디지털 팬/틸트/줌/슬라이드 기술

Digital pan/tilt/zoom/slide technique

권경일, 최영호*

호남대학교 광전자공학과*호남대학교 정보통신공학과

kweon@honam.ac.kr

There have been many researches about extracting rectilinear images from fisheye images.

Some patent even describes an imaging system that is able to perform digital pan/tilt/zoom

operations without a physically moving part(1). In the above invention, however, vertical lines

generally do not appear as vertical lines after the software pan/tilt/zoom operation has been

performed, and the obtained images still show distortions.

We have developed image processing algorithms for digital pan/tilt/zoom/slide operations,

where vertical lines appear as vertical lines and the images are distortion-free(2). Figure 1 is

the model of a projection scheme of a general wide-angle lens used in our investigation, and

Fig. 2 is an imaginary fisheye image produced by professor Paul Bourke. Figure 3 is a

schematic diagram illustrating the rectilinear projection scheme. By definition, a lens with a

rectilinear projection scheme is a distortion-free lens, and in mathematical viewpoint, the

characteristics of a rectilinear lens are considered identical to those of a pinhole camera. To

obtain a rectilinear image from a fisheye image obtained with a fisheye lens having a real

projection scheme, the functional relation between the pinhole camera model and the real

projection scheme of a lens must be clarified. For digital pan/tilt/zoom/slide operations, object

plane must be appropriately rotated and translated in three dimensional space. Figure 4 is a

pan/tilt image extracted from the imaginary fisheye image given in Fig. 2, and Fig. 6 is a

pan/tilt image extracted from a real fisheye image given in Fig. 5.

In conclusion, we have developed a mathematically precise image-processing algorithm for

extracting a rectilinear image from a fisheye image as well as digital pan/tilt/zoom technology.

Using this technology, vertical lines always appear as vertical lines in the panned and/or tilted

images, and the images are distortion-free.

Acknowledgement

This work was supported by grant No. RTI04-03-03 from the Regional Technology

Innovation Program of the Ministry of Knowledge Economy (MKE).

(1) S. D. Zimmermann and D. Kuban, "A video pan/tilt/magnify/rotate system with no moving

parts", in DigitalAvionicsSystemsConferenceProc.IEEE/AIAA11th, 523-531 (1992).

(2) G. Kweon, "Method and apparatus for obtaining panoramic and rectilinear images using

rotationally symmetric wide-angle lens", Korean patent 10-0898824 (May 14, 2009).

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Fig. 1: A schematic diagram illustrating the real

projection scheme of a general rotationally

symmetric lens.

Fig. 3: A schematic diagram illustrating the

rectilinear projection scheme.

Fig. 5: An exemplary image of an interior scene

captured using a fisheye lens having a FOV of

190°.

Fig. 2: An exemplary image produced by a

computer assuming that a fisheye lens with an

equidistance projection scheme has been used to

take the picture of an imaginary scene.

Fig. 4: An exemplary rectilinear image obtained

after applying pan·tilt operation to the fisheye

image given in Fig. 2.

Fig. 6: An exemplary rectilinear image obtained

after applying pan·tilt operation to the fisheye

image given in Fig. 5.

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