JP7375789B2 - distance measuring device - Google Patents

Description

The present disclosure relates to a distance measuring device.

Pulsed light such as a laser beam is emitted from the light emitting part, the light reflected from the target is detected by the light receiving part, and the time of flight (TOF) of the light from irradiation to reception is measured. 2. Description of the Related Art Distance measuring devices that detect the presence or absence of an object and measure the distance to an object are known. In such distance measuring devices, the pulsed light is reflected by the window or inside the housing for emitting the pulsed light, and the reflected light of the pulsed light is caused by rain, fog, etc. that exist in the space between the distance measuring device and the target object. Light is called clutter and can become an obstacle in measuring the distance to an object. Specifically, the reflected light from the object and the clutter are combined and detected as a single light reception pulse, which may prevent the flight time from being accurately measured and reduce the accuracy of the measured distance. Therefore, in the distance measuring device of Patent Document 1 below, a value larger than the amplitude value (intensity) of clutter is set as a threshold value for the received light intensity (High threshold value), and the High threshold value is set for the received light intensity of the composite light received pulse. By applying this, the reflected wave (desired wave) from the object is separated from the combined light reception pulse, thereby improving the accuracy of measuring the distance to the object.

Japanese Patent Application Publication No. 2015-194356

For example, when the cause of clutter is fog, the thicker the fog, the greater the amplitude value of the clutter, and the smaller the difference in amplitude between the clutter and the desired wave. Furthermore, for example, if the cause of clutter is a window or housing for emitting pulsed light, the greater the reflectance of the window or housing surface, the greater the amplitude of the clutter, and the amplitude of the clutter and the desired wave increases. The difference becomes smaller. In this way, when the difference in amplitude between the clutter and the desired wave becomes small, the temporal change in the received light intensity of the composite wave becomes like a single mountain. This phenomenon occurs not only when clutter occurs, but also when there are multiple objects at different distances from each other in the same direction relative to the distance measuring device, and the reflected light from these multiple objects can occur in combination. In this way, when the received light intensities of multiple reflected lights are combined into a single mountain-like shape, the distance measuring device of Patent Document 1 cannot separate the desired wave from the received light waves, and the distance measurement accuracy cannot be improved. In Patent Document 1, for example, in a bad environment such as dense fog or heavy rain, distance measurement is not performed, thereby suppressing a decrease in distance measurement accuracy. However, there is a need for a technology that can accurately measure distances even in situations where temporal changes in the received intensity of a plurality of reflected lights are combined into a single mountain-like shape, such as in a bad environment.

As one form of the present disclosure, a distance measuring device (10, 10a) is provided. This distance measuring device includes a light emitting unit (40) that emits pulsed light, a light receiving unit (60) that receives light including reflected light of the pulsed light, and utilizes the flight time of the light received by the light receiving unit. and a calculation unit (20) that calculates an object distance that is a distance to an object that reflects the pulsed light and outputs the reflected light. The calculation unit includes a histogram generation unit (230) that generates a histogram representing the received light intensity at each of the light receiving units at a plurality of flight times; is a peak where the change in distance changes from increase to decrease, and the peak is obtained by combining the distribution of light intensities from a plurality of objects whose distances from the distance measuring device are within a predetermined range. A composite peak estimating unit (240) that estimates whether a composite peak exists; and a composite peak estimating unit (240) that estimates whether a composite peak exists; a flight time identification unit (250) that identifies a rise time that is a shorter flight time and a fall time that is a longer flight time; a base flight time determination unit (260) that determines a base flight time to be used as a basis for calculating the object distance based on either the rise time or the fall time specified for the composite mountain portion; and a distance calculation unit (270) that calculates a distance to one of the plurality of objects as the object distance using the base flight time.

According to the distance measuring device of this form, the base flight time, which is the basis for calculating the object distance, is determined based on either the rise time or the fall time specified for the composite mountain part, Since the object distance is calculated using the determined basic flight time, it is possible to calculate the object distance even in situations where the time changes in the received light intensity of multiple reflected lights are combined into a single mountain-like shape. Can be measured with high accuracy.

1 is a schematic configuration diagram of a distance measuring device as an embodiment of the present disclosure. FIG. 2 is an explanatory diagram schematically showing the configuration of a light receiving array. FIG. 2 is a circuit diagram schematically showing the configuration of a SPAD circuit. FIG. 1 is a block diagram showing the functional configuration of a distance measuring device according to a first embodiment. FIG. 2 is an explanatory diagram showing an example of a histogram having composite peaks. 5 is a flowchart showing the procedure of distance measurement processing in the first embodiment. FIG. 3 is an explanatory diagram showing an example of a histogram that does not have a composite peak. FIG. 2 is a block diagram showing the functional configuration of a distance measuring device according to a second embodiment. 7 is a flowchart showing the procedure of distance measurement processing in the second embodiment. FIG. 7 is a plan view schematically showing the positional relationship between a plurality of objects and a distance measuring device in a second embodiment. FIG. 7 is an explanatory diagram showing an example of a histogram having composite peaks in the second embodiment. FIG. 7 is an explanatory diagram showing an example of a histogram having composite peaks in the second embodiment. FIG. 7 is an explanatory diagram showing an example of a histogram having composite peaks in the second embodiment. FIG. 7 is an explanatory diagram showing an example of a histogram having composite peaks in the third embodiment. 10 is a flowchart showing the procedure of clutter position setting processing in the fourth embodiment. FIG. 7 is an explanatory diagram showing an example of a distance histogram in the fourth embodiment. 12 is a flowchart showing the procedure of clutter position setting processing in the fifth embodiment. FIG. 7 is an explanatory diagram showing an example of a histogram in the fifth embodiment. 12 is a flowchart showing the procedure of distance measurement processing in the sixth embodiment. FIG. 7 is an explanatory diagram showing an example of a histogram in the sixth embodiment. 12 is a flowchart showing the procedure of distance measurement processing in the seventh embodiment.

A. First embodiment:
A1. Device configuration:
The distance measuring device 10 shown in FIG. 1 includes an optical system 30 that emits pulsed light for distance measurement and receives reflected light from an external object, and an arithmetic unit 20 that processes signals obtained from the optical system 30. Be prepared. External objects are also called "reflecting objects." The optical system 30 includes a light emitting unit 40 that emits laser light as pulsed light, a scanning unit 50 that scans the laser light within a predetermined viewing range 80, and an incident light including reflected light from an external object and disturbance light. A light receiving section 60 for receiving light is provided. The distance measuring device 10 is housed in a housing 90 having a window 92 on the front. The window 92 transmits most of the pulsed light emitted from the light emitting section 40 and reflects some of it.

The distance measuring device 10 is, for example, an in-vehicle LiDAR (Laser Imaging Detection and Ranging) mounted on a vehicle such as a car. When the vehicle is running on a horizontal road surface, the horizontal direction of the visual field range 80 coincides with the horizontal direction X, and the vertical direction coincides with the vertical direction Y.

The light emitting unit 40 includes a semiconductor laser element (hereinafter also simply referred to as a laser element) 41 that emits laser light including pulsed light, a circuit board 43 incorporating a drive circuit for the laser element 41, and a semiconductor laser element 41 that emits laser light including pulsed light. It includes a collimating lens 45 that converts the laser beam into parallel light. The laser element 41 is a laser diode capable of oscillating a so-called short pulse laser. In this embodiment, the laser element 41 forms a rectangular laser emission region by arranging a plurality of laser diodes along the vertical direction. The intensity of the laser light output by the laser element 41 is configured to be adjustable according to the voltage supplied to the laser element 41.

The scanning unit 50 is configured by a so-called one-dimensional scanner. The scanning section 50 includes a mirror 54, a rotary solenoid 58, and a rotating section 56. The mirror 54 reflects the laser light that has been made into parallel light by the collimating lens 45. The rotary solenoid 58 receives a control signal from the calculation unit 20 and repeats forward and reverse rotation within a predetermined angular range. The rotating unit 56 is driven by a rotary solenoid 58 and repeats normal and reverse rotations with a rotating shaft whose axial direction is the vertical direction, thereby causing the mirror 54 to scan in one direction along the horizontal direction. The laser beam emitted from the laser element 41 via the collimating lens 45 is reflected by the mirror 54, and is scanned along the horizontal direction by the rotation of the mirror 54. The viewing range 80 shown in FIG. 1 corresponds to the entire scanning range of this laser beam. Since the received light intensity is obtained at each pixel position within the viewing range 80, the distribution of the received light intensity within the viewing range 80 constitutes a kind of image. Note that the scanning section 50 may be omitted, and the light emitting section 40 emits pulsed light over the entire viewing range 80, and the light receiving section 60 receives reflected light over the entire viewing range 80. In this embodiment, each position within the scanning range, in other words, each pixel position within the viewing range 80, is irradiated with pulsed light. Then, the irradiation of the pulsed light and the distance measurement process described below based on the reflected light from each pixel position are performed at predetermined time intervals for each pixel position.

If there is an external object (reflecting object) such as a person or a car, the laser light output from the light emitting section 40 is diffusely reflected on the surface of the object, and a part of it returns to the mirror 54 of the scanning section 50 as reflected light. This reflected light is reflected by the mirror 54, enters the light receiving lens 61 of the light receiving section 60 as incident light together with the disturbance light, is condensed by the light receiving lens 61, and enters the light receiving array 65. Note that the laser beam output from the range finder 10 is diffusely reflected not only by external objects but also by objects inside the range finder 10 , such as the window 92 , and a part of the reflected light is incident on the light receiving array 65 . do.

As shown in FIG. 2, the light receiving array 65 is composed of a plurality of pixels 66 arranged two-dimensionally. One pixel 66 is composed of a plurality of SPAD (Single Photon Avalanche Diode) circuits 68 arranged in H pieces in the horizontal direction and V pieces in the vertical direction. H and V are each integers of 1 or more. In this embodiment, H=V=5, and the SPAD circuit 68 is composed of five SPAD circuits 68 in each of the horizontal and vertical directions. However, it is possible to configure the pixel 66 with an arbitrary number of SPAD circuits 68, and the pixel 66 may be configured with one SPAD circuit 68. The light reception result of one pixel 66 is the light reception intensity at one pixel position within the viewing range 80.

As shown in FIG. 3, the SPAD circuit 68 connects an avalanche diode Da and a quench resistor Rq in series between a power supply Vcc and a ground line, and calculates the voltage at the connection point using one of the logical operation elements. The signal is input to an inverting element INV and converted into a digital signal with an inverted voltage level. The output signal Sout of the inverting element INV is directly output to the outside. In this embodiment, the quench resistor Rq is configured as a FET, and when the selection signal SC is active, its on-resistance works as the quench resistor Rq. When the selection signal SC becomes non-active, the quench resistor Rq enters a high impedance state, so even if light enters the avalanche diode Da, no quench current flows, and as a result, the SPAD circuit 68 does not operate. The selection signal SC is outputted all at once to the 5×5 SPAD circuits 68 in the pixel 66, and is used to specify whether or not to read out the signal from each pixel 66. In this embodiment, the avalanche diode Da is operated in the Geiger mode, but the avalanche diode Da may be used in the linear mode and its output treated as an analog signal. Furthermore, a PIN photodiode may be used instead of the avalanche diode Da.

If no light is incident on the SPAD circuit 68, the avalanche diode Da is kept non-conductive. Therefore, the input side of the inverting element INV is maintained in a pulled-up state via the quench resistor Rq, that is, at a high level H. Therefore, the output of the inverting element INV is kept at low level L. When light enters each SPAD circuit 68 from the outside, the avalanche diode Da becomes energized by the entered light (photons). As a result, a large current flows through the quench resistor Rq, the input side of the inverting element INV becomes low level L, and the output of the inverting element INV is inverted to high level H. As a result of the large current flowing through the quench resistor Rq, the voltage applied to the avalanche diode Da decreases, so power supply to the avalanche diode Da is stopped, and the avalanche diode Da returns to a non-conducting state. As a result, the output signal of the inverting element INV is also inverted and returns to the low level L. As a result, when light (photon) enters each SPAD circuit 68, the inverting element INV outputs a pulse signal that becomes high level for a very short time. Therefore, if the selection signal SC is set to high level H in synchronization with the timing at which each SPAD circuit 68 receives light, the output signal of the inverting element INV, that is, the output signal Sout from each SPAD circuit 68, becomes the output signal of the avalanche diode Da. It becomes a digital signal that reflects the state. The output signal Sout corresponds to a pulse signal generated by the reception of incident light including reflected light and disturbance light that are reflected by the irradiated light from an external object existing in the scanning range, the window 92, etc., and returned.

The calculation section 20 uses the flight time of the reflected light received by the light receiving section 60 to calculate the distance to the object that reflects the pulsed light and outputs the reflected light (hereinafter referred to as "object distance"). calculate. An outline of the method for calculating such distance is as follows. As shown in FIG. 4, the pulsed light P1 emitted from the light emitting section 40 is reflected by the reflecting object OBJ, which is an external object. In other words, the reflecting object OBJ outputs the reflected light P2 of the pulsed light P1. The pulsed light P1 is also reflected on the inner surface of the window 92, and reflected light P3 is output. As a result, reflected lights P2 and P3 reach the light receiving section 60. At this time, the time from the emission of the pulsed light P1 to the reception of the reflected lights P2 and P3 is specified as the light flight time Tf. The calculation unit 200 uses this flight time Tf to calculate the distance from the distance measuring device 10 (the light emitting unit 40 and the light receiving unit 60) to the reflecting object OJB. Note that the reflected light obtained by reflecting the pulsed light P1 on the inner surface of the window 92 and the light that is reflected several times inside the casing of the distance measuring device 10 and received by the light receiving unit 60 are , also called "clutter".

As shown in FIG. 4, the calculation unit 20 includes an addition unit 220, a histogram generation unit 230, a composite peak estimation unit 240, a flight time identification unit 250, a basic flight time determination unit 260, and a distance calculation unit 270. , a control unit 280 , and a memory 290 .

The adding unit 220 adds the outputs of the SPAD circuits 68 included in the pixels 66 that constitute the light receiving array 65. When an incident light pulse enters one pixel 66, a SPAD circuit 68 included in the pixel 66 is activated. The SPAD circuit 68 can detect only one photon incident thereon. However, in the SPAD circuit 68, the detection of the limited amount of light output from the reflecting object OBJ has to be probabilistic. Therefore, the adder 220 adds the output signal Sout from the SPAD circuit 68, which cannot detect incident light only stochastically, by the amount corresponding to all the SPAD circuits 68 included in each pixel 66. OBJ is configured to more reliably detect the reflected light from the reflective object OBJ.

The histogram generation unit 230 generates a histogram of the received light intensity by acquiring the addition results of the addition unit 220 in time series, and stores it in the memory 290. The histogram generated by the histogram generation unit 230 can be said to be a graph representing the received light intensity at each of a plurality of flight times. The received light intensity is the total number of SPAD circuits 68 that received light within one pixel 66.

The composite peak estimation unit 240 estimates whether a composite peak exists in the histogram generated by the histogram generation unit 230. A composite peak is a peak in the histogram where the change in received light intensity with respect to flight time changes from increasing to decreasing after the peak flight time, and the difference in distance from the distance measuring device 10 is within a predetermined range. It means a peak obtained by combining the distribution of light intensity from a plurality of objects.

In FIG. 5, the horizontal axis shows the flight time Tf, and the vertical axis shows the received light intensity I. The histogram hr1 shown by the thick solid line in FIG. 5 is a composite of the histogram hr11 of the received light intensity due to clutter shown by the thin dashed line, and the histogram hr12 of the received light intensity of the reflected light from an object outside the distance measuring device 10 shown by the thin solid line. This is the histogram obtained by Each histogram shown in FIG. 5 represents a histogram when an object outside the range finder 10 is located near the range finder 10 (window 92). In the example of FIG. 5, a composite peak mp0 appears in the histogram hr1. Here, the histogram hr11 and the histogram hr12 overlap each other in time. The peak received light intensity (frequency) of histogram hr11 and the peak received light intensity (frequency) of histogram hr12 are approximately equal to each other. Therefore, as shown in FIG. 5, the composite mountain portion mp0 appears as a single mountain-like shape. The composite peak estimating unit 240 calculates the time from the rise time to the fall time in the peak, in other words, when the time in the histogram in which the received light intensity is equal to or higher than a first threshold described below continues for a predetermined time or more, It is assumed that a composite peak exists in the histogram. The details of each value of the received light intensity I shown in FIG. 5, that is, the noise intensity I1, the first threshold received light intensity I3, and the peak intensity I4 will be described later. Further, details of each value of the flight time Tf shown in FIG. 5, that is, the rise time Tu1, the fall time Td1, the peak time Tp1, and the intermediate time Tc1 will be described later.

In the histogram generated by the histogram generation unit 230, the time-of-flight identifying unit 250 identifies two flight times (rise time and fall time, which will be described later) whose received light intensity matches the first threshold received light intensity. The first threshold received light intensity is a threshold of the received light intensity used when calculating the target distance, and is used to determine the rise time and fall time at the peaks of the histogram. In the example of FIG. 5, the first threshold received light intensity I3 is set. In this embodiment, the first threshold received light intensity is set as a value shown in equation (1) below.
First threshold received light intensity = (peak intensity - noise intensity) x 0.4 + noise intensity... (1)

Here, the peak intensity means the maximum received light intensity at the peak, and in the composite peak mp0 of FIG. 5, the peak intensity I4 corresponds. Further, the noise intensity refers to the received light intensity of light other than the reflected light of the pulsed light (hereinafter referred to as "noise light"). Examples of such noise light include sunlight, reflected light obtained by reflection of sunlight on an external object, and light from street lamps. The noise intensity can be determined as the average value over a predetermined time of the received light intensity measured at a timing when the light emitting unit 40 does not emit pulsed light. (Peak intensity−Noise intensity) in equation (1) is also called reflected light intensity. Therefore, equation (1) means that the received light intensity obtained by adding 40% of the reflected light intensity to the noise intensity is set as the first threshold received light intensity. Note that instead of 40%, any ratio smaller than 40% or larger than 40% may be used. In the example of FIG. 5, the flight time identifying unit 250 identifies the earlier time Tu1 as the rise time Tu1, which is the earlier time Tu1 of the two times Tu1 and Td1 at which the histogram hr1 and the first threshold received light intensity I3 match. In addition, a later time Td1 is specified as the fall time Td1.

The base flight time determining unit 260 determines a base flight time (hereinafter referred to as "base flight time") for calculating the target distance. In this embodiment, the base flight time determining unit 260 determines the falling time as the base flight time, as will be described later. The reason why the fall time is determined as the base flight time will be described later.

The distance calculation unit 270 uses the base flight time determined by the base flight time determination unit 260 to calculate the object distance. Details of the method for calculating the object distance will be described later. The calculated object distance is used, for example, in the process of estimating whether or not a collision with an object will occur in a vehicle equipped with the distance measuring device 10, and in controlling steering and braking to avoid a collision. obtain.

A2. Distance processing:
The distance measurement process shown in FIG. 6 is periodically executed at predetermined time intervals for each pixel position. The distance measurement process is started at a timing after the light emitting unit 40 emits pulsed light, the reflected light is received by the light receiving unit 60, and a histogram is generated by the histogram generating unit 230.

The composite peak estimating unit 240 identifies a composite peak in the generated histogram, and the flight time identifying unit 250 identifies the rise time and fall time (step S105). Specifically, the composite peak estimating unit 240 identifies the composite peak by identifying a portion in the histogram in which the flight time exceeding the first threshold received light intensity continues for a predetermined time or longer. Further, the flight time identifying unit 250 identifies two flight times that match the first threshold value in the composite mountain portion as a rise time and a fall time.

For example, in the example of FIG. 5, the composite peak mp0 is identified, and of the two times Tu1 and Td1 at which the composite peak mp0 and the first threshold received light intensity I3 match, the earlier time Tu1 is the rise time Tu1. , and the temporally later time Td1 is specified as the fall time Td1.

As shown in FIG. 6, the base flight time determining unit 260 determines whether the receiving position of the reflected light matches the position of the clutter (step S110). The clutter, that is, the reflected light of the pulsed light from the window 92 or the inner wall surface of the housing always enters the light receiving section 60 from the same position (direction). Further, the distance to the window 92 and the wall inside the housing is always constant. For this reason, it is possible to specify in advance by experiment or simulation the direction of the pixel position and the flight time in which the reflected light of the pulsed light from the window 92 or the inner wall surface of the housing is specified. Therefore, in this embodiment, the pixel position and flight time of the pulsed light reflected by the window 92 or the inner wall surface of the housing are stored in advance in the memory 290, and the pixel position and the time of flight when the composite peak is detected. By determining whether the flight time of the reflected light matches the pixel position and flight time stored in the memory 290, it is determined whether the receiving position of the reflected light matches the position of the clutter. There is.

If it is determined that the light reception position of the reflected light does not match the clutter position (step S110: NO), the distance calculation unit 270 calculates the distance using a normal method and specifies it as the object distance (step S115). The distance measuring method in step S115 will be explained using FIG. 7.

The vertical and horizontal axes in FIG. 7 are the same as those in FIG. 5, so detailed explanation thereof will be omitted. The peak mp1 shown in FIG. 7 may be caused by, for example, an object existing outside the distance measuring device 10 in a direction different from the direction in which clutter occurs, and the light receiving unit 60 receiving reflected light of the pulsed light from the object. This can occur in certain cases. In this case, since the pixel position (direction) of the peak mp1 is different from (does not include) the position of the clutter, the flight time specifying unit 250 determines that the intermediate time between the rise time Tu2 and the fall time Td2 is the peak time Tp2 of the peak mp1. Identified as Then, the base flight time determination unit 260 determines this peak time Tp2 as the base flight time, and the distance calculation unit 270 uses the peak time Tp2 to calculate the distance from the distance measuring device 10 to these plural objects. .

As shown in FIG. 6, when it is determined that the light reception position of the reflected light matches the clutter position (step S110: YES), the base flight time determination unit 260 sets the fall time specified in step S105 to the base flight time. The flight time is determined (step S120). The distance calculation unit 270 calculates the distance based on the base flight time determined in step S120 (step S125). Specifically, for example, when the fall time Td1 of the composite peak mp0 shown in FIG. Time tp1 is specified as peak time tp1. The distance calculation unit 270 then calculates the target distance using this peak time tp1. More specifically, the target distance is calculated assuming that the peak time tp1 is the flight time Tf of the pulsed light and its reflected light.

As shown in FIG. 5, the time (peak time Tp1) that goes back by time Δt from time Td1 almost coincides with the peak time of histogram hr12. On the other hand, the intermediate time Tc1 between the rise time Tu1 and the fall time Td1 is largely deviated from the peak time of the histogram hr1. Therefore, it can be seen that by calculating the distance using the peak time Tp1 as the base flight time as described above, the distance to the object corresponding to the histogram hr1 can be calculated more accurately than by calculating the distance using the normal method. . The reason why the intermediate time Tc1 deviates significantly from the peak time of the histogram hr1 as described above will be explained. The composite peak mp0 is generated by combining the histogram hr12 of the reflected light output from the reflective object OBJ that is farther away and the histogram h12 of the clutter output from the window 92 that is closer. The rising position Tu1 almost coincides with the rising position of the histogram hr11 whose peak position is earlier in time. Further, the falling position of the histogram hr11 almost coincides with the falling position of the histogram h12 due to reflected light from an object that is located further away (has a longer flight time). On the other hand, the falling position of histogram hr11, which is earlier in time, is largely shifted from the falling position of histogram hr1 due to the presence of histogram hr12, which is later in time. Similarly, the rising position of histogram hr12, which is later in time, is largely shifted from the rising position of histogram hr1 due to the presence of histogram hr11, which is earlier in time. Therefore, even if the intermediate time Tc1, which is the intermediate time between the rise time Tu1 and the fall time Td1, is specified in order to calculate the target distance according to the usual method, the intermediate time Tc1 is different from the peak time of the histogram hr11 and the histogram hr11. This is a time that is significantly different from the peak time of hr12. On the other hand, by using the falling time of the histogram hr1 as a reference, which almost matches the falling time of the object, and setting the time Δt back from the falling time as the base flight time, the peak time of the object can be calculated. It is possible to obtain approximately the same distance as the distance calculated when the flight time is the base flight time.

As shown in FIG. 6, the distance calculation unit 270 determines whether the distance calculated in step S125 is smaller than a predetermined threshold distance (step S130). The threshold distance in step S130 is set as a value obtained by adding a predetermined value to the distance from the light emitting section 40 and the light receiving section 60 to the window 92, as a distance that is recognized as not clutter if it is larger than this distance. This step S130 is executed to confirm that the received reflected light is not caused by clutter, since the distance calculated based on the base flight time is larger than the distance calculated in the case of clutter.

If it is determined that the distance calculated in step S125 is not smaller than the threshold distance (step S130: NO), step S115 described above is executed, and the object distance is calculated by a normal method. On the other hand, if it is determined that the distance calculated in step S120 is smaller than the threshold distance (step S130: YES), the distance calculation unit 270 specifies the distance calculated in step S125 as the object distance. (Step S135). After the above-described step S115 or step S135 is completed, the distance measurement process at the corresponding pixel position is completed, and the distance measurement process for the next pixel position is started.

According to the distance measuring device 10 of the first embodiment described above, when it is estimated that there is a complex peak containing clutter that is reflected light of pulsed light inside the casing such as the window 92 or the inner wall surface of the casing, Since the base flight time is determined based on the fall time, the object distance can be measured with high accuracy even when clutter occurs. Generally, the flight time of the pulsed light reflected from the window 92 or inside the housing is shorter than that of an object existing outside the distance measuring device. In other words, the pulsed light reflected by an external object has a longer flight time than the pulsed light reflected inside the housing. Therefore, the error between the falling position (time) of the composite peak and the falling position (time) of the reflected light of the pulsed light from an external object is small. Therefore, according to the ranging device 10 of this embodiment, the ranging accuracy can be improved when it is estimated that a complex mountain portion exists.

In addition, if there is no clutter, the intermediate time between the rise time and the fall time is determined as the base flight time, so even in such a case, either the rise time or the fall time Compared to a configuration in which the base flight time is determined based on the distance, the object distance can be measured with higher accuracy. One of the reasons for this is that even if an error occurs when specifying the rise time and fall time, by using the intermediate time between them, the base flight time can be calculated based on only either the rise time or the fall time. One of the advantages of this method is that the influence of errors can be suppressed compared to a configuration that determines .

B. Second embodiment:
The configuration of the distance measuring device 10a of the second embodiment shown in FIG. 8 differs from the configuration of the distance measuring device 10 of the first embodiment in that the calculation section 20 additionally includes an intermediate time specifying section 235. The rest of the configuration of the distance measuring device 10a is the same as the distance measuring device 10 of the first embodiment, so the same components are denoted by the same reference numerals, and detailed description thereof will be omitted.

The intermediate time specifying unit 235 determines the intermediate time between two flight times that match the first threshold received light intensity (hereinafter referred to as "first intermediate time") and the two flight times that match the second threshold received light intensity at the composite peak. The intermediate time between the two flight times (hereinafter referred to as the "second intermediate time") is specified. The first threshold received light intensity is the same as the first threshold received light intensity of the first embodiment. The second threshold received light intensity is a received light intensity that is smaller than the first threshold received light intensity, and the noise intensity is also greater. Specifically, in this embodiment, the second threshold received light intensity is set as a value shown in equation (2) below.
Second threshold received light intensity = (peak intensity - noise intensity) x 0.1 + noise intensity... (2)

The distance measurement process of the second embodiment shown in FIG. 9 is different from the first embodiment shown in FIG. 6 in that step S110 is omitted and steps S106, S107, S108, and S123 are additionally executed. This is different from the distance measurement process. The other steps in the distance measurement process of the second embodiment are the same as the distance measurement process of the first embodiment, so the same steps are given the same reference numerals, and detailed description thereof will be omitted.

After completing step S105, the intermediate time specifying unit 235 calculates a first intermediate time and a second intermediate time (step S106).

As shown in FIG. 10, when two objects OBJ1 and OBJ2 exist at a certain pixel position 81, and each object OBJ1 and OBJ2 has exposed areas Ar1 and Ar2 when viewed from the distance measuring device 10a. , the reflected lights output from these two areas Ar1 and Ar2 respectively enter the light receiving section 60 of the distance measuring device 10a. In the example of FIG. 10, the object OBJ1 is located on the front side when viewed from the distance measuring device 10a, and the target object OBJ2 is located on the back side when viewed from the distance measuring device 10a. Furthermore, at the pixel position 81, the exposed area of the area Ar1 viewed from the distance measuring device 10a is larger than the exposed area of the area Ar2. A histogram generated in such a situation will be explained using FIG. 11.

The vertical and horizontal axes in FIG. 11 are the same as those in FIG. 5, so detailed description thereof will be omitted. The histogram hr3 generated in the situation of FIG. 10 has a composite peak mp3 created by combining a large peak and a small peak that peaks later in time. Specifically, the composite peak mp3 is a histogram obtained by combining a histogram hr31 of reflected light from the area Ar1 indicated by a thin dashed line and a histogram hr32 of reflected light from the area Ar2 indicated by a thin solid line. This corresponds to the peak at hr3. As described above, the area Ar1 is located closer to the front and has a larger exposed area. In contrast, region Ar2 is located further back and has a smaller exposed area. Therefore, the peak of the histogram hr31 is located earlier in time than the peak of the histogram hr32, and the peak received light intensity is greater. Therefore, the composite mountain portion mp3 has an irregular mountain shape having a relatively large peak at a temporally earlier position and a relatively small peak at a temporally later position.

In step S106 described above, the intermediate time specifying unit 235 determines, in the above-described step S106, two times (a rise time Tu3 and a fall time) that match the first threshold received light intensity I11 in the composite peak mp3 having such a shape. Td3) is specified, and an intermediate time Tc31 between these two times is specified. Further, the intermediate time specifying unit 235 specifies two times (rise time Tu4 and fall time Td4) that match the second threshold received light intensity I12 in the composite mountain portion mp3, and intermediate time Tc32 between these three times. Identify. In this embodiment, the intermediate time between two times that match the first threshold received light intensity is referred to as a first intermediate time, and the intermediate time between two times that match the second threshold received light intensity is referred to as a second intermediate time. . Therefore, intermediate time Tc31 is also referred to as first intermediate time Tc31, and intermediate time Tc32 is also referred to as second intermediate time Tc32.

As shown in FIG. 9, the composite peak estimating unit 240 determines whether the width between two times that match the second threshold received light intensity (hereinafter referred to as "root width") is larger than the threshold width. Determination is made (step S107). In the example of FIG. 11, in the composite peak mp3, the width between the two times Tu4 and Td4 that match the second threshold received light intensity I12 corresponds to the root width dt31. In a composite mountain part obtained by combining the mountain parts included in the histogram of reflected light from a plurality of objects, such as the composite mountain part mp3, the root width is large. On the other hand, the base width of the peak caused by light reflected from a single object is small. Therefore, a threshold width for identifying a composite peak is determined and set in advance through experiments or the like. As shown in FIG. 9, when it is determined that the root width is not larger than the threshold width (step S107: NO), the above-described step S115 is executed. In this case, since reflected light from a single object is incident, the distance is calculated by a normal method and specified as the object distance.

If it is determined that the root width is larger than the threshold width (step S107: YES), there is a high possibility that the peak is a composite peak. In this case, the base flight time determining unit 260 determines whether the first intermediate time is less than or equal to the second intermediate time (step S108).

In the example of FIG. 11, the first intermediate time Tc31 is shorter (earlier) than the second intermediate time Tc32. Moreover, in the example of FIG. 13, the first intermediate time and the second intermediate time match. Histogram hr5 shown in FIG. 13 is a histogram obtained by combining histogram hr51 and histogram hr52. Histogram hr51 is based on reflected light from object OBJ1 shown in FIG. 10, and histogram hr52 is based on reflected light from object OBJ2 shown in FIG. However, in the example of FIG. 13, unlike the example of FIG. 10, at the pixel position 81, the exposed area of the area Ar1 seen from the distance measuring device 10a is equal to the exposed area of the area Ar2. In this situation, the peak received light intensity of the histogram hr51 due to the reflected light from the target object OBJ1 is equal to the peak received light intensity of the histogram hr52 due to the reflected light from the target object OBJ2. Therefore, the composite mountain portion mp5 has a large mountain shape with one peak. In this example, both the first intermediate time and the second intermediate time are the intermediate time Tc51.

In the examples of FIGS. 11 and 13, in step S108, the first intermediate time Tc31 is determined to be smaller (earlier) than the second intermediate time Tc32. In this way, when it is determined that the first intermediate time Tc31 is smaller (earlier) than the second intermediate time Tc32 (step S108: YES), the base flight time determining unit 260 determines the rise time specified in step S105. is determined as the base flight time (step S123). For example, in the example of FIG. 11, the rise time Tu3 is determined as the base flight time. Furthermore, in the example of FIG. 13, the rise time Tu7 is determined as the base flight time.

Unlike the examples in FIGS. 11 and 13, a case where the first intermediate time is longer (slower) than the second intermediate time will be described using FIG. 12. Histogram hr4 shown in FIG. 12 is a histogram obtained by combining histogram hr41 and histogram hr42. Histogram hr41 is based on reflected light from object OBJ1 shown in FIG. 10, and histogram hr42 is based on reflected light from object OBJ2 shown in FIG. However, in the example of FIG. 12, unlike the example of FIG. 10, at the pixel position 81, the exposed area of the area Ar1 seen from the distance measuring device 10a is smaller than the exposed area of the area Ar2. In such a situation, the peak received light intensity of the histogram hr41 due to the reflected light from the target object OBJ1 is smaller than the peak received light intensity of the histogram hr42 due to the reflected light from the target object OBJ2. Therefore, the composite mountain portion mp4 has an irregular mountain shape having a relatively small peak at a temporally earlier position and a relatively large peak at a temporally later position.

In the example shown in FIG. 12, two times (rise time Tu5 and fall time Td5) that match the first threshold received light intensity I21 are identified in the composite peak mp4, and an intermediate time between these two times is identified. A second intermediate time Tc41 is specified. Further, in the composite peak mp4, two times (rise time Tu6 and fall time Td6) that match the second threshold received light intensity I22 are specified, and a second intermediate time Tc42 that is an intermediate time between these two times is specified. is specified. In this example, the first intermediate time Tc41 is longer (slower) than the second intermediate time Tc42.

As shown in FIG. 9, if it is determined that the first intermediate time is not less than or equal to the second intermediate time (step S108: NO), the above-mentioned step S120 is executed, and the fall time specified in step S105 is determined as time. In the example of FIG. 12, the fall time Td5 is determined as the base flight time.

As shown in FIG. 9, after step S120 or step S123 is completed, steps S125 and S135 described above are executed.

As shown in FIG. 11, when the first intermediate time is less than or equal to the second intermediate time (earlier or the same), as shown in FIG. Large area. In this case, since the object distance is calculated based on the flight time of the reflected light of the pulsed light on the surface of the object OBJ1, the object distance is calculated based on the object that has a greater influence on the vehicle in which the distance measuring device 10a is mounted. The object distance is calculated. Further, as shown in FIG. 12, when the first intermediate time is longer (slower) than the second intermediate time, unlike the example of FIG. The exposed area of OBJ2 is large. In this case, since the object distance is calculated using the flight time of the reflected pulsed light on the surface of the object OBJ2 as the base flight time, this case also has a greater influence on the vehicle equipped with the distance measuring device 10a. The object distance is calculated based on the large object.

The distance measuring device 10a of the second embodiment described above has the same effects as the distance measuring device 10 of the first embodiment. In addition, if the first intermediate time is smaller than the second intermediate time, the base flight time is determined based on the rise time, so multiple objects at different distances in the same direction with respect to the distance measuring device 10a are determined. exists, and when the irradiation area of the pulsed light in that direction is larger for the object on the front side, the distance to the object on the front side can be determined as the object distance. In addition, if the first intermediate time is longer than the second intermediate time, the base flight time is determined based on the fall time, so multiple objects at different distances in the same direction with respect to the distance measuring device 10a are exists, and when the irradiation area of the pulsed light in that direction is larger for the object on the rear side, the distance to the object on the rear side can be determined as the object distance. As described above, according to the distance measuring device 10a of the second embodiment, when there are a plurality of objects having different distances in the same direction with respect to the distance measuring device 10a, it is possible to The distance to the object, that is, the distance to the position where the object actually exists, can be determined as the object distance. In addition, since the distance to the object with a larger irradiation area of the pulsed light is determined as the object distance, the distance to the object with a larger exposed area as seen from the distance measuring device 10a can be determined as the object distance. . Therefore, for example, in a configuration in which the safety function of the vehicle is exerted using the distance to an object, such a function can be exerted in a manner that further ensures safety. In addition, when the first intermediate time and the second intermediate time are the same, the base flight time is determined based on the rise time, so multiple objects at different distances in the same direction with respect to the distance measuring device 10a are In the case where the pulsed light exists and the irradiation area of the pulsed light is equal to each other, the distance to either the front or rear object can be determined as the object distance. Therefore, it is possible to prevent the distance to a position where no target object is present from being determined as the target distance.

Note that, as can be understood from the second embodiment and the first embodiment described above, the base flight time determination unit 260 specifies the composite peak based on the first threshold received light intensity when the composite peak exists. The base flight time can be determined based on either the rise time or the fall time.

C. Third embodiment:
The configuration of the distance measuring device 10a of the third embodiment is the same as that of the distance measuring device 10a of the second embodiment shown in FIG. Omitted. In the distance measuring device 10a of the second embodiment, the threshold received light intensity used to specify the rise time Tu3, the time Td3, and the intermediate time (first intermediate time) Tc31 is the same as the first threshold received light intensity I11. Was. On the other hand, in the third embodiment, the threshold received light intensity used to specify the rise time Tu3 and the time Td3 and the threshold received light intensity used to specify the intermediate time (first intermediate time) are as follows. differ from each other. A detailed explanation will be given below using FIG. 14.

As shown in FIG. 14, in the third embodiment, similarly to the second embodiment, the rise time Tu3 and the fall time Td3 are specified using the first threshold received light intensity I11. On the other hand, in the third embodiment, the threshold light reception intensity I14 for specifying the intermediate time Tc33 is set separately from the above-described first threshold light reception intensity I11. Then, two times that match the threshold received light intensity I14 in the composite peak mp3 are identified, and the intermediate time between these two times is identified as the intermediate time Tc33. This intermediate time Tc33 is used as the first intermediate time instead of the intermediate time Tc31 of the second embodiment. Therefore, for example, in step S108 of the distance measurement process shown in FIG. 9, it is determined whether the intermediate time Tc33, which is the first intermediate time, is less than or equal to the second intermediate time Tc32, which is the second intermediate time. In the third embodiment, the threshold received light intensity I14 is set in advance as a value greater than the first threshold received light intensity I11 and less than or equal to the intensity I13 which is the peak received light intensity of the composite peak mp3. Note that the threshold received light intensity I14 may be set to a value smaller than the first threshold received light intensity I11 and larger than the second threshold received light intensity I12.

The distance measuring device 10a of the third embodiment described above has the same effects as the distance measuring device 10a of the second embodiment. Note that the threshold received light intensity I14 in the third embodiment corresponds to the third threshold received light intensity in the present disclosure.

D. Fourth embodiment:
D1. Device configuration:
The configuration of the distance measuring device 10 of the fourth embodiment is the same as that of the distance measuring device 10 of the first embodiment, so the same components are denoted by the same reference numerals, and detailed description thereof will be omitted. As described in the first embodiment, regarding the clutter that occurs due to the reflected light of the pulsed light by the window 92 or the inner wall surface of the housing, the direction of the pixel position and the flight time to identify it are as follows: It can be determined in advance through experiments and simulations. On the other hand, if foreign matter such as sand or mud adheres to the outer surface of the window 92, the reflected light of the pulsed light at such a position becomes very large, and new clutter may occur. In such a case, the pixel position where clutter occurs differs depending on the position of the foreign object, and therefore cannot be specified in advance. In the distance measuring device 10 of the fourth embodiment, by executing a clutter position setting process to be described later, the position of clutter (in which direction the pixel position is located) caused by foreign matter adhesion as described above is identified and set. do.

D2. Clutter position setting process:
The clutter position setting process shown in FIG. 15 is executed when the distance measuring device 10 is powered on. The histogram generation unit 230 determines whether the object distance has been specified by the distance measurement process shown in FIG. 6 (step S205). When the specification of the object distance is completed, the distance from the distance measuring device 10 to the object for each pixel has been specified.

The histogram generation unit 230 generates a distance histogram for each pixel, including the distance specified by the current distance measurement process (step S210). In this embodiment, the memory 290 stores object distances specified a predetermined number of times for each pixel. The predetermined number of times depends on the size of the memory 290, but for example, a maximum of 100 times may be stored. If a new object distance is specified after 100 object distances have been stored, the newly specified object distance is stored, overwriting the oldest stored object distance. It's okay. The distance histogram for each pixel generated in step S210 corresponds to "statistical value of object distance calculated for each pixel" in the present disclosure.

In FIG. 16, two histograms hd1 and hd2 are shown as examples of histograms generated in step S210. A histogram hd1 indicated by a thick solid line is a histogram for pixels different from positions where clutter is known to occur in advance, and shows a histogram when foreign matter such as mud is attached to the window 92. A histogram hd2 indicated by a thin broken line is a histogram for a pixel different from a position where clutter is known to occur in advance, and is a histogram when no foreign matter such as mud is attached to the window 92.

When foreign matter adheres to the window 92, a peak frequency occurs at a distance corresponding to the position of the window 92. On the other hand, for other distances, because there is a foreign object attached, even if the reflected light were to come from that direction, it would be blocked by the foreign object and the distance based on the reflected light would not be specified, and the frequency at such distances would remain low. becomes. Therefore, as shown in the histogram hd1, a peak occurs at a relatively small distance d1.

On the other hand, if no foreign matter is attached to the window 92 and the vehicle is moving, objects may exist at various distances in the direction corresponding to the pixel. Therefore, as shown in the histogram hd2, the frequency becomes greater than 0 over a wide range of distances, resulting in, for example, a gently hill-shaped histogram.

As shown in FIG. 15, the histogram generation unit 230 determines whether there is a pixel with a frequency exceeding the threshold frequency within a range within the threshold distance (step S215). When the histogram hd1 in FIG. 16 is obtained, the frequency exceeding the threshold frequency THn is recorded within the range within the threshold distance THd, so the pixel corresponding to the histogram hd1 has a threshold frequency within the range within the threshold distance. corresponds to pixels whose frequency exceeds On the other hand, when the histogram hd2 in FIG. 16 is obtained, since no frequency exceeding the threshold frequency THn is recorded within the range within the threshold distance THd, the pixel corresponding to the histogram hd2 has a threshold frequency within the range within the threshold distance THd. It does not correspond to pixels whose frequency exceeds the frequency.

As shown in FIG. 15, if it is determined that there is a pixel with a frequency exceeding the threshold frequency within the range within the threshold distance (step S215: YES), the histogram generation unit 230 generates a pixel within the range within the threshold distance. The positions of pixels whose frequency exceeds the threshold frequency are additionally set as clutter positions (step S220). As described above, since the clutter position is stored in the memory 290, the histogram generation unit 230 reads out the information on the clutter position, adds the pixel position specified in step S215, and stores it in the memory 290. . After completing step S220, the process returns to step S205.

If it is determined in step S215 that there are no pixels with a frequency exceeding the threshold frequency within the range within the threshold distance (step S215: NO), the histogram generation unit 230 determines that all pixel positions are not clutter positions. Additional settings are made (step S225). After completing step S225, the process returns to step S205. In this embodiment, a wiper that wipes the window 92 is provided, and when it is determined in step S215 that there is a pixel whose frequency exceeds the threshold frequency within the range of the threshold distance, the wiper wipes the window 92. You can also use it as If there are pixels with a frequency exceeding the threshold frequency within the range of the threshold distance due to a foreign object such as mud attached to the window 92, after the foreign object is removed by the wiper's wiping operation, step In S215, it is determined that there are no pixels with a frequency exceeding the threshold frequency within the range within the threshold distance, and by executing step S225, the clutter position resulting from a foreign object is updated and set as not a clutter position.

Note that instead of the histogram generation section 230, the distance calculation section 270 or another functional section may execute steps S205 to S220 described above. Further, a new functional unit other than the functional unit shown in FIG. 4 may execute steps S205 to S220 described above. In this way, the functional unit that executes steps S205 to S220 described above corresponds to the “clutter position setting unit” of the present disclosure.

The distance measuring device 10 of the fourth embodiment described above has the same effects as the distance measuring device 10 of the first embodiment. In addition, the distance measuring device 10 of the fourth embodiment generates a histogram of the distance of each pixel, and when it is determined that there is a pixel with a frequency exceeding the threshold frequency THn within the range within the threshold distance THd, the distance measuring device 10 of the fourth embodiment Since the position is set as the clutter position, it is possible to specify the position of clutter caused by foreign matter such as mud adhering to the window 92. Therefore, in step S110 of the ranging process shown in FIG. 6, it is possible to accurately determine whether the position of the reflected light and the clutter position match.

E. Fifth embodiment:
The configuration of the distance measuring device 10 of the fifth embodiment is the same as that of the distance measuring device 10 of the fourth embodiment, so the same components are denoted by the same reference numerals, and detailed description thereof will be omitted. The distance measuring device 10 of the fifth embodiment differs from the distance measuring device 10 of the fourth embodiment in the procedure of clutter position setting processing.

The clutter position setting process according to the fifth embodiment shown in FIG. 17 includes executing step S205a in place of step S205, executing step S210a in place of step S210, and executing step S215a in place of step S215. This differs from the clutter position setting process of the fourth embodiment shown in FIG. 15 in this point. The other steps in the clutter position setting process of the fifth embodiment are the same as the clutter position setting process of the fourth embodiment, so the same steps are given the same reference numerals and detailed explanation thereof will be omitted.

As shown in FIG. 17, the histogram generation unit 230 determines whether a histogram has been generated (step S205a). If it is determined that the histogram has not been generated (step S205a: NO), the process returns to step S205a. That is, the histogram generation unit 230 waits until the histogram has been generated.

If it is determined that the histogram has been generated (step S205a: YES), the histogram generation unit 230 generates a histogram of the flight time and average intensity for each pixel, including the currently calculated histogram (step S210a). ). In this embodiment, the histogram for each pixel generated by the histogram generation unit 230 is stored in the memory 290. Then, in step S210a, the histogram generation unit 230 calculates the average value of the intensity for each flight time Tg for the plurality of histograms stored in the memory 290, and thereby generates a histogram of the average intensity. The histogram of the average intensity generated for each pixel corresponds to the "statistical value of the received light intensity of each pixel" in the present disclosure.

In FIG. 18, two histograms hr61 and hr62 are shown as examples of histograms generated in step S210a. A histogram hr61 indicated by a thick solid line is a histogram for pixels different from positions where clutter is known to occur in advance, and shows a histogram when foreign matter such as mud is attached to the window 92. The histogram hr62 indicated by a thin broken line is a histogram for a pixel different from a position where clutter is known to occur in advance, and is a histogram when no foreign matter such as mud is attached to the window 92.

When foreign matter adheres to the window 92, the peak of the received light intensity I occurs at the flight time Tf corresponding to the position of the window 92 (more precisely, the round trip flight time to the position). On the other hand, regarding other flight times Tf, since there is a foreign object attached, even if the reflected light were to come from that direction, it would be blocked by the foreign object, so the flight time Tf based on the reflected light would not be specified, and such flight The received light intensity I at time Tf remains low. Therefore, as shown in the histogram hr61, a peak occurs at a relatively short time T6.

On the other hand, if no foreign matter is attached to the window 92 and the vehicle is moving, objects may exist at various distances in the direction corresponding to the pixel. Therefore, as shown in the histogram hr62, the received light intensity I becomes greater than 0 over a wide range of flight times Tf, resulting in, for example, a gently hill-shaped histogram.

As shown in FIG. 17, the histogram generation unit 230 determines whether there is a pixel having a peak whose average intensity exceeds the threshold intensity within a range within the threshold flight time (step S215a). When the histogram hr61 in FIG. 18 is obtained, since the flight time T6 exceeding the threshold intensity It1 is recorded within the range within the threshold flight time THt, the pixel corresponding to the histogram hr61 is within the threshold flight time THt. This corresponds to pixels whose frequency exceeds the threshold intensity It1 in the range. On the other hand, when histogram hr62 in FIG. 18 is obtained, the frequency exceeding the threshold intensity It1 is not recorded within the range within the threshold flight time THt, so the pixels corresponding to histogram hr62 are within the threshold flight time THt. The range does not correspond to pixels whose intensity exceeds the threshold intensity It1.

When it is determined that there is a pixel with a peak whose average intensity exceeds the threshold intensity It1 within the threshold flight time THt (step S215a: YES), the histogram generation unit 230 generates a pixel within the threshold flight time THt. The positions of pixels having a peak whose average intensity exceeds the threshold intensity It1 in the range are additionally set as clutter positions (step S220).

On the other hand, in step S215a, if it is determined that there is no pixel having a peak whose average intensity exceeds the threshold intensity It1 within the range within the threshold flight time THt (step S215a: NO), the process returns to step S205a. Therefore, in this case, the clutter position stored in memory 290 will not be updated.

The distance measuring device 10 of the fifth embodiment described above has the same effects as the distance measuring device 10 of the fourth embodiment. In addition, the distance measuring device 10 of the fifth embodiment generates a histogram of the flight time and average intensity for each pixel, and determines that there is a pixel with an intensity exceeding the threshold intensity It1 within a range within the threshold flight time THt. In such a case, since the position of such a pixel is set as the clutter position, the position of clutter caused by foreign matter such as mud adhering to the window 92 can be specified. Therefore, in step S110 of the ranging process shown in FIG. 6, it is possible to accurately determine whether the position of the reflected light and the clutter position match.

F. Sixth embodiment:
The configuration of the distance measurement device 10 of the sixth embodiment is the same as the distance measurement device 10 of the first embodiment except for the detailed procedure of distance measurement processing, so the same components are given the same reference numerals. Detailed explanation will be omitted. The distance measurement process of the sixth embodiment shown in FIG. 19 differs from the distance measurement process of the first embodiment shown in FIG. 6 in that step S132 is additionally executed. The other steps of the distance measurement process in the sixth embodiment are the same as those in the first embodiment, so the same steps are given the same reference numerals and detailed explanation thereof will be omitted.

As shown in FIG. 19, if it is determined in step S130 that the calculated distance is smaller than the threshold distance (step S130: YES), the distance calculation unit 270 determines that the pulse width of the composite peak is set in advance. It is determined whether the width is smaller than a certain threshold width (step S132). In this embodiment, the pulse width in step S132 means the width of the flight time used to determine the first threshold received light intensity, that is, the rise time and fall time at the peak. In the present embodiment, the threshold width in step S132 is determined depending on whether the composite peak is a peak formed from clutter and reflected light from a target object or a peak formed by multiple reflections described below. It means the range of flight time set to distinguish whether there is a Generally, the width of the peak formed by multiple reflections is larger than the width of the peak formed by the clutter and the reflected light from the target object. The discriminable threshold width is determined and set, for example, by experiment or simulation. The above-mentioned "multiple reflection" refers to the pulsed light and the This means that the reflected light goes back and forth multiple times and reflects each other. When a high reflectance object is irradiated with pulsed light, the intensity of the reflected light is high. Therefore, such reflected light may be reflected inside the window 92 or the casing 90, and the reflected light may again irradiate a high reflectance object, resulting in reflected light directed toward the distance measuring device 10 again. When multiple reflections occur by repeating such reflections, multiple histograms are created in which the flight time Tf becomes longer and the received light intensity decreases as the distance measuring device 10 travels back and forth between the high reflectance object and the distance measuring device 10. An integrated histogram will be generated.

For example, in the example shown in FIG. 20, a histogram hr71 obtained by the first reflected light, a histogram hr72 obtained by the second reflected light, and a histogram hr73 obtained by the third reflected light are combined to form a composite peak. A wide histogram hr7 indicating the portion mp7 is obtained. In the example of FIG. 20, among the flight times Tu7 and Td7 during which the received light intensity matching the first threshold received light intensity I3 was obtained, the temporally small flight time Tu7 is specified as the rise time, and the temporally large flight time Td7 is specified as the fall time.

In step S132 shown in FIG. 19, if it is determined that the pulse width of the composite peak is smaller than the preset threshold width (step S132: YES), step S135 described above is executed. If the pulse width of the composite peak is smaller than a preset threshold width, there is a high possibility that the composite peak is composed of clutter and reflected light from the target object. Therefore, in this case, similarly to the first embodiment, the distance calculated in step S125 is specified as the object distance.

On the other hand, if it is determined that the pulse width of the composite peak is not smaller than the preset threshold width (step S132: NO), the above-mentioned step S115 is executed, and the object distance is determined by the normal method. is calculated. That is, the intermediate time between the rise time Tu7 and the fall time Td7 is specified as the peak time, and the object distance is specified using this peak time. If it is determined that the pulse width of the composite peak is not smaller than the preset threshold width, that is, if the pulse width of the composite peak is large and there is a high possibility that multiple reflections have occurred, the first It is desirable to determine the distance based on reflected light. However, in step S135 described above, the distance calculated using the falling position as the base flight time is specified as the object distance, so there is a risk that the identification accuracy will be low. This is because the flight time becomes longer due to repeated multiple reflections, and the longer fall time becomes the base flight time. Therefore, in this embodiment, in such a case, step S135 is not executed, and the distance is calculated by a normal method and treated as the object distance.

The distance measuring device 10 of the sixth embodiment described above has the same effects as the distance measuring device 10 of the first embodiment. In addition, it is determined whether the pulse width is smaller than the threshold width, and if it is not, the distance calculated by the normal method is specified as the object distance, so the composite peak obtained by multiple reflections is , the object distance can be determined more accurately than a configuration in which the object distance is calculated and specified using the falling time as the base flight time.

G. Seventh embodiment:
The configuration of the distance measurement device 10a of the sixth embodiment is the same as the distance measurement device 10a of the second embodiment except for the detailed procedure of distance measurement processing, so the same components are denoted by the same reference numerals. Detailed explanation will be omitted. The distance measurement process of the seventh embodiment shown in FIG. 21 differs from the distance measurement process of the second embodiment shown in FIG. 9 in that step S117 is executed instead of steps S108, S120, and S123. Other steps in the distance measurement process in the seventh embodiment are the same as in the second embodiment, so the same steps are denoted by the same reference numerals and detailed explanation thereof will be omitted.

As shown in FIG. 21, if it is determined in step S107 that the base width is larger than the threshold width (step S107: YES), the base flight time determination unit 260 sets the rise time and fall time based on each. The flight time is determined (step S117). After step S117 is completed, steps S125 and S135 described above are executed. In step S117, the rise time and fall time are each determined as the base flight time, so in step S125, the distance is calculated based on each base flight time, and in step S135, the two calculated distances are Both will be specified as object distances. As shown in FIG. 10, when there are two objects OBJ1 and OBJ2, it may be necessary to calculate the distance for each of the two objects OBJ1 and OBJ2. This is due to, for example, the requirement to accurately specify the distances to two objects located in front and behind each other. According to this embodiment, since the distance is determined using the rise time, that is, the time originating from the object located on the near side as the base time, the object distance for the object located on the near side can be obtained with high accuracy. . Further, since the distance is determined using the falling time, that is, the time originating from the object located on the back side as the base time, the object distance for the object located on the back side can be calculated with high accuracy.

The distance measuring device 10a of the seventh embodiment described above has the same effects as the distance measuring device 10a of the second embodiment. In addition, if the root width is determined to be larger than the threshold width, there is a high possibility that peaks included in the histogram of reflected light from multiple objects are combined to form a composite peak. In this case, the rise time and fall time are each determined to be the base flight time, so the distances to the two objects in front and behind can be accurately specified.

H. Other embodiments:
(H1) If it is estimated that there is no composite peak, that is, if it is determined that the receiving position of the reflected light does not match the position of the clutter in the first embodiment (step S110: NO), In the second and third embodiments, if it is determined that the root width is not larger than the threshold width (step S107: NO), step S115 is executed and the intermediate time between the rise time and fall time of the peak is determined. Although the object distance was calculated as the flight time, the present disclosure is not limited thereto. In such a case, the object distance may be calculated using either the rise time or fall time of the peak as the base flight time.

(H2) In the second and third embodiments, when the existence of a composite peak is estimated, the base flight time is adjusted to the base flight time of the composite peak according to the comparison result between the first intermediate time and the second intermediate time. Although the rise time or the fall time has been determined, the present disclosure is not limited thereto. For example, in a case where the presence of a complex mountain is estimated, the rise time may be determined as the base flight time without comparing the first intermediate time and the second intermediate time. According to this configuration, it is possible to easily determine the distance to an object located further forward as seen from the distance measuring device 10a as the object distance, and it is possible to easily determine the distance to an object located closer to the object that has a greater influence on the vehicle. You can find the distance.

(H3) In the second and third embodiments, when the first intermediate time and the second intermediate time are equal, the base flight time determination unit 260 determines the rise time as the base flight time. Instead of time, the fall time may be determined as the base flight time.

(H4) The configurations of the distance measuring devices 10 and 10a in each embodiment are merely examples, and can be modified in various ways. For example, in the distance measurement process of the first embodiment, step S130 may be omitted. Further, in step S135, the distance may be calculated again based on the base flight time and specified as the object distance. Furthermore, the distance measuring devices 10 and 10a are not limited to vehicles, and may be mounted on any moving object such as an airplane or a ship. Alternatively, it may be used in a fixed manner for purposes such as security. Alternatively, the housing of the distance measuring device 10, 10a may have a configuration in which the housing does not have a window member and is simply provided with an opening.

(H5) The calculation unit 20 and these techniques described in the present disclosure are provided by configuring a processor and memory programmed to execute one or more functions embodied by a computer program. It may also be realized by a dedicated computer. Alternatively, the computing unit 20 and techniques described in this disclosure may be implemented by a dedicated computer provided by a processor configured with one or more dedicated hardware logic circuits. Alternatively, the arithmetic unit 20 and these methods described in the present disclosure may be implemented using a processor configured with a processor and memory programmed to perform one or more functions and one or more hardware logic circuits. It may be realized by one or more dedicated computers configured in combination. The computer program may also be stored as instructions executed by a computer on a computer-readable non-transitory tangible storage medium.

(H6) When generating a histogram in step S210 of the clutter position setting process of the fourth embodiment, the base object distance is specified depending on whether the vehicle is running or not. You may weight the frequency. Specifically, when the vehicle is running, a larger frequency may be accumulated than when the vehicle is not running (that is, when the vehicle is stopped). When the vehicle is stopped, the distance to surrounding objects changes little over time, but when the object is located at a short distance, the histogram shows a high frequency in the short distance range. is likely to be created. For this reason, even though no foreign matter is actually attached to the window 92, a histogram with high frequency is obtained in a short distance range, and there is a possibility that an incorrect clutter position may be specified. On the other hand, when the vehicle is running, the distance to surrounding objects changes significantly over time. For this reason, even if the object exists at a short distance, it will only be present for a short time, so it is unlikely that a histogram with high frequency will be generated in a short distance range. However, if the frequency is high in a short range during such driving, there is a high possibility that foreign matter is attached to the window 92 and clutter is occurring. Therefore, in order to increase the frequency in such a case, a larger frequency may be accumulated when the vehicle is traveling than when the vehicle is not traveling (that is, when the vehicle is stopped). In addition, instead of weighting according to whether or not the vehicle is traveling as described above, the clutter position setting process is performed only when the distance to the object is specified while the vehicle is traveling; The clutter position setting process may not be performed.

(H7) Although the "threshold width" used in step S132 of the sixth embodiment is one fixed value specified in advance through experiments or the like, the present disclosure is not limited to this. The threshold width may be changed depending on the falling time of the composite peak. Specifically, the larger (longer) the falling time of the composite peak portion, the larger the threshold width may be set. If the falling time of the composite peak is long (long), it is assumed that the number of multiple reflections is large. Therefore, in such cases, by setting a larger threshold width, it is possible to prevent multiple reflections from occurring when multiple objects in the same direction but at different distances exist in a relatively long range in the depth direction. It is possible to accurately discriminate between cases where

(H8) In the sixth embodiment, if it is determined in step S132 that the pulse width of the composite peak is not smaller than the preset threshold width (step S132: NO), step S115 is executed and the normal In other words, the distance was calculated using the intermediate time as the base flight time, but the present disclosure is not limited to this method. In this case, unlike the normal method, the distance may be calculated using the rise time as the base time. As described above, when multiple reflections occur, the distance calculated based on the first reflected light is determined as a value closer to the object distance. This is because as the number of times the reflected light increases, such as the second and third times, the round trip time of the reflected light is added, which deviates from the accurate flight time (the round trip time to the reflecting object). Therefore, by adopting the above-described configuration, it is possible to accurately specify the object distance in a situation where multiple reflections occur.

The present disclosure can also be implemented in various forms. For example, realization in the form of a ranging system, a moving object equipped with a ranging device, a ranging method, a computer program for realizing these devices and methods, a non-temporary recording medium that records such a computer program, etc. I can do it.

The present disclosure is not limited to the embodiments described above, and can be implemented in various configurations without departing from the spirit thereof. For example, the technical features in each embodiment that correspond to the technical features in the form described in the summary column of the invention may be used to solve some or all of the above-mentioned problems, or to achieve one of the above-mentioned effects. In order to achieve some or all of the above, it is possible to replace or combine them as appropriate. Further, unless the technical feature is described as essential in this specification, it can be deleted as appropriate.

DESCRIPTION OF SYMBOLS 10, 10a... Distance measuring device, 40... Light emitting part, 60... Light receiving part, 20... Calculating part, 230... Histogram generation part, 240... Compound peak estimation part, 250... Flight time identification part, 260... Base flight time determination Part, 270...Distance calculation part

Claims (8)

A distance measuring device (10, 10a),
a light emitting unit (40) that emits pulsed light;
a light receiving unit (60) that receives light including reflected light of the pulsed light;
a calculation unit (20) that calculates an object distance, which is a distance to an object that reflects the pulsed light and outputs the reflected light, using the flight time of the light received by the light receiving unit;
Equipped with
The arithmetic unit is
a histogram generation unit (230) that generates a histogram representing the received light intensity at each of the light receiving units during the plurality of flight times;
In the histogram, a plurality of objects are peaks in which the change in the received light intensity with respect to the flight time changes from increasing to decreasing after the peak flight time, and the difference in distance from the distance measuring device is within a predetermined range. a composite peak estimating unit (240) that estimates whether a composite peak exists, which is a peak obtained by synthesizing the distribution of the intensity of light from the
In the mountain part, there are two flight times that match the first threshold light reception intensity that is larger than the light reception intensity of noise light including background light, a rise time that is a shorter flight time, and a rise time that is a longer flight time. a flight time identification unit (250) that identifies the fall time;
When it is estimated that the composite peak exists, the base for calculating the object distance is based on either the rise time or the fall time specified for the composite peak. a base flight time determination unit (260) that determines a base flight time;
a distance calculation unit (270) that calculates a distance to one of the plurality of objects as the object distance using the base flight time;
A distance measuring device comprising: The distance measuring device according to claim 1,
The base flight time determination unit is configured to determine an intermediate time between the rise time and the fall time as the base flight time when it is estimated that the composite peak does not exist. In the distance measuring device according to claim 1 or 2,
The base flight time determination unit is a distance measuring device that determines the rise time as the base flight time when it is estimated that the composite mountain portion exists. In the distance measuring device according to any one of claims 1 to 3,
A casing (90) having a window (92) that transmits the emitted pulsed light and the light received by the light receiving section, further comprising a casing that houses the light emitting section and the light receiving section,
The composite peak estimating unit calculates, as the composite peak, clutter that is the reflected light of the pulsed light inside the housing and the reflected light of the pulsed light from an external object that is an object outside the distance measuring device. Estimating whether or not there is a first composite peak including
The base flight time determination unit is a ranging device that determines the base flight time based on the falling time when it is estimated that the first composite peak exists. In the distance measuring device according to any one of claims 1 to 4,
In the composite peak, a first intermediate time that is an intermediate time between two flight times that match the first threshold received light intensity, and two flights that match a second threshold received light intensity that is smaller than the first threshold received light intensity. further comprising an intermediate time specifying unit (235) that specifies a second intermediate time that is an intermediate time of the time;
The composite peak estimating unit determines whether or not there is a second composite peak that includes reflected light of the pulsed light from a plurality of external objects that are external objects of the distance measuring device. Estimate,
The base flight time determination unit, when it is estimated that the second composite peak exists,
If the first intermediate time is smaller than the second intermediate time, determining the base flight time based on the rise time;
The ranging device determines the basic flight time based on the falling time when the first intermediate time is larger than the second intermediate time. In the distance measuring device according to any one of claims 1 to 4,
In the composite mountain portion, a first intermediate time is an intermediate time between two flight times that match a third threshold intensity that is a received light intensity different from the first threshold received light intensity, and a first intermediate time that is an intermediate time between two flight times that match a third threshold intensity that is a received light intensity different from the first threshold received light intensity, further comprising an intermediate time specifying unit (235) that specifies a second intermediate time that is an intermediate time between two flight times that match the two threshold received light intensity;
The composite peak estimating unit determines whether or not there is a second composite peak that includes reflected light of the pulsed light from a plurality of external objects that are external objects of the distance measuring device. Estimate,
The base flight time determination unit, when it is estimated that the second composite peak exists,
If the first intermediate time is smaller than the second intermediate time, determining the base flight time based on the rise time;
The ranging device determines the basic flight time based on the falling time when the first intermediate time is larger than the second intermediate time. The distance measuring device according to claim 5 or 6,
The base flight time determination unit determines the rise time and the fall time if the first intermediate time and the second intermediate time are the same when it is estimated that the second composite peak exists. A distance measuring device that determines the base flight time based on any one of the following. The distance measuring device according to claim 4,
The base flight time determination unit determines whether a light receiving position of the light including the reflected light matches a set clutter position, and when it is determined that the light receiving position matches the clutter position. , determining the base flight time;
The distance calculation unit calculates the object distance when it is determined that the light receiving position matches the clutter position,
The histogram generating unit generates the histogram for each pixel which is a unit of light reception by the light receiving unit,
The distance calculation unit calculates the object distance for each pixel,
The measuring device further includes a clutter position setting unit that sets the clutter position based on at least one of a statistical value of the received light intensity of each of the pixels and a statistical value of the object distance calculated for each of the pixels. range device.

Images