Biomedical subjects
Publications and source records attributed to Emmett N Leith.
It has long been known that image plane holography with low-coherence illumination achieves optical sectioning of a volume object. A method is analyzed that is similar to image plane holography, but the interferometric arrangement utilizes the interference between two object-bearing beams instead of the basic object and reference beams.
A theory of optical sectioning by image plane holography is developed, emphasizing the use of broad-spectrum holographic methods to enhance the process. It is shown that a broad-spectrum source in a grating interferometer imitates the behavior of a monochromatic broad source.
Reconstructing a hologram with spatially incoherent illumination smears the obtained image. We propose a wavelet based holographic recording process which uses the smearing to obtain a reconstruction with improved spatial resolution when incoherent illumination is applied.
We present a generalized holography-based approach with improved spatial resolution for extracting images, viewed through a scattering medium. The various angular directions are encoded either with different wavelengths or by capturing their corresponding images in different time slots. The various encoded images are recorded on a digital hologram with a computer. A digital reconstruction, which includes demodulation of the carrier beam and then a proper decoding algorithm, yields resolved images. The principle is demonstrated by recording image-plane digital holograms. Combining the suggested approach with the first-arriving light technique may further improve the results.
The propagation of scalar waves through random media that provide multiple elastic scattering is considered by derivation of an expression for the angular correlation of the scattered wave amplitudes. Coherent wave transmission is shown to occur through a mechanism similar to that responsible for coherent backscattering. While the properties of the scattered wave are generally consistent with radiative-transfer theory for sufficiently small incident and scattering angles, coherent transmission provides corrections to radiative-transfer results at larger angles. The theoretical angular correlation curves are fit, by specifying the probability densities of two random variables that correspond to material parameters, to measured data of laser light scattering from various polymer microsphere suspensions.
The method of Fourier optics is applied to the problem of time-gated imaging through scattering media. Tb adapt the problem to this treatment, appropriate alterations are made: The continuous medium is replaced by a cascade of thin scatterers, and a spatial filtering process is substituted for the conventional gating processes. Closed-form solutions are derived.