Despite of relatively long tradition and outstanding progress of the CCD
technology in the last few years, computer vision applications have not
reached the signification as could have been expected. Because of lack of
understanding and complexity of applications themselves, introducing computer
vision technology in production lines is still rare. Rarity raises prices and
so we go round in circles. Nowadays computer vision needs effective, simple
and low cost applications, that will approach it to potential customers and
show them all possibilities and gains. Industrial users need solutions instead
of theory. A CCD sensor is widespread in European market (second place after
pressure sensor). It is used in all kind of commercial video cameras, but it
has little implementations in the field of measuring. Therefore an attempt was
made to design a reasonably priced computer vision system for light
distribution measuring. In car industry reflectors are inspected before they
are put in use. We found this as an ideal implementation of computer vision in
the field of measuring. Light distribution measuring is generally quite a time
consuming task. If it is made with contemporary electronic photometers with
probe, connected by fibre optics to processing machine, results are obtained
faster, but illumination at one point only is determined at the time. If a
plane illumination distribution is desired and only a probe photometer is
available, then necessary time consumption arises. Collecting and inputting
results into a computer have to be done separately also. Within this
application these problems were tried to be solved. Also the reliability and
appropriatability of a CCD sensor should have been found out. Standard ways of
inspection and quality control with classic photometers are time consuming and
depend on expensiveness and quality of instruments involved. Contemporary
laboratory photometers are under computer control and so data can be collected
and further represented easily. Ordinary industrial inspection photometers
are usually not sophisticated and all the procedure must be done manually. Car
reflectors should fulfil two main demands:
-they have to produce light distribution of predefined shape on the road
-the intensity of illumination in certain points of "light picture" must be
inside predefined tolerances
Light distribution should be measured at distance of 25m. Because this is
almost impossible in industry production, a special lens is put between the
reflector and the target plane. It simulates the same distribution at the
distance of 1,5m. Intensity is measured at this distance and then recalculated
to 25m, considering inverse square law of photometry.