JP5767149B2 - Target size measuring device - Google Patents

Description

  The present invention relates to a target size measuring apparatus that measures the size of an object using a laser beam.

  2. Description of the Related Art Laser radar devices that measure the distance to an object (target) using a laser beam (laser light) are known. The laser radar device emits a laser beam intermittently while rotating in the horizontal direction (detection direction) within a range of 180 degrees, for example, and receives the reflected light. Then, based on the time from when the laser beam is emitted to when the reflected light of the laser beam is received, the distance to the target that reflected the laser beam is measured (see, for example, Patent Document 1).

  The laser radar device is often used in, for example, a home security system. In that case, a back surface such as a wall surface exists on the back side of the target (the side opposite to the side irradiated with the laser beam). Therefore, the emitted laser beam is irradiated not only on the target but also on the back surface of the target. Therefore, the laser radar apparatus receives reflected light from both the target and the back object. The laser radar device measures the distance using the reflected light from the target among the received reflected light.

  In such a laser radar apparatus, the target size (length in the detection direction) is determined based on the number of distances measured continuously (number of continuous ranging points) and the diameter of the laser beam when the target is irradiated. ) Is measured (estimated). The number of continuous distance measuring points corresponds to the number of received reflected light continuously. Whether or not the reflected light is received is determined, for example, depending on whether or not the level (for example, peak value) of the output signal (light reception signal) of the light receiving unit that receives the reflected light exceeds a predetermined threshold value. The The diameter of the laser beam when it is irradiated onto the target is the diameter of the laser beam at the time of emission (that is, the distance = 0 m), and the diameter of the laser beam at the maximum distance at which the distance to the target can be measured (measured) And it can obtain | require by the calculation using the distance to the measured target. Alternatively, if a map relating the diameter and distance is prepared in advance, the diameter of the laser beam when the target is irradiated can be obtained by referring to the map.

JP 2007-121158 A

  In the conventional method described above, the measurement accuracy of the target size is low, and the difference (measurement error) between the actual target size and the measured size may be large. Hereinafter, the reason why the measurement accuracy by the conventional method is low will be described with reference to FIGS. 15 and 16. As shown in FIG. 15, even when measuring the size of the target 101 having the same length in the detection direction, the number of continuous ranging points changes if the position of the target 101 (position in the detection direction) is different. That is, in the case of FIG. 15A, the number of continuous ranging points is 3, whereas in the case of FIG. 15B, the number of continuous ranging points is 2. Accordingly, in FIGS. 15A and 15B, the target sizes to be measured are different from each other even though the actual sizes are the same.

  Further, as shown in FIG. 16, even when measuring the size of the targets 102a and 102b having the same length in the detection direction and the same position in the detection direction, the reflectance of the target surface is different. The number of continuous ranging points changes. That is, when the surface of the target 102a shown in FIG. 16A has a high reflectance (high reflection), the reflected light by the three laser beams irradiated to the target 102a can be obtained satisfactorily.

  That is, the irradiation rate (irradiation ratio) of the three laser beams to the target 102a is 100% at the center and 50% at both ends. If the reflectance of the surface of the target 102a is 90%, for example, the peak value of the received light signal is about 90% at the center and the peak value at both ends is about 90% based on the peak value of the emitted laser beam. 45%. If the above-described threshold value is set to 30%, for example, all of the received light signals exceed the threshold value, so the number of continuous ranging points is three.

  On the other hand, when the surface of the target 102b shown in FIG. 16B has a low reflectance (low reflection), only the reflected light from one of the three laser beams irradiated to the target 102b is excellent. can get. That is, the irradiation rates of the three laser beams to the target 102b are the same as the irradiation rates of the target 102a described above. However, if the reflectance of the surface of the target 102b is, for example, 40%, the peak value of the received light signal is about 40% at the center and about 20% at both ends. For this reason, since only the light reception signal by the reflected light of the central laser beam exceeds the threshold value, the number of continuous ranging points is one. Accordingly, in FIGS. 16A and 16B, the target sizes to be measured are different from each other even though the actual sizes are the same.

  As described above, in the conventional method, the measurement result of the target size varies greatly depending on the position of the target and the reflectivity of the target surface, so that the measurement accuracy is low, and as a result, the measurement error may increase. Furthermore, the diameter of the laser beam when irradiated to the target increases as the distance to the target increases. Therefore, in the conventional method, the measurement error increases as the distance to the target increases. Therefore, in the conventional method, when the distance to the target is very far, for example, there is a possibility that a situation in which it is impossible to completely determine whether the target is a human or an automobile may occur. There was a problem in terms.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a target size measuring apparatus capable of reducing a measurement error when measuring the size of an object using a laser beam. .

  According to the means of the first aspect, the length in the detection direction of the object (hereinafter also referred to as the target size) is measured using the distance measurement data provided from the laser radar device. The laser radar device emits a laser beam while rotating in the detection direction, receives reflected light of the emitted laser beam, and based on the time from the time when the laser beam is emitted to the time when the reflected light is received, The distance to the object reflecting the laser beam is measured. The distance measurement data includes received light amount data and distance data. The received light amount data is obtained by associating the elapsed time with reference to the time of emission of the laser beam and the received light amount of the received reflected light. The distance data indicates the value of the distance to the measured object. And in this means, the back reflection utilization measurement which measures a target size using the light reception amount of the reflected light of the reflected light from a back surface object is performed. The back object is a fixed object located on the opposite side of the object from the side irradiated with the laser beam, such as a wall surface.

  In back reflection measurement, the amount of light reflected from the back object is used, so the amount of light indicated by the light reception amount data is the amount of light reflected from the object and the amount of light reflected from the back object. Need to be separated. Since the back object and the object are in the positional relationship as described above, the distance from the laser radar device to the back object is longer than the distance from the laser radar device to the object. Therefore, the elapsed time corresponding to the portion representing the reflected light from the back object is longer than the elapsed time corresponding to the portion representing the reflected light from the object. The above-described separation can be performed by paying attention to such a difference in elapsed time.

  In the back reflection utilization measurement, the received light amount of the reflected light from the back object when there is no reflected light from the object is acquired as the reference received light amount using the received light amount data. When the distance data is given, the diameter of the laser beam when the object located at the distance indicated by the distance data is irradiated is acquired as the beam size. The diameter of the laser beam when the object was irradiated was measured by measuring the diameter of the laser beam at the time of emission (distance = 0), the diameter of the laser beam at the maximum distance that can be measured, and the measured value. It can be obtained by calculation using the value of the distance to the object. Alternatively, if a map relating the diameter and distance is prepared in advance, the diameter of the laser beam when the object is irradiated can be obtained by referring to the map.

  Also, among the received light amounts represented by the received light amount data continuously given before and after the time point when the distance data is given, the received light amount corresponding to the reflected light from the back object is acquired as the comparative received light amount. The comparative amount of received light changes (decreases) with respect to the reference amount of received light, which is the amount of reflected light when there is no target, depending on the rate at which the target is irradiated with the laser beam. In this means, paying attention to such a point, based on the change rate of the comparative received light amount with respect to the reference received light amount, the ratio of the target irradiated with the laser beam that is the source of the reflected light corresponding to the comparative received light amount The irradiation rate is required.

  The target size is determined based on the irradiation ratio thus determined and the acquired beam size. That is, from the beam size and the irradiation rate, the length in the detection direction of the portion where the corresponding laser beam is irradiated onto the object can be obtained. Therefore, the target size can be obtained by obtaining the length in the detection direction of the portion of the object irradiated with the laser beam corresponding to each of the continuous received light amount data and adding them all.

  Since the target size obtained by such back reflection measurement is obtained on the basis of the irradiation rate of the laser beam on the object, it is generally constant even if the position of the object in the detection direction changes. It becomes the value of. Moreover, since the said irradiation rate is calculated | required using the light reception amount of the reflected light from a back surface object, the calculated | required target size becomes a substantially constant value irrespective of the reflectance of the surface of a target object. In other words, according to this means, the measurement result of the target size does not change depending on the position of the object or the reflectance of the object surface, so that the measurement accuracy is higher than the conventional method using the number of continuous distance measuring points. Is extremely high. Therefore, according to this means, the measurement error of the target size can be kept low.

  Depending on the installation location of the laser radar device, there may be no back object. In such a case, the means described in claim 2 may be employed. That is, according to the means described in claim 2, when the reflected light from the back object cannot be obtained, the target reflection use size measurement is performed in which the target size is measured using the amount of the reflected light received from the object. Is done. In target reflection utilization size measurement, when the received light amount data is given three or more times before and after the time when the distance data is given, the laser when the object located at the distance indicated by the distance data is irradiated The diameter of the beam is obtained as the beam size.

  Of the three or more consecutive received light quantity data, the laser beam that is the source of the reflected light corresponding to the first and last given data is not necessarily irradiated to the object. This is because these laser beams are applied to the end of the object. On the other hand, the laser beam that is the source of the reflected light corresponding to the three or more consecutive received light amount data except the first and last given data is irradiated to the object. It is thought that. This is because these laser beams are applied to an intermediate portion excluding the end portion of the object. Therefore, the received light amount represented by any one of the received light amount data except for the first and last given light received light amounts is acquired as the reference received light amount. This reference received light amount corresponds to the received light amount of the reflected light when the entire laser beam is irradiated on the object.

  The reason why the received light amount (arbitrary received light amount) represented by any one of the received light amount data except the first and last given data among the three or more continuous received light amount data is used as the reference received light amount. Is as follows. That is, the received light amounts represented by the continuous received light amount data are not the same. This is because the incident angles (angles when the object is irradiated) of the laser beams that are the sources of the reflected light corresponding to them are different from each other. However, normally, the difference in the incident angle of each laser beam continuously irradiated on one object falls within the range of several degrees to several tens degrees. The difference in the level of reflected light (the amount of received light) due to the incident angle differing by several to 10 degrees is slight. Therefore, in the present means, an arbitrary received light amount is acquired as the reference received light amount among the received light amount data except for the first and last given light data among the three or more continuous received light amount data.

  Further, the received light amount represented by each successive received light amount data is acquired as a comparative received light amount. The comparative amount of received light changes according to the ratio of the laser beam irradiated to the object with respect to the reference amount of received light corresponding to the amount of reflected light received when the entire laser beam is irradiated to the object. In this means, paying attention to such a point, based on the change rate of the comparative received light amount with respect to the reference received light amount, the ratio of the target irradiated with the laser beam that is the source of the reflected light corresponding to the comparative received light amount The irradiation rate is required.

  Based on the irradiation rate obtained in this way and the acquired beam size, the target size is obtained in the same manner as the back reflection utilization measurement described in claim 1. Since the target size obtained by such target reflection measurement is obtained based on the irradiation rate at which the laser beam is applied to the object, it is generally constant even if the position of the object in the detection direction changes. It becomes the value of. Moreover, since the said irradiation rate is calculated | required using the light reception amount of the reflected light from the same target object, the target size calculated | required becomes a substantially constant value irrespective of the reflectance of the surface of a target object. That is, this means can provide the same operations and effects as the means described in claim 1.

  However, when the reflectivity of the surface of the object varies depending on the part, the measurement accuracy of the target size may be slightly lowered compared to the means described in claim 1 due to the influence of the difference. However, according to this means, the target size can be measured regardless of whether or not the reflected light from the back object can be used, that is, regardless of the installation environment of the laser radar (the presence or absence of the back object). An effect is obtained.

Schematic configuration diagram of a target size measuring apparatus showing the first embodiment The figure which shows the aspect by which a target and a back object are irradiated with a laser beam The figure which shows received light quantity data of the reflected light from the target and the back object The figure for demonstrating each element used in the conventional measuring method The figure for demonstrating the estimated maximum size and estimated minimum size in case the number of continuous ranging points is 3 points | pieces FIG. 5 equivalent diagram when the number of continuous ranging points is 2. FIG. 5 equivalent diagram when the number of continuous ranging points is 1. Relationship between the difference between the estimated maximum size and estimated minimum size by the conventional measurement method and the target distance Relationship between estimated maximum size and target distance by conventional measurement method Relationship between estimated minimum size and target distance by conventional measurement method FIG. 9 equivalent diagram showing the range of the estimated maximum size when the target is a human and a car. FIG. 10 equivalent diagram showing the range of the estimated minimum size when the target is a human and an automobile. The figure which shows 2nd Embodiment and shows the aspect with which a target is irradiated with a laser beam The figure which shows received light quantity data of the reflected light from the target The figure which shows a prior art and shows an example of the aspect with which a laser beam is irradiated to a target The figure which shows the other example of the aspect by which a laser beam is irradiated to a target

Hereinafter, a plurality of embodiments of the target size measuring device will be described. In each embodiment, substantially the same components are denoted by the same reference numerals and description thereof is omitted.
(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
A laser radar device 1 shown in FIG. 1 includes a light emitting unit that includes a laser diode that emits a laser beam, a light receiving unit that includes a photodiode that receives reflected light from an object, and a control unit that controls them (not shown). ) Etc. The laser radar device 1 emits the laser beam L intermittently while rotating at high speed in the horizontal direction (detection direction) within a range of 180 degrees, for example, and receives the reflected wave. The laser radar device 1 measures the distance to the target 2 (corresponding to an object) based on the time from when the laser beam L is emitted to when the reflected light is received.

  Measurement of the distance to the target 2 (ranging) is performed when the level (for example, peak value) of the output signal (light reception signal) of the light receiving unit that receives the reflected light exceeds a predetermined threshold value. The time when the reflected light is received is the time when the received light signal that changes according to the received reflected light reaches the peak value (peak value). The target size measuring device 3 measures the length (hereinafter also referred to as target size) of the target 2 in the horizontal direction (detection direction) using distance measurement data Da (details will be described later) provided from the laser radar device 1. To do.

The optical conditions in the laser radar apparatus 1 are appropriately changed according to actual specifications. Here, in order to make the explanation about the target size measurement method easy to understand, the following (1) to (3) It is assumed that
(1) The shape of the laser beam is a perfect circle.
(2) The rotation angle resolution (interval at which the laser beam is emitted) is 0.25 °.
(3) The size (diameter) of the laser beam when it reaches the target (when irradiated) and the distance (scanning resolution) between the centers of the laser beams are the same.
The scanning resolution is expressed by the following equation (1).
Scanning resolution = distance to target × tan (rotation angle resolution) (1)

Then, the measuring method of the target size by the said structure is demonstrated.
In this case, as shown in FIG. 2, it is assumed that the back surface object 4 is present on the back surface side of the target 2 (the side opposite to the side irradiated with the laser beam). The back object 4 is a wall surface, for example, and its position is fixed. The distance measurement data Da includes received light amount data and distance data. The received light amount data is obtained by associating the elapsed time with reference to the emission time of the laser beam and the received light amount of received reflected light (integrated value of received light signal = area) (see FIG. 3). The distance data indicates the measured distance value to the target.

  When the reflected light from the back object 4 is obtained, the target size measuring device 3 performs back reflection utilization measurement that measures the target size using the amount of received light of the reflected light. The back surface reflection utilization measurement by the target size measuring apparatus 3 is performed as follows. That is, the target size measuring device 3 uses the received light amount data to obtain the received light amount of the reflected light from the back object 4 when there is no reflected light from the target 2 as the reference received light amount. The reference received light amount may be acquired only once immediately after the target size measuring device 3 is started, or may be periodically (every predetermined interval) to constantly update the reference received light amount value. Good.

  Note that the amount of received light reflected from the target 2 and the amount of received light reflected from the back surface 4 can be separated as follows. The back object 4 and the target 2 are in a positional relationship as described above. Therefore, the distance from the laser radar device 1 to the back object 4 is always longer than the distance from the laser radar device 1 to the target 2. Therefore, as shown in FIG. 3, the elapsed time corresponding to the portion representing the reflected light from the back object 4 in the received light amount data is longer than the elapsed time corresponding to the portion representing the reflected light from the target 2. It will be time. In the present embodiment, the above-described separation is performed by paying attention to such a difference in elapsed time.

When distance data is given from the laser radar device 1, the diameter of the laser beam when the target 2 located at the distance indicated by the distance data is irradiated is acquired as the beam size. The diameter E [mm] of the laser beam when irradiated onto the target 2 can be obtained by the following equation (2). However, the diameter of the laser beam at the time of emission (distance = 0 m) is Emin, the maximum distance that can be measured (for example, 30 m) is Amax, and the diameter of the laser beam at the maximum distance that can be measured is Emax. The value of the distance to the target 2 is A. Emin and Emax are known values determined according to the specifications of the laser radar device 1.
E = Emin + ((Emax−Emin) / Amax) × A (2)
In place of the method of calculating by the calculation based on the above equation (2), a map or the like that associates the diameter and the distance is prepared in advance, and the target is irradiated with reference to the map. The diameter E of the laser beam may be obtained.

  Of the received light amount represented by each of the received light amount data continuously given before and after the time point when the distance data is given, the received light amount corresponding to the reflected light from the back object 4 is acquired as the comparative received light amount. In addition, it is thought that the laser beam which became the origin of the reflected light corresponding to these continuous received light amount data is irradiated to the same target 2 by which the distance was measured.

Then, based on the rate of change (change rate) of the comparative received light amount Xc with respect to the reference received light amount Xr, the rate at which the target 2 is irradiated with the laser beam that is the source of the reflected light corresponding to the comparative received light amount Xc (irradiation) The ratio X) is determined. Specifically, the irradiation ratio X is obtained by the following equation (3). In the equation (3), the term (Xc / Xr) corresponds to the change rate described above.
X = (Xr−Xc) / Xr
= 1- (Xc / Xr) (3)

  For example, when the entire laser beam is irradiated onto the target 2 (irradiation ratio X = 1), there is no reflected light from the back object 4, and the comparative light reception amount Xc becomes zero (FIGS. 2 and 3). (See (b)). Therefore, the irradiation rate X obtained from the above equation (3) is 1 (= 1-0), which matches the actual irradiation rate.

  In addition, when a part of the laser beam is irradiated onto the target 2 (irradiation ratio = N, 0 <N <1), the comparative light reception amount Xc, which is the light reception amount of the reflected light from the back object 4, is the reference light reception amount. With respect to Xr, it decreases by the amount irradiated to the target 2. Therefore, the irradiation rate X obtained from the above equation (3) is N (= 1 − ((1−N) / 1)), which matches the actual irradiation rate.

  For example, when 50% (= 0.5) of the laser beam is irradiated on the target 2 (irradiation ratio X = 0.5), the received light amount Xc that is the amount of reflected light from the back object 4 is This is 50% (= 0.5) of the reference received light amount Xr (see FIG. 2 and FIG. 3C). That is, since the change rate is 0.5, the irradiation rate X obtained from the above equation (3) is 0.5 (= 1-0.5), which matches the actual irradiation rate.

  In addition, when 30% (= 0.3) of the laser beam is irradiated onto the target 2 (irradiation ratio X = 0.3), the comparative light reception amount Xc that is the amount of reflected light from the back object 4 is It becomes 70% (= 0.7) of the reference received light amount Xr (not shown). That is, since the change rate is 0.7, the irradiation rate X obtained from the above equation (3) is 0.3 (= 1−0.7), which matches the actual irradiation rate.

  As described above, in the present embodiment, the irradiation with which the target 2 is irradiated with the laser beam based on the change rate of the reference received light amount Xc with respect to the reference received light amount Xr, which changes according to the rate with which the target 2 is irradiated with the laser beam. The ratio X is obtained.

  Based on the irradiation ratio X thus obtained and the acquired beam size E, the target size is obtained. That is, from the result of multiplying the beam size E and the irradiation ratio X, the length in the detection direction of the portion where the corresponding laser beam is irradiated onto the target 2 can be obtained.

  For example, if the beam size E at a distance (for example, 30 m) where the target 2 is located is 13 cm, for example, in the case of FIG. The length is 13 cm (= 13 cm × 1). In the case of FIG. 3C, the length in the detection direction of the portion irradiated with the laser beam on the target 2 is 6.5 cm (= 13 cm × 0.5). Accordingly, the target size is obtained by obtaining the length in the detection direction of the portion of the target 2 irradiated with the laser beam corresponding to each successive received light amount data, and adding them all.

  The target size measured by such back reflection utilization measurement is obtained based on the irradiation rate X at which the laser beam is irradiated onto the target 2. Therefore, if the actual target size is the same, almost the same measurement result can be obtained regardless of the position of the target 2 in the detection direction. In addition, since the irradiation ratio X is obtained using the reference received light amount Xr and the comparative received light amount Xc, which is the received light amount of the reflected light from the back object 4, if the actual target size is the same, the surface of the target 2 The same measurement result can be obtained regardless of the reflectance. In other words, according to the present embodiment, the measurement result of the target size does not change depending on the position of the target 2 or the reflectance of the surface of the target 2, so that the measurement accuracy is higher than that of the conventional method using the number of continuous ranging points. Is extremely high. Therefore, according to this embodiment, the measurement error of the target size can be suppressed low.

Subsequently, the target size measurement method according to the present embodiment is compared with the conventional measurement method using the number of continuous ranging points.
According to the conventional measuring method using the number of continuous ranging points, the target size F is determined using the distance value A, the rotation angle resolution B, the number of continuous ranging points C, the scanning resolution D, and the beam size E (see FIG. 4). It is obtained as follows. First, the distance value A, which is the value of the distance to the target 2 measured by the laser radar device 1, the rotation angle resolution B, and the number of continuous ranging points C are acquired. The rotation angle resolution B is a fixed value (for example, 0.25 °) determined according to the specifications of the laser radar device 1. Based on the following equation (4), the scanning resolution D, which is the distance between the centers of the laser beams when the target 2 is reached, is calculated.
D = A × sin (B) (4)

Subsequently, the target size F is calculated based on the following equation (5). However, E is the beam size, which is the diameter of the laser beam when it reaches the target 2. The beam size E can be obtained by the same method as in this embodiment.
(C-1) × DE <F <(C + 1) × D + E (5)

  In the above equation (5), the left side is the estimated minimum size (estimated minimum size), and the right side is the estimated maximum size (estimated maximum size). If the left side becomes a negative value, the minimum size is set to zero. As described above, the measurement result of the target size by the conventional measurement method is a value having a width from the estimated minimum size to the estimated maximum size. In the conventional measuring method, the reason why the measurement result of the target size F is wide is to deal with the following cases.

<Continuous distance measuring points C = 3 points>
In the target 21 shown in FIG. 5A, the target size F is slightly shorter than 5 times the beam size E. Therefore, depending on the position of the target 21, the target 21 may be irradiated with five continuous laser beams, but some of the laser beams at both ends of the target 21 may not be irradiated (slightly missing) (FIG. 5). (See (a)). In such a case, when the reflectivity of the surface of the target 21 is low, only the reflected light from the three laser beams irradiated to the target 21 can be obtained satisfactorily. The number of distance points C is 3.

  On the other hand, in the target 22 shown in FIG. 5B, the target size F is slightly longer than 1 time the beam size E. Therefore, depending on the position of the target 22, the target 22 may be irradiated with three continuous laser beams (see FIG. 5B). In that case, only a part of the laser beams at both ends of the three laser beams is irradiated to the target 22 (slightly hit). In such a case, when the reflectance of the surface of the target 22 is high, all the reflected light by the three laser beams irradiated on the target 22 can be obtained satisfactorily, so the number of continuous ranging points C is three. .

  In this way, the number of continuous ranging points C is 3 in both (a) and (b) of FIG. Therefore, in the conventional measurement method, the estimated minimum size of the target size F obtained when the number of continuous ranging points C is 3 is one time the beam size E, and the estimated maximum size is 5 times the beam size E. To be the length of.

<Continuous distance measuring points C = 2 points>
The target 23 shown in FIG. 6A has a target size slightly shorter than four times the beam size E. Therefore, depending on the position of the target 23, the target 23 may be irradiated with four continuous laser beams, but some of the laser beams at both ends of the target 23 may not be irradiated (see FIG. 6A). ). In such a case, when the reflectance of the surface of the target 23 is low, only the reflected light from the two laser beams irradiated to the target 23 can be obtained satisfactorily. The number of distance points C is 2.

  On the other hand, the target 24 shown in FIG. 6B has a target size shorter than 1 times the beam size E. However, depending on the position of the target 24, the target 24 may be irradiated with two continuous laser beams (see FIG. 6B). In this case, only a part of the two laser beams is irradiated onto the target 24 (slightly hit). In such a case, when the reflectance of the surface of the target 24 is high, the reflected light by the two laser beams irradiated on the target 24 can be obtained satisfactorily, so the number of continuous ranging points C is two. .

  In this way, the number of continuous ranging points C is 2 in both (a) and (b) of FIG. Therefore, in the conventional measurement method, the estimated minimum size of the target size F obtained when the number of continuous ranging points C is 2 is zero (0 times the beam size E), and the estimated maximum size is the beam size E. 4 times as long as

<Continuous distance measuring points C = 1 point>
The target 25 shown in FIG. 7A has a target size slightly shorter than three times the beam size E. Therefore, depending on the position of the target 25, the target 25 may be irradiated with three continuous laser beams, but some of the laser beams at both ends of the target 25 may not be irradiated to the target 25 (see FIG. 7A). ). In such a case, when the reflectance of the surface of the target 25 is low, only the reflected light from one of the three laser beams irradiated to the target 25 can be obtained satisfactorily. The number of distance points C is 1.

  On the other hand, the target 26 shown in FIG. 7B has a target size shorter than 1 times the beam size E. Therefore, depending on the position of the target 26, the target 26 may be irradiated with only one laser beam (see FIG. 7B). In this case, only a part of the laser beam is irradiated onto the target 26 (slightly hit). In such a case, when the reflectance of the surface of the target 26 is high, the reflected light by one laser beam irradiated on the target 26 can be obtained satisfactorily, so the number of continuous ranging points C is 1.

  As described above, the number of continuous ranging points C is 1 in any of FIGS. 7A and 7B. Therefore, in the conventional measurement method, the estimated minimum size of the target size F obtained when the number of continuous ranging points C is 1 is zero (0 times the beam size E), and the estimated maximum size is the beam size E. The length is three times as long.

  Thus, in the conventional measurement method, the target size F estimated when the number of continuous ranging points C is 1 has a width corresponding to three times the beam size E. Further, the target size F estimated when the number of continuous ranging points C is 2 and 3 has a width corresponding to four times the beam size E. Note that the target size F estimated when the number of continuous ranging points C is 4 or more has a width corresponding to four times the beam size E, as in the case of 2 points and 3 points. .

  FIG. 8 shows the relationship between the difference between the estimated maximum size (MAX estimated size) and the estimated minimum size (MIN estimated size) by the conventional measurement method and the distance to the target. FIG. 9 shows the relationship between the estimated maximum size according to the conventional measurement method and the distance to the target. FIG. 10 shows the relationship between the estimated minimum size by the conventional measurement method and the distance to the target. 8 to 10 show cases in which the number C of continuous ranging points is 1 to 10 points.

  As shown in FIGS. 8 to 10, in the conventional measurement method, it is understood that the difference between the estimated maximum size and the estimated minimum size (the width of the measurement result) increases as the distance to the target increases. It can also be seen that the relationship between the difference between the estimated maximum size and the estimated minimum size and the distance differs depending on whether the number of continuous ranging points is one or more.

  Subsequently, when the distance to the target is long (distance = 30 m = 30000 mm), it is verified whether or not it is possible to determine whether the target is a human or an automobile by a conventional measurement method. In this case, it is assumed that the length in the detection direction is 500 mm for humans and 1000 mm for automobiles. Further, it is assumed that the reflectance of the target surface is unknown.

  According to FIGS. 11 and 12, when the target is a human, the number of continuous ranging points C may be 2 to 5 points. Therefore, the estimated minimum size of the target size F is 0 mm (corresponding to the estimated minimum size when the number of continuous ranging points C is 2), and the estimated maximum size is 915 mm (estimated maximum when the number of continuous ranging points C is 5). Equivalent to size). Further, when the target is an automobile, the number of continuous ranging points C may be 6 to 9 points. Accordingly, the estimated minimum size of the target size F is 524 mm (corresponding to the estimated minimum size when the number of continuous ranging points is 6), and the estimated maximum size is 1438 mm (estimated maximum size when the number of continuous ranging points is 9). Equivalent).

  Thus, in the conventional measurement method, the measurement result (0 to 915 mm) when the target 30 m ahead is a human (actual target size = 500 mm) and the case where the target is an automobile (actual target size = 1000 mm). The measurement result (524 to 1438 mm) is a result in which a part thereof overlaps. Therefore, in the conventional measurement method, since the measurement accuracy is low, it cannot be determined whether the target 30 m ahead is a human or an automobile.

  On the other hand, according to the measurement method of the present embodiment, the target size is obtained based on the irradiation rate, which is the rate at which the laser beam is applied to the target. Therefore, compared to the conventional measurement method, regardless of the distance to the target. The measurement error is extremely high, and the measurement error is kept low. Therefore, for example, it is possible to determine whether the target 30 m ahead is a human or an automobile.

(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described with reference to FIGS. 13 and 14.
The target size measuring apparatus 3 of the present embodiment uses the amount of received reflected light from the target 2 regardless of whether reflected light from the back object is obtained (whether there is a back object). Execute target reflection utilization size measurement to measure the target size.

  The target reflection utilization measurement by the target size measuring apparatus 3 is performed as follows. That is, the target size measuring device 3 irradiates the target 2 located at the distance indicated by the distance data when the received light amount data is continuously given three times or more before and after the time when the distance data is given. The diameter of the laser beam is obtained as the beam size. The beam size can be acquired by the same method as in the first embodiment.

  Of the three or more consecutive received light amount data, the target 2 is not always irradiated with the laser beam that is the source of reflected light corresponding to the first and last given data. . This is because these laser beams are applied to the end of the target 2. On the other hand, the laser beam that is the source of the reflected light corresponding to the three or more consecutive received light quantity data except the first and last given data is irradiated to the target 2. It is thought that. This is because these laser beams are applied to an intermediate portion other than the end portion of the target 2. Therefore, an arbitrary received light amount is acquired as the reference received light amount among the received light amount data excluding the continuous received light amount data given first and last. That is, this reference light reception amount corresponds to the light reception amount of the reflected light when the entire laser beam is irradiated onto the target 2.

  The reason why the received light amount (arbitrary received light amount) represented by any one of the received light amount data except the first and last given data among the three or more continuous received light amount data is used as the reference received light amount. Is as follows. That is, the received light amounts represented by the continuous received light amount data are not the same. This is because the incident angles (angles when the target 2 is irradiated) of the laser beams that are the sources of the reflected light corresponding to them are different from each other.

  However, normally, the difference in the incident angle of each laser beam continuously irradiated onto one target 2 falls within the range of several degrees to several tens degrees. The difference in the level of the reflected light (the amount of received light) due to the incident angle differing by several to 10 degrees is slight. Therefore, even if the received light amount represented by any of the continuous received light amount data is set as the reference received light amount, the calculation result of the irradiation ratio described later is substantially the same. Therefore, in the present embodiment, an arbitrary received light amount is acquired as the reference received light amount among the received light amount data excluding the first and last given light receiving amount data among three or more continuous received light amount data. Yes.

Further, the received light amount represented by each successive received light amount data is acquired as a comparative received light amount. Then, based on the rate of change (change rate) of the comparative received light amount Yc with respect to the reference received light amount Yr, the rate at which the target 2 is irradiated with the laser beam that is the source of the reflected light corresponding to the comparative received light amount Yc (irradiation) The ratio Y) is determined. Specifically, the irradiation rate Y is obtained by the following equation (6). In addition, the right side in Formula (6) is equivalent to the change rate mentioned above.
Y = Yc / Yr (6)

  For example, when the entire laser beam is irradiated onto the target 2 (irradiation ratio Y = 1), the comparative light reception amount Yc, which is the amount of reflected light from the target 2, shows the same value as the reference light reception amount Yr ( FIG. 13 and FIG. 14 (a)). Therefore, the irradiation rate Y obtained from the above equation (6) is 1, which matches the actual irradiation rate.

  In addition, when a part of the laser beam is irradiated onto the target 2 (irradiation ratio = N, 0 <N <1), the comparative light reception amount Yc that is the light reception amount of the reflected light from the target 2 is the reference light reception amount Yr. On the other hand, it changes in accordance with the ratio of the target 2 being irradiated with the laser beam. Therefore, the irradiation rate Y obtained from the above equation (6) is N (= N / 1), which matches the actual irradiation rate.

  For example, when 50% (= 0.5) of the laser beam is irradiated onto the target 2 (irradiation ratio Y = 0.5), the comparative received light amount Yc that is the amount of reflected light from the target 2 is the reference This is 50% (= 0.5) of the amount of received light Yr (not shown). That is, since the change ratio is 0.5, the irradiation ratio Y obtained from the above equation (6) is 0.5, which matches the actual irradiation ratio.

  In addition, when 30% (= 0.3) of the laser beam is irradiated onto the target 2 (irradiation ratio Y = 0.3), the comparative light reception amount Yc that is the amount of reflected light from the target 2 is the reference This is 30% (= 0.3) of the received light amount Yr (see FIG. 13 and FIG. 14B). That is, since the change rate is 0.3, the irradiation rate Y obtained from the above equation (6) is 0.3, which matches the actual irradiation rate.

  As described above, in the present embodiment, the irradiation with which the target 2 is irradiated with the laser beam is based on the change rate of the comparative received light amount Yc with respect to the reference received light amount Yr that changes according to the rate with which the target 2 is irradiated with the laser beam. The ratio Y is obtained.

  Based on the irradiation rate Y thus determined and the acquired beam size E, the target size is determined. That is, from the result of multiplying the beam size E and the irradiation ratio Y, the length in the detection direction of the portion where the corresponding laser beam is irradiated onto the target 2 can be obtained. Accordingly, the target size is obtained by obtaining the length in the detection direction of the portion of the target 2 irradiated with the laser beam corresponding to each successive received light amount data, and adding them all.

  The target size measured by such target reflection utilization measurement is obtained based on the irradiation rate Y with which the target 2 is irradiated with the laser beam. Therefore, if the actual target size is the same, almost the same measurement result can be obtained regardless of the position of the target 2 in the detection direction. In addition, since the irradiation ratio Y is obtained using the reference light reception amount Yr and the comparative light reception amount Yc, which is the amount of reflected light from the same target 2, the surface of the target 2 can be obtained if the actual target size is the same. The same measurement result can be obtained regardless of the reflectance. In other words, according to the present embodiment, the measurement result of the target size does not change depending on the position of the target 2 or the reflectance of the surface of the target 2, so that the measurement accuracy is higher than that of the conventional method using the number of continuous ranging points. Is extremely high. Therefore, according to this embodiment, the measurement error of the target size can be suppressed low.

  Moreover, according to this embodiment, since the target size is measured using the amount of reflected light from the target 2, the environment around the target 2 (for example, a back surface such as a wall surface on the back surface of the target 2 is present). The target size can be measured regardless of whether the laser radar apparatus 1 is installed, regardless of whether or not the laser radar apparatus 1 is installed.

(Other embodiments)
The present invention is not limited to the embodiments described above and illustrated in the drawings, and the following modifications or expansions are possible.
The detection direction (rotation direction) of the laser radar device 1 is not limited to the horizontal direction.
When the shape of the laser beam is not a perfect circle but an ellipse, the beam size E may be the length in the detection direction of the laser beam.

When the beam size E and the distance between the laser beam centers (scanning resolution D) do not match (E <D), the target size F is obtained by the following equation (7). However, the target size obtained by the measurement method of each of the above embodiments is F ′, and the number of received light amount data continuously given before and after the time when the distance data is given is C ′.
F = F ′ + (C′−1) × (DE) (7)

  The target size measuring device 3 may be configured to be able to perform both the back reflection utilization measurement and the target reflection utilization measurement. In that case, the target size measuring device 3 confirms the presence or absence of the reflected light from the back object 4, and when the reflected light from the back object 4 is obtained, performs the back reflection measurement and reflects from the back object 4. When light cannot be obtained, target reflection utilization measurement may be performed. In this way, if the back object 4 is present, the target size can be measured by back reflection measurement with higher measurement accuracy, and even if the back object 4 is not present, the measurement accuracy is high. The target size can be measured by target reflection utilization measurement.

  Note that whether or not the reflected light from the back object 4 can be obtained can be determined as follows. That is, when the back object 4 does not exist, the received signal includes only the component of the reflected light from the target 2 and there is only one peak (mountain). On the other hand, when the back object 4 is present, the received signal includes components of reflected light from both the target 2 and the back object 4, and there are two (or three or more) peaks. Therefore, whether or not the reflected light from the back object 4 can be obtained can be determined based on whether or not there are a plurality of peaks in the received signal.

  In the second embodiment, in the target reflection utilization measurement, an arbitrary received light amount is used as the reference received light amount among the received light amount data excluding the three or more consecutive received light amount data given first and last. However, the following limitation may be added as the received light amount acquired as the reference received light amount. That is, among the continuous received light amount data, the laser beam irradiated to the central portion of the target 2 in the horizontal direction (for example, if the continuous number is an odd number, it is just the middle, and if it is an even number, the middle two The received light amount of any one of the reflected light may be acquired as the reference received light amount. In this way, the obtained reference received light amount has a uniform difference in the level of the reflected light depending on the incident angle with respect to the received light amount of the reflected light of the laser beam irradiated to both ends (less biased). Become). Therefore, the irradiation rate required based on these, and thus the measurement accuracy of the target size is improved.

  Alternatively, when the target reflection utilization measurement is performed, if the received light amount data is continuously given four or more times before and after the distance data is given, the reference received light amount can be acquired as follows. Good. That is, even if the second given light receiving amount is obtained as the first reference received light amount, the second given light receiving amount is obtained as the second reference received light amount. Good. Then, at least the first reference received light amount is used for calculating the irradiation ratio using the comparative received light amount corresponding to the first received light amount data, and the comparative received light amount corresponding to the last received light amount data. The second reference amount of received light is used for the calculation of the irradiation ratio using. In this way, even when the reflectivity of the surface of the target 2 varies depending on the part (not uniform), the difference in reflectivity results in the calculation result of the irradiation ratio of the laser beam irradiated to both ends of the target 2, and consequently The influence on the measurement accuracy of the target size can be reduced.

  In the drawings, 1 is a laser radar device, 2 is a target (object), 3 is a target size measuring device, and 4 is a back object.

Claims (2)

The laser beam is emitted intermittently while rotating in the detection direction, the reflected light of the emitted laser beam is received, and based on the time from the emission time of the laser beam to the reception time of the reflected light, A target size measuring device for measuring the length of the target in the detection direction using distance measurement data provided from a laser radar device that measures the distance to the target reflecting the laser beam,
The distance measurement data includes a received light amount data in which an elapsed time based on the time of emission of the laser beam and a received light amount of the reflected light received are associated with each other, and a distance indicating a measured distance to the object Data and
The length of the object in the detection direction is determined by using the amount of reflected light from a back object, which is a fixed object located on the opposite side of the object from the side irradiated with the laser beam. Perform back reflection measurement to measure,
In the back reflection utilization size measurement,
Using the received light amount data, obtain the received light amount of the reflected light from the back object when there is no reflected light from the object as a reference received light amount,
Given the distance data,
Obtaining the diameter of the laser beam as the beam size when the object located at the distance indicated by the distance data is irradiated;
Of the received light amount represented by each of the received light amount data continuously given before and after the time when the distance data is given, a received light amount corresponding to the reflected light from the back object is acquired as a comparative received light amount,
Based on the change rate of the comparative received light amount with respect to the reference received light amount, an irradiation rate that is a rate at which the laser beam that is the source of reflected light corresponding to the comparative received light amount is applied to the object is obtained,
A target size measuring apparatus that obtains the length of the object in the detection direction based on the beam size and the irradiation ratio. When the reflected light from the back object is not obtained, the target reflection utilization size measurement is performed to measure the length of the object in the detection direction using the amount of light received from the object.
In the target reflection utilization measurement,
When the received light amount data is given three or more times before and after the time when the distance data is given,
Obtaining the diameter of the laser beam as the beam size when the object located at the distance indicated by the distance data is irradiated;
Among the continuous received light amount data, the received light amount represented by any one of the received light amount data excluding the first and last given data is acquired as a reference received light amount,
The received light amount represented by each of the continuous received light amount data is acquired as a comparative received light amount,
Based on the change rate of the comparative received light amount with respect to the reference received light amount, an irradiation rate that is a rate at which the laser beam that is the source of reflected light corresponding to the comparative received light amount is applied to the object is obtained,
The target size measuring apparatus according to claim 1, wherein a length of the object in the detection direction is obtained based on the beam size and the irradiation ratio.

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