Multi-windowed defocused speckle photographic system for tilt measurement

Defocused speckle photography has long been used to measure rotations of rough surfaces. This paper explains how, by adding a suitably perforated mask, some measurement properties, such as range or lateral resolution, may be changed at wish. Particularly, the maximum measurable tilt can be significantly raised, although at the expense of poorer lateral resolution. Advantages over previously described techniques include independent tuning of speckle size and optical system aperture and more extended adaptability to different measuring needs. The benefits and disadvantages of the new and old techniques are thoroughly compared.