International Archives of Photogrammetry and Remote Sensing. Vol. XXXII, Part 5. Hakodate 1998
A DIGITAL CLOSE-RANGE PHOTOGRAMMETRIC SYSTEM
USED FOR TEXTURE-LACKING OBJECTS IN MEDICINE
Wenhao FENG, Xin LI and Xueliang MEI
Wuhan Technical University of Surveying and Mapping
39 Luoyu Road , Wuhan, 430079
E-mail: whfeng@wtusm. edu. cn
Guangxiang HONG, Yunting WANG and Qishun HUANG
Wuhan TongJi Medical University
CHINA
Commission V, Working Group V/4
Key Words: DLT , Degree of coincidence, hand bone, CCD Camera
Abstract
A digital close range photogrammetric system used
for determining the surface shape of hand bone and
geometric coincidence between two bones was
presented. The system hardware consists of a single
CCD camera , a light source with a specially made
infrared ray, a spinning platform carrying a tiny
control system frame, and a PC computer with image
card Video Blaster. With the help of software, the left
and right images of a stereopair can be displayed on
the screen simultaneously. Screen coordinates of
points are measured through average grey. Space
coordinates are solved by using algorithm of DLT
(Direct Linear Transformation). Performing imitation
of two bone surfaces with a general quadratic surface
and the overlapping of the main orientations of both
surfaces, it is possible to determine the degree of
coincidence between the two bone surfaces
dynamically.
The system can also be used to determine the
appearances of other texture-lacking objects quickly.
1. Introduction
From far away, the wrist of the hand composed of
three bones: distal carpale (first part), wrist joint
(second part) and proximal carpale (third part). When
the second part has to be excised, the ‘surgical
operation, which links the first part third part directly
in order to reconstruct the wirst joint, has an
important medical meaning. This paper is part of the
achievement of research between Wuhan Technical
university of Surveying and Mapping and Wuhan
Tongji Medical University.
The main research content is to select a practical
surveying system, so that the degree of coincidence
of both bones (1st and 3th) can be accurately
surveyed and determined quickly, and so that a
scientific basis can be provided for the feasibility of
these kinds of operations.
The authors hope that the system can also be
used to determine 3-D space coordinates of other
similar objects.
2. Hardware Components of the System
2.1 Designed index of the system
€ Form a digital close-range photogrammetric
system for raising measurement speed;
€ Using a single CCD camera in order to reduce
hardware investment;
€ Form sub-binary image of texture-lacking
objects on the screen in order to simplify the
procedure of image processing and photogrammetric
processing.
2.2 Hardware components
The system hardware shown in Figure 1 consists
of a single CCD camera 1, a light source with infrared
ray near the main optical axis of the CCD 2, power
source 3, a tiny 3-D coordinate control system 4, a
tiny spinning platform with horizontal degrees 5, and
a personal computer with video Blaster software 6.
Retro-reflective targets (RRT) are used in the
surveying procedure.
Figure 1
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