DE112023000936T5 - Hybrid Two-Dimensional Steering Lidar - Google Patents

Abstract

An optical emitter device includes an emitter assembly including a plurality of endfire tapers, each endfire taper configured to selectively emit a respective light beam. A lens system is configured to shape and direct each light beam based on a position of the respective endfire taper relative to an optical axis of the lens system. A rotating reflector including an axis of rotation perpendicular to the optical axis of the lens system is configured to redirect and scan the light beams through a scanning region.

Description

technical field

The present disclosure relates to an optical emitter device, and more particularly to an optical emitter device used in a light detection and ranging (LIDAR) system.

background

On-chip photonics can integrate components such as lasers, detectors and switches in a compact and cost-effective manner. However, for beam forming and two-dimensional beam steering, on-chip photonics consumes a lot of energy and can be architecturally complex. On the other hand, using free-space optics, e.g. lenses and mirrors, for beam forming and beam steering can be architecturally simple and energy efficient, but other discrete components, such as lasers, receivers and switches, are bulky and more expensive than their on-chip counterparts. For demanding applications requiring very high resolution or points per second, the aforementioned problems lead to either bulky and costly LIDAR systems consisting entirely of free-space elements, i.e. multiple lasers, detectors and switches, or to energy-hungry LIDAR systems with limited field of view and low signal-to-noise ratio (SNR) fabricated with purely integrated photonics, e.g. an optical phase array. The present disclosure describes a low-cost and compact hybrid lidar system architecture that combines the best of both worlds, where the photonics chip integrates the laser, detector, and switches, and free-space optics, e.g., mirrors and lenses, are used for beam steering and beam shaping.

Slow response times of thermo-optic switches used in on-chip photonics are a major limiting factor for achieving ultrafast optical beam steering. On-chip optical phased arrays (OPAs) also suffer from high insertion losses, which lead to high power consumption, low frame rate and low signal-to-noise ratio.

One-dimensional OPAs also require wavelength tuning to direct the beam in two dimensions. The range of wavelength tuning is typically in the tens or hundreds of nanometers to obtain a field of view greater than 30°. However, wide-bandwidth, narrow-linewidth tunable lasers (for FMCW lidar) are difficult to design and manufacture.

Summary

• eine erste Emitteranordnung, die eine Vielzahl an ersten Punktemittern umfasst, wobei jeder jeweilige erste Punktemitter so konfiguriert ist, dass er einen jeweiligen ersten Ausgangslichtstrahl emittiert, und so konfiguriert ist, dass er einen jeweiligen ersten Eingangslichtstrahl empfängt;
• ein erstes Linsensystem, das so konfiguriert ist, dass es jeden jeweiligen ersten Ausgangslichtstrahl und jeden jeweiligen ersten Eingangslichtstrahl basierend auf einer Position jedes jeweiligen ersten Punktemitters relativ zu einer ersten optischen Achse des ersten Linsensystems formt und lenkt; und
• einen rotierenden Reflektor, der so konfiguriert ist, dass er jeden jeweiligen ersten Ausgangslichtstrahl in einem Winkel zu der ersten optischen Achse nach außen umlenkt, und der so konfiguriert ist, dass er jeden jeweiligen ersten Eingangslichtstrahl auf die erste Emitteranordnung umlenkt.

Accordingly, a first apparatus includes an optical emitter device comprising:

• a first emitter arrangement comprising a plurality of first point emitters, each respective first point emitter configured to emit a respective first output light beam and configured to receive a respective first input light beam;
• a first lens system configured to shape and direct each respective first output light beam and each respective first input light beam based on a position of each respective first point emitter relative to a first optical axis of the first lens system; and
• a rotating reflector configured to redirect each respective first output light beam outwardly at an angle to the first optical axis and configured to redirect each respective first input light beam onto the first emitter assembly.

Short description of the drawings

• 1 ist eine Draufsicht gemäß einem Ausführungsbeispiel der vorliegenden Offenbarung;
• 2A ist eine Seitenansicht der Vorrichtung aus 1 mit dem rotierenden Spiegel in einer ersten Position;
• 2B ist eine Seitenansicht der Vorrichtung aus 1 mit dem rotierenden Spiegel in einer zweiten Position;
• 3A ist eine Draufsicht auf einen Teil des optischen Emitter-Chips der Vorrichtung von 1;
• 3B ist eine Draufsicht auf einen Teil einer anderen beispielhaften Ausführungsform des optischen Emitter-Chips der Vorrichtung von 1;
• 3C ist eine Draufsicht auf einen Teil einer anderen beispielhaften Ausführungsform des optischen Emitter-Chips der Vorrichtung von 1;
• 3D ist eine Draufsicht auf einen Teil einer anderen beispielhaften Ausführungsform des optischen Emitter-Chips der Vorrichtung von 1;
• 4 ist eine Querschnittsansicht eines beispielhaften optischen Emitter-Chips der Vorrichtung von 1;
• 5 ist eine Querschnittsansicht eines anderen beispielhaften optischen Emitter-Chips der Vorrichtung von 1;
• 6 ist eine Draufsicht auf den optischen Emitter-Chip der Vorrichtung von 5;
• 7 ist eine Draufsicht gemäß einem Ausführungsbeispiel der vorliegenden Offenbarung;
• 8 ist eine Seitenansicht der Vorrichtung von 4; und
• 9 ist eine Seitenansicht eines weiteren Ausführungsbeispiels der vorliegenden Offenbarung;
• 10 ist eine Draufsicht gemäß einem Ausführungsbeispiel der vorliegenden Offenbarung;
• 11 ist eine Seitenansicht der Vorrichtung aus 10;
• 12 ist ein schematisches Diagramm eines Transceiverteils einer der vorgenannten Ausführungsformen;
• 13 ist ein Diagramm eines optischen Lichtwellenleiters des Transceivers aus 12;
• 14 ist ein Querschnitt einer Linse für einige der vorgenannten Ausführungsformen; und
• 15 ist ein Diagramm eines Durchhangs (mm) gegen die Position von der optischen Achse der Linse von 14.

Some embodiments will be described in more detail with reference to the accompanying drawings, in which:

• 1 is a plan view according to an embodiment of the present disclosure;
• 2A is a side view of the device from 1 with the rotating mirror in a first position;
• 2B is a side view of the device from 1 with the rotating mirror in a second position;
• 3A is a plan view of a portion of the optical emitter chip of the device of 1 ;
• 3B is a plan view of a portion of another exemplary embodiment of the optical emitter chip of the device of 1 ;
• 3C is a plan view of a portion of another exemplary embodiment of the optical emitter chip of the device of 1 ;
• 3D is a plan view of a portion of another exemplary embodiment of the optical emitter chip of the device of 1 ;
• 4 is a cross-sectional view of an exemplary optical emitter chip of the device of 1 ;
• 5 is a cross-sectional view of another exemplary optical emitter chip of the device of 1 ;
• 6 is a top view of the optical emitter chip of the device of 5 ;
• 7 is a plan view according to an embodiment of the present disclosure;
• 8 is a side view of the device of 4 ; and
• 9 is a side view of another embodiment of the present disclosure;
• 10 is a plan view according to an embodiment of the present disclosure;
• 11 is a side view of the device from 10 ;
• 12 is a schematic diagram of a transceiver portion of one of the aforementioned embodiments;
• 13 is a diagram of an optical fiber of the transceiver from 12 ;
• 14 is a cross-section of a lens for some of the aforementioned embodiments; and
• 15 is a graph of sag (mm) versus position of the optical axis of the lens of 14 .

Detailed description

Although the present teachings are described in connection with various embodiments and examples, it is not intended that the present teachings be limited to those embodiments. On the contrary, the present teachings encompass various alternatives and equivalents, as may be recognized by those skilled in the art.

With reference to the 1 , 2A and 2B a device includes an optical device 1, e.g. LIDAR, which according to an exemplary embodiment comprises: an optical emitter chip 2, a lens system 3 and a rotating reflector, e.g. a mirror, 4. For beam shaping, one or more highly collimated output beams 5 _o may be emitted when a point emitter 6 ₁ to 6 _n of the optical emitter chip 2 is arranged close to or substantially on the focal plane F of the lens system 3 (infinite conjugation). Reverse propagation also applies based on the reciprocity theorem, where a parallel input beam 5 _i , e.g. one of the output beams 5 _o , reflected from an object and shining on the lens system 3, is focused at a point to be captured by one of the point emitters 6 ₁ to 6 _n with a slight scattering determined by lens aberration and diffraction. For beam steering, the far-field beam angle α of the shaped, e.g. substantially collimated or focused, output beam 5 _o depends on the position of the point emitter 6 ₁ to 6 _n on the focal plane F relative to the longitudinal optical center axis OA of the lens system 3. The following equation applies to the beam angle α: α = arctan(d/f), where d is the distance from the center of the focal plane, ie the point at which the optical axis OA coincides with the focal plane F, and f is the focal length of the lens system 3. Therefore, a complete LIDAR system can be implemented by placing the optical emitter chip 2 of the point emitters 6 ₁ to 6 _n on or near the focal plane F of the lens system 3 and then, with the aid of a control processor 20, selectively switching selected and unselected point emitters 6 ₁ to 6 _n on and off, respectively, to direct the one or more output beams 5 _o in the desired directions with the desired beam angles α. This method is fundamentally different from optical phase-controlled arrangements, since the relative optical phase between the emitters does not need to be controlled and only one point emitter 6 ₁ to 6 _n is switched on at a time. Furthermore, a plurality of point emitters 6 ₁ to 6 _n can be activated simultaneously or sequentially by the control processor 20 to emit a plurality of output beams 5 _o pointing in different directions, ie with different beam angles α ₁ to α _n .

The optical emitter chip 2 may include: a main substrate 7 for supporting an optical waveguide structure comprising an optical emitter assembly 10 comprising a plurality of optical waveguide cores 8 surrounded by a cladding, each optical waveguide core 8 comprising a main optical waveguide core coupled to and terminating at one of the point emitters 6 ₁ to 6 _n . Ideally, the point emitters 6 ₁ to 6 _n are arranged in an array of point emitters 6 ₁ to 6 _n comprising a column (or row) of aligned point emitters 6 ₁ to 6 _n . Preferably, the point emitters 6 comprise ₁ to 6 _n end-fire tapers 9. The optical emitter chip 2 may include the optical waveguide structure comprising one or more optical waveguide layers configured to form the optical waveguide cores 8 with the end-fire tapers 9 coupled to their outer ends, all surrounded by a cladding, ie a material with a lower refractive index. As can be seen from the 2A and 2B , the optical emitter assembly 10 including the point emitters 6 ₁ to 6 _n , the optical fiber cores 8 and the end-fire tapers 9 may be coplanar with the optical axis OA of the lens system 3. The optical fiber cores 8 and the end-fire tapers 9 may comprise silicon (Si) or silicon nitride (SiN), or both Si and SiN, or any other suitable optical fiber core material. The optical fiber structure may be mounted, e.g. grown, on the main substrate 7 with upper and lower cladding 12 and 13 surrounding the optical fiber cores 8 and the end-fire tapers 9. The upper and lower cladding 12 and 13 may be made of an oxide material, e.g. silicon dioxide (SiO ₂ ), e.g. B. 2-5 µm thick, and the main substrate 7 may be made of silicon, quartz or other suitable material. At least some of the endfire tapers 9 may be between 25 µm and 400 µm long and taper from the original width of the optical fiber core 8, e.g. between 400 nm and 500 nm wide and between 200 nm and 250 nm thick, to a tip having a width between 100 nm and 400 nm and the original thickness, e.g. between 200 nm and 250 nm, for example by 25% to 75%, preferably by about 50%, although the thickness may also be tapered to less than the optical fiber core 8 if required. Preferably, the ends of the endfire tapers 9 may be symmetrical, e.g. B. square (200 nm x 200 nm) to ensure that the TE and TM modes at the endfire tapers are substantially the same size. At least some of the endfire tapers 9, e.g. the point emitter 6 ₅ , may comprise inverted tapers that expand, at least in width, from the original dimensions, e.g. the width, of the optical fiber core 8 to a larger width, e.g. 2 to 10 times wider or to a width between 1 µm and 4 µm. The thickness may also be increased if necessary. Some of the endfire tapers 9 may narrow in width and some of the endfire tapers 9 may widen in width. Some of the endfire tapers 9 may narrow more or less than other endfire tapers 9, and some of the endfire tapers 9 may widen more or less than the other endfire tapers 9.

With reference to the 3A to 3D , a small gap g comprising the same material as the cladding may be present between the edge of the optical emitter chip 2 and the end of each endfire taper 9. The gap g may be 0 nm up to 5 µm, preferably 500 nm to 1 µm. The gap g may be the same or different for some or all of the endfire tapers 9. With reference to 3B some of the end-fire tapers 9 may be configured to extend and terminate at an acute angle to the waveguide core 8 and/or a longitudinal central axis of the optical emitter chip 2 and/or the optical axis OA of the lens system 3. In other words, a longitudinal axis of the end-fire taper 9 is arranged at an acute angle relative to a longitudinal axis of the waveguide core 8 and/or the optical axis OA of the lens system 3. In this way, the main ray of light emitted from the end-fire taper 9 toward the lens system 3 or focused by the lens system 3 onto the end-fire taper 9 may be inclined relative to the optical axis OA, i.e. the lens system 3 does not have to be image space telecentric. Such a property can significantly simplify the design of the lens system 3.

Ideally, some or all of the endfire tapers 9 are arranged at an acute angle such that the light emitted from the endfire tapers 9 into free space is parallel to the designed chief ray angle of the lens system 3 at the location in the image plane corresponding to the endfire taper 9. Some of the endfire tapers 9 may be configured to extend substantially in the direction of the optical axis OA and/or the longitudinal central axis of the optical emitter chip 2, i.e. the optical emitter assembly 10. Some of the endfire tapers 9 may extend at a larger acute angle than other endfire tapers 9. Preferably, the acute angle is the larger the further away from the optical axis OA of the lens system 3. Accordingly, the length of the gap g may vary along the arrangement of the end-fire tapers 9. The ends of each end-fire taper 9 may extend to the same distance from the edge of the optical emitter chip 2, ie the same gap length g, with each point emitter 6 ₁ to 6 _n lying substantially along or near a straight focal plane F. Accordingly, some of the end-fire tapers 9 may have a different length than other end-fire tapers 9, and in particular the end-fire tapers 9 at the outer edges of the optical emitter chip 2 are longer than the end-fire tapers 9 in the middle of the optical emitter chip 2, and/or the end-fire tapers 9 gradually increase in length, starting with shorter end-fire tapers 9 in the middle of the optical emitter chip 2, e.g. along the longitudinal central axis of the optical emitter chip 2 and/or the optical axis OA of the lens system 3, and ending at the outer end-fire tapers 9 with longer end-fire tapers 9. Alternatively, the end-fire tapers 9 may all be the same length, but the main optical waveguide cores 8 may be of different lengths to accommodate the different gaps g between the end-fire tapers 9 and the edge of the optical emitter chip 2. emitter chips 2. The optical fiber cores 8 and the end-fire tapers 9 may also be connected by a gradual bend instead of a sharp transition. In some embodiments, the different gap length g may be accommodated by different radii or lengths of these gradual bends. The ends of the end-fire tapers 9 may be perpendicular to the edge of the optical emitter chip 2 and/or perpendicular to the longitudinal center axis of the end-fire taper 9.

With reference to the 3C and 3D , some or all of the endfire tapers 9 may be arranged such that each point emitter 6 ₁ to 6 _n lies substantially along or near a curved focal plane F corresponding to the curved focal plane F of the lens system 3. This curved focal plane F may be approximately spherical, corresponding to a non-zero Petzval sum of the lens system 3, or it may be aspherical. The lens system 3 and the shape of the focal plane F may optimally be designed together such that the curvature of the focal plane F helps to reduce optical aberrations in the lens system 3 or to simplify its design, for example to enable the lens system 3 to comprise fewer elements.

With reference to 3D , the edge of the optical emitter chip 2 may be etched further downwards to form a trench 15, the substantially curved edge of which may extend substantially along or parallel to the curved focal plane F, with the end-fire tapers 9 terminating near the edge of the curved trench 15, e.g. with the gap g therebetween. The ends of each end-fire taper 9 may extend to an equal distance from the edge of the optical emitter chip 2, e.g. the same gap length g, with each point emitter 6 ₁ to 6 _n lying substantially along or near the curved focal plane F. The trench 15 may, if required, also be etched away completely through the upper cladding 12 and the lower cladding 13 and optionally the substrate 7 in order to avoid that the light emerging from the end-fire tapers 9 hits the lower surface of the trench 15, e.g. when the curvature of the trench 15 has a large sagitta. Alternatively, the trench 15 may be partially etched and the substrate 7 thinned from the back until no material remains in the area defined by the trench 15. For sufficiently small sagittas, partial etching of the trench 15 may be sufficient. The ends of the end-fire tapers 9, i.e. their longitudinal central axis, may be directed substantially perpendicular or at an acute angle to the tangent of the edge of the trench 15. The edge of the trench 15 may be curved, e.g. B. colinear or parallel to the curved focal plane F, or may include a series of steps, e.g. one step for each point emitter 6 ₁ to 6 _n . Accordingly, the gap g of the cladding material, ie between the end of the end-fire taper 9 and the curved trench 15, may again have substantially the same length of cladding material for each end-fire taper 9.

With reference to the 3A to 3D , which show a section of the optical emitter arrangement 10 on the optical emitter chip 2, the positions of the point emitters 6 ₁ to 6 _n along the direction perpendicular to the optical axis OA or the edge of the optical emitter chip 2 can be arranged regularly, i.e. at the same distance from each other, or irregularly, i.e. at different distances from each other. The position of the point emitters 6 ₁ to 6 _n with respect to the optical axis OA, in conjunction with the design, i.e. the focal length, of the lens system 3, determines the beam angle α of the output beam 5 _o leaving the lens system 3 and entering free space. In some embodiments, the point emitters 6 ₁ to 6 _n , i.e. the endfire tapers 9, can be intentionally irregularly spaced to address a non-uniform family of angles with the output beams 5 _o . In some embodiments, the lens system 3 may have distortions so that a regular spacing of the point emitters 6 ₁ to 6 _n may produce an irregular angular spacing of the output beams 5 _o . To compensate for such distortions, the spacing of the point emitters 6 ₁ to 6 _n , i.e. the end-fire tapers 9, can be varied and made irregular in the opposite direction so that the angular spacing when leaving the lens system 3 is substantially uniform.

One or more of the above-described changes to the endfire tapers 9 and the facet design may be combined in a single embodiment. In particular, a layout of the point emitters 6 ₁ to 6 _n that allows for focal plane curvature, arbitrary chief ray angle, and corrected distortion significantly relieves the design constraints of the lens system 3 and may allow it to be built from a single element, even at low f-numbers.

4 shows a cross-section of the optical emitter chip 2, i.e. shows one of the point emitters 6 _n in the optical emitter array 10. The array of point emitters 6 ₁ - 6 _n may include some or all of the optical fiber cores 8 consisting of one or two optical fiber layers configured to form single or dual layer optical fiber cores 8 or 8' and single or dual layer endfire tapers 9 or 9', respectively. Incorporating a second layer of optical fiber core material allows the development of mode profiles that also allow for changing the NA of the point emitters 6 ₁ - 6 _n , i.e. launching light into a coupled mode with a wider mode spread results in a smaller NA. The two-layer optical fiber cores 8' and the two-layer end-fire tapers 9' may be made of two similar optical fiber core materials with similar refractive indices, e.g. both silicon (Si) or both silicon nitride (SiN), or of two different optical fiber core materials with different refractive indices, such as a first refractive index, e.g. Si, greater than a second refractive index, e.g. SiN, or of any other suitable optical fiber core material. The optical fiber cores 8 or 8' may be mounted, e.g. grown on, the main substrate 7, with the upper and lower claddings 12 and 13 surrounding and sandwiching the two optical fiber cores 8' and the end-fire tapers 9'. The upper and lower claddings 12 and 13 may be made of an oxide material such as silicon dioxide (SiO ₂ ), eg about 2-4 µm thick, preferably about 3 µm thick, and the main substrate 7 may be made of silicon or another suitable material.

With reference to the 5 and 6 , to further reduce the NA of the point emitters 6 ₁ to 6 _{n ,} a suspended optical fiber structure 50 may be provided which is optically coupled to the end of some or all of the endfire tapers 9 or 9'. The suspended optical fiber structure 50 may consist of the cladding material, e.g. SiO ₂ , which now forms the optical fiber core, and surrounded by a pocket of a material with a lower refractive index, e.g. air, which forms the cladding. The suspended optical fiber structure 50 may be suspended above the main substrate 7 by removing one or more of the substrate materials from the main substrate 7 and/or the cladding material from the upper and lower claddings 12 and 13 below and/or around the suspended optical fiber structure 50 so as to form a pocket or chamber 51 around the suspended optical fiber structure 50. Accordingly, the NA for the suspended optical fiber structure 50/endfire tapers 9 or 9' can be reduced to less than about 0.25, preferably less than about 0.2. The suspended optical fiber structure 50 can extend about 2 µm to 50 µm into the chamber 51, while the endfire taper 9 or 9' can extend slightly into the chamber 51, but less than the entire length of the suspended optical fiber structure 50. The suspended optical fiber structure 50 can have a thickness, e.g., about 6 µm to 8 µm, equal to the entire optical emitter assembly 10, or can be made thinner than the optical emitter assembly 10 by the local removal of a portion of the top cladding 12. The suspended optical fiber structure 50 can have a constant width approximately equal to the thickness, e.g., about 1 µm to 2 µm. B. about 6 µm to 8 µm. The suspended optical waveguide structure 50 may include tapered side and/or top and/or bottom walls, ie, taper in width and/or height towards the outer free end (dashed lines), or it may include conversely tapered side and/or top and/or bottom walls, ie, widen in width and/or height towards the outer free end, ie, along a light transmission direction. Ideally, the endfire taper 9 or 9' is located both vertically and horizontally in the middle of the waveguide structure 50.

The lens system 3 may comprise a variety of lens elements if required. Most of the design of the lens system 3 is a compromise between the f-number, the field of view and the aperture size. However, there may be some design priorities: e.g. a) having a telecentric design for the image plane where the chief rays from the point emitters 6 ₁ to 6 _n are all parallel to the optical axis OA in the image space, b) achieving the diffraction limit in the entire field of view and c) the numerical aperture (NA) in the image space of the lens system 3 substantially equals or exceeds the NA the point emitters 6 ₁ to 6 _n . Minimizing the effect of curvature aberrations of the lenses enables the least scattering of the output beams 5 _o and the best possible focusing of the received input beams 5 _i . The point emitters 6 ₁ to 6 _n preferably emit output beams 5 _o at a beam angle that can be fully captured and transmitted by the lens system 3. For example, if the NA of one or more of the point emitters 6 ₁ to 6 _n is greater than the image space NA of the lens system 3, then part of the light emitted by the point emitters 6 ₁ to 6 _n is not transmitted through the lens system 3 and is therefore counted as a loss.

The optical device 1 may also include at least one light source, preferably an array of light sources, and at least one photodetector, preferably an array of photodetectors, optically coupled to one or more corresponding point emitters 6 ₁ to 6 ₂ in the optical emitter chip 2. Preferably, the array of light sources and the array of light detectors comprise an array of transceivers 11 ₁ to 11 _n . Each transceiver 11 ₁ to 11 _n may comprise a light source, e.g. a laser, that generates at least one of the output beams 5 _o , and one or more photodetectors that detect at least one of the input beams 5 _i . The selective transmission and reception of light to and from the point emitters 6 ₁ to 6 _n may be accomplished by a switching matrix 16 between the transceivers 11 ₁ to 11 _n and the point emitters 6 ₁ to 6 _n . Accordingly, to select a desired point emitter 6 ₁ to 6 _n corresponding to a desired beam angle α, the control processor 20 may select one or more of the light sources in one of the transceivers 11 ₁ to 11 _n corresponding to one or more of the point emitters 6 ₁ to 6 _n in that row or column by turning on and/or off various switches 14 in the switch matrix 16. For example, with four point emitters 6 ₁ to 6 ₄ (m=4) in the row or column of point emitters 6 ₁ to 6 _n connected to the first transceiver 11 ₁ , the switch matrix 16 may have a single input port optically coupling the first transceiver 11 ₁ to a first switch tree comprising (m-1=3) switches 14, e.g. 2x2 on-chip Mach-Zehnder interferometers (MZI), which can be selectively activated by the control processor 20 to output the output beam 5 _o to a desired output port. Any number of branches and switches 14 in the first switch tree, including direct coupling of each transceiver 11 ₁ to each point emitter 6 ₁ to 6 _n , is possible. A plurality of optical fiber cores 8 extend parallel to each other between the output terminals of the switching matrix 16 and the point emitters 6 ₁ to 6 _n . Ideally, the pitch of the point emitters 6 ₁ to 6 _n in the optical emitter chip 2 is 5 µm to 1000 µm or is based on the focal length f, the size L of the optical emitter arrangement 10 and the angular resolution required by the LIDAR system: $$\text{Abstand}=\text{Aufl}\ddot{\text{o}}\text{sung}/\left(2\ast \text{arctan}\left(\text{L}/2\text{f}\right)\right)*\text{L}$$

Likewise, when one of the incoming beams 5 _i is received at the same point emitter 6 ₁ to 6 _n , the incoming beam 5 _i is transmitted in the reverse direction via the corresponding optical fiber core 8 to the switching matrix 16 back to the corresponding photodetector in the corresponding transceiver 11 ₁ to 11 _n .

The optical emitter chip 2 may comprise one or more of the n optical transceivers 11 ₁ to 11 ₀ , the switching matrix 16 and the array of point emitters 6 ₁ to 6 _n ; however, any or more of the n optical transceivers 11 ₁ to 11 _n and the switching matrix 16 may be on separate chips. In any case, the laser output from one of the optical transceivers 11 ₁ to 11 _n is directed to a specific end-fire taper 9 terminating near the edge of the optical emitter chip 2. Each point emitter 6 ₁ to 6 _n , i.e. each end-fire taper 9, is configured to emit an output beam 5 _o from the edge of the optical emitter chip 2, whereupon each output beam 5 _o expands and is directed towards the lens system 3. The edge of the optical emitter chip 2 is aligned at or near the focal plane F of the lens system 3, hence the output beams 5 _o propagating from the end-fire taper 9 are shaped, e.g. collimated, by the lens system 3 and then emitted into the far field. The far field angle of the output beams 5 _o depends on the location of the point emitter 6 ₁ to 6 _n relative to the optical axis OA of the lens system 3, so that a one-dimensional scanning of the beams is provided by selectively turning on each point emitter or several point emitters at the same time, e.g. depending on the number of optical transceivers 11 ₁ to 11 _n .

The second axis of scanning is provided by the rotating mirror 4. The output beam 5 _o emerging from the lens system 3 strikes one of the reflecting surfaces or facets of the rotating mirror 4 and is redirected into the far field for object detection. The input beam 5 _i , which corresponds to the output beam 5 _o reflected from the object, can return via the same reflecting surface and the lens system 3 to the original point emitter 6 ₁ to 6 _n to be reflected from the corresponding to be detected by the photodetector before the rotating mirror 4 rotates out of range, i.e. rotates so far that it is not possible for the corresponding input beam 5 _i to be directed back to substantially the same original point emitter 6 ₁ to 6 _n as the output beam 5 _o within one round trip time, e.g. 0.5 ns to 5 µs for an object 7.5 cm to 750 m away. Typically, an output beam 5 _o from one of the light sources is fired every 2 µs to 1000 µs. In other words, the optical device 1 chirps at about 1 kHz to 500 kHz, i.e. the output beam 5 _o (continuous or pulsed) is fired every 2 µs to 1 ms.

For each orbital period, some or all of the point emitters 6 ₁ to 6 _n may emit an output beam 5 _o , forming a plurality of beams in the same detection plane but at different beam angles α covering an angular detection range, e.g. 10° to 90°. Each light source, e.g. each transceiver 11 ₁ to 11 _m , may emit a light beam which may be split into sub-beams, e.g. 2-8 sub-beams, by the switching matrix 16, ie when all switches 14 are turned off or omitted entirely, and light is transmitted to each waveguide core 8 which are then simultaneously transmitted by the point emitters 6 ₁ to 6 _n .

To reduce the number of light sources and photodetectors required while maintaining a maximum or desired optical threshold power, the control processor 20 may also cycle through a group of the point emitters, e.g., 6 ₁ through 6 ₄ , that are optically coupled to one of the transceivers, e.g., transceiver 11 ₁ , by turning selected switches 14 on and off to sequentially transmit a different output beam 5 _o to each of the point emitters, e.g., 6 ₁ through 6 ₄ , in the group. Some or all of the light sources, e.g., 6 1 through 6 4 , may be switched on or off. B. some or all of the transceivers 11 ₁ to 11 _m , may be optically coupled to another group of waveguide cores 8, whereby a first subset of output beams 5 _o can be transmitted simultaneously with one another, i.e., one output beam 5 _o from each light source transmitted via one of the group of waveguide cores 8 coupled to it. Under the control of the control processor 20, each light source then sequentially passes through each of the waveguide cores 8 in the corresponding group of waveguide cores 8 coupled thereto, being switched to each emitter, e.g., 6 _i - 6 ₄ , for at least a single round trip period. The round trip period should be at least as long as the time it takes for the light to travel from the point emitter light source, e.g., 6 ₁ to 6 ₄ , to the target and back to the point emitter photodetector, e.g., 6 ₁ to 6 ₄ . Accordingly, only a portion of the total number of output beams 5 _o (and input beams 5 _i ) covering the entire range of beam angles α can be transmitted at one time. The control processor 20 can coordinate the light sources, the switching matrix 16, an angular position of the rotating mirror 4, and the photodetectors to transmit and receive each output beam 5 _o and each input beam 5 _i sequentially via the first switching matrix 16 and the plurality of first point emitters 6 _i - 6 _n .

Then, as the rotating mirror 4 rotates, one or more output beams 5 _o can be scanned, i.e. rotated, over a predetermined scanning range, e.g. an angle, depending on the number of facets and the size of the facets on the rotating mirror 4. There are angular ranges for which the output beams 5 _o (and input beams 5 _i ) incident on one of the facets of the rotating mirror 4 are not clipped at the edges, and the total optical scanning range is twice this angular range. The duty cycle can be defined as the percentage of the full rotation cycle at which the output and input beams 5 _o and 5 _i are entirely incident on a facet of the rotating mirror 4 without being clipped. For example, four facets with a square area of 30 × 30 mm provide a scanning range of about 100° with a duty cycle of 60%, and three facets of the same size provide a scanning range of about 120° with a duty cycle of 50%. As the rotating mirror 4 rotates, the angle of each facet relative to the output beams _5o changes continuously through the angular range between a first minimum angle, i.e. which is directed on a first edge or corner of the rotating mirror 4 and deflects the output beams to one side of the rotating mirror 4 ( 2A) , up to substantially perpendicular (intermediate angle), after which the output rays 5 _o are deflected to a remote side of the rotating mirror 4, and then up to a second maximum angle, ie directed to a second edge or corner of the rotating mirror 4 ( 2B) . After the maximum angle of each facet, the output beams 5 _o will hit the subsequent facets one after the other and be deflected by them, passing through the scanning angle range from the first minimum angle via the intermediate angle to the second maximum angle for each facet of the rotating mirror 4.

If the output light rays 5 _o are directed onto an edge of a rotating mirror 4 between the facets, the light can be scattered in different directions. Accordingly, the Control processor 20 may reduce or eliminate false measurements by one or more error-reducing schemes by coordinating the position of rotating mirror 4 with the control of the light sources and photodetectors, such as turning off the light sources and/or photodetectors in transceivers 11 ₁ through 11 _n for a period of time while output beams 5 _o are directed to an edge, or by simply ignoring any measurements from the photodetectors for the period of time while output beams 5 _o are directed to an edge.

The rotating mirror 4 may consist of a polygonal prism comprising a plurality, e.g. 3 or 4 or 5 or 6, of facets, each of which has a reflective surface and a longitudinal axis of rotation 24 which may or may not be aligned with the axis of rotation of a spinning motor 25. The spinning motor 25 may be any type of rotating motor, such as a stepper motor, DC motor or servo motor. The longitudinal axis of rotation 24 may not be aligned with the axis of the spinning motor 25 if the axes are connected via a belt or gear system. The longitudinal axis of rotation 24 of the rotating mirror 4 may be perpendicular to the optical axis OA of the lens system 3 and/or parallel to a first plane in which the emitter assembly 10 lies. The optical axis OA may lie in a second plane which is perpendicular to the first plane and perpendicular or normal to the axis of rotation 24.

A direct reflection of the output beam 5 _o directly back into the point emitter 6 ₁ to 6 _n , i.e. the endfire taper 9, can be prevented and the field of view (FOV) increased by arranging the rotation axis 24 in the longitudinal direction of the rotating mirror 4 offset by the distance t from the optical axis OA of the lens system 3, i.e. the rotation axis 24 must not intersect with the optical axis OA. In general, the region of the unobstructed field of view begins at a position where the output beam 5 _o misses (re-reflects) the lens system 3 and ends when the output beam 5 _o begins to clip the edges of the mirror facet.

The corners of the rotating mirror 4 may create dead zones in which accurate transmission/return measurements are not possible, depending on the size and number of facets.

The rotation speed (revolutions per second or rps) of the rotating mirror 4 depends on the switching scheme; however, the rotation speed can be equal to or less than the LIDAR frame rate, i.e. how long it takes to scan the entire scan area. For example, at 3 frames/second, divided by the number of facets, e.g. 3-6 facets, gives 1~0.5 rps. The rotation speed is preferably kept below a threshold speed at which errors can occur if the sweep is too fast, so that the input beam 5 _i is not reflected back to the same point emitter 6 ₁ - 6 _n (or even hits nothing). Ideally, this means that the angular velocity of the motor (in degrees per second), e.g. B. between 1 and 50 rps or 360 and 18000 degrees per second, is smaller than the divergence of the input beam 5 _i (in degrees), e.g. between 0.2° and 0.002°, divided by the round trip time that the light needs to travel from the mirror system 3 to the target and back (in seconds). For example, with a beam divergence of 0.02° and a target 500 m away, the round trip time is 3.33 µs, so the mirror ideally rotates slower than 0.02 degrees / 3.33 µs, ie 6000 degrees/s or about 17 rps / #facets

With reference to the 7 and 8 , an exemplary optical emitter device 1' includes a plurality of optical emitter chips 2 ₁ to 2 _n and corresponding lens systems 3 ₁ to 3 _n sharing a single polygonal rotating mirror 4. The advantage of this approach is that the field of view is expanded in a single system. A smaller number of facets, e.g. 3 to 6, is desirable in order to keep the volume size of the rotating mirror 4 relatively small.

9 shows an exemplary optical emitter device 1", in which three sets of optical emitter chips 2 ₁ to 2 ₀ and corresponding lens systems 3 ₁ to 3 _n share a single three-legged polygonal reflecting mirror 4.

The term “controller” or “processor” may include a microcontroller or a field programmable array (FPGA) equipped with suitable non-volatile memory for storing the control parameters via computer software.

To control the system, if the spinning motor 25 is a stepper motor, the controller 20 may contain a dedicated microcontroller or FPGA controller that sends control signals, e.g. pulses, to move the rotary motor (stepper motor) 25 in fixed step sizes. Therefore, the Microcontroller or the FPGA can immediately determine the instantaneous position, i.e. the angle, of the rotating mirror 4 based on the control signals. To avoid the control becoming asynchronous over time because the rotating (stepper) motor 25 may skip steps, an optical slit interrupter can be incorporated into the rotating mirror 4 and spinning motor 25 system. An interrupt pin can also be attached to both ends of the rotating mirror 4, which can slide in and out of the optical slit interrupter, thereby temporarily blocking the light detection in the optical slit interrupter while the spinning motor 25 and/or the rotating mirror 4 are rotating. Therefore, the optical interrupter provides a pulse signal to the microcontroller/FPGA with each rotation of the rotating mirror 4 and/or the spinning motor 25.

All types of spinning motors 25 have a dedicated rotary encoder, either built into the spinning motor 25 or an external rotary encoder module, which supplies the absolute or relative angular position of the rotating mirror 4 to the microcontroller/FPGA.

If the controller 20, e.g. the microcontroller/FPGA, has the angular position of the rotating mirror 4, a correct lidar image can be created.

With reference to 10 and 11 , another exemplary embodiment of an optical emitter device 101 comprises: the optical emitter chip 2 and the lens system 3 as described above, and a rotating (oscillating) mirror 104, e.g. a reflector. As described above, for beam shaping, one or more highly collimated output beams 5 _o can be transmitted when the point emitter 6 ₁ to 6 _n of the optical emitter chip 2 is arranged near or substantially on the focal plane F of the lens system 3 (infinite conjugation). Reverse propagation also applies based on the reciprocity theorem, where a parallel input beam 5 _i , e.g. one of the output beams 5 _o reflected from an object and shining on the lens system 3, is focused at a point to be captured by one of the point emitters 6 ₁ to 6 _n , with a slight scattering determined by lens aberration and diffraction. For beam steering, the far-field beam angle α of the shaped, e.g. substantially collimated or focused, output beam 5 _o depends on the position of the point emitter 6 ₁ to 6 _n on the focal plane F relative to the longitudinal optical center axis OA of the lens system 3. The following equation applies to the beam angle α: α = arctan(d/f), where d is the distance from the center of the focal plane, ie the point at which the optical axis OA coincides with the focal plane F, and f is the focal length of the lens system 3. Therefore, a complete LIDAR system can be implemented by placing the optical emitter chip 2 of the point emitters 6 ₁ to 6 _n on or near the focal plane F of the lens system 3 and then using a controller 20 to selectively switch selected and unselected point emitters 6 ₁ to 6 _n on and off, respectively, to direct the one or more output beams 5 _o in the desired directions with the desired beam angles α. The point emitters 6 ₁ to 6 _n can comprise any of the aforementioned point emitters, e.g. as shown in the 3A to 6 described.

The rotating mirror 104 may comprise an oscillating mirror, e.g., an optical galvanometer scanner comprising a single facet with a single reflective surface and having a longitudinal axis of rotation 124 that may or may not be aligned with the axis of rotation of a spinning motor 125. The spinning motor 125 may be any type of rotating motor, e.g., a stepper motor, DC motor, or servo motor. The longitudinal axis of rotation 124 may not be aligned with the axis of the spinning motor 125 if the axes are connected via a belt or gear system. The longitudinal axis of rotation 124 of the rotating mirror 104 may be perpendicular to the optical axis OA of the lens system 3 and/or parallel to a first plane in which the emitter assembly 10 lies. The optical axis OA may lie in a second plane that is perpendicular to the first plane and perpendicular or normal to the axis of rotation 124. The spinning motor 125 may be driven by an electrical signal comprising a triangular wave, i.e. it starts with a minimum voltage (current) at a maximum angle of rotation, increases substantially linearly to a maximum voltage (when the mirror is substantially perpendicular to the optical axis OA and then decreases substantially linearly to the other maximum angle of rotation. The rotating mirror 104 may oscillate at about 2.5 Hz to 50 Hz, preferably at about 20 Hz. The rotating mirror 104 may have a width configured to receive 16-256, preferably 32, output light beams 5 _o and input light beams 5 _i . Alternatively, the rotating mirror 104 may comprise a microelectromechanical system (MEMS) device, wherein the motor 125 comprises, for example, an electrostatic, electromagnetic or piezo actuator.

A direct reflection of the output beam 5 _o directly back into the point emitter 6 ₁ to 6 _n , ie the end-fire taper 9, can be prevented and the field of view (FOV) can be increased by the rotation axis 124 is arranged in the longitudinal direction of the rotating mirror 104 offset by the distance t from the optical axis OA of the lens system 3, ie the axis of rotation 124 must not intersect with the optical axis OA. In general, the region of the unobstructed field of view begins at a position where the output beam 5 _o misses the lens system 3 (is reflected back) and ends when the output beam 5 _o begins to clip the edges of the mirror facet.

As described above, to reduce the number of light sources and photodetectors required while maintaining a maximum or desired optical threshold power, the controller 20 may also cycle through a group of the point emitters, e.g., 6 ₁ through 6 ₄ , that are optically coupled to one of the transceivers, e.g., transceiver 11 ₁ , by turning selected switches 14 on and off to sequentially transmit a different output beam 5 _o to each of the point emitters, e.g., 6 _{1 through 6 4 , in the group. Some or all of the light sources, e.g., 6 1} through 6 ₄ , may be selectively coupled to one of the transceivers, e.g., transceiver 11 1 . Some or all of the transceivers 11 ₁ to 11 _m may be optically coupled to another group of waveguide cores 8, whereby a first subset of output beams 5 _o may be transmitted simultaneously with one another, i.e., one output beam 5 _o from each light source transmitted through one of the group of waveguide cores 8 coupled to it. Under the control of the controller 20, each light source then sequentially passes through each of the waveguide cores 8 in the corresponding group of waveguide cores 8 coupled thereto, being switched to each emitter, e.g., 6 ₁ - 6 ₄ , for at least a single round trip period. The round trip time should be at least as long as the time it takes for the light to travel from the point emitter light source, e.g., 6 ₁ to 6 ₄ , to the target and back to the point emitter photodetector, e.g., 6 ₁ to 6 ₄ . Accordingly, only a portion of the total number of output beams 5 _o (and input beams 5 _i ) covering the entire range of beam angles α can be transmitted at one time. The controller 20 can coordinate the light sources, the switching matrix 16, an angular position of the rotating mirror 4, and the photodetectors to transmit and receive each output beam 5 _o and each input beam 5 _i sequentially via the first switching matrix 16 and the plurality of first point emitters 6 _i - 6 _n .

There may be dead zones where accurate transmission/return measurements are not possible, which arise when the rotating mirror 104 reaches or exceeds a maximum angle of rotation from the OA, at which points the rotating mirror 104 begins to rotate in the opposite direction to scan the point emitters 6 ₁ to 6 _n in the opposite direction. The rotating mirror 104 may oscillate back and forth in opposite directions about the axis of rotation 124 by an angle of about 45°, giving a scanning range of about 90°, with a nominal position where the rotating mirror 104 is at an angle of about -45° to the OA (CW is +), and a normal N is at an angle of about +45° to the OA, with the output beams 5 _o directed at an angle of about 90° to the OA, e.g. out of the side of 10 At the ends of the movement EOT1 (end of travel) and EOT2, the rotating mirror 104 can be at an angle of - 67.5° and -22.5° to the OA, respectively, while the normal N is at an angle of +22.5° and +67.5° to the OA, respectively (+/- 22.5° from the 45° center), as in 11 Accordingly, the control processor 20 may activate the switches 14 to cycle through the various waveguide cores 8 in each group of point emitters, e.g., 6 _i - 6 ₄ , during periods when the rotating mirror 104 is in a dead zone or near the end of its range of motion. The activation of the switches 14 may be approximately synchronized with the deceleration and acceleration of the rotating mirror 104 at the ends of its range of motion.

The control processor 20 can also alternate during which pass (clockwise or counterclockwise) the light source illuminates each point emitter 6 ₁ to 6 _n by activating only some, e.g. every other one, of the light sources and switches 14. The switching of the alternating channels can also occur during the time that the rotating mirror 104 is in a dead zone. Each group of emitters 6 _i that is active during a particular mirror pass produces a partial image of the captured pixels. By assembling multiple sets of active emitters 6 ₁ to 6 _n, the entire scene can be interrogated over multiple clockwise and counterclockwise passes of the rotating mirror 104.

The oscillation rate (cycles per second or cps) of the rotating mirror 104 depends on the switching scheme; however, the oscillation rate may be the same or lower than the LIDAR frame rate, i.e. how long it takes to scan the entire scan area. For example, at 3 frames/second multiplied by the number of sub-images (i.e. groups of emitters 6 _i being switched between), e.g. 2 sub-images, this gives 6 clockwise or counter-clockwise scans per second, or an oscillation rate of 3 cycles per second. The number of sub-images may be varied depending on the application or selected by the user during operation. The instantaneous rotation speed of the mirror 104 is preferably kept below a threshold speed at which errors can occur if the sweep is too fast, so that the input beam 5 _i is not reflected back to the same point emitter 6 ₁ - 6 _n (or even hits nothing). Ideally, this means that the angular velocity of the motor (in degrees per second), e.g. between 360 and 18000 degrees per second, is smaller than the divergence of the input beam 5 _i (in degrees), e.g. between 0.2° and 0.002°, divided by the round trip time that the light needs to travel from the lens system 3 to the target and back (in seconds). For example, with a beam divergence of 0.02° and a target 500 m away, the round trip time is 3.33 µs, so the mirror ideally rotates slower than 0.02 degrees/3.33 µs, i.e. 6000°/s.

With reference to the 12 and 13 some or all of the above example optical devices may include a polarization duplex system 200 for measuring both polarization mode components of the returning input beams 5 _i . The output beams 5 _o may be emitted with a single polarization mode, e.g. TE (transverse electric) mode; however, due to different surface textures of the obstacle, the input beams 5 _i may return with a first component of TE mode and a second component of orthogonal polarization, e.g. TM (transverse magnetic) mode. In some conventional LIDAR systems, the second component would simply be scattered or lost, which may constitute a large portion of the input beams 5 _i depending on the surface of the obstacle.

Each of the aforementioned transceivers 11 ₁ to 11 _m may include a laser source 201 to transmit the output beam 5 _o with a single polarization mode, e.g. TE mode. The output beam 5 _o may be transmitted through a beam splitter 202 so that a portion, e.g. 40%-60%, preferably 50%/50%, is branched off to provide local oscillator light (LO) 5 _LO to the first photodetectors 203 in a first photodetector circuit 204. The output light beam 5 _o passes to the switching matrix 16, the selected optical fiber core 8, the selected point emitters 6 ₁ to 6 _n , the lens system 3 and the rotating mirror 4 or 104. The input light beam 5 _i returns from the rotating mirror 4 or 104 through the lens system 3 to the selected point emitters 6 ₁ to 6 _n , the selected optical fiber core 8, the switching matrix 16, to the beam splitter 202 which redirects a portion of the input light beam 5 _i to the photodetectors 203 in the first photodetector circuit 204.

The polarization duplex system 200 includes a polarization beam splitter 210 disposed between the point emitters, e.g., 6 ₁ through 6 _{11 ,} and the transceivers 11 ₁ through 11 _m and configured to split the input beam 5 _i into a first, e.g., TE mode, component 211 and a second, e.g., TM mode, component 212. The first component 211 may be transmitted to first photodetectors 203 in the first photodetector circuit 204 (as previously disclosed herein), which provides a first electrical signal to the control processor 20 corresponding to the optical power in the first component 211. The second component 212 may be transmitted to second photodetectors 205 in a second photodetector circuit 206, which provides a second electrical signal to the control processor 20 corresponding to the optical power in the second component. Ideally, the polarization mode of the second component may be converted, e.g. rotated, to the same polarization mode of the first component, e.g. to the TE mode, to facilitate transmission in the on-chip waveguide cores 8 and the switching matrix 16. Accordingly, the polarization beam splitter 210 may comprise a polarization beam splitter/rotator as is known in the art.

13 shows a more detailed example of the polarization duplex system 200 in which four of the optical fiber cores 8 are shown, each with a polarization beam splitter 210 with the ability to rotate the polarization. As in the previous examples, each group, e.g. two pairs, of fiber cores 8 has a first switch 14 which allows the control processor 20 to select between the two pairs of fiber cores 8, and a second and a third switch 14 which allows the control processor 20 to select between the fiber cores 8 in each pair, e.g. the corresponding point emitter 6 ₁ to 6 _n . For the polarization duplex system 200, a second set of switches 214 may be provided on the switch matrix 16 and a second set of optical fiber cores 208 may be provided on the optical emitter assembly 10 to select which of the second components from the input light beams 5 _i are transmitted back to the second photodetector circuit 206 corresponding to the first components selected by the first set of switches 14. Because the physical distance of a first (TE) optical path TE Sig between the polarization beam splitter 210 and the first photodetector circuit 204 for the first component 211 may be different than the physical distance of a second (TM) optical path TM Sig between the polarization beam splitter 210 and the second photodetector circuit 206 for the second component 212, an additional length, e.g., a loop, of the optical fiber 221 may be provided in one of the first or second optical paths TE Sig or TM Sig or in the local oscillator optical paths TM LO and TE LO between the beam splitter 202 and the respective first and second photodetector circuits 204 and 206. In addition, a phase shift tuner 222 may be provided in the additional length 221 (affecting TE Sig) or in one of the first or second optical paths TE Sig or TM Sig, configured to tune the optical path length of the first or second optical path TE Sig or TM Sig to ensure that the beat tones received at the photodetector circuits 204 and 206 are in phase. This can be ensured in particular if the relative phase between TE Sig and TE LO is equal to the phase between TM Sig and TM LO, up to a factor of 2 pi. The adjustment of the relative phases enables a more accurate measurement when the first and second electrical signals generated by the photodetector circuits 204 and 206 are compared or combined, or when the electrical signals after the photodetector circuits 204 and 206 are added directly. A phase shift tuner 222 can alternatively be arranged in the local oscillators in the photodetector circuits 204 and 206 or in the local oscillator paths TM LO and TE LO for the same purpose.

The local oscillator light 5 _LO split by the beam splitter 202 may be transmitted along a suitable optical fiber to a splitter 225, wherein a first portion of the local oscillator light 5 _LO is combined with the first component 211 in a first mixer 231 for transmission to the first photodetectors 203, and a second portion of the local oscillator light 5 _LO is combined with the second component 212 in a second mixer 232 for transmission to the second photodetectors 205. A variable attenuator or a pair of variable attenuators 235 may be provided between the beam splitter 202 and the first and second mixers 231 and 232 for attenuating the local oscillator light 5 _LO to ensure that the local oscillator light 5 _LO does not overexpose the first photodetectors 203 and/or the second photodetectors 205. In the example shown, a pair of variable attenuators 235 is provided after the divider 225, wherein a variable attenuator 235 is provided for the first part of the local oscillator light 5 _LO and a second variable attenuator 235 is provided for the second part of the local oscillator light 5 _LO .

A first tap 241 ₁ , e.g. a 1%-5% optical splitter, and a first monitoring photodetector 242 ₁ may be provided in one of the first or second optical paths, e.g. in one of the optical fiber cores 8, for monitoring the output beam 5 _o and/or the input beam 5 _i . A first electrical monitoring signal may be sent from the first monitoring photodetector 242 ₁ to the control processor 20, whereby the control processor 20 can monitor the output beam 5 _o and/or the input beam 5 _i and make adjustments to other components, e.g. the light source 201 or the switches 14. Similarly, a second tap 241 ₂ , e.g. B. an optical splitter of 1% to 5%, and a second monitoring photodetector 242 ₂ may be provided before and/or after one or more of the variable attenuators 235 for monitoring the first part of the local oscillator light 5 _LO and/or the second part of the local oscillator light 5 _LO . Second and/or third electrical monitoring signals may be sent from the second monitoring photodetector 242 ₁ to the control processor 20, whereby the control processor 20 can monitor the first part of the local oscillator light 5 _LO and/or the second part of the local oscillator light 5 _LO and can make an adjustment of the variable attenuator(s) 235.

The control processor 20 may simply add the optical power of the first component, e.g., the first electrical signal, to the optical power of the second component, e.g., the second electrical signal, to obtain a total optical power (combined electrical signal) of the input beam 5 _i . Additionally or alternatively, the control processor 20 may use the second electrical signal, or a comparison of the second electrical signal to the first electrical signal, to monitor or characterize the surface from which the input beam 5 _i is reflected. For example, vehicles and signs containing highly reflective, e.g., metallic, surfaces may reflect relatively small portions of the light that are converted to the second polarization mode. Accordingly, the highly reflective surface may be characterized by a relatively low magnitude second electrical signal or a relatively low magnitude ratio of second electrical signal to first electrical signal. In contrast, concrete buildings or asphalt roads, which contain rough and poorly reflective surfaces, may reflect relatively larger portions of the light that are converted to the second polarization mode. Accordingly, the poorly reflective surface may be characterized by a second electrical signal of relatively high magnitude or a ratio of second electrical signal to first electrical signal of relatively high magnitude.

With reference to 14 , an exemplary lens system 3 for use in some or all examples in which the endfire tapers 9 are arranged such that each point emitter 6 ₁ - 6 _n lies substantially along or near a curved focal plane F may consist of a single element curved facet lens 303. The single element lens 303 may be predominantly meniscus-shaped with both a front surface 311 and a back surface 312 being aspherical.

An optical stop 315 in front of the lens 303 is preferably >7 mm, preferably between 7 mm and 30 mm and more preferably between 12 mm and 16 mm distance between the stop 315 and the lens 303 to create a mechanical clearance for the rotating mirror 4 or 104.

The front surface 311 (near the stop 315) may be highly aspherical, substantially flat near the optical axis OA, and concave near the outer edges. The front surface 311 may be considered substantially flat, although it may have a locally convex curvature at some points near the optical axis OA. The rear surface 312 (nearest the image) produces most of the optical power and is highly convex with a radius of curvature of 10 mm - 20 mm, preferably about 15 mm. The surface of the image, i.e. the focal plane F, is concave toward the lens 303.

The center thickness of the lens 303 may be greater than 10 mm, preferably between 15 mm and 25 mm, more preferably about 19 mm. If the center thickness is insufficient, aberrations are difficult to correct, especially in wide fields of view, and the required curvature of the front surface 311 and the rear surface 312 becomes extreme and difficult to manufacture.

The thicknesses, spacings and radii described here preferably apply to a lens system with a total focal length of 22 mm and would scale linearly with focal length for other design focal lengths, e.g., the center thickness may be greater than 5 mm and preferably between 7.5 mm and 12.5 mm for a system focal length of 11 mm. The center thickness may be equal to or greater than half the focal length of the first lens 303.

The optical material of the lens 303 may be glass or plastic, preferably with a negative thermo-optic coefficient, e.g. dn/dt approximately -5×10 ^-6 / °C. The lens 303 may have a refractive index of n > 1.6, preferably n > 1.75, and more preferably between 1.7 and 1.8. The housing of the lens may have a positive thermal expansion coefficient, e.g. aluminum, 23.6×10 ^-6 / °C. Accordingly, the combination of the material with a negative thermo-optic coefficient in the lens 303 and the material with a positive thermo-optic coefficient in the housing results in the focal point shift of the lens 303 being approximately zero over a desired temperature range, e.g. from -40 °C to 105 °C. Accordingly, the focal plane F will not shift significantly with temperature changes.

The single element lens 303 can be designed without regard to dispersion or chromatic aberration when the optical emitter device 1, 1', 1" or 101 operates at a single wavelength or a small range of wavelengths in the near IR, e.g. between 1200 and 1700 nm.

It is desirable to design an optical emitter device 1, 1', 1" or 101 using a single lens element 303 rather than a plurality of elements because it reduces mechanical constraints in the device, such as aligning and centering multiple optical elements and precision machining of a housing to achieve this alignment. However, eliminating optical aberrations, particularly spherical aberration and coma, is more difficult with fewer surfaces. Using aspherical surfaces in a design that is approximately concentric about the stop 315 allows these aberrations to be minimized. The curved focal plane F also eliminates the need to correct the field curvature of the optical system, which would otherwise typically require more lens elements.

Beispiel Linsensystem-Daten Brennweite 22 mm f/# 2.2 Voll-Winkel Sichtfeld 30 Grad Entwurfs-Wellenlänge 1550 nm Beispiel Oberfläche Daten Oberfläche 315 (Stop) 311 312 6 (Bild) Radius ∞ 105.38 -17.69 -37.24 Abstand zur nächsten Oberfläche 14 18.72 20.32 Index (n_d) 1.778 Abbe-Zahl (v_d) 23.91 k 0 0 A₂ 6.07E-05 -5.85E-06 A₄ -6.07E-05 4.90E-06 A₆ -2.59E-07 -1.43E-08 A₈ 3.71E-10 -4.41E-11 A₁₀ -3.26E-11 -1.30E-13 A₁₂ 0 1.23E-15 The following are the numerical data of an exemplary single element lens 303 in units of mm with reference to 14 where the coefficients A ₂ , A ₄ , A ₆ , A ₈ , A ₁₀ and A ₁₂ are aspherical coefficients for the surface sag z (ie the displacement in the direction of the optical axis) for a given radial distance from the optical axis r, where c is the inverse of the spherical radius of curvature and k is the cone constant, according to the equation $$z=\frac{\mathrm{<figure-callout\; id="2"\; label="c\; r"\; filenames="DE112023000936T5\_0003.png,DE112023000936T5\_0004.png"\; state="\{\{state\}\}">c</figure-callout>}{r}^{}{}^2}{1+\sqrt{1-\left(1+k\right)c^2{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="DE112023000936T5\_0003.png,DE112023000936T5\_0004.png"\; state="\{\{state\}\}">r</figure-callout>}}^2}}+A_2{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="DE112023000936T5\_0003.png,DE112023000936T5\_0004.png"\; state="\{\{state\}\}">r</figure-callout>}}^2+A_4{\mathrm{<figure-callout\; id="4"\; label="r"\; filenames="DE112023000936T5\_0003.png,DE112023000936T5\_0004.png"\; state="\{\{state\}\}">r</figure-callout>}}^4+A_6{\mathrm{<figure-callout\; id="6"\; label="r"\; filenames="DE112023000936T5\_0015.png,DE112023000936T5\_0019.png"\; state="\{\{state\}\}">r</figure-callout>}}^6+A_8{\mathrm{<figure-callout\; id="8"\; label="r"\; filenames="DE112023000936T5\_0003.png,DE112023000936T5\_0004.png"\; state="\{\{state\}\}">r</figure-callout>}}^8+A_{10}{\mathrm{<figure-callout\; id="10"\; label="r"\; filenames="DE112023000936T5\_0003.png,DE112023000936T5\_0004.png"\; state="\{\{state\}\}">r</figure-callout>}}^{10}+A_{12}{\mathrm{<figure-callout\; id="12"\; label="r"\; filenames="DE112023000936T5\_0004.png,DE112023000936T5\_0009.png"\; state="\{\{state\}\}">r</figure-callout>}}^{12}$$

Example lens system data focal length 22 mm f/# 2.2 full-angle field of view 30 degrees design wavelength 1550 nm Example Surface Data surface 315 (Stop) 311 312 6 (picture) radius ∞ 105.38 -17.69 -37.24 distance to the nearest surface 14 18.72 20:32 Index (n _d ) 1,778 Abbe number (v _d ) 23.91 k 0 0 A ₂ 6.07E-05 -5.85E-06 A ₄ -6.07E-05 4.90E-06 A ₆ -2.59E-07 -1.43E-08 A ₈ 3.71E-10 -4.41E-11 A ₁₀ -3.26E-11 -1.30E-13 A ₁₂ 0 1.23E-15

The dimensions of the lens system described above are suitable for a focal length of 22 mm.

The foregoing description of one or more exemplary embodiments has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teachings. It is intended not to limit the scope of the disclosure by this detailed description.

Claims (20)

An optical emitter device comprising: a first emitter assembly comprising a plurality of first point emitters, each respective first point emitter configured to emit a respective first output light beam and configured to receive a respective first input light beam; a first lens system configured to shape and direct each respective first output light beam and each respective first input light beam based on a position of each respective first point emitter relative to a first optical axis of the first lens system; and a rotating reflector configured to redirect each respective first output light beam outward at an angle to the first optical axis and configured to redirect each respective first input light beam onto the first emitter assembly. The optical emitter device according to claim 1 , wherein the first emitter arrangement lies in a first plane which is substantially parallel to an axis of rotation of the rotating reflector. The optical emitter device according to claim 2 , wherein the first optical axis of the first lens system lies in a second plane which is perpendicular to the first plane and normal to the axis of rotation of the rotating reflector. The optical emitter device according to claim 1 , wherein the rotating reflector has an oscillating reflective surface that rotates about an axis of rotation in a first direction and in a second direction opposite to the first direction. The optical emitter device according to claim 4 , wherein the rotating reflector rotates by approximately 45° in the first direction and by approximately 45° in the second direction. The optical emitter device according to claim 4 , wherein the rotation axis is offset from the first optical axis. The optical emitter device according to claim 4 , wherein the axis of rotation is perpendicular to the first optical axis of the first lens system. The optical emitter device according to claim 1 , further comprising: at least one light source for generating the respective first output light beams; a first photodetector circuit for detecting the first input light beams received from the plurality of point emitters; and a beam splitter for directing the respective first output light beams to the plurality of point emitters and the respective first input light beams to the first photodetector circuit. The optical emitter device according to claim 8 , wherein the beam splitter is also configured to direct a portion of the respective first output light beams as local oscillator light to the first photodetector circuit. The optical emitter device according to claim 8 further comprising a first switching matrix configured to selectively direct the respective first output light beams to one of the plurality of point emitters and configured to selectively direct the respective first input light beams to the first photodetector circuit. The optical emitter device according to claim 10 further comprising a controller configured to coordinate the at least one light source, the first switching matrix, an angular position of the rotating reflector, and the first photodetector circuit to transmit each first output light beam and receive each first input light beam sequentially via the first switching matrix and the plurality of first point emitters. The optical emitter device according to claim 8 , further comprising: a second photodetector circuit; and a polarization beam splitter for splitting the first input light beams into a first sub-beam having a first polarization mode for transmission to the first photodetector circuit and into a second sub-beam having a second polarization mode for transmission to the second photodetector circuit. The optical emitter device according to claim 12 , further comprising a polarization rotator for converting the second polarization mode of the second partial beam into the first polarization mode. The optical emitter device according to claim 12 , further comprising: a first switching matrix configured to selectively direct the respective first output light beams to one of the plurality of point emitters and configured to selectively direct the first sub-beams to the first photodetector circuit; a second switching matrix configured to selectively direct the second sub-beams to the second photodetector circuit; a controller configured to coordinate the at least one light source, the first switching matrix, the second switching matrix, an angular position of the rotating reflector, the first photodetector circuit, and the second photodetector circuit to transmit each first output light beam to the plurality of first point emitters and to receive each first sub-beam at the first photodetector circuit and each second sub-beam at the second photodetector circuit. The optical emitter device according to claim 12 further comprising an additional length of optical fiber in a first optical path between the polarization beam splitter and the first photodetector circuit or in a second optical path between the polarization beam splitter and the second photodetector circuit to ensure that the first optical path and the second optical path are equidistant. The optical emitter device according to claim 12 , wherein the beam splitter is also configured to direct a first portion of the respective first output light beams as first local oscillator light to the first photodetector circuit and a second portion of the respective first output light beams as second local oscillator light to the second photodetector circuit; and further comprising a phase shifter in at least one of the first local oscillator, the second local oscillator, a third optical path between the beam splitter and the first photodetector circuit, or in a fourth optical path between the beam splitter and the second photodetector circuit, configured to substantially equalize a first relative phase between the first sub-beam and the first local oscillator light and a second relative phase between the second sub-beam and the second local oscillator light. The optical emitter device according to claim 1 wherein an outer end of at least some of the plurality of first point emitters are disposed substantially in a first focal plane of the first lens system. The optical emitter device according to claim 17 , wherein the first focal plane of the first lens system includes a substantially curved portion, and wherein the outer end of at least some of the plurality of first point emitters is disposed proximate the first focal plane. The optical emitter device according to claim 18 wherein the first lens system consists of a single lens comprising: a front aspherical surface and a rear substantially convex aspherical surface, and a center thickness of more than one-half a focal length of the first lens system. The optical emitter device according to claim 19 wherein the first lens system comprises a material having a negative thermo-optic coefficient and a lens housing having a positive thermal expansion such that the focal plane does not move significantly with temperature.

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