International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B5. Istanbul 2004
Figure 1. Image data
3.3 Experimental Results
There are respectively 113 points, 84 points, 115 points and 97
points extracted out from the four images with the projected
grid ant there are 409 points in total. Using the algorithm to
compute these observation values of the points, the parameters
of the slide projector are computed by the calibration method
mentioned above shown in Table 1.
yo (pixel)
381.938052
f (pixel) Xo (pixel)
1676.835624 509.105746
Table 1. Parameters of the slide projector
In order to verify the results of calibration, the space
coordinates of the points projected in 4 images are calculated
respectively using the parameters of the slide projector
calibration and the parameters of the digital camera calibration.
Comparing the two sets of the calculated coordinates, the root-
mean-square errors of the space coordinate residuals are
calculated. The number of points and the values of the root-
mean-square error are shown in Table 2.
Number of points RMSEx (mm) RMSEy (mm)
409 0.594 0.892
Table 2. The root-mean-square error of the coordinates of the
points
Because the control ground is not very stable and exquisite,
there exists system error in the designed space coordinates
integrally. At the same time, the distance between the projector
and the planar grid is relatively far so that the distortion of the
projector is relatively hard. Because of the two reasons above,
the values of the root-mean-square error in this experiment are
poor relatively. However, the results of the experiment are
satisfied with the requirement of the close-range
photogrammetry essentially.
4. CONCLUSIONS
The paper provides a flexible technique to calibrate the slide
projector easily and practically. The technique only requires an
ordinary slide projector, a digital camera, and a planar grid and
it is hardly affected by the space factor or time factor. The
paper also deduces the detail algorithm of this technique and
supplies the real data slide projector calibration. These two
aspects have proved that the technique this paper prospered is
feasible and proper.
ACKNOWLEDGMENTS
Thanks for the supporting from Specialized Research Fund for
the Doctoral Program of Higher Education, P. R. China (No.
2001048601 1).
REFERENCES
Deren Li, 1992, Analytical Photogrammetry, Wuhan
University Press, Wuhan, China.
Huynh, D. Q., Owens, R. A., and Hartmann, P. E., 1999.
“Calibrating a Structured Light Stripe System: A Novel
Approach," Int. J. Comput. Vis., 33, No. 1, pp. 73-86.
Jianging Zhang, Jun Tao, Zuxun Zhang, 2003. A flexible
technique for the slide projector calibration, Proceedings of
SPIE - The International Society for Optical Engineering,
Beijing, China, v 5286, n 1, pp. 187-190.
Wenhao Feng, 2002. Close-Range Photogrammetry, Wuhan
University Press, Wuhan, China.
Zhang Zhengyou, 1998. A Flexible New Technique for
Camera Calibration, Technical Report, Microsoft Research,
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Zhizhuo Wang, 1990. Principles of Photogrammetry,
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Zuxun Zhang, and Jianging Zhang, 2000. Digital
Photogrammetry, Wuhan University Press, Wuhan, China.
Zuxun Zhang, and Yongjun Zhang, 2002. Digital Camera
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