KR20170072119A - Transparent display device and method for driving the same - Google Patents

Abstract

The present invention provides a transparent display device and a method of driving the same that can adaptively adjust an image according to a driving characteristic and a back surface background characteristic of a transparent display device to improve image quality. The transparent display device according to an exemplary embodiment of the present invention may selectively compensate an image using one of a gamma correction method and a sharpness improvement method in consideration of a transmittance characteristic of a light shielding plate and a brightness characteristic of an input image and a back surface background, Can be improved.

Description

TECHNICAL FIELD [0001] The present invention relates to a transparent display device and a method of driving the same.

BACKGROUND OF THE INVENTION 1. Field of the Invention [0002] The present invention relates to a transparent display device and a driving method thereof that can improve image quality by adaptively adjusting an image according to a driving characteristic of a transparent display device and a background background characteristic.

BACKGROUND ART In recent years, a transparent display device using a liquid crystal display (LCD) device or an organic light emitting diode (OLED) display device has been developed as a display device.

Since the transparent display device transmits light in both forward and backward directions, information can be displayed in both directions of the display device, and each user facing the display device can see beyond the transparent display device.

Transparent display devices can be applied to various applications such as automobile glass, building glass, advertisement display board, cooler door, screen door, and the like.

Since a transparent display device can not realize black in a state of high transmittance, a technique of controlling transmittance using a shading plate has been developed.

However, there is a problem that it takes a considerable time to close the shading plate after the shading plate operates due to the limitation of the material of the shading plate material.

Accordingly, there is a problem that the image quality of the transparent display device is deteriorated due to the influence of the perceived image quality depending on the transmittance characteristic of the light shielding plate, the back surface background characteristic of the transparent display device, and the characteristics of the input image before the light shielding plate is closed.

For example, when the transmissivity is high before the light blocking plate of the transparent display device is closed, the black can not be realized, so that the image quality degrades like a lump in the low gradation area. When the background of the rear surface of the transparent display device is bright, more light is transmitted and the visibility of the image is deteriorated, so that the image quality deteriorates. When the input image is dark, it is difficult to realize black in the transparent display device, and image quality deterioration occurs.

In addition, the transparent display device may not include the light shielding plate when it is required to recognize the back side background together with the image information according to the use environment, or may display the image while keeping the light shielding plate in the transmission mode.

In this case, since the image is recognized along with the background background, the transparency display device has a problem that the image quality is deteriorated due to the degradation of the image sharpness according to the brightness of the image and the brightness of the background background.

The present invention provides a transparent display device and a method of driving the same that can adaptively adjust an image according to a driving characteristic and a back surface background characteristic of a transparent display device to improve image quality.

A transparent display device according to an embodiment of the present invention includes a transparent display unit, a shading plate, a display driving unit, a shading plate driving unit, a background sensor disposed on the rear surface of the transparent display device for sensing a background background, and an image processing unit.

The image processing unit analyzes the input image, determines the image characteristics indicating whether the input image is a dark image or a bright image, and analyzes the background signal sensed from the background sensor to determine a background background indicating whether the background is a light background or a dark background And judges the transmittance characteristic of the shading plate.

The image processing unit is one of the remaining image quality degradation conditions except for the normal image, which is a bright image and the background image, and when the transmissivity exceeds the first reference value, the image processing unit performs gamma correction on the input image , And outputs gamma corrected image data to the display driver.

The image processor outputs the input image to the display driver without gamma correction regardless of the transmittance when the image characteristic and the background characteristic are in a normal condition. When the transmittance is lower than the first reference value, And outputs it to the display driver without correction.

A method of driving a transparent display device according to an embodiment of the present invention includes analyzing an input image and determining an image characteristic indicating whether the input image is a dark image or a bright image, Analyzing the sensed backside background signal to determine a background characteristic indicative of whether the backside background is a light background or a dark background; and determining a light transmittance characteristic of the light shield plate.

In addition, the driving method of the present invention is applicable to any one of the remaining image quality degradation conditions except for the normal image, which is a bright image and the dark image, and the image characteristic and the background characteristic, and when the transmittance exceeds the first reference value, Performing gamma correction on the image; And outputting the gamma corrected image.

According to another aspect of the present invention, there is provided a method of driving a liquid crystal display, comprising the steps of: outputting an input image without gamma correction regardless of transmittance when the image characteristic and the background characteristic are normal; Without gamma correction on the input image.

According to an embodiment of the present invention, there is provided a transparent display device including a transparent display unit, a background sensor, a display driver, and a display unit that divides the input image into a plurality of pixel blocks, The sharpness enhancement strength of each block is determined in units of pixel blocks according to the brightness characteristics of the backside of the sensed background, the sharpness of the input image is corrected on a pixel block basis by applying intensity of block sharpness improvement to the input image, To the display driver.

The image processing unit includes a low pass filter, a mask generating unit, a sharpness improving strength adjusting unit, a sharpness improving mask determining unit, and an image correcting unit. The low-pass filter low-pass filters an input image to generate and output a blurred image. The mask generation unit generates an edge mask image by subtracting the blurred image supplied from the low-pass filter from the input image, and outputs the generated edge mask image. The sharpness enhancement intensity controller adjusts the sharpness enhancement intensity of each block according to the brightness characteristics of the input image and the background of the sensed background. The sharpness improvement mask determination unit generates a sharpness improvement mask image by applying the block sharpness enhancement strength supplied from the sharpness improvement strength adjustment unit to the edge mask image supplied from the mask generation unit. The image correction unit combines the sharpness enhancement mask image supplied from the sharpness enhancement mask determination unit and the input image, and outputs the corrected image to the panel driver.

According to another aspect of the present invention, there is provided a method of driving a transparent display device, including: generating a blur image by low-pass filtering an input image; generating an edge mask image by subtracting a blur image from an input image; Determining sharpness enhancement strength for each block on a pixel-by-pixel block basis according to a brightness characteristic of each block calculated on a pixel-by-pixel block basis and a brightness characteristic of a sensed background, dividing the plurality of pixel blocks into a plurality of pixel blocks, Generating a sharpness enhancement mask image by applying sharpness enhancement strength, and displaying the corrected sharpness enhancement mask image and the input image on the transparent display unit.

The step of determining the brightness enhancement strength for each block includes the steps of calculating an average gray level of each block with respect to the input image, determining a maximum value and a minimum value of the brightness enhancement strength according to the brightness of the sensed background, (Kmax, Kmin) of the sharpness improving intensity and the average gradation L of each block are less than a preset threshold value Lth, Determining a strength (K), and determining a preset minimum value as the sharpness improving strength of the block when the average gradation per block is equal to or greater than a threshold value.

A transparent display device and a driving method thereof according to an embodiment of the present invention analyze both the transmittance characteristic of the shading plate, the luminance characteristic of the input image, and the luminance characteristic of the background image, When the background corresponds to the image quality degradation condition, the image quality is improved by adjusting the gamma by correcting the image data.

The transparent display device and the driving method thereof according to an embodiment of the present invention improve sharpness and image quality by applying appropriate sharpness enhancement strength according to image and viewing environment by adjusting intensity of sharpness improvement according to brightness of image and background brightness .

The transparent display device and the driving method thereof according to an embodiment of the present invention adjusts the brightness enhancement intensity according to the brightness of the image and the brightness of the background of the backlight so that when meaningful information is transmitted between the image and the backlight, The visibility of both the image and the background can be improved.

FIG. 1 is a graph showing transmittance characteristics according to elapsed driving time of a shading plate in a transparent display device according to the prior art of the present invention.
FIG. 2 is a photograph showing a result of image display according to the transmittance of a shading plate in a transparent display device according to the prior art of the present invention.
FIG. 3 is a photograph showing a comparison of image display results according to the image characteristics and the background characteristics in the transparent display device according to the prior art of the present invention.
4 is a block diagram schematically showing a configuration of a transparent display device according to an embodiment of the present invention.
5 is an equivalent circuit diagram illustrating a configuration of a subpixel according to an embodiment of the present invention.
6 is a block diagram illustrating a configuration of an image processing unit of a transparent display device according to an embodiment of the present invention.
FIG. 7 is a flowchart illustrating a method of processing an image of a transparent display device according to an exemplary embodiment of the present invention.
8 is a graph illustrating distribution ratios of input images according to an embodiment of the present invention.
FIG. 9 is a graph illustrating distribution ratios of background images according to an exemplary embodiment of the present invention.
10 is a graph illustrating various gamma curves according to an embodiment of the present invention.
11 is a photograph showing an image before and after gamma correction and an image in which gamma correction is unnecessary according to an embodiment of the present invention.
12 is a block diagram schematically showing a configuration of a transparent display device according to an embodiment of the present invention.
13 is a block diagram illustrating a configuration of an image processing unit according to an embodiment of the present invention.
FIG. 14 is a flowchart showing a step of an image processing method according to an embodiment of the present invention.
15 is a graph illustrating a sharpness enhancement intensity function according to a block average gray level according to an embodiment of the present invention.
FIG. 16 is a view illustrating an image obtained by adjusting the brightness enhancement intensity according to the brightness of the image and the brightness of the background in the transparent display device according to an embodiment of the present invention, in contrast to the image of the prior art.

Prior to the description of the embodiments of the present invention, the image degradation phenomenon of the transparent display device according to the prior art of the present invention will be described first.

FIG. 1 is a graph showing a transmittance characteristic of a light shielding plate according to the elapsed driving time in a transparent display according to the prior art of the present invention. FIG. 2 is a graph showing a result of image display according to the transmittance of a light shielding plate in the transparent display according to the prior art of the present invention FIG. 3 is a photograph showing a comparison of image display results according to the image characteristic and the background characteristic when the transmissivity of the shading plate is 70% in the transparent display device according to the prior art of the present invention.

Referring to FIG. 1, it can be seen that the shading plate of the transparent display device according to the related art takes a considerable time of about 3 minutes from the start of driving until the transmissivity reaches 10% or less.

Accordingly, as shown in FIG. 2 (a), if the light transmittance of the light shielding plate is 80%, the light shielding plate can not be implemented in black, so that the background of the backlight is visible due to the transparent property and more light is transmitted through the rear surface, Able to know. As shown in FIG. 2 (b), when the light blocking plate is closed with a transmittance of 10% or less, the black image of the light blocking plate improves the visibility of the display image.

3 (a) and 3 (b), when the shading plate transmittance is 70%, the image quality is lowered on the background (b) which is lighter than the dark background (a) (a) and the bright image (b), the background of the background is visible and the visibility of the display image is degraded.

Further, when the shielding plate is not provided or the recognition of the background is required and the shielding plate is maintained in the transmissive mode, the transparency display device according to the prior art determines the degree of recognition of the background in accordance with the brightness characteristics of the image and the background So that the sharpness of the image may be degraded depending on the degree of recognition of the background.

In order to solve the problems of the prior art, the present invention selectively takes into consideration the transmittance characteristic of the shading plate, corrects the image in consideration of the brightness characteristic of the input image and the brightness characteristic of the background (i.e., viewing environment) A transparent display device and a driving method thereof that can improve image quality by improving the visibility according to the environment are proposed.

Hereinafter, preferred embodiments of the present invention will be described.

A transparent display device according to an embodiment of the present invention uses at least one of a gamma correction method and a sharpness improvement method as an image processing method for improving visibility according to an image and a viewing environment.

FIG. 4 is a block diagram schematically showing a configuration of a transparent display device according to an embodiment of the present invention, and FIG. 5 is an equivalent circuit diagram illustrating a configuration of a subpixel according to an embodiment of the present invention.

4, a transparent display device according to an exemplary embodiment of the present invention includes an image processing unit 100, a timing controller 150, a data driver 200 and a gate driver 300, a transparent display unit 400, A generating unit 500, a background sensor 600, a light shield plate 700, and a light shield plate driving unit 800. Here, the timing controller 150, the data driver 200, and the gate driver 300 may be represented as a display driver for driving the transparent display unit 400.

The transparent display unit 400 displays an image through a pixel array in which pixels are arranged in a matrix form. The basic pixel of the pixel array includes at least three or more sub-pixels (W / R) capable of white representation by color mixing among white (W), red (R), green (G) / G, B / W / R, G / B / W, R / G / B, or W / R / G / B).

 As the transparent display unit 400, a liquid crystal panel, an organic light emitting diode (OLED) panel, or the like can be used. Hereinafter, an OLED panel will be described as an example.

5, each subpixel SP includes a light emitting region EA in which the OLED element is located and a light emitting region EA in which the light is transmitted from the front / rear side of the transmissive region TA ). The light emitting region EA of the OLED element may overlap or not overlap with the pixel circuit.

5, the pixel circuit includes an OLED element connected between a high potential power supply (EVDD) line and a low potential power supply (EVSS) line, a first and a second switching TFTs ST1 and ST2 for independently driving the OLED element, ST2), a driver TFT (DT), and a storage capacitor (Cst), and the pixel circuit configuration is not limited to the structure of FIG.

The OLED element includes an anode connected to the driving TFT DT, a cathode connected to the low potential voltage EVSS, and a light emitting layer between the anode and the cathode to emit light proportional to the amount of current supplied from the driving TFT DT Occurs.

The first switching TFT ST1 is driven by the gate signal of one gate line GL1 to supply the data voltage from the corresponding data line DL to the gate node of the driving TFT DT and the second switching TFT ST2 Is driven by the gate signal of the other gate line GL2 to supply a reference voltage from the reference line REF to the source node of the driving TFT DT. The second switching TFT ST2 is further used as a path for outputting the current from the driving TFT DT to the reference line REF in the sensing mode.

The storage capacitor Cst connected between the gate node and the source node of the driving TFT DT is connected between the data voltage supplied to the gate node through the first switching TFT ST1 and the data voltage supplied to the source node through the second switching TFT ST2. And supplies the difference voltage to the driving voltage of the driving TFT DT.

The driving TFT DT controls the current supplied from the high potential power supply EVDD according to the driving voltage supplied from the storage capacitor Cst to supply a current proportional to the driving voltage to the OLED element to emit the OLED element.

4, the light blocking plate 700 is disposed on the rear surface of the transparent display unit 400 and can be driven by the light blocking plate driving unit 800 in the light blocking mode or the transmissive mode when the transparent display unit 400 displays an image . When the electric field is applied by the shading plate driver 800, the shading plate 700 displays black to realize the shading mode, and if the electric field is not applied, the transmissive mode can be realized. When the light blocking plate 700 is driven in the light blocking mode by the light blocking plate driving unit 800, the light blocking plate 700 implements black to prevent light transmission, thereby improving the visibility of the displayed image on the transparent display unit 400.

For example, as the light shielding plate 700, an electrochromic device, an electro-wetting device, or the like known as an electrochromic filter may be used, or a liquid crystal can be used to switch light transmission Device.

The shield plate 700 may be disposed on at least one of the front surface and the rear surface of the transparent display unit 400.

The background sensor 600 is mounted on the rear surface of the transparent display device, and senses the background background of the transparent display device and supplies the sensed background information (brightness or image) to the image processing unit 100. As the background sensor 600, a well-known illuminance sensor, a CMOS image sensor, or the like can be applied.

The image processing unit 100 analyzes the input image supplied from the outside to determine image characteristics, and analyzes background information (brightness or image) sensed from the background sensor 600 to determine characteristics of the background. The image processing unit 100 may determine the transmittance of the shield plate 700 according to the transmissive mode and the shield mode of the shield plate 700 by the shield plate driving unit 800. [ When the light blocking plate 700 is driven in the light blocking mode, the image processing unit 100 measures the transmittance of the light blocking plate 700 according to an elapsed driving time of the light blocking plate 700 and stores the transmittance in the form of a look-up table (LUT) . The image processing unit 100 can determine the transmittance of the light shield plate 700 according to the driving time of the light shield mode when the light shield plate 700 is driven by the light shield plate driving unit 800 in the light shield mode.

The image processing unit 100 determines whether the input image is a dark image or a bright image by analyzing the input image, and analyzes the background information to determine whether the background is a bright environment or a dark environment. A detailed description thereof will be described later.

The image processing unit 100 determines that the image quality is degraded when the input image is dark and the background is bright, the input image is dark and the background is dark, the input image is bright and the background is bright, And compensates the image quality by outputting the gamma corrected image by performing gamma correction according to the transmittance of the input image when the transmittance of the shading plate 700 exceeds the first reference value (for example, 10%).

On the other hand, the image processing unit 100 determines whether the input image is bright and the background is dark, the transmittance exceeds the first reference value (for example, 10%), or the transmittance is the same regardless of the characteristics of the input image and the background When the first reference value is less than or equal to the first reference value, the input image is output without gamma correction.

The image processing unit 100 converts the three-color data (R, G, B) into four-color data (W, R, G, B) by using a normal RGB-to-WRGB conversion method before or after the above- Can be converted. The image processing unit 100 may further perform necessary image processing such as power consumption reduction, data rendering, image quality compensation, degradation compensation, and the like before or after the above-described gamma correction. The image processing unit 100 supplies the image data and the timing control signals to the timing controller 150.

The image processing unit 100 may embody hardware in the timing controller 100 or may be an image processing module of software stored in a memory.

The timing controller 150 generates a data control signal DCS and a gate control signal GCS using the timing control signals supplied from the image processing unit 100 and outputs them to the data driver 200 and the gate driver 300, do. The timing control signals include a dot clock, a data enable signal, a vertical synchronizing signal, and a horizontal synchronizing signal. The vertical synchronizing signal and the horizontal synchronizing signal can be omitted because they can be generated by counting the data enabling signal. The data control signals may include a source start pulse for controlling driving of the data driver 200, a source sampling clock, a source output enable signal, and the like. The gate control signals may include gate start pulses, gate shift clocks, and the like, which control the driving of the gate driver 300.

The timing controller 150 supplies a deviation of driving characteristics (threshold voltage, mobility, OLED threshold voltage, etc.) of each subpixel of the transparent display unit 400 to the data driver 200 to perform necessary image processing such as external compensation or deterioration compensation, and then output to the data driver 200.

The data driver 200 receives data control signals and video data from the timing controller 150. The data driver 200 is driven in accordance with the data control signal to divide the set of reference gamma voltages supplied from the gamma voltage generator 500 into the gray voltages corresponding to the gray levels of the data, Converts the digital image data into analog data signals, and supplies the analog data signals to the data lines of the transparent display unit 400, respectively.

The data driver 200 includes a plurality of data driver ICs for dividing and driving the data lines of the transparent display unit 400. Each data driver IC includes a tape carrier package (TCP), a chip on film (COF) Circuit or the like and mounted on the transparent display unit 400 by a tape automatic bonding (TAB) method or on a transparent display unit 400 by a COG (Chip On Glass) method.

The gate driver 300 drives the plurality of gate lines of the transparent display unit 400 using the gate control signal GCS supplied from the timing controller 150. The gate driver 300 supplies the gate-on voltage to the respective gate lines in response to the gate control signals, and supplies the gate-off voltages during the remaining periods. The gate driving unit 300 receives the gate control signal GCS from the timing controller 150 or receives the gate control signal GCS from the timing controller 150 via the data driving unit 200, Via a power supply circuit (not shown).

The gate driver 300 includes at least one gate IC and is mounted on a circuit film such as TCP, COF, FPC or the like to be attached to the transparent display unit 400 in a TAB manner or mounted on a transparent display unit 400 in a COG manner . Alternatively, the gate driver 300 may be formed on the thin film transistor substrate together with the thin film transistor array constituting the pixel array of the transparent display unit 400, thereby forming a GIP (Gate In Panel) type As shown in FIG.

FIG. 6 is a block diagram illustrating an internal configuration of an image processing unit 100 according to an embodiment of the present invention. FIG. 7 is a flowchart illustrating an image processing method according to an exemplary embodiment of the present invention, 7 will be described.

Referring to FIG. 6, the image processing unit 100 includes a transmission LUT 102, an image characteristic analyzer 104, a background characteristic analyzer 106, a determiner 108, and a gamma corrector 110. The image processing unit 100 may further include other image processing blocks known in the art.

The image characteristic analyzing unit 104 receives the input image from the outside and analyzes the input image to calculate the inclusion degree of the dark image, that is, the degree of darkness. The image characteristic analyzer 104 calculates the degree of darkness of the input image, And outputs a determination signal to the determination unit 108. (S12)

For example, the image characteristic analyzing unit 104 may calculate a weighted average image level, which indicates the distribution rate occupied by the low gray level values in the input image of each frame, that is, Level (WAPL_Low below) as a percentage (%).

&Quot; (1) "

n is the number of subpixels included in a unit frame of the input image, and Gray is a gray value of each subpixel.

If the WAPL_Low calculated from Equation (1) is smaller than the second reference value alpha%, the image characteristic analyzing unit 104 determines that the input image is a dark image. If the WAPL_Low is equal to or greater than the second reference value alpha% And outputs a first determination signal indicating whether the input image is a dark image or a bright image to the determination unit 108 according to the determination result. (S12) Here, the second reference value alpha% is predetermined by the designer, and is suitable as a reference value for judging whether or not the image of 30?? 50 is dark depending on the characteristics of the transparent display device and the light shielding plate 700. [

When the WAPL_Low calculated from Equation (1) is smaller than the second reference value?% (30??? 50), as shown in the graph of the distribution ratio of the input image shown in FIG. 8, the distribution ratio of the low gradation region is relatively large .

The background characteristic analyzing unit 106 receives the background image sensed by the background sensor 600 and analyzes the background image to calculate the degree of brightness, and determines a second determination signal indicative of whether the background is bright or dark depending on the degree of brightness And outputs it to the gamma correction unit 108. (S14)

For example, when the background information to be sensed is background information, the background characteristic analyzer 106 calculates the degree of occupation of the number of pixels of the high tone value in the background image of each frame, that is, (Hereinafter referred to as " WAPL_High ") is calculated as a percentage (%).

&Quot; (2) "

n is the number of subpixels included in the unit frame of the background image, and Gray is the gray value of each subpixel.

If the WAPL_High calculated from Equation (2) is larger than the third reference value beta%, the background characteristic analyzing unit 106 determines that the background image is bright. If the WAPL_High is equal to or less than the second reference value beta% And outputs to the determination unit 108 a second determination signal indicating whether the background image is bright or dark according to the determination result. (S14) Here, the second reference value [beta]% is predetermined by the designer, and differs depending on the characteristics of the transparent display device and the light shielding plate 700, but 50??? 70 is suitable as a reference value for determining a bright background.

When the WAPL_High calculated from the equation (2) is larger than the third reference value?% (50??? 70), as shown in the graph of the distribution of the gradation of the background image shown in FIG. 9, .

The transmittance of the shield plate 700 is measured and stored in advance in the transmittance LUT 102 according to the elapsed driving time. The transmittance LUT 102 receives the drive time of the shield plate 700 from an external system (not shown), selects the transmittance according to the drive time of the shield plate 700, and supplies the transmittance to the determination unit 108 (S16). The transmittance LUT 102 can classify and store a plurality of transmittance sections according to driving time. For example, the transmittance (t) period can be classified and stored as t> 70, 60 <t≤70, ..., 20 <t≤30, 10 <t≤20, t≤10. The transmittance LUT 102 may output information on the transmittance (t) section corresponding to the driving time to the determiner 108. (S18)

The determination unit 108 compares the first determination signal indicating whether the input image supplied from the image characteristic analysis unit 104 is dark or light and the second determination signal indicating whether the background supplied from the background characteristic analysis unit 106 is bright or dark The signals are logically combined to determine whether to perform gamma correction. The determination unit 108 outputs the signal for which the gamma correction is determined and the transmittance information supplied from the transmittance LUT 102 to the gamma correction unit 110. [ The determination unit 108 can output the maximum transmittance information to the gamma correction unit 110 when the light blocking plate 700 is in the transmission mode by the light blocking plate driving unit 800. [

The judgment unit 108 judges whether the first judgment signal from the image characteristic analysis unit 104 and the second judgment signal from the background characteristic analysis unit 106 correspond to the first judgment signal (S18, YES), which corresponds to one of the first to third conditions (dark image and bright background, dark image and dark background, bright image and bright background) (S20, YES), the gamma correction section 110 outputs a gamma correction necessity signal to the gamma correction section 110. The gamma correction section 110 outputs the gamma correction required signal to the gamma correction section 110. [ The determination unit 108 also outputs the transmittance information together with the gamma correction required signal to the gamma correction unit 110. [

<Table 1>

On the other hand, the determination unit 108 determines that the first determination signal from the image characteristic analysis unit 104 and the second determination signal from the background characteristic analysis unit 106 correspond to the fourth condition Dark background), a gamma correction unnecessary signal is output to the gamma correction unit 110 regardless of the transmittance information (S18, NO)

On the other hand, when the transmittance information supplied from the transmittance LUT 102 is equal to or smaller than the first reference value (for example, 10%), the determination unit 108 outputs a gamma correction unnecessary signal to the gamma correction unit 102, (110). (S20, NO)

The gamma correction unit 110 receives the gamma correction necessity signal from the determination unit 108 and outputs the gamma correction required signal to the input image signal processing unit 110 via the image characteristic analysis unit 104 in accordance with the transmittance information supplied via the determination unit 108. [ (S22), and outputs the gamma corrected image (S24).

On the other hand, when the gamma correction unnecessary signal is supplied from the determination unit 108, the gamma correction unit 110 outputs the input image supplied via the image characteristic analysis unit 104 without gamma correction (S24).

The gamma correction unit 110 stores a plurality of gamma correction LUTs having different gamma values (values defining gamma curves representing the output gamma values for the input gamut values) as shown in FIG. 10 according to the transmittance information have.

For example, the gamma correction unit 110 selects different gamma values (GMA) according to the transmittance (t) information as shown in Table 2 below, and uses the LUT corresponding to the selected gamma value to convert each data (Output grayscale value) corresponding to the input image (output grayscale value), and outputs the gamma-corrected image by subjecting the input image to differential gamma correction according to the transmittance.

<Table 2>

The 2.2 gamma value corresponding to the case where the transmittance (t) information is less than 10% in Table 2 means that the input image is output without gamma correction at the basic setting value of the transparent display device.

As shown in Table 2, as the transmittance increases, the gamma value increases. As shown in FIG. 9, the output tone value for the input tone value decreases as the gamma value increases.

11 is a photograph showing an image before and after gamma correction and an image in which gamma correction is unnecessary according to an embodiment of the present invention.

When the light-shielding plate transmittance is 70% and the input image is dark and the background is bright, as shown in FIG. 11 (a), when the image is displayed using 2.2 gamma before the present invention is applied, the visibility of the display image is deteriorated , And FIG. 11 (b), the present invention is applied to display an image using 3.4 gamma, thereby improving visibility and image quality.

On the other hand, when the background is dark and the input image is bright as shown in FIG. 11 (c), gamma correction is not necessary.

As described above, the transparent display device and the driving method thereof according to an embodiment of the present invention analyze both the transmittance characteristics of the shading plate, the luminance characteristics of the input image, and the luminance characteristics of the background image, And the back-side background corresponds to the image quality degradation condition, the image quality can be improved by adjusting the gamma by correcting the image data.

12 is a block diagram schematically showing a configuration of a transparent display device according to an embodiment of the present invention.

The transparent display device shown in FIG. 12 differs from the embodiment shown in FIG. 4 in that the image processing unit 1000 has a degree of sharpness degradation of an image (a backlight background) The image quality of the image is improved by adaptively adjusting the sharpness of the image according to the degree of recognition. Since the remaining components except for the image processing unit 1000 in FIG. 12 are the same as FIG. 4, description of the same components as those in FIG. 4 will be omitted.

The transparent display device shown in FIG. 12 requires recognition of the background on the back with the image display. The transparent display device shown in FIG. 12 omits the shield plate 700 and the shield plate driving part 800 shown in FIG. 4 . 4, the light blocking plate 700 can maintain the light transmission mode by the light blocking plate driving unit 800. [0156] In addition, in the case of the light blocking plate 700 and the light blocking plate driving unit 800 shown in FIG.

The image processing unit 1000 may employ a sharpness improvement method that improves the sharpness in proportion to the edge strength of the image by applying unsharp masking in order to improve the sharpness of the image. Also, in order to prevent at least one of the sharpness and the image quality from being degraded, the brightness of the image and the brightness of the background of the background are changed according to the brightness of the image and the brightness of the background, To adjust the sharpness enhancement intensity adaptively according to the brightness. As a result, the image processing unit 1000 can improve the sharpness appropriately in the image and the viewing environment by adjusting the sharpness improvement intensity in consideration of both the edge strength characteristic of the image, the brightness characteristic of the image, and the brightness characteristic of the background background, Can be improved.

Specifically, in the transparent display device, the background of the bright region of the image is not well recognized due to the bright image, whereas the background region of the image is recognized together with the background of the background region, The sharpness of the image can be reduced. In order to prevent the sharpness of the image from being degraded according to the brightness of the image, the image processing unit 1000 increases the sharpness enhancement strength because the darkness of the image has a high degree of recognition of the background, The brightness of the background is low and the degree of sharpness reduction is low, thereby reducing the sharpness improving strength. For this purpose, the image processing unit 100 divides the image frame into a plurality of pixel blocks to calculate an average gradation for each pixel block, and adjusts the sharpness improvement strength for each block according to the average gradation (average brightness per block) for each block.

Also, the image processor 100 adjusts the sharpness enhancement intensity according to the brightness of the background background, in order to prevent the background visibility from increasing as the brightness of the background is higher. In the case of the dark background, the image processing unit 100 reduces the degree of sharpness degradation because the degree of recognition of the background is low, thereby reducing the intensity of sharpness enhancement. In the bright background, Increases strength. For this, the image processing unit 100 senses the brightness of the back background and adjusts the brightness enhancement strength according to the average gray level of each image by varying the background weight according to the background brightness, Adjust the sharpness improvement intensity accordingly. A detailed description thereof will be described later.

FIG. 13 is a block diagram illustrating a configuration of an image processing unit 1000 of a transparent display device according to an exemplary embodiment of the present invention. FIG. 14 is a flowchart illustrating a method of processing an image of a transparent display device according to an exemplary embodiment of the present invention. And FIG. 15 is a graph of a function for determining sharpness enhancement strength according to an average gradation of each block of an image according to an embodiment of the present invention. Hereinafter, a description will be given with reference to Figs. 13 to 15. Fig.

The image processing unit 1000 shown in FIG. 13 includes a sharpness enhancement intensity adjuster 1200 that adjusts the sharpness enhancement intensity K according to the brightness of a video image and a background image, an input image FD through an unsharp masking process, And an unsharp mask filter 1100 for improving the sharpness of the image in proportion to the sharpness improving intensity K and outputting the image FD 'improved in sharpness.

The unsharp mask filter 1100 includes a low-pass filter 1110, a mask generating unit 1120, a sharpness improving mask determining unit 1130, and an image correcting unit 1140.

The low-pass filter 1110 low-pass-filters the input image FD on a frame basis to generate a blurred image in which the luminance difference between pixels is reduced and outputs a blurred image.

The mask generation unit 1120 generates an edge mask image MD representing an edge component of the input image FD by subtracting the blurred image supplied from the low pass filter 1110 from the input image FD, (MD). (S42)

The sharpness improvement mask determination unit 1130 determines the sharpness enhancement intensity K (k) adjusted according to the image brightness and the background background brightness in the sharpness enhancement intensity adjuster 1200 to the edge mask image MD supplied from the mask generator 1120. [ ) To determine the sharpness improving mask image MD 'and output the sharpness improving mask image MD'. (S54) The sharpness improvement mask determination unit 1130 multiplies the edge mask image MD by the sharpness improvement strength K so that the strength of the edge component in the edge mask image MD is increased by the sharpness improvement strength K Thereby generating a sharpness improving mask image MD '. The sharpness improving intensity controller 1200 outputs the sharpness improving intensity K for each block adjusted according to the average gradation for each pixel block and the backside background brightness. Accordingly, the sharpness improvement mask determination unit 1130 generates the sharpness improvement mask image MD 'by applying the sharpness enhancement strength K for each block in units of pixel blocks of the edge mask image MD.

The image correcting unit 1140 generates the output image FD 'having improved sharpness by combining the input image FD and the sharpness improving mask image MD' supplied from the sharpness improving mask determining unit 1300, And outputs an output image FD '. (S56)

The sharpness improving intensity controller 1200 uses the average gradation L for each block of the plurality of pixel blocks obtained by dividing the input image FD and the weight Kmax and Kmin adjusted according to the brightness of the background, The sharpness improvement strength (K) is determined for each block, and the sharpness improvement strength (K) for each block is output. The sharpness enhancement intensity adjuster 1200 includes an average gray scale calculator 1210, a background weight determiner 1220, and a sharpness intensity determiner 1230. [

The average gradation calculation unit 120 divides the input image FD into a plurality of pixel blocks, calculates an average gradation L for each block, and outputs an average gradation L for each block. (S44) The size (n * n, n is the number of pixels) of each pixel block for calculating the average gradation L can be variously set. For example, in order to reflect the average brightness characteristic by region, n? 10 is suitable.

The background weight determiner 1220 determines weights Wmax and Wmin in accordance with the brightness information E of the background background sensed from the background sensor 600 (Kmax, Kmin) according to the brightness of the back side background are determined by applying them to the maximum and minimum sharpness enhancement intensities (K0max, K0min) of the preset darkroom environments such as the maximum and minimum sharpness enhancement intensities (Kmax, Kmin) as a background weight value. (S50)

&Quot; (3) &quot;

Kmax = K0max * Wmax

Kmin = K0min * Wmin

In other words, the background weight determiner 1220 varies the maximum and minimum sharpness enhancement intensities (Kmax, Kmin) according to the brightness (E) of the background background. For example, the maximum value (Kmax) of the sharpness improving strength on the basis of the office illuminance environment is preferably about 1.5? Kmax? 3.0, and the minimum value (Kmin) is preferably about 0.01? Kmin? 0.5.

The sharpness intensity determiner 1230 determines the sharpness intensity of each block based on the block average gray level L supplied from the average gray level calculator 120 and the background weights supplied from the background weight determiner 1220, The sharpness improving strength (K) for each block is determined and output as shown in Equation (4) below using the minimum sharpness improving strength (Kmax, Kmin). (S52)

&Quot; (4) &quot;

In Equation (4), Lth denotes a threshold value of the average gray level of each block. The determination of the sharpness improving strength K using Equation (4) is applied only when the average gradation L of each block is smaller than the threshold value Lth. (S52) When the average gradation L of each block is equal to or higher than a certain level, the background of the background is not recognized well. Therefore, the sharpness intensity determiner 1230 sets the threshold Lth and the average gradation L When the threshold value Lth is equal to or larger than the threshold value Lth, the sharpness improving strength K of the block is determined as the minimum value which is the set value. (S48) For example, the threshold value Lth of the average gradation is suitably about 128 &amp;le; Lth &amp;le; 255.

15, the sharpness intensity determiner 1230 determines the average gradation L for each block using the quadratic function of Equation (2) if the average gradation L for each block is larger than the threshold value Lth It is found that the sharpness improving strength (K) is reduced as the number of pixels increases. If the maximum and minimum sharpness enhancement intensities (Kmax, Kmin) are varied according to the brightness of the background, the curve graph of the quadratic function shown in FIG. 15 is varied, and the sharpness enhancement intensities (K) is also variable. In Fig. 15, when the average gradation L for each block is equal to or greater than the threshold value Lth, the sharpness improving strength K for each block is determined as the minimum value Kmin.

As described above, the transparent display device and the driving method thereof according to an embodiment of the present invention adjusts the intensity of sharpness enhancement according to the brightness of the image and the brightness of the background of the backlight so that appropriate sharpness enhancement strength is applied according to the image and the viewing environment, The image quality can be improved. Therefore, when both the image and the background are conveying meaningful information, the boundary between the background and the image can be emphasized to improve the visibility of both the image and the background.

FIG. 16 is a view illustrating an image obtained by adjusting the brightness enhancement intensity according to the brightness of the image and the brightness of the background in the transparent display device according to an embodiment of the present invention, in contrast to the image of the prior art.

Referring to FIG. 16A, the prior art transparent display device has a problem that a dark area of an image is influenced by a bright rear background, resulting in a decrease in sharpness. In contrast, in an embodiment of the present invention, It can be seen that the edge strength is improved and the sharpness is improved by increasing the sharpness improving strength according to the background in the background.

Referring to FIG. 16B, in the transparent display device of the related art, since the influence of the background in the bright region of the image is small and the sharpness reduction is low, an embodiment of the present invention reduces the sharpness enhancement intensity in the bright region of the image It is possible to know that the image quality deterioration is low even in the case where the image quality is low.

Referring to FIG. 16 (c), in the prior art transparent display device, when the brightness of the background of the background is dark, the darkness of the image is low and the brightness of the darkness of the image is low. Therefore, even if the sharpness improvement strength is decreased, the image quality deterioration is low.

As described above, the transparent display device and the driving method thereof according to an embodiment of the present invention perform image processing of one of the gamma correction method and the sharpness improvement method in consideration of the brightness characteristics of the input image and the background, It is possible to improve the visibility and image quality of the image appropriately according to the image and the viewing environment by correcting the image.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims.

100, 1000: image processor 102: transmittance LUT
104: image characteristic analyzing unit 106: background characteristic analyzing unit
108: Judgment section 110: gamma correction section
150: timing controller 200: data driver
300: gate driver 400: transparent display part
500: gamma voltage generator 600: background sensor
700: Shading plate 800: Shading plate driving part
1100: Unsharp mask filter 1110: Low pass filter
1120: mask generation unit 1130: sharpness improvement mask determination unit
1140: image correction unit 1200: sharpness improvement intensity adjustment unit
1210: Average grayscale calculation unit 1220: Background weight determination unit
1230: Sharpness intensity determination unit

Claims (16)

A transmissive display area including a transmissive area and a light emitting area for displaying image data;
A light shielding plate disposed on one side of the transparent display unit and having a variable transmittance,
A background sensor disposed on a rear surface of the transparent display device for sensing a background background,
A display driver for supplying the image data and driving the transparent display unit,
A light shield plate driving unit for driving the light shield plate,
And an image processing unit for performing image processing for improving an image quality of an input image and supplying the image data to the display driver,
The image processing unit analyzes the input image to determine an image characteristic indicating whether the input image is a dark image or a bright image, and analyzes the backside background signal sensed by the background sensor to determine whether the backside background is a light background or a dark background And determines the transmittance characteristic of the light shielding plate so as to correspond to any one of the remaining image quality degradation conditions except for the image in which the image characteristic and the background characteristic are bright and the normal condition which is the dark background, And performs gamma correction on the input image when the first reference value is exceeded to output gamma-corrected image data to the display driver. The method according to claim 1,
The image processing unit
And outputting the input image to the display driver without gamma correction regardless of the transmittance when the image characteristic and the background characteristic are the normal conditions, and when the transmittance is equal to or less than the first reference value, And outputs the input image to the display driver without gamma correction. The method according to claim 1,
The image processing unit
Up table (hereinafter referred to as &quot; LUT &quot;) having a different gamma value according to the transmittance when the gamma correction is required, and selects one of the plurality of gamma correction look- And outputs the selected output data,
And selects a gamma correction LUT having a larger gamma value as the transmittance increases. The method according to claim 1,
The image processing unit
Wherein the transmittance characteristic is determined by outputting a transmittance corresponding to a driving time of the light shielding plate by using a transmittance LUT stored in an LUT form and selecting a transmittance corresponding to the drive time after the operation of the light shielding plate. The method according to claim 1,
The image processing unit
The input image is analyzed to calculate a low grayscale weighted average image level (hereinafter referred to as &quot; WAPL_Low &quot;) as a percentage in units of frames in the input image as shown in Equation 1 below,
&Quot; (1) &quot;

(n is the number of subpixels included in the frame of the input image, and Gray is a gray value of each subpixel)
If the calculated WAPL_Low is compared with the second reference value?% (30??? 50), the input image is judged to be the dark image if it is smaller than the second reference value?%, . The method according to claim 1,
The image processing unit
(WAPL_High) is calculated as a percentage (%) in units of frames in the background image by analyzing the background image sensed by the backside background signal,
&Quot; (2) &quot;

(n is the number of subpixels included in the frame of the background image, and Gray is a gray value of each subpixel)
Compares the calculated WAPL_High with the third reference value?% (50??? 70), judges the light background as being larger than the third reference value?%, And judges the dark background as the opposite. The method according to claim 1,
The image processing unit
Wherein the image quality determining unit determines the image quality degradation condition to be one of the dark image and the bright background, the dark image, the dark background, the bright image, and the bright background. Analyzing an input image and determining an image characteristic indicating whether the input image is a dark image or a bright image;
Sensing a back side background of the transparent display device and analyzing the sensed back side background signal to determine a background characteristic indicating whether the back side background is a light background or a dark background;
Determining a transmittance characteristic of the shading plate,
When the transmittance of the input image exceeds the first reference value, image quality improvement is performed on the input image when the transmittance exceeds the first reference value, Performing gamma correction for the gamma correction;
And outputting the gamma-corrected image. The method of claim 8,
Outputting the input image without gamma correction regardless of the transmittance when the image characteristic and the background characteristic are the normal conditions;
And outputting the input image without performing gamma correction on the input image regardless of the image characteristic and the background characteristic when the transmittance is equal to or less than the first reference value. The method of claim 8,
The step of performing gamma correction
Selecting one of a plurality of gamma correction LUTs having different gamma values according to the transmittance and selecting and outputting output data corresponding to the input image data using the selected gamma correction LUT,
And selects a gamma correction LUT having a larger gamma value as the transmittance increases. The method of claim 8,
The step of determining the transmittance
And selecting and outputting a corresponding transmittance according to a driving time after the operation of the shading plate by using a transmittance LUT in which the transmittance according to the driving time of the shading plate is stored in an LUT form. In a transparent display device,
A transparent display portion including a transmissive region, a light emitting region,
A background sensor disposed on a rear surface of the transparent display device for sensing a background background,
A display driver for supplying an output image to the transparent display unit,
A brightness enhancement strength for each block is determined for each block in accordance with a brightness characteristic of each block calculated on a pixel block basis and a brightness characteristic of a background of the sensed back surface by dividing an input image into a plurality of pixel blocks, And an image processor for correcting the sharpness of the input image in units of the pixel block by applying the sharpness improving strength for each block and outputting the corrected sharpness image to the display driver. The method of claim 12,
The image processing unit
A low pass filter for low pass filtering the input image to generate and output a blur image;
A mask generator for subtracting the blurred image supplied from the low-pass filter from the input image to generate and output an edge mask image,
A sharpness enhancement intensity adjuster for adjusting the sharpness enhancement intensity for each block according to the brightness characteristics of the input image and the sensed background,
A sharpness enhancement mask determination unit for generating and outputting a sharpness enhancement mask image by applying the sharpness enhancement strength for each block supplied from the sharpness enhancement strength adjuster to the edge mask image supplied from the mask generator,
And an image correcting unit for synthesizing the sharpness improving mask image supplied from the sharpness improving mask determining unit and the input image and outputting the corrected image with sharpness to the panel driving unit. Claim 13
The sharpness improving strength adjusting unit
An average gradation calculation unit for calculating an average gradation of each block of the plurality of pixel blocks with respect to the input image,
A background weight determiner for determining a maximum value and a minimum value of the sharpness enhancement intensity according to the brightness of the sensed back surface background and outputting the background weight value,
(Kmax, Kmin) of the sharpness enhancement strength supplied from the background weight determiner and a function of the following equation, using the average gradation L for each block supplied from the average gradation calculator and the maximum and minimum values And a sharpness improving strength determining section for determining the star sharpness improving strength (K)

The sharpness improving strength determining unit
Determines the sharpness improving strength K of the corresponding block when the average gray level L of each block is less than a preset threshold value Lth,
And determines a preset minimum value as the sharpness improving strength of the block when the average gray scale value of each block is equal to or greater than the threshold value. Generating a blur image by low-pass filtering an input image;
Generating an edge mask image by subtracting the blurred image from the input image;
Dividing the input image into a plurality of pixel blocks and determining brightness enhancement intensities for each block in units of the pixels in accordance with the brightness characteristics of each block calculated on a pixel block basis basis and the brightness characteristics of the sensed background,
Generating a sharpness enhancement mask image by applying the block sharpness enhancement strength to the edge mask image;
And combining the sharpness improving mask image and the input image to display an image having a corrected sharpness on a transparent display unit. 16. The method of claim 15,
The step of determining the block-by-block sharpness improving strength
Calculating an average gray level of each of the plurality of pixel blocks with respect to the input image;
Determining a maximum value and a minimum value of the sharpness enhancement intensity according to the brightness of the sensed background;
(Kmax, Kmin) of the sharpness enhancement intensity and a function of a function of the following equation (Lmax) when the average gray-scale L of each block is less than a preset threshold value Lth Determining a sharpness improvement strength (K) for each block by using the block sharpness improving strength (K)

And determining the preset minimum value as the sharpness improving strength of the corresponding block when the average gradation of each block is equal to or greater than the threshold value.

Images