COMPARISON OF
LIGHT TRANSMISSION THROUGH ANTI-REFLECTION COATED AND UNCOATED
WINDOWS
APPARATUS
two
window viewers
202-21-D4
document camera
201
DESCRIPTION
Each viewer contains a stack of
eight 3-mm thick float glass windows separated by spacers.
One set is uncoated (reflectance is about 5%), the other has
broadband multi-layer anti-reflection coatings (average
reflectance ≤ 0.5%) on each
face. Pass them around or use the document camera to show
the view through each. The transmittance of a single
coated window averages about 98% over the visible range, so the
stack of eight windows transmits about (0.98)^8 = 85% of the
incident light. For the uncoated windows, with ~91%
transmittance, the total transmittance of the stack is
47%. This demonstrates that while the effect
of the coating on a single optical element may not seem
significant, the effect can be pronounced for an optical
instrument with multiple elements, such as a camera lens or a
telescope.