The system images the volume of a turbid medium and detects the contents.
The medium can be water or air, or living tissue, or almost any other
material which is at least partially light-transmissive. The system
includes a light source for producing a series of discrete fan-shaped
pulse beams that are substantially uniform in intensity or have been
peaked at the edges of the fan to illuminate sections of the medium, a
streak tube with a large, thin-slit-shaped photocathode for collecting the
maximum amount of light from weak returns, a field-limiting slit disposed
in front of the cathode for removing multiply scattered light, a
large-aperture optical element for collecting and focusing the reflected
portions of the pulse beam on the field-limiting slit and the cathode, and
an array of detectors. A volume display of the medium is generated by
translating the transmitter and receiver normal to the longitudinal axis
of the pulse beam, to illuminate adjacent sections of the medium, and
combining the sections to provide a volume display. All, or substantially
all, of the light returned from each pulse beam is used. Vehicle motion
can be used to provide the scan of the beam. Applications range from foggy
sky surveillance at multiple-kilometer scale to location of
fractional-millimeter tumors in a human breast.
