Optical ranging system with multi-mode operation using short and long pulses

Abstract

A device including a time-of-flight (TOF) sensor system having an illuminator operable to emit pulses of light toward an object external to the device. The illuminator is operable in a first mode, in which the illuminator emits pulses having a first width, and in a second mode, in which the illuminator emits pulses having a second width that is longer than the first width. The TOF sensor system further includes a photodetector operable to detect light generated by the illuminator and reflected by the object back to the device. An electronic control device is operable to control the light emitted by the illuminator and is operable to estimate the distance to the object based on the time elapsed between the emission of one or more pulses by the illuminator and the detection of the reflected light by the photodetector.

Description

Technical Field

[0001] The present disclosure relates to optical ranging systems. Background Art

[0002] A time-of-flight sensor is an example of a range-finding imaging system that resolves distance based on the known speed of light. As an example, a "direct" time-of-flight sensor can emit a pulse of light toward an object and detect the light that reflects from the object and returns to the sensor. The distance between the object and the sensor can be determined based on the duration between the light emission and the light returning to the sensor (e.g., the "time of flight" of the light from the sensor to the object and back to the sensor). Summary of the invention

[0003] This disclosure describes an optical ranging system with multi-mode operation using short and long pulses.

[0004] For example, in one aspect, the present disclosure describes a device that includes a time-of-flight (TOF) sensor system. The TOF sensor system includes an illuminator operable to emit light pulses to an object external to the device, wherein the illuminator is operable in a first mode and a second mode, in which the illuminator emits pulses having a first width; in which the illuminator emits pulses having a second width greater than the first width. The TOF sensor system further includes a photodetector operable to detect light generated by the illuminator and reflected back to the device by the object. The electronic control device is operable to control the light emitted by the illuminator and is operable to estimate the distance to the object based on the time elapsed between the emission of one or more pulses by the illuminator and the detection of the reflected light by the photodetector.

[0005] Some implementations include one or more of the following features. For example, in some instances, when the luminaire is operated in a first mode if the distance to the object is within a first distance measurement range, the electronic control device is operable to estimate the distance to the object based on a signal from the photodetector, and wherein when the luminaire is operated in a second mode if the distance to the object is within a second distance measurement range different from the first distance measurement range, the electronic control device is operable to estimate the distance to the object based on the signal from the photodetector.

[0006] In some cases, the illuminator includes a plurality of vertical cavity surface emitting lasers (VCSELs). A first subset of the VCSELs is operable to emit light pulses having a first width, and a second subset of the VCSELs is operable to emit light pulses having a second width. In some instances, the VCSELs in the first subset are of a different type than the VCSELs in the second subset, and the VCSELs of the first subset and the VCSELs of the second subset are in the same single chip. In some implementations, the electronic control device is operable to alternately activate one of the subsets of the VCSELs at a time.

[0007] Further, in some cases, a third subset of the VCSELs is operable to emit light pulses having a third width different from the first width and the second width, wherein the illuminator is operable in a third mode in which the third subset of the VCSELs emit pulses having the third width, and wherein when the illuminator is operated in the third mode if the distance to the object is within a third distance measurement range different from the first distance measurement range and the second distance measurement range, the electronic control device is operable to estimate the distance to the object based on the signal from the photodetector.

[0008] The details of the pulse width and power depend on the specific implementation. In some cases, the illuminator may be operated in a first mode to emit pulses having a width of less than 100 psec, and may be operated in a second mode to emit pulses having a width greater than 100 psec. In addition, in some instances, the illuminator may be operated in a first mode to emit pulses having a first optical power level, and the illuminator may be operated in a second mode to emit pulses having a second optical power level greater than the first optical power level. For example, in some implementations, the illuminator may be operated in a first mode to emit pulses having a power of less than 100 mW, and the illuminator may be operated in a second mode to emit pulses having a power greater than 100 mW.

[0009] In another aspect, the present disclosure describes a host device that includes a time-of-flight (TOF) sensor system, a display screen, and a processor that adjusts brightness of the display screen in response to a distance estimated by an electronic control device.

[0010] On the other hand, the present disclosure describes a method comprising emitting light pulses to an object, wherein emitting pulses comprises emitting pulses alternately in a first mode and a second mode. In the first mode, the pulse has a first width, and in the second mode, the pulse has a second width longer than the first width. The method comprises detecting light reflected by the object and estimating the distance to the object based on the time elapsed between emitting one or more pulses and detecting the light reflected by the object. In some instances, different subsets of a VCSEL (or other light emitting element) group may be used for each respective mode. In some cases, different types of VCSELs are provided in the same VCSEL chip, and a selected one of the VCSELs is activated according to the operating mode.

[0011] The implementations described herein can provide a variety of benefits. In some implementations, a time-of-flight sensor can obtain more accurate and / or more precise measurements (e.g., compared to measurements taken without the performance of the disclosed techniques). In particular, the disclosure can help expand the effective distance measurement range of a time-of-flight sensor.

[0012] Other aspects, features, and advantages will be apparent from the following detailed description, the accompanying drawings, and the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a schematic diagram of an example time-of-flight sensor system.

[0014] Figure 2 is a diagram illustrating an example use of a time-of-flight sensor system.

[0015] Figure 3A and Figure 3B is an example plot of the number of bins (distance) versus the number of counts.

[0016] FIG. 4A to FIG. 4D Figure shows an example of a VCSEL array for a luminaire.

[0017] Figure 5 is a flow chart of a method of operation of a time-of-flight sensor system.

[0018] Figure 6 is an example of a host device that includes a time-of-flight sensor system. DETAILED DESCRIPTION

[0019] A time-of-flight (TOF) sensor can resolve the distance between the sensor and an object. The distance resolution of a TOF sensor depends at least in part on the sensor's ability to accurately determine the time elapsed between the emission of light and the return of reflected light (e.g., using one or more timing components such as a time-to-digital converter (TDC)).

[0020] exist Figure 1 An example TOF sensor system 100 is shown in FIG. The sensor system 100 includes an illuminator 102 operable to emit light pulses, a photodetector 104 operable to detect light of the same wavelength as the light generated by the illuminator 102, and an electronic control device 106. In an example use of the sensor system 100, the illuminator 102 generates a light pulse (e.g., infrared) that is emitted toward an object (e.g., an object in proximity to the sensor system 100). The photodetector 104 measures the light reflected from the object and returned to the sensor system 100. The electronic control device 106 is operable to determine the distance between the object and the sensor system 100 based on the time that elapses between the light being emitted and the reflected light being sensed. In some cases, the electronic control device 106 is housed in the TOF sensor module itself; in other cases, it can be housed in a host device in which the TOF sensor module is arranged.

[0021] For illustration purposes, Figure 2 An example use of the sensor system 100 is shown. In this example, the sensor system 100 approaches an object 200. The illuminator 102 is operable (e.g., based on instructions from the electronic control device 106) to generate light R, which is directed toward the object 200. At least some of the emitted light is reflected from the object 200 and returns to the photodetector 104 in the form of a reflection signal T. The photodetector 104 measures the reflection signal T and transmits information about the measurement to the electronic control device 106. The electronic control device 106 then determines the distance (d) to the object 200, for example, based on the elapsed round-trip time (t) and the speed of light (c) (e.g., d=(t×c) / 2).

[0022] In some examples, each incoming signal detected by the photodetector 104 can be classified into one of a plurality of bins, where each bin represents, for example, a narrow time range from when the output signal is emitted by the illuminator 102 until the signal is detected by the photodetector 104. The number of counts for each corresponding bin can be integrated over a specified time interval. The electronic control device 106 can use the bin histogram to estimate the distance to the object 200.

[0023] In some applications, the sensor 100 is arranged under the protective glass of the host device (e.g., a smart phone). In this example, the photodetector 104 can sense reflections from both the protective glass and the object 200. In some cases, such as Figure 3A As shown in FIG. 3 , the reflection from the protective glass can be identified as a peak signal 302, which is separated from the peak signal 304 representing the reflection from the object 200. However, if the object is very close to the protective glass, the two peaks 302, 304 may merge, making them not easily distinguishable (see FIG. 3 ). Figure 3B). Since the signal representing the reflection from the protective glass reduces the signal-to-noise ratio, the distance to the object 200 cannot be easily obtained.

[0024] In order to avoid the aforementioned problems, the illuminator 102 is operable in at least two modes: a first mode in which the illuminator 102 emits relatively short pulses at relatively low power; and a second mode in which the illuminator 102 emits relatively long pulses at relatively high power. As an example, in some implementations, the illuminator 102 is operable to emit pulses having a width of the order of 100 picoseconds (psec) or less and a power of 100 milliwatts (mW) or less during the first operating mode. During the second operating mode, the illuminator 102 emits pulses having a width greater than 100 psec and a power greater than 100 mW. The pulse width may refer to, for example, the full width at half maximum (FWHM), i.e., the width of the time interval at which the power is at least half of the peak power. The first operating mode is particularly advantageous for measuring relatively short distances, while the second operating mode is particularly advantageous for measuring relatively long distances.

[0025] In some cases, the illuminator 102 includes a plurality of light emitting elements, such as an array of vertical cavity surface emitting lasers (VCSELs). A first subset of VCSELs is composed of VCSELs operable to emit shorter pulses at lower power, while a second subset of VCSELs is composed of VCSELs operable to emit longer pulses at higher power. In some implementations, the first subset of VCSELs is particularly advantageous for measuring relatively short distances (e.g., a few millimeters (mm)), while the second subset of VCSELs is particularly advantageous for measuring relatively long distances (e.g., up to meters (m)). Subsets of VCSELs may also be optimized for other ranges (e.g., by using VCSELs with appropriate pulse widths and powers).

[0026] The arrangement and number of VCSELs may vary depending on the particular implementation. FIG. 4A to FIG. 4D The figure shows several examples of VCSEL arrangements including VCSELs 402 in a first subset (i.e., operable to emit shorter pulses) and VCSELs 404 in a second subset (i.e., operable to emit longer pulses). One factor that affects the number of VCSELs in each subset is the total optical power required for each operating mode. Generally, the optical power received by the photodetector 104 is inversely proportional to the square of the distance to the object 200. Therefore, more power is generally required to determine the distance as the object 200 is further away rather than closer. Although FIG. 4A to FIG. 4D A 4x4 VCSEL array is shown, but other sized arrays or configurations may be used.

[0027] In some implementations, there is a greater number of VCSELs in the second subset 404 than in the first subset 402. Thus, in the illustrated example, the ratio of the VCSELs in the first subset 402 to the VCSELs in the second subset 404 is 1:3. However, in other implementations, the ratio may be different. For example, in some cases, a ratio of approximately 1:10 is suitable. The VCSELs in the first subset 402 may be of a different type than the VCSELs in the second subset 404. For example, depending on the arrangement of the VCSELs, the emission fields of the first subset of VCSELs and the second subset of VCSELs may be identical to each other. In other instances, the VCSELs of both subsets 402 and 404 may be of the same type, but each VCSEL may be dedicated to operating in a specific mode. Different subsets of VCSELs may be optimized for the number of VCSELs in each subset as well as the routing and location. Their shapes and manufacturing may also be different.

[0028] In some cases, the VCSELs of the first subset and the second subset may be implemented in or on the same single semiconductor chip.Wire bonds or other electrical connections of the shorter pulse VCSELs may be adjusted to reduce capacitance and ensure high speed operation.

[0029] The photodetector 104 may be implemented, for example, as a single photon avalanche diode (SPAD) operable to measure the intensity of light emitted from the light source 102 and reflected from an object back to the photodetector 104. Although other types of photodetectors may be used, a SPAD may be used to detect low intensity signals and to time the arrival of photons with high temporal resolution (e.g., tens of picoseconds).

[0030] The electronic control device 106 is coupled to the illuminator 102 and is operable to control, for example, which VCSELs in the illuminator are turned on or off at a particular time. The electronic control device 106 can also control the operation of the photodetector 104. For example, the electronic control device 106 can be coupled to the photodetector 104 and can selectively turn the photodetector 104 on or off (e.g., to measure light during selected time periods, such as during measurement operations). Further, the electronic control device 106 can obtain information describing characteristics of the measured light (e.g., the time of the measured light and the intensity of the measured light).

[0031] According to some implementations, in operation, the electronic control device 106 controls the luminaire 102 to operate in a first mode to activate (i.e., turn on) the shorter pulse, lower power VCSELs of the first subset 402, while the longer pulse, higher power VCSELs of the second subset 404 are disabled (i.e., turned off) ( Figure 5500). Some of the transmitted pulses may be reflected by the object back to the TOF system and detected by the photodetector. The electronic control device 106 reads or otherwise obtains the output signal from the photodetector and determines whether the signal indicates at least two different peaks (e.g., one peak represents a signal reflected by the protective glass and the other peak represents a signal reflected by an object outside the TOF system but relatively close to the protective glass of the main device) (502). If the electronic control device 106 determines that there are at least two such peaks (503), it can use information associated with one or both peaks to calculate the distance to the object outside the system (504). For example, the electronic control device 106 can extract information associated with a peak representing a signal reflected by an object outside the TOF system and calculate the distance based only on the data of that peak. In other implementations, the electronic control device 106 can calculate the distance based in part on the interval between the two peaks. Assuming that one of the peaks represents a signal reflected by the protective glass at a known fixed distance, that peak can be used as a reference.

[0032] If, at 503, the electronic control device 106 determines that, for example, two or more distinct peaks of the signal detected by the photodetector are not clearly discernible, the electronic control device 106 controls the luminaire 102 to operate in a second mode to disable (i.e., turn off) the shorter pulse, lower power VCSELs of the first subset 402 and activate (i.e., turn on) the longer pulse, higher power VCSELs of the second subset 404 ( Figure 5 506). As previously described, some of the transmitted pulses may be reflected by an object back to the TOF system and detected by the photodetector. The electronic control device 106 reads or otherwise obtains the output signal from the photodetector and determines whether the signal indicates at least two different peaks (e.g., one peak represents a signal reflected by the protective glass and the other peak represents a signal reflected by an object outside the TOF system but at a relative distance from the protective glass of the main device) (508). If the electronic control device 106 determines that there are at least two such peaks (509), it can use information associated with one or both peaks to calculate the distance to an object outside the system (510). For example, the electronic control device 106 may extract information associated with a peak representing a signal reflected by an object outside the TOF system and calculate the distance based only on the data of that peak. In other implementations, the electronic control device 106 may calculate the distance based in part on the interval between the two peaks. As described above, assuming that one of the peaks represents a signal reflected by the protective glass at a known fixed distance, that peak may be used as a reference.

[0033] In some instances, there may be no peak corresponding to reflections from the cover glass. However, switching between the first pulse mode and the second pulse mode is still advantageous because short pulses can provide better accuracy for detecting short distances. Further, in some cases, there may be multiple peaks due to multiple reflections from the scene (e.g., translucent objects).

[0034] In some implementations, the electronic control device 106 controls the illuminator 102 to operate in the second mode and then in the first mode. Further, in some implementations, the electronic control device 106 controls the illuminator 102 to repeatedly alternate between the operation in the first mode and the operation in the second mode. For example, for a three-dimensional pixel matrix, it may be desirable to alternately operate the two modes because some pixels can sense nearby objects while other pixels cannot.

[0035] In some instances, the short pulses emitted during the first operating mode may be much less than 100psec. For example, in some cases, the pulses may have a width of 50psec or less. Smaller pulse widths can help measure smaller distances (e.g., on the order of 1-2cm). On the other hand, in some instances, the longer pulses emitted during the second operating mode may be much greater than 100psec. For example, in some cases, the pulses may have a width of 250psec or greater. Larger pulse widths can help measure larger distances (e.g., on the order of 1 meter or more). In any event, the use of both modes can help expand the overall effective TOF distance measurement range, with each mode using a pulse having a corresponding width that is different from the width of the pulse of the other mode. In some instances, the configuration of the TOF photodetector 104 is adjusted when the pulse length and / or pulse power is modified to optimize detection. In addition, in some cases, the photodetector (e.g., a SPAD or SPAD array with a time-to-digital converter (TDC)) can be operated differently depending on the selected pulse mode.

[0036] In some examples, two or more different pulse lengths with different corresponding pulse power settings can be used to optimize detection of more than two depth ranges. Thus, for example, the illuminator can include a third subset of VCSELs operable to emit light pulses having a third width different from the first width and the second width. The illuminator is operable in a third mode in which the third subset of VCSELs emits pulses having a third width, and wherein when the illuminator is operated in the third mode if the distance to the object is within a third range different from the first range and the second range, the electronic control device is operable to estimate the distance to the object based on the signal from the photodetector.

[0037] In some instances, the sensor systems described in the present disclosure can improve the performance of a host device. For example, using the techniques described herein, a sensor system can obtain more accurate and / or more precise measurements or consume less power (e.g., compared to measurements taken without performing the disclosed techniques). Further, a host device (e.g., a vehicle, robot, mobile device, etc.) can use these measurements to more accurately determine its surroundings and adjust its operations more effectively based on this information.

[0038] As an example, Figure 6 A host device 700 is shown including a time-of-flight sensor system 100 (including an illuminator 102, a photodetector 104, and an electronic control device 106), which is arranged behind a protective glass of the host device. The host device 700 may also include several additional components, including one or more computer processors 710 (e.g., to implement the electronic control device 106 and / or provide other computing functions), a display screen 720, one or more power sources 730 (e.g., batteries, charging circuits), one or more transceivers 740 (e.g., radios, WiFi radios, cellular radios, Bluetooth radios), and one or more camera modules 750. During operation of the host device 700, the host device 700 may use the sensor system 100 to obtain information about its surroundings (e.g., information about the presence of objects close to the host device 700 and the distances of these objects from the host device 700).

[0039] Further, in some implementations, the master device 700 is operable to modify its operation based on information based on the sensor system 100. For example, when the master device 700 is a smart phone, in response to determining the distance between an object (e.g., a user's ear or other portion of the user's head) and the sensor system 100, the master device 700 can adjust the brightness of the display screen 720 to save power when the user is not looking at the screen.

[0040] In other instances, the master device 700 is operable to adjust the focus of one or more camera modules based on the estimated distance (e.g., to obtain a clearer or sharper image of the detected object). As another example, the master device 700 can generate a map or other spatial representation of its environment, including information about the location of the object in the environment. As another example, the master device 700 can generate one or more graphic display elements that change according to the surrounding environment (e.g., an "augmented reality" graphical user interface including a video or image of the surrounding environment and one or more graphic overlays that identify objects in the video or image). Further, the master device 700 can send information about the object to one or more other devices (e.g., one or more other master devices) so that the other devices can also access the information.

[0041] The TOF sensor system described in this article can also be used in other applications, such as other types of portable computing devices (e.g., tablet computers, wearable devices, personal digital assistants (PDAs)) as well as robotic systems, spacecraft navigation, augmented reality and virtual reality (AR / VR), (drone-based) surveillance, vehicle sensing systems including advanced driver assistance systems (ADAS), and autonomous vehicles.

[0042] The various aspects of the subject matter and functional operations described in this specification (e.g., electronic control device 106) can be implemented in digital electronic circuits or computer software, firmware, or hardware, or a combination of one or more thereof, including the structures disclosed in this specification and their equivalent structures. The embodiments of the subject matter described in this specification can be implemented as one or more computer program products, i.e., one or more modules of computer program instructions encoded on a computer-readable medium, for execution or control of its operation by a data processing device. The computer-readable medium can be a machine-readable storage device, a machine-readable storage substrate, a storage device, a material composition that affects a machine-readable propagation signal, or a combination of one or more thereof. The terms "data processing device" and "computer" cover all devices, equipment, and machines for processing data, including, for example, a programmable processor, a computer, or multiple processors or computers. In addition to hardware, the device may include code that creates an execution environment for the computer program in question, such as code that constitutes processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more thereof.

[0043] Aspects of the processes and logic flows described in this specification can be performed by one or more programmable processors executing one or more computer programs to perform functions by operating on input data and generating output. The processes and logic flows can also be performed by special purpose logic circuitry, and the apparatus can also be implemented as special purpose logic circuitry, such as an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit).

[0044] For example, processors suitable for executing computer programs include general and special purpose microprocessors, and any one or more processors of any kind of digital computer. Typically, the processor will receive instructions and data from a read-only memory or a random access memory or both. The basic elements of a computer are a processor for executing instructions and one or more storage devices for storing instructions and data. Typically, the computer also includes or is operatively coupled to one or more large-capacity storage devices for storing data, such as magnetic disks, magneto-optical disks, or optical disks, to receive data from or transmit data to, or both. However, the computer does not need to have such a device. In addition, the computer may be embedded in another device (e.g., a mobile phone). Computer-readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media, and memory devices, including semiconductor memory devices, such as EPROM, EEPROM, and flash memory devices; magnetic disks, such as internal hard disks or removable disks; magneto-optical disks; and CDROM and DVD-ROM disks. The processor and memory may be supplemented by or incorporated into a dedicated logic circuit.

[0045] Although this document contains many specific implementation details, these specific implementation details should not be interpreted as limitations on any invention or the scope that may be claimed, but should be interpreted as descriptions of features specific to specific embodiments of specific inventions. Certain features described herein in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, the various features described in the context of a single embodiment may also be implemented in multiple embodiments or in any suitable sub-combination, respectively. In addition, although features may be described above as being effective in some combinations, and even initially claimed to be so, in some cases, one or more features may be deleted from the claimed combination, and the claimed combination may be directed to a sub-combination or a variation of the sub-combination. Therefore, other implementations are also within the scope of the claims.

Claims

1. An optical distance measuring device, comprising: Time of Flight TOF sensor system, including: an illuminator operable to emit pulses of light toward an object external to the device, wherein the illuminator is operable in a first mode in which the illuminator emits pulses having a first width and in a second mode in which the illuminator emits pulses having a second width that is longer than the first width; and a photodetector operable to detect light generated by the illuminator and reflected by the object back to the device; The apparatus further comprises an electronic control device operable to control the light emitted by the illuminator and operable to estimate the distance to the object based on the time elapsed between emission of one or more of the pulses by the illuminator and detection of reflected light by the photodetector, wherein when the luminaire is operated in the first mode if the distance to the object is within a first distance measurement range, the electronic control device is operable to estimate the distance to the object based on the signal from the photodetector, and wherein when the luminaire is operated in the second mode if the distance to the object is within a second distance measurement range different from the first distance measurement range, the electronic control device is operable to estimate the distance to the object based on the signal from the photodetector, wherein the illuminator comprises a plurality of vertical cavity surface emitting lasers (VCSELs), wherein a first subset of the VCSELs is operable to emit pulses having the first width, and wherein a second subset of the VCSELs is operable to emit pulses having the second width, Wherein a first subset of the VCSELs is dedicated to emitting pulses having a first width in a first mode, and wherein a second subset of the VCSELs is dedicated to emitting pulses having a second width longer than the first width in a second mode.

2. The apparatus of claim 1, wherein the number of VCSELs in the second subset is greater than that in the first subset.

3. The apparatus of claim 1, wherein the VCSELs in the first subset are of a different type than the VCSELs in the second subset, and wherein the VCSELs of the first subset and the VCSELs of the second subset are in a same single chip.

4. An apparatus according to any one of claims 1 to 3, wherein the electronic control device is operable to alternately activate one of the subset of VCSELs at a time.

5. An apparatus according to any one of claims 1 to 3, wherein a third subset of the VCSELs is operable to emit light pulses having a third width different from the first width and the second width, wherein the illuminator is operable in a third mode in which the third subset of VCSELs emit pulses having a third width, and wherein when the illuminator is operated in the third mode if the distance to the object is within a third distance measurement range different from the first distance measurement range and the second distance measurement range, the electronic control device is operable to estimate the distance to the object based on a signal from the photodetector.

6. The device according to any one of claims 1 to 3, wherein the illuminator is operable in a first mode to emit pulses having a width less than 100 psec, and is operable in a second mode to emit pulses having a width greater than 100 psec.

7. A device according to any one of claims 1 to 3, wherein the illuminator is operable in a first mode to emit pulses having a first light power level, and wherein the illuminator is operable in a second mode to emit pulses having a second light power level greater than the first light power level.

8. The apparatus of claim 7, wherein the illuminator is operable in a first mode to emit pulses having a power less than 100 mW, and wherein the illuminator is operable in a second mode to emit pulses having a power greater than 100 mW.

9. An optical distance measurement main device, comprising: Time of Flight TOF sensor system, including: an illuminator operable to emit light pulses toward an object external to the host device, wherein the illuminator is operable in a first mode in which the illuminator emits pulses having a first width and in a second mode in which the illuminator emits pulses having a second width that is longer than the first width; and a photodetector operable to detect light generated by the illuminator and reflected by the object back to the host device; The main device further comprises: an electronic control device operable to control light emitted by said illuminator and operable to estimate a distance to said object based on the time elapsed between emission of one or more said pulses by said illuminator and detection of reflected light by said photodetector; display screen; and a processor to adjust the brightness of the display screen in response to the distance estimated by the electronic control device, wherein when the luminaire is operated in a first mode if the distance to the object is within a first distance measurement range, the electronic control device is operable to estimate the distance to the object based on the signal from the photodetector, and wherein when the luminaire is operated in a second mode if the distance to the object is within a second distance measurement range different from the first distance measurement range, the electronic control device is operable to estimate the distance to the object based on the signal from the photodetector, wherein the illuminator comprises a plurality of vertical cavity surface emitting lasers (VCSELs), wherein a first subset of the VCSELs is operable to emit pulses having the first width, and wherein a second subset of the VCSELs is operable to emit pulses having the second width, Wherein a first subset of the VCSELs is dedicated to emitting pulses having a first width in a first mode, and wherein a second subset of the VCSELs is dedicated to emitting pulses having a second width longer than the first width in a second mode.

10. The host device of claim 9, wherein the VCSELs in the first subset are of a different type than the VCSELs in the second subset, and wherein the VCSELs of the first subset and the VCSELs of the second subset are in the same single chip.

11. A master device according to claim 9 or 10, wherein the electronic control device is operable to alternately activate one of the subset of VCSELs at a time.

12. The master device of claim 9 , wherein a third subset of the VCSELs is operable to emit light pulses having a third width different from the first width and the second width, wherein the illuminator is operable in a third mode in which the third subset of VCSELs emit pulses having a third width, and wherein when the illuminator is operated in the third mode if the distance to the object is within a third distance measurement range different from the first distance measurement range and the second distance measurement range, the electronic control device is operable to estimate the distance to the object based on a signal from the photodetector.

13. An optical distance measurement method, comprising: emitting light pulses toward an object using a plurality of vertical cavity surface emitting lasers (VCSELs), wherein the emitting pulses include: emitting pulses of a first group using light emitting elements in a first mode and emitting pulses of a second group using light emitting elements different from the first group in a second mode, wherein in the first mode the pulses have a first width, and wherein in the second mode the pulses have a second width longer than the first width; detecting light reflected by the object, the detected light comprising reflected emission pulses from the first group of light emitting elements and reflected emission pulses from the second group of light emitting elements; and estimating a distance to the object based on a time elapsed between emitting one or more of the pulses and detecting the light reflected by the object, comprising determining whether at least two peaks are detected from the light reflected by the object and estimating the distance based on at least one of the two detected peaks, wherein a first subset of the VCSELs is operable to emit pulses having the first width, and wherein a second subset of the VCSELs is operable to emit pulses having the second width, Wherein a first subset of the VCSELs is dedicated to emitting pulses having a first width in a first mode, and wherein a second subset of the VCSELs is dedicated to emitting pulses having a second width longer than the first width in a second mode.

14. The method of claim 13, wherein in the first mode, the pulses have a first optical power level, and wherein in the second mode, the pulses have a second optical power level greater than the first optical power level.

15. The method according to claim 14, comprising: if the distance to the object is within a first distance measurement range, estimating the distance to the object based on operation in the first mode, and If the distance to the object is within a second distance measurement range different from the first distance measurement range, the distance to the object is estimated based on operation in the second mode.

16. The method of any one of claims 13 to 15, wherein the first group of light emitting elements is activated in the first mode, and wherein the second group of light emitting elements is activated in a separate second mode.

17. The method of claim 15, wherein transmitting pulses further comprises a third set of transmitting pulses using the light emitting element in a third mode, wherein in the third mode, the pulses have a third width different from the first width and the second width; the method further comprising: If the distance to the object is within a third distance measurement range different from the first distance measurement range and the second distance measurement range, the distance to the object is estimated based on the operation in the third mode.

18. The method of any one of claims 13 to 15, comprising emitting the light pulses from a smartphone, wherein the object is external to the smartphone.

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