JP2016170053A - Laser radar device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve detection accuracy of a laser radar device.SOLUTION: In a step S3, a light reception signal from each light reception element is subjected to sampling, thereby to measure a light reception value. In a step S4, a peak of the light reception value of each light reception element is detected, thereby to detect a detection distance in each detection region. In a step S5, with a correction table different in each light reception system, the detection distance of each detection region is corrected according to the difference between the detection distance and a sampling distance. In a step S6, on the basis of the corrected detection distance of each detection region, an object is detected. This invention, for example, can be applied to a laser radar device for a vehicle.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a laser radar device, and more particularly to a laser radar device that improves detection accuracy.

  Conventionally, measurement light, which is pulsed laser light, is projected onto a predetermined monitoring area, reflected light from an object is received by a light receiving means, and based on the difference between the measurement light projection time and the reflected light reception time. A distance measuring device that measures the distance to an object is known. In such a distance measuring device, a light reception signal corresponding to the intensity of the received reflected light is output from the light receiving means, and the light reception signal is amplified. Then, the time at which the amplified light reception signal peaks is regarded as the light reception time, and a difference from the measurement light projection time is detected.

  Conventionally, techniques for improving the detection accuracy of the light reception time have been proposed. For example, Patent Document 1 proposes a technique for obtaining a light reception time at which a light reception signal reaches a peak based on an intermediate time between two times at which the waveform of the light reception signal intersects a predetermined threshold (hereinafter referred to as a crossing time). Has been. Specifically, data indicating a correspondence relationship between a time width that is a width of two intersection times and fluctuates depending on reception intensity and a correction time that is a difference between the light reception time and the intermediate time is obtained in advance. Then, the time width and the intermediate time are measured, the correction time corresponding to the measured time width is obtained from the above data, and the light reception time is obtained by correcting the measured intermediate time with the obtained correction time. .

  Furthermore, for example, a method for detecting a light reception time at which a light reception signal reaches a peak is known by performing an interpolation operation using discrete sampling data obtained by sampling the light reception signal at a predetermined time interval. .

JP-A-9-236661

  On the other hand, waveform distortion occurs when the received light signal is amplified, and the peak position of the received light signal is shifted. Therefore, it is difficult to accurately detect the light reception time at which the light reception signal reaches a peak due to the distortion of the waveform of the light reception signal even if the technique and the interpolation calculation described in Patent Document 1 are used.

  Therefore, the present invention is to improve the detection accuracy of the laser radar device. In particular, the detection accuracy of a laser radar device that measures a distance using a light reception value obtained by sampling a light reception signal is improved.

  A laser radar device according to one aspect of the present invention includes a light projecting unit that projects measurement light that is pulsed laser light, a light receiving unit that includes a light receiving element that receives reflected light of the measurement light, and light reception from the light receiving element. By measuring the received light value by sampling the signal at a plurality of sampling times set at a predetermined sampling interval, and performing a predetermined interpolation calculation using a plurality of received light values at the plurality of sampling times , A peak detection unit for detecting a detection distance that is a distance corresponding to a peak time when the received light signal reaches a peak, and a memory that stores correction information that is set for each detection distance and indicates a correction amount that is used to correct the detection distance And a correction unit that corrects the detection distance based on the correction information, and the correction amount is half the distance that the laser beam travels during the sampling interval. Detection distance interval distance is equal for each increase or decrease.

  In the laser radar device according to one aspect of the present invention, measurement light that is pulsed laser light is projected, reflected light of the measurement light is received, and a plurality of samplings in which the received light signal is set at a predetermined sampling interval. The light reception value is detected by sampling at each time, and the detection distance that is the distance corresponding to the peak time at which the light reception signal peaks by performing a predetermined interpolation calculation using a plurality of light reception values at a plurality of sampling times. Is set for each detection distance, and is a correction amount used to correct the detection distance, and the detection distance increases or decreases by the sampling interval distance that is half the distance traveled by the laser beam during the sampling interval. The detection distance is corrected based on the correction information indicating the correction amount having the same value every time.

  Therefore, the detection accuracy of the laser radar device is improved. In particular, the detection accuracy of a laser radar device that measures a distance using a light reception value obtained by sampling a light reception signal is improved.

  For example, the light projecting unit includes a drive circuit, a light emitting element, a light projecting optical system, and the like. This light receiving element is formed of, for example, a photodiode. This measurement part is comprised by A / D converter, for example. The peak detection unit and the correction unit are configured by an arithmetic device such as a microcomputer and various processors, for example.

  The correction information is data indicating the relationship between the detection distance and the correction amount within the range of the detection distance fluctuation range of the sampling distance, and the correction unit corrects the detected detection distance based on the data. The amount can be obtained, and the detected distance can be corrected using the obtained correction amount.

  Thereby, the detection distance can be accurately corrected by a simple process.

  The correction information includes a function indicating the relationship between the detection distance and the correction amount. The correction unit calculates a correction amount for the detected detection distance using the function, and uses the calculated correction amount. The detection distance can be corrected.

  Thereby, the detection distance can be accurately corrected by a simple process.

  The light receiving unit is provided with a plurality of light receiving elements that receive reflected light from different detection directions in the horizontal direction, the measuring unit detects the light receiving value of each light receiving element, and the peak detecting unit Based on the light receiving value of the light receiving element, the detection distance is detected for each detection direction, the correction information indicates the correction amount for each detection direction, and the correction unit uses the correction amount for each detection direction. The detection distance in each detection direction can be corrected.

  Thereby, the detection accuracy of the detection distance in a plurality of detection directions is improved.

  According to one aspect of the present invention, the detection accuracy of the laser radar device can be improved. In particular, according to one aspect of the present invention, it is possible to improve the detection accuracy of a laser radar device that measures a distance using a light reception value obtained by sampling a light reception signal.

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 measurement light projector. It is a block diagram which shows the structural example of a light-receiving part. It is a figure which shows the position of each detection area typically. It is a schematic diagram which shows the relationship between each light receiving element and each detection area. It is a block diagram which shows the structural example of a measurement part. 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 demonstrating the sampling process of a received light signal. It is a graph which shows the relationship between the actual distance at the time of calculating | requiring a detection distance only based on the sampling result of a light reception value, and a detection distance. It is a figure for demonstrating the example of the calculation method of detection distance. It is a figure which shows the example of the distortion of the waveform of a received light signal. It is a graph which shows the example of the error of detection distance. It is a figure which shows the example of a correction table. It is a figure which shows the specific example of the correction result of detection distance. 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.

Hereinafter, modes for carrying out the present invention (hereinafter referred to as embodiments) will be described. The description will be given in the following order.
1. Embodiment 2. FIG. Modified example

<1. Embodiment>
{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 monitors the front 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 measurement 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 measurement light projector 22 projects measurement light, which is pulsed laser light (laser pulse) used to detect 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 for the reflected light from the light receiving unit 23 based on the analog light reception signal supplied from the light receiving unit 23, and supplies the digital light reception signal indicating the measured light reception value to the calculation unit 25. To do.

  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.

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

  Here, a specific example of the detection region of each light receiving element 202 will be described with reference to FIGS. 4 and 5. FIG. 4 schematically shows the position of each detection region when the host vehicle C provided with the laser radar device 11 is viewed from above. FIG. 5 schematically shows the relationship between each light receiving element 202 and each detection region when the light receiving unit 23 is viewed from above. In FIG. 5, only the light rays passing through the center of the lens of the light receiving optical system 201 out of the reflected light from each detection region are schematically shown for easy understanding of the drawing.

  The light receiving elements 202 are arranged in a line in the order of the light receiving elements 202-1, 202-2, 202-3... From the right in the traveling direction of the host vehicle C. On the other hand, the monitoring area of the laser radar device 11 is composed of detection areas A1 to A16 that radiate in front of the host vehicle C, and each detection area is a detection area from the left in the traveling direction of the host vehicle C. A1, A2, A3... Are arranged in this order. For example, the light receiving element 202-1 receives reflected light from the detection area A1 which is the left end in the monitoring area and indicated by the oblique line in front of the left side of the host vehicle C. The light receiving element 202-16 receives reflected light from the detection area A16, which is the right end in the monitoring area and indicated by the oblique line in front of the right side of the host vehicle C. Furthermore, the light receiving elements 202-8 and 202-9 receive the reflected light from the detection areas A8 and A9 indicated by the hatching in the center of the monitoring area.

{Configuration example of measurement unit 24}
FIG. 6 shows a configuration example of the measurement unit 24 of the laser radar device 11. The measurement unit 24 is configured to include a current / voltage conversion unit 251, an amplification unit 252, and a sampling unit 253. The current-voltage converter 251 is configured to include trans-impedance amplifiers (TIAs) 261-1 to 261-16. The amplifying unit 252 is configured to include programmable gain amplifiers (PGA) 262-1 to 262-16. The sampling unit 253 is configured to include A / D converters (ADC) 263-1 to 263-16. In addition, the TIA 261-i, the PGA 262-i, and the ADC 263-i (i = 1 to 16) are connected in series.

  Hereinafter, when it is not necessary to individually distinguish TIA 261-1 through 261-16, PGA 262-1 through 262-16, and ADC 263-1 through 263-16, TIA 261, PGA 262, and ADC 263 are simply Called. Hereinafter, each circuit from the light receiving elements 202-i to ADC 263-i (i = 1 to 16) connected in series is referred to as a light receiving system i. For example, the light receiving system 1 is configured by circuits from the light receiving element 202-1 to the ADC 263-1.

  Each TIA 261 performs current-voltage conversion of the light reception signal supplied from the light receiving element 202 under the control of the control unit 21. That is, each TIA 261 converts a 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 261 supplies the amplified received light signal to the subsequent PGA 262.

  Under the control of the control unit 21, each PGA 262 amplifies the voltage of the light reception signal supplied from the TIA 261 with the gain set by the control unit 21, and supplies the amplified signal to the subsequent ADC 263.

  Each ADC 263 performs A / D conversion of the received light signal. That is, each ADC 263 measures the light reception value by sampling the analog light reception signal supplied from the PGA 262 under the control of the control unit 21. Each ADC 263 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 calculation unit 25}
FIG. 7 shows a configuration example of the function of the calculation unit 25. The calculation unit 25 is configured to include a detection unit 301 and a notification unit 302. The detection unit 301 is configured to include a peak detection unit 311, a storage unit 312, a correction unit 313, and an object detection unit 314.

  The peak detection unit 311 detects the peak of the light reception value of each light receiving element 202 as described later. Thereby, as will be described later, peaks in the horizontal direction and the time direction (distance direction) of the intensity of the reflected light of the measurement light are detected. The peak detection unit 311 supplies the detection result to the correction unit 313.

  As will be described later, the correction unit 313 corrects the detection result of the peak of the light reception value of each light receiving element 202 based on the correction table or the correction function stored in the storage unit 312, and displays the corrected detection result. It supplies to the object detection part 314.

  The object detection unit 314 detects an object in the monitoring area based on the detection result of the peak of the light reception value of each light receiving element 202 after correction, and supplies the detection result to the control unit 21 and the notification unit 302.

  The notification unit 302 supplies the detection result of the object in the monitoring area to the vehicle control device 12.

{Object detection processing}
Next, the monitoring process executed by the laser radar device 11 will be described with reference to the flowchart of FIG. Note that this processing is started when, for example, an ignition switch or a power switch of a vehicle provided with the laser radar device 11 is turned on, and is ended when the vehicle is turned off.

  In step S <b> 1, the measurement light projector 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 S2, 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 region in the corresponding direction among the reflected light with respect to the measurement light projected in the process of step S1 via the light receiving optical system 201. Each light receiving element 202 photoelectrically converts the received reflected light into a received light signal that is an electrical signal corresponding to the received light amount, and supplies the obtained received light signal to the TIA 261 at the subsequent stage.

  In step S3, the measurement unit 24 samples the received light signal. Specifically, each TIA 261 performs current-voltage conversion of the light reception signal supplied from each light receiving element 202 under the control of the control unit 21, and uses the gain set by the control unit 21 to change the voltage of the light reception signal. Amplify. Each TIA 261 supplies the amplified light reception signal to the subsequent PGA 262.

  Under the control of the control unit 21, each PGA 262 amplifies the voltage of the light reception signal supplied from each TIA 261 with the gain set by the control unit 21, and supplies the amplified signal to the subsequent ADC 263.

  Each ADC 263 performs sampling of the light reception signal supplied from each PGA 262 under the control of the control unit 21, and A / D converts the light reception signal. Each ADC 263 supplies the received light signal after A / D conversion to the peak detector 311.

  Here, a specific example of the sampling process of the received light signal will be described with reference to the timing chart of FIG.

  The exceptional horizontal axis in FIG. 9 indicates time. The first row shows the emission timing of the measurement light. The second row shows the waveform of the trigger signal that defines the sampling timing of the ADC 263. The third row shows the sampling timing of the received light signal in the ADC 263. The vertical axis in the third stage 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.

  For example, the control unit 21 supplies a trigger signal to each ADC 263 simultaneously with the measurement light projection. Each ADC 263 samples the received light signal a predetermined number of times (for example, 32 times) at a predetermined sampling frequency (for example, several tens of MHz to several GHz) after a predetermined time has elapsed since the trigger signal was input. That is, when the measurement light is projected once, the received light signal is sampled a predetermined number of times at a predetermined sampling interval.

  Hereinafter, the case where the sampling frequency of the ADC 263 is 60 MHz will be described as an example. In this case, sampling is performed at a sampling interval (time interval) of about 16.7 nanoseconds. Therefore, the received light value is sampled at a sampling interval (distance interval) of 2.5 m in terms of distance, and as a result, from each point of 2.5 m interval in the distance direction from the own vehicle in each detection region. The intensity of the reflected light is measured.

  Then, each ADC 263 supplies a digital light reception signal indicating a light reception value (sample value) at each sampling time to the peak detection unit 311 with the light projection time of the measurement light as a reference (light projection time is 0).

  Hereinafter, each sampling time converted into a distance is referred to as a sampling distance. That is, the sampling distance means the distance that the measurement light projected from the laser radar device 11 can reciprocate and return to a certain sampling time. The sampling distance corresponding to each sampling time is obtained based on the time (Time of Flight) from the measurement light projection time to each sampling time. Hereinafter, the light reception value at the sampling time corresponding to each sampling distance is simply referred to as the light reception value corresponding to each sampling distance. Further, hereinafter, the interval of the sampling distance is referred to as a sampling interval distance. The sampling interval distance is equal to half the distance traveled by the laser light during the sampling interval.

  In step S4, the peak detection unit 311 performs peak detection. Specifically, the peak detection unit 311 calculates a peak time when the light reception value of each light receiving element 202 reaches a peak, or a distance corresponding to the peak time (hereinafter referred to as a detection distance). Here, the detection distance is obtained by converting the time (Time of Flight) from the measurement light projection time to the peak time of each light receiving element 202 into a distance. Therefore, this detection distance represents a distance from the host vehicle to a position where the intensity of reflected light peaks in each detection area, that is, a position where there is a high possibility that an object to be detected exists in each detection area.

  Here, an example of a detection distance calculation method will be described with reference to FIGS. 10 and 11.

  For example, the peak detection unit 311 obtains a detection distance by performing an interpolation operation using discrete sampling data, as will be described later.

  On the other hand, FIG. 10 shows the actual distance (actual distance) to the object when the detection distance is obtained based only on the sampling result of the received light value without performing the interpolation calculation performed by the peak detection unit 311. The relationship with the detection distance is shown. In this case, the sampling distance corresponding to the sampling time at which the received light value (sample value) reaches the peak is directly obtained as the detection distance. Therefore, the detection distance is detected with a resolution of 2.5 m, and as shown by the solid line in FIG. 10, at intervals of 2.5 m such as 0 m, 2.5 m, 5.0 m, 7.5 m,. It changes like a staircase. Therefore, for example, when the actual distance is within the range of 30 m ± 1.25 m, that is, when the actual distance is within the range of 28.75 m to 31.25 m, all the detection distances are 30 m, and the maximum is 1.25 m. Quantization error occurs.

  On the other hand, the peak detection unit 311 increases the distance resolution of the detection distance by performing an interpolation operation using the received light value at each sampling time and the sampling distance corresponding to each sampling time, and the quantization error is increased. Reduce. That is, the peak detection unit 311 performs an interpolation operation using sampling data discretely obtained at intervals of 2.5 m by sampling, thereby obtaining a distance (detection distance) at which the light reception value peaks between the sampling distances. presume.

  For example, the peak detection unit 311 obtains a detection distance using a weighted average. Specifically, for example, as shown in FIG. 11, received light values (sample values) s1 to s10 corresponding to sampling distances of 2.5 m intervals from 2.5 m to 25.0 m are obtained. The detection distance d is calculated using a weighted average represented by the following equation (1).

  By this calculation, for example, even when the peak of the light reception value appears between two adjacent sampling distances, the distance (detection distance) at which the light reception value reaches a peak can be accurately estimated. That is, the detection accuracy of the detection distance is improved as compared with the case where the detection distance is obtained without performing the interpolation calculation based only on the sampling result.

  The interpolation calculation used for calculating the detection distance is not limited to the method using the weighted average described above. For example, an interpolation operation that approximates a straight line or a curve using discrete sampling data may be used.

  In addition, the peak detection unit 311 obtains a peak value of the light receiving value of each light receiving element 202 (hereinafter referred to as a light receiving peak value). For example, the peak detection unit 311 obtains, for each light receiving element 202, the maximum value among the light reception values at each sampling time as the light reception peak value. For example, in the example of FIG. 11, the light reception value s5 is obtained as the light reception peak value. In this case, an error occurs from the peak value P of the actual received light value.

  Alternatively, the peak detector 311 may calculate a light reception value (≈peak value P) at the peak time of each light receiving element 202 by interpolation calculation or the like, and use the calculated light reception value as a light reception peak value of each light receiving element 202.

  Then, the peak detection unit 311 supplies the detection result of the detection distance and the received light peak value in each detection region to the correction unit 313.

  In step S5, the correction unit 313 corrects the detection distance.

  FIG. 12 shows an example of the waveform of a received light signal input to the ADCs 263-1 to 263-3 of the light receiving systems 1 to 3 when incident light having the same waveform is incident on the light receiving elements 202-1 to 202-3. ing. The waveform of the incident light is shown in the uppermost stage in the figure, and the waveforms of the received light signals input to the ADCs 263-1 to 263-3 of the light receiving systems 1 to 3 are shown in the second to fourth stages. In the second to fourth stages, the solid line waveform indicates the waveform of the received light signal input to the ADCs 263-1 to 263-3, and the dotted line waveform indicates the waveform of the original incident light.

  As shown in this figure, the waveforms of the received light signals input to the ADCs 263-1 to 263-3 are distorted compared to the incident light, and are different from each other. This is due to the distortion of the received light signal that occurs in the path of each light receiving system from the light receiving element 202 to the ADC 263. For example, distortion of each received light signal is caused by the influence of the rounding of the waveform generated when the signal is amplified by the TIA 261 or the PGA 262, noise generated in the wiring path, and the like. In addition, for example, the waveform distortion differs between the light receiving systems due to individual differences among components, wiring layout differences, and the like.

  Due to the distortion of the waveform of the light reception signal, an error having a different tendency for each light reception system occurs between the detection distance and the actual distance. For example, FIG. 13 schematically shows an example of the calculation result of the detection distance obtained by the interpolation calculation using the discrete received light values (sample values) in the range surrounded by the dotted frame A in FIG. . In FIG. 13, the horizontal axis indicates the actual distance, and the vertical axis indicates the detection distance. The dotted straight line indicates the ideal value of the detection distance, and the detection distance matches the actual distance. On the other hand, the solid curve indicates the calculated value of the actual detection distance, and an error occurs between the detection distance and the actual distance. In this figure, the error of the detection distance is shown larger than the actual value for easy understanding.

  The detection distance error is repeated at the same interval as the sampling interval distance. In other words, the detection distance error has the same value every time the detection distance increases or decreases by the sampling interval distance. That is, in this example, since the sampling interval distance is 2.5 m, as shown in FIG. 13, the detection distance error changes at an interval of 2.5 m. For example, when the detection distance is 24.0 m and when the detection distance is 29.0 m, the difference between the distances is 5.0 m which is an integer multiple of 2.5 m which is the sampling interval distance, so the error is the same value. become. This is because when the same object is detected by being moved by 2.5 m, the received light value is detected as substantially the same waveform with a detection distance shifted by 2.5 m.

  Therefore, the correction unit 313 corrects the detection distance using, for example, a correction table shown in FIG. In this correction table, n is a natural number, and 2.5n is n times the sampling interval distance. For example, when the detection distance is expressed by 2.5n-1.2 (m), in other words, the distance difference D between the detection distance and n times the sampling interval distance (2.5n) is -1.2 m. In some cases, the correction amount is -1.07 cm. When the detection distance is expressed by 2.5n ± 0.0 (m), in other words, when the detection distance is equal to n times the sampling interval distance (2.5n), the correction amount is ± 0.00 cm. Become. When the detection distance is expressed by 2.5n + 0.1 (m), in other words, when the distance difference D between the detection distance and n times the sampling interval distance (2.5n) is +0.1 m, the correction amount Becomes +4.80 cm.

  That is, in this correction table, the correction amount for the distance difference D between the detection distance and n times the sampling interval distance is set at an interval of 0.1 m with reference to n times the sampling interval distance (2.5n). .

  FIG. 15 shows the result of correcting the detection distance using the correction table of FIG. 14 when n = 10. For example, when the detection distance is 23.8 m, the detection distance is closest to 25.0 m, which is 10 times the sampling interval distance, and the distance difference D is −1.2 m. Since the correction amount for the distance difference D = −1.2 m is −1.07 cm, the corrected detection distance is 23.7893 m (= 23.8 m + (− 1.07 cm)). When the detection distance is 25.0 m, the detection distance is equal to 25.0 m, which is 10 times the sampling interval distance, and the distance difference D is 0.0 m. Since the correction amount for the distance difference D = 0.0 m is ± 0.00 cm, the corrected detection distance is 25.0000 m. When the detection distance is 25.1 m, the detection distance is closest to 25.0 m, which is 10 times the sampling interval distance, and the distance difference D is 0.1 m. Since the correction amount for the distance difference D = 0.1 m is +4.80 cm, the corrected detection distance is 25.1480 m (= 25.1 m + 4.80 cm).

  When the detection distance does not completely match the detection distance set in the correction table, for example, the correction amount corresponding to the closest distance among the detection distances set in the correction table is used.

  This correction table is created individually for each light receiving system (for each detection area), and a correction amount is set for each light receiving system (for each detection area) according to the difference between n times the sampling interval distance and the detection distance. The The detection distance in each detection area is corrected using a different correction table.

  Here, an example of a correction table creation method will be described.

  For example, the correction table is created by actually measuring the difference between the detection distance of the laser radar device 11 and the actual distance. Specifically, first, a reflector with less distortion of reflected light with respect to measurement light is installed in the detection region A1 corresponding to the light receiving element 202-1.

  Next, the position of the reflector is adjusted so that the detection distance in the detection area A1 of the laser radar device 11 is 2.5n-1.2 (m). For example, when n = 10, the position of the reflector is adjusted so that the detection distance in the detection area A1 of the laser radar device 11 is 23.8 m. In this state, the actual distance between the laser radar device 11 and the reflector is measured, and a value obtained by subtracting 23.8 m from the actual measurement value is a detection distance of 2.5n-1.2 (m). Is set to the correction amount.

  Next, the position of the reflector is adjusted so that the detection distance in the detection region A1 of the laser radar device 11 is 23.9 m. In this state, the actual distance between the laser radar device 11 and the reflector is measured, and a value obtained by subtracting 23.9 m from the actual measurement value is a correction when the detection distance is 2.5n-1.1 (m). Set to quantity.

  Thereafter, the same operation is repeated in increments of 0.1 m until the detection distance of the detection area A1 reaches 26.2 m, and a correction table for the light receiving system 1 including the light receiving element 202-1 is created.

  The same operation is performed on the detection areas A2 to A16, and correction tables for the light receiving systems 1 to 16 including the light receiving elements 202-1 to 202-16 are created.

  Thus, it is sufficient to set only data in which the fluctuation range of the detection distance is within the sampling interval distance in the correction table. As a result, the data amount of the correction table can be reduced, and the amount of memory for storing the correction table can also be reduced.

  Furthermore, in the example of the correction table in FIG. 14, an example is shown in which the detection distance is expressed in the 2.5n-D format, but the detection distance is not necessarily expressed in this format. For example, the specific detection distance used to create the correction table may be used as it is. Specifically, for example, a correction table including the detection distance and the correction amount in the table of FIG. 15 may be used.

  In this case, for example, when the detection distance is 19 m, 2.5n (m) is added to 19 m, and the correction value for the closest detection distance in the correction table with respect to the calculated value is used. May be corrected. For example, the calculated value is 21.5 m (= 19.0 m + 2.5 m × 1) when n = 1, 24.0 m (= 19.0 m + 2.5 m × 2) when n = 2, and n = In the case of 3, it becomes 26.5 m (= 19.0 m + 2.5 m × 3). Since there is a detection distance in the correction table that matches the calculated value of 24.0 m when n = 2, the detection distance is corrected using the correction amount of −5.20 cm when the detection distance is 24.0 m. The

  Note that the detection distance may be corrected using a predetermined function (hereinafter referred to as a correction function) instead of the correction table. For example, the detection distance of the laser radar device 11 is measured at 0.1 m intervals within a sampling interval distance of 2.5 m, and a correction function approximating the relationship between these detection distances and actual distances is obtained. For example, in FIG. 13, a correction function approximating a curve in the detection range of 27.5 m to 30 m is obtained. Then, the correction function is stored instead of the correction table, and the actual distance is calculated by correcting the detection distance by applying the detection distance obtained by sampling and interpolation to the correction function.

  This correction function is created individually for each light receiving system (each detection area).

  As described above, a correction table or a correction function suitable for each light receiving system (each detection area) is created, and as a result, the detection distance in each detection area is appropriately corrected.

  The method for creating the correction table or the correction function is not limited to the method described above, and any method can be adopted.

  As described above, when the light reception value at the peak time of each light receiving element 202 is calculated as the light reception peak value by interpolation calculation or the like, the light reception peak value may be corrected in accordance with the correction of the detection distance. . That is, when the detection distance is corrected, the peak time corresponding to the detection distance also changes, so that the received light peak value may be corrected in accordance with the change in the peak time.

  Returning to FIG. 8, in step S6, the object detection unit 314 detects an object. Specifically, the object detection unit 314 determines whether or not there is an object such as another vehicle, a pedestrian, or a road accessory in the monitoring area based on the corrected detection distance of each detection area and the light reception peak value. In addition, the type, direction, distance, etc. of the object are detected.

  Note that any method can be adopted as the object detection method of the object detection unit 314.

  Here, an example of the object detection method will be described with reference to FIG.

  The graph of FIG. 16 shows the horizontal distribution of the received light value 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 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.

  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 11 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 light reception values of the respective light receiving elements 202 in the detection region including the vehicle 351, the light reception value particularly at the sampling time tn is increased.

  Further, when the 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 the light receiving value of each light receiving element 202 including the vehicle 351 in the detection region becomes large. In particular, since the reflectance of the left and right reflectors 352L and 352R behind the vehicle 351 is high, the 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. 16, two prominent peaks P11 and P12 appear in the distribution of received light values in the horizontal direction. In addition, since the reflected light reflected by the vehicle body between the reflectors 352L and 352R is also detected, the light reception value between the peak P11 and the peak P12 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 received light values at the same sampling time.

  As described above, by correcting the detection distance, the positions of the peaks P11 and P12 can be detected more accurately. Thereby, for example, the detection accuracy of the reflectors 352L and 352R is improved, and the detection accuracy of the vehicle ahead is improved. For example, the recognition rate of the vehicle ahead, the detection speed of the vehicle ahead, the accuracy of the detection position of the vehicle ahead, etc. are improved.

  In step S7, the calculation unit 25 supplies the detection result. Specifically, the object detection unit 314 supplies the object detection result to the control unit 21 and the notification unit 302. For example, the notification unit 302 periodically supplies the detection result of the object to the vehicle control device 12 regardless of the presence or absence of the object. Or the notification part 302 supplies the detection result of an object to the vehicle control apparatus 12, only when there exists a danger that a vehicle will collide with the object ahead, for example.

  Thereafter, the process returns to step S1, and the processes of steps S1 to S7 are repeatedly executed. That is, the measurement light is periodically projected, and the process of detecting the object based on the received light value is repeated.

  As described above, the object detection accuracy of the laser radar device 11 can be improved by correcting the detection distance in each detection region.

<2. Modification>
Hereinafter, modifications of the above-described embodiment of the present invention will be described.

  The configuration of the laser radar device 11 is not limited to the above-described example, and can be changed as necessary.

  For example, it is possible to integrate the control unit 21 and the calculation unit 25 or to change the sharing of functions.

  Further, for example, the number of light receiving elements 202, TIA 261, PGA 262, and ADC 263 can be increased or decreased as necessary.

  Further, for example, one or more multiplexers (MUX) that receive a plurality of light reception signals and output a light reception signal selected from the input light reception signals may be provided between the light receiving element 202 and the TIA 261. . In this case, a combination of the TIA 261, the PGA 262, and the ADC 263 may be provided by the number of MUXs, and each group may perform processing such as sampling on a light reception signal output from each MUX.

  In this case, light receiving signals from two or more light receiving elements 202 are input to one ADC 263 via one MUX, and a part of the plurality of light receiving systems overlaps. Also in this case, a correction table or a correction function for each light receiving system is created in the same manner as when no MUX is provided, and the detection distance of each detection region is corrected using the created correction table or correction function. That's fine.

  In some cases, two or more peaks of received light values are detected in one detection region. In this case, the detection distance corresponding to each peak can be corrected by the same method. Specifically, for example, the calculation is performed by reducing the number of data used for calculating the weighted average. The number of data sampled at an interval smaller than the assumed peak-to-peak interval is used.

  Furthermore, although the example which correct | amends detection distance was shown in the above description, it is also possible to correct | amend the peak time before converting into distance by the same method. In this case, as in the case of correcting the detection distance, a correction table or a correction function is created individually for each light receiving system (for each detection area), and a sampling time and a predetermined time are set for each light receiving system (for each detection area). The correction amount is set according to the difference from the peak time obtained by calculation.

  The present invention can also be applied to a radar apparatus using measurement light other than a laser.

[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. 17 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 Measuring light projection part 23 Light receiving part 24 Measuring part 25 Calculation part 101 Drive circuit 102 Light emitting element 202-1 thru | or 202-16 Light receiving element 253 Sampling part 263-1 thru | or 263 4 A / D converter 301 Integration unit 302 Detection unit 311 Peak detection unit 313 Correction unit 314 Object detection unit A1 to A16 Detection region

Claims (4)

A light projecting unit for projecting measurement light that is pulsed laser light;
A light receiving unit including a light receiving element that receives reflected light of the measurement light;
A measurement unit that detects a light reception value by sampling a light reception signal from the light receiving element at a plurality of sampling times set at a predetermined sampling interval;
A peak detection unit that detects a detection distance that is a distance corresponding to a peak time at which the light reception signal reaches a peak by performing a predetermined interpolation calculation using the plurality of light reception values at a plurality of the sampling times;
A storage unit that is set for each detection distance and stores correction information indicating a correction amount used for correcting the detection distance;
A correction unit that corrects the detection distance based on the correction information, and
The correction amount becomes the same value every time the detection distance increases or decreases by a sampling interval distance that is half the distance traveled by the laser beam during the sampling interval. The correction information is data indicating a relationship between the detection distance and the correction amount in a range of the detection distance variation within the sampling interval distance.
The laser radar according to claim 1, wherein the correction unit obtains a correction amount for the detection distance detected by the peak detection unit based on the data, and corrects the detection distance using the obtained correction amount. apparatus. The correction information includes a function indicating a relationship between the detection distance and the correction amount,
The laser radar according to claim 1, wherein the correction unit calculates a correction amount for the detection distance detected by the peak detection unit using the function, and corrects the detection distance using the calculated correction amount. apparatus. The light receiving unit includes a plurality of the light receiving elements that receive the reflected light from different detection directions in a horizontal direction,
The measurement unit detects the light reception value of each light receiving element,
The peak detection unit detects the detection distance for each detection direction based on the light reception value of each light receiving element,
The correction information indicates the correction amount for each detection direction,
The laser radar device according to claim 1, wherein the correction unit corrects the detection distance in each detection direction using the correction amount for each detection direction.

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