LaserLightDiffraction, SpatialFiltering, and Reconstruction of MedicalRadiographic Images:A PilotStudy
Ieee Phillip H. Meyers, Charles M. Nice · 1968
Using alaser light source, anoptical bench, transform lenses, andspatial filters ina systemcalled LaserScan,1 we are studying laser light diffraction, spatial filtering, andreconstruction of medical radiographic images, withthehelpofGTS Corporation, whoselaboratories housethelaser computer. Medical radiographs areminified toa35mm second-generation transparency, thentrans- illuminated bymonochromatic, coherent, collimated light froma helium-neon gaslaser. A first transform lensproduces a Fourier Transform oftheminified image intheformofadiffraction pattern thatisphotographed onPolaroid film, and/or viewedwithaCCTV system. Spatial filtering isaccomplished intheplane ofthediffrac- tion pattern byusing various opaqueelements ofappropriate geomet- ricfonntofilter undesired spatial frequencies. Spatial filters take theformofwires, sector-wedges, andcircular apertures, aswell asother empirically determined shapes. A second lensperforns an inverse Fourier transform onthediffraction pattern producing are- constructed, filtered, realimageoftheminified film. Thisrecon- structed imageisalsophotographed onPolaroid filmorviewed on theCCTVscreen. Oneofourgoals istoremovecertain unnecessary pattern detail fromparticular radiographic images sothatcharac- teristic patterns ofdiagnostic picture detail might bemorereadily identified anddiagnosed. Experimental results, including photo- graphs ofdiffraction patterns andsomefiltered reconstructed images, arepresented.