out on different computers (PCs, workstations), operating 
systems (Windows 95/98/NT, Unix, Linux) and browsers 
Explorer from Microsoft and HotJava from Sun). Especially the 
browser is a new module which needs some attention. In 
general, the Java compatibility is ensured by a special plug-in 
or the selection of the language “Java” in the settings. It must 
be ensured that the JVM is the same when developing and 
running the program. In the development the standard font was 
used which does not have to be overwritten by the font selector 
in the browser. Table 1 shows the result of tests. It is obvious, 
(Netscape Navigator and Communicator, Internet 
that today exists platform independence for three major 
browsers from the mentioned version on. Older versions of the 
named browsers will possibly create problems. The browsers 
and the JDK change continuously but not synchroneously. The 
version of the usable browser is therefore important in order to 
ensure a good performance of “LDIPInter”. Some minor 
differences in the display occurred however with the Unix and 
Linux operating systems, namely with the use of Greek letters. 
THEME 1: AUTOMATIC MEASUREMENT 
OF RESEAU CROSSES AND FIDUCIAL MARKS 
Value 
Grey 
Search Matrix 
Target Matrix 
X 
n 
L, 
1 
r = 
0.00 
- The position of the target (Reseau cross or 
fiducial mark) shall be found in the search matrix 
- The densities of the target have 
noise and smear in the image 
- The target matrix is moved pixel by pixel over 
the search matrix 
- At each position a correlation coefficient (r) is 
calculated 
-The position with the greatest value ofris 
the required position 
N Information 
1: I 
L co variare 
if standard dev.^ ■ standard dev.^ 
81- 
. arithmetic mean 1 
in the target area 
L £(&-&)(&-&) 
. arithmetic mean c 
in the search area 
Figure 2: Screen image for a theme in “LDIPInter” 
4. USE OF “LDIPInter” 
In order to run “LDIPInter” one has to call the applet within the 
browser with its URL address from above. This can be done on 
different client machines and browsers (see also Tablel). 
“LDIPInter” is downloaded from the Web within a few 
seconds. The loading time depends on the performance of the 
computer and of the network. Also the “traffic” on the Web 
plays a role. But under good conditions it takes a few seconds 
only. The loading time is considerably reduced by downloading 
the bytecode file onto the disk of the client machine and starting 
from there. This means, however, that the advantage of 
automatic updating for new versions gets lost. 
The application of the program can have three different 
scenarios or cases: 
1. Exercise with a number of students in a room equipped with 
a 
number of personal computers 
2. Demonstration of the themes and part of the exercises by the 
teacher in a classroom during a lecture