Jd. Barter et al., COLLOCATED AND SIMULTANEOUS MEASUREMENT OF SURFACE SLOPE AND AMPLITUDE OF WATER-WAVES, Review of scientific instruments, 64(9), 1993, pp. 2661-2665
We demonstrate by experiment that, in addition to the local surface sl
ope, local surface elevation can also be directly measured using the r
efracted light beam traversing an air-water interface, thus showing th
e feasibility of a new surface slope and wave height amplitude gauge f
or use in studying water waves. We have achieved surface height resolu
tions as small as 40 mum for the range of surface wavelengths lambda a
pproximately 1.2-2.4 cm used in the present experiments. This measurem
ent principle is readily adaptable to waves of different scale. The av
ailable dynamic range defined by the ratio of maximum wave amplitude t
o minimum resolvable amplitude need only be limited by the useful dyna
mic range of the photodetector when matched to a laser of suitable fre
quency and sufficient power.