[Studies in Computational Intelligence 481] Artur Babiarz, Robert Bieda, Karol Jędrasiak, Aleksander Nawrat (auth.), Aleksander Nawrat, Zygmunt Kuś (eds.) - Vision Based Systemsfor UAV Applications (2013, Sprin

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monitoring parts of the process in factories or in observation of surroundings of
unmanned aerial vehicle (UAV) [12]. There are also many other types of video
acquisition devices, e.g. stationary or rotating camera. Each type has its pros and
cons. The project purpose was to create a device, which combines advantages of
other devices and avoids the disadvantages. Basic assumption was that the device
has to have possibility to trace all its surroundings and allow instant changes of
direction of video acquisition.
2 General Concept of Omnidirectional Video Acquisition
The idea of creating a device with a wide range of view is not something new.
Solutions, which offer such video canvassing, already exist. An example of such
appliance can be rotating camera (fig. 1). The wide angle of sight of this camera is
obtained through the movement of the camera in horizontal or/and in vertical direction.
This creates a possibility to direct the camera on the desired area, which is
limited only by the range of its movement. When the designated point in space,
which is supposed to be captured by camera, is not covered by its current field of
view, a latency caused by the time needed to turn rotating camera appears. This
solution, theoretically, provides capturing video with 360º of horizontal field of
view but at a given instant, operator can observe only a little range of this space.
This is why constant operator attention is needed.
Another solution is camera with a "Fisheye" type lens (fig. 1). It allows observation
of the whole half-sphere at one moment. The application of such lens with
a short focal length, increases the angle of the view of the camera but the result of
that operation is considerable image distortion. This “barrel” distortion, is the
main disadvantage of cameras based on fisheye lenses. This aberration occurs,
when with increasing distance from the middle of captured video stream and approaching
the edges of the field of vision, image becomes smaller. It is possible to
try to straighten such an image but it is not easy and involves a considerable loss
of part of image, and reduction of its quality.
Device, which combines the advantages of the rotating camera as well as the
“fisheye” lens is an OVAD (fig. 1). Assembling several cameras enables parallel
multidirectional canvassing. The quantity of the cameras depends on the width of
their visual field. If the sum of the visual fields of all the cameras is greater or
equal than 360º then the image is being registered from all directions. To obtain an
image from desired area all that is need to be done is to choose the appropriate
camera and operator can immediately get access to it, not having to wait until
camera turns to the designated position. Not only does the video stream include
the entire 360° horizontal field of view, but it also is not distorted, so it shows no
signs of the biggest disadvantage of the fisheye lens. Correction of a small barrel
distortion, which appears on video captured by used cameras, can be conducted by
a computer program. An application combining the images from all six cameras
together into one video panorama is an additional advantage of such a solution.