Panoramic photography
has become a popular medium since the advent of the Internet and
software presentation technology such as Apple’s QuickTime
Virtual Reality (QTVR). The combination of a well-commercialized
and low-cost digital scanner with some simple modifications can
net a high quality digital panoramic camera.
The immersive qualities on observers of wrap-around video and
the compelling nature of the ability to interactively pan around
in a
fixed eyepoint environment are well known. Unfortunately, the production
of these images is presently either very tedious or the camera
very expensive. If film is the original medium, it must then be
digitized
for computer use.
Enter the digital hand scanner -- a relatively low-cost collection
of lens, mirrors, linear color CCD sensor, electronics, mechanics,
and software. In it’s off-the-shelf form, it is intended to
connect to a special input card or to the PC’s parallel port
and, while carefully dragging it across a piece of paper or artwork,
transfer the image digitally to the computer. Though not as useful
as a flatbed scanner for normal scanning, the hand scanner’s
portability and small size makes it a natural for use as a camera.
Through modification (some call it butchering) with a knife, file, saw, and
some electronics, it becomes a 360 degree digital panoramic color
camera capable of producing remarkable images exceeding 27 Mbytes,
which are directly importable into presentation technologies such
as QTVR.
click on a thumnail below for a scrolling panoramic view (JPG: 220K)
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Panoramic Image of a boat dock at sunset
We have been experimenting with an inexpensive form of digital
panoramic camera produced from a modified hand scanner. The image
above shows two hand scanners that gave up their lives to become
cameras. The one on the left is a Primax scanner that had initial
trouble and didn’t seem to perform as well as the Logitech
Scanman2000, on the right. We cannot offer a detailed recipe today
though we may eventually publish a complete modification after
we extract all the research and publishing dues we can. Though
the modification is reasonably straightforward, it is not for the
faint at heart and requires a working knowledge of optics, mechanics,
and electronics. A laptop PC and tripod is also required. Total
cost for the camera, not including R&D time, the tripod or
laptop computer, is around $250US. Conversion of the images to
QTVR takes just minutes.
click on the thumnail below for a larger image (640 px 480 px)
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Panoramic Camera Schematic
View the Siggraph ‘97 presentation
slides.
- 1. Actually two separate scans composited - one with the camera
looking up and one with it looking down. The digital accuracy
of the images allows this to be accomplished easily. The hot
spot
in the center is indicative of the lack of dynamic range.
- 2. The lab’s vacation in Destin Florida. This too was
made up of two pans and easily stitched together in Photoshop.
The overall
image is about 360deg x 120deg.
- 3. Demonstrates the stock hand scanner’s inability to
filter InfraRed, but the result is interesting (reminds me of
Kodak’s
Ektachrome IR). This too was made up of two pans - one looking
about 40 degrees down and one looking about 40 degrees up for
a ~360deg x 140deg picture. Note the detail in the grass.
- 4. In an attempt to compensate for the lack of dynamic range
of the scanner (limited to 8 bits), I’ve been experimenting
with an automatic exposure compensation system. These two pans
show the advantages and disadvantages of this method. The upper
image (360 x 90) is of one of our labs, where there’s a
measured 8-stop difference between an averaged meter reading
of the inside
and outside.
- 5. Even though it looks like two differently exposed images
composited together (inside vs outside), it is not. It was exposed
in a single
pan. The second image is of the same lake location as in the
IR image, but with auto-exposure enabled (and no IR). This compensation
tends to make every vertical scan line of the picture a “normal” exposure.
When looking directly into the sun, it compensated by reducing
the exposure, but (aesthetically) overcompensated when exposing
the house and tree. You’ll also notice exposure bands in
the grass as the scanner compensated on-the-fly to the bright
sky above. Having the image immediately available and with appropriate
on-the-fly exposure adjustment should allow for a near-perfect
image in the field.
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Images
Taken with the Panoramic Digital Camera
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