3.2.4 Scan Frequency Generator A frequency
generator provides the scan rate for the two
line-scan cameras. This allows the frequency of
the scan rate to be adjusted, in combination with
the rotation speed, to provide the required field of
view. At present, this unit is manually controlled
but it will eventually be linked to the IBM PC to
allow computer control over this parameter. As a
result, computer control will be achieved over the
image generation start point, the speed of rotation
and the scan rate of the cameras. The computer
could then be used to adjust these variables to
produce an optimum field of view for a particular
application.
3.2.5 Experimental Methodology The aim of
this research is to calibrate the images returned
from the camera rotation. However, before this
can be contemplated, the parameters controlling
human vision have to be considered. Suitable
images for human interpretation are required if
correct calibration data is to be obtained from the
images produced. À major aspect of this work will
be an investigation into determining the extent of
the potential field of view that can be practically
used for human interpretation.
The next stage of the research wil involve
obtaining image data to develop photogrammetric
algorithms. These will allow the system to be
calibrated and the three-dimensional position of
objects within the rotating field of view to be
determined.
4. CONCLUSIONS & FUTURE WORK
4.1 Conclusions
The initial research into lateral movement
line-scan systems established that such devices
could be used in a stereoscopic configuration. This
allowed three-dimensional co-ordinate information
to be determined from a moving object volume to
a sub-millimetre degree of accuracy.
The first pictures produced from the rotational
movement of the line-scan camera have
demonstrated the complexity of the image content.
It has been established that this complexity is
dependent on the relationshıp of the object space
and camera, and the interaction of the scan rate
and the rotational speed.
4.2 Future Work
The principle of generating the two-dimensional
images with a rotational line-scan system is
identical to that of the lateral movement
arrangement. Accordingly, it is expected that a
similar degree of accuracy can be produced from
the rotational movement of the line-scan devices.
However, this will require the development of
specific photogrammetric algorithms due to the
unique nature of this method of image production.
The increased complexity of the returned images
caused by the rotational movement may require
automatic methods of image interpretation to be
considered. Any future research will include an
investigation into this aspect of the work.
5. APPLICATIONS
5.1 Production Line Inspection
Line-scan cameras have been used to produce
two-dimensional images in a production line
environment for some time. Consequently, the
introduction of a stereoscopic line-scan system
into such a manufacturing process should be
possible. This will allow three-dimensional data to
be obtained from a manufactured object passing in
front of the camera system. The simplicity of the
mathematical algorithms, developed as a part of
the initial work, may allow the co-ordinate
measurement to be conducted in 'real time', ie:
without affecting the manufacturing throughput.
5.2 Security/Surveillance Applications
The variable field of view of the images produced
by the rotational line-scan system discussed here
would seem to provide an ideal solution to security
and surveillance applications. In the first instance
a 360 degree view could be used to provide an
indication of the surrounding area. If an area of
this arc proved to be of interest then the
operator/computer could adjust the field of view to
give maximum resolution for that particular area.
These images could then be analysed to determine
