Multiwindowed defocused electronic speckle photographic system for tilt measurement

Defocused speckle photography has long been used to measure rotations of rough surfaces. By addition of a suitably perforated mask, some measurement properties, such as range and lateral resolution, may be changed at will. In particular, the maximum measurable tilt can be significantly increased, although at the expense of poorer lateral resolution. Advantages of this compared with previously described techniques include independent tuning of speckle size and optical system aperture and greater adaptability to various measuring needs. The benefits and disadvantages of the new and old techniques are thoroughly compared.