JP2016057176A - Laser ranging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology capable of achieving in a short time, ranging to a short-distance target having high reflectance.SOLUTION: A state determination part (30:S110) determines whether or not the state is in a specific situation having a possibility of executing steering for moving a vehicle to the irradiation side of a laser beam. When determined that the state is in the specific situation by the state determination part, an output adjustment part (30:S130-S170) lowers intensity of a laser beam to be irradiated furthermore than setting at a normal time until establishment of a recovery condition set beforehand.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a technique for detecting a distance from a target located on a side of a vehicle using a laser beam.

  As shown in FIG. 6, a radar (ranging device) using a laser beam measures a round trip time from irradiation of a pulsed laser beam until the laser beam is reflected by a target and returned. The measured round trip time is converted into a distance. Usually, since the peak of the pulse waveform of the light reception signal is extracted as the light reception timing, the round trip time cannot be measured accurately if the pulse waveform of the light reception signal is disturbed for some reason.

  For example, in a laser range finder that uses the side of the vehicle as an exploration range, it receives reflected light from a highly reflective target that is located at a relatively short distance, such as a reflector on a guardrail installed beside the road. There is. When turning left, it is required to detect a target existing on the left side of the vehicle in order to prevent entrainment and the like. However, when the intensity of the reflected light from the above-described target having a high reflectance exceeds the dynamic range of the light receiving element, saturation or ringing may occur in the waveform of the light receiving signal. As shown in FIG. 7, when the waveform of the light reception signal is saturated, the peak of the waveform of the light reception signal is crushed and the light reception timing cannot be extracted correctly. As a result, there has been a problem that the round-trip time of the laser beam, and hence the distance from the target reflecting the laser beam, cannot be obtained correctly. Furthermore, the waveform of the received light signal (dotted line graph in the figure) based on the reflected wave from another target existing between the vehicle and the guardrail is buried in the waveform disturbed by such saturation (solid line graph in the figure). As a result, there is a problem that the target cannot be detected.

  On the other hand, a technique has been proposed that repeats measurement by reducing the output of the laser beam when the intensity of the reflected wave exceeds the dynamic range of the light receiving element due to the presence of a highly reflective target nearby. (See Patent Document 1).

JP-A-5-265719

  However, in the prior art, when saturation occurs, the laser light irradiation is repeated until the saturation is eliminated, so that there is a problem that a delay occurs in the time until the measurement result is obtained.

  The present invention has been made in view of these problems, and an object of the present invention is to provide a technique for realizing distance measurement for a short-distance target having a high reflectance in a short time.

  The laser distance measuring device of the present invention is mounted on a vehicle and measures the distance from a target present on the side of the vehicle by transmitting and receiving laser light, and includes a situation determination unit, an output adjustment unit, Is provided. The situation determination unit determines whether or not it is a specific situation in which steering for moving the vehicle to the laser light irradiation side is likely to be executed. The output adjusting unit reduces the intensity of the irradiated laser beam from the normal setting until a preset return condition is satisfied when the situation determining unit determines that the situation is a specific situation.

  Note that “steering to move the vehicle to the laser light irradiation side” means a left turn when the left side of the vehicle is set as the search range, and the right side of the vehicle is set as the search range. If it is set to do, it means a right turn.

  According to such a configuration, the light reception signal is disturbed by a high-reflectance target (for example, a guard rail reflector) at the end of the road when turning left if left-hand traffic and right turning if right-hand traffic. (Saturation, ringing, etc.) can be prevented. As a result, not only can the distance to the target with high reflectivity be correctly measured, but also the low reflectivity target can be prevented from being buried in the target with high reflectivity. Even a target can be quickly detected.

  In addition, the code | symbol in the parenthesis described in the claim shows the correspondence with the specific means as described in embodiment mentioned later as one aspect, Comprising: The technical scope of this invention is limited is not.

It is explanatory drawing which shows arrangement | positioning and a search range of a laser range finder. It is a block diagram which shows the structure of a laser ranging apparatus. It is a flowchart of a laser output adjustment process. It is explanatory drawing which shows the operating condition of the laser distance measuring device at the time of a left turn. It is explanatory drawing which shows the operating condition of the laser distance measuring device at the time of a right turn. It is explanatory drawing which shows the principle of ranging. It is a graph which illustrates a waveform when a received light signal is saturated. It is a graph which illustrates a waveform when a received light signal is not saturated.

Embodiments to which the present invention is applied will be described below with reference to the drawings.
[Constitution]
As shown in FIG. 1, the radar system 1 includes a pair of laser distance measuring devices 2 and 3 mounted on a vehicle. One laser range finder 2 is installed on the left side surface of the vehicle, and has a search range in a predetermined angle range (-90 ° to + 90 °) centered on the left direction orthogonal to the forward direction of the vehicle (0 °). AL (hereinafter referred to as “left exploration range”). However, the size of the left search range AL is variable, and the normal left search range is indicated by ALn, and the left search range narrower than the normal time set when a predetermined condition described later is satisfied is indicated by ALs. The other laser range finder 3 is installed on the right side surface of the vehicle and has a search range in a predetermined angle range (−90 ° to + 90 °) centered on the right direction perpendicular to the forward direction of the vehicle (0 °). AR (hereinafter referred to as “the right exploration range”). However, the right exploration range AR is different from the left exploration range AL and its size is fixed.

[Laser ranging device]
As shown in FIG. 2, the laser distance measuring device 2 includes a light emitting unit 10, a light receiving unit 20, an irradiation control unit 30, an AD converter 40, and a distance calculation unit 50. The laser distance measuring device 2 includes a known microcomputer (not shown) constituted by a CPU, a ROM, a RAM, and the like, and the irradiation control unit 30 and the distance calculation unit 50 include the microcomputer (hereinafter referred to as the microcomputer). This is realized by processing executed by the microcomputer. However, realization of the irradiation control unit 30 and the distance calculation unit 50 by software is merely an example, and the whole or a part thereof may be realized by hardware such as a logic circuit.

  The light emitting unit 10 includes a laser diode (LD) 11, an LD driving circuit 12, a light emitting lens 13, a scanner mechanism unit 14, and a scanner driving circuit 15. The LD drive circuit 12 outputs a pulsed laser beam by driving the LD 11 according to the light emission command CL. The laser beam output from the LD 11 is narrowed by the light emitting lens 13, reflected by a mirror constituting the scanner mechanism unit 14, and emitted toward the search range. The scanner driving circuit 15 realizes beam scanning within the left search range AL by laser light by changing the angle of the mirror according to the scan control command CS.

  The light receiving unit 20 includes a light receiving lens 21, a light receiving element 22, and an amplifier 23. The light receiving lens 21 collects the laser light (reflected light) irradiated from the light emitting unit 10 and reflected by the target. The light receiving element 22 receives the reflected light through the light receiving lens and outputs a light receiving signal having a voltage value corresponding to the intensity. The amplifier 23 amplifies the received light signal and supplies it to the AD converter 40.

The AD converter 40 samples the output (light reception signal) from the light receiving unit 20 at a predetermined interval, converts it into a digital value, and supplies the digital value to the distance calculation unit 50.
The irradiation control unit 30 generates a light emission command CL and a scan control command CS to the light emitting unit 10 according to a preset schedule, and supplies an irradiation timing TS that is a timing at which the light emission command CL is generated to the distance calculation unit 50. The irradiation process is executed. In addition, the irradiation control unit 30 executes an output adjustment process for adjusting the intensity of the laser output according to the situation estimated from the detection result of the in-vehicle sensor group 4. In addition, since the content of the irradiation process is a known thing, the description about the detail is abbreviate | omitted. Details of the output adjustment processing will be described later. The in-vehicle sensor group 4 includes a sensor that detects vehicle speed or acceleration in the longitudinal direction of the vehicle, a sensor that detects steering operation (steering angle), a sensor that detects the operation state of the direction indicator, and the current vehicle status. A sensor for detecting a position (for example, a GPS sensor), a device for providing map information (for example, a navigation device), and a sensor for capturing an image of the surroundings of the vehicle (including a device for extracting necessary information from a captured image) are included.

  The distance calculation unit 50 extracts the peak of the pulse waveform from the AD-converted light reception signal as the light reception timing TR, and reflects the time from the irradiation timing TS supplied from the irradiation control unit 30 to the light reception timing TR, that is, reflects the laser light. The time required for the laser beam to reciprocate between the target is obtained. Further, the distance to the target reflecting the radar wave is determined from the determined round-trip time, and provided as target information to other in-vehicle devices. In addition, since the process which the distance calculating part 50 performs is a well-known thing, the description about the detail is abbreviate | omitted.

  Since the laser distance measuring device 3 has the same configuration as the laser distance measuring device 2, the description thereof is omitted. However, in the laser distance measuring device 3, unlike the laser distance measuring device 2, the irradiation control unit 30 does not execute the output adjustment process, and the output of the laser light does not depend on the situation, but the right exploration range AR (see FIG. 1). ) Is set (fixed).

[Output adjustment processing]
Next, output adjustment processing executed by the microcomputer functioning as the irradiation control unit 30 will be described with reference to the flowchart of FIG. In the irradiation process separately executed, the laser beam is output according to the adjustment result by the output adjustment process.

  This process is repeatedly executed while power is supplied to the laser distance measuring device 2. Further, in the initial state, the output of the laser beam is set to a normal state that realizes a wide left search range ALn (see FIG. 1).

  When this process is activated, the microcomputer determines in S110 whether or not it is a specific situation based on information obtained from the in-vehicle sensor group 4. The specific situation here refers to a situation in which it is determined that the driver intends to make a left turn based on the operation status of the direction indicator, or a situation in which it is determined that there is a plan to make a left turn from the setting of the navigation device.

  If it is not a specific situation (S110: NO), this process is once terminated. On the other hand, if the vehicle is in a specific situation (S110: YES), it is determined in S120 whether or not the host vehicle is decelerating based on information obtained from the in-vehicle sensor group 4 (here, sensors for detecting vehicle speed and acceleration). to decide.

  If the vehicle is not decelerating (S120: NO), it is assumed that the left turn operation has not yet started, and the process is temporarily terminated. On the other hand, when the vehicle is decelerating (S120: YES), in S130, the output of the laser beam is decreased so that the narrow left search range ALs (see FIG. 1) is realized.

  In continuing S140, it is judged whether the own vehicle started the left turn based on the information obtained from the vehicle-mounted sensor group. Specifically, the determination is made based on information from the steering angle sensor, information from the navigation device, information obtained by analyzing the image, and the like.

  If the left turn has not been started (S140; NO), it is determined in S150 whether or not the vehicle has passed the planned left turn predicted from the point determined to be in the specific situation in S110 without making a left turn. To do. If it has not passed the planned left turn point (S150: NO), the process returns to S140, and if it has passed the planned left turn point (S150: YES), the process proceeds to S170.

  If it is determined in S140 that a left turn is started (S140: YES), it is determined in S160 whether or not the host vehicle has finished a left turn based on information obtained from the in-vehicle sensor group. In this determination, the same information as that used in the determination in S140 can be used. When the left turn is not finished (S160: NO), the process is repeated by repeating the same steps. When the left turn is finished (S160: YES), the process proceeds to S170.

In S170, the output of the laser beam is returned to the normal state (initial state), and this process is terminated.
[effect]
In the radar system 1 configured as described above, the right exploration range AR is always set to a wide range regardless of the situation (see FIGS. 4 and 5), and the left exploration range AL is a narrow left exploration range ALs ( In other situations, the wide left search range ALn (see FIG. 5) is set. Therefore, as shown in FIG. 4, at the time of a left turn, it is possible to suppress saturation of the light reception signal due to a reflected wave from a highly reflective object such as a reflecting mirror set on the guard rail at the road end. As a result, as shown in FIG. 8, it is possible to detect the peak of the pulse waveform of the received light signal based on the reflected wave from the target having a low reflectance existing between the vehicle and the light reflecting object. Thereby, for example, it is possible to improve the detection accuracy of a target that may be involved when turning left, such as a motorcycle that is about to pass through the right side of the vehicle.

  In addition, the radar system 1 does not decrease the laser output after detecting a light reception signal saturated at the time of the left turn, but reduces the laser output before the left turn, so that necessary target information can be obtained in a short time. Can do.

  Further, in the radar system 1, the right exploration area AR maintains the laser output even when making a right turn and secures a wide exploration area. Therefore, it is possible to obtain information such as an oncoming vehicle approaching from a distance.

[Other Embodiments]
As mentioned above, although embodiment of this invention was described, this invention can take a various form, without being limited to the said embodiment.

  (1) Although the case where the present invention is applied to a vehicle used in a left-hand traffic area has been described in the above embodiment, the present invention may be applied to a vehicle used in a right-hand traffic area. In this case, not the laser distance measuring device 2 installed on the left side surface of the vehicle but the laser output so that the right exploration range AR of the laser distance measuring device 3 installed on the right side surface of the vehicle is narrow when turning right. What is necessary is just to comprise so that it may reduce.

  (2) In the above embodiment, the laser output is reduced at the time of turning left or right. However, in addition to this, a situation in which a short-range target with high reflectivity affects the detection of other targets is predicted. In addition, the laser output may be reduced in advance. In the above embodiment, the laser output is reduced. However, the sensitivity of the light receiving unit 20 may be reduced instead of reducing the laser output.

  (3) The functions of one component in the above embodiment may be distributed to a plurality of components, or the functions of a plurality of components may be integrated into one component. Further, at least a part of the configuration of the above embodiment may be replaced with a known configuration having the same function. Moreover, you may abbreviate | omit a part of structure of the said embodiment. Further, at least a part of the configuration of the above embodiment may be added to or replaced with the configuration of the other embodiment. In addition, all the aspects included in the technical idea specified only by the wording described in the claim are embodiment of this invention.

  (4) In addition to the radar distance measuring device described above, a system including the radar distance measuring device as a constituent element, a program for causing a computer to function as the radar distance measuring device (particularly the irradiation control unit), and a medium on which the program is recorded Further, it can be realized in various forms such as a laser output adjustment method.

  DESCRIPTION OF SYMBOLS 1 ... Radar system 2, 3 ... Laser ranging device 4 ... In-vehicle sensor group 10 ... Light emission part 12 ... LD drive circuit 13 ... Light emission lens 14 ... Scanner mechanism part 15 ... Scanner drive circuit 20 ... Light reception part 21 ... Light reception lens 22 ... Light receiving element 23 ... Amplifier 30 ... Irradiation control unit 40 ... AD converter 50 ... Distance calculation unit AL ... Left search range AR ... Right search range

Claims (11)

In a radar ranging device (2) that is mounted on a vehicle and measures a distance from a target that exists on the side of the vehicle by transmitting and receiving laser light,
A situation determination unit (30: S110) for determining whether or not the steering situation for moving the vehicle toward the laser light irradiation side is likely to be performed;
When the situation determination unit determines that the specific situation is present, an output adjustment unit (30 :) that lowers the intensity of the laser beam to be irradiated from the normal setting until a preset return condition is satisfied. S130 to S170),
A laser distance measuring device comprising: The situation determination unit
A steering completion determination unit (30: S160) for determining whether or not the steering that is the determination target of the specific situation is completed;
A steering cancellation determination unit (30: S150) that determines whether or not the steering that is the determination target of the specific situation has been canceled;
The return condition is that the steering completion determination unit determines that the steering is completed, and the steering cancellation determination unit determines that the steering is stopped. The laser range finder according to claim 1.   3. The laser distance measuring device according to claim 1, further comprising an operation permission unit (30: S <b> 120) that permits the operation of the output adjustment unit when the vehicle is decelerating.   The laser range finder according to claim 3, wherein the operation permission unit determines whether or not the vehicle is decelerating according to information indicating a speed of the vehicle or an acceleration applied in a longitudinal direction of the vehicle.   The laser range finder according to claim 3, wherein the operation permission unit determines whether or not the vehicle is decelerating according to information extracted from an image obtained by imaging the periphery of the vehicle.   4. The laser ranging according to claim 2, wherein the steering completion determination unit and the steering cancellation determination unit determine completion of steering and cancellation of steering according to information indicating a steering state of the vehicle. apparatus.   The steering completion determination unit and the steering cancellation determination unit determine completion of steering and cancellation of steering according to information extracted from an image obtained by imaging the periphery of the vehicle. The laser distance measuring device described.   The said situation judgment part judges whether it is the said specific situation according to the information which shows the operation condition of the direction indicator of the said vehicle, The any one of Claim 1 thru | or 7 characterized by the above-mentioned. Laser distance measuring device.   The said situation judgment part judges whether it is the said specific situation based on the path | route set with the navigation apparatus, and the position of the said vehicle, The any one of Claim 1 thru | or 7 characterized by the above-mentioned. The laser range finder described in 1. The vehicle is used in left-hand traffic areas
The laser range finder according to any one of claims 1 to 9, wherein the laser beam is applied to a left side of the vehicle. The vehicle is used in right-hand traffic areas,
The laser range finder according to any one of claims 1 to 9, wherein the laser beam is applied to the right side of the vehicle.