Patent Description:
A device may determine distances of its surroundings using different depth finding systems. In determining the depth, the device may generate a depth map illustrating or otherwise indicating the depths of objects from the device by emitting one or more wireless signals and measuring reflections of the wireless signals from the scene. Two types of depth finding systems are a time-of-flight (TOF) system and a structured light system.

For a TOF system, a light is emitted, and a reflection of the light is received. The round trip time of the light from the transmitter to the receiver is determined, and the distance or depth from the TOF system of the object reflecting the emitted light is determined from the round trip time. For a structured light system, a known spatial distribution of light is transmitted, and the reflections of the spatial distribution are received. For structured light systems, the transmitter and receiver are separated by a distance, and displacement and distortion of the spatial distribution occurs at a receiver as a result. Triangulation with the displacement and distortion of the spatial distribution and the distance between the transmitter and receiver is used in determining a distance or depth from the structured light system of the object reflecting the emitted light.

A problem with conventional structured light systems is that the distance between the transmitter and receiver (causing or increasing displacement and distortion of the spatial distribution) may cause shadows on or occlusions of the received spatial distribution. As a result, portions of the spatial distribution may be missing or not be correctly identified so that depths of portions of the scene cannot be determined.

Conventional TOF systems have the transmitter and receiver collocated, and therefore do not a have a distance between a transmitter and a receiver as in structured light systems. As a result, shadows and occlusions from an aperture do not interfere with measurements. However, a conventional TOF system emits and relies on a fixed field of emission that is larger than the field of emissions from structured light systems at a common depth from a transmitter. As a result, noise and interference from ambient light (such as sunlight or other external light sources) may cause a conventional TOF system to be unable to identify the reflections from the receiver measurements, and a conventional TOF system may have a shorter effective range than conventional structured light systems.

<CIT> discloses optoelectronics modules with low- and high-power illumination modes for distance measurements. A low-power mode may be used to monitor a scene where object movement can activate a high-power mode.

<CIT> discloses a depth camera assembly including an imaging device, a controller and an illumination source with a plurality of emitters on a single substrate.

<CIT> discloses a time-of-flight depth camera including a vertical-cavity surface emitting laser array.

This Summary is provided to introduce in a simplified form a selection of concepts that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter.

The present disclosure provides a time-of-flight system according to claim <NUM>, a method for performing time-of-flight ranging according to claim <NUM>, and a non-transitory computer-readable medium according to claim <NUM>. Preferred embodiments are subject of the dependent claims.

Aspects of the present disclosure are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements.

Aspects of the present disclosure may be used for TOF systems. According to the invention, a TOF transmitter transmits focused light with different fields. The transmitter includes a plurality of light emitters for transmitting focused light, the plurality of light emitters including a first group of light emitters for transmitting focused light with a first field of transmission and a second group of light emitters for transmitting focused light with a second field of transmission. The first field of transmission at a depth from the transmitter is larger than the second field of transmission at the depth from the transmitter.

In the following description, numerous specific details are set forth, such as examples of specific components, circuits, and processes to provide a thorough understanding of the present disclosure. The term "coupled" as used herein means connected directly to or connected through one or more intervening components or circuits. Also, in the following description and for purposes of explanation, specific nomenclature is set forth to provide a thorough understanding of the present disclosure. However, it will be apparent to one skilled in the art that these specific details may not be required to practice the teachings disclosed herein. In other instances, well-known circuits, systems, and devices are shown in block diagram form to avoid obscuring teachings of the present disclosure. Some portions of the detailed descriptions which follow are presented in terms of procedures, logic blocks, processing and other symbolic representations of operations on data bits within a computer memory. In the present disclosure, a procedure, logic block, process, or the like, is conceived to be a self-consistent sequence of steps or instructions leading to a desired result. The steps are those requiring physical manipulations of physical quantities. Usually, although not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated in a computer system.

Unless specifically stated otherwise as apparent from the following discussions, it is appreciated that throughout the present application, discussions utilizing the terms such as "accessing," "receiving," "sending," "using," "selecting," "determining," "normalizing," "multiplying," "averaging," "monitoring," "comparing," "applying," "updating," "measuring," "deriving," "settling" or the like, refer to the actions and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices.

In the figures, a single block may be described as performing a function or functions; however, in actual practice, the function or functions performed by that block may be performed in a single component or across multiple components, and/or may be performed using hardware, using software, or using a combination of hardware and software. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps are described below generally in terms of their functionality. Also, the example systems and devices may include components other than those shown, including well-known components such as a processor, memory and the like.

Aspects of the present disclosure are applicable to any TOF ranging, and may be included in or coupled to any suitable electronic device or system (such as security systems, smartphones, tablets, laptop computers, digital cameras, vehicles, drones, virtual reality devices, or other devices that may utilize depth sensing). While described below with respect to a device having or coupled to one TOF system, aspects of the present disclosure are applicable to devices having any number of TOF systems.

The term "device" is not limited to one or a specific number of physical objects (such as one smartphone, one controller, one processing system and so on). As used herein, a device may be any electronic device with one or more parts that may implement at least some portion of this disclosure. While the below description and examples use the term "device" to describe various aspects of this disclosure, the term "device" is not limited to a specific configuration, type, or number of objects. Additionally, the term "system" is not limited to multiple components or specific embodiments. For example, a system may be implemented on one or more printed circuit boards or other substrates, have one or more housings, be one or more objects integrated into another device, and may have movable or static components. While the below description and examples use the term "system" to describe various aspects of this disclosure, the term "system" is not limited to a specific configuration, type, or number of objects.

Two types of ranging systems include structured light systems and TOF systems. <FIG> is a depiction of an example structured light system <NUM>. The structured light system <NUM> may be used to generate a depth map (not pictured) of a scene (with objects 106A and 106B at different depths in the scene), or may be used for other applications for ranging of objects 106A and 106B or other portions of the scene. The structured light system <NUM> may include a transmitter <NUM> and a receiver <NUM>.

The transmitter <NUM> may be configured to project a spatial distribution <NUM> onto the scene (including objects 106A and 106B). In some example implementations, the transmitter <NUM> may include one or more light sources <NUM> (such as laser sources), a lens <NUM>, and a light modulator <NUM>. In some embodiments, the light modulator <NUM> includes one or more diffractive optical elements (DOEs) to diffract the emissions from one or more light sources <NUM> (which may be directed by the lens <NUM> to the light modulator <NUM>) into additional emissions. The light modulator <NUM> may also adjust the intensity of the emissions. Additionally or alternatively, the lights sources <NUM> may be configured to adjust the intensity of the emissions.

In some other implementations of the transmitter <NUM>, a DOE may be coupled directly to a light source (without lens <NUM>) and be configured to diffuse the emitted light from the light source into at least a portion of the spatial distribution <NUM>. The spatial distribution <NUM> may be a fixed distribution of emitted light that the transmitter projects onto a scene. For example, a DOE may be manufactured so that the black spots in the spatial distribution <NUM> correspond to locations in the DOE that prevent light from the light source <NUM> being emitted by the transmitter <NUM>. In this manner, the spatial distribution <NUM> may be known in analyzing any reflections received by the receiver <NUM>. The transmitter <NUM> may transmit the light in a spatial distribution through the aperture <NUM> of the transmitter <NUM> and onto the scene (including objects 106A and 106B).

The receiver <NUM> may include an aperture <NUM> through which reflections of the emitted light may pass, be directed by a lens <NUM> and hit a sensor <NUM>. The sensor <NUM> may be configured to detect (or "sense"), from the scene, one or more reflections of the spatial distribution of light. As illustrated, the transmitter <NUM> may be positioned on the same reference plane as the receiver <NUM>, and the transmitter <NUM> and the receiver <NUM> may be separated by a distance <NUM> called the "baseline.

The sensor <NUM> may include an array of photodiodes (such as avalanche photodiodes) to measure or sense the reflections. The array may be coupled to a complementary metal-oxide semiconductor (CMOS) sensor including a number of pixels or regions corresponding to the number of photodiodes in the array. The plurality of electrical impulses generated by the array may trigger the corresponding pixels or regions of the CMOS sensor to provide measurements of the reflections sensed by the array. Alternatively, the sensor <NUM> may be a photosensitive CMOS sensor to sense or measure reflections including the reflected codeword distribution. The CMOS sensor logically may be divided into groups of pixels that correspond to a size of a bit or a size of a codeword (a patch of bits) of the spatial distribution <NUM>.

The reflections may include multiple reflections of the spatial distribution of light from different objects or portions of the scene at different depths (such as objects 106A and 106B). Based on the baseline <NUM>, displacement and distortion of the sensed light in spatial distribution <NUM>, and intensities of the reflections, the structured light system <NUM> may be used to determine one or more depths and locations of objects (such as objects 106A and 106B) from the structured light system <NUM>. With triangulation based on the baseline and the distances, the structured light system <NUM> may be used to determine the differing distances between objects 106A and 106B. For example, if the portion of the spatial distribution <NUM> of the reflections from objects 106A and 106B received at sensor <NUM> are recognized or identified as the same, the distance between the location <NUM> where the light reflected from object 106B hits sensor <NUM> and the center <NUM> of sensor <NUM> is less than the distance between the location <NUM> where the light reflected from object 106A hits sensor <NUM> and the center <NUM> of sensor <NUM>. A smaller distance may indicate that the object 106B is further from the transmitter <NUM> than object 106A. The calculations may further include determining displacement or distortion of the spatial distribution <NUM> to determine depths or distances.

In conventional structured light systems, the points of the spatial distribution <NUM> are uniformly dispersed. In this manner, the space between neighboring points in a first portion of the spatial distribution <NUM> is the same size as the space between neighboring points in a second portion of the spatial distribution <NUM>. However, there may be more difficulty in using the edges of the spatial distribution <NUM> as compared to the center of a spatial distribution <NUM> when determining depths.

The transmitter <NUM> and the receiver <NUM> may be manufactured or oriented so that the apertures <NUM> and <NUM> are along the same plane. As a result, the center of the spatial distribution <NUM> from the transmitter <NUM> may not be reflected onto the center of the sensor <NUM> when reflecting the light off of a flat object parallel to the baseline <NUM>. Further, objects typically are not perfectly flat or parallel to the baseline, which may cause the angle of the reflection approaching the receiver <NUM> to be more severe than if the objects are flat and parallel to the baseline. As a result, the aperture <NUM> of the receiver <NUM> may block portions of the reflected spatial distribution of light. The interference may be most pronounced at the edges of the spatial distribution, as the edge of the emitted light may approach the receiver <NUM> outside the aperture. In one example, interference may be more pronounced for reflections from object 106A than for reflections from object 106B since the angle of arrival to the aperture <NUM> for the reflections from object 106B is less than for the reflections from object 106A. The effective aperture (the appearance of the aperture based on the angle of arrival) may be smaller for reflections from object 106A than for reflections from object 106B. For example, if the perspective or origin of the reflections is off-center from a field of view of the receiver <NUM>, the aperture <NUM> may appear smaller from the perspective than from a perspective that is centered in the field of view of the receiver <NUM>.

One alternative to a structured light system is a TOF system. <FIG> is a depiction of an example TOF system <NUM>. The TOF system <NUM> may be used to generate a depth map (not pictured) of a scene (with surface <NUM> in the scene), or may be used for other applications for ranging surface <NUM> or other portions of the scene. The TOF system <NUM> includes a transmitter <NUM> and a receiver <NUM>. The transmitter <NUM> may be referred to as a "transmitter," "projector," "emitter," and so on, and should not be limited to a specific transmission component. Similarly, the receiver <NUM> may be referred to as a "detector," "sensor," "sensing element," "photodetector," and so on, and should not be limited to a specific receiving component.

The transmitter <NUM> may be configured to transmit, emit, or project signals (such as a field of light) onto the scene (including surface <NUM>). While TOF systems are described in the examples as emitting light (which may include near-infrared (NIR)), signals at other frequencies may be used, such as microwaves, radio frequency signals, sound, and so on. The present disclosure should not be limited to a specific range of frequencies for the emitted signals.

The transmitter <NUM> transmits light <NUM> toward a scene. While the transmitted light <NUM> is illustrated as being directed to surface <NUM>, the field of the emission or transmission by the transmitter extends beyond as depicted for the transmitted light <NUM>. For example, conventional TOF system transmitters have a fixed focal length lens for the emission that defines the field of the transmission from the transmitter. The fixed field of the transmission for a conventional TOF system is larger at a depth from the transmitter than the fixed field of transmissions for each point of the spatial distribution for a conventional structured light system. As a result, conventional structured light systems may have longer effective ranges than conventional TOF systems.

The transmitted light <NUM> includes light pulses <NUM> at known time intervals (such as periodically). The receiver <NUM> includes a sensor <NUM> to sense the reflections <NUM> of the transmitted light <NUM>. The reflections <NUM> include the reflected light pulses <NUM>, and the TOF system determines a round trip time <NUM> for the light by comparing the timing <NUM> of the transmitted light pulses to the timing <NUM> of the reflected light pulses. The distance of the surface <NUM> from the TOF system may be calculated to be half the round trip time multiplied by the speed of the emissions (such as the speed of light for light emissions).

The sensor <NUM> may include an array of photodiodes to measure or sense the reflections. Alternatively, the sensor <NUM> may include a CMOS sensor or other suitable photo-sensitive sensor including a number of pixels or regions for sensing. The TOF system <NUM> identifies the reflected light pulses <NUM> as sensed by the sensor <NUM> when the magnitudes of the pulses are greater than a threshold. For example, the TOF system measures a magnitude of the ambient light and other interference without the signal, and then determines if further measurements are greater than the previous measurement by a threshold. However, the noise or the degradation of the signal before sensing may cause the signal-to-noise ratio (SNR) to be too great for the sensor to accurately sense the reflected light pulses <NUM>.

To reduce interference, the receiver <NUM> may include a bandpass filter before the sensor <NUM> to filter some of the incoming light at different wavelengths than the transmitted light <NUM>. There is still noise sensed by the sensor, though, and the SNR increases as the signal strength of the reflections <NUM> decreases (such as the surface <NUM> moving further from the TOF system <NUM>, or the reflectivity of the surface <NUM> decreasing). The TOF system <NUM> may also increase the power for the transmitter <NUM> to increase the intensity of the transmitted light <NUM>. However, many devices have power constraints (such as smartphones, tablets, or other battery devices), and are limited in increasing the intensity of the emitted light in a fixed field for a TOF system.

According to the present invention, the TOF system is configured to adjust the field of transmission or emission. In decreasing the field of transmission / focusing the light transmissions, the TOF system extends the effective distance for ranging. The TOF system is configured to transmit light with different fields of transmissions, where a first field of transmission at a depth from the transmitter is larger than a second field of transmission at the depth from the transmitter.

<FIG> is a block diagram of an example device <NUM> including a TOF system. In some other examples, the TOF system may be coupled to the device <NUM>. The example device <NUM> may include or be coupled to a transmitter <NUM> (such as transmitter <NUM> in <FIG>), a receiver <NUM> (such as receiver <NUM> in <FIG>), a processor <NUM>, a memory <NUM> storing instructions <NUM>, a TOF controller <NUM> (which may include one or more signal processors <NUM>). The device <NUM> may optionally include (or be coupled to) a display <NUM> and a number of input/output (I/O) components <NUM>. The device <NUM> may also optionally include a camera <NUM> (which may be a single camera, dual camera module, or a module with any number of camera sensors) coupled to a camera controller <NUM> (which may include one or more image signal processors <NUM> for processing captures from the camera <NUM>). The device <NUM> may further optionally include one or more sensors <NUM> (such as a gyroscope, magnetometer, inertial sensor, NIR sensor, and so on). The device <NUM> may include additional features or components not shown. For example, a wireless interface, which may include a number of transceivers and a baseband processor, may be included for a wireless communication device. The device <NUM> may also include a power supply <NUM>, which may be coupled to or integrated into the device <NUM>.

The transmitter <NUM> and the receiver <NUM> may be part of a TOF system (such as TOF system <NUM> in <FIG>) controlled by the TOF controller <NUM> and/or the processor <NUM>. The device <NUM> may include or be coupled to additional TOF systems, one or more structured light systems, or a different configuration for the TOF system. The disclosure should not be limited to any specific examples or illustrations, including the example device <NUM>.

The memory <NUM> may be a non-transient or non-transitory computer readable medium storing computer-executable instructions <NUM> to perform all or a portion of one or more operations described in this disclosure. The processor <NUM> may be one or more suitable processors capable of executing scripts or instructions of one or more software programs (such as instructions <NUM>) stored within the memory <NUM>. In some aspects, the processor <NUM> may be one or more general purpose processors that execute instructions <NUM> to cause the device <NUM> to perform any number of functions or operations. In additional or alternative aspects, the processor <NUM> may include integrated circuits or other hardware to perform functions or operations without the use of software. While shown to be coupled to each other via the processor <NUM> in the example of <FIG>, the processor <NUM>, the memory <NUM>, the TOF controller <NUM>, the optional display <NUM>, the optional I/O components <NUM>, the optional camera controller <NUM>, and the optional sensor <NUM> may be coupled to one another in various arrangements. For example, the processor <NUM>, the memory <NUM>, the TOF controller <NUM>, the optional display <NUM>, the optional I/O components <NUM>, the optional camera controller <NUM>, and/or the optional sensor <NUM> may be coupled to each other via one or more local buses (not shown for simplicity).

The display <NUM> may be any suitable display or screen allowing for user interaction and/or to present items (such as a depth map or a preview image of the scene) for viewing by a user. In some aspects, the display <NUM> may be a touch-sensitive display. The I/O components <NUM> may be or include any suitable mechanism, interface, or device to receive input (such as commands) from the user and to provide output to the user. For example, the I/O components <NUM> may include (but are not limited to) a graphical user interface, keyboard, mouse, microphone and speakers, squeezable bezel or border of the device <NUM>, physical buttons located on device <NUM>, and so on. The display <NUM> and/or the I/O components <NUM> may provide a preview image or depth map of the scene to a user and/or receive a user input for adjusting one or more settings of the device <NUM> (such as adjusting the intensity of the emissions by transmitter <NUM>, determining or switching the mode of the TOF system, adjusting the field of emission of the transmitter <NUM>, and so on).

The TOF controller <NUM> may include a signal processor <NUM>, which may be one or more processors to process measurements provided by the receiver <NUM> and/or control the transmitter <NUM> (such as switching modes). In some aspects, the signal processor <NUM> may execute instructions from a memory (such as instructions <NUM> from the memory <NUM> or instructions stored in a separate memory coupled to the signal processor <NUM>). In other aspects, the signal processor <NUM> may include specific hardware for operation. The signal processor <NUM> may alternatively or additionally include a combination of specific hardware and the ability to execute software instructions.

The transmitter <NUM> may vary its field of emission for different modes of operation. In some example implementations, the transmitter <NUM> may include formable means for adjusting the size of the field of emission / transmission. In one example, mirrors attached to actuators (such as microelectromechanical systems (MEMS) actuators) may adjust the focus of the light emissions from the transmitter <NUM>. In another example, an adjustable holographic optical element (HOE) may adjust the focus of the light emissions from the transmitter <NUM>. In a further example, a formable diffractive optical element (DOE) (such as a piezoelectric material to adjust the shape) may be adjusted to focus the diffracted points of light emitted.

According to the invention, a plurality of light emitters is used. The emitters include a first group of light emitters for emitting light with a first field of transmission. The emitters further include a second or different group of light emitters for emitting light with a second field of transmission. The first field is larger than the second field at a common depth from the transmitter <NUM>. In some example implementations, the first group of light emitters may be active for a first mode of the transmitter <NUM>, and the second group of light emitters may be active for a second mode of the transmitter <NUM>.

<FIG> is a depiction of different fields of emission/transmission for a TOF transmitter <NUM>. The transmitter's first field of transmission <NUM> may be larger than the second field of transmission <NUM> at a depth from the TOF transmitter <NUM>. The first field of transmission <NUM> may also be larger than a third field of transmission <NUM> for the depth from the TOF transmitter <NUM>. Darker fields of emission/transmission indicate a more focused emission (where the field is smaller at a depth from the transmitter the for less focused emission). In some example implementations, the transmitted light includes the first field of transmission <NUM> during a first mode <NUM> in which the TOF transmitter <NUM> operates, the transmitted light includes the second field of transmission <NUM> during a second mode <NUM> in which the TOF transmitter <NUM> operates, and the transmitted light includes the third field of transmission <NUM> during a third mode <NUM> in which the TOF transmitter <NUM> operates. While two modes and three modes are shown in the figures and described below, any number of modes may exist. Further, while the examples depict one field of emission / transmission for each mode, a mode may be associated with any number, or range, of fields of emissions. The present disclosure should not be limited to a specific number of modes, matchings, or fields of emission for the TOF transmitter. The present disclosure uses the terms "emission" and "transmission" interchangeably for signals, and the present disclosure should not be limited by use of one of the terms.

<FIG> is a depiction of a TOF transmitter <NUM> with an array <NUM> of light emitters <NUM> with different fields of emission <NUM>, <NUM>, and <NUM>. In some example implementations, each light emitter <NUM> is configured to emit light of a fixed field. For example, a first group of the light emitters <NUM> may be configured to emit light with a first field of emission <NUM>, a second group of the light emitters <NUM> may be configured to emit light with a second field of emission <NUM>, and a third group of the light emitters <NUM> may be configured to emit light with a third field of emission <NUM>. Any size and number or range of emission fields may be used, and the present disclosure should not be limited to the provided examples. While the array <NUM> is depicted as a two-dimensional array, a one-dimensional array may be used, and any shape of the array and spacing of the emitters for the array may be used.

Emitting or transmitting more focused light a further distance may consume more power than emitting or transmitting less focused light a shorter distance. Further, a device including the TOF system may have power constraints or a limited power supply (such as a battery). The number of emitters emitting more focused light may be less than the number of emitters emitting less focused light. In this manner, the number of light emitters for the third mode may be less than the number of light emitters for the second mode and for the first mode to reduce power consumption and requirements by the TOF system. The different number of emitters for different modes of operation may be used to meet the power constraints for the TOF system.

<FIG> is a depiction of an example layout of a portion of the array of emitters <NUM> for a TOF transmitter. The shade of the emissions for emitters in the array of emitters <NUM> indicates the size of the field of transmission (e.g., a darker shade indicates a smaller field of transmission at a common depth from the transmitter). The array of emitters <NUM> includes an example distribution of the emitters with different size emission fields. However, any suitable distribution may be used. In the example distribution, the first group of emitters (such as operating in a first mode <NUM>) is greater than the second group of emitters (such as operating in a second mode <NUM>) and is greater than the third group of emitters (such as operating in a third mode <NUM>). Further, the second group of emitters is greater than the third group of emitters. For example, the region of light emitters <NUM> is a block of light emitters repeated in the array of emitters <NUM>. The region of light emitters <NUM> corresponds to the emission fields <NUM> (such as for the three modes).

The emissions with different fields of transmission (such as for different modes) may be time division multiplexed so that different times may correspond to different size fields of emission. In this manner, the emitters for a defined emission field may transmit / emit at a first time when the other emitters are not emitting / transmitting. As a result, interference between emitters with different intensities and fields of the emissions is reduced.

<FIG> is a depiction of the coverage of the emission fields <NUM> for the array of emitters <NUM> in <FIG>. The chart of power consumption per light emitter in each mode <NUM> indicates that the power consumption <NUM> in the third mode is greater than the power consumption <NUM> in the second mode, which is greater than the power consumption <NUM> in the first mode. The number of emitters emitting per mode may therefore be different. If the number of emitters of a first group of emitters with more focused light emissions is less than the number of emitters of a second group of emitters with less focused light emissions, the overall coverage of the emissions for the first group may be less than the overall coverage of the emissions for the second group. Referring to the chart of the coverage of emission field per mode <NUM>, the coverage of the emission fields <NUM> in a third mode is less than the coverage of the emission fields 716in a second mode, which is less than the coverage of the emission fields 718in a first mode.

With the third mode having less coverage than the first mode and second mode, less portions of the scene receive and reflect emissions from the TOF transmitter in the third mode than in the first mode or the second mode. Additionally, less portions of the scene receive and reflect emissions from the TOF transmitter in the second mode than in the first mode. As a result, the TOF receiver senses less reflections in the third mode than in the second mode and the first mode, and senses less reflections in the second mode than in the first mode. In this manner, the resolution in sensing the scene may differ between modes. The first mode may provide the greatest resolution, the second mode may provide a resolution less than the first mode but greater than the third mode, and the third mode may provide a resolution less than the first mode and less than the second mode. For example, less pixels of the TOF receiver sensor may sense reflections of the emitted light from the TOF transmitter in the third mode than in the second mode or in the first mode. In this manner, less pixels of the receiver sensor provide measurements to be used in performing ranging / determining depths in a scene. If building a depth map, for example, the resolution with the TOF transmitter in the second mode may be less than the resolution with the TOF transmitter in the first mode. However, a depth map constructed with the TOF transmitter in the second mode may include objects in the scene further from the TOF system than a depth map constructed with the TOF transmitter in the first mode (with the effective range of the TOF system for the second mode higher than for the first mode).

<FIG> is a depiction of the coverage of different emission fields for an array of emitters of a TOF system. In some example implementations, the different fields may be for different modes of the TOF system. The coverages are an example coverage of the array of emitters <NUM> in <FIG> for the different fields (which may be for different modes). The coverage <NUM> in the first mode is the greatest between the three modes. In the example, the coverage <NUM> in the first mode is complete, and all portions of a scene may receive emissions. If the scene is within an effective range of the TOF system for the first mode, approximately all pixels of the receiver sensor may sense reflections of the emissions, and the resolution is the greatest between the modes.

The coverage <NUM> in the second mode is less than the coverage <NUM> in the first mode. As a result, less portions of a scene may receive emissions than in the first mode, and less pixels of the receiver sensor may sense reflections of the emissions. The effective range of the TOF system in the second mode may be greater than in the first mode. In this manner, reflections from portions of the scene outside the effective range in the first mode may not be sensed, while reflections from the same portions of the scene may be sensed in the second mode.

The coverage <NUM> in the third mode is less than the coverage <NUM> in the first mode and the coverage <NUM> in the second mode. In this manner, less pixels of the receiver sensor may sense reflections in third mode than in the second mode or in the first mode. However, portions of the scene outside of the effective range in the first mode and the effective range in the second mode may be sensed in the third mode (which may have a higher effective range). Different modes may be used to perform ranging of the scene for different ranges of distances from the TOF system.

In some example implementations, each light emitter may be a laser (such as a vertical-cavity surface-emitting laser (VCSEL) or other suitable type of laser). In this manner, the array of light emitters may be an array of VCSELs (or other suitable laser). <FIG> is a depiction of an example laser array <NUM> where each light emitter of the TOF transmitter is a laser. The laser array <NUM> includes a plurality of single lasers <NUM>. Each laser <NUM> may be configured to have an emission field that may differ from other lasers. For example, some lasers may have an emission field of a first size, some other lasers may have an emission field of a second size, and some other lasers may have an emission field of a third size. Each laser may be coupled to a separate power supply (not shown), and the power provided to each laser may differ. Alternatively, lasers for each mode may be coupled to the same power supply, with the power to the lasers differing between modes. In another implementation, the power supply may be the same for the lasers, with switches configured to turn off or on the power to each laser <NUM> for the different modes or for when to transmit light with the different fields of transmission / emission. The power supply may also be adjustable. For example, the power supplies for the lasers may be adjusted so that the SNR is approximately the same (with a tolerance) across the modes. In this manner, the same SNR threshold may be used to sense the pulses in the reflections (such as the reflected light pulses <NUM> in <FIG>).

In some other example implementations, a laser may be a light source for one or more light emitters of the TOF transmitter. <FIG> is a depiction of an example laser array <NUM> configured to be the light source for a number of light emitters greater than the number of lasers in the laser array <NUM>. One or more of the lasers may be coupled to a DOE to diffuse the light from the laser to one or more light emissions for the TOF transmitter. In some example implementations, each laser is coupled to its own DOE. The DOE may be manufactured to diffuse the light from the laser into one or more light emissions with a defined field. In this manner, the fields of emission may differ between the DOEs <NUM>. For example, a single laser 1004A may be coupled to a DOE to emit light with a first field, a single laser 1004B may be coupled to a DOE to emit light with a second field, and a single laser 1004C may be coupled to a DOE to emit light with a third field. Similar to the described power supplies for the laser array <NUM> in <FIG>, each laser in the laser array <NUM> may be coupled to a separate power supply, and each laser may be switched on or off, or the power for each laser adjusted, based on the mode of the TOF system or which field size the transmitted light is to have, the SNR measured for the different modes, or other suitable measurements.

<FIG> is a depiction of the first emission field of the example laser array <NUM> in <FIG> (such as in a first mode 1102A). The lasers for the first mode are switched on (such as single laser 1004A). The lasers for the second mode and the third mode are switched off (such as single laser 1004B and single laser 1004C). <FIG> is a depiction of the second emission field of the example laser array <NUM> in <FIG> (such as in a second mode 1102B). The lasers for the second mode are switched on (such as single laser 1004B). The lasers for the first mode and the third mode are switched off (such as single laser 1004A and single laser 1004C). <FIG> is a depiction of the third emission field of the example laser array <NUM> in <FIG> (such as in a third mode 1102C). The lasers for the third mode are switched on (such as single laser 1004C). The lasers for the first mode and the second mode are switched off (such as single laser 1004A and single laser 1004B).

The TOF transmitter may be placed into different modes of operation, and each mode may be associated with a different field of emission for the TOF transmitter. In this manner, the TOF system may be adjusted to perform ranging for different ranges of distances from the TOF system. The modes may correspond to different applications or use cases. In some example implementations, a TOF controller (such as TOF controller <NUM> or the signal processor <NUM> in <FIG>) may determine and control when to switch the TOF transmitter (such as transmitter <NUM> in <FIG>) between modes. In some other example implementations, other components of a device including the TOF system may determine or control when to switch modes. For example, the processor <NUM> in <FIG> may determine when to switch modes for the transmitter <NUM>. While the following examples of controlling or switching the mode of operation include two modes, any number of modes may be used (including three or more). The present disclosure should not be limited to two (or three) modes.

<FIG> is a flow chart depicting an example operation <NUM> of a TOF system transmitting light in a first mode and in a second mode. Beginning at <NUM>, the TOF transmitter transmits signals with a first field of emission in a first mode. For example, the TOF transmitter may transmit light using a first group of light emitters (<NUM>), such as from a laser array <NUM> in <FIG> or from a laser array <NUM> in <FIG>.

If the TOF system is to remain in the first mode (<NUM>), the TOF transmitter may continue to transmit signals with the first field of emission (<NUM>). If the TOF system is to switch to the second mode (<NUM>), the TOF transmitter may be placed into the second mode to transmit signals with a second field of emission that is smaller than the first field of emission (<NUM>) at a common depth from the TOF transmitter. For example, the TOF transmitter may transmit light using a second group of light emitters different from the first group of emitters (<NUM>). If the TOF system is to remain in the second mode (<NUM>), the TOF transmitter may continue to transmit signals with the second field of emission (<NUM>). If the TOF system is to switch from the second mode (<NUM>), the TOF transmitter may be placed back into the first mode (<NUM>).

Other processes for switching modes exists, and the present disclosure should not be limited by the example operation <NUM>. For example, while operation <NUM> begins with the TOF transmitter transmitting in a first mode (<NUM>), the TOF transmitter may begin transmitting in any mode. Further, the TOF transmitter may switch to any mode if more than two modes, and is not limited to a defined sequence of modes when switching.

Determining when to vary the emission field for transmitted light or when to switch modes (such as <NUM> and <NUM> in the example operation <NUM>) may be based on one or more factors and/or may be configurable or adjustable. For example, a device or TOF system manufacturer may initially configure the TOF system (such as manufacturing DOEs for different lasers and configuring the power supplies for the lasers). A user may also configure or adjust the configuration (such as adjusting the power supplied to the lasers or the timing or conditions for switching).

In some example implementations, determining or switching modes is schedule based. For example, if the device <NUM> (<FIG>) is to perform ranging for all distances (such as in generating a depth map), the device <NUM> may use a schedule to switch the transmitter <NUM> between different modes. The schedule may be adjustable, such as for the use case, for compensating for degradation of the TOF system over time, for different ambient light conditions (indoors, outdoors, etc.), for different weather or climate conditions, and so on. Additionally or alternatively, the schedule may be based on the application using the TOF system. For example, a facial and/or iris recognition application may correspond to a schedule with more time for the first mode (with the most coverage by the field of emission of the TOF transmitter) than an object tracking application for objects further from the TOF system.

Claim 1:
A time-of-flight, TOF, system (<NUM>; <NUM>), comprising:
a transmitter (<NUM>; <NUM>; <NUM>; <NUM>; <NUM>) including a plurality of light emitters (<NUM>) for transmitting light (<NUM>), the plurality of light emitters including a first group of light emitters for transmitting light with a first field of transmission (<NUM>; <NUM>) and a first amount of power (<NUM>) per light emitter and a second group of light emitters for transmitting light with a second field of transmission (<NUM>; <NUM>) and a second amount of power (<NUM>) per light emitter, wherein the first field of transmission at a depth from the transmitter is larger than the second field of transmission at the depth from the transmitter and the first amount of power (<NUM>) per light emitter is less than the second amount of power (<NUM>) per light emitter;
a receiver (<NUM>; <NUM>; <NUM>) to receive reflections (<NUM>) of the transmitted light;
one or more processors (<NUM>, <NUM>); and
a memory (<NUM>) coupled to the one or more processors and including instructions that, when executed by the one or more processors, cause the TOF system to perform operations comprising:
determining one or more depths or performing ranging in a scene based on received reflections of transmitted light from the first group of light emitters transmitting in a first mode (<NUM>; <NUM>; <NUM>); and
determining one or more depths or performing ranging in the scene based on received reflections of transmitted light from the second group of light emitters transmitting in a second mode (<NUM>; <NUM>; <NUM>).