KR101615381B1 - Image acquisition method and digital camera system - Google Patents

Abstract

A method of acquiring an image in a digital camera according to the present invention includes: photographing an image; Determining an exposure calculation area according to illuminance of an external environment; Determining a brightness correction value that causes the image of the exposure calculation area to have a set exposure value among the photographed images; And correcting the photographed image with the brightness correction value.

Image acquisition, brightness correction, exposure, illumination, digital camera

Description

IMAGE ACQUISITION METHOD AND DIGITAL CAMERA SYSTEM [0001]

The present invention relates to a method of acquiring an image in a digital camera, and more particularly, to a method of acquiring an image in a manner of correcting an image taken by a driving camera for a vehicle.

Advances in device and image processing techniques for image capture have disclosed various image processing systems for vehicles in motion.

That is, a system that carries out or assists parking of a vehicle using an image photographed by a digital camera module (hereinafter, abbreviated as a digital camera), or a system that photographs and stores an image of a vehicle as a black box as a kind of black box has already been commercialized And an automatic traveling system using a camera that takes an image of the front of the vehicle is under development.

Even digital cameras for automobiles require adjustment of the aperture value for shooting. A diaphragm value for driving an image sensor (for example, a CCD, a CMOS image sensor, etc.) provided in a conventional camera module for a vehicle (e.g., a front camera, a driving recorder, etc.) is set similar to a general digital camera.

That is, a proper aperture value is obtained for acquiring an image of the exposure value set for the entire screen of the image obtained in the preview mode or a partial area thereof (e.g., a rectangular partial area shifted to the center). A region for automatically calculating the aperture value as described above may also be referred to as an ROI (Region of Interest).

However, the ROI and / or exposure value to be applied to daytime and nighttime may be set differently, considering the difference between the daytime and nighttime environments. For example, at night, the ROI area may be wider than the daytime, and / or the exposure value may be lowered.

Thereafter, the obtained diaphragm value is applied to the entire screen in accordance with the type of the image sensor, or brightness correction is performed on the photographed image.

However, the overall brightness of an image photographed in the course of passing through a tunnel or the like during a day can be drastically changed, and the overall brightness of an image photographed by a headlight of a vehicle coming in at night can be drastically changed.

According to the function of keeping the exposure value of the digital camera module constant, the exposure value of the photographed image is kept constant even in the above case. However, the problem is that, in an environment in which the brightness rapidly changes as described above, the brightness of an object of interest for safe driving of the vehicle often does not have the average value of the entire image or the ROI.

For example, if the ROI at the exit of the tunnel is set to a bright area of the exit, the overall brightness is lowered, so that the image is less distinguishable from other vehicles in the tunnel.

Therefore, in an image photographed with a fixed aperture value and / or a brightness-corrected image with a fixed setting, the object of interest may be rather difficult to identify.

Figs. 1A and 1B are for explaining the difficulty of identification in an image photographed by the fixed aperture value and / or in an image photographed with a fixed exposure value.

FIG. 1A is an image photographed in the running direction of a vehicle immediately before leaving a tunnel during a daytime of a vehicle, and is photographed at a fixed exposure value with respect to the entire screen. In order to set the iris for obtaining the fixed exposure value, nine divided screens (W1 to W9) are applied. FIG. 1B is an enlarged view of a region including the forward traveling vehicle of interest in the image of FIG. 1A. As shown in the figure, the diaphragm value is photographed at a too large value, and the image area of FIG. 1B is overexposed, so that it is not possible to identify the license plate of the forward driving vehicle.

The present invention provides a method of acquiring an image from a digital camera so as not to degrade the discrimination of an object of interest.

A method of acquiring images in a digital camera according to an embodiment of the present invention includes: photographing an image; Determining an exposure calculation area according to illuminance of an external environment; Determining a brightness correction value that causes the image of the exposure calculation area to have a set exposure value among the photographed images; And correcting the photographed image with the brightness correction value.

According to another aspect of the present invention, there is provided a digital camera system including: an image sensing unit including a photosensor and generating an image based on sensed values of the photosensor; A sensor module including an internal image processor for performing illumination and an illuminance sensing unit for sensing illuminance of an external environment; And a setting value storage unit for storing setting values to be applied to image processing by the internal image processor, an image input unit for receiving an image from the sensor module, and a day / night recognition unit for recognizing the illuminance sensed by the illumination sensing unit And an image processing chip.

The image acquiring method in the digital camera according to the present invention according to the above configuration has an advantage in that the distinction of the object of interest is not deteriorated even in an environment in which the brightness rapidly changes.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

2 illustrates a method of acquiring an image in a digital camera according to an embodiment of the present invention. The image acquisition method in the digital camera shown in FIG. 2 includes: (S120) photographing an image; Determining an exposure calculation area according to the illuminance of the external environment (S140); A step (S160) of determining a brightness correction value that causes the image of the exposure calculation area among the photographed images to have a set exposure value; And correcting the photographed image with the brightness correction value (S180).

The step of photographing the image (S120) may acquire a still image successively photographed by the digital camera in the moving image mode.

The illuminance in step S140 may be applied in successive values, or may be applied stepwise in such a manner that the illuminance level is classified into a specified number of illuminance levels.

In the step of determining the exposure calculation area (S140), the high and low illuminance of the external environment can be determined by one of the following three methods. The first method is to estimate the illuminance of the external environment according to the current time. For example, if the current time is between the starting time and the sunset time, the illuminance of the outside environment is estimated as 'low' illuminance, and if not, the illuminance of 'night' illuminance is estimated.

The second method is to estimate the illuminance of the external environment from the full brightness of the photographed image. For example, it can be classified into two or more illumination levels according to the sum of the brightness values of all the pixels of the photographed image.

The third method is to apply a separately installed illuminometer to the vehicle. For example, it can be classified into two or more illuminance levels according to illuminance values inputted from an illuminance meter provided outside the vehicle.

In step S140, the exposure calculation area may be a kind of ROI (Region of Interest), and the exposure calculation area may include a center portion of the screen as a partial area of the entire captured image region. In step S140, the size (e.g., area) of the exposure calculation area may be determined according to the illumination. For example, the higher the illuminance or the higher the illuminance level, the greater the size of the exposure calculation area (the larger the area).

In step S160, the brightness correction value may be calculated by applying a predetermined operation to the pixel values included in the exposure calculation area determined in step S140.

The process of step S160 may be similar to the process of calculating an appropriate exposure value by applying a predetermined operation to pixel values included in the exposure calculation area in a preview image in a general digital camera for photographing a still image. However, the exposure value is used for photographing a picture, and the brightness correction value is used for correcting a photographed image after photographing.

In step S180, the brightness correction value calculated in step S160 is applied to the photographed image to perform correction. The brightness correction value may be a ratio value applied in a form of multiplying the brightness value of each pixel or an addition value applied in a form added to the brightness value of each pixel.

Figs. 3A and 3B are for explaining the concept of acquiring an image according to the image acquisition method shown in Fig. The illustrated camera system divides the illuminance of the external environment into two levels of day or night.

The screen shown in FIG. 3A shows that the brightness correction value is calculated by widening the exposure calculation area in the case of the daytime. The exposure calculation area becomes a full screen and the entire screen is divided into nine equal parts and the average exposure level or the brightness level of the sampling pixels (or pixels) (e.g., divided screen center pixel) in each of the divided screens W1 to W9 . Thereafter, the average exposure levels of the nine divided screens W1 to W9 or the brightness levels of the sampling pixels are averaged to determine the exposure level of the full screen. Therefore, the exposure level to be applied to the entire screen determined according to the procedure shown in FIG. 2A becomes the exposure level for the entire screen.

The screen shown in Fig. 3B shows that, in the case of the night, the brightness correction value is calculated by narrowing the exposure calculation region r. In the figure, the exposure calculation region r is divided into nine equal parts, and the average exposure level or the brightness level of the sampling pixels (or pixels) (for example, divided screen center pixels) is detected in each of the divided screens w1 to w9. Thereafter, the average exposure levels of the nine divided screens w1 to w9 or the brightness levels of the sampling pixels are averaged to determine an exposure level to be applied to the entire screen. Therefore, the exposure level to be applied to the entire screen determined according to the procedure shown in FIG. 3B is substantially the exposure level for the narrowed exposure calculation area r, which is a part of the entire screen.

FIG. 4 shows an enlarged image of an image obtained by brightness-correcting an image after using the exposure level for the narrowed exposure calculation area r, which is a part of the entire screen, according to FIG. 3B. As shown in the figure, the entire area is darkened, and the surrounding area is difficult to identify, but it is easy to identify the license plates of other vehicles existing in the area of interest.

In the illustrated implementation, nine split screens are used, but in other implementations, a different number of split screens can be applied. The more divided screens, the more accurately the exposure level to be applied to the entire screen can be determined.

In another implementation, when the average exposure levels of the divided screens or the brightness levels of the sampling pixels are averaged, the addition ratio may be added to the average exposure level of the divided screen at the center or the brightness level of the sampling pixel . This is to prevent a sharp increase or decrease in gain occurring in the exposure calculation area and the outer boundary area.

In addition, the image processing system according to the present invention may set the ROI and / or the exposure value to be applied to the daytime and the nighttime differently in consideration of the difference between the daytime and nighttime environments. For example, at night, the ROI area may be wider than the daytime, and / or the exposure value may be lowered.

Here, the distinction between the daytime and nighttime environments can be classified according to the current time. Alternatively, when the vehicle is passing through a tunnel or the like even during the daytime, the entire brightness of the photographed image may change drastically. Considering that the total brightness of the image photographed by the headlights of vehicles coming in at night is rapidly changed, It can be distinguished by considering the overall illuminance of the environment.

In the latter case, a method of grasping the entire illuminance of the external environment may be calculated from the total brightness of the image obtained from the digital camera or obtained from an illuminometer installed separately in the vehicle.

Meanwhile, in another implementation, the brightness correction value obtained according to the procedure of FIG. 2 may be applied to the exposure value of the next frame of the moving image mode. This is because, rather than simply correcting the brightness after photographing, it is possible to obtain an image of a desired area more precisely by correcting the exposure value before the photographing and then photographing it. For example, if the brightness correction value is a brightness value of the original pixel value, it is determined that the exposure is insufficient, and the exposure value is corrected to increase the exposure value.

The image acquisition method in the case described above is as shown in FIG. 2, except for the added step S190 and the circulation structure thereof, so that redundant description will be omitted.

In step S190, the brightness correction value acquired in step S160 may be applied to the exposure value at the time of photographing the next time, or a value obtained by performing calculation according to a predetermined ratio may be applied to the exposure value.

6 shows an example of a camera system capable of performing an image acquisition method according to an embodiment of the present invention. In the illustrated camera system, a separate illuminance sensor and a photographing image sensor are integrated into a single sensor module, and an image obtaining method according to the present invention is implemented in an image processing chip.

The sensor module 100 of the camera system shown includes an image sensing unit 120 including a photosensor and generating an image at sensed values of the photosensor; An internal image processor 140 for primarily performing image processing on the image generated by the image sensing unit; And a roughness sensing unit 160 for sensing the roughness of the external environment.

The image processing chip 200 of the illustrated camera system includes a setting value storage unit 240 for storing setting values to be applied to image processing by the internal image processor 140; An image input unit 220 for receiving an image from the sensor module 100; A day / night recognizing unit 260 recognizing the day or night in the illuminance sensed by the illuminance sensing unit 160; An image compressing unit 270 compressing the input image continuously to generate a moving image; And a video recording unit 280 for recording the created moving picture.

The image sensing unit 120 may include a photosensitive sensor such as a CCD or a CMOS sensor, a mechanical / electronic diaphragm, and a lens module.

The image sensing unit 120 generates a Bayer image made up of sensing values using a photosensor, and processes the Bayer image according to a predetermined rule of the internal image processor 140. At this time, the internal image processor 140 may perform brightness correction of the Bayer image according to the brightness correction value applied from the image processing chip 200.

The daytime / night recognition unit 260 shown in FIG. 5 recognizes the input illuminance in two steps of day or night, but in other implementations, it can recognize the input illuminance in more steps.

The set value storage unit 240 may store information on the exposure calculation area used to perform the image acquisition method according to the present invention. The set value storage unit 240 may store the area of the exposure calculation area to be applied during the day and the area of the exposure area to be applied at night. In another embodiment, on-screen coordinates of diagonal vertices of the exposure calculation area to be applied to the daytime and on-screen coordinates of diagonal vertices of the exposure calculation area to be applied to the nighttime may be stored.

That is, the register value of the sensor for the functional operation added according to the idea of the present invention may be stored in the setting value storage unit 240 in advance. In another implementation, the set value storage unit 240 may be implemented as an external memory. The set value stored in the set value storage unit 240 may be loaded into the internal image processor 140 according to the illumination change. The internal image processor 140 receives the exposure calculation area information to be applied during the day and the exposure calculation area information to be applied at night according to the operation of the day / 240).

Then, the internal image processor 140 can adjust the exposure calculation area while monitoring the set value storage unit 240 in real time.

Next, the internal image processor 140 divides the exposure calculation area of the entire screen of the Bayer image received from the image sensing unit 120 into divided screens, and calculates average exposure levels of the divided screens, The brightness levels of the pixels may be averaged to determine the exposure level to apply to the full screen. Next, the internal image processor 140 may determine a brightness correction value from an exposure level to be applied to the determined entire screen, and thereby perform brightness correction on the Bayer image received from the image sensing unit 120. [

The image input unit 220; The image compressing unit 270 and the image recording unit 280 are similar to those of a general image processing chip, and thus a detailed description thereof will be omitted.

In another embodiment, the noise reduction function of the image processing chip 200 may be performed according to the illuminance sensed by the illuminance sensing unit 160. For example, since a large amount of noise occurs at a low illuminance, a noise reduction algorithm that can perform fast noise processing rather than image quality is applied, and a noise reduction algorithm having a higher image quality at a high illuminance can be applied.

It is to be noted that the technical spirit of the present invention has been specifically described in accordance with the above preferred embodiments, but it should be noted that the above-mentioned embodiments are intended to be illustrative and not restrictive. In addition, it will be understood by those of ordinary skill in the art that various embodiments are possible within the scope of the technical idea of the present invention.

Figs. 1A and 1B are photographing screens for explaining the difficulty of identification in an image photographed by the fixed aperture value and / or an image brightness-corrected by a fixed setting. Fig.

2 is a flowchart illustrating a method of acquiring an image in a digital camera according to an embodiment of the present invention.

Figs. 3A and 3B are photographing screens for explaining a concept of acquiring an image according to the image acquiring method shown in Fig. 2;

4 is a photographing screen for explaining an improvement effect according to an image acquisition method in a digital camera according to an embodiment of the present invention.

5 is a flowchart illustrating a method of acquiring an image in a digital camera according to another embodiment of the present invention.

6 is a block diagram illustrating a digital camera system according to an embodiment of the present invention.

Claims (10)

Photographing an image; Classifying the illuminance level into two or more illuminance levels according to illuminance values input from an illuminance meter installed outside the vehicle and determining the size of the exposure calculation area based on the illuminance levels; Determining a brightness correction value that causes the image of the exposure calculation area to have a set exposure value among the photographed images; Correcting the photographed image with the brightness correction value; And Applying the determined brightness correction value to an exposure value at the time of photographing of a next frame of a moving image mode; Wherein the digital camera is a digital camera. The method according to claim 1, Wherein the step of determining the exposure calculation area determines the area or coordinates of the exposure calculation area. The method according to claim 1, In the step of determining the exposure calculation area, And setting the size of the exposure calculation area to be larger as the illuminance is higher. The method according to claim 1, Wherein the illuminance is determined to be daytime or nighttime according to the current time. The method according to claim 1, Preferably, And calculating the total brightness of the photographed image or obtained from a separate sensing means. delete An image sensing unit including a photosensitive sensor and generating an image with sensed values of the photosensitive sensor; An internal image processor for primarily performing image processing on the image generated by the image sensing unit, An illuminance sensing unit for sensing the illuminance of the external environment A sensor module including the sensor module; And A setting value storage unit for storing setting values to be applied to the image processing by the internal image processor; An image input unit for receiving an image from the sensor module, The day / night recognition unit recognizes the illuminance sensed by the illumination sensing unit An image processing chip; / RTI > Wherein the sensor module applies the present invention to an exposure value of a next frame based on a set value stored in the set value storage unit. 8. The method of claim 7, In the set value storage section, (Or coordinates) of the exposure calculation area to be applied during the day, and the area of the exposure area (or coordinates) to be applied at night. 8. The method of claim 7, The image processing chip includes: An image compressing unit for continuously compressing the input image to create a moving image; And And a video recording unit The digital camera system further comprising: 8. The method of claim 7, The image sensing unit includes: A photosensor; iris; And a lens module The digital camera system comprising:

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