The OPTIR 1.0 NG 305 X 305 is an Optolite? IR broad band Acrylic Filter has been specially formulated to transmit infra-red radiation at wavelengths greater than approximately 750nm and is thereby virtually opaque to visible light. It is eminently suitable for use in photometric systems which are triggered by near infra-red signals but which must operate in environments with high levels of visible radiation. This eliminates the visible spectrum and so improves the effectiveness of the system by increasing the single-to-noise ratio.