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A novel scheme for the visualization of surface flows is developed. It utilizes the strong adhesion forces between micrometer-sized particles and solid surfaces to register the surface streaklines, or equivalently, streamlines for steady flows. Fluorescent particles are used to allow the spectral separation of particle fluorescence emission from morphology-related elastic light scattering from the surface. This scheme was employed to investigate the surface flow on rotating disks in a disk-drive-like environment. Trajectories of the streaklines were digitized and quantitatively analyzed using image processing for orientation and spatial distribution. The surface streaklines provide information about the boundary layers on the disk while the spreading angle of the jets in the self-pumped through-flow reveal details about the bulk flow outside the boundary layer. The spiral angle of the streaklines over a major portion of the disk surface was found to be in good agreement with the theory for laminar Ekman boundary layers. The spreading of the streaklines, reflecting the width of the self-pumped jets emanating from holes in the hub, was found to increase linearly with radius.

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By polarizing the object and reconstructed wave orthogonally, two interference images are created with a phase difference of 180°, which are separated with a polarizing beam splitter. Using two video cameras, the images are electronically summed and the enhanced image instantaneously displayed. This technique allows independent enhancement of the fringe brightness since the contrast can always be adjusted optimally. The enhancement is most pronounced when the difference between diffraction efficiency of the hologram and the diffuse reflectivity of the object is large and hence is appropriate for low reflectivity objects. We present experimental data on our observed fringe enhancements as well as calculations of the dependence of the fringe enhancement on object reflectivity and diffraction efficiency of the hologram.