Imaging device

Abstract

The present invention provides an imaging device that can smoothly track and photograph objects passing through an area including directly below it. [Solution] The imaging device 1 is an imaging device that tracks and photographs an object passing through a predetermined area, and comprises an imaging unit 10, a drive unit 20 that drives the imaging unit 10 in the pan and tilt directions, a drive control unit 43 that controls the drive unit 20 to track the object while keeping it within the shooting angle of the imaging unit 10, and a tilt angle detection unit 41 that detects the tilt angle indicating the angle of the tilt direction of the imaging unit 10. When the tilt angle detected by the tilt angle detection unit 41 falls within a predetermined angle range, the drive control unit 43 stops driving the imaging unit 10 in the tilt direction and controls the drive unit 20 to perform pan tracking by driving only in the pan direction to track the object while keeping it within the shooting angle of the image.

Description

Technical Field

[0001] The present invention relates to an imaging device.

Background Art

[0002] There is a surveillance camera installed at an upper position of a surveillance area, which tracks and photographs a moving object while appropriately rotating the photographing direction in the pan direction and the tilt direction. In such a surveillance camera that performs photographing, when the tracking target passes near directly below the surveillance camera, before and after the tracking target passes directly below the surveillance camera, the vertical orientation of the photographed tracking target is reversed, making it impossible to recognize the tracking target as the same object, and there is a possibility that smooth tracking cannot be performed.

[0003] In order to address this, there is a technique for correcting the vertical direction of imaging information by rotating the photographing direction of the surveillance camera 180° in the pan direction and then rotating it in the tilt direction and returning it to the original photographing direction after passing directly below (see Patent Document 1). By using this technique, when photographing while tracking an object passing near directly below the surveillance camera, the vertical orientation of the object in the imaging information is corrected.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when using the above-described technique, there is a problem that while the photographing direction of the surveillance camera is rotated 180° in the pan direction and then rotated in the tilt direction, the tracking target may go out of the photographing angle, and the surveillance camera may not be able to continue the tracking process.

[0006] The present invention aims to provide an imaging device that can smoothly track and photograph objects passing through an area including the area directly below them. [Means for solving the problem]

[0007] An imaging device according to one or more embodiments for achieving the above objective is an imaging device for tracking and photographing an object passing through a predetermined area, comprising: an imaging unit; a drive unit for driving the imaging unit in the pan and tilt directions; a drive control unit for controlling the drive unit to track the object while keeping it within the shooting angle of the imaging unit; and a tilt angle detection unit for detecting a tilt angle indicating the angle in the tilt direction of the imaging unit, wherein when the tilt angle detected by the tilt angle detection unit falls within a predetermined angle range, the drive control unit stops driving the imaging unit in the tilt direction and controls the drive unit to drive only in the pan direction to perform pan tracking while keeping the object within the shooting angle of the imaging unit. [Effects of the Invention]

[0008] According to an imaging device in one or more embodiments, tracking is possible even when tracking and photographing an object passing through an area including the area directly below it. [Brief explanation of the drawing]

[0009] [Figure 1] This is a block diagram showing the configuration of an imaging device according to one embodiment of the present invention. [Figure 2] This is an explanatory diagram showing an imaging device according to one embodiment of the present invention in a state where it tracks and photographs a vehicle C traveling on a road R. [Figure 3] This flowchart shows the operation of an imaging device according to one embodiment of the present invention. [Figure 4] This is a state transition diagram relating to the tracking operation performed by an imaging device according to one embodiment of the present invention. [Figure 5] This figure shows the transition of imaging information when an imaging device according to one embodiment of the present invention tracks a vehicle C traveling on a road R. [Figure 6] This is a top view of a road R as captured by an imaging device according to one embodiment of the present invention. [Figure 7] This diagram shows the transition of imaging information when a conventional imaging device tracks a vehicle C traveling on a road R. [Modes for carrying out the invention]

[0010] Below, an imaging device for tracking and photographing an object moving within a monitored area will be described as an embodiment of the present invention with reference to the drawings.

[0011] <Configuration of an imaging device according to one embodiment> Figure 1 is a block diagram showing the configuration of the imaging device 1 according to this embodiment. The imaging device 1 comprises an imaging unit 10, a drive unit 20, a setting information storage unit 30, and a processing unit 40.

[0012] The imaging unit 10 takes images in a predetermined direction. The drive unit 20 drives the imaging unit 10 in the pan and tilt directions.

[0013] The setting information storage unit 30 is composed of, for example, RAM (Random Access Memory) or ROM (Read Only Memory). The setting information storage unit 30 stores information on the tilt angle range of the imaging unit 10, information on the execution frequency of the tracking process of the drive unit 20, and information on the image recognition accuracy for each area within the shooting angle of view of the drive unit 20, which are pre-set and used to switch the control contents of the drive unit 20. Details of each piece of information in the setting information storage unit 30 will be described later.

[0014] The processing unit 40 performs various information processes. The processing unit 40 includes a processor such as a CPU (Central Processing Unit), and memories such as a ROM (Read Only Memory) and a RAM (Random Access Memory). The processing unit 40 may be realized by an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array). The processing unit 40 has a tilt angle detection unit 41, an image processing unit 42, and a drive control unit 43.

[0015] The tilt angle detection unit 41 detects the tilt angle of the imaging unit 10 based on the operating state of the drive unit 20. The tilt angle of the imaging unit 10 indicates the angle in the tilt direction of the imaging unit 10, and is the angle in the tilt direction formed by a predetermined reference direction with the imaging unit 10 as the reference point and the imaging direction of the imaging unit 10.

[0016] The image processing unit 42 analyzes the imaging information captured by the imaging unit 10 and performs image recognition processing to detect the object part in the imaging information.

[0017] The drive control unit 43 switches the control content of the drive unit 20 based on the image recognition processing result by the image processing unit 42, the information stored in the setting information storage unit 30, and the information on the tilt angle of the imaging unit 10 detected by the tilt angle detection unit 41. Specifically, when the object passes through a predetermined area including directly below the imaging unit 10, the drive control unit 43 stops driving in the tilt direction of the imaging unit 10 when the tilt angle detected by the tilt angle detection unit 41 is within a predetermined angle range including the directly downward direction of the imaging unit 10, and controls the drive unit 20 to drive only in the pan direction so that the object fits within the imaging angle of the imaging unit 10.

[0018] <Operation of the imaging device according to an embodiment> In the present embodiment, as shown in FIG. 2, the operation when the imaging device 1 installed directly above the linear road R chases and photographs the vehicle C traveling on the road R in the direction of the arrow B as an object will be described.

[0019] In the setting information storage unit 30 of the imaging device 1, information on the tilt angle range E of the imaging unit 10 used to switch the control content of the drive unit 20 is stored. The tilt angle range E is the range of the tilt angle of the imaging unit 10 including the directly downward direction D perpendicular to the ground from the imaging unit 10 of the imaging device 1, and the road area on the road R corresponding to this tilt angle range E is designated as AR.

[0020] FIG. 3 is a flowchart showing the operation of the imaging device 1. FIG. 4 is a state transition diagram regarding the tracking operation executed by the imaging device 1. FIG. 5 is a diagram showing the transition of the imaging information of the imaging unit 10 during the following of the vehicle C.

[0021] While the imaging unit 10 is photographing the road R and it is determined by the analysis processing of the image processing unit 42 that there is no target object for following within the photographed angle of view G of the imaging unit 10, the drive control unit 43 stops the following process (F0 in FIG. 4). When the vehicle C travels on the road R in the direction of the arrow B and the vehicle C enters the photographed angle of view G, the drive control unit 43 detects this as a target object for following (''YES'' in S1 of FIG. 3, (a) in FIG. 5).

[0022] When the drive control unit 43 detects the vehicle C as a target object for following, it starts the control of the drive unit 20 so that the imaging unit 10 performs normal following with respect to the vehicle C (S2 in FIG. 3). Normal following is a method of following while keeping the center of gravity of the image portion of the vehicle C in the first area Ga within the photographed angle of view G by using the rotation of the imaging unit 10 in the pan direction and the tilt direction. The first area Ga has a center position that is the same as the center position of the photographed angle of view G and is an area smaller than the photographed angle of view G in both the vertical and horizontal directions (F2[F21] in FIG. 4, (b) in FIG. 5). The drive control unit 43 executes the following process according to the execution frequency of the following process stored in the setting information storage unit 30.

[0023] As a result, the imaging unit 10 tracks the vehicle C while keeping its center of gravity within the first area Ga of the shooting angle G, and takes photographs. While the imaging unit 10 is performing normal tracking, the tilt angle detection unit 41 detects the tilt angle of the imaging unit 10 at predetermined time intervals based on the control information of the drive unit 20 from the drive control unit 43.

[0024] While tracking vehicle C, if the tilt angle of the imaging unit 10 falls within the tilt angle range E due to a change in the shooting direction (YES in S3 of Figure 3), the drive control unit 43 stops the tilt direction drive and switches the control of the drive unit 20 to perform pan tracking, which tracks vehicle C using only the pan direction drive (S4 in Figure 3). Once the drive control unit 43 switches the control to perform pan tracking, it determines the movable range of pan rotation for subsequent pan tracking based on the pan angle of the imaging unit 10 immediately before.

[0025] The pan angle of the imaging unit 10 indicates the angle in the pan direction of the imaging unit 10, and is the angle in the pan direction between a predetermined reference direction with the imaging unit 10 as the base point and the shooting direction of the imaging unit 10. The process for determining the movable range of pan rotation when performing pan tracking, which is performed by the drive control unit 43, will now be explained.

[0026] Figure 6 is a top view of the road R captured by the imaging unit 10. In Figure 6, AR indicates the road area on road R corresponding to the tilt angle range E of the imaging unit 10. Road R has lanes r1 and r2 traveling in the same direction. The pan angle of the imaging unit 10 is 0° when the imaging unit 10 is facing the same direction as the direction of travel of vehicles traveling in lane r1 or r2, and the value increases as the orientation of the imaging unit 10 rotates counterclockwise from this pan angle of 0°. In Figure 6, the line passing through the imaging unit 10 and connecting the pan angles of the imaging unit 10 at 0° and 180° is called the reference line h. This reference line h is parallel to the vehicle lanes r1 and r2 on road R.

[0027] Viewed from the imaging unit 10 in the direction of vehicle travel, the area to the left of the reference line h within the road area AR is designated as the left area ARl, and the area to the right of the reference line h is designated as the left area ARr. The left area ARl is a portion of the road area AR corresponding to the pan angle of the imaging unit 10 between 0° and 180°. The right area ARr is a portion of the road area AR corresponding to the pan angle of the imaging unit 10 between 180° and 360°. Lane r1 passes through the right area ARr, and lane r2 passes through the left area ARl.

[0028] When vehicle C is traveling in lane r1, if vehicle C reaches position P3 where lane r1 intersects with the contour of road area AR, the drive control unit 43 switches control to perform pan tracking and performs processing to determine the movable range of pan rotation when performing pan tracking.

[0029] The drive control unit 43 checks the pan angle of the imaging unit 10 when it photographs positions P1 and P2, which are the positions immediately before the vehicle C reaches position P3. Here, the pan angle of the imaging unit 10 when it photographs position P1 is 190°, and the pan angle when it photographs position P2 is 200°.

[0030] The drive control unit 43 determines that the range of motion for pan rotation when tracking the vehicle C is on the right side of the ARr, since the pan angles when capturing positions P1 and P2 correspond to the right area ARr (YES in S5 of Figure 3) → S6). As a result, the drive control unit 43 controls the drive unit 20 so that the pan direction of the imaging unit 10 rotates in the direction of arrow J1.

[0031] Furthermore, when vehicle C is traveling in lane r2, when vehicle C reaches position P6 where lane r2 intersects with the contour of road area AR, the drive control unit 43 switches control to perform pan tracking and performs processing to determine the movable range of pan rotation when performing pan tracking.

[0032] The drive control unit 43 checks the pan angle of the imaging unit 10 when it photographs positions P4 and P5, which are the positions immediately before the vehicle C reaches position P6. Here, the pan angle of the imaging unit 10 when it photographs position P4 is 170°, and the pan angle when it photographs position P5 is 160°.

[0033] The drive control unit 43 determines that the operating range of the pan rotation when tracking the vehicle C is the left area ARl side, since the pan angle when capturing positions P1 and P2 corresponds to within the left area ARl (NO in S5 of Figure 3) → S7). As a result, the drive control unit 43 controls the drive unit 20 so that the pan direction of the imaging unit 10 rotates in the direction of arrow J2.

[0034] In the pan rotation range determination process described above, we explained the case where right areas ARr and ARl are set to define the pan rotation range based on a reference line h parallel to the vehicle's direction of travel. However, the process is not limited to this, and right areas ARr and ARl may be set in advance for any given angular range.

[0035] During pan tracking, the drive control unit 43 tracks the vehicle C by keeping its center of gravity within the second area Gb within the shooting angle of view G. The second area Gb is an area whose center position and vertical length are the same as the center position and vertical length of the shooting angle of view G, and whose horizontal length is smaller than the shooting angle of view G (F2 [F22] in Figure 4).

[0036] When the drive control unit 43 switches the control to perform pan tracking, the position of vehicle C within the shooting angle of view G gradually moves downward (Figure 5(c)), and when the vehicle C's travel position is closest to the position directly below the imaging device 1, the position of vehicle C within the shooting angle of view G is at its lowest (Figure 5(d)). Subsequently, as the vehicle C's travel position moves away from directly below the imaging device 1, the position of vehicle C within the shooting angle of view G gradually moves upward (Figure 5(d)).

[0037] In other words, when the drive control unit 43 is controlling the camera to perform pan tracking, there is a high probability that the vehicle C is located in the lower area of ​​the shooting angle of view G. Due to the characteristics of the lens of the imaging unit 10, distortion or a decrease in resolution of the subject occurs as it moves away from the center within the shooting angle of view G. Therefore, when the drive control unit 43 is controlling the camera to perform pan tracking, the image processing unit 42 may set the image recognition accuracy (e.g., the rate of agreement with the object's learning data) of the lower half of the image information in the shooting angle of view G, where the vehicle C is likely to be located, lower than that of the upper half. This prevents the occurrence of a problem where, when the vehicle C moves below the shooting angle of view G, the vehicle C is no longer recognized due to image distortion, etc., and tracking cannot be continued.

[0038] Subsequently, while pan tracking is being performed, if the center of gravity of vehicle C within the shooting angle G falls within the first area Ga (YES in S8 of Figure 3, (f) in Figure 5), the drive control unit 43 switches the control of the drive unit 20 so that the imaging unit 10 performs normal tracking of vehicle C (S9 in Figure 3, F21 in Figure 4).

[0039] After the center of gravity of vehicle C within the shooting angle G enters the first area Ga, even if normal tracking is performed on vehicle C, the tilt angle of the imaging unit 10 will be outside the tilt angle range E.

[0040] When vehicle C moves out of the field of view G of the imaging unit 10 (YES in S10), the drive unit 20 stops tracking vehicle C (S11, F0 in Figure 4).

[0041] Figure 7 shows the transition of image information when the tracking operation within the tilt angle range E of the imaging unit 10 is not switched from normal tracking to pan tracking, as described above, and normal tracking is performed for the entire period. When shooting in this manner, the vertical orientation of the image information is reversed between (c) and (e), when photographing the vehicle C moving within the tilt angle range E, which may prevent the tracking target from being recognized as the same object, making smooth tracking impossible.

[0042] In contrast, the imaging device 1 of this embodiment can smoothly track an object passing within the tilt angle range E directly below the surveillance camera, without the vertical orientation of the imaging information being reversed.

[0043] In the embodiment described above, the drive control unit 43 may dynamically change the degree of rotation in the pan direction when performing pan tracking based on the degree of change in the tilt angle of the imaging unit 10 just before it reaches the tilt angle range E. For example, the drive control unit 43 may increase the amount of rotation by increasing the rotation speed in the pan direction when performing pan tracking, as the amount of change in the tilt angle per unit time just before the tilt angle of the imaging unit 10 reaches the tilt angle range E is larger.

[0044] The actual distance within the tilt angle range E is short, and the time it takes for a vehicle to pass is short. However, because the rotation angle of the imaging unit 10 due to pan tracking is large, the tracking performance due to pan rotation can be improved by increasing the degree of rotation in the pan direction when performing pan tracking compared to when performing normal tracking. The drive control unit 43 may increase the frequency of execution of tracking processing, including the determination of whether tracking is possible, in order to improve tracking performance due to pan rotation.

[0045] In the embodiments described above, the case in which the setting information storage unit 30, tilt angle detection unit 41, image processing unit 42, and drive control unit 43 are provided within the imaging device 1 has been described. However, the invention is not limited to this, and at least one of these functional units may be provided in an external server that is communicatively connected to the imaging device 1. In this case, the imaging device 1 performs the above-described processing by communicating with the server.

[0046] [Effects of the Embodiment] According to the embodiment described above, the imaging device is an imaging device that tracks and photographs an object passing through a predetermined area, and comprises an imaging unit, a drive unit that drives the imaging unit in the pan and tilt directions, a drive control unit that controls the drive unit to track the object while keeping it within the shooting angle of the imaging unit, and a tilt angle detection unit that detects the tilt angle indicating the angle of the tilt direction of the imaging unit, and when the tilt angle detected by the tilt angle detection unit falls within a predetermined angle range, the drive control unit stops driving the imaging unit in the tilt direction and controls the drive unit to perform pan tracking by driving only in the pan direction to track the object while keeping it within the shooting angle of the image.

[0047] This allows for smooth tracking of objects passing within the tilt angle range directly below the surveillance camera, without the vertical orientation of the image information being reversed.

[0048] Furthermore, when pan tracking is not being performed, the drive control unit may track the center of gravity of the object within the shooting angle of view while keeping it within a first area whose center position is the same as the center position of the shooting angle of view, and which is smaller than the shooting angle of view in both the vertical and horizontal directions. When pan tracking is being performed, the drive control unit may track the center of gravity of the object within the shooting angle of view while keeping it within a second area whose center position and vertical length are the same as the center position and vertical length of the shooting angle of view, and which is smaller than the shooting angle of view in the horizontal direction.

[0049] This allows the camera to track the object while keeping it in an area that is as easily visible as possible within the shooting angle, taking into account that the object's position moves downward within the shooting angle when panning is being performed.

[0050] Furthermore, the drive control unit may change the degree of rotation in the pan direction when performing pan tracking based on the degree of change in the tilt angle before the tilt angle reaches a predetermined angle range. This makes it possible to improve the tracking ability of the object by pan rotation when performing pan tracking.

[0051] Furthermore, the system includes an image processing unit that analyzes the image information captured by the imaging unit and performs image recognition processing to detect the object portion within the image information. The drive control unit controls the drive unit to track the object while keeping it within the imaging unit's field of view based on the image recognition processing results from the image processing unit. When pan tracking is being performed, the image processing unit may lower the image recognition accuracy of the portion below a predetermined position in the image information compared to the portion above the predetermined position.

[0052] This prevents a problem where, when the subject moves below the shooting angle, distortion or a decrease in resolution of the subject in the shooting information causes the desired subject to no longer be recognized, making it impossible to continue tracking.

[0053] Furthermore, the drive control unit may determine the range of pan rotation of the imaging unit when performing pan tracking based on the pan angle, which indicates the angle in the pan direction of the imaging unit before the tilt angle reaches a predetermined angular range. This enables the imaging device to perform pan tracking efficiently and with high precision. [Explanation of symbols]

[0054] 1. Imaging device 10 Imaging Unit 20 Drive unit 30. Configuration Information Storage Unit 40 Processing Unit 41 Tilt angle detection unit 42 Image Processing Unit 43 Drive control unit

Claims

1. An imaging device that tracks and photographs an object passing through a predetermined area, Imaging unit, A drive unit that drives the imaging unit in the pan and tilt directions, A drive control unit controls the drive unit to track the object while keeping it within the field of view of the imaging unit, A tilt angle detection unit that detects the tilt angle indicating the angle in the tilt direction of the imaging unit, Equipped with, The drive control unit controls the drive unit to stop driving the image unit in the tilt direction and drive only in the pan direction to perform pan tracking, which tracks the object while keeping it within the shooting angle, when the tilt angle detected by the tilt angle detection unit falls within a predetermined angle range.

2. The drive control unit, When the aforementioned pan tracking is not performed, the center of gravity of the object is tracked within the shooting angle of view, within a first area whose center position is the same as the center position of the shooting angle of view, and which is smaller than the shooting angle of view in both the vertical and horizontal directions. The imaging device according to claim 1, wherein when pan tracking is performed, the center of gravity of the object is tracked within the shooting angle of view, within a second area whose center position and vertical length are the same as the center position and vertical length of the shooting angle of view, and whose horizontal length is smaller than the shooting angle of view.

3. The imaging apparatus according to claim 1, wherein the drive control unit changes the degree of rotation in the pan direction when performing pan tracking based on the degree of change in the tilt angle before the tilt angle reaches the predetermined angle range.

4. The system further includes an image processing unit that analyzes the image information captured by the imaging unit and performs image recognition processing to detect the object portion within the image information, The drive control unit controls the drive unit to track the object while keeping it within the shooting angle of the imaging unit, based on the image recognition processing result by the image processing unit. The imaging apparatus according to claim 1, wherein when pan tracking is performed, the image processing unit lowers the image recognition accuracy of the portion of the imaging information below a predetermined position to lower the image recognition accuracy of the portion above the predetermined position.

5. The imaging apparatus according to claim 1, wherein the drive control unit determines the movable range of the pan rotation of the imaging unit when performing pan tracking, based on the pan angle which indicates the angle in the pan direction of the imaging unit before the tilt angle reaches the predetermined angle range.

Images