Abstract: A Moire system for linear measurement of an unknown distance defined by two surfaces, a collimated light source, a first grating between light source and the surfaces, a second grating positioned to receive collimated light from the surfaces after the light has reached the surfaces from the first grating, the first and second gratings being rotated relative to each other by a small angle .theta., a screen located after the second grating for receiving Moire patterns caused by the first and second gratings, and a mechanism for shifting the patterns as a function of the unknown distance whereby measurements of the amount of shifting is determinative of the unknown distance.

Abstract: A system and method for determining modulation transfer function (MTF) of an optical element or system employs a moire deflectometer. A selected central portion of monochromatic light is directed to the first grating of the moire deflectometer through or from the optical system, resulting in a moire pattern in which the contrast along an axis incident to the moire fringes is indicative of the MTF of the optical system for a particular spatial frequency, which is dependent on the spacing between the gratings of the moire deflectometer.

Abstract: A night sight assembly includes a backsight and a foresight. The foresight has a glowing portion, while the backsight is in the form of a diffraction grating.

Abstract: An optical instrument arrangement for determining the horizontality of a measured surface, where the arrangement comprises a solid reflecting device on a measured surface, a liquid reflecting device on a measured surface, a collimated light source positioned to direct collimated light beams onto both the solid reflecting device and the liquid reflecting device, a device for generating a first Moire fringe pattern from the solid light reflecting device and for also generating a second Moire pattern from the liquid reflecting device; and a device for simultaneously viewing the first and second Moire patterns to determine the horizontality of the measured surface from the shift of the second Moire pattern relative to the first Moire pattern.

Abstract: A level comprises a sealed casing which holds a liquid and has a flat bottom end. It also includes a light admissive top section, bearing a periodic grating of alternating transparent and opaque stripes. A float is in the liquid inside a compartment of the casing underneath the light admissive top section. The float is capable of changing its position inside the chamber so as to retain its position relative to the horizon when the chamber is filled, and a mirror on the top face of said float.

Abstract: Equipment and method for mapping an object using moire deflectometry wherein collimated radiation deflected from the object is used to generate a moire pattern and wherein by measuring linear deflections in the pattern, variations in characteristics of the object is determined.