Multiple rotation assessment through isothetic fringes in speckle photography

Abstract

The use of different pupils for storing each speckled image in speckle photography is employed to determine multiple in-plane rotations. The method consists of recording a four-exposure specklegram where the rotations are done between exposures. This specklegram is then optically processed in a whole field approach rendering isothetic fringes, which give detailed information about the multiple rotations. It is experimentally demonstrated that the proposed arrangement permits the depiction of six isothetics in order to measure either six different angles or three nonparallel components for two local general in-plane displacements.

Simple method for simultaneously measuring the magnitude and direction of 2D in-plane displacement in white-light speckle photography

“…Since the classical work of Burch et al [8,9], SP has achieved significant developments in many application fields, such as engineering and materials science [5,[10][11][12], biomedicine [7,13] and geography and geology [14]. Numerous physical quantities, including in-plane displacement [15,16], in-plane rotation [15,17], out-of-plane displacement [18,19], angular displacement [20], surface tilt [21,22], velocity [23,24], angular velocity [25], vibration [6,17], stress [5,26], strain [27,28], temperature [4,29] and convection [30], can be evaluated with SP. When improved with some modifications in the optical system, SP can also be used in real-time detection [15,31], dynamic course [18,22] and transient process [2,32].…”

“…double-exposed speckle patterns or specklegrams) or stored with two consecutive images using a CCD camera. Fringe patterns are then produced from the pointwise [38,39] or whole-field [15,17,18] interrogation of the specklegrams. For pointwise filtering, a narrow laser beam is directed perpendicularly onto the photographic plate, and a diffraction halo modulated by a series of equispaced cosine fringes (frequently called Young's fringes) is generated in the far field.…”

Speckle decorrelation influence on measurements quality in vortex metrology

“…In speckle photography, a quantitative analysis of relative displacements between two [1,2] or several [3][4][5] speckled intensity distributions can be achieved by comparing images corresponding to the initial and final states of a diffuser, i.e. the states before and after a rigid movement or a local deformation of a diffusing surface.…”

Multi-user multiplexed scheme for decoding modulated-encoded sequential information

“…In this way, the signal spectrum can occupy an adequate dimension that allows processing it more easily. The introduction of a spatial frequency carrier through the modulation technique has been applied to optical information processing and metrology [17][18][19][20]. Our proposal consists in modulating each encrypted data with a different grating.…”