Electronic display device offering a daytime display function and a display function compatible with night vision instruments

Abstract

An electronic display device comprising a display surface, and on the display surface, an arrangement on said surface of a plurality of elementary components for composing an image, the device further comprising a control circuit for the plurality of elementary components, configured to individually control each of the elementary components of the plurality, each elementary component being constituted by a compact assembly of light-emitting diodes of different colors, a group of light-emitting diodes of the compact assembly comprising a so-called red diode which is closest in the group, by its emission spectrum, to the red end of the visible light spectrum and one or more other light-emitting diodes which together have a common emission spectrum comprising, in nominal operation, proportionally less red than that of the red light-emitting diode,said group being controlled to perform, with the other elementary components, a color display for a naked-eye operator. The compact assembly further includes a light-emitting diode in addition to those of said group, which, in nominal operation, has, relative to said red diode, a wavelength shifted further from red, and, relative to said common emission spectrum, an additional emission spectrum, said additional light-emitting diode being controlled to be illuminated in place of said red diode when said group is controlled to perform, with the other elementary components, a color display compatible with the use by an operator, in the vicinity of the display device, of a near-infrared sensitive night vision tool. Figure for the abbreviation: FIGURE 1A,

Description

Title of the invention: Electronic display device providing a daytime display function, and a display function compatible with night vision instruments Field of invention

[0001] The invention relates to the field of color display screens, in particular for aeronautics. State of the art

[0002] Of particular interest are screens for the control station 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.

[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. It is therefore the TFT thin-film transistors allowing the voltage control of the liquid crystals that define the pixels.To obtain a coloration, three or four liquid crystal cells per pixel are used, each equipped, parallel to the liquid crystal, with a red, green or blue, or even white, colored filter, which allows, by lighting one or more, to obtain the desired color. 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 in PMMA (poly methyl methacrylate acrylic or plexiglass), loaded in its volume to diffuse on the plane, or equipped on the surface with a screen printing of diffusing points for example. The edge-lit is a strip made up of a row of LEDs fixed to the circumference of the panel (in its rectangular frame), emitting horizontally in the diffusing light guide.

[0004] Furthermore, in aeronautics, and in particular in certain specific applications such as maritime patrol activity, or mountain rescue, or military aircraft, pilots or other professional personnel required to be in the cockpit use binoculars or night vision helmets commonly called NVIS for Night Vision Imaging Systems or imaging systems for night vision, which react to the near infrared range (wavelengths from 0.78 to 2.5 pm). These near infrared waves are reflected by surfaces, even cold bodies. These instruments rely on amplifiers or intensifiers of residual light. They use the near infrared waves present in the environment, for example simply due to the presence of the moon in the sky.

[0005] It is then necessary that the displays and indicators in the cockpit of aircraft which are used with night vision equipment are non-emissive or low-emissive elements for the near infrared and by contiguity for the most pronounced red beyond 640 or 650 nm. For simple button indicators, this is done with interference filters or green filters, which do not allow the wavelengths thus mentioned to pass. This makes it possible, for these simple elements and present in cockpits in large numbers for a long time, to protect the environment of the professional, so as not to pollute his field of vision when he wears the night vision equipment.

[0006] But when it comes to LCD display screens, which are increasingly present and of increasing size, the same problem is of course present. It is known to have a two-stage display system: a day function provided by a carpet of LEDs in the background, which generates all the wavelengths of the visible, including the pronounced red, and a night function provided by an edge-lit equipped with filters to prevent the emission of red and infrared wavelengths. Thus, the light which reaches the liquid crystals and the colored filters parallel to them does not contain the wavelengths of the most pronounced red.

[0007] In some constructions, the edge-lit contains unfiltered LEDs that provide white light, including red, and filtered LEDs that provide light suitable for working with night vision binoculars or helmets, without the red end of the visible spectrum. One or the other of the two edge-lit systems is therefore switched on depending on the needs.

[0008] Regardless of these considerations, LCD liquid crystal display technologies, based on the transmission and occultation of light permanently present in the background, are complemented or competed with by technologies where colored light is emitted by a quantum dot (sometimes also called a quantum box), namely a small physicochemical structure capable of emission or fluorescence in a narrow spectral range. Such a quantum dot can be used in a liquid crystal display, and it is also used in LED-based technologies for consumer displays.

[0009] Thus, for example, OLED screens, without liquid crystals and without permanent backlighting, are enjoying success - this is well known - 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 superposition of several organic semiconductor layers and can be placed in groups of 4: one white, one red, one green and one blue, and it is possible to turn them all off at the same time to have a deep black. Color can be obtained in recent models thanks to a quantum dot, even if less sophisticated color filters, which offer less precision in the selection of wavelengths, are also used. Importantly, the lifetime of these products seems insufficient for aeronautical applications.And their luminance potential also seems insufficient for these applications.

[0010] Micro-LEDs, on the other hand, are objects of recent emergence, on the one hand smaller (down to as little as 50 pm in width), 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 for example controlled by CMOS circuits providing digital control.

[0011] The micro-LEDs can be placed in groups of three micro-LEDs each having one of three colors Red (approximately 630 nm) Green (approximately 570 nm) and Blue (approximately 450 nm) or RGB in the visible spectrum, close to each other in a horizontal arrangement, vertical arrangements also existing.

[0012] As they are switched on separately from each other, it is also possible to switch them off simultaneously, which then provides a deep black, and in the end, the contrast is good.

[0013] Micro-LEDs are being considered that are natively different colors, but for the moment, the light output is not sufficient. We can also use natively blue micro-LEDs, which are more energy efficient, with, for two out of three micro-LEDs, a quantum dot to generate from blue, either green or red depending on the size of the quantum dot, in both cases with a line width that is also quite small, at mid-peak of 20 to 30 nm. Instead of quantum dots, a phosphor deposit can be used.

[0014] Micro-LEDs heat up little, have a high luminance, and a short response time. Their lifespan is also advantageous. The manufacturing processes are still being developed (they involve depositing materials on glass or silicon wafers, with dimensions of less than 50 pm), which means that these products are expensive in the immediate future.

[0015] But no NVIS compatible system with micro-LEDs has been proposed at the moment.

[0016] To provide more efficient operation, there is provided an electronic display device comprising a display surface, and on the display surface, an arrangement on said surface of a plurality of elementary components for composing an image, the device further comprising a circuit for controlling the plurality of elementary components, configured to individually control each of the elementary components of the plurality, each elementary component being constituted by a compact assembly of light-emitting diodes of different colors, a group of light-emitting diodes of the compact assembly comprising a so-called red diode which is closest in the group, by its emission spectrum, to the red end of the visible light spectrum and one or more other light-emitting diodes which together have a common emission spectrum comprising, in nominal operation,proportionally less red than that of the red light-emitting diode, said group being controlled to carry out with the other elementary components a color display for an operator with naked eyes.

[0017] The device is remarkable because the compact assembly further comprises a light-emitting diode in addition to those of said group, which has, in nominal operation, with respect to said red diode, a wavelength shifted less close to red, and with respect to said common emission spectrum an additional emission spectrum, said light-emitting diode in addition being controlled to be lit in replacement of said red diode which is then extinguished when said group is controlled to carry out with the other elementary components a color display compatible with the use by an operator and in the vicinity of the display device of a night vision tool sensitive to near infrared.

[0018] Optionally and advantageously:

[0019] - the group may comprise a red diode, a green diode and a blue diode;

[0020] - the less red-shifted wavelength can be shifted by 5 to 50 nm relative to the said diode closest to the red end of the visible spectrum;

[0021] - the less red-shifted wavelength may be less than 640 nm.

[0022] - the light-emitting diodes can be micro-LEDs or micro LEDs inorganic semiconductor scopic;

[0023] The light-emitting diodes can be organic LEDs or OLEDs.

[0024] - the compact assembly may be a group of four light-emitting diodes, each of the light-emitting diodes is rectangular and of identical length and width to the others, and said light-emitting diodes are arranged in a checkerboard pattern, length against length and width against width; The diodes may be shaped diamond-shaped, or hexagonal.

[0025] - the light-emitting diodes may be blue light-emitting diodes which, for some, are covered with a quantum dot to provide a different color;

[0026] - the light-emitting diodes may be blue light-emitting diodes which, for some, are covered with phosphorus to provide a different color;

[0027] - the light-emitting diodes may be na light-emitting diodes tively of distinct colors;

[0028] The light-emitting diodes may comprise electronically excited quantum dots.

[0029] - the device may comprise a low current control circuit for the light-emitting diode having a wavelength shifted less close to red, and for light-emitting diodes used in combination with the light-emitting diode having a wavelength shifted less close to red to form color combinations.

[0030] - the arrangement of the diodes can constitute a paving of the surface. Brief description of the drawings

[0031] 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:

[0032] Figures 1A, 1B, 1C and 1D are schematic representations of examples of display devices according to the invention.

[0033] [Fig.2] is a view of a method according to the invention.

[0034] [Fig. 3] is a representation of the emission wavelengths of the different elements of an embodiment of the invention. Detailed description of the drawings

[0035] The pixel is a basic set of colored light-emitting diodes which, when grouped together, form the image element.

[0036] [Fig.lA] [Fig.lA] is a view of an arrangement of micro-LEDs according to the invention.

[0037] Pixels 1, 2, 3 ... of rectangular shape are arranged in a checkerboard pattern, widths against widths, lengths against lengths. These pixels can be square. The checkerboard arrangement allows for a complete tiling of the display device plane, with no space not covered by the pixels. Of course, between two pixels, there is a thin, non-luminous structural separation strip which allows, depending on the design, mechanical support, electrical connection, electrical or thermal insulation. The separation strip can be reduced to the strict minimum until it is invisible. Each of the pixels 1, 2, 3 ... is composed of four Square micro-LEDs of four constant colors from one pixel to the next and arranged in a 2x2 checkerboard with, preferably, but not absolutely essential, the same relative arrangement in each pixel. The four colors are red, green, blue and orange, and thus in each pixel there are arranged a red micro-LED 10, a blue micro-LED 20, a green micro-LED 30 and an orange micro-LED 40 (or "NVIS red"), the red and orange micro-LEDs being diagonal to each other, although alternatively it is envisaged that they touch each other on the side.

[0038] The orange micro-LED 40 is used as a replacement for the red micro-LED 10 in night vision situations with NVIS equipment. Conversely, the red micro-LED 10 is used in daytime vision situations, and in general in all vision situations without night vision equipment. The micro-LEDs 20 and 30 are used in all circumstances.

[0039] Alternatively, instead of having a square checkerboard tiling of the plane, a tiling is implemented to form hexagonal pixels, or diamond pixels.

[0040] For the orange micro-LED 40, a population of quantum dots is chosen with an emission wavelength (directly dependent on the size of the nanoparticles) for example located between 600 and 620 nm.

[0041] For the red, green and blue pixels, quantum dots tuned to usual wavelengths are used, making it possible to cover the NTSC gamut as much as possible, for example. The quantum dots can be perovskite quantum dots.

[0042] Alternatively, narrow-spectrum phosphors or other luminescent material are used. The phosphor (narrowband) or other luminescent material is chosen to match the desired red saturation for daytime or NVIS mode. Alternatively, micro-LEDs are chosen that natively emit at the desired wavelengths.

[0043] [Fig.lB] [Fig.lB] is a view of an arrangement of micro-LEDs according to a second embodiment of the invention. Here, the light-emitting diodes are diamond-shaped.

[0044] For the diamond arrangement shown in [Fig.IB], the dotted lines represent pixel 5, and in this way we have more pixels contributing to daylight white.

[0045] Depending on the design needs, one chooses to favor one color over another to adapt to the differences in performance from one color to another.

[0046] It is proposed to use proportionally few orange light-emitting diodes, or few blue light-emitting diodes.

[0047] [Fig.lC] In the embodiment of [Fig.lC], the light-emitting micro-diodes are hexagonal. The structure is symmetrical: for a set of two micro-diodes, one green, the other blue, a triangular triplet is formed with an orange micro-diode (for the NVIS mode) or in an opposite direction with a micro-diode red for day mode.

[0048] [Fig.lD] In the embodiment of [Fig.lD], the diodes are hexagonal in shape and the pixel is an octagon. The figure shows an octagonal pixel that contains more red than orange in day mode and an octagonal pixel that contains more orange than red in NVIS mode.

[0049] [Fig.2] [Fig.2] is a diagram of a method of operation of a device according to the invention.

[0050] A step 100 makes it possible to start the system. A step 200 makes it possible to choose whether the system must operate in conventional vision mode, with the three micro-LEDs 10, 20 and 30 which make it possible during the operating mode 300, depending on the respective intensities imposed on them, to produce a light possibly comprising wavelengths across the entire spectrum of visible light, from violet to red.Alternatively, if the choice step 200 makes it possible to decide that the system must operate in vision mode for use of the NVIS hardware, it switches to an operating mode 350 with the three micro-LEDs 10, 20 and 40 which also make it possible, depending on the respective intensities imposed on them, to produce a light possibly comprising wavelengths over a wide range of the visible light spectrum, complete towards violet but this time, unlike the operating mode 300, trimmed at its end towards red, which makes it compatible with the NVIS vision devices.

[0051] It is advantageous to provide two control circuits or one circuit with drivers capable of operating in high current mode or in low current mode. The low current mode will be used to control the four LEDs in NVIS mode, and LED 40 will be controlled only in low current mode.

[0052] [Fig.3] [Fig.3] shows the emission wavelengths of the different elements of the invention. The visible spectrum, from 380 to 780 nm, is represented on the abscissa, and the relative luminous intensity in arbitrary units is represented on the ordinate.

[0053] The curve represented the sum of the emissions of the light-emitting diodes, in variable number depending on the embodiments, which are not the diode closest to the red end of the spectrum. In the most common embodiment, it is the set of a blue diode and a green diode.

[0054] The single curve a can therefore be replaced by a set of several curves, namely the curves of different diodes taken independently of one another, all being diodes which have an emission maximum less close to red than the diode loaded with the rightmost part of the spectrum, which is typically red, and can, according to the invention, be present in two forms, one red and one orange, the first being used in standard conditions, and the second in NVIS compatible usage mode.

[0055] Curve b represents the emission of the red diode with a fairly fine Gaussian shape, with a maximum at approximately 650 nm for a maximum intensity one third higher than the maximum intensity of curve a due to the concentration of energy in a narrow range due to the presence of a single diode. The diode having this curve b as its emission curve is used during operation in day mode.

[0056] Curve c represents the emission of the orange diode with again a fairly fine Gaussian shape, with a maximum at approximately 610 nm. The diode having this curve c as its emission curve is used when operating in NVIS mode, compatible with the use of equipment in night vision mode.

[0057] It is further mentioned here that, for a given diode, the emission spectrum of the diode does not change shape sufficiently as a function of the power supplied to the diode for the change in shape to be taken into account in the disclosure and definition of the invention. Essentially, it is reasonable to retain that the shape of the emission spectrum of an individual diode is constant from zero power to the nominal operating power of the diode, and that it is perfectly possible to use the given diode at any power between zero power and the intended nominal power, or even beyond, without the wavelength of the maximum of the spectrum being significantly modified, nor the width of the Gaussian, for example at half-height.

[0058] Optionally, the device may provide the user with a command for a gradual transition between the daytime operating mode, using the red LED and not using the orange LED, to the NVIS operating mode not using the red LED but using the orange LED. The gradual transition may be made by a manual control of the thumbwheel or rotary knob type, and may be used in circumstances where the NVIS mode is used momentarily, may become momentarily useless, and may become useful again. The command for gradual transition introduces a percentage of power into the red LED and the complementary percentage of power into the orange LED, the percentage being adjustable by the thumbwheel or rotary knob. Optionally, the gradual control is controlled by a processor and an algorithm, and is implemented automatically, for example on the basis of signals from sensors.

Claims

Claims

1. An electronic display device comprising a display surface, and on the display surface, an arrangement of a plurality of elementary components (1, 2, 3) for composing an image, the device further comprising a circuit for controlling the plurality of elementary components (1, 2, 3), configured to individually control each of the elementary components (1, 2, 3) of the plurality, each elementary component (1, 2, 3) being constituted by a compact assembly (10, 20, 30, 40) of light-emitting diodes of different colors, a group of light-emitting diodes (10, 20, 30) of the compact assembly comprising a so-called red diode (10) which is closest in the group (10, 20, 30), by its emission spectrum, to the red end of the visible light spectrum and one or more other light-emitting diodes (20, 30) which together have a spectrum common emission including, in nominal operation,proportionally less red than that of the red light-emitting diode (10), said group (10, 20, 30) being controlled to perform with the other elementary components (1, 2, 3) a color display for an operator with naked eyes, the device being characterized in that the compact assembly (10, 20, 30, 40) further comprises an additional light-emitting diode (40) to those of said group, which has, in nominal operation, with respect to said red diode (10), a wavelength shifted less close to red, and with respect to said common emission spectrum an additional emission spectrum, said additional light-emitting diode (40) being controlled to be lit in replacement of said red diode (10) which is then extinguished when said group (10, 20, 30) is controlled to perform with the other elementary components (1, 2,3) a color display compatible with use by an operator and in proximity to the display device of a night vision tool sensitive to near infrared.,

2. Electronic display device according to claim 1, characterized in that the group (10, 20, 30) comprises a red diode, a green diode and a blue diode.

3. An electronic display device according to claim 1 or claim 2, characterized in that the less red-shifted wavelength is shifted by 5 to 50 nm relative to said diode. closer to the red end of the visible spectrum.

4. Electronic display device according to one of claims 1 to 3, characterized in that the wavelength shifted less close to red is less than 640 nm.

5. Electronic display device according to one of claims 1 to 4, characterized in that the light-emitting diodes (10, 20, 30, 40) are micro-LEDs, or microscopic inorganic semiconductor LEDs.

6. Electronic display device according to one of claims 1 to 4, characterized in that the light-emitting diodes (10, 20, 30, 40) are organic LEDs or OLEDs.

7. Electronic display device according to one of claims 1 to 6, characterized in that the light-emitting diodes are rectangular, hexagonal or diamond-shaped.

8. Electronic display device according to one of claims 1 to 7, characterized in that the light-emitting diodes are blue light-emitting diodes, some of which are covered with a quantum dot to provide a different color, or that the light-emitting diodes are blue light-emitting diodes, some of which are covered with phosphorus to provide a different color, or that the light-emitting diodes are light-emitting diodes natively of distinct colors, or that the light-emitting diodes comprise electronically excited quantum dots.

9. An electronic display device according to one of claims 1 to 8, characterized in that it comprises a low current control circuit for the light-emitting diode having a wavelength shifted less close to red, and for the light-emitting diodes used in combination with the light-emitting diode having a wavelength shifted less close to red to form color combinations.

10. Electronic display device according to one of claims 1 to 8, characterized in that the arrangement of the diodes constitutes a paving of the surface.

Images