The droplet distribution in the spray of a production gasoline engine fuel injector is investigated with optical in-line holography and parallel image processing. The three-dimensional image of the spray, stored on the hologram, is reconstructed and digitized intersection by intersection with an image dissector camera. Each intersection image
is subdivided into subimages for parallel processing in a transputer net. The extracted data yield the spatial distribution of sizes and masses of the droplets and can be used as a criterion for the development of injection systems.