KR20220127183A - Transparent display device and method for driving the same - Google Patents

Abstract

The present invention provides a transparent display device capable of improving image quality by adaptively correcting an image according to driving characteristics and rear background characteristics of the transparent display device and a driving method thereof. The transparent display device according to an embodiment improves image quality by selectively considering transmittance characteristics of a light blocking plate and considering brightness characteristics of an input image and brightness characteristics of a rear background, to correct an image by using one of a gamma correction method and a visibility improvement method.

Description

Transparent display device and its driving method

The present invention relates to a transparent display device capable of improving image quality by adaptively correcting an image according to driving characteristics of the transparent display device and characteristics of a rear background, and a driving method thereof.

With the recent development of display devices, transparent display devices using liquid crystal displays (LCDs) and organic light emitting diodes (OLEDs) have been developed.

Since the transparent display device transmits light in both front and rear directions, information can be displayed in both directions of the display device, and each user facing the display device with the display device therebetween can see beyond the transparent display device.

Since the transparent display device can be applied to various application products such as automobile glass, building glass, advertisement signboard, cooler door, screen door, and the like, the user environment is diversified.

Since a transparent display device cannot realize black in a state of high transmittance, a technology for controlling transmittance using a light blocking plate has been developed.

However, there is a problem in that a considerable amount of time is required for the light blocking plate to close after the light blocking plate operates due to the limitation of the material technology of the light blocking plate.

Accordingly, there is a problem in that the image quality of the transparent display device is deteriorated because the perceived image quality is greatly affected by the transmittance characteristics of the light blocking plate, the back background characteristic of the transparent display device, and the characteristics of the input image before the light blocking plate is closed.

For example, if the transmittance is high before the light blocking plate of the transparent display device is closed, black cannot be realized, and thus image quality deterioration such as aggregation of the low grayscale region occurs. When the rear background of the transparent display device is bright, more light is transmitted and the visibility of an image is deteriorated, and thus image quality is deteriorated. When the input image is dark, it is difficult to implement black in a transparent display device, and thus image quality is deteriorated.

In addition, when it is necessary to recognize the rear background along with image information according to the usage environment, the transparent display device may not include a light blocking plate or display an image while maintaining the light blocking panel in a transmission mode.

In this case, since the image is recognized together with the rear background, the transparent display device has a problem in that the image quality is deteriorated because the sharpness of the image is lowered according to the brightness of the image and the brightness of the rear background.

The present invention provides a transparent display device capable of improving image quality by adaptively correcting an image according to driving characteristics and rear background characteristics of the transparent display device, and a driving method thereof.

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

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

The image processing unit performs gamma correction on the input image when the image characteristics and background characteristics correspond to any one of the other image quality degradation conditions except for the normal condition of a bright image and a dark background, and the transmittance exceeds the first reference value. , and output the gamma-corrected image data to the display driver.

The image processing unit outputs the input image to the display driver without gamma correction regardless of transmittance when the image characteristics and the background characteristics are normal conditions, and when the transmittance is less than the first reference value, gamma the input image regardless of the image characteristics and the background characteristics. Output to the display driver without correction.

A method of driving a transparent display device according to an embodiment of the present invention comprises the steps of analyzing an input image and determining image characteristics indicating whether the input image is a dark image or a bright image; sensing a rear background of the transparent display; and analyzing the sensed rear background signal to determine a background characteristic indicating whether the rear background is a light background or a dark background, and determining a transmittance characteristic of a light shielding plate.

In addition, the driving method of the present invention corresponds to any one of the image quality degradation conditions other than the normal condition in which the image characteristics and the background characteristics are a bright image and a dark background, and when the transmittance exceeds the first reference value, performing gamma correction for The method further includes outputting a gamma-corrected image.

In addition, the driving method of the present invention includes outputting an input image without gamma correction regardless of transmittance when image characteristics and background characteristics are normal conditions, and when the transmittance is less than or equal to a first reference value, the relationship between image characteristics and background characteristics The method further includes outputting the input image without gamma correction.

A transparent display device according to an embodiment of the present invention includes a transparent display unit, a background sensor, a display driver, a brightness characteristic for each block calculated by dividing an input image into a plurality of pixel blocks, and a background sensor. The sharpness improvement intensity for each block is determined in units of pixel blocks according to the brightness characteristics of the sensed back background, and the sharpness improvement intensity for each block is applied to the input image to correct the sharpness of the input image in units of pixel blocks, and the sharpness is corrected image and an image processing unit for outputting to the display driving unit.

The image processing unit includes a low-pass filter, a mask generator, a sharpness improvement intensity control unit, a sharpness improvement mask determiner, and an image correction unit. The low-pass filter generates and outputs a blur image by low-pass filtering the input image. The mask generator generates and outputs an edge mask image by subtracting the blur image supplied from the low pass filter from the input image. The sharpness improvement intensity adjusting unit adjusts the sharpness improvement intensity for each block according to the brightness characteristic of each block of the input image and the brightness characteristic of the sensed back background. The sharpness improvement mask determiner applies the sharpness improvement intensity for each block supplied from the sharpness improvement intensity adjuster to the edge mask image supplied from the mask generator to generate and output the sharpness improvement mask image. The image compensator outputs the sharpness-corrected image to the panel driver by synthesizing the input image with the sharpness-enhancing mask image supplied from the sharpness-improving mask determiner.

A method of driving a transparent display device according to an embodiment of the present invention includes generating a blur image by low-pass filtering an input image, generating an edge mask image by subtracting the blur image from the input image, and Determining the intensity of sharpness improvement for each block in units of pixel blocks according to the brightness characteristics of each block calculated in units of pixel blocks by dividing it into a plurality of pixel blocks and the brightness characteristics of the sensed back background; The method includes generating a sharpness improvement mask image by applying a sharpness improvement intensity, and displaying the sharpness-corrected image on a transparent display by synthesizing the sharpness improvement mask image and an input image.

Determining the sharpness improvement intensity for each block includes calculating the average grayscale for each block for the input image, determining the maximum and minimum values of the sharpness enhancement intensity according to the sensed brightness of the back background, and the average grayscale for each block When (L), the maximum and minimum values (Kmax, Kmin) of the sharpness improvement intensity, and the average grayscale (L) for each block are less than the preset threshold value (Lth), the sharpness improvement for each block is improved using the function of the following equation Determining the intensity K; and determining a preset minimum value as the sharpness improvement intensity of the corresponding block when the average gray scale for each block is equal to or greater than a threshold value.

A transparent display device and a driving method thereof according to an exemplary embodiment of the present invention analyze all of the transmittance characteristics of the light shielding plate, the luminance characteristics of the input image and the luminance characteristics of the background image. When the background corresponds to the image quality degradation condition, the image quality may be improved by correcting the image data by adjusting the gamma.

A transparent display device and a driving method thereof according to an embodiment of the present invention improve sharpness and image quality by applying an appropriate sharpness improvement intensity according to an image and viewing environment by adjusting the sharpness improvement intensity according to the brightness of an image and the brightness of a rear background. can do it

A transparent display device and a driving method thereof according to an embodiment of the present invention control the sharpness improvement intensity according to the brightness of the image and the brightness of the rear background, so that when meaningful information is transmitted on both the image and the rear background, the boundary between the background and the image It is possible to improve the visibility of both the image and the rear background by emphasizing it.

1 is a graph illustrating transmittance characteristics according to the lapse of driving time of a light blocking plate in a transparent display device according to a prior art of the present invention.
2 is a photograph showing a comparison of image display results according to transmittance of a light blocking plate in a transparent display device according to the prior art of the present invention.
3 is a photograph showing a comparison of image display results according to image characteristics and background characteristics in the transparent display device according to the prior art of the present invention.
4 is a block diagram schematically illustrating 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 sub-pixel according to an embodiment of the present invention.
6 is a block diagram illustrating the configuration of an image processing unit of a transparent display device according to an embodiment of the present invention.
7 is a flowchart illustrating an image processing method of a transparent display device in stages according to an embodiment of the present invention.
8 is a graph illustrating a distribution rate for each gray level of an input image according to an embodiment of the present invention.
9 is a graph illustrating a distribution rate for each gray level of a background image according to an embodiment of the present invention.
10 is a graph showing 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 without gamma correction according to an embodiment of the present invention.
12 is a block diagram schematically illustrating a configuration of a transparent display device according to an exemplary embodiment.
13 is a block diagram illustrating the configuration of an image processing unit according to an embodiment of the present invention.
14 is a flowchart illustrating an image processing method step-by-step according to an embodiment of the present invention.
15 is a graph illustrating a sharpness improvement intensity function according to a block average grayscale according to an embodiment of the present invention.
16 is a diagram illustrating an image in the case where the intensity of sharpness improvement is adjusted and applied according to the brightness of the image and the brightness of the rear background in the transparent display device according to an embodiment of the present invention in comparison with an image of the prior art.

Prior to the description of the embodiment of the present invention, the image quality deterioration phenomenon of the transparent display device according to the prior art of the present invention will be first described as an example.

1 is a graph showing the transmittance characteristics of the light blocking plate according to the lapse of driving time in a transparent display device according to the prior art of the present invention, and FIG. 2 is an image display result according to the transmittance of the light blocking plate in the transparent display device according to the prior art of the present invention. 3 is a photograph showing comparison of image display results according to image characteristics and background characteristics when the light-shielding plate transmittance 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 it takes about 3 minutes for the light blocking plate of the transparent display device according to the prior art to close with a transmittance of 10% or less after starting to be driven.

For this reason, as shown in Fig. 2(a), if the transmittance of the light-shielding plate is 80%, it is impossible to implement black of the light-shielding plate, so that the rear background is visible due to the transparent property and more light is transmitted from the rear side, thereby reducing the visibility of the display image Able to know. As shown in FIG. 2(b) , the visibility of the displayed image is improved by implementing the black of the light blocking plate only when the light blocking plate is closed with a transmittance of 10% or less.

In addition, when the light-shielding plate transmittance is 70%, for the same dark image, as shown in FIGS. 3(a) and (b), the image quality is lowered on a bright background (b) than on a dark background (a), and in FIG. 3(c) ) and (d), when the same bright background is used, both the dark image (a) and the bright image (b) show the back background and it can be seen that the visibility of the display image is deteriorated.

Also, when the light blocking plate is not provided or the light blocking plate maintains the transmission mode due to the need to recognize the rear background, the transparent display device according to the prior art determines the degree of recognition of the rear background according to the brightness characteristics of the image and the brightness characteristics of the rear background Therefore, the sharpness of the image may deteriorate depending on the degree of recognition of the background background.

In order to solve the problems of the prior art, the present invention selectively considers the transmittance characteristic of the light shielding plate, and corrects the image in consideration of the brightness characteristic of the input image and the brightness characteristic of the rear background (that is, the viewing environment) to view and view the image. A transparent display device capable of improving image quality by appropriately improving visibility according to an environment and a driving method thereof 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.

4 is a block diagram schematically illustrating 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 sub-pixel according to an embodiment of the present invention.

Referring to FIG. 4 , a transparent display device according to an embodiment of the present invention includes an image processing unit 100 , a timing controller 150 , a data driving unit 200 and a gate driving unit 300 , a transparent display unit 400 , and a gamma voltage. It includes a generator 500 , a background sensor 600 , a light blocking plate 700 , and a light blocking plate driving unit 800 . Here, the timing controller 150 , the data driver 200 , and the gate driver 300 may be expressed as a display driver that drives 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 is at least three or more sub-pixels (W/R) capable of expressing white by color mixing among white (W), red (R), green (G), and blue (B) sub-pixels (SP). /G, B/W/R, G/B/W, R/G/B, or W/R/G/B).

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

When the transparent display unit 400 is an OLED panel, as shown in FIG. 5 , each sub-pixel SP has a light emitting area EA where an OLED element is located and a transmission area TA through which light from the front/rear side is transmitted. ) is included. The light emitting area EA of the OLED device may or may not overlap the pixel circuit.

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

The OLED device includes an anode connected to the driving TFT (DT), a cathode connected to a low potential voltage (EVSS), and a light emitting layer between the anode and the cathode, and emits 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 the 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 includes a data voltage supplied to the gate node through the first switching TFT ST1 and a source node through the second switching TFT ST2. It charges the difference voltage of the reference voltage supplied to , and supplies it as a driving voltage of the driving TFT (DT).

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

4 , the light blocking plate 700 is disposed on the rear side of the transparent display unit 400, and when the transparent display unit 400 displays an image, the light blocking plate driver 800 may drive the light blocking mode or the transmissive mode. . The light blocking plate 700 may implement a light blocking mode by displaying black when an electric field is applied by the light blocking plate driver 800 , and may implement a transmission mode when no electric field is applied. When the light blocking plate 700 is driven in the light blocking mode by the light blocking plate driver 800 , the light blocking plate 700 implements black to block light transmission, thereby improving the visibility of the image displayed on the transparent display unit 400 .

For example, as the light blocking plate 700, an electrochromic device known as an electrochromic filter, an electrowetting device, etc. may be used, or light transmission may be switched using liquid crystal. It may be a device.

Meanwhile, the light blocking plate 700 may be disposed on at least one side of the front and rear surfaces of the transparent display unit 400 .

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

The image processing unit 100 analyzes the input image supplied from the outside to determine the image characteristics, and analyzes the back background information (brightness or image) sensed by the background sensor 600 to determine the characteristics of the back background. The image processing unit 100 may determine the transmittance of the light blocking plate 700 according to the transmission mode and the light blocking mode of the light blocking plate 700 by the light blocking plate driver 800 . In the image processing unit 100, when the light blocking plate 700 is driven in the light blocking mode, the transmittance of the light blocking plate 700 according to the driving time is measured in advance and stored in the form of a look-up table (LUT). can When the light blocking plate 700 is driven in the light blocking mode by the light blocking plate driver 800 , the image processing unit 100 may determine the transmittance of the light blocking plate 700 according to the driving time of the light blocking mode.

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

As a result of determining the characteristics of the input image and the back background characteristics, the image processing unit 100 determines the quality degradation condition when the input image is dark and the background is bright, the input image is dark and the background is dark, or the input image is bright and the background is bright, , when the transmittance of the light blocking plate 700 exceeds a first reference value (eg, 10%), gamma correction is performed on the input image according to transmittance to output a gamma-corrected image to compensate for image quality.

On the other hand, the image processing unit 100 corresponds to a normal condition in which the input image is bright and the background is dark and the transmittance exceeds the first reference value (for example, 10%), or the transmittance is high regardless of the characteristics of the input image and the rear background. When it is less than the first reference value, the input image is output without gamma correction.

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

The image processing unit 100 may refer to an image processing module of software either implemented in hardware in the timing controller 100 or 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 , respectively. do. The timing control signals include a dot clock, a data enable signal, a vertical sync signal, and a horizontal sync signal, and since the vertical sync signal and the horizontal sync signal can be generated by counting the data enable signal, they can be omitted. 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 a gate start pulse, a gate shift clock, and the like for controlling driving of the gate driver 300 .

The timing controller 150 calculates a deviation in driving characteristics (threshold voltage, mobility, OLED threshold voltage, etc. of the driving TFT) for each sub-pixel of the transparent display unit 400 with respect to the image data supplied from the image processing unit 100 to the data driver ( 200 ) may further perform necessary image processing, such as external compensation or deterioration compensation for sensing and compensation, and then output to the data driver 200 .

The data driver 200 receives a data control signal and image data from the timing controller 150 . The data driver 200 is driven according to the data control signal, subdivides the reference gamma voltage set supplied from the gamma voltage generator 500 into gray voltages corresponding to gray values of data, and then divides the subdivided gray voltages. The digital image data is converted into an analog data signal by using the controller, and the analog data signal is respectively supplied to the data lines of the transparent display unit 400 .

The data driving unit 200 includes a plurality of data driving ICs that divide and drive the data lines of the transparent display unit 400 , and each data driving IC includes a Tape Carrier Package (TCP), Chip On Film (COF), and Flexible Print (FPC). Circuit), etc. may be mounted on the transparent display unit 400 and attached to the transparent display unit 400 by a Tape Automatic Bonding (TAB) method, or may be mounted on the transparent display unit 400 by a COG (Chip On Glass) method.

The gate driver 300 drives each of 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 a scan pulse of a gate-on voltage in a corresponding scan period to each gate line in response to a gate control signal, and supplies a gate-off voltage in the remaining period. The gate driver 300 receives the gate control signal GCS from the timing controller 150 , receives the gate control signal GCS from the timing controller 150 via the data driver 200 , or the timing controller 150 . ) may be supplied via a power circuit (not shown).

The gate driver 300 is composed of at least one gate IC and is mounted on a circuit film such as TCP, COF, FPC, etc. to be attached to the transparent display unit 400 in a TAB method, or to be mounted on the transparent display unit 400 in a COG method. can In contrast, the gate driver 300 is formed on the thin film transistor substrate together with the thin film transistor array constituting the pixel array of the transparent display unit 400 , and thus is a GIP (Gate In Panel) type embedded in the non-display area of the transparent display unit 400 . can be provided as

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

Referring to FIG. 6 , the image processing unit 100 includes a transmittance LUT 102 , an image characteristic analysis unit 104 , a background characteristic analysis unit 106 , a determination unit 108 , and a gamma correction unit 110 . The image processing unit 100 may further include other known image processing blocks.

The image characteristic analyzer 104 receives an input image from the outside, analyzes the input image, calculates a degree of inclusion of a dark image, that is, a dark degree, and a first indicating whether the input image is a dark image or a bright image according to the darkness level. A determination signal is output to the determination unit 108 . (S12)

For example, the image characteristic analyzer 104 uses Equation 1 below to determine the distribution ratio of the low gray values in the input image of each frame, that is, the weighted average picture level indicating the degree of inclusion of the dark image. Level; hereafter WAPL_Low) is calculated as a percentage (%).

<Equation 1>

n is the number of sub-pixels included in a unit frame of the input image, and Gray means a gray level value of each sub-pixel.

Then, the image characteristic analysis unit 104 determines the input image as a dark image when the WAPL_Low calculated from Equation 1 is less than the second reference value α%, and on the contrary, when the WAPL_Low is greater than the second reference value α%, the input image is It is determined as a bright image, and a first determination signal indicating whether the input image is a dark image or a bright image is output to the determination unit 108 according to the determination result. (S12) Here, the second reference value α% is preset by the designer, and there is a difference depending on the characteristics of the transparent display device and the light blocking plate 700 , but 30≤α≤50 is suitable as a reference value for determining whether the image is dark.

When WAPL_Low calculated from Equation 1 is smaller than the second reference value α% (30≤α≤50), as shown in the graph showing the distribution rate for each gray level of the input image shown in FIG. 8, the distribution rate of the low gray level region is relatively large. means the case.

The background characteristic analyzer 106 receives the background image sensed by the background sensor 600, analyzes the background image, calculates a brightness level, and generates a second determination signal indicating whether the background is bright or dark according to the brightness level. output to the gamma correction unit 108 . (S14)

For example, when the sensed rear background information is image information, the background characteristic analyzer 106 uses Equation 2 below to determine the degree to which the number of pixels of high grayscale values in the background image of each frame occupies, that is, the brightness of the background image. The high grayscale weighted average image level (hereinafter WAPL_High) indicating the degree is calculated as a percentage (%).

<Equation 2>

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

In addition, the background characteristic analyzer 106 determines that the background image is bright when WAPL_High calculated from Equation 2 is greater than the third reference value β%, and on the contrary, when WAPL_High is less than or equal to the second reference value β%, the background image is dark. and outputs a second determination signal indicating whether the background image is bright or dark to the determination unit 108 according to the determination result. (S14) Here, the second reference value β% is preset by the designer, and although there is a difference depending on the characteristics of the transparent display device and the light blocking plate 700 , 50≤β≤70 is suitable as a reference value for determining a bright background.

When WAPL_High calculated from Equation 2 is greater than the third reference value β% (50≤β≤70), as shown in the graph showing the distribution rate for each gray level of the background image shown in FIG. 9, the distribution rate of the high gray level region is relatively large. means the case.

In the transmittance LUT 102 , the transmittance of the light blocking plate 700 according to the lapse of driving time is measured and stored in advance. The transmittance LUT 102 receives the driving time of the light blocking plate 700 from an external system (not shown), selects the transmittance according to the driving time of the light blocking plate 700 and supplies it to the determination unit 108 (S16). The transmittance LUT 102 may classify and store a plurality of transmittance sections according to the driving time. For example, the transmittance (t) section may 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 about the transmittance (t) section corresponding to the driving time to the determination unit 108 . (S18)

The determination unit 108 includes a first determination signal indicating whether the input image supplied from the image characteristic analysis unit 104 is dark or bright, and a second determination signal indicating whether the background supplied from the background characteristic analysis unit 106 is bright or dark. It determines whether to correct gamma by logically combining the signals. The determination unit 108 outputs a signal for which gamma correction is determined and transmittance information supplied from the transmittance LUT 102 to the gamma correction unit 110 . The determination unit 108 may 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 driver 800 .

The determination unit 108 determines the first determination signal from the image characteristic analysis unit 104 and the second determination signal from the background characteristic analysis unit 106 to determine the first determination signal among the four conditions shown in Table 1 below, in which image quality degradation is predicted. It corresponds to the image quality degradation condition of any one of the first to third conditions (dark image and light background, dark image and dark background, bright image and light background) (S18, YES), and transmittance information supplied from the transmittance LUT 102 When ? exceeds the first reference value (for example, 10%) ( S20 , YES), a gamma correction necessary signal is output to the gamma correction unit 110 . The determination unit 108 outputs the transmittance information together with the gamma correction necessary 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 are evaluated under the fourth condition (bright image and bright image) shown in Table 1 above. dark background), a gamma correction unnecessary signal is output to the gamma correction unit 110 regardless of transmittance information (S18, NO)

On the other hand, when the transmittance information supplied from the transmittance LUT 102 is equal to or less than the first reference value (for example, 10%), the determination unit 108 transmits a gamma correction unnecessary signal regardless of the above-described image characteristics and background characteristics. output to (110). (S20, NO)

When a gamma correction necessary signal is supplied from the determination unit 108 , the gamma correction unit 110 receives the input image supplied through the image characteristic analysis unit 104 according to the transmittance information supplied through the determination unit 108 . gamma correction is performed (S22), and a gamma-corrected image is output (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 through the image characteristic analyzer 104 without gamma correction (S24).

In the gamma correction unit 110, a plurality of gamma correction LUTs having different gamma values (a value defining a gamma curve representing an output gradation value with respect to an input gradation value) are preset and stored as shown in FIG. 10 according to the transmittance information. have.

For example, the gamma correction unit 110 selects different gamma values (GMAs) according to transmittance (t) information as shown in Table 2 below, and uses the LUT corresponding to the selected gamma values for each data (input grayscale) of the input image. By selecting and outputting output data (output grayscale value) corresponding to the value), differential gamma correction is performed on the input image according to transmittance, and the gamma-corrected image is output.

<Table 2>

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

As shown in Table 2, as the transmittance increases, the gamma value increases. As shown in FIG. 9 , as the gamma value increases, the output grayscale value with respect to the input grayscale value decreases.

11 is a photograph showing an image before and after gamma correction and an image without gamma correction according to an embodiment of the present invention.

When the transmittance of the light shielding plate is 70% and the input image is dark and the background is bright, as shown in FIG. , it can be seen that when the present invention is applied and an image is displayed using 3.4 gamma as shown in FIG. 11( b ), visibility is improved and image quality is improved.

On the other hand, it can be seen that gamma correction is not required when the background is dark and the input image is bright as shown in FIG. 11( c ).

As described above, the transparent display device and the driving method thereof according to an embodiment of the present invention analyze all of the transmittance characteristics of the light blocking plate, the luminance characteristics of the input image, and the luminance characteristics of the background image, so that the transmittance is greater than the reference value and the input image When the background and the background fall under the condition for image quality degradation, the image quality can be improved by correcting the image data by adjusting the gamma.

12 is a block diagram schematically illustrating a configuration of a transparent display device according to an exemplary embodiment.

In the transparent display device illustrated in FIG. 12 , in contrast to the embodiment illustrated in FIG. 4 , the image processing unit 1000 decreases the sharpness of the image affected by the brightness of the image and the brightness of the rear background (viewing environment) There is a difference in that image processing is performed to improve image quality by adaptively improving image sharpness according to recognition level). In FIG. 12 , the remaining components except for the image processing unit 1000 are the same as those of FIG. 4 , so a description of the same components as in FIG. 4 will be omitted.

The transparent display device shown in FIG. 12 requires recognition of the rear background together with image display. The transparent display device shown in FIG. 12 omits the light blocking plate 700 and the light blocking plate driver 800 shown in FIG. can Meanwhile, when the light blocking plate 700 and the light blocking plate driver 800 shown in FIG. 4 are provided, the light blocking plate 700 may maintain a transmission mode by the light blocking plate driver 800 .

The image processing unit 1000 may use a sharpness improvement method of improving sharpness in proportion to edge intensity of an image by applying unsharp masking to improve image sharpness. In addition, the image processing unit 1000 may be configured to prevent at least one of sharpness and image quality of an image from being deteriorated by varying the degree of recognition of the rear background according to the brightness of the image and the brightness of the rear background. Adjusts the sharpness improvement intensity adaptively according to As a result, the image processing unit 1000 adjusts the sharpness improvement intensity in consideration of the edge intensity characteristics of the image, the brightness characteristics of the image, and the brightness characteristics of the back background, thereby improving the sharpness appropriately for the image and the viewing environment. can be improved

Specifically, in a transparent display device, in a bright area of an image, the back background is not well recognized due to a bright image, whereas in a dark area of the image, the back background is recognized together with the image and the edge expression power of the image is lowered, so that the brightness of the image is reduced. As it decreases, the sharpness of the image may decrease. In order to prevent the sharpness of the image from being deteriorated according to the brightness of the image, the image processing unit 1000 increases the intensity of sharpness improvement because the dark area of the image has a high degree of recognition of the rear background and thus the sharpness of the image is deteriorated. In the bright area of , the degree of sharpness degradation is low due to the low degree of recognition of the background background, so the intensity of sharpness improvement is reduced. To this end, the image processing unit 100 divides the image frame into a plurality of pixel blocks, calculates an average gray level for each pixel block, and adjusts the sharpness improvement intensity for each block according to the average gray level for each block (average brightness for each block).

In addition, in order to prevent the sharpness of the image from being reduced by increasing the background visibility as the brightness of the rear background increases, the image processing unit 100 adjusts the sharpness improvement intensity according to the brightness of the rear background. In the case of a dark rear background, the image processing unit 100 reduces the intensity of sharpness improvement because the degree of sharpness degradation is low because the degree of perception of the rear background is low in the case of a dark rear background, and in the case of a bright rear background, the degree of sharpness deterioration is high because the degree of reduction of sharpness is high because the degree of recognition of the rear background is high. increase the strength. To this end, the image processing unit 100 senses the brightness of the rear background and varies a function for determining the sharpness improvement intensity according to the average gray level for each block of the image by applying a background weight according to the brightness of the rear background to change the brightness of the rear background. Adjust the sharpness improvement intensity accordingly. A detailed description thereof will be given later.

13 is a block diagram illustrating a configuration of an image processing unit 1000 of a transparent display device according to an embodiment of the present invention, and FIG. 14 is a step-by-step diagram illustrating an image processing method of a transparent display device according to an embodiment of the present invention. 15 is a flowchart illustrating a function for determining the sharpness improvement intensity according to the average grayscale for each block of an image according to an embodiment of the present invention. Hereinafter, it will be described with reference to FIGS. 13 to 15 .

The image processing unit 1000 shown in FIG. 13 includes a sharpness improvement intensity control unit 1200 that adjusts the sharpness improvement intensity K according to image brightness and the brightness of the rear background, and an input image FD through unsharp masking processing. The unsharp mask filter 1100 improves the sharpness of the image in proportion to the edge intensity and the sharpness improvement intensity K of , and outputs an image FD′ with improved sharpness.

The unsharp mask filter 1100 includes a low pass filter 1110 , a mask generator 1120 , a sharpness improvement mask determiner 1130 , and an image corrector 1140 .

The low-pass filter 1110 low-pass-filters the input image FD in units of frames, thereby generating a blurred image having a reduced luminance difference between pixels and outputting the blurred image.

The mask generator 1120 generates an edge mask image MD representing an edge component of the input image FD by subtracting the blur image supplied from the low-pass filter 1110 from the input image FD, and generates the edge mask image. (MD) is output. (S42)

The sharpness improvement mask determiner 1130 adjusts the sharpness improvement intensity K in the edge mask image MD supplied from the mask generator 1120 according to the image brightness and the back background brightness by the sharpness improvement intensity adjustment part 1200 . ) to determine the sharpness enhancement mask image MD' and output the sharpness enhancement mask image MD'. (S54) The sharpness improvement mask determiner 1130 multiplies the edge mask image MD by the sharpness improvement intensity K so that the intensity of the edge component in the edge mask image MD is increased by the sharpness improvement intensity K. A sharpness improvement mask image MD' is generated. The sharpness improvement intensity control unit 1200 outputs the sharpness improvement intensity K for each block adjusted according to the average grayscale for each pixel block and the brightness of the rear background. Accordingly, the sharpness enhancement mask determiner 1130 generates the sharpness enhancement mask image MD′ by applying the sharpness enhancement intensity K for each block of the edge mask image MD in units of pixel blocks.

The image compensator 1140 generates an output image FD' with improved sharpness by synthesizing the input image FD and the sharpness enhancement mask image MD' supplied from the sharpness enhancement mask determiner 1300, The output image FD' is output. (S56)

The sharpness improvement intensity control unit 1200 uses the average gray level L of each block of the plurality of pixel blocks obtained by dividing the input image FD and the weights Kmax and Kmin adjusted according to the brightness of the rear background, The sharpness improvement intensity (K) for each block is determined, and the sharpness improvement intensity (K) for each block is output. (S44, S46, S48, S50, S52) To this end, the sharpness improvement intensity adjusting unit 1200 includes an average grayscale calculating unit 1210 , a background weight determining unit 1220 , and a sharpness intensity determining unit 1230 .

The average grayscale calculator 120 divides the input image FD into a plurality of pixel blocks, calculates the average grayscale L for each block, and outputs the average grayscale L for each block. (S44) The size (n*n, n is the number of pixels) of each pixel block for calculating the average grayscale L may be set variously, for example, 3≤ About n≤10 is suitable.

The background weight determiner 1220 determines weights Wmax and Wmin according to the brightness information E of the rear background sensed from the background sensor 600 ( FIG. 12 ), and calculates the weights Wmax and Wmin by the following equation 3, the maximum and minimum sharpness enhancement intensity (K0max, K0min) of the preset darkroom environment is applied respectively to determine the maximum and minimum sharpness enhancement intensity (Kmax, Kmin) according to the brightness of the rear background, and the maximum and minimum sharpness enhancement intensity (Kmax, Kmin) is output as the background weight. (S50)

<Equation 3>

Kmax = K0max * Wmax

Kmin = K0min * Wmin

In other words, the background weight determiner 1220 varies the maximum and minimum sharpness enhancement strengths Kmax and Kmin according to the brightness E of the rear background. For example, a maximum value (Kmax) of the sharpness improvement intensity of about 1.5≤Kmax≤3.0 is suitable based on an office illuminance environment, and a minimum value (Kmin) of about 0.01≤Kmin≤0.5 is suitable.

The sharpness intensity determiner 1230 determines the average gray level L for each block supplied from the average gray level calculation unit 120 and the background weight supplied from the background weight determiner 1220, that is, the maximum and Using the minimum sharpness improvement intensity (Kmax, Kmin), the sharpness improvement intensity (K) for each block is determined and output as shown in Equation 4 below. (S52)

<Equation 4>

In Equation 4, Lth denotes a threshold value of the average grayscale for each block. The determination of the sharpness improvement intensity (K) using Equation (4) is applied only when the average gray level (L) for each block is smaller than the threshold value (Lth). (S52) When the average gradation L for each block is above a certain level, the background background is not well recognized, so the sharpness intensity determiner 1230 sets a threshold Lth, and the average gradation L for each block is When it is equal to or greater than the threshold value Lth, the sharpness improvement intensity K of the block is determined as a set minimum value. (S48) For example, the threshold Lth of the average gray level is suitably about 128 ≤ Lth ≤ 255.

Referring to FIG. 15 , when the average grayscale L for each block is greater than the threshold value Lth, the sharpness intensity determiner 1230 determines the average grayscale L for each block using the quadratic function of Equation 2 above. It can be seen that the sharpness improvement intensity (K) decreases as it increases. When the maximum and minimum sharpness improvement intensity (Kmax, Kmin) is varied according to the brightness of the back background, the curve graph of the quadratic function shown in FIG. 15 is changed and the sharpness improvement intensity for each block corresponding to the average gray level (L) for each block (K) is also variable. In FIG. 15 , when the average gray level L for each block is equal to or greater than the threshold value Lth, the sharpness improvement intensity K for each block is determined as the minimum value Kmin.

As described above, the transparent display device and the method for driving the same according to an embodiment of the present invention adjust the sharpness improvement intensity according to the brightness of the image and the brightness of the rear background, thereby applying an appropriate sharpness improvement intensity according to the image and the viewing environment to improve sharpness and The picture quality can be improved. Accordingly, when both the image and the background background transmit meaningful information, the visibility of both the image and the background background may be improved by emphasizing the boundary between the background and the image.

16 is a diagram illustrating an image in the case where the intensity of sharpness improvement is adjusted and applied according to the brightness of the image and the brightness of the rear background in the transparent display device according to an embodiment of the present invention in comparison with an image of the prior art.

Referring to FIG. 16( a ) , the transparent display device of the prior art has a problem in that a dark area of an image is affected by a bright rear background and the sharpness is deteriorated, whereas an embodiment of the present invention provides image brightness and a bright image in a dark area. It can be seen that the sharpness is improved because the edge strength is improved by increasing the sharpness improvement intensity according to the back background.

Referring to FIG. 16(b) , in the transparent display device of the prior art, since the effect of the rear background is small in the bright area of the image and thus the sharpness deterioration is low, an embodiment of the present invention reduces the intensity of sharpness improvement in the bright area of the image It can be seen that the image quality deterioration is low even if the image quality is reduced, and image quality deterioration such as over-sharpening due to the increase in sharpness improvement intensity in bright images can be prevented.

Referring to FIG. 16(c) , in the transparent display device of the prior art, when the brightness of the back background is low, the sharpness degradation in the dark area of the image is low, so an embodiment of the present invention provides the image brightness in the dark area and the dark back background. Accordingly, it can be seen that even if the sharpness improvement intensity is reduced, the image quality deterioration is low.

As described above, in the transparent display device and the driving method according to an embodiment of the present invention, one of the gamma correction method and the sharpness improvement method is performed in consideration of the brightness characteristics of the input image and the brightness characteristics of the rear background. By correcting the image, visibility and image quality of the image may be appropriately improved according to the image and viewing environment.

Those skilled in the art from the above description will be able to see that various changes and modifications can be made without departing from the technical spirit of the present invention. Accordingly, the technical scope of the present invention should not be limited to the content described in the detailed description of the specification, but should be defined by the claims.

100, 1000: image processing unit 102: transmittance LUT
104: image characteristic analysis unit 106: background characteristic analysis unit
108: determination unit 110: gamma correction unit
150: timing controller 200: data driver
300: gate driving unit 400: transparent display unit
500: gamma voltage generator 600: background sensor
700: light-shielding plate 800: light-shielding plate driving unit
1100: unsharp mask filter 1110: low pass filter
1120: mask generating unit 1130: sharpness improvement mask determining unit
1140: image correction unit 1200: sharpness improvement intensity control unit
1210: average gray scale calculator 1220: background weight determiner
1230: sharpness intensity determining unit

Claims (7)

In the transparent display device,
A transparent display unit including a transmissive region and a light emitting region;
a background sensor disposed on a rear surface of the transparent display device to sense a rear background;
a display driving unit for supplying an output image to the transparent display unit;
The input image is divided into a plurality of pixel blocks and the intensity of sharpness improvement is determined for each block in units of the pixel blocks according to the brightness characteristics of each block calculated in units of pixel blocks and the brightness characteristics of the sensed back background, and in the input image An edge mask image is generated by extracting an edge component, a sharpness improvement intensity is applied to the edge mask image for each block to generate a sharpness improvement mask image, and the sharpness improvement mask and the input image are synthesized in the pixel block unit. and an image processing unit for correcting the sharpness of the input image and outputting the sharpness-corrected image to the display driver. The method according to claim 1,
The image processing unit
a low-pass filter for generating and outputting a blur image by low-pass filtering the input image;
a mask generator for generating and outputting an edge mask image by subtracting the blur image supplied from the low-pass filter from the input image;
a sharpness improvement intensity adjusting unit for adjusting the sharpness improvement intensity for each block according to the brightness characteristic of each block of the input image and the brightness characteristic of the sensed back background;
a sharpness improvement mask determiner for generating and outputting a sharpness improvement mask image by applying the sharpness improvement intensity for each block supplied from the sharpness improvement intensity adjustment part to the edge mask image supplied from the mask generator;
and an image compensator for synthesizing the input image with the sharpness improvement mask image supplied from the sharpness improvement mask determiner to output the sharpness-corrected image to the display driver. 3. The method of claim 2
The sharpness improvement intensity control unit
an average grayscale calculation unit for calculating and outputting an average grayscale for each block of the plurality of pixel blocks with respect to the input image;
a background weight determining unit that determines the maximum and minimum values of sharpness improvement intensity according to the sensed brightness of the back background and outputs them as background weights;
The block using the average gray level (L) for each block supplied from the average gray level calculation unit, the maximum and minimum values (Kmax, Kmin) of the sharpness improvement intensity supplied from the background weight determination unit, and the function of the following equation and a sharpness improvement intensity determining unit for determining the sharpness improvement intensity (K) of each star;

The sharpness improvement intensity determining unit
When the average gray level (L) for each block is less than a preset threshold value (Lth), the intensity of sharpness improvement (K) of the corresponding block is determined by the above equation,
A transparent display device for determining a preset minimum value as a sharpness improvement intensity of a corresponding block when the average grayscale for each block is equal to or greater than the threshold value. The method according to claim 1,
The image processing unit,
A transparent display device for increasing the sharpness improvement intensity as the brightness of each block decreases, and decreasing the sharpness improvement intensity as the brightness for each block increases. The method according to claim 1,
The image processing unit,
A transparent display device for decreasing the sharpness improvement intensity as the brightness of the back background decreases, and increasing the sharpness improvement intensity as the brightness of the back background increases. generating a blur image by low-pass filtering the input image;
generating an edge mask image by subtracting the blur image from the input image;
dividing the input image into a plurality of pixel blocks and determining the intensity of sharpness improvement for each block in units of the pixel blocks according to the brightness characteristics of each block calculated in units of pixel blocks and the brightness characteristics of the sensed back background;
generating a sharpness improvement mask image by applying the sharpness improvement intensity for each block to the edge mask image;
and displaying the image whose sharpness is corrected by synthesizing the sharpness improvement mask image and the input image on a transparent display unit. 7. The method of claim 6,
The step of determining the sharpness improvement intensity for each block is
calculating an average grayscale for each block of the plurality of pixel blocks with respect to the input image;
determining a maximum value and a minimum value of sharpness improvement intensity according to the brightness of the sensed back background;
When the average gradation L for each block is less than a preset threshold value Lth, the average gradation L for each block, the maximum and minimum values (Kmax, Kmin) of the sharpness improvement intensity, and a function of the following equation determining the sharpness improvement intensity (K) for each block using

and determining a preset minimum value as a sharpness improvement intensity of the corresponding block when the average grayscale for each block is equal to or greater than the threshold value.

Images