Information processing apparatus, control method, and storage medium

Abstract

To provide an information processing device capable of suitably outputting a distance measurement result for an object existing within a measurement range.SOLUTION: A signal processing unit (2) of a rider unit (100) generates, on the basis of a segment signal (Sseg) output from a core unit (1), a polar coordinate space frame (Fp) indicating a scan angle indicating the irradiation direction of a laser beam, a target distance (Ltag), and the received light intensity of the laser beam, converts the frame into a rectangular coordinate space frame (Fo), and outputs the frame to a display control unit (3). For the illumination direction in which the segment signal Sseg output from the core unit 1 indicates the received light intensity equal to or higher than the threshold value Apth, the signal processing unit 2 generates the measurement point information Ip based on the segment signal Sseg and outputs the measurement point information Ip to the point cloud processing unit 5.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to distance measurement technology. [Background technology]

[0002] There are known techniques for measuring the distance to a nearby object. For example, Patent Document 1 discloses a lidar that detects a point cloud on the surface of an object by scanning the horizontal direction while intermittently emitting a laser beam and receiving the reflected light. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-106854 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional lidars generally detect the peak position of the received pulse for each horizontal irradiation direction and perform ranging based on the delay time to the peak position, but when the peak of the received pulse is lower than or equal to the noise, the peak position cannot be detected properly, resulting in the problem that the corresponding point cloud cannot be detected for distant objects, etc. On the other hand, when the output of a lidar is used for recognizing the surrounding environment of a vehicle, it is necessary to detect objects in real time.

[0005] The present invention has been made to solve the above-mentioned problems, and its main object is to provide an information processing device that can suitably output distance measurement results for objects present within the measurement range. [Means for solving the problem]

[0006] The claimed invention is an information processing device, an irradiation unit that irradiates laser light that becomes a pulsed laser while changing the irradiation direction; a light receiving unit that receives the laser light reflected by an object; a detection unit that detects a peak at which the light intensity of the light receiving signal is equal to or greater than a predetermined value from the light receiving signal for each irradiation direction received by the light receiving unit; a generator that generates, as third information, a pulse signal having the same peak position and amplitude; an output unit that outputs first information indicating the irradiation direction and the distance in the irradiation direction from a reference position related to the irradiation position, and the received light intensity of the laser light in the irradiation direction, and for detecting an object other than the object corresponding to the peak; The output unit generates, as the first information, a pulse signal obtained by subtracting the pulse signal of the third information from the light reception signal for each of the irradiation directions including the peak.

[0007] The claimed invention also includes: an irradiation unit that irradiates laser light that becomes a pulsed laser while changing the irradiation direction; a light receiving unit that receives the laser light reflected by an object, a detecting step of detecting a peak at which the light intensity of the light receiving signal is equal to or greater than a predetermined value from the light receiving signal for each irradiation direction received by the light receiving unit; a generating step of generating, as third information, a pulse signal having the same peak position and amplitude; an output step of outputting first information indicating the irradiation direction and the distance in the irradiation direction from a reference position related to the irradiation position, the received light intensity of the laser light, and for detecting an object other than the object corresponding to the peak, The output step is characterized in that a pulse signal obtained by subtracting the pulse signal of the third information from the light reception signal for each of the irradiation directions including the peak is generated as the first information.

[0008] The claimed invention also includes: an irradiation unit that irradiates laser light that becomes a pulsed laser while changing the irradiation direction; a light receiving unit that receives the laser light reflected by an object, a detection unit that detects a peak at which the light intensity of the light receiving signal is equal to or greater than a predetermined value from the light receiving signal for each irradiation direction received by the light receiving unit; a generator that generates, as third information, a pulse signal having the same peak position and amplitude; an output unit that outputs first information indicating the received light intensity of the laser light in the irradiation direction and the distance in the irradiation direction from a reference position related to the irradiation position, and for detecting an object other than the object corresponding to the peak; causing the computer to function as The output unit generates, as the first information, a pulse signal obtained by subtracting the pulse signal of the third information from the light reception signal for each of the irradiation directions including the peak. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic configuration of a rider unit. [Figure 2] The block configuration of the core part is shown. [Figure 3] 1 shows waveforms of a trigger signal and a segment extraction signal. [Figure 4] 1 shows the block configuration of the signal processing unit. [Figure 5] (A) shows the waveform of the segment signal, (B) shows the waveform of the reference pulse, and (C) shows the waveform of the replica pulse. [Figure 6] 10 shows an outline of the replica pulse subtraction process. [Figure 7] FIG. 2 is a block diagram showing the functional configuration of a frame direction filtering unit. [Figure 8] FIG. 2 is a schematic overhead view of the periphery of the rider unit. [Figure 9](A) A diagram showing the point cloud of measurement points detected at the timing of processing the 0th frame, plotted in a Cartesian coordinate system. (B) A diagram showing the point cloud of measurement points detected at the timing of processing the 5th frame, plotted in a Cartesian coordinate system. [Figure 10] (A) A diagram showing the point cloud of measurement points detected at the timing of processing the 10th frame, plotted in a Cartesian coordinate system. (B) A diagram showing the point cloud of measurement points detected at the timing of processing the 15th frame, plotted in a Cartesian coordinate system. [Figure 11] 10 is a display example of a Cartesian coordinate space frame when subtraction processing using replica pulses is not performed. [Figure 12] 10 is a display example of a Cartesian coordinate space frame when subtraction processing using replica pulses is performed. [Figure 13] FIG. 10 shows a block diagram of a signal processing unit in a modified example. [Figure 14] 10 shows the waveform of a signal obtained by subtracting a replica pulse in a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0010] According to a preferred embodiment of the present invention, an information processing device includes an irradiation unit that irradiates laser light while changing the irradiation direction, a light receiving unit that receives the laser light reflected by an object, and an output unit that, based on a light receiving signal output by the light receiving unit, (i) generates and outputs first information indicating the received light intensity of the laser light in the irradiation direction and the distance in the irradiation direction from a reference position related to the irradiation position, and (ii) generates and outputs second information indicating the distance to the object based on the light receiving signal for an irradiation direction in which the light receiving signal indicates a received light intensity equal to or greater than a predetermined value.

[0011] The information processing device includes an irradiation unit, a light receiving unit, and an output unit. The irradiation unit irradiates laser light while changing the irradiation direction. The light receiving unit receives the laser light reflected by the target object. The "target object" refers to an object within the range reached by the laser light. The output unit generates and outputs first information based on a light receiving signal output by the light receiving unit. Here, the first information indicates the irradiation direction, the distance in the irradiation direction from a reference position related to the irradiation position, and the received light intensity of the laser light. Here, the output unit may output the first information to a display for display, or may output the first information to another processing unit. Furthermore, for an irradiation direction in which the light receiving signal output by the light receiving unit indicates a received light intensity equal to or greater than a predetermined value, the output unit generates and outputs second information indicating the distance to the target object based on the received light signal. Here, the output unit may output the second information to a display for display, or may output the second information to another processing unit. Furthermore, the "second information" may include information indicating the received light intensity in addition to information on the distance to the target object. For example, when the second information is output as a point cloud, the information on the received light intensity is converted into a reflection intensity after distance correction and is used for white line detection, etc.

[0012] According to this aspect, the information processing device can output information about objects at a relatively short distance, where the received light intensity is equal to or greater than a predetermined value, as second information, while also outputting information about other objects as first information.

[0013] In one aspect of the information processing device, the output unit outputs first information averaged on a time axis based on a plurality of first information generated over a predetermined time width. This aspect enables the information processing device to generate and output first information in which the influence of noise is suitably reduced.

[0014] In another aspect of the information processing device, the output unit generates third information from the light receiving signal in the irradiation direction in which the second information was generated, and generates the first information by subtracting a signal component of the third information from the light receiving signal output by the light receiving unit. This allows the information processing device to exclude, from the first information, the third information generated from the light receiving signal in the irradiation direction used to generate the second information.

[0015] In another aspect of the information processing device, the output unit generates, for each of the irradiation directions, a signal having the same peak position and amplitude as the waveform of the light receiving signal in the irradiation direction that generated the second information, and subtracts the signal component of the third information from the light receiving signal in the irradiation direction of the target. With this aspect, the information processing device can preferably exclude information of the point cloud of the target detected as the second information from the first information.

[0016] In another aspect of the information processing device, when there are multiple peaks for the corresponding irradiation direction, the output unit generates the third information for each peak and subtracts each signal component of the third information from the light receiving signal for that irradiation direction. With this aspect, even when multiple peaks are detected from the light receiving signal for each irradiation direction due to multipath, the information processing device can output the first information from which information about the peaks has been accurately excluded.

[0017] In another aspect of the information processing device, the information processing device further includes a conversion unit that converts the first information into fourth information indicating the received light intensity in a Cartesian coordinate system (coordinates represented by two orthogonal axes) corresponding to the irradiation plane, thereby enabling the information processing device to output the first information after coordinate conversion so that, for example, the user can easily grasp the object intuitively.

[0018] In another aspect of the information processing device, the fourth information indicates a received light intensity in a two-dimensional space parallel to a horizontal plane, and the information processing device further includes a display control unit that causes a display unit to display an image based on the fourth information. With this aspect, the information processing device allows a user to preferably visually recognize the presence of an object present in the vicinity.

[0019] According to another preferred embodiment of the present invention, there is provided a control method executed by an information processing device including an irradiation unit that irradiates laser light while changing the irradiation direction and a light receiving unit that receives the laser light reflected by an object, the control method including the steps of: (i) generating and outputting, based on a light receiving signal output by the light receiving unit, first information indicating a received light intensity of the laser light in the irradiation direction and a distance in the irradiation direction from a reference position related to the irradiation position; and (ii) generating and outputting, for an irradiation direction in which the light receiving signal indicates a received light intensity equal to or greater than a predetermined value, second information indicating a distance to the object based on the light receiving signal. By executing this control method, the information processing device can output, as second information, information about objects at a relatively close distance in which the received light intensity is equal to or greater than a predetermined value, while also outputting information about other objects as first information.

[0020] According to another preferred embodiment of the present invention, a program executed by a computer of an information processing device including an irradiation unit that irradiates laser light while changing the irradiation direction and a light receiving unit that receives the laser light reflected by an object is provided, the program causing the computer to function as an output unit that (i) generates and outputs first information indicating the received light intensity of the laser light in the irradiation direction and the distance in the irradiation direction from a reference position related to the irradiation position based on a light receiving signal output by the light receiving unit, and (ii) generates and outputs second information indicating the distance to the object based on the light receiving signal for an irradiation direction in which the light receiving signal indicates a received light intensity equal to or greater than a predetermined value. By executing this program, the information processing device can output information about objects at a relatively close distance where the received light intensity is equal to or greater than the predetermined value as second information, while also outputting information about other objects as first information. Preferably, the program is stored in a storage medium. [Example]

[0021] Preferred embodiments of the present invention will now be described with reference to the drawings.

[0022] [Overall configuration] FIG. 1 is a block diagram of a lidar unit 100 according to this embodiment. The lidar unit 100 shown in FIG. 1 is a TOF (Time Of Flight) lidar (Lidar: Light Detection and Ranging, or Laser Illuminated Detection and Ranging) that measures the distance to an object in all horizontal directions. The lidar unit 100 is used, for example, as part of an advanced driver assistance system to assist in recognizing the vehicle's surrounding environment. The lidar unit 100 mainly includes a core unit 1, a signal processing unit 2, a display control unit 3, a display 4, and a point cloud processing unit 5. The lidar unit 100 is an example of the "information processing device" of the present invention.

[0023] The core unit 1 emits a pulsed laser beam in all directions of 360° in the horizontal direction while gradually changing the emission direction. At this time, the core unit 1 emits the pulsed laser beam for each segment (900 segments in this embodiment) obtained by dividing all directions of 360° in the horizontal direction at equal angles. The core unit 1 then receives reflected light of the pulsed laser beam within a predetermined period after emitting the pulsed laser beam and outputs a signal (also referred to as a "segment signal Sseg") relating to the received light intensity for each segment to the signal processing unit 2.

[0024] The signal processing unit 2 detects peak positions from the waveform of the segment signal Sseg for each segment received from the core unit 1, and calculates the distance to the irradiation position (also called "measurement point") of the object irradiated with the laser based on the detected peak positions.The signal processing unit 2 then supplies the point cloud processing unit 5 with a combination of the distance calculated for each segment and the scan angle corresponding to that segment as measurement point information (also called "measurement point information Ip").

[0025] Furthermore, the signal processing unit 2 integrates the segment signals Sseg for each segment received from the core unit 1 to generate a two-dimensional image in polar coordinate space (also referred to as a "polar coordinate spatial frame Fp") that represents the relationship between each segment and the distance from the lidar unit 100 in all directions of 360° in the horizontal direction. Then, based on the polar coordinate spatial frame Fp, the signal processing unit 2 generates a two-dimensional image in Cartesian coordinate space (also referred to as a "Cartesian coordinate spatial frame Fo") based on the scanning plane (irradiation plane) of the pulsed laser, and outputs the image to the display control unit 3. At this time, as will be described later, the signal processing unit 2 performs processing to remove information corresponding to a point cloud (also simply referred to as a "point cloud") of detected measurement points from the segment signals Sseg of each segment before generating the polar coordinate spatial frame Fp. In this way, the signal processing unit 2 prevents relatively close objects detected as a point cloud from being displayed in the Cartesian coordinate spatial frame Fo.

[0026] The display control unit 3 displays an image based on the Cartesian coordinate space frame Fo received from the signal processing unit 2 on the display 4. The point cloud processing unit 5 performs processing based on the measurement point information Ip received from the signal processing unit 2. For example, the point cloud processing unit 5 performs known surrounding environment recognition processing, self-position estimation processing, and / or display processing on the display 4 using the output of the LIDAR.

[0027] [Core configuration] Fig. 2 shows a schematic configuration example of the core unit 1. As shown in Fig. 2, the core unit 1 mainly includes a crystal oscillator 10, a synchronization control unit 11, an LD driver 12, a laser diode 13, a scanner 14, a motor control unit 15, a light receiving element 16, a current-voltage conversion circuit (transimpedance amplifier) ​​17, an A / D converter 18, and a segmentator 19.

[0028] The crystal oscillator 10 outputs a pulsed clock signal "S1" to the synchronization control unit 11 and the A / D converter 18. In this embodiment, as an example, the clock frequency is 1.8 GHz. In addition, hereinafter, the clock indicated by the clock signal S1 is also referred to as the "sample clock."

[0029] The synchronization control unit 11 outputs a pulse-like signal (also called a "trigger signal S2") to the LD driver 12. In this embodiment, the trigger signal S2 is 131072 (=2 17 ) sample clock. Hereinafter, the period from when trigger signal S2 is asserted until the next time it is asserted will also be referred to as the "segment period." Furthermore, synchronization control unit 11 outputs a signal (also referred to as the "segment extraction signal S3") to segmentator 19, which determines the timing at which segmentator 19, described later, extracts the output of A / D converter 18. Trigger signal S2 and segment extraction signal S3 are logic signals, and are synchronized as shown in FIG. 3, described later. In this embodiment, synchronization control unit 11 asserts segment extraction signal S3 for a time width (also referred to as the "gate width Wg") equivalent to 2048 sample clocks.

[0030] The LD driver 12 supplies a pulse current to the laser diode 13 in synchronization with a trigger signal S2 input from the synchronization control unit 11. The laser diode 13 is, for example, an infrared (905 nm) pulse laser, and emits an optical pulse based on the pulse current supplied from the LD driver 12. In this embodiment, the laser diode 13 emits an optical pulse of about 5 nsec.

[0031] The scanner 14 includes a transmitting and receiving optical system, and scans the light pulse emitted by the laser diode 13 360° in a horizontal plane, and also guides the returning light reflected by an object (also referred to as the "target") onto which the emitted light pulse is irradiated, to the light receiving element 16. In this embodiment, the scanner 14 includes a motor for rotation, and the motor is controlled by the motor control unit 15 so that it rotates once in 900 segments. In this case, the angular resolution is 0.4° (=360° / 900) per segment. The LD driver 12 and the scanner 14 are an example of the "irradiation unit" in the present invention.

[0032] Preferably, the scan plane of the scanner 14 is flat rather than umbrella-shaped, and when the LIDAR unit 100 is mounted on a moving object, it is preferably parallel (i.e., horizontal) to the ground surface on which the moving object is traveling. This increases the correlation between the polar coordinate spatial frames Fp generated successively in time series, as will be described later, and enables the surrounding environment to be displayed with higher accuracy.

[0033] The light receiving element 16 is, for example, an avalanche photodiode, and generates a weak current corresponding to the amount of light reflected from the object and guided by the scanner 14. The light receiving element 16 supplies the generated weak current to a current-voltage conversion circuit 17. The current-voltage conversion circuit 17 amplifies the weak current supplied from the light receiving element 16, converts it into a voltage signal, and inputs the converted voltage signal to an A / D converter 18.

[0034] The A / D converter 18 converts the voltage signal supplied from the current-voltage conversion circuit 17 into a digital signal based on the clock signal S1 supplied from the crystal oscillator 10, and supplies the converted digital signal to the segmentator 19. Hereinafter, the digital signal generated by the A / D converter 18 for each clock will also be referred to as a "sample." One sample corresponds to data for one pixel in a polar coordinate spatial frame Fp, which will be described later. The light receiving element 16, the current-voltage conversion circuit 17, and the A / D converter 18 are an example of a "light receiving unit" in the present invention.

[0035] The segmentator 19 generates a digital signal, which is the output of the A / D converter 18 for 2048 sample clocks during the period of the gate width Wg during which the segment extraction signal S3 is asserted, as a segment signal Sseg. The segmentator 19 supplies the generated segment signal Sseg to the signal processing unit 2.

[0036] 3 shows the waveforms of the trigger signal S2 and the segment extraction signal S3 in time series. As shown in Fig. 3, in this embodiment, the segment period, which is the period of one cycle during which the trigger signal S2 is asserted, is set to a length of 131072 sample clocks (denoted as "smpclk" in the drawing), the pulse width of the trigger signal S2 is set to a length of 64 sample clocks, and the gate width Wg is set to a length of 2048 sample clocks.

[0037] In this case, the segment extraction signal S3 is asserted for only the period of the gate width Wg after the trigger signal S2 is asserted, so the segmentator 19 extracts 2048 samples output by the A / D converter 18 while the trigger signal S2 is asserted. The longer the gate width Wg, the longer the maximum measurement distance (measurement limit distance) from the lidar unit 100.

[0038] In this embodiment, the frequency of the segment period is approximately 13.73 kHz (≈1.8 GHz / 131072), and the frame frequency of the polar coordinate spatial frame Fp generated by the signal processing unit 2 based on the segment signal Sseg (i.e., the rotation speed of the scanner 14) is approximately 15.36 Hz (≈13.73 kHz / 900), since one frame consists of 900 segments. Furthermore, the maximum measurement distance, by simple calculation, is 170.55 m (≈{2048 / 1.8 GHz}·c / 2, where "c" is the speed of light), which corresponds to the distance traveled by light in a time period equivalent to the gate width Wg. As will be described later, the maximum measurement distance is slightly shorter than 170.55 m due to electrical and optical delays.

[0039] Here, we will provide additional explanation about the relationship between the delay time (also called "delay time Td") from when the trigger signal S2 is asserted until a sample corresponding to the light pulse emitted based on the trigger signal S2 is output, and the distance to the target object (also called "target distance Ltag").

[0040] If the index of the segment corresponding to the scanning angle of the scanner 14 is "s" (s=0 to 899), and the index of the 2048 samples generated by the A / D converter 18 during the period in which the segment extraction signal S3 is asserted is "k" (k=0 to 2047), the magnitude of the sample index k corresponds to the target distance Ltag. Specifically, the relationship between the sample index k and the delay time Td is as follows, assuming that the clock frequency is "fsmp" (=1.8 GHz), ignoring electrical and optical delays, etc. Td=k / fsmp≒k×0.55555nsec In this case, the relationship between the target distance Ltag and the delay time Td is as follows, ignoring delays, etc. Ltag=Td·(c / 2)=(k / fsmp)·(c / 2) This becomes:

[0041] In reality, electrical and optical delays exist in the transmission route from when the trigger signal S2 is sent from the synchronization control unit 11 to the LD driver 12 until the scanner 14 emits light, and in the reception route from when the returned light enters the scanner 14 until it is converted into a digital signal by the A / D converter 18. Therefore, to calculate the target distance Ltag from the sample index k, it is necessary to provide an offset (also called the "start point offset k0") to the index k and subtract the start point offset k0 from the index k. When the start point offset k0 is taken into account, the target distance Ltag is expressed by the following equation. Ltag={(k-k0) / fsmp}·(c / 2)

[0042] [Details of the signal processing section] (1) Block configuration Fig. 4 is a block diagram showing the logical configuration of the signal processing unit 2. As shown in Fig. 4, the signal processing unit 2 has a segment signal processing unit 21, a point detection unit 22, a reference pulse storage unit 23, a replica pulse generation unit 24, a calculation unit 25, and a frame direction filtering unit 26.

[0043] The segment signal processing unit 21 performs signal processing for noise suppression on the segment signal Sseg. For example, the segment signal processing unit 21 applies a matched filter or the like to maximize the SN ratio of the segment signal Sseg.

[0044] The point detection unit 22 detects peaks from the waveform of the segment signal Sseg processed by the segment signal processing unit 21, and estimates the amplitude (also referred to as "amplitude Ap") and delay time Td corresponding to the detected peak. If there is a peak of the waveform indicated by the segment signal Sseg whose estimated amplitude Ap is equal to or greater than a predetermined threshold (also referred to as "threshold Apth"), the point detection unit 22 supplies information on the amplitude Ap and delay time Td of the peak to the replica pulse generation unit 24. Furthermore, for each peak whose estimated amplitude Ap is equal to or greater than the threshold Apth, the point detection unit 22 generates measurement point information Ip indicating a combination of a distance corresponding to the delay time Td and a scan angle corresponding to the target segment, and supplies the measurement point information Ip to the point cloud processing unit 5. Note that the measurement point information Ip may include information indicating the received light intensity (i.e., information equivalent to the amplitude Ap) in addition to the distance corresponding to the delay time Td. In this case, for example, the point cloud processing unit 5 converts the information on the received light intensity included in the measurement point information Ip into a reflection intensity through distance correction, and uses it for processing such as white line detection. The threshold value Apth is an example of the "predetermined value" in the present invention, and the measurement point information Ip is an example of the "second information" in the present invention.

[0045] The reference pulse storage unit 23 stores in advance the waveform of the segment signal Sseg (also referred to as the "reference pulse") when the light receiving element 16 ideally receives the reflected light. In this embodiment, the reference pulse indicates the waveform of the segment signal Sseg when the light receiving element 16 ideally receives the reflected light when laser light is emitted at an object brought close to the LIDAR unit 100, and is generated in advance based on, for example, an experiment. The reference pulse is read out by the replica pulse generation unit 24.

[0046] The replica pulse generating unit 24 generates a signal (also referred to as a "replica pulse Srep") that indicates the waveform of the peak detected by the point detecting unit 22. Specifically, the replica pulse generating unit 24 generates the replica pulse Srep by correcting the reference pulse read out from the reference pulse storage unit 23 based on the estimated values ​​of the amplitude Ap and delay time Td supplied from the point detecting unit 22. A specific example of a method for generating the replica pulse Srep will be described later with reference to FIG. 5. The replica pulse Srep is an example of the "third information" in the present invention.

[0047] The replica pulse generation unit 24 performs subtraction processing of the replica pulse Srep supplied from the replica pulse generation unit 24 on the segment signal Sseg supplied from the segment signal processing unit 21. Then, the replica pulse generation unit 24 supplies the segment signal Sseg (also referred to as a "peak removal signal Ssub") after subtracting the replica pulse Srep to the frame direction filtering unit 26.

[0048] The frame direction filtering unit 26 generates one polar coordinate spatial frame Fp from the peak-removed signals Ssub extracted from each of the 900 segment signals Sseg, and further performs filtering in the frame direction to generate a Cartesian coordinate spatial frame Fo. The processing performed by the frame direction filtering unit 26 will be described later with reference to FIG. 6. The point detection unit 22 and the frame direction filtering unit 26 are an example of the "output unit" in the present invention.

[0049] (2) Replica pulse generation and subtraction processing Next, a specific example of the process of generating the replica pulse Srep executed by the replica pulse generating section 24 and the process of subtracting the replica pulse Srep executed by the calculating section 25 will be described with reference to FIGS.

[0050] Fig. 5(A) shows an example of the waveform of the segment signal Sseg output for a certain segment by the segment signal processing unit 21. The received light intensity on the vertical axis of Fig. 5(A) is "1" when the light receiving element 16 receives reflected light ideally.

[0051] In this case, the point detector 22 detects a peak (see box 90) having an amplitude Ap equal to or greater than the threshold Apth, and estimates that the amplitude Ap of the peak is "0.233" and the sample index k corresponding to the delay time Td is "231.1".

[0052] 5(B) shows an example of a reference pulse waveform. As shown in FIG. 5(B), in this case, the sample index k corresponding to the delay time Td is near "0," and the amplitude Ap is "1." The reference pulse storage unit 23 stores a reference pulse such as that shown in FIG. 5(B) in advance and supplies it to the replica pulse generation unit 24.

[0053] Fig. 5(C) shows a replica pulse Srep generated based on the amplitude Ap and delay time Td estimated from the segment signal Sseg shown in Fig. 5(A) and the reference pulse shown in Fig. 5(B). In this case, the replica pulse generation unit 24 generates the replica pulse Srep shown in Fig. 5(C) by correcting the reference pulse of Fig. 5(B) based on the amplitude Ap and delay time Td estimated in the example of Fig. 5(A). Specifically, the replica pulse generation unit 24 changes the amplitude Ap of the reference pulse to "0.233," the estimated value of the amplitude Ap obtained from the point detection unit 22, and changes the sample index k of the peak position of the reference pulse to "231.1," the estimated value of the sample index k obtained from the point detection unit 22.

[0054] Fig. 6 is a diagram showing an outline of the subtraction process of the replica pulse Srep executed by the calculation unit 25. As shown in Fig. 6, the calculation unit 25 subtracts the replica pulse Srep of Fig. 5C (see the upper right of Fig. 6) from the segment signal Sseg of Fig. 5A (see the upper left of Fig. 6) to generate a peak-removed signal Ssub (see the lower center of Fig. 6) in which peaks equal to or greater than the threshold Apth are removed from the segment signal Sseg of Fig. 5A. In this way, the calculation unit 25 can generate the peak-removed signal Ssub in which information about the point group detected by the point detection unit 22 is removed from the segment signal Sseg, based on the replica pulse Srep.

[0055] (3) Frame Filtering 7 is a block diagram showing the functional configuration of the frame direction filtering unit 26. The frame direction filtering unit 26 mainly includes a frame generation unit 31, a buffer unit 32, a frame filter 33, and an orthogonal space transformation unit 34.

[0056] The frame generator 31 generates one polar coordinate spatial frame Fp from the peak-removed signals Ssub extracted from each of the 900 segment signals Sseg and stores the frame in the buffer 32. In this embodiment, since there are 2048 samples per segment and a total of 900 segments, the frame generator 31 generates a 900 × 2048 image as the polar coordinate spatial frame Fp. In this manner, when the frame generator 31 receives peak-removed signals Ssub corresponding to 900 segments from index "k=0" to "k=899" from the calculation unit 25, it integrates these signals to generate one polar coordinate spatial frame Fp and stores the signals in the buffer 32. Here, the coordinate space of the polar coordinate spatial frame Fp is a polar coordinate space having a vertical axis corresponding to the scanning angle (i.e., angle) and a horizontal axis corresponding to the target distance Ltag (i.e., radius). The polar coordinate spatial frame Fp is an example of the "first information" of the present invention.

[0057] The buffer unit 32 stores, for at least a predetermined period, the polar coordinate spatial frames Fp generated by the frame generation unit 31. The predetermined period is set to be longer than the period during which the polar coordinate spatial frames Fp, the number of which is used by the frame filter 33, are accumulated in the buffer unit 32.

[0058] The frame filter 33 extracts a predetermined number (e.g., 16 frames) of polar coordinate spatial frames Fp that are consecutive in time series and stored in the buffer unit 32, and performs frame filtering to generate polar coordinate spatial frames Fp (also referred to as "averaged frames Fa") that are averaged on the time axis. In this way, the frame filter 33 generates averaged frames Fa in which noise present in each polar coordinate spatial frame Fp is suppressed. Here, frame filtering may be any process that reduces noise using polar coordinate spatial frames Fp that are consecutive in time series. For example, the frame filter 33 may generate averaged frames Fa by calculating a moving average of the predetermined number of polar coordinate spatial frames Fp extracted from the buffer unit 32, or may generate averaged frames Fa by applying a first-order IIR filter.

[0059] The orthogonal space transformation unit 34 generates a orthogonal coordinate space frame Fo by transforming the coordinate system of the averaged frame Fa output by the frame filter 33 from a polar coordinate system to a orthogonal coordinate system. At this time, the orthogonal space transformation unit 34 generates the orthogonal coordinate space frame Fo by identifying the pixel of the averaged frame Fa that corresponds to each pixel of the orthogonal coordinate space frame Fo. The orthogonal space transformation unit 34 then supplies the generated orthogonal coordinate space frame Fo to the display control unit 3. The orthogonal space transformation unit 34 is an example of a "transformation unit" in the present invention. The orthogonal coordinate space frame Fo is an example of "fourth information" in the present invention.

[0060] (4) Specific examples Next, a specific example of the processing executed by the signal processing unit 2 will be described with reference to FIGS.

[0061] Fig. 8 is a schematic overhead view of the periphery of the lidar unit 100 during the experiment. As shown in Fig. 8, the periphery of the lidar unit 100 mainly includes a plurality of walls, trees, groups of trees, wire mesh 1 and wire mesh 2, and a moving vehicle. Below, a case will be described in which the signal processing unit 2 processes 16 frames from 0th to 15th based on a frame frequency corresponding to the rotation speed of the scanner 14.

[0062] FIG. 9(A) is a diagram plotting the point cloud detected by the point detection unit 22 in the 0th frame processing in a Cartesian coordinate system, and FIG. 9(B) is a diagram plotting the point cloud detected by the point detection unit 22 in the 5th frame processing in a Cartesian coordinate system. Also, FIG. 10(A) is a diagram plotting the point cloud detected by the point detection unit 22 in the 10th frame processing in a Cartesian coordinate system, and FIG. 10(B) is a diagram plotting the point cloud detected by the point detection unit 22 in the 15th frame processing in a Cartesian coordinate system. Here, frame 80 indicates the position of the traveling vehicle, and frame 81 indicates the position of the wall within frame 79 in FIG. 8. The pixels corresponding to each measurement point are set to white, and the other pixels are set to black.

[0063] 9(A), (B) and 10(A) and (B), the traveling vehicle within frame 80 is detected with high accuracy because it is located at a relatively short distance from the LIDAR unit 100. Here, as the traveling vehicle moves, the point cloud corresponding to the traveling vehicle (see frame 80) moves to the left as the frame number increases.

[0064] On the other hand, the wall within frame 81 is located relatively far from the lidar unit 100, and there are trees between it and the lidar unit 100, so it is not detected as a point cloud by the point detection unit 22, and the presence of the target wall cannot be recognized based on the detection results of the point detection unit 22.

[0065] Fig. 11 is a display example of a Cartesian coordinate space frame Fo generated based on the segment signal Sseg not subjected to subtraction processing using the replica pulse Srep. In the example of Fig. 11, the frame direction filtering unit 26 generates polar coordinate space frames Fp based on the segment signal Sseg not subjected to subtraction processing using the replica pulse Srep in frame processing from 0th to 15th frames, and then converts the averaged frame Fa generated from these 16 polar coordinate space frames Fp into Cartesian coordinate space to generate the Cartesian coordinate space frame Fo shown in Fig. 11. In Fig. 11, the higher the value of the digital signal output by the A / D converter 18 (i.e., the received light intensity), the closer to white the image becomes. Here, a frame 80A indicates the position of a traveling vehicle, and a frame 81A indicates the position of a wall within the frame 79 of Fig. 8.

[0066] In the Cartesian coordinate space frame Fo in Fig. 11, averaging processing over 16 frames has enabled relatively distant objects such as walls (see frame 81A) that could not be seen in the frames shown in Fig. 9 and Fig. 10 to be displayed. On the other hand, in the example of Fig. 11, the area with high received light intensity corresponding to the moving vehicle leaves a trail that follows the movement trajectory during the measurement period. In this way, if subtraction processing using the replica pulse Srep is not performed, the point cloud of the moving object will leave a trail in the Cartesian coordinate space frame Fo, and will be detected as a shape that is longer in the movement direction than its actual shape.

[0067] FIG. 12 is a display example of a Cartesian coordinate space frame Fo generated based on the peak-removed signal Ssub after subtraction using the replica pulse Srep according to this embodiment. In this case, the point cloud information displayed in each frame shown in FIGS. 9 and 10, including the point cloud corresponding to the traveling vehicle, has been removed. Meanwhile, in FIG. 12, similar to the example of FIG. 11, relatively distant objects such as a wall (see frame 81A) that could not be confirmed in each frame shown in FIGS. 9 and 10, are displayed. In this way, by performing subtraction processing using the replica pulse Srep, the lidar unit 100 can suitably display relatively distant objects that the point detection unit 22 could not detect in the Cartesian coordinate space frame Fo. Note that even if there is a distant moving object that the point detection unit 22 cannot detect as a point cloud, the moving distance of the moving object on the Cartesian coordinate space frame Fo tends to be shorter than that of nearby moving objects that the point detection unit 22 can detect. Therefore, it is expected that the trailing length will be short to an acceptable extent.

[0068] As described above, the signal processing unit 2 of the lidar unit 100 according to this embodiment generates a polar coordinate spatial frame Fp indicating the scan angle indicating the irradiation direction of the laser light and the target distance Ltag, and the received light intensity of the laser light at that scan angle, based on the segment signal Sseg output by the core unit 1, and converts it into a Cartesian coordinate spatial frame Fo and outputs it to the display control unit 3. Furthermore, for irradiation directions in which the segment signal Sseg output by the core unit 1 indicates a received light intensity equal to or greater than the threshold Apth, the signal processing unit 2 generates measurement point information Ip based on the segment signal Sseg and outputs it to the point cloud processing unit 5. With this configuration, the lidar unit 100 can display objects that are far away in the Cartesian coordinate spatial frame Fo, while outputting the point cloud of objects that are relatively close as measurement point information Ip. In other words, for example, if the lidar unit 100 is mounted on a vehicle for recognizing the surrounding environment, objects that are relatively close (such as other moving objects) can be detected quickly by performing point cloud processing, and objects that are far away can be detected with high accuracy by performing averaging processing on the Cartesian coordinate space frame, for example, on the time axis.

[0069] [Variations] Next, preferred modifications of the embodiment will be described. The following modifications may be applied to the above-described embodiment in any combination.

[0070] (Variation 1) Generally, there may be multiple peaks equal to or greater than the threshold Apth in the segment signal Sseg of one segment due to multipath caused by partial irradiation of the laser beam on the target, etc. In this case, the signal processing unit 2 may repeatedly perform subtraction processing using the replica pulse Srep until there are no peaks equal to or greater than the threshold Apth in the peak-removed signal Ssub.

[0071] Fig. 13 is a block diagram of a signal processing unit 2A in this modification. In the example of Fig. 13, the signal processing unit 2A has a plurality of point detection units 22 (22A, 22B, ...), a plurality of replica pulse generation units 24 (24A, 24B, ...), and a plurality of calculation units 25 (25A, 25B, ...).

[0072] The point detecting unit 22A then detects the peak with the largest amplitude Ap from the segment signal Sseg output by the segment signal processing unit 21. If the amplitude Ap is equal to or greater than the threshold Apth, the point detecting unit 22A supplies the replica pulse generating unit 24A with a sample index k corresponding to the corresponding amplitude Ap and delay time Td, and supplies measurement point information Ip corresponding to the detected peak to the point cloud processing unit 5. Thereafter, the replica pulse generating unit 24A generates a replica pulse Srep based on the amplitude Ap and sample index k received from the point detecting unit 22A, and the calculation unit 25A subtracts the replica pulse Srep generated by the replica pulse generating unit 24A from the segment signal Sseg output by the segment signal processing unit 21.

[0073] Similarly, the point detection unit 22B detects the peak with the largest amplitude Ap from the segment signal Sseg output by the calculation unit 25. If the amplitude Ap is equal to or greater than the threshold Apth, the point detection unit 22B supplies the replica pulse generation unit 24B with a sample index k corresponding to the corresponding amplitude Ap and delay time Td, and also supplies measurement point information Ip corresponding to the detected peak to the point cloud processing unit 5. Thereafter, the replica pulse generation unit 24B generates a replica pulse Srep based on the amplitude Ap and sample index k received from the point detection unit 22B, and the calculation unit 25B subtracts the replica pulse Srep generated by the replica pulse generation unit 24B from the signal output by the calculation unit 25A. Note that if the amplitude Ap of the detected peak is less than the threshold Apth, the point detection unit 22B does not cause the replica pulse generation unit 24B to generate the replica pulse Srep, but instead causes the signal output by the calculation unit 25A to be input to the frame-direction filtering unit 26 as a peak-removed signal Ssub.

[0074] In this way, in the configuration example of FIG. 13, the signal processing unit 2A can detect multiple measurement points from one segment, supply measurement point information Ip relating to these measurement points to the point cloud processing unit 5, and generate a peak-removed signal Ssub from which all information about these measurement points has been removed, thereby generating a Cartesian coordinate space frame Fo.

[0075] 14(A) shows an example of the waveform of the segment signal Sseg output by the segment signal processing unit 21 for a certain segment. In this example, due to multipath of the laser light, there are two peaks with amplitude Ap equal to or greater than the threshold Apth. In this case, the point detection unit 22A first detects the peak with the largest amplitude Ap (see box 91), and supplies a sample index k corresponding to the amplitude Ap and delay time Td of that peak to the replica pulse generation unit 24A. As a result, the replica pulse generation unit 24A generates a replica pulse Srep.

[0076] Fig. 14(B) shows the waveform after the calculation unit 25A subtracts the segment signal Sseg by the replica pulse Srep generated by the replica pulse generation unit 24A. In the waveform of Fig. 14(B), the peak indicated by the frame 91 in Fig. 14(A) has been removed. Then, the point detection unit 22B detects the peak with the largest amplitude Ap (see frame 92) from the signal shown in Fig. 14(B), and supplies the replica pulse generation unit 24B with a sample index k corresponding to the amplitude Ap and delay time Td of that peak. In this way, the replica pulse generation unit 24B generates the replica pulse Srep.

[0077] Fig. 14(C) shows the waveform of the signal output by the calculation unit 25B. In Fig. 14(C), the calculation unit 25B subtracts the replica pulse Srep generated by the replica pulse generation unit 24B from the signal output by the calculation unit 25A, thereby removing the peak indicated by the frame 92. The signal shown in Fig. 14(C) is then input to the frame-direction filtering unit 26 as a peak-removed signal Ssub. In this way, a peak-removed signal Ssub that does not contain peaks whose amplitude Ap is equal to or greater than the threshold Apth is suitably generated.

[0078] (Variation 2) The configuration of the lidar unit 100 is not limited to the configuration shown in FIG.

[0079] For example, the lidar unit 100 may not have the display control unit 3 and the display 4. In this case, for example, the lidar unit 100 may detect a specific object by performing known image recognition processing on the orthogonal coordinate space frame Fo generated by the signal processing unit 2, and may notify the presence of the object by an audio output device (not shown). In another example, the lidar unit 100 may store the orthogonal coordinate space frame Fo generated by the signal processing unit 2 in a storage unit (not shown) together with information such as the current position of the lidar unit 100 output by a GPS receiver (not shown) or the like.

[0080] In addition, the lidar unit 100 may repeat horizontal scanning by the scanner 14 for multiple vertical rows (layers), thereby generating measurement point information Ip by the point detection unit 22 and generating an orthogonal coordinate space frame Fo by the frame direction filtering unit 26 for each layer.

[0081] (Variation 3) The configuration of the core unit 1 shown in Fig. 2 is an example, and the configuration to which the present invention can be applied is not limited to the configuration shown in Fig. 2. For example, the laser diode 13 and the motor control unit 15 may be configured to rotate together with the scanner 14.

[0082] (Variation 4) The lidar unit 100 may generate a Cartesian coordinate space frame Fo based on the segment signal Sseg that is not subjected to subtraction processing using the replica pulse Srep, and display the frame on the display 4.

[0083] In this case, the frame direction filtering unit 26 generates a polar coordinate spatial frame Fp based on the segment signal Sseg that is not subjected to subtraction by the replica pulse Srep, and then generates a Cartesian coordinate spatial frame Fo by converting the averaged frame Fa generated from the polar coordinate spatial frame Fp into Cartesian coordinate space.

[0084] (Variation 5) When the lidar unit 100 is mounted on a vehicle, the lidar unit 100 may determine whether the vehicle on which the lidar unit 100 is mounted is stopped, and may execute processing by the frame filter 23 only when it is determined that the vehicle is stopped. In this case, when the vehicle is traveling, the lidar unit 100 converts the polar coordinate space frame Fp into a Cartesian coordinate space to generate a Cartesian coordinate space frame Fo. This makes it possible to prevent trailing lines from being displayed on the Cartesian coordinate space frame Fo.

[0085] In another example, the lidar unit 100 may determine the number of polar coordinate spatial frames Fp used to generate the Cartesian coordinate spatial frame Fo (i.e., the filter depth), in other words, the time width for averaging the polar coordinate spatial frames Fp, depending on the traveling speed of the vehicle. In this case, the frame filter 23 refers to a predetermined map or the like, and reduces the number of polar coordinate spatial frames Fp used to generate the Cartesian coordinate spatial frame Fo as the vehicle speed increases. The above-mentioned map is a map of the vehicle speed and parameters that determine the number of polar coordinate spatial frames Fp used to generate the Cartesian coordinate spatial frame Fo, and is generated in advance based on, for example, experiments. This example also makes it possible to reduce the appearance of trailing lines on the Cartesian coordinate spatial frame Fo.

[0086] In the above-described (Modification 4), since subtraction processing using the replica pulse Srep is not performed, the point cloud of a nearby object that moves relatively to the lidar unit 100 is displayed as a trailing tail on the orthogonal coordinate space frame Fo. Therefore, this modification is preferably combined with (Modification 4). [Explanation of symbols]

[0087] 1 Core 2, 2A signal processing section 3 Display control section 4. Display 5 Point cloud processing section 100 rider unit

Claims

[Claim 1] an irradiation unit that irradiates laser light while changing the irradiation direction; a light receiving unit that receives the laser light reflected by an object; an output unit that generates and outputs, based on the light receiving signal output by the light receiving unit, (i) first information indicating the received light intensity of the laser light in the irradiation direction and the distance in the irradiation direction from a reference position related to the irradiation position, and (ii) for the irradiation direction in which the light receiving signal indicates a received light intensity equal to or greater than a predetermined value, second information indicating the distance to the target object based on the light receiving signal.

Images