WO1999035850A1

WO1999035850A1 - Multiple camera system

Info

Publication number: WO1999035850A1
Application number: PCT/IB1998/001659
Authority: WO
Inventors: Soumitra Senugupta; Damian Lyons; Thomas Murphy; Daniel Reese
Original assignee: Koninklijke Philips Electronics N.V.; Philips Ab
Priority date: 1997-12-31
Filing date: 1998-10-19
Publication date: 1999-07-15

Abstract

In a multiple camera system (101-103), the views of a plurality of cameras are mapped onto a graphical representation. A user desiring to see an area within the system, points to a corresponding position within the graphical representation thru a user interface (171). The apparatus determines which of the cameras (101-103) contains the indicated point within its field of view, and displays that camera's output on a monitor (150). If more than one camera has the point within its view, the user can choose which camera to display. In an alternate embodiment, alarms (111, 112) are disposed within the viewed area. If an alarm (111, 112) is triggered, it is the equivalent of a user pointing to the location of that alarm on the graphical representation.

Description

Multiple Camera System

Background of the Invention

1. Field of the Invention

This invention relates to a system for controlling multiple video cameras This invention allows for a convenient user interface for selecting and directing a camera within a multi-camera system, as might be used in a security system or a multi-camera broadcasting system

2. Description of Related Art Secuπty systems for airports, casinos, and the like typically employ a multitude of cameras which provide images of selected areas to a control station The images from each of these cameras, or a subset of these cameras, are displayed on one or more monitors at the control station. The operator of the control station is provided an ability to select any one of the cameras for a display of its image on a primary monitor, and, if the camera is adjustable, to control of the camera's field of view Such control systems are also utilized for selecting from among multiple cameras at an event being broadcast, for example, multiple cameras at a sports arena, or studio.

The selection and control of the cameras is typically accomplished by controlling a bank of switches, or by selecting from amongst a list of cameras on a computer terminal. Each camera is identified by a unique number, or by a unique name, for example

"camera 1", "camera 2", etc., or "front hall", "rear entrance", etc To view a particular area, the operator selects the camera associated with that area If the camera is adjustable, the operator subsequently adjusts the selected camera's field of view by adjusting its rotation about a hoπzontal axis (pan) or vertical axis (tilt), or its magnification (zoom) This control is often facilitated by the use of a jovstick

The selection of views may be automated, by having a fixed set of camera selections and associated fields of views predefined, and having each of these predefined views presented to the operator in a peπodic sequence The operator may preempt the sequencing of these views to select alternative views, as needed. The selection and adjusting of a camera may also be automated in response to an alarm signal.

In order for the operator to view a particular scene, the operator must be aware of the potential fields of view of each of the cameras, and the identifying name or number associated with the camera which includes the desired scene. After selecting the appropriate camera, the operator must adjust the camera from its current field of view position to the field of view which contains the desired scene. To alleviate the burden associated with viewing particular scenes, some systems allow for the operator to select from a list of commonly viewed scenes. Again, however, the operator must be aware of the identifying name or number associated with the desired scene. While it may be desirable to have many commonly selected scenes prerecorded, for ease of camera selection and adjustment, each additional prerecorded scene makes the task of identifying a particular scene by name or number more cumbersome.

Summary of the Invention It is an object of this invention to provide for a user interface for a multiple camera system which allows for the display of a desired scene in a manner which is easy to use, intuitive, and does not require a memorization of camera or scene identifiers by the operator.

This object is achieved by providing a graphic representation of the secured area. When the operator selects a point on this representation, the system determines which camera contains this point within its possible field of view, then selects the camera for viewing and adjusts the camera to contain the selected point in the viewed image. If multiple cameras contain the point, the user is provided the option of scrolling through each. The user is also provided a means of easily adjusting the camera after it is automatically selected. By providing the graphic representation, for example, in the form of a floor plan of a secured building, the operator need not memorize the identification name or number of each camera, nor need the operator know which camera or cameras cover a given area. In another embodiment, the operator is provided a graphic representation of the current field of view of a selected camera. Security systems often automatically select a camera associated with an alarm, for presentation of a view of the alarmed area to the operator. Unless the operator is familiar with the view being presented, it often takes a few moments for the operator to determine where, in the actual secured area, the camera is viewing. By presenting a graphic indication of which alarm has been triggered, which camera has been selected, and which view the camera is currently displaying, the operator can more easily be oriented to the displayed scene, and can more easily assess the security situation. The operator can thereafter refine the view of the scene by the aforementioned graphic camera interface capabilities. Various aspects of the invention are defined by the independent claims. The dependent claims define advantageous embodiments.

Brief Description of the Drawings

Fig. 1 shows a multi-camera security system;

Fig. 2 shows a graphic interface for a multi-camera security system, in accordance with this invention;

Figs. 3a-3c show potential fields of view of three cameras;

Fig. 4 shows a flowchart for selecting and adjusting a camera in accordance with this invention; and

Fig. 5 shows a multi-window graphic interface for a security system, in accordance with this invention.

Description of the Preferred Embodiments

Fig. 1 shows a multi-camera security system. The system comprises video cameras 101, 102, 103. Cameras 101 and 102 are shown as adjustable, pan/tilt/zoom, cameras. The cameras 101, 102, 103 provide an input to a video switching system 120; the connections between the cameras and the switch may be direct or remote, for example, via a telephone connection. Monitors 150, 151, 152, 153 are also connected to the switch, for viewing the images from the cameras. One of the monitors, monitor 150, is used as the main viewing screen, typically displaying the image from one of the cameras selected by the operator. The operator controls the security system via an operator's station 170, and controller 130. The operator station comprises a video screen 180, and alternative input devices, such as mouse 171, a digitizer tablet 172, keyboard 173, and joystick 174. The operator typically selects from options presented on the screen 180 to select the camera whose view is presented to the main screen 150, and, using the input devices, controls the selected camera to change its line of sight, via pan and tilt adjustments, or magnification factor, via zoom adjustments. Optionally, the video screen 180 could display the selected camera image in addition to, or in lieu of, the main screen 150. Also shown are optional alarm sensors 1 1 1 and 1 12. These alarm sensors are input to the control 130, and provide for automatic camera selection when an alarm condition is sensed. Each alarm sensor has one or more cameras associated with it; when the alarm is activated, an associated camera is selected and adjusted to a predefined line of sight and the view is displayed on the main screen 150 for the operator's further assessment and subsequent security actions.

In accordance with this invention, the controller 130 also comprises a graphic representation of the secured area, for example, a floor plan as shown in Fig. 2. The floor plan is created and entered in the control system when the security system is installed, using for example Computer Aided Design (CAD) techniques well known to one skilled in the art. Each wall and obstruction is shown, as well as any other identifying characteristics which would make the graphic image easily recognizable to the operator. Also entered and optionally displayed on the image is the location of each camera 101 through 106. Optionally, the location of alarm sensors may also be shown on the floor plan. Note that although a video display of the graphic representation is preferred, the graphic representation could be upon paper, and placed upon the graphics tablet 172; the graphics tablet transmits the coordinates of the pointing device used with the tablet.

Associated with each camera will be a polygon, outlining each camera's potential field of view. Shown in Fig. 3a is the polygon associated with camera 102; Fig. 3b shows the polygon associated with camera 103. Camera 102 is a camera having an adjustable field of view, and thus can view any area within a full 360 degree arc, provided that it is not blocked by an obstruction. Camera 103 is a camera with a fixed field of view, as represented by the limited view angle 203. Camera 102's potential field of view is the polygon bounded by vertices 221 through 229. Camera 103's field of view is the polygon bounded by vertices 230- 239. As shown, the field of view polygon can include details such as the ability to see through passages in obstructions, such as shown by the vertices 238 and 239 in Fig. 3b. Also associated with each camera is the location of the camera, shown for example as 220, 230, 240 in Fig.s 3a, 3b, 3c. The polygon representing the field of view of camera 104 is shown in Fig. 3c, comprising vertices 240 through 256. As shown in Fig. 3c, the field of view polygon can omit details, as shown by the use of vertices 244-245, omitting the actual field of view vertices 264-265. The level of detail of the polygons is relatively arbitrary; typically, one would provide the detail necessary to cover the maximum surveillance area within the secured area. If one area is coverable by multiple cameras, the need is minimal for identifying the fact that a particular camera can also view that area by viewing through a doorway. Conversely, if the only view of an area is through such a doorway, the encoding of the polygon to include this otherwise uncovered area may be worthwhile. Similarly, although an unobstructed view of a camera is infinite, polygon bounds can be defined to merely include the area of interest, as shown for example in Fig. 3c, where the bounds 249-250 and 253-254 are drawn just beyond the perimeter of the area being secured.

The coordinate system utilized for encoding the floor plan can be any convenient form. Actual dimensions, relative to some reference point, may be used; or, scaled dimensions, such as screen coordinates may be used. Techniques for converting from one coordinate system to another are well known to one skilled in the art, and different coordinate systems may be utilized as required. For example, the user input may be in the form of screen coordinates, and the camera locations may be in the form of dimensions used on the blueprints for the building. For ease of understanding, hereinafter the coordinate system used will be the screen coordinates, unless otherwise noted. Alternate views may also be presentable, for example, each floor of a multistoried building may be presented. If multiple plans are presented, the coordinate system will also include an identification of the plan to which the coordinates apply.

In operation, the operator need only point to the area on the floorplan to select a camera to view this area. Consider, for example, the operator pointing to a point P on the floorplan, as shown in Fig. 2, and correspondingly, Figs. 3a, 3b, and 3c. In response to this identification of point P, the system will select and adjust a camera whose view contains this point, as shown in the exemplary flowchart of Fig. 4. In Fig. 4, the various blocks have the following meaning:

400 User selects point P 410 Get P's coordinates XN

420 For each camera i

430 XN within CamPoly(i) ?

435 Mark camera i

440 Next camera 450 Select a marked camera

460 Determine line of sight from camera position to XN

470 Adjust camera to this line of sight

480 User selects alternate camera

490 Remote alarm 492 Mark each camera associated with this alarm

494 Get XN associated with this alarm.

495 Return

Upon receiving the user's selection of point P, at 400, the system determines the coordinates of this point, at 410. The system iterates 420-440 through each camera (I = 1 to Ν), and compares the coordinates of point P to the polygons associated with each camera, CamPoly(I), at 430. If the point P lies within the polygon associated with a camera, that camera identifier is marked for further processing, at 435. As shown in Figs. 3a, 3b, and 3c, the point P is located within the polygons associated with cameras 102 and 103, but not camera 104. After comparing the coordinates of point P with each camera's field of view polygon, the system selects one of the marked cameras, at 450. This selection may be arbitrary or based upon some algorithm, for example, the camera closest to the coordinates of point P may be the selected camera. If the point P does not lie within any of the camera's field of view, an error message may be presented (not shown). Having selected a camera, the direction of the point P from the location of the camera can be determined, at 460. This direction is the desired line of sight for the selected camera; the selected camera is adjusted to this line of sight at 470. Thereafter, the point P will appear in the center of the camera's displayed image in the monitor 150. If the camera is not adjustable, the point P will appear within the camera's displayed image, albeit not at its center. If the camera has a zoom capability, the preferred system will appropriately adjust the zoom in dependence upon the distance of the point P from the camera position. For example, if the point P is very close to the camera position, a low magnification would be employed, whereas if the point P is very far from the camera position, a high magnification would be preferred. In a preferred embodiment, an target span of view will be defined. The zoom will be adjusted dependent upon the distance between the camera and the identified point such that the arc-length of the camera's span of view is equal to this target span of view at the point. After adjusting the camera, the system returns from this routine, at 499, for subsequent user input.

The user is provided a means of selecting another camera, shown at 480. In the preferred system, the operator is provided an ability to sequence through all the marked cameras. The user enters an alternative-select command, and the system selects the next marked camera; if another marked camera does not exist, the system reverts to the selection of the first selected camera, thus cycling through all marked cameras repeatedly. If the system has remote alarm sensors, the occurrence of an alarm will effect a marking of the cameras associated with this sensor, as well as the identification of a target coordinate associated with this alarm. For example, if the alarm sensor is a switch attached to a door, all of the cameras which can view the area immediately adjacent this door will be associated with this switch, and the coordinates of a point on the secured side of the door may be identified as the target coordinate. Upon occurrence of an alarm, at 490, the system will mark each of the cameras associated with this alarm, at 492, and will set the target coordinates at 494. Alternatively, the association of cameras to each alarm need not be explicit; the target coordinate could be provided to the loop 420-440 to determine the cameras associated with the alarm. Thereafter, the system will select and adjust the camera as discussed above, at 460-470, equivalent to the operator having identified the target point directly.

As a further enhancement to the system, the user may be provided a view of the image from the selected camera in another region, or window, on the display screen 180, as shown at 510 in Fig. 5. The system provides the user the ability to point within the displayed image 510 to redirect the selected camera. Pointing, for example to the person 51 1 in the image, effects a movement of the camera, via the control 130, so as to center the person 511 in the image. Zoom-in and zoom-out options will also be provided, using for example, different button switches on the mouse 171. Also, a view from another camera which also includes the point P, or a camera viewing an area in the proximity of the point P, can also be displayed on the display screen 180, at 520, and the operator has the option of selecting a point within that region for camera selection and adjustment.

As shown, in accordance with this invention, the operator need only identify the area to be viewed, using an easy to use and intuitive interface to the control system, to automatically select and adjust a camera from amongst a multitude of cameras, to quickly have a view of the identified area presented for security assessment and subsequent action. The operator need not be concerned with the location, orientation, or identification of any particular camera within the system; the operator need only be concerned with selecting the area of interest. As presented, the utility of this interface is evident with regard to security systems; however, the application of this invention is not limited to security systems. Consider, for example, identifying home plate on a representation of a baseball field while a batter is at the plate will allow for the automatic selection, adjusting, and cycling through of all cameras covering home plate. The operator can thereafter merely point to a base, or to the stands, to obtain a view of actions there. Similarly, in a traffic control or traffic reporting system, the operator need only point to a map of the area to select the camera or cameras covering that area. As would be evident to one skilled in the art, the techniques presented herein could also be used to select input from other sensors, beyond video cameras. Although the maximum advantage of the invention presented herein is realized when the system comprises multiple cameras, the concepts presented are effective for automatically adjusting a single camera to view a particular area within the camera's potential field of view.

The system presented thus far can be enhanced by allowing for the display of the selected camera's current view span, overlaid on the graphic representation of the secured area. The camera's line of sight and angle of view define the camera's span of view; that is, the camera's span of view is the triangular area having an apex at the camera's location, and an apex interior angle equal to the camera's angle of view centered about the camera's line of sight. Displaying this span of view on the graphic representation of the secured area provides the operator with a reference base upon which to more easily assess the image being presented by the camera. That is, in a conventional system, it often takes a moment or two for an operator to discern what is being presented on the screen, particularly when the scene is one selected autonomously by the system. By providing the operator with another reference, the operator can more easily place the image presented "in context" with the secured area. For example, in response to an alert from an alarm sensor, the system in accordance with this invention will automatically select and adjust a camera to view the alarmed scene, and also present a display of where the view is coming from, relative to the floorplan of the secured area. Shown in Fig. 5 is a typical span of view overlay, defined by the angle of view 585 about the line of sight 580 of the camera 102, defined by the bounds 581 and 582. The scene shown at 510 merely displays a person near a doorway. By presenting the overlay comprising the bounds 581, 582, the view 510 is placed in the context of the building floorplan, so that the operator can more quickly and accurately assess the situation.

A preferred embodiment can be summarized as follows. In a multiple camera system 101-103, the views of a plurality of cameras are mapped on to a graphical representation. A user desiring to see an area within the system, points to a corresponding position within the graphical representation thru a user interface 171. The apparatus determines which of the cameras 101 -103 contains the indicated point within its field of view, and displays that camera's output on a monitor 150. If more than one camera has the point within its view, the user can chosse which camera to display. In an alternate embodiment. alarms 1 1 1, 1 12 are disposed within the viewed area. If an alarm 1 1 1, 1 12 is triggered, it is the equivalent of a user pointing to the location of that alarm on the graphical representation.

The foregoing merely illustrates the principles of the invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements which, although not explicitly described or shown herein, embody the principles of the invention and are thus within its scope. Any reference signs in the claims are not to be construed as limiting the scope of the invention as claimed. The word "comprising" does not exclude the presence of other elements or steps than those listed in a claim. The invention can be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the device claim enumerating several means, several of these means can be embodied by one and the same item of hardware.

Claims

Claims:

1. A camera control system for adjusting a camera's (101-103) line of sight, said camera (101-103) having a position and a field of view about this position, said camera ( 101 - 103) also having a line of sight and a span of view about its line of sight, said control system comprising: means (150-153) for displaying a representation of the camera's (101-103) field of view, means for identifying a target point (P) within the representation of the camera's (101-103) field of view, means for determining an orientation angle between the camera's (101-103) position and the target point (P), and means for adjusting the camera's line of sight in dependence upon the orientation angle such that the target point (P) is located within the camera's (101-103) span of view.

2. A camera control system as claimed in claim 1, wherein the representation of the camera's field of view is a floor plan.

3. A camera control system as claimed in claim 1, wherein the means for displaying the representation comprises a video monitor and the representation is an encoding of a floor plan within the control system.

4. A camera control system as claimed in claim 1 , further comprising: means for displaying a representation of an other camera's field of view, means for identifying a target point within the representation of the other camera's field of view, means for determining an orientation angle between the other camera's position and the target point, and means for adjusting the other camera's line of sight in dependence upon the orientation angle such that the target point is located within the camera's span of view.

5. A camera control system as claimed in claim 4, wherein the representation of the camera's field of view, and the representation of the other camera's field of view, are contained within a composite representation, and the composite representation is displayed.

6. A camera control system as claimed in claim 5, further comprising means of displaying an image from the camera and a means of displaying an image from the other camera.

7. A camera control system as claimed in claim 6, further comprising means for selecting (171-174) between the camera and the other camera; wherein: said line of sight adjusting means and said image displaying means are dependent upon said camera selection.

8. A camera control system as claimed in claim 7, wherein said camera selection is dependent upon the identified target point.

9. A security system for monitoring a secured area, the security system comprising: at least two cameras (101-103), each camera (101-103) having an associated field of view, means for selecting a primary camera from among said cameras (101-103), means for displaying (150) an image from the primary camera, means for displaying a representation of the secured area, means for identifying (171-174) a target point (P) within the representation of the secured area, means for determining whether the target point (P) is within each of the fields of view, wherein the selection of the primary camera is dependent upon the determination of whether the target point (P) is within the field of view associated with said primary camera.

10. A security system as claimed in claim 9, wherein each field of view has an associated polygon (221-256) within the representation of the secured area, the target point is identified by a target coordinate pair within the representation of the secured area, and the determination of whether the target point is within each field of view is effected by determining whether the target coordinate pair is within each associated polygon (221-256).

11. A security system as claimed in claim 9, further comprising a means for displaying a representation of the primary camera's field of view upon the representation of the secured area.

12. A security system as claimed in claim 9, further comprising: means for displaying images (150-153) from a plurality of the cameras, means for identifying a target image point within any one of the displayed images, wherein said identification of the target point is effected by the identification of said target image point.

13. A security system as claimed in claim 9, wherein: at least one of said cameras has an adjustable line of sight, said security system further comprises means for adjusting (130) said adjustable line of sight, and said adjustment of the line of sight is dependent upon the identified target point.

14. A security system as claimed in claim 13, further comprising a means for displaying a representation of said one or more adjustable lines of sight upon the representation of the secured area.

15. A security system as claimed in claim 13, further comprising; a means for identifying a target image point within the display of the image from the primary camera, wherein said identification of the target point is effected by the identification of said target image point.

16. A security system as claimed in claim 9, further comprising: one or more alarm sensors (111,112) , each of which has an associated alert signal and an associated alert point, means for identifying a target alert point from among said alert points in dependence upon said alert signals, wherein said identification of the target point is effected by the identification of said target alert point.

17. A camera control method for adjusting a camera's (101-103) line of sight, said camera (101-103) having a position and a field of view about this position, said camera (101- 103) also having a line of sight and a span of view about its line of sight, said control system comprising: displaying (150-153) a representation of the camera's (101-103) field of view, identifying a target point (P) within the representation of the camera's (101-103) field of view, determining an orientation angle between the camera's ( 101 - 103) position and the target point (P), and adjusting the camera's line of sight in dependence upon the orientation angle such that the target point (P) is located within the camera's (101-103) span of view.

18. A method of monitoring a secured area, the method comprising: selecting a primary camera from among at least two cameras (101-103), each camera (101- 103) having an associated field of view, displaying (150) an image from the primary camera, displaying a representation of the secured area, identifying (171-174) a target point (P) within the representation of the secured area, determining whether the target point (P) is within each of the fields of view, wherein the selection of the primary camera is dependent upon the determination of whether the target point (P) is within the field of view associated with said primary camera.