STELLA MARIS: Stellar marine refractive imaging sensor

Viewing an airborne scene from a submerged camera creates a virtual periscope, avoiding the saliency of a real maritime periscope. Random waves in the water-air interface severely distort the view, by refraction. We show a way to handle this. The distortion can be significantly countered, based on an estimate of the wavy water interface, at the instant of imaging. We obtain the interface estimate per frame, by a submerged sensor that simultaneously images the refracted Sun through an array of submerged pinholes. Our use of a stellar cue for estimation (and then correction) of the refractive field has analogy to ground-based astronomy. In astronomy, a guide star is imaged by a Shack-Hartmann sensor, for an estimate of the random refractive field created by atmospheric turbulence. In astronomy, this principle is used for countering blur, mainly by adaptive optics, while we use it for compensating distortions created by water waves. We introduce this novel concept for enabling a virtual periscope, demonstrate it, and analyze some of its limitations.