The surface of finished cells is covered by a screen-printed conductive grid. It is important that the beam does not come into contact with this grid when measuring reflectance. In
view of this, we use a device to reduce the size of the beam and focus it between the bars of the grid. This ensures that only the reflectance generated by the surface involved in photovoltaic conversion is measured. This "small spot size" device consists of a diaphragm and a wheel with 3 lenses for focusing on the transmittance or reflectance positions or on the center of the sphere