WO2023275224A1 - Pixel configuration in light emitting modules - Google Patents

Abstract

The invention relates to an arrangement of light emitting elements for a light emitting module, wherein the light emitting elements are configured in a hexagonal arrangement such that a light emitting element is provided in the center of each hexagon and, each light emitting element is centered on an edge of a hexagon, such that the light emitting elements are arranged along a first, a second and a third row, wherein the light emitting elements have an elongated shape, such as a rectangle, having a length greater than a width, the orientation of the length defining the orientation of the light emitting element, and wherein each pair of two adjacent light emitting elements have a different orientation.

Description

Title: PIXEL CONFIGURATION IN LIGHT EMITTING MODULES

TECHNICAL FIELD BACKGROUND

The present disclosure relates to the field of light emitting modules, arrangement of light emitting elements for light emitting modules, a display comprising such an arrangement, a method and a use of said arrangement.

BACKGROUND

A light emitting display is usually made of a plurality of light emitting modules. Various light emitting modules can be driven by the same carrier (for example a PCB interposer), or each module can have its own dedicated carrier. It is however important that on the assembled light emitting display, the seams between adjacent modules remain invisible.

It is a current tendency to use light emitting elements having a smaller size in order to improve the display resolution. Today's trend is to build displays with for example micro LEDs (pLEDs).

The use of micro LEDs (pLEDs) in LED display technology brings about new challenges to be solved. pLEDs have, as indicated in the name, a micrometer-size scale. Accordingly, they also require micrometer size scale contacting methods. With the introduction of micro-LEDs, a reduction in the pixel pitch brings about new problems in terms of available space for installing the electronic features associated to each individual LED.

It is therefore desirable to arrange the LEDs in such a way that the space around them is optimal for the required driving circuits, connections, electronic switches, etc. as they take a minimal space around or underneath each LED. Indeed, the finer the pixels become, the smaller the pixel pitch, the less space there is in between for the installing the required electronics. Although the smaller the LEDs are, less current is needed to drive them, some components are not scalable in size, and may not be made smaller.

A solution is then to maximize the space around each LED by providing an optimal geometrical arrangement of the LEDs.

It is known to try to arrange LEDs on a display in the most optimal way in order to save space. In fact, each LED requires its own electronics, and the space between the individual LEDs needs to be optimized in order to fit the electronics within this space.

However, regular arrangements of LEDs may also result in visual artifacts such as Moire effect.

An LED display is typically composed of Red, Green and Blue LEDs, the combination of three red, green, and blue LEDs forming a pixel. A known solution is to arrange the LEDs on the display as shown in Figure 1A.

In general, LEDs 100 are arranged in clusters of red (R), green (G) and blue (B)

LEDs, each cluster forming a pixel 110. This has some disadvantages as it provides a new constraint on the use of the space around each LED. If other configurations of LEDs were used, a more optimal use of the space around each LED would be possible.

A more regular distance between individual LEDs would be better than grouping LEDs in an RGB cluster, wherein the middle one has almost no space available for positioning its necessary driving electronic components, as shown in Figure 1A.

A known alternative to overcome this problem is to arrange the LEDs in a square arrangement, as shown in Figure IB. In fact, the Red, Green and Blue LEDs forming pixel 210 are more equally spaced.

Many variations can be made by providing permutations and/or combinations and/or mirroring of the position of the R, G and B LEDs.

A first advantage is that the space is more equally distributed between LEDs. This way, the same area that is needed for driving the electronics is provided to each pixel, at least horizontally and vertically. With a closer look, one can see that there is more space available between a LED and its surrounding diagonal neighbors than with its direct horizontal and vertical neighbors. This observation leads to new possible arrangements, as explained hereunder:

A known alternative shown in Figure 1C is to shift the rows (or columns) by a half pixel pitch.

At first this seems to create more space, however, with a closer look, and looking at Fig. 1C at 45°, it results in similar arrangement as that of Figure IB in terms of equal distance between LEDs.

A honeycomb arrangement, with 60° angles is indeed still better. Around each LED center, one can draw an imaginary hexagon with an LED at each corner. The distance between all LEDs is identical, providing an equal area around each pixel for positioning electronics, as shown in Figure ID. This creates horizontally straight rows and serrated columns.

While there is improved space around each LED, new problems arise. In fact, it is extremely difficult to manufacture a display with serrated borders. In fact, the LEDs are usually assembled on a substrate which is difficult to cut, such as glass. In addition, if two LED modules are assembled next to each other, the tolerances at the edges must be even more precise, otherwise the edges may not fit together, like two pieces of a puzzle. If the LEDs are micro-LEDs, the distance between two consecutive rows would be about 300 microns, and thus the edges of the serrated border would also be in this range of dimensions.

There is thus a need for improvement in the art.

SUMMARY

According to an aspect there is provided an arrangement of light emitting elements for a light emitting module, wherein the light emitting elements are configured in a hexagonal arrangement such that a light emitting element is provided in the center of each hexagon of the hexagonal arrangement and, each light emitting element is centered on an edge of a hexagon of the hexagonal arrangement, such that the light emitting elements are arranged along a first, a second and a third row, the first, second and third rows forming an angle of 120 or 60 degrees one with respect to the other.

Such an arrangement is optimal in terms of space as it provides a higher sampling efficiency and equidistance between light emitting elements. The hexagons of the hexagonal arrangement are fictive. The distance between the light emitting element in the center and the light emitting elements on the edges is constant. In addition, a hexagonal arrangement is closer to the arrangement of photoreceptors in the human eye.

According to an aspect there is provided an arrangement of light emitting elements for a light emitting module, wherein the light emitting elements are configured in a hexagonal arrangement such that a light emitting element is provided in the center of each hexagon of the hexagonal arrangement and, each light emitting element is centered on an edge of a hexagon of the hexagonal arrangement, such that the light emitting elements are arranged along a first, a second and a third row, the first, second and third rows forming an angle of 120 or 60 degrees one with respect to the other, wherein the light emitting elements have an elongated shape with a length and a width, the length being greater than the width, the orientation of the length defining the orientation of the light emitting element, and wherein each pair of two adjacent light emitting elements have a different orientation.

The difference in orientation is preferably of at least 2 degrees, preferably at least 5 degrees, even more preferably at least 10 degrees. When the elongated light emitting elements have different orientation in the arrangement, it breaks the symmetry of the arrangement and thereby reduces artefacts such as Moire.

A difference in orientation of at least 15 degrees, or even 25, or 45 degrees may provide additional advantages.

When the light emitting elements present a higher symmetry, such as with circles or even hexagons, they provide a higher sampling efficiency, equidistance between the light emitting elements, reduced aliasing effect, but also an improved angular resolution.

Optionally, the orientation of the length of the light emitting elements follows a random distribution over the arrangement.

A random distribution in the statistical sense reduces the appearance of visual artefacts drastically to the viewer, such as the appearance of Moire patterns.

Optionally, the light emitting elements which are provided at the edges of a hexagon in the hexagonal arrangement are such that their length is oriented along the edge of the hexagon on which it is centered.

Such an arrangement improves the space around each light emitting element. The available space can be used for arranging the electronics associated to each light emitting element.

Preferably, the light emitting element in the center of each hexagon, has an orientation which is substantially perpendicular to the orientation of any of the two light emitting elements provided on opposing edges of the hexagon.

This further improves the optical rendering of the display and provides additional space in the arrangement.

Preferably, the orientation of the arrangement is defined by the orientation of one of the rows with respect to the horizontal axis, and wherein the orientation of the arrangement is at an angle with respect to the horizontal axis.

Rotating at angle the arrangement is also a possibility to trick the viewer's eye as it reduces the perceived repeatability in the arrangement and thereby reduces visual artefacts.

Preferably, the light emitting elements emit at least red, green, and blue light.

Preferably each light emitting element is a sub-pixel, and each composition of at least a red (R), green (G), and blue (B) sub-pixel forms a pixel, and wherein each type of sub pixel has a different color. Optionally, a pixel may further comprise at least one additional red, green, or blue sub-pixel, such that each pixel is composed of four sub-pixels of which one is duplicated and two are distinct.

This provides the possibility to implement different types of patterns such as a Bayer pattern for RGGB. It further provides the possibility to implement virtual pixels in a display.

Preferably, at least one sub-pixel per pixel comprises six distinct virtual pixels, preferably at least two sub-pixels per pixel, even more preferably three sub-pixels per pixel, and even more preferably four sub-pixels per pixel.

The more sub-pixels of a pixel are capable of providing virtual pixels, the entire arrangement can be filled with virtual pixels uniformly, the virtual pixel pitch is then more uniformly distributed throughout the arrangement. In fact, the virtual pixels around each sub pixel are distributed in a circle around said sub-pixel. When all sub-pixels offer this possibility, a new circle, which defines the new virtual pixel pitch, is obtained around each sub-pixel.

Optionally, the sub-pixels are arranged in each row of the hexagonal arrangement, following an alternating sequence of sub-pixel types, such as R, G, B, R, G, B, etc.

This arrangement is particularly appropriate for pixels composed of a red, a green and a blue sub-pixel.

Preferably, the sub-pixels are arranged along the first and second row of the hexagonal arrangement following a sequence wherein the duplicated sub-pixel is provided between the two distinct sub-pixels, and in alternance, in one out of two third rows of the hexagonal arrangement, alternating the distinct sub-pixels and in the second out of two third rows of the hexagonal arrangement with only the duplicated sub-pixel.

This provides a different arrangement of virtual pixels. However, all sub-pixels do not provide six virtual pixels. It may however still be sufficient for an improved virtual resolution for some applications.

Preferably, the sub-pixels are arranged along the first row of the hexagonal arrangement, by providing, in alternance a first row of the first row with only the duplicated sub-pixel, and a second row of the first row with alternating the distinct sub-pixels, and along the second and third row of the hexagonal arrangement, by providing, in alternance, along a first row of the second row and third row, the duplicated sub-pixel in alternance with one of the distinct sub-pixels, along a second row of the second row and third row, the duplicated sub-pixel in alternance with the other of the distinct sub-pixels. Such an arrangement ensures that all sub-pixels provide six virtual pixels, thereby improving uniformly throughout the arrangement the virtual pixel pitch.

Optionally, the sub-pixels along each row of the first row of the hexagonal arrangement are arranged with the same type of sub-pixels within a row, the type of sub-pixel being alternated between two consecutive rows of the first row.

This arrangement is for example compatible with the pattern of a polarization filter for 3D viewing.

Preferably, alternating the type of sub-pixel between two consecutive rows is performed by providing the duplicated sub-pixel between the two distinct sub-pixels.

Optionally, the arrangement is configured to cooperate with the pattern of a polarization filter to generate 3D images, wherein a first set of virtual pixels is arranged along a pattern of a polarization filter for the left eye, and a second set of virtual pixels is arranged along the pattern of a polarization filter for the right eye.

Such an arrangement can be used simultaneously for 3D viewing purposes but also for 2D, and it additionally provide the possibility to use virtual pixels, and thereby improve the resolution or virtual resolution of the display.

In an aspect there is also provided a light emitting module comprising the arrangement of light emitting elements.

Preferably, the light emitting elements are any one of LEDs, OLEDs, and variations thereof, QD-LEDs, EL-QLEDs, AMOLEDs, mini-LEDs, micro-LEDs.

Optionally, the light emitting elements are provided on a TFT layer.

Preferably, said TFT layer is deposited on a flexible substrate, such as polyimide.

A flexible substrate provides the possibility to facilitate the manufacturing of edges having different shapes, such as serrated edges, or of providing any desired shape to the light emitting module.

In an aspect, there is also provide a display module comprising at least two light emitting modules which comprise the arrangement of light emitting elements, wherein the edges of each light emitting module are serrated such that they follow the light emitting elements arrangement at the edges, and such that when the at least two light emitting modules are assembled to make a display, their edges fit into each other, and the distance between two consecutive light emitting elements remains constant throughout the display.

In an aspect, there is also provided a display module comprising at least three light emitting modules having the arrangement of light emitting elements, wherein the edges of the light emitting module are straight, and wherein at least three different types of light emitting modules are provided, each type having a different shape to provide a rectangular display after assembly of the at least three different types of module, and such that the distance between two consecutive light emitting elements remains constant throughout the display.

Optionally, the different types of modules comprise a triangle or a quadrilateral whose at least one corner has an angle which is a multiple of 60°.

The edges of these individual modules are parallel to the first, second and/or third row of the hexagonal arrangement.

Preferably, the different types of modules comprise at least one of, a first type having a shape of a parallelogram, a second type having the shape of a triangle, and a third type having the shape of a trapezoid.

The combination of all these individual modules provides a tiled display, or display module, having a standard rectangular shape of any size for viewing purposes.

In another aspect, there is provided a computer implemented method for displaying images using the arrangement of sub-pixels as defined previously.

Optionally, the method comprises the step of, at each frame of a sequence of six frames, displaying an image with a different set of virtual pixels for each sub-pixel having six distinct virtual pixels.

Optionally, the method comprises the step of displaying the virtual pixels associated to a pixel in a random order at each frame of a sequence of six frames.

In another aspect, there is provided the use of the arrangement of sub-pixels defined above for displaying images on a display.

The arrangement defined can be used by any type of display technology having sub-pixels.

For example, the display technology is at least one of a LCD display, a LED display, such as OLED display, AMOLED display, plasma display, Quantum dot displays, etc.

Further benefits and advantages of the present invention will become apparent after a careful reading of the detailed description with appropriate reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

The features of the invention believed to be novel are set forth with particularity in the appended claims. The invention itself, however, may be best understood by reference to the following detailed description of the invention, which describes an exemplary embodiment of the invention, taken in conjunction with the accompanying drawings, in which:

Figure 1A shows an arrangement of LEDs according to the prior art.

Figure IB shows another arrangement of LEDs according to the prior art.

Figure 1C shows another arrangement of LEDs according to the prior art.

Figure ID shows a hexagonal arraignment of LEDs according to the prior art.

Figure IE shows an arrangement of four pixels comprising four sub-pixels, according to the prior art.

Figure IF shows the arrangement of Figure IE with the use of virtual pixels, according to the prior art.

Figure 2A shows a possible arrangement of LEDs on a LED module, wherein the LEDs are provided in a hexagonal arrangement.

Figure 2B is the same arrangement as Figure 2A slanted with respect to the horizontal axis.

Figure 3A illustrates a bottom view a light emitting module comprising a serrated layer to accommodate a light emitting elements arrangement, and a rectangular support substrate.

Figure 3B is a side view of Figure 3A.

Figure 4A shows the arrangement of Figure 2A and the lines along which it is possible to cut the arrangement to provide straight edges.

Figure 4B shows the possible different module shapes resulting from the straight cuts to provide a display.

Figure 5A-5F shows virtual pixels for six consecutive frames in a hexagonal pixel arrangement comprising RGB sub-pixels.

Figure 6A-6F shows virtual pixels for six consecutive frames in a hexagonal pixel arrangement comprising RRGB sub-pixels.

Figure 7A-7F shows virtual pixels for six consecutive frames in a hexagonal pixel arrangement comprising RRGB sub-pixels.

Figure 8A shows a possible arrangement of RRGB sub-pixels.

Figure 8B shows an example of the pattern of a polarization filter associated with the arrangement of Figure 8A. Figure 9A shows a possible arrangement of virtual RGB pixels superposed on a pattern of a polarization filter.

Figure 9B shows a possible arrangement of virtual RRGB pixels superposed on a pattern of a polarization filter.

Figure 10 shows a possible arrangement of virtual RRGB pixels superposed with a pattern of a polarization filter for 3D viewing and virtual pixels for 2D viewing in a hexagonal arrangement.

DESCRIPTION OF EMBODIMENTS

Terminology used for describing particular embodiments is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The term "and/or" includes any and all combinations of one or more of the associated listed items. It will be understood that the terms "comprises" and/or "comprising" specify the presence of stated features but do not preclude the presence or addition of one or more other features. It will be further understood that when a particular step of a method is referred to as subsequent to another step, it can directly follow said other step or one or more intermediate steps may be carried out before carrying out the particular step, unless specified otherwise. Likewise it will be understood that when a connection between structures or components is described, this connection may be established directly or through intermediate structures or components unless specified otherwise.

The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. Where the term "comprising" is used in the present description and claims, it does not exclude other elements or steps.

Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein. The terms "about" or "approximate" and the like are synonymous and are used to indicate that the value modified by the term has an understood range associated with it, where the range can be +20%, +15%, +10%, +5%, or +1%. The term "substantially" is used to indicate that a result (e.g., measurement value) is close to a targeted value, where close can mean, for example, the result is within 80% of the value, within 90% of the value, within 95% of the value, or within 99% of the value.

Definitions and Acronyms

Active Matrix. Active matrix is a type of addressing scheme used in flat panel displays. In this method of switching individual elements (pixels), each pixel is attached to a transistor and capacitor actively maintaining the pixel state while other pixels are being addressed.

Active-matrix circuits are commonly constructed with thin-film transistors (TFTs) in a semiconductor layer formed over a display substrate and employing a separate TFT circuit to control each light-emitting pixel in the display. The semiconductor layer is typically amorphous silicon, poly-crystalline silicon and is distributed over the entire flat-panel display substrate. Figure 3 shows a schematic representation of an active matrix. An active matrix display can also be for example an LCD or an electrophoretic reflective transmissive emitting display or similar.

A display sub-pixel can be controlled by one control element, and each control element 15 includes at least one transistor. For example, in a simple active-matrix light- emitting diode display, each control element includes two transistors (a select transistor and a power transistor) and one capacitor for storing a charge specifying the luminance of the sub pixel. Each LED element employs an independent control electrode connected to the power transistor and a common electrode. Control of the light-emitting elements in an active matrix known to the art is usually provided through a data signal line, a select signal line, a power or supply connection (referred to as e.g. VDD) and a ground connection.

BGA Ball Grid Array

Backplane is a board comprising electronic components configured to drive the light emitting display. A backplane can be for example a PCB backplane (e.g., FR4 PCB), or a TFT backplane. Carrier board refers to a board which is configured to receive at least one light emitting module or display module. It serves as a support structure of a tiled display. The carrier board can be a backplane or a mechanical support structure. It can also serve as a distribution panel for power, ground and to distribute driving signals for the light emitting elements.

Driving signals or data signals are the signals which comprise the information for driving the light emitting elements to generate an image on the display. Depending in which stage they are in the transmission flow, they may be digital signals, or analog signals, or optical pulse signals, etc.

Display

A display screen can be composed of light emitting pixel structures referred to as "display pixels" or "pixels" where the amount of display pixels determines the "display resolution", sometimes referred to as the "native display resolution" or the "native pixel resolution". A measure of the display resolution can be the total number of display pixels in a display, for example 1920x1080 pixels. Each display pixel can emit light in all colors of the display color gamut (i.e. the set of colors the display is able to provide).

Each display pixel can be composed of light emitting elements referred to as "sub-pixels", often being able to emit the colors red (R), green (G) or blue (B) (but also white, yellow or other colors are possible). A display pixel can be composed of at least three sub-pixels: One red, one green and one blue sub-pixel. Additionally, the display pixel can comprise other sub pixels in any of the aforementioned colors (to further increase the color gamut). Depending on the types of sub-pixels, the display pixel can then be referred to as a RGB-, RGGB-, RRGB-pixel, etc. While a single display pixel can generate all colors of the display color gamut, a single sub pixel cannot.

The light emission of a single sub-pixel can be controlled individually so that each display pixel can emit the brightness and color required to form the requested image.

There is a distinction between display pixels and sub-pixels, and display pixel resolution and sub-pixel resolution. The sub-pixel structures of a display screen can be arranged in a "sub- pixel layout" or in an "arrangement", defining where each sub-pixel is positioned in the display.

Another measure for the display resolution can be the "pixel pitch" which can be the distance between the centers of the nearest neighboring pixels. For example, in Figure IE, the pixel pitch between the pixels 150 and 160 is the distance 170 between the pixel centers. Alternatively, the pixel pitch can be the distance between any two points located within two neighboring pixels at the same position relative their respective pixel center.

The sub-pixel pitch can be similarly defined as the distance between two sub-pixels of the same color, for example in figure IE the sub-pixel pitch (for sub-pixels of the same color) is the same as the pixel pitch. This is the case for all sub-pixels.

Figure IF on the contrary illustrates the concept of "virtual pixel" and "virtual pixel pitch". Sub-pixel 180 is surrounded by four virtual pixels, as its neighboring sub-pixels can be combined to form four different virtual pixels, each comprising the same combination of colors.

The virtual pixel pitch is then defined as the shortest distance between the centers of two adjacent virtual pixels. The virtual resolution is identical to the virtual pixel pitch.

As the center of a virtual pixel depends on the shape of the pixel, or the arrangement of the sub-pixels composing said pixel, the centers of the virtual pixels may not be arranged along the horizontal axis or vertical axis. Thus, the virtual pixel vector resulting from the distance between two points may have any direction as for example illustrated in Figure 2A illustrating a hexagonal arrangement of sub-pixels.

Display module is a module which comprises at least one light emitting module arranged on a carrier. The carrier of the display module is configured to transfer driving signals and power signals to the at least one light emitting module.

A plurality of display modules can be placed on a bigger carrier board (mechanical interface) to create a tiled display and be connected to an external driver or the display module. The functionalities of the driver can also be embedded in the display module. Duty Cycle The term duty cycle describes the proportion of 'on' time to the regular interval or 'period' of time; a low duty cycle corresponds to low power, because the power is off for most of the time. Duty cycle is expressed in percent, 100% being fully on.

In a hexagonal arrangement of sub-pixels or hexagonal sub-pixel structure, as illustrated for example in Figure 2A, the distance from the middle sub-pixel to all the neighboring sub-pixels is the same. The hexagonal arrangement can be rotated (at any angle) when said arrangement is implemented on a display module or a light emitting module. The hexagonal arrangement determines the relative positions of the sub-pixels one with respect to the other. Instead of a matrix structure with rows and columns as in a square grid arrangement of sub-pixels, the sub pixels are all arranged along three rows of sub-pixels, the three rows being illustrated in Figure 2A for example. The angle between two consecutive rows is 60 degrees.

The horizontal axis (or vertical axis) refers to the horizontal axis (or vertical axis) of a display for a viewer when the arrangement is provided in the display.

LED. Light Emitting Diode

Light Emitting Element. A light emitting element can be e.g., a solid-state light emitting element, such as a light emitting diode such as an LED or an OLED (Organic LED).

Light emitting module

A light emitting module is an opto-mechanical-electronic carrier of a certain size which carries light emitting elements directed towards a viewer and possible light emitting elements driving and control electronics. These light emitting elements are driven to create an image, either static or dynamic (video). In the following the light emitting module will be called an "LED module", although the invention is not restricted to LEDs. Several LED modules or OLED modules can be positioned next to each other to form a display module. Several display modules can be tiled together to form a larger tiled display.

A small LED module which is an atomic element, i.e., indivisible, can be called a "stamp". The light emitting module can have any size and shape. It can be rectangular or square, hexagonal, triangular, any shape, if it fits in a pick and place robot used to place it on a display module. It can also comprise one pixel, which comprises a red, green, and blue light emitting element. The light emitting module comprises at least one backplane. The top surface of the backplane comprises the light emitting elements and associated conducting tracks which connect the various light emitting elements to various electronic components (like e.g., current drivers, power supply contacts etc.). The backplane can be a PCB, TFT on glass, TFT on PI, etc.

The following patent applications, from the same applicant, provide definitions of LED displays and related terms. These are hereby incorporated by reference for the definitions of those terms.

- US7972032B2 "LED Assembly"

US7176861B2 Pixel structure with optimized subpixel sizes for emissive displays US7450085 Intelligent lighting module and method of operation of such an intelligent lighting module

US7071894 Method of and device for displaying images on a display device.

MUX Multiplexer

PAM Pulse Amplitude Modulation

Passive Matrix (PM) Passive matrix addressing is an addressing scheme used in early LCDs.

This is a matrix addressing scheme meaning that only m + n control signals are required to address an m x n display. A pixel in a passive matrix must maintain its state without active driving circuitry until it can be refreshed again.

PWM Pulse Width Modulation

Pulse-width modulation uses a rectangular pulse wave whose pulse width is modulated resulting in the variation of the average value of the waveform. The square wave has a period T, a lower limit 10 (typically 0 in our case), a higher limit II and a duty cycle D. The duration of one pulse P (the time during which the signal is at its higher limit) is D/100 * T (if D is expressed in %). For instance, if D = 50%, the duration of the pulse is ½ T. A more complete definition can be found in WO2019185935A1 from the same applicant.

TGV Through Glass Via

Thin-film technology refers to the use of thin films: A film a few molecules thick deposited on a glass, ceramic, or semiconductor substrate to form for example a capacitor, resistor, coil, cryotron, or other circuit component. A film of a material from one to several hundred molecules thick deposited on a solid substrate such as glass or ceramic or as a layer on a supporting liquid. TFT can be deposited on a substrate such as glass or PI. It comprises multiple layers of wiring, semiconductors, and isolation layers.

A "polarization filter" can comprise areas of different polarization, e.g. s- and p polarization, which in turn can be implemented using e.g. circular or linear polarization. The polarized light can be used for 3D displays where it is desired to divide the image into image content for the left and right eye of a viewer. This can be achieved if the viewer wears eyeglasses having the same polarization filters, so that each eye of the glasses filters out e.g. the s or p polarized light. Circular polarization can be beneficial for applications where rotational symmetry is desired, for example for TV or cinema applications where the effect should be the same even if the viewer tilts his head.

"Colors" - reference to the color "red" refers to a wavelength range of 610-630 nm, "green" to the range 515-545 nm and "blue" to the range 455-480 nm or to equivalent ranges which provide a visible red, green and blue color respectively.

Description

The inventors of the present application have developed a new type of light emitting module and display module. This new type of light emitting module is particularly advantageous when the light emitting elements are micro-LEDs, as it provides additional space for providing the driving circuits, connections, electronic switches etc. to the micro-LEDs.

However, the invention is not limited to micro LEDs, and may also be advantageous to other types of light emitting elements, as described hereunder. Throughout the description, the examples are described for LEDs, or micro LEDs and LED modules, while they also apply to the more generic terms of light emitting elements and light emitting modules.

As mentioned in the introductory part, a hexagonal arrangement of LEDs is the most optimal one in terms of space. However, serrated edges are currently difficult to manufacture. The inventors of the present invention have developed means to overcome these problems. In fact, serrated edges would be an advantage in terms of visual artefacts. Any type of repetitive figure can easily be seen by the eye. Serrated edges are less repetitive, thereby more random than straight edges, and thus less visible by the eye of a viewer.

It would also be an advantage for assembly, as two adjacent modules can be assembled like puzzle pieces.

However, the manufacturing of such serrated edges is extremely complicated.

The tolerances on the corners are very high. For micro-LED displays, the distance between two neighboring LEDs would be in the range of 300 microns,

Figure ID illustrates a schematic hexagonal arrangement of LEDs, as known in the art. The crosses represent the center of each LED.

LEDs assembled on a PCB or TFT layer, have a rectangular shape, with a length and a width, the length corresponding to the largest side of the rectangular LED. LEDs are usually arranged with the same orientation with respect to the display, i.e., all vertically or horizontally.

We assume the abscissa corresponds to the horizontal axis when the light emitting module is assembled in a display for viewing purposes.

The hexagonal arrangement of Figure ID may still be improved by providing the LEDs at an angle with respect to the abscissa, thereby further maximizing the space around each LED while at the same time providing a less repetitive arrangement. Figures 2A and 2B indicate the abscissa (x axis) and the ordinate (y axis) of the LED module when it used for display purposes.

Figure 2A shows a possible arrangement of LEDs on a LED module, wherein the LEDs are provided in a hexagonal arrangement. Each LED is oriented in such a way that its length has the same orientation as the edge of a hexagon. Thus, in each hexagon of the arrangement, two LEDs are vertical, two LEDs are at an angle of 30 degrees with respect to the abscissa, and two LEDs are at an angle of 150 degrees with respect to the abscissa, such that two consecutive LEDs are at an angle of 60 degrees with one another. Such an arrangement maximizes the space around each LED of the LED module.

In addition, each hexagon of the arrangement comprises an LED at its center. The LEDs at the center can either have the same orientation as any of the LEDs on two opposing edges of the hexagon or be perpendicular to such two opposing LEDs. It is preferred to orient them perpendicularly to optimize the space. In the example of Figure 2A, the central LEDs are horizontal and perpendicular to the opposing edges LEDs who are vertical. This results in alternating horizontal and vertical orientation of LEDs over a line, which is even more optimal in terms of space.

Such an arrangement also provides the advantage of reducing Moire-like artefacts for close viewing distance, which is likely to appear when using small LEDs.

Throughout the description, the orientation of the central LEDs defines the orientation of the arrangement with respect to the abscissa of the LED module.

To improve Moire-like artefacts, it is already sufficient to arrange the LEDs in such a way that two adjacent LEDs of the arrangement have a different orientation throughout the display. A difference in orientation of a few degrees is sufficient to break the symmetry, for example at least 2 degrees, preferably at least 5 degrees, and even more preferably at least 10 degrees. To further improve, the orientation of the length of the light emitting elements can follow a random distribution over the arrangement.

By further rotating such an arrangement at an angle, even less Moire-like artefacts would be generated at the edges of repeatable tiles, for close viewing distance with smaller LEDs. Figure 2B illustrates the arrangement of Figure 2A after rotation by an angle a.

However, the invention is not restricted to the use of LEDs having a rectangular shape. Advantageously, the LEDs can have an elongated shape, such as a oblong shape or an ellipse. In fact, LEDs can have any shape and show a more symmetrical shape, for example have a symmetry of at least an order 3, or at least an order 4, as a square, or 5, or 6 has hexagon, or even 8, etc. Thus, the shapes of the light emitting elements (or LEDs) can be any one of triangles, squares, circular, or even hexagonal, octagonal, pentagonal. LEDs in the shape of a triangle or a free form are also possible d

Hexagonal LEDs may be advantageous in a hexagonal arrangement as defined in the present invention. In fact, such LEDs would perfectly fit in the geometrical arrangement, and in addition, the symmetry of a honeycomb structure is very beneficial for viewing purposes.

Figure 2B further shows the serrated edges 220 of a LED module 200 obtained for this particular arrangement of LEDs. The serrated edges 220 of the LED module resemble a post stamp.

When assembling such post stamps together, a certain tolerance is required at the edges such that two post stamps can fit into each other.

Such post stamps, or LED modules with serrated edges are difficult to be manufactured when the LEDs are arranged on a glass carrier, because it is difficult to manufacture straight lines with the required precision at the borders of the post stamp. Serrated borders would come at a very high cost when using glass.

However, using a new technology developed by the inventors of the present patent application described above, there is the possibility to provide such LED modules with serrated edges more easily.

In fact, in this new technology, the LEDs are assembled on a TFT layer. This TFT layer has been processed on polyimide, instead of glass. Since polyimide is a type of plastic, it is easier to be cut with any shape than glass.

Electronics with TFT on glass for LEDs are a lot cheaper than electronics on PCB's. A difficulty here is that not all driving electronic components, made with Thin Film Transistors for LEDs, scale down at the same rate than future mini-LEDs or micro-LEDs themselves will do. For very small LEDs, this TFT on glass approach may not be practical anymore, because there may not be enough space between the LEDs for installing all electronic driving components with TFT on glass for each individual LED. Even with a hexagonal arrangement, there is a limit to the optimal use of space for each individual LED.

A solution is to split the functions of the electronics in more than one layer. For example, if two layers are used, they both could be fabricated with TFT on glass, back-to-back, but it is also possible to realize e.g., one layer on a hard substrate such as a glass substrate for better stability and mechanical stiffness, and a second layer on a flexible substrate such as a flexible PI foil substrate for the LEDs. The first layer on the hard substrate can therefore provide the mechanical stability, while the second flexible substrate, such as PI, may provide the possibility to use any shape. Both layers benefit from the TFT technology with minimal cost. Both layers can be connected electronically for making a working assembly. By splitting the functionalities into two layers, the available surface for driving electronics is also doubled for each LED. This functional splitting can be done in an analogue part (frontside) and a digital part (back side) for example.

Another advantage of using a flexible substrate such as PI is that through holes can be manufactured inside the PI. The through holes can then receive an electrical connection between the TFT layer on top (which comprises the light emitting elements, associated conductive tracks) and the backplane arranged under the PI layer which provides the various signals for driving the light emitting elements.

The electrical connection can be embedded by metalizing the through-holes, providing conductive paste (such as silver paste) and/or even providing nano-entanglements (described in the following patent applications (EP3711462A1 and DE102018122007A). A further advantage of using a flexible substrate, the PI (Polyimide) TFT layer, which is a type of plastic of higher quality, is that the shape of this PI material can easily be formed at the outer borders in any odd looking shape, while still using a straight shape for the Glass TFT layer which is combined with it: e.g., a rectangular glass with a serrated PI layer combined, could make an oddly shaped assembly that can be tiled.

In addition, the integrated circuits for driving the light emitting elements can be provided as an active matrix, said active matrix being implemented in a thin-film-transistor (TFT) layer.

The hexagonal approach with serrated edges, as shown in Figure 2B is also an odd shape. Such an odd shape can more easily be manufactured using a flexible substrate such as PI. Large seamless displays of much bigger formats can thereby be manufactured by combining LED modules having any desired shape.

Some possible arrangements of these alternative designs are shown in Figures 3A and 3B. Figures 3A and 3B illustrate a bottom view and a side view of a light emitting module comprising a layer of TFT on PI 300, having a special shape to accommodate any light emitting elements arrangement, and comprising a bottom layer of TFT on a rectangular glass 310.

To connect the two layers, contacts from the top layer (PI material) could be guided through "Via Holes" (TGV) to the top TFT structure of the glass layer, also easier to fabricate in PI material than in glass.

There is however the possibility to avoid serrated edges of an LED module by providing tiles having different shapes. As shown in Figure 4A, it is possible to provide straight edges with a hexagonal arrangement of LEDs, by "cutting" along lines 401, 402 or 403 which are oriented at an angle of a multiple of 60° with respect to the arrangement orientation. Possible shapes which result from these lines are shown in Figure 4B.

To create a rectangular display with LED modules having edges at an angle of a multiple of 60°, the LED modules can have either a triangular shape, a parallelogram shape, or a trapezoidal shape.

Figure 4B is an example of a display module or tiled display having three types of LED modules, each type having a different shape. The different shapes of the LED modules are such that the shapes fit together to make a display, or the shapes can be assembled as a puzzle, such that the assembled display results in a rectangular display.

For example, as illustrated in Figure 4B, different types of tiles may be as follows: dedicated "central tiles" 42 having a specific shape which is not a rectangle, such as a parallelogram, and dedicated "border tiles" 41, 43, like puzzle parts, such as triangles, where the corners and the sides have a dedicated shape, different from the central puzzle parts, to create a rectangular display having straight borders after assembly.

Border tiles 41 and 43 are different. In this example, they are anti-symmetric.

A serrated solution stays possible of course, but parallelogram shaped central tiles 42, in combination with triangular shaped border pieces for left side 41 and right side 43, could yield a rectangular display with straight lines at all the tile borders and would therefore be even more simple to produce, with any existing technology or materials, and thus also in glass.

In addition, any type of LED display, even a LED module having a glass substrate for the LEDs, can benefit from this improvement.

Again, variations in shapes can be found by choosing different ratios between lengths and widths of the individual tiles, by choosing the number of LEDs per tile, etc.

The present invention not only offers the possibility to provide additional space for electronics, combined with a more optimal arrangement of LEDs (hexagonal arrangement), but it also provides a system for displaying images with virtual pixels (optimal use of space and higher perceived resolution) and 3D possibilities. It is a technology which can be used when LEDs are not clustered but individually positioned, e.g., in a square arrangement.

In Figure IE, each pixel 150, 160 is composed of four sub-pixels, or light emitting elements. Each pixel is also encircled by the dashed square. The pixel pitch 170 corresponds to the distance between the centers of two adjacent pixels. In Figure IF, the light emitting elements are arranged in the same way as in Figure IE, but as illustrated, virtual pixels are shown. The virtual pixels 165 are also encircled by a square. For each sub-pixel, four virtual pixels are possible around the pixel 180. With four subsequent frames in time, four different pixels can be shown with a different combination of RGB LEDs, giving a "perceived virtual pixel pitch", finer than the actual spaced pixel arrangement. Virtual pixels consist in sharing pixels to reduce the perceived pixel pitch, and thereby provide an improved resolution, i.e. a virtual resolution having a virtual pixel pitch.

There are two possibilities to make this an advantage: With less LEDs, an image with a normal perceived number of pixels can be created, which saves cost and space around the LEDs to position the necessary driving electronics and to create space for seams between tiles, or with the normal number of LEDs, even higher number of pixels can be perceived.

In a square arrangement, the use of virtual pixels can thus reduce the pixel pitch by a factor of two.

A new possibility with a hexagonal arrangement is the extended potential to use virtual pixels.

With hexagons, more virtual pixels are available due to the geometry than in an orthogonal configuration, as every sub-pixel (= a central light emitting element) has six direct neighbors, therefore, six virtual pixels around this central LED can be available, assuming the positioning of the individual R, G and B LEDs is well chosen in the hexagonal configuration. In an orthogonal square configuration, only 4 virtual pixels can be created around a central LED.

Thus, it is possible to provide an arrangement of sub-pixels wherein at least one sub-pixel per pixel comprises six distinct virtual pixels, preferably at least two, even more preferably three, wherein the centers of all six virtual pixels are located around said sub-pixel. Therefore, at each frame of a sequence of six frames, an image can be displayed with a different set of virtual pixels for each sub-pixel having six distinct virtual pixels.

Figures 5A to 5F illustrate such a configuration of six consecutive frames (A, B, C,

D, E and F), wherein at each frame, a different set of virtual pixels is used for displaying images of the frame sequence. Each pixel is composed of a set of three red, green and blue sub-pixels. In this example, each type of sub-pixel, i.e., red, green, and blue, comprises six virtual pixels.

Starting with the red R sub-pixel in the center of the hexagon 500 shown in Figures 5A to 5F, each virtual pixel associated to the red R sub-pixel is composed at each frame of the sub-pixels highlighted in grey, and which form a new triangle at each frame of the sequence, for example following the clockwise direction. All the sub-pixels forming the virtual pixels are comprised in the hexagon around the central sub-pixel. To be able to form virtual pixels, all the sub-pixels within the hexagon around the central sub-pixel are of a different type (color) than the central sub-pixel and two consecutive sub-pixels are of a different type. In this case, the central sub-pixel is red, and the six peripheral sub-pixels of the hexagon around the central sub-pixel are alternatively green and blue. The hexagonal arrangement comprises three rows of sub-pixels, as illustrated in Fig. 2A with the dashed-dotted lines. All the sub-pixels in the same row are arranged following an alternating sequence of sub-pixel types, such as R, G, B, R, G, B, etc. or reversed. In addition, as shown in Figures 5A to 5F, two sets of pixels can be used to create a full virtual pixel plane. Each of the two sets of RGB pixels is illustrated by a triangle having a different background color (grey and black).

To obtain a full plane where all sub-pixels are used at all times, next to the virtual (grey) pixel turning around the central red R sub-pixel, a grey dashed parallelogram can be filled with the neighboring RGB LEDs (black background) in the same rows as the virtual grey pixel. Such a parallelogram, containing each time 2 sets of RGB pixels, can be repeated to fill the whole surface of the display, without leaving sub-pixels unused in one timeframe. For each timeframe (A, B, C, D, E and F), such a set of parallelograms can be drawn to obtain maximum use of all sub-pixels available. The perceived virtual pixel pitch corresponds to the smallest distance between the centers of two consecutive virtual pixels. In this case, the center of each virtual pixel corresponds to the center of gravity of each triangle, shown with the dots. In Figure 5F, all six centers of the sequence are arranged in a circle around the central sub-pixel, wherein the radius of the circle corresponds to half of the distance between two sub-pixels. The virtual pixel pitch results in the distance between two consecutive virtual pixel centers of two consecutive frames that can be made with RGB pixels (e.g. the grey dots in Fig. 5F around the central R pixel), this virtual pitch being almost 3 times better than when using only one fixed pixel position set (as shown by the grey dots in Fig. 5A).

The pattern can than be turned or mirrored, or the colors can be swapped to obtain different optical possible advantages of pixels containing 3 (R, G and B) LEDs. Once a favorable configuration is chosen, parallelograms can be chosen or replaced by other shapes that also form repeatable groups for a full filling factor of the display with all LEDs used at each time frame.

The time sequences can also be altered in many ways to obtain minimal optical artefacts. For example, instead of following the clockwise sequence from Fig. 5A to 5F, a random sequence can be chosen. Virtual pixels can also be used when the pixels are composed of four sub-pixels, of which two are identical, and two are distinct. For example, each pixel may be composed of RRGB, or RGGB, or RGBB.

Figures 6A to 6F shows such an arrangement, wherein each pixel is composed of two red, a blue and a green sub-pixel. Figures 6A to 6F illustrate six subsequent frames, each frame having a different virtual pixel with a central green sub-pixel, based on a hexagonal arrangement of pixels. The virtual pixel is shown as the combination of the 4 sub-pixels (RRGB) highlighted in grey.

The hexagonal arrangement provides thus a sequence of six subsequent frames (not 4 as in state of the art orthogonal configuration) of RRGB pixels, grouped in an imaginary parallelogram shape (in dotted line), turning at each time frame by 60° clockwise for example, around a central G sub-pixel, thereby providing six virtual pixels in such a time sequence.

It is also possible in the shown example to provide a sequence having six virtual pixels around a central B sub-pixel. Together, it results in a total of 12 frames which can be used subsequentially to further enhance the perceived pixel pitch.

Flowever, a beneficial positioning of R, G and B LEDs is desired. For example, in the shown configuration, around a central R LED, it would not be possible to provide 6 virtual RRGB pixels, because some parallelograms would be filled with only 2 colours: BBRR or GGRR, hence it would not represent a full pixel, as for example illustrated with the dashed-dotted line in Figure 6C (BRBR).

The sub-pixels in Figures 6A to 6F are arranged along a first 610 and a second 620 row of the hexagonal arrangement, following an alternating sequence of RGRBRGRBRGRB, wherein the duplicated sub-pixel is alternately provided between the two distinct sub-pixels, in alternance, in a first 631 out of two third rows of the hexagonal arrangement, alternating the distinct sub-pixels G, B and in the second 632 out of the two third rows with only the duplicated sub-pixel (R).

A next improvement for an optimal configuration is to ensure that virtual pixel sets are filling the full display at each time frame, with all sub-pixels being used. To obtain a full plane where all sub-pixels can be used in each time frame, a (dotted line) parallelogram shape as shown in Fig. 6A is filled with the virtual (grey) RRGB pixel that is rotating around sub-pixel G following a clockwise rotation. Next to it, another (dotted line) parallelogram is filled with RRGB sub-pixels in the same time frame. Such a dotted line parallelogram shaped RRGB pixel pattern can be repeated to occupy the entire surface of the display, without leaving sub-pixels unused in single timeframes. For each timeframe (A, B, C, D, E and F), a similar combination of sometimes differently oriented RRGB pixel parallelograms can be drawn to obtain full use of all sub-pixels available.

Alternatives can also be provided by changing the order of the time sequences (e.g. 1-3-5-2-4-6...) and/or by providing other positioning of the R, G and B sub-pixels, all yielding different solutions. More than one solution is possible to achieve an acceptable improved optical performance of the virtual pixels, keeping into account that reducing repetitiveness, to the benefit of randomness, is less perceived by the eye, as long as the frame rate is sufficiently high.

If one considers all the centers of the parallelograms forming a pixel at each frame (e.g. grey dots in Fig. 6A), the pixel pitch corresponds to the distance between these pixel centers. The pixel pitch can be different in the horizontal and vertical directions. In general, it is approximately two times the distance between each geometrical sub-pixel position for the hexagonal arrangement shown in the time frame. By increasing the rate of the time frames, it results in a perceived pixel pitch which corresponds to the superposition of all the centers of the alternating pixels. For 6 pixels turning around a central G pixel, this would result in a perceived virtual pixel pitch of approximately half the distance between each geometrical sub pixel position (as indicated with grey center dots in Fig. 6F), hence almost 4 times finer in a hexagonal arrangement, compared to only looking at a fixed pixel position (6A). In a more classical orthogonal square configuration, virtual pixel pitch is only two times finer than the actual pixel pitch.

Besides RRGB parallelogram shapes, other shapes of pixels can be proposed for providing different virtual pixel time sequences, not only with four neighboring sub-pixels (e.g. RGBR as explained in the introduction and above), but also with groups of 2 sets of 3 LEDs (RGB) alternating in time. RGB-triangular pixels, turning around a central sub-pixel also provide valuable results. Virtual pixels grouped per sets of 3 might be beneficial if optical perception of characteristics of pixels are equally distributed among R, G and B LEDs. This might for example be the case for Blue LEDs with Q-dots on top. Another possible configuration is shown in Figure 7A to 7F. This configuration is similar to a Bayer pattern (for RRGB) rotated under an angle and deformed to a hexagonal shape. This configuration can provide additional advantages for generating an increased number of possible virtual pixel positions. RGGB can be used as an alternative, as well as RGBB, for providing the desired optical benefits. The pattern can than further be turned or mirrored to obtain even more geometrical possibilities. Once a favourable configuration is chosen, the time sequences can also be altered in many ways to obtain minimal optical artefacts.

The sub-pixels in Figures 7A to 7F are arranged, along the first row of the hexagonal arrangement:

- by providing, in alternance

^■ a first row 711 of the first row with only the duplicated sub-pixel (R), and

^■ a second row 712 of the first row with alternating the distinct sub pixels (B, G) along the second and third row of the hexagonal arrangement,

- by providing, in alternance,

^■ along a first 721, 731 row of the third row, the duplicated sub-pixel (R) in alternance with one (B) of the distinct sub-pixels,

^■ along a second 722, 732 row of the third row, the duplicated sub-pixel (R) in alternance with the other (G) of the distinct sub-pixels.

With this arrangement, all three types of sub-pixels advantageously comprise six virtual pixels, and thus, the entire display can be filled completely with virtual pixels at each time frame, irrespective of the type of sub-pixel used for virtual pixels.

In addition to providing an optimal configuration for virtual pixels, the hexagonal arrangement can also be used optimally to generate 3D images.

W02020160759A1 of the same applicant discloses a system and method for displaying 3D images using polarization filters. The polarization patterns can be configured to for example optimize the distribution of green sub-pixels in each image and thereby obtain an increased resolution in 3D.

As described in patent application W02020160759A1, 3D images can be generated by using a smart sequence of images for the left and the right eye. The following set up for example can be used, as illustrated in Figures 8A and 8B. In Figure 8A, extra red sub-pixels are provided, however it may also be extra green sub-pixels, and thereby providing a Bayer layout. Figure 8B shows one of the preferred patterns of the polarization filter arranged on the display, according to W02020160759A1.

The P-polarizing and N-polarizing pattern at each LED position, needed for optimal resolution perception, when using different polarized goggles for L and R eye, follows a zig-zag polarization pattern, or snake pattern. The invention is however not limited to this polarization pattern. Other patterns, as described in the patent application may also be used in the present invention.

In Figure 9A, the P polarization is illustrated with the vertical stripes. The N polarization is left blank. Figure 9A shows a new possible arrangement of virtual RGB pixels for each polarization, following the zig-zag pattern. In the first frame, virtual pixels are provided by the combination of RGB sub-pixels encircled in the straight line 91, in a second frame, virtual pixels are provided by the combination of RGB sub-pixels encircled in the dashed line 92.

Thus, each virtual pixel of a first frame is provided by a combination of RGB sub pixels, which follows the polarization pattern. The subsequent virtual pixel, in a second frame, is provided by the next combination of RGB pixels in the polarization pattern, wherein at least one of the three sub-pixels is common to the first frame.

The same approach can be used for RRGB sub-pixels, as shown in Figure 9B. The subpixels of four subsequent frames 901, 902, 903, 904 are shown. Between two subsequent frames, three sub-pixels are common.

The "stairstep figure per polarization direction" for creating 3D virtual pixels through a kind of "snake shift" movement of frames in time, here shown in an orthogonal arrangement, can be slightly deformed to the 60° angled configuration, to also fit in a hexagon arrangement. There also both the virtual RGB or virtual RRGB (or permutations) can be used.

As shown in Figure 10, it is also possible to provide virtual pixels in 3D with a hexagonal arrangement of sub-pixels and at the same time provide virtual pixels for normal use, all in the same hardware configuration, thereby generating a minimal number of necessary LEDs. This could be beneficial for cinema or home applications where both 3D and 2D images or movies need to be shown on the same screen. The main issue for least artefacts and maximum optical performance is to have evenly spread coloured LEDs per eye. The proposed hexagonal configurations provide different solutions to achieve that goal with minimum number of LEDs and maximum perceived resolution.

In addition, spatial interpolation and dithering enhancement algorithms can be beneficial to obtain the best optically perceived impression with these hexagonal arrangements, intended for use with minimal number of small LEDs, when starting with orthogonal image information as image input.

Modifications

While the invention has been described with reference to LEDs, micro LEDs or mini LEDs, the invention is not limited thereto and can be generalized to any type of display in which the sub-pixels are discrete elements. In fact, the arrangement described in the present invention can be used in any type of display, such as a LCD display, a LED display, such as OLED display, AMOLED display, plasma display, Quantum dot displays.

In addition, the light emitting elements can advantageously have any shape, such as rectangular, square, circular, but also hexagonal. Paving a hexagonal arrangement with hexagonal sub-pixels is an advantage as the space occupation can be optimal but also the optical improved outcome of the visual display to the viewer.

The edges of a single light emitting module with hexagonal light emitting elements can also easily be made serrated such that two light emitting modules can easily fit into each other in a display module.

While the invention has been described hereinabove with reference to specific embodiments, this was done to clarify and not to limit the invention. The skilled person will appreciate that various modifications and different combinations of disclosed features are possible without departing from the scope of the invention.

Claims

1. An arrangement of light emitting elements for a light emitting module, wherein the light emitting elements are configured in a hexagonal arrangement such that a light emitting element is provided in the center of each hexagon of the hexagonal arrangement and, each light emitting element is centered on an edge of a hexagon of the hexagonal arrangement, such that the light emitting elements are arranged along a first, a second and a third row, the first, second and third rows forming an angle of 120 or 60 degrees one with respect to the other, wherein the light emitting elements have an elongated shape, such as a rectangle, with a length and a width, the length being greater than the width, the orientation of the length defining the orientation of the light emitting element, and wherein each pair of two adjacent light emitting elements have a different orientation.

2. Arrangement according to claim 1, wherein the difference in orientation is of at least 2 degrees, preferably at least 5 degrees, even more preferably at least 10 degrees or wherein, the orientation of the length of the light emitting elements follows a random distribution over the arrangement.

3. Arrangement according to claim 1 or 2, wherein the light emitting elements which are provided at the edges of a hexagon in the hexagonal arrangement are such that their length is oriented along the edge of the hexagon on which it is centered.

4. Arrangement according to any of the preceding claims, wherein the light emitting element in the center of each hexagon, has an orientation which is substantially perpendicular to the orientation of any of the two light emitting elements provided on opposing edges of the hexagon.

5. Arrangement according to any of the preceding claims, wherein the orientation of the arrangement is defined by the orientation of one of the rows with respect to the horizontal axis, and wherein the orientation of the arrangement is at an angle with respect to the horizontal axis.

6. Arrangement according to any of the preceding claims, wherein the light emitting elements emit at least red, green, and blue light.

7. Arrangement according to any of the preceding claims, wherein each light emitting element is a sub-pixel, and each composition of at least a red (R), green (G), and blue (B) sub-pixel forms a pixel, and wherein each type of sub-pixel has a different color.

8. Arrangement according to claim 7, wherein a pixel may further comprise at least one additional red, green, or blue sub-pixel, such that each pixel is composed of four sub pixels of which one is duplicated and two are distinct.

9. Arrangement according to any of claims 7 or 8, wherein at least one sub-pixel per pixel comprises six distinct virtual pixels, preferably at least two sub-pixels per pixel, even more preferably three sub-pixels per pixel, and even more preferably four sub-pixels per pixel.

10. Arrangement according to any of claims 7 to 9, wherein the sub-pixels are arranged in each row of the hexagonal arrangement, following an alternating sequence of sub pixel types, such as R, G, B, R, G, B, etc.

11. Arrangement according to any of claims 7 to 10, wherein the sub-pixels are arranged along the first and second row of the hexagonal arrangement following a sequence wherein the duplicated sub-pixel is provided between the two distinct sub-pixels, and in alternance, in one out of two third rows of the hexagonal arrangement, alternating the distinct sub-pixels and in the second out of two third rows of the hexagonal arrangement with only the duplicated sub-pixel.

12. Arrangement according to any of claims 7 to 10, wherein the sub-pixels are arranged along the first row of the hexagonal arrangement, by providing, in alternance a first row of the first row with only the duplicated sub-pixel, and a second row of the first row with alternating the distinct sub-pixels, and along the second and third row of the hexagonal arrangement, by providing, in alternance, along a first row of the second row and third row, the duplicated sub-pixel in alternance with one of the distinct sub pixels, along a second row of the second row and third row, the duplicated sub-pixel in alternance with the other of the distinct sub-pixels.

13. Arrangement according to any of claims 7 to 10, wherein the sub-pixels along each row of the first row of the hexagonal arrangement are arranged with the same type of sub pixels within a row, the type of sub-pixel being alternated between two consecutive rows of the first row.

14. Arrangement according to claim 13, wherein alternating the type of sub-pixel between two consecutive rows is performed by providing the duplicated sub-pixel between the two distinct sub-pixels.

15. Arrangement according to any of claims 7 to 14, wherein the arrangement is configured to cooperate with the pattern of a polarization filter to generate 3D images, wherein a first set of virtual pixels is arranged along a pattern of a polarization filter for the left eye, and a second set of virtual pixels is arranged along the pattern of a polarization filter for the right eye.

16. Light emitting module comprising the arrangement of any of claims 1 to 15.

17. Light emitting module according to claim 16, wherein the light emitting elements are any one of LEDs, OLEDs, and variations thereof, QD-LEDs, EL-QLEDs, AMOLEDs, mini-

LEDs, micro-LEDs.

18. Light emitting module according to claim 16 or 17, wherein the light emitting elements are provided on a TFT layer.

19. Light emitting module according to claim 18, wherein said TFT layer is deposited on a flexible substrate, such as polyimide.

20. Display module comprising at least two light emitting modules according to any of claims 16 to 19, wherein the edges of each light emitting module are serrated such that they follow the light emitting elements arrangement at the edges, and such that when the at least two light emitting modules are assembled to make a display, their edges fit into each other, and the distance between two consecutive light emitting elements remains constant throughout the display.

21. Display module comprising at least three light emitting modules according to any of claims claim 16 to 19, wherein the edges of the light emitting module are straight, and wherein at least three different types of light emitting modules are provided, each type having a different shape to provide a rectangular display after assembly of the at least three different types of module, and such that the distance between two consecutive light emitting elements remains constant throughout the display.

22. Display according to claim 21, wherein the different types of modules comprise a triangle or a quadrilateral whose at least one corner has an angle which is a multiple of

60°.

23. Display according to claim 22, wherein the different types of modules comprise at least one of, a first type having a shape of a parallelogram, a second type having the shape of a triangle, and a third type having the shape of a trapezoid.

24. A computer implemented method for displaying images using the arrangement of sub pixels as defined in any claims 1 to 15.

25. Method according to claim 24, comprising the step of, at each frame of a sequence of six frames, displaying an image with a different set of virtual pixels for each sub-pixel having six distinct virtual pixels.

26. Method according to claim 24 or 25, comprising the step of displaying the virtual pixels associated to a pixel in a random order at each frame of a sequence of six frames.

27. Use of the arrangement of sub-pixels according to any of claims 1 to 15 for displaying images on a display.

28. Use of the arrangement according to claim 27 wherein the display is at least one of a

LCD display, a LED display, such as OLED display, AMOLED display, plasma display, Quantum dot displays.