  We propose a concept of multiplexing lobster-eye (MuLE) optics to achieve
significant reductions in the number of focal plane imagers in lobster-eye (LE)
wide-field X-ray monitors. In the MuLE configuration, an LE mirror is divided
into several segments and the X-rays reflected on each of these segments are
focused on a single image sensor in a multiplexed configuration. If each LE
segment assumes a different rotation angle, the azimuthal rotation angle of a
cross-like image reconstructed from a point source by the LE optics identifies
the specific segment that focuses the X-rays on the imager. With a focal length
of 30 cm and LE segments with areas of 10 x 10 cm^2, ~1 sr of the sky can be
covered with 36 LE segments and only four imagers (with total areas of 10 x 10
cm^2). A ray tracing simulation was performed to evaluate the nine-segment MuLE
configuration. The simulation showed that the flux (0.5 to 2 keV) associated
with the 5-sigma detection limit was ~2 x 10^-10 erg cm^-2 s^-1 (10 mCrab) for
a transient with a duration of 100 s. The simulation also showed that the
direction of the transient for flux in the range of 14 to 17 mCrab at 0.6 keV
was determined correctly with 99.7% confidence limit. We conclude that the MuLE
configuration can become an effective on-board device for small satellites for
future X-ray wide-field transient monitoring.
