Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F21—LIGHTING
  • F21S—NON-PORTABLE LIGHTING DEVICES; SYSTEMS THEREOF; VEHICLE LIGHTING DEVICES SPECIALLY ADAPTED FOR VEHICLE EXTERIORS
  • F21S41/00—Illuminating devices specially adapted for vehicle exteriors, e.g. headlamps
  • F21S41/20—Illuminating devices specially adapted for vehicle exteriors, e.g. headlamps characterised by refractors, transparent cover plates, light guides or filters
  • F21S41/25—Projection lenses
  • F21S41/255—Lenses with a front view of circular or truncated circular outline
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F21—LIGHTING
  • F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
  • F21V5/00—Refractors for light sources
  • F21V5/008—Combination of two or more successive refractors along an optical axis
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B19/00—Condensers, e.g. light collectors or similar non-imaging optics
  • G02B19/0004—Condensers, e.g. light collectors or similar non-imaging optics characterised by the optical means employed
  • G02B19/0009—Condensers, e.g. light collectors or similar non-imaging optics characterised by the optical means employed having refractive surfaces only
  • G02B19/0014—Condensers, e.g. light collectors or similar non-imaging optics characterised by the optical means employed having refractive surfaces only at least one surface having optical power
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B19/00—Condensers, e.g. light collectors or similar non-imaging optics
  • G02B19/0033—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use
  • G02B19/0047—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use for use with a light source
  • G02B19/0061—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use for use with a light source the light source comprising a LED
  • G02B19/0066—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use for use with a light source the light source comprising a LED in the form of an LED array
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
  • G03B21/00—Projectors or projection-type viewers; Accessories therefor
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F21—LIGHTING
  • F21S—NON-PORTABLE LIGHTING DEVICES; SYSTEMS THEREOF; VEHICLE LIGHTING DEVICES SPECIALLY ADAPTED FOR VEHICLE EXTERIORS
  • F21S41/00—Illuminating devices specially adapted for vehicle exteriors, e.g. headlamps
  • F21S41/10—Illuminating devices specially adapted for vehicle exteriors, e.g. headlamps characterised by the light source
  • F21S41/14—Illuminating devices specially adapted for vehicle exteriors, e.g. headlamps characterised by the light source characterised by the type of light source
  • F21S41/141—Light emitting diodes [LED]
  • F21S41/151—Light emitting diodes [LED] arranged in one or more lines
  • F21S41/153—Light emitting diodes [LED] arranged in one or more lines arranged in a matrix
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F21—LIGHTING
  • F21S—NON-PORTABLE LIGHTING DEVICES; SYSTEMS THEREOF; VEHICLE LIGHTING DEVICES SPECIALLY ADAPTED FOR VEHICLE EXTERIORS
  • F21S41/00—Illuminating devices specially adapted for vehicle exteriors, e.g. headlamps
  • F21S41/60—Illuminating devices specially adapted for vehicle exteriors, e.g. headlamps characterised by a variable light distribution
  • F21S41/65—Illuminating devices specially adapted for vehicle exteriors, e.g. headlamps characterised by a variable light distribution by acting on light sources
  • F21S41/663—Illuminating devices specially adapted for vehicle exteriors, e.g. headlamps characterised by a variable light distribution by acting on light sources by switching light sources
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F21—LIGHTING
  • F21Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED
  • F21Y2115/00—Light-generating elements of semiconductor light sources
  • F21Y2115/10—Light-emitting diodes [LED]

Definitions

• the present invention relates to the field of lighting and / or signaling and the organs, in particular optical, which participate therein. It finds a particularly advantageous application in the field of motor vehicles.
• this beam can, in particular, be used to form a lighting of the road type, preferably by being associated with a complementary beam.
• the beam produced by the invention can form part of an overall beam of the road type, having a sufficiently high resolution to allow a write function on the road, and be supplemented by another beam , for example having a wider field of lateral projection, but possibly less resolved.
• the invention may allow the production of a light beam, preferably highly resolved, of the pixelated type, in particular for signaling and / or participation in lighting functions at the front of a vehicle.
• the beam, resulting from the different beam segments coming from each of the diodes, is projected using an optical projection device generally comprising one or more lenses.
• an optical projection device generally comprising one or more lenses.
• the main beam adapting to the base beam so as to complete it above the cut-off line; advantageously, this main beam is adaptive to turn on or off certain parts of the projected overall beam, for example for anti-glare functions.
• ADB for Adaptive Driving Beam meaning adaptive driving beam
• the term “segmented beam” is used to refer to a beam whose projection forms an image composed of beam segments, each segment being able to be lit independently.
• a pixelated light source can be used to form these segments.
• Such a source comprises a plurality of selectively activatable emissive elements.
• the emissive elements are typically placed next to each other on a support, with a certain pitch.
• the size of the source is not constrained so that a large visual field can be covered without limitation of applications.
• the resolution of the light sources that is to say the number of pixels is unlimited, which allows very fine definitions.
• An object of the present invention is in particular to provide a solution to this problem, by allowing satisfactory resolutions, in particular for ADB beams.
• an optical device for projecting light beams capable of cooperating with a pixelized light source comprising a plurality of selectively activatable emissive elements, characterized in that it com successively takes, in the direction of the light ray path, a first optical unit, a pupil and a second optical unit, the first optical unit comprising an output diopter located at a first distance (di) from the pupil, the second unit optic comprising an input diopter located at a second distance (d2) from the pupil, the second distance (d2) being substantially identical to the first distance (di), and in that the first unit comprises a converging lens, and in that the second unit comprises a doublet of lenses one of which is Flint glass and the other is Crown glass.
• the lens of the lens doublet which is of Flint glass is divergent, and the lens of the lens doublet which is of Crown glass is convergent.
• a segmented beam is produced, having a resolution that can be greater than that currently encountered, in particular for beams participating in road-type lighting.
• On-road write applications usually not considered in the context of an ADB-type beam are then accessible by virtue of the invention.
• the aberrations are controlled by the symmetry of the optical elements located on either side of a pupil and by the use of a pair of lenses in the second unit, forming an output unit, implementing an alternation of Flint glass and Crown glass.
• This alternation makes it possible in particular to control chromatic aberration, an aberration which is often limiting (which can even lead to a non-regulatory product) given the digital apertures required in road-type lighting beams.
• the thermal expansion coefficients of the flint and crown glasses are preferably chosen so that the Thermal expansions of the 2 glasses compensate for each other and thus allow optimum conservation of performance over the widest possible temperature range.
• an advantage of the present invention is to exploit the capacity of selective activation of the different segments of the beam to achieve an improved road function, of the ADB type, while also allowing a write function on the ground. which normally requires higher resolution than ADB beams.
• the first optical unit comprises a first converging lens forming the entry diopter of the first optical unit, and a second converging lens immediately following the first lens.
• the first convergent lens can be used as a field opening lens, to define the angular amplitude of the projected beam.
• This lens can also serve as an aperture lens: it can be placed close to the light source (in particular between 3 and 6 millimeters, preferably at 5 mm); and its positive meniscus shape with, preferably strong radii of curvature, makes it possible to collect the rays emitted by the source which have very high angles.
• the optical device comprises Flint glass lenses and Crown glass lenses which are alternated so as to form a balanced optical assembly limiting chromatic aberrations; of preferably, the first optical unit comprises a doublet and the second optical unit comprises another doublet, these two doublets being symmetrical so as to have a limited tail aberration.
• the use of alternating Flint and Crown lenses also has the advantage of allowing, in addition to the correction of chromatic aberration, an optimization of performance over a high temperature range by compensation for thermal expansion.
• Another aspect relates to a light module comprising a device and a pixelized light source having a plurality of selectively activatable emissive elements, and configured to emit a segmented light beam.
• Another aspect relates to a motor vehicle equipped with at least one device and / or at least one module.
• Figure 1 shows an example of a projection of a light beam produced by the invention at the front of a motor vehicle.
• Figures 2A and 2B show a first embodiment of an optical device.
• Figures 3A and 3B show a second embodiment of an optical device.
• Figures 4A and 4B show a third embodiment of an optical device.
• the first optical unit comprises a first converging lens forming the input diopter of the first optical unit, and a second converging lens immediately following the first lens; - the entry diopter has a meniscus shape;
• the first optical unit comprises a divergent lens, immediately following the second lens
• the second lens and the diverging lens form a doublet of lenses, one of which is Crown glass and the other is Flint glass;
• the lenses of the lens doublet of the first unit and of the lens doublet of the second unit are lenses of Flint glass and Crown glass alternating in the direction of travel of the light rays;
• the second lens comprises an input diopter located at a third distance (d3) from the pupil
• the doublet of lenses of the second optical unit comprises an output diopter located at a fourth distance (d4) from the pupil, the third distance (d3) and the fourth distance (d4) being substantially identical
• the doublet of the first optical unit and the doublet of the second optical unit have identical optical power, which covers the case where they are very close (that is to say not differing by more than 10%);
• the first optical unit and / or the second optical unit comprises at least one Flint glass lens having an optical index at least equal to 1, 6, preferably at least equal to 1, 7, and preferably at least equal to 1 , 8;
• the first optical unit and / or the second optical unit comprises at least one Crown glass lens having an optical index at least equal to 1. 45, preferably at least equal to 1.5, and preferably at least equal to 1.65;
• the device has a numerical aperture less than 1, preferably less than 0.9, and preferably less than or equal to 0.75;
• - Flint lenses have an Abbe number ⁇ 50, and preferably ⁇ 45 and / or Crown lenses have an Abbe number greater than 45 and preferably greater than 50;
• the light beam performs a writing function on the ground
• the light beam produces at least part of an overall beam of the high beam type.
• the dimension of the emissive elements is identical;
• a computer program product preferably stored in a non-transient memory, comprises instructions which, when they are executed by a processor, make it possible to determine the emissive elements to be activated, in particular to obtain at least one dark zone (in which the elements are not activated) of a surface or a pattern determined to be projected.
• a processor preferably executed by a processor, make it possible to determine the emissive elements to be activated, in particular to obtain at least one dark zone (in which the elements are not activated) of a surface or a pattern determined to be projected.
• vertical and horizontal are used in the present description to denote directions, following an orientation perpendicular to the plane of the horizon for the term “vertical” (which corresponds to the height of the systems), and following an orientation parallel to the plane of the horizon for the term “horizontal”. They are to be considered in the operating conditions of the device in a vehicle.
• the use of these words does not mean that slight variations around the vertical and horizontal directions are excluded from the invention.
• an inclination relative to these directions of the order of + or - 10 ° is here considered as a minor variation around the two preferred directions.
• the inclination is in principle between -5 ° and + 4 ° and it is between -6 ° and + 7.5 ° laterally.
• Motor vehicle headlamps can be provided with one or more light modules arranged in a housing closed by a glass so as to obtain one or more lighting and / or signaling beams at the outlet of the headlamp.
• a light module of the housing comprises in particular a light source which emits a light beam, an optical device comprising one or more lenses and, in certain cases, an optical element, for example a reflector, for directing the light rays. from light sources, in order to form the output light beam of the optical module. The situation is the same for the rear lights.
• the invention can participate in a main beam function which has the function of illuminating the scene in front of the vehicle over a large area, but also over a substantial distance, typically around two hundred meters.
• This light beam by virtue of its lighting function, is mainly located above the horizon line. It may have a slightly ascending optical axis of illumination, for example.
• it can be used to generate a lighting function of the “road supplement” type which forms a portion of a main beam complementary to that produced by a near-field beam, the road supplement seeking at least in part to illuminate at above the horizon line.
• the segmented beam may be protracted. thrown at least 10 m from the projector so that, with the speed, the driver has time to see and interpret the information.
• This distance of 10 m may correspond to an angle value below the horizontal depending on the height of the headlamp on the vehicle in the driving position.
• the headlight will be about 60 cm from the ground, which implies that the 10 m distance corresponds to 3.44 ° below the horizontal; according to another example, for a standard passenger vehicle, the headlight is generally about 75 cm from the ground, which corresponds to an angle of 4.29 ° below the horizontal.
• the headlight is approximately 90 cm from the ground in general, so that the 10 m correspond in this case to 5.15 °.
• the 10 m correspond in this case to 5.15 °.
• These 50m correspond respectively to 0.69 °, 0.86 ° and 1.03 ° below the horizontal for projectors at 0.6m, 0.75m and 0.9m from the ground.
• This arrangement allows display functions of pictograms, very useful to signify information to, for example, the driver. It is thus possible, for illustration, to display an arrow on the tread of the road taken so as to recall a desired turn or change of direction information.
• the shape of the pictograms is not limited by the invention.
• the device can also be used to form other lighting functions via or outside those described above, in particular in relation to adaptive beams.
• a module of the invention can equip a vehicle, and, preferably, the latter is also equipped with at least one other module for the projection of at least one other beam.
• a projector can also be complex and combine several modules which can, moreover, possibly share components.
• some diopters are arranged at identical distances around the pupil.
• substantially identical means distances which may be qualified as similar in the intended application, that is to say having a dimension sufficiently close to produce the desired technical effect, in particular in terms of resolution level.
• these distances are considered to be substantially identical if the value of one does not differ by more than 10% from the value of the other.
• they can be equal to 10 mm, to +/- 1 mm.
• these distances are considered to be substantially identical if the value of one does not differ by more than 20% from the value of the other.
• Figure 1 shows a vehicle 1 to the front of which a beam 2 is projected.
• Figure 1 also shows the possibility, in a zone 3, of producing a writing function on the ground. This is particularly advantageous for generating pictogram patterns. Only one pictogram can be projected. Several pictograms can also be displayed simultaneously or alternately.
• the ground write functions can also activate during an ADB situation.
• the projected beam can come from a light source 4 which is shown diagrammatically in the following figures, and preferably produced with a plurality of emissive elements. Note that the plurality of emissive elements can be controlled so as to activate them selectively.
• emissive elements are not necessarily so multaneously active, that is to say emissive of light. This function allows you to modulate the shape of the rendered beam. In the event that an emissive element is not activated, its image, as projected by the optical device, will be zero. It then creates an illumination void in the resulting overall beam.
• the source 4 preferably comprises a support, one face of which carries selectively activatable emissive elements, for example on the basis of LED technologies, as detailed below.
• the light source 4 is advantageously centered on, and perpendicular to, the optical axis of the optical device, here represented by groups (hereinafter units 5, 6) of lenses.
• the optical axis can be oriented substantially horizontally.
• the light source 4 can in particular be designed in the form of a matrix of emissive elements, the activation of which can be individually controlled, to turn off or turn on any of the emissive elements.
• the shape of the resulting beam is thus varied with very wide flexibility.
• a matrix of emissive elements for example forming 2464 pixels, or even more, arranged in rows and columns, for example 28 rows and 88 or 132 columns.
• the present invention can use light sources of the light-emitting diode type also commonly called LEDs. It may possibly be organic LED (s). In particular, these LEDs can be provided with at least one chip using semiconductor technology and capable of emitting light.
• the term light source is understood here to mean a set of at least one elementary source such as an LED capable of producing a flux leading to the generation of at least one light beam at the output of the module of the invention.
• the output face of the source is of rectangular section, which is typical for LED chips.
• the light-emitting source comprises at least one matrix of monolithic light-emitting elements, also called a monolithic matrix.
• the electroluminescent elements have grown from, or have been carried over, a common substrate, and are electrically connected so as to be selectively activatable, individually or by subset of the electroluminescent elements.
• the substrate can be predominantly of a semiconductor material.
• the substrate may include one or more other materials, for example non-semiconductor.
• each electroluminescent element or group of electroluminescent elements can form a luminous pixel and can emit light when its or their material is supplied with electricity.
• the configuration of such a monolithic matrix allows the arrangement of selectively activatable pixels very close to each other, compared to conventional light emitting diodes intended to be soldered onto printed circuit boards.
• the monolithic matrix within the meaning of the invention comprises electroluminescent elements of which a main dimension of elongation, namely the height, is substantially perpendicular to a common substrate, this height being at most equal to one micrometer.
• the monolithic matrix (s) capable of emitting light rays can be coupled to a unit for controlling the light emission of the pixelated source.
• the control unit can thus control (one can also say control) the generation and / or the projection of a light beam pixelated by the light device.
• the control unit can be integrated into the lighting device.
• the control unit can be mounted on one or more of the dies, thereby forming a light module.
• the control unit may include a central processing unit coupled with a memory on which is stored a computer program which includes instructions allowing the processor to perform steps generating signals allowing control of the light source.
• the control unit can thus for example individually control the emission read miner of each pixel of a matrix.
• the luminance obtained by the plurality of electroluminescent elements is at least 60Cd / mm 2 , preferably at least 80Cd / mm 2 .
• the control unit can form an electronic device capable of controlling the electroluminescent elements.
• the control unit can be an integrated circuit.
• An integrated circuit also called an electronic chip, is an electronic component reproducing one or more electronics and being able to integrate several types of basic electronic components, for example in a small volume (i.e. on a small plate). This makes the circuit easy to set up.
• the integrated circuit can be for example an ASIC or an ASSP.
• An ASIC (acronym for “Application-Specific Integrated Circuit”) is an integrated circuit developed for at least one specific application (that is to say for a customer). An ASIC is therefore a specialized integrated circuit (microelectronics). In general, it bundles a large number of unique or tailor-made features.
• An ASSP (acronym for "Application Specifies Standard Product") is an integrated electronic circuit (microelectronics) bringing together a large number of functions to satisfy a generally standardized application.
• An ASIC is designed for a more particular (specific) need than an ASSP.
• the monolithic matrices are supplied with electricity via the electronic device, which is itself supplied with electricity using, for example, at least one connector connecting it to a source of electricity.
• the source of electricity can be internal or external to the device according to the invention.
• the electronic device supplies the light source with electricity.
• the electronic device is thus able to control the light source.
• the light source preferably comprises at least one monolithic matrix, the electroluminescent elements of which project from a common substrate.
• This arrangement of elements may be the result of growth on the substrate from which they respectively grew, or any other method of production, for example by transfer of the elements by transfer techniques.
• Different arrangements of electroluminescent elements can meet this definition of a monolithic matrix, since the electroluminescent elements have one of their main dimensions along the length substantially perpendicular to a common substrate and the spacing between the pixels, formed by one or more electroluminescent elements grouped together electrically, is small compared to the spacings imposed in known arrangements of flat square chips soldered to a printed circuit board.
• the light source according to one aspect of the invention may comprise a plurality of electroluminescent elements distinct from the others and which are grown individually from the substrate, being electrically connected so as to be selectively activatable, where appropriate by subsets within which rods can be activated simultaneously.
• the monolithic matrix comprises a plurality of electroluminescent elements, of submillimeter dimensions, or even less than 10 miti, which are arranged projecting from a substrate so as to form rods of section hexagonal.
• the electroluminescent rods extend parallel to the optical axis of the light module when the light source is positioned in the housing.
• Electroluminescent rods are grouped together, in particular by electrical connections specific to each assembly, in a plurality of selectively activatable portions. Electroluminescent rods originate on a first side of a substrate.
• Each electroluminescent stick here formed by using gallium nitride (GaN)
• GaN gallium nitride
• the electrolumine hundred sticks could be made from an alloy of aluminum nitride and gallium nitride (AIGaN), or from an alloy of aluminum phosphides, indium and of gallium (AlInGaP).
• Each electroluminescent rod extends along an axis of elongation defining its height, the base of each rod being disposed in a plane of the upper face of the substrate.
• the monolithic matrix may comprise light-emitting elements formed by layers of epitaxial light-emitting elements, in particular a first layer of n-doped GaN and a second layer of p-doped GaN, on a single substrate, for example made of silicon carbide, and which is cut (by grinding and / or ablation) to form a plurality of pixels respectively originating from the same substrate.
• a single substrate for example made of silicon carbide
• the substrate of the monolithic matrix may have a thickness of between 100 ⁇ m and 800 ⁇ m, in particular equal to 200 ⁇ m; each block may have a length and a width, each being between 50 ⁇ m and 500 ⁇ m, preferably between 100 ⁇ m and 200 ⁇ m. In one variant, the length and width are equal.
• the height of each block is less than 500 miti, preferably less than 300 miti.
• the exit surface of each block can be made via the substrate on the side opposite to the epitaxy.
• the separation distance of the contiguous pixels may be less than 1 miti, in particular less than 500 miti, and it is preferably less than 200 miti.
• the number of pixels can be between 250 and several thousand. A typical value around a thousand pixels.
• Form ratio generally between 1: 1 and 1: 5.
• the size of a unit pixel (square in all known cases can be rectangular) is between 100 and 300 miti, or even less (of the order of 40 miti for the latest generations of LEDs) in the state current art.
• the monolithic matrix can also comprise a layer of a polymer material in which the electroluminescent elements are at least partially embedded.
• the layer can thus extend over the entire extent of the substrate or only around a specific group of electroluminescent elements.
• the polymer material which can in particular be based on silicone, creates a protective layer which makes it possible to protect the electroluminescent elements without hindering the diffusion of light rays.
• wavelength conversion means capable of absorbing at least part of the rays emitted by one of the elements and of converting at least a part of said absorbed excitation light into emission light having a wavelength different from that of the excitation light. It is possible to provide indifferently that the phosphors are embedded in the mass of the polymer material, or that they are arranged on the surface of the layer of this polymer material. The phosphors can also be deposited under vacuum on the semiconductor chips, without the polymer layer.
• the light source may further include a coating of reflective material to deflect the light rays to the output surfaces of the pixelated source.
• the electroluminescent elements of submillimeter dimensions end in a plane, substantially parallel to the substrate, a surface determined output. It will be understood that the shape of this exit surface is defined as a function of the number and the arrangement of the electroluminescent elements which compose it. It is thus possible to define a substantially rectangular shape of the emission surface, being in tension that it can vary and take any shape without departing from the context of the invention.
• the selectively activatable emissive elements are secondary light sources.
• a primary light source can illuminate the surface of a micromechanical device with mirrors, for example of the type comprising an array of micromirrors, and the selective reflection on the mirrors forms a secondary light emission which makes it possible to constitute the pixels. .
• the lateral angular sector covered by the field of view of the beam produced is greater than 14 °, or even greater than or equal to 20 ° and / or preferably less than 30 °.
• the pixel matrix of the source 4 can have a rectangular shape having an aspect ratio of at least 2, and / or at most 4, between its largest dimension and its smallest dimension.
• a first embodiment of the projection system is provided with reference to Figures 2A and 2B.
• a first optical unit 5 then consists of a lens 51.
• the latter is advantageously of the meniscus / convex type. It can be made of Crown glass.
• its optical index is advantageously relatively high, for example at least equal to 1.65.
• This lens 51 can have the function of a field lens.
• its optical power can be very low, or even zero.
• the light from the source 4 enters directly into the lens 51. Then, the light rays pass through a pupil 7 having the function of a preferably fixed aperture diaphragm (so as to form a peripheral stop of the rays) and define a passage or opening of rays in the direction of a second optical unit 6.
• the latter comprises at least one doublet, here consisting of a lens 61 and a lens 62.
• the lens 61 is of a divergent nature. Here it has the shape of a bi-concave lens, but it could adopt other configurations allowing negative optical power: for example, concave / plane or convex / con cave configurations of suitable curvature can be good alternatives. Befor- ference, this lens is made of Flint glass. Its index is advantageously greater than or equal to 1.7.
• the output diopter of the first optical unit 5, here formed by the output face of the lens 51 is located at a distance di from the pupil 7; in parallel, the entry diopter of the second optical unit 6, here formed by the entry face of the lens 61, is located at a distance d2 from the pupil 7, on its other side. And we arrange for the distances di and d2 to be identical, with the dimensional tolerance conditions indicated above.
• the second lens 62 of the doublet of the optical unit 6 is advantageously a converging lens; it can be made of Crown glass, and preferably with a high optical index, advantageously greater than or equal to 1.5, or even to 1. 65.
• the lens 62 is, in the illustration of FIG. 2A, of bi-convex shape, but other arrangements making it possible to obtain the desired convergence are possible, such as a planar convex lens, or a concave lens. / convex of adapted curvature.
• At least part, and preferably all, of the diopters of the lenses are spherical (or planes).
• FIG. 2B provides an example of light ray paths according to this embodiment, from different pixels of the source 1.
• FIGS. 3A and 3B give a variant of the situation described above.
• the first optical unit 5 has in this case a second lens 52 of a convergent nature.
• the output diopter of the first unit 5 is formed by the output face of the lens 52. It is then in relation to this face that the measurement di is considered.
• the optical unit 5 is more complex in that it combines three lenses 51, 52, 53.
• the lens 51 can be equivalent to those previously described for the other modes of production. As before, she can fix the projection field. It is, in this configuration, followed by a doublet associating a lens 52 and a lens 53.
• the lens 52 is of convergent nature; it is preferably made of Crown glass and, advantageously, with a high optical index, in particular of at least 1.5, or even 1.65. As in the embodiment of Figure 3A, it is biconvex in the illustration, but other shapes are possible.
• the lens 53 is divergent; it can be made of Flint glass; its optical index can be at least equal to 1, 7. Here it has a concave entry face and a convex exit face, but, as above, other options for achieving a negative power lens are possible. In this case, it is the exit face of the lens 53 which is used to determine the distance di.
• FIG. 4A shows distances d3 and d4, respectively between the entrance face of the first doublet and the pupil 7, and between the pu pill 7 and the entrance face of the second lens 62 of the doublet of the second optical unit.
• the symmetry of the system is thus further increased.
• this allows the Flint glass lenses and Crown glass lenses to be organized in a distributed manner around pupil 7.
• the Flint glass lenses have the same optical index (within 10%). The same is true for the Crown glass lenses of the two doublets.
• the Flint glass lenses of divergent nature are the elements closest to the pu pille 7 while the convergent Crown glass lenses are the outer elements of this pair of doublets.
• FIG. 4B provides an example of a spoke path for this configuration.
• the optical index of the lens 51 may be equal (within 10%) to the index of the Crown glass of the corresponding lenses of the doublets.
• the device can include more than five lenses.
• the second optical unit may be provided with additional lenses (at least one) following the doublet and preferably having a converging nature. You can also alternate glass lenses Flint and Crown.

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