Maximum permissible exposure

The Coherent FAP-System and the Opto Power OPC-D030-795-HBPS infra-red diode lasers emit nominal continuous beams of $30 W$ at a wavelength of $795 nm$. With a limiting aperture size of $0.385 cm^2$ ( $7 mm$ pupil size), this gives an irradiance at the eye of $39 W/cm^2$. With one 30 W laser, the maximum irradiance at the eye is $78 W/cm^2$ As this wavelength is not visible, no blink reflex can occur, and we thus assume a 10 second exposure time. With a correction factor of $CA=1.55$ the calculated MPE is $1.57 mW/cm^2$.

The required filter transmittance is thus 0.000020 , which gives a minimum Optical Density of 4.7. We chose to use safety goggles of Optical density 5, for the wavelength of $795 nm$.