  We investigate, in the context of a real massless scalar field in $1+1$
dimensions, models of partially reflecting mirrors simulated by Dirac
$\delta-\delta^{\prime}$ point interactions. In the literature, these models do
not exhibit full transparency at high frequencies. In order to provide a more
realistic feature for these models, we propose a modified
$\delta-\delta^{\prime}$ point interaction that enables full transparency in
the limit of high frequencies. Taking this modified $\delta-\delta^{\prime}$
model into account, we investigate the Casimir force, comparing our results
with those found in the literature.
