WO2023156014A1

WO2023156014A1 - Light source apparatus for time-of-flight device

Info

Publication number: WO2023156014A1
Application number: PCT/EP2022/054244
Authority: WO
Inventors: Alexandra ALEXANDROVA; Christel Loic Tisse; Philippe Benoit
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2022-02-21
Filing date: 2022-02-21
Publication date: 2023-08-24

Abstract

A light source apparatus for a time-of-flight device includes one or more first light sources with an aperture of a first size configured to emit pulses of light towards a scene. The light source apparatus further includes one or more second light sources with an aperture of a second size configured to emit pulses of light towards the scene, and the second size is greater than the first size. The light source apparatus further includes a controller that is configured to selectively activate and/or adjust an intensity of the one or more first light sources or the one or more second light sources for illuminating the scene. The light source apparatus can vary its light emission for controllable illumination of the scene by that enable measuring a distance map of the scene with hight precision and/or improved lateral resolution.

Description

LIGHT SOURCE APPARATUS FOR TIME-OF-FLIGHT DEVICE

TECHNICAL FIELD

The present disclosure relates generally to the field of laser systems and more specifically, to a light source apparatus for a time-of-flight device, such as a multi-aperture laser system for time-of-flight devices and light detection and ranging (LiDAR) systems.

BACKGROUND

In recent years, laser technology has gained huge popularity in various applications such as in time-of-flight devices and also in light detection and ranging (LiDAR or simply lidar) systems, and the like. Such devices provide depth information of a scene based on the time taken by a laser in transmitting and returning to a receiver (or a sensor) after striking a target. However, if the target is placed at a close distance with the receiver and/or the target has a very high reflectivity, then a high number of photons returns to the receiver that further leads to problems with the obtained data and also causes error in distance measurements. Such a problem also leads to the ghosting effect in which plurality of photons leads to trigger of the receivers. Another problem in such devices is pile-up issues in which when the plurality of photons arrives, then the beginning of a pulse is being detected with high probability as compared to standard cases when a middle part of the pulse needs to be detected with high probability. In addition, the size of the majority of the LiDAR systems and the time-of-flight devices is also limited leading to a reduced precision for long-distance measurements. However, in order to get higher precision of the long-distance measurements much more costly system is required.

Currently, certain attempts have been made to improve the performance of the conventional LiDAR systems the time-of-flight devices, such as in one attempt, pile-up issues are resolved by spreading the incoming light on multiple receivers, but such an attempt was complex to implement and higher in cost. Another issue in conventional time-of-flight devices is related to the ratio of resolution and distance. In addition, the conventional time-of-flight devices are highly expensive, and also face problems to achieve higher precision of the measurements. In addition, the conventional time-of-flight devices further require high power consumption and extremely high data rate. Thus, there exists a technical problem of how to perform distance measurement in the time-of-flight devices without facing the ghosting effect, pile-up issue, and other problems caused by closely located and highly reflective targets.

Therefore, in light of the foregoing discussion, there exists a need to overcome the aforementioned drawbacks associated with the conventional time-of-flight devices.

SUMMARY

The present disclosure provides a light source apparatus for a time-of-flight device. The present disclosure provides a solution to the existing problem of how to perform distance measurement in the time-of-flight devices without facing the ghosting effect, pile-up issue, and other problems caused by closely located and highly reflective targets. An objective of the present disclosure is to provide a solution that overcomes at least partially the problems encountered in the prior art and provides an improved light source apparatus for the time-of- flight device. For example, the solution can be a multi-aperture laser system for time-of- flight devices and light detection and ranging systems (lidars).

One or more objectives of the present disclosure is achieved by the solutions provided in the enclosed independent claims. Advantageous implementations of the present disclosure are further defined in the dependent claims.

In one aspect, the present disclosure provides a light source apparatus for a time-of-flight device or a lidar. The light source apparatus includes one or more first light sources with an aperture of a first size configured to emit pulses of light towards a scene. The light source apparatus further includes one or more second light sources with an aperture of a second size configured to emit pulses of light towards the scene, and the second size is greater than the first size. The light source apparatus further includes a controller that is configured to selectively activate and/or adjust an intensity of the one or more first light sources and the one or more second light sources for illuminating the scene.

The light source apparatus is used to perform the measurement of long and short distances accurately without facing the ghosting effect, pile-up issue, and other problems caused by closely located and highly reflective targets. In addition, the one or more first light sources and the one or more second light sources with different apertures within the same light source apparatus are also beneficial to improve the precision of the measurements at short distances. The one or more first light sources of the light source apparatus are beneficial to avoid crosstalk during the measurement of small distance objects and highly reflective objects. In other words, the one or more first light sources and the one or more second light sources with divergence and/or shape are beneficial to solve different problems, such as long-range lidars data errors in case of high reflectance targets, in case of close targets. As a result, the one or more first light sources and the one or more second light sources are beneficial to improve the lateral resolution of the time-of-flight device, and also to improve the precision of the distance measurements. Therefore, with the light source apparatus the time-of-flight device or lidar measures the distance with improved lateral resolution. At that, the light source apparatus can be used effectively in the time-of-flight device or lidar together with different scanning means.

In an implementation, the controller is configured to selectively activate and/or adjust an intensity of the one or more first light sources and one or more the second light sources for illuminating objects in different distance ranges in the scene.

In another implementation, the one or more first light sources and the one or more second light sources are integrated into the same die and arranged in arrays.

It is advantageous to integrate the one or more first light sources and the one or more second light sources into the same die and to arrange them in arrays as it helps in choosing the light of source as per the requirement.

In a further implementation, the light source apparatus includes an optical means for directing the pulses of light emitted by the one or more first light sources and the one or more second light sources into the same optical path at the output of the light source apparatus.

It is advantageous to use the optical means as it helps in collimating different sizes of the aperture of the one or more first light sources and the one or more second light sources.

In another aspect, the present disclosure provides a time-of-flight device (or lidar) that includes one or more first light sources with an aperture of a first size configured to emit pulses of light of a first intensity towards a scene. The time-of-flight device further includes one or more second light sources with an aperture of a second size configured to emit pulses of light of a second intensity towards the scene, and the second size is greater than the first size and the second intensity is higher than the first intensity. The time-of-flight device further includes one or more light detectors configured to detect a pulse of light emitted by the first light sources or the second light sources and backscattered on a target in the scene. The time-of-flight device further includes a controller configured to determine a time-of- flight (TOF) between the emittance and the detection of each pulse of light detected by the light detectors. The controller is further configured to obtain a distance map of the scene based on the determined TOFs, and selectively activate and/or adjust an intensity of the first light sources and the second light sources for illuminating the scene so to improve a lateral resolution and/or a precision of the distance map. Further, the time-of-flight device or the lidar can make a use of scanning means on either the light receiving side and/or light transmitting side that does not conflict with the use of the light source apparatus.

In an implementation, the controller of the time-of-flight device is configured to selectively activate and/or adjust an intensity of the one or more first light sources and the one or more second light sources for illuminating objects in different distance ranges in the scene.

In further implementation the time-of-flight device comprises a lidar.

The time-of-flight device achieves all the advantages and technical effects of the light source apparatus of the present disclosure.

It has to be noted that all devices, elements, circuitry, units, and means described in the present application could be implemented in the hardware elements or any kind of combination thereof. All steps which are performed by the various entities described in the present application as well as the functionalities described to be performed by the various entities are intended to mean that the respective entity is adapted to or configured to perform the respective steps and functionalities. Even if, in the following description of specific embodiments, a specific functionality or step to be performed by external entities is not reflected in the description of a specific detailed element of that entity, which performs that specific step or functionality, it should be clear for a skilled person that these methods and functionalities can be implemented in respective software or hardware elements, or any kind of combination thereof. It will be appreciated that features of the present disclosure are susceptible to being combined in various combinations without departing from the scope of the present disclosure as defined by the appended claims.

Additional aspects, advantages, features, and objects of the present disclosure would be made apparent from the drawings and the detailed description of the illustrative implementations construed in conjunction with the appended claims that follow.

BRIEF DESCRIPTION OF THE DRAWINGS

The summary above, as well as the following detailed description of illustrative embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the present disclosure, exemplary constructions of the disclosure are shown in the drawings. However, the present disclosure is not limited to specific methods and instrumentalities disclosed herein. Moreover, those in the art will understand that the drawings are not to scale. Wherever possible, like elements have been indicated by identical numbers.

Embodiments of the present disclosure will now be described, by way of example only, with reference to the following diagrams wherein:

FIG. 1A is a block diagram that depicts a light source apparatus for a time-of-flight device, in accordance with an embodiment of the present disclosure;

FIGs. IB to ID are different illustrations that depict arrangement and integration of one or more first light sources, and one or more second light sources, in accordance with different embodiments of the present disclosure;

FIG. 2A is an illustration that depicts an optical means for directing the pulses of light in a light source apparatus, in accordance with an embodiment of the present disclosure;

FIG. 2B is an illustration that depicts a system of optical means for directing pulses of light from different light sources in a light source apparatus, in accordance with another embodiment of the present disclosure; and

FIG. 3 illustrates a block diagram of a time-of-flight device, in accordance with an embodiment of the present disclosure.

In the accompanying drawings, an underlined number is employed to represent an item over which the underlined number is positioned or an item to which the underlined number is adjacent. A non-underlined number relates to an item identified by a line linking the non-underlined number to the item. When a number is non-underlined and accompanied by an associated arrow, the non-underlined number is used to identify a general item at which the arrow is pointing.

DETAILED DESCRIPTION OF EMBODIMENTS

The following detailed description illustrates embodiments of the present disclosure and ways in which they can be implemented. Although some modes of carrying out the present disclosure have been disclosed, those skilled in the art would recognize that other embodiments for carrying out or practicing the present disclosure are also possible.

FIG. 1 A is a block diagram that depicts a light source apparatus for a time-of-flight device, in accordance with different embodiments of the present disclosure. With reference to FIG. 1 A, there is shown a block diagram 100A that depicts a time-of-flight device 102, and a light source apparatus 104. The light source apparatus 104 includes one or more first light sources 106, one or more second light sources 108, and a controller 110.

The time-of-flight device 102 is utilized to measure the distance from an object by analysing a laser signal that reflects after striking the object. The time-of-flight device 102 provides depth information of a scene based on the time taken for emitted light pulses to travel from the one or more first light sources 106, and the one or more second light sources 108 to the object, where it scatters and returns to the receiver.

The light source apparatus 104 is used in the time-of-flight device 102 for emitting laser light to release photons that strike the object and reflect. The light source apparatus 104 used in the time-of-flight device 102 includes multiple light sources such as lasers with different sizes of aperture. In an implementation, the light source apparatus 104 may also be referred as a multi-aperture laser system.

The one or more first light sources 106 of the light source apparatus 104 are used for measuring the distance of nearby objects with high resolution. The one or more first light sources 106 releases the laser with low intensity and small divergence angle. In an example, the diameter of each of the one or more first light sources 106 is around 10 micrometres (pm). However, the diameter of each of the one or more first light sources 106 can have other possible values without limiting the scope of the present disclosure. The one or more second light sources 108 of in the light source apparatus 104 are also used for measuring the distance of objects placed at long distances. The one or more second light sources 108 releases the laser with high intensity and large divergence angle as compared to the one or more first light sources 106. In an implementation, the one or more first light sources 106 and the one or more second light sources 108 include laser sources including one or more laser diodes, vertical cavity surface-emitting lasers (VCSEL), and edge-emitting lasers (EEL). In an example, the diameter of each of the one or more second light sources 108 is around 30 micrometres (pm). However, the diameter of each of the one or more second light sources 108 can have other possible values without limiting the scope of the present disclosure.

The controller 110 may include suitable logic, circuitry, interfaces, and/or code that is configured to control the light source apparatus 104. The controller 110 analyses the distance of the object and then chooses the appropriate light source from the one or more first light sources 106 and the one or more second light sources 108. Examples of implementation of the controller 110 may include but are not limited to a central data processing device, a microprocessor, a microcontroller, a complex instruction set computing (CISC) processor, an application-specific integrated circuit (ASIC) processor, a reduced instruction set (RISC) processor, a very long instruction word (VLIW) processor, a state machine, and other processors or control circuitry.

There is provided the light source apparatus 104 for the time-of-flight device 102. The light source apparatus 104 includes the one or more first light sources 106 with an aperture of a first size configured to emit pulses of light towards a scene. The light source apparatus 104 further includes the one or more second light sources 108 with an aperture of a second size configured to emit pulses of light towards the scene. Further, the second size is greater than the first size. In other words, the light source apparatus 104 includes at least two light sources of different aperture sizes and shape to emit a pulse of light. The light source apparatus 104 includes the one or more first light sources 106, and the one or more second light sources 108 of different sizes and shapes of aperture that are collimated using the same optical means, as further shown in FIG. 3. Moreover, the one or more first light sources 106 emits the pulses of light towards the scene with low power, low intensity. Further, the pulse of light emitted by the one or more first light sources 106 has a small divergence angle to detect short distance targets and also to provide a higher spatial resolution of the scene. The one or more first light sources 106 are beneficial to measure the distance of nearby objects with high resolution. Moreover, the size of the aperture of the one or more first light sources 106 is small, which is beneficial to avoid crosstalk during the measurement of small distance objects and highly reflective objects. Further, the one or more first light sources 106 can emit the pulses of light of different pulse lengths, and the pulse length of the one or more first light sources 106 is selected by the controller 104.

In addition, the one or more second light sources 108 emit the pulses of light towards the scene with high power, high intensity, and with large divergence angle. Further, the one or more second light sources 108 are beneficial for measuring the distance of objects placed at long distances. As the size of the aperture of the one or more second light sources 108 is large, thus, the size of a spot after collimating of the one or more first light sources 106 is smaller than the size of the spot of the one or more second light sources 108. Further, the one or more second light sources 108 can emit the pulses of light of different pulse lengths, and the pulse length of the one or more second light sources 108 is selected by the controller 104

In operation, the controller 110 is configured to selectively activate and/or adjust an intensity of the one or more first light sources 106 or the one or more second light sources 108 for illuminating the scene, including a selection of the pulse length for the one or more first light sources 106 and the one or more second light sources 108. In an implementation, different light sources are selectively activated and/or its intensity is adjusted for illuminating objects in different distance ranges in the scene. In other words, the controller 110 selects an appropriate light source with respect to the distance of the objects in the scene and selects an appropriate intensity and/or pulse length for the selected light source to provide accurate results. In an implementation, the controller 110 is configured to activate the one or more first light source 106 for illuminating objects in short distance ranges in the scene and provide higher spatial resolution for such ranges. In another implementation, the controller 110 is configured to activate the one or more second light sources 108 for illuminating objects in long distance ranges in the scene and provide higher spatial resolution for such ranges. In another implementation, the controller 110 is configured to selectively activate and/or adjust an intensity of the one or more first light source 106 and the one or more second light sources 108 for illuminating objects in the same distance range in the scene, for example, to improve spatial resolution. In an implementation, one or more light detectors are also used to detect the pulse of light emitted by the one or more first light sources 106 or the one or more second light sources 108 and light backscattered on a target light pulse emitted by any laser in the scene. Moreover, by virtue of selectively activating the one or more first light sources 106 or the one or more second light sources 108, the controller 110 is able to determine the distance between the target and the time-of-flight device 102 (or light detection and ranging (lidar) systems). In an example, the distance is determined based on a time-of-flight between the emittance and the detection of light scattered on the target. The controller 110 is further configured to combine the obtained information from at least two apertures, such as from the one or more first light sources 106 and the one or more second light sources 108 to improve the overall measurements of at least distance and resolution and also to improve the distance measurements on the scene.

In an implementation, the measurements obtained via a small aperture of the one or more first light sources 106 are combined with the measurements obtained via the one or more second light sources 108 with a large aperture. Moreover, the controller 110 is configured to ensure improvements on the depth data and also to avoid the ghosting effects, the pile-up issues, and other effects caused by high reflective targets and/or closely located targets. Moreover, by using the lower power light source (or laser), the beams size of the light source is intrinsically smaller, which is beneficial to avoid the crosstalk due to highly reflective targets. As a result, the light source apparatus 104 can be used in order to increase the resolution of the distance measurement map in the time-of-flight device (or lidar) 102. In addition, by virtue of using the small aperture light sources, such as the one or more first light sources 106, the controller 110 ensures to have an angular divergence of a source to be smaller than the angular resolution of a sensor. Further, the resolution of the distance measurements can be increased for a short distance and highly reflective targets, which can be combined with the distance measurements obtained by using the one or more second light sources 108 (or large aperture laser) to obtain a higher resolution distance (or depth) map by the controller 110.

In another implementation, the scene is divided into two zones, such as for short distances and for long distances, and the light source apparatus 104 (or multi-aperture laser system) for the time-of-flight device (or lidar) 102 is used to improve the precision of the measurements. Firstly, the controller 110 is configured to use the same number of bins (i.e. , part of logic) of a sensor signal to analyse the short distances, and then to analyse the long distances. Moreover, different sizes of apertures are used at different laser pulse lengths to improve the precision of the light source apparatus 104. Beneficially, the precision of the measurements at the short distances is improved by statistical analysis as the one or more first light sources 106 with lower power allow to send a higher number of pulses within the eye safety region.

In an implementation, the one or more first light sources 106 and the one or more second light sources 108 include laser sources including one or more laser diodes, vertical cavity surface-emitting lasers (VCSEL), and edge-emitting lasers (EEL). In other words, the laser power output depends upon the type of laser source used. In an example, the VCSEL with different sizes of the aperture is placed in a die. Moreover, in the case of the EEL, either several independent lasers are combined in the same laser driver board, or a multichannel EEL laser is used. The multichannel EEL laser is routinely produced to increase the power achieved from the same chip, which is also performed by using different chip sizes of the EEL. Further, the intrinsic difference between the laser sources of different aperture sizes directly improves the result divergence of one beam compared to another. In addition, the packaging of the laser sources including the one or more laser diodes, the VCSEL, and the EEL is done in a way to support driving of the lasers independently by the controller 110. In an example, the output power of the VCSEL (or the EEL) is proportional to the size of the aperture (or effective emitting area) under the same design’s conditions. For example, the bigger the output aperture, the higher the output power, and similar conditions are defined by the maximum current density allowed by the material of a die, as further shown and described in FIGs. IB to ID.

The light source apparatus 104 is used in a time-of-flight device or lidar to perform the measurement of long and short distances accurately without facing the ghosting effect, pileup issue, and other problems caused by closely located and highly reflective targets. In addition, the one or more first light sources 106 and the one or more second light sources 108 are also beneficial to improve the precision of the measurements at short distances. The one or more first light sources 106 of the light source apparatus 104 are beneficial to avoid crosstalk during the measurement of small distance objects and highly reflective objects. In other words, the one or more first light sources 106 and the one or more second light sources 108 with divergence and/or shape are beneficial to solve different problems, such as long- range lidars data errors in case of high reflectance targets, in case of close targets. As a result, the one or more first light sources 106 and the one or more second light sources 108 are beneficial to improve the lateral resolution of the light source apparatus 104, and also to improve the precision of the distance measurements. Therefore, with the light source apparatus 104 time-of-flight devices or lidars can measure the distance with improved lateral resolution.

FIGs. IB to ID are different illustrations that depict an arrangement and integration of one or more first light sources, and one or more second light sources, in accordance with different embodiments of the present disclosure. FIGs. IB to ID are described in conjunction with elements from FIG 1A. With reference to FIG. IB, there is shown an illustration 100B that includes a die 112, the one or more first light sources 106, and the one or more second light sources 108 With reference to FIG. 1C, there is shown an illustration 100C that includes the die 112, the one or more first light sources 106, and the one or more second light sources 108 that are arranged in arrays. With reference to FIG. ID, there is shown an illustration 100D that includes the die 112, the one or more first light sources 106, and the one or more second light sources 108 that are arranged in arrays.

The die 112 is made of semiconductor material and is also referred to as a laser die, semiconductor dies, and the like. In an example, the length of the die 112 is around 800 micrometres (pm), and the width is around 500 pm.

In an implementation, the one or more first light sources 106 and the one or more second light sources 108 are integrated into the same die and are arranged in arrays. In an example, the one or more first light sources 106 and the one or more second light sources 108 are integrated into the die 112 and works at different times by design of the die 112. The die 112 ensures the independent synchronizations of the one or more first light sources 106 and the one or more second light sources 108 to have the most suitable regime. Moreover, as the one or more first light sources 106 and the one or more second light sources 108 have different aperture sizes, and integrated into the same die, and are arranged in arrays. Therefore, the light source apparatus 104 is beneficial for different range measurements used for distance measurements in the time-of-flight device 102 (or lidar) to ensure higher resolution when using a smaller size aperture.

With reference to FIG. IB, there is shown that the one or more first light sources 106 and the one or more second light sources 108 are arranged in arrays on the die 112 in an implementation. The one or more first light sources 106 and the one or more second light sources 108 are arranged vertically in alternate positions in a column. For example, a first light source is vertically arranged after a second light source and the like. There is further shown that the aperture (i.e., 30 pm) of the one or more second light sources 108 (or the second size) is greater than the aperture (i.e., the 10 pm) of the one or more first light sources 106 (or the first size). There is further shown a pitch of 50 pm. In an example, the pitch represents a vertical distance between the one or more first light sources 106 and the one or more second light sources 108 in a column. With reference to FIG. 1C, there is further shown that the one or more first light sources 106 and the one or more second light sources 108 are arranged in arrays on the die 112 in another implementation. The one or more first light sources 106 are arranged vertically one by one in columns, and the one or more second light sources 108 are also arranged vertically one by one in columns. There is further shown a pitch of 50 pm, which in this case is a vertical distance between two adjacent first light sources 106 in a column and also between two adjacent second light sources 108 in a column.

With reference to FIG. ID, there is further shown an implementation where the one or more first light sources 106, the one or more second light sources 108 and one or more third light sources 108A (with an aperture of a third size) are arranged in arrays on the die 112, such as to direct the light sources for emitting the laser light in a particular direction. Further, arranging in arrays helps the controller 110 to select the one or more first light sources 106 or the one or more second light sources 108, or the one or more third light sources 108A based on the requirement. There are further shown different diameter values for different arrays. For example, the diameter of the first array is around 10 pm, the diameter of the second array is around 30 pm, and the diameter of the third array is around 50 pm, which can have other possible values without limiting the scope of the present disclosure.

In an example, after directing the one or more first light sources 106 and the one or more second light sources 108 in one direction, a pulse of the laser strikes on an object and then on one or more light detectors (or sensors). The one or more detectors are configured to collect information on the time of the arrival of the previous photons. In addition, depth information of the scene is also derived from the time difference between emitting and receiving the photons.

FIG. 2A is an illustration that depicts an optical means for directing pulses of light in a light source apparatus, in accordance with an embodiment of the present disclosure. FIG. 2A is described in conjunction with elements from FIG. 1A to FIG. ID. With reference to FIG. 2A, there is shown an illustration 200A that includes an optical means 202, an object 204, and the light source apparatus 104 (of FIG. 1A).

The optical means 202 is a transmissive optical device with a specific focal length that is configured to focus light rays in a required direction by changing the path of rays of the light, such as by means of refraction. In an example, the optical means 202 is referred to as an optical system that consists of a single piece of transparent material. In another example, the optical means 202 is referred to as an optical system that consists of a plurality of pieces of transparent material. Other possible examples of the optical means 202 may include but are not limited to lens, mirrors, splitter and/or mirrors with holes, and the like. In an example, power density on the scene in the optical means 202 is defined by laser power output, collimating system (i.e., how the laser light is focused), and distance on which the scene is located.

In an implementation, the light source apparatus 104 includes the optical means 202 to direct the pulses of light emitted by the one or more first light sources 106 and the one or more second light sources 108 into the same optical path at the output of the light source apparatus 104. With the optical means 202, the one or more first light sources 106 and the one or more second light sources 108 of the light source apparatus 104 are configured to emit pulses of light towards a scene. For this end, the optical means 202 is configured to direct the pulses of light emitted by the one or more first light sources 106 and the one or more second light sources 108 into the same optical path at the output of the light source apparatus 104 so that the pulses of light are emitted towards the scene. Finally, the light is received by the object 204

In an implementation, due to the intrinsic difference between the aperture of the one or more first light sources 106 and the one or more second light sources 108, the beam size directly improves the result divergence of one beam as compared to another beam. In an example, when the VCSEL (or EEL) lasers are used as a light source, then the output power of such light source is proportional to the size of the aperture (i.e., effective emitting area) under the same design’s conditions. In an example, the bigger the output aperture higher the output power can be at the same conditions, which is defined by the maximum current density allowed by the material of the die 112. At the same time, the final divergence of the output beam after a collimating system is limited by diffraction limits. For example, the laser beam waist is multiplied with output divergence is a constant value, which means that there is a direct correlation between the minimum beam size (or waist) and the result divergence at the long distances. Moreover, the beam size is limited by the smallest aperture of the optical means 202. As a result, within a certain distance, such as Rayleigh length, the result divergence is smaller and defined by the minimum waist size and collimating point within the Rayleigh length. For example, in the close distance, the Rayleigh length can be of the order of meters depending on the designed system. This can be used for an advantage of the designed system in one of more implementations.

FIG. 2B is an illustration that depicts a system of optical means for directing pulses of light from different light sources in a light source apparatus, in accordance with an embodiment of the present disclosure. FIG. 2B is described in conjunction with elements from FIG. 1A to FIG. ID, and FIG. 2 A. With reference to FIG. 2B, there is shown an illustration 200B of a light source apparatus that includes a first light source 206A, a second light source 206B, a third light source 206C, a first optical means 208A, a second optical means 208B, and a third optical means 208C. In the illustrated implementation, the pulses of light of a maximum of four light sources can be directed by means of the system of optical means to have the same output direction.

In an implementation, each of the first light source 206A, the second light source 206B, and the third light source 206C with different apertures sizes are placed to be collimated (or focused) through different optical means in order to carefully control the result divergences. For example, the first light source 206A is collimated with the first optical means 208A, the second light source 206B is collimated with the second optical means 208B, and the third light source 206C is collimated with the third optical means 208C. In an example, additional optical elements such as mirrors, splitters and/or mirrors with holes can be used to combine then the pulses of light (or laser beams) towards the same optical path for the output, as shown in FIG. 2B. For example, the pulses of light of the second light source 206B strike through the second optical means 208B, and then combine with the same optical path for the output as that of the first optical means 208A, and similarly for the third light source 206C. In an example, a final divergence of the output beam after a collimating system is limited by diffraction limits, such as the laser beam waist multiplied with output divergence is a constant value. Thus, there is a direct correlation between the minimum beam size (or waist) the result divergence at the long distances, and the beam size is limited by the smallest aperture. Further, within a certain distance, such as Rayleigh length, the result divergence is smaller and defined by the minimum waist size and collimating point within the Rayleigh length. As mentioned above, this can be used for an advantage of the light source apparatus in one or more implementations.

FIG. 3 illustrates a block diagram of a time-of-flight device, in accordance with an embodiment of the present disclosure. FIG. 3 is described in conjunction with elements from FIG 1A to FIG. 2B. With reference to FIG. 3, there is shown a block diagram 300 of the time-of-flight device 102 such as a lidar that includes one or more light detectors 302, the one or more first light sources 106, the one or more the second light sources 108, and the controller 110.

The one or more light detectors 302 are configured to detect the pulses of light that scatters after striking the scene. The one or more light detectors 302 are also referred as light sensors that are used to provide information related to distance from the scene (or object) by receiving the pulse of light that is reflected after striking the scene. Examples of the one or more light detectors 302 include but are not limited to a single-photon avalanche diode (SPAD) sensor, a silicon photomultiplier (SiPM), an avalanche photodiode (APD) sensor, a positive-intrinsic-negative (PIN) diode, and the like. In an example, the SPAD sensor is a single-pixel or combined into an array of pixels, that detect a single photon. Moreover, the SiPM consists of many SPADs connected to the same output creating the output signal proportional to the number of cells triggered within the one or more light detectors 302. Further, the APD sensor is a single-pixel or combined into an array of pixels, and require a minimum level of photons to trigger the signal.

There is provided the time-of-flight device 102, such as a lidar, that includes the one or more first light sources 106 with an aperture of a first size that is configured to emit pulses of light of a first intensity towards a scene. The time-of-flight device 102 further includes the one or more second light sources 108 with an aperture of a second size configured to emit pulses of light of a second intensity towards the scene. Further, the second size is greater than the first size and the second intensity is higher than the first intensity. In other words, the time-of- flight device 102 includes at least two light sources of different aperture sizes and shape to emit a pulse of light. The time-of-flight device 102 includes the one or more first light sources 106, and the one or more second light sources 108 of different sizes and shapes of aperture that are collimated using the same optical means. Moreover, the one or more first light sources 106 emits the pulses of light towards the scene with low power, low intensity. Further, the pulse of light emitted by the one or more first light sources 106 has a small divergence angle of the collimated beam being able to detect short distance targets and provide a higher spatial resolution of the scene. The one or more first light sources 106 are beneficial to measure the distance of nearby objects with high resolution. Moreover, the size of the aperture of the one or more first light sources 106 is small, which is beneficial to avoid crosstalk during the measurement of small distance objects and highly reflective objects.

The time-of-flight device 102 such as a lidar further includes the one or more light detectors 302 that are configured to detect the pulse of light emitted by the one or more first light sources 106 or the one or more second light sources 108 and backscattered on a target in the scene. In other words, the one or more light detectors 302 are configured to detect the pulses of light that are reflected after striking the scene. After the emission of light from the one or more first light sources 106 or the one or more second light sources 108, the pulse of light strikes on the object, and then the one or more light detectors 302 collects information on the time of the arrival of the send previously photons. In an implementation, the one or more light detectors 302 are configured to detect the pulse of light emitted by the one or more first light sources 106 and backscattered on the target in the scene. In another implementation, the one or more light detectors 302 are configured to detect the pulse of light emitted by the one or more second light sources 108 and backscattered on the target in the scene.

The time-of-flight device 102 such as a lidar further includes the controller 110 that is configured to determine a time-of-flight (TOF) between the emittance and the detection of each pulse of light detected by the one or more light detectors 302. In other words, the controller 110 is configured to determine the time-of-flight (or depth) from the time difference between emitting and receiving of photons of each pulse of light that is each detected by the one or more light detectors 302. In an implementation, for direct TOF, a pulsed laser source radiates pulses towards the scene and then one or more light detectors 302 collects information on the time of the arrival of the previously photons. Alternatively stated, depth is derived from the time difference between emitting and receiving of the photons. Due to the propagation of the light towards the target in the scene, the maximum distance by which the time-of-flight device 102 detects directly depends on the power density of the emitted light.

The controller 110 is further configured to obtain a distance map of the scene based on the determined TOFs, and selectively activate and/or adjust an intensity of the one or more first light sources 106 or the one or more second light sources 108 to illuminate the scene so that to improve a lateral resolution and/or a precision of the distance map. In other words, the determined TOFs are used by the controller 110 to obtain the distance map of the scene. In an implementation, the controller 110 is configured to selectively activate the one or more first light sources 106. In another implementation, the controller 110 is configured to selectively adjust the intensity of the one or more first light sources 106. In yet another implementation, the controller 110 is configured to selectively activate and also to selectively adjust the intensity of the one or more first light sources 106. In another implementation, the controller 110 is configured to selectively activate the one or more second light sources 108. In yet another implementation, the controller 110 is configured to selectively adjust the intensity of the one or more second light sources 108. In another implementation, the controller 110 is configured to selectively activate and also to selectively adjust the intensity of the one or more second light sources 108. Alternatively stated, the controller 110 selects an appropriate light source and/or appropriately adjust the selected light source for illuminating the objects in the scene to provide accurate results. As a result, the controller 110 is configured to control the illumination of objects in the scene, for example, objects in different distance ranges in the scene, to improve a lateral resolution and/or the precision of the distance map. The controller 110 is further configured to combine the obtained information from the one or more first light sources 106 and the one or more second light sources 108 to improve the overall measurements of at least distance and resolution and also to improve the distance measurements on the scene. In an implementation, the time-of-flight device 102 comprises a lidar. In other words, the lidar is the time-of-flight device 102 to measure the distance from the object by analysing the pulse of light that reflects after striking the object. The time-of-flight device 102 provide depth information of the scene based on the time taken for emitted light pulses to travel from an emitter to the object, where it scatters, and returns to the receiver. As a result, the time- of-flight device 102 is used to estimate the distance and applied as a lidar to scan the scene to get information for driving assistance.

The time-of-flight device 102 such as a lidar is used to perform the measurement of long and short distances accurately without facing the ghosting effect, pile-up issue, and other problems caused by closely located and highly reflective targets. Moreover, the time-of- flight device 102 or the lidar measures the distance with improved lateral resolution. At that, a long-range lidar can be limited in its performance by the eye safety regulation dictating the maximum number of photons that is sent to the scene to be eye-safe for all users.

Modifications to embodiments of the present disclosure described in the foregoing are possible without departing from the scope of the present disclosure as defined by the accompanying claims. Expressions such as "including", "comprising", "incorporating", "have", "is" used to describe and claim the present disclosure are intended to be construed in a non-exclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural. The word "exemplary" is used herein to mean "serving as an example, instance or illustration". Any embodiment described as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or to exclude the incorporation of features from other embodiments. The word "optionally" is used herein to mean "is provided in some embodiments and not provided in other embodiments". It is appreciated that certain features of the present disclosure, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable combination or as suitable in any other described embodiment of the disclosure.

Claims

1. A light source apparatus (104) for a time-of-flight device (102), the light source apparatus (104) comprising: one or more first light sources (106) with an aperture of a first size configured to emit pulses of light towards a scene, one or more second light sources (108) with an aperture of a second size configured to emit pulses of light towards the scene, wherein the second size is greater than the first size, and a controller (110) configured to selectively activate and/or adjust an intensity of the one or more first light sources (106) and the one or more second light sources (108) for illuminating the scene.

2. The light source apparatus (104) of claim 1, wherein the controller is configured to selectively activate and/or adjust an intensity of the one or more first light sources (106) and one or more the second light sources (108) for illuminating objects in different distance ranges in the scene.

3. The light source apparatus (104) of claim 2, wherein the one or more first light sources (106) and one or more the second light sources (108) are integrated into the same die and arranged in arrays.

4. The light source apparatus (104) of any of claims 1 to 3, wherein the one or more first light sources (106) and the one or more second light sources (108) are arranged in arrays.

5. The light source apparatus (104) of any of claims 1 to 4, further comprising optical means (202) for directing the pulses of light emitted by the one or more first light sources (106) and the one or more second light sources (108) into the same optical path at the output of the light source apparatus (104).

6. The light source apparatus (104) of any of claims 1 to 5, wherein the one or more first light sources (106) and the one or more second light sources (108) comprise laser sources including one or more of laser diodes, Vertical Cavity Surface Emitting Lasers, VCSEL, and Edge-Emitting Lasers, EEL.

7. A time-of-flight device (102) comprising: one or more first light sources (106) with an aperture of a first size configured to emit pulses of light of a first intensity towards a scene, one or more second light sources (108) with an aperture of a second size configured to emit pulses of light of a second intensity towards the scene, wherein the second size is greater than the first size and the second intensity is higher than the first intensity, one or more light detectors (302) configured to detect a pulse of light emitted by the one or more first light sources (106) or the one or more second light sources (108) and backscattered on a target in the scene, and a controller (110) configured to determine a time-of-flight, TOF, between the emittance and the detection of each pulse of light detected by the one or more light detectors (302), obtain a distance map of the scene based on the determined TOFs, and selectively activate and/or adjust an intensity of the one or more first light sources (106) and the one or more second light sources (108) for illuminating the scene so that to improve a lateral resolution and/or a precision of the distance map.

8. The time-of-flight device (102) of claim 7, wherein the controller (110) is configured to selectively activate and/or adjust an intensity of the one or more first light sources (106) and the one or more second light sources (108) for illuminating objects in different distance ranges in the scene.

9. The time-of-flight device (102) of claim 7 or 8, comprising a lidar.