Lidar system using multiple wavelengths and operating method thereof

Abstract

To provide a LiDAR system that uses multiple wavelengths, and an operating method thereof.SOLUTION: A LiDAR system is provided, comprising: a signal generation unit configured to generate a plurality of multiplexed lights; a transceiver unit including a transmitter configured to simultaneously emit the plurality of multiplexed lights as a transmission signal in units of pixel groups including at least two pixels, and a receiver configured to mix the transmission signal and received signals that is incident when the transmission signal is reflected from a target object and convert the mixed signal into an electrical signal; and an electric circuit connected to the signal generation unit and the transceiver unit to control operation thereof.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a lidar system and a method of operation thereof. [Background technology]

[0002] A typical frequency modulated continuous wave (FMCW) lidar transmits a frequency modulated signal in the form of a triangular wave in terms of time versus frequency.

[0003] Meanwhile, the question arises as to how to implement xy-plane scanning in a solid-state LiDAR system. The main methods include flash, mirror-scanning, optical phased array, dispersive, and focal plane array (hereinafter referred to as FPA), and xy-plane scanning is implemented by combining these scanning methods on the xy axis. Among them, FPA is suitable for the FMCW driving method as it has low control complexity and excellent SMSR (Side Mode Suppression Ratio) characteristics. Summary of the Invention [Problem to be solved by the invention]

[0004] In the FPA method, the number of measurable points is limited to the number of pixels included in the focal plane (or focal plane array), and the number of pixels must be increased for high-resolution scanning, making it difficult to achieve high integration. Also, as the maximum measurement distance increases, there is a limit to the improvement in resolution through an increase in the number of pixels.

[0005] The technical problem that various embodiments aim to solve is to implement high-resolution scanning by introducing wavelength division multiplexing (WDM) into the FPA method.

[0006] The technical problems to be solved by the present invention are not limited to those described above, and other technical problems can be inferred from the following embodiments. [Means for solving the problem]

[0007] A LIDAR system according to one embodiment of the present invention includes a signal generator that generates multiplexed light beams; a transmitter that simultaneously outputs the multiplexed light beams as a transmission signal in units of pixel groups each including at least two pixels; a transceiver that includes a receiver that mixes the transmission signal and a reception signal that is received after the transmission signal is reflected from a target object and converts the mixture into an electrical signal; and a circuit unit that is connected to the signal generator and the transceiver and controls their operations.

[0008] A method for operating a LIDAR system according to one embodiment of the present invention includes generating a plurality of multiplexed lights via a signal generator; simultaneously outputting the multiplexed lights as a transmission signal in units of pixel groups including at least two pixels via a transceiver; and mixing the transmission signal and a reception signal, which is incident upon the transmission signal after being reflected from a target object, via the transceiver to convert the transmission signal into an electrical signal. [Effects of the Invention]

[0009] According to a lidar system and an operating method thereof according to an embodiment of the present invention, a single pixel included in a focal plane array can be simultaneously or sequentially driven for multiple wavelengths to measure a number of spatial points greater than the number of pixels, thereby achieving high-resolution scanning.

[0010] The effects of the embodiments are not limited to the effects described above, and any unmentioned effects will be clearly understood by a person having ordinary skill in the art to which the embodiments pertain from this specification and the accompanying drawings. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram showing a transmission signal sent from an FMCW radar, a received signal that is the transmission signal reflected from a target object and incident thereon, and a beat frequency. [Figure 2] FIG. 1 is a conceptual diagram illustrating a lidar system according to an embodiment. [Figure 3A] 1 is a block diagram illustrating a light source unit that can be applied to a signal generator according to an embodiment; [Figure 3B] 10 is a block diagram illustrating a light source unit that can be applied to a signal generator according to another embodiment. FIG. [Figure 3C] 10 is a block diagram illustrating a light source unit that can be applied to a signal generator according to another embodiment. FIG. [Figure 3D] 10 is a block diagram illustrating a light source unit that can be applied to a signal generator according to another embodiment. FIG. [Figure 4] 1 is a diagram illustrating pixels included in a focal plane array. [Figure 5] FIG. 2 is a block diagram illustrating a circuit unit according to an embodiment. [Figure 6] 1 is a diagram illustrating a driving method of a lidar system according to an embodiment. [Figure 7A] 1 is a diagram for explaining the operation of a MEMS. [Figure 7B] 1 is a diagram illustrating the operation of a microring resonator. [Figure 8] 10 is a diagram illustrating a driving method of a lidar system according to another embodiment. [Figure 9] 1 is a flowchart illustrating an operation method of a lidar system according to an embodiment. [Figure 10] FIG. 1 is a perspective view illustrating an exemplary electronic device to which a LIDAR system according to an embodiment is applied. [Figure 11] FIG. 1 is a conceptual side view showing a case where a lidar system according to an embodiment is applied to a vehicle. [Figure 12] FIG. 1 is a conceptual plan view showing a case where a LIDAR system according to an embodiment is applied to a vehicle. DETAILED DESCRIPTION OF THE INVENTION

[0012] The terms used in this embodiment are currently commonly used terms, and are selected as much as possible while taking into consideration the functions of the embodiment. However, this may vary depending on the intentions of engineers in the relevant technical field, precedents, the emergence of new technologies, etc. In addition, in certain cases, arbitrarily selected terms may be used, and in such cases, their meanings will be described in detail in the description of the embodiment. Therefore, the terms used in this embodiment should be defined based on the meanings of the terms and the overall content of the embodiment, rather than simply the names of the terms.

[0013] In the description of the embodiments, when a part is said to be connected to another part, this includes not only a direct connection but also an electrical connection via another component between them. Furthermore, when a part is said to include a component, this does not exclude the other component, but means that the other component is also included, unless otherwise specified.

[0014] The terms "comprise" or "include" used in this embodiment should not be interpreted as including all of the components or steps described in the specification, but should be interpreted as including some of the components or steps, or as including additional components or steps.

[0015] The following description of the embodiments should not be construed as limiting the scope of the invention, and any description that can be easily inferred by a person skilled in the art should be construed as falling within the scope of the invention. Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings.

[0016] FIG. 1 shows a diagram illustrating a transmission signal sent from an FMCW lidar, a received signal that is reflected from a target object and incident on the transmission signal, and a beat frequency.

[0017] Figure 1(a) shows the transmitted signal sent from an FMCW lidar and the received signal that is reflected from the target object, where the transmitted signal shown by the dotted line and the received signal shown by the solid line have a time difference of about delay time td and a frequency difference of about Doppler frequency fd. Here, B is the modulation bandwidth, and Tm is the modulation period.

[0018] Figure 1(b) shows the beat frequency expressed as the frequency difference between the transmitted signal and the received signal. fbu denotes the upbeat frequency corresponding to the up chirp, and fbd denotes the downbeat frequency corresponding to the down chirp.

[0019] The upbeat frequency and downbeat frequency contain frequency shifts due to the distance and relative velocity of the moving object, which are called the beat frequency (fb) and the Doppler frequency (fd), respectively.

[0020] The upbeat frequency fbu and the downbeat frequency fbd can be expressed as Equations 1 and 2 below.

[0021] [Formula 1] fbu=fb-fd

[0022] [Formula 2] fbd=fb+fd

[0023] Here, a positive Doppler frequency means that the moving object is approaching the lidar, and a negative Doppler frequency means that the moving object is moving away from the lidar. Therefore, the distance between the moving object and the lidar can be calculated by averaging the upbeat frequency fbu and the downbeat frequency fbd, and the moving speed of the moving object can be calculated using the Doppler frequency fd. The upbeat frequency fbu and the downbeat frequency fbd can be calculated by performing a fast Fourier transform (FFT) on the received beat signal.

[0024] FIG. 2 is a conceptual diagram illustrating a LIDAR system according to one embodiment.

[0025] 2, the LIDAR system 1000 may include a signal generating unit 100, a transceiver unit 200, and a circuit unit 300. The signal generating unit 100, the transceiver unit 200, and the circuit unit 300 may be configured on a single chip (or a semiconductor optical device).

[0026] According to one embodiment, the signal generating unit 100 may include a light source unit 110 and an optical coupler 120 .

[0027] The light source unit 110 can generate multiple light beams L having different wavelengths. The multiple light beams L can be multi-wavelength (multi-λ) electromagnetic waves. For example, the multiple light beams L can be multiple laser beams having different wavelengths, or can be other light beams that are not laser beams. The light source unit 110 can simultaneously generate multiple light beams L.

[0028] The optical coupler 120 can simultaneously receive a plurality of light beams L generated by the light source unit 110 and output a multiplexed light beam L'.

[0029] Although not shown in the drawings, the light source unit 110 may further include an optical modulator for modulating a plurality of lights.

[0030] For FMCW driving, the optical modulator (or signal generator 100) can perform frequency modulation (or chirping) as shown in FIG. 1 around wavelengths (e.g., λ1, λ2, through λN). The bandwidth of the frequency modulation (or chirping) determines the depth resolution. For example, for a 10 cm depth resolution, frequency modulation (or chirping) must be performed with a bandwidth of approximately 1.5 GHz. This frequency modulation (or chirping) can be implemented using either open-loop control or closed-loop control. It can also be pre-distorted based on information obtained through prior calibration to improve linearity. It is desirable for the spacing between the wavelengths (λ1, λ2, through λN) to be wider than the bandwidth of the frequency modulation for FMCW driving to limit crosstalk.

[0031] An optical modulator may modulate light in various ways. For example, an optical modulator may modulate the phase of light. Alternatively, an optical modulator may modulate the amplitude of light. Alternatively, an optical modulator may simultaneously modulate the phase and amplitude of light. The optical modulation function of an optical modulator may be varied in various ways. An optical modulator may perform optical modulation using an electrical method, a magnetic method, a thermal method, a mechanical method, or other methods. As a specific example, the optical modulator may include at least one phase shifter or phase shifting element, and the phase shifter may include at least one element selected from the group consisting of a gain element, an all-pass filter, a Bragg grating, a dispersive material element, a wavelength tuning element, a phase tuning element, and the like. Furthermore, the actuation mechanism applied to the optical modulator may include at least one selected from the group consisting of, for example, thermo-optic actuation, electro-optic actuation, electroabsorption actuation, free carrier absorption actuation, magneto-optic actuation, liquid crystal actuation, and all-optical actuation. Such actuation mechanisms are related to the phase tuning. However, the configuration and actuation mechanism of the phase converter specifically described here are merely examples, and embodiments are not limited thereto.

[0032] The specific configuration of the light source unit 110 will be described in detail later with reference to FIGS. 3A to 3D.

[0033] According to one embodiment, the transceiver unit 200 may include a focal plane array FPA in which a plurality of pixels PX (or pixel groups) are arranged in a matrix, and an optical element OP for controlling the light output angle.

[0034] The transceiver 200 may be functionally divided into a transmitter and a receiver. The transmitter corresponds to an optical antenna 220 and an optical amplifier 250 in Fig. 4, which will be described later, and a first optical switch SW1 and a second optical switch SW2 in Fig. 6, which will be described later, while the receiver corresponds to a second optical coupler 230, a balanced photodiode 241, and a transimpedance amplifier 242 in Fig. 4, which will be described later.

[0035] The transmitter may be a focal plane array FPA type in at least one of the x and y axes, and may simultaneously or sequentially emit multiplexed light beams L' as a transmission signal to one pixel PX included in the focal plane array FPA.

[0036] According to one embodiment, the optical element OP may control the multiplexed light beams L′ to have different exit angles depending on the wavelength when emitted from the pixel PX into free space. For example, the optical element OP may include a prism, a microprism array, a diffraction grating, etc.

[0037] The receiver may mix a transmitted signal and a received signal, which is the transmitted signal reflected from the target object OBJ, and convert the mixed signal into an electrical signal. For example, the receiver may be implemented by using a second optical coupler 230 (described later) in FIG. 4 to perform 50:50 coupling and then inputting the signal to a balanced photodiode 241. However, the coupling method is not limited thereto and may be implemented using, for example, a beam splitter. Regardless of the specific mixing method, the signal obtained by the receiver may include tone frequency information for light of each wavelength. Light of each wavelength includes distance and / or velocity information relative to the target object OBJ, which is reflected in the tone frequency.

[0038] The circuit unit 300 is connected to the signal generator 100 and the transceiver 200 and may control their operations. For example, the circuit unit 300 may perform frequency analysis on the electrical signal obtained from the transceiver 200 (or the receiver) and convert it into distance and / or velocity information of the target object OBJ. A specific configuration of the circuit unit 300 will be described in detail below with reference to FIG. 5.

[0039] Hereinafter, the configuration of the light source unit 110 will be described in more detail with reference to FIGS. 3A to 3D.

[0040] FIG. 3A is a block diagram illustrating a light source unit that can be applied to a signal generator according to an embodiment.

[0041] 3A, according to this embodiment, the light source unit 110 may include a plurality of laser sources LD1 to LD4. Here, four laser sources LD1 to LD4 are shown, but the number may vary. The plurality of laser sources LD1 to LD4 may be, for example, laser diodes. The plurality of laser sources LD1 to LD4 may generate lasers with different wavelengths (e.g., λ1, λ2, λ3, λ4). The lasers with different wavelengths (λ1, λ2, λ3, λ4) generated by the plurality of laser sources LD1 to LD4 may be input to the optical coupler 120 and multiplexed.

[0042] FIG. 3B is a block diagram illustrating a light source unit that can be applied to a signal generator according to another embodiment.

[0043] 3B, lasers having different wavelengths (e.g., λ1, λ2, λ3, λ4) generated by a plurality of laser sources LD1 to LD4 may be input to different input couplers IN1 to IN4, respectively. The plurality of input couplers IN1 to IN4 constitute one "input unit 130." The plurality of input couplers IN1 to IN4 may have, for example, an optical fiber structure or other configurations. The plurality of light beams passing through the plurality of input couplers IN1 to IN4 may be multiplexed by the optical coupler 120.

[0044] 3B, the input couplers IN1 to IN4 and the optical coupler 120 may be coupled to a predetermined optical waveguide. In some cases, the input couplers IN1 to IN4 and the optical coupler 120 may be collectively considered as one "input section."

[0045] FIG. 3C is a block diagram illustrating a light source unit that can be applied to a signal generator according to another embodiment.

[0046] 3C, the light source unit 111 may include a laser source LD10 that generates a laser beam having a single wavelength λ0. That is, the light source unit 111 may be configured with a single laser source LD10. The light source unit 111 may further include a wavelength converter 140 that splits the laser beam generated by the laser source LD10 into multiple laser beams having different wavelengths (e.g., λ1, λ2, λ3, and λ4). For example, the wavelength converter 140 may include an input coupler, an optical splitter, and multiple wavelength conversion elements. The laser beam input to the input coupler may be split by the optical splitter and then its wavelength may be converted by the multiple wavelength conversion elements. As a result, multiple beams having different wavelengths (e.g., λ1, λ2, λ3, and λ4) may be output through the wavelength converter 140. The multiple beams may be multiplexed by the optical coupler 120.

[0047] 3C, the laser source LD10 and the wavelength converter 140 may be collectively regarded as a single "light source unit." Such a light source unit generates multiple lights having different wavelengths (e.g., λ1, λ2, λ3, and λ4). Furthermore, at least a portion of the wavelength converter 140 or at least a portion of the optical coupler 120 may be collectively regarded as an "input coupler." Alternatively, the wavelength converter 140 and the optical coupler 120 may be collectively regarded as a single input coupler.

[0048] FIG. 3D is a block diagram illustrating a light source unit that can be applied to a signal generating unit according to another embodiment.

[0049] 3D, the light source unit 112 may include a broadband laser. That is, the broadband laser is a device that generates wideband light. A multi-band pass filter 150 may be provided to split the light generated by the light source unit 112. Light having a plurality of wavelengths (e.g., λ1, λ2, λ3, λ4) that are distinguished from one another may be output through the multi-band pass filter 150. The plurality of lights may be multiplexed by an optical coupler 120.

[0050] 3D, the broadband laser and the multi-bandpass filter 150 can be considered as a single "light source unit." Such a light source unit generates multiple lights having different wavelengths. In this embodiment, the optical coupler 120 can be considered as an "input coupler."

[0051] FIG. 4 is a diagram illustrating pixels included in a focal plane array.

[0052] Referring to FIG. 4, pixel PX may split input signal IS into local oscillator signal LO and transmit signal Tx, couple the transmit signal Tx into free space, couple the receive signal Rx back to pixel PX, and mix the local oscillator signal LO and receive signal Rx.

[0053] A pixel PX according to an embodiment may include a first optical coupler 210, an optical antenna 220, a second optical coupler 230, and an opto-electrical converter 240. The pixel PX may receive a plurality of multiplexed lights (see L' in FIG. 2) as an input signal IS. The first optical coupler 210 may be disposed between an input terminal INT and the optical antenna 220. The first optical coupler 210 may split the input signal IS received at the input terminal INT into a local oscillator signal LO and a transmit signal Tx. The optical antenna 220 may receive a receive signal Rx reflected by a target object.

[0054] The optical antenna 220 is a device that emits light from an on-chip waveguide into free space and / or couples light from free space into an on-chip waveguide. The optical antenna 220 can be embodied as a grating coupler, edge coupler, integrated reflector, or any spot-size converter. The optical antenna 220 is also polarization-sensitive, with higher emission / coupling efficiency for light with a specific polarization (e.g., transverse electric (TE) or transverse magnetic (TM)). The optical antenna 220 can also be reciprocal, and thus can collect a received signal Rx from a measurement object (e.g., an object in the environment). The optical antenna 220 can provide the received signal Rx to a second optical coupler 230. While FIG. 4 shows a coaxial implementation in which light emission and collection are performed through the same optical antenna 220, a dual-axis implementation is also possible, in which light emission and collection are performed separately using separate optical antennas.

[0055] The second optical coupler 230 may generate an output signal OS by mixing the received signal Rx with the local oscillator signal LO split off and provided by the first optical coupler 210. The second optical coupler 230 is also a balanced 2x2 optical mixer.

[0056] The pixel PX may include a photoelectric conversion unit 240 that converts an output signal OS, which is an optical signal, into an electrical signal. The photoelectric conversion unit 240 may include a balanced photodiode 241 configured to convert an optical signal into an electrical signal for tone frequency detection, and a transimpedance amplifier TIA that amplifies the intensity of the electrical signal generated by the balanced photodiode 241. For example, the transimpedance amplifier TIA may amplify the current generated by the balanced photodiode 241 and convert it into a voltage. The electrical signal provided by the transimpedance amplifier TIA may be provided to an analog-to-digital converter (ADC) (or a circuit unit (see 300 in FIG. 5 )).

[0057] According to an embodiment, the pixel PX may further include an optical amplifier 250 disposed between the first optical coupler 210 and the optical antenna 220 to compensate for optical loss. For example, the optical amplifier 250 may be a semiconductor optical amplifier (SOA) and may amplify an optical signal so that the intensity of light generated from the light source unit (see 110 in FIG. 2) is maintained at the optical antenna 220. Alternatively, the optical amplifier 250 may increase the signal-to-noise ratio (SNR).

[0058] FIG. 5 is a block diagram illustrating a circuit unit according to an embodiment.

[0059] Referring to FIG. 5, the circuit unit 300 may include an optical signal control unit 310, a switching control unit 320, and a calculation unit 330.

[0060] The optical signal control unit 310 controls the frequency modulation (or chirping) of the signal generating unit 100 described above, which may include a feedback circuit such as a phase-locked loop (PLL).

[0061] The switching control unit 320 can control the switching of at least one or more focal plane arrays (FPAs) in the transmitter of the transceiver unit 200. In this case, the switching control can also be the operation of an optical MEMS (Micro-Electromechanical System) part. This control can also be the heating (or thermal) control of a thermo-optical element that manipulates phase, such as a micro ring resonator or a Mach-Zehnder interferometer. This control can also be the control for electro-optical modulation by adjusting carrier concentration.

[0062] The calculation unit 330 may perform frequency analysis on the electrical signal obtained by the receiver of the transceiver unit 200 and convert it into distance and / or velocity information of a target object. For example, an analog electrical signal may be binarized through an analog-to-digital converter and then converted into frequency domain information through a fast Fourier transform in a digital calculation unit. The frequency domain information for each pixel may be converted into a point cloud representing a depth or velocity map, and may be used for higher-level applications such as autonomous driving through analysis algorithms including image processing.

[0063] Fig. 6 is a diagram illustrating a driving method of a lidar system according to an embodiment, Fig. 7A is a diagram illustrating an operation of a MEMS switch, and Fig. 7B is a diagram illustrating an operation of a microring resonator.

[0064] 2, 4, and 6, in a LIDAR system 1000 according to an embodiment, a pixel PX included in a focal plane array FPA simultaneously emits a plurality of multiplexed light beams L' as a transmit signal Tx and receives a receive signal Rx reflected back from a target object. In this case, the transmit signal Tx is also a signal from which the local oscillator signal LO has been removed, which has been branched from the plurality of multiplexed light beams L'.

[0065] Specifically, a plurality of light beams L having different wavelengths generated by the light source unit 110 may be converted into multiplexed light beams L' via the optical coupler 120. The multiplexed light beams L' may be provided to the focal plane array FPA through the main bus waveguide MWG.

[0066] When the first optical switch SW1 is on, it can selectively transmit light from the main bus waveguide MWG to the row waveguides W1 to Wm. The first optical switch SW1 can be implemented by an optical MEMS (Micro-Electromechanical System) switch or other methods, and can also be a wideband switch that can simultaneously turn on / off a wide frequency range from λ1 to λn. Therefore, a MZI (Mach-Zender Interferometer) switch or the like can also be used.

[0067] 7A, the first optical switch SW1 may be implemented as an array of a plurality of MEMS (Micro-Electromechanical System) switches MS. Each MEMS switch MS steers an optical input signal IS from a main bus waveguide MWG in response to a control signal received via a corresponding control line CL, thereby selectively providing the optical input signal IS to a plurality of row waveguides (W1 through Wm).

[0068] 2, 4, and 6, when the second optical switch SW2 is in an on state, it can selectively transmit light from the row waveguides (W1 to Wm) selected by the first optical switch SW1 to the pixel PX. While the second optical switch SW2 is illustrated as a microring resonator, it is not limited thereto and can be any switch that can sequentially or simultaneously turn on / off multiple wavelengths (λ1 to λn) depending on the driving method. When the second optical switch SW1 is in an on state, light can be emitted into free space through the optical antenna 220.

[0069] 7B, the second optical switch SW2 may be implemented as an array of microring resonators (MRRs). Each MRR may pick up an optical signal from a row waveguide (e.g., W1 through Wm) when the resonant frequency of the device is aligned with the laser wavelength. According to one embodiment, an electrical control signal (e.g., Ctrl0, Ctrl1 through Ctrln) may be used to set the resonance of each MRR in the array and thereby select a pixel PX to receive the optical signal.

[0070] 2, 4, and 6, the transceiver unit 200 (or the focal plane array FPA) may further include an optical amplifier 250 to compensate for optical attenuation and loss. The optical amplifier 250 may be disposed between the first optical switch SW1 and the second optical switch SW2 on the row waveguides W1 to Wm. The optical amplifier 250 may also be disposed between the second optical switch SW2 and the optical antenna 220 within the pixel PX. For example, the optical amplifier 250 may be a semiconductor optical amplifier (SOA) that amplifies the optical signal so that the light generated by the light source unit 110 maintains its intensity in the optical antenna 220. Alternatively, the optical amplifier 250 may increase the signal-to-noise ratio (SNR).

[0071] When a specific pixel PX is activated through the first optical switch SW1 and the second optical switch SW2, light transmitted through the waveguide can be emitted into free space through the optical antenna 220. In this case, the optical antenna 220 can also be a grating coupler. Light of different wavelengths (λ1 to λn) can have different exit angles depending on the grating coupler and / or optical element (OP in FIG. 2).

[0072] Light reflected and collected by the target object may be transmitted to the waveguide via the optical antenna 220. A portion of the light transmitted to the optical antenna 220 (or a transmission signal Tx) may be mixed with a reception signal Rx via the second optical coupler 230 to transmit a beating optical signal to the opto-electrical converter 24. The opto-electrical converter 240 may convert beating frequency information into an electrical signal. The opto-electrical converter 240 may be embodied as a balanced photodiode 241 and a transimpedance amplifier (TIA). However, the present invention is not limited thereto and may be appropriately embodied using, for example, an avalanche photodiode, a single-photon avalanche photodiode, etc. The opto-electrical converter 240 may further include a low-pass filter or a band-pass filter to remove high-frequency components from the mixed signal and leave only the significant beating frequency.

[0073] Meanwhile, when light of various wavelengths is simultaneously emitted and input from one pixel PX, the circuit unit (see 300 in FIG. 2) (or the calculation unit 330 in FIG. 5) must separate and process the information of each wavelength. Therefore, the pixel PX may include a wavelength demultiplexer 260 in a waveguide at the front end of the second optical coupler 230. For example, the demultiplexer 260 may be embodied as an optical band pass filter, a micro ring resonator, or the like. In this regard, FIG. 6 shows only an embodiment in which the demultiplexer 260 is disposed in a waveguide between the optical antenna 220 and the second optical coupler 230, but the present invention is not limited thereto. For example, the demultiplexer 260 may be disposed in a waveguide between the first optical coupler 210 and the second optical coupler 230.

[0074] Other embodiments will be described below. In the following embodiments, the description of the same configurations as those in the above-described embodiments will be omitted or simplified, and differences will be mainly described.

[0075] 8 is a diagram illustrating a driving method of a LIDAR system according to another embodiment. For convenience of explanation, FIG. 8 illustrates a focal plane array FPA including pixels provided with four different wavelengths and arranged in a 16×4 matrix, but the present invention is not limited thereto.

[0076] The lidar system 1000 shown in Figure 8 differs from the lidar system 1000 of Figure 6, which shows an embodiment in which multiple lights are emitted from a single pixel PX and the pixel PX includes a demultiplexer 260, in that the lidar system 1000 shown in Figure 8 emits multiple lights multiplexed in units of pixel groups PXG, each including a predetermined number of pixels (e.g., PX1, PX2, PX3, PX4), and does not include a demultiplexer in the pixel; the remaining configuration is substantially identical.

[0077] 2, 4, 7A, 7B, and 8, a lidar system 1000 according to one embodiment may include a signal generator 100 that generates multiplexed lights, a transmitter that simultaneously outputs the multiplexed lights as a transmission signal in units of pixel groups PXG each including at least two pixels (e.g., PX1, PX2, PX3, PX4), and a transceiver 200 that includes a receiver that mixes the transmission signal and a received signal that is incident after the transmission signal is reflected from a target object and converts it into an electrical signal, and a circuit unit 300 connected to the signal generator 100 and the transceiver 200 and controls their operation.

[0078] Each pixel group PXG may include a predetermined number of pixels (e.g., PX1, PX2, PX3, PX4), which may be connected in parallel to one another. For example, the focal plane array FPA may have pixels (PX1 to PX4) arranged in a 16x4 matrix, and each pixel group PXG may include four pixels (e.g., PX1, PX2, PX3, PX4) connected in parallel in a column direction. Among the pixels (e.g., PX1 to PX16) included in each pixel group PXG arranged in the column direction, pixels (e.g., PX1, PX5, PX9, PX13) that correspond to the same order may be connected to the same output channel terminal (e.g., ch1).

[0079] According to an embodiment, the circuit unit 300 may repeatedly operate the transceiver unit 200 with one cycle consisting of stages (64 stages) equal in number to the number of pixels (PX1 to PX64) included in the focal plane array FPA (for example, 64).

[0080] During one cycle, the distance and / or velocity of the target object may be calculated based on the value of the electrical signal, which is equal to the number (e.g., 256) of pixels included in the focal plane array FPA (e.g., 64) multiplied by the number (e.g., 4) of pixels (e.g., PX1, PX2, PX3, PX4) included in the pixel group PXG. This allows for simultaneous measurement of a larger number of spatial points (e.g., 256) than the number (e.g., 64) of pixels included in the focal plane array FPA, thereby achieving high-resolution scanning.

[0081] Specifically, light having different wavelengths λ1, λ2, λ3, and λ4 may be sequentially emitted and incident on each of the pixels (eg, PX1, PX2, PX3, and PX4) included in the pixel group PXG.

[0082] In this case, the pixels PX1, PX2, PX3, and PX4 may be simultaneously activated as long as crosstalk at each pixel is limited. To limit crosstalk, the simultaneously activated pixels PX1, PX2, PX3, and PX4 may use light of different wavelengths. For example, the microring resonator MRR may be configured to selectively transmit only specific wavelengths among the wavelengths λ1 through λ4 to the optical antenna 220. In this case, even if light of various wavelengths is collected as the received signal Rx, only wavelength components sufficiently close to the selected wavelength from the transmitted signal Tx can pass through the low-pass filter or band-pass filter after the transimpedance amplifier 242. Therefore, unlike the lidar system 1000 shown in FIG. 6, the demultiplexer 260 may be omitted.

[0083] For example, during the four stages, the first pixel PX1 may emit light at the first wavelength λ1, the second wavelength λ2, the third wavelength λ3, and the fourth wavelength λ4, in that order; the second pixel PX2 may emit light at the second wavelength λ2, the third wavelength λ3, the fourth wavelength λ4, and the first wavelength λ1, in that order; the third pixel PX3 may emit light at the third wavelength λ3, the fourth wavelength λ4, the first wavelength λ1, and the second wavelength λ2, in that order; and the fourth pixel PX4 may emit light at the fourth wavelength λ4, the first wavelength λ1, the second wavelength λ2, and the third wavelength λ3, in that order. Thus, in the first stage, the first pixel PX1 may emit light at the first wavelength λ1, the second pixel PX2 may emit light at the second wavelength λ2, the third pixel PX3 may emit light at the third wavelength λ3, and the fourth pixel PX4 may emit light at the fourth wavelength λ4. That is, the pixels PX1, PX2, PX3, and PX4 included in the same pixel group PXG at the same time (or stage) can simultaneously emit light of different wavelengths.

[0084] As described above, a method for simultaneously driving a plurality of pixels (e.g., PX1, PX2, PX3, PX4) will be described using an example of a two-dimensional focal plane array FPA having four wavelengths (λ1, λ2, λ3, λ4) and 16x4 pixels (PX1 to PX64) in Fig. 8. However, the present invention is not limited thereto, and there are various specific embodiments for grouping and driving pixels.

[0085] The pixels are grouped in columns of four (e.g., PX1 through PX4, PX5 through PX8, etc.) and receive the same power supply. Therefore, multiple pixels (e.g., PX1 through PX4) can be electrically activated. For example, if the pixels connected to the first row waveguide W1 are turned on, 16 pixels can be simultaneously activated. However, only one column is optically selected and activated per stage; unselected columns cannot provide meaningful photoelectric conversion signals even when electrically activated. For example, if the pixels connected to the first row waveguide W1 are turned on and the first column is optically activated, the first channel ch1 through the fourth channel ch4 can provide information from the first pixel PX1 through the fourth pixel PX4, respectively. Therefore, parallel information transmission through four channels is possible at one time.

[0086] Table 1 below shows row waveguides W1 to W4 that are activated at timings t1 to t64 and wavelength information reflected in each channel through which information is transmitted.

[0087] [Table 1]

[0088] For example, from the first stage t1 to the fourth stage t4, the pixel group PXG connected to the first row waveguide W1 may maintain the on state.

[0089] In the first stage t1, the first pixel PX1 may provide a received signal corresponding to the transmit signal having a wavelength of λ1 at the first channel terminal ch1, the second pixel PX2 may provide a received signal corresponding to the transmit signal having a wavelength of λ2 at the second channel terminal ch2, the third pixel PX3 may provide a received signal corresponding to the transmit signal having a wavelength of λ3 at the third channel terminal ch3, and the fourth pixel PX4 may provide a received signal corresponding to the transmit signal having a wavelength of λ4 at the fourth channel terminal ch4.

[0090] In the second stage t2, the first pixel PX1 may provide a received signal corresponding to the transmitted signal having a wavelength of λ2 to the first channel terminal ch1, the second pixel PX2 may provide a received signal corresponding to the transmitted signal having a wavelength of λ3 to the second channel terminal ch2, the third pixel PX3 may provide a received signal corresponding to the transmitted signal having a wavelength of λ4 to the third channel terminal ch3, and the fourth pixel PX4 may provide a received signal corresponding to the transmitted signal having a wavelength of λ1 to the fourth channel terminal ch4.

[0091] In the third stage t3, the first pixel PX1 may provide a received signal corresponding to the transmitted signal having a wavelength of λ3 to the first channel terminal ch1, the second pixel PX2 may provide a received signal corresponding to the transmitted signal having a wavelength of λ4 to the second channel terminal ch2, the third pixel PX3 may provide a received signal corresponding to the transmitted signal having a wavelength of λ1 to the third channel terminal ch3, and the fourth pixel PX4 may provide a received signal corresponding to the transmitted signal having a wavelength of λ2 to the fourth channel terminal ch4.

[0092] In the fourth stage t4, the first pixel PX1 may provide a received signal corresponding to the transmitted signal having a wavelength of λ4 to the first channel terminal ch1, the second pixel PX2 may provide a received signal corresponding to the transmitted signal having a wavelength of λ1 to the second channel terminal ch2, the third pixel PX3 may provide a received signal corresponding to the transmitted signal having a wavelength of λ2 to the third channel terminal ch3, and the fourth pixel PX4 may provide a received signal corresponding to the transmitted signal having a wavelength of λ3 to the fourth channel terminal ch4.

[0093] In this manner, during the first stage t1 to the fourth stage t4, each pixel PX1 to PX4 sweeps the λ1 wavelength to the λ4 wavelength, and then during the fifth stage t5 to the eighth stage t8, the pixel group PXG connected to the second row waveguide W2 may maintain an on state. The remaining stages t9 to t64 may be driven in the same manner as described above. The circuit unit 300 may implement a logic circuit that determines from which channel information is to be acquired for each stage.

[0094] FIG. 9 is a flowchart illustrating an operation method of a lidar system according to an embodiment.

[0095] 1 to 9, an operating method of a LIDAR system 1000 according to one embodiment may include a step of generating a plurality of multiplexed lights via a signal generating unit 100 (S100), a step of simultaneously emitting the plurality of multiplexed lights as a transmission signal Tx via a transceiver 200 in units of a pixel group PXG including at least two pixels PX (S200), and a step of mixing the transmission signal Tx and a reception signal Rx, which is incident after the transmission signal Tx is reflected from a target object, via the transceiver 200 and converting the transmission signal Tx into an electrical signal (S300).

[0096] The transceiver 200 includes a focal plane array FPA, which is arranged in a 16x4 matrix, and each pixel group PXG includes four pixels PX connected in parallel in a column direction, and pixels PX included in each pixel group PXG arranged in the column direction that correspond to the same order can be connected to the same output channel terminal.

[0097] The method of operating the LIDAR system 1000 may further include the steps of repeatedly operating the transceiver unit 200 via the circuit unit 300, with one cycle consisting of stages equal to the number of pixels PX included in the focal plane array FPA, and calculating the distance and / or velocity of the target object via the circuit unit 300 based on the value of the electrical signal that is equal to the number of pixels PX included in the focal plane array FPA multiplied by the number of pixels PX included in the pixel group PXG during one cycle.

[0098] The first pixel group of the pixel group PXG includes a first pixel PX1, a second pixel PX2, a third pixel PX3, and a fourth pixel PX4, and the first pixel PX1, the second pixel PX2, the third pixel PX3, and the fourth pixel PX4 can be in an on state simultaneously.

[0099] For example, from the first stage t1 to the fourth stage t4, the pixel group PXG connected to the first row waveguide W1 may maintain the on state.

[0100] In the first stage t1, the first pixel PX1 may provide a received signal corresponding to the transmitted signal having a wavelength of λ1 to the first channel terminal ch1, the second pixel PX2 may provide a received signal corresponding to the transmitted signal having a wavelength of λ2 to the second channel terminal ch2, the third pixel PX3 may provide a received signal corresponding to the transmitted signal having a wavelength of λ3 to the third channel terminal ch3, and the fourth pixel PX4 may provide a received signal corresponding to the transmitted signal having a wavelength of λ4 to the fourth channel terminal ch4.

[0101] In the second stage t2, the first pixel PX1 may provide a received signal corresponding to the transmitted signal having a wavelength of λ2 to the first channel terminal ch1, the second pixel PX2 may provide a received signal corresponding to the transmitted signal having a wavelength of λ3 to the second channel terminal ch2, the third pixel PX3 may provide a received signal corresponding to the transmitted signal having a wavelength of λ4 to the third channel terminal ch3, and the fourth pixel PX4 may provide a received signal corresponding to the transmitted signal having a wavelength of λ1 to the fourth channel terminal ch4.

[0102] In the third stage t3, the first pixel PX1 may provide a received signal corresponding to the transmitted signal having a wavelength of λ3 to the first channel terminal ch1, the second pixel PX2 may provide a received signal corresponding to the transmitted signal having a wavelength of λ4 to the second channel terminal ch2, the third pixel PX3 may provide a received signal corresponding to the transmitted signal having a wavelength of λ1 to the third channel terminal ch3, and the fourth pixel PX4 may provide a received signal corresponding to the transmitted signal having a wavelength of λ2 to the fourth channel terminal ch4.

[0103] In the fourth stage t4, the first pixel PX1 may provide a received signal corresponding to the transmitted signal having a wavelength of λ4 to the first channel terminal ch1, the second pixel PX2 may provide a received signal corresponding to the transmitted signal having a wavelength of λ1 to the second channel terminal ch2, the third pixel PX3 may provide a received signal corresponding to the transmitted signal having a wavelength of λ2 to the third channel terminal ch3, and the fourth pixel PX4 may provide a received signal corresponding to the transmitted signal having a wavelength of λ3 to the fourth channel terminal ch4.

[0104] FIG. 10 is a perspective view illustrating an exemplary electronic device to which a LIDAR system according to an embodiment is applied.

[0105] 10 is illustrated in the form of a mobile phone or smartphone 3000, the electronic device to which the lidar devices 10, 20, and 30 are applied is not limited thereto. For example, the lidar devices may be applied to tablets or smart tablets, laptop computers, televisions or smart televisions, etc.

[0106] Furthermore, the lidar system according to the embodiment can be applied to autonomously driven equipment.

[0107] 11 and 12 are conceptual diagrams showing a case where the LIDAR system according to the embodiment is applied to a vehicle, and are a side view and a plan view, respectively.

[0108] Referring to FIG. 11 , a LIDAR system 1001 may be applied to a vehicle 4000 to acquire information related to an object 60. The LIDAR system 1001 may be the LIDAR system described with reference to FIGS. 2 through 8. The LIDAR system 1001 may use a time-of-flight (TOF) method to acquire information related to the object 60. The vehicle 50 may also be an automobile with autonomous driving capabilities. As described with reference to FIG. 11 , the LIDAR system 1001 may divide a target field of view into a plurality of sub-areas and irradiate a set of beams, split into beams one for each of the sub-areas, at predetermined time intervals. If an object is detected within the target area and light reflected from the object is detected, a digital scan of the target area may be initiated to analyze information related to the object 60. The LIDAR system 1001 may be used to detect an object or person, i.e., the object 60, in the direction of travel of the vehicle 4000, and measure the distance to the object 60 using information such as the time difference between a transmitted signal and a received signal. Also, as shown in FIG. 12, information regarding a nearby object 61 and a distant object 62 within the region of interest can be obtained.

[0109] 11 and 12 illustrate an example in which a LiDAR system is applied to an automobile, but the LiDAR system is not limited thereto. The LiDAR system can also be applied to an air vehicle such as a drone, a mobile device, a small walking vehicle (e.g., a bicycle, a motorbike, a stroller, a board, etc.), a robot, a human / animal assistive device (e.g., a cane, a helmet, accessories, clothing, a watch, a bag, etc.), an IoT (Internet of Things) device / system, a security device / system, etc.

[0110] The above-described lidar system has been described with reference to the embodiment shown in the drawings, but this is merely an example, and those skilled in the art will recognize that numerous modifications and equivalent embodiments are possible. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of this specification is set forth in the claims, not the foregoing description, and should be interpreted to include all variations within the scope of equivalents thereto. [Explanation of symbols]

[0111] 1000 Lidar System 100 signal generation unit 110 Light source section 120 Optical Coupler 200 Transmitter / Receiver 210 First optical coupler 220 Optical Antenna 230 Second optical coupler 240 Photoelectric conversion unit 300 Circuit section 310 Optical signal control unit 320 Switching control section 330 Arithmetic section

Claims

1. a signal generating unit that generates a plurality of multiplexed lights; a transmitting / receiving unit including a transmitting unit that simultaneously outputs the multiplexed light beams as a transmission signal in units of pixel groups each including at least two pixels, and a receiving unit that mixes the transmission signal and a reception signal that is the transmission signal reflected from a target object and incident thereon, and converts the mixed signal into an electric signal; a circuit unit connected to the signal generating unit and the transceiver unit and controlling their operations; Including the Rider system.

2. The signal generation unit a light source unit that generates the plurality of light beams having different wavelengths; an optical coupler that simultaneously receives and multiplexes the plurality of lights; an optical modulator for modulating the plurality of light beams; 10. The lidar system of claim 1, comprising:

3. the light source unit includes a plurality of laser sources; 3. The lidar system of claim 2, wherein the plurality of laser sources generate lasers having different wavelengths.

4. the transceiver unit includes a focal plane array in which the pixel groups are arranged in a matrix; 10. The lidar system of claim 1, wherein the focal plane array receives the transmit signals via a main bus waveguide.

5. Each of the pixels is a first optical coupler that splits an input signal into the transmit signal and a local oscillator signal; an optical antenna for emitting the transmission signal into free space and / or receiving the reception signal from free space; a second optical coupler that mixes the local oscillator signal with the received signal to generate an output signal; a photoelectric conversion unit that converts the output signal into an electrical signal; 5. The lidar system of claim 4, comprising:

6. 6. The lidar system of claim 5, wherein the input signal is a frequency modulated continuous wave (FMCW) laser signal.

7. 7. The LIDAR system according to claim 6, wherein the photoelectric conversion unit includes a balanced photodiode that converts an optical signal into an electrical signal and a transimpedance amplifier that amplifies the intensity of the electrical signal.

8. 7. The LIDAR system of claim 6, wherein the circuit unit includes an analog-to-digital converter for binarizing the electrical signal, and the photoelectric conversion unit further includes an LPF (low pass filter) or a BPF (band pass filter) for removing high-frequency components of the electrical signal.

9. further comprising a first optical switch and a second optical switch coupled to the focal plane array; the first optical switch selectively provides the input signals to the focal plane array on a row-by-row basis; 7. The lidar system of claim 6, wherein the second optical switch selectively provides the input signal to the focal plane array on a column-by-column basis.

10. 10. The lidar system of claim 9, wherein each of the pixel groups includes a predetermined number of pixels, the predetermined number of pixels being connected in parallel to one another.

11. 11. The lidar system of claim 10, wherein the first optical switch and the second optical switch are one of a MEMS (Micro-Electromechanical System) switch array and a micro-ring resonator array.

12. 12. The lidar system of claim 11, further comprising an optical amplifier disposed between the first optical switch and the optical antenna to compensate for optical losses.

13. the focal plane array is arranged in a 16x4 matrix; Each of the pixel groups includes four pixels connected in parallel in a column direction, The LIDAR system of claim 12 , wherein pixels included in each pixel group arranged in a column direction and corresponding to the same order are connected to the same output channel terminal.

14. The circuit unit includes: repeatedly operating the transmitter / receiver in a cycle consisting of a number of stages equal to the number of pixels included in the focal plane array; 14. The LIDAR system of claim 13, wherein the distance and / or velocity of the target object is calculated based on the value of the electrical signal, which is equal to the number of pixels included in the focal plane array multiplied by the number of pixels included in the pixel group during the one cycle.

15. Among the pixel groups, a first pixel group includes a first pixel, a second pixel, a third pixel, and a fourth pixel, the first pixel, the second pixel, the third pixel, and the fourth pixel are simultaneously in an ON state; In a first stage, the first pixel provides a received signal corresponding to a transmission signal having a wavelength of λ1 to a first channel terminal, the second pixel provides a received signal corresponding to a transmission signal having a wavelength of λ2 to a second channel terminal, the third pixel provides a received signal corresponding to a transmission signal having a wavelength of λ3 to a third channel terminal, and the fourth pixel provides a received signal corresponding to a transmission signal having a wavelength of λ4 to a fourth channel terminal; In a second stage, the first pixel provides a received signal corresponding to a transmission signal having a wavelength of λ2 to a first channel terminal, the second pixel provides a received signal corresponding to a transmission signal having a wavelength of λ3 to a second channel terminal, the third pixel provides a received signal corresponding to a transmission signal having a wavelength of λ4 to a third channel terminal, and the fourth pixel provides a received signal corresponding to a transmission signal having a wavelength of λ1 to a fourth channel terminal; In a third stage, the first pixel provides a received signal corresponding to a transmission signal having a wavelength of λ3 to a first channel terminal, the second pixel provides a received signal corresponding to a transmission signal having a wavelength of λ4 to a second channel terminal, the third pixel provides a received signal corresponding to a transmission signal having a wavelength of λ1 to a third channel terminal, and the fourth pixel provides a received signal corresponding to a transmission signal having a wavelength of λ2 to a fourth channel terminal; 14. The lidar system of claim 13, wherein in a fourth stage, the first pixel provides a received signal corresponding to a transmit signal having a λ4 wavelength to a first channel terminal, the second pixel provides a received signal corresponding to a transmit signal having a λ1 wavelength to a second channel terminal, the third pixel provides a received signal corresponding to a transmit signal having a λ2 wavelength to a third channel terminal, and the fourth pixel provides a received signal corresponding to a transmit signal having a λ3 wavelength to a fourth channel terminal.

16. 1. A method of operating a lidar system, comprising: generating a plurality of multiplexed lights via a signal generator; simultaneously outputting the multiplexed lights as a transmission signal in units of pixel groups each including at least two pixels through a transceiver; mixing the transmission signal and a reception signal, which is the transmission signal reflected from a target object and incident thereon, via the transceiver unit, and converting the mixed signal into an electrical signal; A method of operating a lidar system, including:

17. Each of the pixels is a first optical coupler that splits an input signal into the transmit signal and a local oscillator signal; an optical antenna for emitting the transmission signal into free space and / or receiving the reception signal from free space; a second optical coupler that mixes the local oscillator signal with the received signal to generate an output signal; a photoelectric conversion unit that converts the output signal into an electrical signal; 20. The method of operating a lidar system of claim 16, comprising:

18. the transceiver unit includes a focal plane array, the focal plane array being arranged in a 16x4 matrix; Each of the pixel groups includes four pixels connected in parallel in a column direction, 18. The method of claim 17, wherein pixels included in each pixel group arranged in a column direction and corresponding to the same order are connected to the same output channel terminal.

19. repeatedly operating the transmitter / receiver through a circuitry, the number of stages being equal to the number of pixels included in the focal plane array; calculating, via the circuit unit, a distance and / or a velocity of the target object based on a value of the electrical signal, the value being equal to the number of pixels included in the focal plane array multiplied by the number of pixels included in the pixel group during the one cycle; 20. The method of operating a lidar system of claim 18, further comprising:

20. Among the pixel groups, a first pixel group includes a first pixel, a second pixel, a third pixel, and a fourth pixel, and the first pixel, the second pixel, the third pixel, and the fourth pixel are simultaneously turned on; In a first stage, the first pixel provides a received signal corresponding to a transmission signal having a wavelength of λ1 to a first channel terminal, the second pixel provides a received signal corresponding to a transmission signal having a wavelength of λ2 to a second channel terminal, the third pixel provides a received signal corresponding to a transmission signal having a wavelength of λ3 to a third channel terminal, and the fourth pixel provides a received signal corresponding to a transmission signal having a wavelength of λ4 to a fourth channel terminal; In a second stage, the first pixel provides a received signal corresponding to a transmission signal having a wavelength of λ2 to a first channel terminal, the second pixel provides a received signal corresponding to a transmission signal having a wavelength of λ3 to a second channel terminal, the third pixel provides a received signal corresponding to a transmission signal having a wavelength of λ4 to a third channel terminal, and the fourth pixel provides a received signal corresponding to a transmission signal having a wavelength of λ1 to a fourth channel terminal; In a third stage, the first pixel provides a received signal corresponding to a transmission signal having a wavelength of λ3 to a first channel terminal, the second pixel provides a received signal corresponding to a transmission signal having a wavelength of λ4 to a second channel terminal, the third pixel provides a received signal corresponding to a transmission signal having a wavelength of λ1 to a third channel terminal, and the fourth pixel provides a received signal corresponding to a transmission signal having a wavelength of λ2 to a fourth channel terminal; 19. The method of claim 18, wherein, in a fourth stage, the first pixel provides a received signal corresponding to a transmission signal having a wavelength of λ4 to a first channel terminal, the second pixel provides a received signal corresponding to a transmission signal having a wavelength of λ1 to a second channel terminal, the third pixel provides a received signal corresponding to a transmission signal having a wavelength of λ2 to a third channel terminal, and the fourth pixel provides a received signal corresponding to a transmission signal having a wavelength of λ3 to a fourth channel terminal.

Images