WO2024017477A1

WO2024017477A1 - A lidar system

Info

Publication number: WO2024017477A1
Application number: PCT/EP2022/070521
Authority: WO
Inventors: Alexandra ALEXANDROVA; Christel Loic Tisse; Philippe Benoit; Cristina Fernandez
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2022-07-21
Filing date: 2022-07-21
Publication date: 2024-01-25

Abstract

A LIDAR system and a scanning method for a LIDAR system. An optical arrangement (107) comprises a combination lens (108) which combines an emission lens element (109) and a receiver lens element (110), the emission lens element (109) having a first focal length 5 and functional to collimate light emitted from a light transmitting arrangement (103) towards a scene (100) and the receiver lens element (110) having a second, different focal length and functional to focus light reflected from the scene (100) on a light receiving arrangement (104), and is actuated to direct light from the combination lens (108) for scanning the scene (100) in accordance with a scan pattern. A beam shift compensation function is effected for 10 maintaining a common scanning angle of the light transmitting arrangement (103) and light receiving arrangement (104) during scanning the scene (100).

Description

A LIDAR SYSTEM

Field of the Invention

The present application relates to a LIDAR system and to a scanning method for a LIDAR system.

Background of the Invention

It is known for a LIDAR (“light detection and ranging”) system to be used to obtain a 3- dimensional characterization of a scene, in which pulse or continuous modulated light is sent to the scene and then detected through sensors for analysis based on the time-of-flight principle or based on mixing received light with emitted light.

Features often desired of a LIDAR system include: low cost and easy manufacturability (for example, from having a relatively simple construction and being based on existing, readily available components), small size (for example, being thin and suitable for embedding in a device), general physical robustness (for example, to be able to withstand external stress, such as shock), high frame rate (for example, 30 frames-per-second (fps) and higher), high angular resolution (for example 0.05° and lower), ability to measure long distances (for example, at least a distance of 200 m), wide field of view (by way of a non-limiting example, up to 20° in the vertical direction and up to 120° in the horizontal direction), resilience to high sun exposure (for example, up to 100 klx). Technical challenges encountered when seeking to provide preferred features of a LIDAR system include an improvement to one aspect being detrimental to another (for example, increasing resolution resulting in increased production cost).

Architectural approaches for a LIDAR system include a biaxial architecture, in which different optics are used for emitting light and collecting reflected light, and a coaxial architecture, in which part of the optical path for the transmitted and received beam is aligned. Coaxial systems based on a mirror-scanning approach, whether utilising traditional mirrors, galvo-mirrors, voice-coil-motor (VCM) mirrors or MEMS mirrors, are known; however, the mirrors of these systems introduce significant design limitations when targeting high key performance indicators (such as high fps, high resolution, long distances, high sun exposure, wide field of view). It is desirable to provide a LIDAR system based on the coaxial architecture that offers improvements over existing designs.

Summary of the Invention

According to a first aspect there is provided a LIDAR system, comprising: a light emitting and detecting arrangement, comprising: a light transmitting arrangement functional to emit light towards a scene, the light transmitting arrangement comprising at least one light source, and a light receiving arrangement for detecting light reflected from the scene, the light receiving arrangement comprising an array of light detecting sensors; an optical arrangement, comprising: a combination lens, disposed between the light emitting and detecting arrangement and the scene, the combination lens comprising an emission lens element and a receiver lens element; the emission lens element of the combination lens having a first focal length and arranged to collimate light emitted from the light transmitting arrangement, and the receiver lens element of the combination lens having a second, different focal length and arranged to focus light reflected from the scene on the light receiving arrangement; and a scanning arrangement functional to: actuate the optical arrangement to direct light from the combination lens for scanning the scene in accordance with a scan pattern, and effect a beam shift compensation function for maintaining a scanning angle of the light transmitting arrangement and light receiving arrangement during scanning the scene.

The combination lens advantageously combines receiving beam and transmitting beam lenses. The scanning angle of the receiving beam is kept equal to the scanning angle of the receiving beam during the scanning of a scene.

In an example, the array of light detecting sensors is provided by a multi-pixel sensor.

In an example, the light transmitting arrangement comprising an array of light sources. In a specific example, the array of light sources comprises a plurality of laser light sources.

In an example, the scanning arrangement is functional to move the combination lens along a shift axis extending perpendicular to a central axis of the combination lens, and to move the light receiving arrangement, synchronously with, and in an opposite direction to, the combination lens. The scanning angles for the transmitting and receiving beams may therefore be matched by amplifying the receiving beam shift by moving the light receiving arrangement in the opposite direction to the combination lens.

In another example, the scanning arrangement is functional to move the combination lens along an axis extending perpendicular to a central axis of the combination lens, and to move the light transmitting arrangement, synchronously with, and in the same direction as, the combination lens. The scanning angles for the transmitting and receiving beams may therefore be matched by compensation of the transmission beam shift by moving the light transmitting arrangement in the same direction as the combination lens.

In an example the scanning arrangement is further functional to, for each of a plurality of different positions of the combination lens along the shift axis, activate, to emit light, a different group of one or more light sources of the array of light sources.

In an example the light transmitting arrangement comprises for at least one group of one or more light sources of the array of light sources, a respective optical element, disposed between the array of light sources and the combination lens, for aligning light emitted from that group of one or more light sources of the array of light sources in accordance with the particular scan pattern being used.

In an example the scanning arrangement is further functional to, for each different group of one or more light sources of the array of light sources, activate, to detect light reflected from the scene, a respective different group of light detecting sensors of the array of light detecting sensors.

In an example the optical arrangement comprises an adjustable optical element disposed between the combination lens and the scene, the scanning arrangement being functional to actuate adjustment of the adjustable optical element to direct light from the combination lens for scanning the scene in accordance with the particular scan pattern being used.

The combination lens may be monolithic.

The receiver lens element may be provided by a single lens component having aspherical opposite surfaces. The emission lens element may be provided by a single lens component having freeform opposite surfaces. The emission lens element may be configured to collimate light emitted from the light transmitting arrangement in the fast and slow axes concurrently.

The emission lens element may alternatively be provided by a pair of lens components, disposed one on each of opposite sides of the receiver lens element. An air-filled tunnel may extend through the receiver lens element, between the pair of lens components of the emission lens element.

In an example, the refractive index of the receiver lens element differs from that of the emission lens element.

In an example, the emission lens element is offset from an optical axis of the receiver lens element.

The LIDAR system may be configured as a ID LIDAR system or as a 2D LIDAR system.

According to a second aspect there is provided a scanning method for a LIDAR system, comprising: activating a light transmitting arrangement to emit light towards a scene, activating a light receiving arrangement to detect light reflected from the scene, the light receiving element comprising an array of light detecting sensors; and actuating an optical arrangement, the optical arrangement comprising a combination lens, the combination lens comprising an emission lens element and a receiver lens element; the emission lens element of the combination lens having a first focal length and arranged to collimate light emitted from the light transmitting arrangement towards the scene and the receiver lens element of the combination lens having a second, different focal length and arranged to focus light reflected from the scene on the light receiving arrangement, to direct light from the combination lens for scanning the scene in accordance with a scan pattern, and effecting a beam shift compensation function for maintaining a scanning angle of the light transmitting arrangement and light receiving arrangement during scanning the scene.

The light transmitting arrangement may comprise an array of light sources.

In an example, the actuating an optical arrangement comprises moving the combination lens along a shift axis extending perpendicular to a central axis of the combination lens, and the beam shift compensation function comprises moving the light receiving arrangement, synchronously with, and in an opposite direction to, the combination lens.

The scanning method for a LIDAR system may be used to perform ID scanning or 2D scanning.

Further particular and preferred aspects of the invention are set out in the accompanying dependent claims.

Brief Description of the Drawings

The present invention will now be more particularly described, with reference to the accompanying drawings, in which:

Figure 1 shows features of a LIDAR system according to a first example;

Figure 2 illustrates features of a LIDAR system according to a first specific example;

Figure 3 illustrates a feature of operation of the LIDAR system of Figure 2;

Figure 4 shows steps in performing ID scanning using the LIDAR system of Figure 2;

Figure 5 shows steps in performing 2D scanning using the LIDAR system of Figure 2;

Figure 6 illustrates displacement of an array of light detecting sensors of the LIDAR system of Figure 2 during an example 2D scanning mode;

Figure 7 illustrates features of a LIDAR system according to a second specific example;

Figure 8 illustrates features of a LIDAR system according to a third specific example;

Figure 9 shows a front view of a combination lens according to a first specific example;

Figure 10 shows a side view of the combination lens of Figure 9;

Figures 11, 12 & 13 illustrate features of a combination lens according to the first specific example, at different scan positions;

Figure 14 shows a front view of a combination lens according to a second specific example;

Figure 15 shows a schematic of a combination lens according to a third specific example; and

Figure 16 shows a side view of the combination lens of Figure 15.

Description

Examples are described below, with reference to the accompanying drawings, in sufficient detail to enable those of ordinary skill in the art to implement the apparatus, systems and/or processes described herein. However, it is to be understood that the invention is not limited to the precise examples described and/or shown and that various changes and modifications can be effected by one skilled in the art without departing from the scope of the invention as defined by the appended claims.

In the following description, all orientational terms, such as upper, lower, radially and axially, are used in relation to the drawings and should not be interpreted as limiting the scope of the invention as defined by the appended claims unless the context clearly indicates otherwise.

The drawings are not necessarily drawn to scale, and in some instances the drawings may have been exaggerated or simplified for illustrative purposes only.

Unless otherwise defined, all terms (including technical and scientific terms) used herein are to be interpreted as is customary in the art. In addition, features referred to herein in the singular can number one or more, unless the context clearly indicates otherwise. Similarly, the terms “comprises”, “comprising”, “includes”, “including”, “has” and/or “having” when used herein, specify the presence of the stated feature or features and do not preclude the presence or addition of one or more other features, unless the context clearly indicates otherwise.

A LIDAR system and a scanning method for a LIDAR system are disclosed herein. An optical arrangement comprising a combination lens which combines an emission lens element and a receiver lens element, the emission lens element having a first focal length and functional to collimate light emitted from a light transmitting arrangement towards a scene and the receiver lens element having a second, different focal length and functional to focus light reflected from the scene on a light receiving arrangement, and is actuated to direct light from the combination lens for scanning the scene in accordance with a scan pattern. A beam shift compensation function is effected for maintaining a common scanning angle of the light transmitting arrangement and light receiving arrangement during scanning the scene.

Further disclosure follows with reference to the accompanying drawings. A LIDAR system 101 is shown in Figure 1. The LIDAR system 101 comprises a light emitting and detecting arrangement, indicated generally at 102.

The light emitting and detecting arrangement 102 comprises a light transmitting arrangement, indicated at 103, which is functional to emit light towards a scene 100. The light transmitting arrangement 103 comprises at least one light source 105. In an example, the light transmitting arrangement 103 comprises an array of light sources 105. According to a specific example, the array of light sources 105 comprises a plurality of laser light sources.

The light emitting and detecting arrangement 102 also comprises a light receiving arrangement, indicated at 104, for detecting light reflected from the scene 100. The light receiving arrangement 104 comprises an array of light detecting sensors 106. In an example, the array of light detecting sensors 106 is provided by a multi-pixel sensor.

The LIDAR system 101 further comprises an optical arrangement, indicated generally at 107. The optical arrangement 107 comprises a combination lens 108, which is disposed between the light emitting and detecting arrangement 102 and the scene 100. The combination lens 108, which will be described in further detail, comprises both an emission lens element 109 and a receiver lens element 110. The emission lens element 109 of the combination lens 108 has a first focal length and is arranged to collimate light emitted from the light transmitting arrangement 103. The receiver lens element 110 of the combination lens 108 has a second, different focal length and is arranged to focus light reflected from the scene 100 on the light receiving arrangement 104. As can be seen, the emission lens element 109 of the combination lens 108 has a relatively small size compared to the receiver lens element 110 of the combination lens 108. In a specific example, the combination lens 108 is monolithic.

Also indicated are an emission optical arrangement 111 of the light emitting arrangement 103 through which light emitted from at least one light source 105 is directed towards the combination lens 108, and a reception optical arrangement 112 of the light receiving arrangement 104 through which reflected light from the combination lens 108 is directed towards at least one light detecting sensor 106. The LIDAR system 101 further comprises a scanning arrangement, indicated generally at 113, which is functional to actuate the optical arrangement 107 to direct light from the combination lens 108 for scanning the scene 100 in accordance with a scan pattern, and is functional to effect a beam shift compensation function for maintaining a scanning angle of the light transmitting arrangement 103 and light receiving arrangement 104 during scanning the scene 100. The scanning arrangement 113 may comprise any suitable controller and any suitable actuator arrangement. Specific example arrangements for keeping the scanning angle of the light transmitting arrangement 103 and of the light receiving arrangement 104 the same (equal) during scanning the scene 100 are described below.

The LIDAR system 101 is usable to perform a scanning method in which the light transmitting arrangement 103 is activated to emit light towards a scene 100, the light receiving arrangement 104 is activated to detect light reflected from the scene 100, the optical arrangement 107 is actuated to direct light from the combination lens 108 for scanning the scene 100 in accordance with a scan pattern, and a beam shift compensation function is effected for maintaining a scanning angle of the light transmitting arrangement 103 and light receiving arrangement 104 during scanning the scene 100. The scan pattern may be any suitable scan pattern.

The emission lens element 109 of the combination lens 108 gathers light emitted from the light emitting arrangement 103 and collimates this in order to send a parallel beam to scan the scene 100. The receiver lens element 110 of the combination lens 108 collects the reflected light from the scene and focuses it to the light receiving arrangement 104.

As will be described further, the architecture of the disclosed LIDAR system enables the combination lens to be moved for scanning a scene and one or both of the at least one light source of the light transmitting arrangement and the array of the light detectors of the light receiving arrangement to be moved correspondingly to ensure the same scanning angle and speed for the light transmission and light reception. A controller may be functional to control multiple actuators, for example a first actuator operatively associated with the combination lens and a second actuator operatively associated with the light transmitting arrangement and/or light receiving arrangement, and may also be functional to control other componentry.

A first specific example 101A of the LIDAR system 101 will now be described with reference to Figures 2 & 3. Referring firstly to Figure 2, a central axis 201 of the combination lens 108 and a shift axis 202 that extends perpendicular to the central axis 201 of the combination lens 108 are shown.

In this example, the scanning arrangement 113 is functional to move the combination lens 108 along the shift axis and move the light receiving arrangement 104, synchronously with, and in an opposite direction to, the combination lens 108. Thus, as the combination lens 108 is moved by the scanning arrangement 113 in the direction indicated by arrow 203, the light receiving arrangement 104 is moved by the scanning arrangement 113 in the direction indicated by arrow 204, which is opposite to the direction indicated by arrow 203, and along a second shift axis 205 that is parallel to the shift axis 202 along which the combination lens 108 is moved.

As already mentioned, the focal lengths of the emission and receiver lens elements 109, 110 differ, resulting in different respective angular shifts when the combination lens 108 is moved along the shift axis. In this specific example, the scanning angles for the transmitting and receiving beams are matched by amplifying the receiving beam shift by moving the light receiving arrangement 104 in the opposite direction to the combination lens 108.

More specifically, in an example, amplification of the receiving beam shift is by a shift in an opposite direction to that of the combination lens by PixelsReceiverSize*X/SizeLaserWidth in the case of the transmitting beam and receiving beam angular size being the same (in which: “PixelsReceiverSize” is the size of the pixels of the light detecting sensor of the light receiving arrangement, “X” is the extent of shift of the combination lens element, and “SizeLaserWidth” is the size of the laser beam (used for calculations of parameters of the scene/beams) considered at the beam waist or, for example in the case of vertical-cavity surface-emitting lasers (VCSELs)/edge-emitting lasers (EELs), the size of the output aperture). In this example, the scanned angle will be atan(X*PixelsReceiverSize/AngularResolution). For example, if the laser width is 10 pm, the receiver pixel size is 20 pm, and the required resolution is 0.1 degree, the shift of the combination lens is +- 1 mm leading to the scanned angle (transmitting beam) being around 20 degrees. If the combination lens can be scanned using a linear scanning approach, then the displacement of the light transmitting arrangement should be (1- PixelsReceiverSize/SizeLaserWidth) of the displacement of the combination lens, i.e. -1 mm in the presented case (the minus sign indicates opposite direction of movement to that of the combination lens). A first laser source 105a and a second laser source 105b of the light transmitting arrangement 103 are indicated. The second laser source 105b is spaced from the first laser source 105a in the direction indicated by arrow 203 (along the shift axis 201, further way from the central axis 201). An optical element 205, through which light emitted by the second laser source 105b is directed towards the combination lens 108, is also indicated. In addition, first and second positions Pl, P2 of the combination lens 108 along the shift axis 202 are indicated, the second position P2 being reached through movement from the first position Pl in the direction indicated by the arrow 203.

It is to be appreciated that more than two laser sources 105a, 105b may be utilised in this illustrated example, as will also now be described. The distance that the laser sources are spaced apart will depend on various aspects of the LIDAR system, including the dimensions of the emission lens element. It is to be understood that in a series of laser sources, the distance between adjacent laser sources may vary within the series (for example, the distance between second and third laser sources of the series being different from the distance between first and second laser sources of the series).

As illustrated in Figure 3, when the emission lens element 109 is at position Pl, a beam of light emitted by laser source 105a is collimated by emission lens element 109 into plane A. As the position of the emission lens element 109 shifts from Pl to P2 (following movement of the combination lens), the beam of light from laser source 105a is collimated into plane A towards plane B. When the emission lens element 109 is at position P2 (following further movement of the combination lens), the emission lens element 109 is no longer in proper sight of the laser source 105a and a switch is made from laser source 105a to laser source 105b after which a beam of light emitted by laser source 105b is collimated into plane B’, which is parallel to plane B. As already indicated, laser source 105b is provided with a respective optical element 205, which is used to align its plane with that of laser source 105a (the previous light source from which light was being collimated to scan the scene). As movement of the emission lens element 109 along the shift axis continues in the same direction towards position P3, the beam of light from laser source 105b is collimated into plane B’ towards plane C. As position P3 is entered, the beam of light emitted by laser source 105b is no longer in proper sight of the emission lens element 109 and a switch from laser source 105b can be made to continue the scanning of the scene. Depending on the actuator arrangement utilised for shifting optical components of the LIDAR system, different trajectories can be used, such as saw-tooth like, triangular, which supports linear scanning across the required field of view, or sinusoidal.

Steps in performing ID scanning using the LIDAR system 101 of Figure 2 are shown in Figure 4. In this Figure and accompanying description, scanning is in the horizontal direction, N designates the number of a light source within an array of light sources, X and Y indicate required displacement of the combination lens in the horizontal and vertical directions, X’ and Y’ indicate required opposite displacement of the light receiving arrangement in the horizontal and vertical directions to maintain a desired scanning angle, and Z indicates the distance between adjacent light sources in the array of light sources.

At step 401, first laser source 105a is activated. At step 402, shifting of the combination lens 108 and light receiving arrangement 104 is activated, with combination lens 108 being moved a required distance in one direction along the horizontal axis and light receiving arrangement 104 being moved a required distance in the opposite direction along the horizontal axis. At step 403, a question is asked as to whether the combination lens 108 has moved the distance along the vertical axis to the second laser source 105b. If the question is answered in the negative, step 403 is re-entered, and the question asked again. If the question is answered in the affirmative, step 404 is entered and the second laser source 105b is activated. It is to be appreciated that other steps will be performed to complete a scanning event.

While single laser sources are mentioned in the foregoing description, it is to be appreciated groups of light sources of the array of light sources 105 may be switched on and off as the position of the combination lens changes, and that such a group may comprise a single of the light sources or more than one of the light sources of the array.

The scanning arrangement 113 may therefore be functional to, for each of a plurality of different positions of the combination lens 108 along the shift axis 202, activate, to emit light, a different group of one or more light sources of the array of light sources 105.

As indicated already, the light transmitting arrangement 102 may comprise, for at least one such group of one or more light sources of the array of light sources 105, a respective optical element 205, disposed between the array of light sources 105 and the combination lens 108, for aligning light emitted from that group of one or more light sources of the array of light sources 105 in accordance with the scan pattern.

The scanning arrangement 113 may be further functional to, for each different group of one or more light sources of the array of light sources 105, activate, to detect light reflected from the scene 100, a respective different group of light detecting sensors of the array of light detecting sensors 106.

Figure 5 shows example steps in performing 2D scanning using the LIDAR system 101 of Figure 2.

In this Figure and accompanying description, N, M designates the number of a light source within an array of light sources, with N indicating the column number in a row and M indicating the row number in a column, X and Y indicate required displacement of the combination lens in the horizontal and vertical directions, X’ and Y’ indicate required opposite displacement of the light receiving arrangement in the horizontal and vertical directions to maintain a desired scanning angle, and Z and Z’ indicates the distance between adjacent light sources in the array of light sources.

At step 501, a first light source is activated. At step 502, shifting of the combination lens 108 and light receiving arrangement 104 is activated, with combination lens 108 being moved a required distance in one direction along the horizontal axis and one direction along the vertical axis and light receiving arrangement 104 being moved a required distance in the opposite directions along the horizontal and vertical axes.

At step 503, a question is asked as to whether the position of the combination lens 108 in the horizontal direction is between adjacent light sources in a row. If the question is answered in the affirmative, step 504 is entered, at which a question is asked if the row number of the column is even. If this question is answered in the affirmative, a determination is made at 505 that N=N+1 and step 507 is then entered; alternatively, if the question is answered in the negative, a determination is made at 506 that N=N-1 and then step 507 is entered. At step 507, a question is asked whether the combination lens 108 has moved the distance in the vertical direction to the next row number of the column. If this question is answered in the affirmative, a determination is made at 508 that M=M+1 and step 509 is then entered, at which the next light source is activated. If the question is answered in the negative, step 510 is entered at which a question is asked as to whether the light source N, M is activated. If this question is answered in the negative, step 509 is entered. If this question is answered in the affirmative, step 503 is re-entered and steps for checking the horizontal and vertical positioning of the combination lens 108 are repeated. If the question asked at step 503 is answered in the negative, step 507 is entered. It is to be appreciated that other steps will be performed to complete a scanning event.

It is to be appreciated that different scanning patterns may be used in other examples, with the specific steps performed adapted to suit the specific scanning pattern used.

Figure 6 illustrates an example displacement of the array of light detecting sensors 106 of the light receiving arrangement 103 of the LIDAR system 101 during a 2D scanning mode. A path of travel is indicated at 601, the fast axis (in the horizontal direction) is indicated by arrow 602 and the slow axis (vertical direction) is indicated by arrow 603. In this example, the amplitude of the actuations in the horizontal and vertical axes differ, in this specific illustrated example being greater in the horizontal direction, but in another example could be the same.

It is to be appreciated that different scanning patterns may be used in other examples, with the specific displacement of the array of light detecting sensors adaptable to suit the specific scan pattern used.

A second specific example 101B of the LIDAR system 101 will now be described with reference to Figure 7.

This second specific example differs from the first specific example in that the light transmitting arrangement rather than the light receiving arrangement is moved when the combination lens is moved.

In this example, the scanning arrangement 113 is functional to move the combination lens 108 along the shift axis 202 and move the light transmitting arrangement 103, synchronously with, and in the same direction as, the combination lens 108. Thus, as the combination lens 108 is moved by the scanning arrangement 113 in the direction indicated by arrow 203, the light receiving arrangement 104 is moved by the scanning arrangement 113 in the direction indicated by arrow 701, which is the same as the direction indicated by arrow 203, and along a second shift axis 702 that is parallel to the shift axis 202 along which the combination lens 108 is moved.

As mentioned already, the focal lengths of the emission and received lens elements 109, 110 differ, resulting in different respective angular shifts when the combination lens 108 is moved along the shift axis. In this specific example, the scanning angles for the transmitting and receiving beams are matched by compensation of the transmission beam shift by moving the light transmitting arrangement 103 in the same direction as the combination lens 108.

More specifically, in an example, compensation of the transmitting beam shift is by the transmitting beam shift in same direction as the combination lens by SizeLaserWidth*X/PixelsReceiverSize in the case of the transmitting beam and receiving beam angular size being the same. In this example, the scanned angle will be atan(X* AngularResolution/PixelsReceiverSize). For example, if the laser width is 10 pm, the receiver pixel size is 20 pm, and the required resolution is 0.1 degree, the shift of the lens is +- 1 mm leading to the scanned angle (transmitting beam) being around 10 degrees. If the combination lens can be scanned using a linear scanning approach, then the displacement of the light transmitting arrangement should be (1-SizeLaserWidth/PixelsReceiverSize) of the displacement of the combination lens, i.e. 0.5 mm.

Features mentioned in relation to the first specific example 101 A may be incorporated in the second specific example. For example, the scanning arrangement 113 may be functional to, for each of a plurality of different positions of the combination lens 108 along the shift axis 202, activate, to emit light, a different group of one or more light sources of an array of light sources 105 and may be further functional to, for each different group of one or more light sources of the array of light sources 105, activate, to detect light reflected from the scene 100, a respective different group of light detecting sensors of the array of light detecting sensors 106.

Thus, the LIDAR system 101 is usable to perform a scanning method in which the light transmitting arrangement 103 is activated to emit light towards a scene 100, the light receiving arrangement 104 is activated to detect light reflected from the scene 100, the optical arrangement 107 is actuated to direct light from the combination lens 108 for scanning the scene 100 in accordance with a scan pattern, and a beam shift compensation function is effected for maintaining a scanning angle of the light transmitting arrangement 103 and light receiving arrangement 104 during scanning the scene 100, in which the combination lensl08 is moved along a shift axis 201 extending perpendicular to a central axis 202 of the combination lens 108, and the beam shift compensation function comprises according to the first specific example 101 A moving the light receiving arrangement 104, synchronously with, and in the opposite direction to, the combination lens 108 and according to the second specific example 10 IB moving the light transmitting arrangement 103, synchronously with, and in the same direction as, the combination lens 108.

A controller of the scanning arrangement 113 may have any suitable form and comprise any suitable device or devices, for example a microprocessor.

An actuator arrangement of the scanning arrangement 113 may comprise any suitable number and type or types of actuator, for example piezo-electric, voice coil motor (VCM), or shape memory alloy (SMA).

A multi-pixel sensor 106 of the light receiving arrangement 104 may be any suitable type, for example comprising a single-photon avalanche diode (SPAD) sensor, a silicon photomultiplier (SiPM) sensor, an avalanche photodiode (APD) sensor. The pixel size may be any suitable size, for example in the range 5 pm to 50 pm. The array size may be any suitable size, for example 4 x 16.

In the combination lens, the ratio between the sizes of the receiving beam and transmitting beam lens elements defines the efficiency of the collected receiving beam, one of the most critical points in the LIDAR architecture; however, while the size of the receiving lens element can be increased to ensure full collection of the light even when the combination lens is shifted, this cannot be for afforded for the transmitting beam lens element since this part of the combination lens is ideally as small as possible to minimize the occupied volume within the combination lens and, in turn, maximize the collection efficiency. A problem exists with ensuring that the laser field is correctly collimated by the lens element without missing a part of the field, leading to a high level of receiving beam-transmitting beam crosstalk, loss of laser power on the scene and high aberration. This problem can be overcome by using an array of lasers, within which each laser works in sequence to match a shift of the actuator driving the combination lens and to have an optical element to match the scanning required field of view. The light transmitting arrangement 103 may comprise an array of laser light sources of any suitable type and that are separated by any suitable distance, for example EELs with a separation distance in the range 100-200 pm or VCSELs with a separation distance in the range 30-50 pm.

Optical elements provided for each laser group (of one or more lasers of the array), so that the laser group has a beam inclination that matches that of a previous beam in order to ensure the continuation of the scanning pattern, may comprise any suitable optical elements, for example inclined prisms, off-centre optics, meta-surfaces, diffractive elements, a single element with progressive inclination apparent angle for the next laser group. The scanning arrangement, in particular the controller and actuators it comprises, synchronise switching between laser groups (deactivate the previous laser(s) and activate the next lasers) in sequence with the actuators operating to progress the scanning pattern; as appropriate, switching between light detecting sensor groups is also synchronised. This approach ensures a proper continuation of the scanning, reduces any aberrations caused by the laser groups, reduces potential crosstalk, and ensures highest collection efficiency by design.

A third specific example 101C of the LIDAR system 101 will now be described with reference to Figure 8.

In an example, the optical arrangement comprises an adjustable optical element disposed in front of the combination lens and/or at least one light source of the light transmitting arrangement and/or the array of light detecting sensors of the light receiving arrangement.

In this illustrated example, the optical arrangement 107 comprises an adjustable optical element 801 that is disposed between the combination lens 108 and the scene 100, and the scanning arrangement 113 is functional to actuate adjustment of the adjustable optical element 801 to direct light from the combination lens 108 for scanning the scene 100 in accordance with a scan pattern. Further, the reception optical arrangement 112 comprises a second adjustable optical element 802 that is disposed between the combination lens 108 and the array of light detecting sensors 106 of the light receiving arrangement 104, and the scanning arrangement 113 is functional to actuate adjustment of the second adjustable optical element 802 to direct reflected light from the scene 100 to the array of light detecting sensors 106. In an example, the adjustable optical element 801 is a lens supported by a mechanism that enables an angle of inclination thereof to be adjusted, changing the inclination of both the transmitting beam and the receiving beam, and the second adjustable optical element 802 is similarly arranged to be adjusted in synchrony with the adjustable optical element 801.

In an example, the adjustable optical element 801 is tiltable between a lesser and a greater angle of inclination, relative to a plane 803 that the central axis 201 is perpendicular to, as indicated by doubled-headed arrow 804 and outline shape 805, and the second adjustable optical element 802 can likewise be tilted between different angles of inclination, as indicated by outline shape 806.

In an alternative example, each optical element is a prism filled with a liquid refractive material and associated with a mechanism that allows the refractive index to be changed through varying a voltage or that allows the surface profile thereof to be changed through applying different pressure to the sides of prism.

It is to be appreciated however that each adjustable optical element used may have any form suitable for achieving the functionality described above.

A combination lens 108 A according to a first specific example is shown in Figures 9 & 10. As shown, the central axis 201 of the combination lens 108A passes through the centre of the receiver lens element 110. The emission lens element 109 is offset from the central axis 201, and hence also the centre of the receiver lens element 110.

In an example LIDAR system, such as in the illustrated first specific example 101A, the receiver lens element is centred with respect to the optical axis of the system and aligned with the centre of the array of light detecting sensors, to define an initial position; the transmitting lens element is decentred with respect to the receiver lens element and therefore the transmitting beam is located to one side of the receiving beam, parallel to it. The position of the emission lens element relative to the receiver lens element can vary between examples, depending on the scan movements to be performed and the size of the optical elements.

In an example, and in this illustrated example, the receiver lens element 110 is provided by a single lens component 1001 having aspherical opposite surfaces 1002, 1003. In an example, and in this illustrated example, the emission lens element 109 is provided by a single lens component 1004 having freeform opposite surfaces 1005, 1006. Advantageously, the freeform surfaces are functional to collimate the transmitting beam in the fast axis and the slow axis at the same time, without the use of any additional componentry.

In an example, and in this illustrated example, the emission lens element 109 is embedded within the receiver lens element 110, in such a way that there are no discontinuities inside to reduce stray light reflections (monolithic construction). The combination lens 108A may be manufactured by diamond turning in glass or a plastics material. In an example, and in this illustrated example, each side, such as opposite sides 1007, 1008, of the combination lens 108 is coated with an antireflective (AR) coating, to reduce losses by reflection.

In an example, the emission lens element 109 has a first refractive index and the receiver lens element 110 has a second, different refractive index. In an alternative example, the refractive indexes of the emission lens element 109 and the receiver lens element 110 are the same.

The combination lens 108A according to the first specific example is illustrated in Figures 11, 12 & 13 at different scan angles (with the scan and displacement of elements in the Y direction). In the specific example, the array of light detecting sensors is a 4 x 16 array of SPADs of 10 pm size, for a resolution of 0.05°, the receiver lens element has a focal length of 11.5 mm, an aperture of F/0.8, and an entrance pupil of 14 mm; the emission lens element has a focal length of 6 mm and an entrance pupil of 4 mm.

In Figure 11, the combination lens 108A is shown at a 0° scan position. In this specific illustrated example, the distance between the centre of the array of light detecting sensors 106 and the activated light source(s) 105 is 5.7 mm. The combination lens 108A is shown in Figure 12 at a -10° scan position and is shown in Figure 13 at a +10° scan position. To achieve +- 10° scan position, in the case of the first specific example LIDAR system 101A (in which the light receiving arrangement is moved when the combination lens is moved) the relative movement between the combination lens 108A and the light receiving arrangement 104 is +- 2 mm; in the case of the second specific example LIDAR system 101B (in which the light transmitting arrangement is moved when the combination lens is moved) the relative movement between the combination lens 108A and the light transmitting arrangement 103 is +- 1.325 mm. A combination lens 108B according to a second specific example is shown in Figure 14. As shown, the central axis 201 of the combination lens 108B passes through the centre of the receiver lens element 110 and the centre of the emission lens element 109. Thus, the emission lens element 109 is centred with respect to an optical axis of the receiver lens element 110.

In an example LIDAR system, the transmission lens element is centred with respect to the optical axis of the system and the receiver lens element is designed to direct reflected light to an array of light detecting sensors offset therefrom.

A combination lens 108C according to a third specific example is shown in Figures 15 & 16.

In this example, the emission lens element 110 is provided by a pair of lens components, 1501, 1502 disposed one on each of opposite sides 1007, 1008 of the receiver lens element 109. In this specific example, an air-filled tunnel, indicated at 1503, extends through the receiver lens element 109, between the pair of lens components 1501, 1502 of the emission lens element 110, with a refractive index equal to one. In another example, the space between the pair of lens components 1501, 1502 is filled with the material of the receiver lens element 109, with a refractive index higher than 1.

The lens components 1501, 1502 may be manufactured and then aligned and assembled with the receiver lens element 109 in any suitable way, using any suitable material or materials and any suitable process or processes. In a specific example, the two lens components are made from plastic and adhered to the receiver lens element.

According to this specific illustrated example, lens component 1501 has one surface having a freeform shape and an opposite surface that is flat, and lens component 1502 has one surface having a freeform shape and an opposite surface that is spherical.

A LIDAR system according to the present disclosure can feature:

Using a combination lens that combines receiving beam and transmitting beam lenses (instead of separate light transmitted and light received optics with a beam separator such as a beam splitter or mirror(s) with holes as found in the prior art). Advantages of this feature include reducing complexity in the system, reducing the number of components used in the system, improving the simplicity and cost to achieve proper alignment, reducing the physical size/overall volume of the system.

Using a multi-pixel matrix as a sensor in the light receiving arrangement and performing partial resolution by the sensor. Advantages of this feature include providing for high key performance indicators (such as, but not limited to, high fps, high resolution, long distances, high sun exposure, wide field of view) without associated high constrains on the optics for transmitting beam and receiving beam as well as reducing requirements for scanning speeds and the scanning mechanism, which in turn provides for reducing the physical size/overall volume of the system, improving the simplicity and cost of the system (with greater potential to utilise off-the-shelf components), improving shock resiliency.

Using actuators to move the (a) combination lens for the receiving beam and the transmitting beam to scan the scene for both the receiving beam and the transmitting beam, (b) sensor element to ensure the compensation of the scanning pattern for receiver due to different focal length and hence different shifts due to actuation, and/or (c) light source (laser) element to compensate for the scanning pattern (instead of using a mirror as a scanning element as found in the prior art).

Using a multi-aperture laser die for reducing optical aberration due to small transmitting beam lens on the combination lens to ensure a high efficiency for the collection part of the combination lens.

Benefits of a LIDAR system according to the present disclosure include enabling the provision of a more compact system, in particular in the thickness direction thus making possible a relatively very thin device, in which a laser source array can be utilised to maximise receiving beam/transmitting beam efficiency in a coaxial architecture design, an actuation arrangement can be utilised to accommodate different focal lengths of the receiving beam/transmitting beam lens element, and off-the-shelf components can be used in the system build.

Although illustrative embodiments and examples of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is to be understood that the invention is not limited to the precise embodiment and examples shown and/or described and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the invention as defined by the appended claims.

Claims

1. A LIDAR system, comprising: a light emitting and detecting arrangement, comprising: a light transmitting arrangement functional to emit light towards a scene, the light transmitting arrangement comprising at least one light source, and a light receiving arrangement for detecting light reflected from the scene, the light receiving arrangement comprising an array of light detecting sensors; an optical arrangement, comprising: a combination lens, disposed between the light emitting and detecting arrangement and the scene, the combination lens comprising an emission lens element and a receiver lens element; the emission lens element of the combination lens having a first focal length and arranged to collimate light emitted from the light transmitting arrangement, and the receiver lens element of the combination lens having a second, different focal length and arranged to focus light reflected from the scene on the light receiving arrangement; and a scanning arrangement functional to: actuate the optical arrangement to direct light from the combination lens for scanning the scene in accordance with a scan pattern, and effect a beam shift compensation function for maintaining a scanning angle of the light transmitting arrangement and light receiving arrangement during scanning the scene.

2. The LIDAR system of claim 1 , the light transmitting arrangement comprising an array of light sources.

3. The LIDAR system of claim 2, the light transmitting arrangement comprising an array of laser light sources.

4. The LIDAR system of any one of claims 1 to 3, the array of light detecting sensors provided by a multi-pixel sensor.

5. The LIDAR system of any one of claims 1 to 4, the scanning arrangement functional to: move the combination lens along a shift axis extending perpendicular to a central axis of the combination lens, and move the light receiving arrangement, synchronously with, and in an opposite direction to, the combination lens.

6. The LIDAR system of any one of claims 1 to 4, the scanning arrangement functional to: move the combination lens along an axis extending perpendicular to a central axis of the combination lens, and move the light transmitting arrangement, synchronously with, and in the same direction as, the combination lens.

7. The LIDAR system of claim 5 or claim 6, when dependent upon claim 2 or claim 3, the scanning arrangement further functional to: for each of a plurality of different positions of the combination lens along said shift axis, activate, to emit light, a different group of one or more light sources of said array of light sources.

8. The LIDAR system of claim 7, the light transmitting arrangement comprising, for at least one said group of one or more light sources of said array of light sources, a respective optical element, disposed between said array of light sources and said combination lens, for aligning light emitted from that group of one or more light sources of said array of light sources in accordance with the scan pattern.

9. The LIDAR system of claim 7 or claim 8, the scanning arrangement further functional to: for each different group of one or more light sources of said array of light sources, activate, to detect light reflected from the scene, a respective different group of light detecting sensors of said array of light detecting sensors.

10. The LIDAR system of any one of claims 1 to 4, the optical arrangement comprising an adjustable optical element disposed between the combination lens and the scene, the scanning arrangement functional to actuate adjustment of the adjustable optical element to direct light from the combination lens for said scanning the scene in accordance with a scan pattern.

11. The LIDAR system of any one of claims 1 to 10, wherein the combination lens is monolithic.

12. The LIDAR system of any one of claims 1 to 11, the receiver lens element provided by a single lens component having aspherical opposite surfaces.

13. The LIDAR system of any one of claims 1 to 12, the emission lens element provided by a single lens component having freeform opposite surfaces.

14. The LIDAR system of claim 13, the emission lens element configured to collimate light emitted from the light transmitting arrangement in the fast axis and the slow axis concurrently.

15. The LIDAR system of any one of claims 1 to 12, the emission lens element provided by a pair of lens components, disposed one on each of opposite sides of the receiver lens element.

16. The LIDAR system of claim 15, wherein an air-filled tunnel extends through the receiver lens element, between the pair of lens components of the emission lens element.

17. The LIDAR system of any one of claims 1 to 16, the emission lens element having a first refractive index and the receiver lens element having a second, different refractive index.

18. The LIDAR system of any one of claims 1 to 16, the emission lens element offset from an optical axis of the receiver lens element.

19. The LIDAR system of any one of claims 1 to 18, configured as one of: a ID LIDAR system, a 2D LIDAR system.

20. A scanning method for a LIDAR system, comprising: activating a light transmitting arrangement to emit light towards a scene, activating a light receiving arrangement to detect light reflected from the scene, the light receiving element comprising an array of light detecting sensors; and actuating an optical arrangement, the optical arrangement comprising a combination lens, the combination lens comprising an emission lens element and a receiver lens element; the emission lens element of the combination lens having a first focal length and arranged to collimate light emitted from the light transmitting arrangement towards the scene and the receiver lens element of the combination lens having a second, different focal length and arranged to focus light reflected from the scene on the light receiving arrangement, to direct light from the combination lens for scanning the scene in accordance with a scan pattern, and effecting a beam shift compensation function for maintaining a scanning angle of the light transmitting arrangement and light receiving arrangement during scanning the scene.

21. The scanning method for a LIDAR system as claimed in claim 19, the light transmitting arrangement comprising an array of light sources.

22. The scanning method for a LIDAR system as claimed in claim 20 or claim 21, the actuating an optical arrangement comprising moving the combination lens along a shift axis extending perpendicular to a central axis of the combination lens, and the beam shift compensation function comprising moving the light receiving arrangement, synchronously with, and in an opposite direction to, the combination lens.

23. The scanning method for a LIDAR system of any one of claims 20 to 22, used to perform one of: ID scanning, 2D scanning.