancement level is output from the digital signal processing circuit 30, and the CPU 33 controls the digital / analog converter 34 based on the result of detecting the enhancement level to control the gain control voltage Eh and the black level. By controlling the voltage of the control voltage Egblack and the DC output of the iris control and controlling the digital signal processing circuit 7 to perform various video signal corrections such as gamma correction, appropriate video signal processing linked with two-dimensional contrast enhancement is performed.

[0023]

As described above, the external two-dimensional contrast enhancement and the image quality adjusting function of the color camera are linked. Alternatively, it is possible to easily discriminate a thick fog or a fog over a long distance from a subject component of an output video signal by simply adding a devise of various detection functions of internal calculation of a color camera and an image quality adjusting function. Therefore, it is possible to realize an image pickup apparatus for long-distance monitoring, which is small in power consumption and small in size without causing an increase in cost.

[Brief description of drawings]

FIG. 1 is a diagram showing an incident light amount response of a solid-state imaging device showing the operation of the present invention.

FIG. 2 is a diagram showing an incident light amount response of a solid-state imaging device showing a conventional operation.

FIG. 3 is a diagram showing an incident light amount response of a solid-state imaging device showing the operation of the present invention.

FIG. 4 is a diagram showing an incident light amount response of a solid-state imaging device showing a conventional operation.

FIG. 5 is a block diagram of a color camera that is an embodiment of the present invention.

[Explanation of symbols]

1, 2, 3: Solid-state image sensor, 4, 5, 6: Analog / digital converter, 9: Aperture, 10: Spot filter, 1
1: Lens, 12: Color separation optical system with optical low-pass filter or optical low-pass filter, A1, A2, A3:
Gain control amplifier circuit 7, 30: Digital signal processing circuit, 14 to 19: Line memory, 31, 32: Field memory 33: CPU, 34: Digital / analog converter Lin: Incident light, Lir: Red incident light, Lig: Green incident light, Lib:
Blue incident light, Vir: Red solid-state imaging output, Vig: Green solid-state imaging output, Vib: Blue solid-state imaging output, VBSm, VBSo: Camera composite video signal SDIm, SDIo: Camera serial digital video signal IEEE1394m, IEEE1394o: Camera serial digital video signal

Claims (3)

[Claims] 1. At least one image pickup device,
Variable gain, automatic aperture control, automatic electronic sensitivity control, black level variable, gamma variable, dark part expansion compression variable, white compression expansion variable, high brightness color expansion, color difference calculation enhancement, color signal gain variable, contour enhancement variable, flare correction In an image pickup apparatus having at least one function of: gain, automatic aperture, automatic electronic sensitivity, black level, gamma correction, dark part expansion, dark part compression, white compression, white expansion, and color difference calculation enhancement in conjunction with two-dimensional contrast enhancement. A color camera, wherein at least one of color signal gain, contour enhancement, and flare correction is variable. 2. At least one image pickup device,
At least one of the following functions: black level variable, gamma variable, dark area compression / expansion, white compression / expansion, high-brightness color expansion, color difference calculation enhancement, color signal gain variable, edge enhancement variable, color edge enhancement variable, flare correction, and iris control DC output. In the image pickup apparatus having the above, if the increase in the dark level of the input video signal is less than the predetermined value, the gamma correction or the dark part expansion is strongly weakened and the dark part compression is weakened, and if the predetermined value or more, the gamma correction or the dark part expansion is weakened and the dark part compression is strengthened. And detecting an increase in the dark level of the input video signal, varying at least one of the black level, gamma, dark area compression / expansion, and flare correction,
Keeping the dark level of the output video signal constant, increasing the edge enhancement, and detecting the decrease of the highlight peak of the input video signal, and varying the white compression / expansion to keep the highlight peak of the output video signal constant. And increasing the high-luminance color expansion, and detecting the color signal peak (saturation) reduction of the input video signal to detect at least high-luminance color expansion, color difference calculation enhancement, color signal gain, and color contour enhancement. At least one of varying one to make the color signal peak of the output video signal constant and generating an iris control DC output using the video signal having a constant dark level. Color camera. 3. A color camera according to claim 1 or 2, wherein the corresponding variable processing is performed before analog / digital conversion or with an accuracy of 9 bits or more.