KR101436835B1 - Apparatus and method for determining data for performing backlight correction in a digital image processor - Google Patents

Abstract

The present invention relates to a digital image processing apparatus and method, and more particularly, to a digital image processor for providing an exposure bracketing image as a reference data for performing backlight correction, Apparatus and method. The data determination device for performing the backlight correction in the digital image processor is a digital image processor. When a plurality of persons are searched for the face recognition result of the live view image, the exposure of the detected multiple faces is measured, And digital signal processing means for providing as reference data for performing backlight correction.

Face Recognition, Exposure Measurement, Exposure Bracketing, WDR

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data decision apparatus and method for performing optical backlight correction in a digital image processor,

The present invention relates to a digital image processing apparatus and method, and more particularly, to a digital image processor for providing an exposure bracketing image as a reference data for performing backlight correction, Apparatus and method.

Currently, the digital image processing apparatus is equipped with a face recognition algorithm as a basic feature. And the automatic exposure and the automatic exposure are performed by using this technique. In the case of automatic exposure, the exposure value is determined based on the exposure evaluation data. Since the exposure evaluation value is generally based on the brightness of the ideal gray state, if the exposure evaluation data is different from the reference data on which the algorithm is designed There is a disadvantage in that there is an error.

For example, if an algorithm is created with a person with a common skin color in the Asian world, if the face is evaluated as an exposed person, then the under-exposure phenomenon occurs. If the face is evaluated based on the black person, The phenomenon can not but occur. However, since it is difficult for a digital camera to determine which color of a person who is a subject at the time of photographing has the skin, it is difficult to avoid the above phenomenon when the conventional algorithm is used.

Referring to FIG. 6, after detecting faces and acquiring exposure evaluation data on the detected faces, an average is taken based on the luminance data, and compared with Natural Gray, -Ev when general exposure evaluation value data is large, When the evaluation data is small, + Ev is applied, and the degree is determined according to the difference in brightness is the conventional face recognition based exposure system.

Conventional digital image processor makers are based on Japan, so they have often made algorithms based on a person with a skin color of Asian skin color. This is because the skin color reflectance of Oriental people is close to Natural Gray. However, it is important to catch the reference point because the subject of the digital image processing apparatus can be not only Asian but also white and black skin color person. Furthermore, when two or more subjects are photographed, it is disadvantageous that the exposure fails if the color of the face differs significantly (for example, black and white), or both. To overcome this exposure difference, there is a method of wide dynamic range (WDR), but there is no clear standard for acquiring the data to be used when doing this.

SUMMARY OF THE INVENTION The present invention provides a data determination apparatus and method for performing a backlight correction in a digital image processor that provides an exposure bracketing image as a reference data for performing backlight correction .

According to an aspect of the present invention, there is provided a digital image processor for performing a backlight correction in a digital image processor. In the digital image processor, when a plurality of persons are searched for a face recognition result of a live view image, And a digital signal processing means for performing exposure bracketing photography and providing the reference data as reference data for performing backlight compensation.

In the present invention, the digital signal processing means may include a face recognition unit for performing face recognition on the live view image; An exposure measuring unit for measuring exposure of the multiple faces detected as the face recognition result; A control unit for performing exposure bracketing photographing based on the measured exposure value; And an optical backlight compensation performing unit for performing backlight compensation using the image photographed by the exposure bracket as input data.

In the present invention, the control unit may be configured to photograph the image on the basis of a face having the lowest exposure value measured by the exposure measuring unit at the time of exposure bracketing, and to shoot the image based on a face having the highest exposure value can do.

According to an aspect of the present invention, there is provided a method for determining a data backlight correction in a digital image processor, the method comprising: (a) performing face recognition of a live view image; (b) measuring the exposure of the multiple faces when the multiple faces are searched as a result of the face recognition; And (c) providing an exposure bracketing photograph based on the measured exposure value as reference data for performing backlight compensation.

In the present invention, at the time of the exposure bracketing in the step (c), the image is photographed based on the face having the lowest exposure value measured, and the image is photographed based on the face having the highest exposure value .

As described above, according to the present invention, exposure bracketing images recognized as multiple faces are provided as reference data for performing backlight correction, thereby reducing the exposure failure due to the difference in the reflectance of the face.

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

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view showing the front and top contours of a digital image processor.

The shutter-release button 11 is opened and closed to expose the CCD or film to light for a predetermined time, and the image is recorded on the CCD by properly exposing the subject in cooperation with the aperture (not shown).

The shutter-release button 11 generates the first and second image pickup signals by the photographer input. When the first shutter-release button 11 is input as a half-shutter signal, the digital image processor focuses and adjusts the amount of light. At this time, the display unit 25 lights green. When the focus of the first shutter-release button 11 is focused and the amount of light is adjusted, a second shutter-release button 11 as a full shutter signal is input to capture an image.

The power button 13 is input for supplying power to the digital image processor and operating it.

The flash 15 illuminates bright light momentarily when shooting in a dark place. The flash mode includes auto flash, forced flash, no flash, red-eye reduction, and slow synchro flash.

The auxiliary light 17 supplies light to the subject so that the digital image processor automatically catches the focus quickly and accurately at the time of lack of light or at night.

The lens unit 19 receives light from an external light source and processes the image.

FIG. 2 is a rear view showing the rear external appearance of the digital image processor shown in FIG. 1. The wide-angle zoom button 21w, the telephoto-zoom button 21t, the display unit 23, Input buttons B1 to B14 (hereinafter referred to as buttons B1 to B14).

The wide-angle zoom button 21w or the telephoto-zoom button 21t widens the view angle or narrows the view angle depending on the input, in particular, when the size of the selected exposure area is to be changed. When the wide angle-zoom button 21w is input, the size of the selected exposure area is reduced, and when the telephoto-zoom button 21t is input, the size of the selected exposure area is increased.

The buttons B1 to B14 are provided in the rows and columns of the display unit 23. The buttons B1 to B14 provided in the row and column of the display unit 23 are provided with a touch sensor (not shown) or a contact type switch (not shown).

That is, the touch sensors are provided on the buttons B1 to B14 to move up / down / left / right while touching the buttons B1 to B7 of the horizontal row or the buttons B8 to B14 of the vertical row, It is possible to select any value (e.g., color or brightness) of the items, or activate a submenu icon included in the main menu icon.

In addition, the buttons B1 to B14 are provided with a contact type switch, so that the main menu icon and the sub menu icon can be directly selected to execute the corresponding function. The touch sensor requires a relatively weak touch compared to the contact switch input, but the contact switch input requires a relatively strong touch compared to the touch sensor input.

3 is a block diagram showing the configuration of a data determination apparatus for performing the backlight correction in the digital image processor according to the present invention. The data determination apparatus includes a display unit 23, a user input unit 31, an image pickup unit 33, 35, a storage unit 37, and a digital signal processing unit 39.

The user input unit 31 includes a shutter-release button 11 that is opened and closed to expose a CCD or a film to light for a predetermined period of time, a power button 13 that inputs power to supply power, A wide angle-zoom button 21w and a telephoto-zoom button 21t for narrowing the angle of view and a touch sensor or a contact-type switch provided in the horizontal and vertical columns around the display unit 23 for character input or menu selection and execution, And buttons B1 to B14 provided with buttons.

The imaging section 33 includes a shutter, a lens section, a diaphragm, and a charge coupled device (CCD) and an ADC (not shown). The shutter is a mechanism that adjusts the amount of light that is exposed with the iris. The lens unit receives light from an external light source and processes the image. At this time, the diaphragm adjusts the amount (light amount) of the incident light according to the degree of opening and closing. The opening / closing degree of the diaphragm is controlled by the digital signal processing section 39. [

The CCD accumulates the amount of light input through the lens unit and outputs the image captured by the lens unit according to the accumulated light amount in accordance with the vertical synchronization signal. Image acquisition by a digital image processor is performed by a CCD which converts the light reflected from the subject into an electrical signal. In order to obtain a color image using a CCD, a color filter is required, and a filter (not shown) called a color filter array (CFA) is employed in most cases. CFA has a regularly arranged structure that passes only light that represents one color per pixel, and it has various forms according to the arrangement structure. The ADC converts the analog video signal output from the CCD into a digital signal.

The image processing unit 35 processes the digitally converted RAW data so that it can be displayed. The image processing unit 35 removes a black level due to the dark current generated in the CCD and the CFA filter which are full of temperature change. The image processing unit 35 performs gamma correction to encode information in accordance with the nonlinearity of human vision. The image processing unit 35 performs CFA interpolation for interpolating a Bayer pattern implemented with RGA and RGB lines of gamma-corrected predetermined data into RGB lines. The image processing unit 35 converts the interpolated RGB signals into YUV signals, performs edge compensation for filtering the Y signals by a high-pass filter, and calculates color values of the U and V signals using a standard color coordinate system Corrects the color correction, and removes these noises. The image processing unit 35 compresses and processes the Y, U, and V signals from which the noise has been removed to generate a JPEG file, and the generated JPEG file is displayed on the display unit 23 and stored in the storage unit 37 . All the operations of the image processing unit 35 operate under the control of the digital signal processing unit 39. [

The digital signal processing unit 39 measures exposure of the detected multiple faces and performs exposure bracketing photography to provide reference data for performing backlight compensation when a plurality of persons of the face recognition result of the live view image are searched.

To this end, the digital signal processing unit 39 includes a face recognizing unit 39-1, an exposure measuring unit 39-2, a WDR performing unit 39-3, and a control unit 39-4.

The face recognition unit 39-1 detects at least one face information, that is, the face size, position and direction, from an arbitrary live view image under the control of the control unit 39-4. The facial recognition unit 39-1 can detect the face area based on the color or detect the face area based on the edge at the time of detecting the size of the face, and at the time of detecting the face position, And the center of the display unit 23, and the face direction can be detected in the form of a triangle composed of the eyes and mouth from the extracted face at the time of detecting the direction of the face. Since details of the face information detection by the face recognition unit 39-1 are well known in the art, a detailed description thereof will be omitted.

The exposure measuring unit 39-2 measures the exposure (EV) of the multiple faces retrieved by the face recognition unit 39-1. At this time, the exposure measuring unit 39-2 searches for the lowest exposure value and the highest exposure value from the multiple faces.

The control unit 39-4 photographs the face with the lowest exposure value measured by the exposure measuring unit 39-2 on the basis of one shutter-release button 11 input, And controls the bracketing shooting based on the face having the highest exposure value measured by the camera. The control unit 39-4 provides the bracketing photographing result to the WDR performing unit 39-3.

The WDR performing unit 39-3 performs the backlight correction using the image photographed by the exposure bracketing as input data.

Fig. 4 is a diagram for explaining WDR performance. The dynamic range can be seen as the ratio of the brightest and darkest areas within the identifiable range. The dynamic range (Db) = 20 log (X2 / X1) can be expressed as dB if the ratio of the brightest portion X2 to the darkest portion X1 in the identifiable range in FIG. 4A is expressed in dB. However, if two or more faces in the face recognition have a dynamic range (exposure difference of X1 and X2 or more) that the image processor allows, either one of them is inevitable. In order to solve this problem, a method of giving a gain value to a single image differently depending on the luminance of a pixel, a method of correcting a gamma curve, or a method of processing two images of the same scene, The dynamic range is used. Hereinafter, the description of the dynamic range will be omitted since it is already known.

The image photographed based on the face having the lowest exposure value obtained by the bracketing photographing control of the control unit 39-4 and the face photographed with the face having the highest exposure value is input to the WDR performing unit 39-4 , The WDR performing unit 39-4 processes the two images of the same exposure, which are the same as those described above, and then combines them to perform the backlight correction.

Hereinafter, a data determination method for performing the backlight correction in the digital image processor according to the present invention will be described in detail with reference to FIG. The data determination method for performing the backlight correction in the digital image processor according to the present invention can be performed in the digital image processor as shown in FIG. 3. According to the embodiment, May be performed in the digital signal processing unit 39 with the help of the components.

When the digital image processor is set to the WDR face recognition mode (step 501), the digital signal processing unit 39 displays the live view image on the display unit 23 and performs face recognition (step 503). The digital signal processing unit 39 detects at least one face information, that is, the size, position, and direction of a face from the live view image, and performs AF based on the detected size, position, and direction. The details of the face detection are described above and will be omitted here.

When the first shutter-release button 11 input is received from the user in step 505, the digital signal processor 39 calculates an exposure value based on all recognized faces on the basis of face recognition in step 507. FIG. At this time, the digital signal processor 39 searches for the lowest exposure value and the highest exposure value from the multiple faces.

When the second shutter release button 11 is input from the user in step 509, the digital signal processing unit 39 determines whether there are two or more recognized faces in step 511.

If the recognized face is a single person, the digital signal processing unit 39 controls automatic exposure adjustment based on the recognized face of one person so as to perform normal photography in step 513.

However, if the number of recognized faces is two or more, the digital signal processing unit 39 performs exposure bracketing shooting, captures an image based on a face having the lowest exposure value with one second shutter-release button 11 input (Step 515), and the image is captured with reference to the face having the highest exposure value (step 517).

When the exposure bracketing is completed, the digital signal processing unit 39 displays the same scene for the image photographed based on the face having the lowest exposure value obtained by the bracketing shooting control and the face having the highest exposure value The two images of different exposure are processed and combined to perform the backlight compensation in step 519.

The digital signal processor 39 then stores the backlight-corrected image (step 521).

According to the present invention, it is possible to record an image having the minimum exposure value after the face detection and an image having the average exposure value of the detected faces according to the WDR performance. This method is advantageous for saving information of the shadow part

In addition, according to the WDR performance, it is possible to capture an image having the maximum exposure value after the face detection and an image having the average exposure value of the detected faces. This method is advantageous for saving information in the Highlight part.

In addition, based on the exposure value obtained from the face recognition, the designer can carry out the WDR with the data obtained on the basis of the exposure side mount converted according to the additional exposure algorithm.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view showing the front and top contours of a digital image processor.

FIG. 2 is a rear view showing the rear external shape of the digital image processor shown in FIG. 1; FIG.

3 is a block diagram illustrating the configuration of a data determination apparatus for performing the backlight correction in the digital image processor according to the present invention.

FIG. 4 is a diagram for explaining WDR performance in FIG.

5 is a flowchart illustrating an operation of a data determination method for performing backlight correction in a digital image processor according to the present invention.

6 is a view for explaining exposure adjustment based on face recognition according to the prior art.

Claims (5)

As a digital image processor, And a digital signal processing means for measuring the exposure value of the searched multiple faces and providing digital image data as reference data for performing backlight compensation by performing exposure bracketing photographing when multiple faces of a live view image are searched for, A data determination device for performing backlight correction. The digital signal processing apparatus according to claim 1, wherein the digital signal processing means A face recognition unit for performing face recognition on the live view image; An exposure measuring unit for measuring an exposure value of multiple faces detected as the face recognition result; A control unit for performing exposure bracketing photographing based on the measured exposure value; And And performing a backlight correction using the image obtained by the exposure bracketing as input data. 3. The apparatus of claim 2, wherein the control unit Wherein the control unit controls to shoot the image based on a face having the lowest exposure value measured by the exposure measuring unit and to photograph the image based on a face having the highest exposure value at the time of exposure bracketing, A data determination device for performing a correction. A method of operating a digital image processor, (a) performing face recognition of a live view image; (b) if the multiple faces are searched as a result of the face recognition, measuring the exposure value of the searched multiple faces; And (c) performing exposure bracketing photographing based on the measured exposure value to provide reference data for performing backlight compensation. 5. The method according to claim 4, wherein, in the step (c) Wherein the image is photographed based on a face having the lowest exposure value among the measured exposure values and the image is photographed based on a face having the highest exposure value among the measured exposure values, Data determination method.

Images