KR20220004925A - Color control method for low-illumination of CCTV systems and CCTV systems with a color control at low intensity - Google Patents

Abstract

The present invention relates to a CCTV system having a color control function in low light and a method for controlling color in a low-light condition of the CCTV system. The CCTV system has a lens, an image sensor, an image signal processor and a codec, wherein the image signal processor includes: a digital slow shutter controller for adjusting exposure time so that a subject is taken with mood; a digital noise attenuator for conducting function to set a range for preventing an afterimage from remaining in low-illuminance mode by suppressing noise through digital signal processing, and determine the degree of attenuation of noise; a gamma controller for conducting functions to maintain an LCD Mode during day time, and change a condition when night time is recognized through an automatic gain controller in order to increase low-light sensitivity; and the automatic gain controller for automatically adjusting a gain to a maximum value for easily identifying the subject. Therefore, the CCTV is operated in low light, so as to identify colors even through the steps of increasing exposure time, increasing low light sensitivity, and removing noise. In addition, the identification of a moving subject is not impaired, so that the commerciality of the low-light CCTV system itself and the reliability according to the purpose of use are greatly improved.

Description

Color control method for low-illumination of CCTV systems and CCTV systems with a color control at low intensity

The present invention relates to a Closed-Circuit Television (CCTV) system having a color control function in low light and a color control method in low light of a CCTV system. It relates to a CCTV system having a color control function in low light, and a color control method in low light of the CCTV system, which are invented so that the color can be identified through and the identification of a moving subject is not hindered.

In general, a CCTV camera (closed circuit TV camera) is a filming device that allows you to check whether there is an abnormality in a filmed place or object by taking a picture of a specific place or object and sending it to a closed circuit TV. It is managed in buildings, parking lots, apartment complexes, etc. B. Its uses are being greatly diversified, such as being used not only as a general surveillance camera to enhance the efficiency of security, but also as a vehicle safety device.

On the other hand, CCTV has no choice but to operate in a dark place, that is, in low light due to its purpose or characteristics of use. In this case, an infrared camera or lighting in the visible range is used.

In particular, in conventional security surveillance cameras (Day & Night), in order to increase the sensitivity of low-light images, the black-and-white screen is converted to a black-and-white screen, which significantly reduces color discrimination and increases the sensitivity of low-light images. This causes a problem in that it is difficult for the observer to distinguish the subject.

That is, the conventional security surveillance camera (Day & Night) uses a color CCD (Charge Coupled Device) at the same time during the day and at night, and reproduces the image in color during the day, and the image captured in color at night is black and white by software. There is a problem in that the color discrimination is significantly lowered because the mode conversion method is adopted, and the monitor cannot accurately distinguish the subject due to the image dragging phenomenon and the afterimage phenomenon caused by increasing the sensitivity of the low-light image.

In addition, in order to respond to changes in illuminance according to seasons, time zones, and installation locations of CCTV cameras, and to respond to factors affecting object identification such as clouds, snow, rain, and fog, various methods are also proposed. to be.

On the other hand, even with these various methods, the noise is maximized and the image quality is deteriorated. In particular, when the shutter speed is maximized when used in a lighting device at night, image data may be damaged by reflected light.

In addition, while the camera generally has the advantage of displaying a vivid color shape during daytime photography, color noise due to color burst appears during night photography, so there is a problem that it cannot properly perform its role as a surveillance camera. By using the common image sensor of , there is inevitably a problem that the focus is shifted due to different wavelengths of visible light and infrared bands.

Therefore, in the prior Republic of Korea Patent Registration No. 10-1169017, "It is installed on the front side of the body so that the front can be photographed, and one side is provided with a remote control receiver for receiving CdS for detecting ambient illuminance and external radio signals, and night photography is provided. An encoder that converts the digital image signal transmitted from the high-resolution CMOS camera and CCD camera and the high-resolution CMOS camera to an analog signal through the signal processing algorithm stored in the first EEPROM, and the CCD camera. AGC (Auto Gain Control) that automatically controls the gain of the transmitted analog video signal, and ISP (Image Signal Processor) that compares the signal controlled by the AGC with the data value stored in the second EEPROM and converts it into an image signal from which noise has been removed first and second video amplifiers (VIDEO AMPs) amplifying the signals output from the encoder and the ISP; A day/night automatic switching type surveillance camera to which a high-resolution CMOS camera configured including a separate switching video switch is applied" has been proposed.

In addition, in Republic of Korea Patent Registration No. 10-1322829, “a digital camera that generates an image file by photographing a target object and the digital camera are connected to the digital camera, and the image file is corrected according to the illuminance of the surrounding environment. An automatic compensation device for compensating exposure of a digital camera, wherein the automatic compensation device includes a sunrise and sunset time collection module for collecting sunrise and sunset times of a set region from a sunrise and sunset time DB in which sunrise and sunset times for each region are stored, and the sunrise and sunset A CCTV system comprising an exposure correction module that corrects the exposure of the camera according to the sunrise and sunset times extracted from the time extraction module” has been proposed.

However, in a day/night automatic switching type surveillance camera to which a high-resolution CMOS camera configured as described above is applied, when color is reproduced at night, there is a problem in object identification due to color noise. If it is reduced, the color reproducibility problem and the sensitivity of the subject at night are lowered, which is also a problem for subject identification.

That is, in the existing CCTV cameras, by giving priority to sensitivity over color reproducibility, the color is converted to black and white to eliminate color noise, and a method of increasing the sensitivity in a black and white screen is taken.

The present invention has been devised to solve the problems of the related art. In order to increase the sensitivity of the existing low-light image, the color discrimination is significantly reduced by switching to a black-and-white screen, and the image generated by increasing the sensitivity of the low-light image In order to prevent a phenomenon in which the role of a surveillance camera is reduced because it is difficult for a monitor to distinguish a subject due to dragging and afterimage phenomena, an important element of a CCTV camera is accurate identification of the subject, so night sensitivity and subject color, which are essential elements to increase identification, are essential. By proposing a color noise suppressor, low-light sensitivity enhancer, and low-light noise attenuator to improve all An object of the present invention is to provide a CCTV system having a low-illuminance color control method of the CCTV system.

In order to achieve the above object, the CCTV system having a color control function during low illumination of the present invention is a CCTV system having a lens, an image sensor, an image signal processor and a codec,

The image signal processor suppresses noise with a digital signal processing and a digital slow shutter controller that controls the exposure time so that the subject can be taken with a feeling, and an afterimage in low light mode of 0.05 to 0.08 lux or less Digital Noise Reducter, which attenuates noise within 80% of the total noise, maintains LCD Mode during the daytime, and the automatic gain controller to increase low-light sensitivity. The gamma controller that adjusts the gamma by applying the output gamma of the image as 0.55 gamma, which is the LCD mode, and 0.35 gamma in low light conditions, and the function of automatically adjusting the gain to the maximum value for easy identification of subjects. It is characterized in that the automatic gain controller (Auto Gain Control; AGC) is provided.

In this case, the digital slow shutter controller is characterized in that the number of output frames is 7 frames per second or more in order to prevent dragging in the low-illuminance mode of 0.05 to 0.08 (LUX) or less.

In addition, the digital noise attenuator compares a predetermined reference frame with two previous frames among a plurality of image frames sequentially input through the digital slow shutter controller to attenuate the deviation. Reducter) and a 3D-NR (3-Digital Noise Reducter) that compares three sequentially input image frames in a state in which the primary noise is attenuated through the 2D-NR and attenuates the deviation. do.

In addition, it is characterized in that the lens uses a lens of F2.0 or higher (Fixed type or Varifocal type), and the image sensor uses a sensor capable of maintaining a sensitivity of at least 800mV or higher.

In addition, the image sensor is characterized in that it has a high resolution of 1.5M pixels or more having a resolution of 1440×1024.

On the other hand, the low-illuminance color control method of a CCTV system for achieving the above object is a low-illuminance color control method of a CCTV system having a lens, an image sensor, an image signal processor, and a codec. In configuring , the image signal processor determines whether the illuminance of the image signal received through the image sensor is in a low illuminance state, and when it is determined that the illuminance is low, adjusting the exposure time of the image sensor, followed by the low illuminance It is characterized in that the subroutine for adjusting the low-illuminance color is performed according to the gain value of the image taken in , the step of attenuating the low-illuminance noise, and the steps of adjusting the low-illuminance image output gamma.

In this case, the criterion for determining that the illuminance of the image signal transmitted through the image sensor from the image signal processor is low is set to 0.05 to 0.08 lux or less.

In addition, the subroutine for adjusting the low illuminance color determines whether the gain value for recognizing the current illuminance is less than or equal to a predetermined Low value, whether greater than Low and less than or equal to a predetermined Middle, or whether greater than the Middle and less than or equal to a predetermined High, Alternatively, the step of sequentially determining whether it is greater than a predetermined High and the step of maintaining the maximum color gain without color correction if the current gain value for recognizing the illuminance is less than or equal to the Low value as a result of sequentially determining as described above and the current gain value If it is greater than this Low value and less than or equal to the Middle value, the color gain suitable for the current illuminance is applied, but a step of linear interpolation to correct the color signal when the illuminance is lowered and the current gain value is greater than the Middle value and less than or equal to the High In order to suppress the increase in noise, linear interpolation for the color gain is performed, but if the current gain value is greater than the High value, the illuminance is regarded as completely dark and the minimum value of the color gain is maintained. do.

At this time, the Low value is set to 1 [DB], the Middle value is set to 35.1 [DB], and the High value is set to exceed 35.1 [DB].

As described above, according to the CCTV system having a low-illuminance color control function and the low-illuminance color control method of the CCTV system of the present invention as described above, the image signal among CCTV systems having a lens, an image sensor, an image signal processor, and a codec The processor determines whether the illuminance of the image signal received through the image sensor is in a low illuminance state. If it is determined that the illuminance is low, the processor adjusts the exposure time of the image sensor, and then adjusts the exposure time of the image sensor according to the gain value of the image captured in the low illuminance. After executing the subroutine to adjust the illuminance color, by attenuating the low illuminance noise and adjusting the low illuminance image output gamma, the CCTV works under low illuminance, increasing the exposure time, increasing the low illuminance sensitivity and removing the noise. It is a very useful invention, such as being able to identify colors and not hindering the identification of moving subjects, greatly improving the commerciality and reliability of the low-light CCTV system itself according to the purpose of use.

1 is a block diagram of a CCTV system having a color control function during low illumination to which the present invention is applied.
2 is a flowchart for explaining the method of the present invention;
3 is a flowchart for explaining a low-illuminance color adjustment subroutine in FIG. 2;
4 is a graph illustrating an exposure control method performed by a digital slow shutter controller in an ISP.
Figure 5 is a detailed block diagram of the ISP of the low-illuminance CCTV system to which the present invention is applied.
6 is a detailed block diagram of the digital noise attenuator of FIG. 5;
7 is an exemplary graph for controlling the image output depreciation in the gamma controller in the ISP.
8 is a block diagram of a codec in the present invention.
9 is a graph showing a form of controlling an exposure time in an ISP.
10 is a graph showing a color suppression section in the present invention.
11 (a) to (d) are graphs showing each region when color is suppressed in the ISP in the present invention.

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

That is, the following is merely illustrative of the principles of the present invention. Therefore, those skilled in the art will be able to devise various devices that, although not explicitly described or shown herein, embody the principles of the present invention and are included within the spirit and scope of the present invention. In addition, all conditional terms and examples listed herein are, in principle, expressly intended only for the purpose of understanding the concept of the present invention, and it should be understood that they are not limited to the specifically enumerated embodiments and states as such. do.

Moreover, it is to be understood that all detailed description reciting the principles, aspects, and embodiments of the invention, as well as specific embodiments, are intended to cover structural and functional equivalents of such matters. It should also be understood that such equivalents include not only currently known equivalents, but also equivalents developed in the future, i.e., all devices invented to perform the same function, regardless of structure.

In addition, when conventional technology is applied to the description of the present invention, a detailed description of the conventional technology may be omitted.

1 shows a block diagram of a CCTV system having a color control function in low light to which the present invention is applied.

First, in general CCTV, color sensitivity is 1.5 (LUX) and black and white is 0.15 (LUX). There are cases in which black and white images are obtained using

However, in the present invention, it is an object to provide a technology for realizing a color image even at 0.05 to 0.08 (LUX) or less.

That is, the CCTV system having a low-illuminance color control function to which the present invention is applied is, as shown in FIG. 1, a lens 10, an image sensor 20, and an image signal processor (hereinafter referred to as "ISP") (30) ) and a codec (Codec) 40 is provided.

In addition, the image finally made through the codec 40 is transmitted to a necessary place through the wired/wireless communication network 50 .

In this case, the wired/wireless communication network 50 may use various communication networks such as the Internet, Ethernet, Wi-fi, and the like, as well as use a communication module.

On the other hand, among the components of the CCTV system having a color control function in low light to which the present invention is applied, the lens 10 is preferably a lens with good performance, but a general lens (Fixed type or Varifocal type) of F2.0 or higher. ) can also be applied.

In addition, as the image sensor 20, one having a high resolution of 1.5M pixels or more having a resolution of 1440×1024 may be used, and the higher the resolution, the better the effect can be obtained.

However, color over 270K or 410K pixels that reproduces 480 or 600 TV lines is acceptable. In addition, for clearer shooting, a high-definition camera having a high resolution such as 1027 X 768 , 1280 X 960 , 1920 X 1080 may be employed.

In addition, the signal photographed through the image sensor 20 is transmitted to the ISP (30).

In addition, at the illuminance at which the ISP 30 may generate color noise, color noise is appropriately removed through color suppression.

5 shows a detailed block diagram of an ISP among the low-illuminance CCTV systems to which the present invention is applied, and FIG. 6 shows a detailed block diagram of the digital noise attenuator in FIG.

In the ISP (Image Signal Processor) 30, the image signal photographed in low light output from the image sensor 20 is largely used through a predetermined algorithm to generate an image signal capable of color identification without afterimage and dragging. Algorithm, that is, the above-described FIGS. 2 and 3 are performed.

At this time, in the ISP 30, a digital slow shutter controller 31, a digital noise reducer 32, a gamma controller 33, and an auto gain controller Control; AGC) 34 and the like.

In addition, the lens 10, which is the optical unit used in the present invention, uses a general lens (Fixed type or Varifocal type) of F2.0 or higher, and it is essential for the image sensor 20 to maintain a sensitivity of at least 800 mV or higher.

On the other hand, the digital slow shutter controller 31 in the ISP 30 performs a function of adjusting the exposure time so that the subject can be taken with a feeling, and dragging does not occur in the low-illuminance mode of 0.05 to 0.08 (LUX) or less. In order to avoid this, it is desirable to operate so that the number of output frames is 7 frames per second or more.

4 is a graph showing an exposure control method performed by the digital slow shutter controller in the ISP. The luminance component in the digital slow shutter controller 31 is controlled by a microcomputer (not shown) in the digital slow shutter controller 31. (Y) That is, it shows that the total exposure is controlled based on the value representing the current brightness.

The main content of the present invention focuses on color reproducibility in the gray region of FIG. 4, that is, in the low light region, and shows how the camera performs overall exposure control.

When it becomes bright from a completely dark state, it is controlled by the steps of Slow Shutter -> Gain -> Iris -> Shutter. > Control is performed in the order of Slow Shutter. At this time, the relationship between light and dark is judged based on the luminance component (Y), and the degree of low light can be regarded as starting from the stage where gain is applied.

For example, from the point of view of the sensor, it means Long Exposuer Time, and when the shutter value is 1/60 in 720p/60 standard, the Long Exposuer Time scaled by 4 frames is 16.67ms(1/60) * 4 = 66.68ms( It means increasing the exposure time to about 15 fps).

In addition, the digital noise attenuator 32 includes a 2D-NR 321 and a 3D-NR 322 and suppresses noise by digital signal processing so that an afterimage does not remain in a low-illuminance mode of 0.05 to 0.08 lux or less. It performs the function of attenuating noise within 80% of the total noise.

At this time, the 2D-NR 321 compares a predetermined reference frame with two previous frames among a plurality of image frames sequentially input through the digital slow shutter controller 31 and attenuates noise in response to the deviation. When the noise attenuation is increased in this 2D-NR 321, in order to prevent the adverse effect that the resolution deteriorates in proportion to the noise attenuation degree, about 10% of the total noise attenuation is accounted for.

In addition, the 3D-NR 322 compares three frames among the sequentially input image frames in a state in which the primary noise is attenuated through the 2D-NR 321, and attenuates the noise in response to the deviation. In this 3D-NR (322), if the degree of noise attenuation is increased, 70% of the total noise attenuation is performed so that adverse effects such as image drag and afterimage do not occur.

That is, the digital noise attenuator 32 attenuates noise within 80% of the total noise so that no afterimage remains at 0.05 to 0.08 lux in low-illuminance mode. 3D-NR (322) and 2D-NR (321) Both are used to attenuate noise, and the sensitivity can be adjusted separately by day/night.

In addition, the gamma controller 33 maintains the LCD mode during the day, and when night is recognized through the automatic gain controller in order to increase the low-light sensitivity, the output gamma of the image is applied as the LCD mode of 0.55 gamma, and 0.35 in the low-light state. It performs the function of adjusting the gamma by applying gamma.

For example, the condition for recognizing night time is to apply luminance and gain values at the same time. The standard LCD standard gamma is 1.0, but 0.55 gamma changed while tuning is applied, and the gain is about 27.3 based on the camera's default value Under the condition of dB or higher, when the luminance is less than about 4 lux, it is regarded as nighttime, and the gamma value is applied as 0.35 gamma.

In addition, the automatic gain controller 34 is an essential element of low illuminance sensitivity, and a lot of dot noise is generated according to an increase in gain, and performs a function of setting a maximum value for easy object identification.

In addition, the codec 40 compares three frames from among the sequentially input image frames in a state in which noise is secondarily attenuated through the 3D-NR 322 in the digital noise attenuator 32, and compares them to the deviation It has a 3D-NR 41 that attenuates noise correspondingly, and takes 20% of the total noise attenuation so as not to cause a reduction in resolution. .

That is, in the CCTV system having a color control function in low light to which the present invention is applied, the ISP 30 processes the entire image signal (signal processing that converts an image photographed in low light into an identifiable color image and an image without afterimage) about 80% of the video signal processing is performed, and the codec 40 performs about 20% of the entire image signal processing.

At this time, the drag and afterimage of the image appear conspicuously when the noise attenuation is strengthened through the 3D-NR 41 in the codec 40, and the degree of noise attenuation in the image is determined through the first to third noise attenuators. Since it can be adjusted, adverse effects such as dragging and afterimage of the image do not occur.

In addition, although not shown in FIG. 1 , a video amplifier or the like may be further provided to amplify an image signal and output it to the outside.

On the other hand, FIG. 2 shows a flowchart for explaining the method of the present invention. When the CCTV starts to operate (S1), the ISP 30 based on the image signal received through the lens 10 and the image sensor 20 ) to perform a predetermined algorithm.

First, in the ISP 30, it is determined (S2) whether the image signal received through the image sensor 20 is in a low illuminance state (for example, 0.05 to 0.08 (LUX) or less). The exposure time of (20) is adjusted as shown in FIG. 9 (S3).

At this time, the determination of low illuminance is determined by the gain value reflected in a separate image, or also determined by the visible light sensor, and the exposure control method performed by the digital slow shutter controller 31 shown in FIG. 4 is shown. As shown in the graph, if the step of controlling the exposure of the camera proceeds with Shutter -> Iris -> Gain, it is judged as low illumination when entering the gain step.

9 is a graph showing a form of controlling the exposure time in the ISP 30 (when the minimum gain x1 vs. x8 is set as the maximum gain), and when the brightness becomes dark or bright in the Long Exposure section Accordingly, the exposure time of the maximum gain of x8 is automatically controlled. At this time, the exposure time of the image sensor 20 moves along the blue curve section.

Next, the ISP 30 performs low-illuminance color adjustment (S4), low-illuminance noise attenuation through the digital noise attenuator 32 (S5), and low-illuminance image output gamma adjustment through the gamma controller 33 (S6) is done.

Here, to adjust the output gamma of the image, compressed gamma is used as shown in FIG. 7 (a) in a general situation (in a bright situation) in order to improve the contrast of the image, and is uniform as shown in FIG. 7 (b) in a low light. Gamma pattern and high luminance area can be expressed evenly.

As a result, the ISP 30 can identify the color through the process of performing the above-described steps in the image taken in low light, and completes the process of converting the image into an image that can identify a moving subject and ends (S7) ), or when it is determined that the illuminance is not low in step S2, the algorithm is immediately terminated (S7).

FIG. 3 is a flowchart illustrating the low-illuminance color adjustment subroutine S4 of FIG. 2 .

In general, in order to suppress the occurrence of color noise during low illumination, each color is suppressed. At this time, the illumination is determined by the gain value reflected in the image, and the degree of color suppression is linear according to the change of the image. An interpolation method is adopted.

11 is a graph showing each region when color is suppressed in the ISP of the present invention, and is tuned and used according to each illuminance by adjusting the color suppression gain as described above.

That is, conventionally, color suppression by applying a fixed gain value did not keep color expression power equal to noise, but in the present invention, color expression power versus noise can be equally maintained and a linear interpolation method capable of reducing color noise is used. did

11( a ) is an area in which color is expressed with the maximum gain because color noise is not derived by judging by the general illuminance environment, and is controlled by Equation 1 . The region (b) of FIG. 11 is controlled according to Equation 2 so that the color expression power is not inhibited and color noise is strongly suppressed by lowering the gain by determining that the region (a) enters the environment with low illuminance.

In addition, the region (c) of FIG. 11 is a point in time at which low illuminance is entered and color noise is increased, and the color gain is controlled by Equation 3. The region (d) of FIG. 11 is the region determined by the lowest illuminance and is controlled by Equation 4.

In this way, when color suppression is performed in the ISP 30, color is lost, and in this case, color expression is smoothed by tuning the color suppression gain at low illumination.

At this time, in order to increase the expressive power of color, it is necessary to adjust the color suppression compared to the color noise. In order to reduce the color noise and maximize the expressive power of the color, as shown in the graph of the color suppression section of the present invention shown in FIG. It is divided into 4 steps, and each area is suppressed for each color as shown in (a) to (d) of FIG. 11 .

The reason for applying separately in each stage like this is that since the size of noise varies according to the level of gain, the degree of color suppression must also change at each stage, so that color reproducibility can be adjusted compared to color noise.

Meanwhile, the principle of low-illuminance color adjustment will be described with reference to FIG. 3 and FIGS. 10 and 11 (a) to (d) above.

First, when the step of adjusting the color (S4) after adjusting the exposure time (S3) of the sensor in the ISP 30 is started (S40), whether the current gain value is less than or equal to the predetermined Low value (S41), or greater than the Low It is sequentially determined whether it is less than or equal to the predetermined Middle (S43), or greater than the Middle and less than or equal to the predetermined High (S45), or whether it is greater than the predetermined High (S47).

As a result of determining the magnitude of the current gain value in the ISP 30 as described above, if it is less than or equal to the predetermined Low (Yes in S41), the low illuminance color is corrected to the maximum correction gain value to maintain the maximum gain value (S42). ).

That is, if the current gain value for recognizing illuminance is less than or equal to the Low value, the maximum color gain is maintained without color correction.

However, if the current gain value is greater than the predetermined Low (No in S41) and less than or equal to the Middle (Yes in S43), the low illuminance color gain is linearly interpolated according to the change of the image (S44).

That is, if the current gain value is greater than the Low value and less than or equal to the Middle value (refer to (b) of FIG. 11), a color gain suitable for the current illuminance is applied, but the linear interpolation for correcting the color signal in case of a decrease in illuminance is shown in FIG. As shown in (b), the color gain value is interpolated and applied according to the change in illuminance of the corresponding area.

In addition, as a result of judging the size of the current gain value, if it is greater than Middle (No in S43) and less than or equal to High (Yes in S45), the low-illuminance color gain is linearly interpolated as shown in (c) of FIG. It will do (S46).

That is, if the current gain value is greater than the Middle value and less than or equal to High (refer to FIG. 11(c)), in order to suppress the increase in color noise, linear interpolation for the color gain is shown in FIG. 10(c). As shown, the color gain value is interpolated and applied according to the change in illuminance of the corresponding area.

On the other hand, as a result of determining the magnitude of the current gain in the ISP 30, if it is greater than High, see FIG. If the value is greater than the High value, the illuminance is regarded as completely dark and the minimum value of the color gain is maintained (S48), and then the algorithm for low-illuminance color adjustment is finished (S49).

In other words, in the color adjustment method performed by the ISP 30, when the gain for recognizing illuminance is less than or equal to a predetermined Low (eg, Approx. 1 [dB]) value, the maximum color gain is obtained without color correction. keep it

However, when the illuminance is changed to a darker state, that is, the gain value is larger than Low and set Middle (for example,

Approx. 35.1[dB]) value, apply a color gain suitable for the current illuminance, but perform linear interpolation to correct the color signal in case of a decrease in illuminance.

In addition, when it is judged that the illuminance is darker than that, that is, when the gain value is greater than Middle and less than or equal to the High (eg Approx. 35.1 [dB] or more) value, the color gain is applied to suppress the increase in color noise. Linear interpolation is performed for the , and when the gain value is greater than High, the illuminance is regarded as a completely dark state and the minimum value of the color gain is maintained.

10: lens 20: image oath
30: image signal processor (combined with "ISP")
31: digital slow shutter controller 32: digital noise attenuator
341 : 2D-NR 342 : 3D-NR
33: gamma controller 34: automatic gain controller
40: codec 41: 3D-NR
50: wired and wireless communication unit

Claims (10)

CCTV system equipped with lens, image sensor, image signal processor and codec
In this case, the image signal processor suppresses noise with a digital slow shutter controller and digital signal processing that adjusts the exposure time so that the subject can be taken with a feeling, so that the afterimage is reduced in low illuminance mode of 0.05 to 0.08 lux or less. Digital Noise Reducter, which attenuates noise within 80% of the total noise, maintains LCD Mode during the daytime, and an automatic gain controller to increase low-light sensitivity. The gamma controller that adjusts the gamma by applying the output gamma of 0.55 gamma, which is the LCD mode, and 0.35 gamma in low-light conditions, and the automatic function that automatically adjusts the gain to the maximum value for easy subject identification. It consists of a gain controller (Auto Gain Control;AGC), but the digital slow shutter controller sets the number of output frames to 7 frames per second or more to prevent dragging in low-illuminance mode 0.05 to 0.08 (LUX) or less. CCTV system with color control function in low light, characterized in that it operates. The method according to claim 1, wherein the digital noise attenuator compares a predetermined reference frame and two previous frames among a plurality of image frames sequentially input through the digital slow shutter controller to attenuate the primary noise in response to the deviation. 3D-NR, which compares 3 sequentially input image frames in a state in which the primary noise is attenuated through 2D-NR and the 2D-NR, and attenuates secondary noise in response to the deviation; CCTV system with color control function in low light. The method according to claim 2, wherein the 2D-NR is responsible for 10% of the total noise attenuation in order to prevent an adverse effect that the resolution deteriorates in proportion to the noise attenuation degree when the noise attenuation is increased, and the 3D-NR is the noise attenuation degree CCTV system with color control function in low light, characterized in that 70% of the total noise is attenuated so that adverse effects such as dragging of images and afterimages do not occur when the value is increased. The method according to claim 1, wherein the codec compares each of three frames among the sequentially input image frames in a state in which noise is secondarily attenuated through 3D-NR in the digital noise attenuator, and reduces the tertiary noise in response to the deviation. CCTV system with color control function in low light, characterized in that it further comprises 3D-NR to attenuate. The CCTV system with a color control function in low light according to claim 4, wherein the 3D-NR in the codec is responsible for 20% of the total noise attenuation so as not to cause a reduction in resolution. The CCTV system with a color control function in low light according to claim 1, wherein the lens uses a lens of F2.0 or higher (Fixed type or Varifocal type). The CCTV system with a color control function in low light according to claim 1, wherein the image sensor uses a sensor capable of maintaining a sensitivity of at least 800mV, but has a high resolution of 1.5M pixels or more with a resolution of 1440×1024. . In configuring the low-illuminance color control method of a CCTV system having a lens, an image sensor, an image signal processor, and a codec, the image signal received from the image signal processor through the image sensor A subroutine of determining whether the illuminance is in a low illuminance state, adjusting the exposure time of the image sensor if it is determined to be low illuminance, and then adjusting the low illuminance color according to the gain value of the image taken in low illuminance is performed. Steps, attenuating low-illuminance noise, and adjusting the low-illuminance image output gamma are performed, but the subroutine for adjusting the low-illuminance color determines whether the gain for recognizing the current illumination is less than or equal to a predetermined Low value; Or the step to sequentially determine whether it is greater than Low and less than or equal to the determined Middle, or greater than the Middle and less than or equal to the predetermined High, or whether it is greater than the predetermined High and the result of sequential judgment as above,
If the current gain value for recognizing illuminance is less than or equal to the Low value, the stage of maintaining the maximum color gain without color correction. A step of linear interpolation to correct a color signal due to a decrease in illuminance, and if the current gain value is greater than the middle value and less than or equal to the high value, the step of performing linear interpolation on the color gain to suppress the increase in color noise; When the gain value is greater than the High value, the illuminance is regarded as completely dark and the color control method in low illuminance of a CCTV system, characterized in that it consists of the step of maintaining the minimum value of the color gain. The method according to claim 8, wherein the criterion for determining that the illuminance of the image signal received through the image sensor from the image signal processor is low is set to 0.05 to 0.08 lux or less. . The method of claim 8, wherein the Low value is set to 1 [DB], the Middle value is set to 35.1 [DB], and the High value is set to exceed 35.1 [DB] How to control color.

Images