Beam steering system and light emission system

Abstract

The present disclosure relates to a beam steering system (200) including: a first mirror arrangement (202) comprising a plurality of first mirrors (206) on a first rotatable support structure (212); a second mirror arrangement (204) comprising a plurality of second mirrors (208) on a second rotatable support structure (214), wherein a first mirror (206) directs an input light beam (218) towards the second mirror arrangement (204), and a second mirror (208) directs the input light beam (218) towards a field of view (210) as output light beam (220); and a control circuit (230) configured to: control a first rotational movement of the first rotatable support structure (212) at a first rotational speed, and a second rotational movement of the second rotatable support structure (214) at a second rotational speed, such that the output light beam (220) remains at fixed spatial coordinates in the field of view (210) until the first rotational movement causes another first mirror (206) to direct the input light beam (218) towards the second mirror arrangement (204).

Description

BEAM STEERING SYSTEM AND LIGHT EMISSION SYSTEMTechnical Field

[0001] The present disclosure relates generally to a beam steering system including a plurality of mirror arrangements, and to a light emission system including the beam steering system.Background

[0002] In general, light-based distance measurements provide a simple, yet powerful approach to collect information about a scene. This type of measurements allows estimating the distance between an obstacle and a sensor, thus allowing to create a map of the scene and to collect information about the obstacle, such as location, velocity, direction of motion, and the like. Various approaches exist for light-based distance measurements, e.g. based on direct time-of-flight (ToF), based on amplitude modulation of emitted light, based on frequency modulation of emitted light, etc. Sensors configured for light-based distance measurements have a wide range of applications, for example for assisting automated driving in a vehicle, for indoor monitoring systems, for smart farm systems, for movement tracking, and the like. Improvements in light-based distance measurements may thus be of particular relevance for the further advancement of several technologies.Brief Description of the Drawings

[0003] In the drawings, like reference characters generally refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various aspects of the invention are described with reference to the following drawings, in which:FIG.1A shows an optical sensor for light-based distance measurements in a schematic representation, according to various aspects;FIG. IB shows a beam steering system in a schematic representation, according to various aspects;FIG.2A, FIG.2B, FIG.2C, and FIG.2D show an adapted beam steering system in a schematic representation, according to various aspects;FIG.3A, FIG.3B, and FIG.3C show possible configurations of mirror arrangements of the adapted beam steering system in a schematic representation, according to various aspects;FIG.4A and FIG.4B show an adapted beam steering system with a plurality of first mirror arrangements in a schematic representation, according to various aspects;FIG.5 shows a light emission system including the beam steering system in a schematic representation, according to various aspects;FIG.6 shows an optical sensor including the light emission system in a schematic representation, according to various aspects; andFIG.7A to FIG.71 show various graphs illustrating simulations of an operation of the adapted beam steering system, according to various aspects.Description

[0004] The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and aspects in which the invention may be practiced. These aspects are described in sufficient detail to enable those skilled in the art to practice the invention. Other aspects may be utilized and structural, logical, and electrical changes may be made without departing from the scope of the invention. The various aspects are not necessarily mutually exclusive, as some aspects may be combined with one or more other aspects to form new aspects.

[0005] In general, light-based distance measurements may include emitting light (e.g., a light signal, a light beam) towards a scene and detecting the light reflected back from the scene towards the sensor. A distance measurement sensor may include a beam steering system to direct the emitted light beam towards different portions of the field of view of the sensor. Illustratively, the sensor may include a beam steering system that enables a scan of the field of view using the emitted light, e.g. in one dimension or two dimensions (usually the horizontal and / or vertical direction). A scanning of the field of view in the horizontal and vertical directions allows the sensor to create a map of the scene in the form of a point cloud in which three-dimensional information is assigned to each point in the form of horizontal coordinate (x), vertical coordinate (y), and depth information (z).

[0006] In this framework, a beam steering system may include a rotating mirror to guide the emitted light (e.g., a laser beam) and scan the environment with a line or by covering an area. For some implementations such as FMCW LiDAR (where LiDAR is an acronym for Light Detection and Ranging, and FMCW is an acronym Frequency Modulated Continuous Wave) it may be advantageous to maintain the emitted (laser) beam stationary during a measurement (illustratively, the measurement of the path from the source to the obstacle and back to the detector). For example, in FMCW LiDAR the optical beam should remain at fixed coordinatesduring a relatively long measurement time per pixel, e.g. a few microseconds (compared to direct time-of-flight where the measurement occurs at the nanosecond scale).

[0007] However, common mechanical systems are not capable of moving quickly in the required time interval and reaching a new stable position without oscillating. Illustratively, beam diameters in the centimeter range require correspondingly large mirrors and moving mechanics, which do not ensure a fast scanning time while maintaining the beam stable during a measurement. For example, in FMCW, the integration over several microseconds causes the mechanical motion to influence the measurement. Scan concepts without mechanically moving parts are currently only achievable in a laboratory environment and also exhibit effects that stand in the way of commercial implementations in the foreseeable future. Thus, conventional scanning approaches tend to operate with a relatively low velocity and a relatively low resolution, but for practical purposes shorter scanning times would be needed to generate the point cloud.

[0008] Aspects of the present disclosure may be based on the realization that a combination of a plurality of rotating mirrors may enable scanning a field of view with emitted light while maintaining the illuminated spot in the field of view stable for a certain period of time (illustratively, a measurement time). The beam steering system proposed herein may include two or more rotating mirrors. In the configuration with two rotating mirrors a first rotating mirror may direct the light towards a second rotating mirror, and the second rotating mirror may direct the light towards the field of view (or field of illumination). The present disclosure may be based on the realization that a proper control of the respective rotational speed of the rotating mirrors may allow to maintain the emitted light at stable coordinates in the field of view for a certain period of time. By way of illustration, two rotating mirrors in combination may generate discrete measurement points while remaining in constant motion and accordingly not requiring deceleration and acceleration.

[0009] According to various aspects, a beam steering system may be provided, the beam steering system including a first rotating mirror and a second rotating mirror disposed such that the first rotating mirror directs light towards the second rotating mirror, and the second rotating mirror directs the light received from the first rotating mirror towards a field of view (or field of illumination), and wherein a ratio between a first rotational speed of the first rotating mirror and a second rotational speed of the second rotating mirror causes an area (e.g., a light spot) in the field of view illuminated by the light directed from the second rotating mirror to remain at stable spatial coordinates for a predefined period of time.

[0010] According to various aspects, a beam steering system may be provided, the beam steering system including: a first mirror arrangement including a plurality of first mirrors mounted on a first rotatable support structure; a second mirror arrangement including a plurality of second mirrors mounted on a second rotatable support structure, wherein the first mirror arrangement and the second mirror arrangement are configured such that when the first mirror arrangement is illuminated with an input light beam a first mirror of the plurality of first mirrors receives the input light beam and directs the input light beam towards the second mirror arrangement, and a second mirror of the plurality of second mirrors receives the input light beam from the first mirror and directs the input light beam towards a field of view of the beam steering system as output light beam; and a control circuit configured to: control a first rotational movement of the first rotatable support structure at a first rotational speed, wherein the first rotational movement of the first rotatable support structure varies which first mirror of the plurality of first mirrors receives the input light beam; and control a second rotational movement of the second rotatable support structure at a second rotational speed, wherein the second rotational movement of the second rotatable support structure varies which second mirror of the plurality of second mirrors receives the input light beam from the first mirror, wherein the control circuit is configured to select the first rotational speed and the second rotational speed such that the output light beam directed from the second mirror towards the field of view of the beam steering system remains at fixed spatial coordinates in the field of view until the first rotational movement of the first rotatable support structure causes another first mirror of the plurality of first mirrors to receive the input light beam and direct the input light beam towards the second mirror arrangement.

[0011] In the proposed configuration a light source (e.g., a laser source) may irradiate a first rotating mirror, which directs the beam onto the actual scanner mirror in a relatively narrow scan area. When the rotational speeds are coordinated, the first mirror compensates for the continuous movement of the second mirror and, as a result, the emitted beam hits a fixed point for the time during which a segment of the first mirror is illuminated.

[0012] The beam steering system adapted as described herein provides the possibility to obtain adjustable discrete points for stable measurements. Furthermore, the adapted beam steering system may operate with a relatively low energy consumption as the moving mass is not accelerated / decel erated for each measurement point (illustratively, the mirrors may rotate at a respective constant rotational speed). As a further aspect, the components used in the beam steering system may provide a robust configuration. Furthermore, the effect is not limited tothe close range exemplarily illustrated in the figures, but a temporally stable angle is output, which remains independent of the distance of the obstacle.

[0013] In some aspects, the first mirror may have a higher number of segments compared to the second mirror. This configuration may enhance the resolution of the beam steering system and enable a finer control over the scanning of the field of view. It is however understood that the aspects described herein are not limited to a specific fixed number of segments for either the first mirror or the second mirror, and are not limited to specific absolute rotational speeds.

[0014] In some aspects, more than one “first mirror” may be used to direct light towards the second mirror. In this configuration, the second mirror used to scan the field of view may receive light from a plurality of first mirrors, e.g. disposed to surround or partially surround the second mirror. This configuration may extend the scanning range, e.g. up to 360°, via the combined use several sub-systems arranged around the one scanner mirror. Furthermore, a configuration with a plurality of first mirrors may be beneficial in terms of eye safety, which is an important aspect in every application. By distributing several beams over the total field of view, more power per single beam may be employed compared to conventional configurations. Illustratively, using each first mirror to cover a respective region in the field of view, the accumulation of multiple beams in the same area may be avoided (as instead is the case with conventional stacked emitters), which could cause damage if hitting the eye of a user.

[0015] A beam steering system configured as proposed herein may be implemented in any type of system or device in which light is used to scan a certain area with light. A relevant use case of the proposed configuration may be for FMCW LiDAR, for which the proposed beam steering system allows to obtain a stable illumination during the integration time, while ensuring a sufficiently rapid scanning for practical applications. Thus, in the following some terminology may pertain to the specific context of FMCW LiDAR. It is however understood that the proposed beam steering system may also be part of different types of systems or devices, e.g. any suitable light-based distance measuring sensor, or any suitable device for which the type of scanning that may be obtained with the combination of rotating mirrors may be advantageous. Another application example may be in the field of material processing, in which the light (e.g., laser light) may be used to process (e.g., to structure) a material or a substrate. In this application the beam steering system may ensure a rapid processing while achieving stable illumination conditions to enable a uniform structuring of the material.

[0016] In the context of the present disclosure, the term “field of view” may be used to indicate an area or region towards which light may be directed and, in some aspects, an area or region from which light may be collected (and detected). For example, the “field of view of a beamsteering system” may be an area or region towards which the scanner mirror(s) of the beam steering system may direct a received light beam, e.g. the area or region towards which the scanner mirror(s) may be oriented or facing. In this regard, the term “field of view” may be used in an analogous manner as “field of illumination”, e.g. as “field of illumination of a beam steering system”. In some aspects, the “field of view” of the beam steering system may be or may correspond to the field of view of an optical sensor including the beam steering system.

[0017] FIG.1A shows an optical sensor 100 in a schematic representation, according to various aspects. The optical sensor 100 may be configured for light-based distance measurements, and may provide an exemplary application scenario of a beam steering system configured as proposed herein. The basic principles of light-based distance measurements, as well as the possible variants, or possible basic hardware / software components are generally known in the art. A brief description is provided herein to introduce aspects relevant for the present disclosure. A detailed description of the adapted beam steering system herein will be provided in relation to FIG.2A.

[0018] The optical sensor 100 may include, in general, a light emission system 102, a light detection system 104, and a processing circuit 106. In general, light is not the only option as a signal for carrying out distance sensing, e.g. sound waves or radio waves may also be used, as other examples. However, light may be a preferred choice since it ensures high traveling speed, safety of operation, and allows having a compact and portable system.

[0019] As an abridged overview, the optical sensor 100 may be configured to determine the distance d at which an object 110 is located with respect to the sensor 100 by emitting light 108 and detecting the light that hits the object 110 and is reflected back (as reflected light 112) towards the sensor 100. The light emission system 102 may thus be configured to emit a light signal 108 towards the field of view of the optical sensor 100. The emitted light signal 108 may hit an object 110 in the field of view, and at least part of the emitted light may be reflected back towards the optical sensor 100. The light detection system 104 may receive and detect a reflected light signal 112 corresponding to the back reflection of the emitted light signal 108, and the processing circuit 106 may be configured to calculate the distance d based on the reflected light signal 112. The object 110 may be any type of target in the field of view of the sensor 100, e.g. any type of inanimate object or animate object, such as a car, a tree, a traffic sign, an animal, a person, etc. An “object” may also be referred to herein as “target”, or “obstacle".

[0020] Various approaches exist to implement the distance measurement. As an example, the optical sensor 100 may be configured as a direct time-of-flight (DTOF) sensor. In a DTOFconfiguration, the light emission system 102 may be configured to emit a light signal 108 with a single light pulse, and the processing circuit 106 may be configured to carry out a timing measurement to measure a time difference between the emission of the light pulse and the reception of the reflected light pulse back at the sensor 100. From the time difference At (illustratively, the round-trip time of flight), the processing circuit 106 may calculate the distance d at which the object 110 is located via the formula d= At*c / 2, where c is the speed of light in the medium (e.g., air in a common use case, or water, as examples), and the factor 1 / 2 is to take into account the round-trip from the sensor 100 to the object 110 and back to the sensor 100. The processing circuit 106 may be configured to adjust the calculated distance by using one or more correction factors, e.g. to take into account effects of the optics of the optical sensor 100 as an example. A DTOF sensor may thus have a simple architecture, e.g. using a time-to-digital-converter to measure the time difference between a start signal representing the emission of the light signal 108, and a stop signal representing the arrival time of the reflected light signal 112.

[0021] As another example, the optical sensor 100 may be configured as an indirect time-of- flight (ITOF) sensor. In an ITOF configuration, the light emission system 102 may be configured to emit a light signal 108 that is a continuous light signal having a predefined modulation. At the receiver side, the processing circuit 106 may determine a phase shift between the modulation of the emitted light signal 108 and a modulation of the received light signal 112. The processing circuit 106 may then convert the phase shift into a corresponding distance d using the formula d = (c*cp) / (2*27t*f), where cp is the phase shift, c is the speed of light in a given medium (e.g., air or water, as examples) and f is the modulation frequency. An ITOF configuration may be preferred in the context of three-dimensional imaging as it allows capturing more data points compared to a DTOF approach.

[0022] An optical sensor 100 for light-based distance measurements may also be referred to as LiDAR sensor. A LiDAR sensor may be configured, for example, as time-of-flight LiDAR in case the sensor carries out the distance measurement using the round-trip time-of-flight, as AMCW LiDAR (Amplitude Modulated Continuous Wave) in case the sensor carries out the distance measurement using amplitude modulation of emitted light, or as FMCW LiDAR in case the sensor carries out the distance measurement using frequency modulation of emitted light.

[0023] For example, for FMCW LiDAR part of the outgoing light 108 may be mixed with the received light 112 and the processing circuit 106 may extract the range d (and optionally the velocity of the object 110) via a Fourier transformation of the received waveform. In thisscenario, the received light 112 may include information about the distance d at which the object 110 is located in the form of a frequency shift. The processing circuit 106 may thus determine (e.g., calculate, estimate) the range d as a function of the frequency shift between the emitted light 108 and the received light 112, as known in the art. Compared to DTOF, FMCW LiDAR may provide higher detection sensitivity and accuracy, and may allow to resolve the velocity of a detected object instantaneously.

[0024] An optical sensor 100 may include a beam steering system (e.g., as part of the light emission system 102) to control the direction into which light 108 is emitted, e.g. to enable a one-dimensional or two-dimensional scanning of the field of view. In a simple configuration, as shown in FIG. IB in a top view, a beam steering system 150 may include a single rotating mirror 152. The rotating mirror 152 may receive light from a light source (e.g., a laser beam from a laser source) and may direct the received light towards the field of view of the optical sensor 100. The rotation of the mirror may vary the spatial coordinates of the illuminated area or illuminated spot, e.g. along the horizontal direction or vertical direction of the field of view.

[0025] However, a beam steering system 150 configured as shown in FIG. IB may be unsuitable for applications in which the emitted light 108 should remain stable for a certain period of time, e.g. to allow integration of received photons, or to enable processing of a material, and the like. A configuration as in FIG. IB causes a continuous variation of the coordinates of the illuminated area or spot (e.g., along the horizontal and / or vertical direction), and may thus be unsuitable to ensure fixed illumination without excessively reducing the overall speed of the arrangement.

[0026] The present disclosure may be based on the realization that a plurality of rotating mirrors with properly tuned rotational speeds may allow maintaining the emitted light to illuminate a fixed area or spot in the field of view for a certain period of time before moving onto the next scanning position. The proposed arrangement may thus provide a suitable scanning speed while enabling a stable illumination, which may be advantageous in certain applications such as FMCW LiDAR, material processing, and the like.

[0027] FIG.2A and FIG.2B show a beam steering system 200 in a schematic representation, according to various aspects. The beam steering system 200 may be configured according to the strategy proposed herein, and may include a plurality of rotating mirrors with suitably controlled rotational speeds, as discussed below. The beam steering system 200 may also be referred to herein as adapted beam steering system 200. In some aspects, an optical sensor, e.g. the optical sensor 100, may include the beam steering system 200 to control the illumination of the field of view. The principles of the beam steering system 200 will be described in FIG.2A (top view) and FIG.2B (perspective view) in relation to a configuration with two rotatingmirrors. It is however understood that the configuration of the beam steering system 200 may be extended to more than two rotating mirrors (e.g., three, four, five, ten, or more than ten), as discussed in further detail in relation to FIG.4A and FIG.4B. The principles of the beam steering system 200 will be further described in relation to FIG.2C and FIG.2D to illustrate a scenario with a plurality of mirror pairs (illustratively, a plurality of beam steering sub-systems).

[0028] In general, the beam steering system 200 may include a scanner mirror (or scanning mirror) configured to direct light towards a field of view 210, and one or more auxiliary mirrors configured to direct light towards the scanner mirror. In the configuration in FIG.2 A, the beam steering system 200 may include a first mirror arrangement 202 (as auxiliary mirror), and a second mirror arrangement 204 (as scanner mirror). In other aspects, the beam steering system 200 may include a plurality of auxiliary mirrors directing light towards a scanner mirror (see FIG.4A and FIG.4B). In other aspects, the beam steering system 200 may include a plurality of scanner mirrors, each with one or more auxiliary mirrors associated therewith.

[0029] The aspects discussed in relation to the first mirror arrangement 202 may apply in general to any “auxiliary mirror” or “auxiliary mirror arrangement” of a beam steering system adapted as described herein, and the aspects discussed in relation to the second mirror arrangement 204 may apply in general to any “scanner mirror” or “scanner mirror arrangement” of the adapted beam steering system.

[0030] The first mirror arrangement 202 may include a plurality of first mirrors 206 mounted on a first rotatable support structure 212, and the second mirror arrangement 204 may include a plurality of second mirrors 208 mounted on a second rotatable support structure 214. In general, a “mirror arrangement” described in the context of the adapted beam steering system may include a plurality of mirrors and may be configured to allow for a rotation of the mirrors around a common axis of rotation. A “mirror arrangement” may illustratively be a mirror including a plurality of mirror segments or mirror faces. For example, the first mirror arrangement 202 may be a first rotating mirror with a plurality of first mirror segments 206, the second mirror arrangement 204 may be a second rotating mirror with a plurality of second mirror segments 208, etc. Stated in a different fashion, a “mirror arrangement” may be an optical component including a plurality of reflective surfaces disposed on a support element that may rotate to vary the reflective surface on which the light incoming onto the mirror arrangement impinges.

[0031] Aspects discussed in relation to a “mirror arrangement with a plurality of mirrors” may apply in a corresponding manner to a “mirror with a plurality of mirror segments (or faces)”, and vice versa. In the following, a “mirror arrangement” (with mirrors mounted on a rotatablesupport structure) may also be referred to simply as “rotating mirror” (with a plurality of segments). It is also understood that aspects discussed in relation to a “mirror of a mirror arrangement” may apply in a corresponding manner to a “mirror segment of a (rotating) mirror”, and vice versa.

[0032] The term “mirror” may be used herein to indicate a surface that reflects light, as commonly understood in the art. A “mirror” may be a surface with a reflectivity greater than 80% in a wavelength range of interest, for example a reflectivity greater than 90% in the wavelength range of interest, for example a reflectivity greater than 95% in the wavelength range of interest. A “mirror” may be adapted to any suitable wavelength range of interest depending on the desired application, e.g. visible range, infrared range, near-infrared range, and the like. A “mirror” may include or may be made of any suitable material, e.g. a mirror may include one or more reflective layers, e.g. one or more metal layers including any suitable metal such as silver, nickel, chromium, aluminum, as examples.

[0033] In general, a “mirror” of a mirror arrangement may have any suitable shape or structure. In a preferred configuration, the mirrors of a mirror arrangement may have a planar configuration, e.g. a mirror arrangement may include a plurality of plane mirrors. Such configuration may allow an easier fabrication process and an easier coupling of the mirrors with the rotatable support structure. It is however understood that a “mirror” of a mirror arrangement may also have another configuration, e.g. a mirror may be a convex mirror or a concave mirror, as other examples.

[0034] In various aspects, the mirrors 206, 208 of a mirror arrangement 202, 204 may each be facing towards a respective direction (around the rotatable support structure 212, 214). For example, each first mirror 206 (or each first mirror segment) may be facing towards a respective direction with respect to a (first) axis of rotation 216 around which the first rotatable support structure 212 may rotate. In a corresponding manner, each second mirror 208 (or each second mirror segment) may be facing towards a respective direction with respect to a (second) axis of rotation 217 around which the second rotatable support structure 214 may rotate. Stated differently, each mirror 206, 208 may face away from the axis of rotation 216, 217 of the respective rotatable support structure 212, 214 and may have an optical axis aligned in a respective direction (different from the other mirrors of the mirror arrangement).

[0035] In general, a rotatable support structure 212, 214 as described herein may have any suitable configuration to allow a coupling with the mirrors 206, 208 and to enable a rotation of the mirrors 206, 208 around the respective axis of rotation 216, 217. In a preferred configuration, a rotatable support structure (e.g., the first rotatable support structure 212 andsecond rotatable support structure 214) may have a prism shape with a plurality of faces (illustratively, a plurality of lateral sides). In this configuration, a rotatable support structure may have two parallel polygonal bases and rectangular sides. The mirrors of a mirror arrangement may be disposed each on a respective face (lateral side) of the prism. For example, each first mirror 206 may be mounted on a corresponding face of the first prism-shaped rotatable support structure 212, and each second mirror 208 may be mounted on a corresponding face of the second prism-shaped rotatable support structure 214. In this configuration, the shape of the bases of the rotatable support structure (and accordingly of the prism) may be any suitable shape, which may be adapted depending on the number of mirrors to be used for the mirror arrangement. As examples, the base of a rotatable support structure (e.g., the first rotatable support structure 212 and second rotatable support structure 214) may have a triangular shape, a square shape, a pentagonal shape, a hexagonal shape, an octagonal shape, etc. Stated in a different fashion, the base of a rotatable support structure may have three sides, four sides, five sides, six sides, seven sides, eight sides, or more than eight sides (e.g., more than ten sides, or more than twenty sides).

[0036] As another exemplary configuration, a rotatable support structure (e.g., the first rotatable support structure 212 and / or second rotatable support structure 214) may have a cylinder shape. In this configuration, the rotatable support structure may have two parallel circular bases, and the mirrors of a mirror arrangement may be disposed on the lateral surface of the cylinder.

[0037] In general, the mirrors of a mirror arrangement may form a continuous mirror surface around the respective rotatable support structure. Illustratively, a mirror arrangement may be free of gaps between adjacent mirrors (or mirror segments), thus ensuring a smooth and continuous steering of the light to be used for illuminating the field of view. For example, the first mirrors 206 may form a continuous mirror surface (illustratively, a continuous reflective surface) around the first rotatable support structure 212. In a corresponding manner the second mirrors 208 may form a continuous mirror surface around the first rotatable support structure 214.

[0038] In general, in the adapted beam steering arrangement, the auxiliary mirror(s) may direct light towards the scanner mirror, and the scanner mirror may direct light towards the field of view. With reference to the configuration of FIG.2A, the first mirror arrangement 202 and the second mirror arrangement 204 may be configured such that when the first mirror arrangement is illuminated with an input light beam 218 a first mirror 206(1) of the plurality of first mirrors 206 may receive the input light beam 218 and may direct the input light beam 218 towards thesecond mirror arrangement 204. A second mirror 208(1) of the plurality of second mirrors 208 may receive the input light beam 218 from the first mirror 206(1) and may direct the input light beam 218 towards the field of view 210 of the beam steering system as output light beam 220. The “input light beam” may also be referred to as “input light signal”, or simply as “input light”, and the “output light beam” may also be referred to as “output light signal”, or simply as “output light”.

[0039] Stated differently, the first mirror arrangement 202 may be disposed (and oriented) with respect to the second mirror arrangement 204 and with respect to a direction of arrival of the input light beam 218 in such a way that a first mirror 206(1) illuminated with the input light beam 218 reflects the input light beam 218 towards a second mirror 208(1) of the second mirror arrangement 204. The second mirror 208(1) becomes illuminated with the input light beam 218 and reflects the input light beam 218 towards the field of view 210 (as output light beam 220). It is understood that the light beam is denoted as “input light beam” and “output light beam” to distinguish the functionality of the first mirror arrangement 202 and second mirror arrangement 204, but the properties of the light beam (e.g., wavelength, phase, amplitude, etc.) may in general remain constant in the propagation, so that the “input” light beam may have properties that correspond to properties of the “output” light beam.

[0040] The beam steering system 200 may further include a control circuit 230 configured to control the rotational movement of the rotatable support structures (e.g., the first and second rotatable support structure 212, 214). The control circuit 230 may control the rotational movement in any suitable manner. In an exemplary configuration, a rotatable support structure 212, 214 may include a motor (e.g., a DC motor) or may be coupled with a motor, and the control circuit 230 may control the motor (e.g., via controlling a supply of electrical power to the motor) to control the rotational movement of the rotatable support structure. For example, the rotation of a rotatable support structure around the respective axis of rotation may be actuated mechanically, and the control circuit 230 may control the mechanical actuator of the rotatable support structure to cause the rotation. A further possible configuration will be discussed in relation to FIG.4B.

[0041] For the adapted scanning proposed herein, the control circuit 230 may be configured to control the rotational movements of the scanner mirror and auxiliary mirror(s) (around the respective rotation axis) at suitably selected rotational speeds to ensure a stable illumination of the field of view 210. In the configuration in FIG.2A, the control circuit 230 may be configured to control a first rotational movement of the first rotatable support structure 212 at a first rotational speed, and to control a second rotational movement of the second rotatable supportstructure 214 at a second rotational speed. In some aspects, the control circuit 230 may be configured to cause a first rotational movement of the first rotatable support structure 212 at a first rotational speed, and to cause a second rotational movement of the second rotatable support structure 214 at a second rotational speed. A “rotational speed” may also be referred to as rotational frequency or rotational rate. A “rotational movement” may also be referred to simply as “rotation” around the axis of rotation of the support structure.

[0042] The rotational movement of a rotatable support structure may vary the relative position of the mirrors of the mirror arrangement with respect to the incoming light beam. Illustratively, rotating a mirror arrangement around the axis of rotation may bring the mirror segments, in sequence, under illumination by the incoming light. By way of illustration, the rotation of the mirror arrangements 202, 204 may vary which mirror is “active” or “illuminated” at a certain time point, or during a certain time period.

[0043] With reference to FIG.2A and FIG.2B, the first rotational movement of the first rotatable support structure 212 may vary which first mirror 206 receives the input light beam 218. Illustratively, considering an input light beam 218 coming from a fixed direction, the first rotational movement may cause different first mirrors 206, in sequence, to receive and be illuminated by the input light beam 218. During an initial time period one of the first mirrors 206(1) may receive the input light beam 218, at a subsequent time period another one of the first mirrors 206(2) may receive the input light beam 218, at a further subsequent time period a further one of the first mirrors 206(3) may receive the input light beam 218, etc.

[0044] In a corresponding manner, the second rotational movement of the second rotatable support structure 214 may vary which second mirror 208 receives the input light beam 218 from the first mirror arrangement 202 (illustratively, from the illuminated first mirror 206). Considering the input light beam 218 coming from the first mirror arrangement 202, the second rotational movement may cause different second mirrors 208, in sequence, to receive the input light beam 218 and be illuminated by the input light beam 218. During an initial time period one of the second mirrors 208(1) may receive the input light beam 218, at a subsequent time period another one of the second mirrors 208(2) may receive the input light beam 218, at a further subsequent time period a further one of the second mirrors 208(3) may receive the input light beam 218, etc.

[0045] In various aspects, the mirror arrangements may rotate in the same direction. Illustratively, in various aspects, the control circuit 230 may be configured to control the first rotational movement and the second rotational movement to cause a rotation of the first rotatable support structure 212 and the second rotatable support structure 214 in the same senseof rotation. The sense of rotation may be clockwise for both mirror arrangements or counterclockwise for both mirror arrangements.

[0046] The adapted configuration proposed herein may be based on the realization that the use of two rotating mirror arrangements allows compensating the rotation of the scanner mirror via suitably tuning the rotational speed of the auxiliary mirror(s) with respect to the rotational speed of the scanner mirror. The compensation of the rotation leads to an illumination of the field of view at fixed spatial coordinates for a certain period of time (depending on the rotational speed of the mirrors), before moving to different spatial coordinates. Thus, the compensation of the rotation provides a scanning of the field of view in which the scanning points do not vary “instantaneously”, but rather at a slower rate, which for example may allow integrating the collected light (e.g., for FMCW LiDAR).

[0047] The control circuit 230 may thus be configured to select rotational speeds for the mirror arrangements that compensate the rotation of the second (scanner) mirror arrangement and produce a desired illumination pattern. With reference to FIG.2A and FI.2B, the control circuit 230 may be configured to select (and apply) the first rotational speed and the second rotational speed such that the output light beam 220 remains at fixed spatial coordinates in the field of view 210 until the first rotational movement causes another first mirror 206(2) to receive the input light beam 218 and direct the input light 218 beam towards the second mirror arrangement 204. The control circuit 230 may be configured to drive the first rotational movement and second rotational movement at rotational speeds that cause an illuminated spot (point) or area in the field of view 210 to be at fixed coordinates (e.g., horizontal and vertical coordinates) for the period of time during which one of the first mirrors 206 is illuminated by the input light beam 218.

[0048] As mentioned above, the rotation of the mirror leads to different mirrors 206, 208 to be illuminated, in sequence. The rotation of the first mirror arrangements 202 causes different first mirrors 206 to receive the input light beam 218 and reflect it towards the second mirror arrangement 204. The sequential illumination of the first mirrors 206 causes a scanning of the field of view 210, wherein for each first mirror 206 the output light beam 220 is at respective (fixed) spatial coordinates in the field of view 210. With reference to FIG.2A and FIG.2B, the first mirror arrangement 202 and the second mirror arrangement 204 may be configured such that when the other first mirror 206(2) receives the input light beam 218 and directs the input light beam 218 towards the second mirror arrangement 204 the output light beam 220 remains at further fixed spatial coordinates in the field of view 210 until the first rotational movement causes another further first mirror of the plurality of first mirrors 206(3) to receive the inputlight beam 218 and direct the input light beam 218 towards the second mirror arrangement 204, and so on.

[0049] For example, when one of the first mirrors 206(1) is illuminated, the output light beam 220 may be at first spatial coordinates 222(1), when another one of the first mirrors 206(2) is illuminated, the output light beam 220 may be at second spatial coordinates 222(2), when a further one of the first mirrors 206(3) is illuminated, the output light beam 220 may be at third spatial coordinates 222(3), etc.

[0050] The “spatial coordinates” of the output light beam 220 may be understood as (x,y)-coordinates in the field of view, e.g. as a horizontal and vertical coordinate of an area illuminated by the output light beam. The “illuminated area” may also be referred to as “illuminated spot” or “illuminated point”, and the dimensions of the illuminated area may vary with the dimensions of the input light beam. For a certain second mirror 208(1) being the “active” mirror, the first rotational movement causes a scanning of the field of view (e.g., in the horizontal direction) in which for each “active” first mirror the spatial coordinates of the light output beam 220 vary (e.g., the horizontal coordinate varies while the vertical coordinate remains substantially the same, in the exemplary case of a horizontal scanning). For another second mirror 208(2) being the “active” mirror, in view of the second rotational movement, the scanning of the field of view 210 may “go back” to the initial position and continue along the scanning direction following the rotation of the first mirror arrangement.

[0051] The ratio between the rotational speed of the auxiliary mirror(s) (e.g., the first rotational speed) and the rotational speed of the scanner mirror (e.g., the second rotational speed) may be adapted to provide the compensation of the rotation of the scanner mirror based on various system parameters, such as the size of the mirrors 206, 208, the distance between the mirror arrangements 202, 204, or the number of mirrors 206 in the auxiliary mirror arrangement(s). In this regard it is worth noting that the relevant parameter is the ratio between the rotational speeds, rather than the absolute values of the rotational speeds. In the following, exemplary ratios are provided, which have been found by way of simulation and experimentation to provide the desired illumination pattern. It is however understood that also other ratios may be provided, e.g. for different system parameters.

[0052] According to various aspects, the ratio of the (second) rotational speed of the scanner mirror to the (first) rotational speed of the auxiliary mirror may be in the range from 1 to 2. As a preferred configuration, which has been found to provide a robust and reproducible operation of the beam steering arrangement to obtain steady state plateaus for typical dimensions of mirrors used in applications of interest, the ratio of the (second) rotational speed of the scannermirror to the (first) rotational speed of the auxiliary mirror may be in the range from 1 to 1.3, e.g. greater than 1 and less than or equal to 1.3. For example, the ratio of the (second) rotational speed of the scanner mirror to the (first) rotational speed of the auxiliary mirror may be 1.3. As mentioned, also other ratios may be provided, e.g. with an opposite behavior in which the scanner mirror rotates slower than the auxiliary mirror(s), with different range boundaries, and the like.

[0053] In this regard, the distance between mirror arrangements 202, 204 may be adapted in any suitable range, e.g. depending on the dimension of an end-device in which the beam steering system 200 should be integrated. The distance between mirror arrangements 202, 204 may be defined, for example, as distance 224 between the respective axes of rotation 216, 217 (considering axes of rotation 216, 217 parallel with one another). As another example, the distance between mirror arrangements 202, 204 may be defined as a surface-to-surface distance between the surface of the “active” first mirror 206 and the surface of the “active” second mirror 208. As a numerical example, the distance 224 between the first mirror arrangement 202 and the second mirror arrangement 204 may be in the range from 5 mm to 100 mm, for example in the range from 10 mm to 50 mm.

[0054] As mentioned above, the relevant parameter for the proposed approach is the ratio between the rotational speeds. The rotational speeds themselves may have any suitable value that may be obtained with the available components. In general, the rotational speed may be selected taking into account the end-system, e.g. measure time, parallel channels, pixel count, frame rate, mechanical limitations, etc. As a numerical example, the (first) rotational speed of the auxiliary mirror(s) and / or the (second) rotational speed of the scanner mirror may be in the range from 1 rad / s (radian per second) to 20 rad / s, for example in the range from 2 rad / s to lO rad / s. As other numerical examples the (first) rotational speed of the auxiliary mirror(s) and / or the (second) rotational speed of the scanner mirror may be higher, e.g. equal to or greater than 100 rad / s, e.g. equal to or greater than 1000 rad / s, e.g. equal to or greater than 10000 rad / s.

[0055] Compared to other beam steering approaches, the beam steering system 200 may achieve scanning of the field of view without having to accelerate or decelerate (e.g. brake) the movement of the rotating mirrors and without having to change the sense of rotation of the mirrors. With reference to FIG.2A and FIG.2B, the first rotational movement of the first support structure 212 controlled / caused by the control circuit 230 may be a (first) continuous rotational movement (around the axis of rotation 216). In a corresponding manner, the second rotational movement of the second support structure 214 controlled / caused by the control circuit 230 may be a (second) continuous rotational movement (around the axis of rotation 217). Stateddifferently, the first rotational movement may be a continuous rotational movement in a same sense of rotation during the scanning of field of view 210 (e.g., during a predefined measurement time, or scanning period), and the second rotational movement may be a continuous rotational movement in a same sense of rotation during the scanning of field of view 210.

[0056] In various aspects, the control circuit 230 may be configured to maintain the first rotational speed constant during a predefined measurement time / scanning period, e.g. during a period of time during which a plurality of first mirrors 206 are sequentially illuminated by the input light beam 218, illustratively a period of time during which the first rotational movement causes a plurality of first mirrors 206 to receive the input light beam 218. In a corresponding manner, additionally or alternatively, the control circuit 230 may be configured to maintain the second rotational speed constant during the predefined measurement time / scanning period, e.g. during a period of time during which a plurality of second mirrors 208 are sequentially illuminated by the input light beam 218, illustratively a period of time during which the second rotational movement causes a plurality of second mirrors 208 to receive the input light beam 218 from first mirror arrangement 202 (from the active first mirror 206). The proposed strategy may thus be implemented without acceleration / deceleration, which could otherwise cause additional stress on the mechanical components.

[0057] As mentioned above, in various aspects the scanning may be along one direction. Illustratively, the scanning may include a spatial coordinate along a first direction (e.g., the horizontal direction) varying over time following the rotation of the mirrors 206, 208, and a second spatial coordinate along a second direction (e.g., the vertical direction) remaining substantially constant. In this scenario, the scanning may occur in a single plane, and one spatial coordinate varies along one direction within the plane.

[0058] A scanning in more than one direction and more than one plane may be implemented in various ways. As an example, an emission direction of the input light beam 218 may be varied, such that the input light beam 218 may impinge onto the first mirrors 206 at different coordinates along the axis of rotation 216 of the first mirror arrangement 202 (e.g., different vertical coordinates). For example, during a first scanning period the input light beam 218 may impinge onto the first mirrors 206 at a first coordinate along the axis of rotation 216, during a second scanning period the input light beam 218 may impinge onto the first mirrors 206 at a second coordinate along the axis of rotation 216 different from the first coordinate, during a third scanning period the input light beam 218 may impinge onto the first mirrors 206 at a third coordinate along the axis of rotation 216 different from the first coordinate and secondcoordinate etc. For example, the coordinate along the axis of rotation 216 at which the input light beam 218 impinges onto the first mirrors 206 may be varied to carry out the scanning in a second plane after the field of view has been scanned completely in the first plane, e.g. after the second mirror arrangement 204 completed a full rotation around its axis 217.

[0059] As an exemplary configuration, the coordinate at which the input light beam 218 impinges onto the first mirrors 206 may be varied by varying the emission direction of light from a light source that is optically coupled with the beam steering system 200. As another exemplary configuration, as shown in FIG.2C, the beam steering system 200 may receive a plurality of input light beams 218, e.g. a first input light beam 218(1) at a first coordinate along the axis of rotation 216, a second input light beam 218(2) at a second coordinate along the axis of rotation 216, a third input light beam 218(3) at a third coordinate along the axis of rotation 216, etc. In this scenario, the beam steering system 200 may be optically coupled with a plurality of light sources, each emitting a respective input light beam 218(1), 218(2), 218(3). For example, the plurality of light sources may be stacked with respect to one another, e.g. may include a plurality of stacked emitters. In the scenario in FIG.2C, the active first mirror 206 may receive a plurality of input light beams 218(1), 218(2), 218(3), and direct the plurality of input light beams 218(1), 218(2), 218(3) towards the active second mirror 208(1). The active second mirror 208(1) may direct the received beams 218(1), 218(2), 218(3) towards the field of view as a plurality of output light beams 220(1), 220(2), 220(3).

[0060] For example, the active first mirror 206 may simultaneously receive the input light beams 218(1), 218(2), 218(3), thus providing a parallel scanning in a plurality of parallel planes (e.g., three planes in the exemplary configuration in FIG.2C). As another example, the active first mirror 206 may receive the input light beams 218(1), 218(2), 218(3) at different coordinates along the axis of rotation 216 in a sequence, thus providing a sequence of scanning each carried out in a respective plane. As a further example, the active first mirror 206 may receive a subset of the available input light beams 218(1), 218(2), 218(3) (e.g., by driving light emission by a subset of the available light sources), to provide scanning in a plurality of planes of interest. A “subset” of input light beams 218(1), 218(2), 218(3) may include more than one input light beam 218(1), 218(2), 218(3) but less than a total number of the available input light beams 218(1), 218(2), 218(3).

[0061] As a further exemplary configuration, as shown in FIG.2D, the scanning in a plurality of planes may be obtained by combining a plurality of beam steering sub-systems. Illustratively, the scanning in a plurality of planes may be obtained by combining a plurality of “auxiliary mirror(s)-scanner mirror” pairs, in which a first pair is configured to provide a scanning ontothe first mirrors 206 of the second pair, and in which the second pair is configured to provide the scanning of the field of view. It is understood that an “auxiliary mirror(s)-scanner mirror pair” may in principle include more than one auxiliary mirror, as discussed above. For the sake of simplicity, the term “pair” is used to describe the arrangement in FIG.2D, but the aspects discussed in relation to FIG.2D may apply in a corresponding manner to a configuration in which a beam steering sub-system includes more than one auxiliary mirror (e.g., as shown in FIG.4A and FIG.4B). It is also understood that although a configuration with two sub-systems is illustrated, the configuration may be extended to more than two sub-systems, e.g. to a configuration with a plurality of (further) sub-systems disposed around a central sub-system.

[0062] As shown in FIG.2D, the beam steering system 200 may include a second beam steering sub-system that includes a third mirror arrangement 202b (with a plurality of third mirrors 206b) and a fourth mirror arrangement 204b (with a plurality of fourth mirrors 208b). The third mirror arrangement 202b and fourth mirror arrangement 204b may generally be configured as the first mirror arrangement 202 and second mirror arrangement 204.

[0063] In this configuration, the third and fourth mirror arrangements 202b, 204b may scan the input light beam 218 onto the first beam steering sub-system that includes the first mirror arrangement 202, thus effectively defining a plurality of input light beams 218(1), 218(2), 218(3), etc. for the first mirror arrangement 202. The first mirror arrangement 202 may then receive the plurality of input light beams 218(1), 218(2), 218(3) according to the scanning of the third and fourth mirror arrangements 202b, 204b, and direct the input light beams 218(1), 218(2), 218(3) towards the second mirror arrangement 204 for illuminating the field of view. In this scenario, the overall system may be coupled with a single light source (and receive a single input light beam 218), with the scanning in multiple planes being implemented via the plurality of beam steering sub-systems.

[0064] Illustratively, the third mirrors 206b may be mounted on a third rotatable support structure, and the fourth mirrors 208b may be mounted on a fourth rotatable support structure. When a third mirror 206b is illuminated by the input light beam 218, the third mirror 206 directs the input light beam 218 towards a fourth mirror 208b of the fourth mirror arrangement 204b. The (active) fourth mirror 208b receives the input light beam 218 from the (active) third mirror 206b and directs the received light beam towards the first mirror arrangement 202, as (further) input light beam for the (active) first mirror 206 of the first mirror arrangement 202. In this scenario, the relative rotation of the third mirror arrangement 202b and fourth mirror arrangement 204b maintains the input light beam at a fixed spatial (e.g., vertical) coordinate at the first mirror arrangement 202 (along its axis of rotation 218), until the rotation of the thirdmirror arrangement 202b changes the active third mirror 204b that receives the input light beam 218. When another third mirror 204b directs the input light beam 218 towards the (active) fourth mirror 208b, the first mirror arrangement 202 is illuminated at a further fixed spatial (e.g., vertical) coordinate, etc.

[0065] In the configuration in FIG.2D, the control circuit 230 may control or cause a third rotational movement of the third rotatable support structure at a third rotational speed to vary which third mirror 206b receives the input light beam 218. The control circuit 230 may further control or cause a fourth rotational movement of the fourth rotatable support structure at a fourth rotational speed to vary which fourth mirror 208b receives the light beam from the third mirror arrangement 202b.

[0066] The control circuit 230 may select the third rotational speed and the fourth rotational speed such that the further input light beam 218(1), 218(2), 218(3) directed from the fourth mirror 208b towards the first mirror arrangement 202 reaches the (active) first mirror 206 at a fixed spatial coordinate in a direction parallel to an axis of rotation 216 of the first rotatable support structure 212, e.g. a fixed vertical coordinate. When the third rotational movement of the third rotatable support structure causes another third mirror 206b to receive the input light beam 218, the spatial coordinate at which the first mirror arrangement 202 receives the light beam from the fourth mirror arrangement 204b varies along the direction parallel to the axis of rotation 216.

[0067] In this configuration, the mirror arrangements belonging to different sub-systems may have the axes of rotation of the respective mirrors at an angle with respect to one another. Illustratively, the axes of rotation of the mirror arrangements belonging to a same sub-system (e.g., the same pair) may be parallel to one another, and may be at an angle with respect to the axes of rotation of the mirror arrangements belonging to a different sub-system (e.g., a different pair). As shown in FIG.2D, the first axis of rotation 216 of the first mirror arrangement 202 may be parallel to the second axis of rotation 217 of the second mirror arrangement 204. In a corresponding manner, the third axis of rotation 216b of the third mirror arrangement 202b may be parallel to the fourth axis of rotation 217b of the fourth mirror arrangement 204b. The axes of rotation 216, 217 of the mirror arrangements 202, 204 may be at an angle with respect to the further axes of rotation 216b, 217b of the further mirror arrangements 202b, 204b. In a preferred configuration, the axes of rotation 216, 217 may be perpendicular to the further axes of rotation 216b, 217b. It is however understood that the axes of rotation 216, 217 may be at any suitable angle greater than 0° and less than 180° with respect to the further axes of rotation 216b, 217b.

[0068] According to various aspects, as shown in FIG.2D the beam steering system 200 may further include optics 232 (e.g., an optical element, or optical system) disposed between the beam steering sub-systems and configured to provide a parallelization of the beams output from the initial beam steering sub-system (from the further second mirror arrangement 208b) to direct parallel beams towards the other beam steering sub-system.

[0069] The architecture of the mirror arrangements, e.g. in terms of size of the mirrors, number of mirror segments, etc. may be freely adapted to meet product requirements, e.g. in terms of resolution, scanning speed, and the like. In this regard, FIG.3A, FIG.3B, and FIG.3C show possible configurations of mirror arrangements of the adapted beam steering system to illustrate possible parameters and properties that may be adjusted. Illustratively FIG.3 A, FIG.3B, FIG.3C show possible configurations 300a, 300b, 300c of a first mirror arrangement 302a, 302b, 302c including a plurality of first mirrors 306 (e.g., exemplary realizations of the first mirror arrangement 202, or third mirror arrangement 202b) and of a second mirror arrangement 304a, 304b, 304c including a plurality of second mirrors 308 (e.g., exemplary realizations of the second mirror arrangement 204, or fourth mirror arrangement 204b).

[0070] In a simple configuration 300a, the first (auxiliary) mirror arrangement 302a and the second (scanner) mirror arrangement 304a may be configured in the same manner. For example, the first mirror arrangement 302a and the second mirror arrangement 304a may have the same number of mirrors 306, 308. As another example, additionally or alternatively, the first mirrors 306 and the second mirrors 308 may have the same configuration, e.g. the same dimensions. This configuration may provide a simple setup for implementing the proposed strategy.

[0071] In other aspects, as shown in the second configuration 300b in FIG.3B, the (first) mirrors 306 of the first mirror arrangement 302b may be smaller than the (second) mirrors 308 of the second mirror arrangement 304b. In general, a mirror may have a certain aperture and a certain surface area (for example a certain diameter considering a mirror with a circular surface, or a certain height / width considering a rectangular surface). A first mirror 306 may have a first aperture and a first surface area (e.g., a first diameter, a first height, a first width), and a second mirror 308 may have a second aperture and a second surface area (e.g., a second diameter, a second height, a second width).

[0072] In various aspects, the second aperture of at least one (e.g., each) second mirror 308 may be greater than the first aperture of at least one (e.g., each) first mirror 306. As a numerical example, the second aperture may be at least 1.5 times greater than the first aperture, for example at least 2 times greater than the first aperture, for example at least 5 times greater than the first aperture. The second aperture being larger may ensure that the second mirrors 308 maycover the angles generated by the first mirror(s) 306 in reflecting the input light beam towards the second mirror arrangement 304b.

[0073] In a corresponding manner, the second surface area of at least one (e.g., each) second mirror 308 may be greater than the first surface area of at least one (e.g., each) first mirror 306. As a numerical example, the second surface area may be at least 1.5 times greater than the first surface area, for example at least 2 times greater than the first surface area, for example at least 5 times greater than the first surface area. For example, a second diameter or a second height (and width) of at least one (e.g., each) second mirror 308 may be greater than the first diameter or first height (and width) of at least one (e.g., each) first mirror 306. Only as a numerical example, the first surface area of at least one (e.g., each) first mirror 306 and / or the second surface area of at least one (e.g., each) second mirror 308 may be in the range from 1 mm2(square millimeter) to 1 cm2(square centimeter), for example in the range from 10 mm2to 50 mm2.

[0074] In this configuration, the (first) rotatable support structure of the (first) auxiliary mirror may be scaled accordingly to be smaller than the (second) rotatable support structure of the (second) scanner mirror, or may have the same dimensions of the (second) rotatable support structure of the (second) scanner mirror and just the mirrors may be adapted.

[0075] In various aspects, as shown in the third configuration 300c in FIG.3C, the first mirror arrangement 302c may include more mirrors 306 than the second mirror arrangement 304c. This configuration 300c may be implemented in combination with the second configuration 300b, or with the first configuration 300a. In general, a mirror arrangement may include a certain number of mirrors (e.g., a certain number of mirror segments). The first mirror arrangement 302c may include a first number of first mirrors 306, and the second mirror arrangement 304c may include a second number of second mirrors 308. In the configuration in FIG.3C, the first number of first mirrors 306 may be greater than the second number of second mirrors 308. As a numerical example, the first number of first mirrors 306 may be at least two times greater than the second number of second mirrors 308, for example at least five times greater, for example at least ten times greater. Using more mirrors for the auxiliary mirror arrangement may increase the resolution of the beam steering, illustratively the resolution over the scanning of the field of view. In this scenario, for example, the first rotatable support structure may be a prism with a greater number of lateral sides / faces than the second rotatable support structure. It is however understood that, in principle, also the opposite configuration may be provided in which the second number of second mirrors 308 is greater than the first number of first mirrors 306. Only as a numerical example, the first number of first mirrors 306and / or the second number of second mirrors 308 may be in the range from two to fifty, e.g. in the range from three to forty, e.g. in the range from five to twenty.

[0076] As mentioned above, the capabilities of the adapted beam steering system may be enhanced by introducing a plurality of auxiliary mirrors. This configuration in which multiple sub-systems are assigned to a scanner mirror allows expanding the scanning area, e.g. up to 360°. Illustratively, with a single “first mirror arrangement” as discussed in relation to FIG.2A and FIG.2B, the scanning may be carried out in a certain angular range, e.g. in a certain “cone” originating from the scanner mirror arrangement. Introducing multiple auxiliary mirrors (and accordingly multiple input light beams) allows illuminating more than one mirror of the scanner mirror arrangement, and thus directing output beams in different directions to cover different portions of a 360° field of view around the beam steering system. As mentioned, such configuration may also improve eye safety compared to conventional approaches.

[0077] FIG.4A shows a beam steering system 400 including a plurality of auxiliary mirror arrangements 402, according to various aspects. The beam steering system 400 may illustratively include a scanner mirror arrangement 404 and a plurality of auxiliary mirror arrangements 402 disposed around the scanner mirror arrangement 404. In general, an auxiliary mirror arrangement 402 may be configured as the first mirror arrangement 202, 302 described in relation to FIG.2A to FIG.3C, e.g. the plurality of auxiliary mirror arrangements 402 may also be referred to as plurality of first mirror arrangements. In a corresponding manner, the scanner mirror arrangement 404 may be configured as the second mirror arrangement 204, 304 described in relation to FIG.2A to FIG.3C, e.g. the scanner mirror arrangement 404 may also be referred to as second mirror arrangement.

[0078] In general, the plurality of auxiliary mirror arrangements 402 may be disposed around the scanner mirror arrangement 404 at any suitable position, e.g. depending on the desired coverage of the field of view. Considering a 360° angle around the scanner mirror arrangement 404, the auxiliary mirror arrangements 402 may be disposed at any suitable angular distance from one another. For example, in the exemplary configuration in FIG.4A with eight auxiliary mirror arrangements 402, the auxiliary mirror arrangements 402 may be disposed at 45° intervals around the scanner mirror arrangement 404. As other examples, the auxiliary mirror arrangements 402 may be disposed at 30° intervals, 60° intervals, 90° intervals, etc. around the scanner mirror arrangement 404. The angular interval between auxiliary mirror arrangements 402 may be the same for each pair of auxiliary mirror arrangements 402, or may vary among different pairs of auxiliary mirror arrangements 402.

[0079] In a preferred configuration, which may enable a simpler setup and control of the mirror arrangements, the auxiliary mirror arrangements 402 may be disposed each at a same distance from the scanner mirror arrangement 404, e.g. at a same “radius” considering a circumference around the scanner mirror arrangement 404. In other aspects, different auxiliary mirror arrangements 402 may be disposed at a different distance from the scanner mirror arrangement 404, e.g. a first auxiliary mirror arrangement 402(1) may be disposed at a first distance from the scanner mirror arrangement 404, a second auxiliary mirror arrangement 402(2) may be disposed at a second distance from the scanner mirror arrangement 404 different from the first distance, etc. This other configuration may allow tailoring the setup of the beam steering system 400 to specific system requirements.

[0080] In the exemplary configuration in FIG.4A, the beam steering system 400 is shown with eight auxiliary mirror arrangements 402(l)-402(8). It is however understood that the beam steering system 400 may include any suitable number of auxiliary mirror arrangements 402, e.g. two, three, four, five, ten, or more than ten. Furthermore, in a preferred configuration, which may enable a simpler setup and control of the mirror arrangements, the auxiliary mirror arrangements 402 may have the same configuration, e.g. in terms of number of mirrors, dimensions, type of mirrors, etc. In other aspects, however, different auxiliary mirror arrangements 402 may have different configurations. As an example, a first auxiliary mirror arrangement 402(1) may have a different number of mirrors compared to a second auxiliary mirror arrangement 402(2). A third auxiliary mirror arrangement 402(3) may have a different number of mirrors compared to the first and second auxiliary mirror arrangements 402(1), 402(2), etc. As another example, a mirror of the first auxiliary mirror arrangement 402(1) may have a different aperture and / or surface area compared to a mirror of the second auxiliary mirror arrangement 402(2), etc.

[0081] In some aspects, as discussed in relation to FIG.2D, the configuration of the beam steering system 400 may be extended to a scenario in which for each auxiliary mirror arrangement 402, or for a subset of auxiliary mirror arrangements 402, a further beam steering sub-system is provided to provide scanning in a plurality of planes. Illustratively, in some aspects, the beam steering system 400 may include a plurality of further beam steering sub-systems each configured to scan an input light beam onto a respective auxiliary mirror arrangement 402 of the plurality of auxiliary mirror arrangements 402.

[0082] In general, each auxiliary mirror arrangement 402 may include a respective plurality of mirrors mounted on a respective rotatable support structure. Each auxiliary mirror arrangement 402 may be configured such that when the auxiliary mirror arrangement 402 is illuminated witha respective input light beam (not shown in FIG.4A), a mirror receives the input light beam and directs the input light beam towards the scanner mirror arrangement 404. A mirror of the scanner mirror arrangement 404 receives the input light beam and directs the input light beam towards the field of view of the beam steering system 400 (illustratively, the respective portion of field of view) as output light beam.

[0083] Each auxiliary mirror arrangement 402 may direct the respective input light beam towards a different mirror of the scanner mirror arrangement 404 (illustratively, towards a different mirror segment or face). For example, a first auxiliary mirror arrangement 402(1) may direct the respective input light beam towards a mirror of the scanner mirror arrangement 404, a second auxiliary mirror arrangement 402(2) may direct the respective input light beam towards a different mirror (or in general a different portion) of the scanner mirror arrangement 404, etc. Thus, by using a plurality of input light beams and controlling the plurality of auxiliary mirror arrangements 402 simultaneously (e.g., during the same scanning period), the simultaneous illumination of different portions of the field of view may be obtained.

[0084] For example, a first auxiliary mirror arrangement 402(1) may direct the respective input light beam towards the scanner mirror arrangement 404 to obtain a first output light beam 420(1). A second auxiliary mirror arrangement 402(2) (illustratively, a further “first” mirror arrangement) may direct the respective input light beam towards the scanner mirror arrangement 404 to obtain a second output light beam 420(2), etc.. The first output light beam 420(1) and the second output light beam 420(2) may be in a different angular range around the scanner mirror arrangement 404. For example, the first output light beam 420(1), or in general the first scanning including the first auxiliary mirror arrangement 402(1), may be in a first angular range around the scanner mirror arrangement 404. The second output light beam 420(2), or in general the second scanning including the second auxiliary mirror arrangement 402(2), may be in a second angular range around the scanner mirror arrangement 404, etc. The first angular range may be, for example, in the angular range from 0° to 45° considering a circumference around the scanner mirror arrangement 404. The second angular range may be, for example, in the angular range from 45° to 90° considering a circumference around the scanner mirror arrangement 404, etc. The input light beams impinging onto different auxiliary mirror arrangements may be at the same (vertical) coordinate along the axis of rotation of the respective auxiliary mirror arrangement, or may be at different (vertical) coordinates along the axis of rotation of the respective auxiliary mirror arrangement.

[0085] The control circuit of the beam steering system 400 (not shown in FIG.4A) may be configured to control the rotational movement of the auxiliary mirror arrangements 402 at arespective rotational speed to compensate for the rotational movement of the scanner mirror arrangement 404, as discussed in relation to FIG.2A and FIG.2B. For each auxiliary mirror arrangement 402 the control circuit may be configured to select the respective rotational speed (with respect to the rotational speed of the scanner mirror arrangement 404) such that when a mirror of the auxiliary mirror arrangement 402 receives the input light beam, the respective output light beam is at stable (fixed) spatial coordinates in the field of view until the rotational movement of the rotatable support structure causes another mirror of the auxiliary mirror arrangement 402 to receive the input light beam.

[0086] The individual rotational speeds of the auxiliary mirror arrangements 402 may be adapted depending on the respective configuration, e.g. in terms of number of mirrors, dimensions, distance from the scanner mirror arrangement 404, etc. In a simple configuration, the rotational speeds of the auxiliary mirror arrangements 402 may be equal to one another. For example, a first rotational speed of the first auxiliary mirror arrangement 402(1) may be equal to a second (or “further first”) rotational speed of the second auxiliary mirror arrangement 402(2), etc. In other aspects, different auxiliary mirror arrangements 402 may have different rotational speeds, e.g. to obtain the stable light emission for different configurations of the auxiliary mirror arrangements 402. For example, the first rotational speed of the first auxiliary mirror arrangement 402(1) may be different from the second rotational speed of the second auxiliary mirror arrangement 402(2), etc.

[0087] As discussed in relation to FIG.2A to FIG.2D, the rotation of the mirror arrangements may be realized in any suitable manner, e.g. via dedicated motors coupled with the mirror arrangements. In some aspects, as shown for the configuration 400b in FIG.4B the beam steering system 400 may include a gear arrangement 430 configured to mechanically couple the scanner mirror arrangement 404 with the auxiliary mirror arrangements 402. For the sake of simplicity FIG.4B shows only three auxiliary mirror arrangements 402(1), 402(2), 402(3) but it is understood that the aspects discussed in relation to FIG.4B may apply in a corresponding manner to any suitable number of auxiliary mirror arrangements 402 (e.g., one, two, three, four, five, etc.). It is also understood that the gear arrangement 430 may also be provided in the configuration with a single auxiliary mirror arrangement (e.g., as shown in FIG.2A).

[0088] Illustratively, the gear arrangement 430 may include a plurality of gears that provide a mechanical coupling of the mirror arrangements, such that the rotation of the scanner mirror arrangement 404 drives or causes a corresponding rotation of the auxiliary mirror arrangements 402(1), 402(2), 402(3). In this scenario, the beam steering system 400 may include a (e.g.,single) motor coupled with the scanner mirror arrangement 404 to drive its rotation, and the gears of the gear arrangement 430 may be configured to transfer the rotation of the rotatable support structure of scanner mirror arrangement 404 to the rotatable support structures auxiliary mirror arrangements 402(1), 402(2), 402(3). The gears of the gear arrangement 430 may be configured to define the respective rotational speeds of the scanner mirror arrangement 404 and auxiliary mirror arrangements 402(1), 402(2), 402(3) to obtain the scanning at fixed spatial coordinates described in relation to FIG.2A to FIG.2D.

[0089] For example, the gear arrangement 430 may include a central gear element 432 (also referred to as scanner gear) coupled with the scanner mirror arrangement 404, e.g. coupled with the support structure of the scanner mirror arrangement 404. The gear arrangement 430 may further include “auxiliary” gear elements 434(1), 434(2), 434(3) each coupled with a respective auxiliary mirror arrangement 402(1), 402(2), 402(3), e.g. with the respective rotatable support structures. In the exemplary configuration in FIG.4B, the gear arrangement 430 may include a first (auxiliary) gear element 434(1) coupled with the first auxiliary mirror arrangement 402(1) (e.g., with its support structure), a second (auxiliary) gear element 434(2) coupled with the second auxiliary mirror arrangement 402(2), a third (auxiliary) gear element 434(3) coupled with the third auxiliary mirror arrangement 402(3), etc.

[0090] The “auxiliary” gear elements 434(1), 434(2), 434(3) may each be individually coupled with the central gear element 432, e.g. directly or via one or more intermediate gears. The gear ratio of the central gear element 432 and one of the “auxiliary” gear elements 434(1), 434(2), 434(3) may be configured to define the ratio of rotational speeds that ensures directing the output beam towards the field of view at stable spatial coordinates. The configuration 400b may thus include a fixed gear box instead of individual controlled motors to adjust speed and speed ratio of individual mirrors, thus simplifying the overall mechanical setup.

[0091] FIG.5 shows a light emission system 500 including an adapted beam steering system 502, according to various aspects. In the exemplary configuration in FIG.5, the adapted beam steering system 502 may be configured as the beam steering system 200 illustrated in FIG.2A to FIG.2D. It is however understood that the aspects discussed in relation to the beam steering system 502 may apply to any suitable configuration of the beam steering system, e.g. to a configuration with a plurality of first (auxiliary) mirror arrangements as shown in FIG.4A and FIG.4B.

[0092] In general, the light emission system 500 may include the adapted beam steering system 502 and a light source 504 configured to emit light (e.g., a light beam). The light source 504 may be configured to emit a light beam towards the beam steering system 502 as input lightbeam for the auxiliary mirror arrangement (e.g., the first mirror arrangement 202). In this configuration, the field of view 510 may be a field of view or field of illumination of the light emission system. It is understood that the representation in FIG.5 may be simplified, and that the light emission system 500 may include additional components with respect to those shown, e.g. additional optical components (mirrors, lenses, beam splitters, etc.) along the propagation path of the light from the light source 504 to the auxiliary mirror arrangement.

[0093] The light source 504 may be configured to emit light having a predefined wavelength, for example in the visible range (e.g., from about 380 nm to about 700 nm), infra-red and / or near infra-red range (e.g., in the range from about 700 nm to about 5000 nm, for example in the range from about 860 nm to about 1600 nm, or for example at 905 nm or 1550 nm), or ultraviolet range (e.g., from about 100 nm to about 400 nm). Illustratively, the light source 504 may include at least one of an infrared light source, an ultraviolet light source, or a visible light source.

[0094] In principle, the light source 504 may be configured to emit a light beam having any suitable dimension (e.g., any suitable diameter, or radius). In an exemplary configuration, which may correspond to a relevant use case of the proposed approach. The light source 504 may be configured to emit a light beam having a diameter in the range from 10 mm to 2 cm, for example in the range from 50 mm to 1 cm.

[0095] In some aspects, the light source 504 may be or may include an optoelectronic light source (e.g., a laser source). As an example, the light source 504 may include one or more light emitting diodes. As another example the light source may include one or more laser diodes, e.g. one or more edge-emitting laser diodes or one or more vertical cavity surface emitting laser diodes. In some aspects, the light source 504 may be configured to emit modulated light (see also FIG.6), e.g. the light source 504 may include a driver circuit configured to control the light emission to impose a modulation on the emitted light beam (e.g., a frequency modulation, an amplitude modulation, and / or the like).

[0096] In a preferred configuration, the first (auxiliary) mirror arrangement may be disposed with respect to the light source 504 so that the first mirror(s) receive the input light beam at an angle of incidence of 0°. Illustratively, the light source 504 may emit light towards the first (auxiliary) mirror arrangement, and the light emission system 500 may be configured such that the light impinges onto the (first) mirrors of the first (auxiliary) mirror arrangement at an angle of incidence of 0°. This configuration may allow to obtain symmetrical output characteristics.

[0097] It is however understood that, in principle, also an oblique coupling of the input light beam with the first mirror arrangement may be provided. In other aspects, the first (auxiliary)mirror arrangement may be disposed with respect to the light source 504 so that the first mirror(s) receive the input light beam at an angle of incidence different from 0°, e.g. an angle of incidence in the range from 0° to 75°, for example an angle of incidence in the range from 10° to 60°, for example an angle of incidence in the range from 20° to 45°. The angle of incidence may be adapted, for example, based on system considerations, e.g. a geometry of an end device in which the light emission system 500 should be integrated.

[0098] As discussed in relation to FIG.2C, in some aspects the light source 504 may include a plurality of light sources (e.g., vertically stacked) configured to illuminate the first mirror arrangement 202 at different coordinates along the direction parallel to the axis of rotation of the first mirror arrangement 202.

[0099] In case the beam steering system 502 includes a plurality of auxiliary mirror arrangements (a plurality of “first” mirror arrangements), e.g. as shown in FIG.4A and FIG.4B, the light emission system 500 may be configured to deliver a corresponding input light beam to each auxiliary mirror arrangement. As an example, the light emission system 500 may include a respective light source 504 for each auxiliary mirror arrangement, e.g. a second light source to emit a second input light beam towards a second auxiliary mirror arrangement, a third light source to emit a third input light beam towards a third auxiliary mirror arrangement, etc. In some aspects, the different light sources may be configured in the same manner. In other aspects, different light sources may emit light with different properties (e.g., different wavelength, different power, etc.).

[0100] For example, a first light source for a first auxiliary mirror arrangement may be configured to emit light with a first wavelength (or in a first wavelength range), and a second light source for a second auxiliary mirror arrangement may be configured to emit light with a second wavelength (or in a second wavelength range) different from the first wavelength. As another example, the first light source may be configured to emit light with a first modulation (e.g., a first frequency modulation), and the second light source may be configured to emit light with a second modulation (e.g., a second frequency modulation) different from the first modulation. Using light with different properties may enable a tailored scanning of the field of view, e.g. to adapt the light emission to known or expected properties of the obstacles in the field of view.

[0101] As another exemplary configuration, the light emission system 500 may include a single light source 504, or in general fewer light sources 504 than auxiliary mirror arrangements, and may include an optical system to split the light emitted by the light source 504 into a plurality of input light beams for different auxiliary mirror arrangements.

[0102] As mentioned above, the approach proposed herein may be applied in various technical contexts. As an example, the adapted beam steering system (and corresponding light emission system) may be part of an optical sensor for light-based distance measurements, as discussed in further detail in relation to FIG.6. As other examples, a laser projection system may include the adapted beam steering system / light emission system. As a further example, a material processing device (e.g., a scanner for material treatment) may include the adapted beam steering system / light emission system.

[0103] FIG.6 shows an optical sensor 600 including the adapted beam steering system, according to various aspects. In general, the optical sensor 600 may include a light emission system 602, a light detection system 604, and a processing circuit 606. The light emission system 602 may include the adapted beam steering system described herein. For example, the light emission system 602 may be configured as the light emission system 500 shown in FIG.5. In the exemplary configuration in FIG.6, the adapted beam steering system may be configured as the beam steering system 200 illustrated in FIG.2A and FIG.2B. It is however understood that the aspects discussed in relation to the beam steering system in FIG.6 may apply to any suitable configuration of the beam steering system, e.g. to a configuration with a plurality of first (auxiliary) mirror arrangements as shown in FIG.4A and FIG.4B (and correspondingly a plurality of input light beams).

[0104] In general, the light detection system 604 may be configured to receive light from the field of view 610 of the optical sensor 100 (as reflected light 612), and the processing circuit 606 may be configured to derive information on the field of view 610 by analyzing the received light 612. Illustratively, the light detection system 604 may receive the light that is emitted by the light emission system 602 and that comes back towards the optical sensor 600 (e.g., due to back-reflection, scattering, and the like).

[0105] The light detection system 604 may be configured to deliver to the processing circuit 606 a detection signal representative of the received light 612. In general, the light detection system 604 may include a light sensing element 614 configured to provide the detection signal. The light sensing element 614 may be sensitive for light in the wavelength range in which the light emission system 602 emits light. The light sensing element 614 may be configured to receive a light signal and to provide a representation of the light signal received at the sensing element 614. As an example, the light sensing element 614 may be configured to provide an analog signal (e.g., a current or a voltage) associated with the light signal 612 received at the sensing element 614. For example, the light detection system 604 may further include a digital- to-analog converter to convert the analog detection signal into a digital signal for processing atthe processing circuit 606. In some aspects, the light detection system 604 may include a plurality of light sensing elements 614. In this configuration, the plurality of sensing elements 614 may form an array, e.g. a one-dimensional or two-dimensional array.

[0106] In some aspects, the light detection system 604 (e.g., the light sensing element 614, or each light sensing element 614) may include at least one photo diode. The photo diode may be configured to generate an analog signal (e.g., a photo current) in response to a light signal 612 (a light beam) impinging onto the photo diode. As examples, the photo diode may include at least one of a PIN photo diode, an avalanche photo diode (APD), a single photo avalanche diode, or a silicon photomultiplier.

[0107] In case the beam steering system includes a plurality of auxiliary mirror arrangements to deliver a plurality of output light beams, the light detection system 604 may include a plurality of light sensing elements 614, each associated with a corresponding auxiliary mirror arrangement to detect the reflection of the corresponding light output beam.

[0108] As shown in FIG.6, the light detection system 604 may include receiver optics 616, e.g. one or more optical components to manipulate the received light 612 prior to delivering the received light to the light sensing element 614. As examples, the receiver optics 616 may include one or more lenses, one or more mirrors, one or more filters, one or more attenuators, and the like.

[0109] In a preferred configuration, the processing circuit 606 may be configured to carry out a light-based distance measurement using the emitted / received light. For example, the optical sensor 600 may be a LiDAR sensor. For example, the light source of the light emission system 602 may be configured to emit a modulated light beam as input light beam for the auxiliary (first) mirror arrangement, and the light detection system 604 may be detect the back-reflection of the (modulated) output light beam from the field of view 610 of the optical sensor 600. The processing circuit 606 may be configured to carry out a distance measurement based on a difference between a modulation of the back-reflection of the output light beam and the modulation of the input light beam.

[0110] In a preferred configuration, the modulation may be a frequency modulation, and the processing circuit 606 may be configured to carry out the distance measurement based on a difference between the frequency of the back-reflection of the output light beam and the (initial) frequency of the input light beam. Illustratively, the optical sensor 600 may be a FMCW LiDAR sensor. In this configuration, the optical sensor 600 may include an optical system to combine part of the emitted light with the received light 612, and the processing circuit 606 may be configured to carry out the distance measurement via a Fourier transformation of the signalresulting from the combination of the emitted light with the received light 612. In this scenario the light sensing element 614 may be a balanced photodetector.

[0111] For example, in the context of FMCW LiDAR, the processing circuit 606 may be configured to carry out an integration of the received light 612 (illustratively, an integration of the signal delivered by the light sensing element 614) during the predefined measurement time / scanning period during which the output light beam remains at stable spatial coordinates due to the controlled rotation of the scanner mirror and auxiliary mirror. Illustratively, the processing circuit 606 may be configured to carry out the distance measurement for a certain spot / area in the field of view 610 during the scanning period in which one of the first mirrors of the auxiliary mirror arrangement receives the input light beam.

[0112] It is understood that the type of light emission and / or processing may be adapted depending on the desired approach. As other examples, the processing circuit 606 may be configured to carry out object recognition, object tracking, and / or object classification based on the received data, to analyze the object(s) present in the monitored scene. In some aspects, the processing circuit 606 may further control the light emission system 602, e.g. to trigger or control a light emission by the light source, and / or to instruct or control the rotational speeds of the auxiliary mirror(s) and scanner mirror(s). For example, the processing circuit 606 may act as control circuit of the beam steering system.

[0113] FIG .7A to FIG.7I show various graphs illustrating simulations of an operation of the adapted beam steering system for various configurations.

[0114] FIG.7A shows various graphs 702-714 illustrating the operation of the adapted beam steering system for different number of mirrors of the scanner mirror. The graph 702 shows the case with a scanner mirror arrangement with three mirrors (e.g., a rotatable support structure with three lateral sides), the graph 704 shows the case with a scanner mirror arrangement with four mirrors, the graph 706 shows the case with a scanner mirror arrangement with five mirrors, the graph 708 shows the case with a scanner mirror arrangement with six mirrors, the graph 710 shows the case with a scanner mirror arrangement with seven mirrors, the graph 712 shows the case with a scanner mirror arrangement with eight mirrors, the graph 714 shows the case with a scanner mirror arrangement with nine mirrors, and the graph 716 shows the case with a scanner mirror arrangement with ten mirrors. Plateaus in the emitted (output) light may be obtained by suitably controlling the rotation of the auxiliary mirror arrangement s) with respect to the scanner mirror arrangement.

[0115] FIG.7B shows a graph 720 illustrating the operation of the beam steering system simulated for the case in which the input light beam reaches the first mirror at an angle ofincidence different from 0°, illustratively an “oblique” incidence. Also in this case it may be seen that plateaus in the emitted (output) light may be obtained by suitably controlling the rotation of the auxiliary mirror arrangement s) with respect to the scanner mirror arrangement.

[0116] FIG.7C shows a graph 730 illustrating the operation of a beam steering system including a light source (denoted as (1)) that emits a light beam (2) towards a first mirror arrangement (3) illuminating a first mirror (4). The first mirror (4) directs the light beam towards a second mirror arrangement (5), e.g. towards a second mirror (6). The resulting illumination pattern is simulated considering a screen (7), and the beam position on the screen over time (8) is represented. As shown, if only the second mirror arrangement rotates while the first mirror arrangement remains stationary, the coordinates of the output light beam vary continuously. On the other hand, if both mirror arrangement rotates at suitably adapted rotational speeds stable spatial coordinates for a certain period of time may be obtained.

[0117] As mentioned above, the first mirror may be smaller in diameter since the incident beam may be fixed and well defined, whereas the second mirror may cover a wider range of angles generated by the first mirror and thus may be mechanically larger. In general, there is no rule about number of segments. The first mirror arrangement may have less segments than the second mirror arrangement, or the same number of segments as the second mirror arrangement, or more segments than the second mirror arrangement. In FIG.7C a one-dimensional scan of the field of view is illustrated. A two-dimensional scan may be obtained by combining multiple emitters, for example.

[0118] As discussed, the rotational speed may be the relevant parameter, which may be engineered taking into consideration system parameters such as mirror position and number of segments to get the desired “step-like” illumination pattern and reach a steady plateau.

[0119] FIG.7D shows three graphs 740, 742, 744 illustrating the effect of varying the ratio between the rotational speeds for a certain setup. The first graph 740 refers to the scenario in which the first mirror arrangement rotates faster than optimum. The second graph 742 refers to the scenario in which the first mirror arrangement rotates slower than optimum. The third graph 744 refers to the scenario in which the first mirror arrangement rotates at the correct rotational speed thus allowing to obtain plateaus in the illumination pattern.

[0120] The graph 750 in FIG.7E shows that the absolute resolution may be higher than the steady levels per scan. Depending on number of mirror segments, mechanical design and rotation speeds the scan patterns repeat after a certain number of scans.

[0121] FIG.7F to FIG.71 show simulations carried out with the following parameters: a first mirror arrangement with 50 mirror segments having radius 3 (in arbitrary units) and a horizontalshift to the right of 7 (in arbitrary units); and a second mirror arrangement with 12 mirror segments having radius 10 (in arbitrary units) and a horizontal shift to the left of 7 (in arbitrary units). The mirror arrangements are illuminated with a laser source, and both mirror arrangements are at the same vertical position.

[0122] A speed control is used to increase the rotation speed when going close to 0 and change rotation direction when negative. For the given example, a first rotational speed of 1.3 and a second rotational speed of 1 (in arbitrary units) may offer horizontal steady state plateaus, as shown in the graph 760 in FIG.7F. By increasing the distance between the mirrors by 10 units the steady plateaus are lost, as shown in the graph 762 in FIG.7G. The plateaus may be obtained again by slowing down rotation speed of the first mirror arrangement from 1.3 to 1.65 (illustratively, by having a second rotational speed 1.65 times greater than the first rotational speed), as shown in the graph 764 in FIG.7G.

[0123] As mentioned, the absolute rotational speeds are not the relevant parameter to obtain steady state plateaus, but rather the relative ratio between the speeds is the parameter to be adapted. This is shown in the graph 770 in FIG.7H which illustrates the operation of the beam steering system with both mirror arrangements slowed down by a factor 5.

[0124] FIG.71 shows two graphs 782, 784 illustrating the exemplary configuration in which the input light beam is not crossing mechanical components.

[0125] The term “control circuit” (or processing circuit) as used herein may be understood as any kind of technological entity that allows handling of data. The data may be handled according to one or more specific functions that the control circuit may execute. Further, a control circuit as used herein may be understood as any kind of circuit, e.g., any kind of analog or digital circuit. A control circuit may thus be or include an analog circuit, digital circuit, mixed-signal circuit, logic circuit (e.g., a hard-wired logic circuit or a programmable logic circuit), microprocessor, Central Processing Unit (CPU), Graphics Processing Unit (GPU), Digital Signal Processor (DSP), Field Programmable Gate Array (FPGA), integrated circuit, Application Specific Integrated Circuit (ASIC), etc., or any combination thereof.

[0126] The word “exemplary” is used herein to mean “serving as an example, instance, or illustration”. Any embodiment or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or designs.

[0127] The phrase “at least one” and “one or more” may be understood to include a numerical quantity greater than or equal to one (e.g., one, two, three, four, [...], etc.). The phrase “at least one of’ with regard to a group of elements may be used herein to mean at least one element from the group consisting of the elements. For example, the phrase “at least one of’ with regardto a group of elements may be used herein to mean a selection of: one of the listed elements, a plurality of one of the listed elements, a plurality of individual listed elements, or a plurality of a multiple of individual listed elements.

[0128] All acronyms defined in the above description additionally hold in all claims included herein.

[0129] While the invention has been particularly shown and described with reference to specific aspects, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The scope of the invention is thus indicated by the appended claims and all changes, which come within the meaning and range of equivalency of the claims, are therefore intended to be embraced.List of reference signs100 Optical sensor 218(2) Second input light102 Light emission system 218(3) Third input light104 Light detection system 220 Output light106 Processing circuit 220(1) First output light108 Emitted light 220(2) Second output light110 Object 220(3) Third output light112 Reflected light 222(1) First illumination spot150 Beam steering system 222(2) First illumination spot152 Rotating mirror 222(3) First illumination spot200 Beam steering system 224 Distance200b Beam steering system 230 Control circuit202 First mirror arrangement 232 Optics202b Third mirror arrangement 300a First configuration204 Second mirror arrangement 300b Second configuration204b Fourth mirror arrangement 300c Third configuration206 First mirror 302a First mirror arrangement206b Third mirror 302b First mirror arrangement206(1) First mirror segment 302c First mirror arrangement206(2) Second mirror segment 304a Second mirror arrangement206(3) Third mirror segment 304b Second mirror arrangement208 Second mirror 304c Second mirror arrangement208b Fourth mirror 306 First mirror208(1) First mirror segment 308 Second mirror208(2) Second mirror segment 400 Beam steering system208(3) Third mirror segment 400b Configuration of the beam steering210 Field of view system212 First support structure 402 Auxiliary mirror arrangements214 Second support structure 402(1) First auxiliary mirror arrangement216 First axi s of rotation 402(2) Second auxiliary mirror217 Second axis of rotation arrangement218 Input light 402(3) Third auxiliary mirror arrangement218(1) First input light 402(4) Fourth auxiliary mirror arrangement402(5) Fifth auxiliary mirror arrangement 606 Processing circuit402(6) Sixth auxiliary mirror arrangement 610 Field of view402(7) Seventh auxiliary mirror 612 Received light arrangement 614 Light sensing element402(8) Eighth auxiliary mirror arrangement 616 Receiver optics404 Scanner mirror arrangement 702 First graph420(1) First output light beam 704 Second graph420(2) Second output light beam 706 Third graph420(3) Third output light beam 708 Fourth graph420(4) Fourth output light beam 710 Fifth graph420(5) Fifth output light beam 712 Sixth graph420(6) Sixth output light beam 714 Seventh graph420(7) Seventh output light beam 716 Eighth graph420(8) Eighth output light beam 720 Graph430 Gear system 730 Graph432 Central gear element 740 First graph434(1) First gear element 742 Second graph434(2) Second gear element 744 Third graph434(3) Third gear element 750 Graph500 Light emission system 760 Graph502 Beam steering system 762 First graph504 Light source 764 Second graph510 Field of view 770 Graph600 Optical sensor 782 First graph602 Light emission system 784 Second graph604 Light detection system

Claims

Claims1. A beam steering system (200) comprising: a first mirror arrangement (202) comprising a plurality of first mirrors (206) mounted on a first rotatable support structure (212); a second mirror arrangement (204) comprising a plurality of second mirrors (208) mounted on a second rotatable support structure (214), wherein the first mirror arrangement (202) and the second mirror arrangement (204) are configured such that when the first mirror arrangement (202) is illuminated with an input light beam (218) a first mirror (206) of the plurality of first mirrors (206) receives the input light beam (218) and directs the input light beam (218) towards the second mirror arrangement (204), and a second mirror (208) of the plurality of second mirrors (208) receives the input light beam (218) from the first mirror (206) and directs the input light beam (218) towards a field of view (210) of the beam steering system (200) as output light beam (220); and a control circuit (230) configured to: control a first rotational movement of the first rotatable support structure (212) at a first rotational speed, wherein the first rotational movement of the first rotatable support structure (212) varies which first mirror (206) of the plurality of first mirrors (206) receives the input light beam (218); and control a second rotational movement of the second rotatable support structure (214) at a second rotational speed, wherein the second rotational movement of the second rotatable support structure (214) varies which second mirror (208) of the plurality of second mirrors (208) receives the input light beam (218) from the first mirror (206), wherein the control circuit (230) is configured to select the first rotational speed and the second rotational speed such that the output light beam (220) directed from the second mirror (208) towards the field of view (210) of the beam steering system (200) remains at fixed spatial coordinates in the field of view (210) until the first rotational movement of the first rotatable support structure (212) causes another first mirror (206)of the plurality of first mirrors (206) to receive the input light beam (218) and direct the input light beam (218) towards the second mirror arrangement (204).

2. The beam steering system (200) according to claim 1, wherein the first mirror arrangement (202) and the second mirror arrangement (204) are configured such that when the other first mirror (206(2)) of the plurality of first mirrors (206) receives the input light beam (218) and directs the input light beam (218) towards the second mirror arrangement (204), the output light beam (220) directed from the second mirror (208) towards the field of illumination remains at further fixed spatial coordinates in the field of illumination until the first rotational movement of the first rotatable support structure (212) causes another further first mirror (206(3)) of the plurality of first mirrors (206) to receive the input light beam (218) and direct the input light beam (218) towards the second mirror arrangement (204).

3. The beam steering system (200) according to claim 1 or 2, wherein the control circuit (230) is configured to maintain the first rotational speed constant during a predefined scanning period in which the first rotational movement causes a plurality of first mirrors (206) to receive the input light beam (218); and / or wherein the control circuit (230) is configured to maintain the second rotational speed constant during the predefined scanning period in which the second rotational movement causes a plurality of second mirrors (208) to receive the input light beam (218) from the first mirror (206).

4. The beam steering system (200) according to any one of claims 1 to 3, wherein the plurality of first mirrors (206) comprises a first number of first mirrors (206); wherein the plurality of second mirrors (208) comprises a second number of second mirrors (208); andwherein the first number is greater than the second number.

5. The beam steering system (200) according to any one of claims 1 to 4, wherein at least one first mirror (206) of the plurality of first mirrors (206) has a first aperture; wherein at least one second mirror (208) of the plurality of second mirrors (208) has a second aperture; and wherein the second aperture is greater than the first aperture.

6. The beam steering system (200) according to any one of claims 1 to 5, wherein a ratio of the second rotational speed to the first rotational speed is in the range from 1 to 2.

7. The beam steering system (200) according to any one of claims 1 to 6, further comprising: a third mirror arrangement (202b) comprising a plurality of third mirrors (206b) mounted on a third rotatable support structure; a fourth mirror arrangement (204b) comprising a plurality of fourth mirrors (208b) mounted on a fourth rotatable support structure, wherein the third mirror arrangement (202b) and the fourth mirror arrangement (204b) are configured such that when the third mirror arrangement (202b) is illuminated with the input light beam (218) a third mirror (206b) of the plurality of third mirrors (206b) receives the input light beam (218) and directs the input light beam (218) towards the fourth mirror arrangement (204b), and a fourth mirror (208b) of the plurality of fourth mirrors (208b) receives the input light beam (218) from the third mirror (206b) and directs the input light beam (218) towards the first mirror arrangement (202) as input light beam (218(1), 218(2), 218(3)) for the first mirror arrangement (202).The beam steering system (200) according to claim 7, wherein the control circuit (230) is further configured to: control a third rotational movement of the third rotatable support structure at a third rotational speed, wherein the third rotational movement of the third rotatable support structure varies which third mirror (206b) of the plurality of third mirrors (206b) receives the input light beam (218); and control a fourth rotational movement of the fourth rotatable support structure at a fourth rotational speed, wherein the fourth rotational movement of the fourth rotatable support structure varies which fourth mirror (208b) of the plurality of fourth mirrors (208b) receives the input light beam (218) from the third mirror (206b), and wherein the control circuit (230) is configured to select the third rotational speed and the fourth rotational speed such that the input light beam (218(1), 218(2), 218(3)) directed from the fourth mirror (208b) towards the first mirror arrangement (202) reaches a first mirror (206) at a fixed spatial coordinate in a direction parallel to an axis of rotation(216) of the first rotatable support structure (212), until the third rotational movement of the third rotatable support structure causes another third mirror (206b) of the plurality of third mirrors (206b) to receive the input light beam (218) and direct the input light beam (218) towards the fourth mirror arrangement (204b). The beam steering system (200) according to claim 7 or 8, wherein the first rotatable support structure (212) has a first axis of rotation (216), wherein the second rotatable support structure (214) has a second axis of rotation(217) parallel to the first axis of rotation (216), wherein the third rotatable support structure has a third axis of rotation (216b), wherein the fourth rotatable support structure has a fourth axis of rotation (217b) parallel to the third axis of rotation (216b), and wherein the first axis of rotation and second axis of rotation are at an angle greater than 0° and less than 180° with the third axis of rotation and fourth axis of rotation.

10. The beam steering system (200, 400) according to any one of claims 1 to 9, further comprising: a further first mirror arrangement (402(2)) comprising a plurality of further first mirrors mounted on a further first rotatable support structure, wherein the further first mirror arrangement (402(2)) and the second mirror arrangement (204, 404) are configured such that when the further first mirror arrangement (402(2)) is illuminated with a further input light beam a further first mirror of the plurality of further first mirrors receives the further input light beam and directs the further input light beam towards the second mirror arrangement (204, 404), and a second mirror of the plurality of second mirrors receives the further input light beam from the further first mirror and directs the further input light beam towards the field of illumination of the beam steering system (200, 400) as further output light beam (420(2)); and wherein the control circuit (230) is further configured to: control a further first rotational movement of the further first rotatable support structure at a further first rotational speed, wherein the further first rotational movement of the further first rotatable support structure varies which further first mirror of the plurality of further first mirrors receives the further input light beam; and wherein the control circuit (230) is configured to select the further first rotational speed and the second rotational speed such that the further output light beam (420(2)) directed from the second mirror towards the field of illumination of the beam steering system (200, 400) remains at fixed spatial coordinates in the field of illumination until the further first rotational movement of the further first rotatable support structure causes another further first mirror of the plurality of further first mirrors to receive the further input light beam and direct the further input light beam towards the second mirror arrangement (204, 404).

11. The beam steering system (200, 400) according to claim 10, wherein the first mirror arrangement (202, 402(1)), the second mirror arrangement (204, 404) and the further first mirror arrangement (402(2)) are configured such that the illuminated first mirror and the illuminated further first mirror direct the input lightbeam and the further input light beam towards different second mirrors of the plurality of second mirrors.

12. The beam steering system (200, 400) according to claim 10 or 11, further comprising: a gear arrangement (434) configured to mechanically couple the second mirror arrangement (204, 404) with the first mirror arrangement (202, 402(1)) and with the further first mirror arrangement (402(2)), wherein the gear arrangement (434) is configured to cause a transfer of the rotational movement of the second rotatable support structure to the first rotatable support structure and further first rotatable support structure to cause a corresponding rotational movement of the first rotatable support structure and further rotational movement of the further first rotatable support structure.

13. A light emission system (500) comprising: the beam steering system (200, 502) according to any one of claims 1 to 12; and a light source (504) configured to emit a light beam towards the beam steering system (200, 502) as input light beam (218) for the first mirror arrangement (202).

14. The light emission system (500) according to claim 13, wherein the light source (504) comprises a plurality of light sources, wherein each light source of the plurality of light sources is configured to emit a respective light beam as input light beam for the first mirror arrangement (202) at a respective spatial coordinate along the axis of rotation (216) of the first mirror arrangement (202).

15. An optical sensor (600) comprising: the light emission system (500, 602) according to claim 13 or 14,wherein the light source (504) is configured to emit a modulated light beam as input light beam (218) for the first mirror arrangement (202); a light detection system (604) configured to detect a back-reflection of the output light beam (220) from a field of view (210, 610) of the optical sensor (600); and a processing circuit (606) configured to carry out a distance measurement based on a difference between a modulation of the back-reflection of the output light beam (220) and the modulation of the input light beam (218).

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