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Binoculars are tested on an optical bench. The MTF (modulation transfer
function) is a measure of how well an optical system maintains the contrast
of an object in its image. In a theoretically perfect optical system, the
contrast of an image would be identical to the contrast of the object being
imaged. In all real optical systems, there is always some loss in contrast
due to internal scatter, aberrations, defocus, poor centering, internal
reflections among components, etc. In practice, the MTF is determined by
measuring the contrast of the images of sine wave targets (targets which
vary brightness across space in a sinusoidal fashion) and comparing it to
the contrast of the targets themselves. A range of spatial frequencies
(finely spaced waves to very coarse waves) are measured. The MTF is a
standard metric for describing the general quality of optical systems.
Alan
Alan L. Lewis
"Victoria"
Gulfstar 41 #160
Lying Kittery, ME
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