Method for controlling frequency of optical signal using OPLL, fmcw lidar to which control method is applied, and autonomous vehicle driving method using fmcw lidar to which control method is applied

Abstract

A method for controlling a frequency of an optical signal using an optical phased locked loop (OPLL), according to a first aspect of the present invention, comprises the steps of: separating an optical signal outputted from a laser diode into a Tx signal and an OPLL signal; separating the OPLL signal into an OPLL reference signal and an OPLL delay signal; and controlling a frequency of the optical signal outputted from the laser diode on the basis of a time difference at which the OPLL reference signal and the OPLL delay signal are received by a photo diode (PD).

Description

A method for controlling the frequency of an optical signal using OPLL, an FMCW lidar to which the control method is applied, and a vehicle autonomous driving method using an FMCW lidar to which the control method is applied.

[0001] The present invention relates to a method for controlling the frequency of an optical signal using an OPLL, an FMCW lidar to which the control method is applied, and an autonomous driving method for a vehicle using an FMCW lidar to which the control method is applied. This research was conducted with the support of the Korea Institute for Advancement of Technology (KIAT) with funds from the Ministry of Trade, Industry and Energy (Government) (Project Identification Number: 2410008035; Project Number: P0025240; Research and Development Project: International Joint Technology Development Project; Research Project Name: Multi-Channel (200,000 Channels) Parallel Processing Solid-State FMCW Technology-Based LiDAR for Vehicles; Project Period: January 1, 2024 - December 31, 2024).

[0002] For reference, this application claims priority to Korean Patent Application No. 10-2024-0091581, filed July 11, 2024. The entire contents of that application, which serves as the basis for this priority claim, are incorporated herein by reference.

[0003] LiDAR (light detection and ranging) is a sensor that transmits near-infrared light, visible light, and ultraviolet light to a target object, and detects the light that hits the target, reflects, and returns using an optical sensor to collect three-dimensional information (x, y, z) of the target object.

[0004] Typically, lidar uses light of a fixed frequency and can measure the time it takes for it to reflect back and the intensity of the light.

[0005] FMCW (frequency modulated continuous wave) lidar is similar to a general lidar that collects 3D information about the surrounding environment in terms of the way it transmits and receives light, but it differs from a general lidar in that it modulates the frequency of the light it transmits.

[0006] Since FMCW lidar emits light while rapidly changing its frequency, the emitted light can have a continuously changing frequency. When the emitted light hits an object or obstacle, some of the light may be reflected. The light reflected by the object or obstacle is collected by the FMCW lidar's receiver, and the receiver can measure this frequency difference by comparing the frequency of the transmitted light with the frequency of the reflected light. Here, the FMCW lidar can separately extract a certain percentage of the laser generated by the laser diode and use it as a reference signal to detect the frequency of the transmitted light.

[0007] FMCW lidar can obtain distance information by comparing the difference between the reference signal (left straight graph of Fig. 1(a)) and the Rx signal (right straight graph of Fig. 1(a)), as shown in Fig. 1(a). An ideal FMCW lidar can calculate one distance data at one distance because the slopes of the reference signal and the Rx signal corresponding to the reference signal are the same. When the slopes of the reference signal and the Rx signal corresponding to the reference signal are the same, it can be said that the reference signal and the Rx signal maintain linearity. When the reference signal and the Rx signal maintain linearity, one frequency data can be calculated by performing a fast Fourier transform on the Rx signal. Conversely, if the reference signal and the Rx signal do not maintain linearity, multiple frequency data can be calculated by performing a fast Fourier transform on the Rx signal.

[0008] Unlike ideal FMCW lidar, real-world FMCW lidar lacks linearity between the reference and Rx signals, resulting in multiple range data points being generated for a single distance. For example, measuring a single person or object through a point cloud can result in multiple people or objects being measured, or the frequency bandwidth can be widened, resulting in reduced resolution.

[0009] Fig. 1(a) shows the signal form of an ideal FMCW lidar, in which the reference signal and the Rx signal are in the form of parallel straight lines. In contrast, Fig. 1(b) shows the signal form of an actual FMCW lidar, in which the reference signal (left straight graph of Fig. 1(b)) and the Rx signal (right straight graph of Fig. 1(b)) are nonlinear. Due to such nonlinearity of the signal, the Fourier transformed signal may generate a wider frequency peak, which may deteriorate the accuracy and resolution of the FMCW lidar. Fig. 1(c) shows that ripples occur in the signal of the FMCW lidar. Due to the occurrence of such ripples, multiple distance data may be generated from a single distance.

[0010] For example, as shown in Fig. 2(a), an ideal FMCW lidar should produce one distance data corresponding to 3 MHz when the frequency difference between the transmission and reception signals is 3 MHz, but in actual measurement, as shown in Figs. 2(b) and 2(c), the bit signal is not linear, so when an actual FMCW lidar measures one distance data corresponding to a frequency difference between the transmission and reception signals of 3 MHz, various distance data corresponding to a frequency difference between the transmission and reception signals of 2 MHz to 4 MHz may be produced.

[0011] To improve the above-mentioned problems, an optical phased locked loop (OPLL) can be applied to FMCW lidar. Here, OPLL can refer to a system that controls and stabilizes the phase of an optical signal. However, since optical waveguides have the disadvantage of high loss per unit length, an OPLL can be configured by splicing long optical fibers. However, this method has the disadvantage of making the FMCW lidar system bulky. In addition, the bending radius of the optical fiber is in the order of mm, as shown in Figure 3, and the commonly used G652 type optical fiber has a bending radius of tens of mm, which limits the implementation of miniaturization of the optical module.

[0012] The present invention aims to provide a method for controlling the frequency of an optical signal using an OPLL, thereby resolving the aforementioned problems. Furthermore, the present invention provides a method for autonomous driving a vehicle using an FMCW lidar, to which the OPLL-based method for controlling the frequency of an optical signal is applied.

[0013] However, the problems to be solved by the present invention are not limited to those mentioned above, and other problems to be solved that are not mentioned can be clearly understood by a person having ordinary skill in the art to which the present invention pertains from the description below.

[0014] A method for controlling the frequency of an optical signal using an OPLL (optical phased locked loop) according to one embodiment of the first aspect of the present invention includes the steps of separating an optical signal output from a laser diode into a Tx signal and an OPLL signal, separating the OPLL signal into an OPLL reference signal and an OPLL delay signal, and controlling the frequency of the optical signal output from the laser diode based on a time difference at which the OPLL reference signal and the OPLL delay signal are received by a photodiode (PD).

[0015] In the step of separating into the Tx signal and the OPLL signal, the Tx signal and the OPLL signal can be separated using a micro lens array (MLA).

[0016] The frequency of the optical signal output from the above laser diode can be periodically increased or decreased.

[0017] The frequency of the optical signal output from the above laser diode can be continuously changed over time.

[0018] The step of separating the OPLL reference signal and the OPLL delay signal may include the step of propagating the OPLL reference signal through an OPLL reference line and the step of propagating the OPLL delay signal through an OPLL delay line.

[0019] The length of the above OPLL delay line can be configured to be longer than the length of the above OPLL reference line.

[0020] The step of controlling the frequency may include a step of predicting a theoretical frequency difference between the OPLL reference signal propagated through the OPLL reference line and the OPLL delay signal propagated through the OPLL delay line based on at least one of an internal refractive index and a length of the OPLL delay line.

[0021] The step of controlling the frequency may include the step of measuring an actual frequency difference between the OPLL reference signal propagated through the OPLL reference line and the OPLL delay signal propagated through the OPLL delay line.

[0022] In the step of controlling the frequency, the frequency of the optical signal output from the laser diode can be controlled by changing the voltage applied to the laser diode in a direction that reduces the error between the theoretical frequency difference and the actual frequency difference.

[0023] The method may further include a step of separating the Tx signal into a Tx transmission signal and a Tx reference signal.

[0024] The method may further include a step of receiving a signal reflected from an object by the Tx transmission signal and a step of estimating at least one of position information and relative velocity of the object based on the Tx reference signal and the reflected signal.

[0025] A vehicle autonomous driving method using an FMCW lidar with an OPLL applied according to another embodiment of the first aspect of the present invention includes the steps of transmitting a Tx signal from the FMCW lidar, receiving a signal reflected by an object from the transmitted signal as an Rx signal, obtaining information on the object based on the Tx signal and the Rx signal, and controlling the driving direction and speed of the vehicle based on the information on the object.

[0026] An FMCW lidar to which an OPLL is applied according to a second aspect of the present invention includes a light source for outputting an optical signal, a first beam splitter for separating the output optical signal into a Tx signal and an OPLL (optical phased locked loop) signal, a second beam splitter for separating the OPLL signal into an OPLL reference signal and an OPLL delay signal, a photodiode (PD) for receiving the OPLL reference signal and the OPLL delay signal, a memory capable of storing computer-executable instructions, and a processor for controlling a frequency of an optical signal output from the laser diode based on a time difference at which the OPLL reference signal and the OPLL delay signal are received by the photodiode by executing the instructions.

[0027] The FMCW lidar to which the OPLL is applied can transmit a Tx signal, receive a signal reflected by an object from the transmitted signal as an Rx signal, obtain information on the object based on the Tx signal and the Rx signal, and provide information for controlling the driving direction and speed of the vehicle based on the information on the object.

[0028] A non-transitory computer-readable recording medium storing computer-executable instructions according to a third aspect of the present invention, wherein the computer-executable instructions, when executed by a processor, cause the processor to perform a method including the steps of: separating an optical signal output from a laser diode into a Tx signal and an OPLL (optical phased locked loop) signal; separating the OPLL signal into an OPLL reference signal and an OPLL delay signal; and controlling a frequency of an optical signal output from the laser diode based on a time difference at which the OPLL reference signal and the OPLL delay signal are received by a photodiode (PD).

[0029] A computer program stored in a non-transitory computer-readable recording medium according to a fourth aspect of the present invention, wherein the computer program comprises instructions for causing the processor to perform a method, the method comprising the steps of: separating an optical signal output from a laser diode into a Tx signal and an OPLL (optical phased locked loop) signal; separating the OPLL signal into an OPLL reference signal and an OPLL delay signal; and controlling a frequency of an optical signal output from the laser diode based on a time difference at which the OPLL reference signal and the OPLL delay signal are received by a photodiode (PD).

[0030] According to the present invention, by applying an OPLL to an FMCW lidar, the linearity of data received from the photodiode can be maintained. Furthermore, by maintaining the linearity of the data, the resolution and measurement accuracy of the FMCW lidar can be improved.

[0031] Furthermore, by using a lens to separate the beam, the damage threshold of the optical waveguide caused by the laser can be increased. Furthermore, as the damage threshold of the optical waveguide is increased, an FMCW lidar with an OPLL that can be implemented on a single chip can be provided.

[0032] The effects that can be obtained from the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by a person having ordinary skill in the art to which the present disclosure pertains from the description below.

[0033] Figure 1 is a graph showing the signal shape of an ideal FMCW lidar and the signal shape of an actual FMCW lidar.

[0034] Figure 2 is an example diagram conceptually showing the signal shape of an ideal FMCW lidar and the signal shape of an actual FMCW lidar.

[0035] Figure 3 is an example diagram showing the bending radius of an optical fiber.

[0036] Figure 4 is a graph showing the signal forms of the Tx, Rx, and beat signals of the FMCW lidar.

[0037] Figure 5 shows the results of measuring the chirp shape of an optical signal output from a laser diode and the shape of an optical signal received from a photodiode (PD).

[0038] Figure 6 is an example diagram showing the separation of an optical signal by attaching a micro lens array (MLA) to a laser diode.

[0039] Figure 7 is an example diagram showing that optical signals separated according to Figure 6 proceed along different paths.

[0040] Figure 8 is an exemplary diagram showing an optical system to which OPLL is applied according to the present invention.

[0041] FIG. 9 is an exemplary diagram showing a specific configuration of an OPLL to which a single-channel reference optical waveguide is applied according to the present invention.

[0042] FIG. 10 is an example diagram showing that the frequency is maintained without fluctuation as a result of performing a fast Fourier transform (FFT) on data received from an OPLL photodiode according to the present invention.

[0043] FIG. 11 is a flowchart exemplarily showing a method for controlling the frequency of an optical signal using an OPLL according to the first aspect of the present invention.

[0044] Fig. 12 is a block diagram exemplarily showing an FMCW lidar to which an OPLL is applied according to the second aspect of the present invention.

[0045] Fig. 13 is a block diagram exemplifying the function of a frequency control program for an optical signal using OPLL.

[0046] The advantages and features of the present invention, and the methods for achieving them, will become clearer with reference to the embodiments described in detail below together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various different forms. These embodiments are provided solely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined solely by the scope of the claims.

[0047] When describing embodiments of the present invention, detailed descriptions of known functions or configurations will be omitted if they are deemed to unnecessarily obscure the gist of the invention. Furthermore, the terms described below are defined in light of their functions in the embodiments of the present invention and may vary depending on the intent or custom of the user or operator. Therefore, their definitions should be based on the overall content of this specification.

[0048] The terms used in this specification will be briefly explained, and the present invention will be described in detail.

[0049] The terms used in this specification have been selected from widely used, current terms, taking into account the functions of the present invention. However, these terms may vary depending on the intentions of those skilled in the art, precedents, the emergence of new technologies, etc. Furthermore, in certain cases, terms may be arbitrarily selected by the applicant, in which case their meanings will be described in detail in the relevant description of the invention. Therefore, the terms used in this invention should not be defined simply as names, but rather based on their inherent meanings and the overall content of the present invention.

[0050] When a part of a specification is said to 'include' a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise stated.

[0051] Also, the term 'part' used in the specification means a software or hardware component such as an FPGA or ASIC, and the 'part' performs certain functions. However, the 'part' is not limited to software or hardware. The 'part' may be configured to reside on an addressable storage medium or may be configured to play one or more processors. Thus, as an example, the 'part' includes components such as software components, object-oriented software components, class components, and task components, as well as processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables. The functionality provided within the components and 'parts' may be combined into a smaller number of components and 'parts' or further separated into additional components and 'parts'.

[0052] Below, with reference to the attached drawings, an embodiment of the present invention is described in detail so that a person having ordinary skill in the art to which the present invention pertains can easily practice it.

[0053] In this specification, a laser diode (LD) may be referred to as LD, and a photo diode (PD) may be referred to as PD.

[0054] Figure 4 is a graph showing the signal forms of the Tx, Rx, and beat signals of the FMCW lidar.

[0055] FMCW lidar can use a certain percentage of the generated lasers as Tx, and extract the remaining percentage as a reference signal. At this time, wavelength division techniques can be used to obtain interference signals based on the laser wavelength. Here, Tx can refer to a transmission signal for object detection, and Rx can refer to a reception signal reflected from the object.

[0056] FMCW lidar can change the refractive index of a laser resonator by varying the voltage. Changing the refractive index of the laser resonator alters the wavelength of the resonating light, modulating the frequency of the output optical signal. However, the actual refractive index can change nonlinearly due to factors such as the Kerr effect and the Pockels effect.

[0057] A beat signal is a signal generated by the frequency difference between a transmitted signal and a received signal, and can be generated by combining the transmitted and received signals. The frequency of the beat signal can be determined as follows.

[0058]

[0059] Here, f b is the frequency of the beat signal, c is the speed of light, R is the distance between the FMCW lidar and the object, B is the frequency sweep or chirp bandwidth, and T is the period of the frequency sweep or the period of the chirp. Using Equation 1, the distance between the FMCW lidar and the object can be determined from the frequency difference between the transmitted and received signals.

[0060] Since the present invention is based on an FMCW lidar, the frequency of an optical signal output from a laser diode can linearly increase or decrease over time. In addition, an OPLL delayed signal propagated through an OPLL delay line can be received with a delay compared to an OPLL reference signal at the OPLL photodiode, and since the frequency of the optical signal changes in real time over time, the frequencies of the OPLL reference signal and the OPLL delayed signal received at the OPLL photodiode at the same time can be different. In addition, the frequency of a beat signal can be calculated according to mathematical expression 1 based on the frequency difference between the signal propagated through the OPLL reference line and the signal propagated through the OPLL delay line. At this time, the frequency difference between the signal propagated through the OPLL reference line and the signal propagated through the OPLL delay line can be calculated based on the internal refractive index of the OPLL delay line and the length of the OPLL delay line. Therefore, an FMCW lidar with an OPLL applied can control the frequency of an optical signal output from a laser diode based on the internal refractive index of the OPLL delay line and the length of the OPLL delay line.

[0061] When the Tx signal and the Rx signal are in the form of parallel straight lines as in Fig. 2(a), the beat signal generated by combining the Tx signal and the Rx signal can be measured in the form of a sine wave having a single frequency as shown in Fig. 4. In addition, the beat signal can be measured through an interferometer that directly inputs an optical signal from the LD to the PD. That is, by applying a delay line to the optical fiber through which the optical signal propagates, it is possible to confirm whether the calculated frequency and the actually measured frequency match.

[0062] Figure 5 shows the results of measuring the chirp shape of an optical signal output from a laser diode and the shape of an optical signal received from a photodiode (PD).

[0063] As shown in Fig. 5, if we zoom in on a portion of a single chirp output from the laser diode, we can see that the beat signal received by the photodiode is in the form of a sine wave, i.e., has a single frequency. Accordingly, we can confirm that the laser diode is operating in FMCW mode and that the photodiode is properly receiving the signal. In other words, we can confirm that the frequency calculated using the above-described method matches the actually measured frequency.

[0064] Figure 6 is an example diagram showing the separation of an optical signal by attaching a micro lens array (MLA) to a laser diode.

[0065] As shown in Fig. 6, by connecting a microlens array to a laser diode, the optical signal output from the laser diode can be immediately separated. Accordingly, the optical signal output from the laser diode can be initially incident and propagated along a different path along the optical waveguide. At this time, the frequency of the optical signal can be periodically increased or decreased. In other words, frequency modulation of the optical signal can be performed in real time.

[0066] Figure 7 is an example diagram showing that optical signals separated according to Figure 6 proceed along different paths.

[0067] In one embodiment, the optical signals separated according to FIG. 6 can be propagated along different paths along the optical waveguide from the beginning, as shown in FIG. 7. In this case, one optical signal of FIG. 7 can be used as an OPLL signal, and the remaining optical signals can be used as Tx signals.

[0068] In another embodiment, since the larger the diameter of the optical waveguide, the higher the damage threshold of the optical waveguide, when the diameter of the optical waveguide is greater than a predetermined value, the optical signal output from the laser diode may first be incident on the optical waveguide, and then the optical signal may be separated within the optical waveguide.

[0069] Figure 8 is an exemplary diagram showing an optical system to which OPLL is applied according to the present invention.

[0070] An optical system using an OPLL may include a splitter for separating an optical signal, a Tx line, an optical system, an OPLL line, and an OPLL photodiode. In this case, the splitter directly connected to the laser diode may be replaced with a lens. The OPLL line may include an OPLL reference line and an OPLL delay line. The OPLL photodiode may receive an optical signal propagated through the OPLL reference line and an optical signal propagated through the OPLL delay line, respectively.

[0071] Figure 9 is an exemplary diagram showing a specific configuration of an OPLL to which a single-channel reference optical waveguide is applied according to the present invention. For convenience of explanation, Figure 9 assumes a single channel, but is not limited thereto.

[0072] First, the optical signal output from the laser diode can be separated into a Tx signal (901) and an OPLL signal (902) through a lens or a splitter. The intensity ratio of the separated Tx signal (901) and OPLL signal (902) can be predetermined. Thereafter, the Tx signal (901) propagated through the optical waveguide can be separated into a Tx transmission signal (903) and a Tx reference signal (904) through a splitter. At this time, the Tx reference signal (904) can be propagated through a delay line. The Tx transmission signal (903) can be transmitted to the outside of the FMCW lidar through a circulator and a quarter wave plate. The Tx transmission signal transmitted to the outside can be reflected by an object and received as an Rx signal (905) through the quarter wave plate and the circulator.

[0073] A Tx reference signal (904) and an Rx signal (905) can be combined to generate a beat signal. At this time, since the optical signal output from the laser diode can increase and decrease periodically, the frequencies (905) of the Tx reference signal (904) and the Rx signal can be different from each other. By analyzing the generated beat signal, the distance between the FMCW lidar and the object, the relative speed of the object, etc. can be calculated.

[0074] Meanwhile, some optical signals among the OPLL signals (902) may be propagated through the OPLL delay line, and the remaining optical signals may be propagated through the OPLL reference line. Here, the length of the OPLL delay line may be configured to be longer than the length of the OPLL reference line. The OPLL delayed signal (906) propagated through the OPLL delay line may be received with a delay compared to the OPLL reference signal (907) at the OPLL photodiode. Since the frequency of the optical signal changes over time in real time, the frequencies of the OPLL reference signal (907) and the OPLL delayed signal (906) received at the OPLL photodiode at the same time may be different. In addition, the frequency of the beat signal may be calculated (908) according to mathematical expression 1 based on the frequency difference between the signal (907) propagated through the OPLL reference line and the signal (906) propagated through the OPLL delay line. At this time, the frequency difference between the signal (907) propagated through the OPLL reference line and the signal (906) propagated through the OPLL delay line can be calculated according to the internal refractive index of the OPLL delay line and the length of the OPLL delay line (908). Therefore, since the frequency difference between the signal (907) propagated through the OPLL reference line and the signal (906) propagated through the OPLL delay line is the frequency of the beat signal, the error between the frequency of the calculated beat signal and the frequency of the beat signal actually received from the OPLL photodiode can be calculated (908). Accordingly, the FMCW lidar to which the OPLL is applied can control the frequency of the optical signal output from the laser diode by changing the voltage applied to the laser diode based on the error between the frequency of the calculated beat signal and the frequency of the beat signal actually received from the OPLL photodiode (908).

[0075] FIG. 10 is an example diagram showing that the frequency is maintained without fluctuation as a result of performing a fast Fourier transform (FFT) on data received from an OPLL photodiode according to the present invention.

[0076] Referring to FIG. 10, when the frequency is controlled according to the frequency control method of the optical signal using the OPLL of the present invention, it can be seen that the frequency of 2.5 MHz of the bit signal calculated through calculation is actually measured, and the frequency is maintained stably without fluctuation.

[0077] Fig. 11 is a flowchart exemplarily showing a method for controlling the frequency of an optical signal using an OPLL according to the first aspect of the present invention. Hereinafter, the method for controlling the frequency of an optical signal using an OPLL will be described on the assumption that it is performed by an FMCW lidar to which an OPLL is applied.

[0078] As shown in FIG. 11, a method for controlling the frequency of an optical signal using an OPLL according to the first aspect of the present invention includes a step (S1110) of separating an optical signal output from a laser diode into a Tx signal and an OPLL (optical phased locked loop) signal, a step (S1120) of separating the OPLL signal into an OPLL reference signal and an OPLL delay signal, and a step (S1130) of controlling the frequency of the optical signal output from the laser diode based on a time difference at which the OPLL reference signal and the OPLL delay signal are received by a photodiode (PD).

[0079] Fig. 12 is a block diagram exemplarily showing an FMCW lidar to which an OPLL is applied according to the second aspect of the present invention.

[0080] As shown in Fig. 12, the FMCW lidar (1200) to which OPLL is applied may include an input unit (1210), an output unit (1220), a processor (1230), a memory (1240), and a communication unit (1260).

[0081] Hereinafter, for the convenience of explanation, an example is provided in which an FMCW lidar (1200) to which OPLL is applied includes an input unit (1210), an output unit (1220), a processor (1230), a memory (1240), and a communication unit (1260), but the present invention is not limited thereto. That is, each unit configuration may be provided outside the FMCW lidar (1200) to which OPLL is applied and may operate in a manner that interacts with the FMCW lidar (1200) to which OPLL is applied.

[0082] The input unit (1210) may include a user interface for receiving commands, information, etc. used to control the FMCW lidar (1200) to which the OPLL is applied. In addition, the input unit (1210) may be a hardware device (e.g., a keyboard, a touch pad, a voice recognition microphone, etc.) that can directly receive commands, information, etc. used to control the FMCW lidar (1200) to which the OPLL is applied.

[0083] The input unit (1210) may include a light receiving module capable of receiving a reflected light reflected from an object from a transmitted light.

[0084] In one embodiment, the input unit (1210) can receive information from a user required for a method of controlling the frequency of an optical signal using an OPLL.

[0085] The output unit (1220) may include a light transmission module that transmits light whose frequency is modulated around the FMCW lidar (1200) to which the OPLL is applied.

[0086] The output unit (1220) can provide information related to an object, such as information appearing in the frequency control process of an optical signal using OPLL, information on the result of generation, information on the position of the object, and relative velocity, to the user as visual information through an interface or display device.

[0087] The processor (1230) can control the overall operation of the FMCW lidar (1200) to which the OPLL is applied in order to perform the present invention.

[0088] The processor (1230) can load the program for controlling the frequency of an optical signal using OPLL (1250) and information necessary for executing the program for controlling the frequency of an optical signal using OPLL (1250) from the memory (1240) to execute the program for controlling the frequency of an optical signal using OPLL (1250).

[0089] The processor (1230) can control to store data received from an external device through the communication unit (1260) in the memory (1240). In addition, the processor (1230) can control to transmit information related to an object, such as information appearing in the process of controlling the frequency of an optical signal using OPLL, information on the result of generation, position information of the object, and relative velocity, to the external device through the communication unit (260).

[0090] The processor (1230) may refer to a processing device such as a microprocessor, a central processing unit (CPU), a graphic processing unit (GPU), a processor core, a multiprocessor, an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), or a micro controller unit (MCU), but is not limited to the above-described embodiment.

[0091] The memory (1240) can store information necessary for executing a frequency control program (1250) of an optical signal using OPLL and a frequency control program (1250) of an optical signal using OPLL. In addition, the memory (1240) can also store a processing result by the processor (1230).

[0092] The frequency control program (1250) of an optical signal using OPLL may mean software including commands programmed to perform a method according to the present invention.

[0093] The memory (1240) can store information related to an object, such as information appearing in the frequency control process of an optical signal using an OPLL, information on the generation result, information on the position of the object, and relative velocity. In addition, the memory (1240) can store information received from an external device via the communication unit (1260).

[0094] Memory (1240) may refer to a computer-readable recording medium, such as a magnetic media such as a hard disk, a floppy disk, and a magnetic tape, an optical media such as a CD-ROM, a DVD, a magneto-optical media such as a floptical disk, a random access memory such as a dynamic random access memory (DRAM) and a static random access memory (SRAM), and a hardware device specifically configured to store and execute program instructions such as a flash memory, but is not limited to the above-described embodiment.

[0095] The communication unit (1260) may be a wireless communication module capable of performing wireless communication by adopting a communication method such as CDMA, GSM, W-CDMA, TD-SCDMA, WiBro, LTE, EPC, 5G, wireless LAN, Wi-Fi, Bluetooth, Zigbee, WFD (Wi-Fi Direct), UWB (Ultra Wide Band), infrared communication (IrDA; infrared data association), BLE (Bluetooth Low Energy), or NFC (Near Field Communication), but is not limited to the above-described embodiment.

[0096] Additionally, information input and output through the input unit (1210) and output unit (1220), information stored in the memory (1240), and information transmitted and received through the communication unit (1260) include all information related to the present invention, and are not limited to the above-described embodiment.

[0097] The function or operation of the frequency control program (1250) of an optical signal using OPLL will be examined in detail with reference to FIG. 13.

[0098] Fig. 13 is a block diagram exemplifying the function of a frequency control program for an optical signal using OPLL.

[0099] As shown in Fig. 13, the frequency control program (1250) of an optical signal using OPLL may include a separation unit (1310), a receiving unit (1320), a control unit (1330), and an estimation unit (1340). The separation unit (1310), the receiving unit (1320), the control unit (1330), and the estimation unit (1340) are exemplary divisions of the functions of the frequency control program (1250) of an optical signal using OPLL, and are not limited thereto.

[0100] According to an embodiment, the functions of the separation unit (1310), the reception unit (1320), the control unit (1330), and the estimation unit (1340) can be merged / separated, and can be implemented as a series of commands included in at least one program.

[0101] The separation unit (1310), the receiving unit (1320), the control unit (1330), and the estimation unit (1340) may be implemented by the processor (1230), and may mean a data processing device built into hardware having a physically structured circuit to perform a function expressed by a code or command included in a frequency control program (1250) of an optical signal using an OPLL stored in a memory (1240).

[0102] The separation unit (1310) can separate the optical signal output from the laser diode into a Tx signal and an OPLL (optical phased locked loop) signal. In addition, the separation unit (1310) can separate the OPLL signal into an OPLL reference signal and an OPLL delay signal. Here, the frequency of the optical signal output from the laser diode can be periodically increased or decreased. In addition, the frequency of the optical signal output from the laser diode can continuously change over time.

[0103] When separating into a Tx signal and an OPLL signal, the separation unit (1310) can separate into the Tx signal and the OPLL signal using a micro lens array (MLA).

[0104] When separating into an OPLL reference signal and an OPLL delay signal, the separation unit (1310) can propagate the OPLL reference signal through an OPLL reference line and propagate the OPLL delay signal through an OPLL delay line. Here, the length of the OPLL delay line can be configured to be longer than the length of the OPLL reference line.

[0105] The separation unit (1310) can separate the Tx signal into a Tx transmission signal and a Tx reference signal.

[0106] The receiving unit (1320) can receive a Tx transmission signal, an Rx signal reflected from an object, a Tx reference signal, an OPLL reference signal, and an OPLL delay signal.

[0107] The control unit (1330) can control the frequency of the optical signal output from the laser diode based on the time difference between the OPLL reference signal and the OPLL delay signal being received by the receiving unit (1320).

[0108] The control unit (1330) can calculate a frequency difference between an OPLL reference signal propagated through the OPLL reference line and an OPLL delayed signal propagated through the OPLL delay line based on at least one of an internal refractive index and a length of the OPLL delay line. In addition, the control unit (1330) can control the frequency of an optical signal output from the laser diode based on an error between the calculated frequency difference and the frequency differences of the OPLL reference signal and the OPLL delayed signal. For example, the control unit (1330) can control the frequency of the optical signal output from the laser diode by changing a voltage applied to the laser diode.

[0109] The estimation unit (1340) can estimate at least one of the position information and relative velocity of the object based on the Tx reference signal and the reflected signal.

[0110] As described above, according to the present invention, by applying an OPLL to an FMCW lidar, the linearity of data received from the photodiode can be maintained. Furthermore, by maintaining the linearity of the data, the resolution and measurement accuracy of the FMCW lidar can be improved.

[0111] Furthermore, by using a lens to separate the beam, the damage threshold of the optical waveguide caused by the laser can be increased. Furthermore, as the damage threshold of the optical waveguide is increased, an FMCW lidar with an OPLL that can be implemented on a single chip can be provided.

[0112] The embodiments of the present invention described above may be implemented through various means. For example, the embodiments of the present invention may be implemented using hardware, firmware, software, or a combination thereof.

[0113] The combination of each block of the block diagram and each step of the flowchart attached to the present invention may be performed by computer program instructions. These computer program instructions may be installed in an encoding processor of a general-purpose computer, a special-purpose computer, or other programmable data processing equipment, so that the instructions executed by the encoding processor of the computer or other programmable data processing equipment create a means for performing the functions described in each block of the block diagram or each step of the flowchart. These computer program instructions may also be stored in a computer-available or computer-readable memory that can direct a computer or other programmable data processing equipment to implement the functions in a specific manner, so that the instructions stored in the computer-available or computer-readable memory can also produce an article of manufacture that includes an instruction means for performing the functions described in each block of the block diagram or each step of the flowchart. Since the computer program instructions can also be installed on a computer or other programmable data processing device, a series of operational steps are performed on the computer or other programmable data processing device to create a computer-executable process, and the instructions that cause the computer or other programmable data processing device to perform the steps for executing the functions described in each block of the block diagram and each step of the flowchart can also provide steps for executing the functions described in each block of the block diagram and each step of the flowchart.

[0114] Additionally, each block or step may represent a module, segment, or portion of code that includes one or more executable instructions for performing a specific logical function(s). In some embodiments, the functions mentioned in the blocks or steps may occur out of order. For example, two blocks or steps depicted in succession may actually be performed substantially simultaneously, or the blocks or steps may sometimes be performed in reverse order depending on the corresponding function.

[0115] The above description is merely an illustrative illustration of the technical idea of ​​the present invention, and those skilled in the art will appreciate that various modifications and variations can be made without departing from the essential quality of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate, rather than limit, the technical idea of ​​the present invention, and the scope of the technical idea of ​​the present invention is not limited by these embodiments. The scope of protection of the present invention should be interpreted by the following claims, and all technical ideas within a scope equivalent thereto should be interpreted as being included in the scope of the rights of the present invention.

Claims

1. In a method for controlling the frequency of an optical signal using an OPLL (optical phased locked loop) performed by an FMCW (frequency modulated continuous wave) lidar, A step of separating an optical signal output from a laser diode into a Tx signal and an OPLL signal; A step of separating the OPLL signal into an OPLL reference signal and an OPLL delay signal; and A step of controlling the frequency of an optical signal output from the laser diode based on the time difference between the OPLL reference signal and the OPLL delay signal being received by the photodiode (PD), A method for controlling the frequency of an optical signal using an OPLL.

2. In paragraph 1, In the step of separating the Tx signal and the OPLL signal, Separating the Tx signal and the OPLL signal using a micro lens array (MLA), A method for controlling the frequency of an optical signal using an OPLL.

3. In paragraph 1, The frequency of the optical signal output from the above laser diode increases and decreases periodically. A method for controlling the frequency of an optical signal using an OPLL.

4. In paragraph 3, The frequency of the optical signal output from the above laser diode changes continuously over time. A method for controlling the frequency of an optical signal using an OPLL.

5. In paragraph 1, The step of separating into the OPLL reference signal and the OPLL delay signal is: A step of propagating the OPLL reference signal through an OPLL reference line; and A step of propagating the OPLL delay signal through an OPLL delay line, A method for controlling the frequency of an optical signal using an OPLL.

6. In paragraph 5, The length of the above OPLL delay line is configured to be longer than the length of the above OPLL reference line. A method for controlling the frequency of an optical signal using an OPLL.

7. In paragraph 5, The step of controlling the above frequency is: A step of predicting a theoretical frequency difference between the OPLL reference signal propagated through the OPLL reference line and the OPLL delay signal propagated through the OPLL delay line based on at least one of the internal refractive index and the length of the OPLL delay line, A method for controlling the frequency of an optical signal using an OPLL.

8. In paragraph 7, The step of controlling the above frequency is: Comprising a step of measuring the actual frequency difference between the OPLL reference signal propagated through the OPLL reference line and the OPLL delay signal propagated through the OPLL delay line, A method for controlling the frequency of an optical signal using an OPLL.

9. In paragraph 8, In the step of controlling the above frequency, Controlling the frequency of the optical signal output from the laser diode by changing the voltage applied to the laser diode in a direction that reduces the error between the theoretical frequency difference and the actual frequency difference. A method for controlling the frequency of an optical signal using an OPLL.

10. In paragraph 1, The above method, Further comprising a step of separating the Tx signal into a Tx transmission signal and a Tx reference signal, A method for controlling the frequency of an optical signal using an OPLL.

11. In paragraph 10, The above method, A step of receiving a signal reflected from an object by the Tx transmission signal; and Further comprising a step of estimating at least one of position information and relative velocity of the object based on the Tx reference signal and the reflected signal. A method for controlling the frequency of an optical signal using an OPLL.

12. A light source that outputs a light signal; A first beam splitter that separates the output optical signal into a Tx signal and an OPLL (optical phased locked loop) signal; A second beam splitter that separates the OPLL signal into an OPLL reference signal and an OPLL delay signal; A photodiode (PD) that receives the OPLL reference signal and the OPLL delay signal; A memory capable of storing computer-executable instructions; and By executing the above command, A processor that controls the frequency of an optical signal output from the light source based on the time difference between the OPLL reference signal and the OPLL delay signal being received by the photodiode. FMCW lidar with OPLL applied.

13. In paragraph 12, The above first beam splitter, including a micro lens array (MLA), FMCW lidar with OPLL applied.

14. In paragraph 12, The frequency of the optical signal output from the above light source is Periodically increasing and decreasing, FMCW lidar with OPLL applied.

15. In paragraph 14, The frequency of the optical signal output from the above laser diode is continuously changing over time, FMCW lidar with OPLL applied.

16. In paragraph 12, The above second beam splitter, The above OPLL reference signal is propagated through the OPLL reference line, Propagating the above OPLL delay signal through the OPLL delay line, FMCW lidar with OPLL applied.

17. In paragraph 16, The length of the above OPLL delay line is, It is configured to be longer than the length of the above OPLL reference line, FMCW lidar with OPLL applied.

18. In paragraph 12, The above processor, Predicting the theoretical frequency difference between the OPLL reference signal propagated through the OPLL reference line and the OPLL delay signal propagated through the OPLL delay line based on at least one of the internal refractive index and the length of the OPLL delay line, Measure the actual frequency difference between the OPLL reference signal propagated through the OPLL reference line and the OPLL delay signal propagated through the OPLL delay line, Controlling the frequency of the optical signal output from the laser diode by changing the voltage applied to the light source in a direction that reduces the error between the theoretical frequency difference and the actual frequency difference. FMCW lidar with OPLL applied.

19. In paragraph 12, The FMCW lidar to which the above OPLL is applied is Transmit the Tx signal, Receive the reflected signal from the object of the transmitted signal as an Rx signal, Obtain information about the object based on the Tx signal and the Rx signal, Providing information for controlling the driving direction and speed of the vehicle based on the information of the above object. FMCW multi-channel lidar.

20. A non-transitory computer-readable recording medium storing computer-executable instructions, wherein the computer-executable instructions, when executed by a processor, A step of separating an optical signal output from a laser diode into a Tx signal and an OPLL (optical phased locked loop) signal; A step of separating the OPLL signal into an OPLL reference signal and an OPLL delay signal; and A method for causing the processor to perform a method including a step of controlling the frequency of an optical signal output from the laser diode based on a time difference between the OPLL reference signal and the OPLL delay signal being received by the photodiode (PD). Non-transitory computer-readable recording medium.

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