BE1026642A1 - COLOR CALIBRATION METHOD FOR A REAL-TIME DEFORMABLE AND TRANSPARENT DISPLAY - Google Patents

Abstract

The invention relates to a color calibration method, which is performed by a processing system of a display system comprising a storage module. The display system is, for example, composed of a deformable display, more in particular a flexible, stretchable and transparent deformable display based on light-emitting elements such as, for example, light-emitting diodes (LEDs). With this color calibration technique, the colors of the pixels within the deformable display can be dynamically adjusted in real time depending on the content of the video or images, giving the impression that much deeper saturated colors can be seen.

Description

COLOR CALIBRATION METHOD FOR A REAL-TIME DEFORMABLE AND TRANSPARENT DISPLAY

Technical field

The invention relates to a deformable display screen, more particularly the invention relates to a flexible, stretchable and transparent deformable display screen that uses or is based on light-emitting elements such as, for example, light-emitting diodes (LEDs). The invention also relates to the use and applications of such a deformable display, including systems and methods using such a deformable display. In addition, the invention relates to a flexible, stretchable and transparent display that is deformable in real time while retaining deformability.

Background of the invention

Transparent displays, such as LCD and OLED screens as currently known, typically use indium tin oxide layer (ITO) as thin films with optical transparency and comprising electrically conductive material. However, the high resistivity of such ITO layers allows very little current to be transferred, and thus results in very slow-reacting or switching circuits. As a result, transparent displays of the art are not really suitable for video applications.

State-of-the-art flexible displays either represent one-time flexibility or remain flexible, although such flexibility is always limited in some way. The latter flexible display that remains flexible can usually be thought of as a combination of several small rigid bodies that are movably connected or hingedly connected. Due to this partially movable configuration, the bending of such flexible screens is limited. In the case of one-time flexibility, the flexible display is bent and then usually held in a certain shape. The shape or shape is therefore generally defined during installation. It is further noted that the majority of such a one-off flexibility view is not transparent because multiple components must generate (and therefore focus on) flexibility. In fact, bending flexible printable displays (e.g., possibly OLED displays) is limited to one

BE2019 / 5970 single direction or cardinal, therefore multiple bending or deformation of the flex display sheet is highly subject to wear, defective joints or even broken components or connecting parts. In other words, current flexible screens are an interesting technical problem with only limited flexibility and represent the need to improve the robustness of the display due to its frequent bending or deformation use.

Existing stretchable electronics are generally based on serpentine circuits, or meander geometry of interconnects as used, for example, in smartphone displays, or more broadly using a folded or semi-curved electronic link for adaptive enlargement (and then being able to reduce again ) and from there stretching (and later being able to compress again) the distance between the electronic components. Thus, stretchable electronics means that more material, i.e. longer distance or connection, is used to make the interconnects such that the stretching functionality can be performed. But more material also means that there is less space between the electronic components, such as LEDs, for creating a higher resolution. Therefore, the use of known art stretchable electronics limits the resolution required for a display application, as we would often expect for a non-stretch standard display system.

Object of the invention

The object of the invention is to provide a real-time deformable and transparent display or pixel (addressed) device in general, which retains its deformable character at any time, such as being able to bend and stretch, for example. More specifically, the object of the invention is to provide a real-time deformable and transparent display capable of displaying high resolution video images.

Summary of the invention

In a first aspect of the invention, there is provided a method of manufacturing a deformable display (or display), the method comprising providing a printed circuit board and providing an arrangement of pixels on the printed circuit board. The method also includes providing connections on the circuit board to provide power to the pixels

BE2019 / 5970 and / or to connect two or more pixels together, preferably between two or more pixels at least one data connection from one pixel to another. For example, deformable display means that the display can be bent or rolled, or reshaped, or even stretched. The method further includes selectively, i.e. selectively, removing a substantial portion of the printed circuit board in the areas where none of the pixels or connections therebetween are present, such that a degree of transparency is achieved and such that the remaining part of the the printed circuit board becomes deformable, while the deformability is preserved. The method may include providing a drive module with each individual pixel for controlling the pixels at the individual pixel level. In one embodiment, the method comprises providing an arrangement of functional nodes (or nodes) between the arrangement of pixels, the functional nodes being connected to the pixels, the pixels being, for example, light-emitting elements, such as light-emitting diodes (LEDs) , and wherein the functional nodes are, for example, photovoltaic (PV) cells, with or without storage capacity, accelerators, gyroscopes, sensors, microphones / speakers, piezo elements, ultrasonic components, light-emitting elements. The method may further comprise providing a thermoplastic material in which the pixels connected to each other are embedded pixels, the thermoplastic material being, for example, transparent. The thermoplastic material can be provided with perforations and / or hardened parts, and / or connecting parts, and / or mechanical adaptations or appendages, either globally for the entire device, or otherwise applied locally. In addition, the thermoplastic material can be provided with fire-retardant material and / or with acoustically permeable material and / or sound-absorbing material, and / or optical components such as, for example, lenses, diffusers or polarizers.

In a second aspect of the invention, there is provided a deformable display system comprising a plurality of printed circuit boards and an arrangement of pixels on the plurality of printed circuit boards such that at least a portion of the plurality of printed circuit boards have one or more of the pixels mounted thereon, and such that the pixels are linked together. Within the deformable display system, connections are provided between the pixels, i.e. on printed circuit board material, while the pixels are mounted thereon, or directly on the printed circuit boards. Such connections are intended to supply power to the pixels and / or to connect two or more pixels together. Preferably, at least one data connection from one pixel to another is provided between two or more pixels. It

BE2019 / 5970 arrangement of pixels on the number of printed circuit boards, including connections therebetween, acts as a mesh-net support that is always deformable in any direction, without losing its deformability. The deformable display system may include a drive module for each individual pixel, applied to the printed circuit board material, for controlling the individual pixel. The pixels can be light-emitting elements, such as, for example, light-emitting diodes (LEDs), such that the deformable display system is a light-emitting display system, such as, for example, an LED display system. The printed circuit boards may be flexible printed circuit boards and / or the pixels may be connected together by conductive paths, e.g. stretchable conductive paths, e.g. made of copper.

In a third aspect of the invention, a color calibration method is provided, the method (or method) being performed by a processing system of a display system comprising a storage module. By way of example, the display system may be a deformable display system in accordance with the second aspect of the invention. The method consists of the following steps. A first set of color points is defined, with at least one color, e.g., blue, being in the minority, and a second set of color points, wherein the at least one color, e.g. blue according to, for example, in the majority. Next, an array formula is defined in which colors to be added to the first or second set of color points are calculated to determine target colors for the first or second set of color points. Target colors are defined as the colors to be perceived on the display system. A first calibration matrix is then defined by the matrix formula for the first set of color points, and a second calibration matrix is defined by the matrix formula for the second set of color points. A matrix factor, being selectively chosen in relation to the at least one color, e.g. blue, being in the minority or the majority of the first or second series of color points and thus their observation as small or important, is defined as a real number between 0 and 1. A final calibration matrix is defined by the first and second calibration matrix, where both are weighted based on the matrix factor.

In a fourth aspect of the invention, a color calibration method is provided for calibrating a display system with respect to color points for a specific viewing angle. Depending on the viewing angle, under which one looks at the display system, colors can be perceived quite differently. By way of example, the display system may again be a

BE2019 / 5970 deformable display system are in accordance with the second aspect of the invention. The method performed by a processing system of a display system comprising a storage module includes the following steps. A first set of color points is defined for a first viewing angle, a second set of color points is defined for a second viewing angle, and a third set of color points is defined for a third viewing angle. Next, an array formula is defined in which colors to be added to the first, second, or third set of color points are calculated to achieve target colors for the first, second, or third set of color points. Three calibration matrices are then defined. A first calibration matrix is defined by the matrix formula for the first set of color points, while a second calibration matrix is defined by the matrix formula for the second set of color points, and a third calibration matrix is defined by the matrix formula for the third set of color points. A matrix factor, selectively chosen in relation to first, second and third viewing angle color points, is defined as a real number between 0 and 1. A final calibration matrix is defined by the first, second and third calibration matrix, each of which is weighted based on the matrix factor .

In a fifth aspect of the invention, a color calibration method is provided for calibrating a display system depending on a display characteristic related to color. Depending on the specifications, characteristics or variable parameters of such a display characteristic, colors can be interpreted quite differently. For example, the perceived colors may be affected by the temperature or amount of current flowing through light-emitting elements such as LEDs of the display system. By way of example, again the display system may be a deformable display system in accordance with the second aspect of the invention. The method performed by a processing system of a display system comprising a storage module includes the following steps. A first to n-th -n being an integer series of color points is defined for a first to nth display characteristic, respectively, with respect to color. An array formula is defined in which colors to be added to the first to nth series of color points are calculated to achieve target colors for the first to nth series of color points. Then n calibration matrices are defined in which the first to nth calibration matrix is respectively defined by the array formula for the first to nth series of color points. A matrix factor, which is selectively chosen in relation

BE2019 / 5970 to the first to nth display characteristics with respect to color, is defined as a real number between 0 and 1. A final calibration matrix is defined by the first to nth calibration matrix, each of which is weighted based on the matrix factor .

The color calibration method according to the third, fourth or fifth aspect of the invention can be applied to a deformable display system in accordance with the second aspect of the invention.

In accordance with another aspect of the invention, a run-time color calibration method is provided by a processing system of a display system comprising a storage module, the method comprising: (i) loading operational conditions, e.g. with respect to at least one color, e.g. blue, that is in the minority or majority of the display system, (ii) calculation, possibly in real time, of a final calibration matrix, based on the operating conditions, by combining or weighing from first and second or first, second and third, or else first to n-th calibration matrix, as determined, for example, by the methods according to the third, fourth or fifth aspect of the invention, respectively, and thus these numbered calibration matrices relate to the determination of target colors to be achieved, more specifically in connection with 'what to add' or adding colors to the existing colors to achieve the target colors, while these numbered calibration matrices, i.e. first, second ... to n- the calibration matrix is retrieved for storage in the storage module; and (iii) applying the calculated final calibration matrix. By way of example, again the display system may be a deformable display system in accordance with the second aspect of the invention.

According to an aspect of the invention, a computer program product is provided, operating on a processing machine, for performing one of the steps of the methods in accordance with third, fourth or fifth aspect of the invention. According to an additional aspect of the invention, a non-temporary machine-readable storage medium stores the computer program product in accordance with the above.

According to an aspect of the invention, a real-time deformable and transparent pixel-addressed device is provided, comprising a carrier comprising a printed circuit board and conductive paths mounted thereon, and an array of pixels mounted on the carrier, the pixels connected to each other by by means of the conductive paths, with the printed circuit board partially removed, defining a mesh net shape with

BE2019 / 5970 transparency for the support with open spaces between the conductive paths and the pixels, and where the mesh support provided with transparency is always deformable in any direction without losing its deformability. Pixel-addressed device means a device (e.g., a display, but also, for example, a lamp or a light-emitting device can generally be interpreted) in which one or more individual pixels or one or more clusters of pixels can be given different data , such as color data. A cluster of pixels can be displayed as a whole as if it were just one pixel, or interpreted as a single pixel. In other words, the cluster appears as a whole.

According to an aspect of the invention, a calibration technique is provided for a pixel-addressed device, for example, a real-time deformable and transparent pixel-addressed device in accordance with the preceding aspect above. With this calibration technique, more specifically a color calibration technique, the colors of the pixels within the pixel-addressed device can be dynamically adjusted in real time depending on the content of the video or images, giving the impression that much deeper saturated colors can be seen.

Overview of the drawings

Figure 1 shows the aspect of multiplexing within a display matrix, here for example for an OLED display, in accordance with the prior art.

Figure 2 shows an embodiment of the control signal generated in different ways in accordance with the invention, wherein in (a) each LED or pixel node is connected sequentially, while in (b) there is only one single control line for all LEDs or pixels.

Figure 3 shows an embodiment of local control or local interface for enabling modularity within a display system, in accordance with the invention.

Figure 4 illustrates a chromaticity diagram also known as the color space CIE 1931. Figure 5 schematically illustrates an embodiment of different types of display images, from (a) fixed to (b) deformable, to (c) real-time deformable image, for which calibration may be used in accordance with the invention.

Figure 6 shows an embodiment of a real-time deformable and transparent pixel-addressed device in accordance with the invention.

BE2019 / 5970

Figure 7 illustrates a viewing angle graph of an exemplary LED in accordance with the art.

Description of the invention

The invention provides a real-time deformable and transparent pixel-addressed device, such as a display (or display), or more particularly, for example, an LED display, which retains its deformable character at any time, for example by being able to e.g. to bend and stretch. The invention additionally provides a real-time deformable and transparent display capable of displaying high resolution video images. Real-time deformable display means that the display can be deformed directly or immediately upon request, or as a user of the display desires. In addition, the display is deformable while retaining the deformability. In other words, the display can be deformed with reversibility, which means that the display can not only be deformed but is also able to return to an original state or an earlier state or shape.

The invention relates to a solution to the problems or drawbacks as set forth in the background of the invention described above. The way in which one of these problems was addressed, solutions arose and ultimately how all parts of the invention came about will now be described.

As mentioned earlier, current transparent displays, for example based on LCD or OLED with an acceptable resolution, due to their high resistance ITO layers, are not really suitable for video applications. As a solution, one could think of adding more metal to the display structure to improve conductivity and reduce resistance, but this would also mean that transparency would decrease. Using more metal would further result in a kind of mirror effect due to the reflections from the added metal. In addition, such a solution would considerably complicate the production process.

Although there is a transparent LED display, avoiding ITO layers and their negative impact on video applications, the resolution of such an LED screen is so poor that it cannot be taken into account, since there is actually no comparison made. For example, as an indication of this low resolution, the pixel pitch is in the range of> 8 mm. In addition, standard LED displays all have rather heavy and bulky equipment, including for example the mechanical carriers, PCB boards with components and

BE2019 / 5970 driver chips. A high resolution lightweight, transparent LED display solution is not available in the art.

Lightweight high-resolution display solutions can be found among the flexible displays. However, as described above, prior art flexible displays are usually limited in bending or deforming, have only flexibility in one direction, and are therefore highly susceptible to wear, defective connections or even broken components or connecting parts.

Adding more flexibility in multiple directions instead of, for example, one or two orthogonals can be achieved with stretchable electronics, although on the other hand, this results in more material and thus less space available for making a high-resolution application. A possible solution for this lack of space, in the case of an LED display for example, provides the LEDs (for example RGB LEDs) in a grid or matrix structure while being assembled on a multi-layer PCB ensuring all connections and interconnections from anode to cathode . Reducing the number of connections can also be achieved through multiplexing of connections within the circuit. A well-known technique in the display industry, multiplexing is often referred to as scanning, while rows or matrices are scanned one by one and the necessary LEDs are sequentially exposed in only one row or array at a time. Anyway, through stretchable electronics, and in particular circuit layout and display architecture, there is another high resolution display solution available. The high-resolution display can now be made transparent, for example by removing unused or uncovered PCBs between the electronic circuit components and interconnections. To make a high-resolution transparent display flexible, the PCB used (either single layer or multilayer) is not a standard epoxy but instead provides a flexible PCB with the electronic circuit including stretchable electronics to provide greater flexibility than ordinary flexible screens with standard deformability. In accordance with the invention, a transparent stretchable and flexible high-resolution display is provided characterized by being deformable, and moreover, it can be deformability in real time while retaining deformability. In one embodiment, the stretchable electronics covering a flexible PCB include meandering paths, e.g. made of copper, between rigid or rigid electronic components representing, for example, the nodes where light-emitting diodes (LEDs) or light-emitting elements in general can be

BE2019 / 5970 fitted. In order to achieve transparency, the flexible PCB material that is not covered with stretchable electronics, nor with any other electronics and thus uncovered or unused flexible PCB material that has no electronic functionality, can be removed, for example, by means of laser, punching, water jet, milling or other potentially abrasive process.

The aspect of multiplexing as a possible solution for reducing the number of connections within a circuit is now further considered, referring to Figure 1, which illustrates multiplexing within a display matrix - for example, an OLED display is shown here - as known in the art . Traditional LEDs in display applications are usually driven using a passive matrix structure, referring for example to the common anode principle, although common cathode is also an option. Applying multiplexing within the passive matrix LED display will result in many connections. For example, when a rectangular LED display is considered, highly and efficiently multiplexed, only one of the four display sides is e.g. equipped with a huge amount of connections, especially in the case of a high resolution configuration. Such an enormous amount of compounds causes difficulties and is in fact not desirable. In accordance with the invention, a solution is provided to address this problem and thus reduce the number of connections between the pixel nodes of a light-emitting display. In one embodiment, a local pixel driver or LED driver for each individual pixel or LED is provided on each of the pixel nodes where an LED is mounted. As a result, only one LED voltage and one control signal are provided per pixel node or per LED node, and three connections (eg Vled, GND and a - possibly digital - signal) are sufficient per LED or pixel node for such voltage and control signal. The control signal at a certain LED will communicate with the LED driver via a protocol (for example on driver IC or electronics) how much light must be emitted by this LED. Generally, in display applications, a large amount of similar or identical LEDs are used, therefore comparable or identical LEDs are used across a given display surface and therefore (the same) LED voltage can be offered at each individual LED or pixel button. A significant number of plywood connections have not yet been eliminated. The control signal, possibly digital, can be generated in several ways, as illustrated in Figure 2. A first option is for example NeoPixel, the Adafruit brand for individually addressable RGB color pixels and strips based on the WS2812, WS2811

BE2019 / 5970 and SK6812 LED / drivers, using a single wire control protocol. Traditionally, this uses an input and output signal in which each node is connected sequentially, as shown schematically in Figure 2 (a) in which a node 202 as well as the sequential control signal are illustrated as input 201 and output 203. With this configuration, the position of an LED in the grid can be determined by sending certain information or data (data), for which further reference can be made to data sheets of the LED drivers. Alternatively, unlike the NeoPixel principle, each driver IC has a unique address so that the control signal no longer has to be sent via input / output but can be offered on each individual pixel node, each powered by an individual LED driver . Hence, the other option requires only a single control signal or control line for all LEDs or pixels, as shown in Figure 2 (b) showing a pixel node 206 and the control line 204 including a branch 205 thereof to the respective pixel node 206. As a result, routing becomes much easier and, in addition, some kind of redundancy is provided, in the event that the control signal is interrupted somewhere, the rest of the circuit can remain active. For both ways of generating the control signal, the advantage is that, for example, a square or rectangular (or other polygonal) display can be cut into arbitrary shapes without loss of video or image. However, in the case of the alternative option (unlike those based on the NeoPixel principle) for generating the control signal, the potential in arbitrary shapes is quite unlimited, while for the other control signal configuration the number of possibilities is limited due to the sequential line or circuit.

It is noted that the LED driver or pixel driver could be a TFT circuit or a traditional silicon based driver.

As noted above, according to an embodiment of the invention, a local driver system is provided for each individual pixel or LED, resulting in far fewer connections required compared to traditional multiplex systems, meaning multilayer PCBs or multilayer flexible (or flex) PCBs are required . The local driver system can therefore offer cheaper display systems due to a significant reduction in the number of (flex) PCB layers, although the additional costs of the individual LED or pixel drivers are taken into account. On the other hand, instead of cheaper systems,

BE2019 / 5970, more efficient and better performing multilayer systems can be offered with additional redundancy. For example, making further use of the multi-layer architecture, not only one LED voltage Vled, but a number of LED voltages Vledi, V _L ed2 ... Vledh connected in parallel, could be supplied for 1, 2 ... n layers ( flex) PCB material. If a V _L EDi line or circuit fails, for example, the other V _L ed2 ... Vledh lines will still be usable. In addition, if such a plurality of parallel-connected LED voltages Vledi, V _L ed2 ... Vledh is provided for a particular circuit part, rather than just one Vled voltage line, the total resistance of this specific circuit part will decrease, causing the current to increase, and thus will improve the efficiency of the LED display. Referring further to the multi-layered configuration, having more Vledi, V _L ed2 ... Vledr lines results in more cutting options for reforming and / or (re) design based on arbitrary shapes. In addition, with the local driver system and pixel node addressing accordingly, in addition to more cutting options, more pasting options are also feasible. In other words, there is more freedom or flexibility, and there are more ways to seamlessly assemble screens or display display segments. Therefore, a modular system 301, 304 can be built, as illustrated by way of example in Figure 3. Multiple display segments 302, 305 can be seamlessly joined and each includes a local controller 303, 306 or local interface. Figure 3 (a) and Figure 3 (b) illustrate a difference in display segment design, respectively, in terms of location chosen to provide the local controller 303, 306. In Figure 3 (a), the local controller 303 is positioned for each display segment 302 in the upper left corner of each display segment 302, while in Figure 3 (b), the local controller 306 for each display segment 305 is positioned in the center of each display segment 305. The applicability and use of the local controller 303, 306 is a result of, primarily with a local pixel driver or local LED driver for each individual pixel or LED, and consequently applying only a single control signal or control line for all LEDs or pixels.

Since much less connections are now required with the local driver system, more technical space is available to provide additional nodes between the existing LED or pixel nodes with the LED matrix, offering additional functionality. For example, photovoltaic (PV) cells can be mounted or assembled on the additional nodes, and thus a power system can be integrated into the display application. The PV system can furthermore have an integrated battery solution or

BE2019 / 5970 storage device. Thus, a standalone display system can be offered without the need for an additional external power supply or a wired connection to the mains. The additional nodes can also be equipped with infrared light-emitting elements, or so-called active markers, which are used in an optical tracking system. Via selective camera systems, the infrared light, which is invisible and has a safe intensity to the human eye, can act as feedback to source images that allow compensation for geometric distortion of a display. Furthermore, resistive or capacitive nodes can be integrated to provide interaction with the display, such as, for example, touch screen pressure sensors. In addition to any additional functionalities for the aforementioned additional nodes, one can also refer to other well-known internet-of-things (loT) applications, including e.g. gyroscope, accelerator pedal, microphone / speaker, piezo elements, ultrasonic components and sensors such as motion sensors.

Figure 4 illustrates a chromaticity diagram, in particular the CIE 1931 color space, which is provided as a reference for the discussion regarding real-time positional and content-dependent calibration for the currently described real-time deformable and transparent pixel-addressed device . Since many different LEDs are used, it is known in the art that calibration of the LEDs is an important aspect, while each individual LED may differ in color, brightness, etc. The calibration principle to light-emitting elements (eg LEDs, OLEDs) or making pixels uniform on a screen is common, as is the math behind it. This principle is based on individual measurements at a given drive current for each pixel in the display. In the case of an RGB (red, green, blue) screen, the measurements are e.g. executed in the color space CIE 1931, where each color is represented in (x, y) and Y, for example:

Rin = (Rinx, Riny, RinY) = (RinX, RinY, RinZ)

Gin = (Ginx, Giny, GinY) = (GinX, GinY, GinZ)

Bin = (Binx, Biny, BinY) = (BinX, BinY, BinZ)

It is noted that (x, y) are normalized values of X, Y and Z being the so-called tristimulus values, while Y is a measure of the luminance of a color.

As mentioned, there is a deviation in color and light output for all LEDs or pixels. After analyzing these deviations, a 'common' target for the individual colors can be set. In general, this common divisor is the value of the light output and color that each LED or

BE2019 / 5970 pixel can reach. Target colors are defined for clarity. In the case of the RGB display, therefore, three target colors are determined: Rtarg, Gtarg and Btarg, for example for the color red:

Rtarg = (Rtargx, Rtargy, RtargY) = (RtargX, RtargY, RtargZ) and

RtargX = RinX. RonR + GinX. GonR + BinX. BonR

RtargY = RinY. RonR + GinY. GonR + BinY. BonR

RtargZ = RinZ. RonR + GinZ. GonR + BinZ. BonR

Here, RonR is the factor required for the red color individually, while GonR specifies how much green to add and BonR is the amount of blue to add to red so that the desired new target red color can be achieved.

In matrix format this leads to the equation:

RonR RinX GinX BinX -1 RtargX GonR = RinY GinY BinY RtargY BonR. RinZ GinZ BinZ. RtargZ.

Or for all three colors we have:

RonR RonG RonB RinX GinX BinX -1 RtargX GtargX BtargX GonR Gong GonB = RinY GinY BinY RtargY GtargY BtargY BonR BonG BonB. RinZ GinZ BinZ. .RtargZ GtargZ BtargZ.

According to one aspect of the invention, when applying the calibration principle, it is not necessary to make the entire set of parameters positive, moreover it may even be preferable to achieve better color saturation in the individual colors. Thus, negative coefficients are allowed and can generally yield the correct mixed color, especially when white is considered. Negative coefficients mean that the individual color cannot be calibrated (with corresponding calculations) to the target saturated color. However, when negative coefficients are always taken into account, they remain and can still have an effect when mixing other input colors, preserving the desired color when mixed. When negative coefficients are allowed, deeper or more saturated colors may be displayed, or virtual deeper colors may be charged for the calibration calculations.

The above calibration principle works fine, but there is a serious error in the ClE definition of colors. This standard was created long ago when monochromatic light sources or narrowband emitters, such as LEDs, did not exist. All the more, the chromaticity diagram does not hold

BE2019 / 5970 take into account differences in brightness of colors. In addition, a known problem is that when narrowband emitters are mixed together, the color perception of the mixed color may be completely different from what is measured with a spectrometer, for example. Two colors with the exact same reading on the spectrometer could be perceived quite differently by the human eye due to e.g. mixing narrowband emitters and / or not considering the brightness. This is especially the case when, for example, the blue color is calibrated and shifted to a less saturated blue color. The mixing ratio (addition of red and green color) to the native blue can have completely different visual effects. The human eye or brain locks out the most perceived 'sharp' color (usually red), completely omitting the other colors with a less sharp perception (such as blue). So, although - as according to CIE 1931 - colors measure exactly the same, they are perceived completely differently by the human eye. It is also well known in the display industry that less bright colors are considered more saturated, i.e. deeper, which means closer to the edge of the ClE curve. With reference to both narrowband emitter mixing and brightness problems above, it is perfectly possible to adjust, for example, two different blue colors by, for example, changing the brightness of the less saturated color, i.e., deepening its perception. For example, by decreasing the brightness of the less saturated color, one can achieve the more saturated or deeper color (as observed). Applying this in conjunction with light calibration (also known as clipping, which means that an artificial limit is imposed for adding red or green to blue for further calibration of the brightness) results in a display that is calibrated to correctly perceived colors of the human eye. However, an important consequence is that since the brightness is changed, this means that for that particular color, when mixed with other saturated colors, the desired perceived color is no longer achieved. So, when using that calibrated color with less light output, the mixed color points are wrong. This can be easily solved by choosing the original (computationally correct) values.

In accordance with an aspect of the invention, the calibration data is calculated in real time (and thus not stored) according to the current video content per individual pixel. Therefore, saturated colors are adjusted independently of mixed white so that the adjusted white point does not change with changing saturated colors. The main advantage is to use visual

BE2019 / 5970 to overcome perception problems not yet documented by the CIE color standards, without assuming brightness variations. Especially for narrowband emitters (e.g. LEDs), mixed colors can give a visual perception that is completely different from what is measured. In one aspect of the present invention, the colors of the light-emitting elements can be dynamically adjusted depending on the content of the video or images, using a color calibration technique, giving the impression that much deeper saturated colors can be seen. This color calibration technique overcomes the disadvantages described above (e.g. visual perception problems) and provides us with a means of adjustment and correction. Initial design should use this technique, especially for the blue channel (but can be used for all different channels if needed).

Human eye factors can be distinguished in terms of resolution perception on the one hand and color perception on the other. Regarding resolution perception, it should be noted that it is most sensitive in the red component, and much less sensitive in the blue component (for example, try reading blue text on a black background). In the case of color perception, given the situation of the same brightness, the most sensitive is observed in x direction and less sensitive in y direction. Considering the color perception with luminance variation, an extra dimension needs to be added, while less luminance is perceived as deeper or more saturated color.

The above is further taken into account in terms of color calibration calculations. According to an aspect of the invention, two calibration matrices are proposed instead of one for defining the final calibration and this provides a solution to the visual perception problems described above. One calibration matrix, further referred to as MixMatrix, is defined as the matrix to be used when multiple colors are displayed simultaneously. The other matrix, further referred to as BlueMatrix, is defined as the matrix to be used when displaying the target saturated color (blue in this example). This is usually the matrix in which the brightness of the blue color is reduced, resulting in a deeper color perception. To obtain correct mixed colors and maintain the correct white point, a formula must be applied where the final calibration matrix, hereinafter referred to as FinalMatrix, is a function of the input color values and can therefore be defined as a

BE2019 / 5970 function of the MixMatrix and the BlueMatrix, both related respectively to a certain type of content. The color calibration technique according to the invention is therefore also called content-dependent calibration, while a weight factor depending on the content is used to calculate the final calibration matrix.

FinalMatrix = Factor. MixMatrix + (1 - Factor). BlueMatrix

The Factor in the above formula is 1 when only the blue saturated target color is to be displayed, i.e. no red and green colors are to be displayed. The Factor equals 0 when all (or more than one) color is available. All kinds of variations for the Factor can be derived. For example, the Factor can be:

Factor = 2 (Rin + Gin) / (Rin + Gin + Bin) where 0 <Factor <1

With the Factor definition above, the Factor is indeed 0 if there is no red or green in the signal. Then FinalMatrix = BlueMatrix. If there is a total signal R = 1, B = lenG = 0, then Factor 1. In other words, if there is a total mix with a different color, the Factor becomes 1.

MixMatrix or Matrixl and BlueMatrix or Matrix2 can be stored for each individual pixel of the display. The Factor is calculated using RGB input values (content) for that specific pixel. According to the formula, FinalMatrix can be calculated and then the traditional pipeline or calculation as described for the traditional calibration principle can be used. According to an embodiment, while Matrixl and Matrix2 are stored, FinalMatrix is calculated in real time. The principle can be used and / or extended for all three or more primary colors in a display. In the case of a real-time deformable and transparent pixel-addressed device, such as a display, in accordance with the invention, one can use the same pipeline on top of that to compensate for viewing angle differences.

Figure 7 refers to the viewing angle graph of an example of an LED. It is striking that the brightness of the individual colors differs at an angle. However, this fact becomes very important in the case of a continuously moving position of the display or screen. By moving the position, an observer looking at the screen will also perceive different brightness of the individual pixels. If multiple primary colors are displayed, this basically means that the color points are no longer correct. The above color calibration technique of the invention can be used with two or more matrices, e.g. Matrixl is the matrix at viewing angle 0 °, Matrix2 is the matrix at a viewing angle of 45 ° horizontally and a third matrix

BE2019 / 5970

For example, Matrix3 is for the viewing angle of the LED at an angle of 45 ° vertically. For the final calculation of the calibration matrix, FinalMatrix can be defined as: FinalMatrix = A. Matrixl + B. Matrix? + C. Matrix3 where A + B + C = 1

Depending on the angle of view, FinalMatrix will adapt. Therefore, one can compensate in real time for color and brightness differences on the display.

For example, to detect angle variations on the display, one can e.g. add local gyroscopes or local infrared markers. Such infrared markers can be interpreted by a processing system where feedback is given on the matrix processing side to determine R, G and B.

As mentioned previously, the invention provides a real-time deformable and transparent pixel-addressed device, such as a display (or display). The deformable character means that the calibration must also take place at an angle. In accordance with the invention, Figure 5 illustrates an embodiment of different types of display images 501, 503, 505, more particularly, in Figure 5 (a) a solid image 501, in Figure 5 (b) become a deformable image, and in Figure 5 (c) a real-time deformable image respectively shown for which calibration can be applied. The fixed character of the fixed image 501 is indicated by straight lines 502, while the deformable character of the deformable image 503, 505 is indicated by curved lines 504, 506. In addition, the real-time deformability is further indicated in Figure 5 (c). with the arrow t where t stands for time.

The mechanical aspects of a real-time deformable and transparent pixel-addressed device, such as a display, in accordance with the invention are now discussed. In general, these mechanical aspects refer, for example, to the interconnection between different parts of a display in accordance with the invention, as well as encapsulating such a display, e.g. by means of silicone, stretched in a frame, whether or not combined with nylon. To improve robustness while maintaining transparency, the real-time deformable and transparent display according to an embodiment of the invention can be embedded in a transparent thermoplastic material. In addition, the transparent thermoplastic material applied over the LED can lead to a lens function (including, for example, a Fresnel lens), diffusion or other possible optical effect (for example, stereoscopic, 3D or holographic). Polarizers could be provided with or in the transparent material to create a 3D

BE2019 / 5970 representation could be generated. In addition, due to the very high transparency of the display according to the invention, the display could also be used in typical Pepper's Ghost setup, thereby generating a kind of 3D display. In another embodiment, not only is a transparent thermoplastic material provided, but the display also continues to have a degree of perforation, as is particularly desirable for outdoor applications. The perforation can be arbitrary or can correspond to the original display structure, in any case resulting in a lighter display in weight and less vulnerable to wind load. The transparent thermoplastic material, or possibly another - whether or not transparent - material in which the screen is embedded, can additionally be provided with further functionality such as, for example, local hardening, mechanical reinforcements, hooks, rings, knobs or interruptions for mechanical stiffness, or a connecting piece for fixing a mechanical design according to the application, eg honeycomb floor mats or curtains. The local surfacing can be used, for example, for a variety of mechanical attachments or devices, such as holes for screws, cords, buttons or knots. The stretching functionality or deformable character of the display according to the invention can be frozen locally by locally hardening certain parts of the display, instead of, for example, the entire display. According to an embodiment, the thermoplastic material is not only transparent, but also acoustically permeable, such that a display can be mounted in front of a loudspeaker, and therefore the display does not interfere in terms of audio signal reduction. According to a specific embodiment, a real-time deformable and transparent acoustic permeability display is provided on a stretched transparent MYLAR film, and then this MYLAR film is controlled by the electrostatic loudspeaker principle as known in the art. That is why a system is provided that provides sound and images together. Obviously, such MYLAR film requires stretch and continuous deformability, as does the display applied to it. In contrast to acoustic permeability, according to an embodiment the display according to the invention could also be provided with sound-absorbing material. Referring further to connecting or attaching other parts to a display in accordance with the invention, it is noted that a display generally represented by a mesh or grid structure can be interpreted as traditional textiles, in terms of

BE2019 / 5970 connectivity through all possible connecting textile principles, including knitting, sewing, crocheting, sewing, sticking or sticking. Attachment of display parts or material to textiles, as well as joining display parts together are interpreted here. By way of example, display parts could also be linked together by means of a zipper. In addition to those bonding textile mechanisms, embodiments also include attaching display parts (e.g. to each other or to a particular surface) by means of a permanent (e.g. adhesive, epoxy) or semi-permanent (e.g. post-it) adhesive.

According to a special embodiment, the deformable screen according to the invention is combined with 3D printing applications. For example, 3D printed material can be combined with a certain shaped deformable display.

It is specifically mentioned that a deformable, i.e., stretchable and flexible display in accordance with the invention can be rolled up because of its flexibility (and stretchability), and thus transportation of such a display can be facilitated, in terms of space and manageability.

Especially for outdoor display applications, LEDs are more favorable while more robust than LCD, OLED or plasma and therefore resistant to harsher environmental conditions in terms of e.g. temperature or other weather conditions. For example, transparent OLED screens in automotive applications, e.g. affixed to the rear window of a car are used, although they quickly become worn out or worn out due to decomposition of the organic material due to high temperatures from direct sun impact. According to an embodiment of the invention, such a rapid deterioration (or deterioration) will not occur with a transparent LED display.

Given the above design choice of a real-time deformable and transparent display, the invention further addresses that the display and the support, ie the PCB, are one resulting in a much lighter display system than other standard comparable displays, requiring an additional frame is where further components are mounted. It is worth emphasizing that when using a flexible PCB as previously described, not only one side (front), but in fact both sides (front and back) of the flexible PCB can be used and therefore possible covered with circuit components, LED nodes in particular, and stretchable electronics, for example

BE2019 / 5970 meander electronic paths between the circuit components of an LED matrix display structure. In other words, the back side next to the front of the flexible PCB can be assembled and manufactured to display a display, thus generating a double-sided deformable display, in accordance with the invention. The video or images or settings accordingly need not be similar or even identical on both sides and may therefore differ so that, for example, one side uses high quality video with high resolution, while the other side is used for example to display text only. , such as for example an auto queue for broadcasting applications.

Referring now to Figure 6, an embodiment is given for a real-time deformable and transparent pixel-addressed device 601, such as a display, in accordance with the invention. Vertical 603 and horizontal 602 conductive paths are illustrated herein, as are pixels or LEDs 604 at nodes where these vertical 603 and horizontal 602 paths intersect. In places between the pixels or LEDs 604 further functionality can be added by means of the additional nodes 606, e.g. photovoltaic PV cells or infrared markers or sensors. However, such further functionality can also replace a regular LED or pixel by mounting the additional node 606a, in case that would be desired or required by the design of the pixel-addressed device 601, which can be embedded in or covered with thermoplastic material 605.

Claims (8)

Conclusions A color calibration method performed by a processing system of a display system, comprising a storage module, the method comprising - a first set of color points is defined, at least one color being in the minority; - a second set of color points is defined, the at least one color being the majority; - an array formula is defined in which colors to be added to the first or second set of color points are calculated to achieve target colors for the first or second set of color points; - a first calibration matrix is defined by the matrix formula for the first set of color points; - a second calibration matrix is defined by the matrix formula for the second set of color points; an array factor, being selectively chosen in relation to the at least one color that is in the minority or majority of the first or second set of color points, is defined as a real number between 0 and 1; - a final calibration matrix is defined by the first and second calibration matrix, both of which are weighted based on the matrix factor. 2. A color calibration method performed by a processing system of a display system, comprising a storage module, the method comprising a first set of color points is defined for a first viewing angle; a second set of color points is defined for a second viewing angle; - a third set of color points is defined for a third viewing angle; - an array formula is defined in which colors to be added to the first, second or third set of color points are calculated to achieve target colors for the first, second or third set of color points; - a first calibration matrix is defined by the matrix formula for the first set of color points; BE2019 / 5970 - a second calibration matrix is defined by the matrix formula for the second set of color points; - a third calibration matrix is defined by the array formula for the third set of color points; an array factor, being selectively chosen in relation to first, second and third viewing angle color points, is defined as a real number between 0 and 1; - a final calibration matrix is defined by the first, second and third calibration matrix, each of which is weighted based on the matrix factor. A color calibration method performed by a display system processing system, comprising a storage module, the method comprising a first to nth set of color points is defined for a first to nth display characteristic related to color, respectively; - an array formula is defined in which colors to be added to the first to nth set of color points are calculated to achieve target colors for the first to nth set of color points; - a first to nth calibration matrix is defined by the array formula for the first to nth set of color points; an array factor, being selectively chosen in relation to the first to nth display characteristic related to color, is defined as a real number between 0 and 1; - a final calibration matrix is defined by the first to nth calibration matrix, each of which is weighted based on the matrix factor. The color calibration method according to claims 1 to 3, which is applied to a deformable display system comprising: - a number of printed circuit boards; an arrangement of pixels on the number of printed circuit boards, such that at least part of the number of printed circuit boards have one or more of the pixels mounted thereon, and such that the pixels are connected to each other; connections to provide power to the pixels and / or to connect two or more of the pixels together are provided between the pixels or on the printed circuit boards; BE2019 / 5970 wherein preferably between two or more of the pixels at least one data connection from one pixel to another is provided; and wherein the arrangement of pixels on the plurality of printed circuit boards, including connections therebetween, acts as a mesh-net support that is deformable in any direction at any time. The color calibration method according to claim 4 applied to the deformable display system further comprising: a driver module for each individual pixel, provided on the at least one of the number of printed circuit boards, for controlling the individual pixel. The color calibration method according to claim 4 or 5 applied to the deformable display system, wherein at least part of the plurality of printed circuit boards are flexible printed circuit boards and / or the pixels are connected to each other by conductive paths, e.g. stretchable conductive paths, e.g. made of copper. The color calibration method according to claims 4 to 6 applied to the deformable display system, wherein the pixels are light-emitting elements, such as, for example, light-emitting diodes (LEDs), such that the deformable display system is a light-emitting display system, such as, for example, an LED display system . A run-time color calibration method performed by a display system processing system, comprising a storage module, the method comprising: (i) loading operational conditions of the display system; (ii) calculating a final calibration matrix, based on the operational conditions, by combining or weighing first to nth calibration matrix, related to the determination of target colors to be achieved and stored in the storage module, in particular according to a from methods 1 to 7; and (iii) applying the final calibration matrix as calculated in step (ii).