By illuminating a single particle in an air channel, one can record the light scattering signature with a CMOS image sensor and then classify particles. This signature is optically pre-processed with an advanced, millimeter-sized, monolithic, refracto-reflective optical system. It performs notably a Fourier transform with very wide field of view of scattering angles, and includes as well integrated fluidics and alignment. Functional prototypes were fabricated by FEMTOprint using laser micro machining on glass, selective polishing, and afterwards were replicated with epoxy resin using a molding process.