  In previous works we presented a novel multiparametric sensor to
simultaneously measure the refractive index and the speed of sound in a liquid
by means of the acousto-optic effect. The sensor requires an illumination
system that expands the laser beam so that it interacts effectively with the
liquid under study. Also, a projection system is necessary in order to
adequately capture the diffraction pattern at the cell exit. In this article,
we present the optimization of the sensor illumination and projection system
using the optical design computational tool Zemax OpticStudio. The considered
range of refractive indices of the liquid samples is between 1.33 and 1.51. The
results show a correct expansion of the incident beam on the cell, and the
projection system achieves an image with very few aberrations and an adequate
angular separation between the maxima of the diffraction pattern. Based on the
resulting dimensions of the sensor after optimizing the illumination and
projection system, we confirm that it is compact and portable.
