GB2586499A - Multi-pixel coherent LIDAR imaging - Google Patents

Multi-pixel coherent LIDAR imaging Download PDF

Info

Publication number
GB2586499A
GB2586499A GB1912050.0A GB201912050A GB2586499A GB 2586499 A GB2586499 A GB 2586499A GB 201912050 A GB201912050 A GB 201912050A GB 2586499 A GB2586499 A GB 2586499A
Authority
GB
United Kingdom
Prior art keywords
channel optical
optical
signal
wavelength
channel
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
GB1912050.0A
Other versions
GB201912050D0 (en
Inventor
Silver Mark
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Thales Holdings UK PLC
Original Assignee
Thales Holdings UK PLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Thales Holdings UK PLC filed Critical Thales Holdings UK PLC
Priority to GB1912050.0A priority Critical patent/GB2586499A/en
Publication of GB201912050D0 publication Critical patent/GB201912050D0/en
Publication of GB2586499A publication Critical patent/GB2586499A/en
Pending legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/88—Lidar systems specially adapted for specific applications
    • G01S17/89—Lidar systems specially adapted for specific applications for mapping or imaging
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
    • G01S17/06—Systems determining position data of a target
    • G01S17/08—Systems determining position data of a target for measuring distance only
    • G01S17/32—Systems determining position data of a target for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
    • G01S17/06—Systems determining position data of a target
    • G01S17/08—Systems determining position data of a target for measuring distance only
    • G01S17/32—Systems determining position data of a target for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
    • G01S17/36—Systems determining position data of a target for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated with phase comparison between the received signal and the contemporaneously transmitted signal
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
    • G01S17/50—Systems of measurement based on relative movement of target
    • G01S17/58—Velocity or trajectory determination systems; Sense-of-movement determination systems
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/88—Lidar systems specially adapted for specific applications
    • G01S17/89—Lidar systems specially adapted for specific applications for mapping or imaging
    • G01S17/894—3D imaging with simultaneous measurement of time-of-flight at a 2D array of receiver pixels, e.g. time-of-flight cameras or flash lidar
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/491—Details of non-pulse systems
    • G01S7/4912—Receivers
    • G01S7/4913—Circuits for detection, sampling, integration or read-out
    • G01S7/4914—Circuits for detection, sampling, integration or read-out of detector arrays, e.g. charge-transfer gates
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/481—Constructional features, e.g. arrangements of optical elements
    • G01S7/4818—Constructional features, e.g. arrangements of optical elements using optical fibres

Abstract

Multi-pixel coherent LIDAR imaging system 10 comprises a lens 24 for transmitting single-channel optical measurement signals 22a to different positions in a scene 72, the signals 22a have wavelengths arranged in corresponding wavelength channels. Optical return signals 74 are reflected from positions in the scene 72. A multiplexer 22 wavelength-multiplexes the return signals 74 into a multi-channel optical return signal 76. The return signal 76 and an optical local oscillator (LO) signal 68 are combined 26 to form signals 80a, 80b. System 10 includes wavelength-demultiplexers 28a, 28b and a photodetector 30. System 10 defines two interferometric optical paths: (i) a measurement arm extending from the measurement signal 66 output of a splitter 16 to the return signal 76 input of the combiner 26 via an object at a corresponding position in the scene 72; and (ii) a reference arm extending from the LO signal 68 output of the splitter 16 to the LO signal 68 input of the combiner 26. Controller 36 utilises a beat frequency of signal 84 alongside frequency modulation information from modulator 14 to determine an optical path length difference between the measurement arm and the reference arm. 

Description

MULTI-PIXEL COHERENT LIDAR IMAGING
FIELD
The present disclosure relates to a system and a method for use in multi-pixel coherent light detection and ranging (LIDAR) imaging and, in particular though not exclusively, for use in multi-pixel coherent frequency-modulated continuous wave (FMCVV) LIDAR imaging.
BACKGROUND
Known coherent LIDAR imaging systems transmit measurement light to an object in a scene and receive return light after the measurement light is reflected from the object in the scene. To produce an image of the scene, such known LIDAR imaging systems generally include some form of beam scanner to move the measurement light across the scene. However, this requires that the LIDAR imaging system looks long enough in time at each pixel in order for the measurement light to travel to the object and for the return light to travel back to the LIDAR imaging system. For a distance between the LIDAR imaging system and the object of hundreds or thousands of metres, this may result in a "stare time" per pixel of the order of microseconds. As a result, the time it takes to acquire information from many pixels (e.g. up to 10,000 pixels or more per image) may be impractical for some imaging applications. Accordingly, known LIDAR imaging systems are generally limited in terms of the pixels per image and/or the image acquisition rate.
SUMMARY
It should be understood that any one or more of the features of any one of the following aspects of the present disclosure may be combined with any one or more of the features of any of the other following aspects of the present disclosure.
According to an aspect of the present disclosure there is provided a system for use in multi-pixel coherent light detection and ranging (LIDAR) imaging, the system comprising: an imaging arrangement configured for.
transmitting a plurality of single-channel optical measurement signals to a corresponding plurality of different positions in a scene, the plurality of single-channel optical measurement signals comprising a corresponding plurality of different wavelengths arranged in a corresponding plurality of different wavelength channels, and receiving a plurality of single-channel optical return signals from the corresponding plurality of different positions in the scene, each single-channel optical return signal comprising a returning portion of the corresponding single-channel optical measurement signal; a wavelength-processing arrangement for wavelength-multiplexing the plurality of single-channel optical return signals to form a multi-channel optical return signal; an optical combiner for optically combining the multi-channel optical return signal with a multi-channel optical local oscillator signal to form a multi-channel optical combined signal, wherein the multi-channel optical local oscillator signal comprises the same plurality of different wavelengths arranged in the same plurality of different wavelength channels as the plurality of single-channel optical measurement signals; a wavelength-demulfiplexing arrangement for wavelength-demultiplexing the multi-channel optical combined signal to form a plurality of single-channel optical combined signals; and a photodetector arrangement comprising a plurality of photodetectors configured so that each photodetector receives a different one of the plurality of single-channel optical combined signals corresponding to a different one of the different wavelength channels and therefore also corresponding to a different one of the positions in the scene.
The system may reduce the amount of scanning of an optical beam required to image a scene for a given pixel count compared to known coherent LIDAR imaging systems which rely solely on scanning of an optical beam. Depending on the pixel count, the system may even avoid any requirement to scan an optical beam to image a scene. The system may allow coherent LIDAR imaging to be performed more rapidly for a given measurement distance and a given pixel count when compared to known coherent LIDAR imaging systems which rely solely on scanning of an optical beam. Additionally or alternatively, the system may allow coherent LIDAR imaging to be performed over a greater measurement distance for a given measurement time and a given pixel count when compared to known coherent LIDAR imaging systems which rely solely on scanning of an optical beam Moreover, such a system enables LIDAR measurements to be performed at a plurality of positions simultaneously in the scene using a single optical combiner to combine the multi-channel optical return signal and the multi-channel optical local oscillator (LO) signal, wherein the number of positions is determined by the number of wavelength channels. Further, such a system enables LIDAR measurements to be performed at a plurality of positions simultaneously in the scene, using a single wavelength-demultiplexing arrangement and a single photodetector array, wherein the number of positions is determined by the number of wavelength channels.
It should be understood that, depending on whether there are any objects present in the scene and/or depending on the nature of any objects present in the scene, it is possible that the intensity of the returning portion of any one or more of the single-channel optical measurement signals may be small or even zero, and therefore, that the intensity of any one or more of the single-channel optical return signals may be small or even zero.
The system may comprise a multi-channel optical signal generation arrangement for generating a multi-channel optical signal comprising the same plurality of different wavelengths arranged in the same corresponding plurality of different wavelength channels as the plurality of single-channel optical measurement signals.
The system may comprise an optical splitter for splitting the multi-channel optical signal to form a multi-channel optical measurement signal and the multi-channel optical local oscillator signal.
The wavelength-processing arrangement may be configured to wavelength- demultiplex the multi-channel optical measurement signal to form the plurality of single-channel optical measurement signals.
The multi-channel optical signal generation arrangement may comprise: a plurality of optical sources emitting a corresponding plurality of single-channel optical signals, each single-channel optical signal comprising a different one of the plurality of different wavelengths arranged in a different one of the plurality of different wavelength channels; and a wavelength-multiplexing arrangement for wavelength-multiplexing the plurality of single-channel optical signals to form the multi-channel optical signal.
Each optical source may be a continuous-wave (CVV) optical source.
Each optical source may be amplitude-modulated and/or pulsed, for example using the same amplitude-modulation signal. Using amplitude-modulated and/or pulsed optical sources may enable the system to measure a distance or a range from the system to one or more objects in the scene.
Each optical source may comprise a coherent optical source, a monochromatic optical source, a narrow linewidth optical source, or a single-wavelength optical source.
One or more of the optical sources may comprise a laser.
One or more of the optical sources may comprise an optical parametric oscillator.
One or more of the optical sources may comprise a laser diode such as a distributed feedback (DFB) laser diode or a distributed Bragg reflector (DBR) laser diode.
One or more of the optical sources may comprise a fibre laser.
One or more of the optical sources may comprise a solid state laser.
Each optical source may be frequency-chirped, for example using the same frequency modulation signal.
The multi-channel optical signal generation arrangement may comprise a multi-wavelength optical source such as a multi-wavelength laser or an optical frequency comb-generator.
The multi-wavelength optical source may be a continuous-wave (OW) multi-wavelength optical source.
The multi-wavelength optical source may be amplitude-modulated and/or pulsed. Using an amplitude-modulated and/or pulsed multi-wavelength optical source may enable the system to measure a distance or a range from the system to one or more objects in the scene.
The multi-wavelength optical source may be frequency-chirped, for example using a frequency modulation signal.
The system may comprise an amplitude modulation arrangement for amplitude-modulating the multi-channel optical signal. Amplitude-modulating the multi-channel optical signal may enable the system to measure a distance or a range from the system to one or more objects in the scene.
The system may be configured for coherent frequency-modulated continuous wave (FMCVV) LIDAR measurements.
The system may comprise a frequency-modulator arrangement.
The frequency-modulator arrangement may comprise one or more frequency-modulators.
The system may comprise a frequency-modulator for frequency modulating the multi-channel optical signal, for example using a frequency modulation signal. Frequency modulating the multi-channel optical signal may enable the system to measure a distance or a range from the system to one or more objects in the scene.
Frequency modulating the multi-channel optical signal may enable the system to determine a velocity of one or more objects in the scene towards or away from the system using a Doppler technique.
The system may comprise a frequency-modulator for frequency modulating the multi-channel optical measurement signal, for example using a frequency modulation signal. Frequency modulating the multi-channel optical measurement signal may enable the system to determine a velocity of one or more objects in the scene towards or away from the system using a Doppler technique.
The system may comprise a frequency-modulator for frequency modulating the multi-channel optical return signal, for example using a frequency modulation signal.
Frequency modulating the multi-channel optical return signal may enable the system to determine a velocity of one or more objects in the scene towards or away from the system using a Doppler technique.
The system may comprise a frequency-modulator for frequency modulating the multi-channel optical local oscillator signal, for example using a frequency modulation signal. Frequency modulating the multi-channel optical local oscillator signal may enable the system to determine a velocity of one or more objects in the scene towards or away from the system using a Doppler technique.
The system may comprise a frequency-modulator for frequency modulating one of: the multi-channel optical measurement signal; the multi-channel optical return signal; or the multi-channel optical local oscillator signal.
The frequency-modulator arrangement may comprise a first frequency-modulator configured to frequency-modulate the multi-channel optical measurement signal using a frequency modulation signal and a second frequency-modulator configured to frequency-modulate the multi-channel optical local oscillator signal using the same frequency modulation signal.
The optical combiner may comprise a fibre-optic beam combiner.
The optical combiner may comprise two outputs.
The optical combiner may be configured to optically combine the multi-channel optical return signal and the multi-channel optical local oscillator signal to form a further multi-channel optical combined signal.
The system may further comprise a further wavelength-demultiplexing arrangement, wherein the further wavelength-demultiplexing arrangement is configured to wavelength-demulfiplex the further multi-channel optical combined signal so as to form a further plurality of single-channel optical combined signals.
The photodetector arrangement may comprise a further plurality of photodetectors configured so that each photodetector of the further plurality of photodetectors receives a different one of the further plurality of single-channel optical combined signals corresponding to a different one of the different wavelength channels and therefore also corresponding to a different position in the scene.
The plurality of photodetectors and the further plurality of photodetectors may be balanced so as to define a plurality of balanced pairs of photodetectors, wherein each photodetector of a balanced pair of photodetectors receives a corresponding single-channel optical combined signal corresponding to the same wavelength channel and therefore also corresponding to the same position in the scene. Using a plurality of balanced pairs of photodetectors may improve measurement sensitivity of the system. The system may comprise an optical circulator configured to transmit the multichannel optical measurement signal to the wavelength-processing arrangement and to transmit the multi-channel optical return signal from the wavelength-processing arrangement to the optical combiner.
The system may comprise a further optical splitter.
The system may comprise a plurality of optical sub-assemblies, wherein each optical sub-assembly comprises: an optical circulator; a wavelength-processing arrangement; an optical combiner; a wavelength-demulfiplexing arrangement; and a photodetector arrangement.
The further optical splitter may be configured to split the multi-channel optical measurement signal into a plurality of multi-channel optical measurement signals, and to transmit each multi-channel optical measurement signal to a different optical subassembly.
For each optical sub-assembly: the optical circulator may be configured to transmit a corresponding multi-channel optical measurement signal to a corresponding wavelength-processing arrangement; the wavelength-processing arrangement may be configured to wavelengthdemultiplex the corresponding multi-channel optical measurement signal to form a corresponding plurality of single-channel optical measurement signals; the wavelength-processing arrangement may be configured to wavelength-multiplex a corresponding plurality of single-channel optical return signals to form a corresponding multi-channel optical return signal; the optical circulator may be configured to transmit the corresponding multi-channel optical return signal to the optical combiner; the optical combiner may be configured to optically combine the corresponding multi-channel optical return signal with the multi-channel optical local oscillator signal to form a corresponding multi-channel optical combined signal, wherein the multi-channel optical local oscillator signal comprises the same plurality of different wavelengths arranged in the same plurality of different wavelength channels as each of the multi-channel optical measurement signals; the wavelength-demultiplexing arrangement may be configured to wavelengthdemultiplex the corresponding multi-channel optical combined signal to form a corresponding plurality of single-channel optical combined signals; and the photodetector arrangement may comprise a corresponding plurality of photodetectors configured so that each photodetector receives a different one of the corresponding plurality of single-channel optical combined signals corresponding to a different one of the different wavelength channels and therefore also corresponding to a different one of the positions in the scene.
Each photodetector may comprise a different photodetector element of a photodetector array or a different light-sensitive element or pixel of an image sensor. The system may comprise a plurality of optical fibres such as a plurality of single-mode optical fibres for optically coupling at least some of the various optical components of the optical system.
The wavelength-processing arrangement may comprise an arrayed waveguide grating (AWG).
The wavelength-demultiplexing arrangement may comprise an AWG.
The wavelength-multiplexing arrangement may comprise an AWG.
The imaging arrangement may be configured for transmitting the plurality of single-channel optical measurement signals along a corresponding plurality of paths and for receiving the plurality of single-channel optical return signals along the same corresponding plurality of paths. Such an imaging arrangement may enable monostafic coherent LIDAR measurements.
The imaging arrangement may comprise a lens.
The imaging arrangement may comprise a telescope arrangement.
The imaging arrangement may comprise a transmitting arrangement for transmitting the plurality of single-channel optical measurement signals along a corresponding plurality of transmission paths, and a separate receiving arrangement for receiving the plurality of single-channel optical return signals along a corresponding plurality of return paths. The wavelength-processing arrangement may comprise a wavelength-demultiplexer for wavelength-demultiplexing the multi-channel optical measurement signal to form the plurality of single-channel optical measurement signals and a separate wavelength-multiplexer for wavelength-multiplexing the plurality of single-channel optical return signals to form the multi-channel optical return signal.
Such an imaging arrangement and a wavelength-processing arrangement may enable bistatic coherent LIDAR measurements.
Each wavelength of the plurality of different wavelengths may lie in a wavelength range from 400 nm to 10 pm, from 1,400 nm to 1,600 nm or from 1,525 nm to 1,575 nm.
A frequency spacing of the wavelength channels may be greater than 10 GHz, greater than 100 GHz and/or greater than 1 THz. A frequency spacing of the wavelength channels may be substantially equal to 250 GHz.
A frequency bandwidth of each photodetector may be less than, for example, one or more orders of magnitude less than, a frequency spacing of the wavelength channels.
A frequency bandwidth of each photodetector may be 200 MHz or less.
According to an aspect of the present disclosure there is provided a method for use in multi-pixel coherent light detection and ranging (LIDAR) imaging, the method comprising: transmitting a plurality of single-channel optical measurement signals to a corresponding plurality of different positions in a scene, the plurality of single-channel optical measurement signals comprising a corresponding plurality of different wavelengths arranged in a corresponding plurality of different wavelength channels; receiving a plurality of single-channel optical return signals from the corresponding plurality of different positions in the scene, each single-channel optical return signal comprising a returning portion of the corresponding single-channel optical measurement signal; wavelength-multiplexing the plurality of single-channel optical return signals to form a multi-channel optical return signal; optically combining the multi-channel optical return signal with a multi-channel optical local oscillator signal to form a multi-channel optical combined signal, wherein the multi-channel optical local oscillator signal comprises the same plurality of different wavelengths arranged in the same plurality of different wavelength channels as the plurality of single-channel optical measurement signals; wavelength-demultiplexing the multi-channel optical combined signal to form a plurality of single-channel optical combined signals; and receiving the plurality of single-channel optical combined signals on a corresponding plurality of photodetectors so that each photodetector receives a different one of the plurality of single-channel optical combined signals corresponding to a different one of the different wavelength channels and therefore also corresponding to a different one of the positions in the scene.
The method may comprise generating a multi-channel optical signal comprising the same plurality of different wavelengths arranged in the same corresponding plurality of different wavelength channels as the plurality of single-channel optical measurement signals.
The multi-channel optical signal may be pulsed and/or amplitude-modulated. The method may comprise splitting the multi-channel optical signal to form a multi-channel optical measurement signal and the multi-channel optical local oscillator signal.
The method may comprise wavelength-demultiplexing the multi-channel optical measurement signal to form the plurality of single-channel optical measurement signals.
The multi-channel optical signal may be frequency-modulated, for example by a frequency modulation signal.
The multi-channel optical measurement signal may be frequency-modulated, for example by a frequency modulation signal.
The multi-channel optical return signal may be frequency-modulated, for example by a frequency modulation signal. The multi-channel optical local oscillator signal may be frequency-modulated, for example by a frequency modulation signal.
One of the multi-channel optical measurement signal, the multi-channel optical return signal or the multi-channel optical local oscillator signal may be frequency-modulated, for example by a frequency modulation signal.
The multi-channel optical measurement signal may be frequency-modulated using a frequency modulation signal and the multi-channel optical local oscillator signal may be frequency-modulated using the same frequency modulation signal.
Generating the multi-channel optical signal may comprise: generating a plurality of single-channel optical signals, each single-channel optical signal comprising a different one of the plurality of different wavelengths arranged in a different one of the plurality of different wavelength channels; and wavelength-multiplexing the plurality of single-channel optical signals to form the multi-channel optical signal.
Generating the plurality of single-channel optical signals may comprise generating each single-channel optical signal using a corresponding optical source such as a monochromatic optical source, a narrow linewidth optical source, or a single-wavelength optical source.
Generating the multi-channel optical signal may comprise generating the multi- channel optical signal using a multi-wavelength optical source such as a multi-wavelength laser or an optical frequency comb-generator.
Optically combining the multi-channel optical return signal with the multichannel optical local oscillator signal to form the multi-channel optical combined signal may comprise optically combining the multi-channel optical return signal with the multi-channel optical local oscillator signal so as to form the multi-channel optical combined signal and a further multi-channel optical combined signal.
The method may further comprise wavelength-demultiplexing the further multichannel optical combined signal so as to form a further plurality of single-channel optical combined signals.
The method may further comprise receiving the further plurality of single-channel optical combined signals on a corresponding further plurality of photodetectors, so that each photodetector of the further plurality of photodetectors receives a different one of the further plurality of single-channel optical combined signals corresponding to a different one of the positions in the scene.
The plurality of photodetectors and the further plurality of photodetectors may be balanced so as to define a plurality of balanced pairs of photodetectors, wherein each photodetector of a balanced pair of photodetectors receives a corresponding single-channel optical combined signal corresponding to the same wavelength channel and therefore to the same position in the scene.
The method may comprise scanning the plurality of single-channel optical measurement signals across the scene so as to illuminate different pluralities of different positions of the scene at different times.
One of ordinary skill in the art will understand that the system or method described above may be applied to different wavelength ranges. For example, each wavelength of the plurality of different wavelengths may lie in a wavelength range from 400 nm to 10 pm, from 1,400 nm to 1,600 nm or from 1,525 nm to 1,575 nm.
A frequency spacing of the wavelength channels may be greater than 10 GHz, greater than 100 GHz and/or greater than 1 THz. A frequency spacing of the wavelength channels may be substantially equal to 250 GHz.
A frequency bandwidth of each photodetector may be less than, for example, one or more orders of magnitude less than, a frequency spacing of the wavelength channels.
A frequency bandwidth of each photodetector may be 200 MHz or less.
BRIEF DESCRIPTION OF THE DRAWINGS
A system and method for use in multi-pixel coherent light detection and ranging (LIDAR) imaging will now be described by way of non-limiting example only with reference to the following drawings of which: FIG. 1 is a schematic of a multi-pixel coherent light detection and ranging (LIDAR) imaging system comprising an optical system; and FIG. 2 is a schematic of an alternative optical system for use in place of the optical system of the multi-pixel coherent light detection and ranging (LIDAR) imaging system of FIG. 1.
DETAILED DESCRIPTION OF THE DRAWINGS
One of ordinary skill in the art will understand that one or more of the features of the embodiments of the present disclosure described below with reference to the drawings may produce effects or provide advantages when used in isolation from one or more of the other features of the embodiments of the present disclosure and that different combinations of the features are possible other than the specific combinations of the features of the embodiments of the present disclosure described below.
Referring initially to FIG. 1, there is shown a system generally designated 10 for use in multi-pixel coherent frequency-modulated continuous wave (FMCVV) light detection and ranging (LIDAR) imaging. The system 10 includes an optical system generally designated 11 which includes multi-channel optical signal generation arrangement generally designated 12, a frequency-modulator arrangement in the form of a frequency-modulator 14, a 99%/1% optical splitter 16, an optical amplifier 18, an optical circulator 20, a wavelength-processing arrangement in the form of an arrayed waveguide grating (AWG) 22, an imaging arrangement in the form of a lens 24, an optical combiner 26, first and second wavelength-demultiplexing arrangements in the form of AWGs 28a and 28b, and a photodetector arrangement in the form of a balanced photodetector array 30.
The multi-channel optical signal generation arrangement 12 includes a plurality of optical sources in the form of four distributed feedback (DFB) laser diodes 40, each DFB laser diode 40 being configured to emit continuous wave (CW) light at a different wavelength in the range 1,400 -1,600 nm to each of the other DFB laser diodes 40, with each wavelength arranged in a different wavelength channel. The multi-channel optical signal generation arrangement 12 further includes a wavelength-multiplexing arrangement in the form of an AWG 42 for wavelength-multiplexing light emitted from the DFB laser diodes 40.
As shown in FIG. 1, AWG 22 defines a plurality of single-channel outputs in the form of four single-channel optical fibre outputs 22a. Each single-channel optical fibre output 22a is located at a different known position in the back focal plane of the lens 24.
The optical system 11 further includes a plurality of single-mode optical fibres 50 for optically coupling the optical components/arrangements of optical components 40, 42, 14, 16, 18, 20, 22, 26, 28a, 28b and 30 as shown in FIG. 1. Specifically, each DFB laser diode 40 is optically coupled to a corresponding input of the AWG 42 by a corresponding single-mode optical fibre 50. An output of the AWG 42 is optically coupled to an input of the frequency modulator 14 by a single-mode optical fibre 50.
An output of the frequency modulator 14 is optically coupled to an input of the optical splitter 16 by a single-mode optical fibre 50. A measurement signal output of the optical splitter 16 is optically coupled to an input of the optical amplifier 18 by a single-mode optical fibre 50. An output of the optical amplifier 18 is optically coupled to a first port of the optical circulator 20 by a single-mode optical fibre 50. A second port of the optical circulator 20 is optically coupled to an input of the AWG 22 by a single-mode optical fibre 50. A third port of the optical circulator 20 is optically coupled to a return signal input of the optical combiner 26 by a single-mode optical fibre 50. A local oscillator (LO) signal output of the optical splitter 16 is optically coupled to a LO signal input of the optical combiner 26 by a single-mode optical fibre 50. A first output of the optical combiner 26 is optically coupled to an input of the AWG 28a by a single-mode optical fibre 50 and a second output of the optical combiner 26 is optically coupled to an input of the AWG 28b by a further single-mode optical fibre 50. Each output of the AWG 28a is optically coupled to the balanced photodetector array 30 by a corresponding single-mode optical fibre 50. Similarly, each output of the AWG 28b is optically coupled to the balanced photodetector array 30 by a corresponding single-mode optical fibre 50.
The system 10 includes a plurality of electrical amplifiers 32 and a plurality of analogue-to-digital converters (ADCs)/fast Fourier transform (FFT) processors 34. As will be described in more detail below, each electrical amplifier 32 and each ADC/FFT processor 34 is configured to amplify and process an electrical signal generated by a corresponding pair of balanced photodetector elements of the balanced photodetector array 30. The system 10 further includes a controller 36 and an electrical signal generator 37 for generating a frequency modulation signal. The plurality of electrical amplifiers 32, the plurality of ADCs/FFT processors 34, the controller 36, the electrical signal generator 37, and the frequency-modulator 14 are connected via electrical conductors 38 as shown in FIG. 1.
In use, the plurality of DFB laser diodes 40 emits four single-channel optical signals 60, each single-channel optical signal 60 comprising a different wavelength in the range 1,400-1,600 nm, each different wavelength arranged in a different one of a plurality of different wavelength channels. The AWG 42 wavelength-multiplexes the single-channel optical signals 60 to form a multi-channel optical signal 62. The electrical signal generator 37 generates a saw-tooth frequency modulation signal. The frequency-modulator 14 modulates the optical frequency of the multi-channel optical signal 62 using the saw-tooth frequency modulation signal so as to generate a frequency-modulated multi-channel optical signal 64.
The optical splitter 16 splits the frequency-modulated multi-channel optical signal 64 into a multi-channel optical measurement signal 66 and a multi-channel optical local oscillator (LO) signal 68. Specifically, the optical splitter 16 directs 99% of the power of the frequency-modulated multi-channel optical signal 64 to form the multi- channel optical measurement signal 66 and 1% of the power of the frequency-modulated multi-channel optical signal 64 to form the multi-channel optical local oscillator (LO) signal 68.
The multi-channel optical measurement signal 66 is amplified by the optical amplifier 18 and then directed towards an input of the AWG 22 via the optical circulator 20. The AWG 22 wavelength demultiplexes the multi-channel optical measurement signal 66 into four single-channel optical measurement signals 70 at the single-channel optical fibre outputs 22a of the AWG 22. The lens 24 transmits the four single-channel optical measurement signals 70 along four different optical paths to four different positions in a scene 72 and receives a four single-channel optical return signals 74 from the four different positions in the scene 72 along the same four different optical paths, each single-channel optical return signal comprising a returning portion of the corresponding single-channel optical measurement signal 70. The AWG 22 wavelength-multiplexes the four single-channel optical return signals 74 to form a multichannel optical return signal 76.
The optical circulator 20 directs the multi-channel optical return signal 76 to the return signal input of the optical combiner 26. The LO signal input of the optical combiner 26 receives the multi-channel optical LO signal 68. The optical combiner 26 combines the multi-channel optical return signal 76 with the multi-channel optical LO signal 68 to form a first multi-channel optical combined signal 80a at the first output of the optical combiner 26 and a second multi-channel optical combined signal 80b at the second output of the optical combiner 26. One of ordinary skill in the art will understand that each of the first and second multi-channel optical combined signals 80a, 80b include all of the wavelengths of the multi-channel optical return signal 76 across all of the wavelength channels and all of the wavelengths of the multi-channel optical LO signal 68 across all of the wavelength channels.
The AWG 28a wavelength-demulfiplexes the first multi-channel optical combined signal 80a to form a first plurality of single-channel optical combined signals 82a. The AWG 28b wavelength-demultiplexes the second multi-channel optical combined signal 80b to form a second plurality of single-channel optical combined signals 82b.
The balanced photodetector array 30 includes an array of balanced pairs of photodetectors, wherein a first photodetector of a balanced pair of photodetectors receives one of the first plurality of single-channel optical combined signals 82a and a second photodetector of the same balanced pair of photodetectors receives a corresponding one of the second plurality of single-channel optical combined signals 82b corresponding to the same wavelength channel and therefore to the same position in the scene. Each balanced pair of photodetectors of the balanced photodetector array 30 receives a different pair of the first and second pluralities of the single-channel optical combined signals 82a, 82b corresponding to a different one of the different wavelength channels and therefore also corresponding to a different one of the positions in the scene.
From the foregoing description, one of ordinary skill in the art will understand that the optical system 11 defines two optical paths: (i) a measurement arm extending from the measurement signal output of the optical splitter 16 to the return signal input of the optical combiner 26 via an object at a corresponding position in the scene 72; and (h) a reference arm extending from the LO signal output of the optical splitter 16 to the LO signal input of the optical combiner 26. 99% of the light in any given wavelength channel of the frequency-modulated multi-channel optical signal 64 at the input of the optical splitter 16 is directed along the measurement arm to form return light at the optical combiner 26, whereas 1% of the light in the given wavelength channel of the frequency-modulated multi-channel optical signal 64 at the input of the optical splitter 16 is directed along the reference arm to form LO light at the optical combiner 26. Furthermore, as a consequence of the frequency modulation or as a consequence of the Doppler effect from a moving target, the difference in the optical path lengths between the measurement and reference arms results in the return light and the LO light arriving at the optical combiner 26 with different optical frequencies. In addition, one of ordinary skill in the art will understand that the difference in the optical path lengths and the frequency modulation signal are chosen for a desired range for the system 10 so that the difference in the frequencies of the return light and the LO light at the optical combiner 26 is sufficiently small that the return light and the LO light at the optical combiner 26 remain in the same wavelength channel as the light at the input of the optical splitter 16 from which the return light and the LO light at the optical combiner 26 originate.
Moreover, the bandwidth of the each of the photodetectors of the balanced photodetector array 30 is less than, for example, one or more orders of magnitude less than, a frequency spacing of the wavelength channels. For example, the bandwidth of each of the photodetectors may be limited to the order of 200 MHz and the frequency spacing of the wavelength channels may be 250 GHz for a wavelength channel spacing of 2nm at 1550nm. Consequently, one of ordinary skill in the art will understand that, when any one of the single-channel optical combined signals 82a or 82b is incident on a corresponding one of the photodetectors, the photodetector concerned is only capable of detecting the beat-frequency between the optical frequency of the return light and the optical frequency of the LO light in the wavelength channel of the single-channel optical combined signal 82a or 82b and that the photodetector is not capable of detecting the sum of the optical frequency of the return light and the optical frequency of the LO light in the wavelength channel of the single-channel optical combined signal 82a or 82b. Consequently, each of the different electrical beat-frequency signals 84 generated by the different balanced pairs of photodetectors of the balanced photodetector array 30 corresponds to a different wavelength channel and therefore also corresponds to a different position in the scene.
Each electrical beat-frequency signal 84 is amplified by a corresponding electrical amplifier 32, and converted into a digital signal and then subjected to FFT processing by a corresponding ADC/FFT processor 34 to determine a magnitude and a frequency of the electrical beat-frequency signal 84.
One of ordinary skill in the art will understand that for each electrical beat-frequency signal 84, the controller 36 uses the determined frequency of the electrical beat-frequency signal 84 and information relating to the frequency modulation signal applied by the frequency modulator 14, to determine the optical path length difference between the measurement arm and the reference arm in the relevant wavelength channel. The controller 36 uses the determined optical path length difference for each wavelength channel and knowledge of the arrangement of the AWG 22 and the lens 24 to determine distances to one or more objects located at the different positions in the scene 72 corresponding to the different wavelength channels. The controller 36 also uses the determined magnitude of each electrical beat-frequency signal 84 to determine the amount of scattering from one or more objects located at the different positions in the scene 72 corresponding to the different wavelength channels. One of ordinary skill in the art will also understand that the controller 36 may determine a velocity of one or more objects located at the different positions in the scene 72 based on the Doppler effect.
From the foregoing description, one of ordinary skill in the art will appreciate that the system 10 enables monostatic coherent FMCW LIDAR measurements to be performed simultaneously at four different positions in a scene. Although FIG. 1 only uses four wavelength channels, one of ordinary skill in the art will understand that the number of DFB laser diodes 40 and the number of AWG channels, may be greater than or fewer than four, with each DFB laser diode 40 being configured to emit continuous wave (CW) light at a different wavelength in the range 1,400 -1,600 nm. For example, the number of DFB laser diodes 40 and the number of AWG channels may be 25, with each DFB laser diode 40 being configured to emit OW light at a different wavelength in the range 1,400 -1,600 nm and the wavelength channels having a wavelength channel spacing of 2nm. Such a system would enable monostatic coherent FMCW LIDAR measurements to be performed simultaneously at 25 different positions in a scene.
One of ordinary skill in the art will understand that the coherent FMCW LIDAR imaging system 10 may reduce the amount of scanning of an optical beam required to image a scene for a given pixel count compared to a known coherent LIDAR imaging system which relies solely on scanning of an optical beam. Depending on the pixel count, the coherent FMCW LIDAR imaging system 10 may even avoid any requirement to scan an optical beam to image a scene. In effect, this may allow coherent LIDAR imaging to be performed more rapidly for a given measurement distance and a given pixel count. Additionally or alternatively, this may allow coherent LIDAR imaging to be performed over a greater measurement distance for a given measurement time and a given pixel count.
Moreover, the coherent FMCW LIDAR imaging system 10 uses only a single optical combiner 26 to combine the multi-channel optical return signal 76 and the multi-channel optical LO signal 68 when performing LIDAR measurements at a plurality of positions simultaneously in the scene 72, wherein the number of positions is determined by the number of wavelength channels. Further, the coherent FMCW LIDAR imaging system 10 uses only two AWG's 82a, 82b and one balanced photodetector array 30 when performing LIDAR measurements at a plurality of positions simultaneously in the scene 72, wherein the number of positions is determined by the number of wavelength channels.
The use of single-mode optical fibres 50 is not only advantageous for the convenience of optically coupling the optical components/arrangements of optical components 40, 42, 14, 16, 18, 20, 22, 26, 28a, 28b and 30 as shown in FIG. 1, but may also be advantageous because at least some of optical components may be fibre-optic components or may comprise optical fibres. For example, the optical splitter 16 may be a 1x2 optical fibre coupler, the optical amplifier may be an optical fibre amplifier, and/or the optical combiner 26 may be a 2x2 optical fibre coupler. The use of more such fibre-optic components may be advantageous because this may enable the use of higher optical powers for LIDAR imaging over longer distances than would be possible if fewer of the optical components were fibre-optic components.
Referring now to FIG. 2, there is provided an alternative optical system generally designated 111 for use in place of the optical system 11 of FIG. 1. The alternative optical system 111 of FIG. 2 and the optical system 11 of FIG. 1 have many like features with the features of the alternative optical system 111 of FIG. 2 being identified with the same reference numeral as the corresponding feature of the optical system 11 of FIG. 1 incremented by "100". Specifically, the alternative optical system 111 includes a multi-channel optical signal generation arrangement generally designated 112, a frequency-modulator 114, a 99%/1% optical splitter 116, and an optical amplifier 118.
The alternative optical system 111 of FIG. 2 further includes a 1x3 optical splitter 119, and three optical sub-systems 121, 121' and 121". Each optical subsystem 121, 121' and 121" includes an optical circulator 120, a wavelength-processing arrangement in the form of an arrayed waveguide grating (AWG) 122, an optical combiner 126, a first wavelength-demultiplexing arrangement in the form of a first AWG 128a, a second wavelength-demulfiplexing arrangement in the form of a second AWG 128b, and a photodetector arrangement in the form of a balanced photodetector array 130. Each one of the optical sub-systems 121, 121' and 121" operates independently of the other optical sub-systems 121, 121' and 121". One of ordinary skill in the art will understand that each optical sub-system 121, 121' and 121" of the alternative optical system 111 of FIG. 2 is essentially identical to an optical sub-system 21 of the optical system 11 of FIG. 1, which optical sub-system 21 includes the optical circulator 20, the AWG 22, the optical combiner 26, the AWG's 28a, 28b, and the balanced photodetector array 30.
The alternative optical system 111 of FIG. 2 further includes an imaging arrangement in the form of a lens 124. As shown in FIG. 2, the AWGs 122 together define a plurality of single-channel outputs in the form of a plurality of single-channel optical fibre outputs 122a. Each single-channel optical fibre output 122a is located at a different known position in the back focal plane of the lens 124.
The multi-channel optical signal generation arrangement 112 includes a plurality of optical sources in the form of four distributed feedback (DFB) laser diodes 140, each DFB laser diode 140 being configured to emit continuous wave (OW) light at a different wavelength in the range 1,400 -1,600 nm to each of the other DFB laser diodes 140, with each wavelength arranged in a different wavelength channel. The multi-channel optical signal generation arrangement 112 further includes a wavelength-multiplexing arrangement in the form of an AWG 142 for wavelength-multiplexing light emitted from the DFB laser diodes 140.
The alternative optical system 111 of FIG. 2 includes a further 1x3 optical splitter 125 so as to provide each optical combiner 126 with a corresponding multi-channel optical local oscillator signal.
The alternative optical system 111 also includes a plurality of single-mode optical fibres 150 for optically coupling the optical components/arrangements of optical components 140, 142, 114, 116, 118, 119, 120, 122, 125, 126, 128a, 128b and 130 as shown in FIG. 2.
In use, each one of the optical sub-systems 121, 121' and 121" of the alternative optical system 111 of FIG. 2 operates in essentially the same way as the optical sub-system 21 of FIG. 1. One of ordinary skill in the art will understand that, although the alternative optical system 111 of FIG. 2 utilises only four different DFB laser diodes 140 to generate four different wavelengths, the use of three independent optical sub-systems 121, 121' and 121" enables the alternative optical system 111 of FIG. 2 to perform monostatic coherent FMCW LIDAR measurements simultaneously at 12 different positions in a scene 172.
Although FIG. 2 only uses four wavelength channels, one of ordinary skill in the art will understand that the number of DFB laser diodes 140 and the number of AWG channels may be greater than or fewer than four, with each DFB laser diode 140 being configured to emit continuous wave (CW) light at a different wavelength in the range 1,400-1,600 nm. For example, the number of DFB laser diodes 140 and the number of AWG channels may be 25, with each DFB laser diode 140 being configured to emit CW light at a different wavelength in the range 1,400 -1,600 nm and the wavelength channels having a wavelength channel spacing of 2nm. The use of the three separate optical sub-systems 121, 121' and 121" would then enable monostatic coherent FMCW LIDAR measurements to be performed simultaneously at 75 different positions in the scene 172.
Additionally or alternatively, although FIG. 2 only shows three independent optical sub-systems 121, 121' and 121", the number of independent optical subsystems may be greater than or fewer than three so as to enable monostatic coherent FMCW LIDAR measurements to be performed simultaneously at more or fewer positions in the scene 172 as appropriate.
One of ordinary skill in the art will understand that various modifications are possible to the system and methods described above. For example, although the use of a sawtooth frequency modulation signal was described above in the context of the systems of FIGS. 1 and 2, other types of frequency modulation signals may be used.
For example, a sinusoidal frequency modulation signal may be used.
Furthermore, although the frequency-modulators 14, 114 are located in the optical path before the optical splitters 16, 116 in FIGS. 1 and 2 respectively, a frequency-modulator may be located at a different position in the system 10, 110 and the controller 36 may be programmed accordingly so as to determine a distance between the system 10, 110 and one or more objects in the scene 72, 172 and/or a velocity of one or more objects in the scene 72, 172. For example, a frequency-modulator may be located between the optical splitter 16, 116 and the corresponding optical amplifier 18, 118. A frequency-modulator may be located between the optical circulator 20, 120 and the corresponding optical combiner 26, 126. A frequency-modulator may be located between the optical splitter 16, 116 and the corresponding optical combiner 26, 126.
In a further alternative variant, a frequency-modulator arrangement may be used comprising first and second frequency modulators, wherein the first frequency modulator is located between the optical splitter 16, 116 and the corresponding optical amplifier 18, 118 and the second frequency modulator is located between the optical splitter 16, 116 and the corresponding optical combiner 26, 126, and wherein each of the first and second frequency modulators is driven by a common frequency modulation signal.
In yet another variant, rather than using a frequency-modulator arrangement comprising one or more frequency modulators, each optical source may be frequency-chirped, for example using the same frequency modulation signal.
In other variants, the multi-channel optical signal generation arrangement may comprise a multi-wavelength optical source such as a multi-wavelength laser or an optical frequency comb-generator. Rather than using a frequency-modulator arrangement, the multi-wavelength optical source may be frequency-chirped using a frequency modulation signal.
The multi-channel optical signal generation arrangement 12, 112 may be pulsed and/or amplitude-modulated. For example, each DFB laser diode 40, 140 may be pulsed and/or amplitude-modulated, for example using the same amplitude-modulation signal. Additionally or alternatively, the system 10, 110 may include an amplitude modulator for modulating an amplitude of the multi-channel optical signal 62. Using a pulsed and/or amplitude-modulated multi-channel optical signal generation arrangement 12, 112 for modulating the amplitude of the multi-channel optical signal 62 may enable the system to measure a distance or a range from the system to one or more objects in the scene when the frequency-modulator arrangement is configured to frequency modulate one of: the multi-channel optical measurement signal; the multichannel optical return signal; or the multi-channel optical local oscillator signal. Although the systems 10, 110 of FIGS. 1 and 2 include balanced photodetector arrays 30, 130, each balanced photodetector array 30, 130 having a plurality of balanced pairs of photodetectors with each balanced pair of photodetectors corresponding to a different wavelength channel, the system may use a non-balanced photodetector array having a plurality of photodetectors with only one photodetector corresponding to a different wavelength channel. When using such a non-balanced photodetector array, the system may use a 2x1 optical combiner instead of the 2x2 optical combiner 26, 126, and only a single demultiplexing AWG instead of first and second demultiplexing AWGs 28a, 28b and 128a, 128b. Using such a non-balanced photodetector array may, however, decrease measurement sensitivity compared with the use of a balanced photodetector array.
Although the systems 10, 110 of FIGS. 1 and 2 may be used to perform monostatic coherent FMCW LIDAR measurements simultaneously at a plurality of positions in a scene without using a beam-scanning arrangement of any kind, one of ordinary skill in the art will also understand that the systems 10, 110 of FIGS. 1 and 2 may also be used in combination with a beam-scanning arrangement for scanning the plurality of single-channel optical measurement signals across the scene so as to illuminate different pluralities of different positions of the scene at different times.
Although the systems 10, 110 of FIGS. 1 and 2 are monostafic systems, one of ordinary skill in the art will understand that it may be possible to adapt the systems 10, 110 for bistatic operation. For example, the imaging arrangement may comprise a transmitting arrangement such as a first lens for transmitting the plurality of single-channel optical measurement signals along a corresponding plurality of transmission paths, and a separate receiving arrangement such as a separate second lens for receiving the plurality of single-channel optical return signals along a corresponding plurality of return paths. At the same time, the wavelength-processing arrangement may comprise a first wavelength-demultiplexer for wavelength-demultiplexing the multi-channel optical measurement signal to form the plurality of single-channel optical measurement signals and a separate second wavelength-multiplexer for wavelength-multiplexing the plurality of single-channel optical return signals to form the multichannel optical return signal.
The multi-channel optical signal generation arrangement 12 may include a plurality of optical sources other than DFB laser diodes. For example, each optical source may comprise a coherent optical source, a monochromatic optical source, a narrow linewidth optical source, or a single-wavelength optical source or any kind. Each optical source may comprise a laser of any kind. Each optical source may comprise a laser diode of any kind. For example, each optical source may comprise a distributed Bragg reflector (DBR) laser diode. Each optical source may comprise a fibre laser. Each optical source may comprise an optical parametric oscillator (0P0). Each optical source may be configured to emit light at a different wavelength in a wavelength range from 400 nm to 10 4m, from 1,400 nm to 1,600 nm or from 1,525 nm to 1,575 nm.

Claims (25)

  1. CLAIMS1. A system for use in multi-pixel coherent light detection and ranging (LIDAR) imaging, the system comprising: an imaging arrangement configured for: transmitting a plurality of single-channel optical measurement signals to a corresponding plurality of different positions in a scene, the plurality of single-channel optical measurement signals comprising a corresponding plurality of different wavelengths arranged in a corresponding plurality of different wavelength channels, and receiving a plurality of single-channel optical return signals from the corresponding plurality of different positions in the scene, each single-channel optical return signal comprising a returning portion of the corresponding single-channel optical measurement signal; a wavelength-processing arrangement for wavelength-multiplexing the plurality of single-channel optical return signals to form a multi-channel optical return signal; an optical combiner for optically combining the multi-channel optical return signal with a multi-channel optical local oscillator signal to form a multi-channel optical combined signal, wherein the multi-channel optical local oscillator signal comprises the same plurality of different wavelengths arranged in the same plurality of different wavelength channels as the plurality of single-channel optical measurement signals; a wavelength-demultiplexing arrangement for wavelength-demultiplexing the multi-channel optical combined signal to form a plurality of single-channel optical combined signals; and a photodetector arrangement comprising a plurality of photodetectors configured so that each photodetector receives a different one of the plurality of single-channel optical combined signals corresponding to a different one of the different wavelength channels and therefore also corresponding to a different one of the positions in the scene.
  2. 2. A system as claimed in claim 1, comprising: a multi-channel optical signal generation arrangement for generating a multichannel optical signal comprising the same plurality of different wavelengths arranged in the same corresponding plurality of different wavelength channels as the plurality of single-channel optical measurement signals; and an optical splitter for splitting the multi-channel optical signal to form a multichannel optical measurement signal and the multi-channel optical local oscillator signal, wherein the wavelength-processing arrangement is configured to wavelength- demultiplex the multi-channel optical measurement signal to form the plurality of single-channel optical measurement signals.
  3. 3. A system as claimed in claim 2, wherein the multi-channel optical signal generation arrangement comprises: a plurality of optical sources emitting a corresponding plurality of single-channel optical signals, each single-channel optical signal comprising a different one of the plurality of different wavelengths arranged in a different one of the plurality of different wavelength channels; and a wavelength-multiplexing arrangement for wavelength-multiplexing the plurality of single-channel optical signals to form the multi-channel optical signal.
  4. 4. A system as claimed in claim 3, wherein each optical source comprises a coherent optical source, a monochromatic optical source, a narrow linewidth optical source, or a single-wavelength optical source.
  5. 5. A system as claimed in claim 3 or 4, wherein one or more of the optical sources comprises a laser or an optical parametric oscillator.
  6. 6. A system as claimed in any one of claims 3 to 5, wherein one or more of the optical sources comprises a laser diode such as a distributed feedback (DEB) laser diode or a distributed Bragg reflector (DBR) laser diode, or wherein one or more of the optical sources comprises a fibre laser.
  7. 7. A system as claimed in claim 2, wherein the multi-channel optical signal generation arrangement comprises a multi-wavelength optical source such as a multi-wavelength laser or an optical frequency comb-generator.
  8. 8. A system as claimed in any one of claims 2 to 7, wherein the multi-channel optical signal is frequency-chirped or comprising a frequency-modulator configured to frequency modulate the multi-channel optical signal.
  9. 9. A system as claimed in any one of claims 2 to 7, comprising a frequency-modulator configured to frequency modulate one of: the multi-channel optical measurement signal; the multi-channel optical return signal; or the multi-channel optical local oscillator signal.
  10. 10. A system as claimed in any one of claims 2 to 9, wherein the multi-channel optical signal generation arrangement is pulsed and/or amplitude-modulated, and/or wherein the system comprises an amplitude-modulator for modulating an amplitude of the multi-channel optical signal.
  11. 11. A system as claimed in any preceding claim, wherein the optical combiner comprises a fibre-optic beam combiner.
  12. 12. A system as claimed in any preceding claim, wherein the optical combiner comprises two outputs.
  13. 13. A system as claimed in claim 12, wherein the optical combiner is configured to optically combine the multi-channel optical return signal and the multi-channel optical local oscillator signal to form the multi-channel optical combined signal and a further multi-channel optical combined signal, wherein the system further comprises a further wavelength-demulfiplexing arrangement, wherein the further wavelength-demultiplexing arrangement is configured to wavelength-demultiplex the further multi-channel optical combined signal so as to form a further plurality of single-channel optical combined signals, wherein the photodetector arrangement comprises a further plurality of photodetectors configured so that each photodetector of the further plurality of photodetectors receives a different one of the further plurality of single-channel optical combined signals corresponding to a different one of the different wavelength channels and therefore also corresponding to a different position in the scene, and wherein the plurality of photodetectors and the further plurality of photodetectors are balanced so as to define a plurality of balanced pairs of photodetectors, wherein each photodetector of a balanced pair of photodetectors receives a corresponding single-channel optical combined signal corresponding to the same wavelength channel and therefore also corresponding to the same position in the scene.
  14. 14. A system as claimed in any one of claims 2 to 13 when dependent on claim 2, comprising an optical circulator configured to transmit the multi-channel optical measurement signal to the wavelength-processing arrangement and to transmit the multi-channel optical return signal from the wavelength-processing arrangement to the optical combiner.
  15. 15. A system as claimed in any one of claims 2 to 14 when dependent on claim 2, comprising: a further optical splitter; and a plurality of optical sub-assemblies, wherein each optical sub-assembly comprises: an optical circulator; a wavelength-processing arrangement; an optical combiner; a wavelength-demultiplexing arrangement; and a photodetector arrangement, wherein the further optical splitter is configured to split the multi-channel optical measurement signal into a plurality of multi-channel optical measurement signals, and to transmit each multi-channel optical measurement signal to a different optical subassembly, and wherein, for each optical sub-assembly: the optical circulator is configured to transmit a corresponding multi-channel optical measurement signal to a corresponding wavelength-processing arrangement; the wavelength-processing arrangement is configured to wavelengthdemultiplex the corresponding multi-channel optical measurement signal to form a corresponding plurality of single-channel optical measurement signals; the wavelength-processing arrangement is configured to wavelength-multiplex a corresponding plurality of single-channel optical return signals to form a corresponding multi-channel optical return signal; the optical circulator is configured to transmit the corresponding multi-channel optical return signal to the optical combiner; the optical combiner is configured to optically combine the corresponding multi-channel optical return signal with the multi-channel optical local oscillator signal to form a corresponding multi-channel optical combined signal, wherein the multi-channel optical local oscillator signal comprises the same plurality of different wavelengths arranged in the same plurality of different wavelength channels as each of the multi-channel optical measurement signals; the wavelength-demultiplexing arrangement is configured to wavelength-demultiplex the corresponding multi-channel optical combined signal to form a corresponding plurality of single-channel optical combined signals; and the photodetector arrangement comprises a corresponding plurality of photodetectors configured so that each photodetector receives a different one of the corresponding plurality of single-channel optical combined signals corresponding to a different one of the different wavelength channels and therefore also corresponding to a different one of the positions in the scene.
  16. 16. A system as claimed in any preceding claim, wherein each photodetector comprises a different photodetector element of a photodetector array or a different light-sensitive element or pixel of an image sensor.
  17. 17. A system as claimed in any preceding claim, comprising a plurality of optical fibres such as a plurality of single-mode optical fibres for optically coupling at least some of the various optical components of the optical system.
  18. 18. A system as claimed in any preceding claim, wherein the wavelength-processing arrangement comprises an arrayed waveguide grating (AWG) and/or the wavelength-demultiplexing arrangement comprises an arrayed waveguide grating (AWG)
  19. 19. A system as claimed in any preceding claim when dependent on claim 3, wherein the wavelength-multiplexing arrangement comprises an arrayed waveguide grating (AWG).
  20. 20. A system as claimed in any preceding claim, wherein the imaging arrangement is configured for transmitting the plurality of single-channel optical measurement signals along a corresponding plurality of paths and for receiving the plurality of single-channel optical return signals along the same corresponding plurality of paths.
  21. 21. A system as claimed in any one of claims 1 to 19, wherein the imaging arrangement comprises: a transmitting arrangement for transmitting the plurality of single-channel optical measurement signals along a corresponding plurality of transmission paths; and a separate receiving arrangement for receiving the plurality of single-channel optical return signals along a corresponding plurality of return paths, wherein the wavelength-processing arrangement comprises a wavelengthdemultiplexer for wavelength-demultiplexing the multi-channel optical measurement signal to form the plurality of single-channel optical measurement signals and a separate wavelength-multiplexer for wavelength-multiplexing the plurality of single-channel optical return signals to form the multi-channel optical return signal.
  22. 22. A method for use in multi-pixel coherent light detection and ranging (LIDAR) imaging, the method comprising: transmitting a plurality of single-channel optical measurement signals to a corresponding plurality of different positions in a scene, the plurality of single-channel optical measurement signals comprising a corresponding plurality of different wavelengths arranged in a corresponding plurality of different wavelength channels; receiving a plurality of single-channel optical return signals from the corresponding plurality of different positions in the scene, each single-channel optical return signal comprising a returning portion of the corresponding single-channel optical measurement signal; wavelength-multiplexing the plurality of single-channel optical return signals to form a multi-channel optical return signal; optically combining the multi-channel optical return signal with a multi-channel optical local oscillator signal to form a multi-channel optical combined signal, wherein the multi-channel optical local oscillator signal comprises the same plurality of different wavelengths arranged in the same plurality of different wavelength channels as the plurality of single-channel optical measurement signals; wavelength-demulfiplexing the multi-channel optical combined signal to form a plurality of single-channel optical combined signals; and receiving the plurality of single-channel optical combined signals on a corresponding plurality of photodetectors so that each photodetector receives a different one of the plurality of single-channel optical combined signals corresponding to a different one of the different wavelength channels and therefore also corresponding to a different one of the positions in the scene.
  23. 23. A method as claimed in claim 22, comprising: generating a multi-channel optical signal comprising the same plurality of different wavelengths arranged in the same corresponding plurality of different wavelength channels as the plurality of single-channel optical measurement signals; splitting the multi-channel optical signal to form a multi-channel optical measurement signal and the multi-channel optical local oscillator signal; and wavelength-demultiplexing the multi-channel optical measurement signal to form the plurality of single-channel optical measurement signals.
  24. 24. A method as claimed in claim 22 or 23, comprising scanning the plurality of single-channel optical measurement signals across the scene so as to illuminate different pluralities of different positions of the scene at different times.
  25. 25. A system as claimed in any one of claims 1 to 21 or a method as claimed in any one of claims 22 to 24, wherein at least one of: each wavelength of the plurality of different wavelengths lies in a wavelength range from 400 nm to 10 pm, from 1,400 nm to 1,600 nm or from 1,525 nm to 1,575 nm; a frequency spacing of the wavelength channels is greater than 10 GHz, greater than 100 GHz, greater than 1 THz and/or substantially equal to 250 GHz; a frequency bandwidth of each photodetector is less than, for example, one or more orders of magnitude less than, a frequency spacing of the wavelength channels; and a frequency bandwidth of each photodetector is 200 MHz or less.
GB1912050.0A 2019-08-22 2019-08-22 Multi-pixel coherent LIDAR imaging Pending GB2586499A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB1912050.0A GB2586499A (en) 2019-08-22 2019-08-22 Multi-pixel coherent LIDAR imaging

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB1912050.0A GB2586499A (en) 2019-08-22 2019-08-22 Multi-pixel coherent LIDAR imaging

Publications (2)

Publication Number Publication Date
GB201912050D0 GB201912050D0 (en) 2019-10-09
GB2586499A true GB2586499A (en) 2021-02-24

Family

ID=68108857

Family Applications (1)

Application Number Title Priority Date Filing Date
GB1912050.0A Pending GB2586499A (en) 2019-08-22 2019-08-22 Multi-pixel coherent LIDAR imaging

Country Status (1)

Country Link
GB (1) GB2586499A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102020215663A1 (en) 2020-12-10 2022-06-15 Peter Westphal Device for spatially resolved distance and speed measurement

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2021262278A2 (en) * 2020-04-03 2021-12-30 Aqronos, Inc. Frequency information rapid extraction for ranging applications

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2796890A1 (en) * 2011-12-21 2014-10-29 Mitsubishi Electric Corporation Laser radar device
EP3081961A1 (en) * 2013-12-09 2016-10-19 Mitsubishi Electric Corporation Laser radar device
EP3276371A1 (en) * 2016-07-29 2018-01-31 Samsung Electronics Co., Ltd Beam steering device and optical apparatus including the same
US20190004151A1 (en) * 2017-06-29 2019-01-03 Rockley Photonics Limited Optical scanner and detector
EP3525003A1 (en) * 2016-11-02 2019-08-14 Mitsubishi Electric Corporation Laser radar device

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2796890A1 (en) * 2011-12-21 2014-10-29 Mitsubishi Electric Corporation Laser radar device
EP3081961A1 (en) * 2013-12-09 2016-10-19 Mitsubishi Electric Corporation Laser radar device
EP3276371A1 (en) * 2016-07-29 2018-01-31 Samsung Electronics Co., Ltd Beam steering device and optical apparatus including the same
EP3525003A1 (en) * 2016-11-02 2019-08-14 Mitsubishi Electric Corporation Laser radar device
US20190004151A1 (en) * 2017-06-29 2019-01-03 Rockley Photonics Limited Optical scanner and detector

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102020215663A1 (en) 2020-12-10 2022-06-15 Peter Westphal Device for spatially resolved distance and speed measurement

Also Published As

Publication number Publication date
GB201912050D0 (en) 2019-10-09

Similar Documents

Publication Publication Date Title
US11486986B2 (en) LIDAR system with solid state spectral scanning
US20210316756A1 (en) Device and method for scanning measurement of the distance to an object
JP2021531475A (en) LIDAR system based on light modulators and coherent receivers for simultaneous distance and velocity measurements
CN112764050B (en) Laser radar measurement method and laser radar system
WO2022099806A1 (en) Laser radar system
US11009593B1 (en) Device and method for scanning measurement of the distance to an object
WO2022062105A1 (en) Array coherent ranging chip and system thereof
WO2020163717A1 (en) Ranging using a shared path optical coupler
CN109891263B (en) Laser radar device
WO2023125093A1 (en) Transmission apparatus, detection system, and detection method of laser radar
US11378689B2 (en) Highly multiplexed coherent LIDAR system
GB2586499A (en) Multi-pixel coherent LIDAR imaging
WO2021199027A1 (en) Method and apparatus for mapping and ranging based on coherent-time comparison
US20240077611A1 (en) Techniques for range and velocity measurements in a non-degenerate lidar system
CN114609610A (en) Two-dimensional surface type multi-beam ranging system based on array waveguide grating
US20200408918A1 (en) Laser radar device
CN112130130A (en) Silicon optical chip and laser radar system
US20220334227A1 (en) Device and method for scanning frequency-modulated continuous-wave lidar range measurement
JP6705610B1 (en) Laser equipment
Bogaerts et al. Integrated Optical Beam Scanning and FMCW Ranging using Multiplexed Tunable Lasers
CN114814856A (en) Laser radar system based on heterodyne detection
CN117561459A (en) Apparatus and method for scanning FMCW LiDAR distance measurements
CN113267763A (en) Transmitting device for FMCW laser radar and laser radar
CN117406233A (en) Linear frequency modulation continuous wave laser radar parallel ranging method based on electro-optical comb
WO2022096575A1 (en) Photonic integrated circuit