Distance measurement from a moving object based on speckle velocity detection

Spatial filtering velocimetry of objective speckles for measuring out-of-plane motion

“…In case the object carries out an in-plane movement of v xy τ during the time lag τ (i.e., v z 0), the position of the correlation peak describes a similar in-plane translation of the speckles in the observation plane. The relation between movement of the speckles and object is specified as Δp 1 z∕Rv xy τ, as it can be found in [9,10,14]. The decorrelation length of the speckles equals the radius w 0 of the beam at incidence at the object.…”

“…When objective speckles are observed at a distance L from the object, the speckle dynamics, due to an in-plane object motion, will reflect the ratio (L∕R) of the distance of propagation (L) to the radius (R) of curvature of the phase front of the illuminating beam at incidence with the object plane [9,10]. Thus, by measuring the corresponding velocity of the speckles in two axially displaced observation plans (L 1 and L 2 ), given the radius of curvature R, the absolute distance to the moving object can be determined in nearly real-time by using OSFV [11].…”

Scanning ultra fast distance sensor based on acousto-optic deflection

“…This method was initially proposed by Giglio et al for measurement the distance to a moving surface [1]. The method belongs to the diffraction-based technique of the distance measurements.…”

“…It is also known that the dynamic motion of speckles is preferably of the translation type in both divergent and convergent part of a light beam providing that the focused beam crosses the object surface out of the Rayleigh range [4]. For a translated speckle pattern one can define the velocity, V §, which is a function of (i) the object surface speed, Vo, (ii) the distance between points of observation and illumination, D5, and (iii) the wavefront curvature of the illuminating coherent beam, 1/R, assuming that this curvature is much larger than the curvature of the object surface within the illuminated area [1,5]:…”

Lézeres szórási interferencia kontrasztelemzésen alapuló véráramlásmérő rendszer építése

“…Csak ezután jelentek meg olyan alkalmazások, amelyek éppen magát a szórási interferenciát használták fel [11]. Manapság számtalan területen alkalmazzák a jelenséget, többek közt sebesség- [12]- [14] és távolságmérésre [14], [15], felületelemzésre [16], [17], véletlenszám-generálásra [18], [19] stb. Ma már bármelyik szaküzletben vásárolhatunk lézeres optikai egeret, amely (a LED-es megvilágítást alkalmazó típusoktól eltérően) nem közvetlenül a felület elmozdulását figyeli, hanem a lézerfény által létrehozott szórási interferenciakép változásaira reagál, így akár a fény hullámhosszával összemérhető elmozdulást is képes érzékelni.…”