WO2023044538A1

WO2023044538A1 - An optical beam director

Info

Publication number: WO2023044538A1
Application number: PCT/AU2022/051144
Authority: WO
Inventors: Ran Li
Original assignee: Baraja Pty Ltd
Priority date: 2021-09-24
Filing date: 2022-09-21
Publication date: 2023-03-30

Abstract

Described is an optical beam director. The optical beam director includes a dispersive component configured to receive light and to steer the received light across a first dimension based on its wavelength. The optical beam director also includes a beam rotator configured to convert the light steered across the first dimension to light steered across a second dimension that is orthogonal to the first dimension or that includes a substantial component that is orthogonal to the first dimension.

Description

AN OPTICAL BEAM DIRECTOR

FIELD OF THE DISCLOSURE

The present disclosure relates to methods and systems for directing light into multiple directions. More particularly, embodiments of the present disclosure relate to a beam director for use in a LiDAR (light detection and ranging) system.

BACKGROUND OF THE DISCLOSURE

Optical beam direction has several applications, including but not limited to LiDAR applications, in which light is sent into an environment for mapping purposes. In two or three-dimensional mapping by LiDAR, one of the dimensions relates to the range of a point from the origin of the optical beam, whereas the other one or two dimensions relate to one or two-dimensional space across which the light is directed. Locations within these dimensions may be referenced by a Cartesian coordinate system, a polar coordinate system or another coordinate system.

There has recently been substantial interest in the development and use of LiDAR systems, for example for use as an environmental sensor of vehicles, including as an environmental sensor for autonomous or semi-autonomous systems of vehicles. As in many industries, the size of the components and cost of production are relevant considerations to the design of a beam director, including in LiDAR systems, in addition to performance parameters such as the range of operation, resolution and field of view.

SUMMARY OF THE DISCLOSURE

A first aspect of the disclosure relates to an optical beam director, the optical beam director including: a dispersive component configured to receive light and to steer the received light across a first dimension based on its wavelength; and a beam rotator configured to convert the light steered across the first dimension to light steered across a second dimension that is orthogonal to the first dimension or includes a substantial component that is orthogonal to the first dimension.

In some embodiments, the beam rotator includes a first mirror and a second mirror each with a reflective surface facing each other.

In some embodiments, the beam rotator includes a dove prism.

In some embodiments, the beam rotator includes a K-mirror system.

In some embodiments, the optical beam director further includes a steering component configured to receive the light steered across the second dimension and steer it across a third dimension, whereby the first and third dimensions form a two-dimensional field of view. In some embodiments, the first dimension and the third dimension are aligned. In some embodiments, the steering component steers the light steered across the third dimension through mechanical movement.

In some embodiments, the optical beam director further includes a beam compressor configured to magnify light dispersion in the light from the dispersive component.

In some embodiments, the optical beam director further includes a beam compressor configured to converge the light steered across a second dimension. In some embodiments, the beam compressor is configured to magnify light dispersion in the light from the dispersive component. In some embodiments, the steering component is placed near or at a converged location created by the beam compressor. In some embodiments, the beam compressor includes a first lens followed by a second lens, wherein each of the first lens and the second lens has a positive focal length. In some embodiments, the beam compressor is followed by the beam rotator. In some embodiments, the beam rotator is placed between the first lens and the second lens.

In some embodiments, the steering component includes at least one of a rotating reflector and a rotating refractor. In some embodiments, the steering component includes a polygon mirror. In some embodiments, the beam compressor includes a first set of one or more surfaces associated with a first magnification in the first dimension and a second set of one or more surfaces associated with a second magnification in the second dimension. In some embodiments, the first set of one or more surfaces include at least a first surface in a first cylindrical lens, and the second set of one or more surfaces include a second surface in a second cylindrical lens, the first surface having a first curvature in the first dimension and the second surface having a second curvature, different from the first curvature, in the second dimension.

A second aspect of the disclosure relates to an optical beam director, the optical beam director including: a dispersive component configured to receive light and to steer the received light across a first dimension based on its wavelength; and a beam compressor configured to magnify light dispersion in the light from the dispersive component, the beam compressor including a first set of one or more surfaces associated with a first magnification in the first dimension and a second set of one or more surfaces associated with a second magnification in the second dimension.

In some embodiments, the one or more surfaces include a first surface in a first cylindrical lens and a second surface in a second cylindrical lens, the first surface having a first curvature in the first dimension and the second surface having a second curvature, different from the first curvature, in the second dimension. In some embodiments, the beam compressor is arranged to cause the steered light to have a first numerical aperture in the first dimension and a second numerical aperture, larger than the first numerical aperture, in the second dimension.

A third aspect of the disclosure relates to a spatial estimation system, the system including: a light transmission path, including: an optical beam director in accordance with the first aspect or the second aspect; and a light source for generating outgoing light and providing the outgoing light to the optical beam director; a light reception path, including: optical reception components configured to receive light from an environment, the received light including the outgoing light reflected by the environment; detector circuitry to detect light received by the optical reception components and generate a signal indicative of the outgoing light reflected by the environment.

A fourth aspect of the disclosure relate to a method of providing outgoing light in a spatial estimation system, the method including: generating outgoing light, the outgoing light having a range of wavelengths and providing the outgoing light to a beam director; and by the beam director: directing different wavelengths of the outgoing light into different directions, so that the outgoing light is spread across a first dimension; converting the outgoing light spread across the first dimension to outgoing light spread across a second dimension that is orthogonal to the first dimension or includes a substantial component that is orthogonal to the first dimension; steering the outgoing light across a third dimension, whereby the light spread across the first and the third dimensions form a two-dimensional field of view of the spatial estimation system.

In some embodiments, the first dimension and the third dimension are aligned.

In some embodiments, steering the outgoing light across a third dimension includes mechanical steering and wherein the method includes, prior to steering the outgoing light, converging the outgoing light spread across the second dimension.

Further aspects of the present disclosure and further embodiments of the aspects described in the preceding paragraphs will become apparent from the following description, given by way of example and with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 illustrates an example arrangement of a spatial profiling system.

Fig. 2 illustrates an example of a light source for the spatial profiling system of Fig.

Figs. 3A-3C illustrate application examples of beam directors of a spatial profiling system, integrated into a roof lining of a vehicle.

Fig. 4 illustrates a flow diagram of a method of beam direction by a beam director to direct outgoing light of a spatial profiling system.

Figs. 5A-5D each illustrates an exemplary configuration of a dispersive component, a beam compressor and a beam rotator of a beam director.

Fig. 5E illustrates two example fields of view.

Fig. 6A illustrates an embodiment of a beam director including a dispersive component, a beam compressor, a beam rotator and a scanning component in the XZ plane.

Fig. 6B illustrates the scanning component of Fig. 6A in the YZ plane.

Fig. 7A illustrates the beam director of Fig. 6A with a polygon mirror as the scanning component, at a rotational angle of as .

Fig. 7B illustrates the beam director of Fig. 6A with the polygon mirror as a scanning component, at a rotational angle of 04.

Figs. 8A-8C each illustrate an embodiment of the beam rotator for a beam director, for example the beam director of any of Figs. 5-7.

Fig. 9 illustrates an example of electrical adjustment of an acousto-optic dove prism.

DETAILED DESCRIPTION OF EMBODIMENTS

A beam director for directing light into multiple directions is described. The beam director is suitable for spatial profiling applications, which generate an image, for example a three-dimensional image, of a surrounding environment.

“Light” hereinafter includes electromagnetic radiation having optical frequencies, including far-infrared radiation, infrared radiation, visible radiation and ultraviolet radiation. A spatial profiling system using light may be referred to as a light detection and ranging (LiDAR) system. LiDAR involves transmitting light into the environment and subsequently detecting the light returned by the environment. By determining the time it takes for the light to make a round trip to and from, and hence the distance of, reflecting surfaces within a field of view (FOV), an estimation of the spatial profile of the environment may be formed.

Embodiments of a spatial profiling system including the disclosed optical beam director may be useful in monitoring an environment, including relative movement or change in the environment with respect to the optical beam director. For example, in the field of autonomous vehicles (land, air, water, or space), a spatial profiling system can estimate from the vehicle’s perspective a spatial profile of the environment in which the vehicle is to navigate, including the distance to environmental objects, such as an obstacle or a target ahead.

As the vehicle and/or one or more environmental objects move, the spatial profile as viewed from the vehicle may change and may be re-estimated. For example, in an autonomous land vehicle, the estimated spatial profile may include objects such as a road ahead, other vehicles, pedestrians, animals, objects on or near the road and road signs. As another example, in the field of docking, the spatial profiling system can estimate from a container ship’s perspective a spatial profile of the dock, such as the proximity of the container ship to particular parts of the dock, to facilitate successful docking. As yet another example, in the field of line-of-sight communication, such as free-space optical or microwave communication, the spatial profiling system may be used for alignment purposes. Where a transceiver in the communication system has moved or is moving, it may be tracked so as to align the optical or microwave beam.

As further examples, the applicable fields for systems including an embodiment of the disclosed beam director include but are not limited to, industrial measurements and automation, site surveying, military, safety monitoring and surveillance, robotics and machine vision, printing, projectors, illumination, attacking and/or flooding and/or jamming other laser and IR vision systems.

Fig. 1 illustrates an arrangement of a spatial profiling system 100. As shown in the figure key, in the diagram electrical connections (e.g. electrical conductors) are represented by a solid line connector and guided optical connections (e.g. waveguides or optical fibres) are represented by dashed lines. In this embodiment the spatial profiling system 100 also includes, in the optical path for outgoing light and in the optical path for incoming light, light traversing free space, which is represented by a (bidirectional) striped arrow shape. The blocks represent functional components of the spatial profding system 100. It will be appreciated that functionality may be provided by distinct or integrated physical components. For example, a light source may include an integrated amplifier.

The system 100 includes a light source 101 for generating outgoing light. The system 100 may also include an optical amplifier 102 to amplify (providing gain to) light from the light source 101. In some embodiments the optical amplifier 102 is an Erbium- doped fibre amplifier (EDFA) of one or more stages. In other embodiments one or more stages of a semiconductor optical amplifier (SOA), a booster optical amplifier (BOA), or a solid state amplifier (e.g. a Nd:YAG amplifier) may be used. In some embodiments, the optical amplifier 102 may be omitted.

The outgoing light from the optical amplifier 102 is received by transmission optics (Tx optics) for directing light to a beam director 104. The transmission optics may also condition the light, for example by including one or more collimators to form one or more beams of light. In some embodiments the transmission optics form a light transceiver 103, configured to both provide outgoing light to the beam director 104 and receive collected incoming light from the beam director 104. In other embodiments, the outgoing and incoming light paths may be separate, in whole or in part. For example in other embodiments the receive aperture and associated optical components (i.e. reception (Rx) optics) for receiving the incoming light may not form part of the transmission optics for outgoing light.

The beam director 104 functions to direct light over one or two dimensions (a first and/or a second dimension) into the environment to be estimated by the spatial estimation system 100. In some embodiments the beam director 104 includes bidirectional components, whereby both the outgoing light to the environment and incoming light from the environment traverse substantially the same path through the beam director 104, in opposite directions. Figure 1 represents this by the bidirectional arrow for the light traversing free space. If the outgoing light hits an object, at least part of the outgoing light may be reflected (represented in striped arrows), e.g. scattered, by the object back to the beam director 104 as incoming light. The beam director 104 directs the incoming light to the reception optics (e.g. the light transceiver 103), which collects the light and passes it to a light detector circuitry 105.

The light detector circuitry 105 includes one or more photodetectors. An example photodetector is an avalanche photodiode (APD). The light detector circuitry 105 generates incoming electrical signals that are representative of the detected incoming light. The light detector circuitry 105 may include a trans-impedance amplifier following the APD. An analog -to-digital converter 106 may convert analog incoming electrical signals to digital incoming electrical signals. The incoming digital signals are received and processed by a control system 107. The light source 101 and the amplifier 102 may be also controlled by the control system 107. The control system 107 may determine a round trip time for the light based on its control or knowledge of the outgoing light and based on the incoming light signals.

Fig. 2 illustrates an arrangement of the light source 101. In this example, the light source 101 may include a wavelength-tunable light source, such as a wavelength-tunable laser diode, providing light of a tunable wavelength. The wavelength may be based on one or more electrical currents (e.g. the injection current into the one of more wavelength tuning elements in the laser cavity) applied to the laser diode. The light source 101 accordingly is configured to provide outgoing light at a selected one or more of the multiple wavelength channels (each represented by its respective centre wavelength Xi, X2, ... XN). The light source 101 may include a single tunable laser or more than one tunable laser (or other types of lasers). The light source 101 may select one wavelength channel at a time or may simultaneously provide two or more different selected wavelength channels (i.e. channels with different centre wavelengths). In another example, the light source 101 may include a broadband light source and one or more tunable spectral filters to provide substantially continuous-wave (CW) light intensity at the selected wavelength(s). In another example, the light source 101 includes multiple laser diodes, each wavelength-tunable over a respective range and whose respective outputs are combined to form a single output. The respective outputs may be combined using a wavelength combiner, such as an optical splitter or an arrayed waveguide grating (AWG). In one arrangement, the light source 101 is configured to provide the outgoing light to include at least one time-varying profile at the selected one or more of the multiple wavelength channels. The time-varying profile may be used in determining the round trip time of the light. In the example of Fig. 2, the light source 101 includes a modulator 204 for imparting a time-varying profde on the outgoing light. This modulation may be in addition to any wavelength tuning as herein before described. In other words, the modulation would be of light at the tuned wavelength. It will be appreciated that the tuned wavelength may refer to a center frequency or other measure of a wavelength channel that is generated. The time varying profile may, for example, be one or more of a variation in intensity, frequency, phase or code imparted to the outgoing light. In some embodiments, the light source 101 emits pulses of light, which pulses may include the timevarying profile. In other embodiments the difference between the presence of a pulse and the absence of a pulse is a time varying profile for use in determining the round trip time of light. In other embodiments, the outgoing light from the light source 101 has a different form, for example individual pulses for detecting the round trip time of the individual pulses instead of detecting the round trip time of a series of modulated pulses.

In one example, the modulator 204 is a semiconductor optical amplifier (SOA) or a Mach Zehnder modulator integrated on a laser diode of the light source 101. The electrical current applied to the SOA may be varied over time to vary the amplification of the CW light produced by the laser over time, which in turn provide outgoing light with a time -varying intensity profile. In another example, the modulator 204 is an external modulator (such as a Mach Zehnder modulator or an external SOA modulator) to the laser diode. In another example, the modulator 204 is a phase modulator. Although Fig. 2 illustrates that the modulator 204 is located before the optical amplifier 102, it will be appreciated that the modulator may be located either before or after the optical amplifier 102 in the outgoing light path. In yet another example, instead of including an integrated or external modulator, the light source 101 includes a laser having a gain medium into which an excitation electrical current is controllably injected for imparting a time-varying intensity profile on the outgoing light.

In some embodiments the light source 101, optical amplifier 102 and a modulator are provided by a sampled-grating distributed Bragg reflector (SG-DBR) laser. By way of example, the SG-DBR laser may be controllable to provide 10 Gbps modulation, may operate across a 35 nm wavelength range and change from one wavelength to another in less than 100 nanoseconds. The wavelengths may have centre frequencies about 20 MHz or more apart. The operation of the light source 101, such as one or both of the wavelength- tunable laser 202 (e.g. its wavelength) and the modulator 204 (e.g. the modulating waveform), may be controlled by the control system 107. The control system may include an application specific device configured to perform the operations described herein, such as a configured programmable logic device, or a general purpose computing device with computer readable memory storing instructions to cause the computing device to perform the operations.

In the instance of an application specific device, the instructions and/or data for controlling operation of the processing unit may be in whole or in part implemented by firmware or hardware elements, including configured logic gates. In the instance of a general purpose computing device, the control system 107 may include, for example, a single computer processing device (e.g. a central processing unit, graphics processing unit, or other computational device), or may include a plurality of computer processing devices. The control system 107 may also include a communications bus in data communication with one or more machine readable storage (memory) devices which store instructions and/or data for controlling aspects of the operation of the processing unit. The memory devices may include system memory (e.g. a BIOS), volatile memory (e.g. random access memory), and nonvolatile memory (e.g. one or more hard disk or solid state drives to provide non-transient storage). The operations for spatial profding are generally controlled by instructions in the non-volatile memory and/or the volatile memory. In addition, the control system 107 includes one or more interfaces. The interfaces may include a control interface with the light source 101 and a communication interface with the light detector circuitry 105.

In some embodiments, light from the light source 101 is also provided to the detector circuitry 105 to provide a reference signal via a light path (not shown) from the light source 101 to the detector circuitry 105. For example, the light from the light source may first enter a sampler (e.g. a 90/10 fiber-optic coupler), where a majority portion (e.g. 90%) of the light is provided to the beam director and the remaining sample portion (e.g. 10%) of the light is provided instead to the detector circuitry. The detector circuitry may then be configured to inhibit detection of non-reflected light based on a difference in wavelength or modulation between the outgoing light and the non-reflected light. For example, the detection circuitry 105 includes one or more balanced detectors to coherently detect the reflected light mixed with reference light at the one or more balanced detectors. In the embodiment of Fig. 1, the spatial profiling system 100 separates the functional components into two main physical units, i.e. an engine 108 and a sensor head 109. In one example, the engine 108 and the sensor head 109 are substantially collocated. The collocation allows these components to be compactly packaged within a single unit or in a single housing. In another example, the sensor head 109 is remote from the engine 108. In this variant, the engine 108 is optically coupled to the remote sensor head 109 via one or more waveguides, such as optical fibres. In yet another variant, a spatial profiling system 100 may include a single engine 108 and multiple sensor heads. Each of the multiple sensor heads may be optically coupled to the engine 108 via respective waveguides. The multiple sensor heads may be placed at different locations and/or orientated with different fields of view.

Taking the example of an automotive application, Figs. 3A-3C illustrates some examples where one or more units 100a, 100b, 100c, lOOd and 100c of a spatial profiling system are integrated into roof lining of a vehicle 301. The one or more units may include the spatial profiling systems of Fig. 1 or the one or more units may include the sensor heads of the spatial profiling system of Fig. 1 and not the engine 108. In particular, Fig. 3A illustrates four units including sensor heads and/or spatial profiling systems, each placed at a comer of the roof lining of the vehicle 301. Figs. 3B and 3C illustrates one unit including a sensor head or spatial profiling system, placed at the centre of the front roof lining of the vehicle 301.

As best depicted in Fig. 3C, each unit 100a, 100b, 100c, lOOd and 100c may have a relatively low-profile or horizontally-flat form factor. It would be appreciated that a low- profile or horizontally-flat form factor in the spatial profiling system and in particular in the sensor head may facilitate integration with the carrier of the spatial profiling system. For example, the low-profile or horizontally -flat form factor in the spatial profiling system and in particular in the sensor head may facilitate its integration into a roof lining of a vehicle. In another example, the low -profile or horizontally-flat form factor in the spatial profiling system and in particular in the sensor head may improve aerodynamics (e.g. reducing aerodynamic drag) when the spatial profiling system or the sensor head is installed outside the vehicle. In another example, when the spatial profiling system or the sensor head is installed inside the vehicle the low-profile or horizontally -flat form factor may reduce the amount of interior space occupied by it. Fig. 4 illustrates a flow diagram of a method of beam direction, by a beam director, to direct outgoing light into two dimensions, which may provide the low-profile or horizontally-flat form factor in the beam director. At step 402, the light of multiple wavelengths from the light transceiver 103 is steered into different directions across a first dimension based on wavelength. The light of different wavelengths may be received sequentially or simultaneously. For example, the light source (e.g. the light source 101) may generate a plurality of wavelength channels and cycle or scan through the wavelength channels. In some embodiments the light source may simultaneously generate a plurality of wavelength channels, less than all, and cycle or scan through subsets of the available wavelength channels to cycle through or scan across a wavelength range.

Step 402 may be performed by a dispersive component including one or more dispersive elements. It would be understood that the one or more dispersive elements are generally configured in the same dimension as the dimension that the light is spread across. In other words, the one or more dispersive elements would generally be configured with a vertical footprint if the light is to be spread across a vertical dimension. Similarly, the one or more dispersive elements would generally be configured with a horizontal footprint if the light is to be spread across a horizontal dimension. In some embodiments the one or more dispersive elements include one or more gratings. In some embodiments the one or more dispersive elements include or consist of an arrayed waveguide grating. In some embodiments the one or more dispersive elements include one or more refractive components, such as a prism.

In some embodiments the light dispersion is magnified, by a beam compressor, at step 404. While the term “beam compressor” is used herein, it has been known to be referred to as “beam expander”. The power of the magnification may be less than one (in which case the beam is compressed), one (in which case the beam is neither compressed nor expanded) or greater than one (in which case the beam is expanded). The power of magnification also be positive or negative. Further, the magnification may be different for different lateral axes of an optical beam. In addition or alternatively, a spatial point where the dispersed light beams converge (i.e. a multiple -wavelength converged point) may be created at step 404. One or both of magnifying the dispersion and creating a multiple-wavelength converged location may facilitate embodiments of beam directors with a reduced footprint. In other embodiments, step 404 is omitted (as indicted by the dashed line), where the light spread across the first dimension is directly converted to the second dimension without dispersion magnification and/or without multi-wavelength converged location creation.

At step 406, the light beams spread across the first dimension are converted to a second dimension, different to the first dimension. The second dimension may be orthogonal to the first dimension by a beam rotator. In other words, the conversion may involve rotating the first dimension by 90 degrees. Conversion to an orthogonal dimension may facilitate minimisation of the footprint of the beam director across the second dimension. With this beam converting step (i.e. step 406), the beam director may provide vertically spread light beams using a horizontally flat footprint and vice versa. In other embodiments, the second dimension may be rotated with respect to the first dimension, but not orthogonal to the first dimension. These other embodiments may, for example, facilitate embodiments in which there is a relatively increased footprint across the second dimension and a relatively decreased footprint across the first dimension (in comparison to like embodiments with conversion to an orthogonal dimension). In some embodiments, step 406 is omitted.

At step 408, the light beams spread across the second dimension are further steered by a steering component over the first dimension for two-dimensional scanning. In some embodiments step 408 is performed by a mechanical beam steerer. A mechanical beam steerer uses physical movement to direct light in a range of directions. For example, a mechanical beam steerer may include rotating or tilting mirror. In other embodiments, step 408 is performed by dispersive components, which may be of the same type as, or of different type to, the dispersive components used in step 402.

Fig. 5A illustrates an exemplary configuration of an optical system 500A, including a dispersive component 504, a beam compressor 506 and a beam rotator 508 of a beam director, for example the beam director 104 of Fig. 1. The following description is made with reference to its use in an embodiment of the system of Fig. 1. Only transmission (Tx) optics are described. In embodiments in which there is a transceiver 103, additional optical components, such as an optical circulator may be in the light path, so as to direct received light to the detector circuitry 105. For example, an optical circulator may be located before or after the collimating lens 103 (see below). Examples of optical circulators are described in PCT/AU2018/051175, published as WO 2019/084610 Al (Baraja Pty Ltd), which is hereby incorporated herein by reference. A beam director having the dispersive component 504, the beam compressor 506 and the beam rotator 508 in Fig. 5A also has application to other LiDAR systems and to other systems for directing light with different configurations to that shown in Fig. 1.

Light 501 is generated by the light source 101 or the optical amplifier 102 including wavelength channels Xi, X2, ... XN. AS described herein, single wavelength channels may be generated sequentially or a plurality of wavelength channels may be generated simultaneously. A collimating lens 103 receives the light 501 and produces collimated light 505. The collimating lens 103A as shown in Fig. 5A is for illustrative purposes only. The collimation function may be performed by a single element, for example a single lens, or by a collection of elements, for example a lens system comprising two or more lenses. The shape and refractive index of the optical elements is selected to achieve collimation of the light 501 and may or may not scale and/or invert the image of the light 501.

The collimated light 503 is received by a dispersive component 504 for steering the collimated light 503 in multiple directions based on wavelength over a first dimension. The first dimension may, for example, extend horizontally. The first dimension may be linear or non-linear. In one embodiment, the dispersive component 504 includes one or more prisms, one ore more diffractive gratings or a combination of one or more prisms and one or more diffractive gratings. A combination of a prism and a diffractive grating may include two separate elements (i.e. a prism and a diffractive grating) or a single element, such as a grism. As one example, the grism is a silica grism. As another example, the grism is a silicon grism. A silicon grism may provide a higher degree of dispersion than a silica grism. In another embodiment, the dispersive component 504 is or includes a meta-optics element made from a metamaterial. The dispersive component 504 steers the light beams 505 over the first dimension (e.g. along the x axis depicted in Fig. 5 A, with or without some deviation over the y axis and/or z axis) based on wavelength (Xi, X2, . . . ). In the configuration as illustrated in Fig. 5 A, the dispersive component 504 includes a first grating 504A, followed by a second grating 504B and a prism 504C following the second grating 504B.

The dispersive component 504 is followed by the beam compressor 506. In the example as illustrated in Fig. 5A, the beam compressor 506 includes a first lens 506A followed by a second lens 506B each with a positive focal length. The beam compressor 506 creates a multi-wavelength converged location 515 for output light beams 509 where the light beams 509 of multiple wavelengths converge to a minimum waist dimension. It will be appreciated that creating the multiple -wavelength converged location may facilitate reducing the footprint of the beam director 104. The beam compressor 506 may also converge the beam of each wavelength channel. For example, Fig. 5A illustrates the beams 507 of two wavelength channels Xi and X2 converging towards respective converged locations 515-Xi and 515-7,2. In the embodiment of Fig. 5A the second lens 506B is located after the converged locations 515-Xi and 515-7,2, in other embodiments the second lens 506B may be located before the converged locations 515-Xi and 515-72.

The beam compressor 506 may also function to magnify the light dispersion originally created by the dispersive component 504 and output dispersion-magnified light beams 509, to be received by the beam rotator 508. The dispersion magnification factor may be determined by the focal length of the first lens 506A and the second lens 506B.

The beam rotator 508 converts the input light beams 509 spread across the first dimension to a second dimension. For example, the beam rotator may include at least two reflective surfaces to convert the input light beams 509 spread across the first dimension (e.g. along x axis as illustrated in Fig. 5A or horizontally) to a second dimension that is orthogonal to the first dimension (i.e. light beams 511 spread along y axis, or vertically, as illustrated in Fig. 5A and its inset). In this regard, the beam director 104 with the dispersive element 504, the beam compressor 506 and the beam rotator 508 that are in the horizontally flat footprint can provide vertically spread light beams (and vice versa), which may facilitate creating a low-profile or horizontally-flat form factor.

Fig. 5B illustrates an exemplary configuration of an optical system 500B, including the dispersive component 504, a beam compressor 506-1 and the beam rotator 508. In Fig. 5B like components and features to those described with reference to Fig. 5A are shown with like reference numerals. The configuration of Fig. 5B is different from the configuration of Fig. 5A in that the beam rotator 508 is placed between the first lens 506A and the second lens 506B (i.e. within the beam compressor 506-1). In this arrangement, the beam rotator 508 receives light beams 507a from the first lens 506A and converts the light beams 507a spread across the first dimension (e.g. along x axis as illustrated in Fig. 5B or horizontally) to light beams 51 la that are spread across the second dimension orthogonal to the first dimension (e.g. along y axis, or vertically, as illustrated in Fig. 5B and its inset (a)). The light beams 511a are then received by the second lens 506B of the beam compressor 506. The second lens 506B outputs light beams 511b which may magnify the dispersion of the light beams 505.

In some embodiments, a reflecting or refracting element 510 receives the light beams 51 lb, to change the light transmission directions, outputting light beams 511c (e.g. as illustrated in more detail in inset (b) of Fig. 5B). In other embodiments, the reflecting or refracting element 510 may be omitted as illustrated in the optical system 500C of Fig. 5C (like reference numerals between Fig. 5C and 5B referencing like components). The multiwavelength converged location 515a created by the beam compressor 506 for the light beams 51 lb is also illustrated in the inset (b) of Fig. 5B.

The optical systems 500A to 500C provide for wavelength-based beam direction across a dimension and includes rotation of the dimension. The optical systems 500A to 500C function to implement steps 402 to 406 of Fig. 4. The second dimension of step 406 may therefore be described as a “wavelength dimension” or “dispersion dimension”, as the directionality of the outgoing light is dependent on the wavelength of the outgoing light. It will be appreciated that the wavelength dimension is orthogonal to (or at least includes a substantial component orthogonal to) the plane in which the dispersive components that operably steer the light are located.

Figure 5D illustrates an exemplary configuration of an optical system 500D, including a dispersive component 504, a beam compressor 506-3, and a beam rotator 508. In some embodiments, the beam rotator 508 is disposed within the beam compressor 506-3, as shown in Fig. 5D. Alternatively, the beam rotator is disposed outside of the beam compressor. Still alternatively, the beam rotator is omitted. In Figure 5D like components and features to those described with reference to Figures 5A, 5B and 5C are shown with like reference numerals. The configuration of Figure 5D is different from the configurations of Figures 5 A to 5 C in that the beam compressor 506-3 is associated with a different magnification along different lateral axes of an optical beam. The beam compressor 506-3 may include one or more lens sets 506C and 506D. Each of the lens sets 506C and 506D may include one or more lenses. For example, the lens set 506C may include one lens. The lens set 506D may include two lenses. The beam compressor 506-3 is configured to magnify light dispersion and/or a light beam along a first lateral axis of the optical beam (e.g. along x- axis in the example of Fig. 5D) with a different magnification compared to a second lateral axis, orthogonal to the first lateral axis, of the optical beam (e.g. y-axis in the example of Fig. 5D). The first lateral axis may be parallel to wavelength dimension, caused by the dispersive component 504. The second lateral axis may be orthogonal to the wavelength dimension.

The lens set 506C comprises a first surface 506C-1 having a first curvature along the first lateral axis and a second surface 560C-2 having a second curvature along the second lateral axis. For example, as Figure 5D illustrates, the lens set 506C may comprise a single lens, having the first surface 506C-1 and the second surface 506C-2 as two opposed surfaces. Alternatively, as Figure 5D alternatively illustrates, the lens set 506C may include two cylindrical lenses, comprising a first cylindrical lens having the first surface 506C-1 and an opposed plane surface and a second lens having the second surface 506C-2 and an opposed plane surface. Similar to the lens set 506C, the lens set 506D comprises a third surface 506D- 1 having a third curvature along the first lateral axis and a fourth surface 560D-2 having a fourth curvature along the second lateral axis. For example, as Figure 5D illustrates, the lens set 506D may comprise a single lens, having the third surface 506D-1 and the fourth surface 506D-2 as two opposed surfaces. Alternatively, as Figure 5D alternatively illustrates, the lens set 506D may include two cylindrical lenses, comprising a third cylindrical lens having the third surface 506D-1 and an opposed plane surface, and a fourth cylindrical lens having the fourth surface 506D-2 and an opposed plane surface. The first curvature may be the same as or different to the second curvature. The third curvature may be the same as or different to the fourth curvature. In one example, the lens set 506C comprises two cylindrical lenses, where the first curvature is different to the second curvature, and the lens set 506D comprises a single spherical lens, where third curvature is the same as the fourth curvature.

In other words, the beam compressor 506-3 provides two sets of one or more surfaces, comprising a first set and a second set, with each set being associated with a respective one of two orthogonal lateral axes of the optical beam. The first set of one or more surfaces is associated with a first magnification along the first axis. The second set of one or more surfaces is associated with a second magnification along the second axis, orthogonal to the first axis. The first magnification is different from the second magnification. The light beam and/or light dispersion is/are magnified in the wavelength dimension and its orthogonal (non-dispersion) dimension, respectively, based on one of the first curvature and the second curvature, and one of the third curvature and the fourth curvature. In the embodiment of Figure 5D, where the beam rotator 508 is located in between the lens set 506C and the lens set 506D, the first curvature and the fourth curvature together determine magnification of light dispersion along the dispersion dimension, whereas the second curvature and the third curvature together determine beam magnification along the non-dispersion dimension. In other embodiments, where the beam rotator 508 is located outside of the lens set 506C and the lens set 506D (e.g. after lens set 506D), the first curvature and the third curvature together determine magnification of light dispersion along the dispersion dimension, whereas the second curvature and the fourth curvature together determine beam magnification along the non-dispersion dimension.

Figure 5E illustrates two example fields of view (FOVs) 550A and 550B. Both the FOVs 550A and 550B extend in the dispersion dimension (x-axis in Fig. 5E), along which the optical beam is steered based on dispersive effects. That is, light of different wavelengths (XI, A2 . . . AN) is directed to different directions. Both the FOVs 550A and 550B extend in the non-dispersion dimension (y-axis in Fig. 5E), along which the optical beam is steered based on non-dispersive effects, such as mechanical means described herein. The FOV 550A results from an optical system, such as the optical system of 500C, where the beam compressor is associated with the same magnification along different lateral axes of an optical beam. In comparison, the FOV 550B results from an optical system, such as the optical system of 500D, where the beam compressor is associated with different magnification along different lateral axes of an optical beam. The FOV 550A corresponds to optical beams that have a circular or substantially circular beam shape 520A. The FOV 550A is defined by a first FOV extent 522A in the dispersion dimension and a second FOV extent 425A in the non-dispersion dimension. Based on different magnification along orthogonal axes, the resulting light beams may be shaped, such as to an elliptical shape. For example, as illustrated in the FOV 550B, the optical light beam has an elliptical beam shape 520B. Compared to the beam shape 520A, the beam shape 520B has different beam widths along one or both lateral axes. Further, based on the different magnification along the orthogonal axes, the FOV has a controllable aspect ratio. For example, the FOV 550B is defined by a third FOV extent 522B in its dispersion dimension and a fourth extent 524B in its non- dispersion dimension. The third FOV extent 522B may be the same as or different from the first extent 522A, and the fourth FOV extent 524B may be the same as or different from the second extent 524A. In other words, the beam ellipticity (or the numerical aperture along the orthogonal axes (e.g. x and y axes)) is independently configurable based on selection of the two sets of surface curvature. Alternatively or additionally, the field of view along one or both of orthogonal dimensions (e.g. dispersion dimension and non-dispersion dimension) is/are independently configurable based on selection of the two sets of surface curvature.

As a general trade-off, in the dispersion dimension, the optical beam width decreases as the FOV extent in the dispersion dimension increases. For example, the beam compressor may be arranged, such as by respectively designing the curvature along the two orthogonal dimensions, to cause the light beams to have a smaller numerical aperture along a first dimension (e.g. x-axis in Fig. 5D) than a second orthogonal dimension (e.g. y-axis in Fig. 5D). A smaller numerical aperture along the dispersion dimension may be beneficial, in that the extent of beam direction, hence the field of view along that axis, is maximised. Additionally or alternatively, it may be beneficial to have a larger numerical aperture along, for example, a second dimension orthogonal to the first dimension (or y-axis in Fig. 5D) to compensate for the small numerical aperture along the first axis. Independently configuring the FOV extents and/or beam shape along different dimensions allows an adjustment of the overall numerical aperture to cause a corresponding adjustment to light collection efficiency. That is, a decrease in numerical aperture along the first dimension may be compensated by an increase in numerical aperture along the second, orthogonal dimension. Further, separating magnification into orthogonal dimension allows for configuration or adjustment of FOV extent and range, which are both related to the numerical aperture. Figure 6A illustrates an optical system 600, which includes the optical system 500C additionally configured to provide for beam direction across another dimension, for instance the first dimension referred to in Fig. 4. In other words, the optical system 600 is configured to implement steps 402 to 408 of Fig. 4.

To achieve two-dimensional scanning, the beam director 104 also includes a scanning component 512, to further steer the light beams 511c (or the light beams 51 lb in embodiments in which the reflecting or refracting element 510 is omitted) over a dimension that is, or at least includes a substantial component that is, orthogonal to the second dimension. In that way, the beam director 104 as a whole directs light over a first dimension and a second dimensional orthogonal to the first dimension.

The scanning component 512 may achieve the scanning operation in whole or in part by mechanical movement of one or more physical components and accordingly the first dimension referred to in Fig. 4 may be called the mechanical dimension. The mechanical movement may be rotation, for example continuous rotation or tilting of the physical component. The scanning component 512 may be positioned at or near the multi -wavelength converged location 515a. Positioning the scanning component 512 at or near the multiwavelength converged location may facilitate beam director with a reduced foot print.

The scanning component 512 may include at least one reflector and/or at least one refractor. In one example, the scanning component 512 is reflector in the form of a polygon mirror. The polygon mirror may rotate continuously. In another example, the scanning component 512 is a rotating reflector, for example a mirror that rotates discontinuously, by cycling through rotation in one direction and then in the reverse direction and so forth. In another example, the scanning component 512 is a rotating grating, which may rotate continuously or discontinuously.

The scanning component 512 is rotated, for example about an axis A shown in Fig. 6A, for steering outgoing light 513. The wavelength dimension and the mechanical dimension may be represented in Cartesian (x, y) or polar (r, phi) coordinates. The rotation may be, for example, by an electric motor that is mechanically or electromechanically connected to a housing of the scanning component 512. In one example, rotating the scanning component 512 may be realised by placing the scanning component 512 in a hollow-core motor (not shown). The scanning component 512 may be rotated at either a constant or a variable speed within the rotation cycle or over multiple rotation cycles. For the purposes of the present disclosure, referring to “rotation”, “rotated”, “rotating” or similar includes any form of angular adjustment and includes but is not limited to elements that are constantly or continuously rotating and to elements that are rotated through a full 360 degrees. Fig. 6 A illustrates the mechanical dimension, with outgoing light 513 scanned across the XZ plane, including outgoing light beams 513-al when the scanning component 512 is rotated by an angle al and outgoing light beams 513-a2 when the scanning component 512 is rotated by an angle a2 (al a2). Fig. 6B illustrates the wavelength dimension, with outgoing light 513 scanned and/or spread across the YZ plane, based on separation by wavelength of the light beams 511, 51 lb or 511c.

Figs. 7A and 7B illustrate the beam director 600 of Fig. 6A with a polygon mirror 512a as the scanning component, rotated with an angle of as and a4 (as a4), respectively. The polygon mirror 512a is rotated about an axis A, which is located at the geometric centre of the polygon mirror 512a. With the rotation, the relative angle of the reflecting surface of the polygon mirror 512a changes. As a result, the outgoing light from the light source 101 or the optical amplifier 102 is steered.

By placing the polygon mirror 512a at or near the aforementioned multi -wavelength converged location, the span of the light beams 511c in the Y direction of Figs. 7A, 7B at the point where the light beams 511c are reflected by the polygon mirror 512a is relatively small. This in turn allows for the height (in the Y direction) of the polygon mirror 512a to be correspondingly small. For example the height of the reflecting surfaces of polygon mirror 512a may be approximately equal to (e.g. equal to or within 10 percent of), or less than the maximum height of the active areas of the beam director that create the wavelength dimension. The active areas for creating the wavelength dimension are the areas of the optical components between the light source 101 (or the optical amplifier 102 in the examples where the optical amplifier 102 is used) and the scanning component 512 (i.e. the polygon mirror 512a in this example) that receive light. In other embodiments the height of the reflecting surfaces of polygon mirror 512a may be greater than the active areas for the wavelength dimension, for example up to two times the height of the active areas or up to three, four or five times the height of the active areas.

In other embodiments, the scanning component 512 may achieve the scanning operation without mechanical movement. In these embodiments the beam director may include no moving parts. For example, the scanning component 512 may comprise gratings and/or prisms, which direct light based on wavelength. The scanning component 512 may have a configuration like that of the dispersive component 504. In these embodiments, the beam director may be described as having wavelength dimensions, instead of one wavelength dimension and one mechanical dimension.

Figs. 8A-8C each illustrates an embodiment of the beam rotator 508 used in the configurations of Figs. 5-7.

In the embodiment of Fig. 8A, the beam rotator 508a has a first mirror 508a- 1 and a second mirror 508a-2 each with a reflective surface facing each other. The incoming light beams across the first dimension (e.g. the light beams 509 from the second lens 506B of the beam compressor 506 or the light beams 507a from the second lens 506A of the beam compressor 506) are first reflected by the first mirror 508a-l and further reflected by the second mirror 508a-2 to output light beams across the second dimension (e.g. the light beams 511 corresponding to the incoming light beams 509 or the light beams 511a corresponding to the incoming light beams 507a).

In the embodiment of Fig. 8B, the beam rotator includes a dove prism 508b. The incoming light beams across the first dimension (e.g. the light beams 509 from the second lens 506B of the beam compressor 506 or the light beams 507a from the second lens 506A of the beam compressor 506) enters a first surface 508b-l and are refracted to a second surface 508b-2 within the dove prism 508b. The refracted beams are further reflected by the second surface 508b-2 within the dove prism 508b and exit from a third surface 508b-3 with beams across the second dimension (e.g. the light beams 511 corresponding to the incoming light beams 509 or the light beams 511a corresponding to the incoming light beams 507a).

In the embodiment of Fig. 8C, the beam rotator includes a K-mirror system 508c having a first plane mirror 508c-l, a second plane mirror 508c-2 and a third plane mirror 508c-3, which are arranged in a way that the second plane mirror 508c-2 looks like the backbone of a capital letter “K” while the first and second plane mirrors 508c- 1 and 508c-3 look like the legs of the capital letter “K” when looking the K-mirror system 508c parallel to the mirror surfaces where only the edges of the mirrors 508c- 1, 508c-2 and 508c-3 remain visible. The incoming light beams across the first dimension (e.g. the light beams 509 from the second lens 506B of the beam compressor 506 or the light beams 507a from the second lens 506A of the beam compressor 506) are first reflected by the first mirror 508c-l and hit the second mirror 508c-2. The reflected light beams are then reflected by the second mirror 508c-2 and hit the third mirror 508c-3 and further reflected by the third mirror 508c-3 to output light beams across the second dimension (e.g. the light beams 511 corresponding to the incoming light beams 509 or the light beams 511a corresponding to the incoming light beams 507a).

In some embodiments, the beam rotator 508 is rotated over time along or about an axis parallel to the light propagation direction (e.g. z-axis in Figs. 5B, 5C, 6A, 7A and 7B). This time-varying rotation of the beam rotator 508 results in a time-varying rotation of the wavelength dimension, which in turn results in a 2D circular scan pattern. In the example of the beam rotator 508 being a dove prism, for example the dove prism 508b as illustrated in Fig. 8B, every 0 (theta) rotation of the dove prism 508b corresponds to 2x0 rotation of the wavelength dimension. For example, a 90-degree rotation of the dove prism 508b over time corresponds to a 180-degree rotation of the wavelength dimension overtime. In one example, the dove prism 508B may be placed in a hollow core motor that is operated to provide the time-varying rotation.

Alternatively, the equivalence of a mechanically rotating dove prism may be achieved using a non-mechanical method, such as by using electrical adjustment of an acousto-optic dove prism 900. As illustrated in Fig. 9, an example acousto-optic dove prism 900 includes a multi-faceted cylindrical mirror 902 in between two acousto-optic crystals 904 and 906. Each mirror facet corresponds to a different amount of beam rotation. Light passes through the first acousto-optic crystal 904 and is deflected towards a specific one of the mirror facets of the multi-faceted cylindrical mirror 902, responsive to an electrical voltage applied to the first acousto-optic crystal 904. The second acousto-optic crystal 906 reverses the deflection caused by the first acousto-optic crystal 904.

It will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention.

Claims

1. An optical beam director including: a dispersive component configured to receive light and to steer the received light across a first dimension based on its wavelength; and a beam rotator configured to convert the light steered across the first dimension to light steered across a second dimension that is orthogonal to the first dimension or includes a substantial component that is orthogonal to the first dimension.

2. The optical beam director of claim 1, wherein the beam rotator includes a first mirror and a second mirror each with a reflective surface facing each other.

3. The optical beam director of claim 1, wherein the beam rotator includes a dove prism.

4. The optical beam director of claim 1, wherein the beam rotator includes a K-mirror system.

5. The optical beam director of claim 1, further including a steering component configured to receive the light steered across the second dimension and steer it across a third dimension, whereby the first and third dimensions form a two-dimensional field of view.

6. The optical beam director of claim 5, wherein the first dimension and the third dimension are aligned.

7. The optical beam director of claim 5, wherein the steering component steers the light steered across the third dimension through mechanical movement.

8. The optical beam director of claim 1, further including a beam compressor configured to magnify light dispersion in the light from the dispersive component.

9. The optical beam director of claim 5, further including a beam compressor configured to converge the light steered across the second dimension.

10. The optical beam director of claim 9, wherein the beam compressor is configured to magnify light dispersion in the light from the dispersive component.

11. The optical beam director of claim 9, wherein the steering component is placed near or at a converged location created by the beam compressor.

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12. The optical beam director of claim 9, wherein the beam compressor includes a first lens followed by a second lens, wherein each of the first lens and the second lens has a positive focal length.

13. The optical beam director of claim 9, wherein the beam compressor is followed by the beam rotator.

14. The optical beam director of claim 12, wherein the beam rotator is placed between the first lens and the second lens.

15. The optical beam director of claim 5, wherein the steering component includes at least one of a rotating reflector and a rotating refractor.

16. The optical beam director of claim 15, wherein the steering component includes a polygon mirror.

17. The optical beam director of claim 8, wherein the beam compressor includes a first set of one or more surfaces associated with a first magnification in the first dimension and a second set of one or more surfaces associated with a second magnification in the second dimension.

18. The optical beam director of claim 17, wherein the first set of one or more surfaces include at least a first surface in a first cylindrical lens, and the second set of one or more surfaces include a second surface in a second cylindrical lens, the first surface having a first curvature in the first dimension and the second surface having a second curvature, different from the first curvature, in the second dimension.

19. An optical beam director including : a dispersive component configured to receive light and to steer the received light across a first dimension based on its wavelength; and a beam compressor configured to magnify light dispersion in the light from the dispersive component, the beam compressor including a first set of one or more surfaces associated with a first magnification in the first dimension and a second set of one or more surfaces associated with a second magnification in the second dimension.

20. The optical beam director of claim 19, wherein the one or more surfaces include a first surface in a first cylindrical lens and a second surface in a second cylindrical lens, the first surface having a first curvature in the first dimension and the second surface having a second curvature, different from the first curvature, in the second dimension.

21. The optical beam director of claim 19, wherein the beam compressor is arranged to cause the steered light to have a first numerical aperture in the first dimension and a second numerical aperture, larger than the first numerical aperture, in the second dimension.

22. A spatial estimation system including: a light transmission path, including: an optical beam director as claimed in any one of claims 1 to 21 ; and a light source for generating outgoing light and providing the outgoing light to the optical beam director; a light reception path, including: optical reception components configured to receive light from an environment, the received light including the outgoing light reflected by the environment; detector circuitry to detect light received by the optical reception components and generate a signal indicative of the outgoing light reflected by the environment.

23. A method of providing outgoing light in a spatial estimation system, the method including: generating outgoing light, the outgoing light having a range of wavelengths and providing the outgoing light to a beam director; and by the beam director: directing different wavelengths of the outgoing light into different directions, so that the outgoing light is spread across a first dimension; converting the outgoing light spread across the first dimension to outgoing light spread across a second dimension that is orthogonal to the first dimension or includes a substantial component that is orthogonal to the first dimension; steering the outgoing light across a third dimension, whereby the light spread across the first and the third dimensions form a two-dimensional field of view of the spatial estimation system.

24. The method of claim 23, wherein the first dimension and the third dimension are aligned.

25. The method of claim 23 or claim 24, wherein steering the outgoing light across a third dimension includes mechanical steering and wherein the method includes, prior to steering the outgoing light, converging the outgoing light spread across the second dimension.

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