Verification of switched liquid crystal eye protection filters.

Protective eye-wear which utilizes switched liquid crystal can provide protection for operators using intense pulsed light sources (IPLs). Such eye protection devices combine the properties of useful visual transmittance in the nonactivated state and low light transmission in the active blocking state. The performance of a specific LightSpeed device has been determined using a series of bandpass optical filters coupled to photodiode detectors with signals being captured using a USB interface. Such measurements have allowed key switching parameters of these devices to be determined as part of the process of assessing their effectiveness. Measurements of optical density of transmitting state and blocking state were also determined using a double grating spectroradiometer. A simple model of active filter function was developed and applied to specific IPL pulse profiles.