Title :
A new optical instrument for the study of bubbles at high void fractions within breaking waves
Author :
Stokes, M.D. ; Deane, G.B.
Author_Institution :
Marine Phys. Lab., California Univ., San Diego, La Jolla, CA, USA
fDate :
7/1/1999 12:00:00 AM
Abstract :
An optical imaging system (BubbleCam) has been tested for the quantification of bubble distributions at high void fractions formed beneath breaking waves. The instrument consists of a CCD video camera, stroboscopic light source, and optics allowing adjustable magnification, a fixed imaging volume, and the resolution of bubbles 3 pixels in radius and larger (equivalent to a minimum bubble radius of about 200 μm in the test configuration). BubbleCam has been deployed in a shore-based configuration (data and power supplied via shore-connected cables) as well as an autonomous device in the open sea with its own power supply and data storage. The resulting images are processed using a variant of the Hough transform which allows computer-automated counting and measurement of the bubbles within the video frames. In addition, images can be qualitatively examined to provide insights into bubble plume evolution and creation mechanisms
Keywords :
CCD image sensors; Hough transforms; bubbles; geophysical signal processing; ocean waves; oceanographic equipment; oceanographic techniques; video signal processing; 200 micron; BubbleCam; CCD video camera; Hough transform; adjustable magnification; air-sea interface; autonomous device; breaking wave; bubble creation mechanisms; bubble plume evolution; computer-automated counting; fixed imaging volume; high void fractions; optical imaging system; optical instrument; quantification of bubble distributions; shore-based configuration; stroboscopic light source; surf zone; Charge coupled devices; Charge-coupled image sensors; High-resolution imaging; Image resolution; Instruments; Light sources; Optical imaging; Pixel; Power supplies; System testing;
Journal_Title :
Oceanic Engineering, IEEE Journal of
