Optical transmission element

Abstract

Optical transmission element (1), with - a first planar microlens arrangement (2) and - a second planar microlens arrangement (3) arranged parallel to the first microlens arrangement (2), - wherein a planar aperture arrangement (4) with a plurality of aperture elements (5) each having at least one aperture (6) is arranged between the two microlens arrangements (2, 3) and parallel thereto, - wherein each aperture element (5) is assigned to a microlens (7, 8) of the first and second microlens arrays (2, 3) and is arranged in their focal plane (F), and - wherein the microlens arrays (2, 3) and the aperture array (4) are arranged such that light incident on the first microlens array (2) is, depending on its angle of incidence (W), either transmitted through the aperture array (4) and the second microlens array (3) or absorbed or reflected at the aperture array (4), characterized in that - the diaphragm elements (5) are each arranged within the focal plane (F) of the microlens arrays (2, 3) and at the same time offset from the optical axis (A) of the microlens arrays (2, 3), and that - the optical transmission element (1) is formed as a film into which the diaphragm arrangement (4) is completely embedded, and on one side of which the first microlens arrangement (2) and on the other side of which the second microlens arrangement (3) are arranged.

Description

[0001] The invention relates to an optical transmission element.

[0002] Optical transmission elements are known in a wide variety of designs from the state of the art and are used in a variety of ways to create optical effects, for example to change the optical properties of a surface of a light source or to act as an optical filter.

[0003] A multilayer body for viewing the front and back sides in transmitted light is already known from the publication DE 10 2006 005 000 A1. The multilayer body consists of a transparent first layer and a second layer with a micropattern consisting of opaque first subregions and transparent second subregions. The first layer has a surface profile on its surface facing away from the second layer, forming an arrangement of a plurality of microlenses. The thickness of this first layer roughly corresponds to the focal length of the microlenses.

[0004] US Pat. No. 5,351,151 A discloses an optical filter device consisting of two parallel arrays of lenses. Each lens in the first array opposes a lens in the second array to form a pixel. The lens pairs in a pixel are separated by the sum of their focal lengths and contain, in their common focal surface, a "smart" layer for modulating the light passing through the focal surface. The "smart" layer can be a mask with partially transparent areas and partially opaque areas, thus achieving angle-selective transmission. Preferred embodiments include, among others, car rearview mirrors, sunglasses, night driving glasses, laser goggles, nuclear goggles, sun visors, sunshades, windshields, helmet visors for space suits, protective devices for optical instruments, window filters, and energy-saving devices.

[0005] US Pat. No. 5,439,621 A relates to a method for manufacturing a microlens array in which the microlenses have focal lengths that vary depending on their geometric position within the array. The focal lengths of the microlenses in the center of the array are shorter than the microlenses in the periphery.

[0006] Finally, the document DE 10 2018 202 777 A1 discloses a color sensor with at least one photosensitive element and at least one color filter, wherein at least one array of microlenses and apertures associated with the microlenses is formed above the photosensitive surface between the light entry side and the photosensitive surface of the photosensitive element. The apertures are arranged between the microlenses and the photosensitive surface, and the spacing and dimensions of the microlenses and apertures are selected such that the array of microlenses and apertures associated with the microlenses only allows portions of the optical radiation incident on the light entry side of the color sensor to reach the photosensitive surface that impinge on the light entry side within a limited angle of incidence range.

[0007] The invention is based on the object of providing an optical transmission element which has improved optical properties compared to known optical transmission elements and in particular has an angle-dependent transmission or filtering capability.

[0008] The object is achieved according to the invention by an optical transmission element according to claim 1. Advantageous developments of the invention are specified in the dependent claims.

[0009] The optical transmission element according to the invention comprises a first planar microlens array and a second planar microlens array, wherein the two microlens arrays are arranged parallel to one another. Furthermore, a planar aperture array is arranged between the two microlens arrays and simultaneously parallel thereto, wherein the aperture array comprises a plurality of aperture elements, each having at least one aperture. Each of these aperture elements is assigned to a microlens of the first and second microlens arrays and arranged in their focal plane. The microlens arrays and the aperture array are further arranged such that light incident on the first microlens array, depending on its angle of incidence, is either transmitted through the aperture array and the second microlens array or absorbed and / or reflected by the aperture array.What is characteristic of the present invention is that the aperture elements are each arranged within the focal plane of the microlens arrays and at the same time offset from the optical axis of the microlens arrays, and that the optical transmission element is formed as a film into which the aperture array is completely embedded, and on one side of which the first microlens array is arranged and on the other side of which the second microlens array is arranged.

[0010] The inventive arrangement of the aperture arrangement in the optical transmission element advantageously enables two different modes of operation of the transmission element depending on the angle of incidence of the incident light. In particular, the invention enables the provision of an angle-of-incidence-dependent transmission filter in a particularly simple manner. A further advantage of the invention is that the optical transmission element according to the invention provides an optical system in the form of a microarray, which is therefore particularly compact.

[0011] An optical transmission element within the meaning of the invention is, first of all, any object or component that is fundamentally intended for the transmission of light, wherein, under at least one condition and / or in at least one state, the predominant portion of the incident light is transmitted, i.e., is guided through the optical transmission element. However, the invention provides that the incident light is essentially not transmitted at at least one angle of incidence, but is at least partially, preferably completely, absorbed and / or reflected.

[0012] Numerous different applications are possible for such an optical transmission element, for example, as a light grid, for LIDAR (Light Detection and Ranging) sensor optics, in optical metrology, or for limiting the angle of a display and / or lighting. The optical transmission element can be arranged either in the area of ​​a light source or in the area of ​​a light receiver or an optical sensor. Furthermore, it can be used as an optical spatial filter, for example, to eliminate interference caused by dust particles on optical elements or in the air.

[0013] The optical transmission element can, in principle, be formed from any number of components and any materials. However, the optical transmission element preferably comprises only at least two microlens arrays and at least one aperture array. Furthermore, a carrier material or a material enclosing the components of the optical transmission element can be provided. The carrier material and / or the microlens arrays are particularly preferably formed exclusively from plastic.

[0014] The first and / or second microlens array can, in principle, be any array of multiple microlenses. Preferably, the microlens array has numerous microlenses arranged side by side, in particular directly adjacent to one another, on one side or on one surface. Most preferably, the microlenses are formed integrally with a carrier material, in particular a film. In principle, the microlenses can have any desired optical characteristic, with each of the microlenses preferably being a converging lens, in particular a plano-convex or biconvex lens. In the case of a plano-convex lens shape, the convex side of the lens in the optical transmission element is preferably arranged facing away from the aperture array. Preferably, the light incident on the optical transmission element first strikes the first microlens array and only strikes the second microlens array if transmitted through the aperture array.Most preferably, the optical transmission element is formed or constructed mirror-symmetrically to the focal plane, so that the same effect, in particular the same angular selectivity, is present in both possible directions of the incident light.

[0015] Furthermore, both microlens arrays preferably have an identical number of microlenses, with each microlens of the first microlens array being particularly preferably arranged in a fixed spatial relationship to exactly one microlens of the second microlens array. Very particularly preferably, both microlens arrays are formed identically to one another and / or arranged mirror-symmetrically to one another or with respect to the focal plane.

[0016] The diaphragm arrangement can initially be a plurality of diaphragm elements of any desired design, with all diaphragm elements of the diaphragm arrangement preferably being arranged side by side and in particular directly adjacent to one another. Most preferably, the spacing and / or arrangement of the diaphragm elements relative to one another is adapted to the spacing and / or arrangement of the microlenses of one or both microlens arrangements. The diaphragm element can be formed from any desired material, which is preferably at least partially, particularly preferably completely, opaque. The material of the diaphragm element can be provided primarily for reflecting the incident light or primarily for absorbing it. Furthermore, the material of the diaphragm element can also partially absorb and partially reflect the incident light.Particularly preferably, the aperture element is metallic and / or formed on a wafer, in particular made of silicon.

[0017] The aperture elements of the aperture arrangement are preferably arranged regularly. The microlenses of the first and / or second microlens arrangement are also preferably arranged regularly, whereby a regular arrangement is understood to mean an arrangement of microlenses or aperture elements that follows fixed rules regarding the position of the individual microlenses or aperture elements in relation to one another. Particularly preferably, the arrangement of the microlenses and / or aperture elements repeats periodically in at least one spatial direction, preferably in both spatial directions. Very particularly preferably, the distance between two adjacent microlenses and / or aperture elements is the same for all microlenses and / or aperture elements in at least one spatial direction, preferably in both spatial directions.

[0018] According to the invention, both the microlens arrays and the aperture array are formed in a planar manner, with the area of ​​the first microlens array and / or the second microlens array and / or the aperture array preferably being of equal size. Particularly preferably, the first microlens array and / or the second microlens array and / or the aperture array have identical lengths to one another in at least one, and very particularly preferably in both, spatial directions. Particularly preferably, both microlens arrays and the aperture array have identical areas and are particularly preferably arranged congruently.

[0019] Furthermore, the aperture arrangement is arranged parallel to the microlens arrangements and between them, wherein the aperture arrangement is preferably arranged exactly centrally between the two mutually parallel microlens arrangements, in particular centrally along an optical axis of the microlenses and / or along a direction perpendicular to the surface of the optical transmission element.

[0020] According to the invention, the diaphragm arrangement comprises a plurality of diaphragm elements, which are preferably formed identically to one another, wherein each diaphragm element has at least one diaphragm opening. In principle, however, each diaphragm element can have any number of diaphragm openings. The diaphragm opening can in principle be round or have any other shape, wherein the individual diaphragm opening and / or multiple diaphragm openings of an diaphragm element are preferably arranged rotationally symmetrically about the optical axis of the associated microlens. Furthermore, the diaphragm geometry of all diaphragm elements of the diaphragm arrangement is preferably the same. In this case, all diaphragm elements particularly preferably have an identical shape and / or size.

[0021] According to the invention, each aperture element is assigned to a microlens of the first and second microlens arrays, which initially simply means that the same number of aperture elements are provided as the optical transmission element has microlenses in each of the microlens arrays, and / or that each aperture element is arranged in the optical transmission element such that the light incident on a microlens falls or can fall on a specifically assigned aperture element. Accordingly, two microlenses and one aperture element in the optical transmission element form a functional unit that interacts with at least one incident light beam.

[0022] The focal plane of a microlens array is the plane within which all focus or focal points of the microlenses lie. Accordingly, the focal plane is also commonly referred to as the focal plane or focal point plane. According to the invention, the diaphragm element is arranged in the focal plane of a microlens of the first and / or second microlens array, particularly preferably simultaneously in the focal plane of both microlens arrays. Accordingly, the two microlens arrays are preferably arranged such that the focal planes of both microlens arrays lie within or on top of each other.

[0023] According to the invention, the optical transmission element is formed such that the transmission angle of the incident light is limited, i.e., incident light is transmitted in a first angular range, while incident light is reflected and / or absorbed, in particular by the diaphragm arrangement, at least in a second angular range deviating from the first angular range. Accordingly, the optical transmission element is angle-selective according to the invention. This angle selectivity is achieved by the relative arrangement of the diaphragm elements of the diaphragm arrangement to the microlenses of the microlens arrangements, in particular the first microlens arrangement.

[0024] A preferred embodiment of the optical transmission element according to the invention provides that a microlens of the first microlens arrangement has a common optical axis with a microlens of the second microlens arrangement, so that two microlenses of the first and second microlens arrangements can interact optimally and thereby form an optical unit. The optical axis preferably runs through the center and / or at right angles to the surface of the respective microlens. Furthermore, the optical axis is preferably an axis of symmetry of a rotationally symmetrical microlens. A common optical axis is understood to mean that the optical axes of the two microlenses are arranged on top of one another or so that they extend one another, ie that both optical axes lie on a common straight line.

[0025] According to the invention, the diaphragm element and particularly preferably an opening of the respective diaphragm element is arranged within the focal plane of the microlens arrays and at the same time offset from the common optical axis of two microlenses of the microlens arrays, whereby an angular selectivity of the optical transmission element can be achieved in a simple manner in that transmission takes place only in a predefined range of the angles of incidence, wherein this predefined range is not arranged at right angles to the surface of the transmission element according to this embodiment.

[0026] In an advantageous development of the optical transmission element according to the invention, the diaphragm elements of the diaphragm arrangement have a non-circular diaphragm opening and / or are each formed with a plurality of diaphragm openings, whereby the transmission behavior and in particular the angular selectivity of the optical transmission element can be adjusted particularly precisely in a simple manner. Each of the diaphragm openings of an diaphragm element is preferably arranged outside the optical axis of the microlens arrangements. Furthermore, a plurality of diaphragm openings of an diaphragm element are preferably arranged such that an diaphragm opening arrangement is created that is delimited and / or distinguishable from other diaphragm elements. In this case, the at least one diaphragm opening orThe arrangement of the apertures of a diaphragm element can be selected such that the incident light is transmitted in precisely one continuous angular range or, alternatively, in several separate or interrupted angular ranges. Furthermore, the angular ranges can extend in one or two spatial directions, or the angular ranges of the incident light in which transmission occurs can differ from one another in both spatial directions.

[0027] Angular selectivity of the optical transmission element can also be achieved by having the diaphragm elements of the diaphragm arrangement each have an annular aperture. An annular aperture allows for direction-independent angular selectivity, i.e., as long as the angle of the incident light is greater than a predetermined angle of incidence relative to the optical axis, transmission through the optical transmission element occurs regardless of the direction of incidence. Furthermore, the transmission angle range can be adjusted particularly easily using the inner and outer diameters of the aperture ring.

[0028] The optical transmission element can comprise any number of identical arrangements of two microlenses and one aperture element, whereby each position on the surface of the optical transmission element has the same optical properties. However, it is also conceivable in principle for an offset or deviation of the position of the aperture element from the optical axis of the two associated microlenses of the microlens arrangements to vary across the surface of the optical transmission element, whereby different positions on the surface have different optical properties and, in particular, a different angular selectivity is achieved in one or both spatial directions of the surface of the optical transmission element.

[0029] A systematic variation is preferred and a deviation that changes continuously, in particular increases, in one or more spatial directions is particularly preferred. The variation can run from one side of the optical transmission element to the other, for example with the smallest deviations on one side and the largest deviations on the opposite side. Alternatively, the deviation can also be formed starting from the center of the optical transmission element with the largest or smallest deviation in the center of the optical transmission element and a correspondingly decreasing or increasing deviation towards the edges. In addition, at least two, preferably several sharply demarcated regions with different optical properties are conceivable due to a respective changed deviation in this region. The deviation orthe offset preferably within the plane of the aperture arrangement and / or perpendicular to the optical axis.

[0030] Furthermore, in a preferred embodiment of the optical transmission element according to the invention, the geometry of the aperture elements and / or the microlenses is varied across the surface of the optical transmission element, whereby different optical properties can also be achieved at different positions of the optical transmission element. The geometry of the aperture elements refers to all spatial properties and dimensions that can influence the optical properties of the aperture element or the microlens, in particular the size, shape, and / or orientation of the aperture elements and / or the microlenses.

[0031] In principle, the individual components of the optical transmission element can be of any size. However, it is preferred that the diameter of the microlenses and / or the aperture elements be between 1 µm and 100 µm, thereby achieving particularly uniform optical properties and a good optical effect. This preferably applies to a diameter within the plane of the aperture arrangement and / or perpendicular to the optical axis.

[0032] According to the invention, the optical transmission element is formed as a film into which the diaphragm arrangement is completely embedded, thereby achieving a particularly simple structure and, at the same time, a particularly robust and insensitive design. The film can in principle be formed from any desired material and have any desired number of identical or different layers. Furthermore, according to the invention, the optical transmission element is formed as a film, with the first microlens arrangement being arranged on one side of the film and the second microlens arrangement on the other side. Preferably, the microlenses of at least one, preferably both, microlens arrangements are formed by texturing the film surface. Furthermore, the diaphragm arrangement is embedded in the film or arranged between two layers of the film.

[0033] Several embodiments of an optical transmission element according to the invention are explained in more detail below with reference to the drawings. The figures show: Fig. 1 a schematic view of a first embodiment of an optical transmission element, Fig. 2 an enlarged schematic view of a section of the Fig. 1 shown optical transmission element with a transmitted light beam, Fig. 3 an enlarged schematic view of a section of the Fig. 1 shown optical transmission element with an absorbed light beam, and Fig. 4 a schematic partial view of a second embodiment of an optical transmission element with annular apertures.

[0034] In a Fig. In the optical transmission element 1 schematically illustrated in FIG. 1, a diaphragm arrangement 4 is arranged exactly centrally between two mutually parallel microlens arrangements 2, 3. The entire optical transmission element 1 is formed as a plastic film, with the diaphragm arrangement 4 being arranged inside the film or between two layers of a multilayer film. The microlens arrangements 2, 3 are each formed from a plurality of microlenses 7, 8 arranged directly adjacent to one another. Each of the microlenses 7, 8 is a plano-concave lens, with the flat side of the lens oriented toward the diaphragm arrangement 4.

[0035] The aperture arrangement 4 is arranged precisely within the focal plane F of both microlens arrangements 3, 4 and has a plurality of aperture elements 5 arranged directly adjacent to one another. The optical transmission element 1 is designed as an angle-selective filter such that, in a first angular range including the perpendicular to the surface of the optical transmission element 1, incident light is completely reflected or absorbed by the aperture arrangement 4, while in a second angular range, incident light is completely transmitted.

[0036] The aperture elements 5 of the aperture arrangement 4 have, in a first, enlarged and sectionally in Fig. 2, each embodiment of an optical transmission element 1 has exactly one round aperture 6 which is displaced relative to an optical axis A of the microlenses 7, 8 in the focal plane F, so that only the light beam L irradiated at an angle of incidence W deviating from the optical axis A can shine through the optical transmission element.

[0037] The microlenses 7, 8 of the two microlens arrays 2, 3 are arranged opposite each other in pairs such that the optical axis A of a microlens 7 of the first microlens array 2 is arranged in the extension of the optical axis A of a microlens 8 of the second microlens array 3. This means that both microlenses 7, 8 have a common optical axis A.

[0038] If the angle of incidence W of the light beam L relative to the optical axis A is reduced below a transmission limit angle, the light beam L incident through the microlenses 7 of the first microlens arrangement 2 hits the diaphragm arrangement 4 outside one of the diaphragm openings 6 and is accordingly not transmitted, but reflected or absorbed (see Fig. 3).

[0039] A further embodiment of the optical transmission element 1 differs from the first embodiment in that the diaphragm elements 5 do not have a round, but rather a ring-shaped diaphragm opening 6, wherein the closed center M of the ring-shaped diaphragm opening 6 lies exactly in the optical axis A of a respective microlens 7 of the first microlens arrangement 2, so that a light beam L incident perpendicularly or with a small angle of incidence W is not transmitted. At larger angles of incidence W, however, the incident light beam L passes through the ring-shaped diaphragm opening 6 regardless of the direction of the light incidence, so that transmission is possible.If the angle of incidence W is further increased, an angular range is again reached in which the light beam L incident through the first microlens array 2 strikes the aperture array 4 in a region outside the outer diameter of the annular apertures 6 and is therefore again not transmitted. Accordingly, such a design of the optical transmission element enables selective angle filtering of the incident light beam L with regard to both a required minimum angle and a maximum possible maximum angle of the incident light to be transmitted. List of reference symbols 1 optical transmission element 2 first microlens array 3 second microlens array 4 aperture arrangement 5 aperture element 6 aperture 7 Microlens of the first microlens array 8 Microlens of the second microlens array F focal plane W angle of incidence A optical axis M center L light beam

Claims

[1] Optical transmission element (1), with - a first planar microlens arrangement (2) and - a second planar microlens arrangement (3) arranged parallel to the first microlens arrangement (2), - wherein a planar aperture arrangement (4) with a plurality of aperture elements (5) each having at least one aperture (6) is arranged between the two microlens arrangements (2, 3) and parallel thereto, - wherein each aperture element (5) is assigned to a microlens (7, 8) of the first and second microlens arrays (2, 3) and is arranged in their focal plane (F), and - wherein the microlens arrays (2, 3) and the aperture array (4) are arranged such that light incident on the first microlens array (2) is, depending on its angle of incidence (W), either transmitted through the aperture array (4) and the second microlens array (3) or absorbed or reflected at the aperture array (4), characterized by , that - the diaphragm elements (5) are each arranged within the focal plane (F) of the microlens arrays (2, 3) and at the same time offset from the optical axis (A) of the microlens arrays (2, 3), and that - the optical transmission element (1) is formed as a film into which the diaphragm arrangement (4) is completely embedded, and on one side of which the first microlens arrangement (2) and on the other side of which the second microlens arrangement (3) are arranged. [2] Optical transmission element according to claim 1, characterized bythat a microlens (7) of the first microlens arrangement (2) has a common optical axis (A) with a microlens (8) of the second microlens arrangement (3). [3] Optical transmission element according to claim 1 or 2, characterized by that the diaphragm elements (5) of the diaphragm arrangement (4) have a non-circular diaphragm opening (6) and / or are each formed with a plurality of diaphragm openings (6). [4] Optical transmission element according to one of the preceding claims, characterized by that a deviation of the position of the diaphragm element (5) from the optical axis (A) of the microlens arrangements (2, 3) varies over the surface of the optical transmission element (1). [5] Optical transmission element according to one of the preceding claims, characterized by that the geometry of the aperture elements (5) and / or the microlenses (7, 8) varies over the area of ​​the optical transmission element (1). [6] Optical transmission element according to one of the preceding claims, characterized by that the diameter of the microlenses (7, 8) and / or the aperture elements (5) is between 1 µm and 100 µm.

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