KR20160083247A - Transparent display apparatus and a method for controling the same - Google Patents

Abstract

According to an embodiment of the present invention, provided is a transparent display device. The transparent display device comprises: a transparent displaying unit; a light shielding unit; and a control unit. The transparent displaying unit has a transmission area to transmit at least part of introduced external light, and a light emitting area for displaying an image. The light shielding unit overlaps the transparent displaying unit, and the light shielding unit is configured to reduce the transmissivity for the external light, when a voltage is applied. The control unit is configured to control the transmissivity of the light shielding unit, based on the gray scale of an image. Accordingly, the light shielding unit is selectively driven depending on the gray scale of an image, thereby reducing power consumption of the light shielding unit and improving the durability of the same.

Description

TECHNICAL FIELD [0001] The present invention relates to a transparent display device and a control method thereof,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent display device and a control method thereof, and more particularly to a transparent display device with improved power consumption and durability and a control method thereof.

The organic light emitting diode (OLED) is a self-emissive type display device, and unlike a liquid crystal display (LCD), a separate light source is not required, so that it can be manufactured in a light and thin shape. Further, the organic light emitting display device is advantageous not only in power consumption in accordance with low voltage driving but also in response speed, viewing angle, and contrast ratio, and is being studied as a next generation display.

There is an attempt to manufacture such an organic light emitting display device as a transparent display device. The pixel region of the transparent display device is divided into a light emitting region that is an area where an organic light emitting element emits light and displays an image and a transmissive region that is an area that transmits external light, and the transmissivity of the transparent display device is secured through the transmissive region.

[Related Technical Literature]

1. Transparent display device (Korean Patent Application No. 2011-0029664)

There is an attempt to make a stationary display device transparent among display devices. The fixed display device refers to a display device used in a generally fixed position such as, for example, a transparent television, a transparent monitor, or the like. When a fixed display device is implemented as a transparent display device, there is no sense of heterogeneity between the background behind the fixed display device and the background visible directly without passing through the fixed display device when the display device is off, Feeling increases.

On the other hand, regarding the visibility of the display image displayed on the transparent display device, the background of the rear surface of the transparent display device is recognized as interference or noise to the display image. That is, in view of the visibility of the display image, the visibility of the displayed image is improved as the amount of light incident on the back surface is smaller. Thus, when the transparent display device is turned on, the transparent display device may be provided with a light shielding portion in order to shield external light. The light shielding portion is configured to transmit external light when the transparent display device is in an off state and absorb or scatter external light when the transparent display device is in an on state.

By changing the arrangement of the polymer dispersed liquid crystal, the light shielding portion can scatter or transmit light incident from the outside. The light shielding portion may be configured to cut off light by applying power, and to transmit light when power is not applied. Alternatively, the shielding portion may be configured to transmit light by applying power, and to block light when power is not applied.

When the power is applied, the light shielding unit that transmits light is supplied with electric power in order to operate in a transparent mode when the transparent display device does not consume power when displaying an image but when it is not displayed. Accordingly, the power consumption in the standby state in which the transparent display device does not operate is high, and the durability of the light shielding portion can be low for a long time during the standby state.

When the power is applied, the shielding part shielding the light has almost no power consumption in a standby state in which the transparent display device does not operate, but the driving voltage may be higher than the shielding part transmitting the light when power is applied. Further, when the transparent display device for a long time is operated, the durability of the light-shielding portion can be lowered.

The inventors of the present invention have found that when the brightness of the image displayed by the transparent display device is high, interference from the rear of the transparent display device is hardly recognized. Accordingly, when the gray scale of the displayed image is substantially high, it is recognized that the visibility of the user's image is not lowered even if the shielding unit does not completely block the external light.

The inventors of the present invention also recognized that the power consumption of the light-shielding portion can be lowered by adjusting the transmittance of the light-shielding portion with respect to the external light within a range in which the visibility of the user's image is not significantly lowered.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a transparent display device employing a light shielding portion for shielding light when power is applied by adjusting the transmittance of the light shielding portion to the external light according to the gray scale of the image, And to provide a transparent display device capable of reducing power and a control method thereof.

Another object of the present invention is to provide a transparent display device and a control method thereof, in which the light shielding portion is selectively operated even when the transparent display device is in the on state for a long time to improve the durability of the light shielding portion.

The problems of the present invention are not limited to the above-mentioned problems, and other problems not mentioned can be clearly understood by those skilled in the art from the following description.

In order to solve the above problems, a transparent display device according to an embodiment of the present invention is provided. The transparent display device includes a transparent display portion, a light shielding portion, and a control portion. The transparent display portion has a light emitting region for displaying an image and a transmissive region for transmitting at least part of the incident external light. The shielding portion overlaps the transparent display portion and is configured to lower the transmittance to external light when a voltage is applied. The control unit is configured to control the transmittance of the light-shielding portion in accordance with the gray scale of the image. Accordingly, since the shielding portion is selectively driven according to the gray scale of the image, the power consumption of the shielding portion can be reduced and the durability of the shielding portion can be improved.

According to another aspect of the present invention, the light-shielding portion includes a liquid crystal portion, and the liquid crystal portion of the light-shielding portion is formed of a polymer dispersed liquid crystal.

According to another aspect of the present invention, when an electric field is applied to the liquid crystal, the liquid crystal of the liquid crystal unit has a disordered phase arrangement for scattering light.

According to another aspect of the present invention, the control unit is configured to adjust the transmissivity of the light-shielding unit to the lowest achievable transmittance when the ratio of the pixels of the first gray-scale value or less in one frame is equal to or greater than a predetermined ratio.

According to another aspect of the present invention, the control unit is configured to adjust the transmittance of the light-shielding portion to a transmittance higher than the minimum transmittance when the ratio of the pixels in the first frame to the first gray-scale value or less is less than a predetermined ratio .

According to another aspect of the present invention, when the ratio of the pixels in the one frame that is smaller than the second gray scale value and smaller than the second gray scale value is less than the predetermined ratio, the transmissivity of the light shielding portion is adjusted to the highest achievable transmittance . Transparent display device.

According to still another aspect of the present invention, the shielding portion is characterized in that it operates at an adjusted transmittance while one frame is displayed.

According to another aspect of the present invention, the control unit determines the cumulative pixel ratio from the ratio of the gray scale value pixels that are zero in one frame to the ratio of the gray scale value pixels that are greater than zero, To adjust the transmittance of the light emitting layer.

According to still another aspect of the present invention, one frame is characterized in that a ratio of pixels having a first gray scale value or less among the plurality of frames is the highest.

According to still another aspect of the present invention, the light-shielding portion operates at an adjusted transmittance while a frame following a plurality of frames is displayed.

According to still another aspect of the present invention, the transparent display device further includes an illuminance sensor for obtaining illuminance, and the control unit is configured to control the transmittance of the shielding portion according to the illuminance and the minimum gray scale of the image.

According to still another aspect of the present invention, the transparent display portion is a transparent organic light emitting display device.

According to an aspect of the present invention, there is provided a method of controlling a transparent display device. A method of controlling a transparent display device includes the steps of obtaining a grayscale histogram of an image displayed on a transparent display portion having a light emitting region for displaying an image and a transmissive region for transmitting at least a part of incident light, Determining whether the number of pixels is equal to or larger than a predetermined value; calculating a transmittance of the light-shielding portion overlapping the transparent display portion when the number of pixels is equal to or larger than a predetermined value; And adjusting the transmittance of the light-shielding portion to a transmittance higher than the minimum transmittance when the number of pixels is less than a predetermined value.

According to another aspect of the present invention, the gray scale histogram is a gray scale histogram of one frame.

According to another aspect of the present invention, a single frame is a frame having the largest number of pixels of 0 to n gray scale values among a plurality of frames.

The details of other embodiments are included in the detailed description and drawings.

The present invention provides a transparent display device and a control method thereof, in which power consumption of a light-shielding portion is minimized by driving a light-shielding portion at a low voltage when a high-gray-scale image is displayed.

The effects according to the present invention are not limited by the contents exemplified above, and more various effects are included in the specification.

1 is a schematic block diagram of a transparent display device according to an embodiment of the present invention.
2 is a flowchart illustrating a method of controlling a transparent display device according to an exemplary embodiment of the present invention.
3A to 3C are schematic cross-sectional views for explaining the operation of the transparent display device according to an embodiment of the present invention.
4 is a diagram for explaining modes of operation of the light-shielding portion of the transparent display device according to an embodiment of the present invention.
5A and 5B are schematic diagrams for explaining an operation mode determination step of a transparent display device according to an embodiment of the present invention.
6A and 6B are schematic diagrams for explaining the operation mode determination step of the transparent display device according to another embodiment of the present invention.
7 is a schematic cross-sectional view illustrating a transparent display device according to another embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. It should be understood, however, that the invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims.

The shapes, sizes, ratios, angles, numbers, and the like disclosed in the drawings for describing the embodiments of the present invention are illustrative, and thus the present invention is not limited thereto. Like reference numerals refer to like elements throughout the specification. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. Where the terms "comprises", "having", "done", and the like are used in this specification, other portions may be added unless "only" is used. Unless the context clearly dictates otherwise, including the plural unless the context clearly dictates otherwise.

In interpreting the constituent elements, it is construed to include the error range even if there is no separate description.

In the case of a description of the positional relationship, for example, if the positional relationship between two parts is described as 'on', 'on top', 'under', and 'next to' Or " direct " is not used, one or more other portions may be located between the two portions.

It is to be understood that an element or layer is referred to as being "on" another element or layer, including both intervening layers or other elements directly on or in between.

Although the first, second, etc. are used to describe various components, it goes without saying that these components are not limited by these terms. These terms are used only to distinguish one component from another. Therefore, it goes without saying that the first component mentioned below may be the second component within the technical scope of the present invention.

Like reference numerals refer to like elements throughout the specification.

The sizes and thicknesses of the individual components shown in the figures are shown for convenience of explanation and the present invention is not necessarily limited to the size and thickness of the components shown.

It is to be understood that each of the features of the various embodiments of the present invention may be combined or combined with each other partially or entirely and technically various interlocking and driving is possible as will be appreciated by those skilled in the art, It may be possible to cooperate with each other in association.

Various embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

1 is a schematic block diagram of a transparent display device according to an embodiment of the present invention. The transparent display device 100 includes a transparent display portion 110, a light shielding portion 120, and a control portion 130.

The transparent display unit 110 may be a transparent organic light emitting display. A transparent organic light emitting display includes a light emitting region and a transmissive region. The luminescent region is an area in which an actual image is realized, and the transmissive area means an area transmitting at least a part of the external light. Accordingly, when the transparent organic light emitting display device is not driven, the user can visually recognize the background, that is, the object behind the transparent display device 100, through the transparent region. In this specification, the front and rear surfaces of the transparent display device 100 are defined on the basis of light emitted from the transparent display device 100. In this specification, the front surface of the transparent display device 100 refers to a surface on which light is emitted from the transparent display device 100, and the rear surface of the transparent display device 100 is a surface on which light is emitted from the transparent display device 100 Means the opposite side.

The light shielding portion 120 means a structure that changes the light path or changes the light characteristic, such as transmitting, scattering, absorbing, or shielding light incident on the shielding portion 120.

The light-shielding portion 120 of the transparent display device 100 according to an exemplary embodiment of the present invention includes a liquid crystal portion of a polymer dispersed liquid crystal (PDLC). When the electric field is applied, the arrangement of the polymer dispersed liquid crystal is changed, so that light incident from the outside can be scattered or transmitted. Alternatively, the shielding part 120 may be an electro wetting device or an electrochromic device. Hereinafter, the shielding part 120 of the transparent display device 100 will be referred to as a polymer And is a light-shielding portion 120 including a dispersed liquid crystal.

The light shielding part 120 may include electrodes facing each other, a liquid crystal part interposed therebetween and having a polymer dispersed liquid crystal. In a state in which no voltage is applied to the electrode of the shielding part 120, the shielding part 120 transmits light. That is, the polymer dispersed liquid crystal is oriented so as to transmit light in a state in which no voltage is applied to the electrode of the light shielding portion 120. When a voltage of a certain magnitude is applied to the electrode of the light-shielding part 120, the arrangement of the polymer dispersed liquid crystal is changed by the formed electric field, so that the light-shielding part 120 has a disordered phase arrangement for scattering light. So that the shielding part 120 scatters or absorbs at least part of the external light. Accordingly, when the power source is applied, the light-shielding unit 120 lowers the transmittance of the external light. The light is transmitted through the light shielding unit 120 in a state where no voltage is applied to the light shielding unit 120, so that the power consumption can be minimized in the off state in which the transparent display device 100 is not driven.

The light shielding part 120 is disposed on the front surface or the rear surface of the transparent display part 110 and overlaps with the transparent display part 110. The light shielding part 120 is preferably disposed on the rear surface of the transparent display part 110 to shield light from the rear surface.

The controller 130 may refer to a processor capable of performing various operations. The processing unit may include a timing controller included in the transparent display device 100, a controller 130 for driving the light shield 120, a computing device such as a MAP (Multimedia Application Processor), an ISP (Image Signal Processor) Lt; / RTI > may be a combination of one or more devices.

The control unit 130 is configured to control the transmittance of the shielding unit 120 according to the gray scale of the image. The controller 130 obtains a histogram of the displayed image and calculates the number of pixels having a predetermined gray scale value or less. The control unit 130 determines the transmittance of the light shielding unit 120 according to the number of pixels having a gray scale value equal to or less than a predetermined gray scale value and controls the light shielding unit 120 to be driven with a driving voltage, do.

With respect to the visibility of the display image displayed on the transparent display device 100, the background of the back surface of the transparent display device 100 is recognized as interference or noise to the display image. That is, in view of the visibility of the display image, the visibility of the displayed image is improved as the amount of light incident on the back surface is smaller. Accordingly, when the transparent display device 100 is turned on, and the image is displayed on the transparent display unit 110, the shielding unit 120 is configured to block external light.

In order to improve the visibility of the display image, when the light incident on the rear surface of the transparent display device 100 is completely blocked, a high driving voltage is applied to the shielding portion 120. [ The high driving voltage of the shielding part 120 causes high power consumption of the shielding part 120 and increases the total power consumption of the transparent display device 100.

The control unit 130 of the transparent display device 100 according to an exemplary embodiment of the present invention determines whether the image displayed on the transparent display unit 110 is a dark image or a bright image through histogram analysis. A bright image or an image composed of pixels having a high gray scale value may not be recognized as interference because the brightness of the image itself is high. However, in the case of a dark image or an image composed of pixels having a low gray scale value, the background of the background can be recognized as relatively interference.

Therefore, when a bright image that may not be recognized as interference by the back side is displayed on the transparent display unit 110, the viewer can recognize the image without interference even if the shielding unit 120 does not block the external light. The transparent display device 100 according to an exemplary embodiment of the present invention operates so that the light shielding unit 120 does not block external light for a bright image. On the other hand, when a dark image that can be recognized as an interference of the back side is displayed on the transparent display unit 110, the light shield unit 120 operates to block external light. Also, the controller 130 may control the light shield 120 to block only a part of the external light according to the gray scale of the image. Accordingly, since the shielding unit 120 is selectively driven according to the gray scale of the image, the power consumption of the shielding unit 120 can be reduced and the durability of the shielding unit 120 can be improved.

2 is a flowchart illustrating a method of controlling a transparent display device according to an exemplary embodiment of the present invention. The steps described below can be performed by the control unit in Fig.

First, a histogram of an image is obtained (S210). The histogram is a diagram formed by dividing a range in which an image exists, for example, into 256 gray-scale sections and detecting the number of appearances of pixels in each section. Hereinafter, gray scale is described as having 256 intervals, but it is not limited thereto. The histogram may be a histogram for one frame, but the present invention is not limited thereto. The histogram may be a mean value or a sum of the number of pixel appearances in a plurality of frames. When the histogram for a plurality of frames is used, the control precision of the light shielding portion can be improved.

Next, the number of pixels having 0 to n gray scale values in the histogram is calculated (S220). Where n is a positive integer. The gray scale value n may be a predetermined value, and may be a gray scale value for distinguishing whether the image is a dark image or a bright image. In various embodiments, it may be implemented to determine a frame having the largest number of pixels of 0 to n gray scale values among a plurality of frames, and to use the number of pixels of the frame. Accordingly, since the light shielding unit is controlled based on the darkest frame of the image, the visibility of the user can be maintained high.

Next, it is determined whether the number of pixels having 0 to n gray scale values is equal to or greater than a predetermined value (S230). If the number of pixels is equal to or larger than the predetermined value, the displayed image is determined as a dark image. When the number of pixels is equal to or larger than the predetermined value, the transmissivity of the light-shielding portion is adjusted to the lowest achievable transmittance (S240). Since the dark image is sensitive to the interference by the background, the light shielding part must block the external light incident on the rear surface of the transparent display device so that the user can visually recognize the image without interference.

When the number of pixels is less than the predetermined value, the transmissivity of the light-shielding portion is adjusted to be higher than the lowest transmissivity (S250). If the image is determined to be brighter than the reference, the transmittance of the light-shielding portion is adjusted to be higher than the minimum transmittance in a line in which the visibility of the user is not lowered, thereby lowering the power consumption of the light-

On the other hand, in the embodiment in which the histogram of each frame is analyzed and the light-shielding portion is operated with the adjusted transmittance, the light-shielding portion can operate with the adjusted transmittance while the frame is displayed on the transparent display portion. In the embodiment using the average number of pixels of a plurality of frames or the sum of the number of pixels, the light shielding portion operates with the adjusted transmittance while displaying a frame following a plurality of frames. Accordingly, the transmittance of the shielding portion can be adjusted to correspond to the analyzed image.

An image can be distinguished by a plurality of criteria without distinguishing a bright image or a dark image from one reference. According to the plurality of criteria, if the number of pixels in step S240 is less than the predetermined value, it may be determined whether the number of pixels having the 0 to m gray scale value is equal to or greater than a predetermined value. Where m is a gray scale value greater than n. The transmittance of the light-shielding portion can be adjusted according to the gray scale value used as a reference. Further, by repeating the steps of calculating the number of pixels and determining whether the number of pixels is equal to or greater than a predetermined value, further finer shielding control may be possible.

In various embodiments, the light shielding portion of the transparent display device may be implemented with a first mode for completely blocking external light incident, a second mode for partially blocking incident external light, and a third mode for shielding external incident light. The driving voltage of the light-shielding portion operating in the second mode may be lower than the driving voltage of the light-shielding portion operating in the first mode.

In the method of controlling a transparent display device according to an embodiment of the present invention, images are classified by comparing the number of pixels. However, the present invention is not limited to this, and the number of pixels may be classified into a ratio of pixels having 0 to n gray scale values Can be distinguished. For example, when the ratio of pixels in a frame that is lower than a specific gray scale value is equal to or greater than a predetermined ratio, the light shielding portion can operate at the lowest transmittance that can be realized. Further, when the ratio of the pixels in the one frame that is lower than the specific grayscale value is less than the predetermined ratio, the light shielding portion can operate at a higher transmittance than the lowest transmittance. Alternatively, if the ratio of pixels that are below a gray scale value that is greater than a particular gray scale value is less than a predetermined ratio, the light blocking section may operate at the highest transmittance achievable.

3A to 3C are schematic cross-sectional views for explaining the operation of the transparent display device according to an embodiment of the present invention. FIGS. 3A to 3C are cross-sectional views for explaining image display and shading according to the operation of the transparent display device 100. FIG.

In Fig. 3A, the transparent display device 100 is in an off state. In the off state, the transparent display unit 110 does not display any image, and the external light L is transmitted through the shielding unit 120 because no voltage is applied thereto. The external light L is transmitted through the transparent display device 100 and reflected on the wall behind the transparent display device 100 so that the user can recognize the wall through the external light L passing through the transparent display device 100 .

3B, the transparent display device 100 is in the ON state. In the ON state, the transparent display unit 110 displays the image D1. The image D1 displayed on the transparent display unit 110 is a dark image. The control unit determines the image D1 as a dark image and applies a voltage to the shielding unit 120 to cut off the external light L. [ Accordingly, the user can visually recognize the dark image D1 without interference.

3C, the transparent display device 100 is in the ON state. The transparent display unit 110 displays the image D2 in the on state and the image D2 displayed on the transparent display unit 110 is the bright image. The control unit does not apply a voltage to the shielding unit 120 or applies a voltage lower than that of FIG. 3B, thereby blocking only a part of the external light L. Accordingly, although the external light L is reflected on the wall to reach the user, the brightness of the image D2 may be relatively brighter than the external light L, so that the visibility of the user may not be reduced.

4 is a diagram for explaining modes of operation of the light-shielding portion of the transparent display device according to an embodiment of the present invention. In FIG. 4, the x-axis represents the driving voltage of the light-shielding portion by V, and the y-axis represents the transmittance of the light-shielding portion in%.

In Fig. 4, the relationship between the driving voltage and the transmissivity of the light-shielding portion and the operation mode and driving voltage of the light-shielding portion will be described. Referring to FIG. 4, as the driving voltage increases, the transmittance of the light-shielding portion decreases. For example, when the shielding portion operates in the first mode where the transmittance is 70 to 100%, the drive voltage of the shielding portion may be between 0 and A V. [ When the shielding portion operates in the second mode in which the transmittance is 70 to 20%, the drive voltage of the shielding portion may be A to B V. When the shielding portion operates in the third mode in which the transmittance is 20% or less, the drive voltage of the shielding portion may be, for example, C V. The driving voltage may vary depending on the design of the light shielding portion, and is not limited to a specific range.

Referring to FIG. 4, in the case of driving with a high transmittance, the driving voltage is significantly lower than that in the case of driving with a low transmittance. Accordingly, when the light shielding part is driven dynamically, the power consumption reduction effect can be very large.

5A and 5B are schematic diagrams for explaining an operation mode determination step of a transparent display device according to an embodiment of the present invention. One frame Ia is shown in Figure 5a. A grayscale histogram for one frame Ia is shown below. The ratio of pixels having a gray scale value of 63 or less in the histogram is calculated as 64.2%. And, the predetermined ratio for determining the dark image may be, for example, 25%. Since the ratio of pixels is equal to or greater than a predetermined ratio, the control unit of the transparent display device determines one frame Ia as a dark image and operates in a third mode having the lowest transmittance, for example, 0% .

In Fig. 5B, one frame Ib is shown. A gray scale histogram for one frame Ib is shown below. The ratio of pixels having a gray scale value of 63 or less in the histogram is calculated as 5.7%. Since the ratio of the pixels is less than the predetermined ratio, the ratio of pixels having the next gray scale value of 140 or less is calculated. The ratio of pixels having a gray scale value of 140 or less is calculated as 70.5%. Since the ratio of the pixels is equal to or larger than the predetermined ratio, the control unit can operate the light shielding unit in the second mode having a transmittance of, for example, 40%. When the ratio of the pixels having the gray scale value of 140 or less is less than the predetermined ratio, the control unit may adjust the transmittance of the light shielding portion to 95%, which is the highest achievable transmittance.

6A and 6B are schematic diagrams for explaining the operation mode determination step of the transparent display device according to another embodiment of the present invention. The control section of the transparent display device may calculate the cumulative pixel ratio in one frame and adjust the transmittance of the light shielding section in accordance with the cumulative pixel ratio.

The cumulative pixel ratio is a value obtained by accumulating the ratios of pixels by sequentially increasing the gray scale values from the ratios of the pixels having the gray scale value of zero. The control unit may be configured to store the gray scale value when the cumulative pixel ratio becomes a predetermined cumulative pixel ratio, and adjust the transmittance of the light shielding unit based on the stored gray scale value. For example, the control unit may use a look up table in which the transmissivity of the light shielding portion corresponding to each of the range and the range of the gray scale value is stored.

Referring to FIG. 6A, the gray scale value when the cumulative pixel ratio becomes 25% in the histogram of one frame Ia is calculated to be 54. When the cumulative pixel ratio reaches 25% between gray scale 0 to 63, the transmissivity of the light shielding portion may be, for example, 10%. The control section of the transparent display device can operate the shielding section in a mode having a transmittance of 10%.

Referring to FIG. 6B, the gray scale value when the cumulative pixel ratio becomes 25% in the histogram of one frame Ib is calculated to be 74. The transmittance of the light shielding portion corresponding to the gray scale 74 may be, for example, 60%. The control section of the transparent display device can operate the light blocking section in a mode having a transmittance of 60%. In the transparent display device according to another embodiment of the present invention, the image is analyzed with a minimized calculation amount to control the light shielding portion of the transparent display device, and the power consumption of the light shielding portion can be reduced by selective control.

7 is a schematic cross-sectional view illustrating a transparent display device according to another embodiment of the present invention. The transparent display device 700 of FIG. 7 is substantially the same as the transparent display device 100 of FIG. 3A, except that the light intensity sensor 740 is added, and redundant description of the overlapping components will be omitted.

The transparent display device 700 includes an illuminance sensor 740 for obtaining illuminance. The user's perceiving power against the image may be different depending on the illuminance and the interference due to the external light L may increase as the illuminance increases. Accordingly, the control unit of the transparent display device 700 is configured to control the transmittance of the shielding unit 120 according to the illuminance to be measured and the gray scale of the image. When the illuminance is equal to or greater than a certain nit, the transmittance of the shielding portion 120 can be adjusted lower than the case where the illuminance is less than a certain nit. In the transparent display device 700 according to another embodiment of the present invention, the transmittance of the shielding unit 120 can be adjusted so as to lower the power consumption regardless of the intensity of the external light L.

Although the embodiments of the present invention have been described in detail with reference to the accompanying drawings, it is to be understood that the present invention is not limited to those embodiments and various changes and modifications may be made without departing from the scope of the present invention. . Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. Therefore, it should be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

100, 700: transparent display device
110: transparent display part
120:
130:
W: Wall
740: Light sensor

Claims (15)

A transparent display portion having a light emitting region for displaying an image and a transmissive region for transmitting at least a part of incident external light;
A light shielding portion overlapping the transparent display portion and configured to lower the transmittance to the external light when a voltage is applied; And
And a control unit configured to control a transmittance of the light-shielding unit in accordance with a gray scale of the image. The method according to claim 1,
Wherein the light-shielding portion includes a liquid crystal portion,
Characterized in that the liquid crystal portion of the light-shielding portion is made of a polymer dispersed liquid crystal. 3. The method of claim 2,
Wherein when an electric field is applied to the liquid crystal unit, the liquid crystal of the liquid crystal unit has a disordered phase arrangement for scattering light. The method according to claim 1,
Wherein the control unit is configured to adjust the transmissivity of the light-shielding unit to the lowest achievable transmittance when the ratio of the pixels of the first gray-scale value or less in one frame is equal to or larger than a predetermined ratio. 5. The method of claim 4,
Wherein the controller is configured to adjust the transmittance of the light-shielding portion to a transmittance higher than the lowest transmittance when a ratio of pixels in a frame that is lower than a first gray scale value is less than a predetermined ratio. 6. The method of claim 5,
Wherein the control unit is configured to adjust the transmissivity of the light-shielding unit to the highest achievable transmittance when a ratio of pixels in a frame that is smaller than a second gray-scale value larger than the first gray-scale value is less than a predetermined ratio . Transparent display device. The method according to claim 5 or 6,
Wherein the shielding portion operates at an adjusted transmittance while the one frame is displayed. The method according to claim 1,
Wherein the control unit is configured to determine a cumulative pixel ratio from a ratio of a gray scale value pixel that is zero in one frame to a ratio of a gray scale value pixel that is larger than zero and adjust the transmittance of the light shielding unit based on the cumulative pixel ratio And the transparent display device. The method according to any one of claims 4 to 6 and 8,
Wherein the one frame is a frame having a highest ratio of pixels having a first gray scale value or less among a plurality of frames. 10. The method of claim 9,
And the shielding portion operates with the transmittance adjusted while displaying the frames subsequent to the plurality of frames. The method according to claim 1,
Further comprising an illuminance sensor for obtaining illuminance,
Wherein the control unit is configured to control the transmittance of the light-shielding unit according to the illuminance and the minimum gray scale of the image. The method according to claim 1,
Wherein the transparent display portion is a transparent organic light emitting display device. Obtaining a grayscale histogram of an image displayed on a transparent display portion having a light emitting region for displaying an image and a transmitting region for transmitting at least a part of incident external light;
Calculating a number of pixels of 0 to n gray scale values in the histogram, wherein n is a positive integer;
Determining if the number of pixels is greater than or equal to a predetermined value;
Adjusting a transmittance of the light-shielding portion overlapping the transparent display portion to a lowest achievable transmittance when the number of the pixels is equal to or greater than a predetermined value; And
And adjusting the transmittance of the light-shielding portion to a transmittance higher than the lowest transmittance when the number of pixels is less than a predetermined value. 14. The method of claim 13,
Wherein the gray scale histogram is a gray scale histogram of one frame. 15. The method of claim 14,
Wherein the one frame is a frame having the largest number of pixels of the 0 to n gray scale values among a plurality of frames.

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