Electronic display device of the emissive pixel screen type, for aircraft cockpit

Abstract

Emissive pixel screen for an aircraft cockpit, comprising a planar substrate carrying a plurality of light-emitting diodes of the same emission spectrum (101, … 10n) and in which each pixel consists of at least one compact group of several of said light-emitting diodes. In a pixel of the screen, the light-emitting diodes of one of said groups are covered with a layer (201, 202, 203) forming a common cover for said light-emitting diodes of said group and relaying diffuse light, with or without photoluminescence, in reaction to the emission of light by the light-emitting diodes of the group. Figure for abstract: FIGURE 1

Description

Title of the invention: Electronic display device of the emissive pixel screen type, for aircraft cockpit Field of the invention

[0001] The invention relates to the field of color display screens for aeronautics, and more precisely for airplane or helicopter cockpits, as well as their design, and their evolution during the - particularly long - life of a given aircraft model. State of the art

[0002] Of particular interest are screens for the control station - or cockpit - of an aircraft - airplane or helicopter - civil or military, of 3”, 10” or 15” diagonals, for example, these dimension values ​​constituting simple examples. These screens are used for navigation, cartography, visualization of the artificial horizon, or taxiing on the ground, in particular, but other applications exist and are conceivable, including 20” screens. Compared to screens for consumer applications, these screens for aeronautics must withstand more demanding operating conditions, such as high (75°C), low (-40°C) temperatures, with potentially rapid temperature variations, which can be several tens of °C in one minute. These screens must also be storable, outside their operating period, at temperatures ranging from -55°C to +85°C.They must withstand very prolonged exposure to ionizing radiation such as that present at the altitudes where aircraft operate, for example 10,000 m above sea level, or sometimes even more. They must have an operating lifetime of several decades, and therefore have a form of immunity to failures, either because no failure affects them, or because forms of redundancy take over from components experiencing difficulties. The brightness performance must also be stable over the mentioned lifetime. Manufacturing technologies are therefore adapted to these requirements, both in terms of the choice of materials, the chassis, the electrical and mechanical sizing, the choice of electrical circuit designs, and the choice of elementary components.The affected displays can be placed in a Line Replaceable Unit (LRU) with a specific function, or implemented as part of an integrated architecture in an avionics suite.

[0003] These screens are often designed with LCD (liquid crystal display) technology. Liquid crystal displays use the variable birefringence properties of crystals, whose orientation is varied according to an electric field. A backlight is maintained permanently, recently by white LEDs (light-emitting diodes) (but historically, these were CCFL - Cold Cathode Fluorescent Lamp or cold cathode fluorescent lamps, still commonly used today), and depending on the orientation of the liquid crystals, the light is punctually transmitted or not transmitted since the liquid crystal is placed between two crossed polarizers. White LEDs can be blue LEDs on which a luminophore called yellow phosphor (often YAG:Ce3+) has been deposited, which by fluorescence and addition of the blue of the diode not absorbed by the phosphor and the yellow produced by fluorescence gives white.

[0004] These are the TFT thin-film transistors used to control the voltage of the liquid crystals that define the pixels. To obtain a coloring, three liquid crystal cells per pixel are used, each equipped, parallel to the liquid crystal, with a red, green or blue colored filter, which allows, by lighting one or more, to obtain the desired color, by additive synthesis. These filters are passive filters, which absorb (and in any case prevent the transmission of) certain wavelengths, and allow other wavelengths to pass, generally by a phenomenon of transmission in a straight line.

[0005] The backlight LEDs, which can be 2 to 3 mm wide, can naturally be placed in a carpet, but can also be placed on the side (in a configuration called "edge-lit"), with a planar waveguide for example made of PMMA (poly methyl methacrylate acrylic or plexiglass), loaded in its volume to diffuse on the plane or provided on the surface with a screen printing of diffusing points for example. The backlight LEDs are permanently lit.

[0006] LCD liquid crystal display technologies, based on the transmission and occultation of light permanently present in the background, are competing with technologies in which monochrome or colored light is emitted by LEDs, which are switched on and off to produce the image - these are called self-emissive or emissive pixels.

[0007] Thus, for example, OLED screens, without liquid crystals and without permanent backlighting, are enjoying success in the consumer sector, for example in smartphones - the pixels can be 150 pm for example. OLEDs or organic LEDs whose dimension is of the order of magnitude of the pixel are formed by superimposing several organic semiconductor layers.

[0008] OLEDs can be placed in groups of LEDs of different colors, including red, green and blue, and it is possible to turn them all off at the same time to have a deep black. The color can be achieved natively by adapting the OLED chemistry to obtain a given color or, if the OLEDs emit white light, by the use of passive filters that absorb wavelengths other than those desired for the LED in question. It is also possible, in recent models, to shift the emission wavelength using a quantum dot (sometimes also called a quantum box), namely a very small physicochemical structure - semiconductor nanocrystals - capable of photoluminescence or more precisely fluorescence in a narrow spectral range.

[0009] The lifespan of OLED products appears, to date, to be insufficient for aeronautical applications, in particular due to the organic nature of the material of OLEDs.

[0010] Further forward, micro-LEDs are objects of recent emergence, on the one hand smaller (down to as little as 50 pm in width, or even less), using in particular gallium-indium nitride InGaN and gallium nitride GaN semiconductors, and offering interesting prospects for the aeronautical field, with high anticipated lifetimes, very short response times, of the order of a few nanoseconds, as well as low consumption. Micro-LEDs are controlled by CMOS circuits on silicon or by TFT thin-film transistors and can also be found on PCB printed circuit supports. By these control circuits, a current command is transmitted to them.

[0011] Micro-LEDs heat up little, have a high luminance, and a short response time. Their lifetime is also advantageous. The manufacturing processes use the deposition of materials on glass or silicon wafers, by epitaxy, with dimensions of less than 50pm, then the transfer (mass transfer) onto a CMOS matrix (for example) of certain micro-LEDs thus manufactured.

[0012] The micro-LEDs can be placed in groups of three colored micro-LEDs each having one of three colors Red (maximum emission around about 630 nm) Green (maximum emission around about 570 nm) and Blue (maximum emission around 450 nm) or RGB (RGB in English) in the visible spectrum, close to each other in a horizontal arrangement, vertical arrangements also existing. Since they are switched on separately from each other, it is also possible to switch them off simultaneously, which then provides a deep black, and ultimately, the contrast is good.

[0013] To obtain these colored micro-LEDs, micro-LEDs are considered which are natively of different colors, by adjusting the nature and / or the thickness of the semiconductor layers of the stack. It is also possible to use natively blue micro-LEDs, known to be energy efficient and in particular more energy efficient than red micro-LEDs and green micro-LEDs, with, for two out of three micro-LEDs, an active, photoluminescent, generally fluorescent element, possibly of the quantum dot type (also called quantum box as mentioned above -), to generate, from blue, either green or red depending on the size of the quantum dot, in both cases with a line width also quite low, at mid-peak of 20 to 30 nm.

[0014] For the cockpits of existing aircraft fleets, the prospect of changing the display is very low or non-existent, because crews must benefit from the same experience in each aircraft, and safety standards combined with the costs of a possible simultaneous change on a large number of aircraft in circulation do not open the prospect of any variation.

[0015] The replacement of LCD screens (with CCFL or LED backlighting) of devices in circulation, as and when maintenance operations are carried out, for example following rare breakdowns that occur or during preventive maintenance, must be done without crew members being confronted with a change in their perceptions of these screens.

[0016] Thus, since the devices are equipped with LCD screens with a given resolution, it is not particularly envisaged to replace them with screens with emissive pixels of higher resolution, although these offer various advantages and can have a competitive cost. In addition, one may wish not to change the resolution of the video streams which circulate between the devices, which makes it a priori useless to install a screen of higher resolution.

[0017] Nevertheless, the installation of emissive technology screens may nevertheless be necessary due to the scarcity or even the disruption of the sources of supply of all or part of the transmissive technology screens. In the same vein, and without going as far as the disruption of the supply of transmissive technology screens, emissive technology screens may also become less expensive than transmissive technology screens, which justifies seeking to integrate them into existing aircraft, or into new examples of models certified many years previously, the certification having been carried out with transmissive technology screens.

[0018] Generally speaking, we want to benefit from solutions for the evolution of existing products requiring only a few modifications to the construction principles from one evolution of the product to another, in order to easily meet the needs of the market or users.

[0019] And it is also desired that the proposed products can easily be maintained in service even in the event of failure of one diode among a large number of diodes, and it is therefore desired that solutions are available to overcome such a failure, without modifying the product.

[0020] The invention provides in this context a solution for providing maintenance solutions to devices in circulation based on the emissive technology of LED screens.

[0021] To provide a suitable service, an emissive pixel screen for an aircraft cockpit is proposed, comprising a flat substrate carrying a plurality of light-emitting diodes with the same emission spectrum, for example blue micro-LEDs, and in which each pixel consists of at least one compact group of several of said light-emitting diodes.

[0022] This device is particular because in a pixel of the screen, the light-emitting diodes of the group are covered with a layer forming a cover common to said light-emitting diodes of said group and relaying a diffuse light, with or without photoluminescence, in reaction to the emission of light by the light-emitting diodes of the group. There is generally a cover for each group: the cover is specific to the given group.

[0023] Due to these characteristics, available products are used, namely micro-LEDs or any small LEDs, and wider pixels are formed, compatible with the environments of aircraft cockpits for which they are intended, and which, as has been said, complicate and make more expensive, if not impossible, the modification of the resolution compared to previous technologies. Energy consumption is reduced, since screens with emissive technology consume less energy than screens of the same brightness based on transmissive technology.The product is made more reliable by providing redundancy in the light sources, since each group of diodes, forming either a pixel or a sub-pixel of a given color, is made up of several diodes which, if one fails, can be used to keep the product operating just as well, by increasing the power communicated to the non-defective diodes in the group.

[0024] This therefore constitutes a major advance in the field of display screens (in color or monochrome) for aeronautics, since it is now also possible to install a screen with emissive pixels in different aircraft cockpits, on the basis of a supply of micro-LED substrates with a very fine, constant pitch, potentially imposed by a supplier or by the supply conditions, and with screen resolutions that are nevertheless different since it is sufficient to adapt the extension of the layers forming the cover in the two dimensions of the plane of the screen.

[0025] According to optional and advantageous characteristics,

[0026] - the layer may comprise quantum dots so that light scattered is of higher wavelength than the light received from the diodes electroluminescent and that the layer has an angularly extended light emission.

[0027] We thus benefit from a double property of quantum dots: they modify the wavelength of the light by absorbing the incident light and emitting light of a higher wavelength, and they emit this new light in a wide solid angle - it is therefore light modified in wavelength and directionality which is relayed by the cover, due to the quantum dots.

[0028] - the pixel may comprise several groups of light-emitting diodes, and for each group of the pixel, a layer of specific colorimetric property (photoluminescent or not, in particular) covers the light-emitting diodes of said group forming a cover specific to each of the groups. We can then proceed with a display by additive synthesis, which opens the way to a wide variety of colors.

[0029] - the layer of one of said several groups of light-emitting diodes can include a diffusing charge and be without photoluminescent properties. In this case, the cover diffuses a light of the same color as that of the diodes, namely generally a blue light.

[0030] - the pixel may comprise a red group, a green group and a blue group. The red and green groups are formed by the presence of quantum dots chosen to fluoresce red light and green light respectively in the covers associated with the groups concerned.

[0031] The screen can thus be a color screen offering a very wide range of colors by additive synthesis of green, red and blue groups. The groups of the three colors are formed by the association, for each of them, of a cover layer with the underlying diodes to provide the desired color.

[0032] But the screen can also be a monochrome flight control unit screen, green if each pixel comprises a single group, and the associated cover layers provide, by association with the underlying diodes, a green light.

[0033] - the light-emitting diodes may be gallium nitride-based diodes called micro-LEDs. They consume little energy and have a long lifespan.

[0034] - the light-emitting diodes can be blue diodes, which are particularly energy efficient.

[0035] - each group of diodes can be formed by bringing together substrates squares of light-emitting diodes comprising nine diodes in three rows of three diodes, and more generally, each group can be formed by bringing together rectangular substrates of light-emitting diodes comprising diodes in several rows.

[0036] - a high optical density material can be placed between the groups of diodes, this which prevents the illumination of a cover by the diodes of the neighboring cover.

[0037] - the colored layer may have been deposited by inkjet or screen printing, or other methods.

[0038] - the colored layer can form an encapsulation of the diodes, or be placed on a layer of glass glued to the diodes.

[0039] - the covering layer may comprise quantum dots or phosphors to define its color, which is compatible with the fact that all diodes can be of the same nature, the wavelength of their light being modified by the covering layer.

[0040] - the layer may comprise phosphorus granules or quantum dots, and each pixel may also comprise a group of several controlled light-emitting diodes covered with an essentially untinted diffusing layer common to said several light-emitting diodes of the group, which makes it possible to diffuse the native light of the light-emitting diodes, which are for example blue diodes.

[0041] The invention also proposes a method for replacing a display screen in an aircraft control station, comprising a step of removing a screen, for example a liquid crystal screen with backlighting, and a step of replacing said screen with a screen of resolution identical to the resolution of said liquid crystal screen.

[0042] The method is remarkable because the screen of identical resolution is chosen as an emissive pixel screen according to the preceding principles, the number of light-emitting diodes in the groups being chosen so that, taking into account the number of groups, the size of the pixel is that of the pixels of the screen

[0043] Thus, we change technology and benefit from the advantages of diodes, including first and foremost micro-LEDs, but we retain the resolution of the old screen, and we are therefore able to satisfy the requirements of operating companies, manufacturers and regulatory authorities. This remarkable result is obtained thanks to the layers forming a cover common to the diodes in a group, the fact that there are at least two diodes per group, and the fact that the covers relay diffuse light.

[0044] The invention also provides a method for industrializing an aircraft, comprising a regulatory qualification step carried out while a copy of the aircraft for the purposes of qualification is equipped with a liquid crystal screen with backlighting, and a subsequent step of installing, in a copy of the aircraft for the purposes of delivery for operation, a screen of identical resolution. to the resolution of said liquid crystal display, this display having been the subject of a qualification in itself. The display of identical resolution is chosen as an emissive pixel display according to the invention, the number of light-emitting diodes in the groups being chosen so that, taking into account the number of groups, the size of the pixel is that of the pixels of the liquid crystal display with backlighting. In general, the invention also makes it possible to give flexibility to the designer in the context of a new design.

[0045] A method for adapting a cockpit display screen of an aircraft according to the invention is also proposed. It comprises a step of mapping the potential light power of the screen at the date of adaptation, which can immediately follow the manufacture of the module, then, depending on the areas of lower light power identified on the screen, a modification of the control of the screen by increasing the power emitted by the diodes of one of said groups of diodes of the screen corresponding to an area of ​​lower light power, in order to compensate for a weakness of one of the diodes of said group by the other diodes of the group. Conversely, it is also possible to reduce the power of the stronger diodes. Thus, the solution makes it possible to manage the case of a given micro-LED failing by an adjustment on the other micro-LEDs of its group. This can be carried out in the factory during calibration of the screen, or later, during maintenance.Thus, the invention makes it possible to use LED redundancy in the event of failure of an individual component. A colored pixel is based on several micro-LEDs, which makes it possible to manage the failure of a given micro-LED, by deliberately increasing the light power generated by the others, to compensate for the power lost due to the failure. Brief description of the drawings

[0046] The invention will be better understood and other advantages will appear on reading the description which follows, given without limitation and thanks to the appended figures among which:

[0047] [Fig.l] is a view of an initial arrangement of micro-LEDs according to two embodiments of the invention.

[0048] Figures 2A and 2B are sectional views of one of the embodiments of [Fig.l], in two variants.

[0049] [Fig.3] is a representation of an alternative embodiment.

[0050] Figures 4 and 5 are representations of two methods according to the invention. Detailed description of the drawings

[0051] [Fig.l] [Fig.l] shows a support 100, which is a rigid or semi-rigid planar object with two faces, of constant thickness (or planar substrate) carrying micro-LEDs 101, ... lOn arranged in a rectangular mesh pattern, or a checkerboard pattern on one of its faces. The micro-LEDs 101, ... lOn are square in geometry, seen from above. They are separated from each other by a distance that is of the same order of magnitude as their dimension, or a little smaller. In the figure, the micro-LEDs 101, ... lOn are 11 by 6 in a rectangular mesh pattern, or 66 micro-LEDs. These are blue micro-LEDs, known for their good energy efficiency. They emit light with a relatively narrow wavelength peak, leading to this blue color.

[0052] The micro-LEDs 101, ... 101 were deposited on the surface of the support 101 by mass transfer, involving their laser cutting on an initial substrate, then their transfer from the initial substrate, thanks to a separation layer and an elastomeric pad or another mass transfer solution. Each micro-LED can have a side of the order of 100 pm, and be separated from the next, in the alignment direction, by a space of 100 pm.

[0053] [Fig.l] proposes two ways of using the support 100, by depositing on the face which carries the micro-LEDs, plates which, for some, convert the light power of the blue micro-LEDs into light power with another wavelength peak, corresponding to a green or red light, in particular.

[0054] In a first embodiment, shown in the upper right part of the figure, rectangular plates 201, 202 and 203 are chosen to cover 3x6 micro-LEDs (rectangular compact arrangement) and they are placed on the support 100, one next to the other, and seen from above as proposed in the figure, separated by a deposit of high optical density material (called black matrix). Two rows of 6 micro-LEDs are covered, incidentally, by the high optical density material.

[0055] The plate 201 is, in one embodiment, a cover based on synthetic resin loaded with red quantum dots (even if, as regards the load, less sophisticated solutions are possible, in particular the use of phosphors) uninterrupted and homogeneous above the 3x6 micro-LEDs that it covers. The plate 202 is a cover also based on synthetic resin loaded with green quantum dots (or possibly phosphors), also uninterrupted and homogeneous above the 3x6 micro-LEDs that it covers. The plates 201 and 202 have, by their nature and their reduced thickness, a function of transmitting light power, and by their chemical or physicochemical load, a function of modifying the spectrum of the light by concentrating it around a particular wavelength. By virtue of the choice of using quantum dots, they are therefore photoluminescent components.They also have, by virtue of their constitution based in particular on a diffusing arrangement and configuration of the quantum dots in the cover, a function of diffusion of the transmitted light, which has the effect of... consequence that their surface above the spaces between two micro-LEDs is substantially as much a source of transmitted and diffuse light as their surface directly above a given micro-LED, and with an equally similar, and ideally uniform, angular distribution. The observer does not individually distinguish the micro-LEDs that it covers, their light intensity being diffuse and distributed over the entire surface of the plate 201 or the plate 202. Thus, the micro-LEDs are relayed by the associated cover, which modifies the spectrum of the light and diffuses it angularly. The micro-LEDs are essentially a source of light power and their light is relayed by the cover.

[0056] Quantum dots behave like sources and emit in all directions, randomly.

[0057] In the blue colored sub-pixel, the light is not emitted by photoluminescence but by a light-emitting diode mechanism, this intervenes in a privileged direction.

[0058] Macroscopically, the light from the green and red sub-pixels is therefore diffuse while that from the blue could be directive. In order for the resulting perceived color mixing not to depend on the viewing angle, it was chosen to make the blue sub-pixel diffuse, like the green and red sub-pixels.

[0059] The plate 203 is uninterrupted and homogeneous above the 3x6 micro-LEDs that it covers and is formed by a diffusing material - based on a synthetic resin again, for example the same synthetic resin as that used for the plates 201 and 202 - as for it without photoluminescent charge - it does not modify the spectrum in wavelength and therefore keeps unchanged the blue emitted by the micro-LEDs - which is chosen so that the surface above the spaces between two micro-LEDs is substantially as much a source of transmitted and diffuse light as the surface directly above a given micro-LED, and with again an equally similar, and ideally uniform, angular distribution. Thus, the micro-LEDs are relayed by the associated cover, which angularly diffuses the light and this time keeps its spectrum essentially unchanged.

[0060] The plates 201, 202 and 203 are preferably constructed so that the angular diffusion is close or even the same (we are trying to approach an orthotropic light source or Lambertian light source). The plate 203 therefore lets through a blue light, like the underlying micro-LEDs, but the light that it emits is more diffuse and uniform over a larger surface than the light emitted by a single micro-LED, and the observer does not individually distinguish the micro-LEDs that it covers, their light intensity being diffuse and distributed over the entire surface of the plate 203.

[0061] The set of three plates 201 to 203 and the micro-LEDs that they cover constitute a controllable colored pixel, since the three colors formed make it possible, by combination, to obtain all the colors of the visible by additive synthesis, and the 66 micro-LEDs are therefore controlled so as to provide the color and the brightness desired for a pixel of this size, which corresponds to a sub-optimal resolution given the small size of the micro-LEDs, but which can be quite similar to the resolution obtained with older technologies, such as LCD screens and backlighting.

[0062] In a second embodiment, shown in the lower right part of the figure, covers consisting of rectangular plates 301, 302 and 303 are chosen to cover 1x2 micro-LEDs (rectangular compact arrangement) and they are placed on the support 100, one next to the other, separated, in top view, by a thin deposit of the high optical density material (called black matrix) 350, this material again surrounding the support around the 66 LEDs. It results from this arrangement that a pixel capable of achieving a mixture of the three colors is constituted by six micro-LEDs, arranged in a 2x3 arrangement. And the support 100 offers space to install nine pixels, occupying a 9x6 space.

[0063] The diodes are controlled by intensity variation or pulse width modulation (PWM), to ultimately modify an average power over a unit of time.

[0064] The high optical density material ensures that when the micro-LEDs associated with a color are lit, their light does not contaminate the neighboring cover, associated with another color. In the event that the high optical density material is placed vertically above certain micro-LEDs, which is the case for the top right arrangement of [Fig.l], in one embodiment, the hidden micro-LEDs are not controlled and remain off.

[0065] [Fig.2A] [Fig.2A] shows a method of manufacturing the structures of [Fig.1]. It shows that the micro-LEDs are present on the surface of the support 100, and that a glass sheet 200 is placed on the micro-LEDs in the thickness of which or on the surface of which are installed the plates 201 and 202 each constituting a photoluminescent cover and the plate 203 constituting a diffusing cover, and which may be thin, in particular thinner than the glass sheet 200. The plates 201 and 202 are deposited for example by inkjet or screen printing of a polymer or a synthetic resin in which the quantum dots (or so-called “phosphor” compositions) are mixed. The plate 203 is deposited for example by the same method, in the form of a deposit of a synthetic resin or a polymer initially fluid and containing a diffusing powder.

[0066] A high optical density material 250 fills the spaces between the areas forming the sub-pixels and thus masks the metallizations and the substrate present between the micro-LEDs. It can also take the form of a synthetic resin or a polymer, comprising a black or very dark pigment.

[0067] Nevertheless, the high optical density material 250 may be a metallic deposit, without resin or polymer, in which case, it may be deposited in the form of a metallic oxide by spraying or evaporation, in particular before the deposition by inkjet printing of the plates 201, 202 and 203. It is then thinner than the resin or polymer layers. It may in particular comprise a chromium oxide or molybdenum.

[0068] The deposition of the three plates 201, 202 and 203 as well as the high optical density material is carried out for example in a single rectangular thinned surface of the glass sheet. In this figure the covers constituted by the plates 201 and 202 and the cover constituted by the plate 203 are present on the face of the glass sheet 200 which is turned towards the side opposite the LEDs 101... 10x, but it is also possible that the covers, while having been deposited on the glass sheet 200, are present on the face of the latter turned towards the LEDs 101, ... 10x, and therefore come into contact, at the time of assembly, with the external face thereof. In any event, the deposition of the covers and the high optical density material is in this variant carried out on a continuous flat surface of the glass plate, but the glass plate may also have reliefs if necessary, while generally being without holes.

[0069] Alternatively to this structure, variants are also implemented.

[0070] [Fig.2B] In [Fig.2B], the colored component has been deposited on the upper part diodes. The glass sheet has received the high optical density material 250, and is deposited on the assembly composed of the diodes and the covers. More precisely, the covers being made of a polymer or a synthetic resin, they are deposited on the top of the diodes, although empty spaces are present between the diodes. The viscosity and thickness of the deposited material is sufficient so that the deposited material forms a continuous layer forming bridges from the top of one diode to the top of the next diode, and that the layer is homogeneous and flat despite the relief on which it was deposited.

[0071] The high optical density material 250 was deposited by evaporation or spraying of metal oxides onto the glass plate, or by depositing a resin loaded with a black powder. When bringing together the glass sheet carrying the high optical density material and the covers, the correct alignment of the separations between the colored elements and the lines of high optical density material is ensured.

[0072] The glass sheet can receive a metal plane for electromagnetic shielding type screening (seeking electromagnetic compatibility - EMC). Such a metal grid closes a metal cage of the unit carrying the screen, and thus forms a Faraday cage which protects the contents of the unit.

[0073] It can receive anti-reflective treatment.

[0074] It is connected to the support 100, on the face of the latter carrying the LEDs 101, ... 10x, for example by an optical glue which polymerizes, between the LEDs and the covers, or if the covers were placed on the LEDs initially, between the covers and the glass.

[0075] The support 100 comprises TFT thin film transistors or a CMOS circuit or another microelectronic substrate, and is fixed to a mechanical frame, forming a chassis which also carries the electronic control cards of the diodes.

[0076] [Fig.3] [Fig.3] shows an embodiment in which the micro-LEDs are carried by small square supports which accommodate 9 of them, in a 3x3 arrangement. It is chosen to use covers consisting of active plates 601 and 602 (with change of wavelength of the light, by photoluminescence) and passive 603 (without photoluminescence) each having a Lambertian angular emission, of rectangular shape and of dimension chosen to cover two squares corresponding to 9 micro-LEDs each, placed one next to the other, to thus form three sources of juxtaposed colored light as in the structure of the upper part of [Fig.l]. Thus 6 supports 501-506 were used for three plates 601-603.In such a circumstance, the fact that the supports are not positioned on an underlying support, in a totally controlled manner, to within a few degrees of angles, or to within a few micrometers in translation, is visually overcome once the plates 601-603 are laid, since the angular imperfections are masked by the plates.

[0077] [Fig.4] In [Fig.4] a method according to the invention is shown. During a step 1, a liquid crystal screen, or a light-emitting diode screen with emissive technology, present in the dashboard of an aircraft, and which requires replacement, due to obsolescence or breakdown, or development proposed to the operator, is deposited.

[0078] During a step 2, a micro-LED screen configuration conforming to the principles of the invention is identified which offers the same resolution as the deposited screen, regardless of the technology thereof.

[0079] For this, a stock of rectangular or square micro-LED supports is available, comprising micro-LEDs arranged on a surface of the support.

[0080] The support has dimensions in both dimensions of the plane. In addition, the micro-LEDs are arranged on the surface of the support with a given and known density. On this basis, we choose, depending on the desired pixel size, to size the colored plates which will be placed above the micro-LEDs so that they cover an appropriate number of micro-LEDs, taken as a rectangle of nxm micro-LEDs, with at least n or m greater than or equal to 2.

[0081] In step 3, the micro-LED screen is installed in place of the LCD screen. It receives the same video stream as the previous screen, which is typically a digital video stream transferred by a data bus, for example in LVDS format, with a resolution of 1920 x 1080 pixels, and a refresh rate of 50 to 60 Hz.

[0082] [Fig.5] In [Fig.5], another method according to the invention is shown. It is specified also that the structure which is proposed also makes it possible to compensate for any defective micro-LEDs, since the micro-LEDs are grouped in groups of several micro-LEDs and it is therefore possible to compensate for the failure of a micro-LED (detected by mapping the luminance to detect anomalies) by imposing a greater light on the micro-LEDs placed under the same plate, by the command which is transmitted to them, or even by activating micro-LEDs not used until then and kept as a reserve for failures.

[0083] Thus, during a step 5 of mapping different similar display systems of a fleet of display systems, those which need a modification of the display due to the failure of certain micro-LEDs are identified, and from this diagnosis, the command applied to the screens without defects is kept unchanged (step 6), and the command applied to the screens for which it has been found that one or more micro-LEDs was defective is modified (step 7), to compensate by the neighboring micro-LEDs which are under the same plate, the loss of luminous intensity of the defective micro-LED(s).

[0084] Generally speaking, blue micro-LEDs have been considered in the text as constituent elements of the system, but violet micro-LEDs are used in a variant. Furthermore, the glass sheet 200 may be made of another material allowing the wavelengths concerned to pass through, in particular a flexible material, of a polymeric nature.

[0085] Screens have been presented offering a wide range of colors by additive synthesis, for each pixel, of three colored sources, one blue, the other red and the third green, each constituting a sub-pixel. But the screen can alternatively be a monochrome screen of a flight control unit, in which each pixel comprises a single sub-pixel, with a single color, which can be green. In this case and in one embodiment, blue micro-LEDs are again used, and this time a green phosphor or a green quantum dot is added to them in a cover common to several micro-LEDs for wavelength conversion and diffusion. In this case there is a single type of pixel composed of a certain number of blue micro-LEDs and a green fluorescent element, layer or plate, covering the group of micro-LEDs, and behaving like a single light source, due to the diffuse nature of the light it relays.

[0086] The covering plates have been described as being made of synthetic or polymer resin, including in the volume forming a layer of a certain thickness a dispersion of quantum dots or dispersing powder, the resin remaining present during the life of the product. Alternatively, the covering function can be obtained by depositing the quantum dots or dispersing powder on a flat surface - the surface of the glass sheet - in a solvent which evaporates after deposition, and which therefore leaves only a thin deposit of low thickness, the solvent having disappeared. The deposit is flat and homogeneous.

[0087] Alternatively, the cover plates are formed by depositing phosphorus granules on the glass sheet. The deposit is flat and homogeneous.

Claims

Claims

1. Emissive pixel screen for an aircraft cockpit, comprising a planar substrate (100) carrying a plurality of light-emitting diodes of the same emission spectrum (101, ... 10n) and in which each pixel is made up of at least one compact group of several of said light-emitting diodes, the screen being characterized in that in a pixel of the screen, each group of diodes is made up of the bringing together of rectangular substrates (501-506) of light-emitting diodes comprising diodes in several rows of diodes and the light-emitting diodes of the group of diodes are covered with a layer (201, 202, 203) forming a common cover for said light-emitting diodes of said group of diodes and relaying diffuse light, with or without photoluminescence, in reaction to the emission of light by the light-emitting diodes of the group.

2. An emissive pixel display according to claim 1, characterized in that the layer (201, 202) comprises quantum dots so that the scattered light is of higher wavelength than the light received from the light-emitting diodes and that the layer (201, 202) has an angularly extended light emission.

3. Emitting pixel screen according to claim 1 or claim 2, characterized in that the pixel comprises several groups of light-emitting diodes, and for each group of diodes of the pixel, a layer (201, 202, 203) of specific colorimetric property covers the light-emitting diodes of said group forming a cover specific to each of the groups.

4. Emissive pixel screen according to claim 3, characterized in that the layer (203) of one of said several groups of diodes comprises a diffusing charge and is without photoluminescent property.

5. Screen with emissive pixels according to one of claims 1 to 4, characterized in that the light-emitting diodes (101, ... 10n) are gallium nitride-based diodes known as micro-LEDs with identical emission spectra.

6. Emissive pixel screen according to one of claims 1 to 5, characterized in that a high optical density material (250) is placed between the groups of diodes.

7. Emissive pixel screen according to one of claims 1 to 6, characterized in that the layer forms an encapsulation of the diodes, or is placed on a layer of glass bonded to the diodes.

8. Method for replacing a cockpit display screen of an aircraft, comprising a step of removing (1) a liquid crystal screen with backlighting, and a step of replacing (3) said screen with a screen of resolution identical to the resolution of said liquid crystal screen, the replacement method being characterized in that the screen of identical resolution is chosen (2) as an emissive pixel screen for an aircraft cockpit, comprising a planar substrate carrying a plurality of light-emitting diodes of the same emission spectrum (101, ...lOn) and wherein each pixel consists of at least one compact group of several of said light-emitting diodes, and wherein in a pixel of the screen, the light-emitting diodes of the group of diodes are covered with a layer (201, 202, 203) forming a common cover for said light-emitting diodes of said group of diodes and relaying diffuse light, with or without photoluminescence, in reaction to the emission of light by the light-emitting diodes of the group, the number of light-emitting diodes in the groups being chosen so that, taking into account the number of groups, the size of the pixel is that of the pixels of the liquid crystal screen with backlighting.

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