BE1026642B1 - COLOR CALIBRATION PROCEDURE 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 that includes a storage module. The display system is, for instance, composed of a deformable display, more in particular a flexible, stretchable and transparent deformable display based on light-emitting elements such as for instance 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 PROCESS FOR A REAL-TIME DEFORMABLE

The invention relates to a deformable display, more particularly the invention relates to a flexible, stretchable and transparent deformable display that uses or is based on light-emitting elements such as for example light-emitting diodes ( LEDs). The invention also relates to the uses and applications of such a deformable display, including systems and methods utilizing 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 (ITO) film 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 responding or switching circuits. As a result, transparent art displays are not really suitable for video applications. State-of-the-art flexible displays either represent a 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 seen as a combination of several small rigid bodies that are movably connected to each other or hinged together. Because of this partially movable configuration, 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 display is not transparent because several components have to generate the flexibility (and therefore have to focus on it). In fact, the bending of flexible printable displays (e.g. possibly OLED displays) is limited to a single direction or cardinal, and therefore multiple bending or deformation of the flex display sheet is highly susceptible to wear, broken joints or even broken components or joints.

In other words, current flexible displays present 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 distortion use.

Existing stretchable electronics are generally based on serpentine circuits, or meander geometry of interconnects as used, for example, in smartphone displays, or in a broader sense, using a folded or semi-curved electronic link for adaptive magnification (and then again being able to reduce } and hence stretching (and recompressing later) the distance between the electronic components.

Stretchable electronics thus 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 less space is available between the electronic components, such as LEDs, for creating a higher resolution.

Therefore, the use of known stretchable electronics in the art limits the required resolution for a display application, as we would often expect for a non-stretchable 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 maintains its deformable character at all times, 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 printed circuit board to provide power to the pixels and / or to connect two or more pixels together, preferably between two or more pixels at least one data link from one pixel to another.

By deformable display is meant, for example, that the display can be bent or rolled up, or brought into another shape or shape, or even stretched.

The method further comprises selectively, i.e., selectively, removing a substantial portion of the printed circuit board in the areas where none of the pixels or interconnects therebetween are present, such that a degree of transparency is achieved and such that any remaining portion of the printed circuit board is present. the printed circuit board becomes deformable, while the deformability is retained.

The method may include providing a driver module at each individual pixel for controlling the pixels at an individual pixel level.

According to one embodiment, the method comprises providing an arrangement of functional nodes (or nodes) in 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 where 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 wherein the pixels that are connected together are embedded pixels, the thermoplastic material being transparent, for example.

The thermoplastic material may be provided with perforations and / or hardened parts, and / or connecting parts, and / or mechanical modifications 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 instance 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 connected to each other.

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 link from one pixel to another is provided between two or more pixels.

The arrangement of pixels on the plurality of printed circuit boards, including connections therebetween, acts as a mesh support that is deformable in any direction at all times, without losing its deformability. The deformable display system may include a driver module for each individual pixel, disposed on the printed circuit board material, for controlling the individual pixel. The pixels may 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 be connected together by means of conductive paths, for example stretchable conductive paths, eg made of copper.

In a third aspect of the invention there is provided a color calibration method, wherein the method (or method) is performed by a processing system of a display system that includes 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, wherein at least one color, e.g. blue, is in the minority, and a second set of color points is defined, wherein the at least one color, e.g. blue, for example, is in the majority. An array formula is then defined that calculates colors to be added to the first or second set of color points to determine target colors for the first or second set of color points. Target colors are defined as the colors to be seen on the display system. A first calibration matrix is then defined by the array formula for the first set of color points and a second calibration matrix is defined by the array formula for the second set of color points. A matrix factor, being selectively selected in relation to the at least one color, e.g. blue, being in the minority or majority of the first or second set of color points and thus its perception as minor or significant, 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 the display system is viewed, colors can be perceived quite differently. 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 that includes a storage module comprises 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

5 viewing angle and a third set of color points are defined for a third viewing angle.

An array formula is then defined that calculates colors to be added to the first, second, or third set of color points 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 array formula for the first set of color points, while a second calibration matrix is defined by the array formula for the second set of color points, and a third calibration matrix is defined by the array formula for the third set of color points.

A matrix factor, which is 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 feature related to color.

Depending on the specifications, characteristics or variable parameters of such a display feature, colors can be interpreted quite differently.

The perceived colors can be influenced, for example, by the temperature or the 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 that includes a storage module comprises the following steps.

A first to nth - n integer sequence of color points are defined for a first to nth display feature with respect to color, respectively.

An array formula is defined in which colors to be added to the first to nth color point series are calculated to achieve target colors for the first to nth color point series.

Next, n calibration matrices are defined in which the first to nth calibration matrix, respectively, is defined by the array formula for the first to nth set of color points.

A matrix factor, which is selectively chosen in relation to the first to nth display characteristics 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 defined as 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. According to another aspect of the invention, a run-time color calibration method is provided by a display system processing system comprising a storage module, the method comprising: (i) loading operational conditions, e.g. with respect to at least one color, for example blue, which is in the minority or majority of the display system, (ii) calculation, possibly in real time, of a final calibration matrix, based on the operational conditions, by combining or weighing of first and second or first, second and third, or else first to nth 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 reached, more specifically in relation to 'what to add' or add colors to the existing colors to achieve the target colors, while these numbered calibration matrices, i.e. first, second ... to nth calibration matrix 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 one aspect of the invention, there is provided a computer program product, operating on a processing machine, for performing any of the steps of the methods in accordance with third, fourth or fifth aspect of the invention. In accordance with 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, there is provided a real-time deformable and transparent pixel-addressed device comprising a support comprising a printed circuit board and conductive paths mounted thereon, and an array of pixels mounted on the support, the pixels being connected to the support. each other by means of the conductive paths, with the printed circuit board partially removed from the support, defining a mesh shape with transparency to the support with open spaces between the conductive paths and the pixels, and wherein the mesh support provided with transparency is deformable at all times is in any direction without losing its conformability. By pixel-addressed device is meant a device (e.g. a display, but also e.g. 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, for example. 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 one aspect of the invention, there is provided a calibration technique for a pixel-addressed device, e.g., a real-time deformable and transparent pixel-addressed device in accordance with the preceding aspect above. With this calibration technique, more specifically being 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, where in (a) each LED or pixel node is connected sequentially, while in (b) there is only one 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 various types of display images, from (a) fixed to (b} deformable, to (c) real-time deformable image, for which calibration can be performed. are 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.

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 monitor), or more particularly, for example, an LED display, which maintains its deformable character at all times, for example by is able to eg to bend and stretch. The invention further provides a real-time deformable and transparent display capable of displaying high-resolution video images. By real-time deformable display is meant that the display is deformable directly or immediately upon request, or as a user of the display desires. In addition, the display is deformable while retaining its deformability. In other words, the display can be deformed with reversibility, which means that the display can not only be deformed but also able to revert to an original state or previous state or shape.

The invention relates to a solution to the problems or disadvantages mentioned in the background of the invention described above. The manner in which one of these problems was addressed, solutions emerged, 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, are not really suitable for video applications due to their high resistance ITO layers. As a solution, one could consider adding more metal to the display structure to improve conductivity and reduce resistance, but this would also mean decreasing transparency. Using more metal would further result in some sort of mirror effect due to the reflections of the added metal. In addition, such a solution would significantly 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, as it actually cannot be compared made. As an indication for this low resolution, for example, the pixel pitch is in the range of> 8 mm, for example. In addition, standard LED displays all have rather heavy and bulky equipment, including, for example, the mechanical carriers, PCB boards with components and driver chips. A lightweight, transparent, high-resolution 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, known flexible displays are usually limited in bending or deformation, have flexibility only in a single direction, and are therefore highly susceptible to wear, broken joints or even broken components or joints.

Adding more flexibility in multiple directions instead of say 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 to create a high-resolution application. A possible solution to this space constraint, in the case of an LED display for example, provides the LEDs (e.g. RGB LEDs) in a grid or matrix structure while being assembled on a multilayer PCB ensuring all connections and interconnections from anode to cathode . Reducing the number of connections can also be achieved by multiplexing connections within the circuit. Multiplexing, a technique well known in the display industry, is often also referred to as scanning, as rows or matrices are scanned one by one and the required LEDs are sequentially illuminated in only one row or array at a time. However, through stretchable electronics, and in particular circuit layout and display architecture, another high-resolution display solution is available. The high resolution display can now be made transparent, for example by removing unused or uncovered PCBs between the electronic circuit components and interconnects. To make a high resolution transparent display flexible, the PCB used (either single layer or multilayer) is not a standard epoxy but instead a flexible PCB is provided with the electronic circuitry including stretchable electronics to provide greater flexibility than common flexible screens with limited deformability as standard. In accordance with the invention, there is provided a transparent high-resolution stretchable and flexible display characterized by being deformable, and in addition, it may be real-time deformability while retaining deformability. In one embodiment, the stretchable electronics covering a flexible PCB include meander paths, e.g. made of copper, between rigid or rigid electronic components that represent, for example, the nodes where light-emitting diodes (LEDs) or light-emitting elements in general can be mounted. In order to achieve transparency, the flexible PCB material which is not covered with stretchable electronics, nor with any other electronics and thus uncovered or unused flexible PCB material which has no electronic functionality can be removed, for example by lasering, punching, water jet, milling or any other potentially abrasive process.

The aspect of multiplexing as a possible solution for reducing the number of connections within a circuit is now considered further, with reference to Figure 1, which illustrates multiplexing within a display matrix - an OLED display is shown here by way of example - as known in FIG. the technique. Traditional LEDs in display applications are usually driven using a passive matrix structure, referring to, for example, the common anode principle, although common cathode is also a possibility. Using multiplexing within the passive matrix LED display will result in many connections. For example, when considering a rectangular LED display, highly and efficiently multiplexed, only one of the four display sides is e.g. features an enormous amount of connections, especially in the case of a high-resolution configuration. Such an enormous amount of connections causes difficulties and is in fact undesirable. In accordance with the invention, a solution is provided to address this problem and thus to reduce the number of connections between the pixel nodes of a light-emitting display. In one embodiment, at each of the pixel nodes where an LED is mounted, a local pixel driver or LED driver is provided for each individual pixel or LED. As a result, only one LED voltage and one control signal are provided per pixel node or per LED node, and three connections (eg Vie, GND and one - possibly digital - signal) are sufficient per LED or pixel node for such voltage and control signal. The control signal for a particular 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 number of similar or identical LEDs are used, and therefore similar or identical LEDs are used over a given display area and therefore (the same) LED voltage can be offered at each individual LED or pixel node. A considerable number of multiplex 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 and SK6812 LED / drivers, using a one-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) illustrating a node 202 as well as the sequential control signal 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 reference can be made further to data sheets of the LED drivers. Alternatively, contrary to 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 provided at each individual pixel node, each driven 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 sort of redundancy is provided, while 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 polygon-shaped) display can be cut into arbitrary shapes without loss of video or image. However, in the case of the alternative option (as opposed to the one based on the NeoPixel principle) for generating the control signal, the potential in arbitrary forms 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 mentioned above, according to one 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 multiplexing systems, meaning multi-layer PCBs or multi-layer flexible (or flex) PCBs are required . Thus, with the local driver system, cheaper display systems can be offered due to a significant reduction in the number of (flex) PCB layers, although the additional cost of the individual LED or pixel drivers is taken into account. On the other hand, instead of cheaper systems,

more efficient and better performing multi-layer systems can be offered with additional redundancy.

For example, further using the multi-layer architecture, not just one LED voltage Vip, but a number of LED voltages Vie, Vien2… Viepn connected in parallel, could be supplied for 1, 2… n layers of (flex) PCB material.

When a e.g.

Visp1 line or

circuit fails, the other Vien2… Vienn lines will still be usable.

In addition, if such a plurality of parallel connected LED voltages Veni, Vienz ... Vienn are provided for a particular circuit part, instead of just one Vip voltage line, the total resistance of this particular circuit part will decrease, increasing the current, and thus the efficiency of the LED display will improve.

Referring further to the multilayer configuration, having more Veni, Vienz… Viepn lines results in more "cutting" capabilities for reshaping and / or (re) designing based on arbitrary shapes.

In addition, with the local driver system and pixel node addressing accordingly, in addition to more cutting options, more "slice" options are also achievable.

In other words, there is more freedom or flexibility, and there are more ways to seamlessly assemble screens or display display segments.

A modular system 301, 304 can therefore be built, as illustrated by way of example in Figure 3. Multiple display segments 302, 305 can be seamlessly joined and each has a local control 303, 306 or local interface.

Figure 3 (a) and Figure 3 (b) respectively illustrate a difference in display segment design, in terms of location selected to provide the local control 303, 306. In Figure 3 (a), the local control 303 is positioned for each display segment 302. in the top left corner of each display segment 302, while in Figure 3 (b), the local control 306 for each display segment 305 is positioned in the center of each display segment 305. The applicability and use of the local control 303, 306 is a result of, primarily with a local pixel driver or local LED driver for each individual pixel or LED, and consequently apply only a single control signal or control line for all LEDs or pixels.

As far fewer connections are now required to the local driver system, more technical space is available to provide additional nodes between the existing LED or pixel nodes of 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 may further include an integrated battery solution or storage device.

A standalone display system can thus be offered without the need for an additional external power supply or a wired connection to the mains.

The additional nodes can also be provided with infrared light-emitting elements, or so-called active markers, which are used in an optical tracking system.

Through 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, 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 vary in color, brightness, etc.

The calibration principle to determine light-emitting elements (eg.

LEDs, OLEDs) or pixels to appear 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. performed 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 is for 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 can be set for the individual colors.

In general, this common denominator is the value of the light output and color that each LED or pixel can achieve.

Target colors are defined here for clarity.

In the case of the RGB display, three target colors are therefore determined: Rtarg, Gtarg and Btarg, where 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 is the amount of green to be added and BonR is the amount of blue to be added 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] * [RtargX one = [and GinY gin. [car BonR RinZ GinZ BinZ RtargZ Or for all three colors we have: RonR RonG RonB RinX GinX BinX] [RtargX GtargX BtargX one GonG cons = ens GinY Ein | ; | Rcargr GtargY Bur 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 full set of parameters positive, moreover, it may even be preferable to achieve a better color saturation in the individual colors.

Thus, negative coefficients are allowed and can generally produce the correct mixed color, especially when white is considered.

Negative coefficients mean that the individual color cannot be calibrated (with corresponding calculations) to the saturated target color.

However, if negative coefficients are always taken into account, they will remain "present" and can still have an effect when mixing other input colors, maintaining the desired color when mixed.

When negative coefficients are allowed, deeper or more saturated colors can be displayed, or virtually deeper colors are charged for the calibration calculations.

The above calibration principle works fine, but there is a serious flaw in the CIE definition of colors.

This standard was created long ago when monochromatic light sources or narrowband emitters, such as LEDs, did not exist.

Moreover, the chromaticity diagram does not 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 can be completely different from what is measured with, for example, a spectrometer.

Two colors with exactly the same reading on the spectrometer could be perceived quite differently by the human eye due to e.g. mixing narrowband emitters and / or disregarding the brightness.

This is especially the case when, for example, the blue color has been calibrated and is shifted to a less saturated blue color.

The mixing ratio (adding red and green color) to the native blue can have completely different visual effects.

The human eye or brain locks the most perceived 'sharp' color

(usually red), with the other colors with less sharp perception (such as blue) being completely omitted.

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, meaning closer to the edge of the CIE curve.

With reference to both the mixing of narrowband emitters 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. making its perception deeper.

For example, by reducing the brightness of the less saturated color, one can achieve the more saturated or deeper color (as seen). Applying this in conjunction with light calibration (also known as clipping, meaning an artificial boundary is imposed on adding red or green to blue to further calibrate brightness) results in a display calibrated to correctly perceived colors from the human eye.

However, an important consequence is that since the brightness is changed, it 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 one 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 as saturated colors change.

Its main advantage is to overcome visual perception problems not yet documented by the CIE color standards, without assuming variations in brightness. Especially for narrowband emitters (e.g. LEDs), mixed colors can give a visual perception that is completely different from what is being 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 pictures, by means of a color calibration technique, giving the impression that much deeper saturated colors can be seen. This color calibration technique overcomes the drawbacks 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 in terms of color perception on the other. Regarding resolution perception, it should be noted that this is most sensitive in the red component, and much less sensitive in the blue component (for example, try to read blue text on a black background). In the case of color perception, given the same brightness situation, the most sensitive is perceived in x direction and less sensitive in y direction. Given 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 considered in terms of color calibration calculations. In accordance with one aspect of the invention, two calibration matrices are proposed instead of one to define the final calibration and provide 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 use when the saturated target color (blue in this example) is to be displayed. This is usually the matrix where 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, further referred to as FinalMatrix, is a function of the input color values and can therefore be defined as a function of the MixMatrix and the BlueMatrix, both respectively related to a particular type of content. The color calibration technique according to the invention is therefore also referred to as 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 should be displayed, i.e. no red and green colors should be displayed. The Factor is equal to 0 when all (or more than one) color is available. All kinds of variations for the Factor can be derived. By way of example, the Factor can be: Factor = 2 (Rin + Gin} / (Rin + Gin + Bin) where 0 <Factor <1 With the above definition of the Factor, the Factor is indeed O if there is no red or green in it. the signal is. Then FinalMatrix = BlueMatrix. If there is a total signal R = 1, B = 1 and G = 0 then Factor 1. In other words, if there is a total mix with a different color, the Factor becomes 1. MixMatrix or Matrix1 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 particular pixel. According to the formula, FinalMatrix can be calculated and then the traditional pipeline or calculation can be as described for the traditional calibration principle. In one embodiment, while storing Matrix1 and Matrix2, FinalMatrix is calculated in real-time. The principle can be used and / or extended for all three or more primary color and 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, the same pipeline can be used on top of it to compensate for viewing angle differences. Figure 7 refers to the viewing angle graph of an example of an LED. It is noticeable that at an angle the brightness of the individual colors is different. 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, it basically means that the color points are no longer correct. The above color calibration technique of the invention can be applied with two or more matrices, e.g. Matrix1 is the matrix at a viewing angle of 0 °, Matrix2 is the matrix at a viewing angle of 45 ° horizontal and a third matrix

For example, Matrix3 is for the viewing angle of the LED at an angle of 45 ° vertical. For the final calculation of the calibration matrix, FinalMatrix can be defined as: FinalMatrix = A. Matrix1 + B. Matrix2 + C. Matrix3 where A + B + C = 1 Depending on the viewing angle, FinalMatrix will adapt. Therefore, one can compensate 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 that provides feedback to the matrix processing side to determine R, G and B.

As previously stated, the invention provides a real-time deformable and transparent pixel-addressed device, such as a monitor (or display). The deformable character means that the calibration must also be done at an angle. In accordance with the invention, Figure 5 illustrates an embodiment of different types of display images 501, 503, 505, more specifically, in Figure 5 (a) a fixed image 501, in Figure 5 (b) a deformable image, and in Figure 5 (c) A real-time deformable image respectively shown for which calibration can be applied. The solid 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 the encapsulation of such 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, in accordance with one 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 some other possible optical effect (for example, stereoscopic, 3D or holographic). Polarizers could be provided with or in the transparent material so that a 3D

display 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 a typical Pepper's Ghost set-up, thus also generating a kind of 3D display.

In another embodiment, not only is a transparent thermoplastic material provided, but the display also retains a degree of perforation, as is particularly desirable for outdoor applications.

The perforation can be arbitrary or can match the original display structure, in any case resulting in a lighter display in weight and less vulnerable to wind loads.

The transparent thermoplastic material, or possibly another - whether or not transparent - material in which the display is embedded, can moreover be provided with further functionality such as, for example, local hardening, mechanical reinforcements, hooks, rings, buttons or interruptions for mechanical stiffness, or a connector for attaching a mechanical design according to the application, eg honeycomb floor mats or curtains.

For example, the local pavements can be used for a variety of mechanical attachments or fixtures, such as holes for screws, cords, buttons or buttons.

The stretch functionality or the deformable character of the display according to the invention can be locally "frozen" by means of locally hardening certain parts of the display, instead of, for example, the entire display.

According to one 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.

In a specific embodiment, a real-time deformable and transparent display with acoustic permeability is provided on a stretched transparent MYLAR film, and then this MYLAR film is driven by the electrostatic loudspeaker principle as known in the art.

That is why a system is provided that supplies sound and images together.

Obviously, such MYLAR film requires stretchability and continuous deformability, as well as the display applied to it.

In contrast to acoustic permeability, according to one 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 which is generally represented by a mesh or grid structure can be interpreted as traditional textiles, in terms of connectability by means of all possible connecting textile principles, including for example knitting, sewing, crocheting, sewing, gluing or pasting. Fastening display parts or material to textile, as well as connecting display parts with each other are interpreted here. By way of example, display parts could also be joined together by means of a zipper. In addition to those connecting 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., glue, 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 particular shaped deformable display. In particular, it is mentioned that a deformable, i.e. stretchable and flexible display according to the invention, can be rolled up because of its flexibility (and stretchability), and therefore transportation of such a display can be facilitated, in terms of space and manageability. In particular for outdoor display applications, LEDs are more favorable while being more robust than LCD, OLED or plasma and therefore resistant to more severe environmental conditions in terms of e.g. temperature or other weather conditions. For example, transparent OLED screens in automotive applications, e.g. applied to the rear window of a car, although they quickly become exhausted or worn out due to degradation of the organic material due to high temperatures from direct impact from the sun. With a transparent LED display, according to one embodiment of the invention, such rapid deterioration (or deterioration) will not occur. Given the above design choice of a real-time deformable and transparent display, the invention further addresses that the display and support, i.e. the PCB, are one resulting in a much lighter display system than other standard comparable displays, further requiring an additional frame. is on which further components are mounted. It is worth emphasizing that when using a flexible PCB as previously described, not only one side (in the front) but in fact both sides (front and back) of the flexible PCB can be used and therefore possible are covered with circuit components, LED junctions in particular, and stretchable electronics for example meander electronic paths between the circuit components of an LED matrix display structure. is displayed, and thus a double-sided deformable display is generated, 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 such that, for example, high quality video on one side is one high resolution is applied, while the other side, for example, is used to display text only, such as an auto queue for broadcasting applications, for example.

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. At locations 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 6064, should that 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 (11)

Conclusions A color calibration method performed by a processing system of a light-emitting display system based on light-emitting elements and comprising a storage module, the method comprising - performing a color measurement of a plurality of light-emitting elements of the display system; - determining color space values for the color measurement of the amount of light-emitting elements; - defining for the amount of light-emitting elements of a first set of target colors in color space values; - defining for the amount of light-emitting elements at least a second set of target colors in color space values; - calculating a first calibration matrix based on the color measurement and on the first set of target colors; - calculating at least a second calibration matrix based on the color measurement and on the at least second set of target colors; - defining a matrix factor, selected selectively in relation to the first and / or the at least second set of target colors, as a real number; - calculating a final calibration matrix, defined by the first and the at least second calibration matrix, each being weighted based on the matrix factor. A color calibration method according to claim 1, wherein the first set of target colors is defined such that at least one color is in the minority and / or the at least second set of target colors is defined such that at least one color is in the majority. A color calibration method according to claim 1, wherein the first set of target colors is defined for a first viewing angle and / or the at least second set of target colors is defined for a second viewing angle. A color calibration method according to claim 1, wherein the first and at least second set of target colors are defined for a first and at least second display feature related to color, respectively. A color calibration method according to claims 1 to 4, wherein the color space values are X, Y, Z tristimulus values. A color calibration method according to claims 1 to 5, wherein the matrix factor is a real number between 0 and 1. The color calibration method according to claim 1 to 6, which is applied to a deformable display system comprising: - a plurality of printed circuit boards; An arrangement of light-emitting elements on the plurality of printed circuit boards, such that at least a part of the plurality of printed circuit boards have one or more of the light-emitting elements mounted thereon, and such that the light-emitting elements are interconnected; wherein connections for providing power to the light-emitting elements and / or for connecting two or more of the light-emitting elements together are provided between the light-emitting elements or on the printed circuit boards; wherein at least one data link from one light-emitting element to the other is preferably provided between two or more of the light-emitting elements; and wherein the arrangement of light-emitting elements on the plurality of printed circuit boards, including connections therebetween, acts as a mesh support which is deformable in any direction at any time. The color calibration method of claim 7 applied to the deformable display system, further comprising: - a driver module for each individual light-emitting element, provided on the at least one of the plurality of printed circuit boards, for controlling the individual light-emitting element. The color calibration method of claim 7 or 8 applied to the deformable display system, wherein at least a portion of the plurality of printed circuit boards are flexible printed circuit boards and / or the light-emitting elements are interconnected by means of conductive tracks, for example stretchable conductive tracks, eg made of copper. The color calibration method of claims 7 to 9 applied to the deformable display system, wherein the light-emitting elements are, for example, light-emitting diodes (LEDs), such that the deformable display system is 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 a first and at least a second calibration matrix, related to the determination of target colors to be reached and stored in the storage module, in particular according to any one of methods 1 to 10; and (iii) applying the final calibration matrix as calculated in step (ii).