Optics, sensors and displays for irradiance redistribution

Abstract

The optical element (1) is described in detail, comprising: a transparent body (2), the transparent body (2) having a flat light coupling-in surface (21) and a flat light coupling-out surface (22), the light coupling-in surface (21) being configured to couple electromagnetic radiation (3) into the transparent body, and the light coupling-out surface (22) being configured to couple electromagnetic radiation (3) out of the transparent body (2); a first reflective layer (41) on the region of the light coupling-in surface (21); a second reflective layer (41) on the region of the light coupling-out surface (22); A first reflective layer (42) is provided, wherein the light coupling-in surface (21) and the light coupling-out surface (22) are parallel to each other; the first reflective layer (41) comprises an opening (43), and the electromagnetic radiation (3) is coupled into the transparent body (2) through the opening (43); and the first reflective layer (41) and the second reflective layer (42) are arranged so that the geometric length of the optical path (5) of the electromagnetic radiation (3) inside the transparent body (2) is at least three times greater than the distance (D) between the light coupling-in surface (21) and the light coupling-out surface (22). In addition, a sensor (10) and a display device (100) comprising the optical element (1) are described in detail herein.

Description

[0001] This article describes in detail the optical components, sensors, and display devices.

[0002] At least one object of certain embodiments is to specify a particularly compact optical element for irradiance redistribution. Furthermore, a sensor and a display device comprising the optical element are specified herein.

[0003] According to at least one embodiment, an optical element comprises a transparent body having a flat light coupling-in surface and a flat light coupling-out surface, wherein the flat light coupling-in surface is configured for coupling electromagnetic radiation into the transparent body and the flat light coupling-out surface is configured for coupling electromagnetic radiation out of the transparent body. In particular, the transparent body is at least partially transparent for electromagnetic radiation. For example, at least 90% of the electromagnetic radiation coupled into the transparent body is transmitted through the transparent body. In other words, at most 10% of the electromagnetic radiation coupled into the transparent body via the light coupling-in surface is not coupled out of the transparent body via the light coupling-out surface.

[0004] In particular, the light coupling-in surface and the light coupling-out surface are planar and arranged on opposite sides of the transparent body. For example, the transparent body comprises a glass or plastic material or a semiconductor material like silicon, or consists of one of these materials. In particular, the transparent body comprising or consisting of silicon can be used for electromagnetic radiation having a wavelength in the short-wavelength infrared and / or mid-infrared spectral range (e.g. a wavelength of at least 1100 nm).

[0005] The electromagnetic radiation may include, for example, wavelengths between infrared and ultraviolet light. For example, the electromagnetic radiation includes or is electromagnetic laser radiation. The electromagnetic laser radiation is generated by a stimulated emission process. Compared to electromagnetic radiation generated by spontaneous emission, the electromagnetic laser radiation has a larger coherence length, a smaller spectral width and / or a higher degree of polarization. Alternatively, the electromagnetic radiation coupled into the optical element may be focused or collimated electromagnetic radiation generated by spontaneous emission.

[0006] According to at least one further embodiment, the optical element comprises a first reflective layer in the region of the light coupling-in surface. The first reflective layer is configured to reflect at least a portion of the electromagnetic radiation propagating inside the transparent body. For example, the reflectivity of the first reflective layer for the electromagnetic radiation is at least 80%, preferably at least 99%, and particularly preferably at least 99.9%.

[0007] The area of ​​the light coupling-in surface on which the first reflective layer is arranged may include a part of the light coupling-in surface or the entire light coupling-in surface. In particular, the first reflective layer includes a metal layer and / or a dielectric layer sequence, or is composed of one or more of these layers. In particular, the dielectric layer sequence forms a Bragg mirror.

[0008] For example, a Bragg mirror comprises a series of alternating dielectric layers with different refractive indices. In particular, the thickness of the dielectric layers and the reflectivity contrast between the alternating dielectric layers are adjusted so that the Bragg mirror has a high reflectivity for electromagnetic radiation.

[0009] According to at least another embodiment, the optical element has a second reflective layer in the region of the light outcoupling surface. The second reflective layer is configured to reflect at least a portion of the electromagnetic radiation propagating inside the transparent body. Preferably, the reflectivity of the second reflective layer is less than the reflectivity of the first reflective layer. Furthermore, the second reflective layer preferably transmits at least a portion of the electromagnetic radiation propagating inside the transparent body. For example, the reflectivity of the second reflective layer for electromagnetic radiation is at least 10%, preferably at least 50% and particularly preferably at least 80%. For example, the transmittance of the second reflective layer for electromagnetic radiation is at most 90%, preferably at most 50% and particularly preferably at most 20%.

[0010] The area of ​​the light outcoupling surface on which the second reflective layer is arranged may include a part of the light outcoupling surface or the entire light outcoupling surface. In particular, the second reflective layer includes a metal layer and / or a dielectric layer sequence, or is composed of one or more of these layers. In particular, the dielectric layer sequence forms a Bragg mirror.

[0011] According to at least one further embodiment of the optical element, the light coupling-in surface and the light coupling-out surface are parallel to each other. In particular, the light coupling-in surface and the light coupling-out surface are parallel to each other within a manufacturing tolerance. Here and hereinafter, the light coupling-in surface and the light coupling-out surface are considered to be parallel if the normal direction of the light coupling-in surface and the normal direction of the light coupling-out surface deviate by at most 5°, preferably at most 1°. For example, the light coupling-in surface and the light coupling-out surface are opposite surfaces of a planar transparent body. Alternatively, the light coupling-in surface and the light coupling-out surface may form an angle between them. Furthermore, the light coupling-in surface and / or the light coupling-out surface may be curved.

[0012] According to at least one further embodiment of the optical element, the first reflective layer comprises an opening through which the electromagnetic radiation is coupled into the transparent body. In particular, the light coupling-in surface has no reflective layer inside the opening. The opening can have an arbitrary shape, such as a circle, an ellipse, an oval, a square, a rectangle or a polygon. In particular, the diameter of the opening in the first reflective layer is equal to or greater than the beam width of the electromagnetic radiation on the light coupling-in surface. Here and hereinafter, the beam width of the electromagnetic radiation is defined as the radial diameter in a plane perpendicular to the propagation direction, wherein the intensity of the electromagnetic radiation has dropped to 13% of the maximum intensity in said plane.

[0013] For example, due to the openings in the first reflective layer, only a small portion of the electromagnetic radiation is reflected by the first reflective layer when coupling electromagnetic radiation into the transparent body. For example, less than 5%, preferably less than 1%, of the electromagnetic radiation is reflected by the first reflective layer when coupling electromagnetic radiation into the transparent body.

[0014] According to at least one further embodiment of the optical element, the first reflective layer and the second reflective layer are arranged such that a geometric length of an optical path of electromagnetic radiation inside the transparent body is at least three times greater than a distance between the light coupling-in surface and the light coupling-out surface. In particular, the optical path corresponds to a ray of electromagnetic radiation which is coupled into the transparent body via the light coupling-in surface and coupled out of the transparent body via the light coupling-out surface.

[0015] For example, at least a portion of the electromagnetic radiation coupled into the transparent body via the light coupling-in surface is reflected by the second reflective layer on the light coupling-out surface and redirected toward the first reflective layer on the light coupling-in surface. The first reflective layer may further redirect most or all of the incident electromagnetic radiation toward the light coupling-out surface, where the incident electromagnetic radiation is coupled out of the transparent body or is reflected again by the second reflective layer. In particular, at least a portion of the electromagnetic radiation coupled into the transparent body may be reflected multiple times between the first reflective layer and the second reflective layer before being coupled out of the transparent body. Preferably, different reflected components of the electromagnetic radiation do not interfere within the transparent body. In other words, the optical path of the electromagnetic radiation inside the transparent body is such that there is little or no overlap between different reflected components of the electromagnetic radiation inside the transparent body.

[0016] According to a preferred embodiment, the optical element comprises:

[0017] a transparent body having a planar light incoupling surface configured for coupling electromagnetic radiation into the transparent body and a planar light outcoupling surface configured for coupling electromagnetic radiation out of the transparent body,

[0018] a first reflecting layer, which is in the region of the light coupling-in surface,

[0019] - a second reflective layer on the region of the light outcoupling surface, wherein

[0020] - the light coupling-in surface and the light coupling-out surface are parallel to each other,

[0021] - the first reflective layer comprises openings through which electromagnetic radiation is coupled into the transparent body, and

[0022] The first and second reflecting layers are arranged such that a geometric length of an optical path of electromagnetic radiation inside the transparent body is at least three times as large as a distance between the light coupling-in surface and the light coupling-out surface.

[0023] The optical elements described herein enable the irradiance of electromagnetic radiation to be redistributed, for example, by increasing the cross-section and / or beam width of the electromagnetic radiation. In particular, the optical element can be used to reduce the maximum irradiance of the electromagnetic radiation near the electromagnetic radiation emitter, while the beam characteristics of the electromagnetic radiation at a greater distance from the emitter remain almost unchanged.

[0024] Advantageously, the optical element can have a particularly small thickness and can be integrated in a compact package.Here and hereinafter, thickness refers to the distance between the light coupling-in surface and the light coupling-out surface of the optical element.

[0025] For example, electromagnetic radiation is emitted by a sensor, such as a distance sensor for measuring the distance between the sensor and an external object. In particular, the electromagnetic radiation emitted by the sensor may pass through another element, such as a display screen, before being emitted toward the external object. If the irradiance of the electromagnetic radiation on the display screen is too great, the brightness of the display screen may be visibly distorted at the location where the electromagnetic radiation passes through the display screen. By redistributing the irradiance of the electromagnetic radiation on the display screen using the optical element disclosed herein, such visible distortion can be reduced or eliminated. In addition, the performance and / or functionality of the sensor remains unaffected by the optical element, because the characteristics of the electromagnetic radiation at a large distance from the sensor are hardly affected by the optical element.

[0026] According to at least one further embodiment, the optical element reduces the maximum irradiance of the electromagnetic radiation on a reference plane downstream of the optical element by at least 50%, preferably by at least 90%. Here and hereinafter, irradiance specifies the radiant flux of the electromagnetic radiation received per unit area by a surface such as the reference plane. In particular, irradiance is expressed in W / m 2 Measurement.

[0027] In particular, the reference plane refers to a plane downstream of the optical element, where the irradiance can be measured. Preferably, the reference plane is parallel to the light outcoupling surface. For example, the distance between the reference plane and the light outcoupling surface is less than or equal to the thickness of the optical element.

[0028] For example, due to the increased geometric length of the optical path of the electromagnetic radiation inside the transparent body, the beam width of the electromagnetic radiation coupled out of the optical element increases. Thus, the irradiance on the reference plane is reduced compared to the absence of the optical element as described herein.

[0029] According to at least one further embodiment of the optical element, the beam divergence of the electromagnetic radiation coupled out of the optical element is at most 20% greater or smaller than the beam divergence of the electromagnetic radiation coupled into the optical element, preferably at most 10%. Here and hereinafter, the beam divergence is an angular measure of the increase in the beam width along the propagation direction of the electromagnetic radiation. In particular, the beam divergence specifies the opening angle of the cone, in which the majority of the electromagnetic radiation propagates.

[0030] Preferably, the optical element does not change the beam divergence of the electromagnetic radiation. In other words, the optical element neither focuses, collimates, nor defocuses the electromagnetic radiation.

[0031] Preferably, the electromagnetic radiation coupled into the optical element is incident on the light coupling-in surface along a direction parallel to the surface normal of the light coupling-in surface. In other words, the electromagnetic radiation is preferably incident on the light coupling-in surface at an angle perpendicular to the light coupling-in surface. Alternatively, the electromagnetic radiation can be coupled into the optical element at any angle of incidence relative to the light coupling-in surface.

[0032] For example, electromagnetic radiation is coupled into the optical element at an angle such that the electromagnetic radiation propagates in a lateral direction inside the transparent body while reflecting multiple times between a first reflective layer and a second reflective layer before being coupled out of the optical element. Here and hereinafter, "lateral" refers to a direction parallel to the light coupling-in surface and / or parallel to the light coupling-out surface. In particular, when propagating in the lateral direction, the beam width of the electromagnetic radiation increases, thereby reducing the irradiance at the light coupling-out surface.

[0033] According to at least one further embodiment of the optical element, an antireflection coating is arranged on the light coupling-in surface inside the opening in the first reflective layer. In particular, the antireflection coating is arranged directly on the light coupling-in surface of the transparent body. For example, the antireflection coating reduces the portion of electromagnetic radiation reflected at the light coupling-in surface when the electromagnetic radiation is coupled into the transparent body by at least 50%.

[0034] According to at least one further embodiment of the optical element, the first refractive optical element is arranged on the light coupling-in surface and covers the opening in the first reflective layer. For example, the first refractive optical element can be arranged directly on the light coupling-in surface of the transparent body inside the opening of the first reflective layer, or the first refractive optical element can be arranged directly on the first reflective layer so that it covers the opening. In particular, the region of the first reflective layer surrounding the opening can also be covered by the refractive optical element.

[0035] According to at least one further embodiment of the optical element, the first refractive optical element is configured to reduce the irradiance of the electromagnetic radiation on the light outcoupling surface. In particular, the first refractive optical element reduces the maximum irradiance of the electromagnetic radiation on the light outcoupling surface. For example, the first refractive optical element comprises a lens, a microlens, a lens array and / or a microlens array.

[0036] Furthermore, the first refractive optical element may be configured to reduce light losses. For example, the first refractive optical element is configured to reduce the portion of electromagnetic radiation that is reflected by the second reflective layer back into the opening in the first reflective layer and that may thus be coupled out of the optical element through the light incoupling surface.

[0037] According to at least one further embodiment of the optical element, the first refractive optical element comprises a concave conical lens or is a concave conical lens. In other words, the first refractive optical element comprises a concave axicon or is a concave axicon. In particular, the concave conical lens comprises a transparent material for electromagnetic radiation, such as glass or plastic (e.g. epoxy resin). Furthermore, the concave conical lens comprises a concave conical surface with a fixed apex angle. For example, the concave conical lens images a point light source onto a ring. Compared to a non-conical concave lens, a concave conical lens has a higher adjustment tolerance and is therefore easier to arrange on a light coupling-in surface.

[0038] According to at least one further embodiment of the optical element, a first diffractive optical element is arranged on the light coupling-in surface and covers the opening in the first reflective layer. For example, the first diffractive optical element can be arranged directly on the light coupling-in surface of the transparent body inside the opening of the first reflective layer, or the first diffractive optical element can be arranged directly on the first reflective layer so that it covers the opening. In particular, the area of ​​the first reflective layer surrounding the opening can also be covered by the first diffractive optical element.

[0039] According to at least one further embodiment of the optical element, the first diffractive optical element is configured to reduce the irradiance of electromagnetic radiation on the light outcoupling surface. In particular, the first diffractive optical element has the same function as the first refractive optical element. All functional features disclosed for the first refractive optical element are also applicable to the first diffractive optical element, and vice versa.

[0040] For example, the first diffractive optical element comprises or consists of a concentric grating or a metalens. For example, the metalens comprises a nanostructured surface. In particular, the nanostructured surface comprises a non-periodic array of nanopillars, which is configured to impart a spatially correlated phase to the incident electromagnetic radiation. For example, the first diffractive optical element is realized by nanoimprinting of a transparent light coupling-in surface, or by nanoimprinting of an at least partially transparent layer arranged on the light coupling-in surface.

[0041] According to at least one further embodiment of the optical element, the second reflective layer comprises a first sub-region and a second sub-region, and the reflectivity of the first sub-region is different from the reflectivity of the second sub-region. In particular, the reflectivity specifies the portion of the incident electromagnetic radiation reflected by each respective sub-region. Preferably, the first sub-region and the second sub-region are directly adjacent to each other. For example, the second sub-region has a smaller reflectivity than the first sub-region, and vice versa. For example, the first sub-region has a reflectivity between 90% and 100%, inclusive, and the second sub-region has a reflectivity between 70% and 90%, inclusive.

[0042] The second reflective layer may also include more than two sub-regions with different reflectivities and / or transmittances. For example, the second reflective layer includes a plurality of sub-regions with different reflectivities for electromagnetic radiation. The second reflective layer may also have a continuously varying reflectivity gradient along a direction parallel to the light outcoupling surface. For example, the reflectivity of the second reflective layer decreases continuously with increasing radius away from the center of the second reflective layer.

[0043] According to at least one further embodiment of the optical element, the second sub-region completely surrounds the first sub-region in a plan view of the light outcoupling surface. In particular, the first sub-region and the second sub-region are arranged concentrically. For example, in a plan view of the light outcoupling surface, the first sub-region has a circular shape and the second sub-region has an annular shape.

[0044] According to at least one further embodiment of the optical element, a second refractive optical element is arranged on the second reflective layer and / or on the light outcoupling surface. For example, the second refractive optical element is a lens, a microlens, a lens array or a microlens array. Preferably, the second refractive optical element is arranged directly on the second reflective layer and / or directly on the light outcoupling surface of the transparent body.

[0045] According to at least one further embodiment of the optical element, the second refractive optical element is configured to reduce the beam divergence of the electromagnetic radiation coupled out of the optical element. For example, the first refractive optical element increases the beam divergence, while the second refractive optical element reduces the beam divergence, so that the electromagnetic radiation coupled out of the optical element has the same or similar beam divergence as the electromagnetic laser radiation coupled into the optical element. In particular, the first refractive optical element and the second refractive optical element are configured such that the beam width of the electromagnetic radiation coupled out of the optical element is increased, while the beam divergence is not affected by the optical elements.

[0046] The second refractive optical element may be configured to adjust the properties of the electromagnetic radiation coupled out of the optical element. In particular, the second refractive optical element is configured to adjust the beam divergence of the electromagnetic radiation. For example, the second refractive optical element may be configured to collimate and / or focus the electromagnetic radiation.

[0047] According to at least one further embodiment of the optical element, the second refractive optical element comprises a convex conical lens. In particular, the convex conical lens comprises a transparent material for electromagnetic radiation, such as glass or plastic (e.g. epoxy resin). In addition, the convex conical lens comprises a convex conical surface with a fixed vertex angle.

[0048] Preferably, the convex conical lens comprises two or more segments arranged concentrically. For example, each segment comprises a portion of a convex conical surface, and the segments are arranged in a staggered manner along the axial direction of the convex conical surface. In other words, the convex conical lens is a Fresnel-shaped lens. Preferably, in a plan view of the light outcoupling surface, the shape of the segment is consistent with the shape of the sub-region of the second reflective layer and directly overlaps. In other words, each segment of the convex conical lens is, for example, directly arranged on a corresponding sub-region of the second reflective layer. In particular, a portion of the electromagnetic radiation transmitted through the sub-region of the second reflective layer further propagates through the corresponding segment of the convex conical lens.

[0049] According to at least one further embodiment of the optical element, the vertex angle of the concave conical lens and the vertex angle of the convex conical lens are equal. In particular, the vertex angles are equal within manufacturing tolerances. For example, the vertex angle of the convex conical lens and the vertex angle of the concave conical lens may differ by at most 5°, preferably by at most 1°. By matching the vertex angles of the convex conical lens and the concave conical lens, the beam width of the electromagnetic radiation coupled out of the optical element is increased, while the beam divergence of the electromagnetic radiation remains unaffected.

[0050] According to at least one further embodiment of the optical element, a second diffractive optical element is arranged on the second reflective layer and / or on the light outcoupling surface. Preferably, the second diffractive optical element is arranged directly on the second reflective layer and / or directly on the light outcoupling surface of the transparent body.

[0051] According to at least one further embodiment of the optical element, the second diffractive optical element is configured to reduce the beam divergence of the electromagnetic radiation coupled out of the optical element. In particular, the second diffractive optical element has the same function as the second refractive optical element. All functional features disclosed for the second refractive optical element are also applicable to the second diffractive optical element, and vice versa.

[0052] For example, the second diffractive optical element comprises or consists of a concentric grating or a metalens. For example, the metalens comprises a nanostructured surface. In particular, the nanostructured surface comprises a non-periodic array of nanopillars configured to impart a spatially correlated phase to the incident electromagnetic radiation. For example, the second diffractive optical element is realized by nanoimprinting of the light outcoupling surface of the transparent body, or by nanoimprinting of a second reflective layer arranged on the light outcoupling surface of the transparent body, or by nanoimprinting of an at least partially transparent layer arranged on the light outcoupling surface and / or on the second reflective layer.

[0053] Furthermore, the sensor is described in detail herein. Preferably, the sensor comprises an optical element as described herein. All features of the optical element for the sensor are also disclosed, and vice versa.

[0054] According to at least one embodiment, the sensor comprises an optical element. In particular, the sensor comprises an optical element as described above.

[0055] According to at least one further embodiment, the sensor comprises an emitter for emitting electromagnetic radiation. For example, the emitter emits electromagnetic radiation with a wavelength between infrared light and ultraviolet light. In particular, the emitter comprises a laser diode or a light emitting diode. For example, a laser diode comprises an optical resonator and an epitaxial semiconductor layer stack having a pn junction. The pn junction together with the optical resonator is configured to convert an electric current into electromagnetic laser radiation. In contrast, a light emitting diode may not comprise a resonator and generates electromagnetic radiation by spontaneous emission.

[0056] According to at least one further embodiment, the sensor comprises a detector configured to detect at least a portion of the electromagnetic radiation reflected by the external object. In particular, the electromagnetic radiation emitted by the emitter and coupled out of the sensor is partially reflected by the external object. At least a portion of the reflected electromagnetic radiation is coupled into the sensor and detected by the detector. In particular, the detector converts the incident electromagnetic radiation into an electrical signal.

[0057] According to at least one further embodiment of the sensor, the emitter, the optical element and the detector are arranged such that electromagnetic radiation emitted by the emitter passes through the optical element before being coupled out of the sensor and electromagnetic radiation coupled into the sensor does not pass through the optical element before being projected onto the detector.

[0058] For example, the sensor is a distance sensor, a heart rate sensor or an oxygen saturation sensor. In particular, the distance sensor measures the distance between the sensor and an external object. For example, the distance sensor measures the flight time of a laser pulse emitted by the sensor toward the external object, reflected by the external object and finally detected by the detector. Alternatively or additionally, the distance sensor can determine the distance to the external object by measuring the intensity of the detected electromagnetic radiation.

[0059] For example, a heart rate sensor or oxygen saturation sensor can determine heart rate or oxygen saturation in the blood by measuring changes in the relative intensity of reflected electromagnetic radiation.

[0060] According to at least one further embodiment of the sensor, the emitter comprises a vertical cavity surface emitting laser diode. In particular, the vertical cavity surface emitting laser diode emits electromagnetic laser radiation in a direction perpendicular to a main extension plane of the semiconductor layers in the semiconductor layer stack. In other words, the electromagnetic laser radiation is emitted in a direction parallel to the epitaxial growth direction of the semiconductor layer stack.

[0061] Advantageously, the radial beam profile of the electromagnetic laser radiation emitted by the vertical cavity surface emitting laser diode has a depression at the center of the beam. In other words, the intensity of the electromagnetic laser radiation emitted at a small but finite emission angle is higher than the intensity of the electromagnetic laser radiation emitted in the forward direction at an emission angle of zero degrees. The depression of the beam profile at the center of the beam can advantageously be used to reduce the portion of the electromagnetic laser radiation that is reflected back by the optical element towards the emitter and thus potentially lost.

[0062] According to at least one further embodiment of the sensor, the detector comprises a photodiode, a phototransistor, a single photon avalanche diode, a photodiode array and / or a single photon avalanche diode array. For example, the detector comprises an epitaxial semiconductor layer stack having a pn junction, which is configured to convert incident electromagnetic radiation into an electrical output current. In particular, the photodiode array comprises a plurality of photodiodes, for example, arranged in a plane. The single photon avalanche diode array comprises a plurality of single photon avalanche diodes, for example, arranged in a plane.

[0063] Furthermore, the present invention describes a display device in detail. Preferably, the display device comprises a sensor as described above. All features disclosed for the sensor are also applicable to the display device, and vice versa.

[0064] According to at least one embodiment, the display device comprises a sensor. In particular, the display device comprises a sensor as described above. For example, the sensor is a distance sensor, a heart rate sensor and / or an oxygen saturation sensor.

[0065] According to at least one further embodiment, the display device comprises a partially transparent display screen, which is arranged such that the electromagnetic radiation emitted by the sensor is transmitted through the display screen before being coupled out of the display device towards an external object. In particular, the display screen is at least partially transparent to the electromagnetic radiation emitted by the sensor.

[0066] For example, the display screen emits electromagnetic radiation in the visible spectrum. Preferably, the display screen and the sensor have the same or similar emission directions for the corresponding electromagnetic radiation. For example, the sensor is a distance sensor, and the display device changes the information shown on the display screen depending on the distance between the sensor and an external observer.

[0067] According to at least one further embodiment of the display device, the display screen comprises a plurality of individually addressable pixels. For example, the display screen is configured to display information in the form of an image. In particular, the plurality of individually addressable pixels are arranged in the form of a two-dimensional array.

[0068] According to at least one further embodiment of the display device, each pixel comprises an organic light emitting diode and / or a micro-LED. In particular, the organic light emitting diode comprises an organic functional layer stack configured to convert an electric current into electromagnetic radiation. The organic functional layer stack comprises a layer having organic molecules as organic semiconductors.

[0069] Alternatively or additionally, each pixel may include a light emitting semiconductor diode and / or a thin film transistor. For example, the display screen is a micro-LED display or a thin film transistor (TFT) liquid crystal display. In particular, each pixel of the micro-LED display includes a light emitting semiconductor diode having an edge length of at most 50 μm, preferably at most 20 μm. For example, each micro-LED has an edge length of about 12 μm.

[0070] According to at least one further embodiment of the display device, the optical element reduces the maximum irradiance of the electromagnetic radiation emitted by the sensor on the display screen so that the light density of the display screen changes by at most 2%, preferably at most 0.5%, due to the irradiation with the electromagnetic radiation. For example, the electromagnetic radiation emitted by the sensor may cause visible distortion of the image displayed on the display screen. Advantageously, the optical element reduces the maximum irradiance of the electromagnetic radiation on the display screen so that no visible distortion is observed on the display screen by an external observer. Furthermore, the optical element preferably does not significantly change the directional radiation characteristics of the emitter. Thus, the function of the sensor is not affected by the optical element.

[0071] Further advantageous embodiments and other embodiments of the optical element, the sensor and the display device may become apparent from the exemplary embodiments described below in conjunction with the attached drawings.

[0072] Figure 1 A schematic cross section of an optical element according to an exemplary embodiment is shown.

[0073] Figure 2 A schematic plan view onto a light outcoupling surface of an optical element according to an exemplary embodiment is shown.

[0074] Figure 3 and Figure 4 Shown is a schematic irradiance distribution of electromagnetic laser radiation coupled out of an optical element according to an exemplary embodiment.

[0075] Figure 5 A schematic cross section of an optical element according to another exemplary embodiment is shown.

[0076] Figure 6 A schematic plan view onto a light outcoupling surface of an optical element according to a further exemplary embodiment is shown.

[0077] Figure 7A schematic irradiance distribution of electromagnetic laser radiation coupled out of an optical element according to another exemplary embodiment is shown.

[0078] Figures 8 to 10 A schematic cross section of an optical element according to a further exemplary embodiment is shown.

[0079] Fig.11 A schematic perspective view showing a second refractive optical element of an optical element according to an exemplary embodiment is shown.

[0080] Fig.12 A schematic irradiance distribution according to an example is shown.

[0081] Fig.13 Schematic irradiance distribution according to an exemplary embodiment is shown.

[0082] Fig.14 A schematic cross section of a sensor according to an exemplary embodiment is shown.

[0083] Fig.15 and Fig.16 A schematic cross section of a display device according to an exemplary embodiment is shown.

[0084] Identical, similar or functionally identical elements are indicated by the same reference numerals in the drawings. The drawings and the proportions of the elements shown in the drawings should not be regarded as true proportions. Rather, individual elements, in particular layer thicknesses, may be shown exaggeratedly for better representation and / or better understanding.

[0085] according to Figure 1 The optical element 1 of the exemplary embodiment shown comprises a transparent body 2, a first reflective layer 41 and a second reflective layer 42. The transparent body 2 comprises glass and has a planar light coupling-in surface 21 and a planar light coupling-out surface 22 parallel to the light coupling-in surface 21 on opposite sides of the transparent body 2.

[0086] The first reflective layer 41 is arranged directly on the light coupling-in surface 21. The first reflective layer 41 completely covers the light coupling-in surface 21 except for the opening 43 through which the electromagnetic laser radiation 3 is coupled into the transparent body 2. The opening 43 has a circular shape or a shape that matches the beam profile of the electromagnetic laser radiation 3. In particular, the diameter of the opening 43 is equal to or greater than the beam width of the electromagnetic laser radiation 3 on the light coupling-in surface 21. The first reflective layer 41 comprises a metal layer or a Bragg mirror and preferably has a reflectivity of at least 99.9% for the electromagnetic laser radiation 3.

[0087] The second reflective layer 42 is arranged directly on the light outcoupling surface 22. It covers a circular area of ​​the light outcoupling surface 22 opposite the opening 43 in the first reflective layer 41. The second reflective layer 42 comprises a metal layer or a Bragg mirror and preferably has a reflectivity for the electromagnetic laser radiation 3 of at least 80%.

[0088] The electromagnetic laser radiation 3 is emitted by an emitter 11 which is not part of the optical element 1. The electromagnetic laser radiation 3 has a beam divergence α before being coupled into the optical element 1. The optical element 1 does not change the beam divergence α of the electromagnetic laser radiation 3. In particular, the electromagnetic laser radiation 3 coupled out of the optical element 1 has the same beam divergence α as the electromagnetic laser radiation 3 coupled into the optical element 1.

[0089] Before the electromagnetic laser radiation 3 is at least partially reflected by the second reflective layer 42, the diameter of the second reflective layer 42 is equal to the beam width of the electromagnetic laser radiation 3 on the light outcoupling surface 22. In other words, all electromagnetic laser radiation 3 coupled into the transparent body 2 via the opening 43 in the first reflective layer 41 and transmitted through the transparent body 2 is incident on the second reflective layer 42.

[0090] also, Figure 1 An optical path 5 or light of the electromagnetic laser radiation 3 is shown. In particular, at least a portion of the electromagnetic laser radiation 3 coupled into the transparent body 2 through the openings 43 in the first reflective layer 41 propagates through the transparent body 2 and is reflected by the second reflective layer 42 back towards the first reflective layer 41. The first reflective layer 41 further redirects the electromagnetic laser radiation 3 towards the light outcoupling surface 22 where the electromagnetic laser radiation 3 is coupled out of the optical element 1.

[0091] Thus, the geometric length of at least some of the optical paths 5 inside the transparent body 2 is at least three times greater than the distance D between the first reflective layer 41 and the second reflective layer 42. Here, the distance D corresponds to the thickness of the transparent body 2. As a result, the optical element 1 changes the irradiance distribution of the electromagnetic laser radiation 3 at a fixed distance from the emitter 11. In particular, the beam width of the electromagnetic laser radiation 3 coupled out of the optical element 1 is increased by the optical element 1. As a result, the irradiance of the electromagnetic laser radiation 3 is reduced by the optical element 1.

[0092] Figure 2 Shown according to the combination Figure 1 A plan view onto the light outcoupling surface 22 of the optical element 1 of the depicted exemplary embodiment. The second reflective layer 42 has a circular shape and covers only a portion of the light outcoupling surface 22. The circular second reflective layer 42 advantageously produces an approximately radially symmetrical beam profile of the electromagnetic laser radiation 3 coupled out of the optical element 1.

[0093] Figure 3 and Figure 4 Shown according to the combination Figure 1 Schematic irradiance E distribution of the electromagnetic laser radiation 3 coupled out of the optical element 1 according to the exemplary embodiment described. In particular, Figure 3 and Figure 4 The irradiance E distribution in a plan view of the light outcoupling surface 22 at a fixed distance from the light outcoupling surface 22 is shown.

[0094] Figure 3 The irradiance E distribution shown in corresponds to the optical element 1, in which both the first reflective layer 41 and the second reflective layer 42 have a reflectivity of almost 100% and a transmittance of almost 0%. Therefore, the electromagnetic laser radiation 3 has an annular irradiance E distribution, in which the irradiance E is limited between the inner and outer diameters of the ring, otherwise the irradiance E nearly vanishes.

[0095] In contrast, Figure 4 The irradiance E distribution shown in corresponds to an optical element 1 in which the first reflective layer 41 has a reflectivity of 100% and the second reflective layer 42 has a reflectivity of 90% and a transmittance of 10% for the electromagnetic laser radiation 3. Figure 3 In contrast, due to the portion of the electromagnetic laser radiation 3 that is transmitted through the second reflecting layer 42, the irradiance E is limited inside the inner diameter of the ring.

[0096] and Figure 1 In comparison, according to Figure 5 The optical element 1 of the exemplary embodiment in the embodiment includes a second reflective layer 42, which has a first sub-region 421 and a second sub-region 422 directly adjacent to the first sub-region 421 and completely surrounding the first sub-region 421. In particular, the first sub-region 421 is configured similar to the combination Figure 1 The second sub-region 422 is annular and has an inner diameter that matches the diameter of the first sub-region 421. The outer diameter of the second sub-region 422 is configured such that the optical path 5 of the electromagnetic laser radiation 3 incident at the edge of the first sub-region 421 is redirected by the first reflective layer 41 toward the outer edge of the second sub-region 422 away from the first sub-region 421.

[0097] For electromagnetic laser radiation 3, the first sub-region 421 has a reflectivity of 90% and a transmittance of 10%, while the second sub-region 422 has a reflectivity of 80% and a transmittance of 20%. Figure 1 Compared with the disclosed optical element 1, Figure 5 The optical element 1 shown has a broader irradiance distribution. In particular, the geometric length of some optical paths 5 of the electromagnetic laser radiation 3 is at least five times greater than the distance D between the first reflecting layer 41 and the second reflecting layer 42 .

[0098] Figure 6 Shows the combination Figure 5 Plan view onto the light coupling-out surface 22 of the depicted optical element 1. The second reflective layer 42 has a circular first sub-region 421 and an annular or ring-shaped second sub-region 422 which are directly adjacent to one another.

[0099] Figure 7 Shown according to the combination Figure 5 Schematic irradiance E distribution of the electromagnetic laser radiation 3 coupled out of the optical element 1 according to the exemplary embodiment described. In particular, Figure 7 The irradiance E distribution is shown in a plan view of the light outcoupling surface 22 at a fixed distance from the light outcoupling surface 22. The irradiance E distribution comprises a circular inner region and two concentric annular outer regions.

[0100] In particular, the inner circular region includes electromagnetic laser radiation 3 transmitted through the first sub-region 421 of the second reflective layer 42, while the inner annular region includes electromagnetic laser radiation 3 transmitted through the second sub-region 422 of the second reflective layer 42. The outer annular region of the irradiance E distribution includes electromagnetic laser radiation 3 reflected by the second sub-region 422 of the second reflective layer 42 toward the first reflective layer 41 and further redirected by the first reflective layer 41 toward the light outcoupling surface 22.

[0101] Combined with Figure 5 Compared with the described embodiment, according to Figure 8 The optical element 1 of the exemplary embodiment in further comprises a first refractive optical element 61. The first refractive optical element 61 is a concave conical lens arranged on the light coupling-in surface 21 of the transparent body 2. In particular, the concave conical lens covers the opening 43 in the first reflective layer 41 and is configured to increase the beam diameter of the electromagnetic laser radiation 3. An anti-reflective coating (44) may be arranged between the first refractive optical element 61 and the light coupling-in surface 21. In addition, the concave conical lens reduces light losses by reducing the portion of the electromagnetic laser radiation 3 that is reflected by the second reflective layer 42 and coupled out of the optical element 1 through the opening 43 in the first reflective layer 41 on the light coupling-in surface 21.

[0102] Combined with Figure 8 Compared with the disclosed optical element, according to Fig. 9 The optical element of the exemplary embodiment in further comprises a second reflective layer 42 having an additional third sub-region 423. The third sub-region 423 is arranged concentrically around the second sub-region 422. For example, the reflectivity and transmittance of the first sub-region, the second sub-region and the third sub-region 421, 422, 423 can be adjusted to achieve a more uniform irradiance distribution of the electromagnetic radiation 3 coupled out of the optical element 1.

[0103] Furthermore, the optical element 1 comprises a second refractive optical element 62. The second refractive optical element 62 is a convex conical lens and is arranged directly on the second reflective layer 42. The second refractive optical element 62 is configured to recollimate the electromagnetic laser radiation 3. In particular, the second refractive optical element 62 reduces the beam divergence of the electromagnetic laser radiation 3. For example, the second refractive optical element 62 compensates for the increase in beam divergence caused by the first refractive optical element 61. Advantageously, the top angle of the conical surface of the first reflective optical element 61 is Equal to the vertex angle of the conical surface of the second refractive optical element 62 within the manufacturing tolerance By matching the vertex angles of the concave and convex conical lenses The beam divergence of the electromagnetic laser radiation 3 passing through the optical element 1 remains unaffected by the optical element 1 .

[0104] The convex conical lens is a Fresnel-like lens having a circular central segment surrounded by two concentric annular segments in a plan view of the light outcoupling surface 22. In a plan view of the light outcoupling surface 22, the segments of the convex conical lens overlap with corresponding sub-regions of the second reflective layer 24. By using a Fresnel-like convex conical lens, the optical element 1 is advantageously more compact.

[0105] Fig.10 Shown according to the combination Fig. 9 The optical path 5 of the electromagnetic laser radiation 3 through the optical element 1 of the exemplary embodiment is described. First, the electromagnetic laser radiation 3 is deflected by the first refractive optical element 61 so that the beam width of the electromagnetic laser radiation 3 is increased inside the transparent body 2. In addition, the electromagnetic laser radiation 3 is partially transmitted and partially reflected by the first sub-region 421 of the second reflective layer 42. This transmitted part of the electromagnetic laser radiation 3 is re-collimated by the first section of the second refractive optical element 62 and coupled out of the optical element 1.

[0106] The portion of the electromagnetic laser radiation 3 reflected by the first sub-region 421 is further redirected by the first reflective layer 41 onto the second sub-region 422. The electromagnetic laser radiation 3 incident on the second sub-region 422 is partially transmitted and partially reflected. The transmitted portion is re-collimated by the segments of the second refractive optical element 62 and coupled out of the optical element 1. The reflected portion is further redirected by the first reflective layer 41, coupled out by the third sub-region 423, and re-collimated by the third segment of the second refractive optical element 62 before coupling out of the optical element 1. In this example, the third sub-region 423 does not reflect the incident electromagnetic radiation 3.

[0107] according to Fig.11The second refractive optical element 62 of the optical element 1 of the exemplary embodiment shown is a Fresnel-shaped convex conical lens. In particular, the convex conical lens includes conical surface segments that are concentrically arranged in a staggered manner along the axial direction. Each conical surface segment has the same vertex angle.

[0108] Fig.12 The irradiance E distribution shown in corresponds to the irradiance E of the electromagnetic laser radiation 3 emitted by a vertical cavity surface emitting laser diode (VCSEL). In particular, the irradiance E is shown as a contour plot on a surface perpendicular to the propagation direction of the electromagnetic laser radiation 3 at a fixed distance from the vertical cavity surface emitting laser diode. Furthermore, corresponding line plots of the irradiance E are shown along the x-direction and along the perpendicular y-direction.

[0109] The electromagnetic laser radiation 3 has an approximately circular beam profile, and the irradiance E has a depression at the beam center. In other words, the electromagnetic laser radiation 3 emitted by the vertical cavity surface emitting laser diode is not a Gaussian beam having a maximum value of the irradiance E at the beam center. In contrast, the irradiance E is maximum along an annular profile concentric with the beam center.

[0110] Fig.13 The irradiance E distribution shown corresponds to Fig.12 1 and 2 show the irradiance E of a vertical cavity surface emitting laser diode after being transmitted through an optical element 1 according to an exemplary embodiment. Fig.12 Compared with the irradiance E distribution shown in Fig.13 The irradiance distribution in φ therefore has a larger spatial extension in the x- and y-direction and the maximum irradiance E is lower.

[0111] according to Fig.14 The sensor 10 of the exemplary embodiment shown comprises an emitter 11 and a detector 12 arranged on a carrier 13. The emitter 11 is a vertical cavity surface emitting laser diode and the detector 12 is a photodiode, while the carrier 13 is a printed circuit board with electrical contacts for the emitter 11 and the detector 12. Alternatively, for example, the emitter 11 may comprise a light emitting semiconductor diode and focusing or collimating optics.

[0112] During operation, the emitter 11 emits electromagnetic laser radiation 3 in a direction perpendicular to the carrier. The electromagnetic laser radiation 3 passes through the optical element 1 so that the irradiance E is redistributed in a lateral direction parallel to the main surface of the carrier 13. The electromagnetic laser radiation 3 reflected by external objects and incident on the detector 12 does not pass through the optical element 1.

[0113] The optical element 1 is attached to a carrier 13 via a housing 14 (e.g. a frame). For example, the housing 14, the optical element 1 and the carrier 13 form a hermetic seal to protect the emitter 11 from environmental influences such as humidity, harmful substances and / or mechanical forces. By using the optical element 1 as a cover for the emitter 11, the sensor 10 can be incorporated into a particularly compact package. Similarly, a cover 15 is arranged above the detector 12. The cover 15 is a window that is transparent to the electromagnetic laser radiation 3 and protects the detector 12 from environmental influences such as humidity, harmful substances and / or mechanical forces.

[0114] according to Fig.15 The display device 100 of the exemplary embodiment shown includes a display device 100 in combination with Fig.14 The exemplary embodiment shown depicts a sensor 10, and a display screen 101. The display screen 101 is arranged above the sensor 10. The sensor 10 can also be arranged directly on the display screen 101. In particular, the electromagnetic laser radiation 3 emitted by the sensor 10 is at least partially transmitted through the display screen 101 before propagating towards an external object.

[0115] The display screen 101 comprises a plurality of individually addressable pixels in order to display information, for example in the form of an image. Each pixel comprises an organic light emitting diode which emits electromagnetic radiation in the visible spectral range. In contrast, the sensor 10 emits electromagnetic laser radiation 3 in the infrared spectral range. For example, the sensor 10 is a distance sensor which is configured to measure the distance between the display device 101 and an external object. The emission direction of the electromagnetic radiation of the display screen 101 coincides with the emission direction of the electromagnetic laser radiation 3 of the sensor 10.

[0116] The optical element 1 in the sensor 10 is configured to reduce the irradiance of the electromagnetic laser radiation 3 on the display screen 101. In particular, the irradiance is reduced so that the electromagnetic laser radiation 3 does not cause visible distortions in the image displayed on the display screen 101. However, the beam divergence of the electromagnetic laser radiation 3 is not affected by the optical element 1 so that the sensor 10 remains functional.

[0117] Fig.16 1 shows a numerically simulated optical path 5 or light rays of electromagnetic laser radiation 3 emitted by an emitter 11 and passing through an optical element 1 and a display screen 101 of a display device 100 (the detector 12 of the display device 100 is not in the display screen 101). Fig.16 ). The optical element 1 corresponds to the combination Fig. 9 Exemplary embodiments are described.

[0118] The optical element 1 increases the beam width, thereby reducing the irradiance of the electromagnetic laser radiation 3 on the display screen 101. The optical properties of the electromagnetic laser radiation 3, such as beam divergence, remain unchanged by the optical element 1.

[0119] This patent application claims the priority of German patent application DE 102022121629.2, the disclosure content of which is incorporated herein by reference.

[0120] The invention is not limited to the exemplary embodiments due to the description based on the exemplary embodiments. Rather, the invention covers any new features and any combination of features, which in particular includes any combination of features in the patent claims and any combination of features in the exemplary embodiments, even if the feature or the combination itself is not explicitly stated in the patent claims or the exemplary embodiments.

[0121] Reference Mark List

[0122] 1Optical elements

[0123] 2 Transparent body

[0124] 21 Light coupling into the surface

[0125] 22 Optical coupling out of the surface

[0126] 3 Electromagnetic radiation

[0127] 41 first reflection layer

[0128] 42 second reflection layer

[0129] 421 First Sub-Area

[0130] 422 Second sub-area

[0131] 423 Third Sub-Area

[0132] 43 Opening

[0133] 44 Anti-reflective coating

[0134] 5 Optical Path

[0135] 61 first refractive optical element

[0136] 62 second refractive optical element

[0137] 10 Sensors

[0138] 11 Transmitter

[0139] 12 detectors

[0140] 13 Carrier

[0141] 14 Shell

[0142] 15 Cover

[0143] 100 display devices

[0144] 101 Display

[0145] D distance

[0146] E-Irradiance

[0147] α beam divergence

[0148] Top angle.

Claims

1. An optical element (1), comprising: a transparent body (2), the transparent body (2) having a planar light coupling-in surface (21) and a planar light coupling-out surface (22), the light coupling-in surface (21) being configured for coupling electromagnetic radiation (3) into the transparent body, the light coupling-out surface (22) being configured for coupling the electromagnetic radiation (3) out of the transparent body (2), - a first reflecting layer (41) on the region of the light coupling-in surface (21), - a second reflective layer (42) on the region of the light outcoupling surface (22), wherein - the light coupling-in surface (21) and the light coupling-out surface (22) are parallel to each other, - the first reflective layer (41) comprises an opening (43) through which the electromagnetic radiation (3) is coupled into the transparent body (2), and - The first reflective layer (41) and the second reflective layer (42) are arranged so that the geometric length of the optical path (5) of the electromagnetic radiation (3) inside the transparent body (2) is at least three times greater than the distance (D) between the light coupling-in surface (21) and the light coupling-out surface (22).

2. An optical element (1) according to the preceding claim, wherein: The optical element (1) reduces the maximum irradiance (E) of the electromagnetic radiation (3) at a reference plane downstream of the optical element (1) by at least 50%.

3. The optical element (1) according to any one of the preceding claims, wherein: The beam divergence (α) of the electromagnetic radiation (3) coupled out of the optical element (1) is at most 10% greater or smaller than the beam divergence (α) of the electromagnetic radiation (3) coupled into the optical element (1).

4. The optical element (1) according to any one of the preceding claims, wherein An anti-reflection coating (44) is arranged on the light coupling-in surface (21) inside the opening (43) in the first reflective layer (41).

5. Optical element (1) according to the preceding claim, wherein a first refractive optical element (61) and / or a first diffractive optical element is arranged on the light coupling-in surface (21) and covers the opening (43) in the first reflective layer (41), and The first refractive optical element (61) and / or the first diffractive optical element is configured to reduce the irradiance (E) of the electromagnetic radiation (3) on the light outcoupling surface (22).

6. Optical element (1) according to the preceding claim, wherein The first refractive optical element (61) comprises a concave conical lens.

7. An optical element (1) according to any one of the preceding claims, wherein: - the second reflective layer (42) comprises a first sub-region (421) and a second sub-region (422), and - The reflectivity of the first sub-region (421) is different from the reflectivity of the second sub-region (422).

8. Optical element (1) according to the preceding claim, wherein In a plan view of the light outcoupling surface (22), the second sub-region (422) completely surrounds the first sub-region (421).

9. The optical element (1) according to any one of the preceding claims, wherein: a second refractive optical element (62) and / or a second diffractive optical element is arranged on the second reflective layer (42) and / or on the light outcoupling surface (22), The second refractive optical element (62) and / or the second diffractive optical element is configured to reduce a beam divergence (α) of the electromagnetic radiation (3) coupled out of the optical element (1).

10. Optical element (1) according to the preceding claim, wherein The second refractive optical element (62) comprises a convex conical lens.

11. The optical element (1) according to claim 6 and 10, wherein: The vertex angle of the concave conical lens The vertex angle of the convex conical lens equal.

12. A sensor (10), comprising: - An optical element (1) according to any one of claims 1 to 11, - a transmitter (11) for emitting electromagnetic radiation (3), and - a detector (12) configured to detect at least a portion of the electromagnetic radiation (3) reflected by an external object, wherein The emitter (11), the optical element (1) and the detector (12) are arranged such that the electromagnetic radiation (3) emitted by the emitter (11) passes through the optical element (1) before being coupled out of the sensor (10), and the electromagnetic radiation (3) coupled into the sensor (10) does not pass through the optical element (1) before being projected onto the detector (12).

13. The sensor (10) according to the preceding claim, wherein - the emitter (11) comprises a vertical cavity surface emitting laser diode, and - The detector (12) comprises a photodiode, a phototransistor, a single photon avalanche diode, a photodiode array and / or a single photon avalanche diode array.

14. A display device (100), comprising: - A sensor (10) according to any one of claims 12 or 13, and A partially transparent display screen (101) arranged such that the electromagnetic radiation (3) emitted by the sensor (10) is transmitted through the display screen (101) before being coupled out of the display device (100) towards the external object.

15. The display device (100) according to the preceding claim, wherein - the display screen (101) comprises a plurality of individually addressable pixels, and -Each pixel comprises an organic light emitting diode and / or a micro-LED.

16. The display device (100) according to any one of claims 14 or 15, in, The optical element (1) reduces the maximum irradiance (E) of the electromagnetic radiation (3) emitted by the sensor (10) on the display screen (101) so that the brightness of the display screen (101) changes by at most 2% due to the irradiation of the electromagnetic radiation (3).

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