IEEE Consumer Electronics Magazine - January/February 2022 - 18

Smart Omnidirectional Video Capturing
& IN RECENT YEARS, there has been increased
interest in the capture of 360 photographs and
videos from omnidirectional cameras, which cameras
equipped on either side with fisheye lenses
with a 180 field of view. Applications for omnidirectional
cameras are increasing, because they
allow one-shot capture of panoramic images.
Figure 1 shows an image acquired by an omnidirectional
camera. There are two circular images,
each simultaneously captured by one of the two
fisheye lenses on either side of the camera.
There are many potential applications for
omnidirectional cameras, including interior
views for real estate listings, drive recorders, surveillance
cameras, 1, 2 marine photography when
equipped with a waterproof housing,3,4 aerial
photography when mounted on a drone,5 and
production of virtual reality scenes.6-10 Application
fields therefore include entertainment, business,
and crime prevention. Recent research on
omnidirectional cameras has included work
related to encryption and other topics related to
the images themselves,11-16 as well as the application
of omnidirectional cameras in robot control
and advanced road traffic systems.17-22
Omnidirectional cameras have a fisheye lens
on either side (see Figure 1), so when mounting
them on robots, drones, or automobiles, they
must be mounted so that the fields of view of the
fisheye lenses will not be obstructed, sometimes
making it difficult to select a good mounting
position. In some cases, the robot or vehicle on
which the camera is mounted will be partially
included in images no matter where the camera
is affixed.
For example, installation on a humanoid
robot in a manner that does not obstruct the
field of view might require mounting on top of its
head, therefore interfering with operations. In
contrast, a mounting like that shown in Figure 2,
with cameras affixed to the front and back of the
head, would allow image acquisition that does
not interfere with operations.
However, in contrast to using a single omnidirectional
camera, using two hemispherical cameras
can result in differences in distance or height
between the cameras. In this article, we focus on
this situation. When the differences in distances
or height between the cameras are very long,
stitching the images from both cameras becomes
18
complicated since it is difficult to acquire the common
information from the both camera images to
be used for the stitching process. However, by
considering particular applications such as installing
robots, we target to generate omnidirectional
images from the two hemispherical camera
images by keeping these distances maximum of
50 cm. In this article, we used two hemispherical
cameras capable of capturing images with a 185
field of view in all directions, placing a circular
object in the overlapping region in the field of
view. By detecting the same circle within this
overlapping region, parameters of the circle can
be used to stitch together the images from each
camera to realize the same kind of panoramic
image as that from an omnidirectional camera,
even without the back-to-back lens structure. In
conventional methods, stitching is generally realized
by matching feature points and feature areas
in each image.23-26 Here, we prepareacircular
object, detect it in each camera image, and stich
the images together by matching parameters of
the two detected circles. This approach has the
following advantages.
Circular shapes experience little deformation
in hemispherical images, so high-performance
stitching is possible even for distorted images.
Stitching is performed by matching circle
parameters, so the process from circle detection
to stitching can be realized within a few
seconds, improving applicability.
When using two fixed cameras, stitching is
performed once at the start of imaging, then
imaging continues according to the stitching,
allowing acquisition of omnidirectional images.
We confirmed the effectiveness and usefulness
of the proposed method by performing several
experiments using the proposed method for
omnidirectional imaging while changing horizontal
and vertical distances between the cameras.
PROPOSED METHOD
Hemispherical Cameras
In this article, we used two Casio EX-FR200
hemispherical cameras, which are easily mountable
and have a removable camera lens and control
device. This camera uses a fisheye lens
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IEEE Consumer Electronics Magazine - January/February 2022

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