In single component development, a monolayer of charged toner is put on a donor roll and presented to a charged image on a photoreceptor. The donor and photoreceptor can either be put in contact or development can occur across a small gap between the photoreceptor and the donor roll. When there is a gap, one can directly observe the toners traversing the gap optically. We have designed a system where we capture the image of the transmitted light through the development gap with a high resolution CCD camera. From these digital images, we can quantitatively extract the toner density, toner size and toner velocity as the particles traverse the nip. Using time delay photography with microsecond resolution we measure the response of the cloud to incoming images. Using an organic film, which can form a permanent latent image, we are able to capture images of fine line development. Quantifying the density and motion of toners in single component development across a gap has allowed us to generate accurate physical models of the development process.
Howard Mizes, Jim Beachner, Palghat Ramesh, "Optical Measurements of Toner Motion in a Development Nip" in Journal of Imaging Science and Technology, 2000, pp 210 - 218, https://doi.org/10.2352/J.ImagingSci.Technol.2000.44.3.art00005