EYE-SAFE OPTICAL WIRELESS COMMUNICATION

Description

[0001] The present invention relates to optical wireless or optical wireless communication, in particular to a communication node for wireless optical communication, to a wireless optical transmission system having such a communication node, and to a method for providing separation optics for a wireless optical transmission system. The present invention further relates to a high-power transmitter for eye-safe optical wireless communication.

[0002] In optical wireless communication, the goal is always to increase the detected optical power at the receiver, as this leads to a better signal-to-noise ratio (SNR) at the receiver [2]. A high SNR allows for a low bit error rate, i.e., reliable data transmission. Furthermore, a high SNR can be used to increase the data rate of the link, for example, by increasing the modulation bandwidth or using a multi-level modulation scheme. A direct way to maximize the SNR at the receiver is to increase the signal power at the transmitter. For particularly high data rates, lasers (light amplification by stimulated emission of radiation) or laser diodes are used today due to modulation bandwidths of several gigahertz to several tens of gigahertz. Beams emitted by lasers are particularly ordered, i.e.Their etendue (product of the beam cross-section and the divergence angle of the beams) is particularly low. This allows them to be focused to a very small point using lenses. This focusability is also present when laser light hits the human eye. For this reason, the permissible laser power is more strictly regulated by eye safety standards (DIN EN 60825-1:2015-07 [3]) than for conventional lamp devices. For a laser to be used for communication without the need for shielding measures, the laser must comply with laser class 1 / 1R or laser class 2 / 2R (if the laser is visible). The extent to which the SNR at the receiver can be increased by increasing the transmission power is therefore limited.

[0003] In practice, there are different approaches to classifying the transmitter of an optical wireless link as laser class 1 / 1 R or laser class 2 / 2R: 1. The laser driver is limited so that the laser power is restricted to ensure that eye safety limits are met. This results in the disadvantage of low transmission power, which results in a short range. 2. The laser is modulated so that it only emits light for very short periods of time, or only emits light in one direction for short periods of time. For example, LIDAR (Light Detection and Ranging, light-based distance measurement) emits strong pulses, but only for a short time, or these pulses only spread out in one direction for a short time. The exposure energy for the eye can thus be kept below the limits. The disadvantage of this is that only a fraction of the total time can be used for communication. Accordingly, the data rate is limited. 3. A diffuser is placed in front of the laser [2] to scatter the light.However, the light then spreads randomly in all directions, so that a significant portion of the light output is lost for communication. 4. A so-called "engineered diffuser" [6] is used. These optical elements have an optimized structure that directs light with a defined input angle (typically 0°, i.e., parallel light rays) to a defined output profile. The high efficiency is advantageous for communication. Disadvantages, however, are the high manufacturing costs and the defined input angle. The latter is typically 0°, so an additional collimator lens is required. 5. Use of a holographic diffuser [2,4]. The resulting high efficiency is advantageous for communication. These diffusers can sometimes be manufactured more cheaply than engineered diffusers. The disadvantage is the defined angle of incidence. The output angle is typically larger than the angle of incidence.For small fields of view, an additional collimator lens is required, meaning two optical components are needed. Another disadvantage is that the output profile follows a Gaussian distribution. For optical wireless communication, a top-head profile is often required / preferred to optimize the dynamic range of the link. 6. Use of multiple laser sources [5]. By using multiple emitters, for example, a VCSEL array (vertical-cavity surface-emitting laser), the total power can be distributed among several sub-sources. The disadvantage of this is the complex structure.

[0004] US 2003 / 0026002 A1 describes a light source device that is safe for the human eye.

[0005] WO 02 / 056507 A2 describes an optical communication infrastructure that generates a plurality of partial beams.

[0006] US 2011 / 0116520 A1 describes a laser-based light source for generating laser light.

[0007] What would be desirable would be communication nodes and communication systems as well as concepts for providing them that enable eye-safe communication with a high range and data rate.

[0008] The object of the present invention is therefore to create communication nodes and communication systems that enable eye-safe high-speed communication with a high range and data rate.

[0009] This problem is solved by the subject matter of the independent patent claims.

[0010] A core concept of the present invention is the recognition that, by using suitable separation optics, the light output of an optical emitter can be split to obtain multiple optical sub-signals. The multiple optical sub-signals are focused on different local areas on the receiver side and / or the eye side, which is why the split light output impinges on separate focus areas. This allows transmission with high light output while reducing or preventing damage to the human eye. The high transmission power enables communication with a long range and data rate.The aforementioned tasks can be achieved by designing a corresponding separation optics, by integrating such a separation optics into a communication node and by using such a communication node in an optical wireless communication network.

[0011] According to one embodiment, a communication node configured for optical wireless communication in an optical wireless communication network comprises an input interface configured to receive a data signal. The communication node further comprises an optical transmitter configured to convert the data signal into an optical signal having an optical power. Furthermore, the communication node has separation optics configured to spatially divide the optical signal into a plurality of optical sub-signals with an associated spectral range in order to divide the optical power among a plurality of optical sub-signals, wherein the plurality of spectral ranges at least partially coincide. The communication node is configured to transmit the plurality of optical sub-signals for optical wireless communication.The majority of optical partial signals are focused at spatially disjoint locations of an image plane when focusing together, when using a receiver-side optics or when focusing on or in the human eye.

[0012] According to one embodiment, an optical wireless transmission system is provided, which has an aforementioned communication node and further comprises a receiver configured to receive at least a portion of the plurality of partial signals, wherein a field of view of the communication node is adapted to a receiving optics of the receiver. The advantage of this is that losses in the optical wireless transmission path can be reduced or avoided by this adaptation.

[0013] According to one embodiment, a method for providing separation optics for an optical wireless communication node having a plurality of optically active surfaces comprises a plurality of steps performed for each of the optically active surfaces. The method includes projecting an inhomogeneous radiant power of an optical emitter onto a projection area by defining a plurality of sub-areas of the projection area such that a partial radiant power of the radiant power incident on the sub-area is equal within a tolerance range in the plurality of sub-areas.The method comprises defining input angles of the radiation power onto the optically active surface of the separation optics and assigning a respective output angle to the plurality of partial radiation powers from the separation optics, wherein the output angles are derived from the sub-regions of the projection region. The method comprises defining the plurality of sub-regions for the optically active surface element of the separation optics such that, upon arrival of the radiation power, the optically active surface element converts it, using the plurality of optically effective surfaces, into a partial radiation power for the projection region assigned to a respective sub-region. The method further comprises producing the separation optics with the plurality of optically effective surfaces.The method is carried out in such a way that the plurality of optical partial signals are focused at spatially disjoint locations of an image plane during a joint focusing, when using a receiver-side optics or when focusing on or in the human eye.

[0014] Further advantageous embodiments are defined in the dependent patent claims.

[0015] Embodiments of the present invention are explained below with reference to the accompanying drawings. They show: Fig. 1 shows a schematic block diagram of a communication node according to an embodiment; Fig. 2a shows a schematic block diagram of an optical wireless transmission system according to an embodiment, in which the communication node has a transmitter with a modulated radiation source; Fig. 2b shows a schematic block diagram of an optical wireless transmission system according to an embodiment, in which the communication node has a transmitter with an unmodulated radiation source; Fig. 3a shows a schematic side sectional view of a separation optics with a planar surface according to an embodiment; Fig. 3b shows a schematic side sectional view of a separation optics with two curved surfaces according to an embodiment; Fig. 3c shows a schematic side sectional view of a communication node having an element for propagation time difference compensation, according to an embodiment;4a shows a schematic side sectional view of a part of a communication node according to an embodiment with a separation optic that is at least partially reflective; Fig. 4b shows a schematic side sectional view of a part of a communication node according to an embodiment in which a separation optic is also reflective and in which an optical transmitter is arranged in a plane of the separation optic; Figs. 5a-b show schematic representations of separation optics according to embodiments that include totally reflective surfaces; and Fig. 6 shows a schematic flow diagram of a method for providing a separation optic in accordance with embodiments described herein.

[0016] Before exemplary embodiments of the present invention are explained in more detail below with reference to the drawings, it is pointed out that identical, functionally equivalent or equivalent elements, objects and / or structures in the different figures are provided with the same reference numerals, so that the description of these elements shown in different exemplary embodiments is interchangeable or can be applied to one another.

[0017] The embodiments described below are described in conjunction with numerous details. However, embodiments may also be implemented without these detailed features. Furthermore, for clarity, embodiments are described using block diagrams instead of detailed illustrations. Furthermore, details and / or features of individual embodiments may be readily combined with one another, unless explicitly described otherwise.

[0018] The following embodiments relate to optical wireless signal transmission or data transmission. This is also referred to as Li-Fi (Light Fidelity) in the context of the embodiments described herein. The term "Li-Fi" refers to terms such as IrDA (Infrared Data Association) or OWC (Optical Wireless Communication). This means that the terms "optical wireless data transmission" and "Li-Fi" are used synonymously. Optical wireless data transmission is understood to mean the transmission of an electromagnetic signal through a free transmission medium, such as air or another fluid. For this purpose, wavelengths in the ultraviolet (UV) range of at least 53 nm and the infrared range, for example, of at most 1550 nm, can be used, although other wavelengths that differ from those used for radio standards are also possible.Optical wireless data transmission must also be distinguished from fiber-based optical data transmission, which is implemented, for example, using fiber optic cables or optical fibers.

[0019] Fig. 1 shows a schematic block diagram of a communication node 10 according to an exemplary embodiment. The communication node 10 comprises an input interface 12 configured to receive a data signal 14. The data signal 14 can be wired and / or received wirelessly, with any transmission method being possible for this purpose, for example, wireless networks and / or wireless optical transmission media.

[0020] The communication node further comprises an optical transmitter 16 configured to convert the data signal 14 into an optical signal 18 having an optical power. The optical transmitter 16 may comprise, for example, a laser or a laser diode. Other examples of an optical transmitter include light-emitting diodes (LEDs), particularly high-speed LEDs such as RC-LEDs (resonant cavity LEDs) or micro-LEDs. Alternatively, however, other elements for generating the optical signal 18 are also possible, for example, fluorescent emitters or other light sources. Combinations of the aforementioned options are also possible.

[0021] Although the communication node 10 is described as a transmitter of an optical wireless signal, it can be configured to transmit and / or receive wireless optical signals based on a corresponding configuration of the transmitter 16, such as a receiver. This means that the transmitter 16 can also be configured as a pure receiver or a pure transmitter, or as a combination thereof.

[0022] The communication node 10 further comprises a separation optics 22 configured to spatially divide the optical signal 18 into a plurality of optical sub-signals 18a-c. The number of optical sub-signals 18a-18c can be at least 2, at least 3, at least 4, at least 5, or more, and the number can also be at least 10, at least 100, or at least 1000. The separation optics 22 is designed to spatially divide the optical signal 18, meaning that the wavelength ranges of the sub-signals 18a-18c can coincide entirely or partially and also coincide with the optical signal 18. However, differences in the wavelength ranges can arise, for example, from different absorptions or attenuations acting on the optical signal 18 in respective sub-regions of the separation optics 22. However, the sub-signals 18a-c have an identical source, namely the optical signal 18.In other words, the separation optics 22 can be used to split the optical signal 18 into the optical sub-signals 18a-c, which are spatially spaced from each other, but furthermore coincide in terms of information content and wavelength range.

[0023] The communication node 10 is configured to transmit the plurality of optical sub-signals for optical wireless communication. The optical sub-signals 18a-c have a substantially identical direction, which can be directed, for example, toward a receiver that receives at least a portion, a large portion, or all of the optical sub-signals 18a-c and combines them with one another. Due to the combination of the received optical sub-signals 18a-c, the sum of the received optical power at the receiver is high, and a high SNR can be achieved. This enables high transmission quality and thus a high bandwidth.By splitting the optical signal 18 into the partial signals 18a-c, a high level of eye safety can also be achieved, since the majority of the partial optical signals are focused at spatially disjoint locations of an image plane when jointly focused, for example when using appropriate optics on the receiver side or when focusing on or in the human eye. This can lead to stress or damage at the spatially disjoint locations of an image plane of the human eye, the retina. This means that before corresponding damage occurs, a higher overall light power can be transmitted, so that a higher signal power can be transmitted compared to a single partial beam, while at the same time eliminating the losses of a diffuser, which is advantageous for the power budget.For example, a distance of focal points can be obtained with a joint focus whose individual radiant power lies below the aforementioned standard DIN EN 60825-1 or IIC 60825-1: 2014. For example, each of these focal points can meet the corresponding standard. However, because the focal points are spatially spaced, the eye is not damaged to an extent that reaches the corresponding limit values, which is why comparatively higher light powers are permissible in the output signal 18. The limit value can therefore be understood as a flexible value. It can be calculated according to a calculation rule that includes the extent of the so-called apparent source, for which the extent of the focal point can be measured. If, for example, two or more focal points were considered, the diameter that these two or more focal points together form could be used to determine the limit value.However, the resulting limit is significantly higher than with a single focal point because the diameter is larger. To be classified as eye-safe, both criteria may be required, i.e.: Each focus point is – considered individually – eye-safe (for this consideration, the limit is comparatively low, but the performance of the one focus point is also low). All focus points taken together are eye-safe (here the limit is now significantly higher).

[0024] The optical transmitter 16 can be configured to provide the optical signal 18 at a communication wavelength. The separation optics 22 can be configured with low absorption for this communication wavelength range, enabling low optical losses.

[0025] The communication node 10 can be configured to transmit the optical wireless signal at a wavelength visible to the human eye and to use the optical wireless signal to illuminate the surroundings of the communication node. This enables synergistic use of radiant power, both for data transmission and illumination. This is unproblematic insofar as the separation optics 22 protect the human eye from damage, even when high light outputs are used. Alternative embodiments include using a wavelength spectrum invisible to the human eye. For example, the infrared, near-infrared, or ultraviolet spectrum could be used for this purpose.

[0026] Fig. 2a shows a schematic block diagram of an optical wireless transmission system 200 according to an embodiment. The optical wireless transmission system 200 comprises a communication node 20 according to an embodiment and a receiver 25 according to an embodiment. The receiver 25 is configured to receive at least a portion of the plurality of partial signals 18a-18c. A field of view of the communication node 20 is adapted to a receiving optics 24 of the receiver 25. The receiver 25 is configured to generate a data signal 14' based on the partial signals 18a-18c, the content of which is based on the data signal 14.

[0027] A typical radiation angle in the sense of a half-angle of the transmitter 16, i.e., a half-angle of the beam bundle 26, can, for example, be in a range from 3° to 50°, preferably between 6° and 30°, and particularly preferably between 8° and 20°, particularly when using VCSELs or other lasers that can have a rotationally symmetric output profile. Edge emitters, which can be polygonal, for example, rectangular, can, in contrast, have a radiation angle between 1°x3° and 15°x45°, preferably between 3°x8° and 12°x30°, and particularly preferably between 6°x12° and 9°x25°.

[0028] The receiver 25 can be arranged such that the receiving optics 24 receives at least 70% of an area portion of a total field of view of the communication node 20, that is, at least 70% of an area illuminated by the total number of optical partial signals 18a-18c is received by the receiving optics 24, which enables a high SNR or low light power.

[0029] The communication node 20 can be constructed similarly to the communication node 10. The communication node 10 can also be arranged alternatively or additionally in the optical transmission system 200. The separation optics 22 can be configured to split a beam 26 of the optical transmitter 16, i.e., a beam forming the optical signal 18, and a plurality of partial beams 28a-28c, each of which can be represented by the partial signals 18a-c. The plurality of partial beams 28a-c can, taken together, form an overall field of view or illumination area of ​​the communication node 20. It is possible and preferred, but not necessary, for the beams 28a-c to overlap.

[0030] The optical transmitter 16 of the communication node 20 can include a driver 32 configured to provide a driver signal or signal current 34 based on the data signal 14 to control an emitter 36, such as an LED, a laser, or a laser diode, to thereby generate the optical signal 18. For this purpose, the input interface 12 can, for example, be connected to the driver 32 or be part of it. The use of a laser / laser diode is particularly advantageous, since the separation optics 22 enables the use of high transmission powers.

[0031] Fig. 2b shows a schematic block diagram of another optical wireless transmission system 200' according to an embodiment. In comparison to the optical wireless transmission system 200 of Fig. 2a A communication node 20' is provided in a configuration different from communication node 20 to generate optical signal 18. For example, an emitter 36' can be operated as an unmodulated, i.e., constant radiation source to obtain an unmodulated, possibly information-free optical signal 18'. This is manipulated or modulated by a modulator 38, which can receive data signal 14 via input interface 12, to obtain optical signal 18.

[0032] It is pointed out that a location of the input interface 12 in the embodiments described herein is chosen merely as an example and the interface can also be arranged at a different location and can be transferred to another location by means of data transmission within the communication node.

[0033] In other words, the Fig. 2a and 2btwo different possible designs of the entire data transmission path with high-performance optical transmitters.

[0034] The system from Fig. 2a uses a transmitter with direct modulation of the emitter. The system according to Fig. 2b uses an emitter with external signal modulation. In Fig. 2a An incoming signal 14 is shown, which is to be transmitted optically and wirelessly. This can be, for example, a broadband modulated signal (e.g., modulated with on-off keying) or a narrowband modulated signal (e.g., comprising a single carrier or multiple carriers, for example, in orthogonal frequency division multiplexing). The signal is fed into a driver 32, which drives a signal current 34 through the emitter 36 or applies the corresponding signal voltage to the emitter (e.g., LED, laser, laser diode) with the aim of modulating the optical output signal 18 accordingly. The signal 18 is emitted with a profile characteristic of the emitter 36. The separation optics 22 are used to divide the optical signal 18 into several beam bundles 18a-c or 18 i (i∈ [1; N], with N ≥ 2), which then illuminate the field of view accordingly. Several or even all beam bundles 18 impinge on the optical receiver 25 i However, this usually means that only parts of the light output of the beams 18 i The optical signal is incident on the receiver, as sometimes attempts are made to illuminate a large area in order to achieve broad coverage. The receiver 25 converts the optical signal into an electrical output signal 14' and consists, for example, of the usual optical, optoelectronic, electronic, and electrical components. Therefore, a detailed description of the receiver 25 is omitted here.

[0035] Fig. 2b represents an incoming signal, which is also to be transmitted optically and wirelessly. Analogous to Fig. 2a it is already broadband or narrowband modulated. The signal 14 is fed into an external modulator 38, for example comprising a Mach-Zehnder modulator, acousto-optical modulators, electro-optical modulators, modulators based on multi-quantum layers, or the like. The modulator 38 modulates the optical output signal 18' of the emitter 36'. In contrast to the system 200, the emitter 36' in the system 200' is, for example, an unmodulated radiation source, i.e., the output power is at least approximately constant (for example, in the sense of a CW value (CW = continuous wave), and the external modulator 38 changes, for example, its absorption properties to generate a modulated optical output signal 18. The components 26, 22, 18 i , 25 and 14' can be identical or at least similar to those in the optical wireless transmission system 200.

[0036] This means that the communication node can be configured to receive and process the data signal as a broadband or narrowband modulated data signal. As described in Fig. 2a As shown, the optical transmitter 16 may comprise a modulating radiation source 36. Alternatively or additionally, as shown in Fig. 2b As shown, the optical transmitter 16 may include, in addition to the optical emitter 36' for providing an optical signal 18', a modulator 38. The modulator 38 may be configured to receive and modulate the optical signal 18' to thereby provide the optical signal 18 as a modulated signal. The modulator 38 may be configured to modulate the optical signal 18' based on current control, for example, by implementing intensity modulation and / or polarization modulation.

[0037] Fig. 3a shows a schematic side sectional view of a communication node 30 1 with a separation optics 22 1 according to an embodiment, which can be used in the communication node 10 and / or the optical-wireless transmission system 200 or 200' in order to separate the optical signal 18 into the partial signals 18 i An example of this is the transmitter 16, which is basically in accordance with the explanations for Fig. 1 , Fig. 2a and / or Fig. 2b The separation optics 22 1 can have a plurality or multiplicity of optically effective surfaces 42, which can be arranged, for example, in a two-dimensional array or field, in particular an NxM field. The optically effective surfaces are therefore designated by indices i with (i ∈ [1; N ] and j denoted by j ∈ [1; M]), in the form 42 i , jAt least one of N and M is ≥ 2. The indices can provide an indication of the placement of the respective element in the field and can be used for differentiation. An example is shown in the Fig. 3a a number of three elements for N = 1, that is, optically effective surfaces 42 1,1 , 42 2,1 , and 42 3,1 . The optically effective surfaces 42 can be referred to simply as a partial lens of a lens combination, that is, at least one of the optically effective surfaces is formed as a partial lens designed to refract an associated portion of the optical signal 18, in particular the portion of the optical signal 18 that impinges on the optically effective surface 42. Each of the optically effective surfaces 42 can be formed as a freeform.

[0038] A center point 44 of the separation optics, such as a center of mass or a geometric center point, can be arranged on an optical axis 46 of the transmitter 16 with a maximum deviation of 2 mm, 0.5 mm, or 0.1 mm. Regardless of this, a deflection of the optical partial signals 18a, 18b, and / or 18c can be achieved through the design of the optically effective surfaces, which will be described in detail later. Alternative embodiments provide for the center point 44 to be arranged away from the optical axis 46 of the optical transmitter 16. This allows a further degree of freedom in which an angle of incidence of optical radiation emanating from the optical transmitter 16 onto the surface can be varied, both for flat, planar surfaces 52 and for curved surfaces 52'.

[0039] Beams 48 i , j a respective optically effective surface 42 i , jassigned and by means of the optically effective surface 42 i , j an effect on the beam 48 i,j be defined, such as focusing, scattering and / or change of direction.

[0040] A surface 52 of the separation optics 22 1 facing the transmitter 16 can be planar or flat, as shown in Fig. 3a shown, but may also deviate from this and / or be optically effective, as is the case for the surface 52' of the separation optics 22 2 from Fig. 3b is shown. The surface 52' can be adapted as desired, for example, at least partially as a spherical surface, at least partially as an aspherical surface, convex or concave, or even as a freeform or other shape, for example to reduce or increase a lens volume or to achieve tolerance compensation or runtime compensation.

[0041] Both separation optics 22 1 and 22 2, like the other separation optics described herein, enable the optical partial signals 18 i with consistent data information, since they can all originate from a single data source. The separation optics can be arranged in a communication node such that the separation optics receive at least 80%, at least 90%, or at least 95% of the radiated power emitted by the optical transmitter. The optical signal power of the optical signal can be configured such that, without the separation optics, it exceeds the eye safety level for the human eye, meaning it is damaging or does not meet the respective standard / requirement, while the majority of the optical sub-signals, taken together, maintain eye safety thanks to the separation optics.

[0042] This can be achieved, as described, by focusing the different beams or partial signals spatially apart from one another, which locally leads to a fall below the limit values ​​and also enables a fall below the limit values ​​on average. The separation optics 22 can generate a multiple image of the optical signal 18 of the transmitter, so that, just as an image, a data content of the partial signals 18 is also generated. i identical or equal. Each optical sub-signal 18 i can be adapted to a common overall field of view of the plurality of optical sub-signals, i.e., a field of view or an illumination area of ​​the communication node. For example, target specifications regarding a radiated power distribution at the receiver can be incorporated into the design, taking into account corresponding information such as the distance, size, and / or position of the receiver optics, and the like.

[0043] Embodiments make it possible to form a communication node without a collimator lens in an optical path starting from the optical transmitter 16.

[0044] In other words, since the separation optics enable a higher optical transmission power, different implementations can be implemented. What they all have in common is that they subdivide the signal 18 of several beam bundles and present it in the form of partial beams 18 i into the field of view. For this purpose, at least one of the surfaces consists of N x M optical elements, where each optical element can be a combination of several optical partial surfaces and for the indices i, j used, it can hold that i ∈ [1; N] and j ∈ [1; M]). Each optical element can be free-form. Each beam sweeps a portion of the entire field of view. For all designs, it is also conceivable for the separation optics 22 to be placed not in the center, i.e. on the optical axis relative to the transmitter 16, but also next to it. If the separation optics 22 is placed on the axis, this results in double axial symmetry for the multipath optics if the field of view and the emission profile of the transmitter 16 are also symmetrical. If the separation optics 22 is placed next to the axis, at least one of these axes of symmetry is omitted, even if the field of view is symmetrical.

[0045] In embodiments, the separation optics / separation optics may be based on refraction, as is the case, for example, in the Fig. 3a and 3b is shown. Fig. 3a shows a system in which the first surface 52 is planar and the second surface consists of the optical elements 42 i , j or at least comprises them. The modulated optical signal 18, which is emitted by the transmitter, can be divided into several beam bundles 48 i , j These first impinge on the first surface 52 of the optics 22 1 . Each of the beams 48 i,j hits a differently shaped surface element 42 i,j the optics 22 1 and is therefore refracted differently, in such a way that the beams 18 i or 18 i,j cover all or part of the field of view.

[0046] The configuration of a communication node 30 2 according to Fig. 3b shows, by way of example, that the first surface 52' of the optics 22 2 can also be designed differently, for example as a spherical surface, aspherical surface, or even as a freeform, in order to reduce the lens volume, for example. Alternatively or additionally, it is possible to achieve tolerance or runtime difference compensation. The system according to Fig. 3b otherwise works analogously to the system Fig. 3a . The beam bundles 48 i , j encounter different surface elements 42 i , j , which the rays 18 i,j into the field of view in such a way that the anticipated irradiance is achieved. In this respect, the Fig. 3a and 3b Schematic representations of exemplary designs of separation optics based on refraction. All elements can be understood as three-dimensional bodies, which are generally not rotationally symmetric.

[0047] Based on the Fig. 3a and 3b A further advantageous embodiment is explained, it being pointed out that these embodiments and features can be readily applied to other embodiments, in particular refractive, reflective separation optics or totally reflective separation optics.

[0048] Due to different materials of the surrounding medium and a material of the separation optics, different propagation velocities, the speed of light, of the optical signal 18 or the partial signals 18a-c can occur within the separation optics 22 1 or 22 2 compared to the external medium. A different path length of the optical paths of the partial signals 18a-c to and through the separation optics 22 1 or 22 2 can thus lead to propagation time differences or phase shifts between the partial signals 18a-c. In other words: since the partial signals 18a-c in such a case have traveled a slightly different path or different path lengths to the receiver, for example, because they all hit a different part / area of ​​the separation optics, propagation time differences arise through the optical channel.

[0049] These effects can be used to compensate for different path lengths of the beams outside the medium. For the communication nodes described herein, this can have no relevant adverse effects, since the propagation time difference can be small relative to the symbol duration of the modulated data. For example, at a data rate of 10 Gbit / s or higher (On-Off-Keying - OOK), the effect can become clearly apparent, so that taking it into account brings considerable advantages. For example, the propagation time differences at the separation optics can be compensated by the thickness of the optics (e.g., thicker in the center than at the edge, approximately Fig.3a The following calculations illustrate this effect: A baud rate of 1 gps can result in a bit duration of 1 ns with OOK. Assuming a tolerable jitter of 10%, this can mean: 1 / 10*1 ns = 0.1 ns. Assuming the speed of light in the transmission medium, for example, air, of c~30 cm / ns, this can mean a tolerable path difference of max. 3 cm. With a baud rate of 10 gps, this results in a bit duration of 0.1 ns with OOK. The unchanged jitter of 10% leads to a time offset of 1 / 10*0.1 ns = 0.01 ns, which at c~30 cm / ns means a path difference of max. 3 mm. This can be achieved quickly, for example, if the lens has a diameter of 25 mm, so the exemplary embodiments explained can provide a solution here. Alternatively or additionally, it is provided to compensate for at least part of the path difference by an optical element additional to the refractive optics, which causes the delay.This allows a simpler design of the separation optics without the need for an additional component.

[0050] Depending on the data rate and the spatial extent of the separation optics 22, relevant or critical propagation time differences could arise. Therefore, exemplary embodiments provide for compensating for these propagation time differences in the design of the separation optics.

[0051] The propagation time difference can be divided into two components: A first component arises within the communication node 10 and / or 20, since central beam bundles, such as beam bundle 48 2,1, travel a shorter path than those that impinge on the edge of the separation optics 22 i, such as the beams of beam bundles 48 1,1 or 48 3,1. This component can be at least largely independent of the relative spatial arrangement between transmitter 10 / 20 and receiver 25.

[0052] According to embodiments, the separation optics 22 i are configured to at least partially compensate for a propagation time difference of beams 48 between the optical transmitter 16 and the separation optics 22 i by different propagation times within the separation optics 22 i. The first portion of the propagation time difference can be reduced by utilizing the different propagation speeds of electromagnetic radiation in different media. Since central rays have the shortest path, some embodiments provide for the separation optics to be designed or configured there such that these rays travel the longest path through the optical material in order to extend their propagation time within the separation optics 22 i.According to embodiments, the separation optics have a thicker design in a central region of the separation optics compared to outer regions of the separation optics in order to provide a comparatively greater propagation time shift, so that within the partial regions 42 and / or across the separation optics, a propagation time difference is small, for example with a deviation of at most 50%, at most 20%, or at most 10%. If the propagation time difference for an OOK signal is used, it can be advantageous to implement a small deviation or relative difference, for example max. 20%, max. 15%, or max. 10% or less, in order to avoid transmission errors. Using other modulation types, for example with multiple frequency carriers, can provide more robust systems that allow larger tolerances for the propagation time differences.Alternatively or additionally, the time difference of the beams 48 can also be compensated completely or partially by different materials used in different areas of the separation optics.

[0053] Fig. 3c shows a schematic side sectional view of a communication node 30 3 , which has an element 43 for propagation time difference compensation. The element 43 can be dimensioned depending on a wavelength of the optical signal, a length of the path of one or more beams 48 or their differences, so that a propagation delay can be location-dependent and variable over a course of the element 43. For example, in the case of a spherical propagation of the beams 48, a spherical body can be provided for this purpose, such as a hemisphere or the like. Alternatively, however, a design for parts of the beams 48 i,j can also be carried out, as described in connection with the design of the partial surfaces 42 i,j, which means that the element 43 can have a discontinuous surface.The dimension of element 43 along a direction 45, for example, along a main beam propagation direction, can also be based on a dimension of the separation optics 22 2 , so that the desired propagation time compensation is obtained, for example, by combining the passage through element 43 and the separation optics 22 2 or another separation optics. This also means that compensation can be achieved without element 43 by appropriately designing the separation optics, which can be achieved, for example, in the direction of a body according to . Fig. 3a This means that the element 43 can be arranged to at least partially compensate for the difference in propagation time of beams 48 between the optical transmitter 16 and the separation optics by means of different propagation times within the element 43. The element can also be designed as a plurality of sub-elements which, in combination, provide the desired propagation time correction. Although the element 43 is shown arranged between the separation optics 22 2 and the transmitter 16, the element 43 can alternatively or additionally be arranged in whole or in part such that the separation optics 22 2 is arranged between the element 43 and the transmitter 16. The described concept is readily transferable to other communication nodes.

[0054] Embodiments further provide for the compensation of the transit time difference to be carried out entirely or partially at the receiver, for example by adapting the receiver optics and / or by using an element 43. For this purpose, an imaging design of the receiver optics is necessary so that the individual partial signals 18 i are separated again.

[0055] The second portion of the propagation time relates to the partial signals 18 i with i = a, b, c and can vary with the specific arrangement of the receiver 25 with respect to the transmitter 20. The propagation time difference can, for example, be greatest when the receiver is arranged at an edge of the field of view of the transmitter, i.e., at the maximum offset of the receiver 25 with respect to the transmitter 20, since rays from a first edge of the separation optics 22 to the receiver have the shortest path and those rays from the opposite second edge of the separation optics 22 have a longer or longest path. This second portion can be reduced according to embodiments by the optical partial signals 18 i are generated in such a way that they each illuminate only a part of the field of view. In this configuration, it can be achieved that not all partial signals 18 are visible at the edge of the field of view. iand the maximum propagation time difference between the partial signals arriving at the receiver location can be reduced.

[0056] Both components can also be reduced by reducing the dimensions of the separation optics 22 in relation to the maximum permissible propagation time difference. The maximum permissible propagation time difference can result from the modulation type and the data rate. For an OOK-modulated signal with a baud rate of 10 Gbit / s, the maximum permissible propagation time difference could be 3 mm. A simple numerical example, using the length ratios of right-angled triangles, should convey the order of magnitude: An emission angle of 20° at a lens separation of 100 mm results in a lens diameter of 72 mm and, with negligible lens thickness and without time-of-flight compensation, a path difference of 6.4 mm. Reducing the distance to 30 mm reduces the lens diameter to approximately 22 mm and the path difference to only 1.9 mm.

[0057] A compromise can be made between signal quality (in terms of the propagation time difference) and eye safety, since reducing the size of the separation optics, for example, can lead to an increase in the spatial density of the focal points. With reference to the communication system 200 or 200', the receiver can be designed and configured such that at a location of the receiver 25 or its receiving optics 24, and possibly also at any location in the field of view, the propagation time difference between the incoming partial signals 18 i is small, for example, with a deviation of at most 50%, at most 20%, or at most 10% or less, as explained above.

[0058] Measures to reduce the first component and to reduce the second component of the transit time differences can be used individually or in combination. The use of an additional element 43, or even in combination with the separation optics, can be achieved using suitable materials, with conventional materials being preferred. For example, a conventional plastic glass (such as PMMA, polycarbonate, ...; with refractive indices n of, for example, 1.4 < n < 1.8) can be used. Alternatively or additionally, mineral glass (such as BK-7, ..., with refractive indices of, for example, 1.4 < n < 1.8) can be used. If a transmissive element is used, it can have low absorption; if the element 43 and / or the separation optics have a reflective effect, it can preferably have a high degree of reflection.

[0059] Fig. 4a shows a schematic side sectional view of a part of a communication node according to an embodiment with a separation optics 22 3 which, compared to the separation optics of Fig. 1 , Fig. 2a , Fig. 2b , Fig. 3a and Fig. 3b is at least partially reflective or reflecting or totally reflective. Optically effective surfaces 54 i,j can be designed and shaped based on the same or complementary considerations or designs, wherein the reflective properties of the optically effective surfaces 54 can be used instead of refractive properties. Embodiments provide for combining optically refractive and optically reflective or totally reflective surfaces in a separation optics. Thus, at least one of the optically effective surfaces can be formed to be reflective or totally reflective and / or at least one of the optically effective surfaces can be designed to be refractive. In a configuration in which the separation optics has at least one reflective or totally reflective surface, the optical transmitter 16 can be designed to emit the optical signal 18 in the direction of the separation optics 22 3 . The separation optics 22 3 can be designed to reflect oras a result of reflection. Effects of reduced optical signal power at the receiver, which can be caused by shadowing by the optical transmitter 16, can be at least mitigated by a suitable choice of shape and / or position of the optical transmitter 16. In the embodiment shown in . Fig. 4a In the configuration shown, the optical transmitter 16 is arranged opposite the separation optics 22 3 and the separation optics 22 3 can be used as a reflector.

[0060] Fig. 4b shows a schematic side sectional view of a part of a communication node according to an embodiment in which a separation optic 22 4 also comprises one, several or all optically effective surfaces 54, which can be formed as reflective or totally reflective surfaces. Unlike in Fig. 4a The optical transmitter 16 can be arranged in a plane of the separation optics 22 4. A subreflector 56 can be arranged to receive the optical signal 18 and reflect it back to the separation optics 22 4. It can be provided that a region in which the optical transmitter 16 is arranged in the plane of the separation optics 22 4 is excluded from splitting into the optical partial beams, so that, for example, one of the optically effective surfaces of the separation optics 22 3 of a comparable configuration would be used for the function of emitting the optical signal.However, it is also possible to use partially transmissive surfaces and to provide one of them as an optically effective surface between the optical transmitter 16 and the subreflector 56, so that the radiation reflected by the subreflector 56 is also refracted in the region of the optical transmitter 16, analogous to an optically effective surface 54 1,1 or 54 3,1. Likewise, a surface of the subreflector 56 can be designed such that a division into the beam bundles occurs at least partially at this location.

[0061] Since sub-reflectors 56 may be formed or formed locally smaller than the optical transmitter 16, the effect of shadowing can be reduced by using a sub-reflector 56. While in the configuration according to Fig. 4a the transmitter 16 is designed to transmit the optical signal directly in the direction of the separation optics 22 3, the transmitter 16 is in the configuration according to Fig. 4b designed to transmit the optical signal indirectly, by means of the sub-reflector 56, in the direction of the separation optics 22 4. The separation optics 22 3 and 22 4 are designed to transmit the majority of the optical partial signals 18 i to reflect.

[0062] In other words, the separation optics can also be based on reflection, as in the Fig. 4a and 4b The configuration according to Fig. 4a shows a system in which the separation optics are completely reflective with respect to the communication wavelength. The modulated signal 18 emitted by transmitter 16 can be split into several beam bundles 48, analogous to the refractive optics. i , j separated. Each beam bundle 48 i , jhits a differently shaped surface element 5 i , j the optics 22 3 and is therefore reflected differently, namely in the same way that the beams 18 i ,j cover all or part of the field of view. The sum of the beams 48 i , j corresponds to beam 26.

[0063] In the system shown, Fig. 4a the surface elements are 54 i , j designed so that the edge rays of each element intersect. However, the surface can also be shaped so that they do not intersect, although other solutions are possible for different combinations of optically effective surfaces. A disadvantage may arise from the fact that the transmitter 16 deflects part of the rays 18. i , jblocked. To reduce this effect, the central part, for example the optically effective surface 54 2,1 , can be shaped accordingly, for example by directing a small amount of light output into the blocked area. In addition, the shadowing effect can be further minimized, for example by the design according to Fig. 4b. Fig. 4b shows a system in which the separation optics 22 4 are reflective with respect to the communication wavelength. The transmitter 16 emits the modulated signal 18 in the communication direction. In front of it is a reflector 56, which 48 i,j in the form of beams 18 i,j The surface elements of the optics form the field of view in the form of rays that are reflected by the separation optics 22 4. The Fig. 4a and 4bshow schematic representations of exemplary designs of separation optics using reflection. All elements are understood as three-dimensional bodies, which are generally not rotationally symmetric.

[0064] While the configurations according to Fig. 4a and 4b based on reflection can be configured according to Fig. 5a and 5bTotally reflecting surfaces can also be used. As described for the preceding separation optics, a separation optics can also have a plurality of optically effective surfaces, each of which is assigned to one of the optical partial signals. Likewise, each of the optically effective surfaces can have an individual geometry and / or an individual surface size that is adapted to a relative position between the optically effective surface and the optical transmitter 16. The different optically effective surfaces of the separation optics described herein can have a different size and / or a different aspect ratio of their sides of the optically effective surface.

[0065] At least one of the optically effective surfaces of the separation optics described herein can be formed such that it has no symmetry. This symmetry-free design enables highly precise adaptation of the separation optics to the emission profile of the transmitter 16, the transmission path, and / or the receiver optics.

[0066] Fig. 5a shows a sectional perspective view of an optical transmitter 16 together with a separation optics 22 5 according to an embodiment. The separation optics 22 5 has an NxM field of optically effective surfaces 58 i , j , where N and M are selected as 3, for example. The separation optics 22 5 have a lateral surface 62, which is designed to receive the optical signal 18. An orientation of the lateral surface 62 can, for example, be substantially perpendicular to a radiation direction along which the optical partial signals 18 i,j In principle, any orientation to each other is possible, since the separation optics 22 additional reflective surfaces 64 ij which are designed to guide the beam bundles 48 i , j by means of total reflection and to the respective optically effective surface 58 i , j This allows both the alignment of the transmitter 16 to the separation optics 22 5 as well as an orientation of the lateral surface 62 and an angle of incidence of the reflecting surfaces 64 i , j with respect to the lateral surface 62 or the transmitter 16 to be added later, and can be designed in combination with one another. The lateral surface 62 can have optically effective properties, for example, collimating or such that the corresponding parts of the optical signal 18 are directed onto the reflecting surfaces 64. i,j be directed.

[0067] The optically effective surfaces 58 i,j can be designed in such a way that they have, for example, a divergent or even scattering effect for the respective incident beam 48 i , j provide.

[0068] The separation optics 225 are designed to redirect the optical signal 18 in a different direction by means of total internal reflection or reflection at at least one reflective or totally reflective surface 64. Each optically effective surface 58 i , j A partial area of ​​the at least one reflective or totally reflective surface 64 is uniquely assigned. Separation optics can thus be designed in such a way that multiple reflections occur. This, as well as the alternative or additional use of an optically effective lateral surface, enables multiple directional deflection by the separation optics 225.

[0069] The separation optics 22 5 can also be shaped so that the majority of optically effective surfaces 58 i , j is shaped such that they have a different surface size and / or a different aspect ratio, at least with respect to another surface element. For example, a design can be made such that a surface size increases with a distance from an optical axis of the optical transmitter 16. The optical axis of the transmitter 16 can also be assumed to be reflected or deflected, so that it can, for example, run in a central surface element of the separation optics 22 5, for example by the center point 44 from Fig. 3a passes through this surface element.

[0070] This design may be based on the idea that the radiated power of the optical transmitter 16 is high near the optical axis and decreases towards the edges. By increasing the surface area with increasing distance from the optical axis, it can still be ensured that each surface element 58 i,j a portion of the beam power of the transmitter 16 that is at least equal within tolerance ranges. The transmitter 16 can, for example, be designed to provide an intensity maximum in the optical signal 18 in a region that encompasses the optical axis 46. Separation optics described herein with different surface sizes can be designed to provide, based on the different surface sizes, an optical power per optically effective surface that is equal within a tolerance range of 50%, preferably 30%, and more preferably 10%.

[0071] Fig. 5b shows a schematic side sectional view of a separation optic 22 6 according to an embodiment, which, like the separation optic 22 5, can be used in the communication node according to embodiments described herein.

[0072] The optical signal 18 can be deflected by means of one or more reflecting surfaces 64a and / or 64b, whereby the reflected light can be directed at spatially different areas by means of reflecting surfaces 64 i , j again a deflection to the respective optically effective surface 58 i , j can be effected, wherein at least one or a group of reflecting surfaces 64 ij another reflective surface 64a or 64b and each of the optically effective surfaces 58 i , j a reflective surface 64 i,j can be assigned. Likewise, each of the reflective surfaces 64 i,j be assigned to a partial area of ​​the surfaces 64a or 64b, which can be achieved in particular by collimation or parallel beam guidance of the optical signal in the area between the surfaces 64a or 64b and the associated reflecting surfaces 64 i,j allows to provide a kind of step profile, in which by means of a step in the area of ​​the reflective surface 64 ij a portion of the signal is decoupled. This enables a particularly efficient, planar distribution of the light signal. However, the term "step" is not limited to right angles, but can have any angle of incidence, for example, 45° ± 30°, ± 20°, or ± 10° with respect to the arrival of the signals. By means of the double reflection, a changed relative position of the transmitter 16 with respect to the separation optics 22 can be obtained when a comparison is made between the separation optics 22 5 and 22 6 .

[0073] In other words, the separation optics can use total reflection, as in the Fig. 5a and 5b shown. In Fig. 5a It is shown that a separation optics 22 5 first collimates the modulated signal 18 emitted by the transmitter 16 by means of refraction on the lateral surface 62. The collimated beams are provided with 48 i,j These beams are directed at the corresponding surfaces 64 i,j directed towards the communication. Upon leaving the optics or separation optics 22 5, the beams are deflected at the freeform surfaces 58 i , j refracted to produce the anticipated field of view with the anticipated irradiance. These output rays are 18 i,j In contrast, the Fig. 5b The configuration shown is similar to the configuration shown in Fig. 5a , but the modulated signal 18 can be collimated by the totally reflecting surfaces 64a and 64b of the separation optics 226. The input surface 62' can be optically inactive or contribute to beam shaping. The collimated partial beams that leave the surfaces 64a or 64b and are reflected at 48 i , j can be identified by the areas 64 ij directed in the direction of communication and at the surface elements 58 i ,j be refracted so that the anticipated field of view is generated with the appropriate irradiance. The output beams are 18 i , j This means Fig. 5a and 5b show schematic representations of exemplary embodiments of the separation optics, including those using total internal reflection. All elements are understood as three-dimensional bodies, which are generally not rotationally symmetric.

[0074] The configuration according to Fig. 5b also shows that the exit surface of the separation optics is not completely or completely covered by the freeform surface elements 58 i,j must be filled. It is also possible to distribute the corresponding surface elements further across the output surface. This allows for optically different or optically inactive intermediate areas between the sub-areas. While this increases the size of the separation optics, it also increases the extent of the apparent source, i.e., the spacing of the focal points of the individual partial beams when focused together, so that the limit for the emittable power by the transmitter increases in terms of eye safety.

[0075] The aspects described herein refer to a concept with a transmitter consisting of or comprising a modulator, emitter, and separation optics. The latter is characterized by the fact that the optical, modulated signal is split into partial beams, each of which is assigned a part of the separation optics. This optical component converts each beam to the desired output beam profile through refraction, reflection, and / or total internal reflection. The goal is to increase the apparent size of the source and possibly also the output cross-section, thus raising the limit for permissible radiation according to DIN EN 60825-1:2015-07.

[0076] Fig. 6 shows a schematic flow diagram of a method 600 for providing a separation optic in accordance with embodiments described herein. Such a separation optic can be used for an optical-wireless communication node and can be equipped with a plurality or multiplicity of optically active surfaces. For each of the optically active surfaces, such as the surfaces 42 i,j , 54 i , j and / or 58 i , jThe following steps can be performed. In step 610, an inhomogeneous radiant power of an optical emitter is projected onto a projection area by defining a plurality of sub-areas of the projection area such that the partial radiant powers of the radiant power incident on the sub-area are equal within a tolerance range in the plurality of sub-areas. This means that the spatial distribution of the radiant power can be divided into sub-areas whose area integral with respect to the radiant power is equal within the tolerance range.

[0077] In a step 620, the input angles of the radiation power onto the optically active surface of the separation optics are defined and a respective output angle of the plurality of partial radiation powers from the separation optics is assigned, wherein these output angles are derived from the partial area of ​​the projection area. With exemplary reference to the Fig. 3a and 3b Thus, for example, it is possible to take into account the angle at which the optical signal 18 hits the surface 52 or 52' ​​and the angle at which the beam should be output or how it should be fanned out.

[0078] In a step 630, the plurality of subregions for the separation optics, i.e., the plurality of optically active surfaces, are defined so that, upon arrival of the radiation power, the separation optics converts it with the plurality of optically effective surfaces into a partial radiation power assigned to a respective subregion for the projection area. This means that for each of the optically active surfaces, a plurality or multiplicity of individual beams in a respective sub-beam 48 is assumed, and for each of these individual beams in the beams, a dedicated sub-surface area of ​​the optically active surface is determined, for example, by means of computer simulation or calculation.This can result in the above-mentioned free forms, since this can result in differently inclined, shaped, sized or otherwise different partial surfaces within a surface element, which then form a surface, the optically active surfaces 48. i , j The higher the number of assumed or considered rays within one of the beam bundles 48 i,j the higher the number of sub-area elements.

[0079] Even with regard to these assumed partial surfaces of a single optically active surface, the partial radiation from the beam can be designed to be the same or, within a tolerance range, the same. In other words, each of the optically active surfaces described in the figures presented herein is formed from a plurality or multiplicity of partial surfaces specifically designed, configured, and combined to form the respective optically active surfaces.

[0080] In a step 640, the separation optics with the plurality of optically effective surfaces are manufactured.

[0081] The communication nodes described herein can have a field of view that may depend on the field of application. Depending on the distance to be bridged, the field of view can be between 1° and 50°, preferably between 3° and 30°, and particularly preferably between 5° and 20° relative to the viewing direction of the communication node. The shape of the field of view (e.g., circular cross-section, rectangular cross-section, or elliptical cross-section) can differ before and after an imaging optic, the separation optic.

[0082] In conjunction with the exemplary embodiments described herein, which aim to achieve an expansion of the apparent source, it is advantageous to implement a certain distance between the emitter and the lens, i.e. between the elements 16 and 22. A practical distance can, for example, be in a range between 2 mm and 200 mm, preferably at least 5 mm and at most 100 mm or at least 8 mm and at most 50 mm. A greater distance can (depending on the radiation angle) also lead to a greater lens expansion. The latter is determined by the application. This can be in the sub-millimeter range, but can also amount to several tens of centimeters. The application of classical optics can involve spatial quantities along the longest axis, which lies in a range between at least 5 mm and at most 55 mm. However, reference has only been made here to preferred or standard applications.The exemplary embodiments have the advantage that they can be adapted to any scenario. In the . Fig. 4a and 4b Eye safety can be defined by the dimensions of the large mirror, ie the reflective separation optics, and the number of elements. Fig. 5a and 5b Eye safety can be at least partially independent of the distance from the laser (element 60) to the lens (separation optics), but can at least be influenced by the surface area of ​​the optics, ie, over which area the individual surfaces are distributed into elements. The embodiments from Fig. 5a and 5b can be designed to be particularly flat.

[0083] The number of optically active surfaces can influence eye safety. The design of the number of surface elements, i.e., the selection of the number of elements in N and / or M, can be determined depending on various parameters. It should be taken into account that, compared to a one-way optic, the separation optic according to the exemplary embodiments generates multiple images in the imaging test setup of the eye safety standard. To ensure that the separation optic can fulfill its purpose particularly well, the following conditions can be met. o The permissible limit of accessible radiation (GZS) of the corresponding laser class / lamp group must be observed for all individual sources imaged on the detector. The following applies: P auge = GZS · C6 (Explanations on the C6 value follow). This also applies to the entirety, ie the envelope that includes all sources. The difference to the one-way optics is: ▪ The power of each source considered individually is lower by a factor of N*M, assuming N*M sources and these have the same partial power. ▪ The envelope of all individual sources has a significantly greater extent than the image of a single source in a one-way optics would have. As a result, the permissible C6 value and thus the limit value is increased. The C6 of an individual source will be significantly smaller than the C6 of the entirety. ∘ The number of elements depends on various parameters: manufacturing accuracy, field of view angle, size of the multi-way optics: ▪ On the one hand, the field of view angle determines θ FOV (FOV = Field of View) and the general size of the optics (assumption: radius r optik ) what proportion of the total radiated power P emssion The power reaching the eye can be determined by P auge = P emssion A Auge A FOV z = 10 cm = P emssion π 7 mm 2 r optik + 10 cm ∗ tan θ FOV ∧ 2 π = can be approximated, although minor errors may occur. A eye denotes the pupil area at maximum width, and A FOV denotes the area of ​​the field of view at a distance z of 10 cm. ▪ The extent of the apparent sources describes the effect that the individual sources are focused on different points of the retina and is described using the C6 parameter. The following applies: C 6 = α α min The factor α can only be between α min = 1.5 mrad and α max = 100 mrad vary (if it is smaller, it is set to 1.5 mrad; if it is larger, it is assumed to be 100 mrad). Alpha α is derived from the measurement setup according to eye safety standards. Therefore, if one considers a single source among the multitude of sources, there is a point at which, in terms of the C6 value, it is no longer worthwhile to increase the number of surface elements to further increase the apparent area, or only a small added value is obtained by adding additional surface elements. However, it is worthwhile from the point of view that the performance of each individual source then decreases. Typical values ​​could be: 2*2 surfaces (N=M=2), 8*8 surfaces (N=M=8), 16*16 surfaces (N=M=16), 20*20 surfaces (N=M=20), 40*40 surfaces (N=M=40) or even 100*100 surfaces (N=M=100) - depending on the diameter of the multi-path optics, where N can also be different from M. For example,If the aspect ratio along both axes is not 1 (for example, the cross-section of the beam 26 is an ellipse or a rectangle), the number of elements along the axes can also be different, for example: 2*1 surfaces, 2*4 surfaces, 8*16 surfaces, 20*40 surfaces, 40*80 surfaces, 100*200 surfaces, etc.

[0084] The surface elements do not necessarily have to have the same spatial extent. Single-mode lasers have an intensity maximum for small or medium angles (measured to the optical axis). This is where the most power leaves the emitter and also the optics. Contrary to the simplification made above, this means that not all sources have the same power with a uniform distribution, since the power would not be evenly distributed among all surface elements. In the case described, the surfaces in the center would emit an above-average amount of power. It is therefore possible, within the scope of the embodiments described herein, to design the elements with different spatial extents. For example, the elements in the center could be smaller than those in the outer regions.This can be solved, for example, using an algorithm that determines the total emitted power P emission and divides it by the number N*M of surface elements. The half-space in front of the emitter is then divided into N*M solid angles so that the N*M regions are each passed through by the same power. The individual surface elements are constructed in this region. As a consequence, the individual sources in the measurement setup should then have approximately the same power. In this case, the lens is specifically adapted to the emitter profile, since the position and size of the surface elements are then at least partially determined by the emitter's emission profile. To distinguish the lens from gratings or other diffractive elements, it should be noted here that the functioning of the optics is not due to interference phenomena, i.e. the multiple images are not obtained by interference.Therefore, the separation optics described here can be easily combined with non-coherent sources.

[0085] Embodiments described herein can also be used for lighting applications. Compliance with eye safety is also easier here. Embodiments relate to optical wireless communication, but can also be applied in the field of LIDAR and / or gesture recognition, where, due to less critical eye safety using the embodiments described herein, the average transmission power can be increased compared to known applications. This can mean that the time interval between the LIDAR pulses (with the same pulse duration) can be reduced, so that the environment can be scanned more quickly. Alternatively or additionally, the transmission power can be increased, for example, to increase the range. Embodiments also enable complex light distribution.The freeform optics transform the emitter's beam profile into a different one, such as a brand logo or other desired shape. This separation optics allows for higher power to be used to achieve greater ranges, while simultaneously ensuring less critical eye safety. Embodiments can also be used in measuring devices that use lasers but require reduced eye hazard. For example, if a person taking the measurement needs to be within the measurement range.

[0086] Further embodiments can easily be used in industrial production.

[0087] Embodiments describe a high-performance transmitter for optical wireless communication, which consists of or at least comprises a modulator, emitter (laser), and separation optics. The separation optics make it possible to maintain eye safety despite high transmission power (approximately several hundred milliwatts on average). The higher transmission power allows the link budget to be improved, i.e., the range, coverage, and data rate to be increased. The special multipath lens splits the emitted signal into several partial beams using refraction, reflection, and / or total internal reflection and simultaneously adapts each of the beams to the anticipated field of view. The lens is transparent or reflective in the spectral range of the communication (possibly outside of illumination), i.e., it has the lowest possible absorption there.

[0088] In the classification according to DIN EN 60825-1:2015-07 [3], to determine the laser class of a laser, the source is imaged onto a detector using a spherical lens. Since the beam emitted by the emitter has a low étendue (colloquially a low disorder), it can be focused to a very small point, so that the angular extent of the source is very small and the permissible limit for the transmitter is correspondingly very low. In order to be able to use the highest possible transmission power or to allow it within the framework of the regulations, separation optics are used in exemplary embodiments in order to increase the permissible limit by increasing the angular extent of the source. It is difficult or impossible for the simple spherical lens in the classification setup, and analogously for the human eye, to focus the individual beams to a single point.Instead, there are several focal points.

[0089] The embodiments of a separation optics of the high-power transmitter described here are composed of several optical elements and differ from the prior art mentioned at the beginning in the following points: Each individual element of the optics is freeform and is calculated analytically (e.g. by ray mapping, simultaneous multiple surface method, solution of the Monge-Ampere equation, or comparable methods) or numerically so that it is adapted to the field of view. This means that a large part (ideally: all) of the emitted power is directed into the field of view. The anticipated irradiance is then obtained in the target field (e.g. constant within a plane perpendicular to the optical axis). o In comparison to approach [2], this separation optics enables a higher output power. o In comparison to approach [1], this separation optics enables a higher data rate. o In comparison to approach [3], this separation optics enables higher efficiency. o In comparison to approach [4], this separation optics consists of a smaller number of individual elements, which were calculated individually and would also function individually. An additional collimator lens is not necessary.Furthermore, the lens can specifically reduce signal runtime differences between the center and the edge by (a) varying the thickness between the center and the edge accordingly and (b) not illuminating the entire field of view by each surface element, as described above. ∘ Compared to the approach [5], the freeforms allow for almost any output profile, so that even an output profile with a smaller angular extent than that of the emitter is possible. Furthermore, the freeforms allow for a very "sharp" field of view edge, i.e., the irradiance drops rapidly there. This reduces inter-channel crosstalk and increases the dynamic range of the link. Furthermore, the lens can specifically reduce signal runtime differences between the center and the edge by (a) varying the thickness between the center and the edge accordingly and (b) not illuminating the entire field of view by each surface element, as described above.Since the optical elements are freeform, they are adapted to the source. Although each element potentially illuminates the same target field, all elements must still be shaped differently because the relative position of each optical element to the source is different. ∘ Compared to approach [4], this eliminates the need for a collimator lens; since only a single element is required, material and assembly costs are reduced. ∘ Compared to approach [4], the structure is therefore different at each part of the optics; in approach [4], the "disorder" of the scattering elements is evenly distributed across the entire optics. ∘ Compared to approach [5], this eliminates the need for a collimator lens; since only a single element is required, material and assembly costs are reduced. ∘ Compared to approach [6], a single laser source can be used. The separation optics can be manufactured cost-effectively in large quantities, for example using injection molding.The tool or individual prototypes are formed using ultra-precision turning or ultra-precision machining. ∘ Compared to [4], this enables significantly more cost-effective production. Depending on the design, the optical elements of the separation optics can be configured so that each illuminates the entire field of view. This redundancy increases the reliability of the communication link, as not a single part of the field of view is completely obscured, but only the average irradiance within the field of view is reduced. The separation optics works with a single emitter. ∘ Compared to [6], only a single emitter is required; in [6], a VCSEL array is used in the source; this array is combined with a microlens array.Embodiments also differ from this in that the microlens array is used for tolerance correction (Köhler integration) and all elements of the microlens array are therefore designed identically, in contrast to the embodiments described herein.

[0090] The permissible output power of the emitter is not unlimited, even with multipath optics. It results from the number of optical elements, the spatial dimensions of the optics, and non-ideal scattering. The scattering occurs in the areas between the optical elements. This is typically rounded (with radii in the range of a few to a few hundred micrometers).

[0091] Although some aspects have been described in connection with a device, it is understood that these aspects also represent a description of the corresponding method, so that a block or component of a device can also be understood as a corresponding method step or as a feature of a method step. Similarly, aspects described in connection with or as a method step also represent a description of a corresponding block, detail, or feature of a corresponding device.

[0092] The above-described embodiments are merely illustrative of the principles of the present invention. It is understood that modifications and variations of the arrangements and details described herein will be apparent to others skilled in the art. Therefore, it is intended that the invention be limited only by the scope of the following claims and not by the specific details presented in the description and explanation of the embodiments herein. Literatur

[0093] [1] F. Zafar, M. Bakaul and R. Parthiban, "Laser-Diode-Based Visible Light Communication: Toward Gigabit Class Communication," in IEEE Communications Magazine, vol. 55, no. 2, pp. 144-151, February 2017. [2] E. Säckinger. Analysis and Design of Transimpedance Amplifiers for Optical Receivers. JohnWiley and Sons, 2018. [3] Norm. DIN EN 60825-1:2015-07: "Sicherheit von Lasereinrichtungen - Teil 1: Klassifizierung von Anlagen und Anforderungen (IEC 60825-1:2014)" [4] M. R. Pakravan, E. Simova and M. Kavehrad, "Holographic diffusers for indoor infrared communication systems," Proceedings of GLOBECOM'96. 1996 IEEE Global Telecommunications Conference, London, UK, 1996, pp. 1608-1612 vol.3. [5] WO2013032954 (A1): HIGH SPEED FREE-SPACE OPTICAL COMMUNICATIONS. → Multiple VCSELm Diffusor + Microlens Array [6] Dobroslav Tsonev, Stefan Videv, and Harald Haas, "Towards a 100 Gb / s visible light wireless access network," Opt. Express 23, 1627-1637 (2015).

Claims

1. A communication node configured for optical-wireless communication in an optical wireless communication network and comprising: an input interface (12) configured to receive a data signal (14); an optical transmitter (16) configured to convert the data signal (14) into an optical signal (18) having an optical power; separation optics (22) configured to spatially divide the optical signal (18) into a plurality of optical partial signals (18a-c) having an associated spectral range to divide the optical power onto the plurality of optical partial signals (18a-c), the plurality of spectral ranges at least partially coinciding; wherein the communication node is configured to emit the plurality of optical partial signals (18a-c) for the optical-wireless communication; and wherein the plurality of optical partial signals (18a-c) is focused at spatially disjoint locations of an image plane when focused together, when using receiver-side optics (24) or when focusing at or in the human eye.

2. The communication node according to claim 1, wherein the separation optics is configured to at least partly compensate for a transit time difference of beams (48) between the optical transmitter (16) and the separation optics due to different transit times within the separation optics (22); or wherein an element (43) is arranged to at least partly compensate for a transit time difference of beams (48) between the optical transmitter (16) and the separation optics due to different transit times within the element (43).

3. The communication node according to claim 1 or 2, wherein a spacing of focal points is obtained with focusing together, the radiated power of which are each below a limit defined according to DIN EN 60825-1:2015-07 or IEC 60825-1:2014 and in total exceed this limit.

4. The communication node according to any of the preceding claims, wherein the separation optics (22) comprises a plurality of optically active surfaces, each of which is associated with one of the optical partial signals, wherein each of the optically effective surfaces has an individual geometry and / or an individual area size adapted to a relative position between the optically effective surface and the optical transmitter (16).

5. The communication node according to any of the preceding claims, wherein the separation optics (22) comprises a plurality of optically active surfaces, each of which is associated with one of the optical partial signals, wherein optically effective surfaces of the plurality of optically effective surfaces have a different size and / or different aspect ratio of their sides of the optically effective surface.

6. The communication node according to claim 4 or 5, wherein the separation optics (22) is configured to redirect the optical signal (18) in another direction by means of total reflection at at least one reflective or totally reflective surface, each optically effective surface being unambiguously associated with a partial region of the at least one reflective or totally reflective surface.

7. The communication node according to claim 6, wherein the plurality of optically effective surfaces has a different area size which increases with an increasing distance from an optical axis of the optical transmitter (16).

8. The communication node according to claim 7, wherein the optical transmitter (16) is configured to provide an intensity maximum in the optical signal in a region comprising the optical axis, wherein the separation optics (22) is configured to provide an optical power per optically effective surface which is equal within a tolerance range of 50%, preferably 30%, based on the different area size.

9. The communication node according to claim 8, wherein the separation optics (22) comprises a plurality of optically active surfaces, each of which is associated with one of the optical partial signals, wherein the optically effective surfaces of the plurality of optically effective surfaces have a different size and / or different aspect ratio of their sides of the optically effective surface; and the communication node comprises a subreflector arranged opposite the separation optics (22) and configured to receive the optical signal (18) from the optical transmitter (16) and to reflect it back to the separation optics (22).

10. The communication optics according to claim 9, wherein the optical transmitter (16) is arranged in a plane of the separation optics (22).

11. The communication node according to any of the preceding claims, wherein an optical signal power of the optical signal (18) without the separation optics (22) exceeds an eye safety for the human eye and the plurality of optical partial signals (18a-c) in sum maintains the eye safety.

12. The communication node according to any of the preceding claims, wherein the separation optics (22) is configured to produce a multiple image of the optical signal of the transmitter (16).

13. The communication node according to any of the preceding claims, configured to emit the optical signal (18) in a wavelength range visible to the human eye, and to provide illumination of an environment of the communication node with the wireless optical signal.

14. An optical-wireless transmission system comprising: a communication node according to any of the preceding claims; and a receiver (25) configured to receive at least a portion of the plurality of partial signals (18a-c); wherein a field of view of the communication node is adapted to receiving optics of the receiver.

15. A method of providing separation optics for an optical-wireless communication node having a plurality of optically active surfaces, wherein the following steps are performed for each of the optically active surfaces: projecting (610) an inhomogeneous radiation power of an optical emitter onto a projection region by defining a plurality of sub-regions of the projection region such that partial radiation powers of the radiation power incident on the sub-regions are equal within a tolerance range in the plurality of sub-regions; defining (620) input angles of radiation power onto the optically active area of the separation optics and associating a respective output angle each to the plurality of partial radiation powers from the separation optics, the output angles being derived from the sub-region of the projection region; defining (630) the plurality of sub-regions for the optically active surface of the separation optics such that, when the radiation power arrives, the separation optics transforms the radiation power with the plurality of sub-regions into a partial radiation power for the projection area associated with a respective sub-region; and producing (640) the separation optics having the plurality of optically effective surfaces; such that the plurality of optical partial signals (18a-c) is focused at spatially disjoint locations of an image plane when focused together, when using receiver-side optics (24) or when focusing at or in the human eye.