Figure 1: Holographic retinal photo-stimulation system.
From: Holographic optogenetic stimulation of patterned neuronal activity for vision restoration
(a) A laser beam is projected through a polarizing beam splitter onto a ferroelectric (binary phase) SLM. The SLM is imaged through a square slit onto the objective lens’ entrance aperture, and Fourier-transformed into a sparse pattern at the focal plane (inset: PSF for a 10 × objective). The light pattern excites ChR2-expressing retinal neurons whose responses are recorded using a multielectrode array. (b) The light flux delivered to the sample plane (~700 μW) is diffractively divided among stimulation spots; power per spot decreases monotonically with increasing spot counts. Even at this low flux, hundreds to thousands of stimulation spots can be generated with the nominal intensity level required for optogenetic stimulation. (c) Analog control of individual spot intensity obtained by appropriately weighing the desired pattern during hologram calculation. (d) Sub-millisecond temporal profile of a single binary frame.
