WO2021126083A1

WO2021126083A1 - Lidar transmitter, system and method

Info

Publication number: WO2021126083A1
Application number: PCT/SG2020/050753
Authority: WO
Inventors: Ho Hoai Duc Nguyen
Original assignee: Ams Sensors Asia Pte. Ltd.
Priority date: 2019-12-20
Filing date: 2020-12-17
Publication date: 2021-06-24

Abstract

A LIDAR transmitter system comprising an array of laser energy sources, the laser energy sources arranged in a plurality of spatially separated regions; and a plurality of diffusers. Each diffuser is respectively arranged to cover one of said plurality of spatially separated regions. The respective laser energy sources of each spatially separated region are arranged to emit laser energy through a corresponding diffuser of the plurality of diffusers towards a LIDAR target.

Description

LIDAR Transmitter, System and Method

Technical Field of the Disclosure

The disclosure relates to LIDAR systems and methods, particularly but not exclusively, to a LIDAR transmitter system, a LIDAR system, and a method for emitting a LIDAR signal.

Background of the Disclosure

LIDAR is a technique of measuring a distance to a target. The target is illuminated with laser light emitted from a LIDAR transmitter system and the reflected laser light is detected with a sensor or LIDAR receiver system. A time-of-flight measurement is made to establish the distance between the LIDAR system and different points on the target to build up a three-dimensional representation of the target. The target could be an object, plurality of objects or a whole scene in the field of view of the LIDAR system.

An example of a known LIDAR transmitter system 100 is illustrated in Figure 1a. The known LIDAR transmitter system 100 includes a laser source 101 , for example arranged on a wafer 104, which emits a laser beam 102a.

The laser source 101 of Figure 1a may comprise a plurality of known vertical-cavity surface-emitting lasers (VCSEL) of the type illustrated in Figure 1b. In the VCSEL 105 of Figure 1b, a plurality of distributed Bragg reflector (DBR) layers 106 are positioned on either side of an active region 107, for example comprising one or more quantum wells, for laser energy generation and resonance between the DBR layers 106. These DBR layers 106 and active region 107 may be arranged on a substrate 108, which in turn may be arranged on a printed circuit board 109 (PCB). The VCSEL 104 of Figure 1b is a top-emitting VCSEL however bottom-emitting VCSELs are also known.

Typically, LIDAR applications that require a wide area of LIDAR coverage require a field of view of one hundred degrees or more to efficiently build up the three- dimensional representation of the LIDAR target. To achieve such a wide field of view, known LIDAR transmitter systems 100 use a diffuser 103 to diffuse (i.e. scatter) the laser beam to generate a wide beam angle 102b. Increasing the beam angle causes the intensity of the laser beam to decrease as distance from the LIDAR transmitter system 100 increases. As the intensity decreases, the quality and strength of the light reflecting off the LIDAR target also decreases until the quality and strength of reflected light is too low to reliably perform a time-of-flight measurement. This is described herein as the effective LIDAR range. The effective LIDAR range of known LIDAR transmitter systems 100 thus depends on the beam angle and corresponding field of view of the LIDAR transmitter system 100. The wider the beam angle and corresponding field of view, the shorter the effective LIDAR range, but the greater the area of coverage of the LIDAR system. Conversely, the narrower the beam angle and corresponding field of view, the greater the effective LIDAR range of the LIDAR transmitter system 100 but the lower the area of coverage. Thus, in known LIDAR systems, a trade off must always be made between effective LIDAR range and area of coverage.

Additional problems of known LIDAR transmitter systems will now be explained with reference to the field of object detection and collision avoidance for self-driving vehicles. In order to provide an efficient three-dimensional representation of a scene in front of a self-driving vehicle, different regions around in the field of view of the vehicle have different effective LIDAR range requirements. For example, measuring the distance to the next vehicle in the forward direction requires a high effective LIDAR range given the high speeds at which the vehicle moves in the forward direction. However, the next vehicle typically takes up only a small fraction of the whole field of view. Conversely, objects to the side of the vehicle or in the periphery of the field of view are much less important to collision avoidance so their distance typically does not need to be determined until they are much closer to the vehicle. The effective LIDAR range requirements to measure distances to such periphery objects are thus much lower. However, these types of objects typically take up a much greater proportion of the field of view of the vehicle’s field of view. Known LIDAR systems typically try to circumvent this problem by increasing the power of the laser source while maintaining the wide field of view. This results in an increased beam intensity and thus effective LIDAR range over the whole field of view even though only a small area of the total field of view actually requires the increased range. Optical power is thus ineffectively spread over the field of view and there is an increased risk of potentially dangerous high power hotspots in the output beam which could pose a danger to bystanders or sensitive equipment in the vicinity of the LIDAR system. Furthermore, operating high optical power laser sources has the following additional problems: (i) significant additional heat generation which must be compensated for with heat sinks or other components, (ii) higher operation, maintenance and manufacturing costs, and (iii) significant cross-talk and noise at the LIDAR receiver system - specifically, the inevitable, higher intensity reflections from e.g. background areas in the field of view which are of little use may swamp one or more pixels of the LIDAR receiver system, making it difficult to distinguish the reflections from the LIDAR target.

It is an aim of the present disclosure to provide a LIDAR transmitter system, LIDAR system, and a method for emitting a LIDAR signal that addresses one or more of the problems above or at least provides a useful alternative.

Summary

In general terms, this disclosure proposes to overcome the above problems by segmenting the laser sources and diffuser into regions. The regions each being separately controllable and having a predetermined output beam angle and corresponding field of view. This arrangement provides at least one or more of the following advantages over known LIDAR transmitter systems:

(i) The segmented regions and diffuser provide a means to control the effective LIDAR range and area of coverage of different portions of the output laser beam so that the LIDAR system can provide high range, low coverage LIDAR signals and low range, high coverage LIDAR signals, which may or may not overlap, without the need for additional components or complex LIDAR transmitter arrangements. A LIDAR transmitter system according to the present disclosure does not need to make the trade off between effective LIDAR range and area of coverage.

(ii) The LIDAR transmitter system operates more efficiently compared to known systems because use of higher optical power can be limited to only those segmented regions whose output is chosen to have a higher effective LIDAR range. The optical power of any other regions which are chosen to have a lower effective LIDAR range but wider coverage can be kept lower. This reduces the total heat generation of the LIDAR transmitter system, and reduces the operating, maintenance and manufacturing costs. Similarly, as only a portion of the output beam has a higher optical power, the risk of potentially dangerous high power hotspots in the output beam is reduced, improving safety of the system.

(iii) Cross-talk and noise are minimised because the strength of the reflections that arrive at the LIDAR receiver arising from the lower optical power, lower effective LIDAR range segments of the LIDAR transmitter are weaker than if a high optical power had been used for the whole output beam.

(iv) Particularly, but not exclusively, for object detection and collision avoidance in self driving cars, the LIDAR transmitter can be configured to emit both a laser energy beam having a high effective LIDAR range and low area coverage (i.e. high intensity and narrow field of view) in the direction of travel of the vehicle and a laser energy beam having a low effective LIDAR range but high area coverage (i.e. low intensity and wide field of view) in directions peripheral to the direction of travel.

According to one aspect of the present disclosure, there is provided a LIDAR transmitter system comprising: an array of laser energy sources, the laser energy sources arranged in a plurality of spatially separated regions; and a plurality of diffusers, each diffuser respectively arranged to cover one of said plurality of spatially separated regions, wherein the respective laser energy sources of each spatially separated region are arranged to emit laser energy through a corresponding diffuser of the plurality of diffusers towards a LIDAR target.

Optionally, each diffuser is respectively configured to define a field of view of a respective laser energy beam emitted from the laser energy sources of the corresponding spatially separated region, and the field of view defined by a first diffuser of the plurality of diffusers is narrower than the field of view defined by a second diffuser of the plurality of diffusers.

Optionally, the laser energy beam having the field of view defined by the first diffuser is emitted from a first region of the plurality of spatially separated regions, and the laser energy beam having the field of view defined by the second diffuser is emitted from a second region of the plurality of spatially separated regions. Optionally, the first region is larger and comprises a greater number of laser energy sources than the second region.

Optionally, the field of view defined by the first diffuser overlaps with the field of view defined by the second diffuser.

Optionally, the laser energy sources in the first region are configured to generate a first laser energy flash at a first time, and the laser energy sources in the second region are configured to generate a second laser energy flash at a second time, different to the first time.

Optionally, at a first distance from the LIDAR transmitter system, the intensity of the laser energy beam having the field of view defined by the first diffuser is greater than the intensity of the laser energy beam having the field of view defined by the second diffuser such that the effective LIDAR range of the laser energy beam having the field of view defined by the first diffuser is greater than the effective LIDAR range of the laser energy beam having the field of view defined by the second diffuser.

Optionally, the plurality of diffusers comprise: diffractive, refractive, and/or holographic diffusers.

Optionally, the array of laser energy sources comprises an array of vertical cavity surface emitting lasers (VCSELs) arranged on a wafer.

Optionally, the laser energy sources comprise edge emitters, LEDs and/or integrated laser energy sources.

According to a second aspect of the present disclosure, there is provided a LIDAR system, the LIDAR system comprising: the above described LIDAR transmitter system and a LIDAR receiver system.

According to a third aspect of the present disclosure, there is provided a method for emitting laser energy towards a LIDAR target, the method comprising: emitting laser energy from an array of laser energy sources through a plurality of diffusers towards a LIDAR target, wherein the laser energy sources are arranged in a plurality of spatially separated regions, wherein each diffuser is respectively arranged to cover one of said plurality of regions, and wherein the respective laser energy sources of each spatially separated region are arranged to emit laser energy through a corresponding diffuser of the plurality of diffusers.

Thus, embodiments of this disclosure provide the above described advantages.

Brief Description of the Preferred Embodiments

Some embodiments of the disclosure will now be described by way of example only and with reference to the accompanying drawings, in which:

Figure 1a illustratively shows a known LIDAR transmitter system.

Figure 1b illustratively shows a known VCSEL.

Figure 2 illustratively shows a LIDAR transmitter system in accordance with the present disclosure.

Figure 3 illustratively shows a LIDAR transmitter system in accordance with the present disclosure.

Figure 4 illustratively shows an array of laser energy sources in accordance with the present disclosure.

Figure 5 illustratively shows a diffuser arrangement in accordance with the present disclosure.

Figure 6 illustratively shows a diffuser arrangement in accordance with the present disclosure.

Figure 7 illustratively shows a diffuser arrangement in accordance with the present disclosure.

Figure 8 illustratively shows a diffuser arrangement in accordance with the present disclosure.

Figure 9 illustratively shows a LIDAR system in accordance with the present disclosure. Figure 10 shows a flowchart showing method steps in accordance with the present disclosure. Detailed Description of the Preferred Embodiments

In general terms, this disclosure provides a LIDAR transmitter system comprising an array of laser energy sources arranged in a plurality of spatially separated regions covered by a corresponding diffuser. The respective laser energy sources of the spatially separated regions are arranged to emit laser energy through a corresponding diffuser towards a LIDAR target. By segmenting the laser energy sources and diffusers in this way, the LIDAR transmitter system can control the output beam to have a variety of different effective LIDAR ranges and areas of coverage.

Some examples of the solution provided by this disclosure are given in the accompanying figures.

Figure 2 shows an illustration of a LIDAR transmitter system 200 comprising an array 201 of laser energy sources. The laser energy sources may comprise, for example, vertical cavity surface emitting lasers (VCSELs) of the type shown in Figure 1b (including top emitting and/or bottom emitting VCSELs), edge emitters, LEDs and/or integrated laser energy sources. The laser energy sources 201 are arranged in a plurality of spatially separated regions. The LIDAR transmitter system 200 further comprises a plurality of diffusers 202, each respectively arranged to arranged to cover one of said plurality of spatially separated regions. The diffusers may comprise, for example, diffractive, refractive and/or holographic diffusers. The respective laser energy sources of each spatially separate region are arranged to emit laser energy 203 through a corresponding diffuser towards a LIDAR target. The laser energy sources may be addressable and thus activatable at a column or row level, individual level, or region or section level resolution.

An example of a refractive diffuser is a lens placed over an energy source. If the emitted light from the energy source is a collimated beam, a negative lens can be used to turn the collimated beam into a divergent beam. Alternatively, a positive lens with a focal point which is much shorter than the distance to the illuminated target can be used. A larger diffusing angle, also referred to as a larger field of view, can be achieved using a stronger lens. An array of energy sources can be covered by an array of lenses, with one lens per energy source, but alternatively a refractive lens can be used which has a straight (not curved) profile in a longitudinal direction of a longitudinal array of light sources, while being curved in a direction perpendicular to the longitudinal direction. Alternatively, an array of prisms or other refractive optical elements can be used to diffract the light. The same optical function can be achieved with a micro-structured meta-surface.

Examples of diffractive optical elements are a grating, or a small opening in an opaque screen. A smaller opening will create a larger amount of diffraction, or varying the grating constant will vary the amount of diffraction accordingly. An array of small openings can be used to create a speckle pattern based on interference between the light emerging from the openings. Holographic diffusers can be manufactured with photopolymers, and provide a further option for implementing the invention. Holographic diffusers may provide more precise control over the shape of the output beam and may thus help to homogenise the output beam to reduce a risk of hot spots compared to diffractive and/or refractive diffusers. A holographic diffuser may comprise one or more photopolymer layers comprising pseudo random, non-periodic structures, for example micro-lenses configured to provide a predetermined output field of view.

The skilled person will be able to select accordingly a first diffuser with a first field of view, or a first angle of diffusion, and a second diffuser with a second field or view or angle of diffusion which is different from the first field of view of diffusion angle.

Figure 3 shows an illustration of an example LIDAR transmitter system 300 such as that shown in Figure 2. The LIDAR transmitter system 300 comprises an array 301 of laser energy sources arranged in a plurality of spatially separated regions 301a, 301b, optionally on a wafer 305. The LIDAR transmitter system 300 further comprises a plurality of diffusers 302a, 302b respectively arranged to cover one of said plurality of spatially separated regions 301a, 301b. The respective laser energy sources of each spatially separated region 301a, 301b, are arranged to emit laser energy 303a, 303b, through a corresponding diffuser 302a, 302b towards a LIDAR target.

As described above, the diffusers 302a, 302b diffuse (i.e. scatter) the emitted laser energy 303a, 303b thereby defining a field of view or beam angle of a respective laser energy beam 304a, 304b emitted from the laser energy sources of the corresponding spatially separated regions 301a, 301b. In the example configuration of Figure 3, the emitted laser energy beams 304a, 304b having the field of views defined by the first and second diffusers 302a, 302b are respectively emitted from corresponding first and second spatially separated region 301a, 301b. The field of view each diffuser 302a, 302b may be different to the each other and to other diffusers in the plurality of diffusers. In this way, the effective LIDAR range and coverage of the output beam or beams can be customised and controlled. For example, the field of view defined by a first diffuser 302a of the plurality of diffusers may be narrower than the field of view defined by a second diffuser 302b of the plurality of diffusers. The emitted laser energy beam 304a having the field of view defined by the first diffuser 302a in such an example is narrower and thus has a beam intensity that drops off more slowly at distance and thus has a higher effective LIDAR range and smaller area coverage compared to the emitted laser energy beam 304b having the field of view defined by the second diffuser 302b, which accordingly has a beam intensity that drops off more quickly at distance and thus has a lower effective LIDAR range but higher area of coverage.

Combining different diffuser arrangements thus provides greater freedom to customise and control the effective LIDAR range and area coverage of different parts of the output laser energy beam based on specific LIDAR application requirements and needs.

In some applications, the field of view of one or more diffusers may overlap with the field of view of other diffusers. In the example configuration of Figure 3, the field of view of the emitted laser energy beams 304a, 304b overlap. In this way, the beams together provide a complete and full field of view, albeit with some parts of the combined output beam having different effective LIDAR ranges to others. By way of illustrative example, the LIDAR transmitter system 300 of Figure 3 may be used for object detection and collision avoidance in self-driving vehicles. In this scenario, the first emitted laser energy beam 304a has a high effective LIDAR range with a smaller, focussed area coverage required for long range object detection in front of the vehicle while moving at high speeds in a forwards direction. Conversely, the second emitted laser energy beam 304b has a lower effective LIDAR range with a larger, less focussed area coverage required for secondary object detection not immediately in the movement path of the vehicle (such as vehicles in adjacent lanes, curbs, central reservations and other objects which require only short range detection). In some applications, the sizes and corresponding number of laser energy sources of one or more of the spatially separated regions 301a, 301b may be different to the sizes and number of laser energy sources of other spatially separated regions in the plurality of spatially separated regions. For example, the first region 301a may comprise a greater number of laser energy sources than the second region 301b. It is envisaged that such a configuration may be of particular use where the peripheral parts of a field of view do not require a high effective LIDAR range. Arranging a larger number of laser energy sources in the first region 301a rather than in the second region 301b is thus efficient as less optical power is wasted on providing the wider field of view part of the output laser energy beam. Conversely, in other configurations where a high optical power in the central part of the output laser energy beam is not required but a higher optical power in the wider field of view part of the beam is required, the second region 301b may comprise a greater number of laser energy sources than the first region 301b.

It is envisaged that the present invention may be used for both continuous LIDAR scanning and flash LIDAR. In flash LIDAR, the output laser energy beam is pulsed or flashed at predetermined times. An advantage of flash LIDAR is that the flashes may each have a higher optical power than a beam which is continuously scanned.

In some applications, for example in flash LIDAR applications, it is envisaged that one or more of the spatially separated regions may emit a pulse or flash at different times to other spatially separated regions of the plurality of spatially separated regions. An advantage of emitting sequential flashes is that it reduces cross-talk in the detected energy at the LIDAR receiver. For example, in the configuration of Figure 3, the laser energy sources in the first region 301a may be configured to generate a first laser energy flash or pulse at a first time, and the laser energy sources in the second region 301b may be configured to generate a second laser energy flash or pulse at a second time, different to the first time. In this way, reflected energy detected at the LIDAR receiver from the first laser energy flash or pulse does not interfere with reflected energy detected at the LIDAR receiver from the second laser energy flash and cross talk and other interference is reduced. If higher numbers of regions and diffusers are present, these may each be activated sequentially at different times. Figure 4 shows a top view of an example array 400 of laser energy sources arranged in a plurality of spatially separated regions 401a, 401b. The configuration may be used with the LIDAR transmitter systems of Figures 2 and 3. In the example configuration of Figure 4, the number of laser energy sources in the first region 401a is greater than in the second region 401b. Flowever it is envisaged that different configurations are also possible where the number of laser energy sources in the second region 401b are greater than in the first region 401b, depending on the LIDAR application requirements. Whilst not shown in Figure 4, first and second diffusers are also provided and respectively arranged to cover the first and second regions 401a, 401b in the manner described above in connection with Figures 2 and 3.

Figures 5-8 show illustrative examples of different diffuser shape configurations which may be used with the LIDAR transmitter systems of Figures 2 and 3. Whilst not shown, it is envisaged that the shape and number of spatially separated regions of the array of laser energy sources correspond to the shapes and numbers of diffusers provided. Further, whilst only four examples are shown in Figures 5-8, other shape configurations and numbers of regions and diffusers are also envisaged falling within the scope of the appended claims, the shape configuration and numbers depending on the requirements of the LIDAR application. In particular, as the laser energy sources may be addressable and thus separately activatable at column, row, individual or region level resolution, the dimensions of the spatially separated regions and corresponding diffusers may be segmented customised in any combination and number as required by the LIDAR application. Similarly, the field of view for each segment may be adjusted during manufacture to suit the requirements of the application.

In the example configuration of Figure 5, a first diffuser 501a and a second diffuser 501b is provided, the shapes and sizes arranged to cover correspondingly shaped and sized spatially separated regions of the array of laser energy sources. The first diffuser 501a is partially surrounded by second diffuser 501b. The field of view defined by the first diffuser 501a is wider than the field of view defined by the second diffuser 501b, and the number of laser energy sources in the spatially separated region corresponding to the first diffuser 501a is greater than the number of laser energy sources in the spatially separated region corresponding to the second diffuser 501b. In this way, the effective LIDAR range of the laser energy beam emitted through the first diffuser 501a is higher and has a smaller, focussed area coverage than the laser energy beam emitted through the second diffuser 501b, which has a shorter effective LIDAR range but wider area coverage.

In the example configuration of Figure 6, a first diffuser 601a, a second diffuser 601b and up to an n^th diffuser 601 n are provided and respectively arranged to cover correspondingly shaped and sized spatially separated regions of the array. It is envisaged that each diffuser up to the n^th diffuser 601 n decreases in size and thus comprises an increasingly smaller area and corresponding number of laser energy sources. In this way, the combined output laser energy beam has n-number of different field of views and effective LIDAR ranges to provide a combined field of view with complete coverage of one or more LIDAR targets at a plurality of different effective LIDAR ranges. In the example configuration of Figure 6, the n diffusers in Figure 6 are arranged laterally with respect to each other.

The example configuration of Figure 7 corresponds to the example configuration of Figure 6 in that a first diffuser 701a, a second diffuser 701b, and up to an n^th diffuser 701 n are provided and respectively arranged to cover correspondingly shaped and sized spatially separated regions of the array. As in the case of Figure 6, each diffuser up to the n^th diffuser 701 n decreases in size and thus comprises an increasingly smaller area and corresponding number of laser energy sources. In the example configuration of Figure 7, the second diffuser and up to n^th diffuser partially surround each other to provide a combined field of view with complete coverage of one or more LIDAR targets with a plurality of different effective LIDAR ranges.

The example configuration of Figure 8 corresponds to a plurality of the example configurations of Figure 7 arranged to provide concentric diffuser rings, including a second diffuser 801b and up to an nt^h diffuser 801 n, around one or more central diffusers 801a. As in the example configuration of Figure 7, the diffusers are arranged to cover correspondingly shaped and sized spatially separated regions of the array. In this way, the combined output laser energy beam provides a combined field of view with complete coverage of one or more LIDAR targets a plurality of different effective LIDAR ranges.

In each of the examples of Figures 5-8, it is envisaged that the higher number ordered diffusers from the first diffusers may have a wider field of view than the first diffusers for LIDAR applications where a long effective LIDAR range and small, focussed area coverage is required in the centre of an output laser energy beam but a smaller effective LIDAR range with high area coverage is required in the periphery of the output laser energy beam. An example of this type of application is in the field of object detection and collision avoidance in self-driving vehicles.

Figure 9 illustratively shows a LIDAR system 900 comprising a LIDAR transmitter system 901 such as that described above in connection with Figures 2-9 and a LIDAR receiver system 902. The LIDAR transmitter system 901 is configured to emit laser energy 903a, 903b towards one or more LIDAR targets 904a, 904b, which may be at different distances and positions relative to the LIDAR system 900. Reflected laser energy 905a, 905b propagates towards the LIDAR receiver system 902 where it is detected and used to calculate a distance from the LIDAR system 900 to the one or more LIDAR targets 904a, 904b, for example using a time-of-flight calculation.

The LIDAR system 900 may operate as a flash LIDAR where the LIDAR transmitter system 901 emits laser pulses (for example sub-nanosecond light pulses), or as a scanning LIDAR where the LIDAR transmitter system 901 emits a continuous, directed beam.

The LIDAR receiver system 902 may comprise a plurality of photodetectors, for example photodiodes, such as pin diodes, single photon avalanche diodes, avalanche diodes, or phototransistors configured to detect the laser energy 905a, 905b reflected from the one or more LIDAR targets 904a, 904b. Each photodetector of the LIDAR receiver system 902 acts as a detection pixel typically corresponding to one laser energy source in the array of the LIDAR transmitter system 901. The one-to-one pixel- emitter correspondence may be used to calculating a time-of-flight histogram which may be used to detect and compensate for any internal reflections from, for example, optional cover glass of the LIDAR system 900, or any cross-talk between laser energy sources of the array and a plurality of different detection pixels.

By using a LIDAR transmitter system 901 such as that described in relation to Figures 2-9, the combined output laser energy beam may comprise a plurality of different field of views, effective LIDAR ranges and areas of coverage. In the example configuration of Figure 9, the combined output laser energy beam comprises a first portion 903a and a second portion 903b having a smaller effective LIDAR range and higher area of coverage than the first portion 903a. In this way, any LIDAR targets 904a at higher distances but in smaller, focussed areas may be detected with the first portion 903a of the output laser energy beam, and LIDAR targets 904b at smaller distances but in a wider spread of areas may be detected with the second portion 904b.

As described above, in the case of flash LIDAR, to minimise cross talk, the different portions of the output laser energy beam may be flashed or pulsed sequentially at different times.

Also as described above, as the effective LIDAR range of the second portion 904b of the output laser energy beam of the example of Figure 9 does not need to be high, the optical power of the laser energy sources used to generate it may be lower than that of the first portion 904a of the beam. Accordingly, the total operating power requirements of the present LIDAR system 900 are lower than known LIDAR systems which inefficiently waste optical power in peripheral portions of the output laser energy beam where high effective LIDAR range is not required. Lower operating power requirements reduces the total heat generation and also reduces the operating, maintenance and manufacturing costs of the LIDAR system

Similarly, because the effective LIDAR range of some portions of the beam is lower, the cross-talk from these portions of the beam with the high range portions of the beam at the LIDAR receiver system is lower as the strength of the reflected laser energy from the low range portions of the beam from LIDAR targets at higher distance is small.

Similarly, because high optical power is focussed only in a small area of coverage the output laser energy beam, safety risks (such as eye damage or damage to sensitive equipment) from unexpected hotspots in the output beam are minimised to the small area of focussed energy. In contrast, in known systems, high optical power is emitted across a wide field of view and thus cover a very wide area, increasing the safety risk over a much greater area.

Typically, in known LIDAR systems, the field of view of the receiver is wide to correspond to the wide field of view of the transmitter system. However, this may cause unwanted noise and cross-talk from e.g. stray reflections, reducing the imaging resolution of the system. A LIDAR system according to the present disclosure may have improved resolution over known LIDAR systems by combining field of view information of one or more of the diffusers of the LIDAR transmitter system with information from the LIDAR receiver system to assist in filtering noise and cross-talk. For example, detection pixels in the centre of a LIDAR receiver system would be expected to detect reflected laser energy from the portion of the output laser energy beam having the narrow field of view. Thus, any detected reflected laser energy whose time of flight measurement suggests it originated from outside of the narrow field of view of the output laser may be discarded as noise and/or cross-talk.

Figure 10 shows a flowchart showing method steps in accordance with the present disclosure. In general terms, the method is directed to emitting laser energy towards a LIDAR target and may be used in connection with the above described LIDAR transmitter system and LIDAR system. The method 1000 comprises emitting laser energy from an array of laser energy sources through a plurality of diffusers towards a LIDAR target, wherein the laser energy sources are arranged in a plurality of spatially separated regions, wherein each diffuser is respectively arranged to cover one of said plurality of regions, and wherein the respective laser energy sources of each spatially separated region are arranged to emit laser energy through a corresponding diffuser of the plurality of diffusers. In this way, the advantages described herein with reference to Figures 2-9 are realised.

Embodiments of the present disclosure can be employed in many different applications including, for example, for 3D facial recognition, proximity detection, presence detection, object detection, distance measurements, and/or collision avoidance for example in the field of automotive vehicles or drones, and other fields and industries.

List of reference numerals:

100 known LIDAR transmitter system

101 laser source

102a laser beam

102b wide angle beam

103 diffuser

104 wafer 105 vertical-cavity surface-emitting laser (VCSEL)

106 distributed Bragg reflector layers (DBRs)

107 active region

108 substrate

109 printed circuit board (PCB)

200 LIDAR transmitter system

201 array of laser energy sources

202 plurality of diffusers

203 laser energy

300 LIDAR transmitter system

301 array of laser energy sources 301 a first spatially separated region 301 b second spatially separated region 302a first diffuser

302b second diffuser 303a emitted laser energy

303b emitted laser energy

304a emitted laser energy beam having a first field of view

304b emitted laser energy beam having a second field of view

305 wafer

400 array of laser energy sources

401 a first spatially separated region 401 b second spatially separated region

501a first diffuser 501b second diffuser

601a first diffuser 601b second diffuser 601 n n^th diffuser

701a first diffuser 701b second diffuser 701 n n^th diffuser

801a first diffuser 801b second diffuser 801 n n^th diffuser

900 LIDAR system

901 LIDAR transmitter system

902 LIDAR receiver system

903a first portion of output laser energy beam

903b second portion of output laser energy beam

904a first LIDAR target

904b second LIDAR target

905a reflected laser energy

905b reflected laser energy

1000 method

1001 emitting

The skilled person will understand that in the preceding description and appended claims, positional terms such as ‘above’, ‘along’, ‘side’, etc. are made with reference to conceptual illustrations, such as those shown in the appended drawings. These terms are used for ease of reference but are not intended to be of limiting nature. These terms are therefore to be understood as referring to an object when in an orientation as shown in the accompanying drawings.

Although the disclosure has been described in terms of preferred embodiments as set forth above, it should be understood that these embodiments are illustrative only and that the claims are not limited to those embodiments. Those skilled in the art will be able to make modifications and alternatives in view of the disclosure which are contemplated as falling within the scope of the appended claims. Each feature disclosed or illustrated in the present specification may be incorporated in any embodiments, whether alone or in any appropriate combination with any other feature disclosed or illustrated herein.

For example, whilst some example configurations described herein show only two spatially separated regions and corresponding diffusers (such as the example configuration in Figure 3), it will be appreciated that other numbers and field of view configurations of regions and diffusers are also envisaged. For example, three, four, five, and up to n regions and diffusers are also envisaged to provide the advantages described herein. The number and fields of view to be determined by the needs and requirements of the LIDAR application.

For example, whilst a gap is showing between the example diffusers in Figures 5-8, it is also envisaged that the diffusers may be conjoining and/or integral with each other without a gap.

Claims

CLAIMS:

1 . A LIDAR transmitter system comprising: an array of laser energy sources, the laser energy sources arranged in a plurality of spatially separated regions; and a plurality of diffusers, each diffuser respectively arranged to cover one of said plurality of spatially separated regions, wherein the respective laser energy sources of each spatially separated region are arranged to emit laser energy through a corresponding diffuser of the plurality of diffusers towards a LIDAR target.

2. The LIDAR transmitter system according to claim 1 , wherein each diffuser is respectively configured to define a field of view of a respective laser energy beam emitted from the laser energy sources of the corresponding spatially separated region, and wherein the field of view defined by a first diffuser of the plurality of diffusers is narrower than the field of view defined by a second diffuser of the plurality of diffusers.

3. The LIDAR transmitter system according to claim 2, wherein the laser energy beam having the field of view defined by the first diffuser is emitted from a first region of the plurality of spatially separated regions, wherein the laser energy beam having the field of view defined by the second diffuser is emitted from a second region of the plurality of spatially separated regions.

4. The LIDAR transmitter system according to claim 3, wherein the first region is larger and comprises a greater number of laser energy sources than the second region.

5. The LIDAR transmitter system according to claims 2-4, wherein the field of view defined by the first diffuser overlaps with the field of view defined by the second diffuser.

6. The LIDAR transmitter system according to claims 3-5, wherein the laser energy sources in the first region are configured to generate a first laser energy flash at a first time, and wherein the laser energy sources in the second region are configured to generate a second laser energy flash at a second time, different to the first time.

7. The LIDAR transmitter system according to claims 2-6, wherein, at a first distance from the LIDAR transmitter system, the intensity of the laser energy beam having the field of view defined by the first diffuser is greater than the intensity of the laser energy beam having the field of view defined by the second diffuser such that the effective LIDAR range of the laser energy beam having the field of view defined by the first diffuser is greater than the effective LIDAR range of the laser energy beam having the field of view defined by the second diffuser.

8. The LIDAR transmitter system according to any preceding claim, wherein the plurality of diffusers comprise: diffractive, refractive, and/or holographic diffusers.

9. The LIDAR transmitter system according to claim 1 , wherein the array of laser energy sources comprises an array of vertical cavity surface emitting lasers (VCSELs) arranged on a wafer.

10. The LIDAR transmitter system according to claim 1 , wherein the laser energy sources comprise edge emitters, LEDs and/or integrated laser energy sources.

11. A LIDAR system, the LIDAR system comprising: the LIDAR transmitter system of any of claims 1 -10; and a LIDAR receiver system.

12. A method for emitting laser energy towards a LIDAR target, the method comprising: emitting laser energy from an array of laser energy sources through a plurality of diffusers towards a LIDAR target, wherein the laser energy sources are arranged in a plurality of spatially separated regions, wherein each diffuser is respectively arranged to cover one of said plurality of regions, and wherein the respective laser energy sources of each spatially separated region are arranged to emit laser energy through a corresponding diffuser of the plurality of diffusers.