KR101713255B1 - Device and method for making high dynamic range image - Google Patents

Abstract

The present invention relates to an apparatus and method for generating a high dynamic range image, and more particularly, to a high dynamic range image generating apparatus and method for generating a high dynamic range image by varying exposure for each pixel.

Description

TECHNICAL FIELD [0001] The present invention relates to a device and a method for generating a high dynamic range image,

The present invention relates to an apparatus and method for generating a high dynamic range image, and more particularly, to a high dynamic range image generating apparatus and method for generating a high dynamic range image by varying exposure for each pixel.

High Dynamic Range Imaging (HDRI) refers to a digital image processing technique that can handle a much higher dynamic range than usually allowed. High dynamic range imaging was originally developed to improve the quality of computer rendered images. With the advent of this technique, HDR images have become widely used as a term referring to images generated from multiple images through tone mapping.

The background art of the present invention is disclosed in Korean Patent Registration No. 10-0787190 (published on Dec. 21, 2007, double shuttering method effectively increasing the effective dynamic range of an image sensor).

The present invention provides an apparatus and method for generating a high dynamic range image that efficiently generates a high dynamic range image by varying the exposure for each pixel.

The objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood from the following description.

According to an aspect of the present invention, an apparatus for generating a high dynamic range image is provided.

A high dynamic range image generating apparatus according to an embodiment of the present invention includes an image input unit to which image information is input, a pixel clipping determining unit to determine whether there is a clipped pixel among the pixels of the input image information, A pixel exposure control unit for controlling the exposure, and a high dynamic range image generating unit for generating a high dynamic range image including the pixels whose exposure is controlled.

According to an aspect of the present invention, there is provided a method of generating a high dynamic range image and a computer program for executing the method.

A method of generating a high dynamic range image according to an exemplary embodiment of the present invention and a computer program for executing the method include steps of inputting image information, detecting input image information and converting the sensed image information into an electric signal, Determining whether clipping has occurred for each pixel, if clipping has occurred for each pixel, determining whether it is within a chargeable range for each pixel, and if it is within a chargeable range for each pixel, And controlling the shutter speed by adjusting the charge charge of the shutter speed.

The present invention can efficiently generate a high dynamic range image by changing the exposure for each pixel.

1 to 7 are views for explaining a high dynamic range image generating apparatus according to an embodiment of the present invention.
8 and 9 are views for explaining a method of generating a high dynamic range image according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Also, when a part is referred to as "including " an element, it does not exclude other elements unless specifically stated otherwise.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

1 to 7 are views for explaining a high dynamic range image generating apparatus according to an embodiment of the present invention.

Referring to FIG. 1, a high dynamic range image generation apparatus includes an image input unit 100, a pixel clipping determination unit 200, a pixel exposure control unit 300, and a high dynamic range image generation unit 400.

Referring to FIG. 2, the conventional image capturing apparatus does not cover the entire exposure range of the subject, so that overexposure occurs and the image is often taken too bright or too dark due to insufficient exposure. Particularly, the conventional image capturing apparatus has a limitation in widening the exposure range due to the physical limit value of the apparatus. However, since the high dynamic range image generating apparatus according to the present invention can adjust the exposure range according to the pixels, it can cover the entire object exposure range, and the exposure range is different for each pixel. Therefore, There is no need to shoot at the same time or shoot multiple images to synthesize.

Referring back to FIG. 1, the image input unit 100 receives image information through a lens. The image input unit 100 sets photographing condition information for each pixel of the image in advance. Here, the photographing condition information is information on a photographing condition for each pixel, and may include at least one of shutter speed information, ISO sensitivity information, and aperture information. For example, a camera included in a vehicle black box may be used as the image input unit 100, but the present invention is not limited thereto.

The pixel clipping determination unit 200 determines whether or not there is a pixel in which clipping occurs among pixels of the input image. Here, the clipping is defined as a case in which the luminance information of each pixel of the input image exceeds the luminance limit value of each pixel set in advance.

The pixel exposure control unit 300 controls the exposure of each pixel such that the image of the pixel where clipping occurs is within the reset exposure range. Here, the re-set exposure range may be such that clipping does not occur through the repetitive exposure setting. The pixel exposure control section 300 can control the exposure by individually adjusting the shutter speed or the ISO sensitivity of each pixel.

Referring to FIG. 3, the pixel exposure controller 300 includes a pixel shutter speed controller 310 and a pixel ISO sensitivity controller 320.

The pixel shutter speed controller 310 controls the charging time of the cell charge of each pixel of the photometric sensor to adjust the shutter speed per pixel. The pixel shutter speed controller 310 controls a pixel-by-pixel luminance value by adjusting a shutter speed per pixel.

The pixel ISO sensitivity adjuster 320 controls the pixel gain gain value to adjust the ISO sensitivity per pixel. The pixel ISO sensitivity adjuster 320 controls the per-pixel brightness value by adjusting the ISO sensitivity per pixel.

The high dynamic range image generating unit 400 generates a high dynamic range image including the pixels whose exposure is controlled. In addition, the high dynamic range image generating unit 400 calculates luminance information for each pixel using at least one of the pixel-by-pixel shutter speed information and the pixel-by-pixel ISO sensitivity information and the RGB information of the pixel.

Referring to FIG. 4, the high dynamic range image generating unit 400 includes a high dynamic range image calculating unit 410 and a pixel brightness calculating unit 420.

The high dynamic range image calculation unit 410 generates at least one high dynamic range image without clipping by adjusting at least one of the pixel-by-pixel shutter speed information and the pixel-by-pixel sensitivity information.

The pixel brightness calculation unit 420 generates brightness information for each pixel using at least one of the pixel-by-pixel shutter speed information, the pixel-by-pixel ISO sensitivity information, and the pixel-by-pixel RGB information.

5, the pixel-by-pixel luminance calculation unit 420 includes an exposure information calculation unit 422, an image information processing unit 424, and a luminance information conversion unit 426.

The exposure information calculation unit 422 calculates exposure information from the previously prepared exposure information table using at least one of the shutter speed information and the ISO sensitivity information adjusted for each pixel.

The image information processing unit 424 generates CIE Y information for each pixel using the input image information. The image information processing unit 424 can convert CIE Y information of each pixel by converting the RGB information of the input image.

Here, the CIE Y information can be calculated by the following equation (1).

Y = 0.2989 * R + 0.5870 * G + 0.1140 * B (1)

Here, Y represents CIE Y information, R represents Red information, G represents Green information, and B represents Blue information.

The luminance information converting unit 426 converts the CIE Y information of each pixel into luminance information using a predetermined conversion graph (OECF) according to the exposure information. Here, the Opto-Electronic Conversion Functions (OECF) can be preset for each exposure step determined according to the pixel-by-pixel shutter speed and the pixel-by-pixel ISO sensitivity information.

Referring to FIGS. 6 and 7, the brightness information converting unit 426 may generate and store Opto-Electronic Conversion Functions (OECF) through the following process. The brightness information converting unit 426 can calculate exposure information in a previously prepared exposure step information table using at least one of the shutter speed and the degree of ISO sensitivity of the camera. Next, the luminance information converting unit 426 outputs ISO 14524, and illuminates the back surface, and measures the luminance information for each square (white to black) on the front surface of the output paper. Here, a point luminance meter can be used for measuring the luminance. Next, the brightness information converting unit 426 adjusts the exposure of the photograph so that the background of the output paper is photographed in a gray (Y value 128), checks the Y value for each quadrangle, Draw a graph (OECF) in relation. Then, the brightness information converting unit 426 repeats the above-described processes while changing the intensity of the illumination, and can calculate and store the brightness information and the graph of the Y value for each exposure step.

8 and 9 are diagrams for explaining a method of generating a high dynamic range image according to an embodiment of the present invention.

Referring to FIG. 8, in step S810, the high dynamic range image generating apparatus inputs an image through a lens. Here, the degree of iris diaphragm of the lens is set in advance.

In step S820, the high dynamic range image generating device detects an image input from the photometric sensor and converts the sensed image into an electric signal. Here, the shutter speed for each pixel of the photometric sensor is set in advance, and the pixel-by-pixel shutter speed can be adjusted by controlling the charging time of the cell charge for each pixel of the photometric sensor.

In step S830, the high dynamic range image generating apparatus amplifies the converted electric signal according to a predetermined gain value. Here, the ISO sensitivity per pixel can be adjusted by the amplification gain value per pixel.

In step S840, the high dynamic range image generating apparatus determines whether pixel-by-pixel clipping has occurred. Here, the clipping is defined as a case where the luminance information of the input image deviates from a preset luminance range.

In step S850, the high dynamic range image generating apparatus determines whether the clipping by pixel occurs within the chargeable range for each pixel. Here, the charge limit range may be a pixel chargeable range in the photometric sensor.

In step S860, when the high dynamic range image generating device is within the chargeable range for each pixel, the shutter speed can be controlled by controlling the charging charge of the corresponding pixel of the photometric sensor to prevent clipping.

In step S870, when the high dynamic range image generating device is out of the chargeable range for each pixel, the ISO sensitivity can be controlled by controlling the amplification gain of the clipped pixel to prevent clipping.

In step S880, the high dynamic range image generating apparatus stores RGB information for each pixel and generates a high dynamic range image when no clipping occurs for all the pixels.

Referring to FIG. 9, in the high dynamic range image generating apparatus, when the clipping is generated in a plurality of pixels in the exposure range of the camera because the luminance range is too large as in the left image, at least one of the shutter speed and the ISO sensitivity is controlled A high dynamic range image without clipping can be generated as shown in the right image.

In step S890, the high dynamic range image generating apparatus generates pixel-by-pixel luminance information using at least one of pixel-specific shutter speed information and ISO sensitivity information and pixel-by-pixel RGB information. The high dynamic range image generating apparatus calculates exposure information using at least one of the pixel-by-pixel shutter speed information and the ISO sensitivity information. In addition, the high dynamic range image generating apparatus can calculate exposure information by further using aperture diaphragm information of the lens in addition to pixel-specific shutter speed information and ISO sensitivity information. The high dynamic range image generating apparatus converts RGB information per pixel into CIE Y information. Then, the high-dynamic-range image generating apparatus can calculate pixel-by-pixel luminance information by substituting pixel-specific exposure information and CIE Y information into a predetermined conversion graph (OECF).

The high dynamic range image generation method according to various embodiments of the present invention can be implemented in the form of a program command that can be performed through various means such as servers. Further, a program and an application for executing the method of generating a high dynamic range image according to the present invention may be installed in a computer means and recorded in a computer-readable medium. The computer readable medium may include program instructions, data files, data structures, and the like, alone or in combination. Program instructions to be recorded on a computer-readable medium may be those specially designed and constructed for the present invention or may be available to those skilled in the computer software arts. Examples of computer-readable media include magnetic media such as hard disks, floppy disks, and magnetic tape; optical media such as CD-ROMs and DVDs; magnetic media such as floppy disks; Includes hardware devices specifically configured to store and execute program instructions such as magneto-optical media and ROM, RAM, flash memory, and the like.

The embodiments of the present invention have been described above. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

100:
200: Pixel clipping judgment unit
300: Pixel exposure control section
400: High dynamic range image generating unit

Claims (10)

A high dynamic range image generating apparatus comprising:
A video input unit for inputting video information;
A pixel clipping determining unit for determining whether a clipped pixel exists among pixels of input image information;
A pixel exposure control unit for controlling exposure of the clipped pixel; And
And a high dynamic range image generating unit for generating a high dynamic range image including the pixels whose exposure is controlled,
The high dynamic range image generation unit
A high dynamic range image calculation unit for generating a high dynamic range image without clipping by adjusting pixel-by-pixel shutter speed information and pixel-by-pixel ISO sensitivity information; And
Pixel brightness information by using pixel-by-pixel shutter speed information, pixel-by-pixel ISO sensitivity information, and pixel-by-pixel RGB information,
The pixel luminance calculation unit
An exposure information calculation unit for calculating exposure information in a previously prepared exposure information table using the pixel-specific shutter speed information and the ISO sensitivity information;
An image information processing unit for generating CIE Y information for each pixel using RGB information of an input image; And
Luminance information (CIE Y information) for converting the CIE Y information of each pixel into luminance information using an OECF (Opto-Electronic Conversion Functions) preset for each exposure step determined according to pixel-by-pixel shutter speed information and pixel- A high dynamic range image generation device comprising a conversion section.
The method according to claim 1,
The pixel exposure control unit
A pixel shutter speed adjusting unit for adjusting a shutter speed per pixel by controlling a charge time of a cell charge for each pixel of the photometric sensor; And
And a pixel ISO sensitivity adjusting unit for adjusting a pixel-by-pixel amplification gain value to adjust a pixel-by-pixel ISO sensitivity.
The method according to claim 1,
The pixel exposure control unit
And resetting an exposure range of a pixel in a range where clipping does not occur through repetitive control of at least one of charge charge time and amplification gain of a pixel where clipping has occurred.
delete delete A method for generating a high dynamic range image,
Inputting image information;
Sensing input image information and converting the sensed image information into an electrical signal;
Amplifying the converted electric signal according to a predetermined gain value;
Determining whether pixel-by-pixel clipping has occurred;
Determining whether the pixel-by-pixel clipping is within a chargeable range for each pixel;
Controlling the shutter speed by adjusting charge charge of the corresponding pixel of the photometric sensor when the charge amount is within the chargeable range per pixel;
Controlling the ISO sensitivity by adjusting the amplification gain of the clipped pixel when the pixel-by-pixel chargeable range is exceeded;
Pixel shutter speed information and pixel-by-pixel ISO sensitivity information are adjusted to generate a high-dynamic range image without clipping; And
Pixel per-pixel brightness information using pixel-by-pixel shutter speed information, ISO sensitivity information, and pixel-by-pixel RGB information,
The step of generating luminance information for each pixel using the pixel-by-pixel shutter speed information, the pixel-by-pixel ISO sensitivity information, and the pixel-by-pixel RGB information
Calculating exposure information in a previously prepared exposure information table using the pixel-specific shutter speed information and the ISO sensitivity information;
Generating CIE Y information for each pixel using RGB information of an input image; And
The step of converting the CIE Y information of each pixel into the luminance information by using the preset Opto-Electronic Conversion Functions (OECF) for each exposure step determined according to the pixel-by-pixel shutter speed information and the pixel-by-pixel ISO sensitivity information / RTI >
delete delete delete A computer program recorded on a computer-readable recording medium for executing the high dynamic range image generating method of claim 6.

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