The Airbrush & Spray Gun Speckling Kit is a combination, “spraying method” kit consisting of an airbrush, for 100-200 µm speckling, and two spray guns, for 200-2000 µm speckling. The airbrush has one 0.6 mm nozzle, and each of the two spray guns has a different nozzle size of 0.8 mm / 1.2 mm, respectively. Both the airbrush and spray guns utilize the same, one compressor.
The kit is designed for Fields-of-View (FoV) testing application from 10 mm to 1000 mm and can be used with camera resolutions from 1.1 to 24 Mpx. Through assuming the nozzle diameter is the 1st control parameter, and the air pressure is the 2nd control parameter, the speckle size, at a nominal distance-to-object (DtO), can be assessed using a stereoscopic microscope. Through a parametric study, we have determined the best combination of; apparatus (airbrush/spray gun), nozzle size, pressure, and distance-to-object (DtO) to use for a given speckle size.
With increasing pressure, force applied on the liquid causes it to break into smaller droplets. Furthermore, reducing the nozzle diameter compresses the liquid flow and enhances the surface area for interaction with the air, which further increases the fragmentation and produces finer droplets. As such, smaller speckles result from higher pressures and smaller nozzle sizes.
