JP2008232800A - Laser monitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser monitor of simple constitution, capable of maintaining stably required monitoring performance over a long period, in response to a situation change in a monitoring objective area. <P>SOLUTION: This laser monitor for monitoring the presence of an object in the monitoring objective area, by irradiating the whole area of the monitoring objective area with a pulse laser beam while scanning it over the monitoring objective area at a prescribed period, and by receiving, synchronized with the scanning, a reflected beam of the pulse laser beam in the monitoring objective area, is provided with a laser beam intensity regulating means for setting variably an output intensity of the pulse laser beam, in response to an object detection situation in the monitoring objective area. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a laser monitoring apparatus that scans pulse laser light to monitor the presence or absence of an object in a monitoring target region.

  As a monitoring device that detects the presence or absence of an obstacle in a railroad crossing, a laser monitoring device using a pulsed laser beam is known (see, for example, Patent Document 1). This type of laser monitoring apparatus irradiates a pulsed laser beam in a two-dimensional scan from the monitoring position having a predetermined height overlooking the monitoring target area over the entire area of the monitoring target area, and synchronizes with the pulse. By receiving the reflected light of the laser beam, it is detected whether there is an obstacle for each scanning position, and is also called a laser radar.

In this kind of laser monitoring device (laser radar), in order to ensure the stability of the measurement, the output intensity of the laser beam can be adjusted according to the temperature, or the influence of external noise can be removed and measured. In order to ensure the distance, it has been proposed to optimize and adjust the gain of the light receiving amplifier in accordance with the light receiving signal during the output stop period of the pulse laser beam. (See, for example, Patent Documents 2 and 3).
JP 2006-7818 A JP 9-318747 A Japanese Patent Laid-Open No. 9-318749

  By the way, in the laser monitoring device, it is of course important to have the capability of reliably detecting the presence / absence of an object in a predetermined monitoring target region, but it is also important that the performance can be stably maintained over a long period of time. is there. However, the lifetime of the components of the laser monitoring device, particularly a laser oscillator that generates pulsed laser light, for example, a laser diode, greatly depends on its output intensity and driving time. Moreover, in general, the situation of the monitoring target area is constantly changing, and a stable monitoring environment is not always ensured.

  The present invention has been made in consideration of such circumstances, and its purpose is to provide a simple configuration capable of maintaining the monitoring performance required stably over a long period of time in accordance with a change in the status of the monitoring target area. It is to provide a laser monitoring device.

In order to achieve the above-described object, the present invention irradiates a pulsed laser beam over a whole area of the monitoring target area at a predetermined cycle, and reflects the pulsed laser light in the monitoring target area in synchronization with the scanning. Relating to a laser monitoring device that receives light and monitors the presence or absence of an object in the monitored area
In particular, it is characterized by comprising laser light intensity adjusting means for variably setting the output intensity of the pulsed laser light in accordance with the object detection situation in the monitoring target region.

  Incidentally, the monitoring of the presence or absence of an object in the monitoring target area detects the object by analyzing the received light data of the reflected light detected in synchronization with the scanning of the pulse laser beam, and detects a fixed object in the monitoring target area. In particular, the laser light intensity adjusting means is configured to increase or decrease the output intensity of the pulsed laser light according to the intensity of the reflected light from the detected object.

  Preferably, the laser beam intensity adjusting means obtains, for example, an average reflected light intensity and an average detection distance for each detected object, and the pulse laser according to the average reflected light intensity of the object at the farthest point and the number of effective data thereof. It is determined whether or not to increase the output intensity of the light, and if the output intensity of the pulsed laser light is not increased, the output intensity of the pulsed laser light according to the number of data in which the reflected light intensity is saturated Configured to reduce

  In particular, when reducing the output intensity of the pulsed laser beam, for example, when the number of data in which the reflected light intensity is saturated exceeds a preset threshold, the average distance of the detected data in which the reflected light intensity is saturated Ask for. Based on the relationship between the detection distance obtained in advance and the output intensity of the pulse laser beam necessary for reliably detecting the object at the detection distance, the output intensity of the pulse laser beam is reduced to the intensity corresponding to the average distance. It should be reduced.

  According to the laser monitoring apparatus having the above configuration, the output intensity of the pulsed laser light can be adjusted according to the object detection status in the monitoring target area. For example, the detection data at the farthest point in the monitoring target area recognizes the object. It is possible to determine whether or not the intensity of the reflected light is sufficient by adjusting whether or not the output intensity of the pulse laser beam is adjusted according to the determination result. In particular, when the intensity of the reflected light is sufficient for recognizing an object, the measurement performance can be ensured by increasing the output intensity of the pulse laser beam.

  Further, in a situation where the light reception intensity of the reflected light from the farthest point described above can be sufficiently ensured, for example, it is determined whether or not the intensity of the reflected light from a short distance is not saturated compared to the light reception performance. Thus, it can be determined whether or not the output intensity of the pulse laser beam is excessive. If the output intensity of the pulse laser beam is excessive, the output intensity is reduced to optimize the light reception intensity of the reflected light, and at the same time, the driving conditions of a laser oscillator that generates the pulse laser beam, for example, a laser diode Can be relaxed to extend its life. Furthermore, since the output intensity of the pulse laser beam is reduced, the drive energy can be suppressed and energy can be saved.

A laser monitoring apparatus according to an embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a laser monitoring apparatus. Reference numeral 1 denotes a sensor head provided at a predetermined height position overlooking a predetermined monitoring target area A. FIG. The sensor head 1 includes a light projecting unit 2 that generates pulsed laser light at a predetermined period and outputs the pulsed laser light toward the monitoring target area A, and a light receiving unit that receives reflected light of the pulsed laser light in the monitoring target area A. Part 3 is incorporated. The light projecting unit 2 includes, for example, a laser diode as a laser light source and a collimator lens that converts the laser light output from the laser diode into a parallel beam. The light receiving unit 3 includes, for example, a photodiode as an optical sensor and a condensing lens provided in front of the photodiode.

  In particular, the pulsed laser light output from the light projecting unit 2 is guided to the optical scanner 5 through an optical system including, for example, the reflecting mirror 4a and the half mirror 4b, and the irradiation direction of the optical scanner 5 is constant. 2D deflection control is performed. Specifically, the optical scanner 5 performs horizontal deflection control (main scanning) of the pulse laser beam over an angle θ, and performs vertical deflection control (sub scanning) over an angle φ in synchronization with the horizontal deflection control, Thus, the irradiation position of the pulse laser beam is scanned over the entire monitoring target area A. Then, the reflected light generated in the object irradiated with the pulse laser beam is guided to the light receiving unit 3 through the optical scanner 5 in synchronization with the scanning and received, and the light receiving unit 3 corresponds to the received light intensity. Outputs level detection signal.

  The light projecting unit 2 is driven to emit light every predetermined period T under the control of the sensor control unit 6 and outputs pulse laser light having an intensity corresponding to the driving voltage. The sensor control unit 6 is a higher-level device, and generates the pulse laser light in accordance with an instruction from an information processing device (for example, PC) 7 that functions as a light emission period adjusting means and a laser light intensity adjusting means for the pulse laser light. A function of variably adjusting the period T and its output intensity P is provided.

  The detection unit 8 for inputting the detection signal from the light receiving unit 3 is synchronized with the generation timing of the pulse laser beam described above under the control of the sensor control unit 6 (the received light intensity of the reflected light). ) And a detection signal equal to or greater than a preset threshold value is detected as reflected light of the pulsed laser light from the object. At the same time, the detection unit 8 obtains the time difference between the reflected light detection timing (reflected light reception timing) and the pulse laser light output timing, and obtains this as the object detection distance in the monitoring target region A. The detection data (Q, D) consisting of the received light intensity Q and the detection distance D of the reflected wave obtained in this way is information on the irradiation direction of the pulse laser beam by the optical scanner 5, that is, deflection information (θ, φ). ) And the information processing apparatus 7. Then, the information processing apparatus 7 executes an object detection process in the monitoring target area A according to the detection data and analyzes the detection data as described later to control the driving of the sensor head 1. In particular, the output intensity P of the pulse laser beam is variably set according to the object detection situation in the monitoring target area A, and the generation period T of the pulse laser beam is variably set as necessary.

  Here, the object detection process in the information processing device 7 based on the detection data described above will be briefly described. The information processing device 7 synchronizes with the deflection scanning of the pulse laser beam and scan position (θ which is the deflection direction). , φ), the detection data (Q, D) is analyzed and, for example, detection data from a plurality of points recognized as reflected light from the same object are integrated and labeled. Then, the size is estimated from the scanning positions (θ, φ) of the plurality of detection data integrated with the same label, and the object is detected, and the presence position of the object in the monitoring target area A is detected.

  FIG. 2 schematically shows the above-described object detection method. For example, when the objects a1, a2, and a3 are present in the monitoring target area A that can be viewed from the sensor head 1, as shown in FIG. 2A, the monitoring target area A is scanned with a pulse laser beam (scanning). As a result, the reflected light from the objects a1, a2, and a3 is detected as shown in FIG. These reflected lights form a certain group for each region where the objects a1, a2, and a3 exist, and the size of each group indicates the size of each object a1, a2, and a3. . Therefore, if the b1, b2, b3 of these reflected lights are detected and their sizes are determined, the b1, b2, b3 of reflected lights (detection data) having a predetermined size are recognized as objects, respectively. It becomes possible.

  The detection position of the object detected as described above is the [θ−φ] coordinate when the monitoring target area A is viewed from the sensor head 1 provided at a predetermined height as described above. Therefore, when detecting this as an object position on the ground surface, the detected position of the object may be coordinate-transformed (projected) with respect to the [xy] coordinates representing the ground surface. By this coordinate conversion, the position of the objects c1, c2, and c3 in the monitoring target area A can be easily understood without causing a parallax problem due to the overhead view from the sensor head 1, for example, as shown in FIG. It becomes possible to do.

  Here, a characteristic processing function in this apparatus will be described. The laser monitoring apparatus according to this embodiment has a function (laser light intensity adjusting means) that can variably set the output intensity P of the pulsed laser light under the control of the sensor control unit 6 as described above. The adjustment of the output intensity P of the pulse laser beam is performed in accordance with the object detection status in the monitoring target area A, and the reflected light intensity from the object detected in the monitoring target area A is roughly shown. This is performed by increasing / decreasing the output intensity P of the pulse laser beam according to Q.

Specifically, this laser light intensity adjusting means is realized as a processing function 9 provided in the information processing apparatus 7, for example. For example, for adjusting the output intensity P of the pulse laser beam, first, the average reflected light intensity Qave and the average detection distance Dave are obtained for each object (a group of detection data) detected in the monitoring target area A, and the average detection distance Dave is obtained. It is determined whether or not to increase the output intensity P of the pulsed laser light according to the average reflected light intensity Qave of the object at the farthest point obtained from the above and the effective data number M representing the object (a group of detection data). Be started. For example, for the object at the farthest point, the index K
K = [average reflected light intensity Qave] × [number of valid data M]
It is determined whether or not the index K satisfies a preset minimum object detection condition Kmin, and the average reflected light intensity Qave is increased so as to satisfy at least the minimum condition Kmin, or the effective data number M is determined. To increase the output intensity P of the pulse laser beam.

  When there is no need to increase the output intensity P of the pulse laser beam, the number N of data in which the reflected light intensity Q is saturated is obtained, and the output intensity P of the pulse laser beam is determined according to the data number N. Decrease. Specifically, when the number N of data in which the reflected light intensity Q is saturated exceeds a preset threshold value Nmax, the pulse is increased to an intensity corresponding to the average distance Dave of a plurality of detection data in which the reflected light intensity Q is saturated. By reducing the output intensity P of the laser light, the intensity of the reflected light by the object irradiated with the pulsed laser light is lowered as a whole, and the number N of detection data in which the reflected light intensity Q is saturated is reduced.

  In this way, if the output intensity P of the pulse laser beam is controlled to increase / decrease in accordance with the detection state of the object in the monitoring target area A and the optimization is performed, the above-mentioned minimum condition that can reliably detect the object at the farthest point While satisfying Kmin, the number (number of data) of objects whose reflected light intensity Q is saturated because the detection distance D is short can be reduced, and the intensity Q of reflected light from each object can be suppressed overall. . As a result, the driving conditions of the light projecting unit 2 can be relaxed to extend its life, and the output intensity P of the pulsed laser beam can be reduced, so that the driving energy can be suppressed to save energy. The effect of.

  FIG. 3 shows an example of an increase / decrease control procedure for the output intensity P of the pulse laser beam described above. This control is started by first obtaining data relating to an immutable fixed object in the monitoring target area A and obtaining data excluded from the object detection process as background data <step S1>. In the background data exclusion process, for example, as shown in FIG. 4, object detection is performed in a situation where there is no measurement object <step S21>, and the position coordinates of the detected object are obtained <step S22>. Then, it is determined whether or not these objects are immutable fixed objects in the monitoring target area A <step S23>. If they are immutable fixed objects, information for excluding them from the recognition target as background data; <Step S24>. Specifically, information for masking the reflected light (detection data) from the position recognized as background data so as not to be taken in as a monitoring target is created. In addition to this, in order to remove the reflected light from the ground surface, a threshold for the height from the ground surface is set (step S25). This threshold value processing corresponds to setting the maximum measurement distance for each scanning direction of the pulse laser light described above.

  When the above initial setting process is completed, the process returns to the process procedure shown in FIG. 3 and the normal monitoring process is started <step S2>. Then, the detection data is sent to the host information processing apparatus (PC) 7 to execute object detection processing (step S3). This object detection process is as described above with reference to FIG. For each collection of detection data forming a predetermined unit, this is detected as information on an object detected in the monitoring target area A. At this time, the fixed object in the monitoring target area A is excluded from the monitoring target in accordance with the background data obtained as described above, and further, a removal process for unnecessary reflected light from the ground surface is executed.

Thereafter, for each detected object, an average detection distance Dave and an average received light intensity Qave are obtained from the detection data (step S4). Then, the average detection distance Dave calculated for each object is compared with each other, and the object farthest from the monitoring point where the sensor head 1 is provided in the monitoring target area A is specified. As described above, the index K for evaluating the detection performance of the detected data of K = [average reflected light intensity Qave] × [number of valid data M]
<Step S5>. Incidentally, the index K for measuring performance evaluation for the object at the farthest point is obtained when the pulse laser beam and its reflected light propagate in the atmosphere as the distance from the monitoring point becomes longer (as the detection distance D becomes longer). This is because there is a large amount of attenuation, and it is easily affected by external noise, and the measurement conditions are poor.

  Then, the index K obtained as described above is compared with a predetermined threshold value Kmin, and it is determined whether or not the measurement condition satisfies the minimum condition for reliably detecting the object at the farthest point (step S6). When the index K is less than the threshold value Kmin, for example, the ratio [Qave / Dave] between the average received light intensity Qave and the average detection distance Dave is used as an evaluation value, and is set in advance based on experimental data as shown in FIG. The output intensity of the pulsed laser beam is increased so as to satisfy the relationship with the optimum output intensity P of the pulsed laser beam with respect to the evaluated value (step S7). The increase control of the output intensity of the pulsed laser light is executed by giving an output control command from the information processing device 7 to the sensor control unit 6.

  On the other hand, when the above-described index K exceeds a predetermined threshold value Kmin, at least the output intensity P of the pulse laser beam satisfies the minimum measurement condition that can reliably detect the object at the farthest point. It is judged. In this case, on the contrary, the received light intensity Q of each detected data of the object detected as described above is saturated in order to judge whether the output intensity P of the pulse laser beam is excessive (excessive) or not. And the total number N of detected data in which the received light intensity Q is saturated is obtained <step S8>. It is determined whether or not the output intensity P of the pulse laser beam is excessive (excessive) by comparing the total number N of received light intensity saturation detection data thus obtained with a preset threshold value Nsat <step S9>. . If the output intensity P of the pulsed laser beam is not excessive (excessive), the process returns to the process from step S2 described above and the object monitoring process in the monitoring target area A is continued.

  However, if it is determined that the output intensity P of the pulse laser beam is excessive (excessive), the average detection distance Dsat is calculated for all detection data in which the received light intensity Q is saturated <step S10>, for example, saturation detection The product [Nsat × Dsat] of the total number of data Nsat and the average detection distance Dsat is used as an evaluation value, and the optimum of the pulsed laser beam with respect to the evaluation value obtained in advance based on experimental results as shown in FIG. The output intensity P of the pulse laser beam is decreased so as to satisfy the relationship with the output intensity P (step S11).

  As described above, by controlling increase / decrease of the output intensity P of the pulse laser beam according to the detection state of the object in the monitoring target area A, the above pulse laser is satisfied while satisfying the measurement condition that can reliably detect the object at the farthest point. It becomes possible to suppress the output intensity P of the light, whereby the output intensity P of the pulse laser beam can be optimized. In addition, the suitability of the measurement conditions is evaluated according to the received light intensity Q of the reflected light detected as the object, and the minimum output intensity Pmin of the pulsed laser beam that satisfies the measurement conditions necessary for reliably detecting the object at the farthest point is ensured. However, the output intensity P can be easily suppressed. Accordingly, for example, the output intensity P of the pulsed laser beam is suppressed, so that, for example, the driving conditions of the laser diode as a laser light source are relaxed to extend its life and energy saving can be achieved. An effect is produced.

The present invention is not limited to the embodiment described above. Here, as described above, as an index K for evaluating the measurement condition for the object at the farthest point, K = [average reflected light intensity Qave] × [number of effective data M]
However, it is of course possible to use other indicators. Similarly, the product [Nsat × Dsat] of the total number Nsat of saturation detection data and the average detection distance Dsat is used as an evaluation value for evaluating the output intensity P of an excessive pulse laser beam, but other evaluation values may be used. Is possible.

  Moreover, the object detection situation implemented using a pulsed laser beam is estimated by imaging the monitoring target area A using a camera and analyzing the image, and the output intensity P of the pulsed laser beam is set according to this estimation result. It is also possible to adjust. In addition, the present invention can be variously modified and implemented without departing from the scope of the invention.

The schematic block diagram of a laser monitoring apparatus. The figure which shows typically the method of the object detection by a laser monitoring apparatus. The figure which shows the process sequence of output intensity control of the pulsed laser beam in the laser monitoring apparatus which concerns on one Embodiment of this invention. The figure which shows the detection processing procedure of the fixed object in the monitoring object area | region. The figure which shows the relationship with the optimal output intensity P of a pulse laser beam with respect to ratio [Qave / Dave] of the average received light intensity Qave and the average detection distance Dave used for increase control of the output intensity of a pulse laser beam. The figure which shows the relationship with the optimal output intensity P of a pulse laser beam with respect to the product [Nsat * Dsat] of the total number Nsat of saturation detection data and the average detection distance Dsat used for increase control of the output intensity of a pulse laser beam.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sensor head 2 Light projection part 3 Light reception part 5 Optical scanner 6 Sensor control part 7 Information processing apparatus 8 Detection part 9 Laser beam intensity adjustment means

Claims (4)

Irradiating with a predetermined period while scanning the whole area of the monitoring target area with pulsed laser light, and receiving the reflected light of the pulsed laser light in the monitoring target area in synchronization with this scanning, the object in the monitoring target area A laser monitoring device for monitoring the presence or absence of
A laser monitoring apparatus comprising: a laser beam intensity adjusting unit that variably sets an output intensity of the pulsed laser beam according to an object detection situation in the monitoring target region. The monitoring of the presence / absence of an object in the monitoring target area is performed by detecting the object by analyzing the received light data of the reflected light detected in synchronization with the scanning of the pulse laser beam and monitoring a fixed object in the monitoring target area. It is performed by excluding from the target,
The laser monitoring apparatus according to claim 1, wherein the laser light intensity adjusting unit increases or decreases the output intensity of the pulsed laser light according to the intensity of reflected light from the detected object.   The laser light intensity adjusting means obtains the average reflected light intensity and the average detection distance for each detected object, and outputs the pulse laser light according to the average reflected light intensity of the object at the farthest point and the number of effective data thereof. It is determined whether to increase the intensity, and when the output intensity of the pulse laser beam is not increased, the output intensity of the pulse laser beam is decreased according to the number of data in which the reflected light intensity is saturated. The laser monitoring apparatus according to claim 2.   The decrease in the output intensity of the pulse laser beam is such that when the number of data in which the reflected light intensity is saturated exceeds a preset threshold, the pulse is reduced to an intensity corresponding to the average distance of the detected data in which the reflected light intensity is saturated. The laser monitoring apparatus according to claim 3, which reduces the output intensity of laser light.

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