Method for implementing a device for displaying a real image

Abstract

Method of using a device for displaying a real image of the head-up display (HUD) type in a passenger compartment comprising glazing, notably laminated glazing, said device comprising a source emitting a beam of radiation of the visible UV or IR laser type or of the light-emitting diode type, directed towards a portion of said glazing comprising a fluorescent material absorbing said radiation and re-emitting light in the visible region, the illumination of said portion by the beam enabling a real image to be displayed on the glazing.

Claims

1. A method for displaying a real image on a glazing fitted in a passenger compartment, wherein the displaying occurs with a device comprising a source emitting a beam of radiation of visible UV or IR laser or from a light-emitting diode, directed towards a portion of the glazing comprising a fluorescent material absorbing the radiation and re-emitting light in the visible region, the illumination of the portion by the beam enabling the image to be displayed on the glazing, wherein the method comprises: (a) identifying a set of positions i.sub.[1;n]in the passenger compartment from which the source can illuminate substantially the same portion of the glazing: (b) from a first position i.sub.1 of the source in the passenger compartment, emitting a polarized incident beam in such a way that its electromagnetic field is transverse magnetic; (c) for a whole portion of the glazing illuminated by the beam, measuring variations of an angle of incidence ?.sub.1, and determining a value of an angle ?.sub.1(Rmax) for which a reflection R.sub.1 max of incident radiation by the glazing is maximal in the illuminated area and for the first position i.sub.1 of the source; (d), performing steps (d1) and (d2) so as to determine a value ?.sub.2(Rmax) for which a reflection R.sub.2max of the incident radiation by the glazing is maximal in said illuminated area and for the source location i.sub.2 wherein step (d1) is a step emitting a polarized incident beam in such a way that its electromagnetic field is transverse magnetic from a second position i.sub.2 of the source in the passenger compartment, and step(d2) is a step of, for a whole portion of the glazing illuminated by the beam, measuring variations of an angle of incidence ?.sub.2 and determinin a value of an angle ?.sub.2(Rmax) for which a reflection R.sub.2max of incident radiation by the glazing is maximal in the illuminated area and for the second position i.sub.2 of the source; (e) performing steps (e1) and (e2) for all source positions i.sub.n wherein step (e1) is a step of emitting a polarized incident beam in such a way that its electromagnetic field is transverse magnetic from a n-th position i.sub.n of the source in the passenger compartment, and wherein step (e2) is a step of, for a whole portion of the glazing illuminated by the beam, measuring variations of an angle of incidence ?.sub.n, and determining a value of an angle ?.sub.n(Rmax) for which a reflection R.sub.nmax of incident radiation by the glazing is maximal in the illuminated area and for the n-th position i.sub.n of the source: and (f) locating the source in a position i for which a value R.sub.imax is minimal.

2. The method of claim 1, wherein the source generates a visible UV laser radiation in a range from 380 to 410 nm.

3. The method of claim 1, wherein the source is a device generating UV laser radiation over an angular half-width ?.sub.1/2 in the range from 5? to 25? serving to illuminate the portion of the glazing.

4. The method of claim l, wherein the device is selected from the group consisting of a projector having a MEMS micro-minor with a laser source, a projector having DLP, LCD or LCoS matrices with a laser or LED source, and a projector having galvanometer-mounted mirrors reflecting a laser source.

5. The method of claim 1, wherein the glazing is a laminated glazing comprising an assembly of at least two transparent sheets of inorganic glass or strong organic material, joined together by an interlayer of a thermoformable material or by multilayer sheets incorporating the interlayer, said glazing having a fluorescent material integrated into the interlayer, and permitting display.

6. The method of claim 5, wherein the thermoforinable material forming the interlayer is selected from the group consisting of a PVB, a plasticized PVC, a polyurethane and an ethylene vinyl acetate.

7. The method of claim 5, wherein the fluorescent arterial is a hydroxyakyl terephthalate ROOC-?(OH).sub.xCOOR, having the structural formula: ##STR00002## wherein: ? represents a benzene ring substituted by at least one hydroxy group (OH), R is a hydrocarbonated chain comprising 1 to 10 atoms, and x is equal to 1 or 2.

8. The method of claim 7, wherein the fluorescent material is diethyl-2,5-dihydroxy terephthalate.

9. A passenger compartment, comprising a device for displaying a real image on a glazing, said device comprising a source emitting a beam of a concentrated directional radiation of laser directed towards a portion of the glazing comprising a fluorescent material absorbing the radiation and re-emitting light in the visible region, the illumination of the portion by the beam permitting the display of a real image on the glazing, wherein the source is positioned in the passenger compartment by the method of claim 1.

10. The method of claim 1, wherein the glazing is a laminated glazing.

11. The method of claim 1, wherein the source generates a visible UV laser radiation in at 405 nm.

12. The method of claim 1, wherein the source is a device generating UV laser radiation over an angular half-width ?.sub.1/2 in the range from 10? to 20? serving to illuminate the portion of the glazing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic illustration of a windscreen and a device positioned in a passenger compartment of a motor vehicle (not shown).

(2) FIG. 2 shows various possible configurations of the positioning of the projector in a single vertical plane of the windscreen.

(3) The invention and its advantages will be made more evident by a reading of the following description of an embodiment of the invention, with reference to the attached FIG. 1.

(4) The windscreen 1 is composed of two sheets 2 and 9, which are typically made of glass but which could equally well be made of sheets of strong plastic material of the polycarbonate type. Between the two sheets there is a plastic interlayer 3 such as PVB (polyvinyl butyral), plasticized PVC, PU or EVA, or a multilayer thermoplastic sheet incorporating, for example, PET (polyethylene terephthalate), in which the sequence of layers is, for example, PVB/PET/PVB.

(5) Particles of organic fluorescent material of the terephthalate type according to the invention are deposited on at least one part of the inner surface of the thermoplastic interlayer 3 before the lamination, in other words before the assembly of the various sheets.

(6) The particles of fluorescent material have a size distribution mainly in the range from 1 to 100 microns. The term mainly signifies that more than 90% of the particles forming the commercial powder have a diameter in the range from 1 to 100 microns. Preferably, the particles of terephthalate fluorescent material are subjected to preliminary treatment to promote their impregnation into the thermoplastic PVB sheet. More specifically, the particles are incorporated in a PVB-based binder in advance.

(7) A laser source 4 emitting an exciting light radiation is used to send an incident concentrated radiation 7 with a wavelength of 405 nm towards a portion 10 of the windscreen on which the real image is to be generated. At least this portion of the glazing comprises a suitable fluorescent material. The fluorescent material is advantageously of the hydroxy-terephthalate type as described in the application WO2010/139889, and is, for example, solvated in molecular form in the thermoplastic interlayer 3. The fluorescent material has a high absorption coefficient for incident radiation. It subsequently re-emits radiation in the visible region, in other words radiation close to 450 nm, with an efficiency of more than 80%. Advantageously, the laser projector further comprises a polarizer for polarizing the incident beam, particularly in such a way that its electromagnetic field is transverse magnetic.

(8) For the purpose of the present invention, the term transverse magnetic signifies a TM/TE polarization ratio of at least 100:10, or preferably at least 100:1.

(9) The visible radiation emitted by the fluorescent material is then directly observable by the driver's eye 5, which thus views the object on the windscreen without having to look away from the road. In this way, an image can be directly formed on a laminated windscreen without any need to adapt the structure of the windscreen, in respect of the thickness of the interlayer for example. This enables HUD systems to be manufactured economically.

(10) According to the invention, the source used to generate the concentrated radiation is a UV laser source. The possible sources include, but are not limited to, solid lasers, semiconductor diode lasers, gas lasers, dye lasers and excimer lasers. As a general rule, any known source generating a UV radiation flux which for the purposes of the present invention is directed and concentrated can be used as an excitation source according to the invention. Alternatively, it is possible to use incoherent light sources such as light-emitting diodes, preferably of the power type and operating in the near UV region.

(11) In one possible embodiment, a DLP projector can be used to modulate the exciting radiation by the method described in the application US 2005/231652, paragraph [0021]. It is also possible, according to the invention, to use as the UV excitation source a device as described in the application US2004/0232826, notably one of the type described in relation to FIG. 3.

(12) These systems can be used to illuminate specific portions of the glazing with the laser radiation, in order to display any information useful to the driver while he is driving, notably for the purpose of ensuring his safety, or for navigation.

(13) Clearly, the preceding embodiment does not limit the present invention in any way regarding the aspects described above.

(14) According to the invention, the area in question can be illuminated by a device operating by rapid scanning of said area by the source or by the simultaneous activation of pixels in said area by means of a plurality of mirrors controlled by said source.

(15) In particular, in a first embodiment, a projector based on a MEMS micro-mirror with a laser source can be used. In another embodiment, projectors based on DLP, LCD or LCoS matrices with a laser or LED source are used. Alternatively, it is possible, according to the invention, to use a projector based on galvanometer-mounted mirrors reflecting a laser source.

(16) In the passenger compartment of a vehicle of this kind, the main safety problem during the operation of the device is posed by the reflected part of the radiation on the surface of the windscreen, which may be, in a first approximation, relatively high and directed towards the passengers' eyes, if allowance is made, notably, for the inclination and curvature of the laminated windscreen in the area illuminated by the incident beam.

(17) According to the invention, the source, such as a UV laser source, is positioned in the passenger compartment by the method according to the present invention, so as to minimize the reflection of the incident radiation from the inner wall of the windscreen towards the passenger compartment.

(18) By way of example, in the case of a passenger compartment of a motor vehicle, the projector can be located in numerous positions, including, but not limited to, the most common positions which are on the dashboard, on the ceiling of the vehicle or on the windscreen uprights. For a given passenger compartment, and depending on the portion of the windscreen onto which the image is to be projected, it is thus possible to identify the set of positions where the projector can be installed.

(19) The following examples, based on the modelling of the embodiment described above, demonstrate the advantages obtained by the use of the present method for the positioning of the laser projector with the purpose of minimizing the previously described risks for the passengers in the vehicle, by substantially reducing the degree to which the beam emerging from the source is reflected on the surface of the windscreen.

EXAMPLES

(20) The present examples relate, once again, to the embodiment described previously with reference to FIG. 1, in which the laminated windscreen 1 comprising the fluorescent material is illuminated by the source or projector 4 of the laser radiation which illuminates a portion 10 of the glazing.

(21) The attached FIG. 2 shows various possible configurations of the positioning of the projector in a single vertical plane of the windscreen, for the sake of simplicity (projection 1D). Clearly, in a real case, the illuminated area would also comprise a horizontal component which is not shown here.

(22) It is assumed that the projector used is a visible UV laser with a radiation of 405 nm which is constructed in such a way that it has an angular half/width ?.sub.1/2 of 10?.

(23) The term angular half-width signifies, for the purposes of the present invention, the angle between the most divergent rays which can be emitted by the projector and the optical axis of the projector.

(24) For a first position, the device is placed in a position 1 (FIG. 2), in order to illuminate the area 10 on the windscreen 1. As shown in FIG. 2, and for the purposes of the present description, the angle of incidence ?.sub.1 is defined as the angle between the beam, when this is emitted in the central position of the laser device (in other words along the optical axis of the projector), and the perpendicular to the windscreen at the point of incidence on the glazing, with allowance for the curvature and inclination of the latter.

(25) For each point illuminated in this way, between the intervals ?.sub.1min and ?.sub.1max, corresponding to the limit angular widths of the device (in other words, ??.sub.1/2 and +?.sub.1/2 respectively about the central position of the beam), the percentage R of reflection of the incident radiation is determined, using conventional modelling methods for example.

(26) Finally, a value ?.sub.1(Rmax) and an associated value R.sub.1max, corresponding to a maximum value of the reflection of the radiation, are determined, for conditions in which: the incident radiation is non-polarized (NP), the incident radiation is transverse electric polarized (TE), the incident radiation is transverse magnetic polarized (TM).

(27) The projector is then moved to another position i.sub.2 such that the same area 10 can be illuminated by the projector. In this configuration, the beam strikes the windscreen with another angle of incidence equal to ?.sub.2.

(28) As in the preceding configuration, for each point scanned in this way between the intervals ?.sub.2min and ?.sub.2max, the percentage R of reflection of the incident radiation is determined, together with a value ?.sub.2(Rmax) and an associated value R.sub.2max as a function of the polarization of the incident radiation.

(29) The principal results obtained for different calculated positions are shown in Table 1 below.

(30) TABLE-US-00001 TABLE 1 Maximum reflection (R.sub.imax) Angle ?.sub.i Polarization in the range ? ?.sub.1/2 0? TM 4.54% 0? TE 4.73% 0? NP 4.55% 20? TM 4.36% 20? TE 6.50% 20? NP 4.70% 55? TM 1.16% 55? TE 24.4% 55? NP 12.8% 60? TM 4.04%

(31) The data in Table 1 show that the reflection rate can be limited when the radiation is transverse magnetic polarized (TM) and when the angle of incidence ? of the beam on the windscreen is about 50?, with allowance for the curvature and inclination of the windscreen and the angular width of the source. In a second set of experiments, the source was modified in such a way that its angular half-width ?.sub.1/2 was equal to 20?.

(32) Proceeding in the same manner as before, the present method was used to determine the optimal angle at which the reflection of the incident radiation from the windscreen was minimal. The results obtained and a comparison with the previous example are shown in Table 2 below:

(33) TABLE-US-00002 TABLE 2 Optimal angle Maximum reflection R.sub.max Polarization ? ?.sub.1/2 in the range ? ? ?.sub.1/2 TM 55? 10? 1.16% Non-polarized 0? 10? 4.55% TM 48? 20? 3.12% Non-polarized 0? 20? 4.57%

(34) The combined analysis of the results given in Tables 1 and 2 shows that an optimal positioning of the source can be found by the use of the present method, with allowance for the nature of the passenger compartment and the shape and positioning of the windscreen, on the basis of the principles and parameters set out above.