KR100962307B1 - Method for converting color mode of camera - Google Patents

Abstract

A color mode switching method is disclosed in an imaging device. The color mode switching method in the image capturing apparatus includes the steps of determining whether a current mode is a color mode or a black and white mode in an image capturing apparatus having a color mode and a black and white mode switching function based on the brightness of a subject, Determining whether low light level, which is a function of controlling the time for receiving an image signal from a subject, is set; calculating low light value when the low light level is set; and whether the calculated low light value is equal to or less than a predetermined low light threshold value. Detecting, and switching the black and white mode to the color mode when the low light value is less than or equal to the low light threshold value. And when the low light level is not set, calculating an AGC gain functioning to amplify and attenuate the luminance value of the video signal, detecting whether the calculated AGC gain is equal to or less than a predetermined AGC gain threshold, and calculating the AGC. If the gain is below the AGC gain threshold, switching to the color mode. As a result, the difference between the luminance level at the time of switching to the color mode and the luminance level at the time of switching to the black and white mode can be sufficiently enlarged to prevent malfunction in switching between the color mode and the monochrome mode.

Imaging Device, Surveillance Camera, Day / Night Function, Color Mode, Monochrome Mode

Description

Color mode switching method in the imaging device {Method for converting color mode of camera}

1 is a flowchart illustrating a conventional color mode and monochrome mode automatic switching method;

2 is a block diagram of a surveillance camera according to the invention, and

3 is a flowchart provided to explain a mode switching method of the imaging apparatus according to the present invention.

Explanation of symbols on the main parts of the drawings

200 lens 210 filter part

220: CCD 230: CDS / AGC part

240: digital signal processing unit 250: control unit

260: display unit

The present invention relates to a color mode switching method in an image pickup device, and more particularly, to improve color mode and black and white mode switching timing in an image pickup device having a color mode and a monochrome mode switching function, thereby preventing malfunction of the image pickup device. It relates to a mode switching method of an imaging device.

Surveillance cameras are equipped with day and night functions to obtain an optimized image by switching the filter on the front of the lens according to the brightness of the subject. Select color mode for daytime function and black and white mode for nighttime function. The color mode is selected by turning on the IR (Infra-Red) filter located in the front surface of the lens, and the black and white mode is selected by turning off the IR (Infra-Red) filter in the front surface of the lens. Turning off the IR filter means selecting the focus filter. In general, the color mode and the black and white mode are automatically selected according to the luminance of the subject calculated based on the AE (Auto Exposure) function.

The AE (Auto Exposure) function adjusts the iris, AGC (Auto Gain Control) gain and shutter speed, i.e., low light, so that the captured image is in optimal condition.When the subject is dark compared to a predetermined reference brightness, the aperture Increase the amount of light to be received, increase the AGC gain to amplify the luminance value of the input video signal, and increase the low illumination to slow the shutter speed to brighten the image by receiving the light for a long time. When the subject is brighter than the predetermined reference brightness, the aperture is controlled to reverse the AGC gain and low light so that the image maintains an appropriate brightness.

1 is a flowchart illustrating a conventional color mode and black and white mode automatic switching method. Referring to FIG. 1, first, a luminance level of an image is read from AE data (S100). Then, it is checked whether the currently set mode is a color mode or a black and white mode (S110). If it is in the color mode, it should be checked whether the mode should be switched to the monochrome mode (S120). In general, a user sets a luminance level, which is a reference for switching a color mode to a black and white mode, and usually has a value of about 40 to 60 IRE. Here, the Institute of Radio Engineer (IRE) is a unit representing the magnitude of a video signal, where 100 IRE indicates the highest white amplitude and 0 IRE indicates the black level.

In this embodiment, if the monochrome mode switching level for switching the color mode to the monochrome mode is set to 50IRE, it is checked whether the luminance level calculated in step S100 is smaller than 50IRE. If it is small switch to the black and white mode (S130). If it is determined in step S110 that the black and white mode is determined, it is checked whether the calculated luminance level is greater than the color mode switching level which is a threshold for switching to the color mode (S140). In general, the color mode switching level has a level of about 90 to 110 IRE. In this embodiment, the color mode switching level is determined as 100 IRE. If the brightness level of the current image is 100 IRE or more, the mode is switched to the color mode (S150). In accordance with the color mode switching or the black and white mode switching, the brightness level of the image increases or decreases in a direction approaching a predetermined reference level.

However, when determining the color mode or monochrome mode switching point based only on the luminance level read from the AE data as described above, the difference between the color mode switching level and the monochrome mode switching level is more than a predetermined value because of the AE function that always maintains a constant luminance. It is impossible to increase.

Accordingly, when using a light source such as a halogen lamp, when switching from the color mode to the black and white mode, the brightness level of the image increases by about 80 to 120 IRE, and the increased brightness level is changed from the color mode to the black and white mode. Since the monochrome mode switching level is 90 to 120 IRE or more, switching to the color mode occurs again. As a result of the color mode switching, the luminance level of the image becomes less than the initial 40 IRE and there is a problem in that a phenomenon in which the switching to the black and white mode is repeated repeatedly occurs.

The present invention has been made to solve the above problems, and an object of the present invention is to increase the difference between the two threshold values for switching from the color mode to the black mode or the black and white mode to the color mode than before, the type of external light source The present invention provides a color mode switching method in an image pickup device having a color mode and a black and white mode switching function, which can prevent a phenomenon of flashing that may occur.

According to an aspect of the present invention, there is provided a color mode switching method of an imaging apparatus having a color mode and a black and white mode switching function based on a brightness of a subject, including determining whether a current mode is the color mode or the black and white mode; If it is determined in the black-and-white mode, determining whether or not the low illuminance, which is a function of controlling the time to receive the image signal from the subject is set, if the low illuminance is set, calculating a low illuminance value, the calculated low illuminance value is Detecting whether the light intensity is less than or equal to a predetermined low light threshold value, and switching the black and white mode to the color mode when the low light intensity is less than or equal to the low light intensity threshold value.                     

The low illuminance value is controlled by an Auto Exposure (AE) function that automatically performs optimal exposure setting, and the low illuminance threshold is half of the maximum value of the low illuminance value that the imaging device may have. desirable.

In the color mode switching method according to the present invention, when the low illuminance is not set in the step of determining whether the low illuminance is set, calculating the AGC gain functioning to amplify and attenuate the luminance value of the video signal, Detecting whether the calculated AGC gain is less than or equal to a predetermined AGC gain threshold; and switching to the color mode if the calculated AGC gain is less than or equal to the AGC gain threshold.

Here, the AGC gain is controlled by an auto exposure (AE) function that automatically performs optimal exposure setting, and the AGC gain threshold value is the minimum value of the AGC gain that the imaging apparatus may have. desirable. The color mode switching is performed by switching the filter of the imaging device to an IR (infra-red) filter.

On the other hand, in the mode determining step, when it is determined that the color mode, calculating the brightness level of the input image based on the automatic exposure function, and switching to the black and white mode when the brightness level is less than a predetermined black and white mode switching level In addition, the monochrome mode switching, it is possible to switch the filter of the imaging device to the focus filter. And it is preferable that the said imaging device which concerns on this invention is a surveillance camera.                     

Another method for switching to a color mode of an imaging device having a function of switching between a color mode and a black and white mode based on the brightness of a subject according to the present invention includes determining whether the current mode is the monochrome mode or the color mode; Calculating the AGC gain functioning to amplify and attenuate the luminance value of the image signal when detecting the monochrome mode; detecting whether the calculated AGC gain is equal to or less than a predetermined AGC gain threshold; and calculating the calculated AGC gain. If an AGC gain is less than or equal to the AGC gain threshold, switching to the color mode.

In this case, the AGC gain is controlled by an auto exposure (AE) function that automatically performs an optimal exposure setting, and the AGC gain threshold is a minimum value of the AGC gain that the imaging apparatus may have. Preferably, the color mode switching is performed by switching the filter of the imaging device to an infrared (red) filter.

And in the mode determining step, calculating the brightness level of the input image based on the automatic exposure function when the color mode is determined, and switching to the black and white mode when the brightness level is less than or equal to a predetermined black and white mode switching level. It is preferable to further include. At this time, it is preferable that the monochrome mode switching switches the filter of the imaging device to a focus filter. The imaging device may be a surveillance camera.

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

2 is a block diagram of a surveillance camera according to the present invention. Referring to FIG. 1, the surveillance camera includes a lens 200, a filter 210, a charge-coupled device (CCD) 220, a correlated double sampling hold and automatic gain control (CDS / AGC) unit 230, The digital signal processor 240, the controller 250, and the display 260 are provided.

The lens 200 receives a light drop image of an external object. The filter 210 performs a predetermined filtering on the optical image input from the lens 200, wherein the filter 210 is one of IR filters or focus filters under the control of the controller 250 according to the brightness of the input image. Suitable filters are used. The CCD 220 forms an image signal received and converts the image signal into an electrical signal. The CDS / AGC unit 230 extracts the optimized image signal by adjusting the AGC gain to remove noise from the electrical image signal received from the CCD 220 and to maintain a constant brightness of the image. The A / D converter (not shown) converts the signal received from the CDS / AGC unit 230 into a digital signal. The digital signal processor 240 processes the image signal received from the A / D converter, and in particular, calculates a luminance level from the AE data of the image.

The controller 250 controls the iris, the filter, the CDS / AGC unit 230, and the digital signal processor 240 so that the luminance level of the image is always maintained based on the AE function. That is, when the image is below a predetermined reference level, the AGC gain is adjusted by controlling the CDS / AGC unit 230. In addition, by controlling the digital signal processor 240 to adjust the shutter speed by the user's selection, low light is additionally controlled. The color mode and the black and white mode are switched based on the luminance, the AGC gain, and the low light calculated from the AE data.

In other words, if the low illuminance is set and the current monochrome mode, the AGC gain and low illuminance are operating at the maximum value. In this case, when the low illuminance becomes smaller than the predetermined low illuminance threshold value, the image is brightened, and the controller 250 switches the current mode to the color mode. At this time, the low light threshold is preferably half the maximum low light. That is, when the maximum low light level is 128 times, it is desirable to determine the low light threshold value as 64 times.

If the low light level is not set and the monochrome mode is used, the AGC gain will be set to the maximum when the monochrome mode is switched. At this time, when the AGC gain is less than the predetermined AGC gain threshold, it is determined that the image is bright, and switch to the color mode. Here, the AGC gain threshold is preferably the minimum AGC gain that the present imaging device can have.

On the other hand, if the current color mode is set, as in the conventional case, when the current luminance value is less than or equal to the predetermined monochrome mode switching level based on the luminance value read from the AE data from the digital signal processing unit 240, it switches to the monochrome mode. . In response to the color mode switching, the filter 210 of the front surface of the lens 220 is switched to the IR filter, and the filter 210 is switched to the focusing filter in response to the black and white mode switching.

When switching from the black and white mode to the color mode by the above method, the luminance value at the time of switching is increased by 2 to 3 times compared to the conventional 100 IRE. Therefore, even when there is no change in the threshold value when switching to the black and white mode, the difference between the two levels is approximately twice the difference between the two levels of the conventional can prevent the phenomenon of the conventional phenomenon.

The D / A converter (not shown) receives a digital video signal from the digital signal processor 240 and converts the digital video signal into an analog signal, and the display unit 260 displays an image corresponding to the video signal.

3 is a flowchart provided to explain a mode switching method of the imaging apparatus according to the present invention. 2 and 3, first, a luminance level is calculated from AE data (S300). Then, it is determined whether the current color mode or the black and white mode is set (S310).

If the black and white mode is set, it is checked whether the low light is set (S320). If the low light level is set, it is determined whether the current low light level is equal to or less than a predetermined low light threshold value (S330). If less than the predetermined low light threshold value, the monochrome mode is switched to the color mode (S340). If the low light value is larger than the low light threshold value, the mode switching is not performed. In this case, the low light intensity threshold is preferably about half of the maximum value of the low light value that can be adjusted. That is, when the low light value can be adjusted from 2 times up to 128 times, the low light intensity threshold is preferably determined to be 1 times to 64 times.

If the low illuminance is not set in step S320, it is checked whether the current AGC gain is less than or equal to a predetermined AGC gain threshold (S350). At this time, the predetermined AGC gain threshold is preferably the minimum AGC gain that the present imaging device can have. If the AGC gain is less than or equal to the predetermined AGC gain threshold, the mode is switched to the color mode. Color mode switching is performed by switching the filter 210 to the IR filter.

On the other hand, when it is determined that the color mode in step S300, the luminance level calculated in step S300 is a predetermined Check if it is smaller than the monochrome mode switching level (S360), and if it is small, switch to monochrome mode (S370). If large, no switching is performed and the current state is maintained. In this case, switching to the black and white mode is performed by switching the IR filter, the filter 210 corresponding to the color mode, to the focus filter corresponding to the black and white mode.

In the present invention, since the method of switching from the color mode to the black-and-white mode is the same, the two black-fold mode switching levels are the same, but the luminance level at the time of switching the black-and-white mode to the color mode according to the present invention is the About twice as much. On the basis of only AE data as in the related art, the luminance level at the time of converting to the color mode is inevitably maintained at about 100 IRE, while the present invention detects the color mode switching time through AGC gain and low illumination, and thus the luminance level at the time of switching. It was made larger than 2 times the conventional. As described above, the present invention can sufficiently widen the interval between the luminance level when switching the monochrome mode and the luminance level when switching the color mode, thereby preventing a malfunction such as a conventional flashing phenomenon.

As described above, according to the present invention, the flashing phenomenon in which the interval between the two luminance levels for switching the color mode and the black and white mode of the imaging device is sufficiently widened, and the switching between the black and white mode and the color mode is repeated according to external illumination. Can be prevented. By preventing such a malfunction, the image quality of the captured image can be expected.

In addition, while the above has been shown and described with respect to preferred embodiments of the present invention, the present invention is not limited to the specific embodiments described above, the technology to which the invention belongs without departing from the spirit of the invention claimed in the claims Various modifications can be made by those skilled in the art, and these modifications should not be individually understood from the technical spirit or the prospect of the present invention.

Claims (11)

In the color mode switching method in the image pickup device having a color mode and a black and white mode switching function based on the brightness of the subject, (a) determining whether a current mode is the color mode or the black and white mode; (b) if it is determined in the black and white mode, determining whether or not low light level is set, which is a function of controlling a time for receiving an image signal from a subject by adjusting a shutter speed; (c) calculating a low light value when the low light level is set; (d) detecting whether the calculated low light value is less than or equal to a low light threshold value; And and (e) switching the monochrome mode to the color mode when the low illuminance value is equal to or lower than the low illuminance threshold value. The method of claim 1, wherein the low light value, A method of color mode switching in an imaging device, characterized by being controlled by an Auto Exposure (AE) function that automatically performs optimal exposure settings. The method of claim 2, wherein the low light threshold value, And a half value of the maximum value of the low illuminance value the image pickup apparatus may have. The method of claim 1, In step (b), calculating the AGC gain functioning to amplify and attenuate the luminance value of the video signal when the low illumination is not set; Detecting whether the calculated AGC gain is below an AGC gain threshold; And And switching to the color mode when the calculated AGC gain is equal to or less than the AGC gain threshold. The method of claim 4, wherein the AGC gain, A color mode switching method in an imaging apparatus, characterized by being controlled by an auto exposure (AE) function that automatically performs optimal exposure settings. The method of claim 5, wherein the AGC gain threshold, And a minimum value of AGC gains which the imaging device may have. The method of claim 1, wherein the color mode switching, And switching the filter of the imaging device to an IR (infra-red) filter. The method of claim 1, In the step (a), if it is determined that the color mode, Calculating a brightness level of the input image based on the auto exposure function; And And switching to the black and white mode when the brightness level is equal to or less than the black and white mode switching level. The method of claim 8, wherein the black and white mode switching, And switching the filter of the imaging device to a focusing filter. The method of claim 1, wherein the imaging device, The color mode switching method in the imaging device, characterized in that the camera for monitoring. A color mode switching method of an image pickup apparatus having a function of switching between a color mode and a black and white mode based on a brightness of a subject, (a) determining whether a current mode is the monochrome mode or the color mode; (b) calculating an AGC gain functioning to amplify and attenuate the luminance value of the video signal when it is determined that the monochrome mode; (c) detecting whether the calculated AGC gain is below an AGC gain threshold; And and (d) switching to the color mode when the calculated AGC gain is equal to or less than the AGC gain threshold. 2.

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