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quality, these image processing functions can also be 
used to solve a number of 2D image analysis 
problems. 
4.2.2 Orientations, 3D and 2D Surveying. Like 
the conventional photogrammetric surveying procedure, 
the operation of model surveying for EM images 
follow the usual steps of relative orientation, absolute 
orientation, and various surveying work. 
At the relative orientation phase, only a part of the 
left and the right EM images are displayed on the 
screen at the same time(see Fig.5). In order to 
measure the screen coordinates of any photo point, 
the operator can not only move the two cursors on 
the left and the right images arbitrarily but also 
control the images panning and scrolling automatically. 
The relative orientation is solved by least squares 
using the Eqs. (6). Once the relative orientation is 
completed, the left and the right images are rotated 
respectively according to the 01 and 6 > calculated by 
the relative orientation. The images used in later 
surveying stage are these two rotated images. 
Rotating the left and the right images means that the 
relative orientation elements( 0 4 and 0 z)have been ” 
put” into the left and the right images respectively. 
So, to a given stereomodel, the relative orientation 
needs to be done just one time for subsequent 
surveying work. 
Since the status of the specimen stage, during the 
procedure of taking the left and the right 
micrographs, can be controlled procisely, it is quite 
easy to horizontalize the stereomodel after the relative 
orientation. Usually, one is solely concerned with the 
relative information about the specimen instead of the 
absolute information, therefore, the offset in similarity 
transformation is not needed. Only in the case of the 
status of the specimen stage cann't be controlled 
procisely, the formula of similarity transformation is 
used in the absolute orientation with EM images. 
After relative orientation and absolute orientation, 
various 3D data can be acquired. All 3D data 
processing functions have been listed in Fig.3. 
Surveyiny DSM is the main task of EM images 3D 
processing (volume, 3D area and perspective image all 
use DSM). The system provides two ways for 
surveying DSM. In most situation, automatic generate 
DSM can be used. In this case, the stereomodel of 
the specimen is scannered along the lines parallel to 
the tilt axis of the specimen stage, and the mode 
coordinates are computed at regular intervals on these 
lines. Each new DSM point is marked on the screen 
by a red point superimposed on its conjugate point, 
this helps cheching and keeping track of the operation 
as it proceeds. The best correlated point is determined 
by the maximum value of the following equation: 
cx as sb a 3) 
k = ——— (7) 
253,25 by 
Where as 4 represents the grey value of pixel ij in the 
window of the left image and bs, the grey value of 
pixel ij in the window of the right image. 
Some times, an error correlated point may be 
calculated, in this case, the operator can interfere in 
the procedure by putting the red point on the correct 
conjugate point, then the automatic correlation go on. 
4.2.3 Data, Graphic And Image Editing. In many 
cases, the users want to edit a data file, graphics and 
images. Certainly, the editing work can be done by 
using some popular text and graphics editing 
softwares. But this must lead to inconvenience in 
operating. EM3DPS provides some functions for 
editing data files, graphics and images. Although they 
are not perfect, they can meet most of the 
requirements. 
4.2.4 Data Format Transformation. Electron 
microscope users have various image input 
instruments. To EM3DPS, the only difference of these 
image input instruments is the data format of their 
image files. In order to make EM3DPS surport as 
many as possible image input instruments, the system 
supplies a function of converting several types of 
image files to EM3DPS(input to EM3DPS). In 
adition, the cartographic plotters or printers owned by 
electron microscope users are also manifold. There are 
two methods to solve the problem of outputting the 
cartographic information on various plotters or 
printers: 
e write various drawing drive programs 
corresponding to each kind of plotter or printer. 
® take advantage of the current popular 
graphic softwares, since, usually, these softwares 
surport many types of plotters or printers. 
EM3DPS uses the second method and provides a 
function of converting the graphic file of EM3DPS to 
the *.dwg files of Auto CAD(EM3DPS to Auto 
CAD). 
4.2.5 Results outputting. The main aim of EM 3D 
data acquiring is to analyse the microcosmic structure 
of the specimen. So it is important to provides many 
ways for outputting various 3D or 2D data. Besides 
some conventional cartographic output functions, the 
system also provides some special 3D or 2D output 
functions. The perspective maps can only reflect the 
microcosmic structure qualitatively. In order to display 
the microcosmic structure qualitatively and 
quatitatively, the system gives two functions: color 
perspective map and stereo contour line(see Fig.3). 
The former function means that the contour line 
information are added into the DSM, and when the 
DSM is displayed perspectively, different colors are 
used between two contour lines. In order to reflect the 
microcosmic structure of the specimen more audio- 
visually, the system also provides a function of 
displaying perspective image. This function needs a 
DSM which includes the Z coordinate of each pixel.