Abstract: Biological material is characterized by illuminating the material with a beam of light, measuring light scattered from the material and then determining the condition of the material using the measurements. In one embodiment the angular line shape of the backscattered light is measured and then used to determine the scattering mean free path (1) and the absorption length (la) of the light scattered in the material to find out the condition of the material. These values so obtained are compared to values for a material whose condition is normal to determine if the condition of the material being examined is abnormal or normal. In another embodiment the temporal profile of the scattered pulse is used to determine (1) and (1a).

Abstract: A protective device designed to protect eyes and sensitive photodetectors from high-intensity light over a broad spectral bandwidth while permitting low-intensity and ambient light to be transmitted thereto. In a first embodiment, the device comprises a stack of nonlinear materials having the same linear index of refraction but alternating between a relatively high nonlinear index of refraction and a relatively low nonlinear index of refraction. The respective optical thicknesses of the nonlinear materials are unordered. In a second embodiment, the device comprises a stack of nonlinear materials having the same linear index of refraction and the same optical thickness of a one-half wavelength but unordered nonlinear indices of refraction. In a third embodiment, the device comprises a stack of nonlinear materials having linear indices of refraction alternating between a relatively high linear index of refraction and a relatively low index of refraction and nonlinear indices of refraction which are unordered.

Abstract: The quality of image of an object hidden inside a highly scattering semi-opaque disordered medium is improved by using space gate imaging or time gate imaging or space time gate imaging. In space gate imaging, a small segment of the object is illuminated at a time. The scattered light is passed through a spatial noise filter. On the image plane, an aperture is open at the position of the image segment which correspond to the segment of the illuminated object. A full image is obtained by scanning the object segment by segment and simultaneously recording the signal at the corresponding image segment. In time gate imaging, the unscattered (i.e. ballistic) portion of the pulse which contains the information of the image is temporally separated from the other (i.e. scattered) portions which contains the noise using a ultrafast laser pulse and temporal gating devices. The technique is in space-time gate imaging, the two techniques are combined to produce an image with a much higher signal to noise ratio.