The odd-symmetric quadratic (OSQ) phase mask is examined as a candidate for reduction
of working distance and enhancement of light collection in multiplex imaging systems.
The knowledge gained from the exact mathematical representation of the optical transfer
function of the OSQ phase mask imager is exploited to explain the limits of system
performance and quantify the upper bound on the magnitude of defocus within which this
wavefront coding imager can successfully operate. The sensitivity of this imaging system to
defocus about the special imaging condition that yields an enhanced dynamic range is
examined, and it is shown that the modulation transfer function (MTF) degradation when
the magnitude of misfocus is increased past this condition is much more gradual than the
degradation of a conventional imager past a zero-misfocus state. The condition required
for the spatial frequency and angular resolution of this OSQ phase mask imager to exceed
that of its counterpart scaled imager is established, and results of simulated imaging under
a reduced working distance configuration are presented.
© 2007 Optical Society of America
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