Flexible Mirror Imaging |
 | The field of view of a traditional camera has a fixed shape, which limits how
one can compose scenes. In this project, we designed a novel imaging system
that allows the size and the shape of the field of view to be controlled. Our
system consists of a conventional camera that images the scene reflected in a
flexible mirror sheet. By deforming the mirror, we can generate a wide and
continuous range of smoothly curved mirror shapes, each of which results in a
unique field of view. In order to analyze a captured image we need to know the
shape of the mirror when the image was taken. Towards this end, we have
developed a simple calibration procedure that estimates the 3D mirror shape
from the 2D projection of the mirror boundary visible in the captured image.
Knowledge of the 3D mirror shape allows us to analyze different properties of
the captured image, such as, the locus of viewpoints, the captured field of
view and the resolution characteristics.
An image captured by our system is typically multi-perspective with
spatially varying resolution, and hence has distortions. We have developed an
efficient algorithm that minimizes these distortions by mapping a captured
image to an equi-resolution image -- an image in which all pixels have the same
field of view. Equi-resolution images do not have rectangular boundaries and
hence look odd as we are used to seeing rectangular images. We address this
issue by applying an image warp based on thin plate splines that maps the
boundary of the equi-resolution image to the boundary of a rectangle. In this
way we obtain rectangular images with unconventional fields of view and low
distortion. The ability to control the size and the shape of the field of view
enables us to compose scenes in ways that were not possible before. Extending
this to video permits time-varying composition of dynamic scenes. |
Publications
"Flexible Mirror Imaging,"
S. Kuthirummal and S. K. Nayar,
ICCV Workshop on Omnidirectional Vision, Camera Networks and Non-classical Cameras (OMNIVIS),
Oct, 2007.
[PDF] [bib] [©]
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Images
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Flexible Field of View Imaging System:
The proposed imaging system consists of a conventional camera that images the
scene reflected in a flexible mirror sheet. By deforming the mirror we can
generate a wide and continuous range of smoothly curved mirror shapes, each of
which results in a new field of view with a unique size and shape.
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Seeing Both Sides of a Street:
In this example, the horizontal field of view is increased to see both sides of
the street while keeping the vertical field of view almost the same. Click on
the image to see the captured field of view and the computed equi-resolution
and rectangular images.
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Looking Up a Street:
Here, the vertical field of view is increased to look up a street and the sky.
Click on the image to see the captured field of view and the computed
equi-resolution and rectangular images.
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Two People and a Butterfly:
In this example the field of view was shaped to include the butterfly (while
excluding the scene region above it) and to include the person on the left.
Click on the image to see the captured field of view and the computed
equi-resolution and rectangular images.
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Panning Up:
Here, the vertical field of view is increased, while maintaining the horizontal
field of view. Click on the image to see the captured field of view and the
computed undistorted equi-resolution and rectangular images.
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Birthday Group Photograph:
When taking a group photograph, like at a birthday, we often encounter the
problem that everyone does not fit in the picture. In this example, we
increased the horizontal field of view to fit everyone into the picture. Click
on the image to see the captured field of view and the computed equi-resolution
and rectangular images.
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Videos
If you are having trouble viewing these .wmv videos in your browser, please save them to your computer first (by right-clicking and choosing "Save Target As..."), and then open them.
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Omnivis 2007 Video:
This video shows the proposed imaging system with a flexible field of view and
several compositions of dynamic scenes captured by our system where the field
of view is varied over time. (With narration)
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Flexible Field of View Imaging System:
The construction and working of the proposed imaging system are described in this video. (With narration)
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Seeing Both Sides of a Street:
This video shows how the field of view can be changed to see both sides of a street.
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Conversation:
In this example, the ability to control the shape and the size of the field of
view enables different parts of the scene to be introduced as a conversation
progresses. (With audio)
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Panning Up:
This video shows that a conventional camera captures only the feet of a person,
while the proposed system enables the field of view to be varied to include the
entire person.
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Birthday Group Photograph:
Often when taking a group photograph, like at a birthday, not everyone fits in
the picture. This video shows how the field of view can be varied to include
everyone in the picture.
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Slides
OMNIVIS 2007 presentation With videos (zip file)
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Scene Collages and Flexible Camera Arrays
Catadioptric Cameras for 360 Degree Imaging
Applications of 360 Degree Cameras
Non-Single Viewpoint Imaging: Raxels and Caustics
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