## 2 Description of the Experiment  
### Combined SLIPI-LIF/Mie and SLIPI-Scan Optical Setup  
The schematic of the combined SLIPI-LIF/Mie and SLIPI-scan optical setup is shown in Figure 2. A damaged nozzle of the orifice diameter of 1 mm is used to generate an asymmetric and steady hollow-cone water spray. The liquid is continuously injected at 50 bars injection pressure at room temperature and atmospheric conditions. The defiled nozzle (Order no. 216.324, Lechler Inc., St. Charles, IL, USA) produced completely different droplet size distribution (much larger) and spray pattern (asymmetric) as previously reported with the same nozzle [21]. An asymmetric 3D map of droplets SMD produced with this nozzle is also reported in [23]. In this work, the injected liquid was a solution of water containing fluorescein dye. The dye is excited at 447 nm wavelength using a CW laser (LRD-0447 Series, Laserglow Technologies Inc., Toronto, ON, Canada) producing a broadband LIF signal, which is peaking at 517 nm.  
The structured light sheet is generated using the same optical setup as presented in reference [21] and is detailed in Figure 2. The vertically modulated light sheet was around 58 mm in height and approximately 0.25 mm thick. The laser power at the incident wavelength was \(\sim\)28 mW. A phase Doppler instrument (PDI-TK2 model, Artium Technologies Inc., Sunnyvale, CA, USA) was used, here, for calibration purposes and its measurement probe volume overlapped with the structured light sheet.  
Figure 1: Monte Carlo simulation results from [19] showing a comparison between conventional planar Mie imaging and structured laser illumination planar imaging (SLIPI) for a simulated hollow-cone spray. (**a**) The conventional image; (**b**) the modulated light sheet of T = 1 mm period; (**c**) the single light scattering; and (**d**) the SLIPI images; (**e**) the intensity profiles along the horizontal axis, at 3 mm below the spray orifice. It is observed from the SLIPI image that most of the multiple light scattering is suppressed and that smaller modulation patterns are more efficient in suppressing effects from multiple light scattering.  
For the scanning procedure, the spray nozzle was displaced using a translation stage (Standa Ltd., Vilnius, Lithuania) while keeping the illumination and detection systems fixed. The transmission measurements were done using a fluorescing solution contained in glass cuvette located on the laser exit side of the spray. The cuvette and the spray were both contained within the field-of-view of the cameras. A beam splitter was used to simultaneously record the LIF and Mie signals into two identical EM-CCD cameras (Luca R604, Andor Technologies Ltd., Belfast, United Kingdom--1004 \(\times\) 1002 pixels) denoted as \"CCD1\" and \"CCD2\", respectively, each equipped with individual bandpass filters. The LIF filter was a broadband optical filter centered at 510 nm with 94 nm FWHM (full width at half maximum), while the Mie filter was a narrow-band filter of 447 nm central wavelength with 10 nm FWHM (Edmund Optics Ltd., York, United Kingdom). An identical field-of-view was ensured at a pixel level after calibration using a dotted test pattern. The \"CCD1\" recorded an image of the LIF signal generated from spray droplets, as well as from the dyed cuvette, while the \"CCD2\" recorded the Mie signal scattered from the spray droplets only. All images had an exposure time of 0.08 seconds and an accumulation of 20 images was operated for each modulated sub-image corresponding to 60 images, for the 3 sub-images, used for the reconstruction of the SLIPI image. Using SLIPI-scan, the spray was sectioned into a total number of 31 layers (in a \"bread slicing\" manner), with a step difference of 500 \(\upmu\)m corresponding to a depth of 15 mm. The spray was probed at 37 mm below the nozzle tip and on its periphery to ensure the presence of spherical droplets only. Under such conditions, the optical depth (OD) was \(\sim\)1 only.