LiDAR system using multiple wavelengths and its operating method

Abstract

This invention provides a lidar system that uses multiple wavelengths and a method for operating the same. [Solution] A lidar system according to one embodiment of the present invention includes a signal generation unit that generates a plurality of lights having different wavelengths from each other; a transmitting unit that outputs the plurality of lights as a transmission signal; and a receiving unit that generates a target signal by mixing a first local oscillator signal and a received signal that is reflected from the target and incident on the target, and generates a reference signal by mixing a second local oscillator signal and an optical delay signal generated through a reference arm; and a circuit unit connected to the signal generation unit and the transmitting unit and controlling their operation. The receiving unit includes a combiner that generates a composite signal by superimposing the target signal and the reference signal.

Description

[Technical Field]

[0001] The present invention relates to a lidar system and a method for operating the same. [Background technology]

[0002] In a typical frequency-modulated continuous wave (FMCW) lidar, the frequency-modulated signal is triangular in terms of frequency relative to time, and is transmitted and received.

[0003] A crucial factor determining the measurement accuracy of an FMCW lidar system is generating a transmitted signal that increases or decreases in frequency linearly. If the transmitted signal increases non-linearly, the signal reflected from the target (hereinafter referred to as the received signal) must also return to non-linearity. In such cases, the frequency of the interference signal between the transmitted and received signals (hereinafter referred to as the beat frequency) is not constant but can fluctuate in accordance with the frequency difference between the two signals. That is, the more non-linear the transmitted signal becomes, the lower the spectral peak sharpness of the beat frequency becomes, and thus the signal-to-noise ratio (SNR) of the FMCW lidar system decreases. [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Recently, numerous studies have been conducted to ensure the linearity of transmitted signals. For example, a method is being used to improve the signal-to-noise ratio (SNR) of a lidar system by generating a reference signal through a reference arm with a known optical delay and utilizing the reference signal.

[0005] However, when applying the aforementioned technology to a high-resolution lidar system including a multi-wavelength light source, the complexity of the system increases in order to ensure the linearity of the transmitted signal, reducing system efficiency, and leading to increased costs and computational loads, which presents limitations that make it difficult to apply to actual systems.

[0006] The technical problem that this invention aims to solve is to improve the signal-to-noise ratio (SNR) of a high-resolution lidar system without increasing the complexity of the system.

[0007] The technical problems that this invention aims to solve are not limited to those described above, and other technical problems can be inferred from the following embodiments. [Means for solving the problem]

[0008] A lidar system according to one embodiment of the present invention includes a signal generation unit that generates a plurality of lights having different wavelengths from each other; a transmitting and receiving unit that includes a transmitting unit that outputs the plurality of lights as a transmission signal and a receiving unit that generates a target signal by mixing a first local oscillator signal and a received signal in which the transmitted signal is reflected from a target and incident on it, and generates a reference signal by mixing a second local oscillator signal and an optical delay signal generated through a reference arm; and a circuit unit that is connected to the signal generation unit and the transmitting and receiving unit and controls their operation. The receiving unit includes a combiner that generates a composite signal by superimposing the target signal and the reference signal.

[0009] A method for operating a lidar system according to one embodiment of the present invention includes the steps of: generating a plurality of lights having different wavelengths through a signal generation unit; outputting the plurality of lights as a transmission signal through a transmission / reception unit; generating a target signal by mixing a first local oscillator signal and a received signal in which the transmission signal is reflected from and incident on a target; generating a reference signal by mixing a second local oscillator signal and an optical delay signal generated through a reference arm; receiving a composite signal generated by superimposing the target signal and the reference signal through a single channel via a calculation unit; and correcting the target signal based on the reference signal via the calculation unit. [Effects of the Invention]

[0010] According to the rider system and its operation method according to an embodiment of the present invention, a correction signal based on a reference signal is combined with a received signal (or a target signal) and received in the same channel, thereby improving the SNR of a high-resolution rider system without increasing the complexity of the system.

[0011] The effects according to the embodiments are not limited to the effects described above, and the effects not mentioned will be clearly understood by those having ordinary knowledge in the technical field to which the embodiments belong from this specification and the attached drawings.

Brief Description of the Drawings

[0012] [Figure 1A] It is a drawing showing a transmission signal whose frequency increases linearly sent from an FMCW rider, a received signal obtained by reflecting the transmission signal from a target and incident, and a beat frequency. [Figure 1B] It is a drawing showing a transmission signal and a received signal when the frequency of the transmission signal increases non-linearly. [Figure 1C] It is a graph showing the sharpness of the spectral peak of the beat frequency in FIG. 1B. [Figure 2] It is a conceptual diagram for explaining a rider system according to an embodiment. [Figure 3A] It is a block diagram for explaining a light source unit applied to a signal generation unit according to an embodiment. [Figure 3B] It is a block diagram for explaining a light source unit applied to a signal generation unit according to another embodiment. [Figure 3C] It is a block diagram for explaining a light source unit applied to a signal generation unit according to another embodiment. [Figure 3D] It is a block diagram for explaining a light source unit applied to a signal generation unit according to another embodiment. [Figure 4] It is a drawing for explaining pixels included in a focal plane array. [Figure 5A]It is a graph for explaining a target signal. [Figure 5B] It is a graph for explaining a reference signal. [Figure 5C] It is a drawing for explaining a composite signal. [Figure 6] It is a block diagram for explaining a circuit unit according to an embodiment. [Figure 7A] It is a graph for explaining a method of band-pass filtering a reference signal RS from a composite signal. [Figure 7B] It is a graph for explaining a demodulated reference signal. [Figure 7C] It is a graph for explaining a method of low-pass filtering a reference signal. [Figure 8] It is a block diagram for explaining a clock generation unit for implementing a k-space sampling method. [Figure 9] It is a signal for explaining the clock generation unit of FIG. 8. [Figure 10A] It is a drawing for explaining the effect of the present invention. [Figure 10B] It is a drawing for explaining the effect of the present invention. [Figure 11] It is a drawing for explaining a driving method of a lidar system according to an embodiment. [Figure 12A] It is a drawing for explaining the operation of a MEMS switch. [Figure 12B] It is a drawing for explaining the operation of a micro-ring resonator. [Figure 13] It is a flowchart for explaining an operation method of a lidar system according to an embodiment. [Figure 14] It is a perspective view showing an exemplary electronic device to which a lidar system according to an embodiment is applied. [Figure 15] It is a side view showing a case where a lidar system according to an embodiment is applied to a vehicle. [Figure 16] It is a plan view showing a case where a lidar system according to an embodiment is applied to a vehicle. [Modes for carrying out the invention]

[0013] The terminology used in this embodiment has been selected as widely used and general terms as possible, taking into account the functions of this embodiment. However, this may change depending on the intent of the articulators or precedents in the relevant field, the emergence of new technologies, etc. In certain cases, some terms have been arbitrarily selected, and in such cases, their meanings will be described in detail in the description of the embodiment. Therefore, the terminology used in this embodiment is not simply a set of names, but must be defined based on the meaning of the term and the overall content of this embodiment.

[0014] In describing embodiments, when a part is said to be connected to another part, this includes not only cases where they are directly connected, but also cases where they are electrically connected via other components in between. Furthermore, when a part is said to include a certain component, this means that, unless otherwise stated, it does not exclude other components, but rather includes other components.

[0015] The terms "composed of" or "including" used in this embodiment should not be interpreted as necessarily including all the various components or steps described in the specification, and should be interpreted as meaning that some of these components or steps may not be included, or that additional components or steps may be included.

[0016] The following description of embodiments should not be construed as limiting the scope of rights, and any representation by a person skilled in the art that can be easily inferred should be considered to fall within the scope of rights of the embodiments. Hereinafter, embodiments that are merely illustrative will be described in detail with reference to the attached drawings.

[0017] Figure 1A is a diagram showing the transmitted signal with linearly increasing frequency sent from the FMCW lidar, the received signal which is reflected from the target and incident on, and the beat frequency. Figure 1B is a diagram showing the transmitted and received signals when the frequency of the transmitted signal increases non-linearly. Figure 1C is a graph showing the sharpness of the spectral peak at the beat frequency in Figure 1B.

[0018] Figure 1A(a) shows the transmitted signal sent from the FMCW lidar and the received signal, which is the transmitted signal reflected from the target and incident upon it. The transmitted signal is shown by the dotted line and the received signal is shown by the solid line, with a delay time t. d A time difference of approximately f and the Doppler frequency f d A frequency difference of this magnitude exists. Here, B represents the modulation bandwidth, and Tm represents the modulation period.

[0019] Figure 1A(b) shows the beat frequency, which is expressed as the frequency difference between the transmitted and received signals. bu This refers to the upbeat frequency, which corresponds to up chirp, and f bd This refers to the downbeat frequency, which corresponds to down chirp.

[0020] In this case, referring to the first modulation period Tm in Figure 1A, we can confirm that the frequency of the transmitted signal increases linearly, and consequently, the frequency of the received signal also increases linearly. As a result, the beat frequency is constant at the first modulation period Tm (for example, f bu ) may have.

[0021] The aforementioned upbeat frequency and downbeat frequency include frequency shifts due to the distance and relative velocity to the moving object. These are respectively called beat frequencies (f b ) and Doppler frequency (f d )

[0022] Upbeat frequency f buand the downbeat frequency f bd is expressed as in the following formulas (1) and (2).

[0023] [Equation 1] f bu = f b - f d [Equation 2] f bd = f b + f d

[0024] Here, a Doppler frequency having a positive value means that the moving object is approaching the lidar, and a Doppler frequency having a negative value means that the moving object is separated from the lidar. Therefore, the distance between the moving object and the lidar is obtained by the average of the upbeat frequency f bu and the downbeat frequency f bd , and the moving speed of the moving object can be calculated using the Doppler frequency f d . The upbeat frequency f bu and the downbeat frequency f bd can be obtained by performing a fast Fourier transform (FFT) on the received beat signal.

[0025] On the other hand, in a solid state LiDAR system, there arises a problem of how to implement scanning in the x-y plane. There are roughly methods such as flash, mirror-scanning, optical phased array, dispersive, and focal plane array (hereinafter, FPA), etc., and such scanning methods are respectively combined on the x-y axes to implement x-y plane scanning. Among these, FPA is suitable for the FMCW drive method because of its low control complexity and excellent SMSR (Side Mode Suppression Ratio) characteristics.

[0026] On the other hand, referring to Figure 1B, unlike Figure 1A, the frequency of the transmitted signal increases non-linearly, and it can be confirmed that the frequency of the transmitted signal also increases non-linearly. In such a case, the frequency of the interference signal between the transmitted signal and the received signal (or the beat frequency f) b ) is not constant and can vary in accordance with the frequency difference between the two signals. As a result, as shown in Figure 1C, δf b Because the range widens, the beat frequency f b The sharpness of the spectral peak decreases. That is, the more the nonlinearity of the transmitted signal increases, the lower the beat frequency f b As the spectral peak sharpness decreases, the signal-to-noise ratio (SNR) of the FMCW lidar system decreases. Referring to Figures 2 through 10B below, a configuration that improves the SNR of a high-resolution FMCW lidar system without increasing system complexity will be described in detail.

[0027] Figure 2 is a conceptual diagram illustrating a lidar system according to one embodiment.

[0028] Referring to Figure 2, the LiDAR system 1000 may include a signal generation unit 100, a transmitting / receiving unit 200, and a circuit unit 300. The signal generation unit 100, the transmitting / receiving unit 200, and the circuit unit 300 may be configured on a single chip (or semiconductor optical element).

[0029] According to one embodiment, the signal generation unit 100 may include a light source unit 110 and a coupler 120.

[0030] The light source unit 110 generates multiple beams of light L having different wavelengths. These multiple beams of light L can be described as multi-wavelength (multi-λ) electromagnetic waves. For example, these multiple beams of light L may be multiple lasers with different wavelengths, or they may be other types of light that are not lasers. The light source unit 110 generates these multiple beams of light L simultaneously.

[0031] The optical coupler 120 simultaneously receives multiple light beams L generated from the light source unit 110 and outputs a multiplexed light beam L'.

[0032] Although not shown in the drawings, the light source unit 110 may further include an optical modulator for modulating multiple lights.

[0033] For FMCW driving, the optical modulator (or signal generation unit 100) uses wavelengths (e.g., λ1, λ2, ... λ) N Frequency modulation (or chirping) as shown in Figure 1A is possible, centered around the wavelengths λ1, λ2, ... λ. In this case, the bandwidth of the frequency modulation (or chirping) determines the depth resolution. For example, to achieve a depth resolution of 10 cm, frequency modulation (or chirping) must occur with a bandwidth of approximately 1.5 GHz. The multiple wavelengths λ1, λ2, ... λ N From the standpoint of limiting crosstalk, it is desirable that the interval between them be wider than the bandwidth of the frequency modulation for the FMCW drive.

[0034] Optical modulators can modulate light in a variety of ways. For example, an optical modulator can modulate the phase of light, or it can modulate the amplitude of light, or it can modulate both the phase and amplitude of light simultaneously. Beyond these, the optical modulation function of an optical modulator can vary in many ways. Furthermore, optical modulators can perform optical modulation using various methods, including electrical, magnetic, thermal, and mechanical methods. As a specific example, an optical modulator may include at least one phase shifter (or phase shifting element), which may include at least one element selected from a group consisting of, for example, a gain element, an all-pass filter, a Bragg grating, a dispersive material element, a wavelength tuning element, and a phase tuning element. Furthermore, the actuation mechanism applied to the optical modulator may include at least one selected from the group consisting of, for example, thermo-optic actuation, electro-optic actuation, electroabsorption actuation, free carrier absorption actuation, magneto-optic actuation, liquid crystal actuation, and all-optic alactuation. Such an actuation mechanism is related to the phase tuning described above. However, the configuration and actuation mechanism of the phase converter described herein are illustrative, and the embodiments are not limited thereto.

[0035] The specific configuration of the light source unit 110 will be described in detail later through Figures 3A to 3D.

[0036] According to one embodiment, the transmitting / receiving unit 200 may include a focal plane array FPA in which a plurality of pixels PX (or pixel groups) are arranged in a matrix, and an optical element OP for controlling the light emission angle.

[0037] The transmitting / receiving unit 200 can be functionally divided into a transmitting unit and a receiving unit. The transmitting unit corresponds to the optical antenna 220 and optical amplifier 250 shown in Figure 4, which will be described later, and the first optical switch SW1 and second optical switch SW2 shown in Figure 6, which will be described later. The receiving unit can correspond to the second optical coupler 230, first balanced photodiode 241, first transimpedance amplifier 242, reference arm 260, third optical coupler 270, second balanced photodiode 243, second transimpedance amplifier 244, and combiner 280 shown in Figure 4, which will be described later.

[0038] The transmitting unit has a focal plane array (FPA) configuration in at least one of the x and y axes. Furthermore, the transmitting unit can output multiplexed optical signals L' simultaneously or sequentially as a transmission signal from a single pixel PX included in the focal plane array (FPA).

[0039] According to one embodiment, when the optical element OP emits multiple multiplexed light rays L' from the pixel PX into free space, it can be controlled to have different light emission angles depending on the wavelength. For example, the optical element OP may include a prism, a microprism array, a diffraction grating, and the like.

[0040] The receiving unit can mix the first local oscillator signal LO1 and the transmitted signal Tx, which are reflected from the target OBJ, with the incident received signal Rx to convert them into an electrical signal (or target signal TS). For example, the receiving unit uses the second optical coupler 230 shown in Figure 4 (described later) to perform 50:50 coupling before being incident on the first balanced photodiode 241. However, the coupling method is not limited to this and may be implemented using, for example, a beam splitter. Light of each wavelength has distance and / or velocity information with respect to the target OBJ.

[0041] Furthermore, the receiving unit can mix the second local oscillator signal LO2 and the optical delay signal DS generated through the reference arm 260 to convert them into an electrical signal (or reference signal RS). For example, the receiving unit uses the third optical coupler 270 shown in Figure 4, described later, to perform 50:50 coupling before being incident on the second balanced photodiode 243.

[0042] The circuit unit 300 is connected to the signal generation unit 100 and the transmitting / receiving unit 200, and can control their operation. Furthermore, the circuit unit 300 can perform frequency analysis on the electrical signals obtained from the transmitting / receiving unit 200 (or the receiving unit) and convert them into distance and / or speed information for the target object-oriented network (OBJ). The specific configuration of the circuit unit 300 will be described in detail later with reference to Figure 6.

[0043] The configuration of the light source unit 110 will be described in more detail below with reference to Figures 3A to 3D.

[0044] Figure 3A is a block diagram illustrating a light source unit applied to a signal generation unit according to one embodiment.

[0045] Referring to Figure 3A, according to this embodiment, the light source unit 110 may include a plurality of laser sources LD1 to LD4. Here, four laser sources LD1 to LD4 are shown, but the number can be changed. The plurality of laser sources LD1 to LD4 are, for example, laser diodes. The plurality of laser sources LD1 to LD4 generate lasers of different wavelengths (e.g., λ1, λ2, λ3, λ4). The lasers of different wavelengths λ1, λ2, λ3, λ4 generated from the plurality of laser sources LD1 to LD4 can be input to the optical coupler 120 and multiplexed.

[0046] Figure 3B is a block diagram illustrating a light source unit applied to a signal generation unit according to another embodiment.

[0047] Referring to Figure 3B, lasers of different wavelengths (e.g., λ1, λ2, λ3, λ4) generated from multiple laser sources LD1 to LD4 can be input to different input couplers IN1 to IN4. The multiple input couplers IN1 to IN4 can be said to constitute a single "input section 130". The multiple input couplers IN1 to IN4 may have, for example, an optical fiber structure, or they may have other configurations. Multiple beams of light that have passed through the multiple input couplers IN1 to IN4 can be multiplexed by the optical coupler 120.

[0048] In Figure 3B, the multiple input couplers IN1 to IN4 and the optical coupler 120 can be connected to a predetermined optical waveguide. Depending on the circumstances, the multiple input couplers IN1 to IN4 and the optical coupler 120 may be considered together as a single "input section".

[0049] Figure 3C is a block diagram illustrating a light source unit applied to a signal generation unit according to another embodiment.

[0050] Referring to Figure 3C, the light source unit 111 may include a laser source LD10 that generates a laser of a single wavelength λ0. That is, the light source unit 111 consists of one laser source LD10. A wavelength converter 140 is further provided that splits the laser generated from the laser source LD10 into a plurality of lasers having different wavelengths (e.g., λ1, λ2, λ3, λ4). For example, the wavelength converter 140 may include an input coupler, an optical distributor, and a plurality of wavelength conversion elements. The laser input to the input coupler is split by the optical distributor, and then its wavelength can be converted by the plurality of wavelength conversion elements. As a result, a plurality of light beams having different wavelengths (e.g., λ1, λ2, λ3, λ4) can be output through the wavelength converter 140. The plurality of light beams can be multiplexed by an optical coupler 120.

[0051] In Figure 3C, the laser source LD10 and the wavelength converter 140 can be considered together as a single "light source unit." Such a light source unit can be said to generate multiple beams of light having different wavelengths (for example, λ1, λ2, λ3, λ4). Furthermore, at least a part of the wavelength converter 140, or at least a part of the optical coupler 120, can be considered as an "input coupler." Alternatively, the wavelength converter 140 and the optical coupler 120 can be considered together as a single input coupler.

[0052] Figure 3D is a block diagram illustrating a light source unit applied to a signal generation unit according to another embodiment.

[0053] Referring to Figure 3D, the light source 112 may include a broadband laser. In other words, the broadband laser is an element that generates wideband light. A multi-band pass filter 150 is provided for splitting the light generated from the light source 112. Through the multi-band pass filter 150, light having multiple wavelengths (e.g., λ1, λ2, λ3, λ4) that are separated from each other may be output. These multiple lights may be multiplexed by an optical coupler 120.

[0054] In Figure 3D, the broadband laser and the multibandpass filter 150 can be considered together as a single "light source." Such a light source can be said to generate multiple lights having different wavelengths. In this embodiment, the optical coupler 120 can be considered an "input coupler."

[0055] Figure 4 is a diagram illustrating the pixels included in the focal plane array. Figure 5A is a graph illustrating the target signal TS. Figure 5B is a graph illustrating the reference signal RS. Figure 5C is a diagram illustrating the combined signal SS. For the sake of explanation, the target signal TS and reference signal RS, which are electrical signals, are shown as frequency domain information after being subjected to a Fast Fourier Transform before being input to the combiner 280.

[0056] Referring to Figure 4, a pixel PX according to one embodiment may include a first optical coupler IS that receives an input signal IS and splits it into multiple optical signals, a target signal generation unit for generating a target signal TS, a reference signal generation unit for generating a reference signal RS, and a combiner 280 for combining the target signal RS and the reference signal RS. In this case, the target signal generation unit may include an optical antenna 220, a second optical coupler 230, and a first photoelectric conversion unit 240a, and the reference signal generation unit may include a reference arm 260, a third optical coupler 270, and a second photoelectric conversion unit 240b.

[0057] Pixel PX can receive multiple multiplexed optical signals (see L' in Figure 2) as the input signal IS. The first optical coupler 210 may be positioned between the input terminal INT and the optical antenna 220.

[0058] First, the pixel PX can split the input signal IS into a first local oscillator signal LO1 and a transmit signal Tx, couple the transmit signal Tx to free space, couple the received signal Rx back to the pixel PX, and mix the first local oscillator signal LO1 and the received signal Rx.

[0059] Specifically, the first optical coupler 210 can split the input signal IS received from the input terminal INT into a first local oscillator signal LO1 and a transmit signal Tx. The optical antenna 220 can receive the received signal Rx reflected by the target.

[0060] The optical antenna 220 is a device that emits light from an on-chip waveguide into free space and / or couples light from free space into the on-chip waveguide. The optical antenna 220 can be embodied in a grating coupler, edge coupler, integrated reflector, or any spot size converter. The optical antenna 220 is polarization sensitive with much higher emission / coupling efficiency for light having one specific polarization (e.g., transverse electric or transverse magnetic). The optical antenna 220 is reciprocal and therefore can collect a received signal Rx from a measurement target (e.g., an object in the environment). The optical antenna 220 can provide the received signal Rx to a second optical coupler 230. Figure 4 shows a coaxial embodiment in which light emission and collection are performed through the same optical antenna 220, but a biaxial embodiment in which light emission and collection are performed separately using separate optical antennas is also possible.

[0061] The second optical coupler 230 can generate the first output signal OS1 by mixing the received signal Rx with the first local oscillator signal LO1. The second optical coupler 230 is a balanced 2x2 optical mixer.

[0062] Pixel PX may include a photoelectric conversion unit 240 that converts optical signals into electrical signals. For example, the first photoelectric conversion unit 240a may include a first balanced photodiode 241 configured to convert a first output signal OS1, which is an optical signal, into an electrical signal, and a first transimpedance amplifier 242 that amplifies the intensity of the electrical signal generated from the first balanced photodiode 241. For example, the first transimpedance amplifier 242 can amplify the current generated from the first balanced photodiode 241 and convert it into a voltage. The target signal TS, which is an electrical signal provided by the first transimpedance amplifier 242, may be supplied to the combiner 280.

[0063] A pixel PX according to one embodiment may further include an optical amplifier 250 positioned between the first optical coupler 210 and the optical antenna 220 to compensate for optical loss. For example, the optical amplifier 250 is a semiconductor optical amplifier (SOA) and amplifies the optical signal so that the light generated from the light source (see 110 in Figure 2) maintains its intensity at the optical antenna 220. Alternatively, it may play a role in increasing the signal-to-noise ratio (SNR).

[0064] Furthermore, the first optical coupler 210 can split the input signal IS into a second local oscillator signal LO2 and a reference arm input signal DS. In this case, the second local oscillator signal LO2 is substantially the same signal as the first local oscillator signal LO1. Therefore, unlike the embodiment shown in Figure 4, the second local oscillator signal LO2 may be replaced with the first local oscillator signal LO1. Also, the reference arm input signal DS may be delayed during its passage through a reference arm 260 of known length.

[0065] The third optical coupler 270 can mix the delayed reference arm input signal DS with the second local oscillator signal LO2 to generate the second output signal OS2. The third optical coupler 270 is a 2x2 optical mixer.

[0066] Pixel PX may include a photoelectric conversion unit 240 that converts optical signals into electrical signals. For example, the second photoelectric conversion unit 240b may include a second balanced photodiode 243 configured to convert a second output signal OS2, which is an optical signal, into an electrical signal, and a second transimpedance amplifier 244 that amplifies the intensity of the electrical signal generated from the second balanced photodiode 243. For example, the second transimpedance amplifier 244 can amplify the current generated from the second balanced photodiode 243 and convert it into a voltage. The reference signal RS, which is an electrical signal provided by the second transimpedance amplifier 244, may be provided to the combiner 280.

[0067] As shown in Figure 2 of the present invention's high-resolution FMCW lidar system 1000, when the light emitted from the light source unit 110 has four wavelengths (e.g., λ1, λ2, λ3, λ4), the number of elements corresponding to the pixels PX and circuit unit 300 must increase proportionally to the number of wavelengths. Furthermore, when applying a method to form an additional optical path (e.g., a reference arm 260) to ensure the linearity of the transmitted signal, conventional technology requires not only two photoelectric conversion units (e.g., first photoelectric conversion unit 240a, second photoelectric conversion unit 240b) for the pixels PX, but also twice the number of analog-to-digital converters (ADCs). In other words, for a high-resolution FMCW lidar system 1000 that simultaneously drives four wavelengths with guaranteed accuracy, a set of eight photoelectric conversion units (e.g., first photoelectric conversion unit 240a, second photoelectric conversion unit 240b) and analog-to-digital converters (ADCs) is required. Thus, the configuration of the high-resolution FMCW lidar system 1000 requires an increase in the number of channels, resulting in an increase in components and costs. In particular, when the high-resolution FMCW lidar system 1000 is constructed on a single chip (or semiconductor optical element), the area occupied by the analog-to-digital converter (ADC) is relatively large. Therefore, an increase in the number of ADC components is a major cause of increased size and production cost for the high-resolution FMCW lidar system 1000.

[0068] To solve these problems, the present invention proposes a method of combining a correction signal obtained by applying frequency modulation to a reference signal RS with a target signal TS, and collecting data from the same channel (or the same analog-to-digital converter ADC).

[0069] Referring to Figures 4 and 5A to 5C, the combiner 280 can combine (superposition) the target signal TS shown in Figure 5A and the reference signal RS shown in Figure 5B to generate the combined signal SS shown in Figure 5C, and provide the combined signal SS to a single channel provided in the analog-to-digital converter (ADC).

[0070] The circuit unit 300 (or the calculation unit 330) can frequency modulate the reference signal RS using the carrier frequency, and then synthesize the frequency-modulated reference signal RS and the target signal TS to generate a composite signal SS.

[0071] For example, the reference signal RS shown in Figure 5B has a center frequency of approximately 2 MHz, but as shown in Figure 5C, it can be confirmed that the reference signal RS frequency-modulated using a carrier frequency of approximately 300 MHz has a center frequency of approximately 302 MHz. In this way, by frequency-modulating the reference signal RS, it is possible to prevent the phenomenon of the frequency bands of the target signal TS and the reference signal RS superimposing. This prevents the loss of the reference signal RS used to generate the correction signal (or reference clock signal) during the process of combining the reference signal RS and the target signal TS.

[0072] The method for correcting the target signal TS based on the reference signal RS will be described in detail below with reference to Figures 6 to 10B.

[0073] Figure 6 is a block diagram illustrating a circuit according to one embodiment. Figure 7A is a graph illustrating a method for band-pass filtering a reference signal RS from a composite signal SS. Figure 7B is a graph illustrating the demodulated reference signal RS. Figure 7C is a graph illustrating a method for low-pass filtering a reference signal RS. Figure 8 is a block diagram illustrating a clock generation unit for realizing a k-space sampling method. Figure 9 is a signal illustrating the clock generation unit in Figure 8. Figures 10A and 10B are drawings illustrating the effects of the present invention.

[0074] Referring to Figures 4 and 6, the circuit unit 300 may include an optical signal control unit 310, a switching control unit 320, and a calculation unit 330.

[0075] The optical signal control unit 310 controls the frequency modulation (or chirping) of the signal generation unit 100, which may include a feedback circuit such as a phase-locked loop (PLL).

[0076] The switching control unit 320 can control the switching of at least one axis of the focal plane array (FPA) of the transmitting unit 200. In this case, the switching control is the operation of the optical MEMS (Micro-Electromechanical System) portion. Furthermore, this control is the heating (or thermal) control of thermo-optical elements that manipulate the phase, such as a micro-ring resonator and a Mach-Zender interferometer. This control is also the control for electron-optical modulation by adjusting the carrier concentration.

[0077] The arithmetic unit 330 can perform frequency analysis on the electrical signal received from the receiving unit of the transmitting / receiving unit 200 and convert it into distance and / or speed information for a target. For example, an analog electrical signal can be binary converted through an analog-to-digital converter (ADC), and then converted into frequency domain information via a Fast Fourier Transform in the digital arithmetic unit. The frequency domain information at each pixel can be converted into a point cloud showing a depth or speed map, and after undergoing analysis algorithms including image processing, it can be used in higher-level applications such as autonomous driving.

[0078] Furthermore, the arithmetic unit 330 can extract a frequency-modulated reference signal RS by band-pass filtering the composite signal SS, and then extract a reference signal RS for calculating a correction signal (or reference clock signal) by demodulating and low-pass filtering the frequency-modulated reference signal RS.

[0079] For example, referring to Figure 7A, the combined signal SS contains components of both the target signal TS and the reference signal RS. The target signal TS appears in a frequency band of 100 MHz or less, and the center frequency of the reference signal RS appears at approximately 302 MHz through frequency modulation, as mentioned above. The calculation unit 330 can selectively extract the reference signal RS necessary for calculating the correction signal (or reference clock signal) using a band-pass filter.

[0080] Next, the arithmetic unit 330 can demodulate the frequency-modulated (e.g., 302 MHz) reference signal RS back to its original frequency (e.g., 2 MHz) in order to reduce the amount of computation. Figure 7B shows the reference signal RS in the time domain, and it can be seen that when comparing the same interval (or period), the frequency-modulated reference signal RS on the left contains more waveforms than the demodulated reference signal RS on the right.

[0081] Next, the arithmetic unit 330 can perform noise filtering to reduce noise in the demodulated reference signal RS. In the embodiment described above, the center frequency of the demodulated reference signal RS is approximately 2 MHz, so as shown in Figure 7C, low-band-pass filtering can be used to remove additional noise components other than the reference signal RS.

[0082] Next, referring to Figures 6, 8, and 9, the arithmetic unit 330 can calculate a reference clock signal (or correction signal) by k-space sampling the reference signal RS in Figure 7C.

[0083] In one embodiment, the arithmetic unit 330 may include a clock generation unit CG that generates a reference clock signal (or correction signal) based on the reference signal RS in Figure 7C. The clock generation unit CG may include a 90° phase shifter PS, a plurality of zero-crossing sensing units ZCD, an exclusive OR gate XOR, and a logical OR gate OR.

[0084] The clock generation unit CG can generate a quadrant signal QS from the original reference signal RS using a 90° phase shifter PS (see Figure 9(a)). The reference signal RS and the quadrant signal QS can each be supplied to two zero-crossing sensing units ZCD.

[0085] Each of the two zero-crossing sensing units (ZCD) can output two square waves that are "level high" corresponding to the positive portion of the reference signal RS and the quadrant signal QS, respectively (see Figure 9(b)). The two square waves can be supplied to the exclusive OR gate (XOR).

[0086] Next, the two square waves are combined through an exclusive OR gate (XOR), which generates a "level high" clock pulse only if either of the two square waves is "level high" (see solid line in Figure 9(c)). To fill the gap in the clock pulse, a dummy clock signal (see dashed line in Figure 9(c)) is generated within a time duration that complements the time gate for zero-crossing sensing. This dummy clock signal is then combined with the clock pulse generated from the zero-crossing sensing unit (ZCD) by an OR gate to generate the final reference clock signal (or correction signal).

[0087] The calculation unit 330 can remove distortion from the target signal TS using the reference clock signal CS (or correction signal) and calculate the corrected target signal TS. In other words, if a reference clock signal CS (or correction signal) with non-uniform intervals that are not equal due to the nonlinearity of the signal is calculated and sampling is performed based on this, uniform sampling of the target signal TS is possible.

[0088] The calculation unit 330 can calculate the distance and / or velocity of the target based on the corrected target signal TS. Referring to Figures 10A and 10B, it can be seen that the intensity and sharpness of the corrected target signal TS are improved compared to the intensity and sharpness of the uncorrected target signal TS. In this way, the high-resolution FMCW lidar system 1000 of the present invention can improve the accuracy of the target signal TS without increasing the system complexity.

[0089] Figure 11 is a diagram illustrating the drive method of a lidar system according to one embodiment. Figure 12A is a diagram illustrating the operation of a MEMS switch. Figure 12B is a diagram illustrating the operation of a microring resonator.

[0090] Referring to Figures 2, 4, and 11, a lidar system 1000 according to one embodiment simultaneously outputs multiple optical signals L' as a transmission signal Tx from a single pixel PX included in a focal plane array FPA, and can receive a received signal Rx reflected by a target.

[0091] Specifically, multiple optical beams L having different wavelengths generated from the light source 110 can be converted into multiplexed optical beams L' through the optical coupler 120. The multiplexed optical beams L' can then be supplied to the focal plane array FPA through the main bus waveguide MWG.

[0092] The first optical switch SW1, when in the ON state, can selectively transmit light from the main bus waveguide MWG to the row waveguides W1 or Wm. The first optical switch SW1 can be implemented not only as an optical MEMS (Micro-Electromechanical System) switch but also by other methods, but λ1~λ n This is a wideband switching method that simultaneously switches a wide frequency range on and off. Therefore, MZI (mach-zender interferometer) switches can also be used.

[0093] Referring to Figure 12A, the first optical switch SW1 can be realized as an array of multiple MEMS (Micro-Electromechanical System) switches MS. Each MEMS switch MS manipulates the optical input signal IS from the main bus waveguide MWG by a control signal provided through its corresponding control line CL, thereby selectively providing the optical input signal IS to multiple row waveguides W1 to Wm.

[0094] Referring again to Figures 2, 4, and 11, the second optical switch SW2, when in the ON state, can selectively transmit light from the row waveguide W1 to Wm selected by the first optical switch SW1 to the pixel PX. The second optical switch SW2 is shown as a microring resonator, but is not limited to this, and can transmit multiple wavelengths λ1 to λ depending on the driving method. n Any switch that can turn the devices on / off sequentially or simultaneously will suffice. When the second optical switch SW1 is in the ON state, light can be emitted into free space through the optical antenna 220.

[0095] Referring to Figure 12B, the second optical switch SW2 can be embodied as an array of microring resonators (MRRs). Each microring resonator MRR picks up an optical signal from a row waveguide (e.g., W1 to Wm) when the resonant frequency of the device is aligned with the laser wavelength. In one embodiment, an electrical control signal (e.g., Ctrl0, Ctrl1, to Ctrln) can be used to set the resonance of each microring resonator MRR in the array, thereby selecting the pixel PX from which the optical signal is supplied.

[0096] Referring again to Figures 2, 4, and 11, the transmitting / receiving unit 200 (or the focal plane array FPA) may further include an optical amplifier 250 to compensate for optical attenuation and loss. The optical amplifier 250 may be located between the first optical switch SW1 and the second optical switch SW2 on the row waveguide W1 to Wm. Alternatively, the optical amplifier 250 may be located between the second optical switch SW2 and the optical antenna 220 within the pixel PX. For example, the optical amplifier 250 is a semiconductor optical amplifier (SOA) and amplifies the optical signal so that the light generated from the light source 110 maintains its intensity at the optical antenna 220. Alternatively, it may play a role in increasing the signal-to-noise ratio (SNR).

[0097] On the other hand, if light of various wavelengths is simultaneously output and incident from a single pixel PX, the circuit section (see 300 in Figure 2) (or the calculation unit 330 in Figure 6) must separate and process the information for each wavelength. Therefore, pixel PX may include a wavelength demultiplexer (not shown) in the waveguide between the optical antenna 220 and the front end of the second optical coupler 230 in Figure 4. For example, the demultiplexer may be implemented as an optical band pass filter, a micro ring resonator, etc. However, the placement of the demultiplexer is not limited to this. For example, the demultiplexer may be placed in the waveguide between the first optical coupler 210 and the second optical coupler 230.

[0098] Figure 13 is a flowchart illustrating the operation method of a lidar system according to one embodiment.

[0099] Referring to Figures 1A to 13, the operation method of the lidar system 1000 according to one embodiment may include the steps of generating and outputting multiple multiplexed lights through the signal generation unit 100 (S100), generating a target signal TS (S200), generating a reference signal RS (S300), generating a composite signal SS (S400), and correcting the target signal TS (S500).

[0100] Specifically, in S100, the signal generation unit 100 may include a light source unit 110 and a coupler 120. The light source unit 110 generates multiple optical beams L having different wavelengths. These multiple optical beams L can be described as multi-wavelength (multi-λ) electromagnetic waves. For example, these multiple optical beams L may be multiple lasers with different wavelengths, but they may also be other types of light that are not lasers. The light source unit 110 generates multiple optical beams L simultaneously. The optical coupler 120 can simultaneously receive multiple optical beams L generated from the light source unit 110 and output multiplexed optical beams L'.

[0101] The transmitting / receiving unit 200 may include a focal plane array FPA in which multiple pixels PX (or pixel groups) are arranged in a matrix, and an optical element OP for controlling the light emission angle.

[0102] The transmitting / receiving unit 200 can be functionally divided into a transmitting unit and a receiving unit. The transmitting unit has at least one of the x and y axes as a focal plane array (FPA) system. The transmitting unit can also simultaneously output multiple multiplexed optical signals L' from a single pixel PX included in the focal plane array FPA as a transmission signal.

[0103] According to one embodiment, when the optical element OP emits multiple multiplexed light rays L' from the pixel PX into free space, it can be controlled to have different light emission angles depending on the wavelength.

[0104] In S200, the receiver can mix the first local oscillator signal LO1 and the transmitted signal Tx, which are reflected from the target OBJ, with the incident received signal Rx to convert them into an electrical signal (or target signal TS).

[0105] In S300, the receiver can mix the second local oscillator signal LO2 and the optical delay signal DS generated through the reference arm 260 to convert them into an electrical signal (or reference signal RS).

[0106] In S400, the combiner 280 combines (superpositions) the target signal TS shown in Figure 5A and the reference signal RS shown in Figure 5B to generate the combined signal SS shown in Figure 5C, and can provide the combined signal SS to a single channel provided in the analog-to-digital converter ADC.

[0107] The circuit unit 300 (or the calculation unit 330) can frequency modulate the reference signal RS using the carrier frequency, and then synthesize the frequency-modulated reference signal RS and the target signal TS to generate a composite signal SS.

[0108] For example, the reference signal RS shown in Figure 5B has a center frequency of approximately 2 MHz, but the reference signal RS frequency-modulated using a carrier frequency of approximately 300 MHz shown in Figure 5C has a center frequency of approximately 302 MHz. In this way, frequency-modulating the reference signal RS prevents the phenomenon of the frequency bands of the target signal TS and the reference signal RS superimposing. This prevents the loss of the reference signal RS used to generate the correction signal (or reference clock signal) during the process of combining the reference signal RS and the target signal TS.

[0109] In S500, the calculation unit 330 can extract a frequency-modulated reference signal RS by band-pass filtering the composite signal SS, demodulate the frequency-modulated reference signal RS and perform low-pass filtering to extract a reference signal RS for calculating a correction signal (or reference clock signal).

[0110] For example, referring to Figure 7A, the combined signal SS contains both the target signal TS and the reference signal RS. The target signal TS appears in a frequency band of 100 MHz or less, and the center frequency of the reference signal RS appears at approximately 302 MHz through frequency modulation, as mentioned above. The calculation unit 330 can selectively extract the reference signal RS necessary for calculating the correction signal (or reference clock signal) using a band-pass filter.

[0111] Next, the arithmetic unit 330 can demodulate the frequency-modulated (e.g., 302 MHz) reference signal RS back to its original frequency (e.g., 2 MHz) in order to reduce the amount of computation. Figure 7B shows the reference signal RS in the time domain, and when comparing the same interval (or period), it can be seen that the frequency-modulated reference signal RS on the left contains higher frequency components than the demodulated reference signal RS on the right.

[0112] Next, the arithmetic unit 330 can perform noise filtering to reduce noise in the demodulated reference signal RS. In the embodiment described above, the center frequency of the demodulated reference signal RS is approximately 2 MHz, so as shown in Figure 7C, low-band-pass filtering can be used to remove additional noise components other than the reference signal RS.

[0113] Next, referring to Figures 6, 8, and 9, the arithmetic unit 330 can utilize the reference signal RS in Figure 7C (for example, k-space sampling) to calculate a reference clock signal (or correction signal).

[0114] Next, the calculation unit 330 can remove distortion from the target signal TS using the reference clock signal CS (or correction signal) and calculate the corrected target signal TS. In other words, if a reference clock signal CS (or correction signal) with non-uniform intervals that are not equal due to the nonlinearity of the signal is calculated and sampling is performed based on this, the nonlinear increase or decrease in the frequency of the target signal TS can be linearly corrected.

[0115] The calculation unit 330 can calculate the distance and / or velocity of the target based on the corrected target signal TS. Referring to Figures 10A and 10B, it can be seen that the intensity and sharpness of the corrected target signal TS are improved compared to the intensity and sharpness of the uncorrected target signal TS. In this way, the high-resolution FMCW lidar system 1000 of the present invention can improve the accuracy of distance measurement by increasing the signal-to-noise ratio (SNR) of the target signal TS without increasing the system complexity.

[0116] Figure 14 is a perspective view showing an exemplary electronic device to which a lidar system is applied according to an embodiment.

[0117] Figure 14 is shown in the form of a mobile phone or smartphone 3000, but the electronic devices to which the LiDAR device is applied are not limited to this. For example, it can be applied to tablets or smart tablets, notebook computers, TVs or smart TVs, etc.

[0118] Furthermore, the LiDAR system according to this embodiment can be applied to autonomous driving devices.

[0119] Figures 15 and 16 are conceptual diagrams showing the application of the LiDAR system according to the embodiment to a vehicle, and are a side view and a top view, respectively.

[0120] Referring to Figure 15, the LiDAR system 1001 can be applied to the vehicle 4000, and information about the subject 60 can be obtained using it. The LiDAR system 1001 may employ the LiDAR system described in Figures 2 to 12B. The LiDAR system 1001 can simultaneously measure distance and speed using the FMCW method to obtain information about the subject 60. The vehicle 50 is an automobile with autonomous driving capabilities. As described in Figure 15, the LiDAR system 1001 can divide the target area of ​​the target field of view into multiple sub-regions and irradiate a set of beams, split into one for each sub-region, at predetermined time intervals. If there is a subject within the target area and the reflected light from it is detected to contain frequency components in a specific region, a digital scan of the target area can be started and information about the subject 60 can be analyzed. Using the LiDAR system 1001, an object or person in the direction of travel of the vehicle 4000, i.e., the subject 60, can be detected, and the distance to the subject 60 can be measured using information such as the difference in time and frequency components between the transmitted signal and the received signal. Furthermore, as shown in Figure 12, information about nearby subjects 61 and distant subjects 62 within the target area can be obtained.

[0121] Figures 15 and 16 illustrate, but are not limited to, the application of a LiDAR system to automobiles. LiDAR systems can be applied to flying objects such as drones, mobile devices, small walking devices (e.g., bicycles, motorcycles, strollers, boards, etc.), robots, assistive devices for humans / animals (e.g., canes, helmets, jewelry, clothing, watches, bags, etc.), IoT (Internet of Things) devices / systems, security devices / systems, and more.

[0122] The LiDAR system described above has been explained with reference to the embodiments shown in the drawings, but this is merely illustrative, and a person with ordinary skill in the art will understand that a variety of modifications and equivalent other embodiments are possible. Therefore, the disclosed embodiments should be considered in an explanatory rather than restrictive manner. The scope of this specification is as set forth in the claims and not in the foregoing description, and all differences within that equivalent scope should be construed as being included. [Explanation of Symbols]

[0123] 1000 Rider System 100 Signal generation unit 110 Light source section 120 Optical Coupler 200 Transmitter / Receiver Unit 210 First Optical Coupler 220 Optical Antenna 230 Second Optical Coupler 240 Photoelectric conversion unit 300 Circuit section 310 Optical signal control unit 320 Switching Control Unit 330 Arithmetic section

Claims

1. A signal generation unit that generates multiple lights having different wavelengths from each other, A transmitting and receiving unit including a transmitting unit that outputs the plurality of lights as a transmission signal, and a receiving unit that generates a target signal by mixing a first local oscillator signal and a received signal in which the transmitted signal is reflected from the target and incident, and generates a reference signal by mixing a second local oscillator signal and an optical delay signal generated through a reference arm, It includes a circuit unit connected to the signal generation unit and the transmitting / receiving unit, which controls the operation of the signal generation unit and the transmitting / receiving unit, The receiving unit includes a combiner that superimposes the target signal and the reference signal to generate a composite signal, comprising a lidar system.

2. The signal generation unit, A light source unit that generates a plurality of lights having different wavelengths from each other, A multiplexer that simultaneously receives and multiplexes the aforementioned multiples of light, The lidar system according to claim 1, further comprising an optical modulator for modulating the plurality of lights.

3. The LiDAR system according to claim 1, wherein the circuit unit includes a calculation unit that corrects the target signal based on the reference signal, frequency modulates the reference signal using a carrier frequency, and then superimposes the frequency modulated reference signal and the target signal to generate the composite signal.

4. The aforementioned arithmetic unit, The composite signal is subjected to band-pass filtering to extract the frequency-modulated reference signal. The lidar system according to claim 3, wherein the frequency-modulated reference signal is demodulated and low-pass filtered to extract the reference signal.

5. The lidar system according to claim 4, wherein the calculation unit calculates a reference clock signal using the extracted reference signal.

6. The lidar system according to claim 5, wherein the calculation unit uses the reference clock signal to remove distortion from the target signal and calculates the corrected target signal.

7. The LiDAR system according to claim 6, wherein the calculation unit calculates the distance and / or speed of the target based on the corrected target signal.

8. The LiDAR system according to claim 1, wherein the transmitting unit outputs the transmission signal in units of pixel groups including at least two pixels.

9. The transmitting and receiving unit includes a focal plane array in which the pixel groups are arranged in a matrix, The LiDAR system according to claim 8, wherein the focal plane array is provided with the transmitted signal through a main bus waveguide.

10. Each of the aforementioned pixels is A first optical coupler that divides the input signal into the transmission signal, the reference signal, the first local oscillator signal, and the second local oscillator signal, An optical antenna that emits the transmission signal into free space and / or receives the reception signal from free space, A second optical coupler mixes the first local oscillator signal and the received signal to generate a first output optical signal, A third optical coupler mixes the second local oscillator signal and the reference signal to generate a second output optical signal, A first photoelectric conversion unit that converts the first output optical signal into the target signal, The lidar system according to claim 9, further comprising a second photoelectric conversion unit that converts the second output optical signal into the reference signal.

11. The reference arm is positioned between the first optical coupler and the second optical coupler. The lidar system according to claim 10, wherein the second output optical signal is generated by the reference arm.

12. The lidar system according to claim 10, wherein the input signal is a frequency-modulated continuous wave (FMCW) laser signal.

13. The first photoelectric conversion unit includes a first balanced photodiode that converts the first output optical signal into an electrical signal and a first transimpedance amplifier that amplifies the intensity of the electrical signal. The lidar system according to claim 10, wherein the second photoelectric conversion unit includes a second balanced photodiode for converting the second output optical signal into an electrical signal and a second transimpedance amplifier for amplifying the intensity of the electrical signal.

14. The LiDAR system according to claim 13, wherein the circuit section includes an analog-to-digital converter for binary conversion of the electrical signal, and the combined signal is received on a single channel of the analog-to-digital converter.

15. In the operation method of the RID system, The steps include generating multiple lights having different wavelengths through a signal generation unit, The steps include outputting the multiple lights as a transmission signal through the transmitting / receiving unit, The first local oscillator signal and the transmitted signal are reflected from the target, and the received signal is mixed to generate a target signal. The steps include: generating a reference signal by mixing the second local oscillator signal and the optical delay signal generated through the reference arm; The process involves receiving a composite signal generated by superimposing the target signal and the reference signal through a calculation unit via a single channel, A method for operating a lidar system, comprising the step of correcting the target signal based on the reference signal through the calculation unit.

16. The method for operating a lidar system according to claim 15, wherein the step of correcting the target signal includes the step of frequency modulating the reference signal using a carrier frequency, and then superimposing the frequency modulated reference signal and the target signal to generate the composite signal.

17. The step of correcting the target signal is: The steps include: extracting the frequency-modulated reference signal by applying a band-pass filter to the composite signal; A method for operating a lidar system according to claim 16, comprising the steps of demodulating and low-pass filtering the frequency-modulated reference signal to extract the reference signal.

18. The method for operating a lidar system according to claim 17, wherein the step of correcting the target signal includes the step of calculating a reference clock signal using the extracted reference signal.

19. The method of operating a lidar system according to claim 18, wherein the step of correcting the target signal includes the step of using the reference clock signal to remove distortion from the target signal and calculating the corrected target signal.

20. A method for operating a lidar system according to claim 19, further comprising the step of calculating the distance and / or velocity of the target based on the corrected target signal.

Images