JP2008250772A - Mobile object tracking device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mobile object tracking device, capable of accurately tracking a mobile object. <P>SOLUTION: The mobile object tracking device 1 adapted to track a single mobile object from an input image successively input thereto by use of a template includes an extraction part 30 which extracts a change area resulting from the mobile object from the input image; a template generation part 33 which generates a plurality of different templates from the change area; a storage part 20 which stores the mobile body in association with the plurality of templates; a matching means 42 which extracts a template candidate in which the template stored in the storage part 20 is similar to the input image; a determination means 43 which determines whether the template candidate corresponds to the change area extracted in the input image or not; and an update means which updates the template of the storage part 20 with the template candidate determined to correspond by the determination means 43. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a moving object tracking device, and more particularly to a moving object tracking device that can always accurately track a moving object.

  Conventionally, a moving object tracking device has been used. This type of device is used, for example, as a part of a monitoring device, and the monitoring device is installed in a bank automatic teller machine corner or an elevator mainly for the purpose of crime prevention. In this case, the objects to be tracked by the moving object tracking device are people who move within the tracking area.

  When the tracking area is, for example, an automatic teller machine corner, a plurality of people may move simultaneously in the area having a predetermined range. In the tracking area, a plurality of people may cross and overlap each other due to movement, and then the overlap may be resolved and separated and moved again.

  As described above, when the moving object tracking device is installed for the purpose of crime prevention, it is required to always keep track of the moving people correctly. Therefore, even when a plurality of people cross and overlap during movement, tracking must be performed correctly before and after the overlap.

  By the way, in the technical field of conventional image processing, template matching processing using luminance information or the like is known, and it has been attempted to apply this processing technology to tracking of a moving object. However, even with this processing technique, it is difficult to keep track of correctly when multiple people cross and overlap while moving. This is because, when a plurality of people overlap, the assumption that one moving area corresponds to one moving object is lost, and matching processing cannot be performed.

As a technique for solving this problem, for example, there is an object tracking method described in Patent Document 1.
Patent Document 1 stores feature amounts (color histograms) related to each moving object before the intersection, and when it is detected that the intersection has been resolved, the stored feature amount and the intersection resolution are stored. An object tracking method is disclosed that determines the correspondence between moving objects before and after an intersection by comparing feature amounts obtained for each moving object later.

JP 2002-342762 A

  However, in the method described in Patent Document 1, during the intersection of the moving object, the tracking process for the moving object is not performed, and when it is determined that the intersection is resolved, the correspondence relationship of the moving object before and after the intersection is first determined. decide. Therefore, if the colors and patterns of moving objects (for example, clothes in the case of humans) are approximate, no matter how much the pre-intersection feature (color histogram) is saved, either It can be difficult to determine if you are.

  Therefore, an object of the present invention is to provide a moving object tracking device capable of accurately tracking a moving object.

  In order to solve the above-described problem, a moving object tracking device according to the present invention is a moving object tracking device that uses a template to track the same moving object from sequentially input images, and is caused by the moving object from the input image. An extraction unit that extracts a change area to be generated, a template generation unit that generates a plurality of different templates from the change area, a storage unit that associates and stores the moving object and the plurality of templates, and stores the storage unit in the storage unit Matching means for extracting similar template candidates between the template and the input image, determination means for determining whether the template candidate corresponds to a change area extracted in the input image, Updating means for updating the template in the storage unit with the template candidate determined to be supported by the determination means. And said that you are.

  In the present invention, it is preferable that the template generation unit generates a template so that at least one of the plurality of templates has at least a part of a contour of the change region.

  In the present invention, the storage unit further stores position information for each template, and the position of the template candidate in the input image is used as the position information for each template stored in the storage unit. Preferably, the matching means extracts the template candidates within a range predicted by the prediction means, and the update means also updates the position information of the updated template. .

  In the present invention, it is preferable that the matching unit obtains a matching score by examining matching between the template and the input image, and sets a portion of the input image whose matching score is equal to or greater than a predetermined threshold as a template candidate. .

  In the present invention, the determination means may correspond to the change region when all the template candidates of the plurality of templates corresponding to the same moving object correspond to one change region. If a part of a plurality of template candidates corresponding to the same moving object corresponds to one change area, the template candidate corresponds to the change area based on the sum of the weights of the template candidates. It is preferable to determine whether or not to follow.

  In the present invention, the input image is preferably an image installed on the ceiling and photographed in the downward direction.

  According to the moving object tracking device of the present invention, a moving object can be accurately tracked. In addition, the present invention also enables each moving object after crossing to be moved to the moving object before the crossing by continuously tracking the moving objects in the crossing even when a plurality of moving objects cross and overlap each other due to the movement. Can be tracked in an accurate manner.

  Hereinafter, a moving object tracking device of the present invention will be described based on a preferred embodiment thereof with reference to FIGS.

  FIG. 1 is a functional block diagram of a moving object tracking device 1 (hereinafter also simply referred to as the present device 1) according to an embodiment of the present invention. The device 1 is a device that tracks a moving object captured in an input image. The apparatus 1 can be used, for example, as a part of a monitoring apparatus to track a person who moves in a monitoring area and detect an abnormality from the movement pattern.

As shown in FIG. 1, the apparatus 1 includes an input unit 60 in which images are sequentially input from the outside, an extraction unit 30 that extracts a change region caused by a moving object from the input image that has been input, A storage unit 20 that stores the position of the change area, a tracking unit 40 that tracks a moving object, and a control unit 10 that controls the processing of these components are provided.
In the apparatus 1, the extraction unit 30 generates and associates a plurality of templates with the moving object using the change area, and the tracking unit 40 tracks the same moving object using the plurality of templates.
The apparatus 1 further includes an update unit 50 that updates a plurality of templates, and an output unit 40 that outputs the tracked results to the outside. These processes are controlled by the control unit 10. In the present apparatus 1, digital processing is used as image processing in the extraction unit 30 and the tracking unit 40.

  The hardware configuration of the apparatus 1 can be configured by, for example, a central processing unit (CPU), a numerical arithmetic processor, a semiconductor memory such as a ROM or a RAM, a magnetic recording medium or an optical recording medium, an input / output interface, and the like.

  Hereinafter, the device 1 will be described in more detail.

First, the input unit 60 will be described below.
The input unit 60 is an input interface and mainly has a function of inputting an image of a moving object tracked by the apparatus 1 from the outside. The input image is stored in the storage unit 20. As shown in FIG. 1, an external camera 61 is connected to the input unit 60 of the apparatus 1. For example, when the camera 61 outputs image data as an analog signal, the input unit 60 performs A / D conversion so that the analog signal can be converted into a digital signal and output to each component of the apparatus 1. It preferably has a function.

The camera 61 is an imaging unit that captures an image within the field of view. When a moving object such as a person enters the field of view, the moving object is imaged together with the background image. The camera 61 is preferably installed, for example, downward from the ceiling of the room from the viewpoint of preventing one moving object in the field of view from being hidden behind other moving objects and completely disappearing.
In the present apparatus 1, an image of one frame is captured at a predetermined interval by the camera 61, and this image is output to the input unit 60.

  A known camera 61 can be used, for example, a camera provided with a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS). Further, the resolution of the camera 61 can be selected according to a specific application such as a tracking target, and for example, the NTSC standard, the SDTV standard, or the HDTV standard can be used. Moreover, as a wavelength band used for image capturing, a visible light wavelength or an infrared wavelength is preferably selected according to a specific application such as a tracking target.

  The input unit 60 may also have input means such as a keyboard and a mouse. Using these input means, new information can be input to the storage unit 20 to change the stored information.

Next, the storage unit 20 will be described below.
As illustrated in FIG. 1, the storage unit 20 includes a background image storage area 21 and a tracking information storage area 22. The storage unit 20 stores programs used by the control unit 10, various setting files, parameters, and the like. As this program, for example, there are programs used for extraction processing, tracking processing, and update processing. The various setting files or parameters include, for example, a threshold value used in each process or a flag indicating a process state. The storage unit 20 has a work area when each program is executed.

  The background image storage area 21 stores a background image for extracting a moving object from the image. This background image is an image in a state where there is no moving object in the field of view of the camera 61. The background image is updated according to a predetermined standard by background image update means 51 described later.

  In the tracking information storage area 22, image information output from the input unit 60 at the current and past times is stored for each frame. Specifically, the tracking information storage area 22 stores information on a moving object at each time point, a change area extracted from the moving object, a template associated with the change area, and the like.

  The tracking information storage area 22 manages the position information of the template predicted by the prediction means 41 of the tracking unit 40, which will be described later, the matching score obtained by the matching means 42, the moving object, the change area, and the template. Information such as a number assigned for the purpose and the crossing state of the moving object is also stored.

Next, the extraction unit 30 will be described below.
The extraction unit 30 extracts a change area caused by the moving object from the input image, and uses the change area to generate and associate a plurality of templates with the moving object. As illustrated in FIG. 1, the extraction unit 30 includes a difference processing unit 31, a labeling unit 32, and a template generation unit 33.

The difference processing means 31 creates a difference image from the input image and the background image, and further creates a binary image from the difference image.
Specifically, in the apparatus 1, the difference processing unit 31 first obtains, for each pixel, an absolute value of a difference between the input image acquired by the camera 61 and the background image stored in the background image storage area 21. Then, a difference image is created, and the difference image is then binarized according to a binarization threshold value stored in the storage unit 20. In this way, the difference processing means 31 extracts a pixel having a change of a predetermined value or more from the input image as a pixel having the attribute of the moving object, and creates a binary image.

The labeling means 32 associates the pixels as one area according to a predetermined standard with respect to the pixels having the attribute of the moving object in the binary image generated by the difference processing means 31, and extracts a change area. When there are a plurality of moving objects separated in the input image, the labeling means 32 extracts a change area corresponding to each moving object. The above criteria are incorporated into the program.
Examples of the reference include, for example, connecting a total of 4 pixels in the vertical and horizontal directions to the center pixel, or connecting a total of 8 pixels including pixels in an oblique direction.

  Specifically, in the present apparatus 1, the labeling unit 32 first performs noise removal processing on the binary image created by the difference processing unit 31 using a known technique such as a median filter, a majority decision filter, or a weighted average filter. Go and remove the noise.

  Next, the labeling unit 32 performs a labeling process on the binary image from which noise has been removed according to the above-described criterion, associates pixels as one region, and extracts a pixel connection region. By this labeling process, adjacent pixels are connected to a certain center pixel in accordance with the above-described standard.

  Next, when there are a plurality of extracted pixel connection regions, the labeling unit 32 determines whether the plurality of pixel connection regions are in a predetermined positional relationship, and a plurality of pixels satisfying this positional relationship. The connected areas are combined to create a new pixel connected area.

  As a criterion for determining the positional relationship, for example, regarding the relationship between a certain pixel connection region and another adjacent pixel connection region, the size of each of the two pixel connection regions is the actual moving object assumed from the imaging conditions. For example, the distance is smaller than the size, or the distance between the two pixel connection regions is equal to or less than a predetermined distance.

  Thus, one pixel connection area extracted by the labeling means 32 basically corresponds to one moving object, and this pixel connection area is referred to as a change area in this specification. The change area is assigned a number for individual management. In the change area to which the number is assigned, the image information is stored in the tracking information storage area 22 together with the position information in the image. As position information in the image, for example, coordinates in the image of the center of gravity of the change area can be used.

  The binary image is created for each input image captured by the camera 61, and a change area is extracted and stored for each moving image in the binary image. Therefore, the tracking information storage area 22 stores the position information of the change area in the image for each of the current time and the past time in a time series. In addition, a number for individually managing the moving object associated with each change area is assigned, and the number of the moving object is stored in the tracking information storage area 22 together with the information of the corresponding change area.

  It should be noted that the labeling means 32 checks the characteristics of the shape such as the size or aspect ratio of the change area, and if it is determined that the extracted change area is not suitable as the moving object to be tracked by the apparatus 1, the tracking means 32 It is not necessary to exclude it from the target and store it in the tracking information storage area 22. Examples of such a moving object include a shadow caused by sunlight, or a small animal such as a mouse.

When a new moving object appears in the input image, the template generation unit 33 generates and associates a plurality of templates with the moving object using the change area. That is, when a moving object that does not exist in the image acquired immediately before the input image appears, a plurality of templates are generated for the moving object.
The position and size of the moving object in the input image are stored in the tracking information storage area 22 as the above-described change area information. This information is used when generating the template.

  In this way, by generating and associating a plurality of templates with one moving object, even if one template fails to track the moving object, the remaining object is used to identify the moving object. It will be possible to continue tracking.

  The extraction unit 30 can generate a template so that at least one of the plurality of templates has at least a part of the outline of the change area, even when a plurality of moving objects intersect and overlap each other. It is preferable from the viewpoint that a part of the moving object located behind 61 is included in the template.

  Each of the plurality of generated templates is assigned a number for managing the template associated with the moving object, and the image information is stored in the tracking information storage area 22 together with the position information of the template.

  The above-described template generation method can be appropriately designed according to the specific application of the apparatus 1. For example, when the moving object is a person, the following method can be used. it can.

(1) Method for Generating Template Geometrically When a person is standing and walking in the field of view of the camera 61, the shape of the person is elongated as shown in FIGS. Therefore, the change area extracted from the person who stands and walks has an elongated shape. Therefore, there is a method in which a main axis that is the longitudinal axis of the change region is obtained, and a template is generated geometrically taking into consideration symmetry and the like.

Specifically, as shown in FIG. 2A, the templates may be generated and arranged so that the centers of the templates are arranged at equal intervals on the main axis. Also, as shown in FIG. 2B, one template is generated and arranged so as to cover the outline of the moving object, and the remaining two templates are arranged inside the template so that their centers are aligned on the main axis. May be generated and arranged. Also, as shown in FIG. 2 (c), two templates are generated and arranged so that the center of the template is located on the main axis so as to cover the head and legs of the person, and each shoulder part is further arranged. Two templates may be generated and arranged so as to be shifted from the main axis so as to cover them. As shown in FIG. 2D, a plurality of templates may be generated and arranged so as to cover the head, legs, and shoulders. Further, as shown in FIG. 2 (e), one template is generated and arranged so as to cover the outline of the moving object, and a plurality of templates as shown in FIG. 2 (c) are generated inside this template. May be arranged.
In any of the examples shown in FIGS. 2A to 2E, in any case, one template is generated and arranged so that the entire head is covered.

  The shape of the template is preferably set as appropriate according to the specific application of the apparatus 1. For example, in order to reduce the number of cameras to be installed, a fish-eye lens or a wide-angle lens with a wide field of view may be used as the camera 61. When such a lens is used, even if it is the same moving object, the shape changes greatly at different points in time when it is imaged. Therefore, it is easy to perform image processing by using a circular template with high symmetry in the image. From the viewpoint of Further, it may be generated by correcting the shape of the template according to the distortion aberration of the camera 61. On the other hand, if it can be assumed that the change in the shape of the moving object between the input images is small, it matches the shape of the moving object. It is preferable to select the shape of the template from the viewpoint of improving tracking accuracy.

Further, the dimensions of the template may be changed depending on the size of the moving object, or may be fixed without depending on the size. The number of templates is at least two or more, and the larger the number, the more accurately the tracking of the moving object, but the processing amount increases accordingly. The specific number of templates is preferably set as appropriate according to the application of the apparatus 1.
In general, when tracking a person, it is preferable from the viewpoint described above that the number of tracking templates to be generated is 2 to 8, particularly 3 to 5.
The above-described method for generating a template geometrically is simple and image processing is easy.

  A method for generating still another template will be described below. For the points that are not particularly explained, the explanation in detail regarding the above-described method for generating the template is appropriately applied.

(2) Method for Generating Template Using Characteristic Part of Moving Object Further, it is possible to generate a template so as to include the part by paying attention to the characteristic part of the moving object. For example, information such as texture or color can be used as a feature amount that serves as an index of a portion that differs between moving objects.

Specifically, an example in which a texture is used as a feature amount will be described below.
First, each of a plurality of moving objects is divided into a plurality of segments (segmentation) using a texture as a measure to generate a template.

  As a specific method for expressing the feature amount of the segment, for example, use of a conversion result using a density co-occurrence matrix, entropy, or Gabor conversion can be cited. Further, as the similarity between segments, the Euclidean distance between the feature vectors or the inner product can be used.

  Further, as a method of performing region division using texture as a measure, for example, clustering based on the k-average method can be used. Further, as disclosed in the following technical literature, a method based on a graph cut in which an image is represented by a graph and its cut is obtained may be used.

  M. Galun, E. Sharon, R. Basri, A. Brandt, Texture Segmentation by Multiscale Aggregation of Filter Responses and Shape Elements, Proceedings IEEE International Conference on Computer Vision, 716-723, Nice, France, 2003.

  An example of generating a template using a texture as a feature amount will be described using the example shown in FIG. As shown to Fig.3 (a), there exists the moving object M1, and it has the characteristic part from which the texture differs in the head, the trunk | drum, and the leg part, respectively. The moving object M1 has a characteristic texture different from that of the moving object M2 shown in FIG. 3C at the top of the head, and is vertically long at the center from the trunk to the leg. Has a characteristic texture.

  In this case, as a method of generating a plurality of templates on the moving object M1, as shown in FIG. 3B, the template M1-1 is generated and arranged so as to include the upper part of the head, and For example, the template M1-2 is generated and arranged so as to include the center portion, and the template M1-3 is generated and arranged so as to include the characteristic texture of the legs.

Further, if a color camera is used as the camera 61 and the input unit 60 corresponds to a color image signal, color information may be used as the feature amount instead of the texture.
In the above-described method for generating a template, attention is paid to a characteristic portion different from other moving objects for each piece of image information of a plurality of moving objects, so that high tracking accuracy of the moving objects can be expected.

(3) Method of generating a template so that the luminance dispersion in the template is large Also, the template may be generated so that the luminance dispersion in the template is large, that is, the template includes many luminance values. Good.
Specifically, by shifting the position of the center of the template on the main axis of the moving object and calculating the luminance dispersion inside the template, a plurality of templates are generated, and the generated templates are arranged in descending order of the value of the luminance dispersion. Line up. Then, a necessary number of templates may be selected in descending order of the luminance dispersion value and associated with the moving object.

  Further, as shown in FIG. 4, templates M1-1 and M1-2 may be generated and arranged so as to divide the moving object into a plurality of segments and straddle the plurality of segments using the brightness as a measure. .

The above-described method for generating a template so that the luminance dispersion in the template is large can easily perform image processing because the processing amount is small.
Further, when a template is generated by the above-described geometric method, the luminance dispersion in the template may be extremely small depending on the moving object. In such a case, the template has a single luminance (single color), and a problem that the matching portion cannot be uniquely specified in template tracking (called an opening problem) may occur. If a template is created using this method, such problems can be avoided and tracking can be performed stably.

  The method for generating the three templates described above may be used alone, or a plurality of methods may be used in combination.

Next, the tracking unit 40 will be described below.
As shown in FIG. 1, the tracking unit 40 includes a prediction unit 41, a matching unit 42, and a determination unit 43. The tracking unit 40 performs the tracking process of the moving object for each moving object stored in the tracking information storage area 22 using each template associated with the moving object.

  Hereinafter, each means of the tracking unit 40 will be described.

  The predicting means 41 predicts the position of the current template for each template from the position or speed at the past time. The current moving object is assumed to be located in the vicinity of the position of each template predicted by the prediction means 41.

  For all the templates associated with one moving object, the current template position is predicted by the prediction means 41 from the position or speed of each template at the past time. Further, the position of the template is predicted by the prediction means 41 for all moving objects that are considered to be present in the field of view of the camera 61.

  In the tracking information storage area 22, the position information of the template associated with a certain moving object is stored side by side in time series. Therefore, the movement distance between frames in the image of a certain template is obtained and the movement is performed. By dividing the distance by the imaging interval, the moving speed of the template in the image is obtained. This moving speed is obtained for each template. The obtained movement speed of the template is stored in the tracking information storage area 22.

As a quantity representing the position of the template, for example, the barycentric coordinates of the template can be used. As a prediction method used by the prediction means 41, for example, it is assumed that the moving object is performing a constant velocity motion or a constant acceleration motion, and the position and speed of the template at the past time point stored in the tracking information storage area 22 are assumed. Thus, there is a method for predicting the current template position in time series. Specifically, linear prediction or a Kalman filter generally used in time series analysis can be used.
The predicted position of the template is stored in the tracking information storage area 22 in association with the moving object.

Based on the predicted position of the template, the matching means 42 assumes that a moving object exists in a predetermined range in the vicinity of the current input image, and checks the matching between the template and the above range of the input image. A score is obtained, and a template candidate that has a maximum matching score and is equal to or greater than a predetermined threshold is searched for. It is determined that the moving object exists in a portion where the template candidate has the maximum matching score. The maximum matching score obtained in this way is stored in the tracking information storage area 22 for each template.
In the present embodiment, the position of the template is predicted by the prediction means 41. However, if there is a margin in the processing load of the computer, the prediction means 41 is omitted and a matching score is obtained for the entire image. May be.

  As a matching method used by the matching means 42, a known method can be used. For example, a pattern matching method or a histogram matching method can be used.

  In the case of using the pattern matching method, the template is shifted up and down, left and right or rotated within the search range set around the predicted position of the template, and the matching score is checked. This search range may be fixed, or may be changed dynamically according to the motion of the moving object. Further, an optimization method such as a hill climbing method may be used instead of the shift matching process.

  Instead of the pattern matching method, a histogram matching method using a histogram of template luminance (for example, luminance of each color when a color image is used) may be used. Since the histogram matching method uses a luminance histogram and is not directly affected by the shape of the moving object, the resistance to deformation of the moving object is improved.

  The matching means 42 sets a portion where the maximum matching score is equal to or greater than a predetermined threshold to the extent that it can be regarded as substantially the same as the template as a template candidate.

  Next, the determination unit 43 determines whether the template candidate partially or entirely overlaps with the current input image change area. Then, if the template candidate partially or entirely overlaps the change area of the input image, the template update unit 52 associates the template candidate and its position with the input image as a new template in the tracking information storage area 22. Remember. Further, the difference between the position of the template candidate from which the maximum matching score is obtained and the predicted position of the template is stored in the tracking information storage area 22 as a deviation from the predicted position.

On the other hand, as a result of examining matching with respect to a certain template, when the maximum matching score is less than the threshold value, it is determined by the determination unit 43 that the moving object is lost with respect to the template. In the present apparatus 1, even when it is determined that a moving object has been lost with respect to a certain template, the prediction unit 41 and the matching unit 42 use the template associated with the lost moving object. Processing continues for a predetermined period (eg, 30 seconds). When the determination unit 43 determines that the maximum matching score is equal to or greater than the threshold value, tracking of the moving object using the template is resumed. If a missing moving object is not found even after the predetermined period has elapsed, the tracking of the moving object is stopped and the information stored in the tracking information storage area 22 associated with the moving object is stored. It may be erased. As described above, even when a certain template loses sight of the moving object, the apparatus 1 can perform the tracking process of the moving object using the remaining template.
The threshold value used for the determination of the maximum matching score and the predetermined period used by the matching means 42 described above are stored in the storage unit 20.

  Also, if the current moving object moves out of the field of view of the camera 61, or if it is completely hidden behind other moving objects, any of the templates associated with this moving object Also for the result, the maximum matching score is less than the threshold value. In this way, even when a moving object is lost in all templates associated with a certain moving object, the matching means 42 performs the prediction of the position of the lost moving object and the investigation of matching in a predetermined manner. Continue over the period.

  The determination unit 43 checks the correspondence between the position of the template candidate and the position of the change area extracted from the current moving object, and performs an association process between the template and the change area according to a predetermined criterion.

  Examples of the reference include that the position of the center of gravity of the template is included in the change area, or that the template has an overlap of a predetermined ratio or more in the change area.

  For a moving object, if all of the templates associated with this moving object in the past are associated with one change area, the current position of this moving object has been tracked. become. That is, the change area extracted from the moving object is associated with a plurality of templates at past times. The result is stored in the tracking information storage area 22. Therefore, the moving object is in a state in which tracking is successfully performed by the apparatus 1 from the past time point to the present time point.

On the other hand, when there are a plurality of moving objects in the input image, a plurality of templates associated with one moving object at a past time may be divided into a plurality of change areas and associated.
In such a case, the determination means 43 determines a corresponding moving object by performing a weighted evaluation process as described below.

First, the determination unit 43 obtains an amount δ _s representing the smoothness of the movement of the template from the past time to the current time for each template. For example, δ _s can be obtained by averaging the deviation from the predicted position.
Next, the determination unit 43 obtains an amount δ _m representing the degree of matching between the template and the input image for each template. For example, δ _m can be obtained from the time average of the maximum matching score.

Next, the determination unit 43 obtains a weight using the sum of δ _s and δ _m for each template.

Next, the determination unit 43 obtains an evaluation value from the sum of the template weights for each of the change areas associated with one moving object in the past at a plurality of templates. .
Then, the determination unit 43 considers that the current moving object corresponds to the change area having the maximum evaluation value. In this way, the current position of the moving object is tracked.

  Further, as a situation different from the above case, there is a case where one template exists over a plurality of change regions. In this case, this template may be associated with a change area having a larger overlapping ratio with the template. Or you may divide a weight internally according to the ratio of overlap.

The above description describes a case where a plurality of templates associated with one moving object at a past time point are associated with each of a plurality of change regions at the current time point.
On the other hand, a plurality of templates associated with each of a plurality of moving objects at a past time may be associated with one change region at the present time. This is a case where a plurality of moving objects intersect and overlap each other due to movement, and change areas corresponding to them are combined to form an integrated change area. Such a crossed state is stored in the tracking information storage area 22 as a state change.

  In addition, when a plurality of moving objects that have been in an intersecting state at the previous past time point are in a state in which the intersection has been resolved at the present time, a plurality of templates that are associated with one change region are It will be associated with each of the plurality of change areas. A case where the crossed state is eliminated will be described later using a specific example.

Next, the update unit 50 will be described below.
As shown in FIG. 1, the update unit 50 includes a background image update unit 51 and a template update unit 52.

The background image update means 51 performs an update process on the background image stored in the background image storage area 21 according to a predetermined standard. The updated background image is also stored in the background image storage area 21. The reference is stored in the storage unit 20.
In the situation of the visual field of the camera 61, for example, there is a change over time in brightness or shadow shape due to fluctuations in sunlight. Therefore, the background image is updated by the background image update means 51 under the condition that there is no moving object in the field of view. As the reference, for example, a predetermined time interval may be used.

  As an alternative to the above-described standard, the background image may be updated using a known technique such as a moving average method using past images. For example, when this moving average method is used, the background image B (t) at time t is expressed as B (t) = aB (t−1) + bB (t−2). That is, the background image B (t) at the time t is expressed as a linear sum of the background images at the past times t−1 and t−2. Here, a and b are coefficients, and can be determined from the installation conditions of the camera 61 and the like.

  The template update unit 52 performs the update process of the template that has been successfully tracked by the determination unit 43 described above. The updated template is also stored in the tracking information storage area 22.

  The shape or size of the moving object imaged by the camera 61 may change as the moving object moves. For example, when a camera 61 having a super-wide-angle lens, a wide-angle lens, a fish-eye lens, or the like is used as the camera 61 and the image is captured by the camera 61 installed downward, the moving object in the image is displayed. The shape and size vary particularly greatly depending on the position in the field of view of the moving object.

  In such a case, it is preferable to update each template associated with the moving object for each moving object in the image for each input image. Therefore, the prediction means 41 described above can always perform the prediction process using the latest template.

  For updating the template, for example, a matching portion between the template at the position where the maximum matching score is obtained by the matching means 42 and the current input image can be used as a new template.

  Moreover, as a timing which updates the template mentioned above, the method demonstrated below can be used, for example.

(1) Method of updating a template at a constant interval In this method, a template update process is performed at a predetermined interval (for example, every five frames).

(2) Method of judging from error In this method, when the value of the maximum matching score obtained by the matching means 42 is equal to or less than a predetermined value, a template update process is performed. In other words, the template is updated when it is determined that the maximum matching score at the present time has decreased and the error of the template has increased compared to the maximum matching score at the past time.

(3) Weighted Average Method When the histogram matching method is used in the matching unit 42, in this method, the luminance histogram of the input image at the position where the maximum matching score is obtained by the matching unit 42, and the luminance histogram of the template The luminance histogram can be weighted to obtain a linear sum, and this linear sum can be used as an updated template.

Further, the template update unit 52 may perform a template update process in consideration of the positional relationship between a plurality of templates associated with a certain moving object.
More specifically, a reference template to be used as a reference is selected from a plurality of templates, and the position of the deviation template is corrected by taking into account the position of the reference plate for the deviation template that is more than a predetermined distance away from the reference template. To do. As the reference template, for example, it is preferable to select a template having the highest maximum matching score from the viewpoint of appropriately capturing the movement of the associated moving object. As a method for correcting the position of the deviation template, for example, a method of calculating a linear sum by adding a predetermined weight to the amount of change in the position of the deviation template (for example, the amount of change in the position of the center of gravity) and the amount of change in the reference template Is mentioned. This weight may be a fixed value or may be increased according to the distance between the reference template and the deviation template. Moreover, the said weight may have a different value for every template.

In addition, when there are a plurality of moving objects, the template update unit 52 may perform a template update process using characteristic portions of the respective moving objects.
This template update process will be described with reference to the example shown in FIG. As shown in FIGS. 3A and 3C, there are moving objects M1 and M2, and the head, the trunk, and the legs have characteristic portions with different textures. Specifically, when attention is paid to the moving object M1, the moving object M1 has a characteristic texture different from that of the moving object M2 in the upper part of the head, and the center part extends from the body part to the leg part. Has a vertically long characteristic texture.

  In this case, in order to update the template so as to identify the two moving objects M1 and M2, as described above in the template generation method, the template generation method is used according to the template generation method using the characteristic part of the moving object. be able to. For example, the moving objects M1 and M2 are similarly divided into a plurality of segments, the feature amount of each segment is obtained, and the template having the lowest similarity in the feature amount of the corresponding segment of the moving objects M1 and M2 is used as a template. Generate and update. Specifically, as shown in FIG. 3B, a template of the moving object M1 can be generated and updated.

  Further, the template generation means 33 may appropriately update the shape of the template according to the distortion aberration of the camera 61 and the position on the image.

Next, the output unit 70 will be described below.
The output unit 70 outputs the processing result of the apparatus 1 to the outside. The output unit 70 includes output means such as a screen, a printer, and an output interface. When the apparatus 1 is used as a part of the monitoring apparatus, the tracking result regarding the moving object is output from the output unit 70 to the monitoring apparatus main body. Specifically, the contents of the tracking result include information such as the number of the moving object, the number of the change area extracted from the moving object, and the position and speed at each time point. Further, when the movement of the moving object being tracked is determined to be abnormal according to a predetermined standard, an abnormality alarm may be output from the output unit 70.

Finally, the control unit 10 will be described below.
The control unit 10 controls processing of each component described above based on a program stored in the storage unit 20. Further, the control unit 10 controls a process of inputting data such as an image input from the outside by the input unit 60, and controls a process of outputting information such as a tracking result from the output unit 70 to the outside.

  Hereinafter, an example of the operation procedure of the moving object tracking device of the present invention described above will be described with reference to FIGS.

  FIG. 5 is a flowchart showing an example of the operation procedure of the moving object tracking device of the present invention. FIG. 6 is a flowchart showing in detail the procedure of the association process in FIG. FIGS. 7A to 7E are diagrams showing an example of a change area and a template state in the process of FIG.

  First, in step S <b> 100, an image captured by the camera 61 is input from the input unit 60 and stored in the storage unit 20. The camera 61 captures an image for each frame at a predetermined interval.

  Next, in step S <b> 101, a binary image is generated from the input image captured by the camera 61 by the difference processing unit 31 of the extraction unit 30. The difference processing unit 31 generates a difference image between the input image and the background image stored in the background image storage area 21, and binarizes the difference image to generate a binary image.

  Next, in step S102, the labeling means 32 of the extraction unit 30 performs a change area extraction process on the moving object from the binary image generated in S101. The labeling means 32 associates the pixels as one area with the pixels having the attribute of the moving object in the binary image, extracts the change areas, and assigns numbers. Information on this change area is stored in the tracking information storage area 22.

  Next, the processes of steps S103 to S107 are performed on all moving objects stored in the tracking information storage area 22 of the storage unit 20.

  First, in step S103, the prediction unit 41 of the tracking unit 40 performs prediction processing for all of a plurality of templates associated with a certain moving object. The predicting means 41 predicts the position of the moving object at the current time using the position and speed of the template associated with the moving object at the past time.

  Next, in step S104, the matching unit 42 of the tracking unit 40 performs template matching processing within a predetermined range centered on the position of the predicted moving object in the input image to obtain a maximum matching score.

  Next, in step S105, the determination unit 43 of the tracking unit 40 performs a process of associating the template with the change area. When the maximum matching score is equal to or greater than a predetermined threshold, the determination unit 43 associates the template with the change area extracted from the moving object of the current input image.

  In S106, the determination unit 43 associates the moving object with the change area extracted at the current time. Details will be described later with reference to FIGS.

  On the other hand, as a result of examining the matching of a certain template, if the maximum matching score is less than the threshold value, the determining unit 43 determines that the moving object is missing from the template. And the tracking part 40 continues performing the process by the estimation means 41 and the matching means 42 over a predetermined period using the said template linked | related with this moving object. When the maximum matching score of the template is equal to or greater than the threshold value, the determination unit 43 resumes tracking of the moving object using the template.

  In addition, when the moving object is lost in all the templates associated with a certain moving object, the determination unit 43 determines that the moving object has moved out of the field of view, and The tracking may be stopped, and the information stored in the tracking information storage area 22 associated with the moving object may be deleted. Alternatively, the prediction of the position of the template associated with the missing moving object and the search for matching may continue for a predetermined period of time.

  Next, in step S107, the template update unit 52 of the update unit 50 performs an update process for each template. Further, the background image update means 51 performs background image update processing according to a predetermined standard.

When a moving object that did not exist at the previous past time appears in the current input image, information about the moving object and its extracted change area is still stored in the tracking information storage area 22. Therefore, no processing is performed on this moving object in the above-described procedure. A plurality of templates are generated and associated with the newly appearing moving object according to the following procedure.
Therefore, the process of the following step S108 is performed on all the change areas that are not associated with the template.

  In step S108, the template generation unit 33 of the extraction unit 30 generates and associates a plurality of templates with the change region by using the change region with one change region newly appearing in the input image. At this time, the template is preferably generated so as to include at least a part of the contour of the moving object.

  Each of the generated templates is stored in the tracking information storage area 22 with a number for managing the template associated with the moving object.

  Since the camera 61 inputs images for each frame with a predetermined interval, the above-described processing is performed for each input image.

  Next, with respect to the processing of step S106 by the determination unit 43 described above, an example is illustrated in which a plurality of moving objects that have been in an intersecting state at the previous past time are in a state in which the intersecting has been resolved at this time. 6 and FIGS. 7A to 7E will be described further below.

First, in step S200, the determination unit 43 determines whether all the templates associated with a certain moving object correspond to one change area in the input image.
As shown in FIG. 7A, if all the templates associated with a certain moving object correspond to one change area, the determination in S200 is Yes, and then the step Proceed before S204.
In the example shown in FIG. 7A, all the templates M1-1, M1-2, and M1-3 associated with the moving object correspond to the change area S1 extracted from the moving object M1.

On the other hand, as shown in FIG. 7B, when all the templates associated with a certain moving object do not correspond to one change area, the determination in S200 is No, and steps S201 to S203 are performed. Perform the process.
In the example shown in FIG. 7B, two templates M1-1 and M1-2 correspond to the change area S1 extracted from the moving object M1, and the change area S2 extracted from the moving object M2 Template M1-3 corresponds. This template M1-3 is a template associated with the moving object M1. Actually, at this stage, it is not determined that the change area S1 corresponds to the moving object M1 and the change area S2 corresponds to the moving object M2.

  First, for all templates associated with a certain moving object, template weights are calculated by the process of step S201.

In step S201, the weights of all templates associated with a certain moving object are calculated. As the weight of the template, the weight described in the determination unit 43 described above can be used.
In the example shown in FIG. 7C, the weights of the templates M1-1 and M1-2 corresponding to the change area S1 are 0.7 and 1.2, respectively, and correspond to the change area S2. The weight of the template M1-3 is 1.0.

  Next, the processes in steps S202 and S203 are performed on all the change areas corresponding to the template.

First, in step S202, an evaluation value related to each change area is calculated. As the evaluation value of the change region, the evaluation value described in the determination unit 43 described above can be used.
In the example shown in FIG. 7D, the evaluation value related to the change area S1 is 1.9, and the evaluation value related to the change area S2 is 1.0.

  Next, in step S203, the change area for obtaining the maximum evaluation value is selected as the change area corresponding to the current moving object.

Next, in step S204, the tracking unit 40 associates the moving object with the change area.
As in the example illustrated in FIG. 7E, the change area S1 is associated with the templates M1-1 and M1-2, so that the change area S1 is determined to be the moving object M1.
When the number of templates is decreased due to mistracking like the moving object M1, a template is generated by the template generation unit 33 with reference to the remaining templates and associated with the moving object M1. Also good.

Next, the transition of the storage content in the tracking information storage area 22 of the storage unit 20 will be described with reference to FIGS. 8 and 9 in comparison with the transition of the input image.
In the example shown in FIG. 9, as the stored contents stored in the tracking information storage area 22, the time point, the moving object number, the change area number, the template number associated with the moving object, the situation, and the tracking state are shown. Yes.

  First, at time T0, as shown in FIG. 8, there is no moving object in the input image, and there is no stored content in the tracking information storage area 22, so all are in a NULL state as shown in FIG. is there.

Next, at time T1, a moving object appears and the extraction unit 30 assigns a number M1. In addition, the change area S1 is extracted by the extraction unit 30 and the templates M1-1, M1-2, and M1-3 are generated and associated with the moving object M1.
In the tracking information storage area 22, a moving object number, a change area number, and a template number are stored as information related to the moving object M1. Also, such a situation and the tracking start state are stored.

  Next, at time T2, a new moving object appears as shown in FIG. The input image includes two moving objects M1 and M2, and the extraction unit 30 extracts change areas S1 and S2 corresponding to the two moving objects M1 and M2 included in the image, respectively. Then, the number M2 is assigned to the new moving object M2 by the extraction unit 30. Further, the extraction unit 30 generates and associates templates M2-1, M2-2, and M2-3 by the extraction unit 30 using the change area S2.

  As shown in FIG. 9, the tracking information storage area 22 stores a moving object number, a change area number, and a template number as information related to the moving object M2. Also, such a situation and the tracking start state are stored.

  On the other hand, for the moving object M1 at time T2, the position in the input image has moved, and tracking processing by the tracking unit 40 is performed, and the stored contents of the tracking information storage area 22 are updated.

  Next, at the time point T3, as shown in FIG. 8, the moving object M1 and the moving object M2 intersect and overlap each other due to the movement. The change areas corresponding to them are combined to form an integrated change area, and the change area number S3 is assigned to the change area.

The tracking unit associates the integrated change region S3 with the plurality of templates M1-1 to M3 and M2-1 to M2 1-3 that have been associated with the respective moving objects M1 and M2 before overlapping, and thereby the plurality of moving objects M1. , M2 is tracked.
This state is determined to be an intersection state by the determination means 43, and the tracking information storage area 22 stores the situation as an intersection as shown in FIG.

  Next, at the time T4, as shown in FIG. 8, the crossing state of the moving object M1 and the moving object M2 is eliminated, and each of them moves separately. Change areas S4 and S5 corresponding to the two moving objects M1 and M2 in the input image are extracted by the extraction unit 30, respectively.

  The determination unit 43 tracks the moving objects M1 and M2 using the templates M1-1 to M3 and M2-1 to M2 of the moving objects M1 and M2 stored in the tracking information storage area 22, respectively. And since the change area | region S4 respond | corresponds with the templates M1-1 to M3, the determination means 43 determines corresponding to the moving object M1. Similarly, the determination unit 43 determines that the change area S5 corresponds to the templates M2-1 to M3-1 and corresponds to the moving object M2.

  In the tracking information storage area 22, as shown in FIG. 9, it is stored that the change area S4 corresponds to the moving object M1, the change area S5 corresponds to the moving object M2, and the crossed situation has been resolved. Is stored as a situation. Then, the tracking of the moving objects M1 and M2 is continued.

  According to the apparatus 1 described above, a moving object can always be accurately tracked. In particular, even when a plurality of moving objects intersect and overlap each other due to movement, the apparatus 1 uses a plurality of templates and change areas to keep track of each moving object during the intersection, thereby eliminating the intersection. Each subsequent moving object can be accurately tracked in correspondence with the moving object before the intersection.

  In addition, since the template is generated by the extraction unit so as to include at least part of the contour of the moving object, the tracking accuracy of the moving object is further improved.

  In addition, because it is impossible to associate with a moving object, a template that has lost sight of the corresponding moving object can be tracked again by performing a prediction process and a matching process for a predetermined period of time. Made possible.

  The moving object tracking device of the present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist of the present invention.

  For example, in the above-described embodiment, the moving object tracking device of the present invention is a case where the current moving object moves out of the field of view of the camera 61, and the template or change region associated with the moving object is displayed. If it is estimated from the position or velocity that the moving object has moved out of the field of view at this time, the determination unit 43 stops tracking the moving object, and the tracking information associated with the moving object is stopped. Information stored in the storage area 22 may be deleted. Alternatively, when the current moving object moves out of the field of view of the camera 61, the determination unit 43 may stop tracking the moving object immediately.

  In the above-described embodiment, the background image difference process is used for the difference process of the difference processing unit 31, but an inter-frame difference process may be used for this difference process.

  In the embodiment described above, the tracking unit 40 uses the prediction unit 41, and the template is matched only with a predetermined range in the input image. However, the prediction unit 41 is not used. In addition, the matching process may be performed in the entire range of the template and the input image.

  Furthermore, in the above-described embodiment, the storage unit 20 has the background image storage area 21 and the tracking information storage area 22, but the storage unit 20 does not divide these storage areas into a background image or Information regarding a moving object or the like may be stored.

  The moving object tracking device of the present invention may be used alone or as a part of another device such as a monitoring device or with another device.

FIG. 1 is a diagram showing functional blocks of a moving object tracking device according to an embodiment of the present invention. 2A to 2E are diagrams showing an example of geometrically generating a template. FIG. 3 is a diagram illustrating an example in which a template is generated using a characteristic portion of a moving object. FIG. 4 is a diagram illustrating an example in which a template is generated so that the luminance dispersion in the template becomes large. FIG. 5 is a flowchart showing an example of the operation procedure of the moving object tracking device of the present invention. FIG. 6 is a flowchart showing in detail the procedure of the association process in FIG. FIGS. 7A to 7E are diagrams showing an example of a change area and a template state in the process of FIG. FIG. 8 is a diagram illustrating the transition of images before and after a moving object intersects. FIG. 9 is a diagram showing the transition of the storage content of the additional information storage area in comparison with the transition of the image of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Moving object tracking device 10 Control part 20 Storage part 21 Background image storage area 22 Tracking information storage area 30 Extraction part 31 Difference processing means 32 Labeling means 33 Template generation means 40 Tracking part 41 Predictive means 42 Matching means 43 Determination means 50 Update part 51 background image update means 52 template update means 60 input unit 61 camera 70 output unit

Claims (6)

A moving object tracking device for tracking the same moving object from a sequentially input image using a template,
An extraction unit that extracts a change area caused by a moving object from the input image;
Template generating means for generating a plurality of different templates from the change region;
A storage unit that stores the moving object and the plurality of templates in association with each other;
Matching means for extracting similar template candidates between the template stored in the storage unit and the input image;
Determination means for determining whether or not the template candidate corresponds to the change area extracted in the input image;
Updating means for updating the template of the storage unit with the template candidates determined to be supported by the determination means;
A moving object tracking device comprising:   The moving object tracking device according to claim 1, wherein the template generation unit generates the template so that at least one of the plurality of templates has at least a part of a contour of the change region. The storage unit further stores position information for each template,
Predicting means for predicting the position of the template candidate in the input image based on the position information for each of the templates stored in the storage unit;
The matching means extracts the template candidates in a range predicted by the prediction means,
The moving object tracking apparatus according to claim 1, wherein the updating unit also updates position information of the updated template.   4. The method according to claim 1, wherein the matching unit obtains a matching score by examining matching between the template and the input image, and sets a portion of the input image whose matching score is equal to or greater than a predetermined threshold as the template candidate. A moving object tracking device according to claim 1. When all of the template candidates of the plurality of templates corresponding to the same moving object correspond to one change region, the determination unit associates all of the plurality of template candidates with the change region,
If a part of a plurality of template candidates corresponding to the same moving object corresponds to one change area, the template candidate corresponds to the change area based on the sum of the weights of the template candidates. The moving object tracking device according to claim 1, which determines whether or not.   The moving object tracking device according to claim 1, wherein the input image is an image installed on a ceiling and photographed in a downward direction.

Images