Diffractive optical element with undiffracted light expansion for eye safe operation

Abstract

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.

What is claimed is: 
     
         1 . A system comprising:
 a diffractive optical element (DOE) set comprising one or more optical elements that pass non-diffracted light that is not diffracted, the diffractive optical element set configured to diffract light from a light source that passes through the diffractive optical element set into a pattern of diffracted light, the diffractive optical element set further configured to aberrate the diffracted light; and   a refractive optical element (ROE) optically coupled to the diffractive optical element set, the ROE configured to aberrate the non-diffracted light and the diffracted light, including to aberrate the diffracted light to cancel or substantially cancel aberration of the diffracted light by the diffractive optical element set.   
     
     
         2 . The system of  claim 1  wherein the diffractive optical element set comprises a diffractive optical element encoded with a diffractive lens. 
     
     
         3 . The system of  claim 1  wherein the ROE is downstream, relative to a light source, of the diffractive optical element set. 
     
     
         4 . The system of  claim 1  wherein the ROE is upstream, relative to a light source, of the diffractive optical element set. 
     
     
         5 . The system of  claim 1  wherein the ROE comprises a negative ROE configured to diverge the non-diffracted light. 
     
     
         6 . The system of  claim 1  wherein the ROE comprises a positive ROE configured to focus the non-diffracted light to a point. 
     
     
         7 . The system of  claim 1  wherein the ROE comprises a positive lens configured to focus the non-diffracted light to a stop. 
     
     
         8 . The system of  claim 1  wherein the diffractive optical element set comprises a plurality of separate diffractive optical elements arranged in series. 
     
     
         9 . The system of  claim 1  wherein the light source comprises a laser, the laser optically coupled to a collimating lens, the collimating lens optically coupled to the diffractive optical element. 
     
     
         10 . The system of  claim 1  wherein the light source outputs infrared light. 
     
     
         11 . The system of  claim 1  wherein the diffractive optical element set and the ROE are incorporated into a projection device that outputs a spot pattern of diffracted light. 
     
     
         12 . The system of  claim 11  wherein the spot pattern of diffracted light is detected by a stereo camera set. 
     
     
         13 . The system of  claim 1  wherein the non-diffracted light is refracted to defocus to an eye safe level before reaching a physical barrier. 
     
     
         14 . The system of  claim 1  wherein the non-diffracted light is refracted to defocus to an eye safe level over by reflecting the non-diffracted light over a distance before outputting the non-diffracted light from a device. 
     
     
         15 . The system of  claim 1  wherein a size of the ROE, or a size of at least one diffractive optical element of the set, or both, is based upon an eye safety limit. 
     
     
         16 . The system of  claim 1  wherein a strength of the ROE and a strength of at least one diffractive optical element of the set is based upon an eye safety limit. 
     
     
         17 . A system comprising, a projection mechanism, the projection mechanism configured to output a pattern of diffracted light spots, and to defocus non-diffracted light output therefrom, the projection mechanism comprising optically coupled components including a laser light source, a collimating lens, a refractive optical element (ROE), and a diffractive optical element set comprising at least one diffractive element with encoded diffractive lens, the ROE configured to defocus the non-diffracted light, and to cancel or substantially cancel defocusing of the diffracted light spots by the diffractive lens. 
     
     
         18 . The system of  claim 17  wherein the projection mechanism is incorporated into a device containing a stereo camera set configured to detect the diffracted light spots. 
     
     
         19 . A system comprising, a diffractive optical element set optically coupled with a refractive optical element ROE, the ROE configured to defocus non-diffracted light that is not diffracted by the diffractive optical element set, and to cancel or substantially cancel aberration of diffracted light by the diffractive optical element set. 
     
     
         20 . The system of  claim 19  wherein the diffractive optical element set comprises a diffractive optical element encoded with a diffractive lens