Abstract: A method and an apparatus are provided for the determination of a condition or state of an object based on quasi-elastic interaction between the object and light transmitted to the object. This light is transmitted from a light source through a diffractive optical element. The light that has interacted with the object is collected and detected. The diffractive optical element is designed in such a way that the determination of the condition or state of the object is substantially exclusively defined by the diffractive optical element and substantially independent of properties of the light source. Several diffraction patterns may be integrated in one diffractive optical element, thereby integrating several optical functions, such as lenses, beam splitters, etc. in one optical component. Use: Transit-time-velocity measurement, Doppler velocity measurement, viscoelastic measurement, differential speckle determination, differential vibrometer, distance determination apparatus, etc.

Abstract: A method and apparatus for determining angular displacement of one or more parts of an object (10) comprising detecting in at least one first image sensor first and second one or more distributions of Fourier-transformed speckles before and after angular displacement, respectively, and determining the displacement of the detected images; a method and apparatus for determining twist of a rotating shaft between two or more parts of the shaft subjected to a load; a method and apparatus for simultaneously determining angular displacements and surface translations of one or more parts of an object, and a method of determining the radius of angular displacement of one or more parts of an object.