A sample of 1100x500mm laminated
glass 6.76mm thick was placed on an optical stand used
for testing windscreens to ECE Regulation43 and the
rake angle set to 55°.
The glass was firstly assessed for optical distortion (ECE
Reg.43) and this method entails the projection of an
appropriate slide (raster) onto the display screen through
the safety-glass pane being tested. The change caused
in the shape of the projected image by the insertion
of the safety-glass pane in the line of light provides
a measure of distortion. This test was repeated after
the scratch had been polished.
The next test conducted was the optical deviation
test (ECE Reg.43) with the safety-glass pane
mounted at the specified rake angle in such a way that
the observation is carried out in the horizontal plane
passing through the centre of the target.
The light box was viewed in a semi dark room through
each part of the area being examined, in order to detect
the presence of any secondary image associated with the
illuminated target. This test was repeated after the
scratch had been polished.
To generate the scratch on the
glass, a 1.042kg steel ball was rested on a piece of
44 grit abrasive paper. This was then passed 10 times
over an area 350mm long. The scratched test piece was
then subjected to the distortion and deviation tests.