Holography of Small Objects through High Density Wire Grids

We are investigating the use of holography to replace conventional photography of particle tracks in high resolution streamer chambers. Advantages are the large depth of field with uniformly high resolution and expected greater sensitivity to streamer discharges. In the streamer chamber, tracks of 20-50 micron width must be viewed through high voltage plane electrodes which are grids of 25-micron parallel wires with centers 100 microns apart. We have successfully holographed 25-micron wires through these grids, using a 5 mw He - Ne laser and in-line holography, in spite of a strong striated background. But for good contrast with isotropic tracks of low streamer density, much sparser grids with a wire-to-space ratio of about one percent are required. Fundamental considerations concerning the spatial resolution of holographic images and criteria for estimating and minimizing the background of the grids are briefly discussed.