Refractive Fringe Diagnostic Techniques

Abstract

Refractive fringes, were first observed by Evtushenko (1) et al.They are defined as intereference fringes caused by the interference of light refracted by an object either with other light refracted by the same object or with light that avoided the object by a small distance.The study of these fringes has been extended to five types of refractive body by the authors and co-workers: flames (N Bhagwandin (2); glass microballoon laser fusion targets (0 Willi (3); laser plasmas on plane targets (R N Campbell (4,5)); spark induced shocks in air and compressed air shocks (R N Campbell, J Waltham); gas lenses (M Notcutt (6)). FLAT FLAMES A long flat flame produced by a row of oxyacetylene nozzles, illustrates the formation of two types of refractive fringes, fine and coarse. Fine fringes occur when light penetrates the flame at a shallow depth and having been greatly refracted forms a line focus; light from the line focus interferes with unrefracted light to form a set of fringes spaced according to the relation ync (2n L ) where L is the distance from the focus to the plane of observation (Fig. la) Coarse fringes are formed by rays of different depths refracted from opposite sides of the narrow combustion front interfering with each other. These rays produce a fringe spacing obeying the Young double slit formula Y -L d SPIE Vol. 674 High Speed Photography (Pretoria 1986) / 531 REFRACTIVE FRINGE DIAGNOSTIC TECHNIQUES M M MICHAELIS, P F CUNNINGHAM, R N CAMPBELL M NOTCUTT AND 0 WALTHAM Refractive fringes, were first observed by Evtushenko (1) et al. They are defined as intereference fringes caused by the interference of light refracted by an object either with other light refracted by the same object or with light that avoided the object by a small distance.The study of these fringes has been extended to five types of refractive body by the authors and co-workers: flames (N Bhagwandin (2); glass microballoon laser fusion targets (0 Willi (3); laser plasmas on plane targets (R N Campbell (4,5)); spark induced shocks in air and compressed air shocks (R N Campbell, 3 Waltham); gas lenses (M Notcutt (6)). FLAT FLAMESA long flat flame produced by a row of oxyacetylene nozzles, illustrates the formation of two types of refractive fringes, fine and coarse. Fine fringes occur when light penetrates the flame at a shallow depth and having been greatly refracted forms a line focus; light from the line focus interferes with unrefracted light to form a set of fringes spaced according to the relation y n = (2n L )where L is the distance from the focus to the plane of observation ( Fig. la) Coarse fringes are formed by rays of different depths refracted from opposite sides of the narrow combustion front interfering with each other. These rays produce a fringe spacing obeying the Young double slit formula SPIE Vol. 674 High Speed Photography (Pretoria 1986) / 531 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/23/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx