Lect09_imaging06_Opticalimaging_Sep17 - Definitions...

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1 Department of Biomedical Engineering Department of Biomedical Engineering EBME 105 EBME 105 Biomedical Imaging September 17, 2007 September 17, 2007 Lecture #9: Optical Imaging Optical Imaging Marty Pagel Marty Pagel Wickenden 428 (216) -368 368 -8519 8519 mpagel@case.edu The Electromagnetic Spectrum Near InfraRed (NIR) long wavelength low frequency low energy 2-3 mm penetration depth UltraViolet (UV) short wavelength high frequency high energy 0.1 mm penetration depth VISIBLE LIGHT Definitions Definitions Absorption The intensity of at least one color (frequency) is reduced when passed through an object. Blue & Green absorbed Absorbance Filter 650 750 850 950 0 4 8 12 Wavelength (nm) Absorbance Coefficient ( μ m -1 ) Hbr H 2 O HbO 2 Lipids Low Tissue Absorbance Between 700nm and 900nm Definitions Definitions Refraction Direction change of a ray of light passing from one transparent medium to another with different optical density. A ray passing from less dense medium to more dense medium is bent perpendicular to the surface. Dispersion The separation of light into its constituent wavelengths when entering a transparent medium. A ray passing from less dense medium to more dense medium is bent perpendicular to the surface , with greater deviation for shorter wavelengths. Refractive Index The change in dispersion relative to wavelength. In Phase Out of Phase bright dim Dispersion Affects Intensity Definitions
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Definitions Diffraction Light rays bend around edges. New wavefronts are generated at sharp edges. Smaller apertures cause lower image definition. Edge Effects caused by constructive interference Definitions Definitions Absorption, Refraction, Dispersion, Diffraction and Reflectance Definitions Definitions Magnification: Expansion in size Magnification + Resolution Magnification Only Original Image x45 x100 x45 x100 Definitions Microscope Objective Lenses
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Lect09_imaging06_Opticalimaging_Sep17 - Definitions...

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