Measurement of the point-spread function in a layered system.

A laboratory facility to measure the point-spread function (PSF) of water with the addition of scattering layers is described. The PSF was measuredby using an approximately Lambertian source and a camera that viewed this source but focused at infinity. Measurements for various optical path lengths with the scattering layer in three separate regions, i.e., near the source, near the camera, and an intermediate case, were performed. The PSF was found to depend strongly on the location of the scattering layer. For the same optical path length, the most diffuse PSF was found for the case of a scattering layer near the camera.