JP6965715B2 - Object monitoring device, control method, and control program - Google Patents

Description

The present invention relates to an object monitoring device, a control method, and a control program for monitoring an object by scanning and projecting, for example, laser light or the like.

As an object monitoring device that detects an intruder or the like in a monitoring space, a device that uses a distance image (distance map) has been proposed. Here, the distance image has distance information as a pixel value. Specifically, as shown in Patent Document 1, object monitoring is performed by transmitting a laser beam toward a monitoring space and measuring the distance from the transmission to the reception of reflected light to an object in the monitoring space. The device is known. In such an object monitoring device, distance information regarding a plurality of directions facing the monitoring space can be obtained by sequentially changing the transmission direction of the measurement medium of the laser beam and scanning the inside of the monitoring space two-dimensionally. Form a distance image.

In an object monitoring device using a distance image, background data (background distance map) that is a background in which a moving object does not exist is obtained in advance, and the obtained background image is compared with the input distance image (current image). The so-called background subtraction method is used, in which pixels whose distance has changed by a predetermined value or more are extracted to obtain a change region. Thereby, it is possible to determine whether or not the moving object is the target object to be detected based on the size and shape of the changing region and the distance information in the current image.

Further, in Patent Document 2, the distance is measured by a stereo camera and background data is generated in a state where there is no vehicle as an object in the monitoring space.

Japanese Unexamined Patent Publication No. 2005-30259 Japanese Unexamined Patent Publication No. 2014-74939

In the object monitoring device that generates background data of the monitoring space and detects the intrusion of an object into the monitoring space by the background subtraction method, it has been used until then when the power of the object monitoring device itself is turned off. Background data is lost. After that, when the power is turned on, the background data must be generated again, but if an object other than the background exists in the surveillance space at that point, that object is also recognized as the background and is included in the background data. It will end up. In such a case, since the background data is incorrect, there is a risk that accurate object detection cannot be performed.

The present invention has been made in view of the above circumstances, and even when the power of the object monitoring device is unexpectedly turned off, false detection of an object or omission of detection is prevented when the power is turned on thereafter. The purpose is to do.

The above object of the present invention is achieved by the following means.

(1) A light emitting / receiving unit provided with an emitting unit that emits a light beam into the monitoring space and a light receiving unit that receives a light beam reflected from an object in the monitoring space.
A distance image generation unit that obtains the distance to an object based on the emission and reception timings of the light emitting and receiving unit and generates distance image data indicating the distribution of distance values in the monitoring space.
A non-volatile memory that stores the background data generated based on the acquired distance image data,
A determination unit that recognizes an object in the monitoring space by comparing the background data with the distance image data in the monitoring space generated by the distance image generation unit during monitoring is provided.
The determination unit reads the background data from the non-volatile memory when the power is turned on, compares the read background data with the distance image data generated by the distance image generation unit, and notifies the comparison result .
The non-volatile memory has at least two areas, and the background data is alternately stored in two of the plurality of areas.
The determination unit is an object monitoring device that compares the background data stored in the two areas of the non-volatile memory with the distance image data by using the background data having the newer update date and time.

(2) The determination unit reads the background data from the non-volatile memory when the power is turned on, compares the read background data with the distance image data generated by the distance image generation unit, and the difference between the two is equal to or less than a predetermined value. In this case, the background data read from the non-volatile memory is used to recognize an object in the monitoring space.
The object monitoring device according to (1) above, wherein when the difference exceeds the predetermined value, it is determined that the installation conditions of the object monitoring device have been changed, and a warning is issued as the notification.

(3) The object monitoring device according to (2) above, wherein the determination unit warns the user to reacquire the background data as the warning.

(4) In response to receiving an instruction from the user to reacquire the background data
The determination unit generates new background data based on the distance image data generated by the distance image generation unit at the present time obtained from the monitoring space, and stores the generated new background data in the non-volatile memory. The object monitoring device according to (2) or (3) above.

(5) The determination unit extracts and extracts a pixel group according to the distance to the object as a comparison between the background data read from the non-volatile memory and the distance image data generated by the distance image generation unit. The object monitoring device according to any one of (2) to (4) above, which determines that the installation conditions of the object monitoring device have been changed when the size of the pixel group exceeds the predetermined value.

(6) The object monitoring device according to any one of (1) to (5) above, wherein the non-volatile memory is a flash memory.

(7) pre-Symbol judging unit, during operation, generates a new background data on the basis of the generated range image data, at a predetermined time interval, newly generated in two of the regions among the plurality of regions The object monitoring device according to (6) above , which alternately stores the background data.

(8) The time interval for storing the background data in one of the areas is set to be longer than the time obtained by dividing the product warranty period of the object monitoring device by the maximum number of rewrites guaranteed by the flash memory. The object monitoring device according to (7) above.

(9) A control method in an object monitoring device including a distance image generation unit that generates distance image data in the monitoring space and a non-volatile memory that stores background data generated based on the distance image data acquired in the past. There,
The step (a) of reading the background data from the non-volatile memory when the power is turned on,
In step (b), when the power is turned on, a light flux is emitted into the monitoring space and the light flux reflected from the object in the monitoring space is received.
The distance image generation unit obtains the distance to the object based on the emission and reception timings of the step (b), and the distance image data in the monitoring space is generated in the step (c).
A step (d) of comparing the background data read in the step (a) with the distance image data generated in the step (c) and notifying the comparison result.
Only including,
The non-volatile memory has at least two areas, and the background data is alternately stored in two of the plurality of areas.
In the step (a), the control method of reading out the background data whose update date and time is newer than the background data stored in the two areas of the non-volatile memory.

( 10 ) As a result of comparison in the step (d), when the difference between the background data and the distance image data is equal to or less than a predetermined value, the background data read from the non-volatile memory is used to display an object in the monitoring space. Step (e) to recognize
The control according to (9 ) above, further including a step (f) of determining that the installation conditions of the object monitoring device have been changed and issuing a warning as the notification when the difference exceeds the predetermined value. Method.

( 11 ) The control method according to (10 ) above, wherein in the step (f), as the warning, a warning for prompting the user to reacquire the background data is given.

( 12 ) Step (g) of receiving an instruction to reacquire the background data from the user, and
Step (h) of generating new background data based on the distance image data generated by the distance image generation unit at the present time obtained from the monitoring space, and storing the generated new background data in the non-volatile memory. When,
The control method according to (10 ) or ( 11 ) above, further comprising.

( 13 ) In the step (d), as a comparison between the background data read from the non-volatile memory and the distance image data generated by the distance image generation unit, a pixel group is extracted according to the distance to the object. The control method according to any one of (10 ) to ( 12 ) above, wherein when the size of the extracted pixel group exceeds the predetermined value, it is determined that the installation conditions of the object monitoring device have been changed.

( 14 ) A control program for causing a computer to execute the control method according to any one of (9 ) to ( 13) above.

The object monitoring device according to the present invention reads background data from the non-volatile memory when the power is turned on, compares the read background data with the distance image data generated by the distance image generation unit, and notifies the comparison result. By doing so, even if the power of the object monitoring device is unexpectedly turned off, it is possible to prevent erroneous detection or omission of detection of the object when the power is turned on thereafter.

It is a block diagram which shows the main structure of the object monitoring apparatus which concerns on this embodiment. It is sectional drawing which shows the light-receiving unit of an object monitoring device. It is a schematic diagram which shows the state of scanning in the monitoring space by an object monitoring device. It is a figure which shows the state which looked at the monitoring space from the side. It is a flowchart which shows the comparison process at the time of power-on of the object management apparatus. It is a flowchart which shows the monitoring process of the monitoring space performed following FIG.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicate description will be omitted. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation and may differ from the actual ratios.

FIG. 1 is a block diagram showing a main configuration of an object monitoring device MD according to the present embodiment, and FIG. 2 is a cross-sectional view mainly showing a light emitting / receiving unit 10.

As shown in FIGS. 1 and 2, the object monitoring device MD includes a light emitting / receiving unit 10, a control unit 20, a non-volatile memory 30, a warning unit 40, and an input / output unit 50.

(Light emitting / receiving unit 10)
Referring to FIG. 2, the light emitting / receiving unit 10 of the object monitoring device MD includes a semiconductor laser LD, a collimating lens CL, a mirror unit MU, a lens LS, a photodiode PD, a motor MT, and a housing for accommodating each of these components. Has body CS.

The semiconductor laser LD emits a pulsed laser luminous flux. The collimating lens CL converts the divergent light from the semiconductor laser LD into parallel light. The mirror unit MU scans and projects the laser beam parallel to the collimating lens CL toward the monitoring space (monitoring area) by the rotating mirror surface, and reflects the reflected light from the object. The lens LS collects the reflected light from the object reflected by the mirror unit MU. The photodiode PD receives the light focused by the lens LS and has a plurality of pixels arranged in the Z direction. The motor MT rotates and drives the mirror unit MU. The control unit 20 (details will be described later) obtains distance information (distance image) according to the time difference between the emission timing of these semiconductor laser LDs and the light receiving timing of the photodiode PD. The control unit 20 obtains a distance image by executing a program by the CPU as described later, but may include a dedicated hardware circuit for generating the distance image.

In the present embodiment, the semiconductor laser LD and the collimating lens CL constitute the exit portion LPS, and the lens LS and the photodiode PD constitute the light receiving portion RPS. It is preferable that the optical axes of the emitting unit LPS and the light receiving unit RPS are orthogonal to the rotation axis RO of the mirror unit MU.

The box-shaped housing CS fixed to a rigid wall WL or the like has an upper wall CSa, a lower wall CSb facing the upper wall CSa, and a side wall CSc connecting the upper wall CSa and the lower wall CSb. Have. An opening CSd is formed in a part of the side wall CSc, and a transparent plate TR is attached to the opening CSd.

The mirror unit MU has a shape in which two quadrangular pyramids are joined in opposite directions and integrated, that is, four pairs (but not limited to four pairs) of mirror surfaces M1 and M2 tilted in a pair facing direction. ) Have. The mirror surfaces M1 and M2 are preferably formed by depositing a reflective film on the surface of a resin material (for example, PC (polycarbonate)) in the shape of a mirror unit.

The mirror unit MU is connected to the shaft MTa of the motor MT fixed to the housing CS and is rotationally driven. In the present embodiment, for example, in a state of being installed on the wall WL, the axis (rotation axis) of the axis MTa extends in the Z direction which is the vertical direction, and is formed by the X direction and the Y direction orthogonal to the Z direction. Although the XY plane is a horizontal plane, the axis of the axis MTa may be tilted with respect to the vertical direction.

Next, the object detection principle of the object monitoring device MD will be described. In FIG. 2, the divergent light emitted intermittently in a pulse shape from the semiconductor laser LD is converted into a parallel light flux by the collimating lens CL and incident on the first mirror surface M1 of the rotating mirror unit MU. After that, it is reflected by the first mirror surface M1 and further reflected by the second mirror surface M2, and then is scanned and cast as laser spot light having a vertically long rectangular cross section, for example, through the transparent plate TR and directed toward the external monitoring space. Be lit. The direction in which the emitted laser spot light is reflected by the object and returned as reflected light is called the light emitting / receiving direction. Laser spot light traveling in the same light emitting / receiving direction is detected by the same pixel.

FIG. 3 is a diagram showing a state in which the laser spot light SB (shown by hatching) emitted in response to the rotation of the mirror unit MU scans in the monitoring space of the object monitoring device MD. Here, in the combination of the pair of mirrors (first mirror surface M1 and second mirror surface M2) of the mirror unit MU, the four pairs have different crossing angles. The laser beam is sequentially reflected by the rotating first mirror surface M1 and the second mirror surface M2. First, the laser beam reflected by the first pair of first mirror surfaces M1 and the second mirror surface M2 horizontally moves from left to right in the uppermost region Ln1 of the monitoring space according to the rotation of the mirror unit MU. Is scanned. Next, the laser beam reflected by the second pair of the first mirror surface M1 and the second mirror surface M2 horizontally covers the second region Ln2 from the top of the monitoring space from the left in accordance with the rotation of the mirror unit MU. Scanned to the right. Next, the laser beam reflected by the third pair of the first mirror surface M1 and the second mirror surface M2 horizontally covers the third region Ln3 from the top of the monitoring space from the left in accordance with the rotation of the mirror unit MU. Scanned to the right. Next, the laser beam reflected by the 4th pair of the first mirror surface M1 and the second mirror surface horizontally moves from left to right in the lowermost region Ln4 of the monitoring space according to the rotation of the mirror unit MU. It is scanned. This completes one scan of the entire monitoring space that can be monitored by the object monitoring device MD. The images obtained by scanning the regions Ln1 to Ln4 are combined to obtain one frame FL. Then, after the mirror unit MU makes one rotation, the mirror unit MU returns to the first pair of the first mirror surface M1 and the second mirror surface M2 again, and thereafter, scanning from the uppermost region Ln1 of the monitoring space to the lowermost region Ln4. Is repeated to obtain the next frame FL.

In FIG. 2, a part of the laser beam reflected by hitting the object among the light beams scanned and projected is transmitted through the transparent plate TR again and incident on the second mirror surface M2 of the mirror unit MU in the housing CS. Here, it is reflected, further reflected by the first mirror surface M1, collected by the lens LS, and detected pixel by pixel on the light receiving surface of the photodiode PD. Further, the processing circuit 21 (described later) of the control unit 20 obtains the distance information according to the time difference between the emission timing of the semiconductor laser LD and the light receiving timing of the photodiode PD. As a result, the object can be detected in the entire area in the monitoring space, and a frame FL (see FIG. 3) as a distance image having distance information for each pixel can be obtained. Such a distance image can be transmitted and displayed on a distant monitor via a network (not shown) or the like, or can be stored in a memory in the control unit 20. Further, the distance image obtained as described later may be stored in the non-volatile memory 30 as background image data.

Next, an algorithm for detecting an object to be monitored by the object monitoring device MD using the background subtraction method will be described. FIG. 4 is a diagram showing a state in which the monitoring space is viewed from the side. In the background subtraction method adopted in this embodiment, a background image (also referred to as a reference image) generated and saved in advance is used. Specifically, as a pre-preparation (pre-processing) for monitoring, as shown in FIG. 4A, the laser spot light SB is scanned from the object monitoring device MD in the absence of moving objects such as humans and animals. .. As a result, a background image can be obtained based on the reflected light R1 obtained from the background object BG. The details of the background image generation method will be described later.

During actual monitoring, as shown in FIG. 4B, when an object OBJ (monitoring object) such as an intruder appears in front of the background object BG, the reflected light R2 from the object OBJ is newly generated. Occurs. The processing circuit 21 compares the background image of FIG. 4 (a) with the distance image of FIG. 4 (b), and when a difference occurs, calls attention to the fact that some object has appeared in the surveillance space. Can be done. Further, when the object OBJ is moving, its position changes in the frame obtained by repeating the scanning, so that the processing circuit 21 tracks the object OBJ and obtains the moving direction and the speed (performs moving object detection). Can be done.

(Control unit 20)
As shown in FIG. 1, the control unit 20 includes an internal memory 22 composed of a processing circuit 21, a ROM (Read Only Memory), and a RAM (Random Access Memory). The processing circuit 21 is composed of a CPU (Central Processing Unit), and executes various processes by executing a program stored in the ROM. The processing circuit 21 also functions as a distance image generation unit 211 and a determination unit 212. The control unit 20 may be arranged in the housing CS together with the non-volatile memory 30, the alarm unit 40, and the input / output unit 50 as an embedded system.

The light emitting / receiving unit 10 outputs a light receiving signal of each pixel obtained by scanning the monitoring space of the object monitoring device MD with the laser spot light SB as described above. Based on this received signal, the distance image generation unit 211 generates distance image data (distance map) composed of a plurality of pixels showing the distribution of distance values to an object in the monitoring space.

The determination unit 212 recognizes the monitored object by comparing the "background data" with the distance image data in the monitoring space. Specifically, the background subtraction method is used to extract the foreground data by comparing the background data with the distance image data at the present time. Then, the pixels (pixel group) of the extracted foreground data are divided into clusters according to, for example, the distance value of the pixels. Then, the size of each cluster is calculated. For example, the vertical dimension, the horizontal dimension, the total area, and the like are calculated. The "size" referred to here is an actual size, and is different from the apparent size (angle of view, that is, the spread of pixels), and a mass of pixel groups is determined according to the distance to the object. For example, the determination unit 212 determines whether or not the calculated size is equal to or less than a predetermined size threshold value for identifying the monitored object to be extracted. The size threshold can be arbitrarily set depending on the monitoring location, the monitoring target, and the like. If a person is to be tracked and monitored, the minimum value of the size of a normal person may be used as the size threshold value for clustering. On the contrary, if all objects are to be tracked, the size threshold value may be a smaller value, and if the object is limited to a large object such as a vehicle, the size threshold value may be a larger value.

The "background data" used at this time is stored in the internal memory 22 (RAM area). The "background data" stored in the internal memory 22 is the "background data" stored in advance in the non-volatile memory 30, or a distance image corresponding to one or a plurality of frame FLs generated by the light emitting / receiving unit 10. It is "background data" generated based on the data. The former "background data" stored in the non-volatile memory 30 in advance will be described later.

As the generation method for the "background data" generated based on the latter distance image data, a known kind of method can be adopted. For example, as a first method, distance image data obtained by scanning a monitoring space in which there are no obstacles or moving objects (moving objects), that is, in which only a background object BG exists, based on a user's instruction. Is used as it is. Alternatively, as a second method, the minimum value among the distance values of each pixel obtained by the plurality of frame FLs is set as the maximum distance value of the pixel, and the composite distance image data generated based on the maximum distance value is set to ". Used as "background data". By doing so, it is possible to prevent erroneous recognition by (1) miscellaneous pixels, (2) edge pixels, and (3) dark-colored pixels. With this (1) miscellaneous pixels, for example, the surface of the object (background object) is uneven or the color changes locally, so that the reflection conditions are not stable and the distance value varies relatively. It is a pixel. An example of an object is a tree. (2) Edge pixels are, when scanning the edge of an object with another object behind it, depending on whether it is reflected by the edge or not, depending on the object on the front side and the back side. It is a pixel in which a distribution of two peaks occurs in a distance value in a plurality of frame FLs. (3) The dark-colored pixel is a case where the amount of reflected light is insufficient and cannot be detected depending on the irradiation condition when the laser spot light SB is scanned against an object on a black wall surface. In this case, the pixel is treated as an unmeasurable point, and the distance value becomes unclear. While the object monitoring device MD is continuously operating, the "background data" generated by the second method is sequentially stored and updated in the internal memory 22 (RAM area), for example, every several tens of seconds to several minutes. The updated "background data" is stored in the non-volatile memory 30 at each time interval, that is, every time a predetermined period Tx (for example, several tens of minutes to several hours) described later elapses. The process of saving in the non-volatile memory 30 will be described later. The background data is stored in the RAM area of the internal memory 22, and disappears when the power of the object monitoring device MD is turned off.

The determination unit 212 transmits a control signal for controlling the operation of the light emitting / receiving unit 10 to the light emitting / receiving unit 10. Further, the determination unit 212 transmits a warning signal to the alarm unit 40 when an intruder is detected in the monitoring space or when the background data needs to be reacquired as described later.

The non-volatile memory 30 retains the data stored in the memory area even after the power of the object monitoring device MD is turned off. In the present embodiment, background data is stored, and this data is retained even while the power is turned off. As the non-volatile memory 30, for example, a flash memory can be applied. For example, this flash memory (also referred to as a flash ROM) is divided in units of 64 KB per sector, and data deletion processing is performed in units of one sector, and then writing processing is performed. In the present embodiment, as shown in FIG. 1, two areas A and B are fixedly assigned as areas for storing background data. The size of each area corresponds to the size of the background data, that is, the amount of data in one frame FL. For example, one frame FL has a distance data of 2 bytes for one pixel, a size of 24 pixels in length and 1000 pixels in width, and the amount of data of one background data is about 48 kB. Therefore, one sector (64 kB) is allocated to each of the area A and the area B.

In the present embodiment, as described above, the background data is stored in the flash memory every Tx for a predetermined period. This predetermined period Tx is set in consideration of the durability of the device. For example, if the maximum number of rewrites guaranteed by the flash memory is 100,000 times and the life (warranty period) of the object monitoring device MD is 10 years, the predetermined period Tx is 10 years x 365 days x 24 hours ÷ 100,000 times. = 0.876 hours, or longer. That is, in the object monitoring device MD that operates continuously for 10 years, even if the background data is stored in a specific area of the flash memory every period longer than 0.876 hours, the flash memory is used within the guaranteed number of times. ..

The alarm unit 40 issues a warning signal to the user in response to the warning signal received from the determination unit 212 of the control unit 20. For example, the alarm unit 40 is provided with an LED and / or a speaker, and warns the user that an intruder (intruder) has been detected or reacquires background data by lighting the LED or sounding an alarm. Notice.

The input / output unit 50 is a user interface or a network interface. The input / output unit 50 includes, for example, a display, a keyboard, buttons, and the like. The input / output unit 50 displays various information such as status information of the object monitoring device MD to the user, and receives an instruction to reacquire the background data from the user. The alarm unit 40 may be omitted, and a warning prompting reacquisition or a warning indicating the presence of an intruder may be displayed on the display of the input / output unit 50. Further, the input / output unit 50 is provided with a network interface function, and the user can use it through wired communication (for example, Ethernet (registered trademark), USB (Universal Serial Bus)) or wireless communication (for example, Bluetooth (registered trademark), IEEE802.11). It may be configured to communicate with a terminal such as a PC (personal computer) to be used, and these alarm information may be transmitted to this PC.

(Control method of object monitoring device MD)
Hereinafter, the control method in the object monitoring device MD will be described with reference to the flowcharts of FIGS. 5 and 6. FIG. 5 is a background data comparison process performed by the control unit 20 (determination unit 212) of the object monitoring device MD when the power is turned on (when the power is turned on), and FIG. 6 is a monitoring space performed following FIG. It is a monitoring process of. As described below, in the comparison process, it is determined whether or not the installation conditions have been changed, and in the monitoring process, the background data is updated and saved (registered) in the non-volatile memory 30.

(Comparison processing of background data)
(Step S101)
First, the power of the object monitoring device MD is turned on. This power-on occurs when the user presses the hard switch provided in the input / output unit 50, or when the power supply is restarted when the power failure is restored for some reason. At this point, the background data is not stored (has disappeared) in the internal memory 22.

(Step S102)
The control unit 20 transmits a control signal to the light emitting / receiving unit 10 to start scanning the monitoring space by the light receiving / receiving unit 10 with the laser spot light SB.

(Step S103)
The control unit 20 determines whether or not the non-volatile memory 30 has background data. If there is no background data in the non-volatile memory 30, the process proceeds to step S104, and if it exists, the process proceeds to step S111.

(Step S104)
In this state, the object monitoring device MD corresponds to the first use of the device. The distance image generation unit 211 generates distance image data based on the light receiving signal obtained by scanning the light emitting / receiving unit 10. At this time, it is preferable that only the background object BG exists in the monitoring space.

(Step S105)
The control unit 20 stores (registers) the distance image data generated in step S104 as background data in the non-volatile memory 30 as it is. Alternatively, for the first few tens of seconds, background data is generated based on the distance image data of a plurality of frame FLs by the above-mentioned second method without monitoring the intruder, and the generated background data is stored in the non-volatile memory. It may be stored in 30. After that, the process of FIG. 5 is completed, and the process proceeds to step S201 of FIG.

(Step S111)
Here, the control unit 20 reads out the background data stored in the non-volatile memory 30. At this time, if the background data is saved in the areas A and B (see FIG. 1) of the non-volatile memory 30, the time stamp (update date and time) is new, that is, the last saved background data is read out. It is saved in the internal memory 22.

(Step S112)
The distance image generation unit 211 generates current distance image data from the light receiving signal of the light emitting / receiving unit 10.

(Step S113)
The determination unit 212 extracts the foreground data by the background subtraction method using the background data read into the internal memory 22 in step S111 and the distance image data generated in step S112, and recognizes the object. The recognition of this object is determined by using the clustering process described above. Specifically, the pixels (pixel group) of the foreground data extracted as the foreground data are divided into clusters. If the clustered pixel group is larger than a predetermined size, it is recognized as an object.

(Step S114)
The determination unit 212 determines whether or not the size of the recognized object, that is, the difference between the distance image data and the background data is equal to or less than a predetermined value. If it is equal to or less than a predetermined value (YES), the process of FIG. 5 is terminated, and the process proceeds to step S201 of FIG. In this case, since the background data stored in the non-volatile memory 30 can be used, in the subsequent processing, the object monitoring process is performed using the background data read into the internal memory 22. On the other hand, if it exceeds the predetermined value (NO), the process proceeds to step S115.

Here, the determination as to whether or not the value is equal to or less than the predetermined value in step S114 is determined by, for example, whether or not the size of the object recognized in step S113 is equal to or less than the predetermined value. The "size" referred to here is preferably determined by the actual dimensions as described above. That is, the size of the pixel group block is determined by considering the distance to the object, not the apparent size (angle of view, that is, the spread of pixels). As the predetermined value, for example, if the monitoring space monitors an intruder for a human being, the predetermined value is set to a large size so as not to include a normal human being.

(Step S115)
The determination unit 212 determines that the installation conditions of the light receiving / receiving unit 10, that is, the object monitoring device MD have been changed, and notifies the user of a warning. Here, the "change of installation conditions" is a case where the monitoring space is changed by relocating the object monitoring device MD (light emitting / receiving unit 10) or changing the direction of the light receiving / receiving unit 10.

In this warning, the notification determination unit sends a warning signal to the alarm unit 40 to warn the user to reacquire the background data. For example, the alarm unit 40 informs the user that the background data needs to be reacquired by blinking the LED or the like. As a warning for prompting the reacquisition, characters and marks may be displayed on the display of the PC by transmitting the warning to the PC used by the user through the input / output unit 50.

(Step S116)
When the user receives a reacquisition instruction from the user by pressing a button of the input / output unit 50 or the like, the determination unit 212 proceeds with the process.

(Step S117)
Here, the determination unit 212 generates background data based on one or a plurality of distance image data newly generated by the distance image generation unit 211, and stores the background data in the internal memory 22. Then, the reacquired background data is also stored (registered) in the non-volatile memory 30. Then, the process of FIG. 5 is completed, the process proceeds to step S201 of FIG. 6, and the monitoring process is performed using the reacquired background data existing in the internal memory 22 as shown below.

(Intrusion monitoring process and background data registration)
(Step S201)
In step S201 of FIG. 6, the distance image generation unit 211 newly generates distance image data based on the light receiving signal obtained by scanning the light emitting / receiving unit 10.

(Step S202)
The determination unit 212 extracts the foreground data by the background subtraction method using the background data stored in the internal memory 22 and the distance image data generated in step S201, and detects an object. The detection of this object is determined by using the clustering process described above. Specifically, the pixels (pixel group) of the foreground data extracted as the foreground data are divided into clusters. If the clustered pixel group is larger than a predetermined size according to the object to be monitored, it is detected as an object.

(Step S203)
When the determination unit 212 detects an object of a size corresponding to the monitored object in step S203, it determines that there is an intruder (YES), and proceeds to the process in step S204. On the other hand, if it is determined that there is no intruder (NO), the process proceeds to step S205.

(Step S204)
The determination unit 212 determines that there is an intruder (intruder) in the monitoring space, and transmits a warning signal to the alarm unit 40. The alarm unit 40 issues an alarm to the user based on the received warning signal.

(Step S205)
When there is no intruder in the monitoring space, the background data stored in the internal memory 22 is updated using the distance image data obtained in step S201. This background data update may be replaced with the latest distance image data, may be averaged with the immediately preceding background data, or may be added after being multiplied by a certain weighting coefficient.

(Step S206)
If the predetermined period Tx has elapsed from the time when the background data was saved in the non-volatile memory 30 immediately before or the time when the power was turned on (YES), the process proceeds to step S207. On the other hand, if Tx has not elapsed for a predetermined period (NO), the process is terminated (end), and thereafter, the process from step S201 is repeated. This predetermined period Tx is several tens of minutes to several hours, and is a period corresponding to the warranty period of the object monitoring device MD and the maximum number of rewrites guaranteed by the flash memory as described above.

(Step S207)
The background data stored in the internal memory 22 is stored (updated) in the non-volatile memory 30. At this time, the non-volatile memory 30 is alternately stored in the areas A and B. Specifically, when the past background data is already saved in both areas of the non-volatile memory 30, it is saved in the internal memory 22 at present in the area where the background data with the older time stamp is saved. Overwrite (update) the background data that has been created. After that, the process ends. If the monitoring of the intruder into the monitoring space is to be continued, the processes after step S201 are repeated.

As described above, in the present embodiment, even when the power of the object monitoring device is unexpectedly turned off, as shown in FIG. 5, the background data is read from the non-volatile memory 30 when the power is turned on thereafter. , The read background data is compared with the distance image data generated by the distance image generation unit 211, and the comparison result is notified. By doing so, it is possible to prevent erroneous detection of an object and omission of detection. In particular, if the difference between the background data and the distance image data at this time exceeds a predetermined value, a warning is notified to the user and the background data is urged to be reacquired. It is possible to prevent the monitoring process that causes omission of detection from being performed. If the difference is less than or equal to the predetermined value, the background data can be used as it is, so no special operation is required and the object is continuously monitored in the monitoring space without bothering the user. Can be done.

Further, as shown in FIG. 6, when the continuous monitoring process is performed, the background data is stored in the non-volatile memory 30 every time Tx elapses for a predetermined period, so that the non-volatile memory 30 has some new background data. Can continue to be saved. Further, by appropriately setting the predetermined period Tx according to the warranty period of the object monitoring device MD and the maximum number of rewrites guaranteed by the flash memory (nonvolatile memory 30), the background data stored in the non-volatile memory 30 may not be read properly. It is possible to prevent the trouble of the above from occurring.

The configuration of the object monitoring device described above is the main configuration described in explaining the features of the above-described embodiment, and is not limited to the above-mentioned configuration and can be variously modified within the scope of the claims. .. Further, the configuration provided in the general object monitoring device is not excluded.

For example, in the processing of steps S113 and S114 of FIG. 5, the installation condition of the light emitting / receiving unit is changed depending on whether or not the size of the recognized object is equal to or less than a predetermined value, and whether or not the background data needs to be reacquired. Judged. However, the present invention is not limited to this, and it is determined whether or not the installation conditions have been changed according to the number of objects in which the cluster of pixel groups after the clustering process has a certain size or more, or the total amount (total area) of these objects. May be good. Furthermore, in the processing of steps S113 and S114, the determination may be made in consideration of the case where the distance value is negative, that is, the object exists farther than the background data. Generally, in the background subtraction method, when a negative value is obtained, the detection result is ignored in the object detection algorithm in order to suppress false detection, but the negative distance value does not have to be ignored here. .. For example, many pixels show a negative distance value, and even when a mass obtained by clustering the negative pixel values has a size of a certain size or more, it is determined that the value exceeds a predetermined value.

The means and methods for performing various processes in the image forming apparatus according to the above-described embodiment can be realized by either a dedicated hardware circuit or a programmed computer. The program may be provided by a computer-readable recording medium such as a USB memory or a DVD (Digital Versail Disc) -ROM, or may be provided online via a network such as the Internet. In this case, the program recorded on the computer-readable recording medium is usually transferred and stored in a storage unit such as a hard disk. Further, the above program may be provided as a single application software, or may be incorporated into the software of the device as a function of the object monitoring device.

MD Object monitoring device 10 MU mirror unit MT motor PD photodiode LPS output unit RPS light receiving unit TR transparent plate CS housing 20 Control unit 21 Processing circuit 211 Distance image generator 212 Judgment unit 22 Internal memory 30 Non-volatile memory 40 Information part 50 Input / output part BG Background object FL frame WL wall OBJ Object (intruder)

Claims (14)

A light emitting / receiving unit provided with an emitting unit that emits a light beam into the monitoring space and a light receiving unit that receives a light beam reflected from an object in the monitoring space.
A distance image generation unit that obtains the distance to an object based on the emission and reception timings of the light emitting and receiving unit and generates distance image data indicating the distribution of distance values in the monitoring space.
A non-volatile memory that stores the background data generated based on the acquired distance image data,
A determination unit that recognizes an object in the monitoring space by comparing the background data with the distance image data in the monitoring space generated by the distance image generation unit during monitoring is provided.
The determination unit reads the background data from the non-volatile memory when the power is turned on, compares the read background data with the distance image data generated by the distance image generation unit, and notifies the comparison result .
The non-volatile memory has at least two areas, and the background data is alternately stored in two of the plurality of areas.
The determination unit is an object monitoring device that compares the background data stored in the two areas of the non-volatile memory with the distance image data by using the background data having the newer update date and time. The determination unit reads the background data from the non-volatile memory when the power is turned on, compares the read background data with the distance image data generated by the distance image generation unit, and if the difference between the two is equal to or less than a predetermined value. Using the background data read from the non-volatile memory, the object in the monitoring space is recognized.
The object monitoring device according to claim 1, wherein when the difference exceeds the predetermined value, it is determined that the installation conditions of the object monitoring device have been changed, and a warning is issued as the notification. The object monitoring device according to claim 2, wherein the determination unit warns the user to reacquire the background data as the warning. In response to receiving an instruction from the user to reacquire the background data
The determination unit generates new background data based on the distance image data generated by the distance image generation unit at the present time obtained from the monitoring space, and stores the generated new background data in the non-volatile memory. The object monitoring device according to claim 2 or 3. The determination unit extracts a pixel group according to the distance to the object as a comparison between the background data read from the non-volatile memory and the distance image data generated by the distance image generation unit, and the extracted pixel group The object monitoring device according to any one of claims 2 to 4, wherein it is determined that the installation conditions of the object monitoring device have been changed when the size exceeds the predetermined value. The object monitoring device according to any one of claims 1 to 5, wherein the non-volatile memory is a flash memory. Prior Symbol judging unit, during operation, generates a new background data on the basis of the generated range image data, at a predetermined time interval, a new piece of the background generated in two of the regions among the plurality of regions Save data alternately ,
The object monitoring device according to claim 6. The time interval for storing the background data in one of the areas is set to be longer than the time obtained by dividing the product warranty period of the object monitoring device by the maximum number of rewrites guaranteed by the flash memory. , The object monitoring device according to claim 7. A control method in an object monitoring device including a distance image generator that generates distance image data in a surveillance space and a non-volatile memory that stores background data generated based on distance image data acquired in the past.
The step (a) of reading the background data from the non-volatile memory when the power is turned on,
In step (b), when the power is turned on, a light flux is emitted into the monitoring space and the light flux reflected from the object in the monitoring space is received.
The distance image generation unit obtains the distance to the object based on the emission and reception timings of the step (b), and the distance image data in the monitoring space is generated in the step (c).
A step (d) of comparing the background data read in the step (a) with the distance image data generated in the step (c) and notifying the comparison result.
Only including,
The non-volatile memory has at least two areas, and the background data is alternately stored in two of the plurality of areas.
In the step (a), the control method of reading out the background data whose update date and time is newer than the background data stored in the two areas of the non-volatile memory. As a result of comparison in step (d), when the difference between the background data and the distance image data is equal to or less than a predetermined value, the background data read from the non-volatile memory is used to recognize an object in the monitoring space. Step (e) to be performed and
The control method according to claim 9 , further comprising a step (f) of determining that the installation conditions of the object monitoring device have been changed and issuing a warning as the notification when the difference exceeds the predetermined value. .. The control method according to claim 10 , wherein in step (f), as the warning, a warning is given to the user to reacquire the background data. Step (g) of receiving an instruction to reacquire the background data from the user, and
Step (h) of generating new background data based on the distance image data generated by the distance image generation unit at the present time obtained from the monitoring space, and storing the generated new background data in the non-volatile memory. When,
10. The control method according to claim 10 or 11. In the step (d), as a comparison between the background data read from the non-volatile memory and the distance image data generated by the distance image generation unit, a pixel group is extracted according to the distance to the object, and the extracted pixels. The control method according to any one of claims 10 to 12 , wherein when the size of the group exceeds the predetermined value, it is determined that the installation conditions of the object monitoring device have been changed. A control program for causing a computer to execute the control method according to any one of claims 9 to 13.

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