FR2916286A1 - Backlight display for e.g. military helicopter, has light sources in which one source radiates in visible spectrum and another source radiates in spectrum having radiation pattern, and inverter type switch to light one of sources - Google Patents

Abstract

The display has a lighting plate placed behind a LCD screen (1), and a power supply unit. The lighting plate has two light sources i.e. incandescent bulbs (2, 3) in which one light source radiates in a visible spectrum, and another light source radiates in a spectrum having a radiation pattern that excludes a sensibility pattern of light intensification tubes. The power supply unit has an inverter type switch (5) to light one of the light sources. The incandescent bulb (2) has surrounded with a filter (4) for suppressing the radiations whose wavelength is detected in the sensibility pattern.

Description

The present invention relates to the production of screens

  Backlit, primarily intended for cockpits of aircraft, usable for displaying information both during the day and at night when the crew simultaneously uses night-vision binoculars, equipped with light-intensifying devices, at night to look outside of the device.

  The screens made according to the invention can be used on all types of vehicles for daytime driving and driving at night without lighting with the help of binoculars intensifying light.

  During the last fifteen years, the use of night vision binoculars with intensification of light has become widespread for the piloting first of the military land vehicles then for that of the helicopters and the also military planes and finally for that of the helicopters and civil aircraft. This use has led to the lighting of the cockpits and the edge instruments of these vehicles being adjusted in such a way as to avoid any dazzling of the Light Intensifying tubes, also called IL tubes, used for night vision.

  The appearance in the cockpits of backlit flat screens led to install, for night driving, in front of said flat screens, filters adapted to night vision. These filters let only the light rays to which the tubes IL are not sensitive. The manipulation of these filters and their storage in vehicles, whether terrestrial or air, is a heavy duty that the screen according to the invention allows to remove. This screen is therefore a very important improvement for the night driving of many land vehicles, air or sea.

  The principle of the invention is to install, for the backlight of the screen two types of light sources, one radiating throughout the visible spectrum and the other - 2 - radiating only in the invisible spectrum by the tubes IL, only one type of source being lit at a time. Thus the user can easily, with a simple switch, switch from a daylight position to a night lighting position, a position that will allow him to directly observe the information on the screen and, through the IL tubes, the external environment is very dimly lit.

  The invention therefore relates to a backlit screen of the type comprising: - a liquid crystal screen, - illumination means placed behind the screen, - power supply means, characterized in that the illumination means comprise at least two illumination sources, one radiating mainly in the visible spectrum and the other radiating in a spectrum having a radiation mask that excludes the sensitivity gauge of the intensifying tubes.

  Embodiments of the invention will be described hereinafter, by way of non-limiting examples, with reference to the accompanying drawings in which: FIG. 1 is a presentation of the principle of a backlit screen according to the invention,

  Figure 2 is a variant of the power supply of the screen according to the invention. FIG. 3 is a simplified diagram of a first embodiment of a backlit screen according to the invention, which embodiment uses fluorescent tubes for the backlighting of the screen. FIG. 4 is a drawing in three views of the screen. a first variant of backlit screen according to the invention, variant which uses light-emitting diodes of the coated type for the backlighting of the screen, FIG. 5 is a drawing in three views of a second backlit screen variant according to the invention, variant that uses light-emitting diodes adapted to surface mounting on a printed circuit for the backlighting of the screen,

  FIG. 6 is a three-view drawing of a variant of the screen of FIG. 3, variant which uses a filter for the backlighting of the screen. FIG. 7 is a drawing of the filter of FIG.

  FIG. 8 is a diagram of the transmission template of the filter of FIG. 7. FIG. 9 is a three-view drawing of a preferred variant of the backlit screen according to the invention, which variant uses both surface-mount light emitting diodes and a filter for the backlighting of the screen,

  FIG. 10 is a detailed diagram of the screen supply means of FIGS. 4, 5, 6 and 9 according to the invention,

  FIG. 11 is a three-view drawing of a last variant of a backlit screen according to the invention, in which variant light-emitting diodes are placed on the four sides of the screen for its backlighting.

  Figure 1 shows the basic principle of operation of a backlit screen for day and night vision according to the invention. There is a liquid crystal screen 1, the type of which may be any, and a backlight device composed of light sources placed behind the screen 1, at least one limited spectrum source 2 capable of radiating in a spectrum. light limited and located outside the sensitivity range of the light amplifier tubes used for night vision and at least one wide-spectrum source 3 that can radiate especially in the visible spectrum. These sources can be constituted for example by incandescent lamps of two kinds, a wide spectrum 3 and a limited spectrum 2. The limitation of the radiation spectrum of the first lamp 2 can be obtained by a filter 4 surrounding said lamp and which virtually eliminates all radiation whose wavelengths are in the sensitivity gauge of light intensifying tubes. Said filter 4 may also be part of the outer wall of said lamp 2. These two sources are separately supplied with current by a switch 5, of the inverter type and having two outputs, an output 6 for the day and an output 7 for the night. so that only one of the two sources is lit at a time. The current required is provided by a power supply 8. In the day position, the switch 5, switched on its output 6 feeds the broad-spectrum source 3. An observer 9, placed in front of the screen, sees it lit normally with all the range of colors that it can produce. In the night position, the switch 5 is switched on its output 7 and the observer 9 sees the screen in a smaller color range corresponding to the colors present in the radiation of the limited spectrum source 2. It can also observe the external environment using a night vision instrument 10 with intensification of light, which is not disturbed by the backlight of the screen 1. It should be noted that it can be interesting, in day position , keep both light sources 2 and 3 on. In this case, the supply of said sources is modified, FIG. 2, by adding a shunt 11 on the circuit between the power supply and the output 7 of the switch which supplies the broad-spectrum source 3

  FIG. 3 shows the principle of a first embodiment of a backlit screen according to the invention in which the light source is constituted by a series of electroluminescent tubes 12, substantially parallel, preferably in odd number, to keep a good symmetry at least three tubes and at least five tubes 13, 14, 15, 16 and 17, for example in FIG. 3, the tubes of even rows 14 and 16 radiating in a limited spectrum thanks to a filter 4 which surrounds each of the tubes and tubes odd rows 13, 15, 17 radiating in a wide spectrum and in particular in the visible spectrum.

  FIG. 4 shows the principle of a second embodiment of the invention in which the backlight is produced using light-emitting diodes in the following manner: the liquid crystal screen 1 is placed against an illuminating plate 18 , made of transparent material and whose dimensions, width and height, are substantially the same as those of the screen. This illuminating plate 18 is thicker than the screen and is covered on its rear face 19 by a thin coating 20, preferably white. It is itself illuminated on at least one and preferably two of its parallel sides 21 and 22 by conventional light-emitting diodes 23 and 24, of the encapsulated type of cylindrospheric shape for example, having a radiation axis 25. These light-emitting diodes are placed opposite said sides so that the radiation axis 25 of said diodes is substantially parallel to the plane of said illuminating plate 18 and preferably substantially perpendicular to said sides 21 and 22. The light-emitting diodes 24 radiate in a limited light spectrum to virtually eliminate all radiation whose wavelengths are in the sensitivity pattern of light intensifying tubes. The light-emitting diodes 23 radiate in a broad spectrum, the visible spectrum preferably. The number and distribution of the two types of light-emitting diodes along the sides of the illumination plate depends on the radiation characteristics of said diodes. They will nonetheless be of alternate preference along the sides of said plate being welded to printed circuit boards 26 as shown in FIG. 4.

  FIG. 5 shows a variant of the screen of FIG. 4, in which the cylindro-spherical coated diodes 23 and 24 are replaced by flat diodes 27 and 28 of much smaller dimensions, preferably of the type for surface mounting. on a printed circuit board. These diodes 27 and 28 are also soldered on printed circuit boards 26. In the same way, in this embodiment, the light-emitting diodes 28 radiate in a limited light spectrum. They are also preferably alternated with light-emitting diodes 27 which radiate in a wider spectrum, preferably the visible spectrum.

  In practice, it is preferable to use diodes of the same type to fulfill both functions day and night. For this purpose, and as shown in FIG. 6, where the screen uses conventional coated diodes 29 preferably radiating throughout the visible spectrum, a filter 30 is introduced between said light-emitting diodes 29 and the illuminating plate 18.

  This filter 30 is preferably made in the form of a bar 31, FIG. 7, of a length and a width substantially equal to those of the side of said illuminating plate 18. In order to enable daytime operation, this filter 30, also shown in section in FIG. 6, is pierced with holes 32 placed facing electroluminescent diodes 27, the radiation of which must not be filtered and which will be used for daylighting, preferably one diode out of two alternately. In the case of Figure 6 where light-emitting diodes 29 are placed along two opposite sides 21 and 22 of the illuminating plate 18, two filters 30 of the same type are used.

  The filters 30 are made for example in a filter material having a typical filtering pattern preferably in accordance with that of Figure 8. As shown in this template, the filters pass light radiation for all wavelengths at least included between 420 and 630 nanometers with a transmission coefficient K greater than 2916286 - 7 - at 0.2. The shaded area 48 shows these limits. In the same way, the filters transmit the light rays for all the wavelengths at least between 665 and 730 nanometers with a coefficient less than 0.01 and the wavelength radiations at least between 730 and 880. nm with a coefficient less than 0.001. These latter conditions are represented by the shaded area 49.

  The same filtering device is used in a preferred embodiment of the invention, Figure 9, derived from the variant of Figure 5. In this embodiment, a filter bar 31, pierced with holes 32, similar to that of Figure 7, is placed between flat diodes 33, all identical, soldered on printed circuit boards 26 and the side of the illuminating plate 18 facing it, 21 or 22.

  FIG. 10 shows in more detail the power supply means 20 for backlit displays by light-emitting diodes of FIGS. 6, 9 and 10 and which use filters 30. These supply means comprise, for example:

  a first current regulator 34 which supplies, from a power source 35 from the vehicle on which the screen is installed, the current required for the limited spectrum diodes 36, a second regulator 37 which provides in the same way, the current required by the wide-spectrum diodes 38, 30 - a current control 39 constituted for example by a potentiometer 40 and which acts simultaneously on the two current regulators 34 and 37 to control their output currents, therefore the illumination of the screen, - an attenuator 41 which acts on the regulator 37 to divide the controlled current by a ratio substantially equal to 1 / K or K is the transmission coefficient of the filters 30, - a bipolar inverter 42 which controls the switching from the day mode, position 43, to the night mode, position 44 - 8 - The potentiometer 40 which controls the illumination is preferably of the logarithmic type to allow a fine adjustment of the weak flash screen, which are used in night mode. This potentiometer can be replaced by pushbuttons acting more or less on the value of the controlled illumination, preferably logarithmically.

  The attenuator 41 makes it possible to compensate the effect of the filter on the limited spectrum diodes 36 by decreasing the power supply current of the wide spectrum diodes 38 and thus to keep substantially the same illumination of the screen by switching from the day mode. in the night mode. It should be noted that the bi-polar inverter 42 may be manually operated or automatically controlled, for example triggered by the illumination of night vision binoculars or by a photocell measuring ambient ambient illumination or by any other means. other way.

  It should also be noted that the illumination adjustment potentiometer can be manually controlled or be an electronic potentiometer controlled automatically by ambient lighting, for example.

  Figure 11 shows a variant of the screen where the illuminating plate 18 is illuminated by its four sides. Two of the sides, the high and low sides 21 and 22, for example, are equipped with electroluminescent diodes 45 without filter bars and the other two sides, left 46 and right 47, are each equipped with light-emitting diodes 45 and a bar filter 48, similar to the filter bar 31 but this time without any drilling. 35

Claims (11)

  1. Backlit screen of the type comprising: - a liquid crystal screen, - illumination means placed behind the screen, - power supply means, characterized in that the illumination means comprise at least two sources of illumination, one radiating mainly in the visible spectrum and the other radiating in a spectrum having a radiation mask that excludes the sensitivity gauge of the intensifying tubes of light.   2. backlit screen according to the preceding claim, characterized in that the power supply means comprise an inverter 5 for lighting only one of the light sources (2 or   3) at a time. 3. Backlit screen according to claim 1 or 2, characterized in that the illuminating means placed behind the screen (1) consist of at least two incandescent lamps (2 and 3), at least one of which (2) is surrounded by a filter (4) which substantially eliminates any radiation whose wavelengths are in the sensitivity gauge of the light intensifying tubes of the night vision binoculars (10), said filter (4) can also be part of the outer wall of said lamp (2).   Backlit screen according to one of the preceding claims 1 to 3, characterized in that the light sources consist of electroluminescent tubes (12), preferably in an odd number, at least one of which (14, 16) is surrounded by a filter (4) which virtually eliminates all the rays whose wavelengths are in the sensitivity gauge of the light-intensifying tubes, said filter (4) also being able to be part of the outer wall of said fluorescent tube (14,16).   Backlit screen according to claim 1 or 3 above, of the type comprising: - a liquid crystal screen (1), - an illuminating plate (18) placed behind the screen (1) and having sides (21 and 22) placed for example at the top and bottom of said plate, - illuminating means placed along these sides (21 and 22), characterized in that said illumination means are constituted by two types of light emitting diodes of preferably coated cylindro-spherical type, preferably alternately arranged, light-emitting diodes (23) which illuminate in a wide visible spectrum and diodes (24) which radiate in a limited spectrum of to remove practically all the rays whose wavelengths are in the sensitivity gauge of the intensified tubes.   Backlit display according to one of the preceding claims 1 or 3, of the type comprising: - a liquid crystal screen (1), - an illuminating plate (18) placed behind the screen (1) and having sides (21 and 22) placed for example at the top and bottom of said plate, - illumination means placed along these sides (21 and 22), characterized in that illumination means placed along the sides 21 and 22) of the illuminating plate (18) are constituted by two types of flat-type light-emitting diodes, preferably for circuit board mounting, preferably alternately arranged, the radiation face placed opposite the electroluminescent diodes, sides (21 and 22) of the illumination plate (18), light-emitting diodes (23) which illuminate in a wide visible spectrum, and diodes (24) which radiate in a limited spectrum so as to suppress substantially all the radiation whose wavelengths are in the ga sensitivity of intensified light tubes.   Backlit display according to Claim 5, characterized in that the light-emitting diodes with limited radiation are replaced by broad spectrum electroluminescent diodes (29) and in that the limitation of the spectrum is obtained by filters (30) made for example in strips (31) of filter material, each placed between said light-emitting diodes (29) and one of the sides (21, 22) of the illuminating plate (18), said bar (31) being pierced with placed holes in front of each of the diodes whose radiation must not be filtered, that is to say preferably in front of one diode (29) out of two.   Backlit display according to Claim 6, characterized in that the light-emitting diodes with limited radiation are replaced by wide-spectrum flat light-emitting diodes, preferably for mounting on printed circuits (33) and in that the limitation of spectrum is obtained by filters (30) made for example in strips (31) of filter material, each placed between said light-emitting diodes (33) and one of the sides (21, 22) of the illuminating plate (18), said bar (31) being pierced with holes placed in front of each of the diodes whose radiation must not be filtered, that is preferably in front of one diode (33) out of two.   9. backlit screen according to claim 8, characterized in that the wide-spectrum illumination means, flat-type light-emitting diodes (33) for surface mounting printed circuits, are placed for example on two of the sides ( 21, 22) of the illuminating plate (18) facing each other and in that the illumination means radiating in a limited spectrum, also preferably flat-type light-emitting diodes (33) for surface mounting of the printed circuit boards , are placed on the other two sides (46, 47) of the illumination plate (18), two filters 30 being placed between said sides (46, 47) and the electroluminescent diodes facing them, said filters 30 being devoid of holes.   Backlit screen according to one of the preceding claims 2 to 5 to 9, characterized in that the filters (4, 30), which limit the light radiation of the limited radiation sources, have a transmission mask such as that they let a maximum of light pass with a coefficient K greater than 0.2 for wavelengths of at least less than 630 nanometers and in that they let the minimum of light pass with a coefficient K less than 0.001 for wavelengths at least between 730 and 880 nanometers 15   Backlit display according to one of the preceding claims, characterized in that only the limited spectrum light sources are switched on in a night mode and in that the wide spectrum light sources are switched on in one mode. of day operation and that the transition from day mode to night mode can be controlled automatically.