KR101246914B1 - Method for enhancing dynamic range in digital image processing apparatus - Google Patents

Abstract

The present invention relates to a method of operating a digital image processing apparatus, and more particularly, to a method of enlarging a dynamic range of an image captured by a query to a user. The present invention provides a method of enlarging a dynamic range of a captured image, the method comprising: (a) detecting a brightness of a captured image to determine whether dynamic range expansion is necessary; and (b) querying whether to select a dynamic range expansion mode according to a determination result. And (c) if the mode is selected, performing dynamic range expansion on the captured image.

Description

Method for enhancing dynamic range in digital image processing apparatus

FIG. 1 is a rear view of a rear surface of a digital camera as a digital image processing apparatus.

FIG. 2 is a diagram illustrating the overall configuration of the digital camera of FIG. 2.

3 is a flowchart illustrating a method for expanding a dynamic range in a digital image display device according to the present invention.

The present invention relates to a method of operating a digital image processing apparatus, and more particularly, to a method of enlarging a dynamic range of an image captured by a query to a user.

Images captured by a digital image processing apparatus or the like include various kinds of objects. However, the luminance and color information are often biased or distorted in the captured image according to the performance of the object or the digital image processing apparatus, the shooting conditions, and the like. In this case, if the preprocessing step is performed by a histogram equalization method, the contrast of the image is improved, so that the analysis and feature extraction of the image is easy. Performing the preprocessing step to increase the contrast of the image as described above is called dynamic range expansion.

As the digital image processing apparatus has a lower dynamic range than the dynamic range of the human eye due to its limitations, various dynamic range expansion methods have been developed to solve this problem. However, these dynamic range expansion methods have only two modes that apply unconditionally or do not apply, which makes it difficult for a user to selectively apply this technique.

Dynamic range expansion technology has a big impact on image quality improvement in terms of expanding dynamic range, which is one of the important factors of image quality. However, when the dynamic range magnification mode is set, the quality of the image may be deteriorated because it is unconditionally applied even to an image that the user does not want. In addition, in the mode that does not apply the dynamic range expansion mode, it is cumbersome because a person must visually check and apply it.

The technical problem to be achieved by the present invention is to automatically detect whether to perform the dynamic range enlargement mode and query the user, and apply the dynamic range enlargement mode to the input image only when the user selects the mode in response to the query. The purpose is to provide a more stable and convenient way to achieve dynamic range expansion.

The present invention provides a method of enlarging a dynamic range of a captured image, the method comprising: (a) determining whether dynamic range expansion is necessary by sensing the brightness of the captured image; (b) querying whether the dynamic range enlargement mode is selected according to the determination result; And (c) if the mode is selected, performing dynamic range expansion on the captured image.

In the present invention, step (a) comprises the steps of: (a-1) calculating an average luminance value from the captured image; (a-2) calculating a region in which the average luminance value is out of a range of a reference value; And (a-3) determining that the dynamic range enlargement mode should be applied when the calculated ratio of the area exceeds the reference ratio.

In the present invention, step (a-2) may include (a-11) dividing the photographed image into a predetermined number of areas; And (a-12) calculating an average value with respect to the luminance data of each divided region.

In the present invention, the step (a-1) may include (a-21) calculating the number of regions where the average luminance value is lower than a lower limit reference value; (a-22) calculating the number of regions in which the average luminance value is higher than an upper limit reference value; And (a-23) summing and outputting the calculated number of regions.

In the present invention, before the step (a), receiving a reference value setting signal including a lower limit reference value and an upper limit reference value of the luminance data and a reference ratio setting signal for defining a ratio of an image deviating from the reference value with respect to the entire image. It features.

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

FIG. 1 is a rear view of a rear surface of a digital camera as a digital image processing apparatus.

The shutter release button 21 opens and closes to expose the CCD or film to light for a predetermined time, and records the image on the CCD by properly exposing the subject in conjunction with an aperture (not shown).

The eyepiece unit 23 of the viewfinder is a small window of a camera for setting a composition by looking at a subject to be photographed.

The function button 25 is a key input to execute various menus related to digital camera operation. In particular, the function button 25 is a button used to activate or select an exposure area for controlling exposure or to move an exposure area. In particular, the function button 25 is input at the time of setting the dynamic range enlargement mode and setting the lower and upper limit luminance reference values and reference ratios by the user.

The wide-angle zoom button 27w or the tele-zoom button 27t increases the angle of view or narrows the angle of view depending on the input, particularly when the size of the selected exposure area is to be changed. When the wide-zoom button 27w is input, the size of the selected exposure area is reduced, and when the tele-zoom button 27t is input, the size of the selected exposure area is increased.

FIG. 2 is a diagram illustrating an overall configuration of the digital camera of FIG. 1.

The optical system OPS including the lens unit and the filter unit optically processes light from a subject. The lens unit of the optical system OPS includes a zoom lens, a focus lens, and a compensation lens.

When the user presses the wide-angle zoom button 27w or the telephoto-zoom button 27t included in the user input unit INP, a corresponding signal is input to the microcontroller 512. Accordingly, as the microcontroller 512 controls the lens driver 510, the zoom motor M _Z is driven to move the zoom lens. That is, when the wide angle-zoom button 27w is pressed, the focal length of the zoom lens is shortened to widen the angle of view, and when the telephoto-zoom button 27t is pressed, the focus of the zoom lens is pressed. The longer the length, the narrower the angle of view. Here, since the position of the focus lens is adjusted while the position of the zoom lens is set, the angle of view is hardly influenced by the position of the focus lens.

Meanwhile, in the auto focus mode, the focus motor M _F is driven by the main controller embedded in the digital signal processor 507 controlling the lens driver 510 through the micro controller 512. As a result, the focus lens is moved from the front to the rear, and in this process, the position of the focus lens where the high frequency component of the image signal is the largest, for example, the number of driving steps of the focus motor M _F is set.

The compensation lens compensates for the overall refractive index and is not driven separately. Reference numeral M _A denotes a motor for driving an aperture (not shown).

In the filter portion of the optical system OPS, an optical low pass filter removes optical noise of high frequency components. Infra-red cut filter blocks the infrared component of incident light.

A photoelectric conversion unit (OEC) of a charge coupled device (CCD) or a complementary metal-oxide-semiconductor (CMOS) converts light from an optical system (OPS) into an electrical analog signal. Here, the digital signal processor 507 controls the timing circuit 502 to control the operations of the photoelectric conversion unit (OEC) and the analog-digital conversion unit 501. A CDS-ADC (Correlation Double Sampler and Analog-to-Digital Converter) element 501 as an analog-to-digital conversion section processes an analog signal from the photoelectric conversion section OEC to remove high frequency noise, And then converted into a digital signal.

The real-time clock 503 provides time information to the digital signal processor 507. The digital signal processor 507 processes digital signals from the CDS-ADC device 501 to generate digital image signals classified into luminance and chrominance signals.

Although not shown, a self-timer lamp, an auto-focus lamp, a mode indicating lamp, and a flash are not shown in the light emitting part LAMP driven by the microcontroller 512 under the control of the main controller embedded in the digital signal processor 507. A standby lamp is included. The user input unit INP includes a shutter release button 11, function buttons 21, a wide-angle zoom button 25w, a telephoto-zoom button 25t, and the like.

A digital image signal from the digital signal processor 507 is temporarily stored in a DRAM (Dynamic Random Access Memory) 504. The EEPROM (Electrically Erasable and Programmable Read Only Memory) 505 stores algorithms and setting data necessary for the operation of the digital signal processor 507. In particular, the EEPROM 505 stores algorithms and setting data necessary for the dynamic range enlargement detection operation, and the algorithm is executed by the approach of the digital signal processor 507 to output the setting data. In the memory card interface 506, a user's memory card is detached.

The digital image signal from the digital signal processor 507 is input to the LCD driver 514, whereby the image is displayed on the color LCD panel 29.

On the other hand, the digital image signal from the digital signal processor 507 can be transmitted by serial communication via a universal serial bus (USB) connection portion 31a or an RS232C interface 508 and the connection portion 31b, and a video filter ( 509 and the video output unit 31c may be transmitted as a video signal. Here, the digital signal processor 507 incorporates a microcontroller therein.

The audio processor 513 outputs the audio signal from the microphone MIC to the digital signal processor 507 or the speaker SP and outputs the audio signal from the digital signal processor 507 to the speaker SP.

The dynamic range enlargement method according to the present invention may be performed in a control apparatus for a digital image processing apparatus as shown in FIG. 3. The received signal may be performed in the digital signal processor 507 or the microcontroller 512.

In order to detect whether the dynamic range magnification mode is applied, it is examined whether the input image is too bright or dark in a certain ratio or more, and if it is above a certain ratio, it is determined that the image needs to be applied to the dynamic range magnification mode. query).

This dynamic range expansion method will be described with reference to FIG. 3.

The user inputs the function button 25 to set the dynamic range enlargement detection mode (step 301). When the function button 25 for setting the dynamic range enlargement detection mode is input, the digital signal processing unit 507 or the microcontroller 512 (hereinafter referred to as the digital signal processing unit 507) approaches the EEPROM 505 and provides dynamic information. Load range expansion detection algorithm and setting data.

When the dynamic range enlargement detection mode is set, the user sets the user parameter, that is, the lower limit and upper limit luminance reference values and the reference ratio for limiting the ratio of the image deviating from the reference value for the entire image using the function button 25 (303). step). To set user parameters, the digital signal processor 507 may provide a sub-item for which each parameter is set for the user to select, or allow the user to directly enter each parameter value. The lower and upper luminance reference values and the reference ratios set by the user may be variously set depending on whether the user prefers a dark image or a bright image according to the user's intention. For a user who prefers a dark image, the lower and upper luminance reference values may be set higher, and a reference ratio may be set lower. For users who prefer a bright image, the lower and upper luminance reference values may be set lower, and a reference ratio may be set. Can be set high. When the function button 25 is input for setting a user parameter, the digital signal processor 507 stores the set user parameter.

When the user parameter setting is completed by the input of the function button 25, the digital signal processor 507 waits for an operation until an image is captured by the user's shutter 21 input (step 305).

When an image is captured by the input of the shutter 21, the dynamic range enlargement detection mode operation is executed.

When the dynamic range enlargement detection mode is operated, the digital signal processor 507 divides the captured image into a plurality of regions and calculates an average value of luminance data of each region (step 307).

When the average value calculation is completed, the digital signal processor 507 counts the number of regions that deviate from the upper limit and lower limit threshold values (step 309). The digital signal processor 507 counts the number of regions where the calculated average value is lower than the lower limit luminance reference value, counts the number of regions where the calculated average value is higher than the upper limit luminance reference value, and adds them together.

Subsequently, the digital signal processor 507 compares the percentage of the counted and summed regions in the entire image with the reference ratio set above, and the ratio of the counted and summed regions in the entire image is set as the reference. It is determined whether the ratio is exceeded (step 311).

When the ratio of the counted and summed regions in the entire image exceeds the reference ratio set above, the digital signal processor 507 determines that the dynamic range expansion mode needs to be applied, and the dynamics are applied to the color LCD panel 29. Inquiry whether to apply the range expansion mode (step 313).

The digital signal processor 507 determines whether the application of the dynamic range enlargement mode is selected by the input of the function button 25. The user can check the query message displayed on the color LCD panel 29 and select the application of the dynamic range enlargement mode by inputting the function button 25.

If the application of the dynamic range enlargement mode is selected, the digital signal processor 507 applies the dynamic range enlargement mode to the captured image (step 317). When the dynamic range is applied to the magnification mode, the dark areas become brighter and the bright areas become darker so that all areas of the image can be seen at the same time, while the local outlines are further emphasized to make the image clearer.

As described above, the dynamic range enlargement method in the digital image processing apparatus of the present invention has various effects including the following effects.

The present invention automatically detects whether to perform the dynamic range magnification mode and inquires the user, and applies the dynamic range magnification mode to the input image only when the user selects the mode in response to the query, thereby allowing the user to carefully Since the range expansion can be applied, it becomes stable to use.

The present invention is convenient because it automatically detects whether to perform the dynamic range expansion mode and detects whether the mode is applied.

According to the present invention, the upper and lower limit reference values and the reference ratio for detecting the dynamic range enlargement mode can be easily set to determine whether the mode is detected according to the user's preference.

So far I looked at the center of the preferred embodiment for the present invention. 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.

Claims (5)

As a method of enlarging the dynamic range of captured images, (a) detecting the brightness of the captured image to determine whether dynamic range expansion is necessary; (b) querying whether the dynamic range enlargement mode is selected according to the determination result; And (c) if the mode is selected, performing dynamic range expansion on the captured image. The method of claim 1, wherein step (a) (a-1) calculating an average luminance value from the photographed image; (a-2) calculating a region in which the average luminance value is out of a range of a reference value; And (a-3) determining that the dynamic range expansion mode should be applied when the calculated ratio of the area exceeds a reference ratio. The method of claim 2, wherein step (a-1) (a-11) dividing the captured image into a predetermined number of areas; And (a-12) calculating an average value with respect to the luminance data of each divided region. The method of claim 3, wherein step (a-2) (a-21) calculating the number of regions where the average luminance value is lower than a lower limit reference value; (a-22) calculating the number of regions in which the average luminance value is higher than an upper limit reference value; And (a-23) and summing and outputting the calculated number of regions to increase the dynamic range. The method of claim 2, wherein before step (a) And a reference value setting signal including a lower limit reference value and an upper limit reference value of the luminance data, and a reference ratio setting signal for limiting a ratio of an image deviating from the reference value with respect to the entire image.

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