JP2023181381A - Measuring device, control method, program, and storage medium - Google Patents

Abstract

To provide a measuring device, a control method, a program and a storage medium storing the program, capable of effectively utilizing data of reflected light without removal while suitably removing the influence of background light.SOLUTION: A control part 7 of a rider 100 measures the reflected light intensity distribution in a scanning area by irradiation with irradiation light, and also measures the distribution of the background light intensity in the scanning area without irradiation with the irradiation light. Then, the control part 7 performs smoothing processing on the reflected light intensity distribution, and generates the already-smoothed background light intensity distribution. Then, the control part 7 subtracts the already-smoothed background light intensity distribution from the reflected light intensity distribution.SELECTED DRAWING: Figure 1

Description

The present invention relates to measurement of reflected light of irradiated light.

Conventionally, a measurement target object is irradiated with light and reflected light from the measurement object is detected, and the timing of irradiating the measurement object with light and the timing of detecting the reflected light from the measurement object are known. 2. Description of the Related Art Distance measuring devices that calculate the distance to a measurement target based on a time difference are known. Furthermore, Patent Document 1 describes background light information that is light reception data of the light receiving means when the illumination means is not irradiating light onto the measurement target, and background light information that is the light reception data of the light receiving means when the illumination means is not irradiating light onto the measurement target. A distance measuring device has been disclosed that calculates a difference when subtracted from measurement light information that is light reception data of a light receiving means, and complements light reception data for which the difference is equal to or less than a threshold value with neighboring light reception data.

Japanese Patent Application Publication No. 2008-122223

In Patent Document 1, light reception data at a measurement point where background light noise occurs in spots at random positions is removed, and the light reception data at the removed pixel is complemented based on nearby light reception data. In this case, if reflected light from the irradiation light reflected by an object is detected at a measurement point where background light noise has occurred, data on the reflected light at the measurement point will be removed. At this time, if reflected light is detected only at the measurement point where background light noise has occurred and not at measurement points in the vicinity, the object will no longer be detected by the above-described interpolation process. As described above, in Patent Document 1, there is a possibility that an object that exists far away and is measured at only one measurement point cannot be detected due to the effect of background light noise removal.

Examples of the problems to be solved by the present invention include those mentioned above. An object of the present invention is to provide a measuring device, a control method, a program, and a storage medium storing the program, which can effectively utilize reflected light data without removing it while suitably removing the influence of background light. The main purpose is

The claimed invention is a measuring device that measures a first intensity distribution that is an intensity distribution of reflected light within a measurement target area by irradiating the irradiation light, and measures the measurement target without irradiating the irradiation light. a measurement unit that measures a second intensity distribution that is an intensity distribution of background light in the region; a smoothing unit that performs a smoothing process on the second intensity distribution to generate a third intensity distribution; It is characterized by comprising a subtraction unit that subtracts the third intensity distribution from the intensity distribution.

Further, the claimed invention is a control method executed by a measuring device, in which a first intensity distribution that is an intensity distribution of reflected light in a measurement target area is measured by irradiating irradiation light, and the irradiation light is a measurement step of measuring a second intensity distribution that is the intensity distribution of background light in the measurement target area without irradiating it; and a smoothing step of performing a smoothing process on the second intensity distribution to generate a third intensity distribution. and a subtraction step of subtracting the third intensity distribution from the first intensity distribution.

Further, the claimed invention measures a first intensity distribution that is an intensity distribution of reflected light in a measurement target area by irradiating the irradiation light, and measures a first intensity distribution that is an intensity distribution of reflected light in the measurement target area by irradiating the irradiation light, a measuring unit that measures a second intensity distribution that is the intensity distribution of light; a smoothing unit that performs smoothing processing on the second intensity distribution to generate a third intensity distribution; The present invention is characterized in that a computer functions as a subtraction unit that subtracts the third intensity distribution.

1 shows a schematic configuration of a rider according to an embodiment. FIG. 3 is a diagram showing a lidar scanning area on a virtual plane. FIG. 6 is a diagram schematically showing the transition of the background light measurement area and the reflected light measurement area in a period of 5 frames, and the process of deriving the corrected reflected light intensity distribution. (A) A diagram clearly showing measurement points at which background light is measured within a background light measurement area. (B) A diagram showing the background light intensity distribution around the target measurement point. (C) A diagram showing a background light intensity distribution after replacing the background light intensity of the target measurement point with the background light intensity of surrounding measurement points. (A) shows a time waveform of reflected light intensity measured at a certain measurement point. (B) shows the time waveform of the smoothed background light intensity corresponding to the target measurement point. (C) shows the time waveform of the corrected reflected light intensity at the target measurement point. 7 is a flowchart illustrating a procedure for generating a corrected reflected light intensity distribution based on a first generation method. (A) A diagram showing a background light measurement point and a reflected light measurement point in a certain divided area within the scanning area. (B) A diagram illustrating the measurement timing of background light, the emission timing of irradiation light, and the measurement period of reflected light in chronological order. 7 is a flowchart illustrating a procedure for generating a corrected reflected light intensity distribution based on a second generation method.

In a preferred embodiment of the present invention, the measuring device measures a first intensity distribution that is the intensity distribution of reflected light within the measurement target area by irradiating the irradiation light, and measures the first intensity distribution that is the intensity distribution of reflected light within the measurement target area without irradiating the irradiation light. a measuring unit that measures a second intensity distribution that is an intensity distribution of background light in the background light; a smoothing unit that performs a smoothing process on the second intensity distribution to generate a third intensity distribution; and a subtraction unit that subtracts the third intensity distribution from the distribution. According to this aspect, the measurement device can suitably exclude the influence of background light measured over a plurality of measurement points from the first intensity distribution, which is the intensity distribution of reflected light within the measurement target area. .

In one aspect of the measurement device, the measurement device is configured to determine whether the measurement target area is irradiated with the irradiation light based on a fourth intensity distribution obtained by subtracting the third intensity distribution from the first intensity distribution. The apparatus further includes a point cloud information generating section that generates point cloud information indicating the distance and direction to the object. With this aspect, the measuring device can suitably generate point cloud information indicating the distance and direction of surrounding objects.

In another aspect of the measuring device, the first intensity distribution indicates a time waveform of the intensity of the reflected light at a plurality of measurement points in the measurement target area during the measurement period of the reflected light, and the third intensity The distribution indicates the smoothed intensity of the background light corresponding to the plurality of measurement points, and the subtraction unit calculates the measurement result from the time waveform of the intensity of the reflected light for each of the plurality of measurement points. Subtract the smoothed intensity of the background light, which is assumed to be constant over a period of time. With this aspect, the measuring device can suitably subtract the intensity of background light that is continuously measured over a plurality of measurement points from the first intensity distribution.

In another aspect of the measuring device, the measuring unit measures the first intensity distribution in a first area that is a part of the measurement target area and is set to a different area for each frame, and , the second intensity distribution in a second region that is a region other than the first region within the measurement target region is measured, and the subtraction unit calculates the measured first intensity distribution from the first intensity distribution. A third intensity distribution obtained by smoothing a second intensity distribution measured in a different frame in the same area as the area is subtracted. With this aspect, the measuring device provides a region for measuring the first intensity distribution and a region for measuring the second intensity distribution for each frame, and measures the reflected light intensity in each frame by changing these regions. At the same time, it is possible to suitably perform processing to exclude the influence of background light.

In another aspect of the measurement device, the measurement unit measures the intensity of the background light every time the irradiation light is irradiated and the intensity of the reflected light is measured, thereby determining the measurement target area for each frame. The first intensity distribution and the second intensity distribution covering the entire area are measured. With this aspect, it is possible to suitably perform processing to exclude the influence of background light while measuring the reflected light intensity in the entire measurement target area in each frame.

In another preferred embodiment of the present invention, there is provided a control method executed by a measuring device, in which a first intensity distribution that is an intensity distribution of reflected light within a measurement target area is measured by irradiating irradiation light; a measurement step of measuring a second intensity distribution that is the intensity distribution of background light in the measurement target area without irradiating the area; and performing a smoothing process on the second intensity distribution to generate a third intensity distribution. The method includes a smoothing step and a subtraction step of subtracting the third intensity distribution from the first intensity distribution. By executing this control method, the measurement device suitably excludes the influence of background light measured across a plurality of measurement points from the first intensity distribution, which is the intensity distribution of reflected light within the measurement target area. be able to.

Another preferred embodiment of the present invention is a program executed by a computer, which measures a first intensity distribution that is an intensity distribution of reflected light in a measurement target area by irradiating the irradiation light, and irradiating the irradiation light. a measurement unit that measures a second intensity distribution that is the intensity distribution of background light within the measurement target area without any background light; and a smoothing unit that performs a smoothing process on the second intensity distribution to generate a third intensity distribution. , and the third intensity distribution is subtracted from the first intensity distribution. By executing this program, the computer can suitably exclude the influence of background light measured across multiple measurement points from the first intensity distribution, which is the intensity distribution of reflected light within the measurement target area. can. Preferably, the program is stored on a storage medium.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[Device configuration]
FIG. 1 shows a schematic configuration of a rider 100 according to this embodiment. The lidar 100 is mounted, for example, on a vehicle that provides driving support such as automatic driving. The lidar 100 irradiates a light beam (also referred to as "irradiation light") to a predetermined angular range in the horizontal and vertical directions, and collects light that is reflected back from an object (also referred to as "reflected light"). ), the distance to the object is discretely measured, and point cloud information indicating the three-dimensional position of the object is generated. As shown in FIG. 1, the lidar 100 mainly includes a transmitter 1, a receiver 2, a beam splitter 3, a scanner 5, a piezo sensor 6, and a controller 7.

The transmitter 1 is a light source that emits pulsed irradiation light toward the beam splitter 3 . The transmitter 1 includes, for example, an infrared laser light emitting element. The transmitter 1 is driven based on a drive signal “S1” supplied from the controller 7.

The receiving unit 2 is, for example, an avalanche photodiode, generates a detection signal “S2” corresponding to the amount of received light, and supplies the generated detection signal S2 to the control unit 7.

The beam splitter 3 transmits the pulsed irradiation light emitted from the transmitter 1 . Furthermore, the beam splitter 3 reflects the reflected light reflected by the scanner 5 toward the receiving section 2 .

The scanner 5 is, for example, an electrostatically driven mirror (MEMS mirror), and its inclination (that is, the angle of optical scanning) changes within a predetermined range based on a drive signal "S3" supplied from the control unit 7. Then, the scanner 5 reflects the irradiation light that has passed through the beam splitter 3 toward the outside of the lidar 100 and reflects the reflected light that is incident from the outside of the lidar 100 toward the beam splitter 3. Hereinafter, the area on the virtual plane 9 through which the irradiation light from the lidar 100 passes is scanned with the irradiation light, which will also be simply referred to as a "scanning area" or a "measurement target area." Further, a point on the scanning area where the irradiation light is irradiated is also called a "measurement point."

Further, the scanner 5 is provided with a piezo sensor 6. The piezo sensor 6 detects distortion caused by stress in the torsion bar that supports the mirror portion of the scanner 5. The piezo sensor 6 supplies the generated detection signal “S4” to the control unit 7. The detection signal S4 is used to detect the orientation of the scanner 5.

The control unit 7 includes, for example, a processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit), and a memory such as a RAM (Random Access Memory) or a ROM (Read Only Memory). . The control unit 7 executes a predetermined process by executing a program stored in a memory.

Functionally, the control unit 7 includes a transmission drive block 70, a scanner drive block 71, a reflected light measurement block 72, a background light measurement block 73, a smoothing processing block 74, a subtraction block 75, and a point group. It includes an information generation block 76 and an output block 77.

The transmission drive block 70 outputs a drive signal S1 that drives the transmitter 1. The drive signal S1 includes information for controlling the light emission time of the laser light emitting element included in the transmitter 1 and the light emission intensity of the laser light emitting element. The transmission drive block 70 controls the light emission intensity of the laser light emitting element included in the transmitter 1 based on the drive signal S1.

The scanner drive block 71 outputs a drive signal S3 for driving the scanner 5. This drive signal S3 includes a horizontal drive signal corresponding to the resonance frequency of the scanner 5 and a vertical drive signal for vertical scanning. Further, the scanner drive block 71 detects the scanning angle of the scanner 5 (that is, the irradiation direction of the irradiation light) by monitoring the detection signal S4 output from the piezo sensor 6.

The reflected light measurement block 72 measures the intensity of reflected light at each measurement point based on the detection signal S2 output by the receiving section 2. In this case, the reflected light measurement block 72 measures the time waveform of the reflected light intensity output by the receiver 2 during a predetermined period after the irradiation light is emitted, as the reflected light intensity for each measurement point. Hereinafter, the reflected light intensity at all measurement points within the scanning area where the reflected light measurement block 72 measured the reflected light intensity will also be referred to as a "reflected light intensity distribution." In the reflected light intensity distribution, the reflected light intensity corresponding to each measurement point is represented by a time waveform. The reflected light intensity distribution is an example of the "first intensity distribution" in the present invention.

The background light measurement block 73 measures the background light intensity based on the detection signal S2 output by the receiver 2 when no irradiation light is emitted. The background light intensity at all measurement points within the scanning area, at which the background light measurement block 73 measured the background light intensity, is also referred to as a "background light intensity distribution." The background light intensity distribution is an example of the "second intensity distribution" in the present invention. Further, the reflected light measurement block 72 and the background light measurement block 73 are examples of a "measuring section" in the present invention.

The smoothing processing block 74 applies smoothing processing to the background light intensity distribution generated by the background light measurement block 73 to obtain a smoothed background light intensity distribution (also referred to as a "smoothed background light intensity distribution"). ) is generated. The smoothing processing block 74 smoothes the background light intensity distribution from which background light noise components (also referred to as "background light noise") that occur in spots at random positions are suitably excluded. Generate as background light intensity distribution. The smoothed background light intensity distribution generated by the smoothing processing block 74 is an example of the "third intensity distribution" in the present invention. Further, the smoothing processing block 74 is an example of a "smoothing unit" in the present invention.

Note that the smoothed background light intensity calculated by the smoothing processing block 74 for each measurement point is based on the background light detected continuously and across a plurality of measurement points in the measurement results of the lidar 100 ("continuous background light"). ) is the strength of Continuous background light is, for example, reflected sunlight from objects that have a high reflectivity for near-infrared rays, such as clouds, road surfaces, plants, building walls, and glass, and the objects have a general spatial extent. Because it is large, the rider 100 measures it across multiple measurement points.

The subtraction block 75 subtracts the smoothed background light intensity distribution from the reflected light intensity distribution generated by the reflected light measurement block 72. Specifically, the subtraction block 75 subtracts the time-invariant smoothed background light intensity for each corresponding measurement point from the time waveform of the reflected light intensity for each measurement point indicated by the reflected light intensity distribution. As a result, the subtraction block 75 generates a reflected light intensity distribution (also referred to as a "corrected reflected light intensity distribution") excluding the influence of continuous background light. In the corrected reflected light intensity distribution, the corrected reflected light intensity corresponding to each measurement point is represented by a time waveform. The corrected reflected light intensity distribution is an example of the "fourth intensity distribution" in the present invention. Furthermore, the subtraction block 75 is an example of a "subtraction unit" in the present invention.

The point cloud information generation block 76 generates point cloud information indicating the distance and direction to the object irradiated with the irradiation light for each measurement point within the measurement range of the lidar 100 based on the corrected reflected light intensity distribution. . In this case, the point cloud information generation block 76 calculates the time from when the irradiation light is emitted until the receiving unit 2 detects the reflected light as the time of flight of the light. Then, the point cloud information generation block 76 generates a point cloud in which distance information corresponding to the calculated flight time and information on the irradiation direction of the irradiation light corresponding to the reflected light received by the receiving unit 2 are associated for each measurement point. Generate information. The point cloud information generation block 76 is an example of a "point cloud information generation section" in the present invention.

The output block 77 outputs the point cloud information generated by the point cloud information generation block 76 to a device (also referred to as a "driving support device") that controls driving support such as automatic driving of a vehicle. In this case, the driving support device may be, for example, an ECU (Electronic Control Unit) of the vehicle, or an in-vehicle device such as a car navigation device electrically connected to the vehicle.

[Generation of corrected reflected light intensity distribution]
Next, specific examples of methods for generating the corrected reflected light intensity distribution (first generation method and second generation method) will be specifically described.

(1) First generation method
The first generation method is to generate a corrected reflected light intensity distribution using a measurement method that separates the measurement range of background light intensity and the measurement range of reflected light intensity in each frame (that is, every scan of one round by the scanner 5). It's a method.

FIG. 2 is a diagram showing a scanning area of the lidar 100 on the virtual plane 9. As shown in FIG. A solid arrow in FIG. 2 indicates a locus of a position on the virtual plane 9 where the irradiation light is irradiated. Further, in FIG. 2, the scanning area is divided into three divided areas F1 to F3 (see the broken line frame).

In this case, the control unit 7 defines any one of the three divided regions F1 to F3 as a background light intensity measurement region (also referred to as a "background light measurement region"), and defines the remaining divided regions as a background light intensity measurement region. , defined as a measurement area for reflected light intensity (also referred to as a "reflected light measurement area"). Then, the control unit 7 moves (shifts) the background light measurement area to another divided area for each frame, thereby rotating the background light measurement area among the divided areas F1 to F3 at a cycle of three frames. In this case, the transmission drive block 70 does not emit the irradiation light during the period when the background light measurement area is scanned, but emits the irradiation light during the period when the reflected light measurement area is scanned.

Figure 3 shows the transition of the background light measurement area and the reflected light measurement area at the measurement timing for 5 frames (1st frame to 5th frame), and the corrected reflected light intensity distribution based on the background light intensity distribution and the reflected light intensity distribution. FIG. 2 is a diagram schematically showing the derivation process.

In FIG. 3, in the first frame, the transmission drive block 70 of the control unit 7 sets the divided area F1 as the background light measurement area and the divided area F2 and the divided area F3 as the reflected light measurement area. Controls the irradiation light. Further, the background light measurement block 73 generates a background light intensity distribution in the divided region F1, and the smoothing processing block 74 smoothes the background light intensity distribution to obtain a smoothed background light intensity distribution "B1". generate. The smoothing processing block 74 stores the generated smoothed background light intensity distribution B1 in the memory. This smoothed background light intensity distribution B1 is used to generate the corrected reflected light intensity distribution of the second frame. Further, the reflected light measurement block 72 generates reflected light intensity distributions in the divided regions F2 and F3.

Next, in the second frame, the transmission drive block 70 controls the irradiation light in the transmitter 1 so that the divided area F2 is set as the background light measurement area, and the divided area F1 and the divided area F3 are set as the reflected light measurement areas. conduct. Thereby, the reflected light measurement block 72 generates reflected light intensity distributions in the divided regions F1 and F3. Further, the background light measurement block 73 generates a background light intensity distribution in the divided region F2, and the smoothing processing block 74 smoothes the background light intensity distribution to obtain a smoothed background light intensity distribution "B2". generate. The smoothing processing block 74 stores the generated smoothed background light intensity distribution B2 in the memory.

Furthermore, since the smoothed background light intensity distribution B1 of the divided area F1 is obtained in the first frame, the subtraction block 75 calculates the reflected light intensity distribution "R1" in the divided area F1 obtained in the second frame. Then, the smoothed background light intensity distribution B1 in the same area is subtracted (R1-B1). Thereby, the subtraction block 75 generates a corrected reflected light intensity distribution in the divided region F1, and supplies the generated corrected reflected light intensity distribution to the point cloud information generation block 76. In this case, the point cloud information generation block 76 generates point cloud information in the divided region F1 based on the supplied corrected reflected light intensity distribution.

Next, in the third frame, the transmission drive block 70 controls the irradiation light in the transmitter 1 so that the divided area F3 is set as the background light measurement area, and the divided area F1 and the divided area F2 are set as the reflected light measurement areas. conduct. Further, the background light measurement block 73 generates a background light intensity distribution in the divided region F3, and the smoothing processing block 74 smoothes the background light intensity distribution to obtain a smoothed background light intensity distribution "B3". generate. The smoothing processing block 74 stores the generated smoothed background light intensity distribution B3 in the memory. Further, the reflected light measurement block 72 generates a reflected light intensity distribution "R2" in the divided region F1 and a reflected light intensity distribution "R3" in the divided region F2.

Further, the subtraction block 75 converts the reflected light intensity distribution R2 in the divided area F1 and the reflected light intensity distribution R3 in the divided area F2 obtained in the third frame into the smoothed background light intensity distribution B1 in the same area, respectively. and subtraction by the smoothed background light intensity distribution B2 (that is, "R2-B1" and "R3-B2" are executed). Thereby, the subtraction block 75 generates corrected reflected light intensity distributions in the divided areas F1 and F2, respectively, and supplies the generated corrected reflected light intensity distributions to the point group information generation block 76.

Next, in the fourth frame, the transmission drive block 70 controls the irradiation light in the transmitter 1 so that the divided area F1 is set as the background light measurement area, and the divided area F2 and the divided area F3 are set as the reflected light measurement areas. conduct. Further, the background light measurement block 73 generates a background light intensity distribution in the divided region F1, and the smoothing processing block 74 smoothes the background light intensity distribution to obtain a smoothed background light intensity distribution "B4". generate. The smoothing processing block 74 stores the generated smoothed background light intensity distribution B4 in the memory. In this case, the smoothing processing block 74 may delete from the memory the smoothed background light intensity distribution B1 previously generated for the same divided region F1. Further, the reflected light measurement block 72 generates a reflected light intensity distribution "R4" in the divided region F2 and a reflected light intensity distribution "R5" in the divided region F3.

Further, the subtraction block 75 converts the reflected light intensity distribution R4 in the divided region F2 and the reflected light intensity distribution R5 in the divided region F3 obtained in the fourth frame into the smoothed background light intensity distribution B2 in the same region. and the smoothed background light intensity distribution B3 (that is, "R4-B2" and "R5-B3" are performed). Thereby, the subtraction block 75 generates a corrected reflected light intensity distribution in the divided area F2 and divided area F3, and supplies the generated corrected reflected light intensity distribution to the point group information generation block 76.

Similarly, in the fifth frame, the transmission drive block 70 controls the irradiation light in the transmitter 1 so that the divided area F2 is the background light measurement area, and the divided areas F1 and F3 are the reflected light measurement areas. conduct. Further, the background light measurement block 73 generates a background light intensity distribution in the divided region F2, and the smoothing processing block 74 generates a smoothed background light intensity distribution by smoothing the background light intensity distribution. . The smoothing processing block 74 stores the generated smoothed background light intensity distribution in memory. In this case, the smoothing processing block 74 may delete from the memory the smoothed background light intensity distribution B2 previously generated for the same divided region F2. Further, the reflected light measurement block 72 generates a reflected light intensity distribution "R6" in the divided area F1 and a reflected light intensity distribution "R7" in the divided area F3.

Further, the subtraction block 75 converts the reflected light intensity distribution R6 in the divided area F1 and the reflected light intensity distribution R7 in the divided area F3 obtained in the fifth frame into the smoothed background light intensity distribution B4 in the same area. and the smoothed background light intensity distribution B3 (that is, perform "R6-B4" and "R7-B3"). Thereby, the subtraction block 75 generates a corrected reflected light intensity distribution in the divided area F1 and divided area F3, and supplies the generated corrected reflected light intensity distribution to the point group information generation block 76.

Here, supplementary explanation will be given regarding the processing in FIG. 3. Based on the idea that continuous background light rarely changes significantly over several frames, the control unit 7 divides the target frame (referred to as the "Mth frame") into a divided area (referred to as the "Mth frame") as a background light measurement region. A smoothed background light intensity distribution is generated by smoothing the background light intensity of the "Nth divided area"), and this is applied to the M+1th frame and the M+2th frame. Then, the control unit 7 subtracts the smoothed background light intensity distribution in the divided region from the reflected light intensity distribution in the Nth divided region measured in the M+1th frame and the M+2th frame. The corrected reflected light intensity distribution of the Nth divided area acquired in this way is sequentially output to the point group information generation block 76. When the scanning area is divided into three as in the example of FIGS. 2 and 3, the latest reflected light intensity measurement results are obtained in two of the three divided areas F1 to F3 in one frame. Corrected reflected light intensity distribution and point cloud information that reflect this can be obtained. Therefore, for example, when a driving support device performs obstacle detection based on point cloud information, compared to a case where the scanning area is not divided and the background light measurement area and the reflected light measurement area are switched for each frame, Based on the point cloud information supplied from the rider 100, the driving support device can quickly detect a pedestrian running out or the like.

Note that although FIGS. 2 and 3 show an example in which the scanning area is divided into three as a representative example, the number of divisions of the scanning area is not limited to this, and may be any number of divisions (for example, 1 to 4). good.

Next, the smoothing process executed by the smoothing process block 74 will be explained. Here, as an example, smoothing processing using a median filter that replaces the value (intensity) of a target measurement point with the median value of the values of surrounding measurement points will be described.

FIG. 4(A) is a diagram clearly showing measurement points at which background light is measured within the background light measurement area. In FIG. 4(A), the order of measurement points to be measured is shown by arrows. When the background light intensity of each measurement point within the divided area that becomes the background light measurement area is obtained based on the detection signal S2, the smoothing processing block 74 smoothes each of the measurement points within the divided area that becomes the background light measurement area. , are determined in order as measurement points to be processed. Then, the smoothing processing block 74 performs a process of replacing the value of the measurement point to be processed with the median value of the values of the surrounding measurement points. For example, when the measurement point Ptag is to be processed, the smoothing processing block 74 performs the above-mentioned replacement processing with reference to the intensity of each measurement point within the broken line frame 10 surrounding the measurement point Ptag.

FIG. 4(B) is a diagram showing the background light intensity distribution at measurement points around the measurement point Ptag shown in FIG. 4(A). FIG. 4C is a diagram showing the background light intensity distribution at each measurement point after the background light intensity at the measurement point Ptag is replaced based on the background light intensity at surrounding measurement points.

As shown in FIG. 4B, the measurement point Ptag has a higher value than the intensity of surrounding measurement points due to background light noise. On the other hand, as shown in FIG. 4C, the smoothing processing block 74 changes the value of the measurement point Ptag to "20", which is the median value of the background light intensity at nine measurement points including the measurement point Ptag. ”. Thereby, the smoothing processing block 74 can suitably remove background light noise generated at the measurement point Ptag.

Then, the smoothing processing block 74 repeats the replacement processing shown in FIGS. 4(B) and 4(C) while sequentially changing the measurement points to be processed. In general, background light noise caused by shot noise, thermal noise, light irradiated by other riders, etc. has a high probability of occurring in spots at random positions. Therefore, the smoothing processing block 74 can suitably remove background light noise within the background light measurement region through the above-described processing.

Note that the smoothing processing block 74 may use various filters used for removing image noise, such as a Gaunssian filter and a moving average filter, instead of the median filter, as the smoothing processing.

Next, a specific example of the processing executed by the subtraction block 75 will be described.

FIG. 5(A) shows a time waveform of reflected light intensity measured at a certain measurement point. FIG. 5(B) shows a time waveform of the smoothed background light intensity corresponding to the target measurement point. FIG. 5C shows the time waveform of the corrected reflected light intensity at the target measurement point.

As shown in FIG. 5(A), the reflected light intensity at each measurement point is represented by a time waveform in a time length corresponding to the maximum distance measurement distance. Then, as shown in FIG. 5B, the subtraction block 75 considers the background light intensity to be constant (time-invariant) during the period in which the reflected light intensity is measured. Then, the subtraction block 75 performs the correction shown in FIG. 5(C) by subtracting the time waveform of the reflected light intensity shown in FIG. 5(B) from the time waveform of the reflected light intensity shown in FIG. 5(A). Calculate the time waveform of the reflected light intensity. In this case, the subtraction block 75 can obtain a time waveform of the corrected reflected light intensity from which the continuous background light component has been suitably removed. In this case, as shown in FIG. 5(C), the time waveform of the corrected reflected light intensity is around 0 in time zones other than the peak position measured when the reflected light is received (see broken line circle 90). . Therefore, in this case, the point cloud information generation block 76 can accurately grasp the reception timing of the reflected light and accurately calculate the distance to the object irradiated with the irradiation light by determining the threshold value for the corrected reflected light intensity. can.

The subtraction block 75 calculates the corrected reflected light in the target divided area by executing the processing shown in FIGS. Generate an intensity distribution. Then, the point cloud information generation block 76 generates point cloud information corresponding to the target divided region from the generated corrected reflected light intensity distribution.

FIG. 6 is a flowchart showing a procedure for generating a corrected reflected light intensity distribution based on the first generation method.

First, the background light measurement block 73 of the control unit 7 generates a background light intensity distribution by measuring the background light intensity in a divided area within the scanning area that is a background light measurement area (step S11). At this time, the transmission drive block 70 stops the transmission section 1 from emitting the irradiation light during the measurement period of the target divided region. Then, the smoothing processing block 74 generates a smoothed background light intensity distribution by applying a smoothing process to the background light intensity distribution, and stores the generated smoothed background light intensity distribution in a memory. (Step S12).

In addition, the reflected light measurement block 72 measures the intensity of reflected light corresponding to the irradiation light emitted from the transmitter 1 in a scanning area (i.e., reflected light measurement area) other than the divided area where the background light intensity was measured ( Step S13). Thereby, the reflected light measurement block 72 acquires the reflected light intensity distribution in the reflected light measurement area. Note that the process in step S13 may be performed before the processes in step S11 and step S12.

Then, the subtraction block 75 generates a corrected reflected light intensity distribution by subtracting the smoothed background light intensity distribution obtained in the same area of a different frame from the reflected light intensity distribution in the reflected light measurement area. (Step S14). In this case, the subtraction block 75 generates a corrected reflected light intensity distribution by subtracting the smoothed background light intensity time waveform from the reflected light intensity time waveform for each measurement point in the reflected light measurement area.

The point cloud information generation block 76 calculates the flight time for each measurement point from the corrected reflected light intensity distribution in the reflected light measurement area, and generates point cloud information representing the distance and direction to the object according to the calculated flight time. generate. Then, the output block 77 outputs the point cloud information generated for the reflected light measurement area to the driving support device (step S15).

Then, the control unit 7 determines whether scanning should be stopped (step S16). For example, when the control unit 7 receives a signal to stop scanning from the driving support device, it determines that scanning should be stopped. When the control unit 7 determines that scanning should be stopped (step S16; Yes), the control unit 7 ends the process of the flowchart. On the other hand, when the control unit 7 determines that scanning should not be stopped (step S16; No), it shifts the divided area to be the background light measurement area (step S17). Then, the control unit 7 returns the process to step S11.

(2) Second generation method
The second generation method is a method for generating a corrected reflected light intensity distribution that employs a measurement method that measures both background light intensity and reflected light intensity for the same region in the same frame.

FIG. 7A is a diagram illustrating background light measurement points and reflected light measurement points in a certain divided area within the scanning area. In FIG. 7A, background light measurement points are indicated by "○", and reflected light measurement points are indicated by "●". FIG. 7B is a diagram showing the measurement timing of background light, the emission timing of irradiation light, and the measurement period of reflected light in chronological order.

As shown in FIGS. 7A and 7B, the control unit 7 sets the background light measurement timing immediately before the reflected light measurement timing at each measurement point. Specifically, as shown in FIG. 7B, the control unit 7 emits irradiation light after measuring the background light, sets a period for measuring (receiving) reflected light corresponding to the irradiation light, and Repeat this while changing the emission direction of the irradiation light.

The smoothing processing block 74 of the control unit 7 smoothes the background light intensity distribution in the divided area every time the scanning of the divided area is completed. Then, the subtraction block 75 generates a corrected reflected light intensity distribution by subtracting the reflected light intensity distribution in the target divided area by the smoothed background light intensity distribution calculated by the smoothing processing block 74. Thereafter, the point cloud information generation block 76 generates point cloud information corresponding to the target divided area from the corrected reflected light intensity distribution, and the output block 77 generates point cloud information corresponding to the measurement points in the target divided area. Output. Note that the number of divisions into which the scanning area is divided may be any number greater than or equal to one.

In this manner, according to the second generation method, the lidar 100 outputs point cloud information corresponding to the target divided area every time scanning of the divided area to be scanned within the scanning area is completed. In this case, unlike the first generation method, the lidar 100 can suitably generate point cloud information in all scanning areas for each frame. That is, in the first generation method, since the reflected light intensity cannot be measured in the divided area where the background light intensity was measured, the point cloud information of the divided area is generated in the next frame. On the other hand, in the second generation method, point cloud information corresponding to all divided regions is suitably generated in each frame. In addition, according to the second generation method, since the background light intensity is measured immediately before the measurement of the reflected light intensity, the correction is made based on the background light intensity measured at a timing closer to the measurement timing of the reflected light intensity. A reflected light intensity distribution can be generated.

In addition, in the example of FIG. 6 and FIG. 7, the control unit 7 measured the reflected light intensity after measuring the background light intensity, but instead of this, the control unit 7 measured the background light intensity after measuring the reflected light intensity. It's okay.

FIG. 8 is a flowchart illustrating a procedure for generating a corrected reflected light intensity distribution based on the second generation method.

First, the reflected light measurement block 72 and the background light measurement block 73 of the control unit 7 successively measure the background light intensity and the reflected light intensity for each measurement point (step S21). Then, the control unit 7 determines whether or not the measurement in step S21 within the divided region to be scanned has been completed (step S22). Then, if the measurement in step S21 within the target divided region is not completed (step S22; No), the control unit 7 continues to execute the process in step S21.

On the other hand, when the measurement in step S21 within the target divided area is completed (step S22; Yes), the smoothing processing block 74 smoothes the background light intensity distribution within the target divided area. A background light intensity distribution is generated (step S23). Then, the subtraction block 75 subtracts the smoothed background light intensity distribution from the reflected light intensity distribution within the target divided area (step S24). In this case, the subtraction block 75 regards the measurement point where the background light intensity was measured in step S21 as the same point as the measurement point of the reflected light intensity measured continuously with the background light intensity, and calculates the reflected light intensity for each measurement point. Subtract the time-invariant smoothed background light intensity from the time waveform of . Thereby, the subtraction block 75 generates a corrected reflected light intensity distribution.

The point cloud information generation block 76 calculates the flight time for each measurement point from the corrected reflected light intensity distribution in the reflected light measurement area, and generates point cloud information representing the distance and direction to the object according to the calculated flight time. generate. Then, the output block 77 outputs the point cloud information generated for the reflected light measurement area to the driving support device (step S25).

Then, the control unit 7 determines whether scanning should be stopped (step S26). For example, when the control unit 7 receives a signal to stop scanning from the driving support device, it determines that scanning should be stopped. When the control unit 7 determines that scanning should be stopped (step S26; Yes), the control unit 7 ends the processing of the flowchart. On the other hand, when the control unit 7 determines that scanning should not be stopped (step S26; No), it shifts the target divided area within the scanning area (step S27). Then, the control unit 7 returns the process to step S21.

As described above, the control unit 7 of the lidar 100 according to the present embodiment measures the reflected light intensity distribution within the scanning area by irradiating the irradiation light, and measures the background light intensity distribution within the scanning area without irradiating the irradiation light. Measure the intensity distribution. Then, the control unit 7 performs smoothing processing on the background light intensity distribution to generate a smoothed background light intensity distribution. Then, the control unit 7 subtracts the smoothed background light intensity distribution from the reflected light intensity distribution. Thereby, the control unit 7 can calculate the reflected light intensity that suitably excludes the influence of continuous background light that exists over a plurality of frames.

For example, since the rear reflectors of a vehicle exist as a left and right pair, the rear reflector of a vehicle in front traveling far away may be detected as an object only at two measurement points separated by a certain distance. In this case, if the distance between two measurement points is equivalent to the width of the vehicle, it can be determined that the two measurement points are likely to indicate the rear reflector of the vehicle. Even reflected light that is only measured can contain important information. In this respect, the present invention makes it possible to improve the accuracy of the measured data of reflected light by subtracting the measured data of background light from which noise has been removed, without removing the measured data of reflected light. That is, according to the present invention, it is possible to provide a measuring device that can effectively utilize reflected light data without removing it.

1 Transmitter 2 Receiver 3 Beam splitter 5 Scanner 6 Piezo sensor 7 Control unit 100 Lidar

Claims (1)

A first intensity distribution that is an intensity distribution of reflected light within the measurement target area is measured by irradiating the irradiation light, and a second intensity distribution that is the intensity distribution of the background light within the measurement target area without irradiating the irradiation light. a measurement unit that measures the
a smoothing unit that performs smoothing processing on the second intensity distribution to generate a third intensity distribution;
a subtraction unit that subtracts the third intensity distribution from the first intensity distribution;
A measuring device with

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