JP2008241535A - Laser monitoring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser monitoring device for simplifying a constitution and stably maintaining a required monitoring performance for a long time in response to a change in a condition of a monitored area. <P>SOLUTION: The laser monitoring device irradiates a pulse laser light over the monitored area for a predetermined period, as it scans the pulse laser light, receives a reflection light as the pulse laser light reflected from the to-be-monitored area, in synchronization with the scan, and monitors the existence of an object in the monitored area. The laser monitoring apparatus is provided with an output period adjustment means for variably setting an output period T of the pulse laser light, in response to the object detecting condition of the monitored 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-mentioned object, the present invention irradiates the pulsed laser light generated at a predetermined cycle toward the monitoring target area, and scans the pulsed laser light over the entire monitoring target area. A laser monitoring device that receives reflected light of the pulsed laser light in the monitoring target region in synchronization with and monitors the presence or absence of an object in the monitoring target region,
In particular, it is characterized by comprising output period adjusting means for variably setting the generation period of the pulse laser beam according to 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. Excluded from monitoring. For example, when the monitoring target area does not exist in the monitoring target area, the output cycle adjusting unit sets the generation period of the pulse laser light to a predetermined maximum value, and when the monitoring target object exists in the monitoring target area Is configured to increase / decrease the generation period of the pulsed laser light according to the number of effective data required for each object.

  Preferably, the output period adjusting means is configured to obtain an average detection distance for each object, for example, and increase or decrease the generation period of the pulse laser light according to the number of effective data of the object at the farthest point.

  According to the laser monitoring apparatus having the above-described configuration, the generation period of the pulsed laser light can be adjusted according to the object detection status in the monitoring target region, and thereby the scanning density of the monitoring target region can be adjusted. When there is no object to be monitored in the area, the generation period of the pulsed laser light is lengthened as a predetermined maximum value, and the scanning density is set to be rough, and the appearance of the object to be monitored in the monitoring object area Can be set to a so-called standby mode.

  If there is a monitoring target object in the monitoring target region, for example, the number of effective data is obtained for each detection object, and the generation period of the pulse laser light is obtained so that the number of detection data that can reliably detect the object is obtained. Should be optimized. Specifically, the average detection distance and the number of valid data are obtained for each detected object, and the generation period of the pulse laser beam is optimized so that a sufficient number of detection data can be obtained to detect the object at the farthest point. To do. As a result, the number of output times of the pulse laser beam per fixed time can be reduced without sacrificing the measurement performance, and energy saving can be achieved correspondingly.

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 responsive to an instruction from an information processing apparatus (for example, PC) 7 that is a host device thereof, an output period adjusting means that variably adjusts the generation period T of the pulse laser beam and its output intensity P, and the laser beam intensity. It functions as an adjustment means.

  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, L) consisting of the received light intensity Q of the reflected wave and the detection distance L obtained in this way is information on the irradiation direction of the pulsed laser beam by the optical scanner 5, that is, deflection information (θ, φ). ) And the information processing apparatus.

  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, L) 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 mechanism. 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 includes a function (output period adjusting means) that variably sets the generation period (output period) T of the pulsed laser light under the control of the sensor control unit 6 as described above. . The variable setting of the generation period T of the pulse laser beam is performed independently of the deflection scanning of the pulse laser beam by the optical scanner 5 described above. Therefore, as the generation period T of the pulse laser beam becomes longer, the number of irradiation times of the pulse laser beam when the pulse laser beam is deflected and scanned over a predetermined angle decreases, and the scanning density for the monitoring target region A becomes coarse. Conversely, by shortening the generation period T of the pulsed laser light, the monitoring target area A is scanned precisely, and a large amount of detection data can be obtained even for an object of the same size.

  Incidentally, the adjustment of the generation period (output period) T of the pulse laser beam is performed in accordance with the object detection status in the monitoring target area A, and roughly the object detected in the monitoring target area A This is executed by increasing / decreasing the driving period T of the laser diode as the laser light source, for example, according to the detection distance D and the number M of effective data used for object recognition having a predetermined light reception intensity Q or higher.

  Specifically, this output cycle adjusting means is realized as the processing function 9 provided in the information processing apparatus 7, for example. For example, the adjustment of the generation period (output period) T of the pulsed laser light is performed by first determining whether or not an object is detected in the monitoring target area A. Further, when an object exists in the monitoring target area A, The average reflected light intensity Qave and the average detection distance Dave are obtained for each detected object (a group of detection data), and the pulse laser beam is detected according to the effective data number M representing the object at the farthest point obtained from the average detection distance Dave. This is done by optimizing the output period T.

  That is, when there is no object to be monitored in the monitoring target area A, the generation period T of the pulse laser light is lengthened as a predetermined maximum value Tmax, and the deflection per period in which the pulse laser light is output. By increasing the scanning angle, the scanning density for the monitoring target area A is set coarsely. Then, a so-called standby mode is set in which only the appearance of the monitoring target object in the monitoring target area A is detected. Further, when there is a monitoring target object in the monitoring target region A, for example, the number M of effective data is obtained for each detection object, and the pulse laser beam is obtained so that detection data of a number that can reliably detect the object is obtained. The generation cycle T is optimized. Specifically, the average detection distance Dave and the effective data number M are obtained for each detected object, and the generation period of the pulse laser light is obtained so that a sufficient number of detection data Mmin can be obtained to detect the object at the farthest point. Optimize T.

  In this way, the output period T of the pulsed laser light is variably controlled in accordance with the state of detection of the object in the monitoring target area A to optimize it. For example, the generation period T of the pulsed laser light is set to the maximum value Tmax, By setting the so-called standby mode in which only the appearance of the monitoring target object in the monitoring target area A is detected, it is possible to reduce the driving power of the sensor head 1 and save energy. In addition, since the number of times of driving (driving time) of the laser diode as the laser light source constituting the light projecting unit 2 can be reduced, it is possible to extend the life of the laser diode and prevent deterioration of its characteristics.

  Furthermore, when an object exists in the monitoring target area A, the object at the farthest point is specified according to the detection distance D (average detection distance Dave) of each object, and the object at the farthest point is reliably detected. By setting the output period T of the pulse laser beam so as to satisfy the minimum measurement conditions to be obtained, the above-described laser diode driving conditions can be relaxed. Specifically, in general, the number M of data that forms a predetermined set necessary for recognition as one object is determined according to the detection distance, so that the object with the most severe point as the object detection condition is selected. Paying attention, the number M of effective data that recognized the object and its average detection distance Dave are obtained. The valid data refers to detection data having a predetermined light reception intensity Q or higher. In order to ensure a predetermined effective data number M according to the average detection distance Dave, specifically, according to a ratio [Dave / M] with a predetermined effective data number M according to the average detection distance Dave. The output period T of the pulse laser beam is optimized. As a result, the driving condition of the light projecting unit 2 is relaxed to extend its life, and further, the driving energy is reduced by reducing the driving energy of the pulse laser beam output period T (laser diode driving frequency). Effects such as being able to be achieved are achieved.

  FIG. 3 shows an example of a control procedure for the output period T 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 this 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 S11>, and the position coordinates of the detected object are obtained <step S12>. Then, it is determined whether or not these objects are immutable fixed objects in the monitoring target area A <step S13>. If they are immutable fixed objects, information for excluding them from the recognition target as background data; <Step S14>. 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, a threshold for the height from the ground surface is set in order to remove the reflected light from the ground surface, which becomes a noise component (step S15). This threshold value processing corresponds to limiting the maximum measurement distance for each scanning direction of the pulse laser beam 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, it is determined whether or not an object to be monitored exists in the monitoring target area A <Step S4>. If there is no object to be monitored, the pulse laser beam generation period T is set to the maximum value Tmax so that only the appearance of the monitored object in the monitoring target area A can be detected <step S5>. . Setting the pulse laser beam generation period T to the maximum value Tmax in this way corresponds to setting a so-called standby mode in which the number of times the laser diode is driven is minimized and the driving power is reduced.

On the other hand, when any monitoring target object is detected in the monitoring target area A, the average detection distance Dave is detected from the detection data for each detected object in order to guarantee the minimum detection performance for the object. The number of valid data M is obtained <step S6>. 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. An index S for evaluating the detection performance of the detection data of S = [average reflected light intensity Qave] / [number of valid data M]
Calculate as

  Incidentally, the index S 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. For the index S obtained as described above, the minimum detection condition of the object obtained in advance based on the experimental result or the like can be guaranteed, for example, the index S as shown in FIG. 5 and the optimum output period T of the pulse laser beam, The output period T of the pulse laser beam is adjusted so as to satisfy the relationship <Step S7>. In this way, while adjusting the output period T of the pulsed laser beam, the process returns to the above-described step S2 and the object monitoring process in the monitoring target area A is continuously executed.

  As described above, by optimizing the output period T of the pulse laser beam in accordance with the detection state of the object in the monitoring target area A, the above pulse is satisfied while satisfying the measurement condition for reliably detecting the object at the farthest point. It is possible to suppress the number of times of laser light output. Therefore, as the output period T of the pulse laser beam is increased, for example, the driving condition of the laser diode as a laser light source is 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. For example, in the above embodiment, the index S for evaluating the detection performance is calculated as the ratio [Qave / M] between the average reflected light intensity and the number of effective data. The output period T may be optimized. In addition, the object detection situation performed using the pulse laser beam is estimated by imaging the monitoring target area A using a camera and analyzing the image, and the output period T of the pulse laser beam is set according to the estimation result. Variable setting is also possible. This is particularly useful when setting the above-described standby mode. 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 relationship between the optimum output period T of the pulsed laser beam with respect to the ratio [Dave / M] of the average detection distance Dave of the object at the farthest point and the number of effective data M used for the optimization control of the output period T of the pulsed laser beam FIG.

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 Output period adjustment means

Claims (3)

The pulsed laser light generated at a predetermined cycle is irradiated onto the monitoring target region, and the pulsed laser light is scanned over the entire monitoring target region, and the pulsed laser light in the monitoring target region is synchronized with this scanning. A laser monitoring device that receives the reflected light of the object and monitors the presence or absence of an object in the monitoring target area,
A laser monitoring apparatus comprising: an output period adjusting unit that variably sets a generation period of the pulsed laser light according to an object detection state in the monitoring target region. The monitoring of the presence / 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 monitors a fixed object in the monitoring target area It is done by excluding from the subject,
The output cycle adjusting means sets the generation period of the pulse laser beam to a predetermined maximum value when there is no monitoring target object in the monitoring target region, and when the monitoring target object exists in the monitoring target region. The laser monitoring apparatus according to claim 1, wherein the generation period of the pulsed laser light is increased or decreased according to the number of effective data obtained for each object.   3. The laser according to claim 2, wherein the output cycle adjusting unit calculates an average detection distance for each object, and increases or decreases the generation cycle of the pulse laser beam according to the number of effective data of the object at the farthest point. Monitoring device.

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