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MAKE WIDE-ANGLED AERIAL CAMERA BY COMBINING
SMALL-SIZED AREAL ARRAY CCD SENSORS
WenLing Xuan '^ , Dong Wang”, Jie Sun °
? Information Institute, Wuhan Univ.,129 LuoYu Rd. Wuhan,Hubei Prov. PRC,430079;
B College of Geo-inf. Science & Engineering, Shandong Univ.of S&T, Tai’an, ShandongProv. PRC,271019;
^ Chinese Academy of Surveying & Mapping, 16 BeiTaiPing Rd. Beijing.PRC,100039
paper nstl?yahoo.com.en fax 86 10 68181834
ABSTRACT
A new method for combining small-sized areal array CCD sensors to make one wide-angled digital aerial photography system is
studied in this paper. The method is to install several small-sized areal array CCD cameras in the way that their perspective
projecting centers form a line or a square, with their principal optical axes slanting fixed angle along designed directions. Such
installation aims at getting one big frame of image, which is the exact mosaic of group image captured by combined cameras at one
time, equivalent to the one taken directly by a wide-angled aerial camera. The system parameters: position relationships between
cameras, exact principal distance of each camera and optical distortion parameters of each lens are obtained with high precision
through our designed camera calibration method — space resection with several images of calibration field. The research work and
experiments in this paper can guide the production of whole wide-angled high-resolution digital camera.
Keywords: wide-angle digital camera, multi-camera system, equivalent image, camera calibration, high resolution
aerial image.
1. INTRODUCTION
Due to the limitation of technical level, the size of current
areal CCD sensor is not big enough to be used to make the
high-resolution wide-angled aerial camera. Although it is no
problem to make the normal-angled camera with CCD sensor
of normal size, if using it to capture high-resolution image, its
shortcoming of too small imaging size causes the problem -
the necessary image overlapping area required in conventional
aerial photography is hard to keep under the limited flying
control condition of nowadays. As illustrated in Fig.1, in terms
of same flying control precision, big images in Fig.l, are
able to meet the overlapping requirement, while small images
shown in Fig.l, can even hardly reach the requirement of
seamless overlay.
ST A
a 1,
Fig. 1: Flying control error affects image overlap
On the one hand, what we have is small-sized areal CCD
camera; on the other what we desire is large-sized
high-resolution aerial image. In order to solve this dilemma,
this paper presents a method using small-sized CCD sensors to
compose the wide-angled aerial camera.
2. MULTI-CAMERA COMBINED AERIAL
PHOTOGRAPHY SYSTEM
The wide-angled high-resolution aerial photography system
made from multi-camera combination may have 3- camera
and 4-camera structure. This part studies the two types of
structure, equivalent image converting etc. in detail.
2.1 3-camera combination scheme
1). Structure
The 3 small-sized cameras are laid out on the airplane's
platform in the following way (Fig. 2): the projecting centers
of the three camera (.$5,5,, S4) are in one line, parallel to
airplane's platform and to flying direction. The distance
between two adjacent camera’s projecting centers is AS, .
The middle camera S, has its principal optical axis
SO, perpendicular to airplane's platform, the second camera
$5 's principal optical axis SO, is vertical to flying
direction but tilts left a certain angle from SO, , and the third
camera S3 ’s principal optical axis SO, is vertical to flying
direction but tilts right a certain angle from SO, . In this case,
if there is a set of parallel lines on the ground and they are
vertical to flying direction, the respective image formed in the
3 cameras will be as Fig. 3 shows. That is, image of the middle
camera is parallel lines. Image of the second camera (left-tilt
camera) is left convergent lines and the main vanishing point
is 7,. Image of the third camera (right-tilt camera) is right
