Abstract:
Disclosed is an image processing apparatus and a method of controlling the same. A color contact image sensor (CIS) module employing a single channel line sensor can be used to produce substantially the same performance as a color CIS module employing a three-channel line sensor and having color filters to, for example, reduce manufacturing costs. Moreover, a blurring phenomenon that can occur in a scanned image can be reduced and the quality of the scanned image can be improved.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a divisional of U.S. application Ser. No. 12/642,358, filed Dec. 18, 2009, which claims the benefit of Korean Patent Application No. 10-2008-0133175, filed on Dec. 24, 2008 in the Korean Intellectual Property Office, the disclosures of which are incorporated herein by reference in their entirety. 
     
    
     BACKGROUND 
       [0002]    1. Field 
         [0003]    Embodiments of the present disclosure generally relate to an image processing apparatus, and more particularly, to an image processing apparatus with a contact image sensor (CIS) module employing a single channel line sensor having a multi-color light source that can reduce a color shift of an image signal read by the CIS module, and to a method of controlling the same. 
         [0004]    2. Description of the Related Art 
         [0005]    In an image processing apparatus, such as a scanner or a copier, for example, a contact image sensor (CIS) module can be used. A CIS module is an image sensor module configured to optically read image information of an original document and to convert the optically read image information into an electrical signal. 
         [0006]    The CIS module can include a light source having elements configured to emit light with wavelengths associated with three different colors: red (R), green (G), and blue (B). The R, G, and B colors are often referred to collectively as RGB. The CIS module can include a light guide configured to guide light from the light source to be incident an original document across its width direction and a sensor array configured to detect the light reflected from the document. The sensor array can include multiple sensor integrated circuits (ICs) to perform a photoelectric conversion of the reflected light. The sensor ICs in the sensor array can be linearly arranged to have a length that generally correspond to the width of the document being read, that is, the sensor array can correspond to a line of the image of the original document. 
         [0007]    The light source can be arranged to face the light incident surface of the light guide so that the light radiated by the light source can be incident on the surface of the light guide. The light can be guided to form a line along the main scanning direction of the original document such that the original document, which can be placed on a support such as a glass support, can be substantially uniformly illuminated in a linear shape along the main scanning direction. Red, green and blue light emitting diodes (LEDs) can be used as the light emitting elements of the light source. The light emitting elements can be sequentially driven in a time division manner. The light radiated by the light source and reflected from the original document can be focused by a lens array to form an image on the sensor array. A color image signal, which includes R, G and B color information, can be produced by the sensor array, and can be externally output through an electrical connector, for example. 
         [0008]    When the RGB LEDs are sequentially turned on during one period, the reading of the RGB color image associated with one line can be completed. 
         [0009]    To obtain two-dimensional information of the original document, the document and the CIS module can be moved relative to each other in the sub scanning direction at a predetermined speed. Because the radiation locations of the RGB light on the document in the sub scanning direction can be different, the timing associated with the reading of the RGB information can be different. Accordingly, when the RGB outputs are synthesized to form color image information, a color shifts can occurs in the sub scanning direction. That is, when the original document is read using the CIS module that used a single channel line sensor having a time division multi-color light source, in order to implement the colors, each of the RGB LEDs may be sequentially turned on during ⅓ of an exposure time of one line to scan the colors. Thus, because a registration error of a ⅓ pixel can occur between R-G and G-B, a color shift can occur. For example, an upper portion of an image can appear reddish, a lower portion of the image can appear bluish, and/or fringes can result in the upper and/or lower portions of the image. 
         [0010]    Conventional attempts heretofore to reduce the color shift of the image includes the use of a CIS module employing a three-channel line sensor, and/or the provision of color filters corresponding to the various colors. 
       SUMMARY 
       [0011]    In accordance with one aspect of the present disclosure, an image processing apparatus may be provided to comprise a sensor module, a memory and a processor. The sensor module may have a light source and an optical sensor. The light source may be configured to generate a plurality of lights each of a color different than, and being temporally offset from, other ones of the plurality of lights. The optical sensor may be a single channel line sensor, and may be configured to produce color signals associated with the plurality of lights reflected from a document. The memory may be configured to store data associated with the color signals produced by the optical sensor. The data associated with the color signals may be stored in units of lines. The processor may be configured to determine interpolation ratios of the color signals associated with a current line of data stored in the memory based on a reference color and based on at least one other line of data stored in the memory, and may be configured to generate a new color signal associated with the current line based on the determined interpolation ratios. 
         [0012]    The plurality of colors may include three colors. The image processor may interpolates the color signals associated with each of the three colors based on the reference color. 
         [0013]    The three colors may include red (R), green (G) and blue (B). 
         [0014]    The reference color may be any one of R, G and B. 
         [0015]    The reference color may for example be green. The image processor may determine the interpolation ratios by the equation: R(i)′=⅔×R(i)+⅓×R(i+1), G(i)′=G(i), and B(i)′=⅓×B(i−1)+⅔×B(i). The index i may be the current line index value. 
         [0016]    The reference color may alternatively be red, for example. The image processor may determine the interpolation ratios by the equation: R(i)′=R(i), G(i)′=⅔×G(i)+⅓×G(i−1), and B(i)′=⅓×B(i)+⅔×B(i−1). The index i may be the current line index value. 
         [0017]    With the reference color being green, for example, the image processor determines the interpolation ratios by the equation: R(i)′=⅙×R(i−1)+⅚×R(i), G(i)′=½×G(i−1)+½×G(i), and B(i)′=⅚×(Bi−1)+⅙×B(i). The index i may be the current line index value. 
         [0018]    The image processor may alternatively determine the interpolation ratios by the equation: R(i)′= 3/10×R(i−1)+ 7/10×R(i), G(i)′=⅙×G(i−1)+ 4/6×G(i)+⅙×G(i+1), and B(i)′= 7/10×B(i)+ 3/10×B(i+1). The index i may be the current line index value. 
         [0019]    According to another aspect of the present disclosure, a method of controlling an image processing apparatus may be provided. The image processing apparatus may include a sensor module having a single channel line sensor and a light source configured to produce a plurality of temporally offset lights of different colors. The method may comprise the steps of: scanning a document with the sensor module to produce color signals associated with the scanned document; storing data associated with the color signals; determining interpolation ratios for color signals associated with a current line of stored data based on a reference color and based on color signals associated with at least one other line of stored data; and generating new color signals associated with the current line based on the determined interpolation ratios. 
         [0020]    The plurality of lights may include a light for each of red (R) color, green (G) color and blue (B) color. Any one of the R color, the G color and the B color may be the reference color on which the determined interpolation ratios are based. 
         [0021]    The interpolation ratios may be determined by the equation: R(i)′=R(i), G(i)′=⅔×G(i)+⅓×G(i−1), and B(i)′=⅓×B(i)+⅔×B(i−1). The index i may be the current line index value. 
         [0022]    The interpolation ratios may alternatively be determined by the equation: R(i)′=⅙×R(i−1)+⅚×R(i), G(i)′=½×G(i−1)+½×G(i), and (i)′=⅚×(Bi−1)+⅙×B(i). The index i may be the current line index value. 
         [0023]    The interpolation ratios may alternatively be determined by the equation: R(i)′= 3/10×R(i−1)+ 7/10×R(i), G(i)′=⅙×G(i−1)+ 4/6×G(i)+⅙×G(i+1), and B(i)′= 7/10×Bi+ 3/10×B(i+1). The index i may be the current line index value. 
         [0024]    According to yet another aspect of the present disclosure, an apparatus for acquiring an image from a document may be provided. The acquisition of the image may be realized by exposing the document sequentially with at least a first light of a first color and a second light of second color different from the first color, and by receiving at a single channel line sensor the first and second lights reflected off the document with a temporal offset therebetween. The single channel line sensor may have an array of optical sensors arranged in a line along a main scanning direction, which optical sensors may be configured to output color signals in response to receipt of each of the reflected first and second lights. The apparatus may comprise a memory and a processor. The memory may be configured to store data associated with lines of color signals produced by the optical sensors. Each line of color signals representing color signals contemporaneously output by the optical sensors. The processor may be configured to determine new color signals associated with a current line of at least one color associated with the at least first and second lights based on a reference color and based on the data associated with the current line and at least one other line of color signals. The new color signals may compensate for the temporal offset between the at least first and second lights. 
         [0025]    The apparatus may further comprise a second processor that may be configured to receive the color signals output by the optical sensors and to convert the received color signals into data for storage in the memory. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    Various aspects of the disclosure will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings, in which: 
           [0027]      FIG. 1  is a perspective view of an image processing apparatus according to an embodiment of the present disclosure; 
           [0028]      FIG. 2  is a cross-sectional view of a Contact Image Sensor (CIS) module according to an embodiment of the present disclosure usable in an image processing apparatus; 
           [0029]      FIG. 3  is a circuit diagram of a light source of the CIS module according to an embodiment of the present disclosure; 
           [0030]      FIG. 4  is a diagram of a sensor array of the CIS module according to an embodiment of the present disclosure; 
           [0031]      FIG. 5  is a timing diagram showing sequential turning on of RGB Light Emitting Diodes (LEDs) within one period of a synchronization pulse SP in the CIS module according to an embodiment of the present disclosure; 
           [0032]      FIG. 6  is a block diagram of the image processing apparatus according to an embodiment of the present disclosure; 
           [0033]      FIG. 7  is a block diagram of a scanner interface (I/F) of the image processing apparatus according to an embodiment of the present disclosure; 
           [0034]      FIG. 8  is a diagram describing a process of dividing color image data into RGB data of a single channel and of storing the RGB data in a memory of the image processing apparatus according to an embodiment of the present disclosure; 
           [0035]      FIG. 9  is a diagram describing a method of reducing a color shift of an image in the image processing apparatus according to an embodiment of the present disclosure; 
           [0036]      FIG. 10  is a diagram describing a method of interpolating an image signal in the image processing apparatus according to an embodiment of the present disclosure; and 
           [0037]      FIG. 11  is a diagram describing a method of interpolating an image signal in an image processing apparatus according to another embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0038]    Reference will now be made in detail to several embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. While the embodiments are described with detailed construction and elements to assist in a comprehensive understanding of the various applications and advantages of the embodiments, it should be apparent however that the embodiments can be carried out without those specifically detailed particulars. Also, well-known functions or constructions will not be described in detail so as to avoid obscuring the description with unnecessary detail. It should be also noted that in the drawings, the dimensions of the features are not intended to be to true scale and may be exaggerated for the sake of allowing greater understanding. 
         [0039]      FIG. 1  is a perspective view of an image processing apparatus according to an embodiment of the present disclosure. As shown in  FIG. 1 , the image processing apparatus can include a contact image sensor (CIS) module  20  mounted on the upper portion of a main body  10 . The CIS module  20  can be configured to read an original document laid or placed on a glass  12  and to generate an image signal of that document, while reciprocally moving along a guide member  11 . 
         [0040]      FIG. 2  is a cross-sectional view of the CIS module  20  according to an embodiment of the present disclosure. As shown in  FIG. 2 , the CIS module  20  can include multiple light sources  21 , each of which can be configured to produce light of a different color, a light guide  22  configured to guide light from the light sources  21  along the width direction of an original document P and a sensor array  25  configured to detect light reflected from the document. 
         [0041]    The light sources  21  can be configured to radiate light to the original document P, and can include emission elements  21 - r ,  21 - g , and  21 - b , which produce light having wavelengths associated with primary colors red (R), green (G) and blue (B), respectively. The light radiated by the light sources  21  can be incident on the light guide  22 , which is arranged along the width direction of the original document P, such that the light is guided in the main scanning direction as indicated in  FIG. 2 . The light can be radiated from a light emitting portion of the light guide  22  at a linear light velocity. Thus, the light can be substantially uniform when radiated along the width direction of the original document P placed on the glass  12 . The light produced by the light sources  21  and reflected from the original document P can be focused on the sensor array  25  disposed on a substrate  26  by a lens array  24 . The sensor array  25  can generate an electrical signal corresponding to an image received through the lens array  24 . Such electrical signal can be externally provided as an output of the sensor array  25  through a connector  27  coupled to the sensor array  25 . A frame  23  can be configured to hold the light guide  22 , the lens array  24  and the substrate  26  at their respective predetermined positions. 
         [0042]    As shown in  FIG. 3 , light emitting diodes (LEDs) configured to emit red (R) light, green (G) light and blue (B) light using a common anode can be used as the light emitting elements  21 - r ,  21 - g  and  21 - b , respectively, of the light sources  21 . A signal V_LED can be applied to the common anode of the LEDs. The cathodes of the LEDs  21 - r ,  21 - g  and  21 - b  can be connected to the switching elements Q 1 , Q 2  and Q 3  through resistors r 1 , r 2 , and r 3 , and can be turned on, that is, can be driven sufficiently to produce light, by driving signals R_LED, G_LED and B_LED, respectively. 
         [0043]      FIG. 4  is a diagram of a sensor array of the CIS module according to an embodiment of the present disclosure.  FIG. 4  shows an enlarged diagram of an arrangement of a sensor integrated circuit (IC) that forms the sensor array. As shown in  FIG. 4 , the sensor array  25  can include several chips. For example, the sensor array  25  can include multiple sensor ICs, from sensor IC  25 - 1  to sensor IC  25 - i , each of which can be configured to perform photoelectric conversion. The sensor ICs in the sensor array  25  can be linearly arranged along the main scanning direction. Each of the sensor ICs of the sensor array  25  can include n number of pixels, from P(1) to P(n), for example. The pixels in the sensor IC can be configured to perform photoelectric conversion, and can be linearly arranged along the main scanning direction at a predetermined spacing interval x. The expanded view of sensor IC  25 - 4  is by way of example to illustrate the configuration of the pixels in a sensor IC of the sensor array  25 . 
         [0044]      FIG. 5  is a timing diagram showing the sequential turning-on of the LEDs that produce R, G and B light within one period (TW) of a synchronization pulse (SP) in the CIS module  20  according to an embodiment of the present disclosure. As shown in  FIG. 5 , any one of the three LEDs described above with respect to  FIG. 3  can be controlled within the period of the synchronization pulse. In this example, T_LED refers to a turning-on time associated each LED during one period of the synchronization signal. In this example, when the driving signals R_LED, G_LED and B_LED are sequentially applied within one period TW, the turning-on period of each of the light emitting elements  21 - r ,  21 - g  and  21 - b  can be substantially equal to ⅓ of the period TW (i.e., TW/3) with the timing of light emission between the light emitting elements being temporally offset from one another. 
         [0045]      FIG. 6  is a block diagram of the image processing apparatus according to an embodiment of the present disclosure. As shown in  FIG. 6 , the image processing apparatus can include an analog front end (AFE)  30 , a scanner interface (I/F)  40 , a memory  50 , an image processor  60 , a central processing unit (CPU)  70 , a read only memory (ROM)  80  and a motor controller  90 . Each of the AFE  30 , the I/F  40 , the memory  50 , the image processor  60 , the CPU  70 , the ROM  80 , and the motor controller  90  can include hardware (e.g., analog circuitry, digital circuitry, memory, processor, central processing unit, input/output interfaces), or software (e.g., operating system, firmware, embedded code, applications), or both, and in some embodiments may be implemented as one or more devices that combine some of the functions thereof. 
         [0046]    The CIS module  20  can be configured to produced light with the light sources  21  and to receive the light reflected from the original document P, and may be configured to convert the received light into an electrical signal. In this embodiment, the electrical signal can be an analog signal, for example. 
         [0047]    The AFE  30  can be configured to convert the analog signal obtained from scanning the image by the CIS module  20  into a digital signal. In some embodiments, the output from the CIS module  20  can be a digital signal. In such embodiments, the AFE  30  need not be used. 
         [0048]    The scanner I/F  40  can be connected to the CIS module  20  through the AFE  30 . The scanner I/F  40  can be configured to receive and/or processes the image signal output from the CIS module  20 . The image signal received and/or processed by the scanner I/F can be stored in the memory  50 . 
         [0049]    The image processor  60  can be configured to perform image processing operations, such as interpolation, for example, with respect to the image signal that had been processed and/or stored in the memory  50  by the scanner I/F  40 . 
         [0050]    The CPU  70  can be configured to control the various data processing operations associated with the components shown in  FIG. 6 . The CPU  70  can be configured to control various operations of the image processing apparatus. For example, the CPU  70  can be programmed to control the operations of some or all of the electrical components of the image processing apparatus. 
         [0051]    The ROM  80  can be configured to store computer instructions for an operating or application program(s) that can be executed by the CPU  70  to process data and/or to control the components of the image processing apparatus. 
         [0052]    The motor controller  90  can be configured to control the driving of a motor to move the CIS module  20  in the sub scanning direction such that the CIS module  20  scans the original document in units of lines along the main scanning direction. 
         [0053]    The scanner I/F  40 , the image processor  60  and the memory  50  can be connected via a first bus B 1 . The CPU  80 , the ROM  90 , the motor controller  90  and the memory  50  can be connected via a second bus B 2 . The use of the first bus B 1  and the second bus B 2  are non-limiting examples of electrical connections by which the electric signals may be transmitted between the above-described components. 
         [0054]      FIG. 7  is a block diagram of the scanner I/F  40  of an image processing apparatus according to an embodiment of the present disclosure. As shown in  FIG. 7 , the scanner I/F  40  can include a light source controller  41 , a timing controller  42 , a synchronization controller  43 , and a data controller  44 . As described above with respect to the scanner I/F  40 , each of the light source controller  41 , the timing controller  42 , the synchronization controller  43 , and the data controller  44  can include hardware, or software, or both. 
         [0055]    The light source controller  41  can be configured to control the turning ON and OFF of the light sources  21  (which may include, e.g., R, G, and B LEDs) of the CIS module  20 . The light source controller  41  can be configured to control the synchronization pulse SP and the driving signals R_LED, G_LED and B_LED to control the sequential turn-on of the LEDs corresponding to the color elements of RGB. The timing control provided by the light source controller  41  can be performed in accordance with the synchronization pulse from the timing controller  42 . 
         [0056]    The timing controller  42  can be configured to generate a control signal for controlling the CIS module  20  according to a reading speed and to output the control signal to the CIS module  20 . 
         [0057]    The output signal from the CIS module  20  can be provided as an input to the AFE  30 . The AFE  30  can perform, for example, a signal gain adjustment and/or an analog-to-digital (A/D) conversion of the signal received from the CIS module  20  to convert the analog signal output from the CIS module  20  into a digital signal that can be provided to the scanner I/F  40 . 
         [0058]    The synchronization controller  43  can be configured to set a predetermined threshold level corresponding to the analog signal of the CIS module  20  with respect to the AFE  30 . In addition, the synchronization controller  43  can be configured to generate and output a synchronization clock to control the sampling of the analog signal such that the AFE  30  can produce a digital signal. Moreover, the synchronization controller  43  can be configured to receive the image signal from the AFE  30 . 
         [0059]    The data controller  44  can be configured to receive the image signal from the AFE  30  through the synchronization controller  43  and to store the image signal in the memory  50  via the first bus B 1 . 
         [0060]      FIG. 8  is a diagram describing a process of dividing color image data of a single channel into RGB data and of storing the RGB data in the memory of the image processing apparatus, according to an embodiment of the present disclosure. As shown in  FIG. 8 , when the RGB data corresponding to a first line in the main scanning direction is output in series, the R data can be stored in an R region  51  of the memory  50 , the G data can be stored in a G region  52  of the memory  50 , and the B data can be stored in a B region  53  of the memory  50 . In this example, the R data corresponding to a first line R 1  to R 2  in the main scanning direction of the RGB data can be stored in the R region  51  of the memory  50  according to the line sequence. 
         [0061]    The G data corresponding to a first line G 1  to G 2  in the main scanning direction of the RGB data can be stored in the G region  52  of the memory  50  according to the line sequence. 
         [0062]    The B data corresponding to a first line B 1  to B 2  in the main scanning direction can be stored in the B region  53  of the memory  50  according to the line sequence. 
         [0063]    Once the RGB data corresponding to the first line is stored, R data corresponding to a second line R 3  to R 4  in the main scanning direction of the RGB data can be stored in the R region  51  of the memory  50 . The same approach can be subsequently followed with respect to G data and B data, and for the remaining lines of data. 
         [0064]    Although, in the above-described embodiment, the RGB data is stored in the memory  50  in the line sequence by dividing the memory  50  into R data, G data, and B data regions, the data can be sequentially stored in a same region of the memory  50 . 
         [0065]    In an embodiment of the present disclosure, the image processor  60  can be configured to interpolate the remaining colors based on a reference color with respect to the color-based image signals stored in the memory  50  to, for example, lighten color fringes that may occur in the upper and lower portions of the image, thereby reducing the color shift of the image. 
         [0066]      FIG. 9  is a diagram describing a method of reducing a color shift of an image in the image processing apparatus according to an embodiment of the present disclosure.  FIG. 10  is a diagram describing a method of interpolating an image signal in the image processing apparatus according to an embodiment of the present disclosure. 
         [0067]    Referring to  FIGS. 9 and 10 , the strength of colors associated with a document can be represented digitally by, for example, a range from 0 to 255 with an 8-bit binary number. When the original document includes a region having a gray color with RGB values of (127, 127, 127) and having a width of 2.17 pixels, and that region is painted on a white background having RGB values of (255, 255, 255), reading and printing the original document can result in a color line scanned over four pixels. That is, even for gray color, a color of 1 or 2 pixels may be output, with the upper edge of the line being reddish and the lower edge of the line being bluish, thereby generating color fringes. In addition, a whole line having a width smaller than a width of 5/3=1.7 pixels can be represented by a color without a gray scale. 
         [0068]    To address such occurrences, the image processor  60  can interpolate the red color into the lower side of the green color by a ⅓ pixel and the blue color into the upper side of the green color by a ⅓ pixel using the green color as a reference color with respect to the image signals stored in the memory  50 . That is, when the green color is used as the reference color, two lines can be stored in the vertical direction with respect to the red color and the blue color, interpolation ratios of colors can be determined by Equation 1 below, and the color signals of the colors can be interpolated according to the determined interpolation ratios to generate new color signals. The new color signals generated in this manner can be used for the output of the image. 
         [0000]        R ( i )′=⅔ ×R ( i )+⅓ ×R ( i+ 1),
 
         [0000]        G ( i )′= G ( i ), and
 
         [0000]        B ( i )′=⅓ ×B ( i− 1)+⅔ ×B ( i ), where  i  is a line index value.  Equation 1:
 
         [0069]      FIG. 9  shows the RGB values before interpolation, R 1 G 1 B 1  to R 6 G 6 B 6 , and the corresponding RGB values after interpolation, R 1 ′G 1 ′B 1 ′ to R 6 ′G 6 ′B 6 ′. From these results, it can be seen that the color fringe phenomenon after interpolation is improved when compared to the color fringe phenomenon before interpolation. 
         [0070]    As described above, when the original document is read using the CIS module  20  that has a single channel line sensor and RGB light sources, to implement the RGB colors, each of the RGB LEDs can be sequentially turned ON during ⅓ of an exposure time of one line to scan the colors. As a result, a registration error of a ⅓ pixel can occur between R-G and G-B and a color shift can occur in the image. For example, the red color can be interpolated into the lower side of the green color by a ⅓ pixel and the blue color can be interpolated into the upper side of the green color by a ⅓ pixel when the green color is used as the reference color. 
         [0071]    While in the above-described embodiment the green color is being used as the reference color, other embodiments of the present disclosure need not be so limited. Any one of the red color and the blue color can also be used as the reference color. 
         [0072]    For example, when the red color is set as the reference color, the interpolation ratios of the colors can be determined by Equation 2 described below, and the color signals of the colors can be interpolated according to the interpolation ratios determined using Equation 2. 
         [0000]        R ( i )′= R ( i ),
 
         [0000]        G ( i )′=⅔ ×G ( i )+⅓ ×G ( i− 1), and
 
         [0000]        B ( i )′=⅓ ×B ( i )+⅔ ×B ( i− 1), where  i  is a line index value.  Equation 2:
 
         [0073]    When the blue color is used as the reference color, the interpolation can be performed using an approach that is substantially similar as the above-described approaches. 
         [0074]    The existing color signals can be converted into new color signals by the above-described interpolation methods. The image can be output based on the converted new color signals. 
         [0075]    While in the above-described embodiment the interpolation is being performed based on the current line of the reference color, other embodiments of the present disclosure need not be so limited. For example, an alternative interpolation approach can be based on determining a virtual intermediate line between the current line and a previous line and using the values of the virtual intermediate line when outputting the image. 
         [0076]      FIG. 11  is a diagram describing a method of interpolating an image signal in an image processing apparatus according to another embodiment of the present disclosure. Referring to  FIG. 11 , the interpolation of the image signal can be performed on the basis of the virtual intermediate line between the previous line and the current line, instead of basing the interpolation on the current line of the reference color. 
         [0077]    For example, the green color can be used as the reference color, and the interpolation of the RGB colors based on the virtual intermediate line between the previous line i−1 and the current line i can be performed by determining interpolation ratios of the colors by Equation 3 described below and interpolating the color signals of the colors according to the interpolation ratios determined using Equation 3. 
         [0000]        R ( i )′=⅙ ×R ( i− 1)+⅚ ×R ( i );
 
         [0000]        G ( i )′=½ ×G ( i− 1)+½ ×G ( i );
 
         [0000]        B ( i )′=⅚×( Bi− 1)+⅙ ×B ( i ), where  i  is a line index value.  Equation 3:
 
         [0078]    While in the above-described embodiment the green color is being used as the reference color, other embodiments of the present disclosure need not be so limited, and any one of the red color and the blue color can be set as the reference color. When the red color or the blue color is used as the reference color, the interpolation equation can be obtained by substantially the same approach as the above-described approach. 
         [0079]    The interpolation methods of the image signal using Equations 1 to 3 above can reduce the color shift of the image. The edges of the image, however, can be blurred and the boundary thereof may not be clearly distinguished. Accordingly, the image signal can be interpolated by a method that extends the reference color over three lines to prevent or reduce such blurring. 
         [0080]    An interpolation method that addressed the blurring in the image can be performed by Equation 4. 
         [0000]        R ( i )′= 3/10 ×R ( i− 1)+ 7/10 ×R ( i ),
 
         [0000]        G ( i )′=⅙ ×G ( i− 1)+ 4/6 ×G ( i )+⅙ ×G ( i+ 1), and
 
         [0000]        B ( i )′= 7/10 ×B ( i )+ 3/10 ×B ( i+ 1), where  i  is a line index value.  Equation 4:
 
         [0081]    While several embodiments of the present disclosure have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the disclosure, the scope of which is defined in the claims and their equivalents.