I 
1 
i 
j 
i Abstract: 
B 
| 
It is once again presented and discussed in this paper t 
model presented in this paper is convenient and reliable. 
Introduction: 
It is important for professionals in photogrammetry to do 
the work of calibration for system errors of various image 
  
points including diversified distortion errors. In the 
solutions of single-image spatial resection, direct linear 
transformation and self-calibration correction for — bundle 
adjustment, it is able to compute the parameters of the 
system error model, such as the factors of various 
distortions Ik, Jk, 1... p;[Ip.Clor additional parameters in 
self-calibration correction, while computing the interior and 
exterior orientation elements. The Analytical plumb-line 
calibration method by Brown D.C.[S] can be used as well 
i only to compute the above mentioned distortion 
coefficients. 
A The author proposed a simple method to detect the optical 
distortion in 1988, of which the object is the 120 camera 
: using film. The digital camera is widely used in the present 
| time. The flatness of CCD chips can reach X lum 
without the problem of "negative film distortion". It is of 
great importance and possibility to measure the optical 
distortion of CCD camera in advance. This paper proposes 
again the method of distortion error calibration correction 
based on 2D DLT. It does not compute the parameter values. 
Instead, it directly computes the system error values caused 
by various factors (mainly optical distortion) on each pixel 
on the CCD chips. A series of digital distortion models can 
  
à 
| KEYWORDS: digital, distortion, model, CCD, calibration, error 
974 
CREATION OF DISTORTION MODEL FOR DIGITAL CAMERA (DMDC) 
BASED ON 2D DLT 
FENG Wenhao  LlJiansong YANLi 
| School of Remote Sensing and Information Engineering, Wuhan University 
A 129 Luoyu Road, Wuhan, China, 430079 
| Email: wenhaofeng@tom.com 
hat the method of distortion calibration based on 2D Direct Linear 
Transformation (DLT) is easy and feasible. It 1s emphasized that it is fit for the creation of distortion model for solid-state 
cameras (CCD, CID, PSD) to compensate for the system errors of various image points. The application of the distortion 
be measured with different focuses in an easy and 
convenient way. Thus, the method is quite fit for the 
zooming digital cameras with severe distortion in the 
condition of close-range photographing. 
1. Optical Distortion Calibration based on 2D DLT 
1.1 2D DLT and its characteristics 
The expression for 3D spatial DLT is as follows: 
There are eleven | factors in the expression, which 
respectively has a strict mathematic relational expression 
with the interior orientation factor, exterior orientation 
factor, scale inconsistent factor ds and non-orthogonal 
factor df (11 factors altogether) . 
When the object to be measured is 2D and Z is a constant, 
the expression (1) can be simplified as the 2D DLT 
relational expression (2) after inferring, deduction and 
simplifying symbols. 
LX FLY €17 «f, 0 
LX Xf +1, 2+] 
P LX LY €0Z f, 
LA AZ: 
X+ 
(1) 
y z 
iX * iy + ls 
NY +] 
An 
Hx. Hy 1 
  
X + 
(2) 
With the deduction of the above expression, the relation 
Intern 
  
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