Image processing method, image processing circuit, and display device using the same

An image processing method, an image processing circuit, and a display apparatus using the same are discussed. The image processing method can include sensing a viewing distance of a user and determining a predetermined viewing distance mode, upon determining that the viewing distance corresponds to a short distance mode, performing blurring processing on four-color data of each pixel of an input image for each color channel by applying a predetermined blurring mask to reduce data of an edge portion of the input image and to output the image, and upon determining that the viewing distance corresponds to a long distance mode, performing sharpening processing on white data of four-color data of each pixel of the input image by applying a predetermined sharpness mask to increase the white data of the edge portion of the input image and to output the image.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority benefit of Korean Patent Application No. 10-2015-0104744, filed on Jul. 24, 2015, which is hereby incorporated by reference as if fully set forth herein.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a display apparatus, and more particularly, to an image processing method, an image processing circuit, and a display apparatus using the same, for providing optimum image quality to a viewer by adjusting sharpness according to image characteristics and a viewing distance.

Discussion of the Related Art

Representative examples of an image display apparatus include a liquid crystal display (LCD), an organic light emitting diode (OLED) display apparatus, and so on.

Recently, a transparent display apparatus has been developed along with the development of display apparatuses. Since the transparent display apparatus allows light to pass therethrough in both forward and backward directions, information can be displayed in both the directions and users who face each other across the display apparatus can also look over the transparent display apparatus.

The transparent display apparatus can be applied to various applied products such as a car window, a building window, an electronic display board, a cooler door, and a screen door and, thus, there are various user environments. In addition, a commercial transparent display apparatus includes a touch panel coupled thereto so as to increase a degree of freedom of a viewing distance to a proximity distance from a long distance.

Accordingly, when a user uses the transparent display apparatus at a proximity distance for a touch or the like, pixels are recognized, or when the user uses the apparatus at a long distance, sharpness of an image is degraded and, accordingly, there is a problem with degraded user perceptual quality.

Furthermore, the aforementioned problem can also occur in various display apparatuses as well as a transparent display apparatus and, thus, the present invention is not limited to a transparent display apparatus.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to an image processing method, an image processing circuit, and a display apparatus using the same that substantially obviates one or more problems due to limitations and disadvantages of the related art.

An object of the present invention is to provide an image processing method, an image processing circuit, and a display apparatus using the same, for providing optimum image quality to a viewer by adjusting sharpness according to image characteristics and a viewing distance.

To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, an image processing method includes sensing a viewing distance of a user and determining a predetermined viewing distance mode, upon determining that the viewing distance corresponds to a short distance mode, performing blurring processing on four-color data of each pixel of an input image for each color channel by applying a predetermined blurring mask to reduce data of an edge portion of the input image and to output the image, and upon determining that the viewing distance corresponds to a long distance mode, performing sharpening processing on white data (W data) of four-color data of each pixel of the input image by applying a predetermined sharpness mask to increase the W data of the edge portion of the input image and to output the image.

The image processing may further include, prior to the performing of the blurring or sharpening processing, converting three-color data of each pixel of the input image into the four-color data and storing the four-color data in a memory in units of frames. The four-color data stored in the memory may be updated via the blurring processing and the image may be output or only the W data of the four-color data may be updated via the sharpness processing and the image may be output.

The image processing may further include, after the storing of the input image and prior to the performing of the blurring or sharpening processing, dividing the four-color data into a transmissive region and a non-transmissive region by performing predetermined image analysis on the four-color data stored in the memory. The performing of the blurring processing may include updating four-color data of the non-transmissive region via the blurring processing and outputting four-color data of the transmissive region and the updated four-color data of the non-transmissive region. The performing of the sharpening processing may include updating the W data of the four-color data of the non-transmissive region via the sharpening processing and outputting the four-color data of the transmissive region and the four-color data of the non-transmissive region containing the updated W data.

The image processing may further include, upon determining that the viewing distance corresponds an optimum distance mode, outputting the four-color data stored in the memory without the blurring processing or the sharpening processing.

In another aspect of the present invention, an image processing circuit for performing image processing according to a viewing distance of a user, sensed by an external viewing distance sensor includes a viewing distance determiner for determining a predetermined viewing distance mode according to the viewing distance sensed by the viewing distance sensor, a blurring filter for performing blurring processing on four-color data of each pixel of an input image for each color channel by applying a predetermined blurring mask to correct data of the an edge portion of the input image when the viewing distance determiner outputs a first control signal indicating a short distance mode, and a sharpness filter for performing sharpening processing on W data of four-color data of each pixel of the input image by applying a predetermined sharpness mask to correct the W data of the edge portion of the input image when the viewing distance determiner outputs a second control signal indicating a long distance mode.

The image processing circuit may further include a four-color converter for converting three-color data of each pixel of the input image into the four-color data, and a memory for storing the four-color data from the four-color converter in units of frames. The blurring filter may update the four-color data stored in the memory via the blurring processing in response to the first control signal from the viewing distance determiner and the sharpness filter may update only the W data of the four-color data stored in the memory in response to the second control signal from the viewing distance determiner.

The image processing circuit may further include a non-transmissive region detector connected between the memory, and the blurring filter and the sharpness filter and for dividing the four-color data stored in the memory into a transmissive region and a non-transmissive region by performing image analysis on the four-color data.

The non-transmissive region detector may provide four-color data of the non-transmissive region to the blurring filter in response to the first control signal from the viewing distance determiner and update corresponding four-color data of the memory with the four-color data of the non-transmissive region corrected by the blurring filter.

The non-transmissive region detector may provide W data of the four-color data of the non-transmissive region to the sharpness filter in response to the second control signal from the viewing distance determiner and updates corresponding W data of the memory with the W data of the non-transmissive region corrected by the sharpness filter.

Driving of the blurring filter and the sharpness filter may be turned off when the viewing distance determiner outputs a third control signal indicating an optimum distance mode.

Driving of the blurring filter, the sharpness filter, and the non-transmissive region detector may be turned off when the viewing distance determiner outputs a third control signal indicating an optimum distance mode.

In another aspect of the present invention, a display apparatus includes the aforementioned viewing distance sensor, the image processing circuit for selectively performing the blurring processing and the sharpening processing according to the viewing distance of the user, and a panel driver for driving a display panel to display four-color data output from the image processing circuit on the display panel.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1is a schematic block diagram of a configuration of a display apparatus according to an embodiment of the present invention.FIG. 2is an equivalent circuit diagram of a configuration of a liquid crystal display (LCD) subpixel applied to a display panel40ofFIG. 1.FIG. 3is an equivalent circuit diagram of a configuration of an organic light emitting diode (OLED) subpixel applied to the display panel40ofFIG. 1. All the components of the display apparatus according to all embodiments of the present invention are operatively coupled and configured.

The display apparatus ofFIG. 1may include a timing controller10, a data driver20and a gate driver30as a panel driver, the display panel40, a gamma voltage generator50, a viewing distance sensor60, and so on.

The display panel40may display an image through a pixel array in which pixels are arranged in the form of a matrix. Each pixel of the pixel array may include red (R), white (W), green (G), and blue (B) subpixels (SPs). As the display panel40, a liquid crystal display (LCD) apparatus, an organic light emitting diode (OLED) display apparatus, an electrophoretic display apparatus (EPD), or the like.

For example, when the display panel40is an LCD panel, each subpixel may include a thin film transistor TFT connected to a gate line GL and a data line DL, and liquid crystal capacitor Clc and storage capacitor Cst that are connected in parallel to each other between the thin film transistor TFT and a common electrode, as illustrated inFIG. 2. The liquid crystal capacitor Clc may charge a difference voltage of a data signal supplied to a pixel electrode through the thin film transistor TFT with a common voltage Vcom applied to the common electrode and drive liquid crystal according to the charged voltage to control light transmission. The storage capacitor Cst may stably maintain a voltage charged in the liquid crystal capacitor Clc.

On the other hand, when the display panel40is an OLED panel, each subpixel SP may include a pixel circuit including an OLED device connected between a high-voltage power EVDD line and a low-voltage power EVSS line, first and second switching TFTs ST1and ST2and a driving TFT DT for independently driving the OLED device, and a storage capacitor Cst, as illustrated inFIG. 3, and the pixel circuit may have various configurations and may not be limited to the configuration ofFIG. 3.

The OLED device may include an anode connected to the driving TFT DT, a cathode connected to the low-voltage power EVSS, and a light emitting layer between the anode and the cathode and generates light that is proportional to the amount of current supplied from the driving TFT DT.

The first switching TFT ST1may be driven by a gate signal of one gate line GLa to supply a data voltage from a corresponding data line DL to a gate node of the driving TFT DT and the second switching TFT ST2may be driven by a gate signal of another gate line GLb to supply a reference voltage from a reference line RL to a source node of the driving TFT DT. The second switching TFT ST2may be further used as a path for outputting current from the driving TFT DT to the reference line RL in a sensing mode.

The storage capacitor Cst connected between the gate node and the source node of the driving TFT DT may charge a difference voltage between the data voltage supplied to the gate node through the first switching TFT ST1and the reference voltage supplied to the source node through the second switching TFT ST2to supply a driving voltage of the driving TFT DT.

The driving TFT DT may control current supplied from the high-voltage power EVDD according to the driving voltage from the storage capacitor Cst so as to supply current proportional to the driving voltage to the OLED device to light up the OLED device.

The data driver20may receive data control signal DCS and four-color data RWGB from the timing controller10. The data driver20may be driven according to the data control signal DCS to subdivide a reference gamma voltage set supplied from the gamma voltage generator50to gray scale voltages that respectively correspond to gray scales of data, to convert digital four-color data RWGB into analog data signals using the subdivided gray scale voltages and, then, to supply the analog data signals to data lines of the display panel40, respectively.

The data driver20may include a plurality of data drive ICs for separately driving the data lines of the display panel40. Each data drive IC may be mounted on a circuit film such as a tape carrier package (TCP), a chip on film (COF), and a flexible print circuit (FPC) and may be attached to the display panel40via a tape automatic bonding (TAB) method or may be mounted on the display panel40via a chip on glass (COG) method.

The gate driver30may drive each of a plurality of gate lines of the display panel40using a gate control signal GCS supplied from the timing controller10. The gate driver30may supply a scan pulse of a gate-on voltage to each gate line during a corresponding scan period in response to a gate control signal and supply a gate-off voltage during the remaining period. The gate driver30may receive the gate control signal GCS from the timing controller10or receive gate control signal GCS from the timing controller10through the data driver20. The gate driver30may include at least one gate IC and may be mounted on a circuit film such as TCP, COF, and FPC and may be attached to the display panel40via a TAB method or may be mounted on the display panel40via a COG method. On the other hand, the gate driver30may be formed on a TFT substrate together with a TFT array included in the pixel array of the display panel40so as to be configured as a gate in panel (GIP) type-gate driver which is installed in a non-display region of the display panel40.

The viewing distance sensor60may sense a viewing distance as a distance between the display panel40and a viewer using a general distance sensor and output the sensed viewing distance information to the timing controller10.

The timing controller10may receive image data R, G, and B and a timing signal TCS from an external host system. For example, the external host system may be any one of portable terminals such as a computer, a TV system, a set-top box, a tablet PC, or a cellular phone.

The timing controller10may control each of the data driver20and the gate driver30using input timing signals TCS, may convert input three-color data R, G, and B into four-color data R, W, G, and B, may selectively perform blurring processing or sharpening processing on the four-color data R, W, G, and B according to image characteristics and viewing distance information, and may output the processed data to the data driver20.

To this end, the timing controller10may include a control signal generator110and an image processing circuit120A or120B. The image processing circuit120A or120B may be separated from the timing controller10to constitute a separate IC and may be positioned at a previous end of the timing controller10.

The control signal generator110may generate a data control signal DCS and a gate control signal GCS using the input timing signals TCS and output the data control signal DCS and the gate control signal GCS to the data driver20and the gate driver30, respectively. The timing signal TCS received by the control signal generator110may include a dot clock, a data enable signal, a vertical synchronization signal, and a horizontal synchronization signal, but the vertical synchronization signal and the horizontal synchronization signal may be omitted. When the vertical synchronization signal and the horizontal synchronization signal are omitted, the control signal generator110may count the data enable signal according to the dot clock and generate and use the vertical synchronization signal and the horizontal synchronization signal. The data control signals DCS may include a source start pulse, a source sampling clock, a polarity control signal, a source output enable signal, and so on, for control of driving of the data driver20. The gate control signals GCS may include a gate start pulse, a gate shift clock, a gate output enable signal, and so on, for control of driving of the gate driver30.

The image processing circuit120A according to a first embodiment of the present invention may convert three-color data R, G, and B into four-color data R, W, G, and B using a general RGB-to-WRGB conversion method and perform different image processing operations, i.e., blurring processing or sharpening processing on the four-color data R, W, G, and B according to viewing distance information supplied from the viewing distance sensor60so as to adjust sharpness according to a viewing distance and to output an image. The image processing circuit120A may apply blurring processing to all of the four-color data R, W, G, and B and apply sharpening processing only to the data W of the four-color data R, W, G, and B. The data W is also referred to herein as W data.

On the other hand, the image processing circuit120A may apply blurring processing only to the data W of the four-color data R, W, G, and B or apply sharpening processing to all of the four-color data R, W, G, and B.

Compared with the aforementioned image processing circuit120A according to the first embodiment of the present invention, the image processing circuit120B according to a second embodiment of the present invention applied to a transparent display apparatus may apply a technology of dividing image data into a transmissive region and a non-transmissive region via image analysis and then adjusting sharpness according to the aforementioned viewing distance only to data of the non-transmissive region. The image processing circuit120B according to the second embodiment of the present invention may output data of the transmissive region without adjustment of sharpness so as to prevent transmittance of the transmissive region from being reduced due to unnecessary image processing. The image processing circuit120B according to the second embodiment may perform image analysis for division into the transmissive region and the non-transmissive region only when sharpness needs to be adjusted.

In addition, the image processing circuit120A or120B may further perform necessary image processing such as power consumption reduction, image compensation, and degradation compensation and then output the image to the data driver20.

FIGS. 4A and 4Bare graphs showing contrast sensitivity characteristics and sharpness recognition characteristics according to a viewing distance.

As seen fromFIG. 4A, as a viewing distance of a display apparatus is reduced (as a viewing angle is increased), contrast sensitivity characteristics is increased and a peak frequency of a spatial frequency is reduced. As seen fromFIG. 4B, as a viewing distance is increased, sharpness recognition characteristics are reduced. In consideration of the contrast sensitivity characteristics and sharpness recognition characteristics, the image processing circuit120A or120B may be differently adjust sharpness according to a viewing distance.

FIG. 5is a schematic diagram of a concept of an image processing method according to a viewing distance according to an embodiment of the present invention.

Referring toFIG. 5, when viewing distance information corresponds to a short distance mode, the image processing circuit120A or120B may perform blurring processing on image data so as to reduce edge brightness to reduce sharpness, and when viewing distance information corresponds to a long distance mode, the image processing circuit120A or120B may perform sharpening processing on the image data so as to increase edge brightness to increase sharpness.

Accordingly, a pixel recognition degree when a viewer views an image at a short distance may be reduced, visibility of an object positioned behind a transparent display apparatus may be enhanced, and a sharp image may be provided when the viewer views an image at a long distance so as to provide optimum recognized image quality to a user. The image processing circuit120A or120B may output image data without blurring or sharpening processing when the viewing distance information corresponds to an optimum distance mode.

FIG. 6is a block diagram illustrating an internal structure of the image processing circuit120A according to a first embodiment of the present invention.

The image processing circuit120A illustrated inFIG. 6may include a four-color converter122for converting three-color data Ri, Gi, and Bi into four-color data R, W, G, and B and outputting the four-color data R, W, G, and B, and a sharpness adjuster130A for performing blurring processing or sharpening processing on the four-color data R, W, G, and B from the four-color converter122according to viewing distance information from the viewing distance sensor60(refer toFIG. 1) and outputting the image or outputting the image without image correction.

The image processing circuit120A may further include an inverse gamma corrector at an input end and may further include a gamma corrector at an output end. The inverse gamma corrector may linearize the input three-color data R, G, and B via de-gamma correction and transmit the linearized three-color data Ri, Gi, and Bi to the four-color converter122, and the four-color converter122may convert the linearized three-color data Ri, Gi, and Bi into four-color data R, W, G, and B. The gamma corrector may non-linearize four-color data Ro, Wo, Go, and Bo, sharpness of which is selectively adjusted according to viewing distance information by the sharpness adjuster130A, via gamma correction and transmit the non-linearized four-color data to the data driver20.

The four-color converter122may convert the three-color data Ri, Gi, and Bi into four-color data R, W, G, and B using a general RGB-to-WRGB conversion technology and output the four-color data R, W, G, and B to the sharpness adjuster130A. For example, the four-color converter122may set a minimum value of the input three-color data Ri, Gi, and Bi as data W and subtract the data W from each of the three-color data Ri, Gi, and Bi so as to convert the three-color data Ri, Gi, and Bi into four-color data R, W, G, and B. A RGB-to-WRGB conversion method of the four-color converter122is not limited to the aforementioned method and, thus, may use any one of various known RGB-to-WRGB conversion methods.

The sharpness adjuster130A may include a frame memory132for storing four-color data R, W, G, and B from the four-color converter122, a viewing distance determiner138for selectively driving a blurring filter134and a sharpness filter136according to the viewing distance information from the viewing distance sensor60(refer toFIG. 1), the blurring filter134for performing blurring processing on four-color data R, W, G, and B of the frame memory132in response to a first control signal from the viewing distance determiner138, and the sharpness filter136for performing sharpening processing on at least data W of the four-color data R, W, G, and B of the frame memory132in response to a second control signal from the viewing distance determiner138.

The viewing distance determiner138may determine a viewing distance mode that is pre-set by a designer using viewing distance information sensed by the viewing distance sensor60and output a control signal for driving any one of the blurring filter134and the sharpness filter136or shutting off driving of the blurring filter134and the sharpness filter136according to the determined viewing distance mode.

For example, the viewing distance determiner138may determine whether the sensed viewing distance information corresponds to any one of preset short distance mode, an optimum distance mode, and a long distance mode. Upon determining that the viewing distance corresponds to a short distance mode, the viewing distance determiner138may output a first control signal to drive the blurring filter134, upon determining that the viewing distance corresponds to a long distance mode, the viewing distance determiner138may output a second control signal to drive the sharpness filter136, and upon determining that the viewing distance corresponds to an optimum distance mode, the viewing distance determiner138may output a third control signal to shut off driving of both the blurring filter134and the sharpness filter136.

The frame memory132may store four-color data R, W, G, and B from the four-color converter122in units of frames. When the viewing distance corresponds to a short distance mode, the data R, W, G, and B stored in the frame memory132may be corrected and then output so as to reduce brightness of an edge portion by the blurring filter134, when the viewing distance corresponds to a long distance mode, the data R, W, G, and B may be corrected and then output so as to increase brightness of an edge portion by the sharpness filter136, or when the viewing distance corresponds to an optimum distance mode, the data R, W, G, and B may be output via driving off of the blurring filter134and the sharpness filter136without being corrected. Accordingly, data Ro, Wo, Go, and Bo output from the frame memory132may include data that is selectively corrected according to a viewing distance.

The blurring filter134may be driven upon receiving a first control signal of a short distance mode from the viewing distance determiner138. The driven blurring filter134may correct the data R, W, G, and B so as to reduce brightness of an edge portion by reading the data R, W, G, and B from the frame memory132and applying a blurring mask BM illustrated inFIG. 7for each color channel and may update data of the frame memory132with the corrected data R, W, G, and B.

In detail, the blurring filter134may correct data of a corresponding pixel corresponding to a central cell of the blurring mask BM as illustrated inFIG. 7by reading the four-color data R, W, G, and B from the frame memory132for each color channel and applying the blurring mask BM to each color channel and may update corresponding pixel data of the frame memory132with the corrected data. The blurring filter134may repeatedly perform the aforementioned blurring processing while shifting the blurring mask BM for each color channel in units of pixels so as to update data of one frame stored in the frame memory132.

Referring toFIG. 7, optimum correction factors (X, Y, Z) may be set to each of 3*3 cells of the blurring mask BM according to a prior experiment of a designer. That is, the correction factor X may be set to a central cell of the blurring mask BM, the correction factor Y may be set to four cells adjacent to the central cell in upward, downward, right, and left directions, and the correction factor Z may be set to four cells adjacent to the central cell in a diagonal direction. The correction factors X, Y, Z may have a positive integer less than 1 and have a relationship of X>Y>Z. For example, the correction factors X, Y, Z may have a relationship of X=1/k (k is a natural number), Y=½ k, and Z=¼ k. A size of the blurring mask BM may be varied.

The blurring mask BM may be applied to data of each of the 3*3 pixels for each color channel.FIG. 7illustrates a representative example in which the blurring mask BM is applied to data W of data R, W, G, and B of the 3*3 pixels.

The blurring filter134may apply the correction factors (X, Y, Z) of the blurring mask BM to data W (Wi−1,j−1to Wi+1,j+1) of the 3*3 pixels to perform average calculation shown in Expression 1 below. Accordingly, the data W (Wi,j) of a corresponding pixel corresponding to the central cell of the blurring mask BM may be corrected to an average value (W′i,j) of the data W, which is obtained by applying the correction factors (X, Y, Z) of the blurring mask BM to the data W (Wi−1,j−1to Wi+1,j+1) of nine pixels in a mask to perform average calculation.

The blurring filter134may also apply the blurring mask BM illustrated inFIG. 7to the remaining data R, G, and B of the 3*3 pixels for each color channel in the same way so as to correct data R, G, and B of a corresponding central pixel (i, j) to average values (R′, G′, B′) of data R, G, and B of pixels in a mask to which the correction factors (X, Y, Z) are applied.

Accordingly, the data R, W, G, and B of pixels corresponding to an edge portion of the data R, W, G, and B stored in the frame memory132may be reduced via the aforementioned blurring processing of the blurring filter134so as to reduce brightness of an edge portion.

The blurring filter134may apply the blurring mask BM only on the data W of the four-color data R, W, G, and B stored in the frame memory132so as to perform blurring processing only on the data W.

Upon receiving a second control signal of a long distance mode from the viewing distance determiner138, the sharpness filter136may be driven. The driven sharpness filter136may correct the data W so as to increase brightness of an edge portion by reading only the data W of the data R, W, G, and B from the frame memory132and applying a sharpness mask SM illustrated inFIG. 8and may update data of the frame memory132with the corrected data W. Accordingly, the sharpness filter136may easily and simply increase brightness of the edge portion.

In detail, the sharpness filter136may correct the data W of a corresponding pixel corresponding to a central cell of the sharpness mask SM illustrated inFIG. 8by reading the data W from the frame memory132and applying the sharpness mask SM to the data W and may update the Data W of a corresponding pixel of the frame memory132with the corrected data W.

Referring toFIG. 8, optimum correction factors (L, −M, −N) may be set to each of 3*3 cells of the sharpness mask SM according to a prior experiment of a designer. That is, the correction factor L may be set to a central cell of the sharpness mask SM, the correction factor −M may be set to four cells adjacent to the central cell in upward, downward, right, and left directions, and the correction factor −N may be set to four cells adjacent to the central cell in a diagonal direction. Only the correction factor L of the central cell of the correction factors (L, −M, −N) may have an integer equal to or greater than 1 and the correction factors (−M, −N) of the adjacent cells may have a negative integer and have a relationship of 1>M>N>O. A size of the sharpness mask SM may be varied.

The sharpness filter136may apply the correction factors (L, −M, −N) of the sharpness mask SM to the data W (Wi−1,j−1to Wi+1,i+1) of the 3*3 pixels to calculate a value obtained by summing data W to which the correction factors (L, −M, −N) of pixels in a mask are applied as shown in Expression 2 below and may add a result value obtained via product of the summed value and a sharpness gain value Gain preset by a designer to the data W (Wi,j) of a corresponding pixel corresponding to the central cell of the sharpness mask SM so as to correct the data W (Wi,j) to W″i,j. Here, the sharpness gain value Gain may be preset by a designer according to user preference, the characteristics of a display apparatus, and so on in order to adjust a sharpening degree and may have, for example, a positive integer less than 1.

The sharpness filter136may repeatedly perform the aforementioned sharpening processing while shifting the while shifting the sharpness mask SM in units of pixels so as to update the data W of one frame stored in the frame memory132.

Accordingly, the data W of pixels corresponding to an edge portion among the data R, W, G, and B stored in the frame memory132may be corrected to be increased via the aforementioned sharpness processing of the sharpness filter136so as to increase brightness of the edge portion.

The sharpness mask SM may be applied to each of the four-color data R, W, G, and B stored in an internal memory of the sharpness filter136for each color channel so as to perform sharpening processing on all of the four-color data R, W, G, and B.

Accordingly, the image processing circuit120A according to the first embodiment of the present invention may reduce brightness of the edge portion to reduce sharpness of an image and output the image by performing blurring processing on the four-color data R, W, G, and B when a user views the image at a short distance, and image processing circuit120A may increase the brightness of the edge portion to increase sharpness of an image and output the image by performing sharpening processing on the data W when the user views the image at a long distance. When the user views an image at an optimum distance, the four-color data R, W, G, and B may be output without the aforementioned blurring or sharpening processing.

FIG. 9is a block diagram illustrating an internal structure of the image processing circuit120B according to a second embodiment of the present invention.

In particular, compared with the image processing circuit120A according to the first embodiment illustrated inFIG. 6, the image processing circuit120B according to the second embodiment illustrated inFIG. 9may be applied to a transparent display apparatus and may be different from the image processing circuit120A in that a sharpness adjuster130B is positioned between the frame memory132, and the blurring filter134and the sharpness filter136and the image processing circuit120B further includes a non-transmissive region detector140, control of which is controlled by the viewing distance determiner138. The other components are the same as inFIG. 6and, thus, a repeated description will be omitted or briefly given.

The sharpness adjuster130B of the image processing circuit120B according to the second embodiment applied to a transparent display apparatus may apply a technology of dividing image data into a transmissive region and a non-transmissive region via image analysis and then adjusting sharpness according to the aforementioned viewing distance only to data of the non-transmissive region and may output data of the transmissive region without adjustment of sharpness.

In other words, data of the non-transmissive region from data stored in the frame memory132may be corrected so as to reduce brightness of an edge portion by the blurring filter134when the viewing distance corresponds to a short distance mode or corrected so as to increase the brightness of the edge portion by the sharpness filter136when the viewing distance corresponds to a long distance mode and, thus, the frame memory132may output the corrected data of the non-transmissive region and the non-corrected data of the transmissive region. When the viewing distance corresponds to an optimum distance mode, the data of the non-transmissive region may not be corrected via driving off of the blurring filter134and the sharpness filter136and, thus, the frame memory132may output the non-corrected data of the non-transmissive region and the transmissive region. Accordingly, data Ro, Wo, Go, and Bo output from the updated frame memory132may include data of the non-transmissive region that is selectively corrected according to a viewing distance and the non-corrected data of the transmissive region.

When a viewing distance corresponds to an optimum distance mode and sharpness is not necessarily adjusted, the sharpness adjuster130B according to the second embodiment may also turn off image analysis for dividing the data R, W, G, and B stored in the frame memory132into a transmissive region and a non-transmissive region.

The non-transmissive region detector140may read and analyze the four-color data R, W, G, and B in frame units stored in the frame memory132and divide the data into a transmissive region and a non-transmissive region in response to a control signal indicating a viewing mode from the viewing distance determiner138, may image-process and correct only the four-color data R, W, G, and B of the non-transmissive region by the blurring filter134or the sharpness filter136which is driven according to a viewing distance, and may update data of the non-transmissive region of the frame memory132to the corrected data of the non-transmissive region.

Driving of the non-transmissive region detector140may be turned on only when the non-transmissive region detector140receives a first control signal of a short distance mode and a second control signal of a long distance mode from the viewing distance determiner138and driving of the non-transmissive region detector140may be turned off when the non-transmissive region detector140receives a third control signal of an optimum distance mode.

The non-transmissive region detector140may provide the four-color data R, W, G, and B of the non-transmissive region to the blurring filter134so as to be updated in response to the first control signal of a short distance mode and update data of the frame memory132with the updated four-color data R, W, G, and B of the non-transmissive region.

The non-transmissive region detector140may provide only data W of the four-color data R, W, G, and B to the sharpness filter136so as to be updated in response to the second control signal of a long distance mode and update the frame memory132with the updated W data of the non-transmissive region.

Driving of the non-transmissive region detector140may be turned off when the non-transmissive region detector140receives the third control signal of an optimum distance mode.

In addition, upon receiving the first control signal of a short distance mode or the second control signal of a long distance mode from the viewing distance determiner138, the non-transmissive region detector140may be driven to read four-color data R, W, G, and B from the frame memory132, may determine the four-color data R, W, G, and B as data of a transmissive region when a gray scale of each data is greater than a specific high gray scale, e.g.,250, and may determine the four-color data R, W, G, and B as data of non-transmissive region when a gray scale of each data is smaller than the specific high gray scale. In addition, the non-transmissive region detector140may divide the four-color data R, W, G, and B of the frame memory132into a transmissive region and a non-transmissive region using other general image analysis methods.

In response to the first control signal of a short distance mode, the non-transmissive region detector140may provide the four-color data R, W, G, and B of the non-transmissive region read from the frame memory132to the blurring filter134. The blurring filter134driven in response to the first control signal of a short distance mode may correct the four-color data R, W, G, and B of the non-transmissive region provided from the non-transmissive region detector140by applying the blurring mask BM for each color channel, as described above. The non-transmissive region detector140may update corresponding data items of the frame memory132to the four-color data R, W, G, and B of the non-transmissive region that is corrected by the blurring filter134.

Accordingly, when a user views an image at a short distance, the frame memory132may output the four-color data Ro, Wo, Go, and Bo of the non-transmissive region corrected to reduce brightness of an edge portion via blurring processing and non-corrected four-color data Ro, Wo, Go, and Bo of a transmissive region, as illustrated inFIG. 10.

In response to the second control signal of a long distance mode, the non-transmissive region detector140may provide the data W of the four-color data R, W, G, and B of the non-transmissive region read from the frame memory132to the sharpness filter136. The sharpness filter136driven in response to the second control signal of a long distance mode may correct the data W of the non-transmissive region provided from the non-transmissive region detector140by applying the sharpness mask SM, as described above. The non-transmissive region detector140may update the corresponding data W of the frame memory132with the data W of the non-transmissive region corrected by the sharpness filter136.

Accordingly, when a user views an image at a short distance, the frame memory132may output the data W corrected to increase brightness of an edge portion via sharpening processing, non-corrected data R, and non-corrected four-color data Ro, Wo, Go, and Bo of a transmissive region, as illustrated inFIG. 11.

On the other hand, when the third control signal of an optimum distance mode is input, driving of all of the blurring filter134, the sharpness filter136, and the non-transmissive region detector140is turned off.

Accordingly, the frame memory132may output non-corrected four-color data Ro, Wo, Go, and Bo of the transmissive region and non-transmissive region.

Accordingly, the image processing circuit120B according to the second embodiment of the present invention may reduce brightness of the edge portion to reduce sharpness of an image and output the image by performing blurring processing on the four-color data R, W, G, and B of the non-transmissive region when a user views the image at a short distance, and the image processing circuit120B may increase the brightness of the edge portion to increase sharpness of an image and output the image by performing sharpening processing on the data W of the non-transmissive region when the user views the image at a long distance. When the user views an image at an optimum distance, the four-color data R, W, G, and B may be output without the aforementioned blurring or sharpening processing.

FIG. 12is a set of images as examples of an output image of a short distance mode and an output image of a long distance mode compared with an input image of a transparent display apparatus to which the image processing circuit120B according to the second embodiment illustrated inFIG. 9is applied.

As seen fromFIG. 12, by virtue of the aforementioned image processing circuit120B according to the second embodiment, brightness of an edge portion of a letter in a non-transmissive region of the output image of a short distance mode is reduced to reduce sharpness and brightness of an edge portion of a letter in a non-transmissive region of the output image of a long distance mode is increased to increase sharpness.

As described above, the display apparatus according to the present invention may reduce brightness of an edge portion to reduce a pixel recognition degree via blurring processing when a viewing distance corresponds to a short distance mode and may increase the brightness of the edge portion to increase sharpness via sharpening processing when the viewing distance corresponds to a long distance mode, thereby providing optimum recognizing image quality to the user according to a viewing distance.

In particular, a transparent display apparatus according to the present invention may perform blurring processing or sharpening processing only on a non-transmissive region according to a viewing distance via image analysis so as to prevent transmittance of the transmissive region from being reduced due to image processing as well as to enhance user recognition image quality.

A display apparatus according to the present invention may reduce brightness of an edge portion to reduce a pixel recognition degree via blurring processing when a viewing distance corresponds to a short distance mode and may increase the brightness of the edge portion to increase sharpness via sharpening processing when the viewing distance corresponds to a long distance mode, thereby providing optimum recognizing image quality to the user according to a viewing distance.

In particular, the display apparatus according to the present invention may perform blurring processing or sharpening processing only on a non-transmissive region according to a viewing distance via image analysis so as to prevent transmittance of the transmissive region from being reduced due to image processing as well as to enhance user recognition image quality.