JP2007122508A - Intrusion detection apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem in an intrusion detection apparatus for forming range images by use of reflected laser beams that it is impossible to detect changes in distance from pixels which cannot be measured either in a background range image or the present range image, leading to the possibility of the failure to detect intruders. <P>SOLUTION: A distance calculating part 16 calculates the measurement of a distance to an object based on a reflected laser beam. For each pixel on a range image, a ranging availability data generating part 32 generates ranging availability data showing whether or not ranging by the distance calculating part 16 has been successful. A background difference calculating part 22 refers to the ranging availability data for both the background range image and the current range image, and extracts some pixels as pixels varied, not only when a variation between distance measurements obtained from both range images is equal to or greater than a predetermined value, but also when it is impossible to measure distance because distance measurements cannot be obtained only by either of the range images. An intruder determining part 24 determines whether or not there is an intruding object in the monitored space according to the pixels varied. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an intrusion detection device, and more particularly to improvement of detection accuracy.

  As a monitoring device for detecting an intruding object such as a person into the monitoring space, an apparatus using a distance image has been proposed. Here, the distance image is information having distance information as a pixel value.

  Specifically, it is possible to send a laser beam or the like toward the monitoring space, and measure the distance from the transmission to the reception of the reflected light to the object in the monitoring space. Then, by sequentially changing the sending direction of the measurement medium such as a laser beam and scanning the monitoring space two-dimensionally, distance information regarding a plurality of directions facing the monitoring space is obtained, and the above-described distance image is acquired. The As a distance measuring method, there is a method based on the principle of triangulation based on a phase difference between reflected light at two light receiving units separately disposed, in addition to a method based on the time until the reflected light is received. .

  A monitoring device using a distance image compares a distance image (background image) as a background in which no moving object exists with an input distance image (current image), and extracts pixels whose distance has changed by a predetermined value or more. To find the change area. Then, based on the size / shape of the change area and the distance information in the current image, it is determined whether or not the moving object is the target detection target.

The distance image includes information such as the direction of an object viewed from a transmitting / receiving unit such as a laser beam and the distance to the object. Therefore, the size and shape of the object can be known from the distance image. For example, in an intruder detection application, it is possible to distinguish a relatively large person in the distance from small animals in the vicinity (such as a frog or a cat). It becomes possible, and the detection accuracy of an intruder can be improved.
JP 7-71286

  When distance measurement is performed by the method described above, if the intensity of the reflected light is small, the S / N ratio of the reflected light decreases, and the waveform of the reflected light and the light reception timing cannot be accurately detected, resulting in a decrease in distance measurement accuracy. When the intensity of the reflected light further decreases, the reflected light is buried in a noise component, and the reflected light cannot be detected, and distance measurement is impossible due to failure in distance measurement. For example, such a pixel that cannot be measured can be generated corresponding to an object having low light reflectance. In the distance image, a value (code) indicating that the distance measurement is impossible is assigned to the pixel in which the distance measurement is impossible in this way.

  In the conventional monitoring device using the distance image, when extracting the change area from the current image and the background image, if any one of the two pixel values to be compared between the current image and the background image cannot be measured, Since the distance difference value cannot be obtained for the pixel, there is a problem in that it cannot be determined whether or not there is a change.

  This inability to measure the distance is likely to occur when an object with low light reflectance exists in the monitoring space. When the number of pixels that cannot be measured increases, only a part of the moving object is extracted as the distance change region, and for example, there is a problem that detection omission is likely to occur even if an intruder exists in the monitoring space.

  The present invention has been made to solve the above-described problems, and aims to reduce malfunctions caused by pixels that cannot be measured and improve detection accuracy in an intrusion detection apparatus using a distance image. To do.

  An intrusion detection device according to the present invention determines whether or not there is an intruding object based on a distance image of a monitoring space, and projects light to the monitoring space, and an object existing in the monitoring space based on the reflected light. Ranging means for obtaining a distance measurement value for each pixel of the distance image; and success / failure information generating means for generating distance measurement success / failure information indicating success / failure of distance measurement by the distance measuring means for each pixel of the distance image; The distance measurement success / failure information corresponding to each of the background distance image at the predetermined reference time and the target distance image to be monitored is referred to, and the distance measurement value is obtained in both the background distance image and the target distance image. With respect to the pixel being extracted, if the change in the distance measurement value between the two distance images is greater than or equal to a predetermined value, the pixel is extracted as a change pixel, and the distance is detected only in one of the background distance image and the target distance image. For a pixel for which a measured value cannot be obtained and ranging is impossible, a background difference calculation unit that extracts the pixel as a change pixel, and a determination unit that determines the presence or absence of the intruding object in the monitoring space based on the change pixel , Has.

  In another intrusion detection apparatus according to the present invention, the success / failure information generating means generates the distance measurement success / failure information based on a received light amount of the reflected light used for the distance measurement.

  In another intrusion detection apparatus according to the present invention, the distance measuring unit obtains the distance measurement value based on a response time from light projection to reception of the reflected light, and is determined within a predetermined time from the light projection. A pixel in which the reflected light having a light reception amount equal to or greater than the value cannot be obtained is regarded as being unable to measure the distance.

  The difference in the distance measurement success / failure of a certain pixel between the background distance image at the reference time and the target distance image to be monitored is because the object appearing at that pixel has other reflectances different from each other between the distance images. Or when the distance to the object appearing in the pixel is actually changing. Therefore, it is appropriate to estimate that the difference in distance measurement success / failure is caused by an intruding object. Therefore, the present invention treats pixels with different distance measurement success / failure between the background distance image and the target distance image in the same manner as the pixels in which the distance change is detected, thereby reducing the extraction omission of the pixels in which the moving object appears. To do. As a result, the accuracy of the size and shape of the moving object grasped from the distance image is improved, and the intruding object to be detected can be accurately determined.

  Hereinafter, embodiments of the present invention (hereinafter referred to as embodiments) will be described with reference to the drawings.

  FIG. 1 is a schematic block diagram of an intruder detection device according to an embodiment. The apparatus includes a light projecting unit 2, a light projecting control unit 4, a light projecting timing storage unit 6, a scanning mirror 8, a scanning unit 10, a light receiving unit 12, a light receiving timing extracting unit 14, a distance calculating unit 16, a data generating unit 18, A background data storage unit 20, a background difference calculation unit 22, an intruder determination unit 24, and an alarm unit 26 are included. The data generation unit 18 includes a distance image generation unit 30 and a distance measurement availability data generation unit 32.

  In this apparatus, the scanning mirror 8 is swung around each of two axes, and the laser light emitted from the light projecting unit 2 is reflected by this scanning mirror 8 and projected to the monitoring space. As a result, a laser beam whose projection direction changes two-dimensionally is sent toward the monitoring space. The light receiving unit 12 receives the laser light reflected by the object 40, and measures the distance to the object 40 by, for example, the time-of-flight method based on the reflected light.

  The light projecting unit 2 includes a semiconductor laser as a light source. The light source is supplied with a pulsed voltage signal from the light projecting control unit 4 and generates pulsed light. The light projecting unit 2 emits laser light generated by the light source as a beam by a lens. The laser light from the light projecting unit 2 passes through the half mirror 42 and enters the scanning mirror 8. The scanning mirror 8 is configured using, for example, a galvanometer mirror, and scans an imaging target range two-dimensionally with incident laser light.

  The light projecting control unit 4 starts pulse driving of the semiconductor laser of the light projecting unit 2 in conjunction with the scanning cycle start pulse output from the scanning unit 10. When the pulse driving is started, the light projecting control unit 4 generates a driving voltage pulse for the semiconductor laser based on the light projecting timing recorded in the light projecting timing storage unit 6. The light projection control unit 4 notifies the generation timing of the drive voltage pulse to the light reception timing extraction unit 14 and the distance calculation unit 16.

  The light projection timing storage unit 6 stores information for designating light projection timing according to the scanning angle of the scanning mirror 8. For example, sampling point groups for transmitting and receiving laser light are arranged on a scanning line periodically drawn by the scanning mirror 8, and the scanning timing of each sampling point is stored in the light projection timing storage unit 6 as the light projection timing. The sampling point group is distributed and arranged over the entire scanning target range so that an image can be constituted by information sampled by them, and is basically set so as to have a uniform or close distribution within the scanning target range. . As the scanning line, for example, a Lissajous figure or other nonlinear curve that passes through the entire scanning target range can be used. Details of the method for determining the light projection timing are well known in Japanese Patent Application Laid-Open No. 2004-157796 and the like, and thus the description thereof is omitted.

  The scanning mirror 8 projects the laser light emitted from the light projecting unit 2 onto the object 40 and takes in the laser light reflected by the object 40 into the apparatus. Laser light from the object 40 is guided to the half mirror 42 via the scanning mirror 8, reflected by the half mirror 42, and travels toward the light receiving unit 12.

  The scanning unit 10 starts and stops scanning of the scanning mirror 8. In addition, a signal having a voltage value corresponding to the current scanning angle is output to the data generation unit 18, and a scanning cycle start pulse is given to the light projection control unit 4 in synchronization with the start timing of each scanning cycle.

  The light receiving unit 12 condenses incident light on the optical sensor using a lens. The optical sensor is composed of an avalanche photodiode, a pin photodiode, or the like, and converts the reflected light from the object 40 into an electrical signal corresponding to the amount of received light. The electric signal is amplified and then output to the light reception timing extraction unit 14 as a light reception signal.

  The light reception timing extraction unit 14 receives a pulse generated by the light projection control unit 4 in synchronization with the drive voltage pulse for the light projection unit 2, and grasps the light projection time of the light projection unit 2 based on the pulse. And the light reception time is calculated | required based on the light reception signal input from the light-receiving part 12 within the fixed time range (tau) preset from each light projection time. The light reception timing extraction unit 14 includes a peak detection circuit, and calculates the light reception time from the peak position of the light reception signal and the light reception amount from the peak size.

FIG. 2 is a schematic diagram relating to a light reception signal for explaining the processing in the light reception timing extraction unit 14. In FIG. 2, the horizontal axis represents time, and the vertical axis represents the received light signal voltage. Light projection from the light projecting unit 2 is performed periodically, and FIG. 2 shows an example of a light reception signal for a plurality of light projections. The light reception timing extraction unit 14 detects, as a light reception signal 50, a light reception signal in which the peak position t _P exists within the period of the width τ from the projection time t _S and has a peak height equal to or greater than the threshold value Ib. . Here, the period τ is determined according to the set value of the upper limit distance to be monitored. The period τ can be set within a range equal to or shorter than the light projection interval. The light projection interval is determined according to the frame rate of the distance image and the number of sampling points. When the light projection timing is not constant, the period τ is set to be equal to or less than the minimum value of the light projection interval. The threshold value Ib is set in consideration of the S / N of the light receiving unit 12.

Therefore, what is received at a time exceeding the time range τ from t _S like the light reception signal 52 is reflected light from an object exceeding the upper limit distance to be monitored and is excluded from detection. In this case, peak detection is not performed, and distance measurement is handled as being impossible. For example, in this case, the light reception timing extraction unit 14 outputs a value indicating a predetermined invalidity as the light reception time. Further, when the peak is less than the threshold value Ib as in the light reception signal 54, the light reception signal is buried in noise and difficult to discriminate from the noise, so that it is excluded from detection and treated as being unable to be measured. In this case, the light reception timing extraction unit 14 outputs a value indicating predetermined invalidity as the light reception time and sets the light reception amount to zero. Incidentally, the situation where the intensity of the received light signal becomes weak can occur when the reflectance of the object is low or when the distance to the object is large.

  The distance calculation unit 16 calculates the distance to the object from the difference between the light projection time from the light projection control unit 4 and the light reception time from the light reception timing extraction unit 14. Here, when the light reception time is a value indicating invalidity, a predetermined value indicating that distance measurement is impossible is output as the distance measurement value.

  In the data generation unit 18, the distance image generation unit 30 performs distances in a plurality of directions toward the monitoring space based on the scanning angle at the time of projection from the scanning unit 10 and the distance measurement value from the distance calculation unit 16. Distance information composed of measurement values is generated for each scanning cycle. This distance information has a property as an image capable of grasping the shape of the object by setting many light projection directions, and the image is defined as a distance image.

  The distance measurement availability data generation unit 32 determines the distance measurement availability corresponding to each pixel of the distance image based on the scanning angle at the time of light projection from the scanning unit 10 and the result of the distance measurement availability from the light reception timing extraction unit 14. Ranging availability data (ranging success / failure information) composed of values indicating (ranging success / failure) is generated. It should be noted that distance measurement availability data may be generated by reading a value indicating that distance measurement is not possible in the distance calculation unit 16 and the distance image generation unit 30.

  The background data storage unit 20 stores, as background data, a distance image and distance measurement availability data in a state where there is basically no moving object in the monitoring space (reference time). As the background data, for example, data acquired by scanning the monitoring space when the apparatus is activated can be used. In addition, since the background can change due to, for example, a person moving a stationary object in the monitoring space, the background data may be updated by scanning the monitoring space at an appropriate time such as when monitoring starts.

  The background difference calculation unit 22 receives the monitoring target distance image and distance measurement availability data obtained by scanning the monitoring space during the intruder detection operation as monitoring target data. The background difference calculation unit 22 compares the monitoring target data input for each scanning cycle during the monitoring operation with the background data stored in the background data storage unit 20, and determines an image area determined to have changed in distance. Extract.

  The intruder determination unit 24 determines whether or not the change is caused by an intruder based on data such as the shape and size of the change region extracted by the background difference calculation unit 22 and the distance related to the region. .

  When the intruder determination unit 24 determines that an intruder exists, the alarm unit 26 sends an alarm to a security center, for example, and displays an intruder on the display unit of the device or a buzzer. And so on.

  Next, the operation of this apparatus will be described. FIG. 3 is a schematic process flow diagram for explaining the overall operation of the apparatus. When this apparatus is activated and instructed to start the intruder detection process, the monitoring space is scanned with laser light, and data such as the current distance image is acquired (S100). When the background data is not stored in the background data storage unit 20 (S105), the acquired data such as the current distance image is stored in the background data storage unit 20 as background data (S110). On the other hand, if the background data has already been stored (S105), it is determined whether or not there is an intruder in the current monitoring space using the current distance image data as monitoring target data (S115). ~ S140).

  When the monitoring target data is input, the background difference calculation unit 22 compares the monitoring target data with the background data stored in the background data storage unit 20, for example, an image region that is determined to have changed in distance. A differential binary image with a pixel value of “1” and a pixel value of the other image region as “0” is generated (S115). The details of the process for determining whether or not there is a change in distance in the background difference calculation unit 22 will be described later.

  The background difference calculation unit 22 extracts a portion corresponding to the image region in which the pixel value of the difference binary image is “1” from the current distance image, generates a difference distance image, and the intruder determination unit 24. (S120).

  The intruder determination unit 24 performs a labeling process S125, an integration process S130, an object size calculation process S135, and an object position calculation process S140. In the labeling process S125, when the difference between the pixel value of an arbitrary target pixel in the difference distance image and the pixel values of the pixels around the target pixel is less than a predetermined value, the same target pixel and the surrounding pixels are the same The label number is assigned. Thereby, a plurality of objects having different distances in the difference distance image are identified and extracted by the label number. An image with the label number as the pixel value is referred to as a label image. For a pixel for which a value indicating that distance measurement is not possible is set as distance measurement availability data, a label number that can be distinguished from a general label number given to a pixel having another pixel value is assigned.

  In the integration process S130, regarding a pixel assigned a label number indicating that ranging is not possible in the label image, if a pixel adjacent to the pixel is assigned a general label number, the pixel is the same object as the adjacent pixel. Accordingly, the label number of the pixel that cannot be measured is changed to the general label number of the adjacent pixel.

  In the object size calculation S135, a parameter representing the size is calculated for each object identified by the label number. In this processing, each pixel is converted from coordinates represented by a distance and a direction centered on the light projecting unit 2 and the light receiving unit 12 to coordinates in an orthogonal space. Then, for example, parameters representing the object width are obtained from the pixel coordinate difference between the left end and the right end of each labeled region, and the object height is determined from the pixel coordinate difference between the upper end and the lower end. Coordinate conversion for pixels that cannot be measured is performed using the distance between pixels assigned the same label number. Thus, since the distance of the object is known from the current distance image, the size of the object in real space can be obtained from the distance and the object area on the image.

  In the object position calculation process S140, a parameter representing the position of the object corresponding to the area is calculated based on the position of the pixel area composed of pixels having the same label number. For example, the center of gravity of the pixels constituting the area in the three-dimensional orthogonal coordinates is used as a parameter representing the position of the object.

  The position and size of the object are calculated for each label number, and it is determined from the position and size whether the object is a person. For example, thresholds for width and height for determining a person are set in advance, and it is determined that the person is a person when either the width or height of the object exceeds the threshold. In addition, an intrusion detection area can be set in advance in the monitoring space, and in this case, whether or not the position of the object is within the intrusion detection area can be added to the determination element.

  If it is a person, the intruder determination unit 24 determines that an intruder has occurred in the monitoring space (S145), and notifies the alarm unit 26 of it. The alarm unit 26 receives the notification signal and executes various processes when the intruder is detected (S150).

  On the other hand, while no intruder is detected (S145), the alarm process S150 is not executed, new monitoring target data is acquired by scanning with laser light (S100), and the above-described processes S105 to S145 are periodically repeated. As a result, the monitoring operation is continued.

  FIG. 4 is a schematic process flow diagram of the difference binary image generation process S115. Hereinafter, the notation (i, j) represents the x and y coordinates of the pixel value of the distance image. When the number of pixels in the x and y directions of the distance image is Nx and Ny, the coordinate value i in the x direction is 0 ≦ i ≦ Nx−1, and the coordinate value i in the y direction is 0 ≦ i ≦ Ny−1. Can be expressed as For example, the difference binarization process is started from a pixel with i = 0 and j = 0 (S200). The background difference calculation unit 22 compares and refers to the distance measurement availability data generated for the current distance image and the distance measurement availability data stored in the background data storage unit 20 for the background distance image. Then, a combination pattern that enables / disallows distance measurement is determined for the (i, j) pixels corresponding to each of the current distance image and the background distance image, and the process branches according to the pattern. For example, the background difference calculation unit 22 determines whether or not (i, j) pixels of the current distance image and the background distance image are both unmeasurable (S205), and at least one of both pixels is measured. If the distance is possible, it is next determined whether or not both of them can be measured (S210).

  If both the (i, j) pixels of the current distance image and the background distance image cannot be measured (S205), the value of the (i, j) pixel of the difference binary image is set to have no distance change. It is set to 0 which means (S215).

If both (i, j) pixels of the current distance image and the background distance image can be measured (S210), a distance difference value dd is calculated (S220). If dd is the distance value of (i, j) pixels in the current distance image and d2 (i, j) is the distance value of (i, j) pixels in the background distance image, Given.
dd = | d1 (i, j) -d2 (i, j) |

  This distance difference value dd is compared with a threshold ThD (S225), and if dd is equal to or greater than ThD, the value of the (i, j) pixel of the difference binary image is set to 1 which means that there is a distance change (S230). If it is less than ThD, it is set to 0 (S215). The threshold ThD is preferably set to a sufficient distance difference to detect an intruder.

  Further, the background difference calculation unit 22 determines that (i, j) pixels of either the current distance image or the background distance image cannot be measured (S210), and (i, j) of the difference binary image. j) The pixel value is set to 1 which means that there is a change in distance.

  As described above, when the pixel value of the difference binary image is determined for a certain pixel, the same processing is executed for an unprocessed pixel. For example, the coordinate i in the x direction is incremented by 1, and the difference binarization process is sequentially performed on new pixels (S235). When i increased by 1 in process S235 exceeds the upper limit value Nx-1 (S240), i is reset to 0, and j is increased by 1 to shift to the process of the pixel column adjacent in the y direction. (S245). When j increased by 1 in process S245 exceeds the upper limit value Ny-1 (S250), the difference binarization process for all the pixels of the current distance image is completed.

  FIG. 5 is a schematic diagram for explaining an example of intruder detection processing by this apparatus. In the monitoring space shown in this example, there are a wall 300 standing far away as an object serving as a background, and stationary objects 302 and 304 placed in front of the wall 300. FIG. 5A shows a background distance image. In this distance image, distance measurement is possible for each pixel constituting the wall 300 and the stationary object 302, and a distance measurement value is obtained. On the other hand, the stationary object 304 is made of a surface material having a low light reflectance, for example, and has a small amount of light received from the object 304, and therefore cannot be measured.

  FIG. 5B shows the current distance image. In this distance image, people 306 and 308 appear in front of the stationary objects 302 and 304, respectively. These persons 306 and 308 can measure the distance.

  FIG. 5C shows a binary difference image by the present apparatus based on the background distance image and the current distance image shown in FIGS. 5A and 5B. The image area corresponding to the person 306 can measure both the background distance image and the current distance image, and a distance difference value is obtained. Therefore, by binarizing the distance difference value with the threshold ThD, each pixel value of the image area corresponding to the person 306 of the difference binary image is set to “1”. On the other hand, regarding the image area corresponding to the person 308, a part of the background is the wall 300 and the remaining background is the stationary object 304. Among them, the distance difference value is obtained for the wall portion of the background in the same manner as the image area of the person 306, and “1” is set as the pixel value of the difference binary image by binarizing it with the threshold ThD. The A distance difference value cannot be obtained for a portion where the background is the stationary object 304. Therefore, in the conventional difference binarization process, it cannot be determined that there is a distance change, and “0” is assigned as the pixel value of the difference binary image. Therefore, conventionally, only a part of the person 308 can be extracted into the difference binary image, and there is a possibility that the detection of the person 308 may be missed. On the other hand, in the present apparatus, for pixels in which only one of the background distance image and the current distance image cannot be measured, it is estimated that there is a distance change, and the pixel value of the difference binary image is set to “1”. To do. As a result, the entire person 308 is extracted into the difference binary image, and detection omission is avoided.

It is a schematic block diagram of the intruder detection device of the embodiment. It is a schematic diagram regarding the light reception signal explaining the process in a light reception timing extraction part. It is a rough processing flow figure explaining the whole operation of the intruder detection device of an embodiment. It is a general | schematic process flow figure of a difference binary image generation process. It is a schematic diagram explaining an example of the process of intruder detection by the intruder detection apparatus of embodiment.

Explanation of symbols

  2 light projection unit, 4 light projection control unit, 6 light projection timing storage unit, 8 scanning mirror, 10 scanning unit, 12 light reception unit, 14 light reception timing extraction unit, 16 distance calculation unit, 18 data generation unit, 20 background data storage Unit, 22 background difference calculation unit, 24 intruder determination unit, 26 alarm unit, 30 distance image generation unit, 32 distance measurement availability data generation unit.

Claims (3)

In an intrusion detection device that determines the presence or absence of an intruding object based on a distance image of a monitoring space,
Ranging means for projecting light to the monitoring space and obtaining a distance measurement value for each pixel of the distance image based on the reflected light to an object existing in the monitoring space;
Success / failure information generating means for generating distance measurement success / failure information indicating success / failure of distance measurement by the distance measurement means for each pixel of the distance image;
The distance measurement value is obtained in both the background distance image and the target distance image with reference to the distance measurement success / failure information corresponding to each of the background distance image and the target distance image to be monitored at a predetermined reference time. If the change in the distance measurement value between the distance images is greater than or equal to a predetermined value, the pixel is extracted as a change pixel, and the distance measurement is performed using only one of the background distance image and the target distance image. For a pixel for which no value is obtained and ranging is impossible, background difference calculation means for extracting the pixel as a change pixel;
Determining means for determining the presence or absence of the intruding object in the monitoring space based on the change pixel;
An intrusion detection device comprising: The intrusion detection device according to claim 1,
The intrusion detection device, wherein the success / failure information generation means generates the distance measurement success / failure information based on a received light amount of the reflected light used for the distance measurement. The intrusion detection device according to claim 1 or 2,
The distance measuring means obtains the distance measurement value based on a response time from light projection to reception of the reflected light, and the reflected light having a received light amount equal to or greater than a predetermined value is obtained within a predetermined time from the light projection. An intrusion detection apparatus characterized in that no distance measurement is possible for a pixel that does not exist.

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