JP2015152428A - Laser radar device and object detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the accuracy of detecting an object.SOLUTION: A process for projecting measurement light, receiving reflected light, and, while offsetting, for the sampling of a photo-detection signal, the rise time of a trigger signal that is start timing so as not to cause a time dt1 to occur that appears as a shift in peak corresponding to the vehicle speed of the vehicle, integrating the photo-detection values for each photo-detection element and each sampling time, is executed a prescribed number of times within a one-cycle measurement period. Then, an object detection process is executed on the basis of the integrated value of photo-detection values of the photo-detection signal from the same photo-detection element at the same sampling time, the photo-detection signal being sampled at a time preceding by an offset dt2 the rise time of the trigger signal in accordance with the vehicle speed within a detection period. The present invention can be applied to, for example, a laser radar device for vehicles.

Description

  The present invention relates to a laser radar device and an object detection method, and more particularly to a laser radar device and an object detection method that improve the object detection accuracy.

  Conventionally, in a laser radar device that projects measurement light, which is pulsed laser light, onto a predetermined monitoring region, and receives reflected light from a plurality of directions simultaneously by a plurality of light receiving elements (see, for example, Patent Document 1), Techniques for improving detection accuracy have been proposed.

  However, in the technique described in Patent Document 1, the projected laser beam is difficult to be projected far away due to weather or the like, so that the reflected light reflected by the object is hardly received, and the light receiving sensitivity is reduced. As a result, the object detection accuracy may be reduced.

  Therefore, a technique has been proposed in which the detection sensitivity is improved by integrating the light reception results when receiving reflected light (see Patent Document 2).

JP 2013-096905 A JP 2006-105688 A

  However, in the technique of Patent Document 2, it is assumed that the time until the reflected light reflected from the same target object reaches the laser radar device is the same. However, in a laser radar device or the like mounted on a vehicle, since the distance from the target object changes with time because the own vehicle is moving, the time until the reflected light returns is not the same. Therefore, if the light reception result is simply integrated, the detection accuracy decreases.

  The present invention has been made in view of such a situation, and is intended to improve the accuracy of detection of a stationary object by a laser radar device mounted on a moving body.

  The laser radar device of the present invention is a laser radar device mounted on a vehicle, and emits measurement light, which is pulsed laser light, to a predetermined monitoring region a predetermined number of times within a predetermined measurement period. A light projecting unit that repeats the light within a detection period of a predetermined length, a light receiving unit that includes a light receiving element that receives the reflected light of the measurement light, a sampling unit that samples a light reception signal from the light receiving element, and the detection period A sampling unit that integrates sampling values at the same sampling time of the received light signals from the same light receiving element, and detects an object in the monitoring area based on the integrated sampling values Based on the detection unit and the traveling speed of the vehicle, a control time for calculating an offset time for starting sampling in the sampling unit is calculated. Includes a part, the control unit, with respect to the sampling unit, the start of the sampling for each of the measurement period is offset the offset time.

  With this configuration, the sampling start timing is offset according to the amount of deviation between the peak of the immediately previous measurement period and the peak of the current measurement period, which occurs when the laser radar device approaches a stationary object. It becomes possible to make it. As a result, it is possible to align the timing of the peak of the waveform indicating the position of the stationary object in the sampling, so that the sampling value can be appropriately integrated, and the distance to the object determined by the integrated peak can be obtained. Detection accuracy can be improved.

  The control unit may offset the offset time to output a trigger signal to the sampling unit, and the sampling unit may start the sampling by the trigger signal.

  With this configuration, the sampling start timing is offset according to the amount of deviation between the peak of the immediately previous measurement period and the peak of the current measurement period, which occurs when the laser radar device approaches a stationary object. It becomes possible to make it. As a result, it is possible to align the timing of the peak of the waveform indicating the position of the stationary object in the sampling, so that the sampling value can be appropriately integrated, and the distance to the object determined by the integrated peak can be obtained. Detection accuracy can be improved.

  The light projecting unit has a predetermined process of projecting measurement light, which is pulsed laser light, to a predetermined monitoring region m times (m ≧ 1) within a predetermined first length measurement period. N1 (n1 ≧ 2) light receiving elements that repeat c cycles (c ≧ 2) within the detection period of the second length and receive the reflected light of the measurement light from different directions in the light receiving unit. The sampling unit can sample the received light signals from the n1 light receiving elements s times (s ≧ 2) each time the measurement light is projected. .

  Thereby, the detection direction of a some light receiving element can be integrated, and an object can be detected.

  The integration unit may integrate the sampling values over a plurality of the detection periods.

  As a result, for example, the light reception sensitivity in a specific direction can be increased without reducing the light reception sensitivity in each direction, and the detection accuracy of an object in a specific direction can be increased without reducing the detection accuracy of the object in each direction. Can be improved.

  The object detection method of the present invention is an object detection method for a laser radar device mounted on a vehicle, and the measurement light, which is a pulsed laser beam, is applied to a predetermined monitoring area a predetermined number of times within a predetermined measurement period. A light projecting step that repeats the process of projecting within a detection period of a predetermined length; a light receiving step by a light receiving element that receives the reflected light of the measurement light; a sampling step that samples a light reception signal from the light receiving element; An integration step for integrating sampling values at the same sampling time of the received light signals from the same light receiving elements sampled within the detection period, and an object in the monitoring region based on the integrated sampling values A sampling step in the process of the sampling step based on the detection step of detecting the vehicle and the traveling speed of the vehicle Includes a control step of calculating an offset time of the timing for starting the processing of the control step, the in the process of sampling steps, to offset the sampling start the offset time for each of the measurement period.

  This light projecting step is executed by, for example, a drive circuit, a light emitting element, a light projecting optical system, and the like. This light receiving step is executed by, for example, a light receiving optical system, a light receiving element, or the like. This sampling step is executed by, for example, an A / D converter. This integration step and detection step are executed by an arithmetic device such as a microcomputer or various processors, for example.

  In the present invention, the process in which the measurement light, which is a pulsed laser beam, is projected a predetermined number of times within a predetermined measurement period to a predetermined monitoring region is repeated within a detection period of a predetermined length. The reflected light of the measurement light is received, the received light signal from the light receiving element is sampled, and the sampling values at the same sampling time of the received light signal from the same light receiving element sampled within the detection period are integrated Based on the integrated sampling value, an object in the monitoring area is detected, and an offset time at the timing of starting sampling is calculated based on the traveling speed of the vehicle, for each measurement period. The start of the sampling is offset by the offset time.

  With such a configuration, the laser beam is projected onto the monitoring area, the received light signal of the reflected light received from the monitoring area is sampled and accumulated, and the laser is detected when detecting the object based on the accumulated sampling value. When a vehicle equipped with a radar device approaches a stationary object, the sampling start timing corresponding to the vehicle speed is offset by detecting the stationary object so that the deviation of the peak position of the sampling value caused by the movement of the vehicle is offset. be able to. As a result, it is possible to integrate the sampling waveforms by aligning the peak waveforms indicating the timing for detecting the objects of the sampling values, so that the accuracy of detecting the distance of the object based on the peak of the integrated sampling values is improved. It becomes possible.

  According to the present invention, the peak position indicating the detection distance of the object obtained by integrating the sampling values can be adjusted and the sampling values can be appropriately integrated, thereby improving the object detection accuracy. Can do.

It is a block diagram which shows one Embodiment of the laser radar apparatus to which this invention is applied. It is a block diagram which shows the structural example of a light projection part. It is a block diagram which shows the structural example of a light-receiving part. It is a block diagram which shows the structural example of a measurement part. It is a schematic diagram which shows the structural example of the function of a multiplexer. It is a block diagram which shows the structural example of the function of a calculating part. It is a flowchart for demonstrating an object detection process. It is a timing chart for explaining object detection processing. It is a figure for demonstrating the integration process of a light reception value. It is a figure which shows the example of the combination of the light receiving element allocated to each measurement period. It is a figure explaining the offset in sampling. It is a figure for demonstrating the example of the detection method of a vehicle. It is a block diagram which shows the structural example of a computer.

{Configuration example of laser radar device 11}
FIG. 1 shows a configuration example of a laser radar device 11 which is an embodiment of a laser radar device to which the present invention is applied.

  The laser radar device 11 is provided in a vehicle, for example, and detects an object in the traveling direction of the vehicle. Hereinafter, an area in which an object can be detected by the laser radar device 11 is referred to as a monitoring area. Hereinafter, when it is necessary to distinguish a vehicle provided with the laser radar device 11 from other vehicles, the vehicle is referred to as a host vehicle. Further, hereinafter, a direction parallel to the left-right direction (vehicle width direction) of the host vehicle is referred to as a horizontal direction.

  The laser radar device 11 is configured to include a control unit 21, a light projecting unit 22, a light receiving unit 23, a measurement unit 24, and a calculation unit 25.

  The control unit 21 controls each unit of the laser radar device 11 based on commands and information from the vehicle control device 12.

  The light projecting unit 22 projects measurement light, which is pulsed laser light (laser pulse) used for detecting an object, onto the monitoring area.

  The light receiving unit 23 receives the reflected light of the measurement light and detects the intensity (brightness) of the reflected light from different directions in the horizontal direction. And the light-receiving part 23 outputs the some light reception signal which is an electrical signal according to the intensity | strength of the reflected light of each direction.

  The measurement unit 24 measures the light reception value based on the light reception signal supplied from the light reception unit 23 and supplies the measurement result to the calculation unit 25.

  The calculation unit 25 detects an object in the monitoring area based on the measurement result of the received light value supplied from the measurement unit 24 and supplies the detection result to the control unit 21 and the vehicle control device 12.

  The vehicle control device 12 is configured by, for example, an ECU (Electronic Control Unit) or the like, and performs automatic brake control, a warning to the driver, or the like based on the detection result of the object in the monitoring area.

  The vehicle speed sensor 13 is installed in the vehicle, detects the speed of the host vehicle, and supplies the detected speed to the control unit 21.

{Configuration example of the light projecting unit 22}
FIG. 2 shows a configuration example of the light projecting unit 22 of the laser radar device 11. The light projecting unit 22 is configured to include a drive circuit 101, a light emitting element 102, and a light projecting optical system 103.

  The drive circuit 101 controls the light emission intensity and the light emission timing of the light emitting element 102 under the control of the control unit 21.

  The light emitting element 102 is made of, for example, a laser diode, and emits measurement light (laser pulse) under the control of the drive circuit 101. The measurement light emitted from the light emitting element 102 is projected onto the monitoring area via the light projecting optical system 103 constituted by a lens or the like.

{Configuration example of light receiving unit 23}
FIG. 3 shows a configuration example of the light receiving unit 23 of the laser radar device 11. The light receiving unit 23 is configured to include a light receiving optical system 201 and light receiving elements 202-1 to 202-16.

  Hereinafter, the light receiving elements 202-1 to 202-16 are simply referred to as the light receiving elements 202 when it is not necessary to distinguish them individually.

  The light receiving optical system 201 is configured by a lens or the like, and is installed so that the optical axis faces the front-rear direction of the vehicle. The light receiving optical system 201 receives the reflected light of the measurement light reflected by an object or the like in the monitoring area, and makes the reflected light incident on the light receiving surface of each light receiving element 202.

  Each light receiving element 202 is composed of, for example, a photodiode that photoelectrically converts incident photoelectric charges into a received light signal having a current value corresponding to the amount of light. Each light receiving element 202 is perpendicular to the optical axis of the light receiving optical system 201 and parallel to the vehicle width direction of the host vehicle (that is, horizontal) at the position where the reflected light incident on the light receiving optical system 201 is collected. In the direction). Then, the reflected light incident on the light receiving optical system 201 is distributed and incident on each light receiving element 202 according to the incident angle in the horizontal direction to the light receiving optical system 201. Therefore, each light receiving element 202 receives reflected light from different directions in the horizontal direction among the reflected light from the monitoring region. Thereby, the monitoring area is divided into a plurality of areas (hereinafter referred to as detection areas) in a plurality of horizontal directions, and each light receiving element 202 individually receives the reflected light from the corresponding detection area. The light receiving element 202 photoelectrically converts the received reflected light into a light reception signal having a current value corresponding to the amount of light received, and supplies the obtained light reception signal to the measurement unit 24.

{Configuration example of measurement unit 24}
FIG. 4 shows a configuration example of the measurement unit 24 of the laser radar device 11. The measurement unit 24 is configured to include a selection unit 251, a current-voltage conversion unit 252, an amplification unit 253, and a sampling unit 254. The selection unit 251 is configured to include multiplexers (MUX) 261-1 to 261-4. The current-voltage conversion unit 252 is configured to include trans-impedance amplifiers (TIAs) 262-1 to 262-4. The amplification unit 253 is configured to include programmable gain amplifiers (PGA) 263-1 to 263-4. The sampling unit 254 is configured to include A / D converters (ADC) 264-1 to 264-4.

  Hereinafter, when it is not necessary to individually distinguish the MUXs 261-1 to 261-4, the TIAs 262-1 to 262-4, the PGAs 263-1 to 263-4, and the ADCs 264-1 to 264-4, respectively. They will be referred to as MUX261, TIA262, PGA263, and ADC264.

  Under the control of the control unit 21, the MUX 261-1 selects one or more of the light reception signals supplied from the light receiving elements 202-1 to 202-4 and supplies the selected signals to the TIA 262-1. Note that when a plurality of light reception signals are selected, the MUX 261-1 adds the selected light reception signals and supplies them to the TIA 262-1.

  Under the control of the control unit 21, the MUX 261-2 selects one or more of the light reception signals supplied from the light receiving elements 202-5 to 202-8 and supplies the selected signals to the TIA 262-2. Note that when a plurality of light reception signals are selected, the MUX 261-2 adds the selected light reception signals and supplies them to the TIA 262-2.

  Under the control of the control unit 21, the MUX 261-3 selects one or more of the light reception signals supplied from the light receiving elements 202-9 to 202-12 and supplies the selected signals to the TIA 262-3. When the MUX 261-3 selects a plurality of light reception signals, the MUX 261-3 adds the selected light reception signals and supplies them to the TIA 262-3.

  Under the control of the control unit 21, the MUX 261-4 selects one or more of the light receiving signals supplied from the light receiving elements 202-13 to 202-16 and supplies the selected signals to the TIA 262-4. When the MUX 261-4 selects a plurality of light reception signals, the MUX 261-4 adds the selected light reception signals and supplies them to the TIA 262-4.

  Accordingly, each light receiving element 202 includes a first group including light receiving elements 202-1 to 202-4, a second group including light receiving elements 202-5 to 202-8, and light receiving elements 202-9 to 202-12. Into a fourth group consisting of the light receiving elements 202-13 to 202-16. Then, the MUX 261-1 selects the first group of light receiving elements 202 and outputs a light reception signal of the selected light receiving elements 202. The MUX 261-2 selects the light receiving element 202 of the second group and outputs a light reception signal of the selected light receiving element 202. The MUX 261-3 selects the third group of light receiving elements 202 and outputs a light reception signal of the selected light receiving elements 202. The MUX 261-4 selects the fourth group of light receiving elements 202 and outputs a light reception signal of the selected light receiving elements 202.

  Each TIA 262 performs current-voltage conversion of the received light signal supplied from the MUX 261 under the control of the control unit 21. That is, each TIA 262 converts the received light signal as an input current into a received light signal as a voltage, and amplifies the voltage of the converted received light signal with a gain set by the control unit 21. Each TIA 262 supplies the amplified light reception signal to the subsequent PGA 263.

  Each PGA 263 amplifies the voltage of the light reception signal supplied from the TIA 262 with the gain set by the control unit 21 under the control of the control unit 21, and supplies the amplified signal to the ADC 264 in the subsequent stage.

  Each ADC 264 performs A / D conversion of the received light signal. That is, each ADC 264 measures a light reception value by sampling an analog light reception signal supplied from the PGA 263 under the control of the control unit 21. Each ADC 264 supplies a digital light reception signal indicating a sampling result (measurement result) of the light reception value to the arithmetic unit 25.

{Configuration example of MUX261}
FIG. 5 schematically shows an example of the functional configuration of the MUX 261.

  The MUX 261 includes a decoder 271, input terminals IN1 to IN4, contacts C1 to C4, and an output terminal OUT1. One ends of the contacts C1 to C4 are connected to the input terminals IN1 to IN4, respectively, and the other ends of the contacts C1 to C4 are connected to the output terminal OUT1.

  Hereinafter, the input terminals IN1 to IN4 and the contacts C1 to C4 are simply referred to as the input terminal IN and the contact C when it is not necessary to distinguish them individually.

  The decoder 271 decodes the selection signal supplied from the control unit 21, and individually switches on / off of each contact C according to the content of the decoded selection signal. Then, a light reception signal input to the input terminal IN connected to the contact C that is turned on is selected and output from the output terminal OUT1. When there are a plurality of contacts C that are turned on, a plurality of selected light reception signals are added and output from the output terminal OUT1.

{Configuration example of calculation unit 25}
FIG. 6 shows a configuration example of the calculation unit 25.

  The calculation unit 25 is configured to include an integration unit 301, a detection unit 302, and a notification unit 303. The detection unit 302 is configured to include a peak detection unit 311 and an object detection unit 312.

  The integrating unit 301 integrates the received light values of the same light receiving element 202 at each sampling time, and supplies the integrated value (hereinafter referred to as an integrated received light value) to the peak detecting unit 311.

  The peak detection unit 311 detects the peak in the horizontal direction and the time direction (distance direction) of the intensity of the reflected light of the measurement light based on the integrated light reception value (the intensity of the reflected light) of each light receiving element 202, and obtains the detection result. It supplies to the object detection part 312.

  Here, the peak in the time direction (distance direction) will be described. The laser radar device calculates the distance to the object using the time (referred to as the flight time) until the projected measurement light is reflected by the object and returns to the laser radar device. Since this flight time is proportional to the value obtained by dividing the distance by the speed of light, the distance can be calculated if the time is known. When the time at which a certain light receiving element 202 receives reflected light is t1, the integrated light reception value at time t1 is larger than the integrated light reception values at other times. For each light receiving element 202, a peak can be specified from the sampling time at which the integrated light reception value is maximum and the integrated light reception value at this time. This peak is a peak in the time direction (distance direction). For example, the peak in the distribution of the integrated values of the sampling values with respect to the sampling time shown in the lowermost stage of FIG. 9 described later corresponds to the peak in the time direction (distance direction).

  The horizontal peak will be described. As described above, the light receiving element 202 is disposed horizontally in the width direction of the vehicle. The monitoring area is divided into a plurality of detection areas in the horizontal direction, and each light receiving element 202 receives reflected light from the corresponding detection area. For example, the two reflectors installed in the vehicle are separated from the laser radar device by substantially the same distance, and are also separated by a distance slightly shorter than the vehicle width in the horizontal direction. It is assumed that the light receiving element 202-4 receives light reflected from one of the two reflectors at a certain sampling time, and the light receiving element 202-8 arranged away from the light receives the reflected light from the other of the two reflectors. In this case, of the light receiving elements 202-1 to 202-16 arranged in the horizontal direction, the integrated light receiving value protrudes and becomes large at two positions of the light receiving element 202-4 and the light receiving element 202-8. This is a horizontal peak. For example, a peak in the distribution of integrated light reception values with respect to the horizontal direction shown at the top of FIG. 12 described later corresponds to a peak in the horizontal direction.

  The object detection unit 312 detects an object in the monitoring region based on the horizontal and time direction (distance direction) distribution and peak detection result of the integrated light reception value (reflected light intensity), and controls the detection result. To the unit 21 and the notification unit 303.

  The notification unit 303 supplies the detection result of the object in the monitoring area to the vehicle control device 12.

{Object detection processing}
Next, the object detection process executed by the laser radar device 11 will be described with reference to the flowchart of FIG.

  In step S <b> 1, the control unit 21 initializes the offset time of the timing at which the light receiving unit 23 starts sampling to 0 (zero). That is, the offset time here indicates a deviation in the time direction with respect to a default timing for generating a trigger signal that defines a sampling start timing of the ADC 264 described later. Therefore, in the first process, the offset time is set to 0.

  In step S <b> 2, each MUX 261 selects the light receiving element 202. Specifically, each MUX 261 selects a light reception signal to be supplied to the subsequent TIA 262 from among the light reception signals input to each MUX 261 under the control of the control unit 21. In the following processing, the light reception value of the light receiving element 202 that is the output source of the selected light reception signal is measured. In other words, the intensity of the reflected light from the detection region of the selected light receiving element 202 is measured.

  In step S3, the light projecting unit 22 projects measurement light. Specifically, the drive circuit 101 emits pulsed measurement light from the light emitting element 102 under the control of the control unit 21. The measurement light emitted from the light emitting element 102 is projected onto the entire monitoring region via the light projecting optical system 103.

  In step S4, the light receiving unit 23 generates a light reception signal corresponding to the reflected light. Specifically, each light receiving element 202 receives the reflected light from the detection area in the corresponding direction among the reflected light with respect to the measurement light projected in the process of step S <b> 2 via the light receiving optical system 201. Each light receiving element 202 photoelectrically converts the received reflected light into a light receiving signal that is an electrical signal corresponding to the amount of light received, and supplies the obtained light receiving signal to the subsequent MUX 261.

  In step S5, the measurement unit 24 samples the received light signal. Specifically, each TIA 262 performs current-voltage conversion of the light reception signal supplied from each MUX 261 under the control of the control unit 21 and amplifies the voltage of the light reception signal by the gain set by the control unit 21. To do. Each TIA 262 supplies the amplified received light signal to the subsequent PGA 263.

  Under the control of the control unit 21, each PGA 263 amplifies the voltage of the light reception signal supplied from each TIA 262 with the gain set by the control unit 21, and supplies the amplified signal to the subsequent ADC 264.

  Each ADC 264 samples the received light signal supplied from each PGA 263 based on a trigger signal that defines the sampling start timing generated under the control of the control unit 21 and A / D converts the received light signal. Each ADC 264 supplies the light reception signal after A / D conversion to the integration unit 301. The control unit 21 adjusts the timing so as to shift the offset time from the reference timing, and generates a trigger signal. Therefore, in the first process, the offset time is 0, so that it is generated at the reference timing.

  The details of the sampling process of the received light signal will be described later with reference to FIG.

  In step S6, the integration unit 301 integrates the light reception values up to the previous time and the current light reception values. As a result, as will be described later with reference to FIG. 9, the received light values at the same sampling time of the received light signals from the same light receiving element 202 are integrated.

  In step S <b> 7, the control unit 21 determines whether or not the received light value has been measured a predetermined number of times (for example, 100 times). If it is determined that the received light value has not been measured a predetermined number of times, the process returns to step S2.

  Here, a specific example of the processing of steps S2 to S6 will be described with reference to FIGS.

  FIG. 8 is a timing chart showing a specific example of the sampling process of the received light signal, and the horizontal axis of each figure in the figure shows time.

  The uppermost part of FIG. 8 shows the emission timing of the measurement light. The detection periods TD1, TD2,... Are the minimum unit of the period for performing the object detection process, and the object detection process is performed once in one detection period.

  Each detection period includes four cycles of measurement periods TM1 to TM4 and a pause period TB. The measurement period is a minimum unit for switching the light receiving element 202 for measuring the light reception value. That is, the light receiving element 202 can be selected before each measurement period, while the light receiving element 202 cannot be changed during the measurement period. Therefore, the light reception value of the same type of light receiving element 202 is measured in one measurement period. Thereby, the detection area | region used as the object which measures the intensity | strength of reflected light per measurement period can be switched.

  The second row in FIG. 8 is an enlarged view of the measurement period TM2 of the detection period TD1. As shown in this figure, the measurement light is projected at a predetermined interval of a predetermined number of times (for example, 100 times) at a predetermined interval within a measurement period of one cycle.

  The third row in FIG. 8 shows the waveform of the trigger signal that defines the sampling timing of the ADC 264, and the fourth row shows the sampling timing of the received light signal in the ADC 264. The vertical axis in the fourth row indicates the value (voltage) of the light reception signal, and a plurality of black circles on the light reception signal indicate sampling points, respectively. Therefore, the time between adjacent black circles is the sampling interval.

  The control unit 21 supplies a trigger signal to each ADC 264 after a predetermined period of time including the offset time from the measurement light projection. Each ADC 264 samples the received light signal a predetermined number of times (for example, 32 times) at a predetermined sampling frequency (for example, several tens to several hundreds of MHz) after a predetermined time has elapsed since the trigger signal was input. That is, each time the measurement light is projected, the received light signal selected by the MUX 261 is sampled a predetermined number of times at a predetermined sampling interval. The trigger signal supply timing including the offset time will be described later in detail.

  For example, if the sampling frequency of the ADC 264 is 100 MHz, sampling is performed at a sampling interval of 10 nanoseconds. Therefore, the received light value is sampled at intervals of about 1.5 m in terms of distance. That is, the intensity of the reflected light from each point at intervals of about 1.5 m in the distance direction from the host vehicle in each detection region is measured.

  Each ADC 264 supplies a digital light reception signal indicating a sampling value (light reception value) at each sampling time with the trigger signal as a reference (the time when the trigger signal is input is 0) to the integration unit 301.

  In this way, each time the measurement light is projected, the light reception signal of each light receiving element 202 selected by the MUX 261 is sampled. Thereby, the intensity of the reflected light in the detection region of each selected light receiving element 202 is detected in a predetermined distance unit.

  On the other hand, in the suspension period TB, the measurement light projection and the light reception value measurement are suspended. And the detection process of the object based on the measurement result of the light reception value in measurement period TM1 thru | or TM4, the setting of the light projection part 22, the light-receiving part 23, the measurement part 24, adjustment, a test, etc. are performed.

  Next, a specific example of the light reception value integration process will be described with reference to FIG. FIG. 9 shows an example of integration processing for 100 received light signals output from a certain light receiving element 202 when measuring light is projected 100 times during a measurement period of one cycle. The horizontal axis in FIG. 9 indicates the time (sampling time) with the trigger signal input timing as a reference (time 0), and the vertical axis indicates the received light value (sampling value).

  As shown in this figure, for each measurement light from the first time to the 100th time, the received light signal is sampled at sampling times t1 to ty, and the received light values at the same sampling time are integrated. For example, the received light values at the sampling time t1 for each measurement light from the first time to the 100th time are integrated. In this manner, the received light values at the same sampling time of the received light signals from the same light receiving element 202 sampled within the detection period are integrated. This integrated value is used for subsequent processing.

  Here, when the light receiving signals from the plurality of light receiving elements 202 are added in the MUX 261, the light receiving values of the light receiving signals that coincide with all the light receiving elements 202 are integrated. For example, the light receiving value of the light receiving signal obtained by adding the light receiving signals from the light receiving elements 202-1 and 202-2 is integrated separately from the light receiving value of the light receiving signal from only one of the light receiving elements 202-1 or 202-2. Is done. In other words, the light reception value of the light reception signal obtained by adding the light reception signals from the light reception elements 202-1 and 202-2 and the light reception value of the light reception signal from only one of the light reception elements 202-1 or 202-2. These are distinguished as light reception values obtained by sampling different types of light reception signals, and integrated separately.

  By this integration process, even when the S / N ratio of the received light signal with respect to one measurement light is low, by performing this integration process, signal components are amplified and random noise is averaged and reduced. As a result, the signal component and the noise component can be easily separated from the light reception signal, and the light reception sensitivity can be substantially increased. Thereby, for example, the detection accuracy of a distant object or an object with low reflectivity is improved.

  Hereinafter, a set of measurement processing and integration processing performed a predetermined number of times (for example, 100 times) executed within one cycle of the measurement period is referred to as a measurement integration unit.

  FIG. 10 shows an example of combinations of selection of the light receiving elements 202 of each MUX 261 in each measurement period. In this figure, MUXs 261-1 to 261-4 are abbreviated as MUX1 to MUX4. Further, the numbers in the squares in the figure indicate the numbers of the light receiving elements 202 selected by the MUXs 261-1 to 261-4. That is, the light receiving elements 202-1 to 202-16 are indicated by numbers 1 to 16, respectively.

  For example, in the measurement period TM1, the light receiving elements 202-1, 202-5, 202-9, and 202-13 are selected by the MUXs 261-1 to 261-4, and the light reception values of the selected light receiving elements 202 are measured. Done. In the measurement period TM2, the light receiving elements 202-2, 202-6, 202-10, and 202-14 are selected by the MUXs 261-1 to 261-4, and the light reception values of the selected light receiving elements 202 are measured. . In the measurement period TM3, the light receiving elements 202-3, 202-7, 202-11, and 202-15 are selected by the MUXs 261-1 to 261-4, and the light reception values of the selected light receiving elements 202 are measured. . In the measurement period TM4, the light receiving elements 202-4, 202-8, 202-12, and 202-16 are selected by the MUXs 261-1 to 261-4, respectively, and the light reception value of each selected light receiving element 202 is measured. .

  Therefore, in this example, the light reception values of all the light receiving elements 202 are measured during one detection period. In other words, the intensity of the reflected light from all the detection areas in the monitoring area is measured during one detection period.

  In step S <b> 8, based on the speed of the host vehicle supplied from the vehicle speed sensor 13, the control unit 21 performs an offset time corresponding to the distance traveled by the host vehicle between the immediately preceding measurement period and the current measurement period. Is calculated.

Here, the offset time will be described with reference to FIG. For example, after a trigger signal is generated at time t0 in the time direction distribution shown in the uppermost part of FIG. 11, sampling is started at a time t1 when a predetermined time has elapsed, and a stationary object is detected at a peak at time t2. Shall be.

  When detected in the next measurement period, as shown in the second stage of FIG. 11, the time from the time t1 when the trigger signal is generated to the time t11 when the peak is detected is the time dt1 ( = T2-t11). In other words, the distance between the host vehicle and the stationary object approaches only the distance calculated by multiplying the vehicle speed by the measurement period, and therefore, approximately the same time as the time required for the laser beam to reciprocate the distance. The timing at which the peak is detected by dt1 is advanced.

  Thus, the distance from the host vehicle to the stationary object decreases at a rate corresponding to the traveling speed when the host vehicle travels toward the stationary object. The idea of increasing the light receiving sensitivity by integrating a plurality of light receiving signals is based on the premise that the distance from the vehicle to the stationary object does not change or that the change can be ignored. However, in reality, since this distance changes, the timing at which a peak is detected changes, and there is a possibility that the light receiving sensitivity will not increase even if integration is performed.

  Therefore, in this case, since the difference time dt1 corresponds to the vehicle speed, the control unit 21 determines the difference time dt1 based on the vehicle speed information of the host vehicle supplied from the vehicle speed sensor 13. = Calculated as offset time dt2.

  As a result, in the subsequent step S5, as shown in the lowermost stage of FIG. 11, the timing at which the trigger signal rises is offset at time t21, which is the offset time dt2 before time t0. As a result, sampling is started from time t22 that is earlier than the time t1 by the offset time dt2. As a result, with respect to the data Z1 obtained by the first sampling, the timing detected as a peak is the time t23 corresponding to the time t11 by proceeding at the vehicle speed of the host vehicle in the next measurement period. Data Z2 is obtained. As shown in FIG. 11, each of the data Z1 and Z2 has a waveform in which a peak is obtained at substantially the same time after the trigger signal rises. For this reason, in step S6, it is possible to appropriately repeat the integration by integrating the data Z1 and Z2 having waveforms that substantially coincide with the timing at which the peaks are obtained.

  More specifically, for example, when the vehicle is approaching 1 cm with respect to a stationary object in one measurement period, the sampling start timing is offset so as to be advanced by 1/15 ns. Hereinafter, similarly, in the case of approaching 20 cm and 100 cm, they are offset so as to be advanced by 20/15 ns and 100/15 ns, respectively.

  In step S9, the control unit 21 determines whether or not the measurement period has been repeated a predetermined number of times. If it is determined that the measurement period has not been repeated a predetermined number of times, the process returns to step S2.

  That is, in step S9, steps S2 to S9 are repeatedly executed until it is determined that the measurement period is repeated a predetermined number of times. That is, the measurement period is repeated a predetermined number of times within a detection period of a predetermined length. In addition, for each measurement period, the light receiving element 202 that is a target for measuring the received light value is selected, the detection region that is the target for measuring the intensity of the reflected light is switched, and the peak timing is determined by the offset time. The process is repeated while adjusting.

  On the other hand, if it is determined in step S9 that the measurement period has been repeated a predetermined number of times, the process proceeds to step S10.

  In step S <b> 10, the peak detection unit 311 determines the intensity of the reflected light in the horizontal direction and the time direction (distance direction) of the reflected light within one detection period based on the distribution of the accumulated light reception values at each sampling time of each light receiving element 202. Detect peaks.

  Specifically, the peak detector 311 detects the sampling time at which the integrated light reception value peaks for each light receiving element 202. Thereby, the point where the intensity of the reflected light peaks in the distance direction from the host vehicle is detected for each detection region. In other words, in each detection region, the distance from the host vehicle at the point where the object having the peak reflected light intensity is detected.

  In addition, the peak detector 311 detects the light receiving element 202 (detection region) where the integrated light reception value peaks at each sampling time. Thereby, in the distance direction from the host vehicle, the horizontal position (detection region) where the intensity of the reflected light peaks at every predetermined interval (for example, about every 1.5 m) is detected.

  Then, the peak detection unit 311 supplies information indicating the detection result to the object detection unit 312.

  That is, for example, as shown in FIG. 12, the measurement light is reflected by the vehicle 351 and received by the light receiving element 202, but there is a time difference from light projection to light reception. Since this time difference is proportional to the distance between the laser radar device and the vehicle 351, the reflected light from the vehicle 351 is measured as a light reception value at a sampling timing (sampling time tn) that matches the time difference. Accordingly, among the integrated light reception values of the respective light receiving elements 202 in the detection region including the vehicle 351, the integrated light reception value particularly at the sampling time tn becomes large.

  Note that the graph of FIG. 12 shows the horizontal distribution of the integrated light reception values at the sampling time near the reflected light from the vehicle 351 when the vehicle 351 is traveling in front of the host vehicle. . That is, this graph is a graph in which the integrated light reception values of the respective light receiving elements 202 at the sampling time are arranged in the horizontal axis direction in the horizontal arrangement order of the respective light receiving elements 202.

  Note that any method can be adopted as the peak detection method of the peak detection unit 311.

  In step S11, the object detection unit 312 detects other vehicles, pedestrians, obstacles, etc. in the monitoring area based on the horizontal and temporal distributions of the intensity of the reflected light and the peak detection results within the measurement period. The presence / absence of an object and the type, direction, distance, etc. of the object are detected.

  Note that an arbitrary method can be adopted as the object detection method of the stationary object (including the moving object) of the object detection unit 312.

  That is, for example, as shown in FIG. 12, when a vehicle 351 is present in the front, the reflected light reflected by the vehicle 351 is received by the light receiving element 202, so that each light reception including the vehicle 351 within the detection region. The integrated light reception value of the element 202 increases. In particular, since the reflectance of the left and right reflectors 352L and 352R behind the vehicle 351 is high, the integrated light reception value of each light receiving element 202 including the reflectors 352L and 352R in the detection region is particularly large.

  Therefore, as shown in the graph of FIG. 12, two prominent peaks P1 and P2 appear in the distribution of the accumulated light reception values in the horizontal direction. Further, since the reflected light reflected by the vehicle body between the reflectors 352L and 352R is also detected, the integrated light reception value between the peak P1 and the peak P2 is higher than that in other regions. Thus, it is possible to detect the vehicle ahead by detecting two prominent peaks in the horizontal distribution of the integrated light reception values at the same sampling time.

  In step S12, the notification unit 303 notifies the object detection result to the outside as necessary. For example, the notification unit 303 periodically supplies the detection result of the object to the vehicle control device 12 regardless of the presence or absence of the object. Alternatively, for example, the notification unit 303 supplies the object detection result to the vehicle control device 12 only when there is a risk that the vehicle collides with an object ahead.

  In step S13, the control unit 21 waits for a predetermined time. That is, the control unit 21 waits not to project the measurement light until the suspension period TB in FIG. 8 ends.

  Thereafter, the process returns to step S1, and the processes of steps S1 to S13 are repeatedly executed. That is, the process of detecting an object based on the integrated light reception value is repeated for each detection period.

  With the above processing, the trigger signal generation timing is adjusted so that the peak position in the sampling value consisting of the received light value of the reflected light can be offset according to the vehicle speed of the host vehicle when the host vehicle approaches the stationary object. As a result, sampling values that form waveforms having substantially the same peak positions can be integrated. Thereby, even when the S / N ratio of the received light signal with respect to one measurement light is low, the signal component can be appropriately amplified, and random noise can be averaged and reduced. As a result, the signal component and the noise component can be more easily separated from the light reception signal, and the light reception sensitivity can be substantially increased. Thereby, for example, it becomes possible to further improve the detection accuracy of a distant object or an object having a low reflectance.

  Further, the present invention can also be applied to a laser radar device used for other purposes than for vehicles.

[Computer configuration example]
The series of processes described above can be executed by hardware or can be executed by software. When a series of processing is executed by software, a program constituting the software is installed in the computer. Here, the computer includes, for example, a general-purpose personal computer capable of executing various functions by installing various programs by installing a computer incorporated in dedicated hardware.

  FIG. 13 is a block diagram showing an example of the hardware configuration of a computer that executes the above-described series of processing by a program.

  In a computer, a CPU (Central Processing Unit) 601, a ROM (Read Only Memory) 602, and a RAM (Random Access Memory) 603 are connected to each other by a bus 604.

  An input / output interface 605 is further connected to the bus 604. An input unit 606, an output unit 607, a storage unit 608, a communication unit 609, and a drive 610 are connected to the input / output interface 605.

  The input unit 606 includes a keyboard, a mouse, a microphone, and the like. The output unit 607 includes a display, a speaker, and the like. The storage unit 608 includes a hard disk, a nonvolatile memory, and the like. The communication unit 609 includes a network interface or the like. The drive 610 drives a removable medium 611 such as a magnetic disk, an optical disk, a magneto-optical disk, or a semiconductor memory.

  In the computer configured as described above, the CPU 601 loads the program stored in the storage unit 608 to the RAM 603 via the input / output interface 605 and the bus 604 and executes the program, for example. Is performed.

  The program executed by the computer (CPU 601) can be provided by being recorded on a removable medium 611 as a package medium, for example. The program can be provided via a wired or wireless transmission medium such as a local area network, the Internet, or digital satellite broadcasting.

  In the computer, the program can be installed in the storage unit 608 via the input / output interface 605 by attaching the removable medium 611 to the drive 610. Further, the program can be received by the communication unit 609 via a wired or wireless transmission medium and installed in the storage unit 608. In addition, the program can be installed in the ROM 602 or the storage unit 608 in advance.

  The program executed by the computer may be a program that is processed in time series in the order described in this specification, or in parallel or at a necessary timing such as when a call is made. It may be a program for processing.

  The embodiments of the present technology are not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present technology.

DESCRIPTION OF SYMBOLS 11 Laser radar apparatus 12 Vehicle control apparatus 21 Control part 22 Light projection part 23 Light reception part 24 Measurement part 25 Calculation part 101 Drive circuit 102 Light emitting element 202-1 thru | or 202-16 Light reception element 251 Selection part 254 Sampling part 261-1 thru | or 261 -4 Multiplexer 264-1 to 264-4 A / D converter 301 Integration unit 302 Detection unit 303 Notification unit 311 Peak detection unit 312 Object detection unit

Claims (5)

In a laser radar device mounted on a vehicle,
A light projecting unit that repeats a process of projecting a measurement light, which is a pulsed laser beam, a predetermined number of times within a predetermined measurement period to a predetermined monitoring region within a detection period of a predetermined length;
A light receiving unit including a light receiving element that receives reflected light of the measurement light;
A sampling unit for sampling a light reception signal from the light receiving element;
An accumulating unit that performs sampling of sampling values at the same sampling time of the received light signals from the same light receiving elements sampled within the detection period;
Based on the integrated sampling value, a detection unit for detecting an object in the monitoring region;
Based on the traveling speed of the vehicle, including a control unit that calculates an offset time of timing for starting sampling in the sampling unit,
The control unit causes the sampling unit to offset the start of the sampling by the offset time for each measurement period. The control unit offsets the offset time and outputs a trigger signal to the sampling unit,
The laser radar device according to claim 1, wherein the sampling unit starts the sampling by the trigger signal. The light projecting unit performs a process of projecting measurement light, which is pulsed laser light, m times (m ≧ 1) within a measurement period of a predetermined first length with respect to a predetermined monitoring region. C cycles (c ≧ 2) repeated within a detection length of 2;
The light receiving unit includes n1 (n1 ≧ 2) light receiving elements that receive reflected light of the measurement light from different directions,
The laser radar device according to claim 1, wherein the sampling unit performs sampling of received light signals from n1 light receiving elements s times (s ≧ 2) each time the measurement light is projected. The laser radar device according to claim 1, wherein the integration unit integrates the sampling values over a plurality of the detection periods. In an object detection method of a laser radar device mounted on a vehicle,
A light projecting step of repeating a process of projecting a measurement light, which is a pulsed laser light, a predetermined number of times within a predetermined measurement period with respect to a predetermined monitoring region, within a detection period of a predetermined length;
A light receiving step by a light receiving element that receives reflected light of the measurement light;
A sampling step for sampling a light reception signal from the light receiving element;
An integration step of integrating sampling values sampled at the same sampling time of the received light signal from the same light receiving element, sampled within the detection period;
A detection step of detecting an object in the monitoring region based on the integrated sampling value;
Including a control step of calculating an offset time of timing for starting sampling in the processing of the sampling step based on the traveling speed of the vehicle,
In the process of the sampling step, the start of the sampling is offset by the offset time every measurement period in the process of the sampling step.

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