Patent Publication Number: US-11386869-B2

Title: Display device and driving method thereof according to capturing conditions of an image

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The application claims the benefit of Republic of Korea Patent Application No. 10-2019-0179727, filed on Dec. 31, 2019, which is incorporated by reference in its entirety. 
     BACKGROUND 
     Field of Technology 
     The present disclosure relates generally to a display device and, more particularly, to a display device and a driving method thereof. 
     Description of the Related Art 
     With the development of information technology, the market for a display device that is a connection medium between a user and information is growing. Accordingly, the use of display devices such as a light emitting display (LED), a quantum dot display (QDD), a liquid crystal display (LCD) is increasing. 
     Each sub-pixel of the display device may emit light at a luminance corresponding to the data voltage supplied through the data line. The display device may display an image frame by combining lights emitted from pixels including sub-pixels. 
     Meanwhile, when an image displayed on the display device is captured through a camera, degradation of a quality of the captured image may occur. For example, since the camera capturing conditions may be changed due to lighting at a capturing location or a change in luminance of the displayed image, the image captured through the camera may have moiré artifacts or may include unintended shading. 
     SUMMARY 
     An objective of this disclosure is to provide a display device that converts and displays image data according to luminance suitable for capturing conditions, and detects an edge shape of the image data to reduce moiré artifacts. 
     Another objective of the present disclosure is to provide a method of driving the display device. 
     However, the objective of the present disclosure is not limited thereto, and may be variously extended without departing from the spirit and scope of the present disclosure. 
     A display device according to embodiments of the present disclosure includes an image conversion apparatus receiving a first image signal from the outside and outputting a second image signal by converting a luminance of the received first image signal; a controller generating image data based on the second image signal; a source driver outputting data signals based on the image data; a display panel including a plurality of sub-pixels that emit light based on the data signals; and a memory, wherein the image conversion apparatus generates the second image signal by converting the luminance of the first image signal in such a manner a to satisfy a reference maximum luminance value stored in the memory. 
     An image conversion method according to embodiments of the present disclosure includes calculating a contrast ratio for a first image signal received from the outside; converting a luminance of the first image signal in such a manner as to satisfy a reference maximum luminance value while maintaining the contrast ratio; and generating and outputting a second image signal having the converted luminance, wherein the reference maximum luminance value is determined according to characteristic information of a camera capturing an image displayed according to the second image signal. 
     A computer program for executing the image conversion method according to embodiments of the present disclosure when executed on a computer may be stored in a computer readable medium. 
     A display device and a driving method thereof according to the present disclosure converts image data according to maximum luminance suitable for capturing conditions while maintaining a contrast ratio and a color depth, thereby preventing unintended shadows from being included in the image captured by a camera. 
     In addition, it is possible to detect the edge shape of the image data and thus prevent moiré artifacts from being included in the image captured with a camera by applying a blur mask. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings: 
         FIG. 1  is a conceptual diagram illustrating capturing conditions according to an embodiment of the present disclosure; 
         FIG. 2  is an exemplary diagram illustrating a display device according to an embodiment of the present disclosure; 
         FIG. 3  is an exemplary diagram illustrating an image conversion apparatus according to  FIG. 2  according to an embodiment of the present disclosure; 
         FIG. 4  is a flowchart illustrating a process of generating a second image signal in an image conversion apparatus according to  FIG. 2  in accordance with an embodiment of the present disclosure; 
         FIG. 5  is a flowchart illustrating a process of relieving an edge of a first image signal in an image conversion apparatus according to  FIG. 2  in accordance with an embodiment of the present disclosure; 
         FIG. 6  is an exemplary diagram illustrating image conversion for detecting an edge of a first image signal in a process according to  FIG. 5  according to an embodiment of the present disclosure; and 
         FIG. 7  is a conceptual diagram illustrating a method of detecting an edge of a second image signal in a process according to  FIG. 5  according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, various embodiments of the present disclosure will be described in detail with reference to the accompanying drawings so that those skilled in the art to which the present disclosure pertains can easily implement them. The present disclosure can be implemented in many different forms and is not limited to the embodiments described herein. 
     In order to clearly describe the present disclosure, parts irrelevant to the description are omitted, and the same reference numerals are assigned to the same or similar elements throughout the specification. Therefore, the reference numerals described above may be used in other drawings. 
     In addition, since the size and thickness of each component shown in the drawings are arbitrarily shown for convenience of description, the present disclosure is not necessarily limited to what is illustrated. In the drawings, thickness may be exaggerated in order to clearly express various layers and regions. 
       FIG. 1  is a conceptual diagram illustrating capturing conditions according to an embodiment of the present disclosure. 
     The display device  100  receives an image signal from outside of the display device  100  and displays a first image image A according to the received image signal on the screen. Therefore, in general, how clearly a person can recognize the first image image A without any afterimage or blur becomes an important factor. 
     However, in recent years, the first image image A displayed on the display device  100  is captured with a camera  200 , and how clearly a captured second image image B can be recognized has become an important factor. For example, in a broadcast studio, a broadcast video has been produced in such a manner as to synthesize a background on an image captured in a real space using chroma-key technology. However, in recent broadcast studios, the broadcast image is produced in such a manner as to display the first image image A using the display device  100  in a real space and capture the first image image A and the real space together through the camera  200 . Therefore, how clearly the second image image B obtained by capturing the first image image A with the camera  200  is recognized without any blur has become an important factor. 
     Therefore, in order to improve the quality of the second image image B obtained by capturing the first image image A displayed by the display device  100  with the camera  200 , a method of converting an image signal input from the outside and displaying the first image image A on the screen using the converted image signal is proposed in the display device  100  according to an embodiment of the present disclosure. 
       FIG. 2  is an exemplary diagram illustrating a display device according to an embodiment of the present disclosure. 
     Referring to  FIG. 2 , a display device  100  includes a display panel  110 , a controller  120 , a source driver  130 , a gate driver  140 , a power supply circuit  150 , and an image conversion apparatus  160 . 
     The display device  100  may be a device capable of displaying an image or video. For example, the display device  100  means a TV, a smart phone, a tablet personal computer (PC), a mobile phone, a video phone, an e-book reader, a computer, a camera, or a wearable device, but is not limited thereto. 
     The display panel  110  may include a plurality of sub-pixels PXs arranged in rows and columns According to embodiments, the plurality of subpixels PXs illustrated in  FIG. 2  may be arranged in a lattice structure composed of n rows and m columns (n and m are natural numbers). 
     For example, the display panel  110  may be implemented as one of a liquid crystal display (LCD), a light emitting diode (LED) display, an organic LED (OLED) display, an active-matrix OLED (AMOLED) display, an electrochromic display (ECD), a digital mirror device (DMD), an actuated mirror device (AMD), a grating light value (GLV), a plasma display panel (PDP), an electro luminescent display (ELD), or a vacuum fluorescent display (VFD), but is not limited thereto. 
     According to embodiments, the display panel  110  includes n gate lines GL 1  to GLn connected in units of rows to subpixels PXs arranged in n rows (n is a natural number equal to or greater than 1) and m data lines DL 1  to DLm connected in units of columns to subpixels PXs arranged in m columns (m is a natural equal to or greater than 1). Each of the sub-pixels PX may be connected to one gate line and a data line. For example, the sub-pixel PX disposed in an i-th row (i is a natural number between one and n) and a j-th column (j is a natural number between one and m) may be connected to an i-th gate line and a j-th data line. 
     According to embodiments, the sub-pixels PX of the display panel  110  may be driven on a per-gate line basis. For example, sub-pixels arranged in one gate line are driven during the first period, and sub-pixels arranged on the other one gate line may be driven during the second period after the first period. Herein, a unit time period in which the subpixels PX are driven may be referred to as one horizontal period ( 1 H). 
     The subpixels PXs may include a light emitting element configured to output light and a light emitting element driving circuit driving the light emitting element. The light emitting element driving circuit is connected to one gate line and one data line, and the light emitting element may be connected between the light emitting element driving circuit and a power supply voltage (e.g., ground voltage). 
     According to embodiments, the light emitting element may include a light emitting diode (LED), an organic light emitting diode (OLED), a quantum dot LED (QLED), or a micro light emitting diode (micro LED), but not limited thereto. 
     Each of the sub-pixels PXs may be one of a red element R outputting red light, a green element G outputting green light, a blue element B outputting blue light, and a white element W outputting white light, and the red element, the green element, the blue element, and the white element may be arranged in the display panel  110  according to various ways. 
     The light emitting element driving circuit may include a switching device connected to the gate lines GL 1  to GLn, for example, a thin film transistor (TFT). When a gate-on signal is applied from the gate lines GL 1  to GLn to allow the switching element to be turned on, the light emitting element driving circuit may supply data signals received from the data lines DL 1  to DLm connected to the light emitting element driving circuit to the light emitting element. The light emitting element may output light corresponding to the image signal. 
     The image conversion apparatus  160  receives the first image signal RGB 1  from the outside, and generates a second image signal RGB 2  by converting the first image signal RGB 1  in such a manner as to remove unintended shadows or moiré artifacts captured by the camera  200  when the first image signal RGB 1  is displayed, and transmits the generated second image signal RGB 2  to the controller  120 . 
     Specifically, the image conversion apparatus  160  generates the second image signal RGB 2  by converting the luminance of the first image signal RGB 1  in such a manner as to satisfy a reference maximum luminance value by referring to a look-up table FYLUT (see  FIG. 3 ). Therefore, the image conversion apparatus  160  generates the second image signal RGB 2  by converting the luminance of the first image signal RGB 1 , to allow an image to be displayed according to the second image signal RGB 2  having a luminance corresponding to the capturing conditions (for example, characteristic information of the camera  200 ) and to reduce unnecessary shadows from being included in the image captured by the camera  200 . 
     In addition, the image conversion apparatus  160  may convert the first image signal RGB 1  into a gray scale signal and detect an edge from the gray scale signal. Here, when the edge is detected, the image conversion apparatus  160  may apply a blur mask to the first image signal RGB 1 . Accordingly, the image conversion apparatus  160  applies the blur mask to the first image signal RGB 1  to relieve the edge of the first image signal RGB 1 , thereby preventing moiré artifacts capable of being admitted by the camera  200 . 
     The first image signal RGB 1  and the second image signal RGB 2  may be image signals according to an RGB (red, green, and blue) format or a color system. 
     The controller  120  may receive the second image signal RGB 2  from the image conversion apparatus  160  and generate the image data VDATA on the basis of second image signal RGB 2 . The controller  120  may transmit the image data VDATA to the source driver  130 . 
     The controller  120  may receive a control signal CS from an external host device. The control signal CS may include a horizontal synchronization signal, a vertical synchronization signal, and a clock signal, but is not limited thereto. 
     The controller  120  may generate a first driving control signal DCS 1  for controlling the source driver  130  on the basis of the received control signal CS, and a second driving control signal DCS 2  for controlling the gate driver  140 , and a third driving control signal DCS 3  for controlling a power supply circuit  150 . 
     The controller  120  may transmit the first driving control signal DCS 1  to the source driver  130 , transmit the second driving control signal DCS 2  to the gate driver  140 , and transmit the third driving control signal DCS 3  to the power supply circuit  150 . 
     The source driver  130  generates data signals DS 1  to DSm corresponding to the image displayed on the display panel  110  on the basis of the image data VDATA and the first driving control signal DCS 1 , and transmits the generated data signals DS 1  to DSm to the display panel  110 . The data signals DS 1  to DSm may be transmitted to each of the subpixels PXs, and the sub-pixels may emit light on the basis of the received data signals DS 1  to DSm. For example, the source driver  130  may provide the data signals DS 1  to DSm to be displayed in a  1 H period to subpixels PXs driven in the  1 H period through the data lines DL 1  to DLm for the  1 H period. 
     The gate driver  140  may sequentially provide the gate signals GS 1  to GSn to the plurality of gate lines GL 1  to GLn in response to the second driving control signal DCS 2 . The respective gate signals GS 1  to GSn are signals for turning on the subpixels PX connected to the respective gate lines GL 1  to GLn, and may be connected to a gate terminal of a transistor included in the respective subpixels PXs. 
     The power supply circuit  150  may generate a driving voltage DV to be provided to the display panel  110  on the basis of the third driving control signal DCS 3 , and transmit the generated driving voltage DV to the display panel  110 . The driving voltage DV may include a low potential driving voltage and a high potential driving voltage having a potential higher than the low potential driving voltage. According to embodiments, the power supply circuit  150  may transmit each of the low potential driving voltage and the high potential driving voltage to each of the subpixels PX through separate power lines. 
     In this disclosure, the source driver  130  and the gate driver  140  may be referred to as a panel driving circuit. 
     According to embodiments, at least two of the controller  120 , the source driver  130 , and the gate driver  140  may be implemented as one integrated circuit. In addition, according to embodiments, the source driver  130  or the gate driver  140  may be implemented in such a manner as to be mounted on the display panel  110 . In addition, according to embodiments, the power circuit  150  may be located outside the display panel  110 . 
       FIG. 3  is an exemplary diagram illustrating an image conversion apparatus according to  FIG. 2 . 
     Referring to  FIG. 3 , the image conversion apparatus  160  may include a processor  162  and a memory  164 . 
     The processor  162  may be a circuit having an operation processing function. For example, the processor  162  may be a central processing unit (CPU), a micro controller unit (MCU), a graphic processing unit (GPU), or an application specific integrated circuit (ASIC), but is not limited thereto. 
     The memory  164  may store a lookup table FYLUT defining a reference maximum luminance value Y′max in advance. Here, the reference maximum luminance value Y′max means the maximum luminance value that enables stable image capturing of the camera  200  according to characteristic information of the camera  200  capturing the image displayed on the display device  100 . 
     Herein, the characteristic information of the camera  200  may include an aperture value (F number, F2.0, F2.1, etc. in  FIG. 3 ) of the camera  200 , and therefore, the look-up table FYLUT may define a matching relationship between the aperture value of the camera  200  and a reference maximum luminance value Y′max. 
     The image conversion apparatus  160  generates the second image signal RGB 2  by converting the luminance of the first image signal RGB 1  in such a manner as to satisfy the reference maximum luminance value Y′max indicated by the lookup table FYLUT. Here, the camera  200  may be varied according to capturing conditions, and thus is not limited to a specific camera. 
     According to embodiments, the camera  200  may transmit characteristic information of the camera  200  to the display device  100  through a wired or wireless network, and the image conversion apparatus  160  may retrieve the reference maximum luminance value Y′max corresponding to the characteristic information received from the look-up table FYLUT using characteristic information of the camera  200  transmitted from the camera  200 . 
     In addition, the memory  164  may further store instructions, and the processor  162  may perform at least one step by the instructions stored in the memory  164 . 
     According to an embodiment, the image conversion apparatus  160  may be implemented as one integrated circuit (IC), but is not limited thereto. The image conversion apparatus  160  may be integrated into the controller  120  and included in the controller  120 . 
     The operation of the image conversion apparatus  160  described below may be an operation performed by the processor  162  or an operation indicated by instructions. In addition, the operation of the image conversion apparatus  160  described below may be referred to as a driving method of the display device  100  according to  FIG. 1 . 
       FIG. 4  is a flowchart illustrating a process of generating a second image signal in an image conversion apparatus according to  FIG. 2 . 
     Referring to  FIG. 4 , the image conversion apparatus  160  may calculate a contrast ratio CR for the first image signal RGB 1  (S 100 ). Here, the first image signal RGB 1  may be of an RGB format. Therefore, the image conversion apparatus  160  may first convert the RGB format of the first image signal RGB 1  into an YCbCr format. Specifically, the image conversion apparatus  160  may convert the RGB format of the first image signal RGB 1  into a luminance signal according to the YCbCr format according to Equation 1 below.
 
 Y=K   R   ·R+K   G   ·G+K   B   ·B   [Equation 1]
 
     Referring to Equation 1, R, G, and B may be red, green, and blue signals of the first image signal RGB 1 , in which Y may be a luminance according to the YCbCr format, and K R , K G , and K B  may be coefficients for the red, green, and blue signals, respectively. Herein, the coefficients according to Equation 1 may satisfy the following Equation 2.
 
 K   R   +K   G   +K   B =1  [Equation 2]
 
     According to the ITU-R BT.709 standard, the coefficient K R  for the red signal R is 0.2126, the coefficient K G  for the green signal G is 0.7152, and the coefficient K B  for the blue signal B is 0.0722. 
     In addition, the image conversion apparatus  160  may convert the RGB format of the first image signal RGB 1  into chroma signals according to the YCbCr format according to the following Equations 3 to 4. 
     
       
         
           
             
               
                 
                   
                     C 
                     b 
                   
                   = 
                   
                     
                       1 
                       2 
                     
                     · 
                     
                       
                         B 
                         - 
                         Y 
                       
                       
                         1 
                         - 
                         
                           K 
                           B 
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     3 
                   
                   ] 
                 
               
             
           
         
       
     
     Referring to Equation 3, a blue chroma signal Cb may be calculated using the blue signal B, the coefficient for the blue signal, and the luminance signal Y. 
     
       
         
           
             
               
                 
                   
                     C 
                     r 
                   
                   = 
                   
                     
                       1 
                       2 
                     
                     · 
                     
                       
                         R 
                         - 
                         Y 
                       
                       
                         1 
                         - 
                         
                           K 
                           R 
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     4 
                   
                   ] 
                 
               
             
           
         
       
     
     Referring to Equation 4, a red chroma signal Cr may be calculated using the red signal R, the coefficient for the red signal, and the luminance signal Y. Next, the image conversion apparatus  160  calculates a first maximum luminance value and a first minimum luminance value according to the YCbCr format from the first image signal RGB 1 , thereby calculating a contrast ratio for the first image signal RGB 1 . Specifically, the contrast ratio CR may be calculated according to the following Equation 5. 
     
       
         
           
             
               
                 
                   CR 
                   = 
                   
                     
                       Y 
                       max 
                     
                     
                       Y 
                       min 
                     
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     5 
                   
                   ] 
                 
               
             
           
         
       
     
     Referring to Equation 5, the contrast ratio CR may be calculated by a ratio between a first maximum luminance value Ymax and a first minimum luminance value Ymin of the luminance signal according to the YCbCr format. 
     The image conversion apparatus  160  may convert the luminance of the first image signal in such a manner as to satisfy the reference maximum luminance value while maintaining the calculated contrast ratio (S 110 ). Specifically, the image conversion apparatus  160  may calculate a reference minimum luminance value corresponding to the reference maximum luminance value on the basis of the contrast ratio. 
     For example, the reference minimum luminance value may be determined according to the following Equation 6. 
     
       
         
           
             
               
                 
                   
                     
                       Y 
                       ′ 
                     
                     min 
                   
                   = 
                   
                     
                       
                         Y 
                         ′ 
                       
                       max 
                     
                     CR 
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     6 
                   
                   ] 
                 
               
             
           
         
       
     
     Referring to Equation 6, the reference minimum luminance value Y′min may be determined as a value obtained by dividing the reference maximum luminance value Y′max by the contrast ratio CR. 
     When the reference minimum luminance value is determined, the image conversion apparatus  160  calculates a conversion coefficient using a ratio between the reference minimum luminance value Y′min and the first minimum luminance value Ymin, to convert the luminance of the first image signal RGB 1  according to the calculated conversion coefficient. For example, the conversion coefficient may be determined according to the following Equation 7. 
     
       
         
           
             
               
                 
                   W 
                   = 
                   
                     
                       Y 
                       min 
                     
                     
                       
                         Y 
                         ′ 
                       
                       min 
                     
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     7 
                   
                   ] 
                 
               
             
           
         
       
     
     Referring to Equation 7, the conversion coefficient w may be determined as a value obtained by dividing the first minimum luminance value Ymin by the reference minimum luminance value Y′min. In addition, the image conversion apparatus  160  may convert the luminance of the first image signal RGB 1  according to the following Equation 8.
 
 Y′=w·Y   [Equation 8]
 
     Referring to Equation 8, a converted luminance Y′ may be determined by multiplying the luminance Y of the first image signal RGB 1  by the conversion coefficient w. 
     When the converted luminance Y′ is determined, the image conversion apparatus  160  may generate a second image signal RGB 2  of RGB format having the converted luminance Y′ (S 120 ). Herein, the red signal in the second image signal RGB 2  of RGB format may be determined according to the following Equation 9.
 
 R′=Y′+ 2 ·C   r ·(1 −K   R )  [Equation 9]
 
     Referring to Equation 9, the red signal R′ of the second image signal RGB 2  may be determined according to the converted luminance Y′, the red chroma signal Cr (see Equation 4), and the coefficient K R  for the red signal R. 
     The blue signal in the second image signal RGB 2  of RGB format may be determined according to the following Equation 10.
 
 B′=Y′+ 2 ·C   b ·(1 −K   B )  [Equation 10]
 
     Referring to Equation 10, the blue signal B′ of the second image signal RGB 2  may be determined depending on the converted luminance Y′, the blue chroma signal Cb (see Equation 3), and the coefficient K B  for the blue signal B. 
     The green signal of the second image signal RGB 2  in RGB format may be determined as in the following Equation 11. 
     
       
         
           
             
               
                 
                   
                     G 
                     ′ 
                   
                   = 
                   
                     
                       
                         Y 
                         ′ 
                       
                       - 
                       
                         
                           K 
                           R 
                         
                         · 
                         
                           R 
                           ′ 
                         
                       
                       - 
                       
                         
                           K 
                           B 
                         
                         · 
                         
                           B 
                           ′ 
                         
                       
                     
                     
                       K 
                       G 
                     
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     11 
                   
                   ] 
                 
               
             
           
         
       
     
     Referring to Equation 11, the green signal G′ of the second image signal RGB 2  may be determined according to the converted luminance Y′, the coefficients K R , K G , and K B  for red signal R, green signal G, and blue signal B, and the red signal R′ and blue signal B′ according to Equation 9 and 10. 
     That is, the image conversion apparatus  160  converts the luminance of the first image signal RGB 1 , generates a second image signal RGB 2  having the converted luminance, and displays an image on the display device  100  according to the second image signal RGB 2 . Herein, since the camera  200  captures an image displayed with a luminance according to characteristic information (for example, aperture value) of the camera  200 , it is possible to address a problem in which unnecessary shadows are displayed in the captured image or visibility is degraded. 
     Meanwhile, the first image signal RGB 1  and the second image signal RGB 2  may have the same color depth. For example, when the color depth of the first image signal RGB 1  is 8 bits, the color depth of the second image signal may be also 8 bits. That is, when generating the second image signal RGB 2  by converting the luminance of the first image signal RGB 1 , the image conversion apparatus  160  may maintain the color depth unchanged. 
     Therefore, the color depth and contrast ratio of the first image signal RGB 1  are maintained to be the same in the second image signal RGB 2 , so that even when the display device  100  displays an image according to the second image signal RGB 2  instead of the first image signal RGB 1 , it is possible to prevent the heterogeneity that a viewer can feel. 
       FIG. 5  is a flowchart illustrating a process of relieving an edge of a first image signal in the image conversion apparatus according to  FIG. 2 ;  FIG. 6  is an exemplary diagram illustrating image conversion for detecting an edge of a first image signal in a process according to  FIG. 5 ; and  FIG. 7  is a conceptual diagram illustrating a method of detecting an edge of a second image signal in a process according to  FIG. 5 . 
     As described above, in the case that edges are repeatedly present in a first image signal RGB 1  at a certain interval, moiré artifacts may be recognized when capturing an image displayed by the first image signal RGB 1 . 
     To solve this problem, the image conversion apparatus  160  according to  FIG. 2  detects at least one edge from the first image signal RGB 1  and applies a blur mask to the first image signal RGB 1 , thereby relieving the at least one edge. 
     Referring to  FIG. 5 , since a color component of the first image signal RGB 1  does not affect the edge detection, the first image signal RGB 1  may be converted into a gray scale signal GRAY (S 200 ). 
     Next, the image conversion apparatus  160  may detect at least one edge from the gray scale signal GRAY (S 210 ). Specifically, the image conversion apparatus  160  may generate boundary data composed of edges for the first image signal RGB 1  by applying a Sobel mask to the gray scale signal GRAY. 
     Referring to  FIG. 6 , the boundary data EGRAY generated by applying the Sobel mask to the gray scale signal GRAY may be checked, in which such boundary data EGRAY may be composed of edges of the first image signal RGB 1 . 
     Herein, the image conversion apparatus  160  projects the boundary data EGRAY in a horizontal or vertical direction, and a blur mask may be applied to the first image signal RGB 1  in consideration of the size of the edge included in the projected boundary data EGRAY and the distance between the edges. 
     Specifically, referring to  FIG. 7  it is possible to check a graph HPG showing the length of an edge according to the horizontal location of the boundary data EGRAY, by projecting an output data EGRAY in a horizontal direction. 
     As described above, in the case that edges having a length equal to or greater than a predetermined length Δm are repeatedly present within a predetermined horizontal distance n when projecting the boundary data EGRAY in the horizontal direction, moiré artifacts may be recognized when capturing the image according to the first image signal RGB 1 . Therefore, in this case, a blur mask may be applied to the first image signal RGB 1 . 
     Similarly, in the case that edges having a length equal to or greater than a predetermined length are repeatedly present within a predetermined vertical distance when projecting the boundary data EGRAY in the vertical direction, a blur mask may be applied to the first image signal RGB 1 . 
     According to embodiments, the predetermined length Δm may decrease as characteristic information (e.g., aperture value) of the camera  200  increases. For example, a predetermined length for a first aperture value may be greater than a predetermined length for a second aperture value greater than the first aperture value. However, embodiments of the present disclosure are not limited thereto. 
     According to embodiments, in the case that edges having a length equal to or longer than a predetermined length Δm are repeatedly present within a predetermined horizontal distance n when projecting the boundary data EGRAY in the horizontal direction, a blur mask may be applied to the first image signal RGB 1  when the distance between the edges is less than or equal to a predetermined interval Δn. 
     According to embodiments, the predetermined interval Δn may increase as the characteristic information (e.g., aperture value) of the camera  200  increases. For example, a predetermined interval for the first aperture value may be smaller than a predetermined interval for the second aperture value greater than the first aperture value. However, embodiments of the present disclosure are not limited thereto. 
     When capturing an image according to the first image signal RGB 1 , moiré artifacts may be recognized. Therefore, in this case, a blur mask may be applied to the first image signal (RGB 1 ). 
     That is, the image conversion apparatus  160  applies a blur mask to the first image signal RGB 1  to relieve at least one edge detected in the gray scale signal GRAY and outputs the same to the controller  120  (S 220 ), thereby preventing a moiré artifact from being recognized. 
     The Sobel mask or blur mask according to an embodiment of the present disclosure is not limited to a special form. Since the skilled person may easily apply the Sobel mask or the blur mask in various ways, a detailed description is omitted. 
     Meanwhile, steps S 200  to S 220  according to  FIG. 5  are described for the first image signal RGB 1 , but are not limited thereto. For example, the second image signal RGB 2  generated according to  FIG. 4  is converted into a gray scale signal, an edge is detected from the converted gray scale signal, and then a blur mask is applied to the same. Similarly, steps S 100  to S 120  according to  FIG. 4  should be performed on the first image signal RGB 1  to which the blur mask is applied according to step S 220 . 
     The drawings referenced so far and the detailed description of the described invention are merely illustrative of the present disclosure, which is used for the purpose of describing the present disclosure only and is used to limit the scope of the present disclosure as defined in the claims or the claims. Therefore, it will be appreciated that various modifications and other equivalent embodiments are possible to those skilled in the art. Therefore, the true technical protection scope of the present disclosure should be defined by the technical spirit of the appended claims.