EP2953119A1

EP2953119A1 - Video display device with color purity control

Info

Publication number: EP2953119A1
Application number: EP14171351.1A
Authority: EP
Inventors: Wouter Verlinder
Original assignee: Martin Professional ApS
Current assignee: Harman Professional Denmark ApS
Priority date: 2014-06-05
Filing date: 2014-06-05
Publication date: 2015-12-09

Abstract

A video display device (100) comprises an arrangement of pixels (110) for displaying video content. The arrangement of pixels (110) comprises at least four individual light sources (111, 112, 113, 114) of different colors for each pixel (110). Further, the video display device (100) comprises a controller (120) which is configured to control the light sources (110) to display the video content. Further, the controller (120) is configured to select, depending on a color purity value, between at least a first mode in which the individual light sources (111, 112, 113, 114) are controlled to display the video content according to a first mapping of color information of the video content to intensities of said individual light sources (111, 112, 113, 114), and a second mode in which said individual light sources (111, 112, 113, 114) are controlled to display the video content according to a second mapping of color information of the video content to intensities of said individual light sources (111, 112, 113, 114).

Description

Technical Field

The present invention relates to a video display device, to a video controller, a video system, and to a method of controlling a video display device.

Background

For example in the entertainment industry, it is known to use video display devices for displaying video content. A known way of implementing such video display devices is to use an array of LEDs (Light Emitting Diodes), which can be individually controlled according to pixel information of the video content.
Such video display devices may for example be used in the background of a stage, on the sides of a stage, or at other positions. For example, the displayed video content may show a live picture of an entertainer on the stage, so that a close-up image of the entertainer is also visible in parts of the audience which are located further away from the stage. Alternatively, the displayed video content may also be pre-fabricated an be used to generate a certain atmosphere in combination with various kinds of light effects.
To reproduce color information of the video content, each pixel of the video display device may be provided with a red (R) LED, a green (G) LED, and a blue (B) LED. Such video displays are also referred to as RGB displays. However, it is additionally also possible to add further LEDs, e.g., a white (W) LED, to thereby achieve a higher output brightness or fuller spectrum. Such video displays are also referred to as RGBW displays. In an RGB display, a pixel showing white color is realized by mixing light emitted by the red, green, and blue LED. In an RGBW display, the white LED is additionally available, so that a higher brightness or fuller spectrum can be achieved.
However, the since the white LED is a broadband light source, its additional usage when displaying video content of various colors may affect the overall color appearance, in particular when showing colors which are close to pure red, blue, or green.
Accordingly, there is a need for techniques which allow for efficient usage of a video display device with pixels which are formed of more than three individual light sources of different colors.

Summary

This need is met by the features of the independent claims. The dependent claims define further embodiments of the invention.
According to an embodiment of the invention, a video display device is provided. The video display device comprises an arrangement of pixels for displaying video content. The arrangement of pixels comprises at least four individual light sources of different colors for each pixel. For example, for each pixel a red light source, a green light source, and a white light source may be provided. The individual light sources may be implemented by LEDs. Further, the video display device comprises a controller for controlling the light sources of the pixels. The controller is configured to select, depending on a color purity value, between at least a first mode in which the individual light sources are controlled to display the video content according to a first mapping of color information of the video content to intensities of the individual light sources, and a second mode in which the individual light sources are controlled to display the video content according to a second mapping of color information of the video content to intensities of the individual light sources.
According to an embodiment, the controller is configured to select between a plurality of different modes, each corresponding to a different color purity value and a corresponding mapping of color information of the video content to intensities of said individual light sources. Accordingly, the color purity value may be used to tune the color purity, with a granularity defined by the number of mappings.
The video display device may further comprise an interface which is configured to receive the color purity value. This interface may also be configured to receive the video content. That is to say, the same interface of the video display device may be used to receive the video content and the color purity value. The interface may be configured to receive the video content in a sequence of data packets, and the color purity value may be included in one of the data packets.
According to a further embodiment of the invention, a video controller is provided. The video controller comprises an interface with respect to at least one video display device. The video display device comprises an arrangement of pixels for displaying video content. The arrangement of pixels comprises at least four individual light sources of different colors for each pixel. The video display device may correspond to a video display device as described in the above embodiment. The interface is configured to send a color purity value to the at least one video display device to control the at least one video display device to select between at least a first mode and a second mode. In the first mode the individual light sources are controlled to display the video content according to a first mapping of color information of the video content to intensities of said individual light sources. In the second mode the individual light sources are controlled to display the video content according to a second mapping of color information of the video content to intensities of the individual light sources.
The interface of the video controller may be further configured to send the video content. The interface may be configured to send the video content in a sequence of data packets, and the color purity value may be included in one or more of these data packets.
According to a further embodiment of the invention, a system is provided. The system comprises at least one video display device. Each of such video display devices may be configured as described in connection with the above embodiment. Further, the system comprises a video controller, such as the video controller of the above embodiment. The at least one video display device comprises an arrangement of pixels for displaying video content. The arrangement of pixels comprises at least four individual light sources of different colors for each pixel. The video controller is configured to send a color purity value to the at least one video display device to control the at least one video display device to select between at least a first mode and a second mode. In the first mode the individual light sources are controlled to display the video content according to a first mapping of color information of the video content to intensities of the individual light sources. In and a second mode the individual light sources are controlled to display the video content according to a second mapping of color information of the video content to intensities of the individual light sources.
According to a further embodiment of the invention, a method of controlling a video display device is provided. According to the method an arrangement of pixels of the video display device is controlled to display video content. The arrangement of pixels comprises at least four individual light sources of different colors for each pixel. Depending on a color purity value, a selection between at least a first mode and a second mode is performed. In the first mode the individual light sources are controlled to display the video content according to a first mapping of color information of the video content to intensities of the individual light sources. In the second mode the individual light sources are controlled to display the video content according to a second mapping of color information of the video content to intensities of said individual light sources. The selection between the at least first and second modes and the control operations of these modes may be performed by a controller of the video display device.
In the above embodiments, the color information of the video content may be encoded by intensities of three component colors, e.g., red, green, and blue, and wherein three of the individual light sources may correspond to these component colors, i.e., emit red light, green light, and blue light, respectively. The at least one other of the individual light sources may correspond to a broadband light source, e.g., may emit white light. The color purity value may then control a contribution of the individual light sources corresponding to the three component colors in relation to a relative contribution of the at least one other of said individual light sources to the overall light emission of the pixel. For example, this may allow for selecting a mapping which corresponds to maximum color purity, in which only the light sources corresponding to the component colors are utilized for displaying the video content. Further, also mappings with increased relative contribution of the at least one further light source may be selected. With increasing relative contribution of the at least one further light source, for example higher brightness levels may be achieved. On the other hand, color purity decreases with increasing relative contribution of the at least one further light source. The color purity value allows for selecting a desired tradeoff, e.g., between desired brightness and desired color purity.
In the first mode for each of the three component colors, the intensity value indicated by the color information of the video content may be mapped to a first corresponding intensity of a corresponding one of the three individual light sources and to a first corresponding intensity of at least one other of the individual light sources, while in the second mode, for each of the three component colors, the intensity value indicated in the color information of the video content is mapped to a second corresponding intensity of the corresponding one of the three individual light sources and to a second corresponding intensity of the at least one other of the individual light sources. The first corresponding intensity of the at least one other of the individual light sources is higher than the second corresponding intensity of the at least one other of the individual light sources. The second corresponding intensity of the at least one other of the individual light sources can also be zero, which means that a maximum level of color purity is achieved.
In some embodiments the first mapping and/or the second mapping is determined depending on the color information of the video content. Accordingly, the mapping may be dynamically adjusted. For example, if the color information for a pixel indicates a color which is similar to a color of one of the individual light sources, the mapping may be determined in such a way that the contribution of this individual light source is increased in favor of the contributions from the other light sources. Since the color information of the video content may differ from pixel to pixel, this dynamic adjustment may be accomplished individually for each pixel, which allows for optimizing the desired color purity behavior for each pixel.
Further details of the above and further embodiments will be apparent from the following detailed description in connection with the accompanying drawings.

Brief description of the Drawings

Fig. 1 schematically illustrates a video display device according to an embodiment of the invention.
Fig. 2 schematically illustrates a pixel of the video display device.
Fig. 3 schematically exemplary mappings of color information to intensities of light sources as used in an embodiment of the invention.
Fig. 4 shows a CIE diagram with different color purity areas as utilized in an embodiment of the invention.
Fig. 5 schematically illustrates a video system according to an embodiment of the invention.
Fig. 6 shows a flowchart for illustrating a method according to an embodiment of the invention.

Detailed description

In the following, embodiments of the invention will be described in more detail and with reference to the accompanying drawings. These embodiments relate to video display devices with an arrangement of light sources in the form of an array of LEDs, to a video controller for controlling one or more of such video display devices, and to a method of controlling one or more of such video display devices.
Fig. 1 schematically illustrates an exemplary implementation of the video display device 100. As illustrated, the video display device 100 includes an arrangement of pixels 110. Here, it is to be understood that the illustrated number of pixels 110 and their geometric arrangement in a rectangular matrix is merely exemplary. For example, in alternative implementations a higher or lower number of pixels 110 could be utilized. Further, the arrangement of pixels 110 could alternatively based on other grid types, e.g., a hexagonal grid, or a linear arrangement.
Light emission by the pixels 110 is assumed to be individually controllable, so that one or more of the pixels may be used to show a corresponding pixel of video content. As explained in more detail below, each of the pixels includes at least four individual light sources of different colors. In the illustrated implementation, the four individual light sources of different colors are assumed to be a red LED, a green LED, a blue LED, and a white LED. Each of these LEDs may be individually controlled according to brightness information and/or color information of a corresponding pixel of the video content. For example, the video content may define a Red (R) color channel, a Blue (B) color channel, and a Green (G) color channel. In the following, these color channels will also be referred to as RGB channels.
As further illustrated, the video display device 100 includes a controller 120 and an interface 150. The controller 120 is generally responsible for controlling the arrangement of light sources 110 by generating a drive signal for each of the light sources of the pixels 110. For displaying the video content, the drive signals are generated depending on the video content. The interface 150 may be used to provide the video content to the video display device 100. In addition, as will be further explained below, the interface 150 may be used to provide various kinds of control information to the video display device 100. The interface 150 may be implemented on the basis of a physical layer and MAC (Medium Access Control) layer of an Ethernet technology, i.e., the data packets may correspond to Ethernet packets.
The interface 150 may operate by transmitting the video content in a sequence of data packets. Each video frame of the video content may be transmitted in one or more data packets which contain the data for each pixel of the video frame. In the following, such data packets will also be referred to as pixel data packet. When using the Ethernet technology, in which Ethernet packets are limited to about 1500 bytes in size, approximately 500 pixels with 8 bit resolution of the RGB channels or 250 pixels with 16 bit resolution of the RGB channels may be sent in a single pixel data packet. If the display device 100 is provided with a larger number of pixels, multiple pixel data packets may be utilized to transfer the pixel information of the video frame. Having received the pixel information of a single video frame, the video frame may be buffered by the controller 120, e.g., in the memory 130. This buffering allows for later displaying the video frame at a desired time instance, which is indicated in a specific low-latency data packet, in the following also referred to as Frame Sync data packet. The low latency of the Frame Sync data packet may be achieved by providing the Frame Sync data packet with a small size, e.g., of 80 or less bytes. For example, the payload of the Frame Sync packet may substantially consist of a frame identifier, which indicates which of the previously transmitted video frames shall be displayed. In this way, the time of displaying of a certain video frame is not affected by potential time variations due to transferring the pixel information of the video frame to the display device 100. This is specifically useful if the display device 100 is combined with one or more additional display devices to display video content in a synchronized manner. In such scenarios, the Frame Sync packet may be transmitted in a broadcast mode, so that the Frame Sync packet is received substantially simultaneously by all combined video display devices.
In the illustrated implementation, the video display device 100 is operable to display the video content in different color purity modes. For this purpose, the controller 120 is provided with a video display module 122, which is responsible for generating the drive signals of the light sources 110 depending on the video content, and a color purity control module 124, which is responsible for selecting a mapping of intensities of the RGB channels of the video content to intensities of the individual light sources of the pixels and to apply this mapping for translating the intensities of the RGB channels to intensities of the individual light sources. This selection of the mapping is accomplished depending on a color purity value, which in the illustrated implementation is assumed to be a numerical value in the range of 0 to 100%. Here, the color purity value of 0 corresponds to a mapping in which the white LED of the pixels is utilized to maximum extent, thereby allowing to achieve a high brightness and/or full spectrum of the emitted light. The color purity value of 100% corresponds to a mapping in which the white LED of the pixels is not utilized, thereby achieving a maximum level of color purity. However, it is to be understood that other representations of the color purity value could be utilized as well. For example, color purity levels of "high", "medium", and "low" could be defined. The interface 150 may be used to provide the color purity value to the video display device 100.
The controller 120 may for example be implemented by one or more processors which execute program code stored in a memory 130. Such program code may implement the functionalities of the video display control module 122 and/or of the color purity control module 124. However, it is to be understood that at least a part of the functionalities of the controller 120 may also be implemented by dedicated hardware components. The memory 130 may also be used to store other information, e.g., one or more predefined mappings to be utilized for achieving a desired level of color purity.
Fig. 2 schematically illustrates an exemplary implementation of a single pixel 110 of the video display device 100. As illustrated, the pixel 110 is provided with four individual light sources. In the illustrated implementation, these individual light sources are a red LED 111, a green LED 112, a blue LED 113, and a white LED 114. By individually controlling the intensities of the LEDs 111, 112, 113, 114, various colors of emitted light can be obtained through additive color mixing. However, it is noted that also other combinations different colored LED or even other types of light sources than LEDs could be provided.
Because the RGB channels of the video content provide three different intensities corresponding to the red, green, and blue component colors, a mapping is needed to translate the intensities indicated by the RGB channels to the corresponding intensities of the LEDs 111, 112, 113, 114. Different mappings may be utilized to achieve a certain overall output color of the pixel 110. For example, a white output color can be obtained by controlling the red LED 111, green LED 112, and blue LED 113 to the same intensity, while leaving the white LED 114 deactivated. Further, a white output color may also be obtained by utilizing only the white LED 114. Still further, the red LED 111, green LED 112, and blue LED 113 may be controlled to the same intensity and the white LED 114 may be utilized additionally to obtain a white output color. Similar possibilities of obtaining the same nominal output color also exist for other colors.
In the illustrated implementation, the color purity value is used to control the extent to which the white LED 114 is utilized for obtaining a given output color. In one extreme scenario, the white LED 114 is not utilized at all, and only the red LED 111, the green LED 112, and the blue LED 113 are utilized. This extreme scenario corresponds to a maximum color purity. In another extreme scenario, the white LED 114 is utilized with the same intensity as the red LED 111, the green LED 112, and the blue LED 113 to obtain a white output color, and for other output colors the intensities of the red LED 111, the green LED 112, the blue LED 113, and the white LED 114 are adjusted correspondingly. The color purity value may be used to tune between such extreme scenarios.
Fig. 3 illustrates exemplary mappings which may be utilized to implement the color purity control. The mappings are shown as graphical representations of the intensity of a primary light source (P) and the intensity of a secondary light source (S) as a function of the component color intensity indicated by the color information of the video content. The component color intensity may correspond to the red intensity, the green intensity, or the blue intensity indicated by the RGB channels. When considering the red component color, the primary light source would be the red LED 111, and the secondary light source would be the white LED 114. When considering the green component color, the primary light source would be the green LED 112, and the secondary light source would be the white LED 114. When considering the blue component color, the primary light source would be the blue LED 113, and the secondary light source would be the white LED 114.
In a first mapping (mapping 1), the intensity of the secondary light source S increases as the intensity of the primary light source P increases. The slope of the increase of the intensity of the secondary light source S in relation to the slope of the increase of the intensity of the primary light source is determined by the color purity value. A lower color purity value corresponds to a larger slope of the intensity of the secondary light source S and to a smaller slope of the intensity of the primary light source. The first mapping may be utilized for achieving a higher brightness and/or fuller spectrum of the displayed video content.
In a second mapping (mapping 2), the intensity of the secondary light source S is zero for all intensities of the component color indicated by the color information of the video content. In this case, the intensity of the component color indicated by the color information of the video content is used to control only the intensity of the corresponding primary light source P. The second mapping allows for achieving a maximum level of color purity.
Below some specific examples of mapping the intensities indicated by the RGB channels to intensities of the light sources 111, 112, 113, 114 will be given.

Example A (white output color):

Red RGB value of pixel: 100%
Green RGB value of pixel: 100%
Blue RGB value of pixel: 100%
Color purity value: 100%
Resulting intensity of red light source 111: 100%
Resulting intensity of green light source 112: 100%
Resulting intensity of blue light source 113: 100%
Resulting intensity of white light source 114: 0%

In this example, the white output color is generated by additive mixing of light emitted by the red light source 111, green light source 112, and blue light source 113. The light is thus perceived as white by an observer. However, the spectrum may not be as full as in "natural" white light. The white output color may thus have a somewhat artificial appearance.

Example B (white output color):

Red RGB value of pixel: 100%
Green RGB value of pixel: 100%
Blue RGB value of pixel: 100%
Color purity value: 50%
Resulting intensity of red light source 111: 100%
Resulting intensity of green light source 112: 100%
Resulting intensity of blue light source 113: 100%
Resulting intensity of white light source 114: 50%

In this example, the white output color is generated by additive mixing of light emitted by the red light source 111, green light source 112, and blue light source 113, while additionally adding light emitted by the white light source 114. As compared to Example A, a higher brightness is achieved. Further, the spectrum is fuller than in Example A, which means that the appearance is less artificial, closer to natural white light.

Example C (white output color):

Red RGB value of pixel: 100%
Green RGB value of pixel: 100%
Blue RGB value of pixel: 100%
Color purity value: 0%
Resulting intensity of red light source 111: 100%
Resulting intensity of green light source 112: 100%
Resulting intensity of blue light source 113: 100%
Resulting intensity of white light source 114: 100%

Also in this example, the white output color is generated by additive mixing of light emitted by the red light source 111, green light source 112, and blue light source 113, while additionally adding light emitted by the white light source 114. As compared to Example B, the contribution of the white light source 114 is maximized. As compared to Example B, a still higher brightness is achieved. Further, the spectrum is still fuller than in Example B, which may render the appearance even closer to natural white light.

Example D (pink output color):

Red RGB value of pixel: 100%
Green RGB value of pixel: 50%
Blue RGB value of pixel: 50%
Color purity value: 100%
Resulting intensity of red light source 111: 100%
Resulting intensity of green light source 112: 50%
Resulting intensity of blue light source 113: 50%
Resulting intensity of white light Source 114: 0%

In this example, the pink output color is generated by additive mixing of light emitted by the red light source 111, green light source 112, and blue light source 113. Due to the contributions of the green light source 112 and of the blue light source 113 being reduced as compared to the red light source, the light is perceived as pink by an observer.

Example E (pink output color):

Red RGB value of pixel: 100%
Green RGB value of pixel: 50%
Blue RGB value of pixel: 50%
Color purity value: 50%
Resulting intensity of red light source 111: 100%
Resulting intensity of green light source 112: 33%
Resulting intensity of blue light source 113: 33%
Resulting intensity of white light source 114: 16%

In this example, the pink output color is generated by additive mixing of light emitted by the red light source 111, green light source 112, and blue light source 113, while additionally adding light emitted by the white light source 114. As compared to Example D, a higher brightness is achieved. However, since the white light source 114 also adds contributions from other spectral regions, the pink output color may be perceived as less pure than in example D.

Example F (pink output color):

Red RGB value of pixel: 100%
Green RGB value of pixel: 50%
Blue RGB value of pixel: 50%
Color purity value: 0%
Resulting intensity of red light source 111: 100%
Resulting intensity of green light source 112: 33%
Resulting intensity of blue light source 113: 33%
Resulting intensity of white light Source 114: 33%

Also in this example, the pink output color is generated by additive mixing of light emitted by the red light source 111, green light source 112, and blue light source 113, while additionally adding light emitted by the white light source 114. As compared to Example E, the contribution of the white light source 114 is maximized. Accordingly, an even higher brightness is achieved. However, the pink output color may be perceived as less pure than in example E.
As can be seen from the above examples, when a lower color purity value is selected, the resulting intensity of the white LED 114 gets higher. On the other hand, selecting a higher color purity value allows for generating output colors which are perceived as more pure. This specifically applies to output colors which are similar to the color of one of the individual light sources.
In the above examples, the mapping which is selected depending on the color purity value is assumed to be based on a substantially monotonous dependency of the intensity of the white light source 114 on the intensities of the other light sources 111, 112, 113. However, also more complex dependencies may be applied. For example, in some implementations the mapping itself may be determined depending on the color information of the video content, i.e., on the RGB values of the given pixel. In the following, an exemplary implementation of a dynamic determination of the mapping on a pixel level will be explained with reference to Fig. 4.
Fig. 4 shows an exemplary CIE ("Commission Internationale de l'Éclairage") diagram in which the colors corresponding to the red light source 111, the green light source 112, the blue light source 113, and the white light source 114 are indicated. As illustrated, for each of the individual light sources 111, 112, 113, 114, a corresponding purity region may be defined. In Fig. 4, such purity regions are shown as a region of red purity 411, a region of green purity 412, a region of blue purity 413, and a region of white purity 414. The large triangle defined by the purity regions 411, 412, 413, 414 corresponds to the color gamut defined by the light sources 111, 112, 113 and represents the possible color that can be generated by additive light mixing of the light for these light sources 111, 112, 113.
For dynamically determining the mapping to be applied for a given pixel, the controller 120 may consider the RGB values of this pixel as defined by the color information of the video content and then determine in which of the purity regions the output color defined by the RGB values is located. Then, corresponding to this purity region, a mapping may be selected which emphasizes the contribution of the individual light source 111, 112, 113, 114 corresponding to this purity region. For example, if the RGB values indicate that the output color is within the region of red purity, a mapping may be selected which emphasizes the contribution of the red light source 111, in favor of the contributions from the other individual light sources 112, 113, 114. Similarly, if the RGB values indicate that the output color is within the region of green purity, a mapping may be selected which emphasizes the contribution of the green light source 112, in favor of the contributions from the other individual light sources 111, 113, 114. Further, if the RGB values indicate that the output color is within the region of blue purity, a mapping may be selected which emphasizes the contribution of the blue light source 113, in favor of the contributions from the other individual light sources 111, 112, 114. Still further, if the RGB values indicate that the output color is within the region of white purity, a mapping may be selected which emphasizes the contribution of the white light source 114, in favor of the contributions from the other individual light sources 111, 112, 113. This selection further depends on the purity value. For example, depending on the purity value a set of mappings may be selected, which includes a mapping for each of the purity regions, and depending on the RGB values of a given pixel, the appropriate mapping from the set may be selected.
It is noted that the purity regions as shown in Fig. 4 are merely exemplary. For example, the purity regions may be shaped in a different way. Further, to avoid abrupt changes in the color appearance at the borders of different purity regions, the actually applied mapping may be determined by interpolating the mappings of the different purity regions, depending on the RGB values of the pixel.
It should be noted that also other criteria may be additionally or alternatively used for determining the mapping on a pixel level. For example, due to variations in the characteristics of the light sources 111, 112, 113, 114, the pixels may differ with respect to their response to the drive signals. This may be taking into account by calibrating the pixels, i.e., measuring the response to the drive signals and adjusting the drive signals accordingly. In some implementation, the latter adjustment may be achieved by utilizing mappings which are individualized for each pixel.
Fig. 5 schematically illustrates a video system which includes a plurality of video display devices 100 and a video controller 200 which controls the video display devices 100. Each of the video display devices 100 may be configured and operate as explained above. The video controller 200 is configured to provide the video content and the color purity value to the video display devices 100. The video display devices 100 may be utilized to display the video content in a synchronized manner. Here, it is to be understood that this displaying of the video content in a synchronized manner may involve simultaneously displaying the same video frame on each of the display devices 100. However, it is also possible to use a more complex distribution of the video content over multiple display devices 100, which means that the video frames simultaneously displayed by the display devices 100 may differ from one display device 100 to the other. This may for example be the case if the video display devices 100 are operated as a single display with a larger number of pixels. In such cases, the video controller 200 may also be responsible for spatially mapping the pixels of the video content to the appropriate pixels of the different video display devices 100.
As illustrated, the video controller 200 is provided with one or more processors 220 which implement a video display control module 222 and a color purity control module 224. The video display control module 222 is responsible for generating the video frames to be displayed by the video display devices 100 from the video content. The color purity control module 224 is responsible for determining the color purity value to be applied by the video display devices 100. The video display control module 222 and the color purity control module 224 may be implemented by corresponding program code to be executed by the processor(s) 220. The video content may be stored in a memory 230 of the video controller 200. Alternatively or in addition, the video content 200 may be provided from an external video source 310. The color purity value determined by the color purity control module 224 may be based on user inputs of an operator, such as for example received via a user interface 240 of the video controller 200. Alternatively or in addition, the color purity value determined by the color purity control module 224 may be based on predefined data, such as for example stored in the memory. Still further, the color purity value determined by the color purity control module 224 may be based on inputs received from an external light controller 320.
As illustrated, the video controller 200 is provided with a first interface 250 for connecting the video controller 200 to the video display devices 100, e.g., to the above-mentioned interface 150 of the video display device 100. Accordingly, also the interface 250 may be implemented on the basis of a physical layer and MAC layer of an Ethernet technology and may be used to transmit the above-mentioned pixel data packets and Frame Sync packets. For connecting multiple display devices 100 to the video controller, these display devices 100 may be connected in a chain configuration, as for example illustrated in Fig. 4. That is to say, a first display device 100 of the chain configuration may be connected directly to the first interface 250 of the video controller 200, and from this first display device 100, a connection to the next display device 100 of the chain configuration is provided, and so on. However, it is to be understood that other topologies of connecting multiple display devices to the video controller 200 may be used in addition or as an alternative. For example, a star-type topology could be used, e.g., by connecting a switch to the first interface 250 of the video controller 200 and connecting the display devices 100 individually to the switch. Further, multiple chain configurations could be connected to such switch. Still further, even tree-type topologies with multiple switches and chain configurations are possible.
As further illustrated, the video controller 200 may be provided with a second interface 260 for connecting to the external video source 310 and/or with a third interface for connecting to the external light controller 320. The second interface 310 may be a digital interface, such as a DVI (Digital Visual Interface) or HDMI (High Definition Multimedia Interface). Alternatively, the second interface 310 may be an analog interface, such as a VGA (Video Graphics Array) or Component Video interface. The third interface 270 may for example be a DMX (Digital Multiplex) interface.
The video controller 200 may utilize the above-mentioned Frame Sync packets to achieve synchronized display of the video content by the multiple display devices 100. For this purpose, the video controller 200 may broadcast a Frame Sync packet to the video display devices 100, and upon reception of this Frame Sync packet the video display devices will immediately start displaying the video frame identified by the Frame Sync packet.
Although the video system of Fig. 5 is illustrated as including multiple video display devices 100, it is to be understood that also configurations with only a single video display device 100 are possible. Further, it is to be understood that configurations may be provided in which multiple video display devices 100 of different size, pixel number, and/or geometry are combined.
Fig. 6 shows a flowchart for illustrating a method of controlling a video display device 100. The steps of the method may for example be implemented in the video display device 100 of Fig. 1 or in the video system of Fig. 5. The steps of the method may be performed by a controller, such as the controller 120 of the video display device 100, or the video controller 200 of the video system.
At step 610, an arrangement of pixels of the video display device is controlled to display video content. This may involve generating drive signals for light sources which form the pixels of the video display device, e.g., a red LED 111, a green LED 112, a blue LED 113, and a white LED 114 as illustrated in Fig. 2.
At step 620, a color purity value is determined. For example, a controller of video display device, such as the controller 120, may receive the color purity value, e.g., from a video controller, such as the video controller 200. Step 620 may also involve that a video controller, such as the video controller 200, determines the color purity value. For example, the video controller may determine the color purity value depending on user inputs of an operator and/or depending on inputs from an external light controller. The color purity value may be a numerical value, e.g., in the range of 0 to 100% or from 0 to 255.
The color purity value may be transmitted via an interface to the video display device, such as via the interface 150 of the video display device 100 and the interface 250 of the video controller 200. The same interface may also be utilized for transmitting the video content to the video display device. The interface may be configured for transmission of the video content in a sequence of data packets, and the color purity value may be included in one or more of the data packets, such as in the above mentioned pixel data packets.
At step 630, a mode of mapping color information of the video content to intensities of the individual light sources of the pixels is selected. For example, a mapping corresponding to high brightness and/or a full spectrum of the emitted light may be selected, e.g., such as explained in connection with mapping 1 of Fig. 3. Further, a mapping corresponding to a maximum level of color purity may be selected, such as explained in connection with mapping 2 of Fig. 3. Further, in some implementations also one or more modes of intermediate color purity may be selected, e.g., by using the color purity value to interpolate between the high brightness and/or full spectrum mapping and the maximum color purity mapping.
In some implementations, the selected mapping may be further determined depending on the color information of the video content, e.g., depending on the RGB values of the pixels. The mapping may thus be determined on a pixel level, depending on the respective intended output color. If the color information for a pixel indicates a color which is similar to a color of one of the individual light sources, the mapping may be determined in such a way that the contribution of this individual light source is increased in favor of the contributions from the other light sources, e.g., by utilizing different purity regions as explained in connection with Fig. 4.
It is to be understood that the above embodiments and implementations are merely exemplary and susceptible to various modifications. For example, various other kinds of light sources could be used for implementing the pixels of the video display device. For example in addition or as an alternative to the white LED of the pixels, a yellow LED, or an amber LED could be utilized. Further, between the video display device and the video controller also other interface technologies may be used in addition or as an alternative to the Ethernet technology. Still further, it is to be understood that the video display device or the video controller may be equipped with various kinds of known functionalities of such devices.

Claims

A video display device (100), comprising:
- an arrangement of pixels (110) for displaying video content, the arrangement of pixels (110) comprising at least four individual light sources (111, 112, 113, 114) of different colors for each pixel (110); and

- a controller (120) for controlling the light sources (111, 112, 113, 114) of the pixels (110), the controller (120) being configured to select, depending on a color purity value, between at least a first mode in which said individual light sources (111, 112, 113, 114) are controlled to display the video content according to a first mapping of color information of the video content to intensities of said individual light sources (111, 112, 113, 114), and a second mode in which said individual light sources (111, 112, 113, 114) are controlled to display the video content according to a second mapping of color information of the video content to intensities of said individual light sources (111, 112, 113, 114).
The video display device (100) according to claim 1,
wherein the color information of the video content is encoded by intensities of three component colors and wherein three of said individual light sources (111, 112, 113) correspond to these component colors and the at least one other of said individual light sources (114) corresponds to a broadband light source, and
wherein the color purity value controls a contribution of the individual light sources (111, 112, 113) corresponding to the three component colors in relation to a relative contribution of the at least one other of said individual light sources (114) to the overall light emission of the pixel (110).
The video display device (100) according to claim 2,
wherein the component colors correspond to red, green, and blue, and
wherein a first of said individual light sources (111) emits red light, a second of said individual light sources (112) emits green light, and a third of said individual light sources (113) emits blue light, and
wherein the at least one other of said individual light sources (114) emits white light.
The video display device (100), according claim 2 or 3,
wherein in the first mode, for each of the three component colors, the intensity value indicated by the color information of the video content is mapped to a first corresponding intensity of a corresponding one of the three individual light sources (111, 112, 113) and to a first corresponding intensity of at least one other of the individual light sources (114),
wherein in the second mode, for each of the three component colors, the intensity value indicated in the color information of the video content is mapped to a second corresponding intensity of the corresponding one of the three individual light sources (111, 112, 113) and to a second corresponding intensity of the at least one other of the individual light sources (114), and
wherein the first corresponding intensity of the at least one other of the individual light sources (114) is higher than the second corresponding intensity of the at least one other of the individual light sources (114).
The video display device (100) according to claim 4,
wherein the second corresponding intensity of the at least one other of the individual light sources (114) is zero.
The video display device (100) according to any one of the preceding claims,
wherein the controller (120) is configured to select between a plurality of different modes, each corresponding to a different color purity value and a corresponding mapping of color information of the video content to intensities of said individual light sources (111, 112, 113, 114).
The video display device according to any one of the preceding claims,
wherein the controller (120) is configured to determine the first mapping and/or the second mapping is depending on the color information of the video content.
The video display device (100) according to any one of the preceding claims, comprising:
- an interface (150) configured to receive the color purity value.
The video display device (100) according to claim 8,
wherein the interface (150) is further configured to receive the video content.
The video display device (100) according to claim 9,
wherein the interface (150) is configured to receive the video content in a sequence of data packets, and
wherein the control information is included in one of the data packets.
A video controller (200), comprising:
- an interface (250) with respect to at least one video display device (100) comprising an arrangement of pixels (110) for displaying video content, the arrangement of pixels (110) comprising at least four individual light sources (111, 112, 113, 114) of different colors for each pixel (110),
wherein the interface (250) is configured to send a color purity value to the at least one video display device (100) to control the at least one video display device (100) to select between at least a first mode in which said individual light sources (111, 112, 113, 114) are controlled to display the video content according to a first mapping of color information of the video content to intensities of said individual light sources (111, 112, 113, 114) and a second mode in which said individual light sources (111, 112, 113, 114) are controlled to display the video content according to a second mapping of color information of the video content to intensities of said individual light sources (111, 112, 113, 114).
The video controller (200) according to claim 11,
wherein the interface (250) is further configured to send the video content.
The video controller (200) according to claim 12,
wherein the interface (250) is configured to send the video content in a sequence of data packets, and
wherein the color purity value is included in one of the data packets.
A system, comprising:
- at least one video display device (100) comprising an arrangement of pixels (110) for displaying video content, the arrangement of pixels (110) comprising at least four individual light sources (111, 112, 113, 114) of different colors for each pixel (110); and

- a video controller (200) configured to send a color purity value to the at least one video display device (100) to control the at least one video display device (100) to select between at least a first mode in which said individual light sources (111, 112, 113, 114) are controlled to display the video content according to a first mapping of color information of the video content to intensities of said individual light sources (111, 112, 113, 114) and a second mode in which said individual light sources (111, 112, 113, 114) are controlled to display the video content according to a second mapping of color information of the video content to intensities of said individual light sources (111, 112, 113, 114).
A method of controlling a video display device (100), the method comprising:
- controlling an arrangement of pixels (110) of the video display device (100) to display video content, the arrangement of pixels (110) comprising at least four individual light sources (111, 112, 113, 114) of different colors for each pixel (110); and

- depending on a color purity value, selecting between at least a first mode in which said individual light sources (111, 112, 113, 114) are controlled to display the video content according to a first mapping of color information of the video content to intensities of said individual light sources (111, 112, 113, 114), and a second mode in which said individual light sources (111, 112, 113, 114) are controlled to display the video content according to a second mapping of color information of the video content to intensities of said individual light sources (111, 112, 113, 114).