Wavelength converter system for an imaging system

Abstract

The present invention relates to a wavelength converter system (10) for an imaging system. The wavelength converter system (10) has a plurality of converter elements (11, 11', 11") for wavelength conversion. A plurality of focusing input elements (12) are designed to convert incident excitation light (L e ) onto the converter elements (11, 11', 11"). A plurality of light-bundling output elements (13) are designed to focus the light (L a ) in an output direction (A). The invention also relates to an image generation system comprising such a wavelength converter system (10) and a means of transport comprising such an image generation system.

Description

[0001] The present invention relates to a wavelength converter system for an image generation system and to an image generation system having such a wavelength converter system. The invention also relates to a means of transportation having such an image generation system.

[0002] A head-up display, also known as a HUD, is a display system that allows the viewer to maintain their line of sight by projecting the content into their field of vision. While such systems were originally used primarily in aviation due to their complexity and cost, they are now also being installed in large-scale production in the automotive sector.

[0003] Head-up displays generally consist of an imaging unit or PGU (Picture Generating Unit), an optical unit, and a mirror unit. The imaging unit generates the image using at least one display element. Today's head-up displays typically use displays or scanning systems to generate the image. Displays can be, for example, LC displays (LC: liquid crystal), µ-LED displays (LED: light-emitting diode), LCoS displays (LCoS: liquid crystal on silicon), or DLP / DMD systems (DLP: digital light processing) (DMD: digital micromirror device). An example of a scanning system is a laser scanning system. The optical unit directs the image onto the mirror unit. The mirror unit is a partially reflective, translucent disc.The viewer thus sees the content displayed by the imaging unit as a virtual image and, at the same time, the real world behind the windshield. In the automotive sector, the windshield often serves as the mirror unit, and its curved shape must be taken into account in the display. Due to the interaction of the optical unit and the mirror unit, the virtual image is an enlarged and distorted representation of the image generated by the imaging unit.

[0004] In laser scanning systems, the light from RGB color laser diodes is scanned across the display area using oscillating MEMS (micro-electro-mechanical system) mirrors. The image is then generated on the display area by pulsing the color laser diodes synchronously with the movement of the mirrors. Compared to LCD-based displays, laser scanning systems are characterized by less complex optics, higher energy efficiency, and lower cooling requirements. As an alternative to RGB color laser diodes, a short-wavelength laser can also be used to scan an RGB wavelength converter at a suitable intermediate image plane.

[0005] Against this background, US Pat. No. 8,830,141 B2 describes a head-up display for a vehicle. The vehicle's windshield comprises a transparent substrate and a transparent layer of light-emitting material. The light-emitting material comprises a plurality of light-emitting particles and emits visible light in response to the absorption of ultraviolet light from a light source.

[0006] DE 103 50 529 A1 describes a head-up display in which a flat and largely transparent anti-Stokes or UV element is integrated into a windshield or into a transparent flat display element and, when irradiated with NIR or UV rays, generates information visible to the human eye.

[0007] It is an object of the present invention to provide improved solutions for a wavelength converter system for an imaging system.

[0008] This object is achieved by the features of the independent claims. Preferred embodiments of the invention are the subject of the dependent claims.

[0009] According to a first aspect of the invention, a wavelength converter system for an imaging system comprises: - a variety of converter elements for wavelength conversion; - a plurality of focusing input elements for focusing incident excitation light onto the converter elements; and - a plurality of light-concentrating output elements for concentrating the light emitted by the converter elements in an output direction.

[0010] In the inventive solution, focusing input elements are designed to concentrate the excitation light incident from a scanner onto the converter elements. The visible light emitted by these elements is concentrated by the light-bundling output elements in the direction required for image generation in the further beam path. The inventive solution allows the use of very efficient short-wave lasers to scan the wavelength converter system arranged in an intermediate image plane. By timing the control or by direction-selective structures, optionally in conjunction with multiple lasers, it is possible to determine which color channels are controlled at a given location. In this process, the wavelength converter system simultaneously performs beam shaping.

[0011] According to one aspect of the invention, the wavelength converter system comprises different converter elements for conversion into two or more wavelengths. Converter elements for conversion into red, green, and blue light are preferably present. This is particularly advantageous for generating full-color images. However, multicolor images can also be generated using fewer or more different types of converter elements, or even using other colors. With more than three colors, larger color spaces can also be achieved.

[0012] According to one aspect of the invention, the converter elements are designed as phosphor converters or quantum dots. Phosphor converters, i.e., converter elements based on fluorescent or phosphorescent substances, are available for many excitation and emission wavelengths. Converter elements in the form of quantum dots have the advantage that the wavelengths at which the material absorbs and emits light can be very precisely adjusted via the size and composition.

[0013] According to one aspect of the invention, the wavelength converter system has wavelength-dependent reflector elements on the side of the focusing input elements or on the side of the light-bundling output elements. This makes it possible to take advantage of the fact that the excitation light and the emitted light have different wavelengths and can be shaped independently of one another by appropriate structures in the same zone. The output-side reflector elements reflect the remaining excitation light back in a concentrated manner toward the converter elements. This further increases the light yield. The input-side reflector elements reflect the light emitted by the converter elements back toward the converter elements or into an area adjacent to the converter elements. In this way, the radiating area of ​​the converter elements is virtually enlarged.The other type of light passes through the reflector elements without significant reflection.

[0014] According to one aspect of the invention, the wavelength-dependent reflector elements are designed as dielectric coatings or as systems of holograms or metastructures. Dielectric coatings are easy to implement. Implementation as systems of holograms or metastructures allows the mirror function to be separated from the surface of the focusing or light-bundling elements. This allows the respective functions to be optimized independently of one another, improving their performance, and does not require a compromise.

[0015] According to one aspect of the invention, the focusing input elements or the light-bundling output elements are designed as systems of holograms or metastructures. This allows the focusing input elements and the light-bundling output elements to be very precisely adapted to the properties of the incident light and the emitted light.

[0016] According to one aspect of the invention, the converter elements lie essentially in a plane or on a curved surface. Converter elements lying in a plane are easier to handle in production. However, it may still be advantageous to arrange the converter elements on a curved surface, as this can improve adaptation to the imaging system and a scanner of the imaging system.

[0017] A wavelength converter system according to the invention is preferably used in an image generation system comprising at least one laser source and one scanner. In particular, the image generation system can be a head-up display. The wavelength converter system according to the invention allows the light output from the laser source to the eyebox to be significantly increased and the light distribution to be adapted to the requirements of a head-up display. This allows its image quality and image brightness to be improved. Of course, a wavelength converter system according to the invention can also be used in other laser scanning applications for generating visible images.

[0018] Preferably, an image generation system according to the invention is used in a means of transportation. The means of transportation can be, for example, a motor vehicle, but alternatively also an aircraft, a rail vehicle, or a watercraft. In particular, the display device can be designed as a head-up display. Use in stationary machines, e.g., in a crane, is also possible.

[0019] Further features of the present invention will become apparent from the following description and the appended claims taken in conjunction with the figures. Figure overview Fig. 1 shows schematically a wavelength converter according to the prior art; Fig. 2 schematically shows a first embodiment of a wavelength converter system according to the invention; Fig. 3 schematically shows a second embodiment of a wavelength converter system according to the invention; Fig. 4 schematically shows a third embodiment of a wavelength converter system according to the invention; Fig. 5 shows schematically a head-up display for a means of transport; and Fig. 6 shows schematically a means of transport in which a solution according to the invention is implemented. Character description

[0020] To better understand the principles of the present invention, embodiments of the invention are explained in more detail below with reference to the figures. Like reference numerals are used in the figures for like or equivalent elements and are not necessarily described again for each figure. It is understood that the invention is not limited to the illustrated embodiments and that the described features can also be combined or modified without departing from the scope of the invention as defined in the appended claims.

[0021] Fig. Figure 1 schematically shows a wavelength converter 5 according to the prior art. The wavelength converter 5 has converter surfaces 16, 16', 16" that convert the incident excitation light L from a scanner (not shown here). eeach convert into a different wavelength. The converter surfaces 16, 16', 16" radiate the respective emitted light L a essentially Lambertian in all directions. This makes it difficult to determine the emitted light L a to efficiently use such a wavelength converter 10 in an imaging system, in particular in a head-up display.

[0022] Fig. Figure 2 schematically shows a first embodiment of a wavelength converter system 10 according to the invention. In comparison to the prior art, a plurality of converter elements 11, 11', 11" are used for wavelength conversion instead of converter surfaces. The converter elements 11, 11', 11" can be designed, for example, as phosphor converters or quantum dots. In the example shown, converter elements 11, 11', 11" are present for conversion into red, green, and blue light. This is particularly advantageous for generating full-color images. However, multicolor images can also be generated with fewer or more different types of converter elements 11, 11', 11" or even with other colors. A plurality of focusing input elements 12, shown here as lenses, serve to focus the excitation light L incident from the scanner. eonto the converter elements 11, 11', 11". A plurality of light-bundling output elements 13, here again shown as lenses, serve to concentrate the light L emitted by the converter elements 11, 11', 11". a into a desired output direction A or into a desired output solid angle range. The wavelength converter system 10 thus performs both wavelength conversion and beam shaping. The direction and size of the output solid angle range can be specifically influenced via the lens position or lens section and the focal length.

[0023] Fig. 3 schematically shows a second embodiment of a wavelength converter system 10 according to the invention. The embodiment largely corresponds to the embodiment in Fig. 2. However, wavelength-dependent reflector elements 14, 14', 14' are arranged on the input side of the focusing input elements 12, here as dielectric coatings. These reflect the light L emitted by the converter elements 11, 11', 11" in their direction. a back towards the converter elements 11, 11', 11" or into an area adjacent to the converter elements 11, 11', 11" while reflecting the excitation light L incident from the scanner. e without significant reflection. In this way, the radiating surface of the converter elements 11, 11', 11" is virtually enlarged, which Fig. 3 is indicated by the dashed rectangle, and the proportion of the emitted light L concentrated in the desired output direction A increases. a. On the output side, wavelength-dependent reflector elements 15, 15', 15" are arranged on the light-bundling output elements 13, here again as dielectric coatings. These reflect the remaining excitation light L e concentrated back towards the converter elements 11, 11', 11". This allows the light output to be further increased. The wavelength-dependent reflector elements 15, 15', 15" arranged on the output side are designed in such a way that they reflect the emitted light L a without any significant reflection. Fig. The embodiment shown in Figure 3 makes use of the fact that the excitation light L e and the emitted light L a have different wavelengths and can be formed independently of each other by corresponding structures in the same zone.

[0024] Fig. Figure 4 schematically shows a third embodiment of a wavelength converter 10 according to the invention. In this embodiment, the concave mirror function of the wavelength-dependent reflector elements 14, 14', 14, 15, 15', 15" is separated from the surface of the focusing input elements 12 or the light-bundling output elements 13 and realized, for example, in the form of systems of holograms or metastructures. This allows the respective functions to be optimized independently of one another, which improves their performance, and does not have to be designed as a compromise.

[0025] In the examples shown, the converter elements 11, 11', 11" are essentially located in one plane. Alternatively, they can also be arranged on a curved surface, as this can improve adaptation to the imaging system and a scanner of the imaging system. Furthermore, it is possible to design the focusing input elements 12 or the light-bundling output elements 13 as systems of holograms or metastructures.

[0026] Fig. Figure 5 schematically shows a head-up display for a means of transportation as an example of an image generation system 1. The head-up display comprises an imaging unit 2, an optical unit 3, and a mirror unit 4. A beam SB1 emanates from a display element 21, which is reflected by a first mirror 31 onto a curved mirror 32, which reflects it toward the mirror unit 4. The mirror unit 4 is depicted here as the windshield 41 of the motor vehicle. From there, the beam SB2 travels toward an eye 61 of a viewer.

[0027] The viewer sees a virtual image VB, which is located outside the motor vehicle above the hood or even in front of the motor vehicle. Due to the interaction of optical unit 3 and mirror unit 4, the virtual image VB is an enlarged representation of the image displayed by display element 21. A speed limit, the current vehicle speed, and navigation instructions are symbolically displayed here. As long as the eye 61 is located within the eyebox 62 indicated by a rectangle, all elements of the virtual image are visible to the eye 61. If the eye 61 is located outside the eyebox 62, the virtual image VB is only partially visible to the viewer or not visible at all. The larger the eyebox 62, the less restricted the viewer is in choosing their seating position.The curvature of the curved mirror 32 is adapted to the curvature of the windshield 41 and ensures that the image distortion is stable across the entire eyebox 62. The curved mirror 32 is rotatably mounted by means of a bearing 321. The resulting rotation of the curved mirror 32 enables the eyebox 62 to be moved and thus the position of the eyebox 62 to be adjusted to the position of the eye 61. The first mirror 31 serves to ensure that the path traveled by the beam SB1 between the display element 21 and the curved mirror 32 is long, while at the same time the optical unit 3 remains compact. The optical unit 3 is separated from the environment by a transparent cover 33. The optical elements of the optical unit 2 are thus protected, for example, against dust present in the interior of the motor vehicle.An anti-glare screen 34 serves to reliably absorb the light reflected across the boundary surface of the cover 33, preventing glare to the viewer. In addition to sunlight SL, light from another interfering light source 63 can also reach the display element 21.

[0028] Fig.6 schematically shows a means of transport 100 in which a solution according to the invention is implemented. In this example, the means of transport 100 is a motor vehicle. The image generation system 1 is a head-up display. Data on the vehicle's surroundings can be acquired using a sensor system 101. The sensor system 101 can in particular comprise sensors for environmental detection, e.g., ultrasonic sensors, laser scanners, radar sensors, lidar sensors, or cameras. The information acquired by the sensor system 101 can be used to generate content to be displayed for the image generation system 1. Further components of the motor vehicle in this example are a navigation system 102, by means of which position information can be provided, and a data transmission unit 103. By means of the data transmission unit 103, for example,A connection to a backend can be established, for example, to obtain updated software for components of the motor vehicle. A memory 104 is provided for storing data. Data exchange between the various components of the motor vehicle takes place via a network 105. List of reference symbols 1 imaging system 2 Imaging Unit 21 Display element 3 Optical unit 31 First Mirror 32 Curved Mirror 321 Storage 33 Cover 34 Anti-glare protection 4 Mirror unit 41 Windshield 5 wavelength converters 61 Eye 62 Eyebox 63 stray light source 10 wavelength converter system 11, 11',11" converter element 12 Focusing input element 13 Light-bundling output element 14, 14',12" Wavelength-dependent reflector element 15, 15',15" Wavelength-dependent reflector element 16, 16',16" converter area 100 means of transport 101 Sensor Technology 102 Navigation system 103 Data transmission unit 104 memory 105 Network A Exit direction L a Emitted light L e Incident excitation light SB1 beam SB2 beam SL Sunlight VB Virtual Image QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 8,830,141 B2

[0005] DE 103 50 529 A1

[0006]

Claims

[1] Wavelength converter system (10) for an imaging system (1), comprising: - a plurality of converter elements (11, 11', 11") for wavelength conversion; - a plurality of focusing input elements (12) for focusing incident excitation light (L e ) to the converter elements (11, 11', 11"); and - a plurality of light-concentrating output elements (13) for concentrating the light (L a ) in an output direction (A). [2] Wavelength converter system (10) according to claim 1, wherein the wavelength converter system (10) comprises different converter elements (11, 11', 11") for conversion into two or more wavelengths. [3] Wavelength converter system (10) according to claim 1 or 2, wherein the converter elements (11, 11', 11") are designed as phosphor converters or quantum dots. [4] Wavelength converter system (10) according to one of the preceding claims, wherein the wavelength converter system (10) has wavelength-dependent reflector elements (14, 14', 14", 15, 15', 15") on the side of the focusing input elements (12) or on the side of the light-bundling output elements (13). [5] Wavelength converter system (10) according to claim 4, wherein the wavelength-dependent reflector elements (14, 14', 14", 15, 15', 15") are designed as dielectric coatings or as a system of holograms or metastructures. [6] Wavelength converter system (10) according to one of the preceding claims, wherein the focusing input elements (12) or the light-bundling output elements (13) are designed as systems of holograms or metastructures. [7] Wavelength converter system (10) according to one of the preceding claims, wherein the converter elements (11, 11', 11") lie substantially in a plane or on a curved surface. [8] Image generation system (1) comprising a laser source (2), a scanner (3) and a wavelength converter system (10) according to one of the preceding claims. [9] Imaging system (1) according to claim 8, wherein the imaging system (1) is a head-up display. [10] Means of transport (100) with an image generation system (1) according to claim 8 or 9.

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