  In a previous paper, we discussed an original solution to improve the
performances of coronagraphs by adding, in the optical scheme, an adaptive
hologram removing most of the residual speckle starlight.
  In our simulations, the detection limit in the flux ratio between a host star
and a very near planet (5 lambda/D) improves over a factor 1000 (resp. 10000)
when equipped with a hologram for cases of wavefront bumpiness imperfections of
lambda/20 (resp. lambda/100).
  We derive, in this paper, the transmission accuracy required on the hologram
pixels to achieve such goals. We show that preliminary tests could be performed
on the basis of existing technologies.
