WO2009069996A2

WO2009069996A2 - Apparatus and method for panoramic imaging

Info

Publication number: WO2009069996A2
Application number: PCT/MY2008/000167
Authority: WO
Inventors: Hock Woon Hon
Original assignee: Mimos Berhad
Priority date: 2007-11-27
Filing date: 2008-11-26
Publication date: 2009-06-04
Also published as: WO2009069996A3; MY146163A

Abstract

The present invention relates to an apparatus for panoramic imaging using a wide- angle lens camera with leveling control mechanism and a method for transforming video images using non-linear spatial sampling correction. The apparatus comprises a single video camera mounted with a wide-angle lens that is covered by a transparent dome cover, a level control which consists of a two-axis tilt controller and gear, video capturing device and a joystick for adjustment of the leveling-control. The wide-angle lens is preferably a fisheye lens. The method, on the other hand, comprises capturing a circular image using a fisheye lens, transforming the spherical image produced by the fisheye lens into two hemispherical portions, initiating destination maps fro position of x-axis and y-axis to sepárate the circular image, and transforming resultant circular images using non-linear spatial sampling correction method into a human understandable perspective view.

Description

APPARATUS AND METHOD FOR PANORAMIC IMAGING

The present invention relates panoramic imaging. More particularly, the present invention relates to an apparatus for panoramic imaging using a wide-angle lens camera with leveling control mechanism and a method for transforming video images using non-linear spatial sampling correction.

BACKGROUND TO THE INVENTION

In Image surveillance, there are two preferred methods in surveillance system. First is by using high resolution imaging and second is by using wide coverage imaging. In wide coverage imaging, to maximize the coverage of the surveillance area, one would need to use multiple cameras to cover up large area especially a 360 degree or a single camera with a wide angle lens such as fisheye lens to cover wide field of view.

In surveillance with multiple cameras, a large number of security officers are required to monitor the cameras. On the other hand, if one uses a fisheye camera for surveillance, the images captured are highly distorted and difficult for human interpretation. This effect is particularly apparent as the diameter increases from the centroid due to the nature of the wide angle lenses. The object to image space sampling ratio reduces as it moves from the centroid towards the edge of the circular images.

U.S Patent No. 5,359,363 is an example of a surveillance system that uses a fisheye lens wherein the produced circular image of an entire field of view is mathematically corrected using high speed electronic circuitry. The correction is done by transforming a region of interest into a perspective correct image by an image processing computer. The image processing computer provides direct mapping of the image region of interest using an orthogonal set of transformation algorithms. Thus, it does not transform the entire image input but just the portion of interest.

SUMMARY OF THE INVENTION

The present invention is directed to overcoming one or more of the problems set forth above. In one aspect of the present invention, there is provided an apparatus for panoramic imaging using a camera having a wide angle lens with leveling-control mechanism. The apparatus comprises a video camera having a wide-angle lens that is covered by a transparent dome cover, a level control which consists of a two-axis tilt controller and gear, a video capturing device and a joystick for adjustment of the leveling- control.

In another aspect of the present invention, there is provided a method for transforming video images using non-linear spatial sampling correction. The method comprises capturing a circular image using a camera having a wide-angle lens, transforming the spherical image produced by the wide-angle lens into two hemispherical portions, initiating destination maps from position of x-axis and y-axis to separate the circular image, and transforming resultant circular images using nonlinear spatial sampling correction method into a human understandable perspective view.

The wide-angle lens is preferably a fisheye lens.

It is an advantage of the present invention to address the problem of wide coverage by putting forward a solution using a single camera for panoramic surveillance view. The combination of the apparatus and image transformation techniques enables the cost effective 360 wide-angle view surveillance solution.

It is another advantage of the present invention to produce a 360 degree view using a single camera with a transformation method that incorporates non-linear spatial sampling correction.

It is yet another advantage of the present invention to apply calibration method to ensure a perfect perpendicular position between the camera and the floor for panoramic imaging.

These and other aspects, objects, features and advantages of the present invention will be more clearly understood and appreciated from a review of the following detailed description of the preferred embodiment and appended claims, and by reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

The specific features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where:

Fig. 1a illustrates an apparatus for panoramic imaging using a wide-angle lens camera according to the present invention;

Fig. 1b illustrates the apparatus with a level ing-control mechanism according to the present invention;

Fig. 2 illustrates a method for transforming video images using non-linear spatial sampling correction according to the present invention; and

Fig. 3 illustrates a flowchart of the non-linear spatial sampling correction in detail according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following description of the preferred embodiments of the present invention, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. It is understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention.

In Fig. 1a and 1b, there are shown a single video camera 103 mounted with a fisheye lens 104 is equipped with leveling-control mechanism. The video camera 103 with a fish eye lens 104 is covered and protected by a transparent dome cover 105. The video camera 103 is installed on the ceiling whereby only the dome cover 105 is visible, the video camera 103, on the other hand, is hidden on the upper part of the ceiling.

The leveling-control mechanism is to ensure images captured by the video camera 103 is perpendicular to the ground since imaging arrangement and technique work best when the video camera 103 and the ground forms a 90-degree right angle. The leveling-control mechanism is achieved by a two-axis tilt controller 101 and gear 102.

When video signal is sent to a video capturing device 106, the position of the video camera 103 is adjusted using the leveling control mechanism through a joystick 107. The adjustment is made with an adjustable and tiltable control mechanism with a piece of card 109 that with a cross in the middle. The card 109 is placed on the floor and facing the video camera 103.

The camera view is displayed on the screen of the camera 103 therefore the camera 103 can be adjusted up-down and left-right according to the image appeared on the display. The adjustment is done manually with a joystick 107 or automatically by incorporating image processing to detect the lengths of the cross. The result from the cross measurement is then converted into control signal to adjust the camera 103.

Fig. 2 illustrates a method for transforming video images using non-linear spatial sampling correction.

Circular image 301 produced by the fisheye lens 104 is transformed into two hemispherical portions 303 by separating the circular image 301 into two half of the circle 302. To separate the circular image 301 into half, center point, radius and angle resolution of the circular image 301 has to be determined first by initiating destination maps for position of x-axis and y-axis to separate the spherical image 301.

The geometric transformation is dependent upon the center point of the circular image 301, the radius of the image and angle resolution of the circular image 301.

The two hemispherical portions 303 are then remapped to a rectangular image 305 through image straightening method 304 wherein each of the pixels in the two hemispherical portions 303 is mapped to its rectangular representation and when this is done a spatially distorted rectangular image 305 is formed. The rectangular image 305 is corrected by a non-linear spatial sampling correction 306.

Referring to Fig. 3, the rectangular image 305 is stretched nonlinearly according to the object-to-image space compression that has been experienced by the capture image. The non-linear spatial sampling correction method 306 comprises the following steps:

determining destination image dimension for non-linear re-sampling of y-axis 307;

determining vertical stretching factors for y-axis according to the respective position and destination size of the image 308;

increasing image sampling from the center towards the bottom edge of the image 305 until the end point destination of the y-axis is reached 309; and

achieving linear distribution of vertical lines across the y-axis in the rectangular image 305 which forms a spatially corrected panoramic image 310.

Claims

1. An apparatus for panoramic imaging using a camera (103) having a wide- angle lens with level-control mechanism, comprising:

a two-axis tilt controller (101) and a gear (102) to ensure the camera (103) is perpendicular to the ground;

a dome cover (105) to cover and protect the camera (103);

a video capturing device (106); and

a joystick (107) to control and adjust the leveling control of the camera (103).

2. An apparatus according to claim 1 , wherein the wide-angle lens is a fisheye lens (104).

3. An apparatus according to claim 1 , wherein the camera (103) is installed on a ceiling with only the dome cover (105) is visible.

4. An apparatus according to claim 1 , wherein the position of the camera (103) is adjusted to be perpendicular to the ground using the joystick (107) once the video capturing device (106) receives video signal.

5. A method for transforming video images to rectangular video using non-linear spatial sampling correction, comprising the steps of:

separating a circular image (301) produced by a camera (103) having a wide- angle lens into two hemispherical portions (303) by separating the circular image (301 ) into half of the circle (302); initiating destination maps fro position of x-axis and y-axis to separate the spherical image (301) by determining center point, radius and angle resolution of the spherical image (301);

re-mapping and straightening the two hemispherical portions (303) to a rectangular image (305); and

correcting sampling distribution of the rectangular image (305) through nonlinear spatial sampling correction (306).

6. A method according to claim 5, wherein the non-linear spatial sampling correction comprises:

determining destination image dimension for non-linear re-sampling of y-axis

(307);

determining vertical stretching factors for y-axis according to the respective position and destination size of the image (308);

increasing image sampling from the center towards the bottom edge of the image (305) until the end point destination is reached (309); and

achieving linear distribution of vertical lines across the y-axis in the rectangular image (305) which forms a spatially corrected panoramic image (307).

7. A method according to claim 5, wherein the wide angle lens is a fish eye lens.