LiDAR device and method of operating the same

Abstract

A light detection and ranging (LiDAR) device can include an optical phased array configured to modulate a phase of light incident on the optical phased array and emit the light, a first photodetector configured to detect light emitted from the optical phased array in a first direction toward the first photodetector as reference light and generate a reference signal based on the reference light, a second photodetector configured to detect light emitted from the optical phased array in a second direction toward a target as target light including information about the object and generate a target signal based on the target light, and a processor configured to determine a distance between the LiDAR device and the object based on a cross-correlation between the reference signal and the target signal.

Description

[0001] Cross Reference to Related Applications

[0002] This application claims priority to Korean Patent Application No. 10-2019-0101870, filed on August 20, 2019, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. TECHNICAL FIELD

[0003] Apparatuses and methods consistent with example embodiments relate to a light detection and ranging (LiDAR) device and an operating method thereof. BACKGROUND

[0004] Light detection and ranging (LiDAR) devices are being used in various fields, for example, aerospace, geology, 3D mapping, vehicles, robots, or drones. The basic operating principle of the LiDAR device is the time of flight (ToF) of light. For example, the LiDAR device can emit light toward an object and receive the light through a sensor, thereby measuring the ToF by using a high-speed circuit. Further, the LiDAR device can calculate a distance to the object based on the ToF and generate a depth image of the object using the distance calculated for each position of the object.

[0005] In order for the LiDAR device to accurately process a depth image even in an environment in which there is noise or a target signal is a small signal, a technology that precisely measures the ToF of light can be required. SUMMARY

[0006] Example embodiments address at least the problems and / or disadvantages described above and / or other disadvantages not described above. Also, the example embodiments do not require overcoming of the above disadvantages and can not solve any one of the above problems.

[0007] One or more example embodiments provide a light detection and ranging (LiDAR) device and an operating method thereof, which uses light emitted from an optical phased array as reference light.

[0008] According to an aspect of an embodiment, there is provided a light detection and ranging (LiDAR) device including: an optical phased array configured to modulate a phase of light incident on the optical phased array and emit light; a first photodetector configured to detect light emitted from the optical phased array in a first direction toward the first photodetector as reference light, and generate a reference signal based on the reference light; a second photodetector configured to detect light emitted from the optical phased array in a second direction toward an object as target light including information about the object, and generate a target signal based on the target light; and a processor configured to determine a distance between the LiDAR device and the object based on a cross-correlation between the reference signal and the target signal.

[0009] The LiDAR device can further include a substrate on which at least a portion of the optical phased array and the first photodetector are disposed.

[0010] The optical phased array and the first photodetector can be disposed on a same surface of the substrate.

[0011] The LiDAR device can further include a waveguide configured to receive the reference light from the optical phased array and output the reference light to the first photodetector.

[0012] The waveguide can include a region in which a width decreases from the optical phased array toward the first photodetector.

[0013] The waveguide can include: an input coupler configured to allow the reference light received from the optical phased array to be coupled to the waveguide; and an output coupler configured to output the reference light passing through the waveguide to the first photodetector.

[0014] The input coupler can include a plurality of sub-input couplers disposed to correspond to respective antennas of the optical phased array.

[0015] The waveguide can be disposed on a substrate on which at least a portion of the optical phased array is disposed.

[0016] The waveguide can include an optical fiber.

[0017] The optical fiber can be bonded to a substrate on which at least a portion of the optical phased array is disposed.

[0018] The optical phased array can include a light splitter configured to divide light incident on the optical phased array into a plurality of sub-lights, a phase modulation array configured to modulate a phase of each of the plurality of sub-lights, and an antenna array configured to emit the plurality of sub-lights modulated by the phase modulation array.

[0019] The optical phased array can include an electrode layer, an active layer disposed on the electrode layer, an insulating layer disposed on the active layer, and an antenna layer disposed on the insulating layer, wherein the active layer can be disposed between the electrode layer and the antenna layer, and the active layer is configured to have a resonance characteristic that varies according to a voltage applied between the electrode layer and the antenna layer.

[0020] The processor can determine the distance between the LiDAR device and the object based on a time difference between a first point in time at which the reference signal is detected and a second point in time at which a cross-correlation function value indicating a cross-correlation between the reference signal and the target signal is greater than or equal to a reference value.

[0021] The reference value can be a maximum value of the cross-correlation function value.

[0022] When the target signal is f(t) and the reference signal is g(t), the cross-correlation function can be determined by a mathematical expression .

[0023] The LiDAR device can further include an analog-to-digital converter (ADC) configured to quantize each of the reference signal and the target signal.

[0024] The processor can be configured to convert the reference signal and the target signal into unipolar signals based on absolute values of at least one of the reference signal and the target signal.

[0025] According to another aspect of an embodiment, there is provided an operating method of a light detection and ranging (LiDAR) device, including: emitting light phase-modulated by an optical phased array; detecting, by a photodetector, light emitted from the optical phased array in a first direction toward the photodetector as reference light; detecting, by the photodetector, light emitted from the optical phased array in a second direction toward an object as target light including information about the object; generating a reference signal based on the reference light and a target signal based on the target light; and determining a distance between the optical phased array and the object based on a cross-correlation between the reference signal and the target signal.

[0026] The operation method can further include transmitting the reference light to the photodetector by using a waveguide.

[0027] Determining the distance includes determining the distance between the LiDAR device and the object based on a time difference between a first time point at which the reference signal is detected and a second time point at which a cross-correlation function value indicating a cross-correlation between the reference signal and the target signal is greater than or equal to a reference value.

[0028] The reference value can be a maximum value of the cross-correlation function value.

[0029] The operation method can further include quantizing each of the reference signal and the target signal.

[0030] The operation method can further include converting the reference signal and the target signal into unipolar signals based on an absolute value of at least one of the reference signal and the target signal.

[0031] According to an aspect of another example embodiment, there is provided a distance sensing device including: a light emitter configured to emit light in a first direction toward an object and in a second direction different from the first direction; a light receiver configured to detect light emitted to the object and reflected from the object as an analog target signal, and to directly detect light emitted in the second direction from the light emitter as an analog reference signal; an analog-to-digital converter (ADC) configured to convert the analog target signal and the analog reference signal into a digital target signal and a digital reference signal, respectively; and a processor configured to determine a distance between the distance sensing device and the object based on information of a time point at which a cross-correlation between the digital target signal and the digital reference signal is maximized. BRIEF DESCRIPTION OF DRAWINGS

[0032] Certain example embodiments will be described with reference to the accompanying drawings, in which:

[0033] Figure 1 is a schematic block diagram of a configuration of a LiDAR device according to an example embodiment;

[0034] Figure 2 is a conceptual diagram of an optical phased array according to an example embodiment;

[0035] Figure 3 is a reference diagram illustrating a relationship between a cross-correlation between a reference signal and a target signal and ToF according to an example embodiment;

[0036] Figure 4 is a block diagram of a LiDAR device according to another example embodiment;

[0037] Figure 5A is a graph showing simulation results regarding a reference signal and a target signal output from an analog-to-digital converter according to an example embodiment;

[0038] Figure 5B is a graph showing results of applying a cross-correlation function to an output signal of Figure 5A ;

[0039] Figure 6 is a graph showing simulation results when calculating a ToF of light using an ADC and a time-to-digital counter (TDC);

[0040] Figure 7 is a flowchart of an operating method of a LiDAR device using reference light according to an example embodiment;

[0041] Figure 8 is a block diagram of another example of a LiDAR device according to another example embodiment;

[0042] Figure 9 is a perspective view of an arrangement relationship between a first photodetector and an optical phased array according to an example embodiment;

[0043] Figure 10 is a perspective view of an arrangement relationship between a first photodetector and an optical phased array according to another example embodiment;

[0044] Figure 11 is a perspective view of an arrangement relationship between a first photodetector and an optical phased array according to another example embodiment;

[0045] Figure 12 is a reference diagram for describing a method of connecting a first photodetector and an optical phased array by using an optical fiber according to an example embodiment;

[0046] Figure 13 is a schematic perspective view of an optical phased array according to another example embodiment; and

[0047] Figure 14 is a cross-sectional view of an antenna resonator of the optical phased array of Figure 13 ; DETAILED DESCRIPTION

[0048] Example embodiments are described in greater detail below with reference to the accompanying drawings.

[0049] In the following description, like reference numerals are used to refer to like elements throughout the several views. The contents defined in the description (e.g., detailed construction and elements) are provided to help the overall understanding of the example embodiments. However, it is clear that the example embodiments can be practiced without the specific details given in these specific definitions. In addition, well-known functions or constructions are not described in detail since they would obscure the description with unnecessary detail.

[0050] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. Expressions such as "at least one of," when preceding the list of elements, modify the entire list of elements and do not modify the elements individually. For example, the expression "at least one of a, b, and c" should be understood as including only a, only b, only c, both a and b, both a and c, both b and c, or all of a, b, and c, or any variations of the above examples.

[0051] The terms used in the disclosure have been selected considering the functions in the disclosure from among the general terms widely used at present. However, the terms can vary according to the intention of those of ordinary skill in the art, the precedents, or the emergence of new technologies. Also, for special cases, the meanings of the terms selected by the applicant are described in detail in the description section. Therefore, the terms used in the disclosure are defined based on their meanings with respect to the content discussed in the entire specification, not based on their simple meanings.

[0052] In this specification, when a constituent element "connects" or "is connected" to another constituent element, the constituent element not only directly contacts or connects to the other constituent element, but also electrically contacts or connects to the other constituent element through at least one of other constituent elements interposed therebetween. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. In addition, it will be understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features or components, but do not preclude the presence or addition of one or more other features or components.

[0053] In addition, terms such as "include" or "comprise" can not be interpreted as necessarily including all the constituent elements or operations set forth in the specification. However, these terms can not be interpreted as excluding another constituent element or operation, but can be interpreted as further including other constituent elements or operations.

[0054] However, the following description is not intended to limit the scope of the present disclosure, and the present disclosure should be interpreted to embrace all embodiments that would be readily ascertained by those of ordinary skill in the art. Hereinafter, the present disclosure will be described in detail by explaining preferred embodiments of the present disclosure with reference to the attached drawings.

[0055] Figure 1 is a schematic block diagram of a configuration of a LiDAR device 10 according to an example embodiment.

[0056] Referring to Figure 1 , the LiDAR device 10 can include a light transmitter (or light emitter) 110, a light receiver 130, and a processor 150. The light transmitter 110 can transmit light Lm in a direction toward an object OBJ by modulating a phase of the light Lm. The light receiver 130 can receive a portion of the light Lm emitted from the light transmitter 110 as reference light Lmr, and receive light (i.e., light including information about the object OBJ) reflected from the object OBJ as target light Lmo. Alternatively, the light transmitter 110 can transmit the same light Lm in two different directions (a direction toward the object OBJ and a direction toward the light receiver 130), wherein the light Lm transmitted from the light transmitter 110 to the light receiver 130 is referred to as the reference light Lmr. The processor 150 can determine a distance between the light transmitter 110 and the object OBJ by using an electrical signal corresponding to the reference light Lmr (hereinafter, referred to as a "reference signal") and an electrical signal corresponding to the target light Lmo (hereinafter, referred to as a "target signal).

[0057] The light transmitter 110 can include a light source 112 for emitting light, an optical phased array (OPA) 114 for emitting light by modulating a phase of light emitted from the light source 112, and a light controller 116 for controlling the light source 112 and the optical phased array 114.

[0058] The light source 112 can radiate light in an infrared range. When light in the infrared range is used, mixing with natural light in a visible light range including sunlight can be prevented. However, the present disclosure is not limited thereto, and the light transmitter 110 can include a light source for radiating light of various wavebands, and can radiate light of a plurality of different wavebands. Furthermore, the light transmitter 110 can radiate pulsed light or continuous light.

[0059] The light source 112 can include, for example, a laser diode (LD), an edge emitting laser, a vertical cavity surface emitting laser (VCSEL), a distributed feedback laser, a light emitting diode (LED), or a super luminescent diode (SLD). However, the present disclosure is not limited thereto.

[0060] The optical phased array 114 can emit light modulated in a specific direction by modulating a phase of incident light.

[0061] Figure 2 is a conceptual diagram of an optical phased array 114 according to an example embodiment. As shown, the optical phased array 114 can include a light splitter 210 for splitting incident light into a plurality of sub-lights, an optical phase modulation array 220 for modulating a phase of each of the split sub-lights, and an antenna array 230 for emitting the phase-modulated sub-lights as modulated light. The light splitter 210, the optical phase modulation array 220, and the antenna array 230 are connected to each other through a waveguide 240. Figure 2

[0062] As described above, since the optical phased array 114 can adjust the direction of light without mechanical movement, precise and fast control can be performed. However, the optical phased array 114 can have a loss when the incident light passes through the optical phased array 114. In detail, as the incident light travels through the light splitter 210, the optical phase modulation array 220, the antenna array 230, and the waveguide 240, optical loss occurs. In general, the optical phased array 114 can lose about 10 db of output light compared to input light. The weak power of the light output from the optical phased array 114 can decrease the range of the distance measured by the light receiver 130 and the accuracy of the measured distance.

[0063] The light receiver 130 of the LiDAR device 10 according to an example embodiment can include a first photodetector 132 that receives light output from the optical phased array 114 of the light transmitter 110 as reference light Lmr and a second photodetector 134 that detects target light Lmo reflected from the object OBJ. The target light Lmo can include information about the object OBJ. The first photodetector 132 can output a reference (electrical) signal corresponding to the reference light Lmr, and the second photodetector 134 can output a target (electrical) signal corresponding to the target light Lmo.

[0064] The first photodetector 132 and the second photodetector 134 can be light receiving elements for converting light into an electrical signal. For example, the first photodetector 132 and the second photodetector 134 can include at least one of an avalanche photodiode (APD) or a single photon avalanche diode (SPAD), but the present disclosure is not limited thereto.

[0065] The processor 150 can determine a distance between the LiDAR device 10 and the object OBJ by using cross-correlation between a reference signal corresponding to the reference light Lmr and a target signal corresponding to the target light Lmo.

[0066] ​The reference signal is a detection result of light output from the optical phase modulation array 220, and the target signal is a detection result of light reflected from the object OBJ among the light output from the optical phase modulation array 220. The reference signal and the target signal can be identical to or extremely similar to each other. Thus, when a time point at which cross-correlation between the target signal and the reference signal increases is detected, a time at which light output from the light transmitter 110 is received by the light receiver 130 can be determined.

[0067] For example, the processor 150 can use a cross-correlation function between the target signal and the reference signal. The cross-correlation function is a function indicating a degree of cross-correlation between two functions, and thus the cross-correlation function between the target signal and the reference signal can output a value proportional to cross-correlation between the two signals. For example, assuming that the target signal is y(t) and the reference signal is x(t), the cross-correlation function (Rxy(t)) between the target signal and the reference signal can be calculated by Equation 1.

[0068] [Equation 1]

[0069]

[0070] Since the cross-correlation function is a result of a quantitative calculation of similarity between the target signal and the reference signal, when a time delay of the reference signal is as much as a ToF of light, a shape of the reference signal can be most similar to a shape of the target signal.

[0071] The processor 150 can determine, as a ToF of light, a time from a time point at which the reference signal is detected to a time point at which a value of the cross-correlation function between the reference signal and the target signal is greater than or equal to a reference value. For example, the reference value can be a preset value or a maximum value of the cross-correlation function.

[0072] Figure 3 is a reference graph illustrating a relationship between a cross-correlation between a reference signal and a target signal and a ToF according to an example embodiment.

[0073] As Figure 3 indicated, the first photodetector 132 can detect the reference light Lmr at a first time point and output a reference signal x(t), as indicated in (i) of Figure 3 . The second photodetector 134 can detect the target light Lmo at a second time point and output a target signal y(t), as indicated in (ii) of Figure 3 . The processor 150 can determine, as a ToF of light, a time from a time point at which the reference signal x(t) is detected to a time point at which a value of the cross-correlation function Rxy(t) is greater than or equal to a reference value, by applying the cross-correlation function Rxy(t) to the reference signal x(t) and the target signal y(t), as indicated in (iii) of Figure 3the cross-correlation function value of the cross-correlation function Rxy(t) is greater in magnitude than the target signal y(t) even when the target signal y(t) or the reference signal x(t) is weak. Thus, the processor 150 can easily determine the time point at which the cross-correlation function value is greater than or equal to the reference value.

[0074] Figure 4 is a block diagram of a LiDAR device 10a according to another example embodiment. Reference is made to Figure 1 and Figure 4 , Figure 4 The LiDAR device 10a can further include an analog-to-digital converter 136 for quantizing each of the reference signal and the target signal respectively output from the first photodetector 132 and the second photodetector 134. Alternatively, the LiDAR device 10 can further include a high-pass filter for removing an offset from the reference signal and the target signal, and an amplifier (AMP) for amplifying the reference signal and the target signal.

[0075] When the light receiver 130 includes the analog-to-digital converter 136, the processor 150 can receive the target signal (x k ) and the reference signal (y i+k ) quantized by the analog-to-digital converter 136, and obtain a cross-correlation function (R xyi ) between the target signal and the reference signal by using Equation 2.

[0076] [Equation 2]

[0077]

[0078] In detail, the processor 150 can use a sampling rate S of the analog-to-digital converter 136 and a time index i max at which a result of the calculation of the cross-correlation function is maximum to generate a ToF of light. For example, the processor 150 can determine 2i max / S as the ToF of light, and determine a distance between the optical phased array 114 and the object OBJ as 2ci max / S, where c is a speed of light.

[0079] Alternatively, the cross-correlation function Rxy(t) between the target signal y(t) and the reference signal x(t) can be generated by a fast Fourier transform. The fast Fourier transform can greatly reduce a computation amount for signal processing.

[0080] Figure 5A is a graph showing simulation results regarding the reference signal and the target signal output from the analog-to-digital converter 136 according to an example embodiment. Figure 5B is a graph showing a cross-correlation function Rxy(t) between a target signal y(t) and a reference signal x(t) according to an example embodiment. Figure 5AThe results of applying the cross-correlation function to the output signal of is shown in FIG. The modulation frequency used for the simulation was 100 kHz, and pulsed light with a duty cycle of approximately 50% was used. An analog-to-digital converter 136 with a bandwidth of approximately 1.5 GHz and a sampling rate of approximately 1.25 GHz was used.

[0081] like Figure 5A As shown, it can be seen that the target signal (i.e., the received signal) output from the analog-to-digital converter 136 has a slight time delay compared to the reference signal. It can be seen that a large peak range of the reference signal and the target signal is formed. Therefore, it can be expected that the time delay between the two signals may be inaccurately determined. Figure 5B As shown in FIG, as a result of applying the cross-correlation function to the target signal and the reference signal, it can be seen that the peak of the signal is sharp, and it can be expected that the accuracy of the time delay between the two signals is improved.

[0082] Figure 6 This figure shows simulation results when calculating the ToF of light using an ADC and a time digital counter (TDC). Using the ADC and the cross-correlation function to measure the distance to an object OBJ reveals that the distance to an object OBJ located 150 cm or more can be measured. In contrast, using the TDC reveals that the distance to an object OBJ located 150 cm or more has a distorted average value, and due to a large error range, it is difficult to measure the distance.

[0083] Since the reference signal is based on the light output from the optical transmitter 110, there is no need to consider the time it takes for the light to pass through the light source 112 and the optical phased array 114. When the modulation signal of the light controller 116 is used as the reference signal, temporal noise (e.g., jitter) that may be generated when the light is modulated by the light source 112 may be included in the cross-correlation function. However, since the reference signal according to the example embodiment uses the light output from the optical transmitter 110, temporal noise or jitter is removed. Therefore, the measurement accuracy of the light ToF can be further improved.

[0084] Furthermore, even when the intensity of light output from the optical transmitter 110 and the intensity of light detected by the optical receiver 130 are weak, the distance measurement accuracy can be improved by employing the cross-correlation function because the reference light Lmr and the target light Lmo have similar characteristics.

[0085] When a negative value is included in a signal value indicating a target signal or a reference signal due to noise or oscillation, an amplification effect produced by a cross-correlation function calculation can be reduced. To prevent a reduction in the amplification effect produced by the cross-correlation function calculation due to noise or oscillation, the processor 150 can convert each of the target signal and the reference signal into a unipolar signal. In contrast to a bipolar signal, a unipolar signal can represent a signal in which a signal value has any one of a negative polarity and a positive polarity.

[0086] The processor 150 can convert the reference signal and the target signal into a unipolar reference signal and a unipolar target signal, respectively, based on an absolute value of the reference signal and at least some of the target signal. Alternatively, the processor 150 can convert the target signal and the reference signal into unipolar signals by using a method other than the above-described method using an absolute value. For example, the processor 150 can convert the target signal and the reference signal into unipolar signals by using a method of replacing a signal value among signal values indicating a target signal or a reference signal, in which the value is less than a certain value, or by using a method of squaring a signal value indicating a target signal or a reference signal.

[0087] The processor 150 can calculate a cross-correlation function between the target signal converted into a unipolar signal and the reference signal, and determine a time point at which a calculated value of the cross-correlation function is greater than or equal to a reference value, for example, a time point at which a value of the cross-correlation function is a maximum value, thereby determining a time from a time point at which the reference signal is detected to a time point at which the value of the cross-correlation function is the maximum value as a ToF of light. A distance from the light transmitter 110 to the object OBJ can be determined by using the ToF and a speed of light.

[0088] In addition, according to another example embodiment, when there is no time point at which a calculated value of the cross-correlation function exceeds a preset threshold value, the processor 150 can control the light transmitter 110 to radiate a laser pulse toward the object OBJ a plurality of times, obtain a plurality of target signals from a laser pulse reflected from the object OBJ, and detect a ToF of the laser pulse by using the obtained target signals. The processor 150 can increase a total number including the target signals by a plurality of measurements, and perform noise cancellation by using a technique such as averaging. Accordingly, even in a noisy environment, a reception time point of a reflected laser pulse can be accurately detected.

[0089] Figure 7 is a flowchart of an operation method of the LiDAR device 10 using the reference light Lmr according to an example embodiment.

[0090] In operation S310, the light transmitter 110 can emit light. Under the control of the light controller 116, the light source 112 can provide light of a specific frequency to the optical phased array 114, and the optical phased array 114 can modulate the phase of the incident light and emit light in a specific direction under the control of the light controller 116. The light source 112 can include, for example, a laser diode (LD), an edge emitting laser, a vertical cavity surface emitting laser (VCSEL), a distributed feedback laser, a light emitting diode (LED), or a superluminescent diode (SLD). However, the present disclosure is not limited thereto.

[0091] The optical phased array 114 can include a light splitter 210 for dividing incident light into a plurality of sub-lights, a phase modulation array 220 for modulating the phase of each of the divided sub-lights, and an antenna array 230 for emitting light in a specific direction by emitting a plurality of phase-modulated sub-lights. The optical phased array 114 can include a nanostructure.

[0092] In operation S320, the light receiver 130 can detect light output from the optical phased array 114 as reference light Lmr, and can detect light reflected from the object OBJ among the light output from the optical phased array 114 as target light Lmo. For example, the first photodetector 132 can detect light output from the optical phased array 114 as reference light Lmr, and the second photodetector 134 can detect light reflected from the object OBJ as target light Lmo including information about the object OBJ. The first photodetector 132 and the second photodetector 134 can be different sensors from each other or can be one sensor. The first photodetector 132 and the second photodetector 134 can include at least one of an APD or an SPAD, but the present disclosure is not limited thereto.

[0093] In operation S330, the processor 150 can determine the distance between the optical phased array 114 and the object OBJ by using cross-correlation between the reference signal and the target signal corresponding to the target light Lmo. The processor 150 can determine the ToF of light as the time from the point in time at which the reference signal is detected to the point in time at which the value of the cross-correlation function between the reference signal and the target signal is greater than or equal to a reference value. The processor 150 can determine the distance between the LiDAR device 10 and the object OBJ by using the speed of light and the ToF of light.

[0094] The reference signal is a result of detecting light output from the optical phase modulation array 220, and the target signal is a result of detecting light reflected from the object OBJ among the light output from the optical phase modulation array 220. The reference signal and the target signal can have the same or very similar characteristics. Accordingly, even when the target signal or the reference signal is weak, the processor 150 can obtain a cross-correlation function value having a large amplitude by applying a cross-correlation function to the reference signal and the target signal. A time point at which the cross-correlation function value is greater than or equal to a reference value can be used to determine the ToF of the light. The light receiver 130 can use an analog-to-digital converter.

[0095] In addition, the processor 150 can convert each of the target signal and the reference signal into a unipolar signal to prevent a decrease in an amplification effect resulting from a cross-correlation function calculation due to noise or oscillation, determine the ToF of the light by applying a cross-correlation function to the unipolar reference signal and the unipolar target signal, and determine the distance between the LiDAR device 10 and the object OBJ by using the ToF of the light and the speed of light.

[0096] According to another example embodiment, when there is no time point at which a calculated value of the cross-correlation function is greater than or equal to a reference value, the processor 150 can control the light transmitter 110 to radiate a laser pulse toward the object OBJ a plurality of times, obtain a plurality of target signals from the laser pulse reflected from the object OBJ, and detect the ToF of the laser pulse by using the obtained target signals. The processor 150 can increase the total number of the target signals by a plurality of measurements, and can perform noise cancellation by using a technique such as averaging. Accordingly, even in a noisy environment, a time point at which a reflected laser pulse is received can be accurately detected.

[0097] The above-described operation method of the LiDAR device 10 can be recorded on a computer-readable recording medium on which one or more programs including instructions for executing the method are recorded. Examples of the computer-readable recording medium can include a magnetic medium such as a hard disk, a floppy disk, or a magnetic tape, an optical medium such as a CD-ROM or a DVD, a magneto-optical medium such as a floptical disk, and a hardware device specially configured to store and execute program commands, such as a ROM, a RAM, or a flash memory, specifically configured to store and execute program commands. Examples of the program commands can include not only machine codes created by a compiler but also high-level programming languages that can be executed by a computer using an interpreter.

[0098] Figure 8 is a block diagram of another example of a LiDAR device 10b according to another example embodiment.

[0099] In an example, the LiDAR device 10b may be a LiDAR system provided in an autonomous vehicle or a vehicle employing an advanced driver assistance system (ADAS). However, the present disclosure is not limited thereto, and the LiDAR device 10b may be applied to various fields, such as aerospace, geology, 3D mapping, robotics, or drones. The LiDAR device 10b may obtain information about a scene or landscape of an exposed environment by using a laser beam, and may form a 3D point cloud about the scene or landscape of the exposed environment based on the obtained information.

[0100] refer to Figure 8 , the LiDAR device 10b may include a light source 410 , a light scanner or light diffuser 420 , a first optical lens 430 , a second optical lens 440 , a photodetector 450 , a signal processor 460 , and a computing unit 470 . Figure 8 The light source 410, the light scanner or light diffuser 420 and the first optical lens 430 may be connected to Figure 1 Corresponding to the optical transmitter 110, Figure 8 The second optical lens 440 and the photodetector 450 can be connected with Figure 1 corresponds to the optical receiver 130, and Figure 8 The signal processor 460 and the calculation unit 470 can be used with Figure 1 The redundant description thereof is omitted.

[0101] The light source 410 may include multiple light sources and may radiate light for analyzing the position or shape of the object OBJ. The light source 410 may generate and radiate light of a specific wavelength, such as light of a wavelength band suitable for analyzing the position or shape of the object OBJ. The light source unit 410 may generate and radiate multiple lights having different wavelengths. In addition, the light source 410 may generate and radiate pulsed light or continuous light.

[0102] The light source 410 may radiate light toward the object OBJ under the control of the processor 150. For example, the processor 150 may set a radiation direction or radiation angle of light from each light source and control the light source 410 so that the light source radiates light according to each set radiation angle or radiation direction. The processor 150 that controls the overall operation of the LiDAR device 10b may be connected to the processor 150. Figure 1 Corresponding to the processor 150.

[0103] The light scanner or light diffuser 420 can aim light from the light source 410 to the object OBJ so that a spot light from the light source 410 scans the entire object OBJ by adjusting the aiming direction in time series. A scanning mirror or an optical phased array can be used as the light scanner or light diffuser 420. The aimed light from the light scanner or light diffuser 420 can be radiated toward the object OBJ through the first optical lens 430. The reflected light from the object OBJ can be received by the photodetector 450 through the second optical lens 440.

[0104] The first photodetector 132 can detect the aimed light from the light scanner or light diffuser 420 as the reference light Lmr. The second photodetector 134 can include a plurality of pixelated regions capable of respectively detecting the reflected light from the object OBJ according to positions. For example, the second photodetector 134 can include a detector array divided by a plurality of pixels. A light detection element can be disposed at each pixel. The light detection element, which is a sensor capable of sensing light, can include, for example, a light receiving element that generates an electrical signal from light energy. The light detection element can form a pixel divided according to a position in the detector array, and each pixel can detect the reflected light from the object OBJ according to a radiation angle of light from the light source 410.

[0105] The signal processor 460 and the computing unit 470 can calculate the ToF of light according to the reflected light detected by the photodetector 450. Since the reference Figure 1 A detailed method in which the signal processor 460 and the computing unit 470 calculate the ToF of light is described, and thus a redundant description thereof is omitted. The signal processor 460 and the computing unit 470 can calculate a distance to the object OBJ according to the ToF, and generate a depth image or a 3D point cloud regarding the object OBJ by using the distance calculated for each position of the object OBJ.

[0106] The first photodetector 132 detects light output from the light transmitter 110, and the first photodetector 132 can be disposed close to the light transmitter 110. For example, the first photodetector 132 can be disposed on a substrate on which the optical phased array 114 is disposed.

[0107] Figure 9 is a perspective view of an arrangement relationship between the first photodetector 132 and the optical phased array 114 according to an example embodiment. On the substrate 510, the optical phased array 114 can include one or more light splitters 210, a plurality of phase modulators 222, and a plurality of antennas 232. Figure 9 The phase modulator 222 of can correspond to Figure 2 The optical phase modulation array 220 of can correspond to Figure 9 The antenna 232 of can correspond to Figure 2The antenna array 230 corresponding to the optical phased array 114 can be disposed on the substrate 510. The input coupler 250, the optical splitter 210, the phase modulator 222, and the antenna 232 can be disposed on the substrate 510. The waveguide 240 can be disposed between two adjacent elements, i.e., between the input coupler 250 and the optical splitter 210, between the optical splitter 210 and the phase modulator 222, and between the phase modulator 222 and the antenna 232.

[0108] The optical splitter 210 can have, for example, a multi-mode interference (MMI) structure or various other structures. The phase modulator 222 can have a structure for electrically performing optical modulation, or have other structures, such as a structure for performing optical modulation by a magnetic method, a thermal method, or a mechanical method. In addition, the phase modulator 222 can employ various modulation methods, such as phase modulation or amplitude modulation. The phase modulator 222 can include a plurality of waveguides 240, and can perform optical modulation on light passing through the waveguides 240. The antenna 232 can include, for example, a plurality of waveguides 240, and can further include a grating structure formed on each waveguide 240. Detailed structures of the input coupler 250, the optical splitter 210, the phase modulator 222, and the antenna 232 are not limited to the above description, and can be changed in various ways.

[0109] At least one of the input coupler 250, the optical splitter 210, the phase modulator 222, or the antenna 232 can include at least one of a Group IV material (e.g., Si or Ge), a compound containing a Group IV material (e.g., SiGe), a Group III-V compound, an oxide, a nitride, or a polymer. At least two elements of the input coupler 250, the optical splitter 210, the phase modulator 222, or the antenna 232 can include different materials from each other, as necessary. When the substrate 510 includes silicon Si, or at least one of the input coupler 250, the optical splitter 210, the phase modulator 222, or the antenna 232 includes Si, the optical phased array 114 according to the present example embodiment can be implemented / manufactured by using technologies in the field of "silicon photonics". Silicon photonics technologies can be advantageous in terms of simplification of processes, as the technologies are used compatibly with a complementary metal-oxide semiconductor (CMOS) process.

[0110] Although the optical phased array 114 is illustrated as being disposed on the substrate 510, the present disclosure is not limited thereto. A portion of the optical phased array 114 can be disposed on the substrate 510.

[0111] The first photodetector 132 for detecting reference light can be disposed on the substrate 510 on which the optical phased array 114 is disposed. The first photodetector 132 can be disposed on the same surface of the substrate 510 as a surface on which the optical phased array 114 is disposed.

[0112] Figure 10 is a perspective view of an arrangement relationship between the first photodetector 132 and the optical phased array 114 according to another example embodiment. A waveguide 610 for receiving reference light that is a portion of light emitted from the antenna array 230 and outputting the received reference light to the first photodetector 132 can also be disposed on the substrate 510. An input coupler 612 for inputting the reference light received from the antenna array 230 to the waveguide 610 and an output coupler 614 for outputting the reference light passing through the waveguide 610 to the first photodetector 132 can be disposed on the waveguide 610. The first photodetector 132 can be disposed on the substrate 510 to face the antenna array 230. The shape of a cross section of the waveguide 610 can have a width that narrows from the input coupler 612 to the output coupler 614. Accordingly, the optical density of the reference light incident on the first photodetector 132 can be increased.

[0113] Figure 11 is a perspective view of an arrangement relationship between the first photodetector 132 and the optical phased array 114 according to another example embodiment. As Figure 11 indicated in , a plurality of sub waveguides 620 for receiving sub light output from each of the antennas 232 of the antenna array 230, an optical coupler 630 for coupling the plurality of sub light, and a waveguide 640 for transmitting the coupled light to the first photodetector 132 can be disposed on the substrate 510. Each of the sub waveguides 620 can include a sub input coupler 622 for receiving each of the sub light output from the antennas 232. The plurality of sub light coupled by the optical coupler 630 can be reference light.

[0114] As Figure 10 and Figure 11 indicated, since the waveguides 610, 620, and 640 for transmitting the reference light to the first photodetector 132 are disposed on the substrate 510, the position at which the first photodetector 132 is disposed can be freely determined. For example, the first photodetector 132 can be disposed on a surface of the substrate 510 other than a surface on which the optical phased array 114 is disposed, e.g., on a surface facing the surface on which the optical phased array 114 is disposed.

[0115] When a plurality of layers are deposited on the substrate 510, the waveguides 610 and 640 and / or the sub waveguides 620 shown in Figure 10 and Figure 11 may be integrally formed. However, the present disclosure is not limited thereto. The waveguides 610 and 640 can include optical fibers.

[0116] Figure 12is a reference diagram for describing a method of connecting the first photodetector 132 and the optical phased array 114 by using an optical fiber according to an example embodiment. One end of the optical fiber 650 can be bonded to the substrate 510 provided with the optical phased array 114, and the other end thereof can be disposed to face the first photodetector 132. For example, one end of the optical fiber 650 can be disposed to face the output coupler of the waveguide 640. The first photodetector 132 can be disposed on a different substrate from the substrate 510 provided with the optical phased array 114 by using the optical fiber 650.

[0117] Although the optical phased array 114 is described in Figure 9 to Figure 12 as a structure in which the optical splitter 210, the optical phase modulation array 220, and the antenna array 230 are separated from each other, the present disclosure is not limited thereto. The optical phase modulation array 220 and the antenna array 230 can be integrated, and can not include the optical splitter 210.

[0118] Figure 13 is a schematic perspective view of an optical phased array 114a according to another example embodiment. Referring to Figure 13 , the optical phased array 114a can include a plurality of antenna resonators 700 that operate independently of each other. The antenna resonator 700 can include an antenna layer 740 that extends very long in a first direction. A plurality of antenna layers 740 can be arranged at a certain interval in a second direction perpendicular to the first direction. In the above structure, the incident light Li is reflected and output as light Lm in a certain direction according to a combination of voltages applied to the antenna resonator 700. The plurality of antenna resonators can have a nano structure.

[0119] Figure 14 is a cross-sectional view of an antenna resonator of the optical phased array 114a of Figure 13 . Referring to Figure 14 , each of the antenna resonators 700 can include an electrode layer 710, an active layer 720 disposed on the electrode layer 710, an insulating layer 730 disposed on the active layer 720, and an antenna layer 740 having a nano size and disposed on the insulating layer 730. Although only one antenna layer 740 is illustrated for convenience of explanation, Figure 14 the optical phased array 114a including the antenna resonator 700 can include a plurality of antenna layers 740 arranged on the insulating layer 730 by being separated at regular intervals.

[0120] The electrode layer 710 can serve as a common electrode, and can include a material having an electrical conductivity. Also, the electrode layer 710 can include a material having reflectivity with respect to light emitted from the light source 112. For example, the electrode layer 710 can include copper (Cu), aluminum (Al), nickel (Ni), iron (Fe), cobalt (Co), zinc (Zn), titanium (Ti), ruthenium (Ru), rhodium (Rh), palladium (Pd), platinum (Pt), silver (Ag), osmium (Os), iridium (Ir), gold (Au), an alloy thereof, or a metal nanoparticle dispersed thin film such as Au and Ag. Also, the electrode layer 710 can include a carbon nanostructure or a conductive polymer material in addition to the metal.

[0121] The antenna layer 740 functioning as an antenna with respect to light can generate localized surface plasmon resonance with respect to light of a specific wavelength, and capture and release energy of the localized surface plasmon resonance. The localized surface plasmon resonance is a phenomenon in which a locally greatly increased electric field is generated on a metal surface according to collective vibration of free electrons in the metal when light is incident on the metal. The localized surface plasmon resonance can be generally generated on an interface between a metal and a nonmetal. To this end, the antenna layer 740 can include a metal material having excellent electrical conductivity, for example, Au, Ag, Cu, Al, or Pt. The size and shape of the antenna layer 740 can vary according to a wavelength of incident light. For example, the size of the antenna layer 740 can be smaller than a wavelength of light emitted from the light source 112. For example, when the operating wavelength is visible light or near-infrared light, the width or length of the antenna layer 740 can be about 400 nm or less. Also, the antenna layer 740 can have a simple rod shape, or various patterns such as a circular shape, an elliptical shape, or a cross shape.

[0122] The insulating layer 730 can electrically insulate the antenna layer 740 from the active layer 720 and the electrode layer 710. For example, the insulating layer 730 can include an oxide film such as HfO2, SiO2, Al2O3, TiO2, or ZrO, or a nitride film such as SiNx.

[0123] When the charge density in the active layer 720 is changed by an electric signal (e.g., an electric field formed between the electrode layer 710 and the antenna layer 740), the active layer 720 changes the resonance characteristics in the antenna layer 740. In other words, when a charge accumulation layer or a depletion layer can be generated in the active layer 720 by an electric field formed between the electrode layer 710 and the antenna layer 740, the resonance condition can be changed, and thus the phase of the reflected light can be changed. For example, the active layer 720 can include a crystal material such as potassium niobate (KTN), LiNbO3, or lead zirconate titanate (PZT), a ZnO-based oxide such as indium tin oxide (ITO), indium zinc oxide (IZO), aluminum zinc oxide (AZO), gallium zinc oxide (GZO), or gallium indium zinc oxide (GIZO), a transition metal nitride such as TiN, ZrN, HfN, or TaN, or a semiconductor material such as Si, a-Si, or a group III-V compound semiconductor.

[0124] In the optical phased array 114 having the above structure, the charge density in the active layer 720 can vary according to the intensity of the electric field between the electrode layer 710 and the antenna layer 740. When a common voltage is applied to the electrode layer 710, the distribution of the charge density in the active layer 720 can be changed according to the distribution of the voltage specifically applied to the plurality of antenna layers 740. The change in the charge density in the active layer 720 can change the resonance characteristics of the antenna layer 740, and the changed resonance characteristics can generate a phase shift of the light reflected from the antenna layer 740, thereby changing the phase of the reflected light. Thus, when the distribution of the phase change of the reflected light is determined according to the distribution of the voltage applied to the antenna layers 740 arranged close to each other, the traveling direction of the reflected light can be controlled by the voltage applied to the antenna layers 740. The optical phased array 114a can reflect the incident light by the above method to steer the light in a desired direction.

[0125] Although not limited thereto, the example embodiments can be implemented as computer readable codes on a computer readable recording medium. The computer readable recording medium is any data storage device that can store data which can be thereafter read by a computer system. Examples of the computer readable recording medium include read-only memory (ROM), random-access memory (RAM), CD-ROMs, magnetic tapes, floppy disks, and optical data storage devices. The computer readable recording medium can also be distributed over networked computer systems so that the computer readable code is stored and executed in a distributed fashion. In addition, the example embodiments can be written as computer programs and can be implemented in general-use or special-purpose digital computers that execute the programs using a computer readable medium, such as a computer readable transmission medium (e.g., a carrier wave). Furthermore, it is understood that one or more units of the above-described apparatus and device can include circuitry, a processor, a microprocessor, etc., and can execute computer programs stored in a computer readable medium.

[0126] The above exemplary embodiments are merely examples and should not be construed as limiting. The present teachings can be readily applied to other types of apparatuses. Furthermore, the description of the exemplary embodiments is done in order to explain the present teachings and is not intended to restrict the scope of the claims. Those skilled in the art will readily understand various alternative, modified and equivalent arrangements.

Claims

1. A light detection and ranging (LiDAR) device, comprising: an optical phased array configured to modulate a phase of light incident on the optical phased array and emit phase-modulated light; a first photodetector configured to detect light emitted from the optical phased array in a first direction toward the first photodetector as reference light and generate a reference signal based on the reference light; a second photodetector configured to detect light emitted from the optical phased array in a second direction toward an object as target light including information about the object and generate a target signal based on the target light; and a processor configured to determine a distance between the LiDAR device and the object based on cross-correlation between the reference signal and the target signal, wherein the optical phased array includes a beam splitter, a phase modulation array, and an antenna array, wherein the first photodetector is connected to the antenna array of the optical phased array via a waveguide configured to receive the reference light as a part of light emitted from the antenna array and output the reference light to the first photodetector, and wherein the beam splitter, the phase modulation array, the antenna array, the waveguide, and the first photodetector are disposed on a same surface of a same substrate. The waveguide includes a region in which a width decreases from the optical phased array toward the first photodetector.

2. The LiDAR device of claim 1, wherein, The waveguide includes:

3. The LiDAR device of claim 1, wherein, an input coupler configured to allow the reference light received from the optical phased array to be coupled with the waveguide; and an output coupler configured to output the reference light passing through the waveguide to the first photodetector. The input coupler includes a plurality of sub-input couplers disposed to correspond to respective antennas of the antenna array of the optical phased array.

4. The LiDAR device of claim 3, wherein, 5.The LiDAR device of claim 1, wherein: the beam splitter is configured to divide light incident on the optical phased array into a plurality of sub-lights; the phase modulation array is configured to modulate a phase of each of the plurality of sub-lights; and the antenna array is configured to emit the plurality of sub-lights modulated by the phase modulation array. The optical phased array includes:

6. The LiDAR device of claim 1, wherein, an electrode layer; an active layer disposed on the electrode layer; an insulating layer disposed on the active layer; and an antenna layer disposed on the insulating layer, wherein the active layer is disposed between the electrode layer and the antenna layer, and the active layer is configured to have a resonance characteristic that varies according to a voltage applied between the electrode layer and the antenna layer. The processor is configured to determine the distance between the LiDAR device and the object based on a time difference between a first time point at which the reference signal is detected and a second time point at which a cross-correlation function value indicative of cross-correlation between the reference signal and the target signal is greater than or equal to a reference value.

7. The LiDAR device of claim 1, wherein, The reference value is a maximum value of the cross-correlation function value.

8. The LiDAR device of claim 7, wherein, ​ 9. The LiDAR device of claim 8, wherein, When the target signal is f(t) and the reference signal is g(t), the cross-correlation function value is determined by the mathematical expression ​ 10. The LiDAR device of claim 1, further comprising an analog-to-digital converter (ADC) configured to quantize each of the reference signal and the target signal.

11. The LiDAR device of claim 1, wherein, The processor is configured to convert the reference signal and the target signal into a unipolar signal based on an absolute value of at least one of the reference signal and the target signal.

12. A method of operating a light detection and ranging (LiDAR) device, the method comprising: emitting, by an antenna array of an optical phased array, light that is phase-modulated by the optical phased array; detecting, by a first photodetector, light emitted from the optical phased array in a first direction toward the first photodetector as a reference light; detecting, by a second photodetector, light emitted from the optical phased array in a second direction toward an object as a target light that includes information about the object; generating a reference signal based on the reference light and a target signal based on the target light; and determining a distance between the optical phased array and the object based on a cross-correlation between the reference signal and the target signal, wherein the first photodetector is connected to the antenna array of the optical phased array via a waveguide configured to receive the reference light as part of the light emitted from the antenna array and output the reference light to the first photodetector, wherein the optical phased array further includes a light splitter and a phase modulation array, and wherein the light splitter, the phase modulation array, the antenna array, the waveguide, and the first photodetector are disposed on a same surface of a same substrate.

13. The method of operation of claim 12, wherein, Determining the distance includes determining a distance between the LiDAR device and the object based on a time difference between a first time point at which the reference signal is detected and a second time point at which a cross-correlation function value indicative of a cross-correlation between the reference signal and the target signal is greater than or equal to a reference value.

14. The method of operation of claim 13, wherein, The reference value is a maximum value of the cross-correlation function value.

15. The method of operation of claim 12, further comprising: quantizing each of the reference signal and the target signal.

16. The method of operation of claim 12, further comprising: converting the reference signal and the target signal into a unipolar signal based on an absolute value of at least one of the reference signal and the target signal.

17. A distance sensing device, comprising: an optical phased array configured to modulate a phase of light incident on the optical phased array and emit the phase-modulated light; a light receiver including a first photodetector configured to detect light emitted from the optical phased array in a first direction toward the first photodetector as an analog reference signal and a second photodetector configured to detect light emitted from the optical phased array in a second direction toward an object and reflected from the object as an analog target signal; an analog-to-digital converter (ADC) configured to convert the analog target signal and the analog reference signal into a digital target signal and a digital reference signal, respectively; and ​ a processor configured to determine a distance between the distance sensing device and the object based on information of a time point at which a cross-correlation between the digital target signal and the digital reference signal is maximized, wherein the optical phased array comprises a beamsplitter, a phase modulation array, and an antenna array, wherein the first photodetector is connected to the antenna array of the optical phased array via a waveguide configured to receive a portion of light emitted from the antenna array as reference light and output the reference light to the first photodetector, and wherein the beamsplitter, the phase modulation array, the antenna array, the waveguide, and the first photodetector are disposed on a same surface of a same substrate.

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