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Close-range imaging, long-range vision

T. Noma*“, H. Otani”, T. Ito", M. Yamada", N. Kochi"
* Imaging Laboratory, R & D Center, ® Surveying Instruments Div., Topcon Corporation
75-1, Hasunuma-cho, Itabashi-ku, TOKYO, 174-8550 JAPAN
Commission V, WG V/1
KEY WORDS: Digital Camera, Calibration, Non-Metric, Close Range, Software, Three-dimensional Measurement
Recently the spectacular development of an ordinary mega-pixel digital camera as well as that of computer system made it possible
to use this kind of camera for measuring work.
We have, therefore, developed DC-1000, a software which can easily make camera calibration for 3D measurement with an ordinary
digital camera. We have further developed a system to make possible both calibration and 3D measurement on the actual site, using
the camera’s zoom and auto-focus functions. In this way we can now obtain high quality image and accuracy under almost any given
photographic condition, which used to be difficult before. And further more, by connecting the system with PI-2000, our digital
plotter based on PC and DI-1000, our software to make ortho-image, we succeeded the 3D photo-measurement by the calibration
even on-site.
Thus with this new system we have succeeded to attain the accuracy as high as 2mm for targeted accuracy of lcm, extremely
satisfactory result to measure whole variety of objects on their actual site, archaeological site, for example.
For photo-measurement with an ordinary mega-pixel digital
camera, we definitely need to know the camera's interior
orientation parameters (focal length, principal point position,
Especially we have to solve the problem of its considerable
lens-distortion as well as to obtain the highly accurate focal
length to raise the 3D accuracy.
For this purpose, we have already been using the 3D Target-
field to make camera calibration, but this requires a specially
prepared field of very high precision as in the Figure 1, the skill
and time on the part of the users and complicated costly
adjustment for each newly invented camera constantly flowing
into the market.

Figure 1. 3D Target-field
We have developed, therefore, a handy device even for the non-
skilled users to make the necessary calibration with much ease.
This device is composed of a simple flat sheet and its software
DC-1000, which of course has the capability to make
calibration with 3D Target-field.
Before our new invention, we used to make calibration by
fixing the focal length of the camera and only at this fixed focal
position we could photo the object to measure and analyze. For
this reason, depending on the object and surrounding condition,
we sometimes could not obtain the true focus, nor high quality
image, nor necessary accuracy. Besides, we were often obliged
to change the camera or lens to adjust with the size of the object
or photographing condition or we had to do the calibration all
over again.
To overcome such inconveniences, therefore, we have
developed a system to make calibration on site and confirmed
its capability, by actually making calibration and 3D
measurement with the targeted accuracy within lcm.
In this presentation, therefore, we should like to explain DC-
1000, the software for camera-calibration, its capability and the
result of its test use in 3D measurement on site. In this test we
chose a stone wall as if it were the site of an archaeological ruin.
We have already developed PI-2000, a digital plotter based on
PC and DI-1000, a software to make ortho-image for digital
photogrammetry (Otani, Ito, Kochi and others 2000).
But we have now further developed DC-1000, the system for
camera calibration to complement PI-2000 and DI-1000 in our
line of products.