Optical projection device with three lenses

Abstract

The invention relates to an optical device for projecting a light beam, capable of cooperating with a pixelated light source comprising a plurality of selectively actuable light emitting elements (1), characterized in that it comprises the following components arranged successively along the path of a light ray (11) from the light source: a first converging lens (2), a second diverging or neutral lens (3), a pupil (4) and a third converging lens (5).

Description

Technical Field

[0001] The present invention relates to the field of lighting and / or signaling, and to units contributing thereto, particularly optical units. It is particularly advantageously applicable in the field of motor vehicles.

Background Art

[0002] In the automotive sector, devices are known that are able to emit a light beam (also referred to as lighting and / or signaling function) generally in accordance with regulations.

[0003] In recent years, technologies have been developed that make it possible to generate a segmented beam (also referred to as pixelated beam) in order to perform advanced lighting functions. This is particularly the case for the "supplementary high beam" lighting function. That lighting function is generally based on a plurality of light-emitting units each comprising one (individually controllable) light-emitting diode. This beam can particularly serve to supplement the lighting provided by the low beam in order to form an overall high beam.

[0004] The beam resulting from the various beam segments generated by each diode is projected by a projection optical system comprising a plurality of lenses. For example, it is possible to create a supplementary beam associated with a basic beam, which basic beam is projected entirely or at least partially below a horizontal cut-off line of the type used for the low beam function. Above the cut-off line, a supplementary beam is added to the beam so as to make the basic beam complete. This supplementary beam is adaptive (light distribution variable), i.e., a certain part of the projected overall beam can be lit or extinguished (for example, for anti-glare function). For this type of function, the acronym ADB (for Adaptive Driving Beam) is used.

[0005] In this specification, a beam that forms an image composed of beam segments, where each segment can be illuminated independently, is referred to as a segmented light beam. A pixelated light source may be used to form these segments. Such a light source comprises multiple selectively operable light-emitting elements. The light-emitting elements are typically arranged on a holder at regular intervals from one another.

[0006] To project light generated by light-emitting elements with sufficient quality, lens arrays are currently used. These lens arrays enable the reduction of chromatic aberration at the edges of the non-reflective pixel groups while achieving the highest possible efficiency and sufficient sharpness.

[0007] Figure 1 is a very schematic example of the illumination area (shaded area) in front of the vehicle, where two non-illuminated areas are formed. This is achieved by deactivating at least one light-emitting element for each of these two non-illuminated areas 6. Generally, optical processing of the light must be used to avoid or limit the effects of chromatic aberration on the edges of these areas 6 (otherwise, observers at the illumination site will notice undesirable colored edges that may even be incompatible with the beam reference). At the same time, the projection of each pixel should be as sharp as possible so that the contour 61 of these areas 6 is not perceived as blurred. These optical requirements currently necessitate the use of relatively complex lens systems. [Overview of the Initiative]

[0008] One objective of the present invention is to provide a solution to this problem, thereby achieving sufficient resolution and chromatic aberration correction using less complex equipment (especially for ADB beams).

[0009] Other objectives, features, and advantages of the present invention will become apparent upon examination of the following description and accompanying drawings. It should be understood that other advantages may also be included.

[0010] To achieve this objective, according to one embodiment, an optical device for projecting a light beam is provided, which can interact with a pixelated light source having a plurality of selectively operable light-emitting elements, characterized in that the optical device comprises, in order in the direction of the path of the light ray generated by the light source, a converging first lens, a divergent or neutral second lens, a pupil, and a converging third lens.

[0011] Thus, with a small number of lenses (surprisingly limited to three), a segmented beam derived from the projection of light generated by multiple light-emitting elements is created while achieving sufficient optical processing conditions for projection clarity and limiting the effects of chromatic aberration at the edges of the non-reflective areas.

[0012] By positioning the pupil between the second and third lenses, the optical device can project more light rays, and therefore the projected image can have higher luminosity. For example, the optical device may have a numerical aperture N of 0.7 or less, or even less than 0.5.

[0013] Optionally, the pupil is positioned at approximately the same distance from the exit surface of the second lens to the incident surface of the third lens. Essentially, this configuration improves the clarity of the projection. Generally, the combination formed by the second and third lenses has the added advantage of ensuring at least partial correction of chromatic aberration.

[0014] Another embodiment relates to a module comprising the apparatus and a pixelated light source configured to emit a segmented light beam, equipped with a plurality of selectively operable light-emitting elements.

[0015] Another embodiment relates to an automated vehicle equipped with at least one optical system and / or at least one optical device.

[0016] The object, subject, features, and advantages of the present invention will become clearer from a detailed description of one embodiment, which is illustrated by the accompanying drawings below. [Brief explanation of the drawing]

[0017] [Figure 1] A diagram showing an example of projection of a light beam into a single plane, with areas of no light present. [Figure 2] A figure showing a first example of an embodiment of the present invention. [Figure 3] A figure showing another embodiment. [Figure 4] A diagram showing another modified example of the embodiment. [Modes for carrying out the invention]

[0018] The drawings are provided as examples and are not intended to limit the invention. They are schematic and conceptual depictions intended to facilitate understanding of the invention and are not necessarily drawn to the scale to which they are actually applied.

[0019] Before beginning a detailed examination of the embodiments of the present invention, we will now describe some optional features that may be used selectively in combination or as substitutes: - The first lens 2 is a meniscus lens; - The second lens 3 has an exit surface 32 with a center located on the optical axis of the device, and the third lens 5 has an incident surface 51 with a center located on the optical axis of the device; the pupil 4 is positioned so as not to contact the exit surface 32 of the second lens 3 and the incident surface 51 of the third lens 5; - The pupil 4 is positioned at a certain distance from the center of the exit surface 32 in the second lens 3, and this distance is between 25% and 75% of the distance between the center of the exit surface 32 and the center of the incident surface 51 in the third lens 5; - The pupil 4 is disposed at a certain distance from the center of the exit surface 32 of the second lens 3, and the distance is included between 45% and 55% of the distance between the center of the exit surface 32 and the center of the entrance surface 51 of the third lens 5; - The pupil is in contact with the edge of the exit surface 32 of the second lens 3; - The first lens 2 has an entrance surface for directly receiving light from the pixelated light source; - The second lens 3 is a meniscus lens; - The third lens 5 is configured to cause a segmented light beam to be projected forward of the vehicle; - The third lens 5 is a lens with a uniform refractive index; - The module is a unit for controlling the operation of each light-emitting element, and includes a unit configured to create at least one dark region in the projection beam by stopping the operation of a group of adjacent light-emitting elements, and the control unit is configured to determine the number of light-emitting elements in the group of adjacent light-emitting elements corresponding to the dark region according to the dimension in the width direction of the light-emitting element; - The light beam forms at least a part of the overall high beam; [[ID=十六]]- The second lens 3 is made of flint glass; - The third lens 5 is made of crown glass; - The first lens 2 is made of crown glass; - It is preferable that a plurality of light-emitting elements 1 form a rectangular array, the longitudinal dimension of the rectangular array is oriented in the direction of the lateral dimension (width) of the beam, and the lateral dimension is oriented in the same direction as the horizontal line.

[0020] The system according to the present invention is a unit for controlling the operation of each light-emitting element, and may include a unit configured to create at least one dark region forming a tunnel in the projection beam by stopping the operation of a group of adjacent light-emitting elements, and the control unit is configured to determine the number of light-emitting elements in the group of adjacent light-emitting elements corresponding to the dark region according to the dimension in the width direction of the light-emitting element.

[0021] The control unit may comprise a computer program product (preferably stored in a non-volatile memory). The computer program product comprises instructions that enable (when executed by a processor) determination of the light-emitting elements to be actuated. In particular, it is to obtain at least one defined area of dark regions (where the light-emitting elements are not actuated) taking into account the area where the image of the light-emitting elements can change.

[0022] In the features described below, the vertical state, the horizontal state, and the transverse state (or even the lateral direction), or the equivalent thereof, should be understood as being with respect to the posture intended for the lighting system to be mounted in a vehicle. The terms "vertical (direction)" and "horizontal (direction)" in this specification indicate, with respect to the term "vertical (direction)", the direction of the orientation perpendicular to the horizontal plane (corresponding to the height of the system), and with respect to the term "horizontal (direction)", the direction of the orientation parallel to the horizontal plane. They are to be considered under the operating conditions of the device in the vehicle. The use of these words does not mean that minor variations in the vertical and horizontal directions are excluded from the present invention. For example, an inclination of about + or - 10° with respect to these directions is considered in this case to be a minor variation for the two selected directions. With respect to the horizontal plane, the inclination is generally between -5° and 4°, and in the lateral direction between -6° and 7.5°.

[0023] The headlamp of a motor vehicle may be equipped with one or more light-emitting modules arranged in a housing closed by an outer lens. It is to obtain one or more illumination and / or signaling beams as the output of the headlamp. The vehicle may be equipped with the module of the present invention, but it is preferable that the vehicle is also equipped with at least one other module for projecting at least one other beam. The headlamp may be complex and may further comprise a plurality of modules that can optionally share components.

[0024] The present invention can contribute to a high-beam function, the purpose of which is to illuminate a wide area in front of the vehicle, but at a considerable distance (typically about 200 meters). Due to its illumination function, this light beam is mainly located above the horizon. The beam may, for example, have an illumination axis that is slightly tilted upward. The beam can be used in particular to produce a "supplementary beam" illumination function. It forms a supplementary high-beam portion to what is produced by the near-field beam. While the near-field beam (which may have characteristics specific to a low beam) attempts to illuminate generally, or at least primarily, below the horizon, the supplementary high beam attempts to illuminate generally, or at least primarily, above the horizon.

[0025] The device may also serve to perform other illumination functions, either through the functions described above regarding adaptive beams, or independently of those functions.

[0026] It should be noted that multiple light-emitting elements can be controlled to operate selectively. This means that not all light-emitting elements necessarily operate (i.e., emit light) simultaneously. This feature allows for adjustment of the shape of the resulting beam. If one light-emitting element is not activated, its image (projected, for example, by an optical device) will be missing. This creates a gap in illumination within the resulting overall beam. This gap would be perfect if it were not affected by light source coupling effects or stray light from optical devices.

[0027] The light source preferably comprises a support. One side of the support holds a selectively illuminable light-emitting element 1 (for example, one based on LED technology as described in detail below).

[0028] The light source is preferably an array of light-emitting elements 1 whose centers lie on the optical axis of the optical device that follows it (represented here by a collection of three lenses) and which are perpendicular to that optical axis. The optical axis may be oriented approximately horizontally.

[0029] The light source may take the form of an array of light-emitting elements, where any one of the light-emitting elements can be individually operated to turn on or off. The resulting beam shape can thus be changed with a very high degree of adaptability.

[0030] As is known, the present invention may use light-emitting diodes (commonly referred to as LEDs) as light sources. These may be one or more organic LEDs. These LEDs may, in particular, comprise at least one semiconductor chip capable of emitting light. Furthermore, the expression "light source" in this context should be understood to mean a set of basic light sources, such as at least one LED, capable of producing a luminous flux that causes at least one light beam to be output from the module of the present invention. In one advantageous embodiment, the light-emitting surface of the light source has a rectangular cross-section, which is typical for LED chips.

[0031] The field-emitting light source preferably comprises at least one monolithic array (also called a monolithic matrix array) of field-emitting elements. In the monolithic array, each field-emitting element is grown from or transferred onto a common substrate and is electrically connected to enable selective operation individually or in subsets (small groups) of field-emitting elements. The substrate may be made primarily of semiconductor material. The substrate may also contain one or more other materials (e.g., non-semiconductors). Each field-emitting element or group of field-emitting elements thus forms a single light-emitting pixel and can emit light when power is supplied to the material of its elements. Such a monolithic array configuration makes it possible to arrange selectively operable pixels in much closer proximity to each other compared to conventional groups of light-emitting diodes intended to be soldered onto a printed circuit board. In the spirit of the present invention, the monolithic array comprises field-emitting elements whose main dimension of extension (i.e., height) is substantially perpendicular to the common substrate, and this height is at most 1 micron.

[0032] One or more monolithic arrays capable of emitting light rays may be coupled to a control unit for controlling the emission of light from a pixelated light source. Thus, the control unit can control (or regulate) the generation and / or projection of pixelated light beams by the light source. The control unit may be integrated into the light source. The control unit may be mounted on one or more arrays, so that the assembly forms a light-emitting module. The control unit may include a central processing unit coupled to memory for storing a computer program. The program includes instructions that enable the processor to perform each stage of generating signals that enable control of the light source. Thus, the control unit can, for example, individually control the emission of light from each pixel in the array. Furthermore, the luminance obtained by multiple electroluminescent elements is at least 60 Cd / mm². 2 It is at least 80 Cd / mm 2It is preferable that this be the case.

[0033] The control unit can form an electronic device capable of controlling each electroluminescent element. The control unit may be an integrated circuit. An integrated circuit (also called an electronic chip) is an electronic component that replicates one or more electronic functions, for example, by integrating several types of basic electronic components within a limited volume (i.e., on a wafer). This makes it easier to implement the circuit. An integrated circuit may be, for example, an ASIC or an ASSP. An ASIC (an acronym for "Application-Specific Integrated Circuit") is an integrated circuit developed for at least one specific application (i.e., for one customer). Therefore, an ASIC is a dedicated (microelectronics) integrated circuit. Generally, it brings together a number of unique, or bespoke, functions. An ASSP (an acronym for "Application-Specific Standard Product") is an integrated (microelectronics) electronic circuit that performs a number of functions to meet the requirements of a widely standardized application. An ASIC is designed for a more specific (concrete) need than an ASSP. The monolithic array is powered through an electronic device, which in turn is powered by, for example, at least one connector connecting itself to a power source. The power source may be located inside or outside the device according to the present invention. The electronic device supplies power to the light source. Thus, the electronic device can control the light source.

[0034] According to the present invention, it is preferable that the light source comprises at least one monolithic array, wherein each electroluminescent element of the array protrudes from a common substrate. This arrangement of elements may result from the growth on the substrate from which each element was grown, or from any other manufacturing method (e.g., transfer of each element using transfer techniques). Various arrangements of electroluminescent elements may satisfy the definition of this monolithic array, provided that: each electroluminescent element has one of its principal dimensions of extension that is substantially perpendicular to the common substrate, and the spacing between pixels (formed by one or more electrically coupled electroluminescent elements) is smaller than the spacing imposed in known arrangements of generally flat, square chips soldered to a printed circuit board.

[0035] In particular, a light source according to one aspect of the present invention may comprise a plurality of separate electroluminescent elements grown individually from a substrate. These elements are electrically connected so that they can be operated selectively (for each subset, in which, where appropriate, the rods can be operated simultaneously within them).

[0036] According to one embodiment (not shown), the monolithic array comprises a plurality of electroluminescent elements (sub-millimeter or even less than 10 μm in size). These elements are arranged to protrude from the substrate, forming a group of rods, particularly with a hexagonal cross-section. Each electroluminescent rod extends parallel to the optical axis of the illumination module when the light source is in a predetermined position within the casing.

[0037] These electroluminescent rods are assembled together into multiple selectively operable parts (particularly by electrical connections specific to each set). The electroluminescent rods are fixed to a first side of the substrate. In this case, each electroluminescent rod, formed using gallium nitride (GaN), protrudes perpendicularly or nearly perpendicularly from the substrate. In this case, the substrate is silicon-based, but other materials such as silicon carbide can be used without departing from the scope of the present invention. For example, the electroluminescent rods could be made of an alloy of aluminum nitride and gallium nitride (AlGaN) or an alloy of aluminum, indium, and gallium phosphide (AlInGaP). Each electroluminescent rod extends along an axis of extension that defines its height, and the base of each rod is located in the upper plane of the substrate.

[0038] In another embodiment (not shown), the monolithic array may comprise a group of electroluminescent elements formed from each layer of an electroluminescent element (particularly a first layer of n-type doped GaN and a second layer of p-type doped GaN) epitaxially grown on a single substrate (e.g., one made of silicon carbide), which is then separated (by grinding and / or ablation) to form multiple pixels, each originating from the same substrate. The result of such a design is a group of light-emitting blocks, all originating from the same substrate and electrically connected so that each can be selectively activated.

[0039] In one embodiment of this alternative configuration, the monolithic array substrate may have a thickness between 100 μm and 800 μm, particularly 200 μm, and each block may have a length and width between 50 μm and 500 μm, preferably between 100 μm and 200 μm. In one modification, the length and width are equal. The height of each block is less than 500 μm, but preferably less than 300 μm. Finally, the light-emitting surface of each block may be formed on the side opposite to where epitaxial growth takes place, through the substrate. The distance between adjacent pixels may be less than 1 μm, particularly less than 500 μm, but preferably less than 200 μm.

[0040] According to another embodiment (not shown) applicable to both light-emitting rods (i.e., rods as described above) protruding from the same substrate and light-emitting blocks obtained by separating light-emitting layers laminated on the same substrate, the monolithic array may further include a polymer layer in which each electroluminescent element is at least partially embedded. Thus, the layer may extend over the entire surface of the substrate or only around a given group of electroluminescent elements. The polymer (which may be particularly silicone-based) creates a protective layer that protects the electroluminescent elements without hindering the emission of light rays. Furthermore, wavelength conversion means (e.g., a luminescent phosphorus) can be incorporated into this polymer layer. The wavelength conversion means can absorb at least a portion of the light rays emitted by one of the elements and convert at least a portion of the absorbed excitation light into emitted light having a different wavelength from the excitation light. The luminescent phosphorus may be embedded within the internal substance of the polymer or placed on the surface of the polymer layer. It is also possible to vacuum-deposit a fluorite phosphor onto a semiconductor chip without involving a polymer layer. The light source may further be coated with a reflective material to deflect the light rays toward the light-emitting surface of the pixelated light source.

[0041] Sub-millimeter-sized electroluminescent elements define a given light-emitting area in a plane substantially parallel to the substrate. It should be understood that the shape of this light-emitting area depends on the number and arrangement of the electroluminescent elements forming that area. Thus, it is possible to define a light-emitting area with a substantially rectangular shape, but it should be understood that this shape may change and may be any shape without departing from the scope of the present invention.

[0042] It is not impossible to use a selectively operable light-emitting element 1 as a secondary light source.

[0043] Figure 1 shows an example of projection that can be obtained thanks to the present invention, which has sufficient clarity and a sufficiently colorless (close to the white of the light source) outline 61.

[0044] A first embodiment of an optical module that enables such results is shown in Figure 2. The path of the light rays (from left to right) begins with the generation of light rays 11 by each light-emitting element 1 of the light source (which suitably forms an array of pixels).

[0045] For example, the array of pixels of light source 1 may have the shape of a long, narrow rectangle that is perfectly aligned horizontally.

[0046] Figure 2 shows a light ray 11 entering the first lens 2 of the optical device through the incident surface 21. In this example, the first lens 2 is a meniscus lens and therefore has surfaces 21 and 22 with the same curvature direction. In this case, the incident surface 21 is concave and the exit surface 22 is convex. The first lens 2 is essentially convergent and is configured to direct the transmitted light ray toward the second lens 3, which is spaced apart from the first lens 2.

[0047] The second lens 3 is advantageous to be divergent, but it may be weakly divergent or even optically neutral. In Figure 2, the incident surface 31 is convex and the exit surface 32 is concave.

[0048] The pupil 4 follows the second lens 3 along the path of the light ray. The pupil 4 acts as a suitable aperture diaphragm (forming a peripheral aperture for the light ray) and defines an aperture for the light ray to pass towards the third lens 5. It is advantageous for the pupil 4 to be in a plane perpendicular to the optical axis. In the illustrated example, the pupil 4 is at a distance from the exit surface 32 of the second lens 3 and the incident surface 51 of the third lens 5. Essentially, an intermediate placement of the pupil 4 is preferable for improving sharpness.

[0049] The third lens is, in this respect, a focusing lens. In the case of Figure 2, its incident surface 51 is concave and its exit surface 52 is convex. The light rays projected by the third lens 5 from the pixelated light beam preferably exit the module and illuminate a portion of the road surface in front of (or behind) the vehicle equipped with the module.

[0050] The pupil 4 is preferably positioned midway between plane 32 and plane 51. More specifically, the center of plane 32 (defined as the intersection of this plane and the optical axis of the optical device itself, i.e., the horizontal dashed line in the center of the figure) and the center of plane 51 (defined similarly to the center of plane 32) determine the distance separating the lenses at the centers of their opposing surfaces, and the pupil 4 may be positioned at a distance from plane 32 that falls within 25 to 75% of this separating distance. Optionally, from the viewpoint of improving sharpness, the distance to the center of plane 32 may be between 45 to 50% of the separating distance, and the degree of centralization of the pupil 4 may be greater. However, this would impair the correction of chromatic aberration.

[0051] Now, with reference to Figure 3, another embodiment of the projection module will be described. Figure 3 shows, from left to right, a light source which may be of the type described above but specifically takes the form of an array of light-emitting elements 1, a first lens 2, a second lens 3, a pupil 4, and a third lens 5.

[0052] In this case, the pupil 4 is positioned close to the surface 32 of the second lens, and may even be in contact with the periphery of this surface 32. As in the case described above, lens 3 is a meniscus lens. Lens 2 is of the same type as in the example in Figure 2. In this case, the third lens has a flat incident surface 51 and a convex exit surface.

[0053] The modified form in Figure 4 is quite similar. As described above, it is advantageous for the pupil 4 to be placed close to the surface 32 and to be in contact with it. The second lens 3 is biconcave here. In contrast, the third lens 5 is biconvex. The first lens 2 is still a meniscus lens.

[0054] The combination of the light source 1 described above with an optical device equipped with three lenses emits a segmented composite beam, corresponding to Figure 1, with sufficient clarity and a nearly colorless dark tunneling region 6 outline 61. The system further includes a unit for controlling the selective operation of the light-emitting elements.

[0055] The system may include computerized processing means, particularly a processor, and non-volatile memory for storing computer program instructions. The computer program instructions enable the system to determine which light-emitting elements should be activated and which should be deactivated, depending on the beam to be formed and the dark area to be preserved.

[0056] The present invention is not limited to the embodiments described above, but encompasses any embodiment that aligns with its spirit.

Claims

1. A pixelated light source comprising a plurality of selectively operable light-emitting elements (1) and configured to emit segmented light beams, An optical device for projecting a light beam that can interact with the aforementioned pixelated light source, the optical device comprising a converging first lens (2), a divergent or neutral second lens (3), a pupil (4), and a converging third lens (5), which are sequentially provided in the direction of the path of the light rays (11) generated by the pixelated light source, the first lens (2) being a meniscus lens, and the third lens (5) being configured to produce projection of the segmented light beam toward the front of the vehicle, A module equipped with the following features.

2. The module according to claim 1, wherein the second lens (3) is a meniscus lens.

3. The module according to claim 1, wherein the third lens (5) is a lens with a uniform refractive index.

4. The module according to claim 1, wherein the second lens (3) has an exit surface (32) whose center is located on the optical axis of the optical device, the third lens (5) has an incident surface (51) whose center is located on the optical axis of the optical device, and the pupil (4) is arranged so as not to contact the exit surface (32) of the second lens (3) and the incident surface (51) of the third lens (5).

5. The module according to claim 4, wherein the pupil (4) is positioned at a certain distance from the center of the exit surface (32) of the second lens (3), and the distance is between 25% and 75% of the distance between the center of the exit surface (32) and the center of the incident surface (51) of the third lens (5).

6. The module according to claim 5, wherein the pupil (4) is positioned at a certain distance from the center of the exit surface (32) of the second lens (3), and the distance is between 45% and 55% of the distance between the center of the exit surface (32) and the center of the incident surface (51) of the third lens (5).

7. The module according to claim 5, wherein the pupil is in contact with the edge of the emission surface (32) of the second lens (3).

8. The module according to claim 1, wherein the first lens (2) has an incident surface that directly receives light from the pixelation light source.

9. The module according to claim 1, comprising a unit for controlling the operation of each of the aforementioned light-emitting elements, the unit configured to create at least one dark area in the projection beam by stopping the operation of a group of adjacent light-emitting elements, wherein the unit is configured to determine the number of light-emitting elements in the group of adjacent light-emitting elements corresponding to the dark area, according to the width dimension of the light-emitting elements.

10. The module according to claim 1, wherein the light beam forms at least a portion of the overall high beam.

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