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20 June 2003 Laser safety glasses based on phase distortion
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A new technique is described where laser safety glasses are based on optical distortion of the phase of the laser transmitted through the safety glasses. The glass contains an absorber at the laser wavelength, which heats the glass and therefore changes its index of reflection. The uniqueness of the concept presented is the layout of the absorber and its dependence on the transverse dimensions of the safety glass. Because the absorption varies across the glass, the absorbed power varies and therefore the change in index of refraction also varies. This variation in the optical property causes distortion and a reduction of "coherence" of the laser beam. By combining the phase distortion with absorption, the laser safety glasses can be designed to protect the retina at low intensities and once the phase distortion becomes important at intermediate intensities, it dominates at all higher intensities. These Phase Distortion Safety Glasses are designed to protect the retina from quasi cw lasers at all wavelengths - the near UV, visible, and near IR and the visible light transmission is equal to three percent. Once the threshold is reached the phase distortion will never allow the retina to be damaged no matter how high the laser intensity. These glasses also allow the operator to see the laser beam that is being protected against.
© (2003) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
David C. Smith "Laser safety glasses based on phase distortion", Proc. SPIE 4953, Laser and Noncoherent Light Ocular Effects: Epidemiology, Prevention, and Treatment III, (20 June 2003);

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