Abstract
A miniaturized laser beam transmitter, in which a visible laser module at
λ=650 nm is precisely stacked upon an infrared (IR) module at
λ=905 nm, has been proposed and constructed to provide an IR
collimated beam in conjunction with a collinear monitoring visible beam. In particular, the IR beam
is selectively dispersed through a perforated sheet diffuser, so as to create a rapidly diverging
close-range beam in addition to a highly defined long-range beam simultaneously. The complementary
close-range beam plays a role in mitigating the blind region in the vicinity of the transmitter,
which is inevitably missed by the main long-range beam, thereby uniformly extending the
transmitter's effective trajectory that is sensed by a receiver. The proposed transmitter was
designed through numerical simulations and then fabricated by incorporating a diffuser sheet,
perforated with an aperture of 2 mm. For the manufactured transmitter, the IR long-range beam was
observed to have divergences of ~2.3 and 1.6 mrad in the fast and slow axes, respectively, while the
short-range beam yielded a divergence of ~24 mrad. The angular alignment between the long-range IR
and visible beams was as accurate as ~0.5 mrad. According to an outdoor feasibility test involving a
receiver, the combination of the IR long- and short-range beams was proven to achieve a nearly
uniform trajectory over a distance ranging up to ~600 m, with an average detectable cross-section of
~60×80cm<sup>2</sup>.
© 2012 Optical Society of Korea
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