Abstract: A transmissometer for measuring a volume attenuation coefficient of a column of water, including a transmissometer housing; a light source, producing an optical light beam; a Y-splitter, splitting the optical light beam into two light beams within the transmissometer housing; a pressure proof connector and two optical fibers, routing the two light beams outside the transmissometer housing; two collimators for collimating outputs of the two optical fibers prior to transmission through the column of water; a reflecting prism, reflecting the outputs of the two collimators back into the transmissometer housing via a sensor view port where a distance between a first of the two collimators and the reflecting prism is R1 and a distance between a second of the two collimators and the reflecting prism is R2; two detectors for detecting intensities I1 and I2 of the two light beams reflected by the reflecting prism; and a processor for determining the volume attenuation coefficient of the column of water according to:.

Abstract: A CCD imaging camera is adaptively controlled by: illuminating a reflectance field of view, selectively sensing a desired image field area within the field of view and generating an image signal thereof, reducing low frequency components of the sensed area image signal, generating a contrast signal from the image signal, generating an average or mean signal from a plurality of image contrast signals, comparing the mean signal with a reference signal corresponding to a predetermined contrast maximum value, and thereafter controlling the light level or the range of the camera to the object field.