Diffractive optical element with undiffracted light expansion for eye safe operation

摘要

Aspects of the subject disclosure are directed towards safely projecting a diffracted light pattern, such as in an infrared laser-based projection/illumination system. Non-diffracted (zero-order) light is refracted once to diffuse (defocus) the non-diffracted light to an eye safe level. Diffracted (non-zero-order) light is aberrated twice, e.g., once as part of diffraction by a diffracting optical element encoded with a Fresnel lens (which does not aberrate the non-diffracted light), and another time to cancel out the other aberration; the two aberrations may occur in either order. Various alternatives include upstream and downstream positioning of the diffracting optical element relative to a refractive optical element, and/or refraction via positive and negative lenses.